Patent Application
20110213084
The present invention generally relates to alcohol- and amine-terminated polyisobutylene (PIB) compounds, and to a process for making such compounds. In one embodiment, the present invention relates to primary alcohol- and amine-terminated polyisobutylene compounds, and to a process for making such compounds. In still another embodiment, the present invention relates to polyisobutylene compounds that can be used to synthesize polyurethanes and polyureas, to polyurethane and polyurea compounds made via the use of such polyisobutylene compounds, and to processes for making such compounds. In yet another embodiment, the present invention relates to primary alcohol-terminated polyisobutylene compounds having two or more primary alcohol termini and to a process for making such compounds. In yet another embodiment, the present invention relates to primary amine-terminated polyisobutylene compounds having two or more primary amine termini. In yet another embodiment, the present invention relates to polyisobutylene compounds containing urea or urethane segments therein, and to a method of producing such compounds. In still yet another embodiment, the present invention relates to a polymer having one or more different soft segments and one or more different hard segments.
Various polyurethanes (PUs) are multibillion dollar commodities and are manufactured worldwide by some of the largest chemical companies (e.g., Dow, DuPont, BASF, and Mitsui). Polyurethanes are used in a wide variety of industrial and clinical applications in the form of, for example, thermoplastics, rubbers, foams, upholstery, tubing, and various biomaterials.
Typically, PUs are made by combining three ingredients: (1) a diol (such as tetramethylene oxide); (2) a diisocyanate (such as 4,4′-methylene diphenyl diisocyanate); and (3) a chain extender (such as 1,4-butanediol). Generally, polyurethanes (PUs) contain a soft (rubbery) and a hard (crystalline) component; and the properties of PUs depend on the nature and relative concentration of the soft/hard components.
Even though primary alcohol-terminated PIB compounds, such as HOCH2—PIB—CH2OH, have been prepared in the past, previous synthesis methods have been uneconomical. As such, the cost of manufacturing primary alcohol-terminated PIB compounds has been too high for commercial production. One reason for the high cost associated with manufacturing primary alcohol-terminated PIB compounds, such as HOCH2—PIB—CH2OH, is that the introduction of a terminal —CH2OH group at the end of the PIB molecule necessitates the use of the hydroboration/oxidation method—a method that requires the use of expensive boron chemicals (such as H6B2 and its complexes).
Given the above, numerous efforts have been made to develop an economical process for manufacturing primary alcohol-terminated PIB compounds, such as HOCH2—PIB—CH2OH. For example, BASF has spent millions of dollars on the research and development of a process to make HOCH2—PIB—CH2OH by hydroboration/oxidation, where such a process permitted the recovery and reuse of the expensive boron containing compounds used therein. Other research efforts have met with limited success in reducing the cost associated with producing primary alcohol-terminated PIB compounds, such as PIB—CH2OH or HOCH2—PIB—CH2OH.
With regard to amine-terminated PIBs, early efforts directed toward the synthesis of amine-terminated telechelic PIBs were both cumbersome and expensive, and the final structures of the amine-telechelic PIBs are different from those described below.
More recently, Binder et al. (see, e.g., D. Machl, M. J. Kunz and W. H. Binder, Polymer Preprints, 2003, 44(2), p. 85) initiated the living polymerization of isobutylene under well-known conditions, terminated the polymer with 1-(3-bromopropyl)-4-(1-phenylvinyl)-benzene, and effected a complicated series of reactions on the product to obtain amine-terminated PIBs. Complex structures different from those disclosed herein were obtained and the above method fails to yield amine-terminated telechelic PIB compounds that carry a defined number, for example 1.0±0.05, functional groups.
Given the above, there is a need in the art for a manufacturing process that permits the efficient and cost-effective production/manufacture of primary alcohol-terminated PIB compounds, primary amine-terminated PIB compounds, primary methacrylate-terminated PIB compounds, and/or primary amine-terminated telechelic PIB compounds. Also, there is a need in the art for a polymer having one or more different soft segments and one or more different hard segments, and to a method for synthesizing same.
The present invention generally relates to alcohol- and amine-terminated polyisobutylene (PIB) compounds, and to a process for making such compounds. In one embodiment, the present invention relates to primary alcohol- and amine-terminated polyisobutylene compounds, and to a process for making such compounds. In still another embodiment, the present invention relates to polyisobutylene compounds that can be used to synthesize polyurethanes and polyureas, to polyurethane and polyurea compounds made via the use of such polyisobutylene compounds, and to processes for making such compounds. In yet another embodiment, the present invention relates to primary alcohol-terminated polyisobutylene compounds having two or more primary alcohol termini and to a process for making such compounds. In yet another embodiment, the present invention relates to primary amine-terminated polyisobutylene compounds having two or more primary amine termini. In yet another embodiment, the present invention relates to polyisobutylene compounds containing urea or urethane segments therein, and to a method of producing such compounds. In still yet another embodiment, the present invention relates to a polymer having one or more different soft segments and one or more different hard segments.
In one embodiment, the present invention relates to a method for producing a polyisobutylene compound containing urea hard segments comprising the steps of: (A) providing a primary amine-terminated polyisobutylene having at least two primary amine termini; (B) reacting the primary amine-terminated polyisobutylene with a diisocyanate and a chain extender; and (C) recovering the polyisobutylene compound containing various urea hard segments.
In another embodiment, the present invention relates to a polyisobutylene compound formed from the above method, wherein the polyisobutylene comprises urea hard segment portions.
In still another embodiment, the present invention relates to a method for producing a polyisobutylene compound containing urethane segments comprising the steps of: (a) providing a primary alcohol-terminated polyisobutylene having at least two primary alcohol termini; (b) reacting the primary alcohol-terminated polyisobutylene with a diisocyanate and a chain extender; and (c) recovering the polyisobutylene compound containing various urethane segments.
In still yet another embodiment, the present invention relates to a polyisobutylene compound formed from the above method, wherein the polyisobutylene comprises urethane segment portions.
In still yet another embodiment, the present invention relates to a polymer compound comprising urea or urethane segments therein, the polymer compound comprising: (i) one hard segment, wherein the hard segment is selected from a urea or urethane hard segment; and (ii) two soft segments.
In still yet another embodiment, the present invention relates to a polymer composition as disclosed and described herein.
In still yet another embodiment, the present invention relates to a method for making a polymer composition as disclosed and described herein.
a is a graph illustrating tensile stress (MPa) versus percent hard segment content for various polyurea compounds formed in accordance with the present invention stress versus;
b is a graph illustrating strain (percent elongation) versus percent hard segment content for various polyurea compounds formed in accordance with the present invention;
The present invention generally relates to alcohol- and amine-terminated polyisobutylene (PIB) compounds, and to a process for making such compounds. In one embodiment, the present invention relates to primary alcohol- and amine-terminated polyisobutylene compounds, and to a process for making such compounds. In still another embodiment, the present invention relates to polyisobutylene compounds that can be used to synthesize polyurethanes and polyureas, to polyurethane and polyurea compounds made via the use of such polyisobutylene compounds, and to processes for making such compounds. In yet another embodiment, the present invention relates to primary alcohol-terminated polyisobutylene compounds having two or more primary alcohol termini and to a process for making such compounds. In yet another embodiment, the present invention relates to primary amine-terminated polyisobutylene compounds having two or more primary amine termini. In yet another embodiment, the present invention relates to polyisobutylene compounds containing urea or urethane segments therein, and to a method of producing such compounds. In still yet another embodiment, the present invention relates to a polymer having one or more different soft segments and one or more different hard segments.
Although the present invention specifically discloses a method for producing various PIB molecules-terminated with one —CH2—CH2—CH2—OH group, the present invention is not limited thereto. Rather, the present invention can be used to produce a wide variety of PIB molecular structures, where such molecules are terminated with one or more primary alcohols.
In one embodiment, the primary alcohols that can be used as terminating groups in the present invention include, but are not limited to, any straight or branched chain primary alcohol substituent group having from 1 to about 12 carbon atoms, or from 1 to about 10 carbon atoms, or from 1 to about 8, or from about 1 to about 6 carbon atoms, or even from about 2 to about 5 carbon atoms. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
In one embodiment, the present invention relates to linear, star-shaped, hyperbranched, or arborescent PIB compounds, where such compounds contain one or more primary alcohol-terminated segments. Such molecular structures are known in the art, and a discussion herein is omitted for the sake of brevity. In another embodiment, the present invention relates to star-shaped molecules that contain a center cyclic group (e.g., an aromatic group) to which three or more primary alcohol-terminated PIB arms are attached.
The following examples are exemplary in nature and the present invention is not limited thereto. Rather, as is noted above, the present invention relates to the production and/or manufacture of various PIB compounds and polyurethane and polyurea compounds made therefrom.
The following example concerns the synthesis of a primary hydroxyl-terminated polyisobutylene in three steps:
The synthesis of Ø-(PIB-Allyl)3 followed the procedure described by Lech Wilczek and Joseph P. Kennedy in The Journal of Polymer Science: Part A: Polymer Chemistry, 25, pp. 3255 through 3265 (1987), the disclosure of which is incorporated by reference herein in its entirety.
The first step involves the polymerization of isobutylene to tert-chlorine-terminated PIB by the 1,3,5-tri(2-methoxyisopropyl)benzene/TiCl4 system under a blanket of N2 in a dry-box. Next, in a 500 mL three-neck round bottom glass flask, equipped with an overhead stirrer, the following are added: a mixed solvent (n-hexane/methyl chloride, 60/40 v/v), 2,6-di-t-butyl pyridine (0.007 M), 1,3,5-tri(2-methoxyisopropyl)benzene (0.044M), and isobutylene (2 M) at a temperature of −76° C. Polymerization is induced by the rapid addition of TiCl4 (0.15 M) to the stirred charge. After 10 minutes of stirring the reaction is terminated by the addition of a 3 fold molar excess of allyltrimethylsilane (AllylSiMe3) relative to the tert-chlorine end groups of the Ø(PIB—Cl)3 that formed. After 60 minutes of further stirring at −76° C., the system is deactivated by introducing a few milliliters of aqueous NaHCO3, and the (allyl-terminated polyisobutylene) product is isolated. The yield is 28 grams (85 percent of theoretical) and the Mn=3,000 grams/mole.
A 100 mL three-neck flask is charged with heptane (50 mL) and allyl-telechelic polyisobutylene (10 grams), and air is bubbled through the solution for 30 minutes at 100° C. to activate the allylic end groups. Then the solution is cooled to approximately −10° C. and HBr gas is bubbled through the system for 10 minutes.
Dry HBr is generated by the reaction of aqueous (47 percent) hydrogen bromide and sulfuric acid (95 to 98 percent). After neutralizing the solution with aqueous NaHCO3 (10 percent), the product is washed 3 times with water. Finally the solution is dried over magnesium sulfate for at least 12 hours (i.e., overnight) and filtered. The solvent is then removed via a rotary evaporator. The product is a clear viscous liquid.
where n is an integer from 2 to about 5,000, or from about 7 to about 4,500, or from about 10 to about 4,000, or from about 15 to about 3,500, or from about 25 to about 3,000, or from about 75 to about 2,500, or from about 100 to about 2,000, or from about 250 to about 1,500, or even from about 500 to about 1,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
It should be noted that the present invention is not limited to solely the use of allyl-terminated compounds, shown above, in the alcohol-terminated polyisobutylene production process disclosed herein. Instead, other straight or branched C3 to C12, C4 to C10, or even C5 to C7 alkenyl groups can be used so long as one double bond in such alkenyl groups is present at the end of the chain. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
As a further example regarding the above-mentioned alkenyl groups the following general formula is used to show the positioning of the end double bond:
—R1=CH2
where R1 is the remaining portion of the straight or branched alkenyl groups described above. In another embodiment, the alkenyl groups of the present invention contain only one double bond and this double bond is at the end of the chain as described above.
The olefinic (allylic) protons at 5 ppm present in spectrum (A) completely disappear upon anti-Markovnikov hydrobromination, as is shown in spectrum (B). The aromatic protons present in the 1,3,5-tri(2-methoxyisopropyl)benzene (initiator residue) provide an internal reference. Thus, integration of the terminal methylene protons of the —PIB—CH2—CH2—CH2—Br relative to the three aromatic protons in the initiator fragment yields quantitative functionality information. The complete absence of allyl groups and/or secondary bromines indicates substantially 100 percent conversion to the target anti-Markovnikov product Ø-(PIB—CH2—CH2—CH2—Br)3.
The conversion of the terminal bromine product to a terminal primary hydroxyl group is performed by nucleophilic substitution on the bromine. A round bottom flask equipped with a stirrer is charged with a solution of Ø(PIB—CH2—CH2—CH2—Br)3 in THF. Then an aqueous solution of NaOH is added, and the charge is stirred for 2 hours at room temperature. Optionally, a phase transfer catalyst such as tetraethyl ammonium bromide can be added to speed up the reaction. The product is then washed 3 times with water, dried over magnesium sulfate overnight and filtered. Finally the solvent is removed via the use of a rotary evaporator. The product, a primary alcohol-terminated PIB product, is a clear viscous liquid.
In another embodiment, the present invention relates to a process for producing halogen-terminated PIBs (e.g., chlorine-terminated PIBs rather than the bromine containing compounds discussed above). These halogen-terminated PIBs can also be utilized in the above process and converted to primary alcohol-terminated PIB compounds. Additionally, as is noted above, the present invention relates to the use of such PIB compounds in the production of polyurethanes and polyureas, as well as a variety of other polymeric end products, such as methacrylates (via a reaction with methacryloyl chloride), hydrophobic adhesives (e.g., cyanoacrylate derivatives), epoxy resins, polyesters, etc.
In still another embodiment, the primary halogen-terminated PIB compounds of the present invention can be converted into PIB compounds that contain end epoxy groups, amine groups, etc. Previous efforts to inexpensively prepare primary halogen-terminated PIB compounds were fruitless and only resulted in compounds with tertiary terminal halogens.
As noted above, the primary alcohol-terminated PIBs are useful intermediates in the preparation of polyurethanes by reaction via conventional techniques, i.e., by the use of known isocyanates (e.g., 4,4′-methylenediphenyl diisocyanate, MDI) and chain extenders (e.g., 1,4-butanediol, BDO). The great advantage of these polyurethanes (PUs) is their biostability imparted by the biostable PIB segment. Moreover, since PIB is known to be biocompatible, any PU made from the PIB compounds of the present invention is novel as well as biocompatible.
The primary terminal OH groups can be further derivatized to yield additional useful derivatives. For example, they can be converted to terminal cyanoacrylate groups which can be attached to living tissue and in this manner new tissue adhesives can be prepared.
In one embodiment of the present invention, the starting PIB segment can be mono-, di- tri, and multi-functional, and in this manner one can prepare di-terminal, tri-terminal, or other PIB derivatives. In another embodiment, the present invention makes it possible to prepare a,w di-terminal (telechelic), tri-terminal, or other PIB derivatives. One of the most interesting PIB starting materials is arborescent-PIB (arb-PIB) that can carry many primary halogen termini, all of which can be converted to primary alcohol groups.
In another embodiment, the following equations describe further processes and compounds that can be produced via the present invention. As a general rule, all of the following reactions can be run at a 95 percent or better conversion rate.
(A) Cationic living isobutylene polymerization affords a first intermediate which is, for example, a tert-Cl-terminated PIB chain:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—C(CH3)2—Cl (A)
where ˜˜˜ represents the remaining portion of a linear, star, hyperbranched, or arborescent molecule and n is defined as noted above. As would be apparent to those of skill in the art, ˜˜˜ can in some instances represent another chlorine atom in order to permit the production of substantially linear di-terminal primary alcohol PIBs. Additionally, it should be noted that, in some embodiments, the present invention is not limited to the above specific linking groups (i.e., the —C(CH3)2) between the repeating PIB units and the remainder of the molecules of the present invention.
(B) The next step is the dehydrogenation of (A) to afford the second intermediate shown below:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—C(CH3)═CH2 (B).
(C) The third step is the anti-Markovnikov bromination of (B) to afford the primary bromide shown below:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH(CH3)—CH2—Br (C).
(D) The fourth step is the conversion of the primary bromide by the use of a base (e.g., NaOH, KOH, or tert-BuONa) to a primary hydroxyl group according to the following formula:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH(CH3)—CH2—OH (D).
In another embodiment, the following reaction steps can be used to produce a primary alcohol-terminated PIB compound according to the present invention.
(B′) Instead of the dehydrochlorination, as outlined in (B), one can use an allyl silane such as trimethyl allyl silane to prepare an allyl terminated PIB:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH═CH2 (B′)
(C′) Similarly to the reaction shown in (C) above, the (B′) intermediate is converted to the primary bromide by an anti-Markovnikov reaction to yield the following compound:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH2—CH2—Br (C′).
(D′) (C′) can be converted to a primary alcohol-terminated compound as discussed above to yield the following compound:
˜˜˜C(CH3)2[CH2—C(CH3)2]n—CH2—CH2—CH2—OH (D′).
As discussed above, in another embodiment the present invention relates to primary terminated polyisobutylene compounds having two or more primary termini selected from an amine groups or methacrylate groups. Again, as in other embodiments of the present invention, the following embodiments can be applied to linear, star, hyperbranched, or arborescent molecules with the number of repeating units in the PIB portion of such molecules being the same as defined as noted above.
Synthesis of a primary methacrylate-terminated polyisobutylene is carried out according to the exemplary reaction scheme shown below:
To 1.0 grams of PIB—(CH2)3—Br (Mn=5,160 grams/mole and Mw/Mn=1.065) dissolved in 20 mL of THF is added 10.0 mL NMP to increase the polarity of the medium. To this solution is added 1 gram of sodium methacrylate, and the mixture is refluxed at 80° C. for 18 hours. The charge is diluted by the addition of 50 mL hexanes and washed 3 times with excess water. The organic layer is separated, washed three times with distilled water and dried over MgSO4. The hexanes are removed by a rotavap and the resulting polymer is dried under vacuum, and the yield of PIB—(CH2)3—MA is 0.95 grams (95 percent).
It should be noted that the above embodiment is not limited to just the use of sodium methacrylate, but rather other suitable methacrylate compounds could be used. Such compounds include, but are not limited to, alkaline methacrylate compounds.
Additionally, the present invention is not limited to solely the use of allyl-terminated compounds in the methacrylate-terminated polyisobutylene production process disclosed herein. Instead, other straight or branched C3 to C12, C4 to C10, or even C5 to C7 alkenyl groups can be used so long as one double bond in such alkenyl groups is present at the end of the chain. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
As a further example regarding the above-mentioned alkenyl groups the following general formula is used to show the positioning of the end double bond:
—R1═CH2
where R1 is the remaining portion of the straight or branched alkenyl groups described above. In another embodiment, the alkenyl groups of the present invention contain only one double bond and this double bond is at the end of the chain as described above.
In this embodiment, the synthesis of PIB—(CH2)3—NH2 involves two steps: (a) substitution of the terminal primary bromine to phthalimide-terminated polyisobutylene (PIB—(CH2)3—phthalimide); and (b) hydrazinolysis of the phthalimide terminated polyisobutylene to primary amine-terminated polyisobutylene (PIB—(CH2)3—NH2).
Synthesis of a phthalimide-terminated polyisobutylene (PIB—(CH2)3-phthalimide) is carried out according to the reaction scheme shown below:
To 1.0 gram of PIB—(CH2)3—Br (Mn=5160 grams/mole and Mw/Mn=1.06) dissolved in 20 mL THF is added 10 mL of NMP to increase the polarity of the medium. To this solution is added 1.0 gram of potassium phthalimide and the mixture is refluxed at 80° C. for 4 hours. The reaction mixture is diluted by the addition of 50 mL hexanes and washed 3 times with excess water. The organic layer is separated, washed three times with distilled water and dried over MgSO4.
The hexanes are removed by a rotavap, and the resulting polymer is dried under vacuum. The yield of PIB—(CH2)3—phthalimide is 0.97 grams.
Synthesis of an amine-terminated polyisobutylene (PIB—(CH2)3—NH2) is carried out according to the reaction scheme shown below:
To 1.0 gram of PIB—(CH2)3-phthalimide dissolved in a mixture of 20 mL heptane and 20 mL of ethanol is added 3 grams of hydrazine hydrate. This mixture is then refluxed at 105° C. for 5 hours. Then the charge is diluted with 50 mL of hexanes and washed 3 times with excess water. The organic layer is separated, washed three times with distilled water and dried over MgSO4. The hexanes are removed by a rotavap and the polymer is dried under vacuum. The yield of PIB—(CH2)3—NH2 is 0.96 grams.
It should be noted that the present invention is not limited to solely the use of allyl-terminated compounds, shown above, in the amine-terminated polyisobutylene production process disclosed herein. Instead other straight or branched C3 to C12, C4 to C10, or even C5 to C7 alkenyl groups can be used so long as one double bond in such alkenyl groups is present at the end of the chain. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
As a further example regarding the above-mentioned alkenyl groups the following general formula is used to show the positioning of the end double bond:
R1═CH2
where R1 is the remaining portion of the straight or branched alkenyl groups described above. In another embodiment, the alkenyl groups of the present invention contain only one double bond and this double bond is at the end of the chain as described above.
In another embodiment, the present invention relates to a polyisobutylenes having at least two primary bromine termini as shown in the formula below:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—R3—Br
where ˜˜˜ represents the remaining portion of a linear, star, hyperbranched, or arborescent molecule and n is defined as noted above. As would be apparent to those of skill in the art, ˜˜˜ can in some instances represent another bromine atom in order to permit the production of substantially linear di-terminal primary alcohol PIBs. In the above formula R3 represents the remainder of the alkenyl group left after subjecting a suitable alkenyl-terminated compound to an anti-Markovnikov bromination step in accordance with the present invention. As would be apparent to those of skill in the art, R3 could be either a straight or branched C3 to C12, C4 to C10, or even C5 to C7 alkyl group (the result of the “starting” alkenyl group having only one double bond, with such double bond being present at the end of the chain as described above). In another embodiment, R3 could be either a straight or branched C3 to C12, C4 to C10, or even C5 to C7 alkenyl group (the result of the “starting” alkenyl group having two or more double bonds, with one of the double bonds being present at the end of the chain as described above).
In another embodiment, the present invention relates to amine-telechelic polyisobutylenes (PIBs) that carry a certain amount of functional primary (—NH2), secondary (—NH—R4), or tertiary (═N—R4) amine end groups where R4 is as defined below. In yet another embodiment, the present invention relates to alcohol-telechelic PIBs that carry a certain amount of functional primary alcohol end groups (—OH).
The term telechelic (from the Greek telos=far, and chelos=claw) indicates that each and every terminus of a polymer molecule is fitted with a functional end group. In one embodiment of the present invention the functional end groups of the present invention are hydroxyl or amine end groups. In another embodiment of the present invention, each chain end of a hydroxyl- or an amine-telechelic PIB molecule carries about 1.0±0.05 functional groups (i.e., a total of about 2.0±0.05, i.e., better than about 95 mole percent).
As is noted above, in one embodiment the present invention relates to amine-telechelic polyisobutylenes (PIBs) that carry primary (—NH2), secondary (—NH—R4), or tertiary (═N—R4) amine end groups, where R4 is selected from linear or branched C1 to C30 alkyl group, a linear or branched C2 to C30 alkenyl group, a linear or branched C2 to C30 alkynyl group. In another embodiment, R4 is selected from linear or branched C1 to C20 alkyl group, a linear or branched C2 to C20 alkenyl group, a linear or branched C2 to C20 alkynyl group. In still another embodiment, R4 is selected from linear or branched C1 to C10 alkyl group, a linear or branched C2 to C10 alkenyl group, a linear or branched C2 to C10 alkynyl group, or even C1 to C5 alkyl group, a linear or branched C2 to C6 alkenyl group, a linear or branched C2 to C6 alkynyl group. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
In yet another embodiment, R4 is selected from either a methyl, ethyl, propyl, or butyl group, or in still another embodiment R4 is selected from a methyl or ethyl group.
The simplest telechelic PIB molecule is the ditelechelic structure; for example, a PIB fitted with one —NH2 group at either end of the molecule: H2N—PIB—NH2. A PIB carrying only one —NH2 terminus (i.e., PIB—NH2) is not an amine-telechelic PIB within the definition known to those of skill in the art. A three-arm star amine-telechelic PIB (i.e., a tri-telechelic PIB) carries three —NH2 groups, one —NH2 group at each arm end: abbreviated R5(PIB—NH2)3, where the R5 is selected from any tri-substituted aromatic group. In another embodiment, in the case of a three-arm star amine-telechelic PIB, R5 can be any suitable functional group that can be tri-substituted with three PIB—NH2 groups. A hyperbranched or arborescent amine-telechelic PIB carries many —NH2 termini, because all the branch ends carry an —NH2 terminus (multi-telechelic PIB). In another embodiment, the primary NH2 groups mentioned above can be replaced by the afore-mentioned secondary (—NH—R4), or tertiary (═N—R4) amine end groups with R4 being defined above.
Molecules with less than about 1.0±0.05 hydroxyl or amine groups per chain end, and synthesis methods that yield less than about 1.0±0.05 hydroxyl or amine groups per chain end are of little or no practical interest in the production of compounds for use in the production of polyurethanes and/or polyureas. This stringent requirement must be met because these telechelic PIBs are designed to be used as intermediates for the production of polyurethanes and polyureas, and precise starting material stoichiometry is required for the preparation of polyurethane and/or polyurea compounds having optimum mechanical properties. In the absence of precise (i.e., about 1.0±0.05) terminal functionality, the preparation of high quality polyurethanes and polyureas is not possible.
Polymers obtained by the reaction of hydroxyl-ditelechelic PIB (i.e., HO—PIB—OH) and diisocyanates (e.g., MDI) contain urethane (carbamate) linkages:
˜˜˜OH+OCN˜˜˜→˜˜˜O—CO—NH˜˜˜
and are called polyurethanes, where in this case ˜˜˜ represents the remainder of the polyurethane molecule. Similarly, polymers prepared by amine-ditelechelic PIB (H2N—PIB—NH2) plus diisocyanates contain urea linkages:
˜˜˜NH2+OCN˜˜˜→˜˜˜NH—CO—NH˜˜˜
and are called polyureas, where in this case ˜˜˜ represents the remainder of the polyurea molecule.
Finally, the overall cost of the products, as determined by the cost of the starting materials and the procedures, is of decisive importance because only low cost commercially feasible simple syntheses are considered.
Although the present invention specifically discloses a method for producing various alcohol-telechelic PIBs and amine-telechelic PIBs terminated with at least two alcohol or amine groups, the present invention is not limited thereto. Rather, the present invention can be used to produce a wide variety of PIB molecular structures where such molecules are terminated with two or more primary alcohols or two or more amine groups be they primary amine groups, secondary amine groups, or tertiary amine groups.
In one embodiment, the primary alcohols that can be used as terminating groups in the present invention include, but are not limited to, any straight or branched chain primary alcohol substituent group having from 1 to about 12 carbon atoms, or from 1 to about 10 carbon atoms, or from 1 to about 8, or from about 1 to about 6 carbon atoms, or even from about 2 to about 5 carbon atoms. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
In another embodiment, the present invention relates to linear, star-shaped, hyperbranched, or arborescent PIB compounds, where such compounds contain two or more primary alcohol-terminated segments, amine-terminated segments, or amine-containing segments. Such molecular geometries are known in the art, and a discussion herein is omitted for the sake of brevity. In another embodiment, the present invention relates to star-shaped molecules that contain a center cyclic group (e.g., an aromatic group) to which three or more primary alcohol-terminated PIB arms are attached, or three or more amine-containing PIB arms are attached.
The following examples are exemplary in nature and the present invention is not limited thereto. Rather, as is noted above, the present invention relates to the production and/or manufacture of various primary alcohol-terminated PIB compounds and polyurethane compounds made therefrom.
The following example concerns the synthesis of a primary hydroxyl-terminated polyisobutylene in three steps as is discussed above:
The synthesis of Ø-(PIB-Allyl)3 followed the procedure described by Lech Wilczek and Joseph P. Kennedy in The Journal of Polymer Science: Part A: Polymer Chemistry, 25, pp. 3255 through 3265 (1987), the disclosure of which is incorporated by reference herein in its entirety.
The first step involves the polymerization of isobutylene to tert-chlorine-terminated PIB by the 1,3,5-tri(2-methoxyisopropyl)benzene/TiCl4 system under a blanket of N2 in a dry-box. Next, in a 500 mL three-neck round bottom glass flask, equipped with an overhead stirrer, the following are added: a mixed solvent (n-hexane/methyl chloride, 60/40 v/v), 2,6-di-t-butyl pyridine (0.007 M), 1,3,5-tri(2-methoxyisopropyl)benzene (0.044M), and isobutylene (2 M) at a temperature of −76° C. Polymerization is induced by the rapid addition of TiCl4 (0.15 M) to the stirred charge. After 10 minutes of stirring the reaction is terminated by the addition of a 3 fold molar excess of allyltrimethylsilane (AllylSiMe3) relative to the tert-chlorine end groups of the Ø(PIB—Cl)3 that formed. After 60 minutes of further stirring at −76° C., the system is deactivated by introducing a few milliliters of aqueous NaHCO3, and the (allyl-terminated polyisobutylene) product is isolated. The yield is 28 grams (85 percent of theoretical) and the Mn=3,000 grams/mole.
A 100 mL three-neck flask is charged with heptane (50 mL) and allyl-telechelic polyisobutylene (10 grams), and air is bubbled through the solution for 30 minutes at 100° C. to activate the allylic end groups. Then the solution is cooled to approximately −10° C. and HBr gas is bubbled through the system for 10 minutes.
Dry HBr is generated by the reaction of aqueous (47 percent) hydrogen bromide and sulfuric acid (95 to 98 percent). After neutralizing the solution with aqueous NaHCO3 (10 percent), the product is washed 3 times with water. Finally the solution is dried over magnesium sulfate for at least 12 hours (i.e., over night) and filtered. The solvent is then removed via a rotary evaporator. The product is a clear viscous liquid.
where n is an integer from 2 to about 5,000, or from about 7 to about 4,500, or from about 10 to about 4,000, or from about 15 to about 3,500, or from about 25 to about 3,000, or from about 75 to about 2,500, or from about 100 to about 2,000, or from about 250 to about 1,500, or even from about 500 to about 1,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
It should be noted that the present invention is not limited to solely the use of allyl-terminated compounds, shown above, in the alcohol-terminated polyisobutylene production process disclosed herein. Instead, other straight or branched C3 to C12, C4 to C10, or even C5 to C7 alkenyl groups can be used so long as one double bond in such alkenyl groups is present at the end of the chain. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
As a further example regarding the above-mentioned alkenyl groups the following general formula is used to show the positioning of the end double bond:
—R1═CH2
where R1 is the remaining portion of the straight or branched alkenyl groups described above. In another embodiment, the alkenyl groups of the present invention contain only one double bond and this double bond is at the end of the chain as described above.
The olefinic (allylic) protons at 5 ppm present in spectrum (A) completely disappear upon anti-Markovnikov hydrobromination, as is shown in spectrum (B). The aromatic protons present in the 1,3,5-tri(2-methoxyisopropyl)benzene (initiator residue) provide an internal reference. Thus, integration of the terminal methylene protons of the —PIB—CH2—CH2—CH2—Br relative to the three aromatic protons in the initiator fragment yields quantitative functionality information. The complete absence of allyl groups and/or secondary bromines indicates substantially 100 percent conversion to the target anti-Markovnikov product Ø—(PIB—CH2—CH2—CH2—Br)3.
The conversion of the terminal bromine product to a terminal primary hydroxyl group is performed by nucleophilic substitution on the bromine. A round bottom flask equipped with a stirrer is charged with a solution of Ø-(PIB—CH2—CH2—CH2—Br)3 in THF. Then an aqueous solution of NaOH is added, and the charge is stirred for 2 hours at room temperature. Optionally, a phase transfer catalyst such as tetraethyl ammonium bromide can be added to speed up the reaction. The product is then washed 3 times with water, dried over magnesium sulfate overnight and filtered. Finally the solvent is removed via the use of a rotary evaporator. The product, a primary alcohol-terminated PIB product, is a clear viscous liquid.
In another embodiment, the present invention relates to a process for producing halogen-terminated PIBs (e.g., chlorine-terminated PIBs rather than the bromine containing compounds discussed above). These halogen-terminated PIBs can also be utilized in above process and converted to primary alcohol-terminated PIB compounds. Additionally, as is noted above, the present invention relates to the use of such PIB compounds in the production of polyurethanes, as well as a variety of other polymeric end products, such as methacrylates (via a reaction with methacryloyl chloride), hydrophobic adhesives (e.g., cyanoacrylate derivatives), epoxy resins, polyesters, etc.
In still another embodiment, the primary halogen-terminated PIB compounds of the present invention can be converted into PIB compounds that contain end epoxy groups, amine groups, etc. Previous efforts to inexpensively prepare primary halogen-terminated PIB compounds were fruitless and only resulted in compounds with tertiary terminal halogens.
As noted above, the primary alcohol-terminated PIBs are useful intermediates in the preparation of polyurethanes by reaction via conventional techniques, i.e., by the use of known isocyanates (e.g., 4,4′-methylenediphenyl diisocyanate, MDI) and chain extension agents (e.g., 1,4-butanediol, BDO). The great advantage of these polyurethanes (PUs) is their biostability imparted by the biostable PIB segment. Moreover, since PIB is known to be biocompatible, any PU made from the PIB compounds of the present invention is novel as well as biocompatible.
The primary terminal OH groups can be further derivatized to yield additional useful derivatives. For example, they can be converted to terminal cyanoacrylate groups which can be attached to living tissue and in this manner new tissue adhesives can be prepared.
In one embodiment of the present invention, the starting PIB segment can be mono-, di- tri, and multi-functional, and in this manner one can prepare di-terminal, tri-terminal, or other PIB derivatives. In another embodiment, the present invention makes it possible to prepare α,ω di-terminal (telechelic), tri-terminal, or other PIB derivatives. One of the most interesting PIB starting materials is arborescent-PIB (arb-PIB) that can carry many primary halogen termini, all of which can be converted to primary alcohol groups.
In another embodiment, the following equations describe further processes and compounds that can be produced via the present invention. As a general rule, all of the following reactions can be run at a 95 percent or better conversion rate.
(A) Cationic living isobutylene polymerization affords a first intermediate which is, for example, a tert-Cl-terminated PIB chain:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—C(CH3)2—Cl (A)
where ˜˜˜ represents the remaining portion of a linear, star, hyperbranched, or arborescent molecule and n is defined as noted above. As would be apparent to those of skill in the art, ˜˜˜ can in some instances represent another chlorine atom in order to permit the production of substantially linear di-terminal primary alcohol PIBs. Additionally, it should be noted that the present invention is not limited to the above specific linking groups (i.e., the —C(CH3)2) between the repeating PIB units and the remainder of the molecules of the present invention.
(B) The next step is the dehydrochlorination of (A) to afford the second intermediate shown below:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—C(CH3)═CH2 (B).
(C) The third step is the anti-Markovnikov bromination of (B) to afford the primary bromide shown below:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH(CH3)—CH2—Br (C).
(D) The fourth step is the conversion of the primary bromide by the use of a base (e.g., NaOH, KOH, or tert-BuONa) to a primary hydroxyl group according to the following formula:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH(CH3)—CH2—OH (D).
In another embodiment, the following reaction steps can be used to produce a primary alcohol-terminated PIB compound according to the present invention.
(B′) Instead of the dehydrogenation, as outlined in (B), one can use an allyl silane such as trimethyl allyl silane to prepare an allyl terminated PIB:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH═CH2 (B′).
(C′) Similarly to the reaction shown in (C) above, the (B′) intermediate is converted to the primary bromide by an anti-Markovnikov reaction to yield the following compound:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH2—CH2Br (C′).
(D′) (C′) can be converted to a primary alcohol-terminated compound as discussed above to yield the following compound:
˜˜˜C(CH3)2—[CH2—C(CH3)2]n—CH2—CH2—CH2—OH (D′)
The detailed structure of this example, the amine-ditelechelic PIB, is defined by the following formula. However, the present invention is not limited thereto.
where n and m are each independently selected from an integer in the range of from 2 to about 5,000, or from about 7 to about 4,500, or from about 10 to about 4,000, or from about 15 to about 3,500, or from about 25 to about 3,000, or from about 75 to about 2,500, or from about 100 to about 2,000, or from about 250 to about 1,500, or even from about 500 to about 1,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
The above compound can be produced from a corresponding brominated structure as shown above in (C). The following chemical equations summarize the synthesis method for the above compound:
where n and m are each independently selected from an integer in the range of from 2 to about 5,000, or from about 7 to about 4,500, or from about 10 to about 4,000, or from about 15 to about 3,500, or from about 25 to about 3,000, or from about 75 to about 2,500, or from about 100 to about 2,000, or from about 250 to about 1,500, or even from about 500 to about 1,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
Additionally, the reaction conditions at A are: 30 grams of polymer, 150 mL of heptane (103 grams), reflux at 110° C. for 30 minutes, followed by passing HBr over the polymer solutions for 5 minutes at 0° C.
The Allyl-PIB-Allyl is then converted to the telechelic primary bromide, Br—(CH2)3—PIB—(CH2)3—Br, as described in above. Next, the Br—(CH2)3—PIB—(CH2)3—Br is converted by using: (1) potassium phthalimide; and (2) hydrazine hydrate to yield the target ditelechelic amine: NH2—(CH2)3—PIB—(CH2)3—NH2.
Following the above process, 16 grams of bromo-ditelechelic polyisobutylene (0.003 mol) is dissolved in 320 mL dry THF. Then, 160 mL of NMP and phthalimide potassium (2.2 grams, 0.012 moles) are added to this solution. Next, the solution is heated to reflux at 80° C. for 8 hours. The product is then dissolved in 100 mL of hexanes, extracted 3 times with water and dried over magnesium sulfate. The structure of the intermediate is ascertained by 1H NMR spectroscopy.
Then, the phthalimide-telechelic polyisobutylene (14 grams, 0.0025 moles) is dissolved in 280 mL of heptane, then 280 mL of ethanol and hydrazine hydrate (3.2 grams, 0.1 moles) are added thereto, and the solution is heated to reflux at 110° C. for 6 hours. The product is dissolved in hexanes, extracted 3 times with water, dried over magnesium sulfate, and the hexanes are removed by a rotavap. The structure of the target product is ascertained by 1H NMR spectroscopy.
(1) The Synthesis of the HO—PIB—OH Starting Material:
The synthesis of HO—PIB—OH is as described above. Thus, the starting material, a commercially available (Kaneka Inc.) allyl-ditelechelic PIB (MW=5,500 grams/mole) is hydrobrominated by dissolving it in heptane and bubbling HBr through the solution for 30 minutes at 70° C. Then the product is dissolved in THF, aqueous KOH and n-methyl pyrrolidone are added, and the system is refluxed for 24 hours at 100° C. The structure of the HO—PIB—OH is ascertained by proton NMR spectroscopy.
(2) The Synthesis of a PIB-Based Polyurethane and Demonstration of its Oxidative Stability:
The polyurethane is obtained by reaction of the HO—PIB—OH with methylene-bis-phenyl isocyanate (MDI). The following equations describe the synthesis strategy used:
where n and m are each independently selected from an integer in the range of from 2 to about 5,000, or from about 7 to about 4,500, or from about 10 to about 4,000, or from about 15 to about 3,500, or from about 25 to about 3,000, or from about 75 to about 2,500, or from about 100 to about 2,000, or from about 250 to about 1,500, or even from about 500 to about 1,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
Thus, HO—PIB—OH (2.2 grams, Mn=5,500 grams/mole, hydroxyl equivalent 0.0008 mole) is dissolved in dry toluene (12 mL) and freshly distilled MDI (0.3 grams, 0.0012 moles of isocyanate) and tin dioctoate (0.03 mL) catalyst are added under a dry nitrogen atmosphere. The charge is then heated for 8 hours at 70° C., cooled to room temperature, and poured in a rectangular (5 cm×5 cm) Teflon mold. The system is air dried overnight and finally dried in a drying oven at 70° C. for 24 hours. The polyurethane product is a pale yellow supple rubbery sheet, soluble in THF. Manual examination reveals good mechanical properties.
The oxidative resistance of the polyurethane is tested by placing small amounts (approximately 0.5 grams) of pre-weighed samples in concentrated (65 percent) nitric acid in a 25 mL glass vial, and gently agitating the system at room temperature. Concentrated nitric acid is recognized to be one of the most aggressive and corrosive oxidizing agents. After 24 and 48 hours the appearance of the samples is examined visually and their weight loss determined gravimetrically by using the following expression:
W
loss=(Wb−Wa/Wb)100
where Wloss is percent weight loss and Wb, and Wa are the weights of the samples before and after nitric acid exposure, respectively. The weight loss is experimentally determined by removing the pre-weighed samples from the nitric acid, rinsing them thoroughly with water, drying them till weight constancy (approximately 24 hours), and weighed again. For comparison, the same procedure is also carried out with a “control” polyurethane prepared using a HO—PDMS—OH and MDI, and with another commercially available polyurethane (AorTech Biomaterials, Batch #60802, E2A pellets sample).
The control polyurethane is prepared as follows: 1 gram (0.0002 moles) of hydroxyl-ditelechelic polydimethylsiloxane (DMS-C21, Gelest, Mn=4,500 to 5,500 grams/mole) is dissolved in 10 mL of toluene, and freshly distilled MDI (0.11 grams, 0.0002 moles) followed by (0.03 mL) tin octoate catalyst are added under a dry nitrogen atmosphere. The charge is heated for 8 hours at 70° C., cooled to room temperature, and poured in a rectangular (5 cm×5 cm) Teflon mold. The polyurethane sheet that is produced is air dried overnight and finally dried in a drying oven at 70° C. for 24 hours. The product is a pale yellow supple rubbery sheet, soluble in THF. Manual examination reveals good mechanical properties.
Table 1 summarizes the results of aggressive oxidative/hydrolytic degradation test performed with PIB-, PDMS-based polyurethanes and a PIB-based polyurea. The test reagent is 65 percent HNO3 at room temperature.
According to the data, the PIB-based polyurethanes and polyureas (prepared with HO—PIB—OH/MDI and H2N—PIB—NH2/MDI) do not degrade after 24 hours when exposed to concentrated HNO3 at room temperature. Oxidative/hydrolytic resistance is demonstrated by the negligible weight loss of the polyurethane and polyurea films. After 48 hours exposure to concentrated HNO3 both the PIB-based polyurethane and polyurea films exhibit deep brown discoloration and a visible weakening of the samples. In contrast, the control polyurethane prepared with HO—PDMS—OH/MDI, and a commercial polyurethane (i.e., a material considered highly oxidatively/hydrolytically stable) completely degrades, and becomes largely soluble in the acid after less than 4 hours of exposure.
While not wishing to be bound to any one theory, the spectacular oxidative/hydrolytic resistance of the PIB-based polyurethane and polyurethane formed in accordance with the synthesis processes of the present invention is most likely due to the protection of the vulnerable urethane (carbamate) and urea bonds by the inert PIB chains/domains. In contrast, the PDMS chains/domains cannot impart protection against the attack of the strong oxidizing acid.
(1) The Synthesis of PIB-Based Polyureas and
Demonstration of their Oxidative Stability:
To H2N—PIB—NH2 (1.5 grams, Mn=5,500 grams/mole, amine equivalent 0.00054 moles) dissolved in dry toluene (10 mL) is added freshly distilled MDI (0.125 grams, 0.0005 moles), with stirring, under a dry nitrogen atmosphere. Within a minute the solution becomes viscous. It is then diluted with 5 mL of toluene and poured in a rectangular (5 cm×5 cm) Teflon mold. The system is air dried overnight and finally dried in a drying oven at 70° C. for 24 hours. The polyurea product is a pale yellow supple rubbery sheet, soluble in THF. Manual examination reveals reasonable mechanical properties.
The oxidative/hydrolytic stability of the polyurea is tested by exposing the sample to concentrated HNO3 at room temperature (see Table 1 above). The last entry in Table 1 shows data relating to this Example. Evidently, the PIB-based polyurea resists degradation under the harsh conditions detailed above for 24 hours.
(2) The Synthesis of PIB-Based Polyureas With Increased Hard Segment Content:
Given the above, polyureas with increased hard segment content can be synthesized as will be detailed below. The following process is also applicable to the production of polyurethanes using OH—PIB—OH as is described above. The use of increased hard segments is designed to achieve heretofore unavailable hydrolytically/oxidatively stable biocompatible and biostable high strength elastomers.
Additionally, the present invention also involves conditions for the homogeneous synthesis of polyisobutylene polyureas (PIBUs) by the use of H2N—PIB—NH2 (Mn=2,500 grams/mole), HMDI as the diisocyanate, and various diamine chain extenders (ethylenediamine (EDA), 1,4-diaminobutane (BDA), 1,6-diaminohexane (i.e., hexamethylene diamine or HDA), or 2-methyl-1,5-pentanediamine (MPDA)). In one embodiment, the hard segment content of such polyisobutylene polyureas (PIBUs) is at least about 8 percent by weight, at least about 10 percent by weight, at least about 15 percent by weight, at least about 20 percent by weight, at least about 25 percent by weight, at least about 30 percent by weight, about 35 percent by weight, at least about 40 percent by weight, or even about 45 or more percent by weight.
Through the use of HDA as the chain extender the amount of urea hard segment in a PIBU can be as high as 45 percent by weight without phase separation during synthesis. This product is optically clear and exhibits approximately 20 MPa tensile strength with approximately 110 percent elongation.
The tensile strength of this PIBU increases to approximately 23 MPa upon annealing overnight at 150° C. Additionally, the ultimate elongations of a series of
PIB/HMDI/HDA PIBUs containing increasing amounts of HDA-based hard segments do not fall below approximately 110 percent; this suggests an unexpected morphological feature of great practical interest. Alternatively, charges containing more than approximately 18 percent EDA and/or BDA undergo unacceptable phase separation during chain extension.
With the branched chain extender MPDA, the amount of hard segment could be increase to 40 percent by weight. However, the properties of the PIBU formed with MPDA are in some aspects inferior to those obtained with HDA.
(3) Chain Extension Experiments:
A representative synthesis procedure is as follows. In a 50 mL three-neck round bottom flask equipped with magnetic stirrer are placed, HMDI (0.6 grams, 0.00225 moles) and 2 mL of dry THF under a nitrogen atmosphere. The flask is sealed by a rubber septum, cooled to about 5° C., and H2N—PIB—NH2 (Mn=2,500, 1 gram, 0.0004 moles) is dissolved in 6 mL THF and is added dropwise via a syringe. The pre-polymer charge is stirred at room temperature for 30 minutes, cooled to 5° C., and HDA (0.22 grams, 0.0019 moles) is dissolved in 6 mL THF and is added dropwise. The charge is stirred at room temperature for an additional 1 hour, poured into a Teflon mold, and kept at 60° C. for a day. The 0.2 mm film thus obtained is dried under vacuum for 24 hour at 50° C. All the charges are homogeneous and optically clear during the reaction.
Table 2 below summarizes the various ingredients, relative reagent concentrations, hard segment content, various mechanical properties, and visual observations made during the syntheses.
The elongations of PIBUs prepared with HDA are higher than those prepared with MPDA. For example, at 37 weight percent hard segment, the elongations obtained with HDA and MPDA are 115 percent and 60 percent, respectively. While not wishing to be bound to any one theory, it is believed that the low elongation obtained with MPDA suggests that the methyl side chain of MPDA disrupts the organized alignment of the hard segments.
Annealing enhances the properties of PIBUs. It is found that the tensile strength of PIBUs containing 37 weight percent and 45 weight percent hard segment increases from 13.4 and 19.5 MPa, respectively, to 14.4 and 23 MPa, respectively, after annealing (see
In the compositions contained in Table 2 are prepared with H2N—PIB—NH2 having a Mn=2,500. Additionally, the stress and strain data given in Table 2 is an average of three determinations per sample.
The combination of HMDI diisocyanate and HDA chain-extender produces homogeneous reaction mixtures even with 45 weight percent hard segment content (see Table 2 above). In contrast, the charges became opaque due to phase separation in the presence of more than approximately 18 weight percent EDA and or BDA chain extenders.
(1) Materials:
Hydrogen bromide, hydrazine hydrate, potassium phthalimide, allyltrimethylsilane (allylSiMe3), BCl3 (1 M in dichloromethane) TiCl4, 1,2-diaminoethane (EDA), 1,4-diaminobutane (BDA), 1,6-diaminohexane (HDA) 1,8-diaminooctane (ODA), 2-methyl-1,5-diaminopentane (MPDA), 1,6-hexanediisocyanate (HDI), 4,4′-methylenebis (cyclohexylisocyanate) (HMDI), 4,4′-methylenebis (phenylisocyanate) (MDI) are obtained from Aldrich and are used as received. Isobutylene (Lanxess), methylene chloride (Lanxess), methanol and ethanol (EMD Chemicals Inc), HNO3 (J. T. Baker) are used as received. Hexanes and THF (EMD Chemicals Inc) are distilled over CaH2 prior to use.
The structures below summarize the structures, names and abbreviations of the materials used in the syntheses of the intermediates and polyureas of this section.
(2) Syntheses of Primary Amine Di-Telechelic PIB (H2N—PIB—NH2
The three-step synthesis route shown below illustrates one possible method, within the scope of the present invention, to achieve the synthesis of H2N—PIB—NH2. The first step is the living polymerization of isobutylene to a predetermined molecular weight allyl di-telechelic PIB (allyl-PIB-allyl). The second step is the anti-Markovnikov hydrobromination of allyl-PIB-allyl to the primary bromine di-telechelic PIB(Br—PIB—Br). The third step is the conversion of Br—PIB—Br to the target H2N—PIB—NH2.
In this section, H2N—PIB—NH2 with Mn=2,500 and 6,500 grams/mole are prepared. The structure of the products is characterized by proton NMR spectroscopy, and their molecular weight by GPC and titration.
(3) Polymer Syntheses:
(i) Synthesis of Non-Chain-Extended (Stoichiometric) PIB-Based Polyureas:
A representative synthesis of a non-chain extended PIB-based polyurea is as follows: to H2N—PIB—NH2 (1.5 grams, Mn=5,600 grams/mole, amine equivalent 0.00054 moles) dissolved in 4 mL THF is added dropwise HDI (0.053 grams, isocyanate equivalent 0.00059 moles) dissolved in 1 mL THF under a dry nitrogen atmosphere at room temperature. The mixture is heated for 2 hours at 50° C., poured into the cavity of a Teflon mold (5 cm×5 cm), kept at 50° C. over night, and dried under vacuum (approximately 2 days) until a consistent weight is achieved. The product is a colorless optically clear supple rubbery sheet, soluble in THF.
This one-step procedure is used for the preparation of all non-chain-extended PIB-based polyureas.
(ii) Synthesis of Chain-Extended PIB-Based Polyureas:
A representative one-pot two-step synthesis is as follows. In a 50 mL three-neck round bottom flask equipped with magnetic stirrer are placed, HMDI (0.6 grams, 0.00225 moles) in 2 mL dry THF under a nitrogen atmosphere. The flask is sealed by a rubber septum, cooled to about 5° C., and H2N—PIB—NH2 of Mn=2,500 (1 gram, 0.0004 moles dissolved in 6 mL THF) is added dropwise by a syringe. This prepolymer charge is stirred at room temperature for 30 minutes, cooled to 5° C., and HDA (0.22 grams, 0.0019 moles) dissolved in 6 mL THF is added dropwise. The charge is stirred at room temperature for an additional 1 hour, poured into a Teflon mold, and kept at 60° C. for a day. A 0.2 mm thick film is obtained and is dried under vacuum for 24 hours at 50° C.
All the charges are homogeneous and optically clear during the syntheses, and all the products are colorless and optically clear.
Regarding the polymer abbreviations used herein: the abbreviation of polymers indicate, in sequence, the H2N—PIB—NH2 soft segment, the molecular weight of the soft segment in parentheses, the diisocyanate, the chain extender, and the percent hard segment content. For example, H2N—PIB—NH2(6.2 K)/HMDI+HDA=45 indicate a polyurea containing a PIB soft segment of Mn=6,200 grams/mole, that is reacted with HMDI as the diisocyanate to yield a prepolymer, which is chain extended with HDA to produce a polyurea with 45 percent hard segment.
(4) Instruments and Procedures:
The Mns of H2N—PIB—NH2s are routinely determined by proton NMR spectroscopy and acid-base titration. By titration 0.5 grams of H2N—PIB—NH2 is dissolved in 10 mL toluene and diluted with 6 mL isopropanol. A drop of methylene blue indicator is added and the solution is titrated with 0.1 M aqueous HCl. Averages of three determinations are used for stoichiometric calculations. Molecular weights obtained by titration and 1H NMR spectroscopy are within experimental error.
The hardness (Microshore) of approximately 0.5 mm thick films is determined by a Micro-O-Ring Hardness Tester. The averages of three determinations are reported.
Thermogravimetric analysis (TGA) is carried out by a TGA Q 500 instrument (TA Instruments) in the temperature range from 30° C. to 600° C. using an aluminum pan with 5° C./minute heating rate.
Differential scanning calorimetry is affected by the use of a DSC Q 200 (TA Instruments) working under a nitrogen atmosphere. The instrument is calibrated with indium for each set of experiments. Approximately 10 mg samples are placed in aluminum pans sealed by a quick press, and heated at 10° C./minute scanning rate. The glass-transition temperature (Tg) is obtained from the second heating scan.
Stress-strain profiles of solution cast films are determined by an Instron Model 5543 tester Universal Testing system controlled by Series Merlin 3.11 software. A bench-top die is used to cut 30 mm dogbone samples (30 mm×3.5 mm×0.2 mm) from the films. The samples are tested to failure at a crosshead speed of 10 mm/minute and their load versus displacement recorded. The averages values of three samples are tested for strength, modulus and elongation at failure.
(5) Hydrolytic/Oxidative Stability:
The hydrolytic/oxidative stability of samples is investigated by exposure to boiling distilled water for 15 days, and to concentrated (36 percent) nitric acid for 12 hours at room temperature.
Thus, virgin samples (solution cast films 5 cm×2 cm×0.02 cm) are placed in refluxing water or stirred concentrated (36 percent) nitric acid at room temperature. Visual observations are made during experiments. After desired times the samples are removed from the liquids, and thoroughly rinsed with water. The water-exposed films are cut to dumbbell shaped specimens and their tensile strengths and elongations are measured while keeping the samples moist with moist tissue paper. Water uptake is determined from the change of weight of samples before and after refluxing with water.
The films exposed to nitric acid are thoroughly rinsed with distilled water, dried, and dumbbells are prepared. The mechanical properties of nitric acid exposed samples are determined with dry sample.
(6) Results and Discussion:
(i) Syntheses:
The reaction processes shown below outline various strategies used for the synthesis of PIB-based non-chain-extended and chain-extended polyureas. After considerable preliminary experimentation conditions are developed for the homogeneous synthesis of optically clear colorless products. Leads are pursued only if the solutions are and remained homogeneous during syntheses, and solution cast films are optically clear.
a. Non-Chain-Extended PIBUs
b. Chain-Extended PIBUs
*amount of diisocyanate and chain-extender determines hard segment content, and
** the —(CH2)x— in the chain extender is varied (see above).
The non-chain-extended products are prepared in one step by mixing stoichiometric amounts of H2N—PIB—NH2 and diisocyanates (typically HMDI). Product compositions (hard segment content) are controlled by the molecular weight of the PIB.
Chain-extended polyureas are synthesized by the conventional one-pot two-step prepolymer technique, i.e., prepolymer synthesis followed by chain extension. The prepolymers are prepared with H2N—PIB—NH2 of Mn=2,500 and 5,600 grams/mole, and various diisocyanates, i.e., HDI, MDI and HMDI. The chain extenders are added at about 0° C. to about 5° C. to suppress side reactions (the addition of chain extenders at about 25° C. may produce insoluble particulars).
Table 3 summarizes the various ingredients, relative reagent concentrations, hard segment contents, some mechanical properties, and visual observations made during the syntheses of chain-extended polyureas with up to 45 percent hard segment. Above about 45 percent hard segment the products are judged to be too stiff (micro hardness greater than 70) for applications as soft rubbers, one target for the products of the present invention. In this regard, products with micro hardnesses of greater than 70 are in no way precluded from the scope of the present invention. The data in the table are subdivided by the chain extender employed (EDA, BDA, HDA, ODA, and MPDA), and listed by increasing hard segment content.
Combinations of H2N—PIB—NH2 with Mn in the 2,500 to 6,200 grams/mole range and HMDI plus the chain extenders HDA, ODA and MPDA produced optically clear homogeneous products even with a hard segment content of up to 45 percent (see entries 6 through 12 in Table 3). In contrast, charges with more than about 18 percent EDA and BDA become opaque due to phase separation.
(ii) Characterization:
Mechanical Properties:
a and 8b illustrate the variation of stress and strain as a function of hard segment content, respectively, of two families of polyureas synthesized with H2N—PIB—NH2 of Mn=2,500 and 6,200 grams/mole. Given the data of Table 3, for polyureas synthesized with H2N—PIB—NH2 of Mn=2,500, tensile strengths increase linearly with hard segment content, and the straight line can be smoothly back extrapolated to the origin. The increase of stress with hard segment content suggests that the hard segments are phase separated and homogeneously distributed in the soft PIB matrix.
At the same hard segment content, the tensile strength of polyureas prepared with H2N—PIB—NH2 of 2,500 grams/mole is much higher than those prepared with Mn=6,200 grams/mole. The lower strength of polyureas synthesized at the same hard segment content with the higher molecular weight H2N—PIB—NH2 (Mn=6,200 grams/mole) is probably due to the lower number of hard segments in the rubber than those present in products prepared with the lower molecular weight H2N—PIB—NH2 (Mn=2,500 grams/mole). Also, the hard segment morphology of polyureas synthesized with H2N—PIB—NH2 (Mn=6,200) may not be continuous which would lead to inferior mechanical properties.
Elongations of polyureas prepared with HDA and ODA are superior to those prepared with MPDA. For example, at about the same hard segment content (32 percent to 38 percent), elongations obtained with HDA and MPDA are 115 percent and 60 percent, respectively. Evidently the methyl side group in MPDA disrupts the alignment of the hard segments.
Annealing enhances mechanical properties. For example, annealing at 150° C. for 2 hours increases the tensile strength of polyureas containing 32 percent and 45 percent hard segments from 13.4 and 19.5 MPa, respectively, to 14.4 and 23 MPa. (see
Table 4, below, summarizes the lower glass transition temperatures associated with the PIB domain of polyureas determined by DSC and DMTA. From the data shown below, it can be seen that the Tgs obtained by DSC are substantially lower (about 20° C.) than those obtained from tan delta traces.
The hydrolytic/oxidative vulnerability of conventional polyether- and polyester-based polyurethanes is well documented in the literature and has been discussed by many groups of investigators (see, e.g., R. S. Labow et al.; Biomaterials 1995, 16, 51 through 59). While not wishing to be bound to any one theory, it is generally accepted that hydrolytic damage is due to the presence of carbamate and urethane linkages, and oxidative damage to the —CH2—O— groups in polyurethane chains.
The present invention seeks to prove that hydrolytically/oxidatively resistant continuous PIB soft segments will shield these vulnerable groups from the penetration of aggressive polar penetrants (water, acids, bases) and thus protect PIB-based polyurethanes from hydrolytic/oxidative attack.
The present invention investigates the hydrolytic/oxidative resistance of PIB-based polyureas under rather harsh testing conditions (exposure to boiling water for 15 days, and to concentrated nitric acid for 12 hours at room temperature—see above) and compared their behavior to those obtained with two commercially available “oxidatively resistant” polyurethanes, Bionate® and Elast-Eon®.
Table 5, below, summarizes these results. Resistance to boiling water is exemplified by the first three lines in Table 5. While two representative PIB-based polyureas showed no visible change and only a negligible deficit in mechanical properties upon exposure, the control, Bionate®, became slightly hazy and suffered a significant decrease in hardness (from 75 to 60) and about a 50 percent loss in tensile strength (from 42 to 20.2 MPa at 500 percent elongation). The water uptake of all the samples is negligible.
The degradation of “hydrolytically resistant” commercial products, Bionate® and Elast-Eon®, upon contact to concentrated nitric acid, is quite spectacular: they became discolored gooey masses within about 30 minutes of exposure. In contrast, representative PIB-based polyureas maintained their dimensional integrity and remained sufficiently strong for mechanical testing. While their hardness and tensile strength decreased and their elongation increased proportionately, they still exhibited respectable properties.
Given the above, it can be concluded that the hydrolytically/oxidatively stable PIB moiety is a barrier to the diffusion of water and acid to the vulnerable hard segments and protects these polyureas from degradation.
Amine-telechelic PIB oligomers (H2N—PIB—NH2) of Mn of 2,500, 3,200 and 6,200 grams/mole are prepared by methods described previously. Aminopropyl-telechelic poly(tetramethylene oxide) (H2N—PTMO—NH2) oligomer of Mn of 1,100 grams/mole is obtained from Aldrich. Bis(4-isocyanatocyclohexyl)methane (HMDI) of greater than 99.5 percent purity is supplied by BayerTurk, Istanbul and Bayer, USA, and 2-methyl-1,5-diaminopentane (MPDA) is provided by Du Pont. Reagent grade 1,6-hexamethylene diamine (HDA), isopropanol (IPA), dimethylacetamide (DMAc) and cobalt chloride hexahydrate (98 percent) are from Aldrich and used without further purification. Tetrahydrofuran (THF) from Aldrich is distilled prior to use. H2O2 (30 percent aqueous solution) is obtained from Acros.
Polymerizations are carried out in three-neck round bottom flasks equipped with stirrer, nitrogen inlet, and addition funnel. Polymers are prepared by using a three-step procedure, at room temperature. Calculated amounts of HMDI are weighed into the reactor and dissolved in THF. Desired amounts of H2N—PIB—NH2 and H2N—PTMO—NH2 oligomers are separately weighed into the Erlenmeyer flasks and dissolved in THF. To prepare the prepolymer PIB solution (first step) and PTMO solution (second step) are sequentially added drop-wise into the reactor containing the HMDI solution, under strong agitation. Before chain extension (third) step, IPA or DMAc is added to increase the polarity of the charge. A stoichiometric amount of diamine chain extender dissolved in IPA or DMAc is added drop-wise into the reactor. The progress of the reactions is monitored by FT-IR spectroscopy following the disappearance of the strong isocyanate peak at 2270 cm−1 and the formation of urea (N—H) and (C═O) carbonyl peaks around 3300 cm−1 and 1700 cm−1, respectively. The charges are homogeneous and clear throughout the polymerization. Table 6 shows the composition, segment molecular weight, and mechanical properties of representative polyureas compositions of polymers prepared and characterized.
A typical synthesis of a mixed PIB/PTMO based polyurea is as follows. Into a 50 mL three-neck round bottom flask equipped with magnetic stirrer is placed 0.44 grams (0.00167 mmol) HMDI and dissolved in 1 mL dry THF. The flask is sealed by a rubber septum and kept under a nitrogen atmosphere. H2N—PIB—NH2 (0.8 grams, 0.0004 mmol, Mn=2,000 grams/mole) is dissolved in 4 mL THF in a separate beaker and added dropwise to the HMDI solution by a syringe, and the pre-polymer solution is stirred at room temperature for 10 minutes. H2N—PTMO—NH2 (0.2 g, 0.000181 mol, Mn=1,100 grams/mole) is dissolved in 1 ml THF and added to the HMDI solution by a syringe. The charge is diluted with 2 mL DMAc and stirred for 10 minutes. The chain extender is HDA (0.13 grams, 0.0011 moles) which is dissolved in 3 mL THF and added dropwise into the reactor by a syringe over 10 minutes. The mixture is stirred at room temperature for an additional 15 minutes, poured into a Teflon mold and dried at 60° C. for a day. The approximately 0.2 mm thick film thus obtained is dried further under vacuum for 24 hours at 50° C.
Mixed soft segments containing both PIB and PTMO chains are symbolized by first showing the abbreviation of the PIB segment (and its Mw×1000 in parentheses) followed by a “+” sign and the abbreviations of the PTMO segment (and its Mw×1000 in parentheses). The abbreviation of the soft segment(s) is followed by a “/” sign which separates the soft segment from the hard segment. After the soft segments, we show the abbreviation of the diisocyanate and the chain extender, separated by a “+” sign. Finally the hard segment content of the product is given in percent. For example H2N—PIB—NH2(2.5K)+H2N—PTMO—NH2(1.1K)/HMDI+MPDA=26 stands for a polyurea prepared with a NH2—PIB—NH2 of Mn=2,500 grams/mole and a H2N—PTMO—NH2 of Mn=1,100 grams/mole, and HMDI as the diisocyanate and MPDA as the chain extender; the hard segment content is 26 percent.
Number average molecular weights (Mn) of H2N—PIB—NH2 and H2N—PTMO—NH2 are determined by end-group titration assuming 2.0 end-group functionality. FTIR spectra are recorded on a Nicolet Impact 400D spectrophotometer with a resolution of 2 cm−1, using thin films cast on KBr disks.
Copolymer films (0.2 to 0.5 mm thick) for thermal and mechanical tests are prepared by solution casting in Teflon molds, removing the solvent at room temperature overnight and drying at 65° C., or drying at 50° C. and subsequently in a vacuum oven at 75° C., until constant weight. Polymers films are stored at ambient temperature in sealed polyethylene bags.
Dynamic mechanical thermal analysis (DMTA) is performed by a TA DMA Q800 instrument. Measurements are made in tensile mode at 1 Hz, between −120° C. and 200° C., under a nitrogen atmosphere, at a heating rate of 3° C./minute. Hardness (Microshore) of the 0.5 mm thick films is determined by a Micro-O-Ring Hardness Tester—averages of three determinations are reported.
Stress-strain profiles of polyureas are determined by an Instron Model 5543 Universal Tester controlled by Series Merlin 3.11 software. A bench-top die (ASTM 1708) is used to cut 30 mm dog-bone samples (30 mm×3.5 mm×0.2 mm) from films. Stress-strain traces of polyureas containing H2N—PIB—NH2 of Mn=3,500 grams/mole are obtained by a 4411 Universal Tester. The samples are tested to failure at a crosshead speed of 10 mm/min at room temperature and their load versus displacement behavior is recorded. Average values of at least three samples are used to determine tensile strength, modulus and elongation at failure.
The accelerated hydrolytic/oxidative degradation of samples (solution cast 5 cm×2 cm×0.02 cm films) is investigated by exposure to 100 mL of 0.1 M aqueous CoCl2 solution containing 20 percent hydrogen peroxide for 40 days at 50° C. The solution is changed twice a week to maintain a relatively constant concentration of radicals. After 40 days the samples are removed from the solutions, thoroughly rinsed with distilled water, and dried in a vacuum oven for 24 hours. Dried samples are used for the determination of mechanical properties.
Scanning electron microscopy (SEM) analysis is performed on samples exposed to CoCl2/H2O2 solution with a JEOL JSM-7401 F instrument at 10 kV with up to 5000 magnification. Oxidized samples are thoroughly rinsed with distilled water and dried in a vacuum oven. Five images of different regions are taken of each specimen.
An early article in this series dealt with the cost effective synthesis of H2N—PIB—NH2 and its use for the synthesis of novel PIB-based polyureas exhibiting spectacular oxidative/hydrolytic stability. While phase separation between the soft PIB and hard polyurea sequences is excellent, the mechanical properties of these rubbers are mediocre (about 20 MPa tensile and about 100 percent elongation). One of the objectives of the present invention is to synthesize polyureas with enhanced mechanical properties.
According to rubber reinforcement theory, reinforcement requires chemically linked interfaces or excellent adhesion between interfaces (as, for example, in carbon black reinforced natural rubber or silica reinforced silicone rubber). In the absence of strong interaction between the rubbery matrix and well-dispersed reinforcing particles reinforcement is poor or nonexistent, and the mechanical properties of rubbers suffer.
The present invention shows the mechanical properties of PIB-based polyureas are improved by incorporating PTMO into the networks, which leads to hydrogen bridge formation and improve stress transfer by enhancing the compatibility between the non-polar PIB and polar urea phases. The solubility parameters of PIB and PTMO (16.3 and 18.6 MPa1/2 respectively) are reasonably close to each other promising a measure of compatibility between these segments.
In ; PTMO
; hard segment
; short hard segment connecting two soft segments
; and continuing soft segment
.
The sections that follow summarize experimental verification of the present invention and demonstrate the preparation of novel polyureas with excellent mechanical properties and oxidative/hydrolytic stability.
Table 6 summarizes polyureas prepared, their overall compositions, and select mechanical properties. Subtitles I through V subdivide the numerous examples into coherent groups. Groups I and II contain non-chain extended PIB- and PTMO- based polyureas, respectively; groups III and IV contain chain extended PIB-based polyureas with linear (HDA) and branched (MPDA) chain extenders, respectively; group V contains mixed soft segment PIB/PTMO-based polyureas with a linear (HDA) chain extender. In one embodiment the sample contains between 21 percent and 36 percent hard segments. In another embodiment the sample contains between 21 percent and 32 percent hard segments.
Some of the data in Table 6 is visualized in
As expected, the Young's moduli of PTMO modified PIB-polyureas increases with increasing PTMO content. While not wishing to be bound to any one theory, these results are in line with the hypothesis that PTMO incorporation improves interfacial adhesion between the PIB and urea phases leading to improved stress transfer between phases which in turn leads to improved tensile strengths without much sacrifice in elongation.
The hydrolytic/oxidative stability of PIB-based polyureas has been documented by exposure to concentrated nitric acid and boiling water. These studies are now extended by exposing representative polyureas samples to aqueous CoCl2/H2O2. The strong oxidizing/hydrolitic action of this reagent and the mechanism of oxidation were extensively discussed by earlier workers.
Table 7 together with
Table 7 shows visual observation and mechanical properties of samples before and after exposure to CoCl2/H2O2. While the faintly yellow experimental polyureas darkened only slightly, Bionate became noticeably yellow. The “deficit” columns indicate deterioration in properties due to oxidative/hydrolytic damage. While the properties of the experimental samples diminish only slightly or moderately, Bionate suffers significant oxidative damage.
In
The superior oxidative/hydrolytic resistance of PIB containing polyurethanes is also apparent by surface electron microscopy (SEM).
The superior oxidative/hydrolytic resistance of PIB containing polyureas is due to the protective action of oxidatively inert PIB segments congregating on the surfaces of these materials.
This invention focused on the design, synthesis, characterization and structure/morphology of novel polyureas comprising continuous soft phases of two partially compatible soft segments: PIB and PTMO, embedded into finely dispersed polyurea hard/crystalline phases. The addition of even a modest amount (12% by weight) of PTMO to PIB-based polyureas significantly enhances the mechanical properties with minimum reduction in oxidative/hydrolytic stability. The present invention shows that the PTMO segments strengthen/toughen the polyureas by leading to the formation of hydrogen bridges and by facilitating stress transfer from the soft to hard phases. The surfaces of these polyureas are covered/protected with chemically inert PIB segments which impart oxidative/hydrolytic stability. Polyureas containing mixed PIB/PTMO soft segments exhibit good mechanical properties (e.g., 29 MPa and 200% elongation) and oxidative/hydrolytic stabilities far superior to Bionate® and Elast-Eon®.
In another embodiment, the present invention relates to a polymer compound comprising urea or urethane segments therein, the polymer compound comprising: (i) one hard segment, wherein the hard segment is selected from a urea or urethane hard segment; and (ii) two soft segments. In one instance, the polymer compound of this embodiment have two soft segments that are formed from polyisobutylene and poly(tetramethylene oxide).
(VI) Polyurethanes Containing Mixed PIB/PTMO Soft Segments and Partially-Crystalline Hard Segments:
In this example the synthesis, characterization, and structure-property relationship of polyurethanes containing mixed polyisobutylene (PIB)/poly(tetramethylene oxide) (PTMO) soft segments and partially-crystalline bis(4-isocyanatocyclohexyl)methane HMDI/hexanediol (HD) hard segments is discussed. The mechanical (stress/strain, hardness, and hysteresis) properties of these novel polyurethanes are investigated over a broad composition range. The addition of, for example, 20% by weight PTMO to PIB-based polyurethanes increases both their tensile strength and elongation. Because of the large amount of PIB in the soft segments, these segmented copolymers possess oxidative/hydrolytic/enzymatic stabilities superior to commercially available polyurethanes. These new polyurethanes are softer and exhibit hysteresis superior to conventional polyurethanes. According to initial thermal studies, these materials show good processibility. Overall, the mechanical properties of the hybrid polyurethanes are similar or superior to Bionate® and Elast-Eon®, respectively. While not wishing to be bound to any one theory, the results of this example suggest that the addition of PTMO segments to PIB-based polyurethanes facilitates uniform stress distribution within the hard segment, which strengthens and thus improves the elastomeric properties of PIB-based polyurethanes.
As discussed above, in one embodiment various novel PIB-based polyureas exhibiting unprecedented hydrolytic/oxidative stability together with desirable mechanical properties. Further, the above discussion also illustrates that the mechanical properties of these polyureas can be enhanced by the use of mixed PIB/PTMO soft segments.
In this example, a continued examination of the structure/property relationship of these hybrid polyurethanes is conducted. Additionally, this example also illustrates that by altering the nature and composition of the soft and hard segments, one is able to synthesize and/or assemble PIB-based segmented copolymers having outstanding mechanical properties (tensile strength greater than about 30 MPa and an elongation of about 700%), as well as possessing a hydrolytic/oxidative resistance far superior to the best commercially available polyurethanes.
The preparation of hydroxyl-telechelic polyisobutylenes (HO—PIB—OH) having an Mn equal to 1,500; 4,050 and 11,500 g/mol are prepared as described above. Hydroxyl-telechelic poly(tetramethylene oxide) (HO—PTMO—OH) having a Mn=1,100 and 650 g/mol is obtained from Aldrich. Bis(4-isocyanatocyclohexyl)methane (HMDI), dibutyltin-dilaurate (DBTL), 1,6-hexanediol (HD) are obtained from Aldrich and are used without further purification. Tetrahydrofuran (THF) is obtained from Aldrich and is distilled prior to use. Additionally, it should be noted that the present invention is not limited to just the use of hydroxyl-telechelic poly(tetramethylene oxide) (HO—PTMO—OH) having a Mn=1,100. Instead any suitable hydroxyl-telechelic poly(tetramethylene oxide) having an Mn in the range of about 250 to about 25,000, or from about 500 to about 20,000, or from about 1,000 to about 15,000, or from about 1,500 to about 10,000, or from about 2,000 to about 7,500, or even from about 2,500 to about 5,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
Polymerizations are carried out in three-neck round bottom flasks equipped with a stirrer, and nitrogen inlet. The desired amounts of HO—PIB—OH (and/or HO—PTMO—OH) and HMDI are weighed into the reactor, dissolved in THF, stirred and heated. After the addition of 0.5% dibutyltin dilaurate (DBTDL) the mixture is heated at 65° C. for 3 hours to obtain a prepolymer. A stoichiometric amount of 1,6-hexanediol (HD) is added to the prepolymer solution and heating is continued for an additional 12 hours at 65° C. Progress (and completion) of reactions are monitored by IR spectroscopy as is known to those of skill in the art. The highly viscous solution is diluted with THF and poured into a glass mold. Films are formed by drying the cast solution for 1 day at 70° C. in an air oven and the placing such samples into sealed polyethylene bags for two days at room temperature before measurements.
The number average molecular weights (Mn) of HO—PIB—OH is determined by 1H NMR spectroscopy using a Varian Unity Plus 400-MHz spectrometer with the use of CDCl3 as a solvent. FTIR spectra are recorded on a Nicolet Impact 400D spectrophotometer with of 2 cm−1 resolution, using thin films cast on KBr disks or by using a Shimadzu FTIR 8300 instrument equipped with an ATR head.
Thermal and mechanical tests are carried out on solution cast polymer films (0.2 to 0.5 mm thick). The solvent is removed at room temperature overnight at 65° C. and dried at 50° C. in a vacuum oven, until constant weight.
Differential scanning calorimetry (DSC) is performed with a DuPont 2100 thermal analyzer equipped with a liquid-nitrogen cooling accessory. Measurements are made under a nitrogen atmosphere with 10° C./min heating and cooling. The hardness (Microshore) of approximately 0.5 mm thick films is determined by a Micro-O-Ring Hardness Tester. Averages of three determinations are reported.
Stress-strain behavior is determined by an Instron Model 5543 Universal Tester controlled by Series Merlin 3.11 software. A bench-top die (ASTM 1708) is used to cut 30 mm dog-bone samples (30×3.5×0.2) from films. The samples (Lo=24.0 mm) are tested to failure at a crosshead speed of 20 mm/min at room temperature. Averages of at least 2 measurements are reported.
Regarding the abbreviations of product compositions used throughout the specification, the abbreviations specify the nature of the two soft segments, their molecular weights, and percentages; this is followed by a “/” sign and then the make-up and percentages of the hard segment or segments.
This example is directed to the synthesis and mechanical property characterization of novel polyurethanes containing PIB segments in combination with PTMO soft segments, and partially crystalline HMDI/HD hard segments.
; the PTMO segments by
; the hard segment by
; a short hard segment connecting two soft segments is represented by
; and a continuing soft segment is represented by
.
To gain insight into the effect of the individual components on mechanical properties, the nature and amount of the constituents are varied systematically and stress/strain, and hardness are determined and analyzed.
Table 8 shows the compositions of various exemplary polyurethanes that are prepared together with characterization results. The polyurethanes are prepared with PIBs of having Mns equal to 1,500; 4,050; and 11,500 g/mol in both the absence and presence of PTMO. The two lower molecular weight PIBs (Mns equal to 1,500 and 4,050 g/mol) are similar to the molecular weights used in conventional polyurethanes, whereas the 11,000 g/mol PIB is used because the entanglement molecular weight of PIB is close to this value, thus one should expected improved elongations and hysteresis with this PIB.
The amount of PTMO is varied in the 10% by weight to 30% by weight range and that of the hard segment in the 15% by weight to 50% by weight range. PIBs of Mn=4,050 and 11,500 g/mol are mixed with PTMO having an Mn equal to 1,000 g/mol; however, with the 1,500 g/mol PIB a PTMO having an Mn equal to 650 g/mol is used so as to match the end-to-end distance of the mixed PIB/PTMO soft segments. The lengths of the soft segments PIB and PTMO are very similar in the PIB(4k)/PTMO(1k) and PIB(1.5k)/PTMO(0.6k) products. While not wishing to be bound to any one theory, it is believed that if the end-to-end distances of the soft segments are widely different, the stress distribution may become non-uniform, which in turn could lead to mediocre properties. For comparison purposes polyurethanes with only PTMO are prepared (i.e., in the absence of PIB).
The Mws of unannealed samples are determined by GPC.
According to the data in Table 8 the Mws of the polyurethanes are in the 40,000 to 120,000 g/mol range, which corresponds to a DP of 15 to 75 for the soft segments. Annealing for one day at 70° C. considerably increases the Mw of polyurethanes prepared with PTMO (not shown) and appears to be partially crosslinked, probably because of the formation of allophanates (most of the samples are prepared with a slight excess (about 2 to about 5%) of diisocyanate). Interestingly, this behavior is absent, or is less prominent, with polyurethanes that are prepared only with HO—PIB—OH (i.e., in the absence of HO—PTMO—OH).
PIB-based polyurethanes synthesized earlier by the use of the various diisocyanates and chain extenders exhibit less-desirable mechanical properties. While not wishing to be bound to any one theory, it is theorized that the hard segments of these products fail to provide adequate reinforcement because the highly crystalline hard segments (MDI/BDO) lead to massive phase separation between the polar hard and non-polar soft segments and the lack of interaction between the soft PIB and the crystalline hard MDI/BDO segments lead to unsatisfactory stress transfer. Thus, in one embodiment, the polymers of the present invention have a decreased crystallinity in their one or more hard segments due to the use of combinations of HMDI and HD, which are expected to provide a measure of flexibility and compatibility between the hard and soft segments.
Turning to
Given the above, it is shown that via the addition of a suitable amount of PTMO to PIB-based polyureas an unexpected improvement of the mechanical properties of same can be achieved. Next, an examination of the effect of added PTMO on the mechanical properties of polyurethanes is conducted.
The segment size of chain extended hard segments strongly affects the thermal and mechanical properties of polyurethanes. The degree of polymerization of the hard segment (PHS) is calculated for the chain extended polyurethanes (see Table 8). Because the Mw of the PTMO is much lower than that of the PIB, the PHS's of the products with mixed soft segments are quite low, (close to stoichiometric ratios), particularly for polyurethanes made with 1.5k g/mol PIB/650 g/mol PTMO soft segment combination.
Turning to
Turning to
The microhardness of PIB-based polyurethanes is investigated (see data in Table 8). It is discovered that the hardness of our polyurethanes is strongly affected by both the hard segment content and the molecular weight of the PIB. Microhardness increases linearly with hard segment content for all three PIB MWs. Polyurethanes prepared with 11,000 and 4,050 g/mol PIB show 63 or less hardness at moderate hard segment (HS) contents (15% by weight and 30% by weight). Polyurethanes with 1,500 g/mol PIB have a fairly high hardness. As expected, PTMO addition increases hardness by about 8 to about 18 units within the 30% by weight to 40% by weight hard segment range at identical hard segment contents.
DSC studies are carried out with PIB+PTMO-based polyurethanes. Briefly, it can be stated that the addition of PTMO to PIB-based polyureas decreases the crystallinity of the hard segments. The DSC trace of a representative mixed soft segment polyurethane (
The Mw of PIB affected the thermal properties of polyurethanes as well.
Poly(hexamethylene carbonate) diol (PC) (Mw=860 g/mol), 1,4-butanediol (BDO), dibutyltin dilaurate (DBTDL) are purchased from Aldrich and used without further purification. Tetrahydrofuran (THF) and 4,4′-methylenebis(cyclohexyl isocyanate) (HMDI) are from Aldrich and purified distillation.
PIB+PTMO based polyurethanes and PIB+PTMO based polyureas are synthesized using a method discussed above. PIB+PC based polyurethanes are produced by reacting PIB and PC macrodiols with HMDI and chain-extending the prepolymer with BDO in the presence of DBTDL as a catalyst and THF as a solvent (20% solid content). For example, 1 gram of PIB macrodiol is mixed with 0.59 grams of HMDI in the presence of 4.5 grams of THF at 60° C. Three drops of DBTDL is added. After about 1.5 hours, 0.3 grams of PC macrodiol is added with 1.5 grams of THF and the charge is further reacted for about 1.5 hours. BDO (0.13 grams) is added and reacted for about 3 hours. The reaction is stopped after isocyanate (NCO) is completely consumed which is confirmed with FT-IR by examining NCO peaks at 2270 cm−1.
Polyurethanes/PUrea films (100 to 300 pm thick) are prepared using THF as a solvent and then casting in a Teflon mold and drying at room temperature for a day followed by drying in oven at 70° C. overnight. Samples are stored for a week at room temperature before testing the mechanical properties thereof.
Stress-strain behavior is determined by an Instron Model 5543 Universal Tester controlled by Series Merlin 3.11 software. A bench-top die (ASTM 1708) is used to cut dog-bone samples from films. The samples (25 mm long, 3.5 mm in width at the neck) are tested to failure at a crosshead speed of 25 mm/min at room temperature. FTIR spectra are obtained by a Nicolet 7600 FTIR spectrometer using solution cast films on KBr discs dried with a heat gun. Twenty scans are taken for each spectrum with 2 cm-1 resolution.
Melting temperatures (Tm) and glass transition temperatures (Tg) of polyurethanes and polyureas are obtained by the use of a TA Instruments Q2000 Differential Scanning calorimeter (DSC) with 5 to 10 mg samples enclosed in aluminum pans and heated 10° C./min from −100° C. to 200° C. Dynamic mechanical thermal analysis (DMTA) is performed by a PerkinElmer dynamic mechanical analyzer. Measurements are made in tensile mode at 1 Hz, between −100° C. and 200° C., under a nitrogen atmosphere, at a heating rate of 3° C./min.
Small Angle X-ray Scattering (SAXS) experiments are performed under vacuum with S-Max 3000 SAXS instrument operating at 45 kV and 0.88 mA. MicroMax-002+x-ray generator equipped with Cu tube (wavelength 1.542 Angstroms) is used. SAXS data are collected for exposures of 1,000 seconds at room temperature. Interdomain spacing (d) is determined by:
where qmax is the location of scattering peak in the plot of scattering intensity (I) vs. scattering vector (q). The Atomic Force Microscopy (AFM) image is taken with a Veeco Metrology Group MultiMode Scanning Probe Microscope (Digital Instruments) (a similar method is utilized for the same data in the results above).
The schemes in
Regarding
The addition of PTMO or PC segments to PIB-based polyurethanes and polyureas is expected to affect the thermal behavior of these segmented copolymers. Thus, experiments are carried out to compare the DSC profiles of polyurethanes and polyureas prepared with (a) only PIB, and (b) combinations of hybrid PIB/PTMO or PIB/PC soft segments. Additional DSC studies are carried out with PIB-based polyurethanes synthesized by the use of increasing amounts (0% by weight to 30% by weight) of PTMO.
Table 9 and
Thus, the tensile strengths and elongations of the products reflect the changes observed in thermal behavior. In the absence or presence of only 10% by weight PTMO (see the first and second examples from the top of Table 9) the tensile strengths and elongations are relatively low (15.8 MPa to 17.8 MPa, and 480% to 310%, respectively), however, in the presence of 21% by weight PTMO (see the third example from the top of Table 9) the tensile strength rises to 31 MPa and the elongation also reaches a value of 700%. Increasing the PTMO content to 30% by weight (see the fourth example from the top of Table 9) does not further increase strength or elongation. Apparently, a maximum tensile strength and elongation are reached with 20% to 30%, by weight, PTMO at this hard segment content. The fact that PTMO-based polyurethanes exhibit similar tensile strengths and elongations at this hard segment content supports this conclusion.
Turning to the fifth and sixth examples from the top of Table 9,
The DSC scan obtained with the polyurea containing 12% by weight PTMO (see the sixth example from the top of Table 9) shows two new melting ranges centered at approximately 78° C. and approximately 129° C., which suggest the presence and melting of new H bridged structures. Accordingly, both the tensile strength and elongation of the polyurea prepared with PTMO are significantly higher than that obtained in the absence of PTMO. The proposed model is in line with these observations.
While not wishing to be bound to any one theory, it is believed that the stronger and larger numbers of H bridges in polyureas relative to polyurethanes produce strong interactions between the soft and hard segments and lead to enhanced strength. Excessive strengthening and overly high Tm's can be undesirable with respect to melt processibility because these polyureas will tend to degrade before they melt. The addition of PTMO not only reduces the Tm leading to better melt processibility, but it also improves stress transfer from the soft to the hard segments and improves the mechanical properties.
Additionally, a determination and analysis of the thermal transitions of PIB-based polyurethanes prepared in the absence and presence of PC soft segments is made. The PC segment is selected because polyurethanes prepared with the Poly(hexamethylene carbonate) macrodiol exhibit superior biological, oxidative and/or hydrolytic stabilities to those of PTMO-based polyurethanes. The increased stability of PC-based polyurethanes relative to PTMO-based polyurethanes is due to the lower number of vulnerable acidic hydrogens in the former. In addition, the —O—CO—O— group is a stronger H acceptor than the —CH2—O—CH2— group and is expected to form stronger H bridges.
Table 9 and
A comparison of the Tm's of PIB-based polyurethanes prepared with the same amount (15% by weight) of PC and PTMO (see the eighth and eleventh examples of Table 9) suggests largely similar products, albeit the former shows a transition at 78° C. which is absent in the latter. While their tensile strengths are quite similar, the elongation of the polyurethane made with PTMO is far superior to the one made with PC, at the same (35% by weight) hard segment content (elongations 180% versus 350%, compare the eighth and eleventh examples from the top of Table 9). At the same weight of additive, the number of H bridge acceptor sites in PTMO (ether oxygen atoms) is nearly double that in the PC (carbonate groups). When these polyurethanes are stretched the H bonds break and reform (relax) between adjacent functional groups. Thus, the polyurethane made with PTMO may break and relax at twice the strain than the ones made with PC.
In sum, according to these findings the addition of PTMO or PC soft segments to PIB-based polyurethanes and polyureas lead to improved mechanical properties. Thus, the present invention supports the proposition that these added soft segments form hybrid soft phases with PIB lead to H bridges between the soft and hard phases, which in turn lead to more efficient stress transfer from the soft to the hard phases, and thus yield improved mechanical properties.
To gain further insight into the morphology of these novel polyurethanes AFM studies are carried out.
Thus, further insight into the mechanical-property-enhancing effect of PTMO addition to PIB-based segmented copolymers is gained by SAXS experiments. SAXS provides information as to the interdomain spacing between hard domains dispersed in a continuous soft matrix.
While not wishing to be bound to any one theory, it is theorized that the introduction of PTMO into the continuous soft PIB matrix may increase the extent of dispersion of the hard domains and thus decrease interdomain spacing. Experiments are carried out with PIB-based polyurethanes and a PIB-based polyurea (see the first, fifth, and seventh examples from the top of Table 9), and the same products with added PTMO or PC soft co-segments (see the second to fourth and sixth examples from the top of Table 9 and eighth to tenth examples from the top of Table 9, respectively).
While not wishing to be bound to any one theory, it is believed that the improvement in mechanical strength of polyurethanes and polyureas obtained in the presence of PTMO or PC is not due to increased dispersion of hard domains but to the formation of H-bonds (hydrogen bonds). Enhanced elongation is most likely due to the flexibilization of the hard segments by PTMO segments. The proposed model is in line with these observations and conclusions.
Turning to
The storage moduli and flow temperatures of hybrid (PIB/PTMO)-based polyurethanes are studied by DMTA.
Turning to
Infrared spectroscopy (IR) is a simple informative technique for the investigation of hydrogen bonding. The principle that makes IR useful for polyurethanes is its sensitivity to peak shifts due to the extent of hydrogen bonding between carbonyl groups. Turning to
a shows the carbonyl region of a model compound (CHI—HDO—HMDI—HDO—HMDI—HDO—HMDI—HDO—CHI) prepared for these investigations. The model urethane compound displays a sharp and symmetrical carbonyl (C═O) peak centered at 1693 cm−1, indicating the presence of strongly hydrogen bonded urethane groups.
In the 3450 cm−1 to 3150 cm−1 region (
In light of the above, the present invention relates to various polyurethanes and/or polyureas that contain one or more types of hard segments and one or more types of soft segments. In one embodiment, such polyurethanes and polyureas of the present invention are made in accordance with the methods and examples discussed above using the appropriate reactants selected from those stated below.
Regarding the PIBs utilized in the present invention, in one embodiment the PIBs of the present invention are selected from linear, or star-shaped, or hyperbranched, or arborescent PIB compounds, where such compounds contain one or more primary alcohol-terminated segments and/or one or more primary amine terminated segments. In another embodiment, the PIBs of the present invention are selected from linear, or star-shaped, or hyperbranched, or arborescent PIB compounds, where such compounds contain two or more primary alcohol-terminated segments and/or two or more primary amine terminated segments. In still another embodiment, the PIBs of the present invention are selected from linear, or star-shaped, or hyperbranched, or arborescent PIB compounds, where such compounds contain two primary alcohol-terminated segments or two primary amine terminated segments.
In one embodiment, the number of repeating units in the various repeating PIB portions of an alcohol terminated and/or amine terminated PIB compound is in the range of 2 to about 5,000, or from about 7 to about 4,500, or from about 10 to about 4,000, or from about 15 to about 3,500, or from about 25 to about 3,000, or from about 75 to about 2,500, or from about 100 to about 2,000, or from about 250 to about 1,500, or even from about 500 to about 1,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
In one embodiment, the number of repeating units in the various repeating PTMO portions of the present invention is in the range of 2 to about 5,000, or from about 7 to about 4,500, or from about 10 to about 4,000, or from about 15 to about 3,500, or from about 25 to about 3,000, or from about 75 to about 2,500, or from about 100 to about 2,000, or from about 250 to about 1,500, or even from about 500 to about 1,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
In one embodiment, the number of repeating units in the various repeating aliphatic polycarbonate (PC) portions of the present invention is in the range of 2 to about 5,000, or from about 7 to about 4,500, or from about 10 to about 4,000, or from about 15 to about 3,500, or from about 25 to about 3,000, or from about 75 to about 2,500, or from about 100 to about 2,000, or from about 250 to about 1,500, or even from about 500 to about 1,000. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
In one embodiment, the one or more aliphatic portion of the polycarbonates utilized in conjunction with the present invention are selected from linear or branched C1 to C20 alkyl groups, linear or branched C2 to C20 alkenyl, or linear or branched C2 to C20 alkynyl. In another embodiment, the one or more aliphatic portion of the polycarbonates utilized in conjunction with the present invention are selected from linear or branched C2 to C15 alkyl groups, linear or branched C3 to C15 alkenyl, or linear or branched C3 to C15 alkynyl. In still another embodiment, the one or more aliphatic portion of the polycarbonates utilized in conjunction with the present invention are selected from linear or branched C3 to C10 alkyl groups, linear or branched C4 to C10 alkenyl, or linear or branched C4 to C10 alkynyl. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
Thus, in light of the above the polyurethanes and/or polyureas of the present invention are formed from an appropriate combination of an alcohol terminated and/or amine terminated PIB compound, as described above, with one or more of a PTMO or a PC, as described above. In some embodiments, where desired, at least one suitable chain extender and/or at least one diisocyanate is used in combination with the desired PIB compound and the one or more desired PTMO or PC compounds.
In another embodiment, the polymer compounds of the present invention, where applicable, have soft segment contents in the range of about 10 weight percent to about 98 weight percent, about 15 weight percent to about 95 weight percent, about 20 weight percent to about 90 weight percent, about 25 weight percent to about 85 weight percent, about 30 weight percent to about 80 weight percent, about 35 weight percent to about 75 weight percent, about 40 weight percent to about 70 weight percent, about 45 weight percent to about 65 weight percent, or even about 50 weight percent to about 60 weight percent. In still another embodiment, the polymer compounds of the present invention, where applicable, have soft segment contents in the range of about 50 weight percent to about 70 weight percent, about 52 weight percent to about 68 weight percent, about 54 weight percent to about 66 weight percent, about 56 weight percent to about 64 weight percent, or even about 58 weight percent to about 62 weight percent. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
In another embodiment, the polymer compounds of the present invention, where applicable, have hard segment contents in the range of about 1 weight percent to about 90 weight percent, about 2 weight percent to about 85 weight percent, about 5 weight percent to about 80 weight percent, about 10 weight percent to about 75 weight percent, about 15 weight percent to about 70 weight percent, about 20 weight percent to about 65 weight percent, about 25 weight percent to about 60 weight percent, about 30 weight percent to about 55 weight percent, or even about 35 weight percent to about 50 weight percent. In still another embodiment, the polymer compounds of the present invention, where applicable, have hard segment contents in the range of about 30 weight percent to about 50 weight percent, about 32 weight percent to about 48 weight percent, about 34 weight percent to about 46 weight percent, about 36 weight percent to about 44 weight percent, or even about 38 weight percent to about 42 weight percent. In still yet another embodiment, the polymer compounds of the present invention, where applicable, have hard segment contents in the range of about 1 weight percent to about 12 weight percent, about 1.5 weight percent to about 10 weight percent, or even about 2 weight percent to about 9 weight percent. Here, as well as elsewhere in the specification and claims, individual range limits can be combined to form alternative non-disclosed ranges and/or range limits.
As would be apparent to those of skill in the art, when a polymer composition of the present invention has both hard and soft segments, the amount of both should total to 100 percent or less even though the above ranges for both may exceed in their broadest amounts more than 100 percent when totaled together at their widest amounts.
Although the invention has been described in detail with particular reference to certain embodiments detailed herein, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and the present invention is intended to cover in the appended claims all such modifications and equivalents.
This patent application claims priority to U.S. Provisional Patent Application No. 61/194,896, filed on Oct. 1, 2008, entitled “Polyisobutylenes and Process for Making Same;” U.S. Provisional Patent Application No. 61/204,857, filed Jan. 12, 2009, entitled “Polyisobutylenes and Process for Making Same;” and U.S. Provisional Patent Application No. 61/178,529, filed May 15, 2009, entitled “Polyurethanes Containing Mixed PIB/PTMO and PIB/Aliphatic PC Soft Segments and Partially-Crystalline Hard Segments;” the entireties of which are hereby incorporated by reference herein.
The present invention was made in the course of research that was supported by National Science Foundation (NSF) Grant DMR 02-43314-3. The United States government may have certain rights to the invention or inventions herein.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2009/059269 | 10/1/2009 | WO | 00 | 5/19/2011 |
| Number | Date | Country | |
|---|---|---|---|
| 61194896 | Oct 2008 | US | |
| 61204857 | Jan 2009 | US | |
| 61178529 | May 2009 | US |
