WO2011047369A2 - Vegetable oil-based, waterborne polyurethane dispersion - Google Patents

Abstract

Novel polyurethane resins are provided by the reaction of an epoxidized or partially epoxidized triglyceride (for example, epoxidized soy oil), an isocyanate, and a functional diol selected to impart amphoteric, cationic, anionic character to the resultant polyurethane. These polyurethane resins may be used to provide vegetable oil-based, waterborne polyurethane dispersions which are readily adapted to suit a variety of uses.

Description

VEGETABLE OIL-BASED, WATERBORNE POLYURETHANE DISPERSIONS CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from United States Provisional Patent Application Serial Number 61/252,601, filed October 16, 2009 for "Waterborne Anionic/Cationic Polyurethane Dispersions Derived from Vegetable Oils".

BACKGROUND OF THE INVENTION

[0002] Polyurethanes (PUs) are one of the most versatile polymeric materials with regard to both processing methods and mechanical properties, having a principal chain structure composed of rigid hard and flexible soft segments. Due to the specific micro-phase structure formed between the hard and soft segments, with a proper selection of reactants, PUs ranging from high performance elastomers to tough rigid plastics can be equally synthesized. The resultant wide range of achievable properties make PUs attractive for use in a variety of applications and end uses, including but not being limited to coatings, binders, adhesives, sealants, paints, fibers, elastomers (including for synthetic skin) and foams.

[0003] However, conventional polyurethane products usually contain a significant amount of organic solvents and sometimes even free isocyanate monomers. With increasingly restrictive environmental regulations regarding volatile organic chemicals (VOCs), conventional PUs are increasingly being replaced by aqueous polyurethane dispersions (PUDs), a binary colloidal system where the PU particles are dispersed in a continuous aqueous media. Waterborne PUs present other advantages relative to conventional solvent- borne PUs, including for example a low viscosity at high molecular weight, so that aqueous PUDs are now one of the most rapidly developing and active branches of PU chemistry and technology. The qualities of these aqueous PUDs, notably excellent adhesion properties and low temperature film-forming abilities, have made them very useful in replacement of the conventional solvent-borne PUs as adhesives, coatings and paints.

[0004] Considering the contributions offered by the present invention from a different perspective, polymers from renewable resources have been attracting ever-increasing attention over the past two decades, largely because of environmental concerns and finite petroleum resources. Similar to widely used polymers, like polyethylene, polypropylene and polystyrene, PUs are also generally based on fossil feedstocks. As a consequence of their widespread use in many different applications, significant attention has been directed in recent years toward the possible use of renewable feedstocks as raw materials for PL) production.

[0005] Certain of these investigations have been undertaken to consider the use of vegetable oils for PL) production Vegetable oils are now widely used as renewable raw materials in the chemical and polymer industries, due to their superb environmental credentials, including their inherent biodegradability, low toxicity, avoidance of volatile organic chemicals, ready availability, and relatively low price.

[0006] Petrovic et al. , see, for example, Petrovic er a/. , Polym. Int., vol.

57, pp 275-281 (2008), have extensively studied the use of various soybean oil- based polyols to synthesize polyurethane thermosets whose structures depend on the type of triglyceride used, the nature of the isocyanate group and the degree of crosslinking.

[0007] Recently, Lligadas et al have described the synthesis of polyurethane thermosets, behaving like hard rubbers or rigid plastics, from polyether polyols (through a combination of cationic polymerization of epoxidized methyl oleate and reduction of carboxylate groups to hydroxyl moieties), and triols (prepared by the cyclotrimerization of methyl 10- undecynoate and methyl 9-octadecynoate)(Lligadas et al, Biomacromolecules, vol. 8, pp 1858-1864 (2007), for example).

[0008] In WO 2006/047431 A1 , "Aqueous Polyurethane Dispersions made from Hydroxymethyl-containing Polyester Polyols Derived from Fatty

Acids", branched natural triglyceride oils, like soybean oil, are transesterified by reaction with an alcohol to provide a linear fatty acid ester containing just one long fatty acid ester chain instead of the three branched chains present in the natural oil. The carbon-carbon double bonds in that single chain fatty acid ester material are then reacted with carbon monoxide and hydrogen to attach an aldehyde group through hydroformylation to the fatty acid ester chain. This aldehyde is then reduced to an hydroxymethyl primary alcohol (CH₂OH). This alcohol-containing material is then reacted with the same diisocyanates and dimethylolpropionic acid (DMPA) used in all of the other processes described here to prepare a polyurethane containing carboxylic acid groups. This material is dissolved in /V-methyl-2-pyrrolidone (NMP) during the work-up and eventually the polymer is reacted with triethylamine to produce a waterbome emulsion used as a coating. This polyurethane has the linear fatty acid chains derived from the natural oil hanging off of the main polymer chain as side chains.

[0009] In similar manner, in WO 2008/118287 A1 , "Dual-curable

Waterbome Urethane Dispersion with Good Hardness and Solvent and

Chemical Resistance" , Yang et al. start with the same natural oils and carry out a transesterification of the oil with a petroleum-based polyol such as

C(CH₂OH)₄, to produce a linear fatty acid ester, which contains primary alcohol groups derived from the petroleum-based polyol. The excess alcohol groups of the fatty acid ester polyol are then reacted with diisocyanates and DMPA.

Again the final polymer is derived from primary alcohol-containing linear fatty acid esters and has the fatty acid derived chains hanging off of the main polymer chain.

[0010] In WO 2006/047746 A1 , "Waterbome Dispersion of Oil-modified Urethane Polymers" , the polyols used to make the coatings are derived from the natural oils by reacting a triglyceride drying oil with non-natural

polyfunctional alcohols (polyols) to get linear fatty acid esters including primary alcohol groups. Alternatively, a fatty acid is reacted with a petroleum-based epoxide to make a linear fatty acid ester containing an alcohol group. The polyols obtained and used in the coatings described in this reference contain a multifunctional mixture, which has obvious negative effects on the particle size distribution, and the thermal and mechanical properties of the resulting polyurethane dispersions. Once again, in the resulting coatings, the fatty acid unit exists as a side chain in the final polymer, not in the main chain of the polymer backbone.

[0011] Inexpensive, readily available vegetable oil-based polyols are good candidates for the synthesis of environmentally-friendly, waterborne polyurethane dispersions from renewable raw materials, but present a challenge when employing polyols with high hydroxyl functionality, as the high functionality of some of these polyols may lead to gelation and higher crosslinking and consequent difficulties in dispersing the resulting highly crosslinked PU prepolymers into water. As a result, only soybean oil-based polyol with a relatively low average hydroxyl functionality of about 2.3 has previously been successfully used for the synthesis of waterborne PU dispersions.

SUMMARY OF THE INVENTION

[0012] The present invention provides, in a first aspect, polyurethane resins from the reaction of an epoxidized or partially epoxidized triglyceride having an average hydroxyl functionality of 2.4 or greater, an isocyanate, and a functional diol selected to impart amphoteric, cationic, anionic character to the resultant polyurethane, as well as dispersions including such resins, especially in a continuous aqueous phase. In a second aspect, polyurethane resins are provided (along with dispersions, and especially aqueous dispersions of the same) from the reaction of an epoxidized or partially epoxidized triglyceride, an isocyanate, and a functional diol selected to impart amphoteric, cationic, anionic character to the resultant polyurethane, wherein the process of forming the resin includes a degree of ring opening of epoxide groups in the epoxidized or partially epoxidized triglyceride.

[0013] The inventive natural triglyceride-based polyurethanes and waterborne polyurethane dispersions are quite stable and exhibit a uniform particle size. The biobased polymers according to the present invention, containing typically 40-80 wt% natural triglyceride-based polyols as renewable resources, can range from adhesive to soft and flexible elastomers to tough and rigid plastics, and exhibit good thermal stability and mechanical properties. Significant properties of these biobased PUs/PUDs can be comparable or even improved compared to products based on petroleum-based polyols. Moreover, the thermophysical and mechanical properties of these novel PUs/PUDs can be easily adjusted by changing the polyol functionality, the hard segment structure and content, and the composition of the soft and hard segments. The waterborne PUDs enabled through the present invention may serve as suitable renewable source-based replacements for petroleum-based waterborne polyurethane dispersions, thus reducing waste and preserving our dwindling petroleum reserves.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 depicts an exemplary synthesis method for forming a vegetable oil-based aqueous cationic polyurethane dispersion according to the present invention, in a first aspect;

[0015] FIG. 2 depicts an exemplary synthesis method for forming a vegetable oil-based aqueous anionic polyurethane dispersion according to the present invention, in a second aspect;

[0016] FIG. 3 shows Fourier transform infrared spectra for certain cationic polyurethane dispersions whose synthesis is described below;

[0017] FIG. 4 provides differential scanning calorimeter curves for films made with aqueous cationic polyurethane dispersions from methoxylated soy polyols (prepared by ring opening epoxidized soybean oil with methanol) with different hydroxyl functionalities;

[0018] FIG. 5 provides dynamic mechanical analysis curves for films made with aqueous cationic polyurethane dispersions from methoxylated soy polyols with different hydroxyl functionalities;

[0019] FIG. 6 illustrates the relationship between the hydroxyl functionality and glass transition temperature observed for films prepared from aqueous cationic polyurethane dispersions according to the present invention;

[0020] FIG. 7 shows the results of thermal gravimetric analysis on films from aqueous cationic polyurethane dispersions made using methoxylated soy polyols with different hydroxyl functionalities; [0021] FIG. 8 shows stress-strain curves for PU films from dispersions using methoxylated soy polyols having different hydroxyl functionalities;

[0022] FIG. 9 depicts Fourier transform infrared spectra of anionic polyurethane dispersions prepared according to the present invention, as more particularly described below;

[0023] FIG. 10 provides differential scanning calorimetry thermograms of films from various anionic polyurethane dispersions made according to the present invention and described below;

[0024] FIG. 11 relates the storage modulus and loss factor for films from anionic dispersions made from methoxylated soy polyols of differing average hydroxyl functionalities , as a function of temperature;

[0025] FIG. 12 relates the storage modulus and loss factor associated with films made from anionic dispersions having different hard segment contents, again as a function of temperature;

[0026] FIG. 13 illustrates the relationship of the glass transition temperature of several anionic dispersion films from methoxylated soy polyols having different average hydroxyl functionalities;

[0027] FIG. 14 provides thermal gravimetric analyses for anionic dispersion films prepared using methoxylated soy polyols having different average hydroxyl functionalities;

[0028] FIG. 15 provides stress-strain curves for films from anionic dispersions made with methoxylated soy polyols of differing average hydroxyl functionalities; and

[0029] FIG. 16 shows stress-strain curves for films from anionic dispersions made from a methoxylated soy polyol of a given hydroxyl functionality, but wherein the polyurethanes in the dispersions are characterized by different hard segment contents.

DETAILED DESCRIPTION OF THE INVENTION

[0030] Suitable methods of preparing the inventive polyurethanes and aqueous anionic and cationic polyurethane dispersions contemplated by the present invention are exemplified below, and those skilled in the art will be well able to determine also from the examples and results reported herein the particulars of preferred methods for making anionic and cationic PL⁾ dispersions having certain desirable attributes.

[0031] As well, it will be appreciated that certain modifications and additions may be made to the exemplified or explicitly described natural triglyceride-based polyurethanes and dispersions, to the methods described herein for making the same or to compositions based on or including the polyurethanes or polyurethane dispersions for various applications, without departing from the essential elements of our invention as defined more particularly by the claims below.

[0032] For example, additional polyols, preferably being also of a renewable origin or character, may be used to make the polyurethanes. An example of a biobased polyol of this character would be isosorbide, which might be desirably added to increase the strength and glass transition temperature of the polyurethane. Additional polyols may also include tetrahydrofuran dimethanol, furandimethanol, sorbitan, saccharides, monosaccharides including dioses, such as glycolaldehyde; trioses, such as glyceraldehyde and

dihydroxyacetone; tetroses, such as erythrose and threose; aldo-pentoses such as arabinose, lyxose, ribose, deoxyribose, xylose; keto-pentoses, such as ribulose and xylulose; aldo-hexoses such as allose, altrose, galactose, glucose, dextrose, gulose, idose, mannose, talose; keto-hexoses, such as fructose, psicose, sorbose, tagatose; heptoses, such as mannoheptulose and

sedoheptulose; octoses, such as octolose and 2-keto-3-deoxy-manno-octonate; and nonoses, such as sialose; disaccharides including sucrose (known as table sugar, cane sugar, saccharose, or beet sugar), lactose, maltose, trehalose, cellobiose; oligosaccharides, such as raffinose (melitose), stachycose, and verbascose; glycerol, hydroxymethyl furfural, polyglycerols, plant fiber hydrolyzates, fermentation products from plant fiber hydrolyzates, and various mixtures of any thereof.

[0033] As a further example, while the polyurethane preparations described below and depicted in the reaction schemes of both Figures 1 and 2 utilize methoxylated vegetable (soybean oil, in particular) oil prepared by ring opening epoxide groups in an epoxidized vegetable oil with methanol, other carboxylic acids such as acetic or acrylic acid could also be used to ring-open epoxide groups and provide a range of corresponding secondary alcohol- containing modified vegetable oils for making the polyurethanes and aqueous PU dispersions of the present invention.

[0034] In this regard, an essential difference between the renewable source-based polyurethanes and dispersions described and claimed herein and those described in WO 2006/047431 A1 , in WO 2008/118287 A1 and in WO 2006/047746 A1 is that the triglycerides are not broken down (for example, into linear fatty acid esters) but are provided as epoxidized or partially epoxidized triglycerides, having undergone epoxidation and some subsequent ring-opening of those epoxide groups. The presence of multiple double bonds in preferred triglycerides affords a range of sites for epoxidation, and correspondingly, multiple ring-opening opportunities to form hydroxyl groups that can react with an isocyanate. Because the requisite epoxide groups can be formed fairly heterogeneously in the otherwise largely intact triglycerides, the hydroxyl groups can be formed fairly heterogeneously as well, so that the resins enabled by the present invention can be described by virtue of variable positioning of the hydroxyl groups as having an essentially heterogeneous network structure.

[0035] The manner in which the polyurethanes of the present invention are thus made, makes it possible to achieve a broad range of properties and qualities in the polyurethane dispersions of the present invention than have heretofore been possible, including an ability to make dispersions that are considerably less prone to phase separation over time, to make renewable source-based dispersions wherein the polyurethanes have a desirable amorphous character, to make polyurethanes of certain desired particle sizes for dispersions (for glossy coating applications, for example) and to make renewable source-based polyurethanes with increased hydrophobicity for improved hydrolytic stability. Polyurethanes and stable, aqueous dispersions of polyurethanes made with triglycerides having an average hydroxyl functionality of 2.4 and greater up to about 4.0 are made possible, with the dispersions being suited for use in industrial coatings, paints and the like. The term "hydroxyl functionality," it should be noted, is conventionally understood to indicate the average number of hydroxyl moieties present in the fatty acyl chains of triglycerides having hydroxyl groups. The presence of triglycerides having substantial hydrophobic character imparts improved hydrolytic stability to films formed therefrom, due to repulsion between water and hydrophobic structures.

[0036] The waterborne polyurethane dispersions of the present invention can be used in a variety of applications, as noted previously.

Vegetable oil-based, aqueous polyurethane dispersions have been particularly of interest as an alternative to petroleum-based polyurethane dispersions in an aqueous or organic matrix, for applications wherein a lack of toxicity,

biodegradability and an absence of volatile or hazardous organic compounds generally are needed. No attempt will be made herein, however, to describe in detail the myriad uses to which the present inventive dispersions may be put, as those skilled in the coatings, paints, adhesives, binders, sealants, fibers, foams and elastomer arts will be certainly able to determine how best to make use of the inventive dispersions in these contexts of use without undue

experimentation. It will be briefly noted, in any event, that as would be evident on further examination, the vegetable oil-based, aqueous polyurethane dispersions made according to the present invention (and/or the methods described for making these) provide distinct improvements over even the above- described prior art efforts to develop similar vegetable oil-based , aqueous polyurethane dispersions.

[0037] Aqueous Vegetable Oil-Based Cationic Polyurethane Dispersions:

[0038] Materials: Wesson™ brand soybean oil was purchased at the local supermarket and used directly without further purification. Methoxylated soybean oil polyols (MSOLs) with hydroxyl numbers of 135, 149, 176, 190 and 200 mg KOH/g were synthesized according to the method described in Y. Lu, R. C. Larock, Biomacromolecules, vol. 9, pp 3332-3340 (2008), and these were identified as MSOL-135, MSOL-149, MSOL-176, MSOL-190 and MSOL-200, respectively. A/-Methyl diethanolamine (NMDA) and castor oil (OH number = 163 mg KOH/g) were purchased from Aldrich Chemical Co., Inc. Methylene diphenyl 4,4'-diisocyanate (MDI) was purchased from Alfa-Aesar Inc. Glacial acetic acid and methyl ethyl ketone (MEK) were purchased from Fisher Scientific Company. All materials were used as received without further purification.

[0039] Synthesis of soybean oil-based aqueous cationic polyurethane dispersions

[0040] Synthesis of the soybean oil-based aqueous cationic waterborne polyurethane dispersions was carried out as follows. The MSOL, MDI and NMDA were added to a four-necked flask equipped with a mechanical stirrer, nitrogen inlet, condenser and thermometer. The molar ratio of the NCO groups of the MDI, the OH groups of the MSOL and the OH groups of the NMDA was kept at 2.0 : 1.0 : 0.95. The reaction was first carried out at 60 °C for 30 min under a dry nitrogen atmosphere and then MEK (50 wt % based on the reactant) was added to reduce the viscosity of the system. After 3 hrs reaction, the reactants were cooled to room temperature, and then neutralized by the addition of acetic acid (1.5 equivalents of NMDA), followed by dispersion at high speed with distilled water to produce the cationic PUD with a solids content of about 20 wt % after removal of the MEK under vacuum. The cationic waterbome polyurethane dispersions prepared from MSOL-135, MSOL- 49, MSOL-176, MSOL-190 and MSOL-200 are hereby identified as MSOL-135-PU, MSOL-149- PU, MSOL-176-PU, MSOL-190-PU and MSOL-200-PU, respectively. The corresponding PU films were obtained by drying the resulting dispersions at room temperature in polystyrene petri dishes.

[0041] Characterization, Analytical and Performance Methods

[0042] The FT-IR spectra of the PU films were recorded on a Nicolet 460 FT-IR spectrometer (Madison, USA).

[0043] The morphology of the cationic waterborne polyurethane dispersions was observed on a transmission electron microscope (JEOL 1200EX). The dispersions prepared were diluted with distilled water to about 0.1 wt %. One drop of the diluted dispersion was placed on the coated side of a 200-mesh nickel grid and characterized after drying.

[0044] The soluble fraction of the PU films was determined as follows. Samples of about 1g were cut from the PU films used in this study, weighed and then immersed in an excess of Λ/JV-dimethylformamide (DMF) for 48 hrs at room temperature while stirring. Then the samples were removed from the solvent and dried under a vacuum at 80 °C for at least 24 hrs. The dried samples were then weighed, and the soluble fraction (SF) was calculated using the following equation:

W - W

SF (%) -— ! x 100%

W_t

where H j and W_e are the weight of the initial and the extracted PU films, respectively.

[0045] Differential scanning calorimetry (DSC) was carried out on a thermal analyzer (TA instrument DSC Q20, USA). The samples were heated at a rate of 10 °C/min from 25 to 100 °C to erase their thermal history, cooled to - 70 °C at a cooling rate of 10 °C/min, and then heated again to 150 °C at a heating rate of 5 °C/min. The glass transition temperature (T_g) of the samples was determined from the midpoint temperature in the heat capacity change of the second DSC scan. Samples of about 10-15 mg were cut from the films and used.

[0046] The dynamic mechanical behavior of the PL) films was determined using a dynamic mechanical analyzer (TA instrument DMA Q800, New Castle, DE) with tensile mode at 1 Hz and a heating rate of 5 °C/min in the temperature range from -80 to 150 °C. The glass transition temperature (7_g) of the samples was obtained from the peaks of the tan δ curves.

[0047] A Q50 thermogravimeter (TA instrument TGA Q50, USA) was used to measure the weight loss of the PU films under an air atmosphere. The samples were heated from 100 to 650 °C at a heating rate of 20 °C/min.

Generally, 10-15 mg samples were used for the thermogravimetric analysis.

[0048] The mechanical properties of the PU films were determined using an Instron universal testing machine (model-4502) with a crosshead speed of 50 mm/min. Rectangular specimens of 80 mm x 10 mm (length ^χ width) were used. An average value of at least five replicates of each sample was taken. The toughness of the polymer, which is the fracture energy per unit volume of the sample, was obtained from the area under the corresponding tensile stress- strain curve.

[0049] Results and Discussion

[0050] A) Structure and Morphology

[0051] The soybean oil employed in this work had 4.5 carbon-carbon double bonds per triglyceride. After epoxidization, some of the double bonds are converted into epoxy groups, which subsequently result in methoxylated soybean oil polyols (MSOLs) with 2.4 - 4.0 hydroxyl groups per triglyceride on average after ring opening with methanol as shown in Table 1. All MSOLs obtained are clear, slightly yellow liquids. It is important to point out that the distribution of OH groups within the MSOL molecules varies from molecule to molecule. In fact, the OH numbers determined for the MSOLs are an average distribution of OH groups present in the triglycerides, which is responsible for the different properties and characteristics of these materials when compared with petrochemical-based polyols. The difference in OH functionality plays a key role in controlling the structure, morphology, and thermophysical and mechanical properties of the resulting PU films. As shown in Table 1 , there is a trend towards decreasing soluble fractions in going from the MSOL-135-PU film with 37.1 wt. % to 10.9 wt. % for the film MSOL-200-PU, due to increased crosslink densities for the PU films prepared from MSOLs with higher hydroxyl functionality.

[0052] Each PUD was observed to exhibit a uniform distribution of particle sizes. A particle size of about 45 ± 5 nm diameter was observed for the MSOL-149-PU dispersion, which is translucent with a slight blue color.

Compared with the MSOL-149-PU dispersion, the MSOL-176-PU dispersion exhibited an average particle size of approximately 115 + 17 nm diameter. However, further increasing the hydroxyl number of the MSOL resulted in a decrease in the average particle size to 65 ± 5 nm for the MSOL-200-PU dispersion. Generally, several factors, including the hydrophilicity, the prepolymer viscosity, the ionic group position, the chain rigidity, the chemical structure of the soft segment and the crosslinking, play a key role in the particle size of the PUDs. In this case, the particle size of the PUDs from MSOLs with differing OH functionality might be controlled in two ways. First, the higher OH functionality of the MSOL can increase the crosslinking of the urethane prepolymers, leading to an increase in the particle size of the dispersion.

However, when the OH number of the MSOL increases, the amount of diisocyanate and NMDA also increases if a constant molar ratio between the NCO and OH groups is maintained. As shown in Table 1, the content of the NMDA is found to increase from 7.5 wt. % for MSOL-135-PU to 9.2 wt. % for MSOL-200-PU as the OH number of the MSOL increases from 135 to 200 mg KOH/g. As a dispersing center, the higher amount of NMDA facilitates dispersion of the urethane prepolymers, resulting in a smaller particle size for the corresponding dispersion. The increase in the particle size for the dispersions from MSOL-149-PU to MSOL-176-PU may thus be mainly due to the higher crosslinking, while the decrease in the particle size of the dispersions from MSOL- 76-PU to MSOL-200-PU is attributed to an increased amount of dispersing center.

Table 1 Chemical composition, soluble fraction (SF) and crosslink density ( v_e) of the PL) films from MSOLs with different hydroxyl numbers

acid)],

b NMDA content = [mass of NMDA]/[mass (MSOL + MDI + NMDA + acetic acid)]

[0053] The FT-IR spectra of the PU samples are shown in Figure 3. For the film MSOL-176-PU [Figure 3a], the absorption peak assigned to isocyanate groups at 2270 cm^"1 has disappeared, indicating that the isocyanate groups of the MDI have completely reacted. Meanwhile, the characteristic absorption peaks of the PU are observed at 3450, 3333, 1737-1702, and 1530 cm^"1, assigned to -OH (stretching), -NH (stretching), -C=0 (stretching), and -NH (bending), respectively. In addition, the intensive absorption due to the ring C-C stretching of MDI is also observed at 1600 cm^"1. The most easily interpretable bands in this system are the C=0 stretching, whose frequencies and relative intensities are characteristic of hydrogen-bond formation. As shown in Figure 3, in the C=0 region for the samples MSOL-135-PU (b), MSOL-176-PU (c) and MSOL-200-PU (d), three bands at 1739, 1727 and 1709 cm^"' are observed. The peak at 1739 cm^"1 is typically assigned to free urethane carbonyl stretching, whereas the peaks at 1727 and 1709 cm^"1 are due to hydrogen-bonded carbonyl stretching in the disordered regions. For the stronger hydrogen bonds in ordered or crystalline regions, carbonyl stretching occurs at an even lower frequency ranging from 1684 to 1702 cm^"1 and is not observed in this work, indicating the amorphous nature of the resulting PUs. Upon increasing the hydroxyl functionality from 2.4 (MSOL-135) to 4.0 (MSOL-200), a significant change occurs, with relatively sharp bands at 1709 and 1727 cm^"1 becoming evident, which suggests that more hydrogen bonds are formed for the samples from the polyols with higher hydroxyl functionality; consequently, an increased intermolecular interaction of the hard segments with the soft segments occurs in the corresponding systems. This results because increasing the OH functionality of the soft segments leads to higher crosslinking and increased urethane content in the resulting materials.

[0054] B) Thermal Properties

[0055] The DSC thermograms of the PL⁾ films from the MSOLs with different OH number are shown in Figure 4. No melting or crystallization transition is observed in the DSC curves, indicating the amorphous nature of these vegetable oil-based urethane materials, which is in good agreement with the IR results. All of the films show only one glass transition temperature (T_g), which increases from 9.9 to 34.5 °C with an increase in the OH number of the MSOL from 135 to 200 mg KOH/g. This can be explained by the restricted mobility of the polymer chains, resulting from the higher crosslinking, due to the increasing OH functionality, and the increased content of the hard segments that provide stronger physical crosslinking through hydrogen bonding.

[0056] DMA was used to assess the molecular mobility of the polymeric materials. The storage modulus (£') and loss peaks (tan δ) are plotted as a function of temperature for the PU films from the MSOLs with different OH numbers, as shown in Figure 5. In the glassy state, the E values of all PU films are on the order of 3 x 10⁹ to 6 ^χ 10⁹ Pa, a typical value for polymer glasses. As the temperature increases, the E value of the PU film decreases slightly until a sharp decrease is observed. This decrease in £' value corresponds to an energy dissipation shown in the tan δ - 7 curve, where a maximum, taken as the T_g, is observed in the tan δ curve. Then, at higher temperatures, the storage modulus reaches a rubbery plateau, assigned to the rubbery state, suggesting the nature of the crosslinking. The MSOL-135-PU exhibits a relatively low E value with a T_g of about 54 °C. With an increase in the hydroxyl number of the MSOL, the storage modulus of the resulting PU films dramatically increases over the entire temperature range studied. For example, the £' value of the MSOL-200-PU film at 100 °C is about 9.3 times higher than that of the MSOL- 135-PU film. This can be explained by the higher crosslink density as shown in Table 1 , which has been calculated from the rubbery plateau at T_g + 40 °C. As the molecular motions of the soft segments become more and more restricted, the amount of energy that can be dissipated throughout the polymer specimen decreases dramatically. Therefore, a shift of the T_g to higher temperature is observed for PU films from MSOLs with high OH functionality. Moreover, because of higher crosslinking, the phase mixing of soft segments with hard segments is also increased with an increase in the OH functionality, which is well supported by the narrowed glass-rubber transition in the storage modulus and the narrowed tan δ peak. In addition to higher crosslinking, another reason for the increase in the T_g and phase mixing may be the increased hydrogen bonding, resulting from the higher hard segment content.

[0057] For the PU films, the 7_gs as a function of the OH number of the MSOLs are shown in Figure 6. According to the Fox-Losheak equation relating the crosslinking density and T_g:

T_g = T_gK + L = T_gx + b>

⁸ M_c ^s

where T_gx is the glass transition temperature of the linear polymer of the same structure, v is the number of crosslinks per unit of volume (density/M_c), and K and k are constants for a given system. It should be noted that v should be directly proportional to the OH functionality, provided that the chemical conversion is complete in the system. As shown in Figure 6, the T_g value of the PU film increases linearly with the increasing OH number of the MSOLs, offering respectable r² values of 0.990 and 0.977 for the data from the DSC and DMA analyses, respectively. The T_g values obtained from DMA analysis are relatively high when compared with those from DSC, because of the different nature of these two methods.

[0058] The thermal degradation of PUs has been extensively investigated in terms of the types of diisocyanate (aliphatic or aromatic), polyol (polyester or polyether) and chain extender. Various mechanisms have been proposed to explain the degradation of PUs, including dissociation to isocyanate and alcohol, formation of primary amine and olefins, formation of secondary amine and transesterification. Figure 7 shows typical TGA curves for our PU films, and the detailed results are listed in Table 2 following. All films exhibit thermal decomposition, which mainly occurs in six successive stages. The total weight losses at the first and second stages below 350 °C are in the range of 35-40 wt %. In this case, the first two weight losses are due to degradation of the hard segments in the PUs, as a consequence of the relatively low thermal stability of the urethane groups. The degradation processes in the temperature range of 350-550 °C are attributed to soybean oil chain scission. The last steps in the weight loss rate occur at a temperature of around 600 °C, which corresponds to thermo-oxidative degradation of the PUs. The interesting parameters for the thermal stability of the PU films have been taken from the onset of degradation, which is usually taken as the temperature at which 10% degradation occurs (7io) and the mid-point temperature of the degradation (T₅₀). When the OH number of the MSOL increases from 135 to 200 mg KOH/g, a shift from 407.9 to 39 .6 °C is observed for T₅₀ value. Furthermore, the temperature of the maximum rate of weight loss also decreases as shown by DTGA in Figure 7. This can be explained by the higher content of labile hard segments present in the PU films from MOSLs with higher OH number. When the OH number of the MSOLs increases from 135 to 176 mg KOH/g, quite similar Tio values are observed, probably because of a competition between the increase in the crosslink density and the higher content of labile hard segments.

[0059] C) Mechanical Properties

[0060] The Young's modulus, tensile strength, elongation at break, and toughness of the PU films from MSOLs with OH numbers ranging from 135 to 200 mg KOH/g are summarized in Table 2, and typical tensile stress-strain behaviors are shown in Figure 8. The flexible film MSOL-135-PU shows a relatively low modulus of 33.6 MPa, a viable ultimate tensile strength of about 5.7 MPa, and an elongation at break of approximately 291%. Significant increases of 5 times for the Young's modulus and of 2 times for the ultimate tensile strength are observed for the ductile plastic MSOL-149-PU, when compared with MSOL-135-PU, but the elongation at break decreases slightly from 291 to 277%, because of the relative high crosslinking. The higher OH numbers of MSOL-190 and MSOL-200 result in relatively hard plastics for MSOL-190-PU and MSOL-200-PU. Both samples exhibit a clear yielding behavior, followed by strain softening and strain hardening before breaking. Moreover, the Young's modulus and ultimate tensile strength of the film MSOL- 200-PU reach approximately 554 and 23.2 MPa (Table 2, entry 6), respectively. These changes in the mechanical behavior are a result of an increase in the crosslink density of the PU films from the MSOLs with high OH numbers. It is worth noting that all PU films exhibited excellent elongation at break of higher than 200%, indicating that these samples can effectively sustain the stretch when stressed. For comparison, castor oil (CO), a naturally-occurring triglyceride oil with an OH functionality of approximately 2.7, was also used to synthesize a cationic PUD with the same stoichiometry. However, when compared with MSOL-149-PU prepared from MSOL-149 with an OH

functionality of 2.8, the resulting CO-PU film prepared from castor oil exhibits behavior typical of an elastomer and possesses a Young's modulus of 5.2 ± 0.8 MPa, a tensile strength of 10.9 ± 1.1 MPa and an elongation at break of 671 ± 36%. This difference in the mechanical behavior between MSOL-149-PU and CO-PU can be attributed to thejieterogeneous network structure in the MSOL- 149-PU film, resulting from a less uniform distribution of OH groups in the polyol MSOL-149 when compared with castor oil with its naturally-occurring OH groups. The crosslinking heterogeneity leads to weak points in the structure, resulting in a relatively lower elongation at break.

[0061] Toughness, defined as the amount of energy per volume that a material can absorb before rupturing, is the resistance to fracture of a material when stressed and can be obtained from the area under the corresponding tensile stress-strain curve. As shown in Table 2, MSOL-135-PU shows a relatively low toughness of 12.4 MPa, resulting from the low average hydroxyl functionality of the polyol and the presence of more oligomers. When increasing the OH number of the MSOL from 135 to 200 mg KOH/g, the toughness of the corresponding PL⁾ films increases to as high as 45.9 MPa, indicating the ductile nature of the resulting materials.

Table 2. Thermal and mechanical properties of the cationic PU films from MSOLs with different hydroxyl numbers

E = Young's modulus, a_b = Tensile strength, ¾ = Elongation at break

[0062] Aqueous Vegetable Oil-Based Anionic Polvurethane Dispersions

[0063] Materials: Wesson™ brand soybean oil was purchased at the local supermarket and used directly without further purification. Isophorone diisocyanate (IPDI) and dimethylol propionic acid (DMPA) were purchased from Aldrich Chemical Company. Hydrogen peroxide (30%), formic acid (88%), triethylamine (TEA), magnesium sulfate, methyl ethyl ketone (MEK), and ethyl acetate were purchased from Fisher Scientific Company. All materials were used as received without further purification. [0064] Synthesis of the Epoxidized Soybean Oils and Polvols.

[0065] Epoxidized soybean oils (ESOs) with differing numbers of epoxide groups have been prepared by reaction of the unsaturation sites of the soybean oil with a mixture of formic acid and hydrogen peroxide according to the procedure outlined in Khot, et. al., J. Appl. Polym. Sci. , vol. 82, 703-723 (2001 ). In brief, the soybean oil (100 g) was added to a 500 ml_ flask, then certain amounts of 30% hydrogen peroxide were added, followed by the addition of formic acid under vigorous stirring. The weight ratio between the hydrogen peroxide and the formic acid was held at 0.9: 1. The reaction was carried out at room temperature for 24 hrs. Then, 150 mL of ethyl acetate and 100 ml_ of distilled water were added, resulting in two layers. The organic layer was washed with aqueous sodium bicarbonate solution, until a slightly alkaline pH was obtained, and the organic layer was then dried over MgS0₄ and filtered. Finally, the clear viscous epoxidized soybean oils were obtained after removal of the organic solvent under vacuum. By adjusting the molar ratio of the hydrogen peroxide and the carbon-carbon double bonds in the triglyceride from 2.5 to 3.0, 3.4, 4.1 and 5.0, epoxidized soybean oils averaging 2.0 to 2.3, 2.7, 3.1 and 3.7 epoxide groups per triglyceride (as determined by ¹H NMR spectroscopy; Varian Associates, Palo Alto, CA) have been successfully obtained. ¹H NMR (CDCI₃): δ 0.8-1.1 (CW₃ of the fatty acids), 1.2-1.8 (CH₂ of the fatty acids), 1.9-2.4 (-CH₂C=0-), 2.7 (-C=C-CH₂-C=C-), 2.8-3.2 (-CH of the oxirane rings), 4.1 -4.3 (-CH₂-0-C=0), 5.2-5.6 (-CH=CH-).

[0066] The methoxylated soybean oil polyols (MSOLs) have been prepared by ring opening ESO prepared as just described with methanol.

Briefly, methanol (100 g), water (10 g), isopropanol (100 g) and fluoroboric acid (48% in water, 4.0 g) were mixed in a flask equipped with a magnetic stirrer and a dropping funnel. The resulting mixture was maintained at 40 °C and stirred vigorously, while the epoxidized soybean oil (100 g) was added dropwise. The reaction mixture was stirred for an additional 2 hrs at 50 °C, at which time ammonia (30% in water, 6 mL) was added to quench the reaction. After purification using the same methods used for the epoxidized soybean oil mentioned above, clear and viscous polyols with different hydroxyl numbers were obtained. The OH number of the MSOL was determined according to the Unilever method published by Lligadas, et al., Biomacromolecules, vol. 8, 686- 692 (2007), and the results are collected in Table 3.

Table 3. General properties of methoxylated soybean oil polyols (MSOLs).

[0067] Synthesis of the PU Dispersions.

[0068] Figure 2 depicts the approach used to prepare the anionic PU dispersions. The MSOL (15 g), IPDI and DMPA were added to a four-necked flask equipped with a mechanical stirrer, nitrogen inlet, condenser and thermometer. The molar ratio between the NCO groups of the IPDI, the OH groups of the MSOL and the OH groups of the DMPA is summarized in Table 4 following. The reaction was carried out at 78 °C for 1 hr under a dry nitrogen atmosphere and then 30 g of MEK was added to reduce the viscosity of the system. After an additional 2 hrs reaction, the flask contents were cooled to about 40 °C and then neutralized by the addition of TEA (1.2 equivalents per DMPA), followed by dispersion at high speed with distilled water to produce the anionic PU dispersions with a solids content of about 20 wt % after removal of the MEK under vacuum. [0069] Two groups of anionic PU dispersions were synthesized. In one group, we maintained a constant ratio between the diisocyanate, the polyol and the DMPA (entries 1 , 2, 5, 6 and 7 in Table 4), leading to PUs/PUDs with an increased polyol functionality. In the other, we have varied the molar ratio of the three components (entries 3, 4 and 5 in Table 4), affording PUs/PUDs with the same polyol functionality, but different hard segment content. The

corresponding PU films were obtained by drying the dispersions at room temperature in a glass mold. Table 4. Chemical composition, soluble fraction (SF) and crosslink density of the anionic PU films.

a Hydroxyl molar ratio of the MSOL (the number in parentheses denotes the OH number of the MSOL)

* Hydroxyl molar ratio of the DMPA.

c Hard segment content = Mass (IPDI + DMPA + TEA) Mass (MSOL + IPDI + DMPA +TEA)

[0070] Characterization, Analytical and Performance Methods.

[0071] The FT-IR spectra of the anionic PU films were recorded on a Nicolet 460 FT-IR spectrometer (Madison, USA), while the morphology of the SPU dispersions was observed on a transmission electron microscope (JEOL 1200EX). The dispersions prepared were diluted with distilled water to about 0.1 wt %. One drop of the diluted dispersion was placed on the coated side of a

200-mesh nickel grid in a petri dish and characterized after drying.

[0072] The soluble fraction of the anionic PU films was determined as follows. Samples of about 1g were cut from the films used in this study, weighed and then immersed in an excess of A/,/V-dimethylformamide (DMF) for 48 hrs at room temperature while stirring. Then the samples were removed from the solvent and dried under a vacuum at 80 °C for at least 24 hrs. The dried samples were then weighed, and the soluble fraction (SF) was calculated by

W - W

SF (%) = -! ^e- x 100%

W_t

where W and W_e are the weight of the initial and the extracted SPU films, respectively.

[0073] The dynamic mechanical behavior of the specimens was determined using a dynamic mechanical analyzer (TA instrument DMA Q800, USA) with tensile mode at 1 Hz and a heating rate of 5 °C/min in the

temperature range from -80 to 150 °C. The glass transition temperatures (T_gs) of the samples were obtained from the peaks of the tan δ curves.

[0074] Differential scanning calorimetry (DSC) was carried out on a thermal analyzer (TA instrument DSC Q20, USA). The samples were heated at a rate of 10 °C/min from 25 to 100 °C to erase thermal history, cooled to -70 °C at a cooling rate of 10 °C/min, and then heated again to 150 °C at a heating rate of 5 °C/min. The glass transition temperature (7^* _g) of the samples was determined from the midpoint temperature in heat capacity change of the second DSC scan. Samples of about 10-15 mg were cut from the films and used.

[0075] A Q50 thermogravimeter (TA instrument TGA Q50, USA) was used to measure the weight loss of the SPU films under an air atmosphere. The samples were heated from 100 to 650 °C at a heating rate of 20 °C/min.

Generally, 10-15 mg samples were used for the thermogravimetric analysis.

[0076] The mechanical properties of the SPU films were determined using an Instron universal testing machine (model-4502) with a crosshead speed of 50 mm/min. Rectangular specimens of 80 mm x 10 mm (length ^χ width) were used. An average value of at least five replicates of each sample was taken. The toughness of the polymer, which is the fracture energy per unit volume of the sample, was obtained from the area under the corresponding tensile stress-strain curve.

f0077T Results and Discussion

[0078] A) Structure and Morphology

[0079] The soybean oil employed in this work has 4.5 carbon-carbon double bonds per triglyceride. After epoxidization, some of the double bonds are converted into epoxy groups, which subsequently result in methoxylated soybean oil polyols (MSOLs) with OH functionality ranging from 2.4 to 4.0 after ring opening with methanol as shown in Table 3. All MSOLs obtained were clear, slightly yellow liquids. It is important to point out that the distribution of OH groups within the MSOL molecules varies from molecule to molecule. In fact, the OH numbers determined for the MSOLs is an average distribution of OH groups present in the triglycerides, which is responsible for the different properties and characteristics of these materials when compared with petrochemical-based polyols. This will play a key role in controlling the structure, morphology, and thermophysical and mechanical properties of the resulting anionic PL) films as discussed later.

[0080] Hydrogen bonding is a very important feature in PUs, which has a significant effect on the material properties. The hydrogen bonds involve the N- H bonds of the amide group as the donor, and the urethane carbonyl, the ether oxygen or the carbonyl group in the MSOL as the acceptor. Thus, FT-IR spectroscopy was used to investigate the hydrogen bonding in the anionic PU films to better understand the phase structure. The corresponding FT-IR spectra of the anionic PU films are shown in Figure 9. A single stretching band is observed at around 3336 cm^"1, which corresponds to the hydrogen-bonded N-H stretching vibration. A small shoulder peak at 3400-3500 cm^"1, attributed to non hydrogen-bonded N-H stretching, is relatively weak, indicating that most of the amide groups in the films are involved in hydrogen bonding. The IR spectra of the C=0 stretching region appears to be composed of three bands at around 1740, 1723 and 1710 cm^"1. The peak at 1740 cm^"1 is assigned to free C=0 stretching, while the peaks at 1723 cm^"1 and 1710 cm^"1 are due to hydrogen- bonded C=0 stretching. A urethane carbonyl stretch peak at roughly 1710 cm^"1 is attributed to hydrogen bonding in disordered regions. For the stronger hydrogen bonds in ordered or crystalline regions, stretching occurs at an even lower frequency, ranging from 1684 to 1702 cm^"1. The ordered hydrogen- bonded carbonyl band is not observed, indicating the amorphous nature of these PUs. The intensity ratio of the peaks corresponding to the hydrogen- bonded and the non hydrogen-bonded carbonyl groups is found to increase for SPU-176 [Figure 9a], when compared with that of SPU-135 [Figure 9b], suggesting that more hydrogen bonds may have been formed for SPU-176 than for SPU-135 and consequently there is an increased intermolecular interaction of the hard segments with the soft segments. This is because increasing the OH functionality of the soft segments leads to higher crosslinking and an increased urethane content in the resulting materials. For the SPU-149 series, the intensity of the band attributed to the hydrogen-bonded carbonyl groups, relative to the band attributed to the free carbonyl groups, increases with an increase in the hard segment content from 44 wt % to 47 wt %, indicating that the carbonyl groups in SPU-149II (Figure 9c) are hydrogen-bonded to a greater degree than those in SPU-149 (Figure 9d). In addition to this observation, it is clearly seen that the bonded N-H stretching shifts slightly to a lower wave number for SPU- 14911 when compared with SPU-149!, indicating an increase in the degree of association in the SPU films with higher hard segment content.

[0081] The dependence of the soluble fraction (SF) of the anionic PU films on the OH number of the MSOL is summarized in Table 4 . A trend towards decreasing soluble fraction of the films with an increasing OH number in the polyol is observed. As one would expect, when the OH number of the MSOL is increased, the resulting polyol with higher functionality has a greater chance of being incorporated into the network due to more reactive sites than a lower functionality polyol. This results in anionic PU films with relatively high crosslink densities, which will be confirmed later. The SPU-135 from the lowest functionality polyol, MSOL-135, contains around 30 wt % soluble fraction, while SPU-200 from the highest functionality polyol, MSOL-200, exhibits a soluble fraction of about 19 wt %. For the SPU films made from MSOL-149 with different hard segment contents (Table 4, entries 2-4), the soluble fraction is found to decrease from 23 wt % for SPU-149 with a 40 wt % hard segment content to 18 wt % for SPU-149II with a hard segment content of 47 wt %. As the hard segment content increases, the molar ratio of the diisocyanate to the hydroxyi of the polyols increases, which will insure more OH groups in the SOL will react, leading to a relatively low values for the soluble fraction.

[0082] Generally, several factors, such as the hydrophilicity, prepolymer viscosity, ionic group position, chain rigidity, and the chemical structure of the soft segment, play roles in influencing the particle size of the PL⁾ dispersions contemplated by the present invention. In general, the average particle size of the dispersions is not directly related to the physical properties of the resulting PL) films. However, control of the average particle size is important with respect to the particular application of the PU dispersions. For example, dispersions of relatively larger particles are preferred in surface coatings for rapid drying, and smaller particle sizes are desirable when deep penetration of the dispersion into a substrate is essential. The SPU-135 dispersion was observed to be clear with a slight blue color and exhibited an average particle size of about 12 nm diameter. The particle size of the PU dispersion increases with an increase in the OH functionality of the MSOL, and average particle sizes of approximately 60 and 130 nm diameter were observed for the SPU-149 and SPU-200 dispersions where the OH functionalities of the MSOLs were about 2.8 and 4.0, respectively.

[0083] In sum, the particle size of the dispersions from MSOLs with different hydroxyi functionality can be controlled in two ways. First, higher crosslinking can be obtained for the dispersions by increasing the OH

functionality of the polyols, which results in an increase in particle size.

However, as shown in Table 4, when the OH number of the MSOL increases, the amount of diisocyanate and DMPA in the system also increases in order to maintain a constant molar ratio between the NCO and OH groups. The increased content of hydrophilic DMPA should have the opposite effect.

Therefore, the increase in the particle size for the resulting dispersions with different OH functionality in this study must be due to the occurrence of higher crosslinking in the dispersions. When compared with SPU-149, SPU-149II exhibited a smaller particle size of approximately 30 nm diameter, indicating that the DMPA content seems to be a major governing factor in determining the particle size of the SPU dispersions from the same polyol. The relatively wide range of particle sizes from 12 nm diameter for SPU-135 to 130 nm diameter for SPU-200 suggests that the dispersions prepared by the present invention should be quite promising for applications from adhesives to elastomeric or hard coatings.

[0084] B) Thermal Properties.

[0085] The DSC thermograms of the anionic PL) films are shown in Figure 10. No melting or crystallization transition is observed in the DSC curves, indicating the amorphous nature of these PUs, which is in good agreement with the IR results. All samples show only one glass transition temperature (T_g) from 8.9 to 33.5 °C. The T_g value increases with an increase in the OH number of the MSOL. This is mainly due to the higher crosslinking in the soft segment due to an increase in the MSOL OH functionality and the increased content of the hard segments that provide more physical crosslinking through hydrogen bonding. For the films from MSOL-149 with different hard segment content, as shown in Figure 12, the T_g value increases from 14.9 to 24.7 °C with an increase in hard segment content from 42 to 47 wt %. This increase can be attributed to the restricted mobility of the polymer chains, due to the higher degree of hydrogen bonding between the hard segments and the soft segments.

[0086] DMA was used to investigate the dynamic mechanical behavior of the anionic PUD-derived films, since DMA is more sensitive than DSC to the mobility of the soft segments through relaxation at the molecular level. Figure 1 1 shows the storage moduli and tan delta values of the films from MSOLs with different OH numbers. At temperatures below 0 °C, the films are in the glassy state and their storage moduli (E) decrease slightly with increasing

temperature. Then, a rapid decrease in E value of roughly 3 orders of magnitude is observed in the temperature range from 0 to 100 °C,

corresponding to the primary relaxation process {a) of the resulting materials. This modulus decrease corresponds to an energy dissipation shown in the tan δ - T curve, where a maximum is observed in the tan δ curve. At higher temperatures, the modulus reaches a rubbery plateau, assigned to the rubbery state. As the OH number of the MSOL increases, the storage modulus of the resulting SPU film increases over the entire temperature range. The rubbery plateau modulus can be explained by qualitative consideration of the

crosslinking density (v_c) of the thermosets, according to the kinetic theory of rubber elasticity using the following equation:

E'= 3v_eRT

where 7_g is the glass transition temperature, E'is the storage modulus at 7^" _g + 40 °C, R is the gas constant and 7 is the absolute temperature at 7_g + 40 °C. The crosslink densities of the films increase with increasing OH number of the MSOL and are typically in the range of 6.7 x10¹ - 1.3 x10² mol/m³ as shown in Table 4. This indicates that the triglyceride arms are increasingly incorporated into the PL) networks as the OH number of the MSOL is increased, resulting in a higher crosslinked film with a resulting enhancement in the rubbery modulus.

[0089] The tan δ - 7 curves of the films show only one relaxation process, which involves energy dissipation and cooperative chain motions. When increasing the OH number of the MSOL from 135 to 200 mg KOH/g, the 7_gs of the resulting films shift from 38 to 82 °C, mainly due to the restricted movement of soft segment chains caused by higher crosslinking as mentioned above. In addition to higher crosslinking, there is an increase in the hard segment content, since we have maintained a constant molar ratio between the NCO and OH groups. This is another reason for the increase in 7_g of the resulting SPU films.

[0090] Figure 12 shows the storage moduli and tan δ values for the films with different hard segment content from MSOL-149. A shifting of the 7_g from 60 to 71 °C and an enhancement of the storage modulus are observed as the hard segment moieties increases from 42 to 47 wt %. This can be correlated to the increased number of urethane connections and the increase in intermolecular interactions caused by the hydrogen bonding, indicating a role for hard segments as physical crosslinks and fillers. [0091] Figure 13 shows the dependence of the 7^" _g of the anionic PU films on the OH number of the MSOL According to the Fox-Losheak equation relating the crosslinking density and T_g:

where T_QK is the glass transition temperature of the linear polymer of the same structure, v is the number of crosslinks per unit of volume (density/M_c), and K and / are constants for a given system, should be directly proportional to the OH functionality, provided that the conversion is complete in the system. As expected, a linear relationship between the OH number of the MSOL and the 7^" _g of the resulting film is observed over the range of OH numbers from 135 to 200 mg KOH/g, offering respectable r values of 0.998 and 0.980 for the data from the DMA and DSC analyses, respectively. The T_g values obtained from DMA analysis are relatively high, when compared with those from DSC. Such a difference is very common due to different nature between two methods. DSC measures the change in heat capacity going from frozen to unfrozen chains, whereas DMA measures the change in the mechanical response of these chains.

[0092] Typical TGA curves for the films from MSOLs with different OH numbers are shown in Figure 14, and the TGA data are summarized in Table 5 hereafter. Generally, polyurethanes exhibit relatively low thermal stability, due to the presence of labile urethane groups. The onset of urethane bond

dissociation is somewhere below 300 °C, depending upon the type of isocyanate and polyol employed. In the present study, the films undergo more than one thermal degradation process. The degradation of the films observed in the range of 150-300 °C can be attributed to decomposition of the urethane bonds, which takes place through dissociation to isocyanate and alcohol, the formation of primary amines and olefins, or the formation of secondary amines, resulting in loss of carbon dioxide from the urethane bond. The degradation processes in the temperature range of 300-400 °C are attributed to soybean oil chain scission. The last steps in the weight loss rate centered at a temperature of around 520 °C correspond to thermo-oxidative degradation of the films. For the films from MSOLs with different OH numbers, the temperature of weight loss due to dissociation of the urethane bonds increases with an increase in the OH number of the MSOL. For example, shifts from 280 °C to 249 °C and from 353 °C to 335 °C are observed for the temperature at which 10% (T₁₀) and 50% (T₅₀) degradation occurs, when the OH number of the MSOL increases from 130 to 200 mg KOH/g. This can be explained by the higher content of labile hard segments incorporated in the films in order to compensate for the higher OH number of the MSOL. However, the temperature of the maximum rate of weight loss, Tmax, increases with an increase in the OH number of the MSOL. This is indicative of the fact that higher crosslinking occurs in the films as the OH functionality of the MSOL is increased. For the films with different hard segment content from MSOL- 149, as the hard segment content increases, the Ti₀, Γ50 and Tmax all shift to lower temperatures, which is consistent with the increased presence. of weaker urethane bonds. The thermal stability of these novel anionic PU films is comparable to those of other waterborne PUs based on petroleum-based polyols, such as polytetramethylene glycol.

[0093] C) Mechanical Properties.

[0094]Table 5 summarizes the Young's modulus, tensile strength, elongation at break, and toughness of the anionic PUD-derived films from MSOLs with OH numbers ranging from 135 to 200 mg KOH/g, and typical tensile stress-strain behaviors are shown in Figure 15. The SPU-135 shows a rubbery modulus of 7.7 MPa, a viable ultimate tensile strength of about 4.2 MPa, an elongation at break of approximately 280% (Table 5, entry 1). When further increasing the OH functionality of the MSOL, the Young's modulus and ultimate tensile strength of the resulting SPU-149 obviously increase, but their elongation at break slightly decreases (Table 5, entry 2). Both SPU-135 and SPU-149 exhibit a strain recovery of 100% due to their relatively low crosslink densities, behavior similar to the tensile test behavior of an elastomeric polymer. However, the film SPU-176 exhibits behavior typical of a ductile plastic with a clear yield point and shows a modulus and a tensile strength approximately 41 and 3.6 times higher respectively than those of SPU-135. The higher functionality of MSOL-190 results in a relatively hard plastic SPU-190 (Table 5, entry 6), which exhibits yielding behavior, followed by strain softening. No strain hardening behavior is observed before the specimen breaks. The film SPU-200 from MSOL-200 exhibits characteristics of a very rigid plastic and breaks on the verge of its intrinsic yielding point. Its Young's modulus and ultimate tensile strength reach approximately 720 and 22 MPa (Table 5, entry 7), respectively. These changes in the mechanical behavior are a result of the increases in the crosslink density and hard segment content in the resulting films from the MSOLs with high average OH functionality.

[0095] Stress-strain tests not only afford the modulus and an indication of the strength of the material, but also its toughness. Toughness, defined as the amount of energy per volume that a material can absorb before rupturing, is the resistance to fracture of a material when stressed. Brittle materials have low toughness, while ductile materials are very tough. In a tensile test, the tensile strength and the elongation at break both contribute to the toughness of a material. The toughness of the resulting SPU films illustrated in Table 5 first increases with an increase in the OH number of the MSOL. It reaches a maximum of 23.7 MPa for the ductile plastic SPU-176 (Table 5, entry 5) and then gradually decreases. A rather low toughness of 2.1 MPa is observed for the rigid plastic SPU-200 (Table 5, entry 7), which is presumably due to nonuniform crosslinking in this material.

[0096] Generally, the concentration of hard segments and their intermolecular bonding with the soft segments play critical roles in the tensile behavior of a strained polyurethane material. For the films with different hard segment content from MSOL-149 (Table 5, entries 3-5), a substantial increase in Young's modulus from 56 to 410 MPa, tensile strength from 7.6 to 13 MPa, and toughness from 13.6 to 27 MPa are observed when the hard segment content is increased from 42 to 47 wt %, which is attributed to an increase in hydrogen bonding interactions in the film with a higher hard segment content. It is interesting to note in Figure 16 that the ductile plastic SPU-149II exhibits yielding behavior, although no clear strain softening is evident. Beyond the yield point, the deformation ceases to be elastic and the material starts to deform plastically. Then, this polymer exhibits strain hardening and finally breaks at the maximum strain. The toughness of the anionic PU films (Table 5, entries 3-5 ) significantly increases from 13.6 MPa for SPU-149 to 26.6 MPa for SPU-149II, when increasing the hard segment content from 42 to 47 wt %, due to an improvement in ductility caused by the filler effects of hard segments and the increased hydrogen bonding interactions in the SPU film with a higher hard segment content.

Table 5. Thermal and mechanical properties of the anionic PUD films.

TGA (°C) Mechanical properties

Sample T₅₀ £(MPa) a_b (MPa) fib (%) Toughness

(MPa)

SPU- 135 280 353 305/356 7.7 ±2.4 4.2 + 0.6 280.3124.4 7.210.2

SPU-149 273 350 315/360 55.814.8 7.610.2 273.512.2 13.610.4

SPU- 263 340 314/358 133.4121.6 11.310.9 247.616.3 20.310.7 1491

SPU- 259 334 310/359 410.5144.8 13.011.8 214.8114.1 26.610.2 149Π

265 339 316/364 318.51 15.010.3 196.719.4 23.710.5

SPU- 176

24.9

253 337 321/359 506.41 16.910.6 48.9113.5 8.010.1

SPU- 190

14.1

249 335 321/363 718.61 21.511.8 16.7111.6 2.110.4

SPU-200

58.1

Claims

CLAIMS What is claimed is:

1. A polyurethane resin that is the reaction product of an epoxidized or partially epoxidized triglyceride having an average hydroxyl functionality of 2.4 or greater, an isocyanate, and a functional diol to impart amphoteric, cationic, anionic character to the resultant polyurethane.

2. A polyurethane resin according to claim 1 , which is made from an epoxidized or partially epoxidized vegetable oil.

3. A polyurethane resin according to claim 2, wherein the vegetable oil is soy oil.

4. The polyurethane resin of any of claims 1-3, wherein the functional diol comprises one or more of tetrahydrofuran dimethanol, furandimethanol, isosorbide, sorbitan, saccharides, monosaccharides including dioses, such as glycolaldehyde;

trioses, such as glyceraldehyde and dihydroxyacetone; tetroses, such as erythrose and threose; aldo-pentoses such as arabinose, lyxose, ribose, deoxyribose, xylose; keto-pentoses, such as ribulose and xylulose; aldo-hexoses such as allose, altrose, galactose, glucose, dextrose, gulose, idose, mannose, talose; keto-hexoses, such as fructose, psicose, sorbose, tagatose;

heptoses, such as mannoheptulose and sedoheptulose; octoses, such as octolose and 2-keto-3-deoxy-manno-octonate; and nonoses, such as sialose; disaccharides including sucrose (known as table sugar, cane sugar, saccharose, or beet sugar), lactose, maltose, trehalose, cellobiose; oligosaccharides, such as raffinose (melitose), stachycose, and verbascose; glycerol, polyglycerols, plant fiber hydrolyzates, or fermentation products from plant fiber hydrolyzates.

The polyurethane resin of any of claims 1 through 4, wherein the resin is formed using a ring-opening agent selected from the group consisting of methanol, acetic acid, acrylic acid, and combinations of any thereof.

A polyurethane resin that is the reaction product of an epoxidized or partially epoxidized triglyceride, an isocyanate, and a functional diol to impart amphoteric, cationic, anionic character to the resultant polyurethane, having a characteristic heterogeneous network structure,

A polyurethane resin that is the reaction product of an epoxidized or partially epoxidized triglyceride, an isocyanate, and a functional diol to impart amphoteric, cationic, anionic character to the resultant polyurethane, wherein the process of forming the resin includes a degree of ring opening of epoxide groups in the epoxidized triglyceride.

A polyurethane resin according to either of claims 6 or 7, which is made from an epoxidized or partially epoxidized vegetable oil.

A polyurethane resin according to claim 8, wherein the vegetable oil is soy oil.

A dispersion of polymer particles in a continuous aqueous phase, wherein the dispersed particles include a polyurethane resin as characterized in any of claims 1-9.

The dispersion of claim 6, characterized by an average particle size from 12 nanometers to 130 nanometers.

12. Use of a resin or a dispersion of a resin as characterized in any of claims 1- 1 1 in a coating, binder, adhesive, sealant, paint, fiber, elastomer, synthetic skin, or foam.

13. A film formed from a dispersion of polymer particles in a

continuous aqueous phase per claim 10, wherein the film is characterized as having a single glass transition temperature.

14. The film of claim 13, wherein the glass transition temperature value is 8.9 to 34.5 °C.