Hybrid polymer materials

Details Hybrid polymer materials Hybrid polymer materials

2000-12-06

2003-02-11

Acquah, Samuel A. (Department: 1711)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

C428S364000, C525S050000, C525S055000, C525S056000, C525S066000, C525S420000, C525S540000, C527S103000, C527S200000, C527S201000, C527S203000, C527S207000, C527S300000, C527S311000, C527S312000, C527S313000, C527S400000, C527S600000

Reexamination Certificate

active

06517933

ABSTRACT:

FIELD OF THE INVENTION
This invention is directed to the field of polymer materials, and more particularly to hybrid polymer materials useful for fiber, plastic, and elastomer applications.
BACKGROUND OF THE INVENTION
Naturally occurring polymers, such as cellulose (e.g. cotton and starch) and polyamides (e.g. structural and soluble proteins such as wool or silk) have found widespread usage in the fiber and apparel industries. Cotton- and wool/silk-based clothing articles and home furnishing items are comfortable to wear and are characterized by their superior tactile properties. However, these materials have other characteristics that are often considered to be negative, such as wrinkling; the potential to shrink upon laundering; poor resistance to mildew, moths, or bacteria; and poor flame resistance.
Over the years, a number of chemical finishing agents have been employed in an attempt to improve the properties of natural fibers. For example, crosslinking agents (resins) have been explored to achieve wrinkle resistance and durable-press properties. Resins improve wrinkle recovery, fabric smoothness, dimensional stability, washfastness of some dyes, pilling resistance, ease of ironing, durability of finishes (repellents, hand modifiers, embossing, etc.), and general appearance. However, the presence of the resins also results in losses in tear strength, tensile strength, abrasion resistance, reduced moisture regain, possible damage due to chlorine retention, potential odors, potential discoloration, and sewing problems. Durable-press fabrics also often have stiff, harsh, uncomfortable fabric tactile (hand) properties.
Fabric softeners/lubricants are commonly added to resin-treated fabrics to mitigate some of these deficiencies. Softeners improve the hand of the fabric and increase abrasion resistance and tear strength. However, softeners suffer from a lack of durability to repeated launderings.
Flame-retardants and antibacterial agents have also been applied to natural fibers. However, if they are used in molecular form, they will typically be rapidly leached from the fabric during home laundering and commercial dry-cleanings. To slow their release, they can be dispersed in a polymeric matrix. However, application of such a finish can alter the hand of the fabric.
Synthetic fibers are robust, and can be engineered to exhibit wide-ranging mechanical behavior. They are, however, generally less comfortable to wear than naturally occurring polymers. Much of this perceived discomfort is associated with the lower level of moisture absorption and perspiration transport. The synthetic materials generally possess desirable mechanical performance properties, such as wrinkle resistance, high modulus and strength, and in certain cases, unusual elasticity.
Among the most commonly known synthetic fibers are polyesters and polyamides (nylons). A polyester fiber is manufactured from a substance composed of an ester of a dihydric alcohol and a diacid (such as terephthalic acid). The most widely used polyester is made from the linear polymer of poly(ethylene terephthalate); other examples are poly(butylene terephthalate) and poly(trimethylene terephthalate). Certain polyesters can be engineered with hard and soft segments, forming polyester elastomers. Examples include the Hytrel® series from DuPont. Polyamides contain recurring amide groups as integral parts of the main polymer chains, both aliphatic and aromatic versions, are possible. Aliphatic forms include Nylon 6 (formed from caprolactam) and Nylon 6,6 (formed by hexamethylene diamine and adipic acid), whereas aromatic forms are exemplified by Nomex® (formed of m-phenylene isophthalamide), Kevlar® (formed by p-phenylene diamine and terephthalic acid), and PBI fiber. Polyamides can be shaped into fibers and other forms by standard processes such as spinning, film formation, extrusion, and injection molding.
Other synthetic fibers based on organic synthesis combining hard and soft segments include spandex such as DuPont's Lycra®, which is an alternating linear combination of an aromatic polyurethane block and polyethylene glycol elastomeric block, or DuPont's Tactel®, which has properties of both nylon and spandex. Exceptional elasticity can be achieved by such specially designed microphase-separated morphology of the block copolymer.
Despite the above synthetic accomplishments, little has been attempted in the direction of combining naturally occurring materials and synthetic materials on the nanoscopic level. Nanoscopic mixing begins with the engineering of fundamental molecular building blocks. Existing standard methods of increasing the range of properties and usefulness of cellulosic fibers include (1) formation of blends and composites of cellulosic and synthetic fibers, (2) chemical modification of cellulose (such as cellulose acetate), (3) production of regenerated cellulose (e.g. rayon), and (4) formation of graft copolymers. Indeed, graft copolymers made from cellulose have been intensively studied in the literature, chiefly in the area of vinyl copolymers. Free-radical initiation techniques, often involving high-energy radiation, are used. The resulting systems are heterogeneous on a macroscopic scale, and downstream processing is very difficult to manage.
SUMMARY OF THE INVENTION
This invention is directed to a hybrid polymer material or system that combines naturally occurring building blocks with synthetic building blocks. These hybrid polymers combine the comfort attributes of natural materials with the robustness and design properties of synthetic materials.
More particularly, the hybrid polymers of the invention comprise i) natural materials, as one set of building blocks; and ii) synthetic materials (e.g., those having ester, amide, and acrylate/methacrylate groups) as a second set of building blocks. The natural material building blocks may be comprised of polysaccharides, cellulose and its derivatives (e.g., digested, chemically modified cotton), and polypeptides and derivatives thereof (e.g., digested low grade wool). The building blocks include reactive functional groups, which act as linkages to complete the hybrid architecture. The sets of naturally occurring and synthetic building blocks are mixed and joined on a molecular or nanoscopic level via the reactive functional groups to give homogeneous or microphase-separated morphologies to the resulting mixed polymer system.
The hybrid polymer of the invention may be comprised of an alternating linear combination of naturally occurring building blocks and synthetic building blocks, a random linear combination of natural and synthetic building blocks, a statistical linear distribution of natural and synthetic building blocks, or combinations of these. The hybrid polymer may include diblock, triblock, and multiblock morphologies, as well as graft copolymer morphologies. Alternatively, the hybrid polymer may comprise a crosslinked network, which would occur if two sets of monomers or prepolymers were mixed together. In another embodiment, the hybrid polymer comprises hard or crystalline sections of naturally occurring building blocks linked together by soft or rubbery sections of synthetic building blocks.
The hybrid polymers of this invention are suitable for fiber spinning, as well as for plastic or rubbery object shaping by film formation, injection molding, extrusion and other compounding techniques. The specific properties of the polymer are determined by the molecular design of the component building blocks and the exact composition of the hybrid polymer. The resulting unique materials offer both natural appeal and synthetic robustness.
DETAILED DESCRIPTION OF THE INVENTION
The hybrid polymer materials of the present invention comprise a set of naturally occurring building blocks and a set of synthetic building blocks, the two sets of building blocks being combined at a molecular level via chemical bonds. This gives polymeric materials that are homogeneous or microphase-separated, and also allows for the design of final polymers exhibiting desirable char

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