Fine fibers made from reactive additives

1. A method of making fine fibers, the method comprising:

providing at least one fiber-forming polymer;

providing at least two reactive additives reactive with each other, and optionally reactive with the fiber-forming polymer, wherein the at least two reactive additives are not themselves fiber-forming;

combining the at least one fiber-forming polymer and the at least two reactive additives under conditions effective to form a plurality of fine fibers, wherein the fine fibers have an average diameter of less than 5 microns; and

post-treating the fine fibers under conditions effective to form covalent bonds between the at least two reactive additives and optionally to react at least one of the reactive additives with at least one fiber-forming polymer;

with the proviso that:

at least one of the reactive additives is not a resinous aldehyde composition;

at least one of the reactive additives is an alkoxy-functional reactive additive, a hydroxyl-functional reactive additive, an acid-functional reactive additive, a glycidyl ether-functional reactive additive, an isocyanate-functional reactive additive, an amine-functional reactive additive, and/or a dichloro-functional reactive additive; and

if at least one of the fiber-forming polymers is a polyamide, then none of the reactive additives is a polyamide.

2. A method of making fine fibers, the method comprising:

providing at least one fiber-forming polymer;

providing at least two reactive additives reactive with each other, and optionally reactive with the fiber-forming polymer, wherein the at least two reactive additives are not themselves fiber-forming;

combining the at least one fiber-forming polymer and the at least two reactive additives under conditions effective to form a plurality of fine fibers, wherein the fine fibers have an average diameter of less than 5 microns; and

post-treating the fine fibers under conditions effective to form covalent bonds between the at least two reactive additives and optionally to react at least one of the reactive additives with at least one fiber-forming polymer;

with the proviso that:

at least one of the reactive additives is not a resinous aldehyde composition; and

at least one of the reactive additives has a weight average molecular weight of less than 3000 Daltons.

3. The method of claim 2 further comprising forming covalent bonds between the at least two reactive additives and optionally reacting at least one of the reactive additives with at least one fiber-forming polymer during the combining step.

4. The method of claim 2 wherein post-treating the fine fibers comprises subjecting the fine fibers to conditions effective to form covalent bonds between at least one of the reactive additives and at least one fiber-forming polymer.

5. A fine fiber prepared by a method comprising:

providing at least one fiber-forming polymer;

providing at least two reactive additives reactive with each other, wherein at least one of the reactive additives is reactive with the at least one fiber-forming polymer, and wherein the at least two reactive additives are not themselves fiber-forming;

combining the at least one fiber-forming polymer and the at least two reactive additives to form a plurality of fine fibers, wherein the fine fibers have an average diameter of less than 5 microns, wherein the fine fibers comprise a core phase and a coating phase, and wherein the core phase comprises the at least one fiber-forming polymer and the coating phase comprises the at least two reactive additives; and

post-treating the fine fibers under conditions effective to form covalent bonds between the at least two reactive additives and to react at least one of the reactive additives with the at least one fiber-forming polymer;

with the proviso that:

at least one of the reactive additives is not a resinous aldehyde composition; and

if the fiber-forming polymer is a polyamide, then none of the reactive additives is a polyamide.

6. A fine fiber prepared by a method comprising:

providing at least one fiber-forming polymer;

providing at least two reactive additives reactive with each other, wherein at least one of the reactive additives is reactive with the at least one fiber-forming polymer, and wherein the at least two reactive additives are not themselves fiber-forming;

combining the at least one fiber-forming polymer and the at least two reactive additives to form a plurality of fine fibers, wherein the fine fibers have an average diameter of less than 5 microns, wherein the fine fibers comprise a core phase and a coating phase, and wherein the core phase comprises the fiber-forming polymer and the coating phase comprises the at least two reactive additives; and

post-treating the fine fibers under conditions effective to form covalent bonds between the at least two reactive additives and to react at least one of the reactive additives with the at least one fiber-forming polymer;

with the proviso that:

at least one of the reactive additives is not a resinous aldehyde composition; and

at least one of the reactive additives has a weight average molecular weight of less than 3000 Daltons.

7. A fine fiber prepared by a method comprising:

providing at least one fiber-forming polymer;

providing at least two reactive additives reactive with each other, and not reactive with the at least one fiber-forming polymer, wherein the at least two reactive additives are not themselves fiber-forming;

combining the at least one fiber-forming polymer and the at least two reactive additives to form a plurality of fine fibers, wherein the fine fibers have an average diameter of less than 5 microns, wherein the fine fibers comprise a core phase and a coating phase, and wherein the core phase comprises a fiber-forming polymer and the coating phase comprises the at least two reactive additives; and

post-treating the fine fibers under conditions effective to form covalent bonds between the at least two reactive additives;

with the proviso that:

at least one of the reactive additives is not a resinous aldehyde composition;

at least one of the reactive additives is tri-functional or higher; and

if at least one of the fiber-forming polymers is a polyamide, then none of the reactive additives is a polyamide.

8. A fine fiber prepared by a method comprising:

providing at least one fiber-forming polymer;

providing at least two reactive additives reactive with each other, and not reactive with the at least one fiber-forming polymer, wherein the at least two reactive additives are not themselves fiber-forming;

combining the at least one fiber-forming polymer and the at least two reactive additives to form a plurality of fine fibers, wherein the fine fibers have an average diameter of less than 5 microns, and wherein the fine fibers comprise a core phase and a coating phase, wherein the core phase comprises a fiber-forming polymer and the coating phase comprises the at least two reactive additives; and

post-treating the fine fibers under conditions effective to form covalent bonds between the at least two reactive additives;

with the proviso that:

at least one of the reactive additives is not a resinous aldehyde composition;

at least one of the reactive additives is tri-functional or higher; and

at least one of the reactive additives has a weight average molecular weight of less than 3000 Daltons.

9. The fine fiber of claim 8 wherein at least one of the reactive additives is a surface-migrating agent.

10. The fine fiber of claim 9 wherein the surface-migrating agent is also a crosslinking agent.

11. The fine fiber of claim 10 wherein at least a portion of at least one fiber-forming polymer is crosslinked by the surface-migrating crosslinking agent.

12. The fine fiber of claim 11 wherein the at least one surface-migrating crosslinking agent is a resinous aldehyde composition.

13. A fine fiber comprising:

a core phase comprising at least one fiber-forming polymer;

a coating phase comprising at least two reactive additives that are covalently bonded to each other and that are not themselves fiber-forming;

wherein the at least two reactive additives are optionally covalently bonded to the fiber-forming polymer;

wherein at least one of the reactive additives is self-condensed;

wherein at least one of the reactive additives enhances at least one property of the fine fiber compared to the fine fiber without such reactive additive;

wherein at least one of the reactive additives is not a resinous aldehyde composition; and

wherein the fine fiber has an average diameter of less than 5 microns.

14. The fine fiber of claim 13 wherein at least one of the reactive additives is covalently bonded to at least one of the fiber-forming polymers.

15. A fine fiber comprising a core phase and a coating phase, wherein:

the core phase comprises at least one fiber-forming polymer and the coating phase comprises at least one surface-migrating agent, wherein the surface-migrating agent is capable of migrating to the surface of the fine fiber;

the fine fiber includes at least a second additive that is covalently bonded to the surface-migrating agent and optionally is covalently bonded to the fiber-forming polymer, and enhances at least one property of the fine fiber compared to the fiber without such additive;

the fine fiber has an average diameter of less than 5 microns;

at least a portion of the at least one fiber-forming polymer is crosslinked by at least one of the surface-migrating agent and the second additive; and

at least one of the additives is not a resinous aldehyde composition.

16. The fine fiber of claim 15 wherein the at least one property is a surface property of each fiber or a bulk property of each fiber.

17. The fine fiber of claim 15 wherein the at least one surface-migrating agent is a resinous aldehyde composition.

18. The fine fiber of claim 15 wherein the at least one property is selected from hydrophobicity, hydrophilicity, oleophobicity, oleophilicity, thermal stability, chemical stability, inter-fiber adhesion, adhesion to a substrate, antistatic, conductivity, stain resistance, water and/or oleo resistance, vibration damping, acoustic damping, and combinations thereof.

19. A filter media comprising a filtration substrate and a layer comprising a plurality of fine fibers of claim 15 disposed on the substrate.

20. A filter element comprising a filter media of claim 19 .

21. The fine fiber of claim 13 wherein at least one of the reactive additives is an alkoxy-functional reactive additive, a hydroxyl-functional reactive additive, an acid-functional reactive additive, a glycidyl ether-functional reactive additive, an isocyanate-functional reactive additive, an amine-functional reactive additive, and/or a dichloro-functional reactive additive.