~™ II 1 1 III II IMI II III 1 1 II II II I II (19) J European Patent Office Office europeen des brevets (11) EP 0 763 61 1 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication:ation: (51 ) |nt. CI.6: D01 F 8/1 2, D01 F 8/1 4 19.03.1997 Bulletin 1997/12 (21) Application number: 96112702.4 (22) Date of filing: 07.08.1996 (84) Designated Contracting States: (72) Inventor: Simons, Holmes F. DE FR GB Charlotte, North Carolina (US) (30) Priority: 23.08.1995 US 518627 (74) Representative: von Kreisler, Alek, Dipl.-Chem. et al (71 ) Applicant: HOECHST CELANESE CORPORATION Patentanwalte, Somerville, N.J. 08876 (US) von Kreisler-Selting-Werner, Bahnhofsvorplatz 1 (Deichmannhaus) 50667 Koln (DE) (54) Polyester/polyamide composite fiber (57) An improved polyester/polyamide composite fiber is provided. The composite fiber includes a polya- mide component generally considered to lack compati- bility with a polyester component. Advantageously, the composite fiber includes an adhesion-promoting poly- mer in an amount effective to provide adhesion of the polyamide component to the polyester component. The composite fiber beneficially provides strength and cost advantages. CO CO CO o Q_ LU Printed by Rank Xerox (UK) Business Services 2.13.17/3.4 1 EP 0 763 611 A1 2 Description looked. Despite advances in the prior art, there continues to Field of the Invention be a need for commercially advantageous, polyes- ter/polyamide composite fiber, and in particular for This invention relates to composite fiber. 5 core/sheath heterofil. While there are polyamides that adhere to polyesters, they are expensive specialty poly- Background of the Invention mers, some also of poor physical properties; thus, a need exists for producing adhesion between polyesters Polyester/polyamide composite fiber has a problem and inexpensive commodity polyamides such as nylon of separation, also called fibrillation or presplitting, 10 6 and nylon 6.6, with good physical properties. between the polyester component and the polyamide component. According to U.S. Patent No. 3,489,641 to Summary of the Invention Harcolinski et al, this problem is due to inherent incom- patibility, and may be overcome by use of a certain mod- In accordance with the present invention, improved ified polyester. Harcolinski et al describe nylon 6.6, 15 polyester/polyamide composite fiber is provided. The nylon 6, and polyhexamethylene suberamide as espe- fiber includes a polyamide component generally consid- cially suitable polyamides for combination with the mod- ered to lack compatibility with a polyester component ified polyester. such as nylon 6 or nylon 6.6, and in addition, an adhe- Southern, Martin and Baird, Textile Research Jour- sion-promoting polymer in an amount effective to pro- nal, pp. 411 (1980) describe improved sheath/core 20 vide adhesion of the polyamide component to the adhesion by the use of interface mixing after forming a polyester component. The adhesion-promoting polymer composite melt stream. Nylon 6.6 sheath/PET core het- is beneficially compatible with the polyamide compo- erofil is spun. However, this approach is commercially nent so as to be blendable therewith. By the term "poly- difficult when spinning multiple monofils from a single mer" is meant a high molecular weight, chain-like spinneret. 25 structure formed from monomeric units. U.S. Patent No. 4,620,925 to Bond teaches that a nylon sheath on a polyester core will lack the required Brief Description of the Drawing sheath/core adhesion. Bond describes avoiding the adhesion problem by using either a nylon core with a Reference is now made to the accompanying draw- sheath made from nylon 11, nylon 12, nylon 6.10 or 30 ing, which forms a part of the specification of the nylon 6.12, or a polyester core with a sheath made from present invention. copolyetherester. Bond provides the sheath/core fila- ment thereof with antistatic characteristics by the addi- Figure 1 depicts the clean break observed for the tion of 20 to 30 wt.% carbon to the sheath. polyester core/polyamide sheath monofilament of U.S. Patent No. 4,457,974 to Summers teaches the 35 Example 1 ; use of polyester substantially free of antimony to over- Figure 2 depicts the sheath/core separation come presplitting, and describes nylon 6.6, nylon 6, and observed when prior art monofilament is tested at polyhexamethylene suberamide as suitable polyamides break point; and for the polyester/polyamide composite fiber. In the Figure 3 is a cross-sectional view of a non-woven Background portion of the patent, Summers observes 40 fabric made from composite fiber in accordance that presplitting can be reduced by including aminopro- with the present invention. pylmorpholine and bishexamethylenetriamine in the nylon component. Detailed Description of the Invention According to U.S. Patent No. 5,380,477 to Kent et al, bicomponent spinning will allow two normally incom- 45 According to the present invention, polyester/polya- patible polymers to form strong materials without the mide composite fiber that makes use of inexpensive use of compatibilizing agents. Kent et al broadly commodity polyamides, is provided. The term "fiber" as describe a matrix component selected from virtually any used herein, refers to a unit of matter that forms the thermoplastic material, for instance, polyamides (such basic elements of fabrics and other textile structures. as nylon 6, nylon 6.6, nylon 6.6T, nylon 4.6, nylon 8, so Non-limiting examples of the foregoing definition are nylon 6.10, nylon 1 1 and nylon 12), polyolefins (such as monofilaments, multifilaments, yarns and so forth. The polypropylene, polyethylene, polytetrafluoroethylene fiber may be monofil or a bondable sewing thread, or and polyphenylene ether), polyesters, polyimides, may be made into a fabric, for instance, a spunbonded polysulfones, polyphenylenesulphide, polyvinyls, poly- fabric, paper machine clothing, or a reinforcement struc- ethyleneglycol, styrene-containing copolymers and so 55 ture such as a tire reinforcement structure. Beneficially, forth, and copolymers and blends. The examples teach the fiber has improved strength compared to non-adher- a bicomponent fiber consisting of a PET core and a ing polyester/polyamide composite fiber. nylon 6 sheath, but sheath/core separation during Composite fiber in accordance with the present stretching or drawing of this fiber, and in use, is over- invention, beneficially includes a polyester component, 2 3 EP 0 763 611 A1 4 and in particular polyethylene terephthalate. Other use- ficially, the adhesion-promoting polymer is a polyester- ful polyesters include polybutylene terephthalate. This adhering polyamide, and is miscible in the melt state component beneficially provides characteristics such as with the polyamide component. Particularly useful as strength and dimensional stability to the fiber. Unlike the adhesion-promoting polymer are nylon 1 1 , nylon 12, Summers, it is unnecessary for a polyester useful in the 5 nylon 6.10, nylon 6.12 and blends thereof; however, as present invention, to be free of antimony. may be understood, other adhesion-promoting poly- The term "polyethylene terephthalate" as used mers may be used. This type of polyamide is typically an herein, is used generally to include polymers made by expensive specialty polymer, and may have poor physi- condensing ethylene glycol with terephthalic acid or cal properties. dimethyl terephthalate, no matter how prepared. Fur- 10 I have noted that nylon 1 1 , nylon 1 2, nylon 6. 1 0 and thermore, this term is meant to include polyethylene nylon 6.12 each has a melting point less than that of the terephthalate polymers modified by the inclusion of inherently incompatible polyamide component. While minor amounts, e.g., less than about 25 percent by intending not to be bound by any particular theory at this weight of the polymer, of conventional co-monomers or time, it may therefore be that a relatively lower melting modifying agents, as is well known. Such co-monomers 15 point permits the adhesion-promoting polymer to exude or modifying agents include various diols such as 1 ,4- to the polyester interface to form a tie layer between the butanediol, cyclohexanedimethanol, diethylene glycol polyester and inherently incompatible polyamide. Bene- and 1 ,3-propanediol. Likewise, such co-monomers or ficially, such a tie layer would be axially generally uni- modifying agents may include various aliphatic or aro- form so as to provide adhesion along the entire matic diacids such as isophthalic acid and naphthalene 20 polyester interface. Alternatively, it may be that amide dicarboxylic acid. In addition, this term is meant to interchange in the melt state of a mixture of the inher- include a polyethylene terephthalate polymer blended ently incompatible polyamide and the adhering polya- with a minor amount, e.g., less than about 25 percent by mide, results in a block co-polymer with blocks of weight, of a polyester such as a polyethylene 2,6-naph- adhering polyamide in the molecular chain of the non- thalene dicarboxylate. Accordingly, polyethylene tereph- 25 adhering polyamide. Analysis has indicated some co- thalate homopolymer, a copolymer containing polymer formation when nylon 6 and nylon 1 2 are com- polyethylene terephthalate in a major amount, or a pol- bined in the melt state. yester blend containing polyethylene terephthalate in a The amount of the adhesion-promoting polymer in major amount, is a suitable polyester. the polyamide component will vary depending upon fac- The polyester component may also be a thermo- 30 tors including the particular adhesion-promoting poly- tropic LCP, and in particular may be a wholly aromatic mer selected, and the desired degree of adhesion to the polyester. Thermotropic LCPs exist in a liquid-crystal- polyester component. Thus, for greater adhesion, a rel- line state above their melting point, are melt processa- atively larger loading will be used, whereas for less ble, and are useful for the manufacture of high strength adhesion, a relatively smaller loading will be used.