WO2009045786A1

WO2009045786A1 - Oriented, halogen-free, flame retardant thermoplastic yarns and textile structures made therefrom

Info

Publication number: WO2009045786A1
Application number: PCT/US2008/077336
Authority: WO
Inventors: Timothy D. O'brien; Gerry Bissonnette
Original assignee: Astenjohnson, Inc.
Priority date: 2007-09-28
Filing date: 2008-09-23
Publication date: 2009-04-09

Abstract

An oriented, halogen-free flame retardant thermoplastic filament or yarn having physical properties, in particular tensile strength and elongation, that are similar to (or at least approach) those obtained from comparable filaments or yarns which do not provide any, or only limited, flame retardancy properties, as well as woven or braided components made from such yarns is provided. The yarns are made from a polymer blend of a first polymeric component that is a PET polyester having an organic phosphorus compound backbone with an Intrinsic Viscosity of at least 0.95, and a second component that is a polyester flame retardant concentrate based on an organic phosphonated ester which is combined with a polyester.

Description

[0001] ORIENTED, HALOGEN-FREE, FLAME RETARDANT

THERMOPLASTIC YARNS AND TEXTILE STRUCTURES MADE THEREFROM

[0002] FIELD OF THE INVENTION

[0003] The invention concerns oriented, halogen-free, flame retardant thermoplastic yarns formed of a composition that comprises: a) a polyester polymer including an organic phosphorus compound, and b) a polyester flame retardant concentrate based on an organic phosphonated ester. It is further concerned with monofilaments and fibers formed from the halogen-free flame retardant thermoplastic composition, as well as braided, woven and spirally formed textile structures including the novel yarns. The oriented yarns of the invention exhibit physical properties rendering them suitable for use in various aerospace, automotive and other industrial textile applications.

[0004] BACKGROUND OF THE INVENTION

[0005] Most thermoplastics are flammable and burn easily when heated to a high enough temperature. Thermoplastics containing fire retardants are widespread and their use in homes, offices, automobiles, mass transit vehicles, etc, is well known and frequently mandated by a number of regulations in building codes or by industry-specific standards.

[0006] Plastics combust through a process that begins as heat in the pre- ignition phase and progresses to fire which breaks down their long-chain structure into volatile hydrocarbons, hydrogen and hydroxyl-free radicals. Flame retardants work by interfering either chemically or physically with one or more of the available fuel, oxygen and source of ignition. Flame retardants are added to polyolefins, polycarbonates, polyamides, polyesters and other polymers to increase resistance to ignition, reduce flame spread, suppress smoke formation, and prevent dripping. Flame retardants are often categorized as either halogen- containing, or halogen-free. The most commercially viable flame retardants include brominated, chlorinated and phosphorus based types, and metallic oxides.

[0007] The term "halogen-free" refers to flame retardant products which do not contain compounds derived from any of the non-metallic elements in Group 17 of the periodic table, namely: fluorine, chlorine, bromine, iodine and astatine. Conversely, halogen-containing flame retardant compounds are those which contain one or more of these non-metallic elements from Group 17, examples of which include Teflon® (which contains fluorine) and PVC, or polyvinyl chloride (contains chlorine). Halogens are often incorporated into thermoplastics because they enable the manufacturer to produce a product having performance characteristics that are difficult to duplicate at the same cost in similar halogen-free plastics. However, halogen-free plastic products are in demand because of a concern that halogen-containing compounds will release corrosive and toxic gases if ignited in a fire. The toxicity of smoke is perhaps of highest concern within closed spaces where escape is limited, such as in rail cars, aircraft, ships and the like.

[0008] Many halogen-free flame retardant thermoplastic products are presently available on the market, but none will permit the manufacture of a monofilament yarn that will meet the high physical test requirements for woven or braided structures, no matter what amount of active ingredients are incorporated. This is due, in part, to the relatively low tensile strength and similar physical properties obtained in these prior art halogen-free yarns.

[0009] SUMMARY

[0010] It would be desirable to have a halogen-free thermoplastic material which can be used to produce fiber-like products with physical properties similar to those available in comparable thermoplastic filaments or yarns containing halogen, but which will not produce toxic and corrosive fumes upon ignition. [0011] The present invention provides such a filament or yarn product to address this perceived need.

[0012] The present inventors have discovered that it is possible to produce an oriented, halogen-free flame retardant thermoplastic filament or yarn having physical properties, in particular tensile strength and elongation, that are similar to (or at least approach) those obtained from comparable filaments or yarns which do not provide any, or only limited, flame retardancy properties. The inventors have discovered that a polymer blend of two commercially available products, which have not previously been combined in the disclosed amounts, will allow for the production of an oriented flame retardant thermoplastic monofilament which meets the stringent requirements of the automotive and aerospace industries. Further, the inventors have discovered that, by treating one of the polymer components so as to increase its intrinsic viscosity, it is possible to provide an oriented yarn made from the polymer blend which will have sufficient tensile strength and elongation properties to make it suitable for use in braiding or weaving processes to produce sleeving and the like. It is believed that it will also be possible to produce relatively smaller diameter fibers from the same polymer blend which will find application in e.g. non-wovens.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing Summary as well as the Detailed Description that follows of the preferred embodiment of the invention will be better understood when read in conjunction with the appended drawing. In the drawings:

[0015] Figure 1 shows a flow diagram of the process of making an oriented, halogen-free, flame retardant thermoplastic yarn according to a preferred embodiment of the invention.

[0016] Figure 2 is a perspective view of a braided sleeve made with the yarns produced according to the invention.

[0017] Figure 3 is a woven fabric of the yarns in accordance with the present invention.

[0018] DETAILED DESCRIPTION OF THE PREFERREDEMBODIMENT(S) [0019] Certain terminology used in the present application should be considered as having the following meanings: The terms "a" and "one" are defined as including one or more of the referenced item unless specifically noted. Yarn means any monofilament, multifilament, cabled, wound or other type of fiber strand, that can be used in braiding, weaving, or forming non-woven products.

[0020] Referring to the Figure, the yarns of this invention are presently produced from a polymer blend made from two commercially available products, however, other similar products may be suitable. The two products presently used as components in the blend are:

[0021] Component A) Invista's Avora® Plus flame retardant PET type 8934 polyester. This is a polyethylene terephthalate polyester which has been "solid stated" (i.e. the polymer chain length is increased in a well known manufacturing process involving heat and vacuum) in order to increase the intrinsic viscosity of the polymer from that supplied commercially by the manufacturer (typically about 0.65) to approximately 0.95 or more. Intrinsic viscosity as used herein is determined according to the test method described in ASTM D 4603-96 (with a bath temperature of 3O⁰C and the solvent being a 60/40 blend of phenol and 1.1.2.2. tetrachloroethane). This test method relates to determination of "inherent viscosity"; intrinsic viscosity is similar to inherent viscosity except that the amount of solvent in the measurement is zero. As an alternative to "solid stating", the intrinsic viscosity can be increased by other methods, such as post condensate polymerization.

[0022] Avora® Plus flame retardant (FR) PET type 8934 is available from the Invista company whose corporate headquarters are located at: INVISTA Building, 4123 East 37th Street North, Wichita, KS 67220. According to information currently available from the Invista company, Avora® polymers incorporate a proprietary organic phosphorus compound into the "backbone" of the polyester polymer (i.e., the organic phosphorous compound is reacted directly into the polyester polymer). This appears to be important with respect to the flame retardancy properties of the polymer product produced in this invention. The Avora® FR polyester has a lower melting point than other, similar, polyesters which causes fibers comprised of the polymer to shrink away from flames. Further, the phosphorus component prevents dripping and further burning by rendering the material self-extinguishing. Combustion gases from Avora® are similar to regular polyester and are composed primarily of carbon monoxide (CO), carbon dioxide (CO₂), and water vapor, as well as small quantities of organic compounds which contain primarily aldehyde and keto groups. Gases such as hydrochloric acid (HCI), dioxins, hydrogen cyanide (HCN), nitrous oxides (NO) or sulfur dioxides (S O₂) are not present. The Avora® polymer does not contain any brominated compounds. Figure 1 shows Component A being provided in Box 10.

[0023] Component B) Devan Chemicals' @2 spin PES 278™ concentrate, a polyester flame retardant concentrate based on an organic phosphonated ester and which is combined with a polyester such as PBT (polybutylene terephthalate). This material is composed of a proprietary formulation based on phosphonated esters which can be used as a flame retardant concentrate material in the manufacture of both fiber and nonwoven products. It is said to be completely antimony and halogen-free. Devan

Chemicals is located at : Klein Frankrijk 18, 9600 Ronse, Belgium. Figure 2 shows Component B being provided in Box 20.

[0024] As shown in Box 30 in Figure 1 , to produce the monofilaments of the invention, the components A and B are combined in a ratio of from about

20% parts by weight (pbw) to about 80% pbw of the Component A material with from about 80% to about 20% pbw of the Component B material. Preferably, in the manufacture of the monofilaments of this invention, the ratio of the components is from about 40% pbw to about 70% pbw of the Component A material, with from about 60% to about 30% pbw of the Component B material.

Most preferably, optimum results are achieved using a blend of from between 50 and 60% pbw of the Component A material and from between 40 and 50% pbw of the Component B material.

[0025] In the preferred embodiment, the Avora® polyester is generally available from the manufacturer in pelletized form at an intrinsic viscosity of about 0.65. In order to obtain the desired properties for braiding and similar technical applications in the resulting monofilament, it is necessary that the

Avora® intrinsic viscosity be increased to about 0.95, or more, prior to blending with the @2 spin PES 278™ concentrate. The Avora® material should also first be dried prior to blending.

[0026] In addition to these materials, processing aids and colorants such as would normally be employed in the manufacture of monofilaments may be added to the blend.

[0027] As a further option, we have found that satisfactory results can be obtained by application of e.g. Clariant's Afilan® AFR flame retardant finish to the surface of the monofilament prior to winding onto spools. Afilan® AFR is available from Clariant Corporation of Charlotte, NC.

[0028] In addition to these additives, it may be possible to dilute the formulation by adding up to 20% of a .95 IV commercially available PET and still meet the stringent tests. Also, the addition of clay nanoparticles to suppress dripping and enhance flame retardant attributes is planned but has not yet been trialed.

[0029] The mixed pelletized polymer components, including Component

A, which in the preferred embodiment is the Avora® Plus flame retardant polyethylene terephthalate type 8934 polymer and Component B, which in the preferred embodiment is the @2 spin PES 278™ concentrate, are then loaded into an extruder hopper. The components are heated to a temperature of about 48O⁰F (249°C) to obtain a satisfactory melt processing temperature and extruded through the spinneret head of an extruder, as indicated at Box 40 in Figure 1 , to form monofilament extrudates. If these components are extruded together at higher temperatures such as would be suitable for polyesters (e.g. about 550⁰F) the extrudate will be unsatisfactory for use in forming the yarns of this invention. [0030] Satisfactory monofilament can be produced using either single screw or twin screw extruders. However, it is believed that better mixing occurs and a more consistent product is produced with the co-rotating twin screw extruder. Twin screw extrusion is therefore the preferred process. A suitable twin screw extruder includes the Berstorff extruder available from KraussMaffei Berstorff GmbH of Hanover, Germany, however, other extruders may be suitable.

[0031] Preferably, the monofilament extrudate from the spinneret head is then drawn to form the monofilament according to the invention. In the preferred embodiment, the overall draw is about 4.8:1 ; however, greater or smaller draw ratios can be used, preferably in a range of 3:1 to 6:1. In the preferred embodiment, at least about 97% of the overall draw is carried out during the first stage of orientation through the first oven. This is well outside the typical first draw percentage range for halogen containing polyester flame retardant product, such as Polyfyre E, which is generally in the range of 75% and 80%, with the remaining orientation taking place in the second stage draw. While this has provided satisfactory results, other apportionments of the percent of the draw carried out in the first, second and third drawing stages can be utilized. The resulting monofilament was suitable for the production of monofilaments for industrial applications such as braiding and the like.

[0032] In the preferred embodiment, circular monofilaments having an average diameter of about 0.010 in. (0.25mm) were successfully produced in this manner. The tensile strength and elongation of the monofilament samples was determined using an lnstron tensile testing machine. The tensile strength of the samples ranged from about 2.5 to 3.5 lbs, making them suitable for braiding applications where the specification for products is from 2 to 6 lbs. In addition, the elongation of the samples was from 25% to 40%, where the specification for braiding applications is from 15% to 45%.

[0033] It is believed that by providing Component A with the intrinsic viscosity of at least about 0.95, and preferably the Avora® Plus flame retardant polyethylene terephthalate type 8934 with an IV of at least 0.95 as determined according to ASTM D 4603-96, the resulting monofilament had sufficient strength and integrity for satisfactory braiding in the manufacture of e.g. cable sleeves for automotive and similar applications where both flame retardancy and strength are necessary.

[0034] It is anticipated that yarns produced in accordance with the teachings of the invention, when tested for flame retardancy, should either meet or exceed the requirements provided in the Underwriters Laboratory UL-94 VO flammability tests for "Flame Retardant Epoxies". UL 94 provides for three vertical ratings, V2, V1 and VO which indicate that the material was tested in a vertical position and self-extinguished within a specified time after the ignition source was removed. The vertical ratings also indicate whether the test specimen dripped flaming particles that ignited a cotton indicator located below the sample. These small-scale tests measure the propensity of a material to extinguish or spread flames once it becomes ignited.

[0035] It is similarly anticipated that yarns produced in accordance with the teachings of the invention, when formed into braids or woven structures for sleeving and subsequently tested, will either meet or exceed the requirements of Underwriters Laboratories test UL 1441 "Standard for Safety Coated Electrical Sleeving". These requirements apply to coated electrical sleeving intended for use in connection with the internal wiring of electrical devices and appliances located in dry or damp locations where it is not feasible to employ a standard insulated conductor, such as appliance-wiring material, specifically intended for the purpose.

[0036] The yarns of this invention will be suitable for use in any application where PET polyester or similar polymers may be used. Due to their tensile strength, elongation and other similar physical properties, monofilaments formed from the polymer blend will be particularly suitable for the manufacture of braided and woven structures such as would be used as sleeving for electrical wiring and the like in both automotive and aerospace applications. Figure 2 shows a braided sleeve 12 using the monofilaments 14 according to the invention. Figure 3 shows a woven structure 16 also made using the monofilaments 18 according to the invention. Other uses will be apparent. In addition, it is anticipated that the monofilaments will find use in other woven products, as well as spirally constructed fabrics.

Claims

1. A polymer blended component, comprising: from 20 to 80% of a first polymeric component and from 80 to 20% of a second component, the first polymeric component comprising PET polyester having an organic phosphorus compound backbone with an Intrinsic Viscosity of at least 0.95, and the second component comprising a polyester flame retardant concentrate based on an organic phosphonated ester which is combined with a polyester, the first and second components being generally uniformly mixed and heat fused together to form the component.

2. The polymer blended component of claim 1 , wherein the component is a monofilament extruded from the first and second components.

3. The polymer blended component of claim 1 , wherein the component is a braided structure made from monofilaments extruded from the first and second components.

4. The polymer blended component of claim 1 , wherein the component is a woven structure made from monofilaments extruded from the first and second components.

5. The polymer blended component of claim 1 , wherein the component is sleeving made from at least one of a braided or woven structure comprised of monofilaments extruded from the first and second components.

6. A method of forming an oriented, halogen-free, flame retardant thermoplastic polymer blended yarn, comprising: preparing a PET polyester having an organic phosphorus compound backbone with an intrinsic viscosity of at least 0.95 as component A; providing a polyester flame retardant concentrate based on an organic phosphonated ester which is combined with a polyester as component B; combining component A and component B in a 80:20 to 20:80 mixture; heating and extruding the mixture through a spinneret to form a monofilament extrudate; and drawing the monofilament extrudate through a first stage draw of about 97% of an overall draw.

7. A polymer blend, comprising: from 20 to 80% of a first polymeric component and from 80 to 20% of a second component, the first polymeric component comprising PET polyester having an organic phosphorus compound backbone with an Intrinsic Viscosity of at least 0.95, and the second component comprising a polyester flame retardant concentrate based on an organic phosphonated ester which is combined with a polyester.