HK1068579A - Multilayered packaging materials for electrostatic applications - Google Patents

Description

Multilayer packaging material suitable for electrostatic applications

Technical Field

The present invention relates to multilayer films or sheets, and more particularly to those multilayer films or sheets intended for use in packaging of static-sensitive electronic components, and which claim the right of U.S. provisional application serial No. 60/276,348 filed on 3, 16/2001.

Background

Polyester materials are widely used in applications such as fibers, films, automotive parts, and food and beverage containers as extrusion and injection molding resins. General purpose polyesters include polyethylene terephthalate (PET), poly (1, 4-butylene terephthalate) (PBT), poly (1, 4-cyclohexylenedimethylene terephthalate) (PCT), and poly (ethylene 2, 6-naphthalene dicarboxylate) (PEN). Such polyesters generally have good heat resistance and high glass transition temperatures. For applications where the extrusion or molding temperature must be kept below about 240 ℃, such highly crystalline polyesters are not used because their melting point is too high. In these cases, copolyesters which are amorphous or slowly crystallizing are used because they can be processed at moderate temperatures.

For applications packaging static sensitive electronic components such as floppy disk drive heads and integrated circuits, materials that are conductive or destatic and capable of processing at moderate temperatures are needed. Criteria for optimal suitability for this market include destaticity, dimensional stability, cleanability, thermoformability, acceptable slitting characteristics, peelable sealing of the cover tape, and low migration of condensate from the package to the packaged element. For packaging static electricityThermoplastics for sensitive electronic components are typically composed of blends of non-conductive polymers with Intrinsically Destaticizing Polymers (IDPs), Intrinsically Conductive Polymers (ICPs) or conductive fillers. The IDP-containing blends have a surface resistivity of greater than 10⁵And less than 10¹²Omega/sq. Blends containing ICP or conductive fillers have a surface resistivity of less than 10⁵Omega/sq. While blends of IDPs have been preferred, industry trends have been toward lower surface and volume resistivities and shorter static decay times than IDP blends.

A number of patents disclose IDPs and their use as static dissipative additives for other non-conductive polymers. U.S. Pat. nos. 5,159,053, 5,342,889 and 5,574,104 disclose polyurethane copolymers based on polyethylene glycol-derived materials. Such polyurethane copolymers are available from B.F. Goodrich under the name Stat-Rite^TMAnd can be used as an antistatic agent to blend with other polymers. U.S. Pat. nos. 4,719,263, 4,931,506, 5,101,139 and 5,237,009 disclose ethylene oxide copolymers used to destaticize many polymers. U.S. Pat. nos. 4,230,838 and 5,604,284 disclose polyetheramide ester destaticizing polymers, and U.S. Pat. nos. 5,298,558 and 5,886,098 disclose blends of polyetheramide esters with other polymers. Another source of information disclosing blends of IDP with non-Conductive matrix polymers is "Electrically Conductive Polymer Composites and dBlengths" ("Conductive Polymer Composites and blends"), Polymer engineering and Science 32(1), 36 (1992).

Regarding blends of ICP with non-conductive polymers, WO 91/10237 discloses compositions with antistatic properties comprising a non-conductive matrix polymer and at least two additives. In one embodiment, a copolyester of polyethylene terephthalate containing 1, 4-cyclohexanedimethanol is combined with polyaniline and another conductive material. U.S. patent 5,567,355 also discloses the use of polyaniline to impart electrical conductivity to many polymers, including thermoplastic polyesters. Another source of data disclosing blends of Intrinsically Conductive polymers with non-Conductive matrix polymers suitable for static discharge applications is "Processable intrinsic Conductive Polymer blends", Journal of Vinyl technology, 14, 123 (1992). ICP alone in the market has the disadvantage of outgassing or escaping volatiles.

Some references disclose methods of blending conductive fillers with non-conductive polymers. U.S. Pat. Nos. 5,643,990 and 6,184,280 disclose the use of carbon fibers to impart electrical conductivity to many polymers, including thermoplastic polyesters. A product name produced by Mass, Cambridge, HyperionCatalysis Int' l. is Shock Block^TMThe product of (2) adopts a high-conductivity hollow graphite fiber to make the plastic have conductivity. Shock Block^TMIs a single layer sheet that is destaticised on the side in contact with the electronic component and is electrically conductive on the other side. Carbon black is another conductive filler used to render many polymers, including thermoplastic polyesters, electrically conductive, as disclosed in U.S. Pat. nos. 5,382,384, 5,250,228 and 5,093,036. U.S. Pat. No. 5,643,991 discloses the use of carbon black and an impact modifier to impart electrical conductivity and mechanical toughness to an amorphous copolyester resin. Due to the physical properties of the conductive filler, even when blended with a polymer, problems of particle contamination are often caused.

Multilayer destaticizing structures are disclosed in U.S. patent 5,914,191. The outer layer comprises a blend of copolyester and destaticising polymer and the inner layer comprises a polymer having a haze value of less than 5%.

Summary of The Invention

A multilayer structure comprising at least one destaticising outer layer and a conductive core layer. The outer layer comprises a material selected from the group consisting of: an intrinsically destaticizing polymer, a blend of an intrinsically destaticizing polymer and a non-conductive matrix polymer, a blend of an intrinsically conductive polymer and a non-conductive matrix polymer in an amount sufficient to provide a surface resistivity of greater than 10⁵And less than 10¹²Ω/sq.，And mixtures thereof. The core layer comprises a material selected from the group consisting of: an intrinsically conductive polymer, a blend of an intrinsically conductive polymer and a non-conductive matrix polymer, a blend of a conductive filler and a non-conductive matrix polymer, and mixtures thereof. The multilayer structure unexpectedly provides electrical properties that exceed those of the prior art structures because the surface resistivity of the outer layer in the multilayer structure is lower than the surface resistivity of the outer layer alone or in another multilayer structure that is not in contact with the core layer.

Detailed Description

The present invention relates to a novel class of multilayer structures that can be thermoformed to meet the need for a material that can be destaticised. There are many applications in which the multilayer structures of the present invention can be used, namely packaging of static-sensitive electronic components, cleanroom glazing and multilayer sheets for use as packaging, box products and extruded profiles.

The multilayer structure of the present invention unexpectedly improves the electrical properties of prior art structures in the same type of application. The surface resistivity of the outer layer in the multilayer structure is lower than the surface resistivity of the outer layer alone or in another multilayer structure not in contact with the core layer. The decrease in surface resistivity of the outer layer is a result of its contact with the conductive core layer. This phenomenon can be seen in the examples below. In addition, the multilayer structure has a lower volume resistivity and a shorter static decay time than the single layer destaticizing structure. The multilayer structure also ensures lower particle contamination or chipping compared to the single layer structure using the conductive filler.

The multilayer structure comprises at least one static-dissipative outer layer and a conductive core layer. Preferably with 2 outer layers and 1 core layer sandwiched therebetween. The outer layer has a surface resistivity of about 10⁵-about 10¹²An antistatic layer of Ω/sq. The outer layer comprises a material selected from the group consisting of: an intrinsically destaticizing polymer, a blend of an intrinsically destaticizing polymer and a non-conductive matrix polymer, an intrinsically conductive polymer and a non-conductive matrix polymerBlends of matrix polymers in an amount to provide a surface resistivity greater than 10⁵And less than 10¹²Omega/sq. The core layer has a surface resistivity of less than 10⁵Omega/sq or volume resistivity less than 10⁷Omega-cm of conductive layer. The core layer comprises a material selected from the group consisting of: an intrinsically conductive polymer, a blend of an intrinsically conductive polymer and a non-conductive matrix polymer, a blend of a conductive filler and a non-conductive matrix polymer, and mixtures thereof. The multilayer structure may also have a tie layer between the core layer and each of the outer layers.

The multilayer destaticizing structure comprises at least one outer layer and a core layer. Preferred multilayer structures comprise 3 to 5 layers. The 3-layer structure comprises 2 outer layers and a core layer sandwiched therebetween. The 5-layer structure also has 2 tie layers, each between the core layer and one of the outer layers. Other layers may also be added to the structure depending on the needs of a particular application.

The outer layer of the multilayer structure is a destaticizing material and may be (i) an intrinsic destaticizing polymer, (ii) a blend of an intrinsic destaticizing polymer and a non-conductive matrix polymer, (iii) a blend of an intrinsic conductive polymer and a non-conductive matrix polymer in amounts such that the surface resistivity is greater than 10⁵And less than 10¹²Omega/sq, or (iv) mixtures thereof. Preferably, the IDP or ICP is blended with an amorphous or semi-crystalline polymer, as described below. The IDP or ICP content of the outer layer is sufficient to provide a surface resistivity of about 10 before and after thermoforming⁵-about 10¹²Omega/sq, preferably 10⁷-10¹⁰Omega/sq. Surface resistivity was measured according to ASTM D257-92.

Preferably, the intrinsic destaticizing polymer of the outer layer is a polyether urethane, polyether amide ester or polyether ester and is present in the blend in an amount of from about 3 to about 40 weight percent based on the total weight of the blend. IDP is preferably used in an amount of about 25 to about 35 weight percent. Preferably, the intrinsically conductive polymer of the outer layer is a polyaniline and is present in the blend in an amount of about 3 to about 15 weight percent. Outer layer only, ICPBlending with a non-conductive matrix polymer in order to render the blend electrostatically dissipative and not conductive, so that the ICP is present in an amount sufficient to provide a surface resistivity of greater than 10⁵And less than 10¹²Omega/sq. An example of an IDP is the product Stat-Rite from B.F. Goodrich^TM(ii) a Product Pebax of Atofina^(ii) a Irgastat, product of Ciba Specialty Chemicals^(ii) a Pelestat from Sanyo Chemical Industries, ltd. Examples of ICP are Ormecon, a product of Zipperling Kessler and Company^TM(ii) a And Panipol ltd^。

The core layer of the multilayer structure is a conductive material and may be (i) an intrinsically conductive polymer, (ii) a blend of an intrinsically conductive polymer and a non-conductive matrix polymer, (iii) a blend of a conductive filler and a non-conductive matrix polymer, and (iv) mixtures thereof. Preferably the ICP or conductive filler is blended with an amorphous or semi-crystalline polymer, as described below. The content of ICP or conductive filler in the core layer is enough to make the surface resistivity less than 10⁵Omega/sq or volume resistivity less than 10⁷Omega-cm. Examples of the conductive filler include carbon black powder, carbon fiber, metal powder, metal fiber, and metal oxide. The conductive filler is preferably present in an amount of about 0.5 to about 40 weight percent based on the total weight of the blend. Conductive powders such as conductive carbon black powder or metal powder are preferably used in an amount of about 5 to about 20% by weight. Examples of the conductive carbon black powder include Vulcan, a product of Cabotcorporation^XC72、Vulcan^P and Black Pearls and Ketjenblack EC, a product of Akzo Nobel. The preferred amount of conductive fibers is about 3 to about 15 weight percent. Examples of conductive fibers include Graphite fibers, a product of Hyperion Catalysis International^TMAnd Beki-shield, a product of Bekaert Fiber Technologies^. One preferred ICP is polyaniline and is present in the blend in an amount of about 3 to about 15 weight percent. An example of a polyaniline is Ormecon, a product of Ziegler Kessler and company^TMAnd Panipol ltd^。

The matrix polymers of both the outer and core layers may be any polymer compatible with IDP, ICP or conductive fillers. Representative examples of the matrix polymer include a polyester such as polybutylene terephthalate, polyethylene naphthalate, polyethylene 1, 4-cyclohexanedicarboxylate, or a copolyester thereof; polyvinyl chloride or copolymers thereof; chlorinated polyvinyl chloride; styrene-acrylonitrile copolymers; terpolymers of styrene-acrylonitrile-diene rubber, such as acrylonitrile-butadiene-styrene, and such terpolymers modified with an acrylate elastomer, such as acrylonitrile-butadiene-methyl methacrylate-styrene; styrene-acrylonitrile copolymers modified with acrylate elastomers, such as acrylonitrile-n-butyl acrylate-styrene; copolymers of styrene-diene rubbers modified with acrylate elastomers, such as methyl methacrylate-butadiene-styrene; styrene-acrylonitrile copolymers modified with ethylene-propylene-diene monomer rubber (e.g., acrylonitrile-ethylene/propylene-styrene); polystyrene; rubber-modified polystyrene; polyolefins such as polyethylene or polypropylene; nylon; a polycarbonate; cellulose esters; a polyether ester block copolymer; a polyurethane; polyphenylene ether; a polyacetal; a polyamide; polyacrylonitrile; polyketone; polysulfones; a polyimide; a polybenzimidazole; polyamide elastomers and polymethyl methacrylates.

Preferably, the nonconductive matrix polymer is an amorphous or semi-crystalline polymer. As a major component of the blend, the matrix polymer provides the necessary mechanical properties required for the blend. Even more preferably, the matrix polymer is a copolyester of polyethylene terephthalate containing a sufficient amount of diacid monomer or diol monomer residues to have a melting point below 240 ℃. Suitable diacid monomers include aliphatic diacids having from about 4 to about 40 carbon atoms; cycloaliphatic diacids, such as 1, 4-cyclohexanedicarboxylic acid; and aromatic carboxylic acids such as naphthalenedicarboxylic acid and isophthalic acid. Suitable glycol monomers include those containing from about 3 to about 15 carbon atoms, such as propylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 6-hexanediol, 1, 4-cyclohexanedimethanol, neopentyl glycol, and 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol. Copolyesters of poly (ethylene 2, 6-naphthalate) (PEN copolyesters) or poly (ethylene 1, 4-cyclohexanedicarboxylate) (PECD copolyesters) are also suitable. The most preferred matrix polymer is a copolyester of polyethylene terephthalate modified with 1, 4-cyclohexanedimethanol. The intrinsic viscosity (I.V.) of such copolyesters, as measured in a mixed solvent of 60 wt.% phenol and 40 wt.% tetrachloroethane at 25 ℃, is generally in the range of from about 0.5 to about 1.5 dL/g.

The outer and core layers can comprise other polymeric materials in addition to the matrix polymer. Other polymers included may be impact modifiers to improve the mechanical properties of the polymer, especially polymers with high filler content like the core layer. Compatibilizers may be added to improve the properties of the blend. Other materials such as stabilizers, colorants, flame retardants and reinforcing agents may also be added. Materials that are reground after extrusion or thermoforming operations may be added. The matrix polymer may also be blended with one or more other polymeric materials with the ICP or IDP.

There are many commercial blends that contain amorphous or semi-crystalline matrix polymers with IDPs or ICPs. An example is Eastman Chemical Company under the EastaStastat trade name^TMStat-Rite product of B.F. Goodrich Co^PermaStat, product of RTP Corporation^And product Stat-Loy of LNP Engineering Plastics, Inc^。

The tie layer acts as a compatibilizer to improve the adhesion between the outer layer and the core layer. The connection layer is preferably destaticised or electrically conductive. More preferably, the surface resistivity of the tie layer is less than 10¹²Omega/sq. The destaticizing or conductive connecting layer can be prepared by adding destaticizing agent or conductive filler into the commercial connecting layer.

For packaging applications, the total thickness of the multilayer structure in the present multilayer structure is from about 0.2mm to about 6mm (about 8 to about 250 mils), preferably from 0.2mm to about 1.25mm (8 to 50 mils). For packaging applications, the outer layer thickness is from about 0.0125mm to about 0.5mm (about 0.5 to about 20 mils), preferably from 0.0125mm to about 0.25mm (0.5 to 10 mils). The tie layer has a thickness of about 0.0125mm to about 0.25mm (about 0.5 to 10 mils), preferably 0.025mm to 0.125mm (1 to 5 mils).

The multilayer structure is manufactured using conventional lamination techniques such as co-extrusion, in-line or off-line lamination and extrusion coating. When converting the multilayer structure into a final product by thermoforming, a draw ratio of from about 1.1: 1 to about 4: 1 and a temperature of from about 120 ℃ to about 180 ℃ is used.

The invention is further illustrated by the following examples of preferred embodiments thereof, but it is to be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated. In these embodiments, the following remarks are made.

Eastar^PETG6763 is a copolyester based on terephthalic acid, ethylene glycol, and 1, 4-cyclohexanedimethanol, manufactured and sold by Eastman Chemical Company.

EastaStat^TMGSP12 is a destaticizing polymer blend manufactured and sold by Eastman Chemical Company and comprises Eastar^PETG6763, an intrinsic destaticizing polymer, and a polymer compatibilizer.

EastaStat^TMGSP32 is a conductive polymer blend manufactured and sold by Eastman Chemical Company and contains Eastar^PETG6763, a conductive carbon black filler and an impact modifier.

Surface resistivity and volume resistivity were measured according to ASTM D257-92, entitled "Standard test methods for D-C resistance or conductivity of insulating materials". The reported values represent the average of 6 measurements.

The electrostatic Decay time was measured using a charge panel monitoring device as described in "Decay-time characteristics of ESD Materials for Use with magnetic recording Heads", EOS/ESD Symposium Proceedings 19, 373 (1997). The test steps include: a sample of the film was placed on the plate and charged to about 1100V, then the sample was ground and the charge was monitored over time. The decay time is defined as the time required for the charge to decay from 1000V to 100V or from 1000V to 15V. The reported values represent the average of 6 measurements.

Examples 1 to 3: performance of single layer film

Eastar was produced by cast film extrusion for comparison with the following multilayer films^PETG6763 copolyester, Eastastat^TMGSP12 and EastaStastat^TMA single layer film of GSP 32. The thickness of each film was 0.030 inches. The surface resistivity, volume resistivity and electrostatic decay time are shown in table 1. Eastar as defined in EIA-541^PETG6763 is an insulating material, EastaStastat^TMGSP12 is static electricity eliminating material and EastaStastat^TMGSP32 is a conductive material. Eastar^PETG6763 is a PET copolyester modified with 1, 4-cyclohexanedimethanol (PETG). Eastastat^TMGSP12 contains a non-conductive matrix polymer PETG and IDP. Eastastat^TMGSP32 contains a non-conductive matrix polymer PETG and a conductive filler.

TABLE 1

Example No. 2	Material	Rs(Ω/sq.)	Rv(Ω-cm)	1000-100V decay time(s)	1000-15V decay time(s)
						1	EastarPETG 6763	2.9×1014	3.0×1016	＞60	＞60
2	EastaStatTM GSP12	5.5×109	2.6×1011	0.21	0.42
						3	EastaStatTM GSP32	3.6×104	2.8×106	0.10	0.15

Examples 4 to 6: co-extruding a static electricity removing top layer on the conductive core layer

Using an EastaStat^TMA central layer of GSP32 (i.e., a blend of PETG and a conductive filler) and two EastaStat^TMThe outer layer of GSP12 (i.e., a blend of PETG and IDP) was made into a 3-layer coextruded film structure. The total thickness of the film was 0.030 inch. The surface resistivity, volume resistivity and electrostatic decay time are shown in table 2. The surface resistivity, volume resistivity and static decay time of the multilayer film were all reduced compared to the single layer destaticizing film of example 2. The percentage improvement (% I) in table 2 below is relative to example 2. Thus, destaticisation is achieved by coextrusion over the conductive core layerThe electrical blend achieves improved destaticity, i.e., lower resistivity and shorter static decay time.

TABLE 2

Example No. 2	A/B/A (mil)	Rs(Ω/sq.)	％I	Rv(Ω-cm)	％I	1000-100V decay time(s)	％I	1000-15V decay time(s)	％I
										4	3/24/3	1.4×109	-75.6	4.2×1010	-83.9	0.14	-33.3	0.28	-33.3
5	1.5/27/1.5	1.3×109	-76.4	5.2×1010	-80.0	0.12	-42.9	0.23	-45.2
										6	1/28/1	5.2×108	-90.6	1.5×1010	-94.2	0.09	-57.1	0.16	-61.9

Examples 7 to 9: co-extruding an insulating top layer on the conductive core layer

Using an EastaStat^TMA central layer of GSP32 (conductive material) and two Eastars^The outer layer of PETG6763 (insulating material) is made into a 3-layer co-extruded film structure. The total thickness of the film was 0.030 inch. The surface resistivity, volume resistivity and electrostatic decay time are shown in table 3. The surface resistivity of this multilayer film was slightly decreased compared to the monolayer film in example 1; but neither the volume resistivity nor the electrostatic decay time is reduced. Thus co-extruding insulation on the conductive core layerThe rim material does not achieve an improvement in destaticity.

TABLE 3

Example No. 2	A/B/A (mil)	Rs(Ω/sq.)	Rv(Ω-cm)	1000-100V decay time(s)	1000-15V decay time(s)
						7	3/24/3	1.6×1014	3.0×1016	＞60	＞60
8	1.5/27/1.5	1.6×1014	3.0×1016	＞60	＞60
						9	1/28/1	2.7×1013	5.9×1015	＞60	＞60

Example 10: co-extruding a static electricity removing top layer on the insulating core layer

Using an Eastar^PETG6763 (insulating material) center layer and two EastaStat^TMThe outer layer of GSP12 (destaticizing material) was made into a 3-layer coextruded film structure. The total thickness of the film was 0.030 inch. Surface resistivity and volume resistivity of 9.8X 10 respectively⁹Omega/sq. and 9.8X 10¹⁴Omega-cm. The electrostatic decay times from 1000 to 100V and from 1000 to 15V were 0.28s and more than 60s, respectively. The multilayer film had higher surface resistivity, volume resistivity and electrostatic decay time than the monolayer film in example 2. Therefore, the improvement of the static eliminating property cannot be achieved by co-extruding the static eliminating material on the insulating core layer.

Claims (21)

1. A multilayer structure comprising at least one destaticising outer layer and a conductive core layer, wherein

(a) The outer layer comprises a material selected from the group consisting of: (i) an intrinsically destaticizing polymer, (ii) a blend of an intrinsically destaticizing polymer and a non-conductive matrix polymer, (iii) a blend of an intrinsically conductive polymer and a non-conductive matrix polymer in an amount sufficient to provide a surface resistivity of greater than 10⁵And less than 10¹²Omega/sq, and (iv) mixtures thereof;

(b) the core layer comprises a material selected from the group consisting of: (i) an intrinsically conductive polymer, (ii) a blend of an intrinsically conductive polymer with a non-conductive matrix polymer, (iii) a blend of a conductive filler with a non-conductive matrix polymer, and (iv) mixtures thereof;

wherein the surface resistivity of the outer layer of the multilayer structure is lower than the surface resistivity of the outer layer when not in contact with the core layer.

2. The multilayer structure of claim 1 further comprising a second outer layer, such that said core layer is sandwiched between said outer layers.

3. The multilayer structure of claim 2 further comprising two tie layers, each said tie layer being sandwiched between said core layer and one of said outer layers.

4. The multilayer structure of claim 1 further comprising a tie layer sandwiched between said core layer and said outer layer.

5. The multilayer structure of claim 1 wherein said intrinsic destaticizing polymer in said outer layer is selected from the group consisting of: polyether urethanes, polyether amide esters, and polyether esters.

6. The multi-layer structure of claim 1 wherein said intrinsic destaticizing polymer in said outer layer is blended with said non-conductive matrix polymer in an amount of from about 3 to about 40 weight percent.

7. The multi-layer structure of claim 1 wherein said intrinsically conductive polymer in said outer layer is a polyaniline.

8. The multi-layer structure of claim 1 wherein said intrinsically conductive polymer in said outer layer is blended with said non-conductive matrix polymer in an amount of about 3 to about 15 weight percent.

9. The multilayer structure of claim 1 wherein said nonconductive matrix polymer is selected from the group consisting of: a polyester or copolyester thereof; polyvinyl chloride or copolymers thereof; chlorinated polyvinyl chloride; styrene-acrylonitrile copolymers; terpolymers of styrene-acrylonitrile-diene rubber; styrene-acrylonitrile copolymers modified with acrylate elastomers; styrene-diene rubber copolymers modified with acrylate elastomers; styrene-acrylonitrile copolymers modified with ethylene-propylene-diene monomer rubber; polystyrene; rubber-modified polystyrene; a polyolefin; nylon; a polycarbonate; cellulose esters; a polyether ester block copolymer; a polyurethane; polyphenylene ether; a polyacetal; a polyamide; polyacrylonitrile; polyketone; polysulfones; a polyimide; a polybenzimidazole; polyamide elastomers and polymethyl methacrylates.

10. The multilayer structure of claim 1 wherein said nonconductive matrix polymer in said outer layer is a polyester selected from the group consisting of: polybutylene terephthalate, polyethylene naphthalate, polyethylene 1, 4-cyclohexanedicarboxylate, and copolyesters thereof.

11. The multilayer structure of claim 1 wherein said nonconductive matrix polymer in said outer layer is a copolyester of polyethylene terephthalate containing sufficient diacid monomer or diol monomer residues to have a melting point less than 240 ℃.

12. The multilayer structure of claim 1 wherein said nonconductive matrix polymer in said outer layer is a copolyester of polyethylene terephthalate modified with 1, 4-cyclohexanedimethanol.

13. The multilayer structure of claim 1 wherein said intrinsically conductive polymer in said core layer is a polyaniline.

14. The multilayer structure of claim 1 wherein said intrinsically conductive polymer in said core layer is blended with said non-conductive matrix polymer in an amount of about 3 to about 15 weight percent.

15. The multilayer structure of claim 1 wherein said conductive filler in said core layer is selected from the group consisting of: carbon black powder, carbon fiber, metal powder, metal fiber and metal oxide.

16. The multilayer structure of claim 1 wherein said conductive filler in said core layer is blended with said non-conductive matrix polymer in an amount of from about 0.5 to about 40 weight percent.

17. The multilayer structure of claim 1 wherein said conductive filler in said core layer is a powder and is blended with said non-conductive matrix polymer in an amount of from about 5 to about 20 weight percent.

18. The multilayer structure of claim 1 wherein said conductive filler in said core layer is a fiber and is blended with said non-conductive matrix polymer in an amount of from about 3 to about 15 weight percent.

19. The multilayer structure of claim 1 wherein said non-conductive matrix polymer in said core layer is a polyester selected from the group consisting of: polybutylene terephthalate, polyethylene naphthalate, polyethylene 1, 4-cyclohexanedicarboxylate, and copolyesters thereof.

20. The multilayer structure of claim 1 wherein said nonconductive matrix polymer in said core layer is a copolyester of polyethylene terephthalate containing sufficient diacid monomer or diol monomer residues to have a melting point less than 240 ℃.

21. The multilayer structure of claim 1 wherein said nonconductive matrix polymer in said core layer is a copolyester of polyethylene terephthalate modified with 1, 4-cyclohexanedimethanol.