WO2008133627A1

WO2008133627A1 - Copolyetherester elastomer and polyacetal compositions

Info

Publication number: WO2008133627A1
Application number: PCT/US2007/010426
Authority: WO
Inventors: Shailaja R. Vaidya
Original assignee: E. I. Du Pont De Nemours And Company
Priority date: 2007-04-30
Filing date: 2007-04-30
Publication date: 2008-11-06

Abstract

Blends of copolyetherester elastomer and polyacetal having good heat aging properties, good low temperature impact properties, and good surface appearance.

Description

COPOLYETHERESTER ELASTOMER AND POLYACETAL

COMPOSITIONS

Field of the Invention

The present invention relates to compositions comprising a blend of copolyetherester and polyacetal. The compositions have good heat aging properties, good low temperature impact properties, and good surface appearance.

Background of the Invention

As a result of their excellent tear strength, tensile strength, flex life, abrasion resistance, and suitability for a broad range of end-use temperatures, thermoplastic copolyetherester elastomers (CPEE) are used in a broad range of applications. For many applications, including automotive applications in particular, articles made from CPEE's can be subjected to¹ operating temperatures that can range from about -40⁰C to about 110 ⁰C. At low temperatures, the CPEE's can be subject to embrittlement or loss of impact resistance, while upon exposure (including prolonged exposure) to elevated temperatures, CPEE> can lose mechanical strength (for example, loss in tensile strength or impact resistance may be exhibited at high temperatures).

Various additives, including other polymers, can be used to improve the performance of CPEE's at low or elevated temperatures in resin compositions, but if such materials are not fully compatible with the CPEE's, molded or other articles prepared from the compositions may have a poor surface appearance. For applications where the articles are visible to the end user and aesthetics are important (such as, for example, airbag doors), the surface appearance can be unacceptable and in some cases the surface of the article may need to be painted or otherwise treated to obtain an acceptable surface.

It would thus be desirable to obtain a CPEE composition having good impact resistance at low temperatures and good retention of physical i properties upon exposure to elevated temperatures that may also be formed into articles having a good surface appearance when formed into articles.

US 4,243,580 discloses an elastomeric copolyether-ester composition comprising an oxymethylene polymer.

Summary of the Invention

Disclosed and claimed herein is a thermoplastic copolyetherester elastomer composition comprising;

(a) about 80 to about 99 weight percent of at least one thermoplastic copolyetherester elastomer comprising a multiplicity of recurring long chain ester units and short chain ester units joined head-to-tail

through ester linkages, said long chain ester units being represented by formula (I):

(I) and said short chain ester units being represented by formula (II)

(H) where G is a divalent radical remaining after the removal of terminal hydroxy groups from a poly(alkylene oxide) glycol having a number average molecular weight of about 400 to about 6000; R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight of less than about 300; and D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight of less than about 250; wherein said short chain ester units comprise about 15 to about 99 weight percent of the copolyetherester and said long chain ester units comprise about 1 to about 85 weight percent of the copolyetherester; and

(b) about 1 to about 20 weight percent of at least one polyacetal, wherein the weight percentage of (a) and (b) are based on the total weight of (a) + (b), and wherein the copolyetherester elastomers (a) have a melting point of between about 170⁰C to about 200⁰C; a Vicat softening temperature of at least about 70⁰C; and a glass transition temperature of less than or equal to about -25 ⁰C; and wherein the melt viscosities as measured at about 220⁰C and a shear rate of about 500 s^'1 of the copolyetherester (a) and the polyacetal (b) differ by no more than about 160 Pa-s.

Further disclosed and claimed are articles comprising the composition including automotive airbag doors.

Detailed Description of the Invention

The thermoplastic copolyetherester elastomers used in the present invention are one or more copolymers that have a multiplicity of recurring long-chain ester units and short-chain ester units joined head-to-tail through ester linkages, said long-chain ester units being represented by formula (I):

(D

and said short-chain ester units being represented by formula (II):

(H) wherein

G is a divalent radical remaining after the removal of terminal hydroxyl groups from poly(alkylene oxide)glycols having a number average molecular weight of between about 400 and about 6000, or preferably between about 400 and about 3000;

R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight of less than about 300;

D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight less than about 250;

wherein said copolyetherester(s) preferably contain from about 15 to about 99 weight percent short-chain ester units and about 1 to about 85 weight percent long-chain ester units, or wherein the copolyetherester(s) more preferably contain from about 25 to about 90 weight percent short-chain ester units and about 10 to about 75 weight percent long-chain ester units

As used herein, the term "long-chain ester units" as applied to units in a polymer chain refers to the reaction product of a long-chain glycol with a dicarboxylic acid. Suitable long-chain glycols are poly(alkylene oxide) glycols having terminal (or as nearly terminal as possible) hydroxy groups and having a number average molecular weight of from about 400 to about 6000, and preferably from about 600 to about 3000. Preferred poly(alkylene oxide) glycols include poly(tetramethylene oxide) glycol, poly(trimethylene oxide) glycol, polyφropylene oxide) glycol, poly(ethylene oxide) glycol, copolymer glycols of these alkylene oxides, and block copolymers such as ethylene oxide-capped poly(propylene oxide) glycol. Mixtures of two or more of these glycols can be used.

The term "short-chain ester units" as applied to units in a polymer chain of the copolyetheresters refers to low molecular weight compounds or polymer chain units having molecular weights less than about 550. They are made by reacting a low molecular weight diol or a mixture of diols (molecular weight below about 250) with a dicarboxylic acid to form ester units represented by Formula (II) above.

Included among the low molecular weight diols that react to form short- chain ester units suitable for use for preparing copolyetheresters are acyclic, alicyclic and aromatic dihydroxy compounds. Preferred compounds are diols with about 2-15 carbon atoms such as ethylene, propylene, isobutylene, tetramethylene, 1 ,4-pentamethylene, 2,2-dimethyltrimethylene, hexamethylene and decamethylene glycols, dihydroxycyclohexane, cyclohexane dimethanol, resorcinol, hydroquinone, 1,5-dihydroxynaphthalene, etc. Especially preferred diols are aliphatic diols containing 2-8 carbon atoms, and a more preferred diol is 1 ,4-butanediol. Included among the bisphenols which can be used are bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)methane, and bis(p-hydroxyphenyl)propane. Equivalent ester-forming derivatives of diols are also useful (e.g., ethylene oxide or ethylene carbonate can be used in place of ethylene glycol or resorcinol diacetate can be used in place of resorcinol). As used herein, the term "diols" includes equivalent ester-forming derivatives such as those mentioned. However, any molecular weight requirements refer to the corresponding diols, not their derivatives.

Dicarboxylic acids that can reacted with the foregoing long-chain glycols and low molecular weight diols to produce the copolyetheresters are aliphatic, cycloaliphatic or aromatic dicarboxylic acids of a low molecular weight, i.e., having a molecular weight of less than about 300. The term "dicarboxylic acids" as used herein includes functional equivalents of dicarboxylic acids that have two carboxyl functional groups that perform substantially like dicarboxylic acids in reaction with glycols and diols in forming copolyetherester polymers. These equivalents include esters and ester-forming derivatives such as acid halides and anhydrides. The molecular weight requirement pertains to the acid and not to its equivalent ester or ester- forming derivative. Thus, an ester of a dicarboxylic acid having a molecular weight greater than 300 or a functional equivalent of a dicarboxylic acid having a molecular weight greater than 300 are included provided the corresponding acid has a molecular weight below about 300. The dicarboxylic acids can contain any substituent groups or combinations that do not substantially interfere with the copolyetherester polymer formation and use of the polymer in the compositions of this invention.

The term "aliphatic dicarboxylic acids," as used herein, refers to carboxylic acids having two carboxyl groups each attached to a saturated carbon atom. If the carbon atom to which the carboxyl group is attached is saturated and is in a ring, the acid is cycloaliphatic. Aliphatic or cycloaliphatic acids having conjugated unsaturation often cannot be used because of homopolymerization. However, some unsaturated acids, such as maleic acid, can be used.

Aromatic dicarboxylic acids, as the term is used herein, are dicarboxylic acids having two carboxyl groups each attached to a carbon atom in a carbocyclic aromatic ring structure. It is not necessary that both functional carboxyl groups be attached to the same aromatic ring and where more than one ring is present, they can be joined by aliphatic or aromatic divalent radicals or divalent radicals such as -O— or — SO2— .

Representative useful aliphatic and cycloaliphatic acids that can be used include sebacic acid; 1 ,3-cyclohexane dicarboxylic acid; 1,4- cyclohexane dicarboxylic acid; adipic acid; glutaric acid; 4-cyclohexane-1 ,2- dicarboxylic acid; 2-ethylsuberic acid; cyclopentanedicarboxylic acid decahydro-1,5-naphthylene dicarboxylic acid; 4,4'-bicyclohexyl dicarboxylic acid; decahydro-2,6-naphthylene dicarboxylic acid; 4,4'- methylenebis(cyclόhexyl) carboxylic acid; and 3,4-furan dicarboxylic acid. Preferred acids are cyclohexane-dicarboxylic acids and adipic acid.

Representative aromatic dicarboxylic acids include phthalic, terephthalic and isophthalic acids; bibenzoic acid; substituted dicarboxy compounds with two benzene nuclei such as bis(p-carboxyphenyl)methane; p-oxy-1,5-naphthalene dicarboxylic acid; 2,6-naphthalene dicarboxylic acid; 2,7-naphthalene dicarboxylic acid; 4,4'-sulfonyl dibenzoic acid and C1-C12 alkyl and ring substitution derivatives thereof, such as halo, alkoxy, and aryl derivatives. Hydroxy! acids such as p-(beta-hydroxyethoxy)benzoic acid can also be used provided an aromatic dicarboxylic acid is also used.

Aromatic dicarboxylic acids are a preferred class for preparing the copolyetherester polymers useful for this invention. Among the aromatic acids, those with 8-16 carbon atoms are preferred, particularly terephthalic acid alone or with a mixture of phthalic and/or isophthalic acids.

The copolyetheresters preferably comprise about 15 to about 99 weight percent short-chain ester units corresponding to Formula (II) above, the remainder being long-chain ester units corresponding to Formula (I) above. The copolyetheresters more preferably comprise about 20 to about 95 weight percent, and even more preferably about 25 to about 60 weight percent short- chain ester units, where the remainder is long-chain ester units. More preferably, at least about 70% of the groups represented by R in Formulae (I) and (II) above are 1 ,4-phenylene radicals and at least about 70% of the groups represented by D in Formula (II) above are 1 ,4-butylene radicals and the sum of the percentages of R groups which are not 1 ,4-phenylene radicals and D groups that are not 1 ,4-butylene radicals does not exceed 30%. If a second dicarboxylic acid is used to make the copolyetherester, isophthalic acid is preferred and if a second low molecular weight diol is used, 1 ,4- butenediol or hexamethylene glycol are preferred.

A blend or mixture of two or more copolyetherester elastomers can be used. The copolyetherester elastomers used in the blend need not on an individual basis come within the values disclosed hereinbefore for the elastomers. However, the blend of two or more copolyetherester elastomers must conform to the values described herein for the copolyetheresters on a weighted average basis. For example, in a mixture that contains equal amounts of two copolyetherester elastomers, one copolyetherester can contain 60 weight percent short-chain ester units and the other copolyetherester can contain 30 weight percent short-chain ester units for a weighted average of 45 weight percent short-chain ester units.

Preferably, the copolyetherester elastomers are prepared from esters or mixtures of esters of terephthalic acid and isophthalic acid, 1 ,4-butanediol and poly(tetramethylene ether)glycol or ethylene oxide-capped polypropylene oxide glycol, or are prepared from esters of terephthalic acid, e.g. dimethylterephthalate, 1,4-butanediol and poly(ethylene oxide)glycol. More preferably, the copolyetherester elastomers are prepared from esters of terephthalic acid, e.g. dimethylterephthalate, 1,4-butanediol and poly(tetramethylene ether)glycol.

The copolyetherester elastomers described herein can be made conveniently by methods known to those skilled in the art, such as by using a conventional ester interchange reaction. A preferred procedure involves heating the ester of an aromatic acid, e.g., dimethyl ester of terephthalic acid, with the poly(alkylene oxide)glycol and a molar excess of the low molecular weight diol, 1,4-butanediol, in the presence of a catalyst, followed by distilling off methanol formed by the interchange reaction. Heating is continued until methanol evolution is complete. Depending on temperature, catalyst and glycol excess, this polymerization is complete within a few minutes to a few hours. This product results in the preparation of a low molecular weight prepolymer which can be carried to a high molecular weight copolyetherester by the procedure described below. Such prepolymers can also be prepared by a number of alternate esterification or ester interchange processes; for example, the long-chain glycol can be reacted with a high or low molecular weight short-chain ester homopolymer or copolymer in the presence of catalyst until randomization occurs. The short-chain ester homopolymer or copolymer can be prepared by ester interchange from either the dimethyl esters and low molecular weight diols as above, or from the free acids with the diol acetates. Alternatively, the short-chain ester copolymer can be prepared by direct esterification from appropriate acids, anhydrides or acid chlorides, for example, with diols or by other processes such as reaction of the acids with cyclic ethers or carbonates. Obviously the prepolymer might also be prepared by running these processes in the presence of the long- chain glycol.

The resulting prepolymer is then carried to high molecular weight by distillation of the excess of short-chain diol. This process is known as "polycondensation". Additional ester interchange occurs during this distillation to increase the molecular weight and to randomize the arrangement of the copolyetherester units. Best results are usually obtained if this final distillation or polycondensation is run at less than 1 mm pressure and 240-260 ⁰C for less than 2 hours in the presence of antioxidants such as 1 ,6-bis-(3,5-di-te/f- butyl-4-hydroxyphenol)propionamido]-hexane or 1 ,3,5-trimethyl-2,4,6-tris[3,5- di-te/t-butyl-4-hydroxybenzyl]benzene. Most practical polymerization techniques rely upon ester interchange to complete the polymerization reaction. In order to avoid excessive hold time at high temperatures with possible irreversible thermal degradation, it may be advantageous to employ a catalyst for ester interchange reactions. While a wide variety of catalysts can be used, organic titanates such as tetrabutyl titanate used alone or in combination with magnesium or calcium acetates are preferred. Complex titanates, such as derived from alkali or alkaline earth metal alkoxides and titanate esters are also very effective. Inorganic titanates, such as lanthanum titanate, calcium acetate/antimony trioxide mixtures, and lithium and magnesium alkoxides are representative of other catalysts that can be used. Also preferred are stannous catalysts.

The polyacetals (also possibly referred to as "polyoxymethylene" or "POM") used in the present invention can be one or more homopolymers, copolymers, or mixtures thereof. Polyacetals useful in the present invention are preferably copolymers or blends obtained from mixing two or more copolymers. Homopolymers can be prepared by polymerizing formaldehyde and/or formaldehyde equivalents, such as cyclic oligomers of formaldehyde. It can be preferred that homopolymers have terminal hydroxyl groups end- capped by a chemical reaction with a second reactant. The type of reactant useful in the practice of the present invention can be any that is known or conventional for reacting with hydroxyl groups, but it can be preferred to form ester or ether linkages as terminal-, or end-groups. Preferred end-groups for homopolymers used in the present invention are acetate or methoxy groups.

Polyacetal copolymers can be derived from reaction of one or more known and conventionally used comonomers with formaldehyde and/or formaldehyde equivalents. Comonomers useful herein can be selected from acetals and cyclic ethers having from 2-12 sequential carbon atoms. By sequential, it is meant that the carbon atoms are linked in sequence to each other with no intervening heteroatom(s). Copolymers useful in the practice of the present invention comprise not more than 20 wt%, preferably not more than 15 wt%, and most preferably about 2 wt% comonomers, based on the weight of the polyacetal copolymer. Preferable comonomers are selected from : 1,3-dioxolane; ethylene oxide; and butylene oxide. Preferred polyacetal copolymers comprise about 2 wt% 1,3-dioxolane. For copolymers, it can be preferable to have some free hydroxy ends from the comonomer unit or terminal ether groups. Preferred terminal groups for copolymers are hydroxyl (-OH) and methoxy (-OCH₃).

The polyacetal used in the compositions of the present invention can be branched or linear and will preferably have a number average molecular weight of at least 10,000, and more preferably about 20,000 to about 90,000. The molecular weight can be conveniently measured by gel permeation chromatography in m-cresol at 160 ⁰C using a DuPont PSM bimodal column kit with nominal pore size of 60 and 1000 Angstroms (A). The molecular weight can also be measured by determining the melt flow using ASTM D1238 or ISO 1133. The melt flow will preferably be in the range of 0.1 to 100 g/min, more preferably from 0.5 to 60 g/min, or yet more preferably from 0.8 to 40 g/min. for injection molding purposes.

The CPEE is preferably present in the compositions of the present invention about 70 to about 99 weight percent, or more preferably in about 75 to about 96 weight percent, or yet more preferably in about 85 to about 96 weight percent, based on the total weight of the CPEE and polyacetal.

The polyacetal is preferably present in the compositions of the present invention about 1 to about 30 weight percent, or more preferably in about 4 to about 25 weight percent, or yet more preferably in about 4 to about 15 weight percent, based on the total weight of the CPEE and polyacetal.

Combined, the CPEE and polyacetal preferably comprise about 92 to 100 weight percent of the total composition, or more preferably about 92 to about 96 weight percent of the total composition.

The one or more CPEE's used in the composition each have melting points of about 170⁰C to about 200⁰C, or preferably of about 170 ⁰C to about 190⁰C. Melting points are measured according to ISO 11357-1 /3: 1997(E) at a rate of 10 °C/minute.

The one or more CPEE's used in the composition each have Vicat softening temperatures of at least about 70 ⁰C, or preferably of least about 100 ⁰C. Vicat softening temperatures are measured according to ISO 306:2004(E) at 10 N and 50 °C/h.

The one or more CPEE's used in the composition each have glass transition temperatures of less than or equal to about -25 ⁰C, or preferably of less than or equal to about -30⁰C₁ or more preferably of less than or equal to about -40 ⁰C. Glass transition temperatures are measured according to ISO 6721-5: 1994(E) at 1 Hz.

The one or more CPEE's and one or more polyacetals used in the present invention are selected such that the melt viscosities measured by capillary rheometry at about 220 ⁰C and a shear rate of about 500 s^"1 for the CPEE's and polyacetals differ by no more than about 160 Pa-s. (By "differ by no more than X Pa s" is meant that the absolute value of the CPEE melt viscosity subtracted from the polyacetal melt viscosity is no greater than X Pa s.) It is preferred that the melt viscosities differ by no more than 140 Pa s, more preferred that they differ by no more than 120 Pa s, yet more preferred that they differ by no more than 100 Pa-s, and still more preferred that they differ by no more than 90 Pa s. When more than one CPEE and/or more than one polyacetal are used, the differences in melt viscosity of each CPEE is compared with that of each polyacetal independently.

The compositions of the present invention may optionally further comprise other components and additives, such as, but not limited to, colorants, thermal stabilizers, lubricants, dispersing agents, and the like. The additives are present in 0 to about 4 weight percent, or preferably about 0.1 to about 4 weight percent, or more preferably in about 0.1 to about 2 weight percent.

The compositions of the present invention may optionally comprise one or more ultraviolet light stabilizers. UV light stabilizers include scavengers such as organic UV light stabilizers such as benzotriazoles and hindered amine light stabilizers, and screeners such as titanium dioxide, carbon black, and pigments. The UV light stabilizers are present in 0 to about 4 weight percent, or preferably about 0.1 to about 4 weight percent, or more preferably in about 0.5 to about 4 weight percent, or more preferably in about 0.5 to about 2 weight percent.

The composition of the present invention may be formed by adding other components to the polymerization process when the polyetherester elastomer is made. The compositions of the present invention may also be formed by melt-blending the polymer of the present invention with other additives or by melt blending a composition containing the polyetherester elastomer of the present invention and components incorporated during polymerization with other additives. Any melt-blending method may be used to prepared the compositions of the present invention. For example, the polymeric components and non-polymeric ingredients may be added to a melt mixer, such as, for example, a single or twin-screw extruder; a blender; a kneader, or a Banbury mixer, either all at once through a single step addition, or in a stepwise fashion, and then melt-mixed. When adding the polymeric components and non-polymeric ingredients in a stepwise fashion, part of the polymeric components and/or non-polymeric ingredients are first added and melt-mixed with the remaining polymeric components and non-polymeric ingredients being subsequently added and further melt-mixed until a well- mixed composition is obtained.

The polyetherester elastomers and polyetherester elastomer compositions of the present invention may be formed into articles using methods known to those skilled in the art, such as, for example, injection molding, blow molding, extrusion, thermoforrning, melt casting, rotational molding, and slush molding. The composition may be overmolded onto an article made from a different material. The composition may be extruded into films. The composition may be formed into monofilaments or fibers.

Articles comprising the polyetherester elastomers and polyetherester elastomer compositions of the present invention can include automotive articles (or those used in other vehicles, including in all-terrain vehicles, snowmobiles, golf carts, boats, farm and yard care equipment, construction equipment, and the like) such as air bag doors, dashboard components, exterior and interior trim, seat backs, head rests, glove box doors, center consoles, pillars, instrument panels, side moldings, rear window shelves, arm rests, mats, shit lever knobs, gear shifter slides, electrical outlet covers, instrument panel knobs, interior skins, soft-tough overmoldings, knee bolsters, bumper fascia, door trim, tubing, constant velocity joint boots, bellows, air ducts, hoses, brake hoses, mandrels, and automotive vacuum tubing.

The articles may also be used as arctic mats used in oil exploration and drilling. The articles may be appliance covers (including side panels, housings, and the like), power tool housings, electronic device housings, power tool housings, and the like.

Examples

The compositions of Examples 1-13 (Ex 1-13) and Comparative Examples 1-16 (CE 1-16) were prepared by melt compounding the components shown in Tables 2 and 4 in a 30 mm co-rotating twin screw extruder. The melt blended compositions were extruded through a die, cooled in a water bath, and cut into pellets. The compositions were then injection molded into test specimens for further testing. Table 1 describes the polymeric components referred to in Tables 2 and 4. "Color masterbatch A" refers to a brown pigment masterbatch in a CPEE and "Color masterbatch B" refers to a carbon black masterbatch in CPEE. The absolute value of the difference in melt viscosities of the polyacetal and CPEE used in each example and comparative example where both were present is indicated in Tables 2 and 4 as "Δ MV".

Table 1

^[1] Hytrel®, Delrin®, and Crastin® polymers are supplied by E.I. du Pont de Nemours and Co., Wilmington, DE. 1²³ MVs are measured by capillary rheometry at about 220⁰C and a shear rate of about 500 s^'1.

Testing methods:

Tensile and flexural properties were measured on test bars molded according to ISO 14910-1. Tensile properties were measured according to ISO 527-1/2 at a pull speed of 50 mm/min. Flex modulus was measured according to ISO 178.

Melting points (MP) were measured according to ISO 11357-1/3 at a rate of 10 °C/minute.

Vicat softening temperatures were measured according to ISO 306 at 10 N and 50 °C/h.

Glass transition temperatures (Tg) were measured according to ISO 6721-5.

The compositions were injected molded in a single cavity airbag tool into plaques having dimensions of 4"x4"x2 mm and an 8/1000" deep tear seam.

Multiaxial impact resistance (MAI) was measured according to ISO 6603-2 on 100 mm x 100 mm x 2 mm injection molded test specimens having a tear seam molded in to it. The number of ductile breaks seen for each for each set of specimens tested are given in Tables 3 and 5. The total number of specimens tested are also given in the Tables. Samples that did not exhibit ductile breaks had brittle breaks.

Additionally, the compositions of Examples 4 and 5 and Comparative Example 11 were injection molded into edge-gated passenger side air bag doors having a central horizontal tear seam. The multiaxial impact resistance (MAI) was measured at -40 ⁰C on 100 mm x 100 mm specimens die cut from airbag doors such that the tear seam is in the center of the cut piece. In each case, four out of four samples tested showed ductile breaks. The surface appearance of the airbag plaques was evaluated by visual inspection and rated on a scale of 1 to 5 (where 1 indicates the best overall surface appearance) according to the following criteria:

1 : Homogeneous surface appearance; no surface ghosting; and no flow marks on the surface. 2: Homogeneous surface appearance; some surface ghosting; and no flow marks on the surface. 3: Partially inhomogeneous surface appearance; visible surface ghosting; and no flow marks on the surface. 4: Partially inhomogeneous surface appearance; no surface ghosting; and visible flow marks on the surface.

5: Inhomogeneous surface appearance; surface ghosting; and visible flow marks on the surface.

Tensile elongation at break was determined on samples dry as molded and on samples after air oven aging (AOA) in a vacuum oven at 110 ⁰C for 1000 hours. The results are given in the tables under the headings of "Tensile elongation at break" and "Tensile elongation at break after AOA", respectively. The absolute value of the percent change in tensile elongation after aging is given in the tables under the heading of "|% change|"

Formaldehyde emissions: "n" indicates that no formaldehyde odor was observed during molding; "m" indicates that a mild formaldehyde odor was observed during molding; and "y" indicated that a strong odor was observed during molding.

Table 2

Ingredient quantities are in weight percent based on the total weight of the composition.

10

Table 3

00

Table 4

Table 5

K*

O

Note 1: Test specimens could not be tested because after aging they had degraded to the point that they fell apart when 5 handled.

Claims

What is Claimed is:

1. A thermoplastic copolyetherester elastomer composition comprising;

(a) about 80 to about 99 weight percent of at least one thermoplastic copolyetherester elastomer comprising a multiplicity of recurring long chain ester units and short chain ester units joined head-to-tail through

ester linkages, said long chain ester units being represented by formula (I):

(I) and said short chain ester units being represented by formula (II)

(H) where G is a divalent radical remaining after the removal of terminal hydroxy groups from a poly(alkylene oxide) glycol having a number average molecular weight of about 400 to about 6000; R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight of less than about 300; and D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight of less than about 250; wherein said short chain ester units comprise about 15 to about 99 weight percent of the copolyetherester and said long chain ester units comprise about 1 to about 85 weight percent of the copolyetherester; and (b) about 1 to about 20 weight percent of at least one polyacetal, wherein the weight percentage of (a) and (b) are based on the total weight of

(a) + (b), and wherein the copolyetherester elastomers (a) have a melting point of between about 170⁰C to about 200 ⁰C; a Vicat softening temperature of at least about 70 ⁰C; and a glass transition temperature of less than or equal to about -25 ⁰C; and wherein the melt viscosities as measured at about 220 ⁰C and a shear rate of about 500 s^'1 of the copolyetherester (a) and the polyacetal

(b) differ by no more than about 160 Pa s.

^>. The composition of claim 1, wherein the poly(alkylene oxide) glycol is poly(tertrarnethylene oxide) glycol; the dicarboxylic acid is one or more selected from the group consisting of isophthalic acid, terephthalic acid, and phthalic acid; and the diol is 1 ,4-butanediol.

J. The composition of claim 1 , wherein the polyacetal is at least one hornopolymer.

!•. The composition of claim 1 , wherein the polyacetal is at least one copolymer.

5. The composition of claim 1 , wherein the copolyetherester elastomers (a) have melting points of between about 170 ⁰C to about 190 ⁰C.

5. The composition of claim 1 , wherein copolyetherester elastomers (a) have Vicat softening temperatures of at least about 100 ⁰C.

^r. The composition of claim 1, wherein copolyetherester elastomers (a) have glass transition temperatures of less than or equal to about -40 ⁰C.

5. The composition of claim 1 , wherein the melt viscosities of the copolyetherester (a) and the polyacetal (b) differ by no more than about 120 Pa s.

9. The composition of claim 1 , wherein the melt viscosities of the copolyetherester (a) and the polyacetai (b) differ by no more than about 90 Pa s.

10. The composition of claim 1, further comprising at least one ultraviolet light stabilizer.

11.The composition of claim 9, wherein the ultraviolet light stabilizer is one or more selected from the group consisting of benzotriazoles, hindered amine light stabilizers, titanium dioxide, carbon black, and pigments.

12.An article comprising the composition of claim 1.

13. The article of claim 12 in the form of an airbag door.

14. The article of claim 12 in the form of a film or filament.

15. The article of claim 12 in the form of an arctic mat.

16. The article of claim 12 in the form of an automobile dashboard component, exterior and interior trim component, seat back component, head rest component, glove box door, center console component, instrument panel component, side molding component, rear window shelf component, arm rest component, mat, shit lever knob component, gear shifter slide component, electrical outlet cover, instrument panel knob, interior skin, knee bolster component, bumper fascia, or door trim component.

17. The article of claim 12 in the form of an automobile tube, constant velocity joint boot, bellows, air duct, hose, brake hose, mandrel, or vacuum tube.