GB2197654A

GB2197654A - Thermoplastic compositions

Info

Publication number: GB2197654A
Application number: GB08726795A
Authority: GB
Inventors: Lawrence Clark
Original assignee: Armstrong World Industries Inc
Current assignee: Armstrong World Industries Inc
Priority date: 1986-11-17
Filing date: 1987-11-16
Publication date: 1988-05-25
Anticipated expiration: 2007-11-16
Also published as: DE3738335A1; CA1296821C; GB2197654B; SE8704473L; IT8722638A0; BE1001175A3; JPS63159437A; IT1223126B; SE8704473D0; FR2606780A1; GR871731B; GB8726795D0

Description

1 1 1 2 19 7 6 '5f 11 1 - "Thermoplastic Compositions" This invention

relates to a thermoplastic elastomer, to a process for its manufacture, to a composition comprising the elastomer, and to an article made from the elastomer or a composition comprising it.

The thermoplastic elastomer of the invention is a polymer comprising units derivable from a butadieneacrylonitrile polymer, some of which units are carboxylated, and units derivable from an ethvll--ne/acryl'-c acid-l-asei ionomeric polymer, the thermoplastic elastomer being crosslinked by an epoxy aaent. The elastomer of the invention may comprise units derivable from other moieties than those specified, althouch such moieties will aivantageously in a minor proportion onl,j, and the o- the in-,-enticn c37prise - a nolv.n.er the polymer of the invention.

co-ir.--cszior. for example, as fillers, processinq aids, materials may be aiven be present c 3T.,U E' i o n other than The a'Ls-- co-,.prise materials such, pigments, plasticizers, stabilizers and ant iOX4 dants. Such incorporated to provide, modify, or enhance a characteristic, for example, color, flexibi-I-itv, or hardness.

The epoxy crosslinking agent may be any compound having more than one epoxy moiety; in the case of a crosslinking agent the i7olecule cf which is clearly t least two epoxy moieties definable, the compound has a-, per molecule; the crosslinking agent is sometimes referred to below as a "polyfunctionall epoxv" 1 I-- Although ionomers based on ethylene/acrylic acid copolymers are preferred, the terms nacrylic" and #I acrylate" as used in this specification include both acrylic acid and methacrylic acid, and correspondingly, acrylates and methacrylates.

The elastomer of the present invention is advantageously produced by dynamic crosslinking of the carboxyleted butadiene-acrylonitrile elastomer (herein sometimes referred to as XNBR) and the ionomer. Dynamic crosslinking, as the term is used herein, rfers primarily to a procedure in which a composition ell comprising the elastomer, the ionomer, and the epoxy crosslinker is subjected to shear and, advantageously, heat.

more especially, the invention provides a theriroplastic elastomer produced from the dynamic crosslinking of a carboxylated butadieneacrylonitrile elastomer and an ionomeric ethylene/acrylic acid copolymer using an epoxy crosslinking agent having a minimum of two epoxy moieties per molecule (a polyfunctional epoxy). The compositions of the instant invention may provide a thermoplastic elastomer having the advantages both of being an easily processed thermoplastic elastomer and of having the superior physical properties of conventional vulcanized rubbers.

The compositions of the instant invention may be used to provide articles such, for example, as hoses, 4 - belts, wire and cable insulation, footware, mechanical goods and a wide variety of other rubber products. These thermoplastic elastomers may be extruded, injection-molded or calendered.

The present invention provides a thermoplastic elastomer characterized by the presence of both ionic bonds and covalent bonds. The ionic bonds are formed by the partial neutralization of the carboxyl groups on bcth polymers. The covalent bonds are formed by the reaction of the polyfunctional epoxy crosslinker with car'boxvl grour-s cresent in both the elastomer and the ionomeric copolymer. The presence of both ionic an3 covalent bonds provides a thermoplastic elastomer having the easy processing characteristics which are polymers an also provides superior _:Dic=_1 Of ionic physical properties.

Th e i I I -nsant invention provides a thermoplastic elastomer having both superior physical characteristics and superior processing capabilities allowing it to be easily processed. Such a thermoplastic elastomer more especially comprises a dynamically crosslinked blend of: (a) a carboxylated butadiene-acrylonitrile elastoner (X,N'BR) and (b) an ethylene/acrylic acid copolymer which has been at least partially metal ion neutralized (an ionomer of ethylene and acrylic acid) wherein (a) and (b) have been dynaTnically crosslinked with a polyfunctional epoxy crosslinking agent.

The polyfunctional epoxy crosslinking agent may be any compound having more than one epoxy moiety. The e-khylene/acrylic acid copolymer must have been at least partially neutralized, advantageously with a metal ion, to provide ionic crosslinking in addition to the dynamic crosslinking. Advantageously, the minimum amount of metal ion is that amount of metal needed to provide 0.5 parts of metal per 100 parts of total polymer. Throughout this specification, "parts" are parts by weight.

The dynarr..ic crosslinking reaction that produces the instant composition may be induced by applying shear and heat to a mixture of the elastomer, the ionomerr, and the epoxy crosslinker.

-The pol-vl-un---tional e-joxv crosslinker should advantageously be present in the amount needed to provide a minimum of 0.010 parts of oxirane oxygen per hundred parts of total polymer (PhP).

The thermoplstic elastomer of the invention may preferably be prepared by dynamically crosslinking a homogeneous mixture of the XNBR and the ethylene/acrylic acid copolymer (or ionomer) with the crosslinker normally at elevated temperatures (over 135OC). Shear should be provided during crosslinking. If a metal salt is to be separately added, it may be mixed in either before or after dynamic crosslinking. The polyfunctional epoxy should 6 either a) to induce :ully carell be well blended before raising temperatures dynamic crosslinking, or b) be added to the homogeneous blend during mixing; in order to obtain a uniformly crosslinked product. "Dynamic" crosslinking means that, while the crosElinking reaction occurs (with the polyfunctional epoxv), shear stress is applied to the mixture. Conventional v--,lcanization is avoided, and a product is produced which may be melted again for combination with other ingredients or for forming into a finished oroduct. The product may also be extruded, compression molded, or injection molded into a desired shape.

"he concentrations of the XNBR, the epoxy crossli.-ker, the ethylene/acrylic acid copoly-ner and tne neutralizing metal ion may all be widely varied. in this manner, any particularly desired characteristic can be obtained.

Advantaqeously, the concentration of the carboxylated butadieneacrylonitrile elastomer is within the range of from about 90 to about 10 PhP. concentration of the ethylene/acrylic acid ionomer advantageously correspondingly ranges from about 10 to about 90 parts PhP, although the presence of other units in the polymer is within the scope of the invention. The polyfunctional epoxy crosslinking agent should advantageously be present in an amount sufficient to provide a minimum of about 0.01 parts of ox-rane oxvoen PhP.

The preferred range for the carboxylated butadiene-acrylonitrile elastomer is from about 80 to about 15 PhP, while the most preferred concentration range is from about 75 to about 20 PhP. A preferred concentration range for the ionomer is from about 20 to about 85 PhP, while the most preferred con.centr'ation range is from about 25 to about 85 PhP.

Advantageously, the oxirane oxygen level of the polyfunctional epoxy crosslinker is in the range of from about 0.01 to about 7.0 PhP. A more preferred range, however, is from about 0.020 to about 3 PhP and the most preferred range is from about 0.030 to about 2.5 PhP.

As indicated above, there is advantageously a minimum of 0.5 part of the neutralizing metal ion PhP present in the elastomer-ionomer mixture in order to provide ionic bonding. An advantageous concentration range is from about 0.5 to about 30 parts of metal per hundred parts of resin. A more preferred range is from about 3 to about 15 parts per hundred parts of resin. An even more preferred range is from about 5 to about 10 parts of metal per hundred parts of resin. Advantageous-1v, there should be a minimum of 1 part of free acid (unneutralized acrylic acid after the before crosslinking) PhP addition of the metal ion but and preferably 2 or more parts free acid PhP. A preferred range of unneutralized free acid is from about 1 to about 20 parts PhP.

I--- 8 P polyfunctional epoxy ercsslinki,-q agent is any compounJ havinq rrore than one epoxy functionality per moLecule. Numerous such compounds are commercially available.

Any polyfunctional epoxy compound may be used as the crosslinking agent for this composition.

-able epoxy crosslinking agents are epoxidized soy Accept oil, epoxidized linseed oil, epoxidized tall oil or eL,oxidized natural rubber. An acceptable epoxidized crosslinkina acent may also be selected from the group ccnsistire of: an epoxdized alkyl glycidyl ether, an epoxidized polyglycidyl ether of phenol, an epoxidized glycidyl ether of an arcrn2tic compound, an epoxy cyc2oalkyl carboxylate, an er)oxid. Jzec glycidyl ether of an ali,hatic polyol, an epoxidized th-Loolycidyl resin, dized polvl ster, ar eDcxi lu--aiene, -=n turated polyester, a rnixture of any two unsall such comoounds or a mixture of any one or more such compounds with one or more other unspecified polyfunctional epoxy coirpounds.

A preferred polyfunctional epoxy crosslinking agent is one selected from polyphenol formaldehyde po2y(2,-11-epoxypro)yl) ether; 3, 4epcxycyclohexylirethyl (3,4-epoxy)cyclohexane carboxylate; poly(2,3epoxy prccy'L) ether carboxvlate, tetraolycidoxy tetraphenylethane, 2,2bis[4-(2,3-epoxypropoxy)-3,5-dibromophenyll propane and epoxidized dialycidyl ether of Bis Phenol A.

eiDoxidizpd or more of - 9 Of these, it is to be noted that 3,4-epoxycyclohexylmethyl-(3,4- epoxy)cyclohexane carboxylate is an excellent crosslinker, having good crosslinking activity and a moderately fast reaction rate.

The carboxylated butadiene-acrylonitrile polymer should advantageously contain a minimum of 1% by weight of the carboxylated monomer. An advantageous range for the concentration of the carboxylated units is from about 'L to about 20% by weight. A preferred range is from about 2.5 to about 15% by weight of carboxylated monomer and the most -orefe--red concentration range for the carboxylated monomer is from about 3 to about 10% by weight. The acrylonitrile monomer may advantageously be present in a range of from about 15 to about 50% by weight; preferably, it is present in a range of from about 18 to about 45% by weight, and more preferably 'n a concentration range of from about 20 to I - - L - - 40% by weight. Carboxylated about butadiene-acrylonitrile polymers are commercially available from, for example, such sources as Polysar, Goodyear, and Goodrich.

Ethylene/acrylate ionomers and ethylene/acrylic acid copolymers are both commercially available. If desired an ethvlene/acrylate ionomer may be directly utilized or an ethylene/acrylate copolymer may be used te amount of metal ion provided by and an appropriat adding a metal salt. Suitably, the metal salt may be i 01 - available ionor-ner concentration of before or after r-.et,--1 oxide is added'. by melt blending, either before or after the dynamic crosslinking. Even when using a commercially r it is permissible to increase the thp metal ion by addirp a metal salt dynamic crosslinking. Preferably, a used.

The acrylate moiety of the ionomer should be present in a minimum amount of about 1.0 parts PhP. An advantageous range for the acrylate moeity (includina both neutralized and unneutralized acrviate) is fror, about 1.0 to about 50 parts PhP. A preferred range is from about 5 to about 30 parts PhP and an even more preferred range is from, about 10 to about 25 parts PhP.

The neutra2iz;Lna metal ion, as previously b,,-, Qrovided the ar-'dition of e metal salt. Any metal salt may be used. Preferably, a metal oxide is used. Although generally the metal ion utilized may be any metal (and any metal salt) preferred metals are selected from groups I and 11 of I- the Periodic Table. More preferred metals are zinc, sodium, calcium and magnesium, the oxides or hydroxides of these rretals being most preferred.

Frorn the discussion thus far, it will be appreciated that the process for the preparetion of the instant invention has several eirbodiments. It is permissible to use ethylene/acrylic acid copolymer or 1) ionomer in the blend with the XNBR, with the addition of the metal ion to provide an increase in ionic crosslinking. The metal ion (in the form of a metal salt) may furthermore be added either before or after dynamically crosslinking with the polyfunctional epoxy crosslinker.

It is also possible to vary the temperature at which the crosslinker is added. Furthermore, if the crosslinker is added at temperatures under 1300C (generally 100-130OC), the crosslinker may be mixed with either the XNBR or the ethylene/acrylic acid copolymer (or ionomer) before or after the addition of the other ingredient(s).

In a oreferred embodiment the process comprises d; nc 04:

homogeneous ble- - - f -,, the XNBR, 2) the polyfunctional epoxy crosslinker and 3) the ionomer or -he et'hylene/acrylic acid copolymer at a temperature less than 1350C (preferably from about 110 to about 130OC). The ingredients may be added in any convenient order. After the homogeneous blend is obtained, the temperature is increased (over 1350C) to obtain dynamic crosslinking. Elevated temperatures are desirably maintained until dynamic crosslinking has been completed, the temperature advantageously being kept lower than 2000C. A preferred temperature range is from about 1400C to about 1850C.

When desired, a metal salt may be added at any - 12 convenient time either before or after dynamic crosslinking. When the metal ion is added afterward, the composition should be melt blended until a homogeneous composition is obtained.

While the composition may be prepared by the addition of the crosslinker to the blend at temperatures in excess of 1350C and less than 2000C in a manner effecti've to produce uniform crosslinking, it is preferred not to elevate the temperatures until after a uniform dispersion of the crosslinker is r-,'- t a i n ed. will avoi--I non-iniform cr inferior products which would result from crosslinking a poorly m-'xej combination.

Suital-le mixing apparatus lnclues, for example, 2 mixers, extruderS, and apparatis in common use in the rubber and plastics industry.

The level of covalent cross!inking is varied by increasing or decreasing the oxirane oxygen concentration and/or the level of the available carboxy functionalities in the resin. Because this dynamic (covalent) crosslinking is provided, the instant composition is capable of providing a higher temperature use range than an ionically crosslinked blend of the two polymers. The instant composition also provides superior flexibility, lower tensile set, and higher tear strength. The covalent crosslinking (possibly within the individual polymers as well as 1 between the two polymers), in combination with the ionomer characteristics of the blend, raises the use temperature and improves overall physical properties.

The characteristics of the instant thermoplastic elastomer may be controlled and varied by increasing or decreasing the concentration of the elastomer, the ionomer, the ionic bonding, and/or by increasing or decreasina the 'Level of dynamic crosslinking. In addition to this, it is also within the scope of the instant invention to use plasticizers, 1Diaments, fillers, stabilizers, and antioxidants in the thermoplastic elastomer. Such additives may be added at any time in the mixing sequence. Thus, they may be added to the mixture and homogeneously mixed in at any point before or after dynamic crosslinking, or the finished product 7-ay even be reheated and the additives J- - L - blended in.

The instant invention may be readily undprstood from the examples that follow.

Lhe following examples include data collected from ASTM tests performed on the finished dynamically crosslinked product. Test samples were prepared, and individual specimens for the tests were cut from the sample. The test samples were prepared by compression r-.olding in a 6 x 6 in x 0.075 in (about 150 mm x 150 mm x 1.9 mrr.) mold at 1750C (unless otherwise indicated) 14 using a molding cycle of a two minute warm up without pressure, two minutes under 800 psi (5.5 MPa) and a cool down to 6-501C under pressure before removing from ts performed and their ASTM numbers are:

rnold. The test Hardness, Shore "A" ASTM D2240 Tensile Strength, Modulus ASTM D412 and Elongation Immersion, Vol.

Compression set Melt Index ASTM Th- , - ----r measurement was taken in condition test '0+2% relative procedure:

23-10-- ani Method A chanae in oil. ASTM D471 AS-IM D395 Method B D1238 Brown initial strength, accordance with the following specimens for 24 hours at -v. - h U m' i (5 t 1hree 4 in x ' m,,n x m-r,) 2 in (a--ojz ---1 were cut from the test sample.

was- used: (a) tes lester by clamping the jaws of the Inst--on in (about 25 mm) and D e c im= The following procedure Instron Tensile two legs of the specimen in the Tester, (b) Set jaw separation Instron gauge a, 0, then pull apart at a constant speed of 12 in/min (about 305 Record initial tear strength. m value is zhe average obtained from three specimens of the sneci-iners in same sample :'xarnple 1 Sample blends 1-5 were prepared by mixing the carboxylated butadiene-acrylonitrile elastomer (Krynac at 1 j aws i - 15 211) at temperatures within 120-1300C with the sodium-ethylene/acrylic acid ionomer (Surlyn 8920).

The epoxy crosslinker was added, homogeneously mixed, and the temperature was increased to 1550C. The crosslinking agent used was the epoxy hydrocarbyl crosslinking agent Paraplex G-62, an epoxidized soy oil (approximately 6.8% by wt. oxirane oxygen).

When no epoxy crosslinker was added, the temperature was increased to 1550C after the initial mixinq of the two polymers, and the blend was mixed for five r-ore minutes, -ellowing interaction between the free carboxyl units of the carboxylated nitrile polymer end the metal ion of the ionomer. Such a procedure produces a mixed ionomer of the two polymers.

SiTniller blends, both with and without the epoxy crosslinker, of the copolymers are coiroared in the following table. This series shows that dynamic crosslinkinq is induced with the instant epoxidized crosslinkers to produce thermoplastic elastomers over a wide range of polymer ratios.

Trade Marks - 16 Table 1

Parts 50% Sai,-,le No. & By Modulus Tpnsi2e Elona.

Ingredients Weight PSI PSI % Hardness Brown Tear Shore A Initial lb.

Krynac 211 90 1 Surlyn-Na 10 135 670 750 55 - WITH 2 PARTS Epoxy 210 860 375 59 37 Krynac 21-1 75 2 Surlvn-'a 25 770 580 75 38 WITH 2 PARTS Epoxy 450 1250 340 PO 54 Krynac 211 50 3 Surlyn-Na 50 970 2060 395 93 67 WITP 2 PPR-111S, Emxv 1120 2310 265 94 91 Krynec 211 25 C 8 CC, 215 96 82 WITH 2 PAP--S Ewyv 21C 5 205 9 7 Krynac 211 10 SurIvn-Ne 90 2270 3710 265 98 83 WIT1H 2 PARI'S Epoxy 2500 3590 155 97 - tables pounds per sauare In this and subsequent inch (PSI) may be converted to MPa by multiplying by 0.00669. Conversion of Brown Tear (lb) to Brown Tear (Kq) Tray be effected by multiplication by 0.454.

In thp above exar,-ple, it should be noted that the materials which were prepared with no epoxy (having only ionic crosslinkno and no covalent crosslinkno), 1 -7 - 1 1 - could only be removed from the mill in a whole sheet by first cooling the mill to temperatures between 100-1100C. The blends which were covalently crosslinked with epoxy crosslinker, however, were easily removed from the mill as a single sheet without cooling, thus,demonstrating good processing characteristics at temperatures of 150-1550C.

Example 2

Sample blends 6-10 were prepared according to the following general procedure. The carboxylated bu±a-3.4j---,-ie-acr-vlon2--trile elas"tomer used herein, containing approximately 9% carboxylated monomer, and approximately 25-29% acrylonitrile monomer (Krynac 211 marketed by Polysar, Tnc.) was tlended in the amount indicated below for each sample along with the specified amount of Surlyn 8920 (copolymer of ethylene/acrylic acid with sodium). The blends were made by blending the two polymers on a laboratory mill at 150-1550C. After the initial blending, milling was continued at this temperature for five minutes to induce any interaction between the free carboxylated units of the carboxylated nitrile polymer and the metal ion of the ionomer. Such a blending procedure produces a "mixed" ionomer of the two polymers. Milling characteristics of this "mixed" ionomer were such that the temperature of the mixing mill had to be reduced to 100-1100C before the composition could be removed I- 18 f rom. the Trill as a single sheet. For samples 7-10, the epoxy hydrocarbyl crosslinking agent, Paraplex G-92 epoxidized soy oil, was added to the blend after the initial blending of the two polymers, and milling was continued at 150-1550C for five more minutes to produce the dynamically crosslinked product. During the procedure, crosslinking activity was apparent after o three -i.2nutes of 7,iillnc. As the dynamic cross linking takes place the mix shows greater cohesion, less mill tack, higher viscosity, and increased elasticity. At the more desirable levels of crosslink ing (less than 5 parts) a smoother milled sheet having r-,,,:)re uniform flow and better -processing is produced.

Tne crosslinkeJ '--lends were easily removed from the 150 1550C mill ass a single sheet without the cooling which is reouired when no dynai-ic crosslinking is present.

Table II

Parts 50% Sample No. & By Modulus Tensile Elong.

InQredients Weight PSI PSI % Hardness Brown Tear Shore A Initial lb.

Krynac 60 60 Surlyn-1,4a 40 Epoxy 0 670 1880 445 86 59 Krynac 60 Surlyn 40 Epoxy 1 810 2150 400 88 87 Kr.,,,nac 60 Su 4 3 8 Epoxy 2 930 2440 335 87 89 Trade Mark Table II (continued) Parts 50% Sample No. & BY Modulus Tensile Elong. Hardness Brown Tear Ingredients Weight PSI PSI % Shore A Initial lb.

Krynac 60 Surlyn 40 9 Epoxy 935 2350 275 89 92 Krynac 6C Surlyn 40 Epoxy 5 920 2200 215 90 67 Example_3 -hylene/acrylic acid copolymer (Et/Ac An et copolymer) was used (Primacor 435 maunufactured by Dow Chemical). The acrylic acid monomer content is approximately three percent. This example demonstrates the -h ionic and covalent bonds to produce the nee5 for boll desired thermoplastic elastomer with good processing characteristics and physical properties. The elastomer used was that described in Example 2. The elastomer, (XNBR), the ethylene/acrylic acid copolymer, and the zinc oxide were added and mixed in the amounts shown in the table below at a temperature of 120-1300C. The epoxy crosslinker (the epoxidized soy oil Paraplex G 62 havina about 6.8% oxirane content) was added in the amounts indicated below after which time the temperature was increased to 1550-. The mixture was blended for five minutes while crosslinking occurred to complete the thermoplastic elastomer.

Trade Mark - 20 Table iII

Sam;Dle 11 12 13 14 XNBR 60 60 60 60 Et/Ac copolymer 40 40 40 40 Epoxy -2 3 2 ZnO -- -- 5 ::0% -Osi 360 4 2 0 410 730 Tensile, psi 360 490 580 1,650 Elongation, P 60 250 330 365 Hardness, Shore A 81 81 81 91 Brown Tear, lb 17 20 25 66 Milled Sheet Character i Stics p a n Pough Rough Smooth 7he above blends which were "rough", were undesirable (lumpy, had holes, and did not have a smooth texture).

Example 4

Sample blends 15-18 were prepared according to the procedure explained in Example 2. The same carboxylated butadiene-acrylonitrile elastomer (Krynac 21.1) was used; the other copolymer was a copolymeric ethylene/zinc acrylate ionomer (Surlyn 9020) in the amounts shown in the table below. The same crosslinking agent (Paraplex G-62) was used as in Example 1.

I-1 Table IV

Parts 50% Sample No. & BY Modulus Tensile Elong.

Ingredients weight PSI PSI % Hardness Brown Tear Shore A Initial lb.

XNBR 60 Ionomer 40 EPOXY 0 350 1030 685 79 41 XNBR 60 Ionomer 40 16 E.00xv 1 410 1640 555 79 48 XNBR 60 Ionomer 40 17 Epoxy 2 410 1470 440 78 50 WBR Ionomer 40 18 Epoxy 3 435 1560 340 79 52 - -h - -ureexcel'enl- e above described mix', _L processing characteristics and good physical properties are shown at epoxy levels between 1 and 2.0 PhP (preferred 1.5-2.0 PhP). Comparative Example__5 -This is a comparative example wherein the crosslinker used in Examples 1- 4 is blended in varying amounts with the same (XNBR) used in Exanples 1-4. These two ingredients were blended on a laboratory mill at 150-1550C and compression molded at 1750C with cool down under pressure.

During the milling operation, it was obvious that the XNBR was crosslinked.This composition is - 22 undesirable; good physical properties do not develop. When the crosslinking concentration is high enough to increase tensile strength, the milled sheet itself becomes rouah, full of holes, and crumbly. The following table shows samples 19-21 which were prepared with similar amounts of the same crosslinker used in the previous Examples. The blends of the table below thus only had dynamic (covalent) crosslinking. Table V Parts 50% Samole & 3-1J Modulus Tensile Elong.Hariness Ingredients weight PSI PSI % Shore A XNBR E oo x v X P.1 p PAR-6 2 XNBR i 10 0 1-1 3 92 400 495 49 92 500 440 49 Milled sheet was rough and lumpy, full of hcles an did not flow in the mold well enough to form a good sample.

Comparative Example 6 The follow-'.ng sample blends 22-27 with either the sodium ionomer, Surlyn zinc ionomer, Surlyn 9020. The was Paraplex G-62 also used in samples 22-27 Test specimens cool down under of testing done were prepared 8920, or the epoxy crosslinker used previous examples. Test were prepared by milling at 150-1550C. were compression molded at 1750C with pressure. Table VI shows the results on these samples.

11- 1 23 Table VI

Parts 50% Sample No. & BY Modulus Tensile Elong. Hardness Melt Ingredients Weight PSI PSI % Shore A Index Surlyn 22 8920 100 2475 4470 275 97 48.7 Surlyn 8920 100 2 23 Epoxy 1 2560 4340 230 95 1.1 Surlyn 8920 100 24 Epoxy 2 2660 3290 110 95 Surlvn 902 100 1240 2730 340 94 Surlyn 90,20 100 26 Epoxy 0.5 1530 2670 215 95 Surlyn 9020 100 27 Epoxy 1.0 1540 2750 200 94 Melf- Index q/10 min at 3751C (about 1900C) and 433 PSI (2.98 MPa) (ASTM D1238).

The samples above show both the sodium ionomer, Surlyn 8920 and the zinc ionomer, Surlyn 9020 alone, using the same epoxy crosslinker as was used in Example 2. Both polymers show rapid increases in viscosity on the mixing mill at very low levels of addition of the crosslinker; as low as one part for the sodium and as low as 0.5 for the zinc; with the zinc showing a more rapid viscosity increase than the sodium. At the higher levels of crosslinker the viscosity increased to I,_ a point where the polymer could no longer be effectively processed, as indicated by the low Tnelt index. Such compositions could not be satisfactorily extruded or inection rrolded.

Unlike the individual polymers, blends of a carboxylated butadieneacrylonitrile elastomer and a metal-ion neutralized ethylene/acrylic acid copolymer can be dyna:-ically crcIcs.1inke6 with, the polyfunc--ional epoxy compounds to produce a thermoplastic elastomer having good physical propertips and excellent processinq characteristics.

Exam-cle 7 In this Exarrole, the XNBR elastomer used was Krvnac 23-1 rrarke,ed ty Pclvsa.r, Ltd. wirh had appr-ximatelly 7% c-;-rbcxylal,ed mon07er and a level of acrylonitrilp Tronomer in t,e rarce of 3C-33%. T'is XNBR is shown in Sample 28. Another XNBR which was evaluated ws NX 775 by Goodyear which also contained approximately 7% carboxylated monomer (Sample 29), but had an acrylonitriile monorrer content of about 28%. The ionomer was Surlyn 8920.

T Ihese tlends were prr-pared in accordance with the procedures given for Example 2.

- Table VII

Parts 50% Sample No. & BY Modulus Tensile Elong. Hardness Brown Tear Ingredients Weight PSI PSI % Shore A Initial lb.

Krynac-231 60 28 Surlyn 8920 40 530 1190 485 86 52 With Epoxy 2 920 1890 325 89 75 NX 775 60 29 Sur-lyr 8920 4C, 570 685 29,9 87 36 With Epoxy 2 740 2100 340 89 76 Exei.rT..le 8 This Example shows that fillers,antioxidants and processing aids rray be added to the dynamically crosslinked blend for- purposes such as improvina processina.. increa-t-inq stiffness and hardness or lowering costs. The XNBR used was Krynac 211. The ionomer used was Surlyn 8920 ionomer previously described, the epoxy crosslinking agent used was Paraplex G-62. All of these were used in the amounts indicated in the table below. The sample below was prepared in accordance with the following procedure. The XN5P copolymer and the Surlyn 8920 ionomer were melt blended on a laboratory mill at 150-1550C. After the initial blending, the FEF Black, Carbowax 4000, and Agerite Superlite (di-2-napthyl-p-phenylenediamine) were added, followed by the Paraplex G-62 Trade Marks 26 (epoxy). After the addition of all materials, milling was continued for five minutes at the 150-1550C mill temperature until the dynamic crosslinking had been completed. The table below shows the amounts of each ingredient and the results of tests conducted on this samp e.

Sample No. & Ingredients F-arts By Weight Table VIII

Modulus Tensile Elong. Hardness Brown Tear PSI PSI % Shore A Initial lb.

)C"BR Ionomer Epoxy -e Agerill Su->--rlite Carbowax F-EF Black 3 J 2 1 2 -i:: L - 1392 2220 175 94 Example 9 exa,.7,i:-lr- de-monstrates a referred -,.e-.hod fc,.r the preparation of the instant thermoplastic elastomer. he method applied in this example results in dynamically crosslinked thermoplastic elastomers which have more uniform physical and processing characteristics.

Accordingly, samples 31 to 38 of Table IX below were prepared by blending the epoxidized natural rubber crosslinking agent (epoxy in the table below) on a cold laboratory mixing mill with the XNBR. Lhe blend was then melt blended with the ionoirer at 1200C. After i v 4 - 27 the mixture was blended uniformly, the temperature was raised to 147-1561C and milling continued for five minutes, to induce more rapid corsslinking. The thermoplastic elastomer produced was easily processed on conventional thermoplastic processing equipment.

The table below give the test results of the samples prepared according to the above procedure. The addition of zinc oxide to increase the overall ion the composition shows only a slight increase content of in modulus and reduction in elongation.

Table IX

Parts 50% Sample No. & BY Modulus Tensile Elong. Hardness Ingredients Weiciht PSI PSI % Shore A Krvnac 221 55 )l Surlyn 8920 35 Epoxy 10 704 2325 352 88 Krynac 211 55 32 Surlyn 8920 35 Epoxy 20 ZnO 5 812 2259 320 87 Krynac 211 50 33 Surlyn 8920 -D- - Epoxy 15 870 2003 198 88 Krynac 2-11 so 34 Surlyn 8'-20 35 Epoxy 15 ZnO 5 906 2484 273 90 Krynac- 211 45 Surlyn 8920 35 Epoxy 20 812 2492 307 90 Table IX (continued) Sa,mple No. & Ingredients Krynac 211 36 Surlyn 8920 Epoxy ZnO Krvnac 37 Surlyn E0Oxy z no 211 9020 Krynac 211 38 Surlyn 9020 Ewxy z n3 Parts 50% B, Modulus Tensile Elong. Hardness Weight PSI PSI % Shore A 3 550 1384 483 874 2413 290 40 5 555 1460 446 82 82 Frynac 211 was the carboxylated butadieneacrylon-it,ril,2 elastorper (XNBR of Example 2) (9% carboxylated mono,-n.er and approximately 25-29 percent T h -- e i- o x,j, a n e D o x i J3 J. z e d natural rubber (ENR-50), contained approximately 50 mole percent epoxidation of the double bonds. The epoxidation has been shown to be random.

Example 10

The compositions were mixed in the same manner as sample 7-10 of Example 2 except that the three polymers were melt blended together before the addition of the Paraplex G-62 epoxy crosslinker. After the addition of the Paraplex G-62, rr-'llinQ was continueJ at the 150-1550C mixing temperature for five minutes to complete dynamic crosslinking.

1 1 29 - Elvax 360, an ethylene/vinyl acetate copolymer (containing approximately 25 percent vinyl acetate) was added as a solid plasticizer or modifier and which effectively reduced modulus and hardness without severely limiting tensile strength, elongation, and tear strength. Elvax 360 (a non-reactive thermoplastic resin) does not dynamically crosslink or enter into the ionic structure of the thermoplastic elastomer. Table X Sam-cle No. 39 40 41 Krynac 211 60 60 50 Surlyn 80120 30 25 35 Elvax 360 10 15 15 Parawlex G-62 2.5 50% ','-10(-,-ulus, PSI Tensile, PSI Elongation, % Hardness, Shore A Brown Tear, Initial lb.

610 1,780 280 83 47 52 515 745 1,500 2,080 280 330 87 ExamiDle 11 In this example, the elastoirer, Krynac 211,and the ionomer, Surlyn 8920, were homogeneously blended in the amounts indicated in the table below at a temperature of 120-1300C. The epoxy crosslinker used was added Trade Mark during mixing and the temperature was then increased to 1550C, and the mixture was blended for 5 more minutes while crosslinking occurred to complete the thermoplastic elastomer.

This example shows that this invention is not limited to the crosslinking activity of any one particular polyfunctional epoxy, and demonstrates that any miscible polyfunctional epoxy compound could be used as the dynamic crosslinker. Concentrations required to produce the desired processing characteristics anj ph-,,7sical properties of the resulting thermoplastic elastomer will depend on the molecular structure and the overall oxirane content. Preferably, the oxirane content of the polyfunctional epoxy::rossi-inke-- iS between -1 and' 15 percent by wt. The following epoxy compounds were evaluated.

Code Trade Name Chemical Name Manufacturer A. Drapex 10.4 Epoxidized Linseed Oil (Arqus) B. Drapex 4.4 4,41-octyl epoxy tallate (Argus) C. Epon 828 Digylcidyl ether of (Shell) bisphenol A D. Araldite Polyglycidyl ether of (Ciba-Geigy) EPN 1138 phenol-formaldehyde novolac E. Araldite 3,4-EpoxycyclohexylTr.ethyl (Ciba-Geigy) CY 179 -(3,4-epoxy)cyclohexane carboxylate Epon 1031 Tetraglycidoxy (Shell) tetraphenylethane Trade Marks 1 EPI Rex 5163 Diglycidyl ether of tetrabromo bisphenol A H. Araldite RD1 n-butyl glycidyl ether Table XI (Celanese) (Ciba-Geigy) Parts 50% Sample No. & By Modulus Tensile Elong. Hardness Brown Tear Ingredients Weight PSI PSI % Shore A Initial lb.

42 Krynac 211 60 Surlyn 8920 40 670 1800 445 86 59 43 With Epoxy A 2 900 2360 300 89 89 44 Epoxy B 2 600 1630 300 87 63 --tpoxy '1 2 9is 2160 290 90 66 46 Epoxy C 5 1220 2410 200 90 70 47 Epoxy D 2 780 1700 235 89 57 48 Epoxy --- 1 750 2340 440 90 84 49 Epoxy E 2 800 1960 285 90 70 Epoxy F 2 740 1780 265 88 44 51 Epoxy F 4 870 1970 195 90 49 52 Epoxy G 2 700 1320 250 90 43 53 Epoxy G 4 840 1420 185 90 50 54 Epoxy H 2 575 1230 380 85 37 Crosslinking is indicated by increases in one or more of modulus, hardness and tear strength and a reduction in elongation. Preferred crosslinkers also increase tensile. Epoxy H, n-butyl glycidyl ether, a monofunctional epoxy molecule does not effect crosslinking. Instead, it has a plasticizing effect and reduces modulus, tensile, elongation, hardness and tear strength.

32 - C 1. A thermoplastic elastomeric composition comprising a dynamically crosslinked blend of (a) a carboxyleted but,-dieneacrylenitrile Pjastomer and (b) an ethylene/acrylic acid copolymer which has been at least partially neutralized; wherein (a) and (b) have been dynamically crosslinked with a polyfunctional ei:,oxy crosslinking agent.

2. A composition as claimed in clairn 1, wherein the carboxylated butadiene-acrylonitrile elastor7,--r is present in an airount in the ranqe of from about 10 to about 90 parts by weight; and wherein the ethylene/acrylic acid copolymer is present in an amount in the range of from about 90 to about 10 parts by weight tased on tne total weight of component a) and b).

3. A. composition as clairred in clairn 1 or claiTr 2, wherein the epoxy crosslinking agent is present in an amount sufficient to provide a minimum of 0.010 parts of oxirane oxygen PhP (per hundred parts polymer, by weight).

4. A composition as clairned in any one of claims 1 to 3, wherein the cerboxylated monorrer content of elastomer (e) is in th- renae of fror about 2.5-15% by weicht of the elastomer.

5. A coirposition as claimed in any one of claims 1 to 3, wherein the polyfunctional epoxy crosslinking aaent is selected from epoxidized soy oil, epoxidized 1 111 linseed oil, epoxidized tall oil and epoxidized natural rubber.

6. A composition as claimed in any one of claims 1 to 5, wherein the epoxy crosslinking agent is selected from an epoxidized alkyl glycidyl ether, an epoxidized polyglycidyl ether of phenol, an epoxidized glycidyl ether of an aromatic compound, an epoxy cycloalkyl carboxylate, an epoxidized glycidyl ether of an aliphatic polyol, an epoxidized thioglycidyl resin, a glycidyl ester, an epoxidized polybutadiene, and an epoxidi--ed5 unsaturated po'Lyester.

7. A composition as claimed in any one of claims 1 to 6, wherein the ethylene/acrylic acid copolymer has been neutralized by metal ions.

8. A composition as clairred in clairr. 7, wherein the metal ion is selected from the metals of GroUp T and II of the Periodic Table.

9. A composition as claimed in claim 7 or claim 8, wherein the metal ions are present at at least 0.5 parts PhP.

10. A composition as claimed in any one of claims 1 to 9, which also contains at least one component selected from a filler, an entioxidant, a pia-Trent and a plasticizer.

11. A composition as claimed in any one of claims 1 to 10, which was prepared by mixing at less than 1300C a homogeneous blend of the carboxylated - 34 butadiene-acrylonitrile elastorrer, the epoxy crosslinking agent, and a copolymer of ethylene/acrylic acid and increasing the temperature to in excess of 1350C and TrixinQ for a sufficient lenath of time to allow dynamic crosslinking, and then blending in a metal salt to form a homoceneous product.

12. A composition as claimed in any one of claims 1 to 10, which was prepared by -,ixing a horrogeneous blend of the (a) elastomer, the polyfunctional epoxy crosslinking agent, and (b) the partially neutralized copolymer of ethylene/acrylic acid at a temperature in the range of frorr about 110 to 1300C and then increasing the temperature to in excess of 1350C and mixing for a sufficient time to allow dynamic crosslinkina.

12. A co,-r-osition es cleimed in any one of claims 1 to 12, which also contains a non-reactive thermonlastic resin.

14. A composition comprising (a) a c2rboxylated butadiene-acrylonitrile elastomer (b) an ethylene/ acrylic acid copolymer, the acid groups of which are optionally partly neutralized, and (c) an epoxy cor-iDoi-ind havirc more than one epoxy moiety.

15. A composition as claimed in claim 14, the components of which are as specified in any one of claims 2 to 10.

16. A thermoplastic elastomer obtained by dynamic crosslinking of the composition of claim 14 or claim 15.

17. A shaped article formed of the thermoplastic elastomer of claim 16.

18. A composition as claimed in claim 14 or an elastomer as claimed in claim 16, substantially as described in any one of the Examples herein with reference to any one of SamiDles 1 to 5, 7 to 10, 12 to 14, 16 to 18, 28 to 41 and 43 to 53.

19. A method of forming a thermoplastic e-.astomer carried out substantially as described in any one of the Examples herein with reference to any one of Samples 1 to 5, 7 to 10, 12 to 14, 16 to 18, 28 to 41 and 43 to 53.

20. Any new feature described herein, or any new combination of hereinbefore described features.