Plasticized Composition of Copolyetherester Elastomer and Aromatic Sulfonamide

This invention relates to segmented thermoplastic copolyetherester elastomers generally found in U.S. Pat. class 260, subclass 75, and, more particularly to plasticized compositions containing said elastomers and certain sulfonamides.

Plasticizers are incorporated into polymers to improve properties, such as, enhanced processibility and increased pliability at low temperature. Practicable plasticizers exhibit certain critical characteristics including chemical inertness toward the polymer, low volatility at the polymer fusion temperature, compatibility with the polymer the lack of which leads to exudation of the plasticizer and depending upon the intended use other characteristics such as light stability and solvent resistance. Thermoplastic copolyetherester elastomers exhibit such limited compatbility toward phthalate plasticizers that in order to incorporate significant amounts of plasticizer, the addition of a more compatible polymer such as vinyl chloride polymer is used. Moreover, because of the high melting point of certain copolyetherester. elastomers, the incorporation of plasticizers and vinyl chloride polymer is difficult because processing temperatures can exceed the decomposition temperature of the vinyl polymer. Further, at high processing temperature ester containing plasticizers tend to intercharge with the ester groups of the elastomers. Sulfonamide plasticizers are considered unsatisfactory for polyesters because of incompatibility when the amount of plasticizer exceeds 10 parts plasticizer or more per 100 parts polyester. Accordingly, it was unexpected to find that co-polyetherester elastomers are compatible with certain sulfonamides at high concentrations.

Compositions of the invention comprise thermoplastic copolyetherester elastomer as hereafter defined, and, in an amount effective to plasticize the composition, a normally liquid sulfonamide of the formula ##STR1## in which R and R.sub.1 are hydrogen or alkyl of 1-6 carbon atoms, R.sub.2 is alkyl of 1-12 carbon atoms and R, R.sub.1 and R.sub.2 contain a total of at least 2 carbon atoms. Plasticized compositions of the invention containing sulfonamides in which R, R.sub.1 and R.sub.2 contain a total of 4-12 carbon atoms exhibit an improved balance of proprties including higher compatibility, lower glass transition temperatures and high temperature hysteresis. Compositions containing sulfonamides in which R.sub.1 and R.sub.2 are different alkyl radicals exhibit greater compatibility than sulfonamides in which R.sub.1 and R.sub.2 are the same. Compositions containing sulfonamides in which R and R.sub.1 are hydrogen exhibit better hysteresis at elevated temperatures. Suitable sulfonamide plasticizers of the invention are "normally liquid", i.e., they are stable liquids at room temperature. Solid sulfonamides are unsuitable because they are inherently incompatible leading to excessive blooming from the composition. However, any sulfonamide having a melting point sufficiently near room temperature may be used provided it is blended with sulfonamide of lower melting point to give a normally liquid sulfonamide mixture.

The amount of sulfonamide plasticizer incorporated into the copolyetherester elastomer depends upon the properties desired in the plasticized composition. Quantities of about one to two parts of plasticizer per 100 parts elastomer are sufficient to reduce hardness and the glass transition temperature with both properties progressively decreasing with increasing amounts of plasticizer. The maximum quantity of plasticizer varies depending upon the sulfonamide and elastomer and is reached when excess plasticizer exudes from the elastomer. Generally, satisfactory quantities of plasticizer are from about 2-50 weight percent plasticizer per total weight sulfonamide and elastomer. The copolyetherester elastomer of this invention is distinct from polyesters in its ability to accommodate high levels (more than 10 parts per 100 parts elastomer) of sulfonamide plasticizer. Especially preferred compositions contain between 10-40 weight percent plasticizer per total weight sulfonamide and elastomer.

The plasticizer may be incorporated into the elastomer by any conventional method for incorporating plasticizers into polymers which methods involve masticating and heating the polymer using standard equipment such as heated mills or internal mixers such as Banbury mixers or twin screw extruders.

The sulfonamide plasticizers of the invention belong to a class of known sulfonamide compounds, all of which may be prepared by known procedures. One synthesis route comprises reacting benzene- or alkylsubstituted benzene sulfonyl chloride with a mono- or di-alkylamine. Another synthesis route comprises reacting N-alkyl-arenesulfonamide with haloalkane to give N,N-dialkylarenesulfonamide. Any liquid sulfonamide having a Hildebrand solubility parameter between 9 and 11 is suitable but those sulfonamides having a solubility parameter between 9.7-10.7 exhibit greater compatibility and are preferred. The solubility parameters of sulfonamide plasticizers of the invention are calculated from structural formula and estimated molecular volumes by the method published by P. A. Small, J. App. Chem., 3, p. 71(1953). Examples of satisfactory sulfonamide plasticizers are N-isopropyl benzene sulfonamide, N-tert-butyl benzene sulfonamide, N-pentyl benzene sulfonamide, N-hexyl benzene sulfonamide, N-n-octyl benzene sulfonamide, N-methyl-N-butyl benzene sulfonamide, N-methyl-N-ethyl benzene sulfonamide, N-methyl-N-propyl benzene sulfonamide, N-ethyl-N-propyl benzene sulfonamide, N-ethyl p-ethylbenzene sulfonamide, N-ethyl p(t-butyl)benzene sulfonamide, N-butyl p-butyl benzene sulfonamide, N-butyl (mixed) toluene sulfonamide (mixed meaning a mixture of the ortho and para isomers of toluene), N-t-octyl (mixed) toluene sulfonamide, N-ethyl-N-2-ethylhexyl (mixed) toluene sulfonamide and N-ethyl-N-t-octyl (mixed) toluene sulfonamide.

Thermoplastic copolyetherester elastomers which are suitable in the practice of the invention are defined below. The term "thermoplastic copolyetherester elastomer" as used herein and the claims means a segmented polymer consisting essentially of about 30% to about 80% by weight recurring linear etherester (soft) segments derived from difunctional polyether glycol and dicarboxylic acid and about 70% to about 20% by weight recurring linear ester (hard) segments derived from organic diol and aromatic dicarboxylic acid. Polyether glycols having a molecular weight from about 350 to about 6000 are suitable with polyether glycols having a molecular weight between about 1000 to 4000 being preferred. The aromatic ester hard segment represents a repeating unit of a fiber-forming polyester having a melting point above 150.degree. C, preferably, above 200.degree. in its fiber-forming molecular weight range, for example, polyethyleneterephthalate and polytetramethyleneterephthalate. For further details on the preparation, composition and properties of satisfactory segmented thermoplastic copolyetherester elastomers, see U.S. Pat. Nos. 3,023,192; 3,651,014; 3,766,146; 3,775,373; 3,784,520 and 3,891,604, all assigned to E. I. du Pont de Nemours and Company, the disclosures of which are hereby incorporated by reference. Suitable segmented thermoplastic copolyetherester elastomers derived from terephthalic acid, polytetramethylene ether glycol and 1,4-butanediol may be purchased from du Pont under the trademark Hytrel elastomer. Three grades are available designated 92A, 55D and 63D which indicates a shore A hardness of 92 (equivalent to shore D hardness of 40), a shore D hardness of 55 and a shore D hardness of 63, respectively. The grades 92A, 55D and 63D contain about 33, 58 and 76 weight percent of aromatic polyester hard segment, respectively.

The plasticized compositions of the invention are characterized by conventional test procedures. The stress-strain properties of the compositions are determined in accordance with the test procedures set forth in ASTM D638 and ASTM D1566. Dynamic shear modulus G' is measured as a function of specimen temperature using a torsion pendulum from which data hysteresis, Tan .delta. and T.sub.f, the temperature below which G' is over 45000 psi (3164 Kg./cm.sup.2). The temperature T.sub.f is similar to the glass transition temperature T.sub.g.

Plasticized compositions of the invention are prepared by mixing thermoplastic copolyetherester elastomer and sulfonamide plasticizer in a Brabender mixer at a mixing speed of 100-120 rpm at 215.degree.-220.degree. C. The elastomer is charged to the mixer and masticated until melted. The plasticizer is then added and the mixture is masticated for 3-5 minutes until a homogenous blend is obtained. Specimens are prepared in sheet form by compression molding for 3-5 minutes at 225.degree.-230.degree. C and cooling below 100.degree. C before removal from the mold. Properties of the specimens are evaluated as described above.

Plasticized compositions of the invention consisting of copolyetherester elastomer (Hytrel elastomer, shore D hardness 63) and 10 and 20 weight percent sulfonamide plasticizers are shown in Table I. Stock 1 is a control containing no plasticizer. Stocks 2-9 illustrate compositions of the invention containing normally liquid sulfonamides. The data show that the addition of plasticizer significantly reduces the glass transition temperature and hardness as indicated by the reduction in modulus. The data also show a substantial reduction in hysteresis at room temperature and retention of low hysteresis at elevated temperatures which property is important in dynamic applications where a part is flexed during use such as in belts or tires. Stock 6 indicates that compatibility is reduced when the total number of alkyl carbon atoms exceeds 12. Comparison of Stock 2 with Stock 8 containing a commercially available sulfonamide plasticizer (Santicizer 8) indicates that the reduction in glass transition temperature is greater when the total number of alkyl carbon atoms is four or more.

Compositions of three types of copolyetherester elastomer (Hytrel, each of different hardness) plasticized with N-ethyl (mixed) toluene sulfonamide are shown in Table II. The compatibility of all compositions is excellent including the composition containing 40 weight percent plasticizer. The data indicate that compositions exhibiting a broad spectrum of properties can be achieved by addition of plasticizer. Young's modulus and shear modulus can be reduced by a factor of two or more by incorporation of plasticizer.

An important advantage of the use of sulfonamide plasticizer is illustrated in Table III. The properties of unplasticized copolyetherester elastomer (Hytrel type 92A) is compared with the properties of plasticized copolyetherester elastomer of higher hardness (Hytrel type 55D) containing 30 weight percent N-ethyl (mixed) toluene sulfonamide. The data show that hysteresis, shear modulus, Young's modulus and glass transition temperatures are about the same but that the melting point and recrystallization temperature of the plasticized composition are higher. Higher melting point indicates that the plasticized composition can be used at higher service temperatures while the higher crystallization temperature indicates that shorter molding cycles are required for the plasticized composition. Solu- Plasti- Glass Tensile Elonga- bility cizer Compati- Trans. Str. 100% Young's tion Stock Para- Level, bility Temp..sup.c 100 .times. Tan.delta. at .degree. C Shear Modulus, G' Kg./cm.sup.2 at .degree. C at Break, Modulus, Mod., at Break, No. Plasticizer meter.sup.a,.delta. Wt. % Rating.sup.b Tf, .degree. C 25 70 80 90 100 110 25 70 80 90 100 110 Kg./cm.sup.2 Kg./cm.sup.2 Kg./cm.sup.2 % 1 None 0 -- +1.5.sup.d 10.0 3.40 3.31 3.24 3.12 3.20 1230 571 510 474 425 374 423 204 2341 570 2 ##STR2## 10.41 1020 7 -23.6-33.3 5.16.1 3.494.35 4.003.90 3.803.98 3.663.83 3.563.83 3.563.60 752443 528320 432307 432263 387228 354281 186161 1835 1167 610600 3 ##STR3## 9.86 1020 7 -21.8-34.3 5.85.6 3.994.65 4.154.31 3.903.85 3.834.10 3.663.70 689527 596343 501320 501307 452263 427228 367270 180156 17581857 639560 4 ##STR4## 9.76 1020 7 -22.3-28.6 5.605.20 4.635.10 4.505.58 4.154.80 3.804.37 4 3.52.72 717591 544447 514404 468350 410323 373295 393304 179163 18771904 6 20590 5 ##STR5## 10.05 1020 7 -26.0-38.1 5.404.60 3.735.45 3.735.45 3.734.80 3.605.30 3.485.37 724513 498416 461380 461349 399314 335292 399307 177157 16241223 650610 6 ##STR6## 9.36 1020 4 -234.2-36.2 6.706.40 5.055.05 4.904.70 4.604.60 4.414.60 4.204.80 823548 575401 534361 461330 437301 403271 362260 191159 18701251 550530 7 ##STR7## 9.74 1020 7 -23.0-34 .8 6.105.20 4.204.50 4.044.20 4.304.04 3.694.20 3.553.67 738584 545384 507356 472326 427300 387275 408327 184162 18071202 640620 8 ##STR8## 10.71 1020 7 -18.9-24.5 5.404.30 3.444.80 3.584.90 3.685.84 3.705.20 3.795.20 766605 549379 515350 465324 448285 379259 3658207 178157 17281301 600370 9 ##STR9## 9.94 1020 7 -24.4-38.3 5.605.10 3.454.57 3.884.63 3.994.28 4.004.59 4 3.88.72 745485 531354 469323 450286 411266 373249 410308 188162 18001244 6 30600 .sup.a Calculated values; .sup.b B Bloomed; 0 Heavy exudation at 10 wt. %; 1 Light exudation at 10 wt. %; 2 Very light exudation at 10 wt. %; 3 are for compatible at 10 wt. % but 3 very heavy exudation at 20 wt. %; 4 heavy exudation at 20 wt. %; - Moderate exudation at 20 wt. %; 6 Light exudation at 20 wt. %; 7 Compatible at 10 and 20 wt. % plasticizer level. .sup.c Temperature at which G' is 45Kpsi. .sup.d rg = 2.degree. C

Although the invention has been illustrated by typical examples, it is not limited thereto. Changes and modifications of the examples of the invention herein chosen for purposes of disclosure can be made which do not constitute departure from the spirit and scope of the invention.