Nitrile-diene-carboxylic acid ester copolymers

Abstract

The present invention relates to nitrile-diene-carboxylic ester copolymers, to the preparation thereof, to vulcanizable compositions containing nitrile-diene-carboxylic ester copolymers and the production thereof, and to vulcanizates based on nitrile-diene-carboxylic ester copolymers and to the use thereof in elastomeric components.

Claims

1. Unhydrogenated nitrile-diene-carboxylic ester copolymers comprising: (a) 15% to 40% by weight of at least one α,β-ethylenically unsaturated nitrile unit, (b) 30% to 65% by weight of at least one conjugated diene unit and (c) 20% to 30% by weight of at least one PEG acrylate unit (c), the PEG acrylate unit (c) is butoxy polyethylene glycol (meth)acrylate having 2 repeat ethylene glycol units.

2. Unhydrogenated nitrile-diene-carboxylic ester copolymers according to claim 1, wherein the α,β-ethylenically unsaturated nitrile units (a) are derived from acrylonitrile, methacrylonitrile, ethacrylonitrile, or mixtures thereof.

3. Unhydrogenated nitrile-diene-carboxylic ester copolymers according to claim 1, wherein the conjugated diene units (b) are derived from 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene (piperylene), or mixtures thereof.

4. Unhydrogenated nitrile-diene-carboxylic ester copolymers according to claim 1, wherein copolymers are those containing 15% to 40% by weight of acrylonitrile units, 30% to 65% by weight of 1,3-butadiene units and 20% to 30% by weight of butoxy diethylene glycol (meth)acrylate units.

5. Vulcanizable composition comprising unhydrogenated nitrile-diene-carboxylic ester copolymers according to claim 1 and at least one crosslinker.

6. Process for producing a vulcanizable composition comprising mixing a unhydrogenated nitrile-diene-carboxylic ester copolymer according to claim 1 with at least one crosslinker.

7. Process for producing a vulcanizate based on unhydrogenated nitrile-diene-carboxylic ester copolymers, said process comprising subjecting the vulcanizable composition according to claim 5 to a vulcanization, optionally in a shaping process and optionally at a temperature in the range from 100° C. to 250° C.

8. Vulcanizate obtained by the process according to claim 7.

9. Vulcanizate according to claim 8, which is a molding selected from belts, gaskets and gasket profiles, rollers, membranes, footwear components, hoses, damping elements, insulating materials, stators and cable sheaths.

Description

EXAMPLES

(1) Test Methods:

(2) The values for the Mooney viscosity (ML 1+4@100° C.) are determined in each case by means of a shearing disc viscometer in accordance with DIN 53523/3 or ASTM D 1646 at 100° C.

(3) The nitrogen content for determination of the ACN content in the copolymer rubbers containing nitrile groups is determined by Vario EL cube. Combustion of the sample weighed out in the CHN machine at about 1150° C. in the presence of oxidation catalysts and oxygen, aliquoting of the combustion gases, absorption of the disruptive components and detection of N.sub.2 by thermal conductivity measurement cell (TCD).

(4) The determination of the microstructure and the termonomer content of the individual polymers was effected by means of .sup.1H NMR (instrument: Bruker DPX400 with TopSpin 1.3 software, measurement frequency 400 MHz, solvent 1,1,2,2-tetrachloroethane-d2).

(5) Crosslinking density was determined with a moving die rheometer (MDR 2000E), measuring at an angle of 0.5° and an oscillation frequency of 1.7 Hz at 160° C. for 30 minutes.

(6) For the tensile testing, 2 mm sheets were produced by vulcanization of the vulcanizable mixture at 180° C. The dumbbell-shaped test specimens were punched out of these sheets and tensile strength and elongation were determined to ASTM D2240-81.

(7) Hardness was determined with a durometer to ASTM D2240-81.

(8) The glass transition temperature was obtained with the aid of a DSC measurement according to ASTM E 1356-03 or according to DIN 11357-2. For this purpose, between 10 mg and 15 mg of the sample were weighed into an aluminium boat and sealed. The boat was heated twice from −150° C. to 150° C. at a heating rate of 20 K/min in a DSC instrument from TA Instruments. The glass transition temperature was determined from the second heating curve by the standard mean value method.

(9) TR 10 measurement: The TR measurement was conducted in accordance with ISO 2921, 2005. For this purpose, the sample was stored at −70° C. in silicone oil for 10 minutes. Subsequently, the curve was recorded at 1° C./min and the temperature for a 10% change was read off.

(10) Swelling: To determine swelling, dumbbell-shaped test specimens as used for tensile testing were stored according to DIN ISO 1817 in IRM903 or Fuel C at 100° C. for 72 h or 168 h. Thereafter, the samples were measured and weighed, and the volume swelling and increase in mass were determined. Subsequently, tensile strength and elongation were determined to ASTM D2240-81.

(11) The abbreviations given in the tables below have the following meanings:

(12) “RT” room temperature (23±2° C.)

(13) “S min” is the minimum torque of the crosslinking isotherm

(14) “S max” is the maximum torque of the crosslinking isotherm

(15) “delta S” is “S max-S min”

(16) “TS1” is the time by which the Mooney viscosity has increased by one unit after the Mooney viscosity minimum has been attained, compared to the starting point

(17) “T52” is the time by which the Mooney viscosity has increased by two units after the Mooney viscosity minimum has been attained, compared to the starting point

(18) “t 50” is the time when 50% of S max has been attained

(19) “t 90” is the time when 90% of S max has been attained

(20) “t 95” is the time when 95% of S max has been attained

(21) “M 10” modulus at 10% elongation, measured at RT

(22) “M 25” modulus at 25% elongation, measured at RT

(23) “M 50” modulus at 50% elongation, measured at RT

(24) “M 100” modulus at 100% elongation, measured at RT

(25) “M 300” modulus at 300% elongation, measured at RT

(26) “EB” elongation at break, measured at RT

(27) “TS” tensile strength, measured at RT

(28) “H” hardness, measured at RT

(29) The Following Substances were Used in the Examples:

(30) The following chemicals were purchased as commercial products from the companies specified in each case or originate from production plants of the companies specified.

(31) For the Polymerization:

(32) TABLE-US-00001 ACN acrylonitrile, CAS 107-13-1 BD 1,3-butadiene, CAS 106-99-0 BA butyl acrylate, CAS 141-32-2 PEG-2-MA butoxy diethylene glycol methacrylate (BDGMA), CAS 7328-22-5 Sodium dodecylsulfate CAS 151-21-3 (SDS) Na salt of disproportionated CAS 61790-51-0 resin acid Fatty acid CAS 67701-08-8 Na.sub.2CO.sub.3 CAS 24551-51-7 t-DDM tertiary dodecyl mercaptan; LANXESS Deutschland GmbH Glidox ® 500 pinane hydroperoxide; Renessenz “Premix solution contains 0.986 g of Fe(II)SO.sub.4*7 H.sub.2O and Fe(II)SO.sub.4” 2.0 g of Rongalit ® C in 400 g of water Rongalit C ® sodium salt of a sulfinic acid derivative; commercial product from BASF Diethylhydroxylamine CAS 3710-84-7 Vulkanox ® BKF 2,2′-methylenebis(4-methyl-6-tert-butyl- phenol); LANXESS Deutschland GmbH
Substances Used in the Vulcanizable Composition:

(33) TABLE-US-00002 NBR 5 PERBUNAN ® 2255VP, 22.1% by weight of ACN; Mooney viscosity 55 Mu NBR 6 PERBUNAN ® 2845 F, 28.2% by weight of ACN; Mooney viscosity 43 Mu NBR 7 PERBUNAN ® 3445 F, 34.2% by weight of ACN; Mooney viscosity 43 Mu Corax ® N550/30 carbon black; Orion Engineered Carbons REGAL ® SRF/N772 carbon black; Cabot VULKANOL ® OT 2-[2-(butoxyethoxy)ethoxy]ethanol with 2,2′-thiobis(ethanol) (LANXESS) EDENOR ® C18-98 MY stearic acid (Oleo Solutions Ltd.) VULKANOX ® HS/LG 2,2,4-trimethyl-1,2-dihydroquinoline (LANXESS) VULKANOX ® 4/5-methyl-2-mercaptobenzimidazole MB2/MG (LANXESS) RHENOCURE ® 90-20 insoluble/soluble sulfur in a 90:10 ratio plus 20% mineral oil (LANXESS) ZINKOXYD AKTIV ZnO (LANXESS) VULKACIT ® NZ/EGC N-tert-butylbenzothiazylsulfenamide (TBBS) (LANXESS) VULKACIT ® tetramethylthiuram disulfide (LANXESS) THIURAM/C VULKALENT ® E/C N-phenyl-N- (trichloromethylsulfenyl) benzenesulfonamide (LANXESS) Stabilizer mixture of 2,2′-methylenebis(4-methyl-6- nonyl)phenol (CAS 7786-17-6) and styrenized diphenylamine (CAS 68442-68-2)
I Preparation of the Unhydrogenated Nitrile-Diene-Carboxylic Ester Copolymers (NBR-Carboxylic Esters 1-4)

(34) NBR-carboxylic ester copolymers 1 to 4 as used in the example series which follow were prepared according to the base formulation specified in Table 1, wherein all feedstocks are specified in % by weight based on 100% by weight of the monomer mixture. Table 1 also gives the particular polymerization conditions (temperature, conversion and time).

(35) TABLE-US-00003 TABLE 1 Preparation of the unhydrogenated nitrile-diene-carboxylic ester copolymers (NBR 1-4; inventive examples are identified by an asterisk *). NBR-carboxylic ester 1 2* 3 4 Monomers Acrylonitrile (ACN) 18 27 16 21 1,3-Butadiene (BD) 31 46 32 24 Butoxy diethylene 51 27 glycol methacrylate (PEG-2-MA) Butyl acrylate (BA) 52 55 Total amount of water 190 190 190 190 SDS 2.4 2.4 1.44 1.44 Na salt of dispropor- 0.5 0.5 0.4 0.4 tionated resin acid Na.sub.2CO.sub.3 0.12 0.12 0.12 0.12 pH 10.5 ± 0.5 10.5 ± 0.5 10.5 ± 0.5 10.5 ± 0.5 t-DDM 0.25 0.30 0.29 0.29 Glidox ® 500 0.02 0.02 0.02 0.02 Premix solution FeSO.sub.4 0.03 0.02 0.03 0.03 Diethylhydroxylamine 0.2 0.2 0.2 0.2 stabilizer 0.5 0.5 Polymerization conditions Polymerization tempera- 12 12 12 12 ture [° C.] Polymerization 71.5 72.2 68.4 71.1 conversion [%] Polymerization time [h] 5 7 6.5 7

(36) TABLE-US-00004 TABLE 2 Addition of the increments of the nitrile-diene-carboxylic ester copolymers (NBR 1-4) The increments of the monomers were added at the reported monomer conversions ±5%. NBR 1 2 3* 4* Conversion [%] ACN (a)/BD (b) [% by wt.] 21 3/6 —/— —/— 3.5/6 33 —/— 9/— —/— —/— 42 3/7 —/— 3/6 2.5/3 48 3/6 —/— —/— —/— 63 —/— —/— 2/4 2.5/3 *Conversion at 27%

(37) The nitrile-diene-carboxylic ester copolymers were prepared batchwise in a 51 autoclave with stirrer system. In each of the autoclave batches, 1.25 kg of the monomer mixture and a total amount of water of 2.1 kg were used, as was EDTA in an equimolar amount based on the Fe(II). 1.9 kg of this amount of water were initially charged with the emulsifier in the autoclave and purged with a nitrogen stream. Thereafter, the destabilized monomers and the amount of the t-DDM molecular weight regulator specified in the table were added and the reactor was closed. After the reactor contents had been brought to temperature, the polymerizations were initiated by the addition of the premix solutions and the hydroperoxide.

(38) The progression of the polymerization was monitored by gravimetric conversion determinations. Upon attainment of the conversions reported in Table 1 the polymerization was terminated by adding an aqueous solution of diethylhydroxylamine. Unconverted monomers and other volatile constituents were removed by means of steam distillation.

(39) Before the respective NBR latex coagulated, it was admixed in each case with a 45% dispersion of Vulkanox® BKF (0.1% by weight of Vulkanox® BKF based on NBR solids) or of the stabilizer mixture (2,2′-methylenebis(4-methyl-6-nonyl)phenol (CAS 7786-17-6) and styrenized diphenylamine (CAS 68442-68-2), 0.5% by weight based on NBR solids). This was followed by coagulation with CaCl.sub.2), washing and drying of the crumbs obtained.

(40) The dried NBR rubbers were characterized by Mooney viscosity, ACN content and glass transition temperature and the content of termonomers was determined by .sup.1H-NMR analysis (Table 3).

(41) TABLE-US-00005 TABLE 3 Composition and properties of the unhydrogenated nitrile-diene- carboxylic ester copolymers 1 to 4 and the commercially available nitrile-diene rubbers 5 to 7 (amounts of copolymerized monomer in % by weight; inventive examples identified by an asterisk *) NBR 1 2* 3 4 5 6 7 ACN (a) [% by wt.] 15 25 16 19 22 28 34 BD (b) [% by wt.] 34 51 45 52 78 72 66 PEG-2-MA (c) [% by wt.] 51 24 BA [% by wt.] 39 29 Mooney viscosity MU 17 17 29 39 55 43 43 ML(1 + 4@100° C.)
II Production of Vulcanizates of the Nitrile-Diene-Carboxylic Ester Copolymers (NBR V1 to V7):
Production of the Vulcanizable Compositions:

(42) All the rubber mixtures were produced on a mixing roll mill. The diameter of the rolls was 80 mm, the length 200 mm. The rolls were preheated to 30° C.; the speed of the front roll was 16.5 rpm, that of the rear roll 20 rpm, which achieved a friction of 1:1.2.

(43) The rubber was initially charged and mixed for one (1) minute until a smooth milled sheet had formed. Subsequently, first the carbon black, then the additives and finally the crosslinking chemicals were incorporated. The total mixing time was 10 to 12 minutes.

(44) TABLE-US-00006 TABLE 4 Composition of the vulcanizable compositions (V1 to V7; inventive examples are identified by an asterisk *) Example V1 V2* V3 V4 V5 V6 V7 NBR copolymer % by % by % by % by % by % by % by composition wt. wt. wt. wt. wt. wt. wt. ACN (a) 15 25 16 19 22 28 34 BD (b) 34 51 45 52 78 72 66 PEG-2-MA (c) 51 24 BA (d) 39 29 NBR copolymer parts parts parts parts parts parts parts NBR 1* 100 NBR 2* 100 NBR 3 100 NBR 4 100 NBR 5 100 NBR 6 100 NBR 7 NBR 8 100 Other components phr phr phr phr phr phr phr Corax ® N 550/30 30 30 30 30 30 30 30 Regal ® SRF/N772 50 50 50 50 50 50 50 Vulkanol ® OT 10 10 10 10 10 10 10 Edenor ® C18-98 MY 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Vulkanox ® HS/LG 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulkanox ® MB2/MG 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Rhenocure ® IS 90-20 0.37 0.37 0.37 0.37 0.37 0.37 0.37 Zinkoxyd Aktiv 5 5 5 5 5 5 5 Vulkacit ® NZ/EGC 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulkacit ® Thiuram/C 2 2 2 2 2 2 2 Vulkalent ® E/C 1 1 1 1 1 1 1

(45) TABLE-US-00007 TABLE 5 Crosslinking density of vulcanizates V1 to V7 MDR at 160° C. Unit V1 V2* V3 V4 V5 V6 V7 S min dNm 0.8 1.5 1.1 1.1 2.5 1.4 1.2 S max dNm 12.7 17.4 18.7 16.6 22.1 21.7 21.5 TS 1 min 2.1 1.6 2.0 2.0 1.5 1.5 1.4 TS 2 min 2.3 1.9 2.3 2.3 1.7 1.7 1.5 t 10 min 2.1 1.8 2.2 2.2 1.7 1.7 1.5 t 25 min 2.5 2.1 2.7 2.7 2.0 2.0 1.8 t 50 min 3.0 2.6 3.3 3.5 2.4 2.5 2.2 t 70 min 3.6 3.1 4.0 4.3 2.8 3.0 2.7 t 80 min 4.1 3.5 4.8 5.1 3.1 3.4 3.1 t 90 min 4.8 4.2 6.5 7.0 3.8 4.2 4.0 t 95 min 5.4 5.3 8.7 9.7 4.7 5.2 5.3

(46) The crosslinking properties of the inventive vulcanizate V2 are comparable to butyl acrylate-containing NBR copolymers (V3 and V4) and the commercially available NBR copolymers (V5 to V7).

(47) The mouldings (sheets of thickness 2 mm) for the performance of the further determinations were produced by vulcanization at 160° C. for 15 minutes.

(48) TABLE-US-00008 TABLE 6 Physical properties of the unaged vulcanizates V1 to V7 V1 V2* V3 V4 V5 V6 V7 Tensile test TS MPa 8.3 11.2 10.2 13.1 15.4 14.4 15.1 EB % 210 232 226 250 297 317 340 M50 MPa 1.4 1.8 1.8 1.9 2 2.1 2.1 M100 MPa 3.7 4.2 4.2 4.8 4.1 4.2 4.1 Hardness Shore A 58.1 63.5 64.8 62.5 68.3 69.4 69.7 Glass transition temperature TR 10 ° C. −48.7 −41.8 −39.2 −31.1 −40.8 −32.8 −27 TR 30 ° C. −43.2 −37 −35.3 −26.7 −36 −28.9 −23.4 TR 50 ° C. −38.7 −32.8 −31.9 −23.3 −31.2 −25 −20 TR 70 ° C. −33.1 −27.2 −27.2 −19.1 −23.8 −19.2 −14.9 TR 70 − TR 10 ° C. 15.5 14.6 12 11.9 17 13.6 12.1 DSC Tg ° C. −57.5 −48.5 −44.5 −37.3 −50.0 −38.4 −31.3 The comparison of V1 with V2* and V5 with V6 and V7 shows that the Tg of the vulcanizate falls with a reduced content of ACN.

(49) In the comparison of V2 with V5, it can be seen that the exchange of BD for BDGMA, with about the same amount of ACN, leads to comparable TR10 and DSC values.

(50) V1 has a lower Tg than the inventive vulcanizate V2.

(51) TABLE-US-00009 TABLE 7 Physical properties of the vulcanizates V1 to V7 after storage in IRM 903 at 100° C. for 3 days Ageing properties Unit V1 V2* V3 V4 V5 V6 V7 TS MPa 8.5 14.2 11.5 13.8 15.5 15.3 17.2 EB % 166 234 219 213 273 285 324 M50 MPa 1.7 2.2 1.9 2.1 1.8 2.1 2.4 M100 MPa 4.7 5.4 4.8 5.8 4.3 4.6 5 Hardness Shore A 60 67.2 60 63.7 60.2 66.1 70.9 Δ TS % 2.4 26.8 12.7 5.3 0.6 6.3 13.9 Δ EB % −21.0 0.9 −3.1 −14.8 −8.1 −10.1 −4.7 Δ M50 % 21.4 22.2 5.6 10.5 −10.0 0.0 14.3 Δ M100 % 27.0 28.6 14.3 20.8 4.9 9.5 22.0 Δ hardness Shore A 1.9 3.7 −4.8 1.2 −8.1 −3.3 1.2 Δ volume % 2.4 −0.2 11.9 4.9 18.3 8.1 2.4 Δ weight % 1.0 −1.0 8.2 2.9 13.1 5.7 1.3

(52) The inventive nitrile-diene-carboxylic ester copolymer vulcanizate V2 has reduced swelling (increase in volume) after ageing in IRM 903 for three days, compared to the comparative vulcanizate V1 or the copolymers V5 and V6 with a similar content of acrylonitrile monomers of 22% to 28% by weight.

(53) The inventive vulcanizate V2 with BDGMA as termonomer has both a low glass transition temperature (TR 10 or DSC Tg) of less than −40° C. and simultaneously low swelling in oil.

(54) TABLE-US-00010 TABLE 8 Physical properties of the vulcanizates V1 to V7 after storage in IRM 903 at 100° C. for 7 days Ageing properties Unit V1 V2* V3 V4 V5 V6 V7 TS MPa 10.2 13.3 12 14.8 15.8 14.8 17 EB % 190 208 214 223 260 255 270 M50 MPa 1.9 2.3 1.9 2.3 1.8 2.2 2.7 M100 MPa 4.9 5.6 5 6.1 4.4 4.9 5.6 Hardness Shore A 63.5 69.9 61.8 65.7 60.4 67.7 72.6 ΔTS % 22.9 18.8 17.6 13.0 2.6 2.8 12.6 Δ EB % −9.5 −10.3 −5.3 −10.8 −12.5 −19.6 −20.6 Δ M50 % 35.7 27.8 5.6 21.1 -10.0 4.8 28.6 Δ M100 % 32.4 33.3 19.0 27.1 7.3 16.7 36.6 Δ hardness Shore A 5.4 6.4 −3 3.2 −7.9 −1.7 2.9 Δ volume % 3.4 0.6 13.3 5.9 18.9 8.6 3.7 Δ weight % 0.1 −1.7 7.8 2.2 12.1 4.8 0.8

(55) The inventive vulcanizate V2 has reduced swelling (increase in volume) after ageing in IRM 903 for 7 days, compared to the comparative vulcanizate V1 or the comparative vulcanizates V5 and V6 with a similar content of acrylonitrile monomers of 22% to 28% by weight.

(56) TABLE-US-00011 TABLE 9 Properties of the vulcanizates before and after ageing in Fuel C at 23° C. for 3 days Ageing properties V1 V2* V3 V4 V5 V6 V7 TS MPa 3.8 5.8 4.3 5.6 4.7 6.8 7.1 EB % 88 118 89 102 96 147 157 M50 MPa 1.6 1.7 2 1.9 1.9 1.7 1.6 M100 MPa 4.7 5.4 5.1 4.2 4 Hardness Shore A 45 51.5 49.7 49.8 49.6 52.2 54.6 Δ TS % −54.2 −48.2 −57.8 −57.3 −69.5 −52.8 −53.0 Δ EB % −58.1 −49.1 −60.6 −59.2 −67.7 −53.6 −53.8 Δ M50 % 14.3 −5.6 11.1 0.0 −5.0 −19.0 −23.8 Δ M100 % 11.9 12.5 24.4 0.0 −2.4 Δ hardness Shore A −13.1 −12 −15.1 −12.7 −18.7 −17.2 −15.1 Δ volume % 64.8 45.3 81.2 62.8 79.2 54.9 40.6 Δ weight % 39.3 28.0 51.5 39.0 51.3 35.8 26.4

(57) The inventive vulcanizate V2* likewise has reduced swelling after ageing in Fuel C for 3 days, compared to the comparative vulcanizate V1 or the comparative vulcanizates V5 and V6 with a similar content of acrylonitrile monomers of 22% to 28% by weight.

(58) Vulcanizates V3 and V4 containing terpolymers based on butyl acrylate (BA) are incapable of simultaneously having a low glass transition temperature and a small change in swelling on ageing like the inventive vulcanizate V2*.

(59) The comparison of V1 with V3, both of which have a similar amount of acrylonitrile monomers, shows that the exchange of the butyl acrylate termonomers in V3 for the PEG-2-MA (BDGMA) causes a distinct reduction in change in volume (swelling).

(60) The swelling properties of the inventive terpolymer V2 are similar to those of copolymer V7 which, however, contains much more acrylonitrile (namely 34% by weight compared to only 25% by weight in V2). By comparison with V7, however, the glass transition temperature of the inventive vulcanizate V2* is much lower.

(61) The comparison of V1 with V2* makes it clear that vulcanizates solely based on terpolymers with small amounts of nitrile monomer units are insufficient to simultaneously also achieve particularly low swelling.

(62) The mechanical properties of the inventive vulcanizate V2* have essentially not deteriorated by comparison with the vulcanizate based on the commercially available copolymers V5 to V7.

(63) The particular advantage of the invention is that vulcanizates based on the nitrile-diene-carboxylic ester copolymers according to the invention have low swelling and simultaneously good cold flexibility.

(64) In terms of the combination of these properties, the nitrile-diene-carboxylic ester copolymers according to the invention are superior to nitrile-diene-carboxylic ester copolymers that are commercially available to date or known from the prior art.