USE OF ACRYLATE RUBBERS HAVING IMPROVED LOW-TEMPERATURE PROPERTIES AND GOOD OIL RESISTANCE FOR PRODUCING VULCANIZABLE MIXTURES AND VULCANIZED PRODUCTS

Abstract

The present invention relates to the use of copolymers of alkyl acrylates, specific unsaturated carboxylic esters and optionally ethylene that combine a low glass transition temperature with oil resistance in the manufacture of vulcanizable mixtures, the crosslinking thereof and thereby obtainable vulcanizates and shaped articles.

Claims

1. Copolymers for the manufacture of vulcanizates and vulcanizable compositions, the copolymers comprising: i) 49 to 99 wt % of repeat units derived from at least one alkyl acrylate other than repeat units ii), ii) 1 to 51 wt % of repeat units derived from at least one monomer of general formula (I)
CH.sub.2C(R.sup.1)(COO(R.sup.2O).sub.nR.sup.3)(I) where R.sup.1 represents hydrogen or methyl, R.sup.2 at each occurrence independently represents a linear or branched C.sub.2 to C.sub.6 alkylene group, R.sup.3 represents hydrogen, unsubstituted or C.sub.1-C.sub.3 alkyl substituted phenyl, a linear or branched C.sub.1-C.sub.8 alkyl group or C(O)R.sup.4, R.sup.4 represents hydrogen or a linear or branched C.sub.1-C.sub.8 alkyl group, and n represents a number from 2 to 30, and iii) 0 to 50 wt % of repeat units derived from ethylene, wherein the amounts are each based on the combined amount of repeat units i) to iii).

2. The copolymers according to claim 1, wherein the alkyl acrylates have an alkyl moiety of 1 to 10 carbon atoms and preferably are selected from methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, n-hexyl acrylate, 3-propylheptyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and also mixtures thereof, more preferably methyl acrylate, ethyl acrylate and n-butyl acrylate and also mixtures thereof.

3. The copolymers according to claim 1, wherein the copolymers contain 2 to 40 wt % of monomers of general formula (I), all based on the sum total of repeat units i) to iii).

4. The copolymers according to claim 1, wherein the R.sup.2 moieties at each occurrence are independently selected from the group consisting of ethane-1,2-diyl, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, butane-1,3-diyl, pentane-1,3-diyl, pentane-1,4-diyl, pentane-1,5-diyl and 2-methylbutane-1,4-diyl, preferably from ethane-1,2-diyl, propane-1,3-diyl, propane-1,2-diyl and butane-1,4-diyl, more preferably from ethane-1,2-diyl and propane-1,2-diyl.

5. The copolymers according to claim 1, wherein the R.sup.3 moieties are selected from the group consisting of H, CH.sub.3, CH.sub.2CH.sub.3, CH.sub.2CH.sub.2CH.sub.3, CH.sub.2CH.sub.2CH.sub.2CH.sub.3, CHO, COCH.sub.3, COCH.sub.2CH.sub.3, COCH.sub.2CH.sub.2CH.sub.3 and COCH.sub.2CH.sub.2CH.sub.2CH.sub.3, preferably from H, CH.sub.3, CH.sub.2CH.sub.3 and COCH.sub.3 and more preferably from CH.sub.3, CH.sub.2CH.sub.3 and COCH.sub.3.

6. The copolymers according to claim 1, wherein the copolymers include one or more further copolymerized monomers (iv) in a combined amount of less than 25 wt %, preferably less than 20 wt %, more preferably less than 15 wt %, yet more preferably less than 10 wt %, yet still more preferably less than 5 wt % and most preferably less than 1 wt %, all based on the combined amount of repeat units i) to iii) and of the one or more further copolymerized monomers (iv).

7. The copolymers according to claim 6, wherein the further copolymerized monomers (iv) are selected from epoxy-containing acrylates, epoxy-containing methacrylates, alkoxyalkyl acrylates having an alkoxyalkyl group of 2 to 8 carbon atoms, vinyl ketones, vinylaromatic compounds, conjugated dienes, -monoolefins, vinyl monomers having a hydroxyl group, chlorovinyl acetate, monoalkyl maleate, monoalkyl fumarate, acrylic acid, methacrylic acid, vinylidene fluoride, hexafluoropropene, vinylidene chloride, tetrafluoroethylene, tetrachloroethylene, vinyl chloride, unsaturated amide monomers, carbon monoxide and mixtures thereof, preferably from methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, glycidyl methacrylate, divinyl adipate, methyl vinyl ketone, ethyl vinyl ketone, styrene, -methylstyrene, vinyltoluene, butadiene, isoprene, propylene, 1-butene, -hydroxyethyl acrylate, 4-hydroxybutyl acrylate, 3-cyanoethyl acrylate, acrylamide, N-methylmethacrylamide, 2-methoxyethyl acrylate, chlorovinyl acetate, monoalkyl maleate, monoalkyl fumarate, carbon monoxide and mixtures thereof and more preferably from acrylic add, methacrylic acid, 2-methoxyethyl acrylate, glycidyl methacrylate, chlorovinyl acetate, monoalkyl maleate, monoalkyl fumarate, carbon monoxide and mixtures thereof.

8. The copolymers according to claim 1, wherein the copolymers contain repeat units derived from ethylene, methyl acrylate and polyalkylene glycol (meth)acrylates having 2 to 20 ethylene glycol and/or propylene glycol repeat units, preferably together with repeat units derived from butyl acrylate, monoalkyl maleate and/or monoalkyl fumarate.

9. The copolymers according to claim 1, wherein the copolymers contain repeat units derived from two or more alkyl acrylates, preferably ethyl acrylate and butyl acrylate, and polyalkylene glycol (meth)acrylates having 2 to 20 ethylene glycol and/or propylene glycol repeat units.

10. A process for producing vulcanizable compositions, the process comprising mixing the copolymers according to claim 1 with one or more crosslinkers.

11. Vulcanizable compositions comprising: The copolymers according to claim 1, one or more crosslinkers, and optionally coagents for enhancing the crosslinking yield.

12. A process for producing vulcanizates, the process comprising crosslinking the vulcanizable compositions according to claim 11.

13. Vulcanizates obtained from the copolymers according to claim 1.

14. Articles of manufacture comprising the copolymers according to claim 1 wherein the articles of manufacture are foamed or unfoamed mouldings, cable conduction layers, cable sheathing, gaskets, transport belts, bellows, hoses, cylinder head cover gaskets, and O-rings.

15. Non-volatile plasticizer and/or impact modifier for plastics comprising the copolymers according to claim 1.

16. Plastics or rubbers comprising the copolymers according to claim 1 as a blend component.

17. The copolymer according to claim 1, wherein the copolymer comprises: 55 to 90 wt % of the repeat units derived from the at least one alkyl acrylate other than repeat units ii), 4 to 25 wt % of monomers of general formula (I), and >0 to 45 wt % of repeat units derived from ethylene, wherein the amounts are each based on the combined amount of repeat units i) to iii).

18. The copolymer according to claim 17, wherein the copolymer comprises: 6 to 20 wt % of monomers of general formula (I); and >20 to 45 wt % of repeat units derived from ethylene, all based on the sum total of repeat units i) to iii).

Description

[0053] Two possible modes of carrying out the invention will now be described by way of example:

Process A: Production in Internal Mixer

[0054] At the start, the internal mixer (preferably an internal mixer with intermeshing rotor geometry) is charged with the copolymers of the present invention and comminutes the material. After a suitable period of mixing, the fillers and additives are admixed. The temperature is policed during the mixing process such that the material being mixed spends a suitable period at a temperature in the range from 80 to 150 C. After a further suitable mixing period, the further constituents of the mixturelike optionally stearic acid, coagents, antioxidants, plasticizers, white pigments (titanium dioxide for example), dyes and other processing activesare admixed. After a further suitable mixing period, the internal mixer is vented and the shaft is cleaned. After a further suitable period, the crosslinker is admixed. Mixing temperature must be carefully policed at this stage to prevent any scorching in the mixer, if necessary, rotor speed has to be reduced to lower the mixing temperature. After a further suitable period, the internal mixer is emptied to obtain the vulcanizable mixture. A suitable period is to be understood as meaning a few seconds to some minutes. The vulcanizable mixtures thus obtained may be evaluated in a conventional manner, say in terms of the Mooney viscosity, in terms of Mooney Scorch or in terms of a rheometer test. Alternatively, it is possible to discharge the mixture without admixture of the crosslinker and to admix the crosslinker on a roll mill.

Process B: Production on the Roll

[0055] The ingredients may be added similarly to process A above.

[0056] The vulcanization temperature of the copolymers according to the present invention and/or of the vulcanizable compositions containing same is typically in the range from 100 to 250 C., preferably from 140 to 220 C., more preferably from 160 to 200 C. If necessary or desired, the as-obtained vulcanizates may subsequently be conditioned at a temperature of about 150 to 200 C. for 1 to 24 hours in order to improve their end-product properties.

[0057] The vulcanizates obtainable by said vulcanization also form part of the subject-matter of the present invention. The term vulcanizates thus comprehends vulcanized copolymers of the present invention and vulcanized compositions containing the copolymers of the present invention and preferably one or more crosslinkers. Vulcanizates of this type perform very well in the compression set test at room temperature and 150 C. and exhibit high tensile stress values and good elongation at break values as well as a very good combination of low Oil Swell and low glass transition temperature.

[0058] The copolymers of the present invention and the vulcanizates and/or vulcanizable mixtures produced therefrom are useful in the manufacture of foamed or unfoamed mouldings and also in the manufacture of self-supported film/sheet and of coatings of any kind, in particular in the manufacture of cable conduction layers, cable sheathing, gaskets, transport belts, bellows, hoses, cylinder head cover gaskets and O-rings. The invention thus also encompasses the above mouldings containing the vulcanizates of the present invention. The vulcanizates of the present invention may further be admixed into plastics to serve as a non-volatile antistat. Therefore, the use of copolymers according to the invention to antistaticize polymers and the antistaticized plastics containing the vulcanizates of the present invention also form a further part of the subject-matter of the invention.

[0059] The copolymers of the present invention are further useful as elastomeric phase in thermoplastic vulcanizates and also as blend component in plastics or rubbers, preferably PVC, polyamide, polyester and/or HNBR.

[0060] Further possibilities of employment consist in the use of copolymers according to the present invention as non-volatile plasticizers and/or impact modifiers in plastics, preferably PVC, polyamide and/or polyester.

[0061] Therefore, thermoplastic vulcanizates containing the vulcanizates of the present invention as elastomeric phase and also plastics and rubbers containing the vulcanizates of the present invention, in particular as non-volatile plasticizers, and plastics containing the vulcanizates of the present invention as impact modifiers also form further parts of the subject-matter of the invention.

[0062] One significant advantage of the invention is that the vulcanizates of the present invention are the first to display an effective combination of oil resistance and low glass transition temperature.

EXAMPLES

Test Methods:

[0063] Glass transition temperature (Tg) is determined via Differential Scanning calorimetry (DSC) in accordance with EN ISO 11357-1:2009 and EN ISO 11357-2:2014, using helium as inert gas and determining the glass transition temperature by the inflection point method. Temperature scanning rate is 20 K/min for the copolymers and 10 K/min for the vulcanizates.

[0064] Copolymer composition was determined via .sup.1H NMR (Bruker DPX400 with XWIN-NMR 3.1 software, measurement frequency 400 MHz).

[0065] Gel permeation chromotography (GPC) was carried out in accordance with DIN 55672-1, Gel Permeation Chromotography (GPC) Part 1: Tetrahydrofuran (THF) as eluent, with addition of 0.5 wt % triethylamine. Polystyrene was used as standard.

[0066] Mooney viscosity (ML (1+4)100 C.) values are each determined using a shearing disc viscometer as per ISO 289 at 180 C.

[0067] Slabs to determine the mechanical properties were vulcanized in a Werner & Pfleiderer vulcanization press between Teflon foils under the stated conditions.

[0068] Shore A was determined to ASTM-D2240-81.

[0069] Tensile tests to determine stress as a function of deformation were carried out to DIN 53504 and/or ASTM D412-80.

[0070] Hot-air ageing was carried out to DIN 53508/2000. Method 4.1.1 Ageing in oven with forced air circulation was employed.

[0071] Immersion in oil and water was carried out in accordance with DIN ISO 1817.

Substances with Trade Names:

TABLE-US-00001 VAMAC GLS AEM from DuPont: 62.7 wt % of methyl acrylate, 33.4 wt % of ethylene, 3.9 wt % of monoethyl fumarate, T.sub.G 25.6 C. VAMAC DP AEM from DuPont: 59.0 wt % of methyl acrylate, 41.0 wt % of ethylene, T.sub.G 29 C. SR550 methoxypolyethylene glycol methacrylate (M.sub.w of PEG unit 350 g/mol), from Sartomer Europe SR552 methoxypolyethylene glycol methacrylate (M.sub.w of PEG unit about 553 g/mol), from Sartomer Europe Antilux 110 paraffin wax from Rheinchemie Rheinau GmbH Rhenofit TAC/S triallyl cyanurate 70% on 30% silica from Rheinchemie Rheinau GmbH Rhenofit DDA ageing control agent (diphenylamine derivative) from Rheinchemie Rheinau GmbH Perkadox 14-40 B-PD supported di(tert-butylperoxyisopropyl)benzene from AkzoNobel N.V. Corax N550/30 carbon black from Orion Engineered Carbons GmbH

Production of Copolymers:

M1

[0072] The polymer was produced in a 5 L stirred autoclave. A 1492 g quantity of a solution consisting of 1490.0 g of tert-butanol and 2.0 g of methyl acrylate and also 252.5 g of an activator solution consisting of 2.5 g of AIBN (azobis(isobutyronitrile)), and 250.0 g of tert-butanol solution were successively sucked into the 5 L reactor at 30 C. The reactor was swept with nitrogen and then pressured with 960.0 g of ethylene. The temperature was raised to 70 C., establishing a pressure of about 380 bar. Then, a solution consisting of 200.0 g of methyl acrylate and 50.0 g of SR550 was metered into the reaction mixture for 9 h at a rate of about 0.46 g/min. Throughout the entire polymerization, the pressure was maintained at 380 bar10 bar by injection of ethylene.

[0073] Following a reaction time of 10 h, the ethylene feed was stopped and the polymer solution was slowly forced out of the 5 L reactor into a termination autoclave. The solvent and residual monomers were removed to leave 312.0 g of an SR550-ethylene-methyl acrylate copolymer. [0074] Mn=48 880 g/mol, Mw=109 106 g/mol, Mz=183 890 g/mol [0075] ethylene=36.1 wt %, methyl acrylate=48.2 wt %, SR550=15.7 wt % [0076] ML(1+4) 100 C.=<10; Tg=34 C.

M2

[0077] A four-neck flask fitted with Teflon stirrer and high-intensity condenser was charged under nitrogen with 75 g of water, 5.5 g of sodium dodecylsulphate, 62 g of ethyl acrylate, 24 g of butyl acrylate, 12 g of SR552 and 2 g of monoethyl fumarate. This was followed by the admixture of 0.002 g of sodium formaldehydesulphoxylate and 0.005 g of butyl hydroperoxide. The polymerization started and the temperature rose to 30 C. Following a polymerization time of 0.5 h, the polymer was precipitated with 20% aqueous NaCl solution. The polymer was then washed with water and vacuum dried at 75 C. to obtain 85 g of an acrylate rubber of the following composition: [0078] ethyl acrylate: 62 wt %, butyl acrylate: 24.0 wt %, SR552: 12 wt %, monoethyl fumarate: 2.0 wt % [0079] Tg=31 C.

Production of Vulcanizates and Vulcanizable Mixtures

[0080] The polymers were processed on the roll by method B into the recipes shown in table 1 below.

[0081] Vulcanization was carried out as a press cure at 180 C. (10 min for 2 mm thick slabs/specimens, 12 min for 6 mm thick slabs/specimens). After vulcanization, the slabs/specimens were conditioned at 176 C. for 4 h.

[0082] As can be seen from table 2, the vulcanizates produced from polymers according to the present invention display distinctly reduced glass transition temperatures for a comparable Oil Swell.

TABLE-US-00002 TABLE 1 Recipes of mixing tests, amounts in phr Example No. M1 M2 VM1 VM2 Example 1 100 Example 2 100 Vamac DP 100 Vamac GLS 100 Corax N550 55 55 55 55 Antilux 110 1.0 1.0 1.0 Rhenofit DDA 1.4 1.4 1.4 Luvomaxx CDPA 2 DIAK No 1 0.9 Rhenofit TAC/S 2 2 2 Perkadox 14-40 5 5 5 Sum total 184.4 164.4 164.4

TABLE-US-00003 TABLE 2 Results of mixing tests Example No. M1 M2 VM1 VM2 ethylene content of wt % 36.1 41.0 33.4 copolymer ML(1 + 4)100 C. MU 6 38 41 S min (MDR 180 C.) dNm 0.2 2.6 0.5 0.5 S max (MDR 180 C.) dNm 8.3 11.5 15.8 11.2 S max S min dNm 8.1 8.9 15.3 10.7 T95 (MDR 180 C.) s 501 418 433 484 Vulcanization press cure at 180 C., conditioning at 175 C. for 4 hr hardness ShA 66 60 68 72 elongation at break % 238 112 213 268 Tg (DSC) C. 33 31 29 22 Immersion 70 h/150 C. IRM 903 change in mass % 29 12 35 23 chane in volume % 42 16 49 32 hardness ShA 41 55 50 50 elongation at break % 181 98 149 218

[0083] Example M1, which is in accordance with the present invention, has a distinctly lower glass transition temperature as compared with the comparators VM1 and VM2 while other physical properties, such as elongation at break, Oil Swell, etc., correspond to the ethylene content. The surprisingly lower Mooney viscosity in the case at Working Example M1 would even permit an increase in the peroxide quantity used for the vulcanization, thereby making possible a further reduction in Oil Swell without causing an increase in the glass transition temperature.