SPECIFICATIONThermoplastic elastomer blendsThis invention relates to thermoplastic elastomer blends.
It is known to produce thermoplastic elastomer blends by dynamic valucanisation of a blend of EPDM rubber and polyolefin resin so that the rubber is substantially fully cured. Such thermoplastic elastomers have very useful properties and can advantageously be used in place of conventional thermosetting rubbers. However, it has been found difficult to produce by that process a thermoplastic elastomer of low hardness for example having a Shore A hardness less than 70.
According to the present invention there is provided a thermoplastic elastomer comprising a blend of a polynorbornene and a polyolefin resin, the polynorbornene being cured during blending by the addition of a curative.
The invention also provides a process for producing a thermoplastic elastomer comprising mechanically blending polynorbornene polymer and a polyolefin resin, and during said blending heating the mixture, and adding a curative to the mixture when said mixture is at least substantially molten and continuing said mechanical blending until the polynorbornene phase in said blend is substantially cured.
The essential constituents of the thermoplastic elastomer blend are polynorbornene and a polyolefin resin.
The polynorbornene is preferably produced by polymerising norbornene which is itself produced from ethylene and cylopentadiene by Diels-Alder Synthesis. The polynorbornene is preferably an amorphous polymer in powder form, having a molecular weight above 2,000,000. A commercially available polynorbornene which can be used in the invention is marketed as "Norsorex" has a real density of 0.96 and a second order vitreous transition temperature of 35"C.
The polyolefin resin is preferably a high molecular weight polymer suitable examples of which are polyethylene, polypropylene, ethylene/vinyl acetate copolymers, and ethylene/propylene copolymers.
The curative preferably comprises a phenolic resin which may be halogenated. A metal oxide such as zinc oxide may be included with the phenolic resin.
Curing of the polynorbornene phase of the blend during agitation thereof is known as "Dynamic Vulcanisation". Provided that sufficient polyolefin is present in the blend, generally more than 35 parts by weight based on the total weight of polynorbornene and polyolefin, then the resultant products behaves as a thermoplastic but will feature elastic properties and retain good set resistance at room temperature and at elevated temperatures. Thermoplastic elastomer blends according to the invention of low hardness can be obtained by the addition of a softener if desired to relatively high loadings such as could not be accepted by known thermoplastic elastomer blend formulations comprising a rubber and a plastic.
The elastomer of the invention may include other ingredients. For example, a thermoplastic elastomer such as a styrene-ethylene-butylene-styrene (SEBS) resin preferably with a corresponding reduction in the amount of polyolefin resin in the blend can be added to produce products of low hardness, but still with good set resistance at low temperatures. Black and non-black fillers and extenders can also be added which may modify the physical properties such as hardness and modulus but without significantly affecting the set resistance.
The products are preferably made by blending polynorbornene with molten polyolefin resin in a suitable mixing unit e.g. Banbury mixer, adding required additional product modifiers, e.g.
softeners, fillers, pigments, etc. With the blend at a temperature above the melting point of the polyolefin resin, typically 1 70 C for polypropylene, a curing resin and activator are added, and intimate mixing of the blend continued until cure of the polynorbornene is complete. At this time a suitable antidegradant is preferably added and mixing continued until the antidegradant has been dispersed fully in the blend. The material can be discharged from the mixer and, if desired, sheeted off by passing through a two roll mill.
The following examples further illustrate the invention:In the Examples a polynorbornene and a paraffinic oil were first mixed together to form a first stage. The first stage was then mixed with the remaining ingredients except the curative and antidegradant. Afterr blending of the polymers and other ingredients for about seven minutes accompanied by an increase in temperature to from 165-1 70 C whereat the plastic resins softened and melted the curative was added. Mixing continued for a further ten minutes with the temperature being maintained at 1 65 C or above. The antidegradant was then added and after mixing for a further two minutes the mixture was discharged and formed into a sheet by passing it through a two roll mill.
In the following Table 1 Example 1 is a comparison example in which no phenolic curative was added so that the polynorbornene rubber is unvulcanised.
TABLE I EXAMPLE@ (1) (2) (3) (4)Polynorbornene 1 65.00 65.00 65.00 65.00 Paraffinic Oil 130.00 130.00 130.00 130.00 1st Stage 195.00 195.00 195.00 195.00 1st Stage M/B 195.00 195.00 195.00 195.00Polypropylene 35.00 35.00 35.00 35.00 A Carbon Black - 5.00 5.00 5.00 5.00Stearic Acid 0.58 0.58 0.58 0.58Zinc Oxide 2.90 2.90 2.90 2.90Antidegradants 5 1.15 1.15 1.15 1.15Phenolic curing resin6 - 9.75 9.75 9.75 Chlorinated 7Polyethylene - - 5.00 5.00 oxide - - - 5.00oxide - - - 5,00 1. Norsorex supplied by CDF Chimie, 2. Enerpar 23 supplied by BP, 3. Propathene GWM22"used, supplied by lCl, 4.Sterling 50" IN550) used, supplied by Cabot Carbon, 5. A blend ofIrganox 1010 (Ciba Geigy) and Vulkanox MB2 (Bayer) used in ratio 0.15.1, 6. SP1055Bromomethyl alkylated phenol-formadehyde resin supplied by Schenectady-Midland, 7.
"CM3630" supplied by Bayer, 8. "Saytex 102" supplied by Saytech.
Injection moulded test plaques, were formed using a melt temperature of 1 75 C, from theproducts obtained which were tested. The results are shown in Table II.
TABLE IIEXAMPLE ' (1) (2) (3) (4)Hardness (Shore A) 52 56 56 57Hardness (IRHD) 56 60 60 Modulus @ 100%(MPa) 2.9(1.3) 2.9(1.5) 2.6(1.7) 2.6Elongation @ Break(%) 330(580) 150(280) 130(180) 150Tensile Strength (MPa) 3.0(3.2) 3.0(2.5) 2.8(1.9) 2.9Compression Set,22 hrs @ 23"C (%) 82 27 17 20Compression Set,22 hrs @ 700C (%) 95 40 25 20Stress-Strain values outside parenthesis measured in flow direction, values in parenthesis measured transverse to flow direction.
The effect on compression set by the vulcanisation of the polynorbornene rubber is demonstrated by comparison of the properties of the products of Examples 2 to 4 with the product of Example 1.
In Table Ill the effect of high levels of plastic to rubber is shown in Examples 5, 7 and 9. The effect of fillers can be seen in Examples 6 and 7.
TABLE III EXAMPLE@@@ (5) (6) (7) (8) (9)Polynorbornene (Morsorex Powder) 65.00 30.00 65.00 65,00 65.00Paraffinic Oil 130.00 45.00 130.00 97.50 130.00(Enerpar 23)195.00 75.00 195.00 162.50 195.001st Stage M/B 180.00 75.00 195.00 162.50 195.00Polypropylene 40.00 70.00 35.00 35.00 35.00Carbon Black 5.00 3.00 5.00 50.00 50.00Stearic Acid 0.58 - 0.58 0.58 0.58Zinc Oxide 2.70 1.50 2.90 2.90 2.90ChlorinatedPolyethylene 5.00 3.00 5.00 - 5.00Phenolic curing 9.00 4.50 9.75 7.80 9.75resin (SP1055)Antidegradents 1.15 1.15 1.15 1.15 1.15Calcium Carbonate 9 - 25.0 - - Precipitated Silica - - 10.0 - Decabromodiphenyl oxide - - - - 5.00 (9. "calmote UF";; supplied by Tarmac Poadstone, 10. "VN3" supplied byID Chemicals)Hardness (Shore A) 62 95 55 70 66Hardness (IRHD) 68 (Shore D-42) 60 75 70 Modulus @ 100% (MPa) 3.3(1.9) 10.4 2.7(1.7) 5.4 3.2Elongation @ Break(%) 140(210) 100(80) 140(260) 180 140Tensile strength(MPa)3.6(2.4) 10.4(7.0) 2.9(2.6) 7.1 3.4 CoMpression Set,22. hrs @ 23"C. (%) 22 - 18 - Coopression Set,22 hrs @ 700C (%) 28 48 32 40 21In the following Examples 10 to 13 the effect of using different polyolefins is illustrated.
TABLE IV (10) (11) (12) (13)Polynorbornene 65.0 65.0 60.0 65.0Paraffinic Oil 99.5 97.5 90.0 97.5162.5 162.5 150.0 162.5Blends of polynorbornene and paraffinic oil mixed as1st stage M/B. This then added to the second stage as follows:1st stage M/B 162.5 162.5 150.0 162.5Polypropylene 1 35.0 - 20.0 20.0Polypropylene 2 15.0 - - copo lyine r High density - 20.0 - polyethyleneEthylene propylene 4 - - 20.00 copolymerEthylene Vinyl 5 - - - 15.0Acetate copolymerCarbon black 6 5.0 5.0 5.0 5.0Stearic Acid 0.58 0.58 0.60 0.58Zinc Oxide 2.9 2.9 2.4 2.9Phenolic curing resin7 7.8 7.8 9.0 9.75Chlorinated Polyethylene 8 5.0 5.0 5.0 5.0Antidegradant 9 0.1 0.1 0.1 0.11.Polypropylene honopolymer - Propathene GWM22 used,supplied by ICI2. Polypropylene copolymer - Propathene GWM101 used,supplied by ICI3. High density polyethylene - Vestolen A6016 used, suppliedby Chemische Werke Huls AG 4. Ethylene-propylene - Vistalon 719 used, supplied by Essocopolymer5. Ethylene vinyl acetate - Evatane 18-02 used, supplied by ICI copolymer 6. Carbon black - Sterling SO (N550) used, suppliedby Cabot Carbon7. Phenolic curing resin - SP1055 used, supplied by Schenectady-Midland 8. Chlorinated polyethylene - CM3630 used, supplied by Bayer9.Antidegradant - Irganox 1010 used, supplied byCiba-Geigy Test plaques were formed from the products of Examples 10 to 1 3 by injection moulding at a melt temperature of 1 75 C and the properties measured. The results are shown in Table V.
TABLE V(10) (11) (12) (13)Hardness (Shore A) 64 63 55 52Hardness (IRHD) 70 69 60 56 tRxSuluS @ 100% (MPa) 3.7 3.2 2.9 2.5(2.6) (2.2) (1.9)Elongation @ Break (%) 130 140 170 140(230) (270) (320)Tensile Strength (MPa) 3.9 3.5 3.2 2.7(3.5) (3.8) (4.0) Coopression Set 17 18 18 18 22 hrs @ 23"C (%)Compression Set 30 28 40 50 22 hrs @ 700C (%)Stress-strain values outside parenthesis measured in flow direction, Values inside parenthesis measured transverse to flow direction.
The above Examples show that the use of polypropylene high density polyethylene copolymer tends to produce slightly lower hardness products, than when using straight polypropylene homo-polymer with also higher elongation at break and lower modulus figures.
The ethylene-propylene copolymer used in Example II has a very high ethylene content (approx. 77%) and alone can be processed as a thermoplastic. The incorporation of that material improves processability, by increasing the plastic phase level, whilst maintaining a low product hardness. The compression set at elevated temperatures suffers slightly, whilst elongation and tensile strength at break shown some improvement. Ethylene vinyl acetate copolymer used inExample 1 3. being a much softer, lower softening point material than polypropylene, produces low hardness products, but with rather inferior set resistance at elevated temperatures.
The effect of using a non-halogenated phenolic curing resin is illustrated in the followingExample 14. For comparison with a halogenated phenolic resin Example 10 is set out again withExample 14 in the following Table.
TABLE VITo illustrate the effect of substituting a non-halogenated phenolic resin for a halogenated one, recipe (10) is again listed for reference.
(10) (14)Polynorbornene 65.0 65.0Paraffinic Oil 97.5 97.5Blends of polynorbornene and paraffinic oil mixed as 1st stage M/BThis then added to the second stage as follows 1st Stage M/B 162.5 162.5 Polypropylene 35.0 35.0Carbon Black 5.0 5.0Stearic Acid 0.58 0.58Zinc Oxide 2.9 2.9Halogenated phenolic curing resin 7.8 Nbn-halogenated phenolic curing resm - 7.8Chlorinated Polyethylene 5.0 5.0Antidegradant 0.1 0.11. SP1055--Bromo-methyl alkylated phenol-formaldehyde resin supplied by SchenectadyMidland 2. SP1 045-Dimethylol-p-nonyl phenol-resin supplied by Schenectady-Midland (All other ingredients as listed in the original table for recipe (10) through (13).
The following properties were measured on the products of Examples 10 and 14 after injection moulding test plaques using a melt temperature of 1 75 C.
TABLE VII(10) (14)Hardness (Shore A) 64 63Hardness (IRHD) 70 70Modulus @ 100t (MPa) 3.7 3.6(2.6) (2.4)Elongation @ Break (%) 130 110(230) (260)Tensile Strength (MPa) 3.9 3.7(3.5) (3.6) Coopression Set 22 hrs @ 23"C (%) 17 19Compression Set 22 hrs @ 700C (%) 30 39Stress-strain values outside parenthesis measured in flow direction Values inside parenthesis measured transverse to flow direction.
The use of a non-halogenated phenolic resin produces slightly lower hardness and modulus values with higher set values at elevated temperatures, indicating a lower state of cure of the polynorbornene phase, than that obtained with the halogenated material. Nevertheless the products thus obtained are still interesting.
The following Examples illustrate the use of a sulphur based cure system.
TABLE VIII(15) (16)Polynorbornene 1 65.0 65.0Paraffinic Oil 2 48.75 97.5113.75 162.5Blends of polynorbornene and paraffinic oil mixed as 1st stage M/B This then added to the second stage as follows:1st Stage M/3 113.75 162.5Polypropylene 3 35.0 35.0Carbon Black 4 5.0 5.0Stearic Acid 0.65 0.65Zinc Oxide 3.25 3.25Sulphur 0.325 0.325 4,4'-Dithiodimorpholine 5 0.975 0.975Sulphonamide derivative 6 0.65 0.65Tellurium Diethyldithiocarbamate 7 0.52 0.52Dimethyl-diphenyl-thiuram disulphide 8 0.975 0.975Antidegradant 9 0.15 0.15 1. Norsorex powder - supplied by Mbnchem, produced by CDF Chemie 2. Enerpar 23 - supplied by BP Chemicals 3.Propathene GWM 22 - supplied by ICI 4. Sterling SO (N550) - Cabot Carbon 5. Sulfasan R - supplied by Monsanto 6. Vulkalent E/C - supplied by Bayer 7. Tellurac - supplied by Vanderbilt 8. Vulkalent I - supplied by Bayer 9. Irganox 1010 - supplied by Ciba-Geigy The following properties were measured on the above after injection moulding test plaquesusing a melt temperature of 1 75 C.
TABLE IX (15) (16)Hardness (Shore A) 76 63Hardness (IRHD) 80 69Modulus @ 100% (MPa) 6.3 3.1Elongation @ Break (%) 210 150Tensile Strength (MPa) 7.5 3.2Compression Set 22 hrs @ 700C (%) 49.0 48.3Stress-strain values measured in flow directionThe following Examples illustrate the effect of replacing a portion of the plastic resin (polypropylene) by an "S.E.B.S." type (styrene-ethylene-butylene-styrene) thermoplastic elastomer.
TABLE X(17) (18) (19)Polynorbornene 65.0 65.0 65.0 Paraffinic Oil 2 130.0 130.0 130.0 1st stage 195.0 195.0 195.01st stage 150.0 150.0 150.0Polypropylene3 40.0 30.0 20.0 SEBS4 - 10.0 20.0Stearic Acid 0.5 0.5 0.5Zinc Oxide 3.0 3.0 3.0Chlorinated Polyethylene5 5.0 5.0 5.0Magnesium Oxide 0.5 0.5 0.5Phenolic Curing Resin6 7.2 7.2 7.2Antidegradant7 0.1 0.1 0.1Mixing and moulding methods were used as in the previous examples and the following test results obtained: TABLE XI(17) (18) (19)Hardness (Shore A) 70 65 51Hardness (IRHD) 70 68 53Modulus @ 100% (MPa) 3.6 (1.8) 3.2 (2.0) 1.4 (1.2) Elongation @ e break break (%) 110 (200) 170 (220) 190 (200) Tensile strength (MPa) 3.9 (2.5) 3.8 (2.8) 2.1 (2.2)Compression set 22 hrs & ommat; 70 C 41 41 36 (%)Examples 1 7 to 19 show that "SEBS" can be used to replace polypropylene to constitute theplastic phase of the blend and produce low hardness, rubbery products, whilst still retaininggood set resistance at elevated temperatures.
The following examples illustrate the effects of carbon black loadings, as a potentialreinforcing filler;TABLE XII(20) (21) (22) (23)Polynorbornene 65.0 65.0 65.0 65.0Paraffinic Oil 130.0 130.0 130.0 130.01st stage 195.0 195.0 195.0 195.01st stage 162.5 162.5 162.5 162.5Polypropylene 35.0 35.0 35.0 35.0Carbon Black8 - 15.0 25.0 40.0Stearic Acid 0.58 0.58 0.58 0.58Zinc Oxide 2.9 2.9 2.9 2.9Chlorinated Polyethylene 5.0 5.0 5.0 5.0Phenolic Curing Resin 7.8 7.8 7.8 7.8Magnesium Oxide 0.5 0.5 0.5 0.5Antidegradant 0.1 0.1 0.1 0.1The following test results were obtained:: TABLE XIII(20) (21) (22) (23)Hardness (Shore A) 64 66 68 71Hardness (IRHD) 64 71 72 74Modulus @ 100% (MPa) 3.2(2.5) 4.2(2.6) 3.5(3.0) Elongation @ break (%) 100(120) 120(90) 110(120) 90(90)Tensile Strength (MPa) 3.2(2.9) 4.4(2.6) 3.8(4.4) 3.6(4.2) Compression set 22 hrs & ommat; 70 C (%) 33 33 31 30 Examples 20 to 23 illustrate the effect of increased loadings of carbon black. This material can be used as an 'extender' (cheapener), increasing hardness, modulus, and tensile strength values, while retaining good set resistance at elevated temperatures.
The following examples show the effects of incorporating a non-black 'filler':TABLE XIV(24) (25) (26) (27)Polynorbornene 65.0 65.0 65.0 65.0Paraffinic Oil 130.0 130.0 130.0 130.0 1st stage 195.0 195.0 195.0 195.0 1st stage 162.5 162.5 162.5 162.5Polypropylene 35.0 35.0 35.0 35.0Treated Calcined Clay9 - 15.0 25.0 40.0Stearic Acid 0.58 0.58 0.58 0.58Zinc Oxide 2.9 2.9 2.9 2.9Chlorinated Polyethylene 5.0 5.0 5.0 5.0Phenolic curing resin 7.8 7.8 7.8 7.8Magnesium Oxide 0.5 0.5 0.5 0.5 Antidegradant 0.1 0.1 0.1 0.1The following test results were obtained:: TABLE XV(24) (25) (26) (27)Hardness (Shore A) 64 67 67 72Hardness (IRHD) 64 67 67 74Modulus @ 100% (MPa) 3.2(2.5) 3.5(2.4) 2.7(2.6) 3.6(2.5)Elongation @ break (%) 100(120) 100(100) 100(130) 150(160)Tensile strength (MPa) 3.2(2.9) 3.6(2.5) 3.2(3.0) 4.1(3.0)Compression set (%) 22 hrs & ommat; 70 C 33 33 33 37Examples 24 to 27 show the effect of increased loadings of a non-black 'filler'. This materialincreases harness, slightly increases tensile strength, with some slight sacrifice of set resistanceat higher loadings.
Key to the materials of Examples 17 to 271. Norsorex Powder - produced by CDF Chemie2. Enerpar 23 - supplied by B.P. Chemicals3. Propathene GWM 22 - supplied by ICI4. Kraton 1651 - supplied by Shell5. CM 3630 - supplied by Bayer6. SP 1055 - supplied by SchenectadyMidland 7. Irganox 1010 - supplied by Ciba-Geigy 8. Sterling SO (N550) - supplied by Cabot Carbon 9. Translink 37 - supplied by Croxton & GarryIn the Examples the test methods used were as follows:Shore A hardness ASTM D2240IRHD hardness B.S.903 Part A26Modulus @ 100%Elongation @ Break ) B.S.903 Part A2Tensile StrengthCompression Set B.S.903 Part A6Method A Type 1CLAIMS