HUT73164A - Low-temperature-tolerant gels - Google Patents

Abstract

-The invention relates to low-temperature gel compositions comprising a styrene-alkylene-styrene block copolymer consisting of polyalkylene blocks containing ethylene/propylene units and at least 300 parts by weight of extender liquid/ΊΟΟ0 parts by weight of block copolymer, which liquid is at least partly poly(alpha-olefin) and which extends and softens the polyalkylene blocks of said copolymer.

Description

Representative:

Danubia Patent and

Trademark Office Ltd. Budapest

Low temperature gels

The invention relates to new and improved technical gels comprising a styrene-(ethylene/propylene)-styrene (SEPS) block copolymer and at least 300 parts by weight (preferably at least 400 parts by weight, more preferably at least 500 parts by weight) of a liquid extender relative to 100 parts by weight of block copolymer, which liquid extends and softens the ethylene/propylene polymer blocks in the copolymer. The extender ratios can also be expressed in % by weight relative to the copolymer, such as 300 = 25%, 400 = 20%, 500 = 17%.

The proportion of ethylene/propylene units incorporated into the polyalkylene blocks of the SEPS copolymer can vary between 100% and 20% and these are derived from a mixture of isoprene/butadiene feedstock which is copolymerized and hydrogenated to yield SEPS triple blocks, which SEPS triple blocks contain mixed ethylene/propylene:ethylene/butylene polyalkylene middle blocks. SEPS gels have various advantages when prepared in the presence of ethylene/propylene units, and it is advantageous to increase their proportion to at least

File number: 81890-4547-OE/KmO

- 2 to 30 or 40%, preferably at least 50%, in the polyalkylene middle blocks. Particularly preferred SEPS block copolymers for the present purpose are those in which the polyalkylene middle blocks contain 60% ethylene/propylene units and 40% ethylenic units. It is also preferred that the ratio of ethylene/propylene units is higher, such as at least 80 or 90%, and it is also preferred that it contains essentially a single alkylene block of essentially 100% ethylene/propylene units. The percentages given are by weight.

It is noted that alkylene units other than ethylene/butylene units can be incorporated with ethylene/propylene units to yield suitable SEPS block copolymers, but the ethylene/butylene unit is preferred.

Known gels are prepared from styrene-(ethylene/butylene)-styrene (SEBS) block copolymers, which are described in WO-A-8800603 and WO-A-9005166 together with the characteristic properties of the gels and their determination.

However, SEPS gels have better high-temperature properties and are better able to retain extender fluid when subjected to pressure in various applications. SEPS gels also have higher adhesion than known SEBS gels, thus reducing the addition of adhesion promoters to ensure the desired adhesion for the final application.

Both SEPS and the known SEBS gels are characterized by an undesirable hardening upon cooling to -40 °C, which limits the gels' ability to work in the outer area.

- 3, such as for example in the sealing of electrical cables or casings. The solution according to the present invention improves this property without adversely affecting the other properties of the gels.

The invention relates to a gel composition comprising a styrene-alkylene-styrene block copolymer, the polyalkylene blocks of which consist of ethylene/propylene units, and the composition further comprises at least 300 parts by weight per 100 parts by weight of an extender liquid, which liquid is at least partly poly(alpha-olefin) and which extends and softens the polyalkylene blocks.

The poly(alpha-olefin) extenders are preferably used in admixture with previously used extender oils, such as Vestan A360B (preferred) from Fina Chemicals, Drakeol 34 from Penreco, and Witco 380ΡΘ from Witco. The extender is used in an amount of at least 10%, preferably at least 20%, more preferably at least 30% of the known oils. It has been found that when the known oils are replaced by up to 90%, preferably up to 80%, more preferably up to 70%, very advantageous processing characteristics are provided. It is preferred that the known oils:poly(alpha-olefin) ratio is between 30:70 and 70:30, and for certain purposes it may be advantageous if the mixture corresponds to a ratio of 70:30 to 80:20 or 90:10. The percentages and ratios mentioned are by weight based on the weight of the extender mixture.

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- 4 SEPS gels are preferably soft, high temperature collapse resistant, flexible gel compositions, by which is meant that the polymer composition containing the liquid extender has an ultimate elongation value (as determined according to a modified version of ASTM D412) of greater than 100% - substantially without elastic deformation (i.e., substantially without hysteresis) and a value between at least 100%; an ultimate tensile strength value (ASTM D412) of less than 1 MPa, a dynamic storage modulus value (as defined hereinafter) of less than 50,000 Pa; and exhibits substantially zero collapse at a temperature of up to 100 °C, preferably up to 120 °C, more preferably up to 135 °C, especially up to 150 °C.

The invention particularly relates to gel compositions for certain end uses which comprise 4-20% by weight of SEPS copolymer and at least 500 parts by weight of extender liquid per 100 parts by weight of polymer, and in which the SEPS copolymer constitutes more than 50% by weight, preferably more than 75% by weight, more preferably more than 90% by weight, most preferably more than 95% by weight, of the total gelling polymer present, particularly preferably all of it. Various additives may also be present in the composition, such as adhesion promoters as described in WO-A-9005166, or polyphenylene oxides as described in WO-A-8800603, or styrene-alkylene di-block copolymers as described in co-pending patent application GB-91192612.7, in order to reduce the loss of extender liquid.

- 5 However, the very good properties of the SEPS gels of the invention may reduce or eliminate the use of such additives.

The SEPS gels of the invention are particularly suitable for, among other things, re-accessible sealing of the sheath of electrical connections. The invention accordingly also relates to an apparatus, device, comprising: a sheath for electrical wires, a container containing the gel of the invention, and a means for holding the container containing the composition of the invention, for use against the wire and/or a portion of the sheath to protect the wire from contamination and/or corrosion. In this and other applications, the gel is subjected to continuous pressure, and in this respect its ability to retain extender fluid is important.

The invention is substantially free of polystyrene-compatible components, which may significantly raise or lower the softening point (Ts) of the composition, either in the sense that substantially no such components are present, or in the sense that the amount of such components present is insufficient to significantly affect the softening temperature. The use of such components to characteristically raise the softening temperature is described in the aforementioned WO-A-8800603, and such components may be used in the present case. A reduction in Ts is generally not desirable for the present purposes, and the extender is therefore preferably non-aromatic in nature, meaning that less than 2%,

- 6 more preferably contains less than 1%, and in particular zero, aromatics.

The aforementioned low temperature cure can be improved by using various low-dropping naphthenic oils as extenders, such as Edelex 27, available from Shell, but these do not reduce the Ts to an acceptable level. However, the poly(alpha-olefin) extenders used in the SEPS gels of the present invention not only do not reduce the Ts, but they also significantly increase it, while still reducing the cure to an acceptable level. Although the reduction in cure is also observed with known SEBS gels using poly(alpha-olefin) extenders, these gels are less desirable because they have unexpectedly limited compatibility with the extenders of SEBS polymers. The greater softness of gels made with poly(alpha-olefin) extenders provides easier incorporation into sealing solutions at lower temperatures.

Due to their higher softening temperature, SEPS gels have been found to exhibit improved resistance to collapse at elevated temperatures compared to similar SEBS gels, while still providing the desired softness and flexibility. Collapse typically occurs a few 10 degrees after the softening temperature Ts is reached. In this way, the gels of the invention clearly differ from known cable filler materials, which are designed to collapse and flow upon application.

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- Even with large amounts of extender liquid, the compositions of the invention are substantially stable, homogeneous, and relatively free from extender precipitation, and various properties are improved while maintaining a suitable balance with other properties. The gel compositions, when adhered to another surface or to themselves, tend to readily peel cleanly from the contact surface without any cohesive failure within the gel composition.

Particularly preferred SEPS block copolymers for use in the composition according to the invention are those wherein the copolymer contains 20-50% by weight, preferably 20-40% by weight, especially 28-35% by weight of polystyrene blocks.

The block copolymer preferably contains 80-50% by weight, more preferably 75-60% by weight, especially 72-65% by weight of polyalkylene blocks. The polyalkylene blocks are preferably substantially fully hydrogenated poly(ethylene/propylene) blocks, especially those which predominantly (e.g. >90% or >95%) contain units of the following formula:

-(CH ₂ CH (CH ₃ ) CH ₂ CH ₂ ) optionally together with small amounts of the following isomers: -(CH ₂ )-C (CH ₃ ) (CH ₂ CH ₃ ))-(CH ₂ -CH-[CH(CH ₃ ) ₂ ])The crosslinking of the composition, although not essential, can be carried out if desired according to the patent specifications WO-A-8800603 and EP-A-0224389, and this can further improve the properties.

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Among the characteristic properties of the gel compositions according to the invention, it is advantageous if the final elongation of the composition is at least 200%.

Substantially elastic deformation up to an elongation of at least 200% is also preferred.

The poly(alpha-olefin) extender liquids useful in the block copolymer compositions of the present invention may be any material determined by simple experimentation. For example, products under the Ethylflo brand from Ethyl Corporation are preferred. The minimum boiling point of the extenders is preferably greater than the softening point of the block copolymer(s) and any other added polymer or copolymer. The poly(alpha-olefin) extenders preferably have a dropping point of not more than -30°C, more preferably not more than -40°C, and most preferably not more than -50°C.

Poly(alpha-olefin) extenders can be produced by cracking ethylene from natural gas and/or petroleum to C4-C30 linear alpha-olefins, and the resulting mixture is then polymerized to form poly(alpha-olefins) of the appropriate composition and viscosity.

The commercially available product, Ethylflo 164, contains approximately 84.4% trimer and 14.5% tetramer, with a dropping point of -65°C; the product, Ethylflo 166, contains approximately 33.9% trimer, 43.5% tetramer, 17.4% pentamer and 3.8% hexamer, with a dropping point of -63°C; the product, Ethylflo 168, contains approximately 6% trimer, 55.7% tetramer, 27.5% pentamer, 7% hexamer and 4.1% heptamer, with a dropping point of -60°C; the product, Ethylflo 170, contains approximately 1.1%

- It contains 9 trimers, 42.5% tetramer, 32.3% pentamer, 11.8% hexamer and 12.2% heptamer, and has a dropping point of -54 °C. The viscosity values of the aforementioned Ethylflo 164-170 products expressed in centi-Stokes at -40 °C are 2490, 7877, 18305 and 32650, respectively, while the aforementioned A360B oil is a solid at -40 °C.

Known extender oils added to the mixture of poly(alpha-olefins) comprise essentially non-aromatic paraffinic/naphthenic mineral oils in which the paraffin:naphthenic ratio (P:N) in terms of carbon number is between 1.75:1 and 5:1, preferably between 1.77:1 and 3:1, more preferably between 1.9:1 and 2.7:1, particularly preferably between 2.2:1 and 2.5:1.

These extender oils, especially those with a preferred P:N ratio, are capable of forming gels with characteristics particularly suitable for the purposes of the aforementioned resealable coatings. Preferably, the relative density of the oil at 20°C according to ASTM D2140 is between 0.861 and 0.865, preferably between 0.862 and 0.864.

The compositions of the invention are preferably prepared by mixing the extender with the block copolymer or copolymers at a temperature not lower than the glass transition temperature of the polystyrene blocks of the SEPS block copolymers, as generally described (in the case of SEBS) in WO-A-8800603. A masticating or other mixing operation at a lower temperature, optionally with the aid of a volatile solvent, may also be used if the composition thus obtained is suitable for the intended end use.

The compositions of the invention can be prepared with a wide range of physical properties, such as dynamic storage modulus, ultimate elongation, shear stress, etc., to suit the ultimate requirements. Preferred compositions of the invention have an ultimate elongation of at least 200% (ASTM D 412), and these compositions are particularly suitable as sealants. The compositions of the invention preferably contain more than 500, more preferably not more than 5000 parts by weight of extender liquid per 100 parts by weight of block copolymer.

Various additives may also be used in the compositions according to the invention. Such additives may include, for example, the following: stabilizers, antioxidants, flame retardants, adhesion promoters, corrosion inhibitors, etc. The use of antioxidants in the compositions according to the invention is advantageous.

The compositions of the invention can be used as elastomeric materials in a wide range of applications and are particularly advantageous as sealants for electrical connection covers, such as those disclosed in EP 0108518 and EP0191609, although the compositions of the invention can also be used in many other areas, depending on the application temperature.

The gel or gel-like compositions of the invention are preferably defined according to criteria (1)-(8) summarized in Tables I-V of WO-A-8800603, with no more than one of these criteria (other than (1) or (2)) being outside the ranges given.

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- 11 Preferred SEPS block copolymers that can be used according to the invention include, for example, those manufactured by the Japanese company Kuraray, commercially available under the trade name SEPTON, such as SEPTON 4055, 4155 and 2006. The presence of the required properties in the gel compositions according to the invention is determined by a simple experiment.

The SEPS gels according to the invention using poly(alpha-olefin) extenders are presented below in comparison with gels containing extenders used so far.

The polymers summarized in the following table are masticated with the poly(alpha-olefin) extender (E) and/or the aforementioned Fina Vestan A360B product (A) or the extender oil Edelex 27 in a Z-arm mixer for 50 minutes at a temperature of 195-210 °C under vacuum. The resulting oil/polymer mixture contains the polymer in the indicated weight %. The dynamic storage modulus (G'), softening point (Ts), elongation at break (EB) and tensile strength (T.S) of the product are determined as follows.

In determining the TMA softening point, a stamp of a given mass is placed on top of the gel sample. The sample is then heated and the deflection of the probe as a function of temperature is measured. The resulting trace has a flat linear section (A), followed by a transitional (melting) section (B), and a second flat section (C) where the stamp reaches the end of its travel. This is schematically illustrated in Figure 1. The softening point Ts is the temperature at which the extrapolated straight lines A and B intersect.

- 12 ·· · · · · · · · · · · · • · · · · · » · · ··· ··· • · · · « • · ···· ··· · The Du Pont thermomechanical analyzer (TMA-942) was used for the test with a Du Pont 1090 thermal analyzer. A flat-bottomed, 2.5 mm diameter quartz sample was used with a 2 g load. The gel sample was a 6.25 mm diameter, 2 mm thick disk, the sample was kept at -40 °C for 5 minutes, then heated to 300 °C at a rate of 5 °C/min.

Tensile strength (T.S.) and elongation at break (E.B.) were determined according to ASTM D412, except that a 40 mm long gauge with two weights of BS 903 type was used. The tensile strength was 100 mm/min.

The G' modulus was determined using a Bohlin VOR melt rheometer and software. The rheometer was operated in oscillation mode, using a 25 mm diameter parallel plate measuring system and a 90 gcm torsional transducer. The gel sample was a 25 mm diameter and 3 ± 0.2 mm thick plate. The measurements were performed at the specified temperature with an oscillation frequency of 0.1 Hertz. The instrument was operated up to its maximum angular displacement, which corresponded to a strain of approx. 6% for the samples.

The results obtained are summarized in the following table.

Gel Extender G' modulus at 0.1 Hz, kPa G' ratio Ts E.B. (%) T.S. polymer 20 °C 0 °C -20 °C -40 °C -40 °C/20 °C °C (MPa) % by weight

Septon A360B 5.41 5.61 16.4 61.1 11.29 132 >1800 >0.51 4055 A/E 70:30 7.61 5.82 4.22 16.8 2.21 145 1616 0.78 (12) A/E 50:50 6.6 11.2 5.1 16.2 2.45 148 1619 0.86 A/E 30:70 9.2 12.5 4.8 12.5 1.36 154 1513 0.58

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Gel Extender G' modulus at 0.1 Hz, kPa G' ratio Ts E.B. (%) T.S. polymer 20°C 0°C -20°C -40°C -40°C/20°C °C (MPa) % by weight Ethylflo 168 6.27 7.11 11 26.7 4.26 162 >1800 >0.46 Edelex 27 9.11 9.28 14.9 31.4 3.45 86 >1800 >0.66 Ethylflo 166 7.33 7.39 11.1 36.3 4.95 151 >1800 >0.68 Ethylflo 170 7.92 10.2 19.8 24 3.03 172 >1800 >0.71 Septon A360B 1.46 1.52 7.1 263 180.14 110 1700 0.24 4055 Ethylflo 168 10.78 0.82 3.13 4.69 6.01 109 867 0.07 (6) Septon A360B 17.9 21.4 41.8 326 18.21 152 >1800 >1.03 4055 Ethylflo 168 16.5 27.9 42.2 32.6 1.98 190 1795 0.93 (18) Septon A360B 8.5 9.5 27.8 76 8.94 138 >1468 >0.34 4055/ Ethylflo 168 6.12 5.52 7.51 36 5.88 160 Craton G1701 (11:4) Septon A360B 4.95 5.93 8.13 50.1 10.12 84 1648 0.26 2055 Ethylflo 168 3.84 3.99 4.79 6.49 1.69 100 (12) Septon A360B 4.59 4.17 5.29 36.8 8.02 131 1606 0.46 2006 Ethylflo 168 2.75 23.62 2.86 3.64 1.32 162 (12)

Α/Ε = mass ratio between Α360Β extender oil and Ethylflo poly(alpha-olefin).

- 14 • » *· ··· · ·· • · · · · · · • · · · · · · · ·

Septon 4055 is the aforementioned block copolymer containing mixed EP/EB middle blocks, while Septon 2005 and 2006 contain only EP middle blocks. The weight % of styrene blocks relative to the total block copolymer is approximately 20% for 2005 and approximately 35% for 2006.

The G' ratio in the table clearly shows that with the known A360B extender oil the resulting gel is at least 8 or 10 times harder when cooled from 20°C to -40°C. However, with the Ethylflo poly(alpha-olefin) extender this hardening ratio is less than half that of A360B and in most cases less than 1/3 or even less than 1/10. Similarly, the Edelex 27 naphthenic extender oil reduces the hardening rate, but reduces the Ts value from 132°C to 86°C, while the Ethylflo extender tends to increase the Ts value.

We observed that gels of styrene triblock copolymers containing EB midblocks or mixed EB/EP midblocks show less hysteresis in G' modulus upon heating or cooling, compared to triblock copolymers containing only EP midblocks, where hysteresis is relatively small or not detectable. This lack of hysteresis implies that EP midblock copolymers recover their mechanical properties more quickly after low temperatures.

Claims (14)

Claims A gel composition comprising a steroid block copolymer of polyalkylene blocks containing ethylene / propylene units and at least 300 parts by weight of an extender fluid per 100 parts by weight of a block copolymer, and wherein the fluid is at least partially poly (alpha). olefin) and multiplies and softens the polyalkylene blocks of said copolymer. The composition of claim 1, wherein the extender fluid is a mixture of an extender oil and a poly (alpha-olefin) and the poly (alpha-olefin) is present in an amount of from 10 to 90% by weight of the mixture. The composition according to claim 2, wherein the amount of poly (alpha-olefin) is from 20 to 80%, preferably from 30 to 70% by weight of the mixture. 4. The composition according to any one of claims 1 to 4, wherein the weight ratio of ethylene / propylene units in the polyalkylene blocks is at least 20%, more preferably at least 30%, particularly preferably at least 40%, very particularly at least 50%. The composition of claim 4, wherein the ratio of ethylene / propylene units is at least 80% or at least 90% or substantially 100%. 6. A composition according to any one of claims 1 to 6, wherein the polyalkylene blocks contain ethylene / butylene units. ·· • · »· * ♦ ··· ·· ··« · ··· · - 16th 7. The composition according to any one of claims 1 to 4, wherein the amount of extender fluid is at least 400, preferably at least 500 parts by weight per 100 parts by weight of the copolymer. 8. A composition according to any one of claims 1 to 4, wherein the final elongation value is greater than 100%, preferably at least 200%, up to at least 100% with a substantially elastic deformation. 9. A composition according to any one of claims 1 to 6, having a final tensile strength less than 1 MPa. 10. A composition according to any one of claims 1 to 6, wherein the G 'has a dynamic storage modulus of less than 50,000 Pa at 0.1 Hz. 11. Composition according to any one of claims 1 to 4, comprising 4 to 20, preferably 5 to 15, more preferably 6 to 12% by weight of said block copolymer. 12. The composition according to any one of claims 1 to 4, wherein said block copolymer is 20 to 50% by weight, preferably 25 to 40% by weight, in particular 28 to 35% by weight of polystyrene block and 8 to 50% by weight, preferably 75 to 60% by weight, contains a poly (alkylene) block. 13. A composition according to any one of claims 1 to 5, wherein the blocks ρ ο I (et / i / n) are predominantly units of the following formula: - (CH ₂ CH (CH ₃ ) CH ₂ CH ₂ ) -. 14. A composition according to any one of claims 1 to 6, wherein the poly (alpha-olefin) extender is a droplet point V ·· · * · * · • * * * * »» »« «« «« «« 17 is not more than -30 ° C, preferably not more than -40 ° C, more preferably not more than -50 ° C.