WO2014194155A1

WO2014194155A1 - Vibration damping thermoplastic elastomer with hot creep resistance

Info

Publication number: WO2014194155A1
Application number: PCT/US2014/040125
Authority: WO
Inventors: Laurent Millier
Original assignee: Polyone Corporation
Priority date: 2013-05-31
Filing date: 2014-05-30
Publication date: 2014-12-04
Also published as: DE112014002610B4; DE112014002610T5

Abstract

A thermoplastic elastomer compound is blended from a high molecular weight styrene-isoprene-styrene block copolymer having a hydrogenated vinylic polyisoprene mid-block and a liquid polybutadiene oligomer in replacement or partial replacement of plasticizing oil, in order to maintain a Tan Delta Peak temperature of more than 0C and a compression set of less than about 50% after 22 hours at 70C. Optionally, the compound can also include polyphenylene ether to modify heat properties of the styrenic end blocks, polypropylene to provide processing aid, and filler.

Description

VIBRATION DAMPING THERMOPLASTIC ELASTOMER WITH HOT CREEP RESISTANCE

CLAIM OF PRIORITY

[0001] This application claims priority from U.S. Provisional Patent

Application Serial Number 61/829,978 bearing Attorney Docket Number 12013002 and filed on May 31, 2013, which is incorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates to thermoplastic elastomers, polymer compounds which exhibit elasticity while remaining thermoplastic, which have vibration damping.

BACKGROUND OF THE INVENTION

[0003] The world of polymers has progressed rapidly to transform material science from wood and metals of the 19^th Century to the use of thermoset polymers of the mid-20^th Century to the use of thermoplastic polymers of later 20^th Century.

[0004] Thermoplastic elastomers (TPEs) combine the benefits of elastomeric properties of thermoset polymers, such as vulcanized rubber, with the processing properties of thermoplastic polymers.

[0005] Thermoplastic elastomers can include styrene block copolymers

(SBCs), thermoplastic vulcanizates (TPV), thermoplastic olefins (TPO), copolyesters (COPE), thermoplastic urethanes (TPU), copolyamide (COPA), and most recently olefin block copolymers (OBCs).

SUMMARY OF THE INVENTION

[0006] The art needs a thermoplastic elastomer compound with both good vibration damping properties and also good resistance to hot creep. While a variety of thermoplastic elastomers are already commercial, common types are inapplicable to solving the problem in the art.

[0007] The present invention has found that a high molecular weight styrene-isoprene-styrene block copolymer with hydrogenated vinylic polyisoprene mid-blocks mixed with a liquid polybutadiene oligomer can in a thermoplastic elastomer compound having good vibration damping at room temperature and good hot creep resistance. Hot creep resistance means resistance to deformation of a viscoelastic material over time of continuous stress applied at a temperature exceeding 70°C.

[0008] Compression set is the permanent deformation of a viscoelastic material after being subjected to a constant stress and an elevated temperature.

[0009] More hot creep resistance in a viscoelastic material correlates to a lower compression set of permanent deformation.

[00010] One aspect of the present invention is a thermoplastic elastomer compound comprising: (a) high molecular weight hydrogenated styrene- isoprene-styrene block copolymer with a hydrogenated vinylic polyisoprene mid-block; and (b) liquid polybutadiene oligomer, wherein the compound has a Tan Delta Peak temperature of more than 0°C and a compression set of less than about 50% after 22 hours at 70°C.

[00011] Another aspect of the present invention is the thermoplastic elastomer compound also comprising plasticizer oil.

[00012] Embodiments of the invention are identified after inapplicable combinations are explained.

EMBODIMENTS OF THE INVENTION

[00013] Examples 1 and 2 and Comparative Examples A-C

[00014] Table 1 shows the ingredients, recipes, and test results.

[00015] All examples were extruded using a 25 mm twin screw extruder having a length/diameter ratio of 40. The mixing speed for all examples was 300 rpm. For all examples except Example 2, the mass temperature was 190°C, and all ingredients were added together at the throat of the extruder. For Example 2, two twin screw extrusions were employed. In the first extrusion, one third of resin, oil, PPE and PP were extruded first at 290°C mass temperature to sufficiently disperse the PPE. Then, the second extrusion added the remaining ingredients to the first extrudate and that mixture was extruded at the same 190°C mass temperature as the other Example and Comparative Examples. Mass temperature is the temperature of molten mixture, not the barrier or zone temperatures of the extruder.

[00016] All Examples and Comparative Examples used the same stabilizer package as denominated in Table 1, in addition to the 100 parts of polymer compound. The stabilizer package in each instance totaled 0.75 parts was Sumilizer™ GS stabilizer (CAS 123968-25-2) 0.3 parts; Irganox™ 565 stabilizer (CAS 991-84-4) 0.2 parts; Irgafos™ 168 stabilizer (CAS 31570-04-4) 0.2 parts; Irganox™ 1010 stabilizer (CAS 6683-19-8) 0.25 parts; and Uvinul™ 3027 stabilizer (CAS 3864-99-1) 0.1 parts.

[00017] After pelletizing from the extruder, material from each example was molded into a shape as required by the applicable standardized test, in order to test the physical properties of the examples.

[00018] Below Table 1 is an explanation of the failures of Comparative

Examples A-C in comparison with the successes of Examples 1 and 2, and the progression of experimentation which uncovered the unexpected result of employing a liquid polybutadiene oligomer to plasticize the high molecular weight styrene-isoprene-styrene block copolymer with hydrogenated vinylic polyisoprene mid-blocks to (a) maintain Tan Delta Peak above 0°C and (b) maintain a compression set below 50% after 22 hours at 70°C.

[00019] The Inapplicability of SEBS Block Copolymers

[00020] Styrenic block copolymers (SBCs) are well known polymers to make thermoplastic elastomer compounds. These polymers have two (or less often more) styrenic hard end blocks with Tg close to 100°C and (generally) one soft mid block with lower Tg. The hard block's Tg can be increased in excess of 100°C by adding a high Tg polymer miscible with polystyrene, such as poly(2,6-dimethyl-l,4-phenylene ether) (PPE).

[00021] SEBS is the most common SBC. In this case, the soft block is formally random copolymer of ethylene and butene. Such a soft block has typically Tg = - 60°C. At this temperature, Tan Delta, the ratio of storage to loss modulus is maximum, and the visco-elastic behavior is closer to purely viscous than at any other temperature. Having this viscous behavior lets the SEBS material dissipate the vibratory energy, and this is what gives the SEBS such good vibration damping ability. Because of its soft blocks' low Tg, SEBS is ideal for vibration damping below - 50°C. But most common vibration damping applications need dissipation around +20°C, and SEBS is not suitable for use as vibration dampeners at this typically room temperature.

[00022] The Inapplicability of SIS Block Copolymers

[00023] Instead of SEBS, special SBCs are offered on the market specifically for vibration damping applications. Their soft blocks have different chemical structures resulting in a higher Tg. For example, Hybrar 5127 and Hybrar 7125 copolymers, both by Kuraray, have a vinylic polyisoprene soft block and a hydrogenated vinylic polyisoprene soft block, respectively. Their Tan Delta Peak values occur at +20°C and -5°C, respectively.

[00024] Such SBCs as Hybrar 5127 SIS copolymer and Hybrar 7125 SIS copolymer are suitable to formulate TPE compounds featuring vibration damping at room temperature. As with any TPE, these polymers can be made softer by oil extension. Paraffinic oil is the most popular plasticizer to selectively plasticize the soft blocks. Adding paraffinic oil results in lower hardness and lower melt viscosity but also decreases, severely, the temperature at which Tan Delta is at its Peak. So, for vibration damping properties around room temperature, such SBCs as Hybrar 5127 or 7125 SIS copolymers cannot be oil-extended very much. Naphthenic oil can be used with more or less the same advantages and drawbacks. Aromatic oils cannot be used because they would plasticize the hard styrenic blocks.

[00025] It has just been explained that such vibration damping SBCs like

Hybrar 5127 or 7125 copolymers will generally be compounded with relatively little oil extension, if any. And instead, these grades have relatively low molecular weights to provide the compounds with good processability although little or no oil is added. The relatively low molecular weights show in the melt flow rates (MFR): at 190°C/2.16kg, Hybrar 5127 and 7125 copolymers measure at 5 and 0.7 g/10 min, respectively. In comparison, Kraton G 1651 SBC, a general purpose SEBS for non vibration damping TPEs, is too viscous to have its MFR measurable in these conditions.

[00026] Because of their low molecular weights, Hybrar 5127 and 7125 copolymers do not provide good hot creep properties to the TPE compounds in which they are used. It is well known that such properties connected to hot creep like compression at +70 or +100°C are correlated with the molecular weight of the SBC used in the composition. For example, Comparative Example C above, based on both PPE-modified Hybrar KL-7135 and Hybrar 5127 thermoplastic elastomer compounds has poor compression set at 70°C or 100°C. Those compression set values would be even worse without PPE modification. This poor creep resistance at 70°C or hotter is typical of TPE-S based on a SBC with an insufficient molecular weight.

[00027] Inapplicability of High Molecular Weight Modified SIS

Thermoplastic Elastomer

[00028] Recently, Kuraray has begun selling Hybrar KL-7135 SIS copolymer. The chemical structure is similar to Hybrar 7125, with hydrogenated vinylic polyisoprene mid-blocks, resulting in a similar Tan Delta Peak temperature: +1°C. But, significantly, the molecular weight is much higher, and the melt flow rate (MFR) at 190°C is not measurable, even with the 21.6 kg weight. This polymer is advertised for having good compression set. For these purposes, the polymer generically will be denominated HMW SIS TPE copolymer, that is, a copolymer having a weight average molecular weight high enough for the pure polymer to show no flow when measuring its MFR at 230°C 2.16 kg; and less than 0.05 g/10 min melt flow at 230°C 10 kg.

Preferably, the HMW SIS TPE has a weight average molecular weight ranging from about 200,000 to about 500,000 and hydrogenated vinylic polyisoprene mid-blocks.

[00029] As well as any high molecular weight SBC, hydrogenated HMW

SIS TPE copolymer, such as Hybrar KL-7135 SIS copolymer, is too viscous to be processed as pure polymer. It must be compounded with a sufficient amount of flow-promoting ingredients, generally oil and polypropylene (PP). For example, substituting KL-7135 grade to the 7125/5127 grade mix of

Comparative Example C would result in too viscous a material to be processed or even compounded on the regular twin screw extruder generally used for this purpose. Comparative Examples A and B are formulated with more oil and PP, and they have good injection processability. The compression set of the KL- 7135 grade is good at 70°C, and even at 100°C in the PPE modified

Comparative Example B composition. But adding so much paraffmic oil gets the Tan Delta Peak of the resulting TPE compound down to about -11°C, and unfortunately, this is a temperature colder than desired for most vibration damping applications.

[00030] Applicability of High Molecular Weight Modified SIS

Thermoplastic Elastomer Compounded with Liquid Butadiene Oligomer, Preferably Blended with Paraffmic Oil

[00031] It has been discovered that liquid butadiene oligomer with high vinyl content can plasticize HMW SIS TPE copolymer, such as Hybrar KL- 7135 hydrogenated SIS copolymer, without shifting the Tan Delta Peak temperature down to a cold temperature. "High" vinyl content means over 50% and preferably over 70%. Unexpectedly, use of the liquid butadiene oligomer can even increase the Tan Delta Peak temperature. Example 1 composition has a Tan Delta Peak temperature as warm as +36°C, truly unexpected.

[00032] With that high a Tan Delta value comes a higher hardness, 84 on the Shore A scale, than Comparative Example A has, namely 61 on the Shore A scale. The only difference between Comparative Example A and Example 1 is the replacement of 29 parts of plasticizing oil with 29 parts of liquid

polybutadiene oligomer. The 15 parts of "mineral carrier" replace filler.

[00033] While a Shore A hardness is certainly acceptable for some commercial uses, reduction in hardness without too much reduction in Tan Delta Peak temperature is preferred. Therefore, for compounds based on HMW hydrogenated SIS TPE copolymer, such as Hybrar KL7135 SIS copolymer, meant to damp vibrations at room temperature, it has been found to be preferred that the plasticizing system be a mix of regular paraffinic oil and high vinyl butadiene oligomer. Such a blend can be tuned to be neutral for Tan Delta Peak temperature, and it has fairly good plasticizing efficiency. Example 2 has good compression set, Tan Delta Peak temperature at +16°C, and compression set low at +70°C and fair at +100°C. This lower compression set is obtained because of the addition of PPE to the HMW SIS TPE copolymer, which did not occur in Example 1.

[00034] Indeed, based on the Comparative Examples A-C and Examples

1 and 2, without undue experimentation, a person having ordinary skill in the art can adjust the amounts of liquid polybutadiene oligomer, plasticizing mineral oil, filler, and PPE to tailor the establishment of both Tan Delta Peak

temperature above 0°C and a low compression set below 50% after 22 hours at 70°C. Desirably, the Tan Delta Peak Temperature can be between from about 0 to about 30°C and preferably from about 10 to about 30°C. Desirably, the low compression set can be below 60%> and preferably below 50%>. [00035] Ingredients

[00036] Kuraray is the current commercial source for HMW SIS TPE copolymers with hydrogenated vinylic polyisoprene mid-blocks, particularly Hybrar KL-7135. In the event that other copolymers were to become commercially available which would be HMW SIS TPE copolymers with hydrogenated vinylic polyisoprene mid-blocks, then those resins would be candidates for use in the present invention.

[00037] Liquid butadiene oligomer with high vinyl is commercially available from Sartomer/Cray Valley or from Nippon Soda. The examples above used Ricon 153 from Cray Valley. In Ricon 153, the butadiene is mostly polymerized in the 1,2 (vinylic) pattern. At 85% vinyl content, Ricon 153 is one of the most vinylic liquid polybutadiene oligomers industrially available at this time. Using lower vinyl liquid polybutadiene would result in a TPE compound with colder Tan Delta Peak temperature, and if this were sought, it would be more economically achieved with a plasticizing cocktail containing less of the high vinyl liquid polybutadiene oligomer and more mineral oil, a logical adjustment to the ratio of those two ingredients seen in Example 2. If liquid polybutadiene oligomer becomes commercially available having more than 90% vinyl content, that oligomer would become a good candidate for use in this invention because of the performance of Ricon 153 in Examples 1 and 2.

[00038] Ricon 153 is a viscous liquid. It is available pure in liquid form or as Ricon 153D, loaded on a mineral carrier for compounders who want to handle a powder rather than of a viscous liquid. Ricon 153D was used in Examples 1 and 2, requiring identification of the two fractions for Ricon 153D, one for the (active) organic fraction and one for the mineral (carrier) fraction. The mineral carrier can be considered an additional filler in Examples 1 and 2.

[00039] If a compound is to be made with liquid polybutadiene oligomer and PPE modification of the end blocks of the HMW SIS TPE copolymer, such as in Example 2, it is better to disperse the pure PPE polymer in a concentrate compounded in a first twin screw extrusion at high mass temperature, typically 290°C. Then, Ricon oligomer and possibly other ingredients are added in a second twin screw extrusion at lower mass temperature, typically 190°C.

[00040] Optional Polyphenylene Ether

[00041] As stated above, one difference between the recipe of Example 1 and the recipe of Example 2 is the use of PPE, a well-known polymer commercially available from such worldwide suppliers as SABIC and Bluestar. It is well known by those skilled in making SBC formulations that PPE can improve compression set at 70°C and above in recipes based on HMW SBC. Such HMW hydrogenated SIS as Hybrar KL 7135 are no exception; and the fact that PPE has beneficial effect on compression set in compositions based on them is not unexpected and is not a central element in the invention.

[00042] Optional Polypropylene

[00043] Though all of the examples used PP as part of the recipes, PP is considered optional for use in this invention because it is possible to utilize other processing aids. PP is also very well-known and commercially available in a number of grades from a number of worldwide suppliers, such as Ineos.

[00044] Optional Plasticizer Oil

[00045] As stated above, depending on the hardness of the compound desired, plasticizing oil may be used to improve flow and flexibility of the resulting TPE compound. Any oil conventionally used to plasticize a SBC is a candidate for use, such as mineral oil, vegetable oil, synthetic oil, etc.

Commercially available oils include Puretol 380 brand oil from Petro Canada of Toronto, Canada and Primol 382 brand oil from ExxonMobil.

[00046] Optional Filler

[00047] To lower the cost in some embodiments of the TPE compounds, it has been found that adding an inorganic filler is desirable. Calcium carbonate (CaC0₃) is a suitable filler, although any inorganic filler having sufficient purity for use in contact with food can be a candidate for use in the invention.

[00048] Other Optional Additives

[00049] The compound of the present invention can include conventional plastics additives in an amount that is sufficient to obtain a desired processing or performance property for the compound. The amount should not be wasteful of the additive nor detrimental to the processing or performance of the compound. Those skilled in the art of thermoplastics compounding, without undue experimentation but with reference to such treatises as Plastics Additives Database (2004) from Plastics Design Library (www.elsevier.com), can select from many different types of additives for inclusion into the compounds of the present invention.

[00050] Non-limiting examples of optional additives include adhesion promoters; biocides (antibacterials, fungicides, and mildewcides), anti-fogging agents; anti-static agents; bonding, blowing and foaming agents; dispersants; fillers and extenders; fire and flame retardants and smoke suppresants; impact modifiers; initiators; lubricants; micas; pigments, colorants and dyes; oils and plasticizers; processing aids; release agents; silanes, titanates and zirconates; slip and anti-blocking agents; stabilizers; stearates; ultraviolet light absorbers; viscosity regulators; waxes; and combinations of them. Anti-oxidants are particularly useful for these plastic compounds to provide additional durability.

[00051] Table 2 shows acceptable, desirable, and preferable ranges of ingredients useful in the present invention, all expressed in weight percent (wt. %) of the entire compound. The compound can comprise, consist essentially of, or consist of these ingredients.

[00052] Processing

[00053] The preparation of compounds of the present invention is uncomplicated once the proper ingredients have been selected. The compound of the present can be made in batch or continuous operations.

[00054] Mixing in a continuous process typically occurs in an extruder that is elevated to a temperature that is sufficient to melt the polymer matrix with addition of all additives at the feed-throat, or by injection or side-feeders downstream. Extruder speeds can range from about 200 to about 700 revolutions per minute (rpm), and preferably from about 300 rpm. Typically, the output from the extruder is pelletized for later extrusion or molding into polymeric articles.

[00055] Subsequent extrusion or molding techniques are well known to those skilled in the art of thermoplastics polymer engineering. Without undue experimentation but with such references as "Extrusion, The Definitive Processing Guide and Handbook"; "Handbook of Molded Part Shrinkage and Warpage"; "Specialized Molding Techniques"; "Rotational Molding

Technology"; and "Handbook of Mold, Tool and Die Repair Welding", all published by Plastics Design Library (www.elsevier.com), one can make articles of any conceivable shape and appearance using compounds of the present invention.

USEFULNESS OF THE INVENTION

[00056] Any plastic article needing flexibility, elongation, physical properties of a TPE, and also a low compression set and a Tan Delta Peak temperature above 0°C can benefit from TPEs of the present invention. The plastic article can be shaped from the compound by molding, extruding, calendering, blow molding, and via additive 3-D manufacturing.

[00057] Non-limiting examples of plastic articles include any device for any industry which requires damping of vibrations by relying on the Tan Delta Peak temperature above 0°C. The industrial uses include building and construction articles, and transportation parts. The consumer uses include structures for equipment sensitive to vibrations, electronic protective parts, cradles and silent blocks for motors, and sport bras. Also, it can be used in grip applications such as handheld power tools, electronic consoles and controlling devices, gaming consoles, desk computers, laptop computers, etc. These applications need the vibration damping for longer handheld uses without fatigue in the muscles of the hands.

[00058] The invention is not limited to the above embodiments. The claims follow.

Claims

What is claimed is:

1. A thermoplastic elastomer compound, comprising:

(a) high molecular weight hydrogenated styrene-isoprene-styrene block copolymer with a hydrogenated vinylic polyisoprene mid-block; and

(b) liquid polybutadiene oligomer,

wherein the compound has a Tan Delta Peak temperature of more than 0°C and a compression set of less than about 50% after 22 hours at 70°C.

2. The compound of Claim 1, wherein the compound further comprises plasticizer oil.

3. The compound of Claim 1 or Claim 2, wherein the compound further comprises polyphenylene ether.

4. The compound of Claim 1 or Claim 2, wherein the compound further comprises polypropylene.

5. The compound of Claim 3, wherein the compound further comprises polypropylene.

6. The compound of Claim 4 or Claim 5, further comprising filler.

7. The compound of Claim 6, further comprising an additive selected from the group consisting of adhesion promoters; biocides; anti-fogging agents; anti-static agents; bonding, blowing and foaming agents; dispersants; fillers and extenders; flame retardants and smoke suppresants; impact modifiers; initiators; lubricants; micas; pigments, colorants and dyes; oils and plasticizers; processing aids; release agents; silanes, titanates and zirconates; slip and anti-blocking agents; stabilizers; stearates; ultraviolet light absorbers; viscosity regulators; waxes; and combinations of them.

8. The compound of Claim 7, wherein ingredients by weight percent of the compound are

HMW hydrogenated SIS TPE copolymer 10-40%

Liquid Polybutadiene oligomer 10-40%

Optional PPE 0-10%

Optional PP 0-15%

Optional Plasticizer Oil 0-15 %

Optional Filler 0-50%

Optional Other Additives 0.2-3%

9. The compound of any one of Claims 1-8, wherein the high molecular weight hydrogenated styrene-isoprene-styrene block copolymer has a weight average molecular weight between about 200,000 and 500,000 g/mole and wherein the liquid polybutadiene oligomer has a vinylic content of greater than about 50%.

10. A plastic article formed from the compound of any one of Claims

1-9.

11 A multicomponent plastic article made of several thermoplastic materials, one material of which at least being a compound of any one of claims 1-9.

12. The article of Claim 10 or Claim 11 in the form of a molded article, an extruded article, a calendered article, or an additive 3-D printed article.

13. The article of Claim 12, in the form of an industrial article for structures needing vibration damping at temperatures above 0°C.

14. The article of Claim 12, in the form of a handheld device needing vibration damping at temperatures above 0°C.

15. The article of Claim 12, in the form of a grip for handheld power tools, electronic consoles, electronic controlling devices, gaming consoles, desk computers, and laptop computers.