SHOE SOLE COMPRISING GRAPHENE

Abstract

A shoe sole comprising an elastomeric composition comprising: (D) 100 phr of a mixture of rubbers comprising: i. from 40 to 70% by weight of an isoprene polymer; ii. from 20 to 50% by weight of polybutadiene; iii. from 10 to 40% by weight of an SBR having a glass transition temperature (Tg) from −60 to −40° C.; (E) from 50 to 100 phr of amorphous carbon black having a surface area greater than 85 m.sup.2/g measured with the ASTM D6556 method, and a dibutyl phthalate absorption index (DBPA) greater than 90 measured with the ASTM D2414 method; (F) from 1 to 30 phr of graphene nano-platelets, wherein at least 90% of said graphene nano-platelets has a side dimension (x, y) from 50 to 50000 nm and a thickness (z) of 0.34 to 50 nm, and wherein said graphene nano-platelets have a C/O ratio ≥100:1.

Claims

1-12. (canceled)

13. A shoe sole comprising: an elastomeric composition, said elastomeric composition comprising: 100 phr of a rubber mixture, said rubber mixture comprising: from 40% to 70% by weight of an isoprene polymer, from 20% to 50% by weight of polybutadiene, and from 10% to 40% by weight of an SBR having a glass transition temperature from −60° C. to −40° C.; based on 100 phr of said rubber mixture: from 50 phr to 100 phr of amorphous carbon black, said amorphous carbon black having a surface area greater than 85 m.sup.2/g, measured according to standard ASTM D6556, said amorphous carbon black having a dibutyl phthalate absorption (DBPA) index greater than 90 ml/100 g, measured according to standard ASTM D2414; and from 1 phr to 30 phr of graphene nano-platelets, wherein at least 90% of said graphene nano-platelets have a side dimension from 50 nm to 50,000 nm and a thickness of 0.34 nm to 50 nm, and wherein said graphene nano-platelets have a carbon/oxygen (C/O) ratio greater than or equal to 100:1.

14. The shoe sole of claim 13, wherein said SBR comprises a styrene unit content ranging from 5% to 40% by weight.

15. The shoe sole of claim 13, wherein said SBR comprises a butadiene phase having a 1,2-vinyl unit content ranging from 0% to 30% by weight.

16. The shoe sole of claim 13, wherein said graphene nano-platelets have a CIO ratio greater than or equal to 200:1.

17. The shoe sole of claim 13, wherein the at least 90% of said graphene nano-platelets have a side dimension from 100 nm to nm 25,000 nm and a thickness of 0.34 nm to 20 nm.

18. The shoe sole of claim 13, wherein said rubber mixture comprises: from 45% to 55% by weight of said isoprene polymer, from 25% to 35% by weight of said polybutadiene, and from 15% to 25% by weight of said SBR having a glass transition temperature from −60° C. to −40° C.

19. The shoe sole of claim 13, wherein said SBR has a glass transition temperature from −55° C. to −45° C.

20. The shoe sole of claim 13, wherein said amorphous carbon black has a surface area ranging from 95 m.sup.2/g to 130 m.sup.2/g, measured according to the standard ASTM D6556.

21. The shoe sole of claim 13, wherein said amorphous carbon black has a DBPA index ranging from 95 ml/100 g to 120 ml/100 g, measured according to the standard ASTM D2414.

22. The shoe sole of claim 13, wherein said elastomeric composition comprises from 1 phr to 15 phr of said graphene nano-platelets.

23. The shoe sole of claim 13, wherein said elastomeric composition comprises from 50 phr to 80 phr of said amorphous carbon black.

24. A shoe sole comprising: an elastomeric composition, said elastomeric composition comprising: 100 phr of a rubber mixture, said rubber mixture comprising: from 45% to 55% by weight of an isoprene polymer, from 25% to 35% by weight of polybutadiene, and from 15% to 25% by weight of an SBR having a glass transition temperature from −55° C. to −45° C.; based on 100 phr of said rubber mixture: from 50 phr to 80 phr of amorphous carbon black, said amorphous carbon black having a surface area ranging from 95 m.sup.2/g to 130 m.sup.2/g, measured according to standard ASTM D6556, said amorphous carbon black having a dibutyl phthalate absorption (DBPA) index ranging from 95 ml/100 g to 120 ml/100 g, measured according to standard ASTM D2414; and from 1 phr to 15 phr of graphene nano-platelets, wherein at least 90% of said graphene nano-platelets have a side dimension from 100 nm to 25,000 nm and a thickness of 0.34 nm to 20 nm, and wherein said graphene nano-platelets have a carbon/oxygen (C/O) ratio greater than or equal to 100:1

25. The shoe sole of claim 24, wherein said SBR comprises a styrene unit content ranging from 5% to 40% by weight.

26. The shoe sole of claim 24, wherein said SBR comprises a butadiene phase having a 1.2-vinyl unit content ranging from 0% to 30% by weight.

27. The shoe sole of claim 24, wherein said graphene nano-platelets have a CIO ratio greater than or equal to 200:1.

28. The shoe sole of claim 24, wherein the at least 90% of said graphene nano-platelets have a side dimension from 500 nm to nm 15,000 nm and a thickness of 0.34 nm to 8 nm.

29. A method of fabricating a shoe sole, comprising the steps of: preparing an elastomeric composition, said elastomeric composition comprising: 100 phr of a rubber mixture, said rubber mixture comprising: from 40% to 70% by weight of an isoprene polymer, from 20% to 50% by weight of polybutadiene, and from 10% to 40% by weight of an SBR having a glass transition temperature from −60° C. to −40° C.; based on 100 phr of said rubber mixture: from 50 phr to 100 phr of amorphous carbon black, said amorphous carbon black having a surface area greater than 85 m.sup.2/g, measured according to standard ASTM D6556, said amorphous carbon black having a dibutyl phthalate absorption (DBPA) index greater than 90 ml/100 g, measured according to standard ASTM D2414; and from 1 phr to 30 phr of graphene nano-platelets, wherein at least 90% of said graphene nano-platelets have a side dimension from 50 nm to 50,000 nm and a thickness of 0.34 nm to 50 nm, and wherein said graphene nano-platelets have a carbon/oxygen (C/O) ratio greater than or equal to 100:1; heating said elastomeric composition at a temperature between 50° C. and 100° C. for a time between 3 minutes and 5 minutes; adding accelerators and crosslinkers to said elastomeric composition at a temperature between 50° C. and 80° C. for about 90 seconds; and vulcanizing said elastomeric composition.

30. The method of fabricating the shoe sole according to claim 29, said elastomeric composition further comprising at least one of additives, process agents, antioxidants, or plasticizers.

31. The method of fabricating the shoe sole according to claim 29, wherein the step of vulcanizing comprises compression moulding, injection moulding, compression transfer moulding, or injection transfer moulding.

32. The method of fabricating the shoe sole according to claim 29, wherein said SBR comprises a styrene unit content ranging from 5% to 40% by weight.

Description

EXAMPLES

[0113] The examples also refer to the attached figures, in which:

[0114] FIG. 1 shows hardness tests and rebound resilience of compositions of the examples;

[0115] FIG. 2 shows tests relative to the elastic modulus of compositions of the examples;

[0116] FIG. 3 shows tests relative to the tear strength of compositions of the examples;

[0117] FIG. 4 shows tests relative to the abrasion resistance of compositions of the examples;

[0118] FIG. 5 shows tests relative to the Payne effect of compositions of the examples;

[0119] FIG. 6 shows tests relative to the loss modulus of compositions of the examples;

[0120] FIGS. 7 and 8 show tests relative to the dynamic friction coefficient of compositions of the examples.

PREPARATION OF THE ELASTOMERIC COMPOSITION

[0121] In all the examples an elastomeric composition was prepared, also called “compound”, in a 2.3 litre closed laboratory mixer with a two-phase process and rotor speed between 30 and 40 r.p.m.

[0122] The first phase, lasting overall between 3 and 5 minutes, consists in preparation of the master at a temperature between 50 and 100° C., which comprises all the components except for the accelerators and crosslinkers.

[0123] The second phase consists in addition, again in a closed internal mixer, of the accelerators and crosslinkers for 90 seconds, at a temperature between 50° C. and 80° C. at the discharge, with subsequent continuation in a cylinder mixer and completion of the vulcanization in the final forming mould, in a compression press.

[0124] Two reference compositions were prepared, one without addition of the graphene nano-platelets (designated as Ref 1), and another according to WO 2017/029072 A1 of the same Applicant, relative to an elastomeric composition for tyres, also comprising graphene nano-platelets (designated as Ref 2).

[0125] A composition according to the invention was also prepared, designated as Inv.

[0126] The compositions obtained at the end of the preparation process in two phases are illustrated in Table 1, where the ingredients of the component (A) are expressed as % by weight, while the other components are expressed in parts by weight per 100 parts (phr) of component (A).

TABLE-US-00001 TABLE 1 COMPOSITION Ref 1 Inv Ref 2 (A) Natural rubber (% weight) 50 50 40 Polybutadiene (% weight) 30 30 30 SBR (Tg −50° C.) (% weight) 20 20 0 SBR (Tg −25° C.) (% weight) 0 0 30 (B) Carbon black N220 (phr) 55 55 0 Carbon black N330 (phr) 0 0 30 (C) Graphene nano-platelets (phr) 0 3 6 Silica (phr) 0 0 15 Zinc oxide (phr) 4 4 5 Stearic acid (phr) 2 2 1 Process oil (phr) 8 8 5 Anti-ageing agent (phr) 5 5 11 Process adjuvants (phr) 5 5 6 Accelerators and crosslinkers (phr) 3.2 3.2 5

[0127] The SBR in solution (SSBR) having Tg=−51° C. has a styrene unit content of 26% by weight and in the butadiene phase has a 1,2-vinyl unit content of 24% by weight.

[0128] The natural rubber is SMR (Standard Malaysian Rubber) type.

[0129] The polybutadiene is Europrene Neocis type.

[0130] The carbon black N220 has a surface area of 104 m.sup.2/g and a DBPA index of 114 ml/100 g.

[0131] The carbon black N330 has a surface area of 76 m.sup.2/g and a DBPA index of 102 ml/100 g.

[0132] The graphene of the Inv composition has side dimensions (x-y), expressed as D90, between 10000 and 15000 nm and thickness (z) between 0.34 and 20 nm, and is produced by Directa Plus S.p.A. and marketed under the brand G+. The side dimensions were measured using a Malvern 3000 laser granulometer according to the method developed according to the ISO 9001:2015 standard.

[0133] The compositions Ref 1, Ref 2 and Inv were characterized to measure the properties of interest for application purposes.

[0134] The characterizations entail tests of different type such as tests on the non-vulcanized material (compound) and determination of the vulcanization kinetics via the use of an instrument called “Vulcanograph” by Alpha Technologies, model MDR2000.

[0135] Once the vulcanization kinetics were determined, test pieces were produced suitable for the intended tests. All the tests were performed in the same certified laboratory except for the dynamic tests and tests on the dynamic friction coefficient, which were performed at two specialist laboratories equipped with special instruments. [0136] The vulcanization kinetics were determined by the ISO 3417 method. [0137] The hardness was measured by the ISO 868 method. [0138] The stress strain curves were determined with the DIN 53504 method. [0139] The trouser tear was determined by means of the ISO 34-1 Trouser method. [0140] The abrasion was measured with the DIN D53516 method. [0141] The rebound resilience was determined with the ISO 4662 (Zerbini pendulum) method.

[0142] As regards the characteristics of the vulcanized compositions, the data relative to the hardness tests (in Shore A) should be considered aligned with one another (FIG. 1) while the rebound resilience tests (by means of Zerbini pendulum), of the composition Inv and the composition Ref 2 show an improvement with respect to the composition Ref 1.

[0143] As regards the trend of the moduli, 100% and 300%, in a stress-strain curve (FIG. 2), the histogram shows that the values of the compositions containing G+(Inv and Ref 2) are comparable but superior with respect to the modulus of the reference composition Ref 1. Contrarily, analysing the histogram relative to the 300% modulus, it is observed that the modulus of the reference composition Ref 1 and of the composition according to the invention Inv are much higher than the composition Ref 2. Without being bound to any particular theory, we believe that this is due to the specific degree of carbon black of the composition Inv, having a higher surface area and DBPA index than the carbon black of the composition Ref 2, and to its higher quantity.

[0144] As regards the tear strength properties (FIG. 3), it is observed that the compositions containing G+ show a trend superior to the reference Ref 1. It is, however, important to note that the composition Inv shows a tear strength superior to the composition Ref 2, which we believe is due to the presence of the specific carbon black grade, and to the presence of the styrene-butadiene (SBR) copolymer with Tg equal to −50° C., having a microstructure with very low 1,2 vinyl unit content.

[0145] As regards resistance to abrasion, it can be seen from the histograms of FIG. 4 that the reference composition Ref 2 is greatly inferior to the composition Inv. Comparing the histograms of FIG. 4 it is observed that the reference composition Ref 1 has values lower than the composition Inv. Nevertheless, the abrasion values of the composition Inv are suitable for use in shoe soles since the application specifications require only slightly higher abrasion resistance limit values. Comparing said results with the compound Ref 2, an enormous difference appears evident due once again to the presence of both a polymer grade (SBR) at Tg −50° C. and a specific carbon black grade with higher surface area, better structure and present in greater quantity.

[0146] The analysis of the dynamic-mechanical properties focused on evaluation of the properties correlated with wear on the sole with the dynamic tests according to Payne, called “Payne Effect”. The Payne effect analyses the trend of the dynamic modulus (storage modulus E′ or G′ expressed in MPa) according to the deformation expressed in percentage (%), having fixed the frequency and temperature of the test. High elastic modulus values at low deformations guarantee better wear behaviour. Dynamic-mechanical analyses (DMA) were carried out by means of traction tests with slight constant preload with the instrument TA Instrument Q800, in the following operating conditions: constant temperature of 60° C., frequency 1 Hz, dynamic deformation 0 to 10%.

[0147] FIG. 5 highlights an interesting phenomenon due to the particular interaction between the graphene nano-platelets G+ and the elastomeric matrix. Observing the curves relative to the compounds Ref 1 and Inv, an increase in the elastic modulus (storage modulus) is found in the composition Inv containing the graphene nano-platelets G+. In fact, the values of E′ at low deformations are increased by 19% with respect to the reference composition Ref 1 (FIG. 5). This allows greater wear resistance to be obtained. Without prejudice to the fact that the graphene nano-platelets G+ added to a formulation entail an increase in the storage modulus with respect to the same not containing G+, the curve relative to the compound Ref 2 shows values of E′ lower than the compounds Ref 1 and Inv due to the type of carbon black used, which has a surface area and DBPA index lower than those of the carbon black used in the other two compounds, and is furthermore present in a lower quantity.

[0148] Dynamic-mechanical analyses were also performed at different temperature in a range between −100° C. and +80° C., by means of traction test with slight constant preload with the instrument TA Instrument Q800 at a frequency of 1 Hz. Observing the various spectra in terms of E″ (Loss Modulus, FIG. 6), it is observed that for the entire trend of the spectrum, in the thermal operating range (−10 to +50° C.), the composition Inv is always higher than the references Ref 1 and Ref 2, for the reasons previously given. This is due to the interaction effect of the graphene nano-platelets G+ with the polymers Ai, Aii and Aiii, thus determining an increase in the Loss Modulus, and giving rise to an improvement in the viscous properties (improved grip/dynamic friction coefficient).

[0149] Dynamic friction coefficient (DFC) tests were subsequently performed in compliance with the UNI-EN-ISO 13287 standard, which prescribes both dry and wet tests.

[0150] The results obtained, adimensional values, highlight that the test piece of the composition Inv with respect to Ref 1 shows comparable values in wet conditions, and clearly superior values in dry conditions (FIG. 7 and FIG. 8). The higher the values, the better the dynamic friction behaviour. The composition Ref 2, on the other hand, presents lower dynamic friction values, in both conditions, even though they are considered ideal in the balance for application in the tyre sector.

[0151] The tests discussed above confirm the data obtained via the DMA tests and show that the composition Inv allows improvement in the balance of the wear and grip properties on both wet and dry surfaces. It is therefore ideal as a composition for shoe soles.