(19)
(11)EP 3 619 263 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
09.09.2020 Bulletin 2020/37

(21)Application number: 18717958.5

(22)Date of filing:  24.04.2018
(51)International Patent Classification (IPC): 
C08L 9/00(2006.01)
B60C 1/00(2006.01)
C08L 21/00(2006.01)
C08L 9/06(2006.01)
C10M 105/14(2006.01)
(86)International application number:
PCT/EP2018/060430
(87)International publication number:
WO 2018/202474 (08.11.2018 Gazette  2018/45)

(54)

RUBBER COMPOUND FOR TREAD PORTIONS

KAUTSCHUKVERBINDUNG FÜR LAUFFLÄCHENTEILE

COMPOSÉ DE CAOUTCHOUC POUR PARTIES DE BANDE DE ROULEMENT


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 03.05.2017 IT 201700047751

(43)Date of publication of application:
11.03.2020 Bulletin 2020/11

(73)Proprietor: Bridgestone Corporation
Tokyo 104-8340 (JP)

(72)Inventors:
  • AGORETTI, Pasquale
    00128 Roma (IT)
  • D'ALFONSO, Claudio
    00128 Roma (IT)

(74)Representative: Marchetti, Alessio 
Bridgestone Europe N.V./S.A. - Italian Branch Technical Center Via del Fosso del Salceto, 13/15
00128 Roma
00128 Roma (IT)


(56)References cited: : 
EP-A1- 3 012 291
US-A1- 2003 161 798
JP-A- S59 217 782
US-A1- 2014 100 310
  
  • ENSIKAT H.J.; DITSCHE-KURU,P.; NEINHUIS, C.; BARHLOTT, W.: "Superhydrophobicity in perfection: the outstanding properties of the lotus leaf.", BEILSTEIN JOURNAL OF NANOTECHNOLOGY, vol. 2011, no. 2, 10 March 2011 (2011-03-10), pages 152-161, XP002774911, DOI: 10.3762/bjnano.2.19
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description


[0001] The present invention relates to a rubber compound for a tread portion comprising a wax, wherein the composition thereof is such as to confer an improvement in terms of wet grip without, for this reason, leading to the worsening of other features.

[0002] Part of the research in the field of pneumatic tyres is concentrated on obtaining tread that has improved performance in terms of wet grip.

[0003] Research in the sector has produced various solutions, many of which, however, are not very convenient insofar as-notwithstanding the fact that they favor an improvement in terms of wet grip-they nonetheless lead to the worsening of other characteristics.

[0004] For example, it is now known that an increase within the compound of the quantity of silica or the use of low molecular weight resin, even though they give an improvement in wet grip, lead to worsening respectively in rolling resistance and abrasion resistance.

[0005] The need was therefore felt to have a solution that was able to guarantee improvements in wet grip without these improvements simultaneously leading to the worsening of other characteristics.

[0006] The inventors of the present invention have surprisingly found that the use within a compound of a particular wax makes it possible to satisfy the aforementioned need.

[0007] The object of the present invention is a rubber compound for the preparation of a tread portion for a pneumatic tyre; said rubber compound comprising at least a cross-linkable unsaturated chain polymer base, a filler and a vulcanization system; said rubber compound being characterized in that it comprises a wax composed of at least 50% by weight of nonacosanediols.

[0008] Here and hereinafter by wax is meant a substance that is malleable at ambient temperature, with a viscosity that is relatively low when melted, insoluble in water and hydrophobic.

[0009] Here and hereinafter, by the term "cross-linkable unsaturated-chain polymer base" is meant any natural or synthetic non-cross-linked polymer capable of assuming all of the chemical-physical and mechanical characteristics typically assumed by elastomers after cross-linking (vulcanization) with sulfur- or peroxides-based systems.

[0010] Here and hereinafter, by vulcanization system is meant a complex of ingredients comprising at least sulfur and accelerating compounds that in the preparation of the compound are added during a final blending stage and have the purpose of promoting the vulcanization of the polymer base once the compound is subjected to a vulcanization temperature.

[0011] Preferably, said nonacosanediols comprise a C2-C6 chain arranged between the two hydroxyl groups.

[0012] Preferably, said nonacosanediols are included in the group comprising nonacosane-4,10-diol, nonacosane-5,10-diol, nonacosane-10,13-diol, nonacosane-12,15-diol.

[0013] Preferably, said wax is derived from Lotus leaves. Preferably, said wax is present within the compound in a quantity of between 0.3 and 30 phr, more preferably between 1 and 5 phr.

[0014] Another object of the present invention is a tread portion made with a compound according to the present invention and a pneumatic tyre comprising such a tread portion.

[0015] Still another object of the present invention is the use of a wax composed of at least 50% by weight of nonacosanediols within a rubber compound for the preparation of a portion of pneumatic tyre tread.

[0016] The following are examples of non-limiting embodiments given purely by way of illustration.

[0017] Four rubber compounds were made, of which the first three (Compounds A-C) constitute comparison examples, whilst the last one (Compound D) was made according to the present invention.

[0018] In particular, the first comparison compound (Compound A) is a standard tread compound both of a wax and a low molecular weight resin; the second comparison compound (Compound B) differs from Compound A in the use of a low molecular weight resin; the third comparison compound (Compound C) differs from Compound A in the use of a wax, nonetheless with hydrophobic characteristics but with a composition that differs from that used according to the present invention.

[0019] The compound according to the present invention (Compound D) differs from Compound A in the use of a wax according to the present invention.

[0020] The example compounds were prepared according to the procedure below.

- preparation of the compounds -


(1st productive blending step - MASTERBATCH)



[0021] Before the start of the blending, a mixer with tangential rotors and an internal volume of between 230 and 270 liters was loaded with the cross-linkable unsaturated chain polymer base, the silica, the silane bonding agent and the carbon black reaching a fill factor of 66-72%.

[0022] The mixer was operated at a speed of 40-60 rpm, and the mixture thus formed was discharged once a temperature of 145-165°C had been reached.

(2nd non-productive blending step)



[0023] The mixture from the previous step was reworked in the mixer operating at a speed of 40-60 rpm and subsequently removed once a temperature of 130-150°C had been reached.

(productive blending step)



[0024] The vulcanization system, zinc oxide, stearic acid and, when required, the low molecular weight resin or wax was added to the mixture obtained from the previous step, reaching a fill factor of 63-67%.

[0025] The mixer was operated at a speed of 20-40 rpm, and the mixture thus formed was discharged once a temperature of 100-110°C had been reached.

[0026] Here and hereinafter by "non-productive blending step" is meant a blending step wherein, to the cross-linkable unsaturated chain polymer base are added and mixed the ingredients of the compound with the exception of the vulcanization system; while by "productive blending step" is meant a blending step wherein to the compound under preparation the vulcanization system is added and blended.

[0027] Table I shows the compositions in phr of the Compounds A - D.
TABLE I
 ABCD
First non-productive blending step
S-SBR 80.0
BR 20.0
Silica 80.0
Carbon black 8.0
Silane bonding agent 8.0
Productive blending step
Sulfur 1.5
ZnO 1.5
Stearic acid 1.5
TBBS 1.5
DPG 1.0
Low molecular weight resin -- 2.0 -- --
Wax* -- -- 2.0 --
Wax** -- -- -- 2.0


[0028] S-SBR is a polymer base obtained by means of a polymerization process in a solution with an average molecular weight, respectively, of between 800-1500x103 and of between 500-900x103, with a styrene content of between 10 and 45% and a vinyl content of between 20 and 70%.

[0029] BR is a polymer base constituted from polybutadiene
The silica is a silica with a surface area of about 170 m2/g and marketed under the name Ultrasil VN3 by the EVONIK company.

[0030] The carbon black is N134
The silane bonding agent is marketed under the name SI75 by the EVONIK company.

[0031] TBBS is the acronym for the compound N-tert-butyl-2-benzothiazole sulfenamide, which is used as a vulcanization accelerant.

[0032] DPG is the acronym for the compound Diphenylguanidine used as a vulcanization accelerant.

[0033] The low molecular weight resin is of the type Petroleum Hydrocarbon Resin (CAS 64742-16-1)
The wax* is a paraffin wax that does not satisfy the requirements called for by the present invention. In particular, the paraffin wax used in Compound C is Paraffin wax Sigma Aldrich (mp 58-62°C)

[0034] The wax** is a wax according to the present invention. In particular, the wax used in Compound D is derived from Lotus leaves and is marketed under the name Lotus Floral Wax (INCI: Nelumbo Nucifera Floral Wax) by the company Natural Sourcing, LLC.

[0035] The compounds listed in Table I, once vulcanized, were subjected to a wet grip measurement, a rolling resistance measurement, and an abrasion resistance measurement.

[0036] The wet grip was measured by comparing the friction coefficient of the compounds by means of a linear friction meter, under wet conditions, at a velocity of 500 mm/s and at a temperature of 5°C. The results were obtained by comparing the respective frictions coefficients: the larger the index, the higher the friction coefficient and, therefore, the greater the wet grip.

[0037] The rolling resistance derives from the dynamic properties of the compounds. The rolling resistance parameter is correlated to the tanĪ“ values at 60°C: the lower the tanĪ“ value at 60°C, the better the resulting rolling resistance. The dynamic properties were measured according to the ASTM D5992 standard.

[0038] The abrasion resistance was measured according to the DIN 53516 standard.

[0039] For a more immediate understanding of the advantages of the present invention, Table II reports the values of the measurements above indexed to the values of the comparison compound A.
TABLE II
 ABCD
Wet grip 100 105 100 110
Rolling resistance 100 95 100 100
Abrasion resistance 100 90 100 100


[0040] The higher the values reported in Table II, the better the relative characteristics are to be considered.

[0041] From the values reported in Table II it is evident that the use of the wax according to the present invention makes it possible to impart an improvement to the tread portion in terms of wet grip without, for this reason, leading to the worsening of the other characteristics, such as the resistance rolling or the abrasion resistance.

[0042] In fact, the values in relation to Compound B demonstrate how the use of a low molecular weight resin, even though it guarantees an improvement in wet grip, nonetheless leads to worsening of both the rolling resistance and abrasion resistance.

[0043] Furthermore, from a comparison of Compounds C and D it is evident that a hydrocarbon wax that does not satisfy the requirements called for by the present invention, even though it is hydrophobic, is not capable of conferring those advantages in terms of wet grip that instead, as the values in relation to Compound D demonstrate, the wax according to the present invention confers. This comparison serves to demonstrate that it is not the generic characteristics of the wax, but the presence of at least 50% by weight of nonacosanediols that confers the aforementioned advantages in terms of wet grip.


Claims

1. Rubber compound for the preparation of a tread portion of a pneumatic tyre; said rubber compound comprising at least a cross-linkable unsaturated chain polymer base, a filler and a vulcanization system; said rubber compound being characterized in that it comprises a wax composed of at least 50% by weight of nonacosanediols.
 
2. Rubber compound according to claim 1, characterized in that said nonacosanediols comprise a C2-C6 chain arranged between the two hydroxyl groups.
 
3. Compound according to claim 2, characterized in that said nonacosanediols are comprised in the group comprising nonacosane-4,10-diol, nonacosane-5,10-diol, nonacosane-10,13-diol, nonacosane-12,15-diol.
 
4. Rubber compound according to claim 2, characterized in that said wax is derived from lotus leaves.
 
5. Rubber compound according to one of the preceding claims, characterized in that it comprises said wax in a quantity between 0.3 and 30 phr.
 
6. Rubber compound according to one of the preceding claims, characterized in that it comprises said wax in a quantity between 1 and 5 phr.
 
7. Portion of a tread with a rubber compound according to one of the claims.
 
8. Pneumatic tyre comprising a tread portion according to claim 7.
 
9. Use of a wax composed of at least 50% by weight of nonacosanediols within a rubber compound for the preparation of a portion of pneumatic tyre tread.
 
10. Use according to claim 9, characterized in that said nonacosanediols comprise a C2-C6 chain arranged between the two hydroxyl groups.
 
11. Use according to claim 10, characterized in that said nonacosanediols are comprised in the group comprising nonacosane-4,10-diol, nonacosane-5,10-diol, nonacosane-10,13-diol, nonacosane-12,15-diol.
 
12. Use according to claim 11, characterized in that said wax is derived from lotus leaves.
 


Ansprüche

1. Gummimischung zur Herstellung eines Laufflächenabschnitts eines Luftreifens; wobei die Gummimischung mindestens eine vernetzbare ungesättigte Polymerkettenbasis, ein Füllmaterial und ein Vulkanisationssystem umfasst; wobei die Gummimischung dadurch gekennzeichnet ist, dass sie ein Wachs umfasst, das zu mindestens 50 Gew.-% aus Nonacosandiolen besteht.
 
2. Gummimischung nach Anspruch 1, dadurch gekennzeichnet, dass die Nonacosandiole eine zwischen den beiden Hydroxylgruppen angeordnete C2-C6-Kette umfassen.
 
3. Mischung nach Anspruch 2, dadurch gekennzeichnet, dass die Nonacosandiole in der Gruppe umfassend Nonacosan-4,10-diol, Nonacosan-5,10-diol, Nonacosan-10,13-diol, Nonacosan-12,15-diol enthalten sind.
 
4. Gummimischung nach Anspruch 2, dadurch gekennzeichnet, dass das Wachs aus Lotusblättern gewonnen wird.
 
5. Gummimischung nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass sie das Wachs in einer Menge zwischen 0,3 und 30 phr umfasst.
 
6. Gummimischung nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass sie das Wachs in einer Menge zwischen 1 und 5 phr umfasst.
 
7. Abschnitt einer Lauffläche mit einer Gummimischung nach einem der Ansprüche.
 
8. Luftreifen, umfassend einen Laufflächenabschnitt nach Anspruch 7.
 
9. Verwendung eines Wachses, das zu mindestens 50 Gew.-% aus Nonacosandiolen besteht, in einer Gummimischung zur Herstellung eines Abschnitts einer Lauffläche eines Luftreifens.
 
10. Verwendung nach Anspruch 9, dadurch gekennzeichnet, dass die Nonacosandiole eine zwischen den beiden Hydroxylgruppen angeordnete C2-C6-Kette umfassen.
 
11. Verwendung nach Anspruch 10, dadurch gekennzeichnet, dass die Nonacosandiole in der Gruppe umfassend Nonacosan-4,10-diol, Nonacosan-5,10-diol, Nonacosan-10,13-diol, Nonacosan-12,15-diol enthalten sind.
 
12. Verwendung nach Anspruch 11, dadurch gekennzeichnet, dass das Wachs aus Lotusblättern gewonnen wird.
 


Revendications

1. Composé de caoutchouc pour la préparation d'une partie de bande de roulement d'un pneumatique ; ledit composé de caoutchouc comprenant au moins une base polymère réticulable à chaîne insaturée, une charge et un système de vulcanisation ; ledit composé de caoutchouc étant caractérisé en ce qu'il comprend une cire composée d'au moins 50 % en poids de nonacosane-diols.
 
2. Composé de caoutchouc selon la revendication 1, caractérisé en ce que lesdits nonacosane-diols comprennent une chaîne en C2 à C6 agencée entre les deux groupes hydroxyle.
 
3. Composé selon la revendication 2, caractérisé en ce que lesdits nonacosane-diols sont compris dans le groupe comprenant nonacosane-4,10-diol, nonacosane-5,10-diol, nonacosane-10,13-diol, nonacosane-12,15-diol.
 
4. Composé de caoutchouc selon la revendication 2, caractérisé en ce que ladite cire est dérivée de feuilles de lotus.
 
5. Composé de caoutchouc selon l'une des revendications précédentes, caractérisé en ce qu'il comprend ladite cire en une quantité entre 0,3 et 30 pcc.
 
6. Composé de caoutchouc selon l'une des revendications précédentes, caractérisé en ce qu'il comprend ladite cire en une quantité entre 1 et 5 pcc.
 
7. Partie d'une bande de roulement avec un composé de caoutchouc selon l'une des revendications.
 
8. Pneumatique comprenant une partie de bande de roulement selon la revendication 7.
 
9. Utilisation d'une cire composée d'au moins 50 % en poids de nonacosane-diols au sein d'un composé de caoutchouc pour la préparation d'une partie de bande de roulement de pneumatique.
 
10. Utilisation selon la revendication 9, caractérisée en ce que lesdits nonacosane-diols comprennent une chaîne en C2 à C6 agencée entre les deux groupes hydroxyle.
 
11. Utilisation selon la revendication 10, caractérisée en ce que lesdits nonacosane-diols sont compris dans le groupe comprenant nonacosane-4,10-diol, nonacosane-5,10-diol, nonacosane-10,13-diol, nonacosane-12,15-diol.
 
12. Utilisation selon la revendication 11, caractérisée en ce que ladite cire est dérivée de feuilles de lotus.
 






Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Non-patent literature cited in the description