Patent Application
20160168339
The present invention relates to a rubber tyre compound production method.
One goal on which research in the tyre industry is constantly focused is in improving tyre rolling and abrasion resistance.
In this regard, silica has long been used as a reinforcing filler in tread compounds. Silica is used instead of carbon black and together with special chemical substances (silanes) which interact with the silanol groups of silica to prevent its particles from forming hydrogen bonds. With the right functionality, silanes may also interact with the polymer base to form a chemical bridge between it and the silica and so improve affinity of the polymer with the reinforcing filler. Silica is employed for the advantages it affords in terms of rolling resistance and wet-road-holding performance.
As anyone skilled in the art knows, the better the silica interacts with the polymer base, the better the resulting compound is in terms of rolling and abrasion resistance.
The Applicant has surprisingly discovered a rubber compound production method, in which silica as a reinforcing filler interacts better with the polymer base.
The object of the present invention is a rubber tyre compound production method, characterized by comprising a mixing step, in which at least one cross-linking, unsaturated-chain polymer base, silica, a silane bonding agent, and 0.6 to 5 phr of a chemical of general formula (I) are mixed with one another; and a following mixing step, in which at least stearic acid and a curing system are added to and mixed with the compound being prepared;
wherein:
R1, R2 and R3, which are the same or different, are chosen from the group consisting of: hydrogen and groups in the alkane, alkene, cycloalkane, heterocyclic compound, aromatic compound, amine, imine, amide, sulphide, alcohol, aldehyde, ketone, ether, ester, nitrile, nitro-derivative, and isocyanate families.
Preferably, 0.6 phr or more and less than 5 phr of the chemical of general formula (I) is used.
Tests show that using over 5 phr of the chemical of general formula (I) may cause premature curing problems when extruding the compound. Other potential problems resulting from using over 5 phr of the chemical of general formula (I) include increased viscosity of the compound being produced; and reduced adhesion of the rubber to the metal cords, due to the chemical of general formula (I) migrating in compounds incorporating metal cords.
To safely eliminate one of the above drawbacks, less than 5 phr of the chemical of general formula (I) should be preferably used.
Preferably, R1, R2 and R3, which are the same or different, are chosen from the group consisting of: H, CH3, CH3CH2, CH3CH2CH2, CH3CH2CH2CH2, CH2CHCHCH, CH3CH3CH, C6H5, C6H11, C10H7, CH3C6H4CH3, CH3CH2C6H5, C6H4OH, C4H5O2, CH3C6H4OCH3, CH3OC6H4OCH3, NH2, C6H4NH2, C4H7NH, C6H10NH2, C(CH3)2OH, C5H9NH, NH2CH2C7H12, CHCHOCH2C6H5, C6H10OH, CH2C6H3C3H2NH, SO3C6H4CH3, C6H4NO2, C6H11, C10H7, C6H4OH, CH3OC6H4, (CH3)3CC6H4, CH3C6H3NO2, (CH2)3Cl, CH3X, CH3CH2X, CH3CH2CH2X, CH3CH2CH2CH2X, C6H5X, C6H5CH2X, (CH3)3CX, C4H3X, CH2CHCH2X, C6H4SO3CH3X, C6H4NO2X, C6H11X, C10H7X, OHCH2CH2X, OHC4H4X, CH3OC6H4X, (CH3)3CC6H4X, CH2C6H4CHX, NH2C6H10X, OHC(CH3)2X, NHC5H9X, NHC5H9NC5H9X, NH2CH2C7H12X, OHC6H10X, NHCH2C6H3C3H2X, wherein X may be O or S.
Preferably, R1 and R2 are H, and R3 is NH2.
Preferably, 20 phr or more of silica is used in the first mixing step.
Preferably, the polymer base is chosen from the group comprising styrene-butadiene rubber, butadiene rubber, natural rubber, or mixtures thereof.
Preferably, 1 to 6 phr of stearic acid is used in the final mixing step.
A further object of the present invention is a tread compound produced using the method according to the present invention.
A further object of the present invention is a tread made from the compound produced using the method according to the present invention.
A further object of the present invention is a tyre, at least one part of which is made from the compound produced using the method according to the present invention.
The following are non-limiting examples for a clearer understanding of the present invention.
Two compounds (E1, E2) were produced using the method according to the present invention.
At the first mixing step, the polymer base is mixed with silica, the silane bonding agent, and a chemical of general formula (I). More specifically, the chemical used in example compounds E1, E2 was urea. Stearic acid and the curing system were added at the final mixing step. The compounds produced using the method according to the present invention differ from each other as regards the amount of urea added at the first mixing step, and the type of polymer base.
To correctly evaluate the advantages of the present invention, five control compounds (Ctrl 1-Ctrl 5) were produced. The first two control compounds (Ctrl 1, Ctrl 2) differ from the compounds produced according to the invention by containing no urea, and differ from each other as to the step in which the stearic acid is added: in the first control compound (Ctrl 1), stearic acid is added at the first mixing step, as in a standard method; whereas, in the second control compound (Ctrl 2), it is added at the final step, together with the curing system.
Control compounds Ctrl 3 and Ctrl 4 differ from the compounds produced according to the invention by the stearic acid being added at the first mixing step according to the standard method.
Control compound Ctrl 5 differs from compound E1 produced according to the invention by simply substituting thiourea for the chemical of general formula (I).
The example compounds were produced as follows:
—Compound Preparation—
(First Mixing Step)
Prior to mixing, a 230-270-litre, tangential-rotor mixer was loaded with the ingredients in Tables I and II to a fill factor of 66-72%.
The mixer was operated at a speed of 40-60 rpm, and the resulting mixture unloaded on reaching a temperature of 140-160° C.
(Second Mixing Step)
The resulting mixture was mixed again in the mixer operated at a speed of 40-60 rpm, and the compound unloaded on reaching a temperature of 130-150° C.
(Final Mixing Step)
The ingredients in Tables I and II were added to the mixture from the first mixing step to a fill factor of 63-67%.
The mixer was operated at a speed of 20-40 rpm, and the resulting mixture unloaded on reaching a temperature of 100-110° C.
Table I shows the compositions in phr of the two compounds produced in accordance with the teachings of the present invention.
Table II shows the compositions in phr of the five control compounds.
S-SBR is a polymer base produced by solution polymerization, with a mean molecular weight of 800-1500×103 and 500-900×103 respectively, a 10 to 45% styrene content, and a 20 to 70% vinyl content.
BR is a butadiene rubber.
The silica used is marketed by EVONIK under the trade name Ultrasil VN3 GR, and has a surface area of roughly 170 m2/g.
The silane bonding agent used is in the polysulphide organosilane class, is of formula (CH3CH2O)3Si(CH2)3SS(CH2)3Si(OCH2CH3)3 and is marketed by EVONIK under the trade name SI75.
The Accelerant 1 used is mercaptobenzothiazol-disulphide (MBTS).
The Accelerant 2 used is diphenyl-guanidine (DPG).
The antioxidant used is a mixture of polymerized 1,2-di-hydro-2,2,4-trimethylquinoline (TMQ) and N-1,3-dimethylbutyl-N′-phenyl-paraphenylenediamine (6PPD).
The compounds in Tables I and II were tested to determine their properties related to effective chemical bonding of the silica and the polymer base.
Dynamic properties were measured as per ISO Standard 4664 (as anyone skilled in the art knows, 60° C. tan δ values are closely related to rolling resistance properties: the lower the 60° C. tan δ value, the better the rolling resistance); and abrasion resistance was measured as per ISO Standard 4649. The parameter indicated ‘BOUND RUBBER’ is commonly used in literature to indicate the chemical-physical interaction of the polymer and filler. The test is carried out on green samples, and normally determines the fraction of the compound not solubilised after treatment in THF (24 hours at ambient temperature).
Tables III and IV show the above test results for the compounds produced using the method according to the present invention and for the control compounds respectively. To show more clearly the advantages of the compounds according to the present invention, the test results are indexed on the basis of the results of control compound Ctrl 1 representing the standard methodology.
As shown clearly in Tables III and IV, the compounds produced using the method according to the present invention have better rolling resistance, better interaction between the silica and the polymer base, and better abrasion resistance.
More specifically, as shown by the control compound Ctrl 2, Ctrl 3 and Ctrl 4 figures, simply shifting the stearic acid to the final mixing step or simply using a chemical of general formula (I) is not enough to achieve the advantages achieved by the compounds according to the present invention.
Moreover, as shown by the control compound Ctrl 5 figures, other chemicals of other than general formula (I), even though structurally similar, are not as effective in terms of silica and polymer base interaction.
| Number | Date | Country | Kind |
|---|---|---|---|
| RM2013A000442 | Jul 2013 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2014/063521 | 7/29/2014 | WO | 00 |
