HIGH IMPERMEABILITY INNERLINER COMPOUND AND METHOD FOR THE PRODUCTION THEREOF

Abstract

Method for the manufacture of the innerliner compound comprising: —a first mixing step wherein at least one cross-linkable unsaturated chain polymeric base and one filler system are mixed together; —a final mixing step wherein a vulcanization system is added and mixed with the mixture deriving from an earlier mixing step; and —an intermediate mixing step, interposed between said first mixing step and the final mixing step, and wherein lignin is added and mixed into the mixture deriving from a previous mixing step.

Claims

1-7. (canceled)

8. A method for the manufacture of an innerliner compound, the method comprising: a first mixing step wherein at least one cross-linkable unsaturated chain polymeric base and a filler system are mixed together; a final mixing step wherein a vulcanization system is added and mixed with the mixture deriving from an earlier mixing step; and an intermediate mixing step interposed between said first mixing step and said final mixing step, wherein lignin is added and mixed into a mixture deriving from a previous mixing step.

9. The method of claim 8, wherein the lignin is present in an amount of between 5 and 25 phr.

10. The method of claim 8, wherein the lignin is Kraft lignin.

11. The method of claim 10, wherein the Kraft lignin is composed of particles having an average surface area of less than 400 pmt.

12. An innerliner compound manufactured using at least: a first mixing step wherein at least one cross-linkable unsaturated chain polymeric base and a filler system are mixed together; a final mixing step wherein a vulcanization system is added and mixed with the mixture deriving from an earlier mixing step; and an intermediate mixing step interposed between said first mixing step and said final mixing step, wherein lignin is added and mixed into a mixture deriving from a previous mixing step.

13. The innerliner compound of claim 12, wherein the lignin is present in an amount of between 5 and 25 phr.

14. The innerliner compound of claim 12, wherein the lignin is Kraft lignin.

15. The innerliner compound of claim 14, wherein the Kraft lignin is composed of particles having an average surface area of less than 400 pm.sup.2

16. A pneumatic tire comprising an innerliner layer manufactured using an innerlayer compound, the innerlayer compound manufactured using at least: a first mixing step wherein at least one cross-linkable unsaturated chain polymeric base and a filler system are mixed together; a final mixing step wherein a vulcanization system is added and mixed with the mixture deriving from an earlier mixing step; and an intermediate mixing step interposed between said first mixing step and said final mixing step, wherein lignin is added and mixed into a mixture deriving from a previous mixing step.

17. The pneumatic tire of claim 16, wherein the lignin is present in an amount of between 5 and 25 phr.

18. The pneumatic tire of claim 16, wherein the lignin is Kraft lignin.

19. The pneumatic tire of claim 18, wherein the Kraft lignin is composed of particles having an average surface area of less than 400 pm.sup.2

Description

EXAMPLES

[0024] Ten innerliner compounds were manufactured, wherein four thereof constituted comparative examples and six constituted examples of the invention.

[0025] In particular, compound A is a comparison compound that represents an innerliner compound that is commonly used and devoid of lignin as an ingredient;

[0026] the three compounds B, E and H are comparison compounds that comprise three respective types of lignin but that was added with a procedure that is different from that of the present invention; the six compounds C, D, F, G, I and L are compounds according to the invention which comprise three respective types of lignin added according to the dictates of the present invention. In particular, the compounds of the invention C, D, F, G, I and L require the use of three types of lignin in two different quantities (7 phr and 14 phr).

[0027] Table I shows the compositions in phr of the ten compounds A-L.

TABLE-US-00001 TABLE I A B C D E F G H I L Br-IIR 100 CB 50 Clay 25 ZnO 2 S 1 Lignin* — 7 — — — — — — — — 1MB Lignin* — — 7 14 — — — — — — 2MB Lignin** — — — — 7 — — — — — 1MB Lignin** — — — — — 7 14 — — — 2MB Lignin*** — — — — — — — 7 — — 1MB Lignin*** — — — — — — — — 7 14 2MB

[0028] In Table I the wording 1 MB refers to a first mixing step; whilst the wording 2 MB refers to a second mixing step.

[0029] Br-IIR stands for bromobutyl rubber.

[0030] CB is of the N6 type, which denotes a Carbon Black with a surface area equal to 36 m.sup.2/g.

[0031] Clay is a mineral filler produced and marketed by BASF with the acronym ASP® NC X-1.

[0032] Lignin* is the sulfonated lignin marketed by Borregaard with the acronym Borreseperse NA.

[0033] Lignin** is the Kraft lignin from soft wood marketed by Stora Enso with the acronym Lineo Classic.

[0034] Lignin*** is the Kraft lignin from soft wood marketed by Suzano with the acronym FP602.

[0035] Using an electron microscope (Zeiss brand, Auriga model, Secondary Electron—size of the images analyzed about 1 mm.sup.2), the average area was revealed of the particles of the three types of lignin used. It was found that the particles of Lignin* have an average surface area of 673 μm.sup.2; the Lignin** particles have an average surface area of 263 μm.sup.2, the Lignin*** particles have an average surface area of 194 μm.sup.2.

[0036] Herebelow, the procedure is given for the preparation of the compounds described in the examples.

—Preparation of the Compounds—

(1st Mixing Step—1 MB)

[0037] Before the start of the mixing, a mixer with tangential rotors and an internal volume of between 230 and 270 liters was loaded with the ingredients listed in Table I, excluding the vulcanization system (sulfur, ZnO) and lignin for the compounds of the invention (C, D, F, G, I, L), reaching a fill factor of between 66-72%.

[0038] The mixer was operated at a speed of between 40-60 revolutions/minute, and the mixture thus formed was discharged once a temperature of between 140-160° C. had been reached.

(2.SUP.nd .Mixing Step—2 MB)

[0039] This mixing step only concerned the compounds of the invention (C, D, F, G, I, L). Lignin according to the quantities shown in Table I was added to the mixture produced in the first mixing step. The mixture is discharged once it reaches a temperature of between 130-150° C.

(Final Mixing Step)

[0040] To the mixture obtained from the first mixing step (1 MB) for the comparison compounds (A, B, E, H), and to the mixture obtained from the second mixing step (2 MB) for the compounds of the invention (C, D, F, G, I, L) the vulcanization system (sulfur, ZnO) was added, reaching a filling factor of between 63-67%.

[0041] The mixer was operated at a speed of between 20-40 revolutions/minute, and the mixture thus formed was discharged once a temperature of between 100-110° C. had been reached.

[0042] The compounds A-L, reported above, were used to make respective test specimens, which were subjected to an evaluation test in order to verify properties in terms of fragility (brittleness), M300% and impermeability to oxygen.

[0043] The oxygen impermeability test was performed on materials with a thickness of 0.7 mm and using a conventional apparatus as MOCON® OX-TRA® (model 2/61). The measurements were made at a temperature of 25° C.

[0044] The mechanical tests were performed according to the ISO-812 standard.

[0045] For easier interpretation of the results obtained, the impermeability values are given in a form that is indexed with reference to the results of the comparison compound generally used for the implementation of an innerliner layer (Compound A).

[0046] With regard to the M300 Brittleness and impermeability to oxygen values reported in Tables II and III, it must be specified that the lower the reported value, the better the characteristic.

TABLE-US-00002 TABLE II A B C D E F G M300 3.7 3.3 4.6 4.1 3.2 3.3 3.3 Brittleness 698 698 693 653 841 1048 1107 E′Mpa(−40° C.) Permeability 100 104 90 82 100 81 73

TABLE-US-00003 TABLE III H I L M300 3.4 3.5 3.5 Brittleness 791 649 801 E′Mpa(−40° C.) Permeability 94 86 79

[0047] From the data reported in Tables II and III, it is clear how the compounds according to the present invention ensure a significant improvement in terms of permeability to oxygen, whilst maintaining the mechanical property values within permissible ranges. In fact, as will be immediately obvious to a technician in the field, all of the M300 and Brittleness values reported can be considered to be eligible for an innerliner layer.

[0048] The values reported in Tables II and III demonstrate how the effects of lignin, in terms of impermeability to oxygen, prove to be surprisingly different, if the same lignin is added in the first mixing step or in the second mixing step. In fact, the values in relation to compounds B and E demonstrate that if the lignin is added in the first mixing step then the permeability to oxygen remains unchanged, or is even worse compared to the comparison compound A.

[0049] In light of the above, it can be stated that the technical effect resulting from the addition of the lignin in a mixing step subsequent to the first (wherein all of the ingredients except the vulcanization system are mixed) should clearly be considered to be unexpected and surprising.