Method for preparing a masterbatch of an elastomer and an inorganic reinforcing filler

Abstract

The invention relates to a process for the preparation of a masterbatch of diene elastomer and reinforcing inorganic filler in accordance with the invention comprises the following successive stages: bringing into contact and mixing one or more aqueous dispersions (B) of one or more hydrophobized reinforcing inorganic fillers, which coagulate(s) spontaneously with the said latex, and one or more diene elastomer latexes (A) in order to obtain a coagulum, without requiring a coagulating agent, recovery of the coagulum, then drying the recovered coagulum in order to obtain the masterbatch.

Claims

1. Process for the preparation of a masterbatch of diene elastomer and reinforcing inorganic filler comprising the following successive stages: bringing into contact and mixing one or more aqueous dispersions (B) of one or more hydrophobized reinforcing inorganic fillers, which coagulate(s) spontaneously with the said latex, and one or more diene elastomer latexes (A) in order to obtain a coagulum, without requiring a coagulating agent, recovery of the coagulum, then drying the recovered coagulum in order to obtain the masterbatch.

2. Process according to claim 1, wherein recovery of the coagulum is carried out by a filtering operation.

3. Process according to claim 1, wherein recovery of the coagulum is carried out by a centrifuging operation.

4. Process according to claim 1, wherein the diene elastomer latex is a natural rubber latex.

5. Process according to claim 4, characterized in that the diene elastomer latex is a concentrated natural rubber latex.

6. Process according to claim 1, wherein the filler is chosen from silica (SiO.sub.2), alumina (Al.sub.2O.sub.3), alumina monohydrate (Al.sub.2O.sub.3.H.sub.2O), aluminum hydroxide [Al(OH).sub.3], aluminum carbonate [Al.sub.2(CO.sub.3).sub.3], magnesium hydroxide [Mg(OH).sub.2], magnesium oxide (MgO), magnesium carbonate (MgCO.sub.3), talc (3MgO.4SiO.2.H.sub.2O), attapulgite (5MgO.8SiO.sub.2. 9H.sub.2O), titanium dioxide (TiO.sub.2), titanium black (TiO.sub.2n-1), calcium oxide (CaO), calcium hydroxide [Ca(OH).sub.2], aluminum magnesium oxide (MgO.Al.sub.2O.sub.3), clay (Al2O.sub.3.2SiO.sub.2), kaolin (Al.sub.2O.sub.3.2SiO.sub.2.2H.sub.2O), pyrophyllite (Al.sub.2O.sub.3.4SiO.sub.2.H.sub.2O), bentonite (Al.sub.2O.sub.3.4SiO.sub.2.2H.sub.2O), aluminum silicate (Al.sub.2SiO.sub.5.Al4(SiO.sub.4).sub.3.5H.sub.2O), magnesium silicate (Mg.sub.2SiO.sub.4.MgSiO.sub.3), calcium silicate (Ca.sub.2SiO.sub.4), aluminum calcium silicate (Al.sub.2O.sub.3.CaO.2SiO.sub.2), calcium magnesium silicate (CaMgSiO.sub.4), calcium carbonate (CaCO.sub.3), zirconium oxide (ZrO.sub.2), zirconium hydroxide [ZrO(OH).sub.2.nH.sub.2O], zirconium carbonate [Zr(CO.sub.3).sub.2], and crystalline aluminosilicates comprising atoms of hydrogen compensating for the charges, alkali metals or alkaline earth metals, and mixtures thereof.

7. Process according to claim 6, wherein the filler is silica (SiO.sub.2).

8. Process according to claim 1, wherein the filler is hydrophobized using one or more hydrophobing agents of following formula (I):
E.sub.n-F(Formula I) in which: n is an integer equal to 1 or 2, when n has the value 1, then F is a monovalent group, when n has the value 2, then F is a divalent group, E represents a functional group which is capable of bonding physically and/or chemically to the filler and which comprises, in its structure, at least one alkyl or alkylene chain comprising from 1 to 18 carbon atoms which confers hydrophobing properties on the group E, F represents a group which may or may not bond physically and/or chemically to the diene elastomer.

9. Process according to claim 8, wherein the hydrophobing agent is of following formula (II):
[G(.sub.3-m)(L-K).sub.mSi-L-].sub.n-F(II) with: when n has the value 1, then F denotes the K group defined below and m varies from 0 to 2, and when n has the value 2, then F denotes an amino group, a polysulphide (S.sub.x) group or an epoxy group and m varies from 0 to 2, and for which the G groups are chosen, independently of one another, from a hydrogen atom, a C.sub.1-C.sub.18 hydrocarbon group chosen from linear, branched or cyclic alkyl groups, aralkyl groups, alkylaryl groups and aryl groups, an alkoxy (R.sub.1O) group, in which R.sub.1 represents a saturated C.sub.1-C.sub.8 alkyl radical, a halogen atom, and a hydroxyl group, provided that at least one G group is chosen from an alkoxy group, a chlorine atom or a hydroxyl group, L denotes a saturated or unsaturated and linear, branched or cyclic C.sub.1-C.sub.18 alkylene radical, optionally comprising an oxygen atom, K denotes a hydrogen atom, a halogen atom, or a functional group chosen from an amino group, a polyaminoalkyl group, a mercapto group, an epoxy group, a hydroxyl group, a vinyl group, an acryloyloxy group, a methacryloyloxy group, an SCN group or an R(CO)S group with R being a C.sub.1-C.sub.18 alkyl group.

10. Process according to claim 9, wherein m=0.

11. Process according to claim 10, wherein the hydrophobing agent is of following formula (III):
G.sub.3Si-L-K(III)

12. Process according to claim 10, wherein the hydrophobing agent is of following formula (IV):
[G3Si-L-]2-F(IV).

13. Process according to claim 8, wherein the hydrophobing agent is chosen from chlorotrimethylsilane, chlorotriethylsilane, chlorotripropylsilane, bromotrimethylsilane, bromotriethylsilane, bromotripropylsilane, fluorotrimethylsilane, methoxytrimethylsilane, methoxytriethylsilane, methoxytripropylsilane, chlorotrimethylsilane, dichlorodimethylsilane, trichloromethylsilane, bromotrimethylsilane, dibromodimethylsilane, tribromomethylsilane, methoxytrimethylsilane, dimethoxydimethylsilane, trimethoxymethylsilane, tetramethoxysilane, trimethoxypropylsilane, trimethoxyoctylsilane, trimethoxyhexadecylsilane, dimethoxydipropylsilane, triethoxymethylsilane, triethoxypropylsilane, triethoxyoctylsilane, diethoxydimethylsilane, octenyldimethylchlorosilane, octadecyltrichlorosilane, (-aminopropyl)trimethoxysilane, (-aminopropyl)triethoxysilane, (-hydroxypropyl)tripropoxysilane, (-mercaptopropyl)triethoxysilane, (-aminopropyl)dimethylethoxysilane, (-aminopropyl)dihydroxymethoxysilane, (glycidylpropyl)trimethoxysilane, [-(N-aminoethyl)aminopropyl]triethoxysilane, (-methacryloyloxypropyl)triethoxysilane, (-methacryloyloxypropyl)trimethoxysilane, (-mercaptoethyl)triethoxysilane, [-(N-aminoethyl)aminopropyl]trimethoxysilane, (N-methylaminopropyl)trimethoxysilane, (-thiocyanatopropyl)triethoxysilane, bis-(3-triethoxythiopropyl)silane tetrasulphide, vinyltriethoxysilane, vinylphenylmethylsilane, vinyldimethylmethoxysilane, divinyldimethoxysilane, divinylethyldimethoxysilane, dimethylvinylchlorosilane, bis(3-triethoxysilylpropyl)tetrasulphide and mixtures thereof.

14. Process according to claim 8, wherein the hydrophobing agent, once attached to the filler, comprises at most 30 carbon atoms.

15. Process according to claim 8, wherein the hydrophobing agent is selected from octenyldimethylchlorosilane, bis(3-triethoxysilylpropyl)tetrasulphide and mixtures thereof.

16. Process according to claim 8, wherein the hydrophobized filler has a degree of hydrophobation of greater than or equal to 0.29 carbon atom carried by the hydrophobing agent, once attached to the filler, per nm2 of filler surface area.

17. Process according to claim 1, wherein the process does not use a coagulating agent.

18. Process according to claim 9, wherein aryl groups are chosen from a phenyl and a benzyl group.

19. Process according to claim 9, wherein cyclic alkyl groups are chosen from a cvclopentyl and a cyclohexvl group.

20. Process according to claim 9, wherein the C.sub.1-C.sub.8 alkyl radical is chosen from methyl, ethyl and isopropyl groups.

21. Process according to claim 9, wherein the C.sub.1-C.sub.8 alkyl radical is chosen from at least one methyl and ethyl group.

22. Process according to claim 9, wherein the halogen atom is chosen from fluorine, chlorine, bromine and iodine.

23. Process according to claim 9, wherein C.sub.1-C.sub.18 alkylene radical is of 1 to 8 carbon atoms.

24. Process according to claim 9, wherein C.sub.1-C.sub.18 alkylene radical is chosen from the methylene, ethylene, isopropylene, n-butylene, octadecylene, cyclopentylene and cyclohexylene groups.

Description

EXAMPLES

(1) Equipment Used

(2) Model VCX500 Bricel ultrasound generator (ref. Fisher W75043) with a power of 500 W, used at 60% of its maximum power.

(3) Standard sonication probe having a diameter of 13 mm, suitable for the sonication of volumes of between 10 and 250 ml (ref. Fisher 75482).

(4) One magnetic stirrer plus one magnetic bar.

(5) Glassware: beaker with a size of 15 ml (ref. VWRN 15 ml 213-3916) or 500 ml (ref. VWR 50 ml 212-9301).

(6) Reactant: high ammonia natural rubber latex comprising 60% by weight of natural rubber originating from Trang Latex Co. Ltd, Thailand.

(7) Silica powder ground with a mortar, Zeosil silica 1165MP from Rhodia, with a BET specific surface: 160 m.sup.2/g,

(8) Distilled water.

(9) Preparation of the Hydrophobized Silica

(10) The silica is ground to give a fine powder using a pestle and mortar. The hydrophobicity of the silica is adjusted by silanization of its surface with octenyldimethylchlorosilane (ODCS).

(11) The hydrophobized silica is prepared by reacting 5 g of hydrophilic silica with various amounts of ODCS in the presence of 50 g of toluene (see the table for compositions 1 and 2 below).

(12) The necessary amounts of ODCS are dissolved in toluene. The medium is stirred using a magnetic stirrer. The ground silica powder is added to the medium and the dispersion is left stirring for 2 minutes. The composition is placed in a Petri dish (with a diameter of 18.5 cm) and is placed at a temperature of 70 C. for one hour, so as to make possible the evaporation of the toluene. The powder obtained is dispersed in distilled water after sonication for two minutes.

(13) TABLE-US-00001 1 2 Silica in g 5 5 ODCS in g 0.15 0.20 Toluene 50 g 50 g Nb C atom/nm.sup.2 0.55 0.73

(14) Masterbatches Prepared

(15) The masterbatches are prepared according to a process in accordance with the invention and in the following way.

(16) Preparation of the Aqueous Dispersion A of Natural Rubber Latex

(17) The natural rubber latex is weighed out into a glass beaker, a magnetic bar is added thereto and the latex is subsequently diluted in distilled water down to a concentration of 60% by weight of natural rubber.

(18) Preparation of the Aqueous Filler Dispersion B

(19) 2.32 g of the hydrophobized silica prepared according to compositions 1 and 2 described above are dispersed in 20 ml of water. The combined mixture is then homogenized using an ultrasound probe for two minutes. The silica agglomerated on the probe at the end of the two minutes is incorporated in the mixture using a spatula.

(20) Preparation of the Masterbatch

(21) 3.3 g of aqueous dispersion (B) are introduced into a 15 ml beaker and then 3.3 g of the aqueous dispersion (A) are added thereto. The mixture is mixed using the magnetic stirrer at a speed of 700 rpm. This operation is carried out for each of the aqueous dispersions (B) prepared from compositions 1 and 2.

(22) Conclusion

(23) It was observed that, for each of compositions 1 and 2, the coagulation between the hydrophobized reinforcing inorganic filler and the latex takes place spontaneously.