Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-05-21
2003-01-28
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S424000
Reexamination Certificate
active
06512038
ABSTRACT:
This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR99/02483 filed on Oct. 13, 1999.
The present invention relates to the use as filler, in rubber compositions, of amorphous aluminum hydroxycarbonate, hydroxyoxycarbonate or oxycarbonate.
It also relates to the rubber compositions thus obtained.
Finally, it also relates to finished articles based on these compositions and in particular to tire covers.
It is known to employ reinforcing white fillers in elastomers, such as, for example, precipitated silica or alumina. However, the results are not always those hoped for.
The aim of the invention is to provide a filler for rubber compositions which provides them with a satisfactory compromise with regard to properties, namely, preferably:
very good rheological properties and excellent suitability for vulcanization, comparable with those of highly dispersible precipitated silicas but much better than those provided by alumina,
particularly outstanding dynamic properties, in particular a Payne effect of low amplitude, resulting in a low resistance to rolling for tires based on these compositions, and/or a very high tangent &dgr; at 0° C., resulting in an improved adhesion for tires based on these compositions,
good strengthening in terms of modulus,
a rather high resistance to thermal aging and to UV (ultraviolet radiation) aging.
With this aim, a subject matter of the present invention is the use as filler, in a rubber composition, of at least one compound (A) composed of an amorphous aluminum hydroxycarbonate or an amorphous aluminum hydroxyoxycarbonate or an amorphous aluminum oxycarbonate.
More particularly, said hydroxycarbonate, hydroxyoxycarbonate or oxycarbonate comprises at least 0.01, in particular at least 0.04, mol of carbonate per mole of aluminum; it can comprise at least 0.1 mol of carbonate per mole of aluminum. In general, its carbonate/aluminum molar ratio is at most 0.25, in particular at most 0.2.
The carbonates present in the hydroxycarbonate, hydroxyoxycarbonate or oxycarbonate and which can be detected by infrared spectroscopy are usually covalent.
The compound (A) generally has a BET specific surface area of between 40 and 150 m
2
/g, in particular between 45 and 95 m
2
/g; it can be between 50 and 75 m
2
/g. The BET surface area is determined according to the Brunauer-Emmet-Teller method described in “The Journal of the American Chemical Society”, Vol. 60, page 309, February 1938, which corresponds to NF Standard T 45007 (November 1987).
This compound (A) preferably exhibits a low proportion of reactive surface Al—OH functional groups.
Some preferred but nonlimiting alternative forms of the invention are described below.
According to a first alternative form of the invention, the compound (A) employed is an amorphous aluminum hydroxycarbonate corresponding to the following empirical formula (I)
Al(OH)
x
(CO
3
)
y
.z
H
2
O (I)
in which
0.5≦x≦3, for example 1≦x≦3
0.01≦y≦0.25, for example 0.04≦y≦0.25, in particular 0.1≦y≦0.25
z≦1.5, for example z≦1
In this formula (I), y can be at most equal to 0.2.
In the context in particular of this alternative form of the invention, the compound (A) preferably has the following property: it remains amorphous (its X-ray diffraction spectrum remains flat) after having been calcined (under air) for 2 hours at any temperature between 150 and 700° C. or after having been subjected to a treatment which consists of a rapid dehydration using a gas stream at 600° C., the contact time of the compound with this gas being from 1 to 2 seconds.
In this alternative form of the invention, the compound (A) is generally formed of aggregates of individual particles which are not or not very porous, for example substantially spherical, with a size which can be between 15 and 25 nm.
According to a second alternative form of the invention, the compound (A) employed results from the calcination (in particular under air) at any temperature between 150 and 700° C., in particular between 180 and 650° C., of an amorphous aluminum hydroxycarbonate (known as starting amorphous aluminum hydroxycarbonate), in particular for 1 to 3 hours, for example for 2 hours.
In this alternative form, the starting amorphous aluminum hydroxycarbonate preferably has the following property: it remains amorphous after having been subjected to a treatment which consists of a rapid dehydration using a gas stream at 600° C., the contact time of the compound with this gas being from 1 to 2 seconds.
According to a third alternative form of the invention, the compound (A) employed results from the rapid dehydration of an amorphous aluminum hydroxycarbonate (known as starting amorphous aluminum hydroxycarbonate) using a gas stream at a temperature of between 500 and 700° C., in particular equal to 600° C., the contact time of this starting amorphous aluminum hydroxycarbonate with this gas being between a fraction of a second and 4 seconds, in particular between 1 and 2 seconds.
In this alternative form, the starting amorphous aluminum hydroxycarbonate preferably has the following property: it remains amorphous after having been calcined (under air) for 2 hours at any temperature between 150 and 700° C.
In the second and third alternative forms in particular of the invention, the compound (A) employed advantageously exhibits a high dispersibility. This dispersibility is quantified using the measurement of the level of fines (&tgr;
f
), that is to say of the proportion (by weight) of particles with a size of less than 0.3 &mgr;m, after deagglomeration with ultrasound, carried out according to the test described below.
In this test, the ability of the compound to disperse is measured by a particle size measurement (by sedimentation) carried out on suspension of the compound, which suspension has been deagglomerated beforehand by treatment with ultrasound. The deagglomeration (or dispersion) under ultrasound is carried out using a Branson OSI sonifier (450 W) equipped with a probe with a diameter of 12 mm. The particle size measurement is carried out using a SediGraph particle sizer (sedimentation in the field of gravity+scanning with a beam of X-rays).
4 grams of compound (A) are weighed out in a sample tube (with a volume equal to 75 ml) and the weight is made up to 50 grams by addition of a 1 g/l sodium hexametaphosphate solution: an aqueous suspension comprising 8% of compound (A) is thus prepared, which suspension is homogenized for 2 minutes with magnetic stirring. Deagglomeration (dispersion) under ultrasound is then carried out as follows: after the probe has been immersed over a length of 4 cm, the output power is adjusted so as to obtain a deviation of the power needle indicating 20%. Deagglomeration is carried out for 180 seconds.
The particle size measurement is subsequently carried out by means of a SediGraph particle sizer. For this, the vertical rate of scanning of the cell by the beam of X-rays is first adjusted to 946, which corresponds to an analyzed maximum size of 63 &mgr;m. Deionized water is circulated in said cell and then the electrical zero and the mechanical zero of the paper recorder are adjusted (this adjustment being carried out with the “100%” potentiometer of the recorder at the maximum sensitivity). The pen of the paper recorder is placed at the point representing the starting size of 85 &mgr;m. The suspension of deagglomerated compound (A), optionally cooled beforehand, is subsequently circulated in the cell of the SediGraph particle sizer (the particle size analysis being carried out at 30° C.) and the analysis then begins. The analysis is automatically halted as soon as the size of 0.3 &mgr;m is reached (approximately 45 minutes). The level of fines (&tgr;
f
), that is to say the proportion (by weight) of particles with a size of less than 0.3 &mgr;m, is then calculated.
This level of fines (&tgr;
f
) or level of particles with a size of less than 0.3 &mgr;m increases in proportion as the compound increases in dispersibility.
In the second and t
Chopin Thierry
Ladouce Laurence
Le Goff Pierre-Yves
Martin Michel
Rhodia Chimie
Sanders Kriellion A.
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