Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-09-22
2004-01-06
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S376000, C524S377000, C568S428000, C568S435000
Reexamination Certificate
active
06673856
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved composition of alditol acetal, in particular dibenzylidene sorbitol or one of its derivatives.
It relates in particular to a new powdery composition of an alkylated alditol diacetal.
It is also intended to provide a new process for improving the flow behavior and/or stability of alditol acetal compositions.
Finally the present invention also relates to use of said compositions for preparing plastics materials or jellified materials or additives intended for use in said materials.
BACKGROUND OF THE INVENTION
It is well known that alditol acetals such as dibenzylidene sorbitol and its derivatives may be used as additives, in particular as nucleating agents or clarifying agents for plastics materials such as polyolefins.
These products are also used as agents for jellifying or modifying the viscosity of a variety of materials such as compositions for cosmetic or pharmaceutical use, adhesive compositions or paints. These compositions may also be shaped within other articles such as rods or sticks of glue or cosmetic materials, for example deodorants or air fresheners.
One of the main disadvantages associated with the industrial use of alditol acetals such as dibenzylidene sorbitol and its derivatives relates to the poor flow behavior of these products. This is due, at least in part, to the generally very powdery and very tacky character of these products. This produces problems during industrial operations such as transporting, crushing, bagging, metering, mixing, storing, cleansing, etc.
In particular, alditol acetal powders readily form “domes” in storage tanks and/or transport piping. This prevents or impedes the routing, metering, and/or evacuation of these products when using feeding hoppers and metering systems in industrial units, for example units intended for the preparation of plastics materials or additives for plastics materials.
“Plastics materials” are understood to mean in particular polyolefins, especially all polymers based on propylene and/or ethylene, polyamides, thermoplastic polyesters, vinyl resins, acrylic resins and mixtures of these.
This flow behavior problem of powdery forms of alditol acetals has not yet been resolved in a practical industrial manner, other than by manufacturers and/or users of these products using modified devices such as special pneumatic feeding systems or PTFE-lined hoppers.
In addition to the fact that these types of devIces may be costly and/or complex, they do not always prevent, the “dome” phenomena mentioned above or at the very least fouling problems which appear in hoppers, metering systems or, further downstream, screw conveyors supplying mixtures to preparation units for plastics or jellified materials.
Moreover, even within compositions of materials into which they can be introduced and metered in a satisfactory manner, alditol acetals may exhibit a poor dispersing capacity. This phenomenon can produce, in particular in plastics and jellified materials, a heterogeneity or some degree of degradation of the final characteristics of said materials (general appearance or organoleptic, optical, mechanical characteristics, etc).
A variety of technologies has been proposed in order to alleviate the problems mentioned above of Door dispersibility of alditol acetals, in particular of dibenzylidene sorbitol and its derivatives. For example, Japanese patent JP 60-101131 describes drying then finely crushing an alditol diacetal previously treated with terephthalic acid in the presence of an anionic surfactant.
Lyophilisation of a gel of alditol diacetal in a solvent has also been recommended, as disclosed in Japanese patent JP 62-253646. The lyophilized product thus obtained has a low “after tamping down” density, that is the density is in the order of 100 g/l, and is always significantly less (by a factor of about 3) than that of the initial alditol diacetal.
More recently, patent EP 569 198 has disclosed ultrafine crushing of alditol diacetals on modified devices, for example combining a fluidized bed and a high speed turbine, in order to obtain products with an average particle size which is especially small, that is at most 15 &mgr;m and preferably less than 6 &mgr;m.
On reading example 2 of the above document it seems that this type of ultrafine crushing applied to dibenzylidene sorbitol with the brand name “MILLAD® 3905” is accompanied by a very significant reduction (by a factor of about 3.3) of the “after tamping down” density (“packed bulk density”) of the product.
Still more recently, other technologies have been recommended with the objective of improving the dispersibility of alditol diacetals, in particular:
the preparation, by drying/spraying, of a fine powder based on a mixture of an alditol diacetal and a special phosphite, said mixture having been previously solubilized in a solvent (patent EP 651 006), or
forced drying and crushing, in particular in an instantaneous dryer, of damp alditol diacetal, the dried/crushed product obtained having a very low residual water content (0.01%) and an apparent density in the order of about 200 g/l (patent JP 06-048783).
The result is that the methods recommended for guaranteeing good dispersibility of alditol acetals within plastics materials etc, are generally complex and/or costly or even dangerous, in particular due to the fact that they involve the use of specific drying equipment, crushing equipment and/or solvents.
In addition, as indicated above, these methods generally have the objective of or the effect of significantly reducing the density of alditol acetals, which increases their dusty character and dangerousness (risks of explosion and inhalation) and worsens their ability to flow freely.
Another disadvantage associated with the industrial use of alditol acetals, or at least in some of them such as, for example, certain alkylated or halogenated derivatives of dibenzylidene sorbitol, originates in the unstable character of these products. This instability is exhibited in particular by odiferous problems and by a reduction in effectiveness under some conditions of use.
These problems may be detected organoleptically in the initial product, i.e. even before any processing or special use of the product.
They may be detected organoleptically only when the alditol acetal is actually used in an industrial process, for example during thermoforming of a plastics material in which alditol acetal has been incorporated.
This type of thermal treatment may, inter alia, generate, encourage or amplify decomposition phenomena, in particular hydrolysis and/or sublimation of the alditol acetal and the emission of undesirable odors, in particular of an aldehyde type.
This is particularly undesirable in the case of materials intended to be used in contact with foodstuffs, pharmaceuticals or cosmetics.
This instability, in particular thermal instability, of alditol acetals is generally accompanied by a reduction in their effectiveness as nucleating or clarifying agents, the decomposition or hydrolysis products of alditol acetals not being able to act in this way.
A variety of processes has been suggested for improving the stability, in particular thermal stability, of alditol acetals, in particular dibenzylidene sorbitol and its alkylated or halogenated derivatives, and thus for minimizing or masking, or even suppressing odiferous problems and/or problems of lowering in the effectiveness associated with the use of these products.
These problems may be due in particular to the residual presence, even within the plastics materials, of species which are capable of catalyzing the decomposition of alditol diacetals, such as residual amounts of polymerization catalysts with an acid nature, as described in patent EP 68 773.
The above patent recommends the incorporation, within particular plastics materials (low density linear polyethylenes with a high concentration of residual catalysts), of inhibitors of the decomposition of diacetals selected from a wide variety of chemical families (metal sequestering agents, amines, alkenes,
Rajguru U. K.
Roquette Freres
Seidleck James J.
Sturm & Fix LLP
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