Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-04-01
1998-06-16
Short, Patricia A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523457, 523466, 523468, 523509, 523514, 523527, 524 35, 524425, 524590, C08L 6310, C08L 6706, C08L 7516
Patent
active
057671770
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a thermosetting composition which can be used, in particular, for the manufacture of motor vehicle body parts, a process for the obtaining of said composition, as well as a process for recycling parts made of said composition.
Motor vehicle body parts are already being made at present of thermosetting materials of the BMC (bulk molding compound) type. These materials conventionally contain about 50% mineral filler, such as chalk or alumina, and about 20% glass fibers, the balance being formed of a polyester resin. Such a composition leads to a density of about 1.8.
These known thermosetting compositions have a number of drawbacks.
First of all, they are of relatively high density, so that the parts which are made from these materials are heavier than the same parts made of sheet metal for a given mechanical strength.
Furthermore, the recycling of these parts presents real difficulties. In fact, they frequently cannot be burned due to their content of halogen compounds such as chlorine and bromine.
The present invention is directed at overcoming these drawbacks.
For this purpose, the object of the invention is first of all a thermosetting composition which is characterized by the fact that it comprises approximately, by weight:
33% to 43% of a thermosetting resin;
5% to 15% cellulose fibers;
15% to 21% mineral fillers;
12.5% to 22.5% of reinforcement fibers of high mechanical strength.
Such a composition therefore contains much less mineral filler than the known compositions, in particular the bulk molding compounds.
More particularly, the composition of the invention can comprise about 10% cellulose fibers.
The thermosetting resin can be selected from among polyesters having a maleic, orthophthalic, isophthalic or adipic base, or vinyl esters having a urethane or epoxy base.
The reinforcement fibers can be selected, in particular, at least in part, from among glass, carbon or aramid fibers, such as those sold under the trademark Kevlar by Dupont de Nemours.
The mineral fillers may furthermore be selected at least in part from among calcium carbonate and hydrated alumina.
The composition of the invention can furthermore comprise about 15% to 25% by weight of anti-shrinkage additive.
One composition in accordance with the invention which is particularly advantageous for the production of motor vehicle body parts comprises, by weight, about 30% resin, 20% of an anti-shrinkage additive, 0.5% catalyst, 10% cellulose fibers, 18% mineral fillers, 2% of a mold-release agent, and 17.5% of reinforcement fibers of high mechanical strength.
These reinforcement fibers may more particularly comprise aramid fibers, for instance Kevlar, in an amount of from 1% to 3% of the total weight.
The present invention also has as its object a process for the obtaining of a thermosetting composition such as described above in which, the mineral fillers and the fibers, solids, on the one hand, and on the other hand the other components, liquids, are first of all separately mixed and thereupon the solid mixture is impregnated by the liquid mixture.
The present invention also has as its object a process for the recycling of a part made from a composition such as described above in which said part is burned and the ashes are used as fillers in a new thermosetting composition.
The density of the compositions in accordance with the invention is on the order of 1.3, so that the molded parts of this composition are considerably lighter than the equivalent parts molded from the conventional bulk molding compounds.
This lightness is obtained by the cellulose fibers, which may be of different origin (wood, cotton, sisal, etc.) and of different lengths (a few microns to several millimeters).
Furthermore, as the cellulose fibers absorb a large amount of resin, the latter is present in a stronger proportion than in the conventional bulk molding compounds, which contributes to an improvement in the mechanical properties, which, as will be seen below, are far superior to those of the conventional bulk molding compou
REFERENCES:
patent: 3991005 (1976-11-01), Wallace
patent: 4067845 (1978-01-01), Epel
patent: 5231121 (1993-07-01), Kramer
Landru Lionel
Omente Pedro
Cytec Industry Incorporated
Short Patricia A.
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