Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-12-07
2001-10-16
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S395000, C428S397000, C428S423500, C428S423700, C428S458000, C428S364000
Reexamination Certificate
active
06303221
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to pulp reinforcement of polymer compositions as a means for increasing the tensile moduli of such compositions. The pulp of this invention is a special, two-component, material.
2. Description of Related Art
U.S. Pat. No. 5,830,395, issued Nov. 3, 1998 on the application of G. Vercesi et al., discloses the manufacture of a composition with a pulp uniformly dispersed in a polymer. The pulp is a single-component material.
Research Disclosures 329110 and 330093, published September and October, 1991, respectively, disclose the use of aramid pulp as a reinforcement for elastomer materials.
Japanese Patent Publication Kokai No. 59-163418, published Sep. 14, 1984, discloses fibers comprising 80-99 weight percent poly(p-phenylene terephthalamide) and 1-20 weight percent aliphatic polyamide. The fibers are pulped and used in paper and possibly other applications.
U.S. Pat. No. 5,094,913, issued Mar. 10, 1992, discloses two-component pulp that can be used as reinforcement in polymer compositions.
Japanese Patent Publication Kokai No. 53-111120, published Sep. 28, 1978, discloses fibrids that may be a blended combination of para-aramid and a second polymer, useful, among other things, as a paper component and as reinforcement for rubber tires.
BRIEF SUMMARY OF THE INVENTION
This invention relates to a fibrous reinforcing composition comprising 20 to 99 weight percent elastomer and 1 to 80 weight percent fibrous, polymeric, pulp uniformly combined therewith, wherein the fibrous pulp is a combination of at least two organic polymeric materials and has a surface area of greater than 6 m
2
/g (square meters per gram).
In one aspect of the invention, the components of the pulp are soluble and mutually immiscible in sulfuric acid and the pulp can be a refined fiber floc.
DETAILED DESCRIPTION OF THE INVENTION
There is and has long been a need for elastomer reinforcement that will increase the tensile modulus of articles made using the elastomer. This invention is devoted to that need.
Polymer moduli have been increased in the past by addition of various additives to the polymer. Particles, such as carbon black or silicon dioxide, have been used as reinforcement for rubber to achieve an increased modulus, as have fibrous materials such as pulp.
The present invention aims to further increase elastomer modulus by addition of a pulp to the elastomer. The pulp, however, is a form with qualities especially adapted to dispersion in an elastomer and to increasing adhesion to an elastomer. The pulp of this invention has particularly high surface area and is made from a combination of at least two organic polymeric materials.
Fibrous polymeric pulps of the present invention can be made by refining a floc of fibers made from the desired component polymeric materials; and the floc can be made by cutting fibers that have been spun from a blend of the component polymeric materials. The most usually used pulp for this invention is a pulp that is primarily para-aramid. The para-aramid can be spun from a solution of sulfuric acid; and any other component materials must, in that case, be soluble and stable in sulfuric acid.
By “para-aramid” is meant a polyamide wherein at least 85% of the amide (—CO—NH—) linkages are attached directly, at para-orientation, to two aromatic rings.
Additives can be used with the para-aramid and it has been found that up to as much as 10 percent, by weight, of other polymeric material can be blended with the para-aramid or that copolymers can be used having as much as 10 percent of other diamine substituted for the diamine of the para-aramid or as much as 10 percent of other diacid chloride substituted for the diacid chloride of the para-aramid. Poly (p-phenylene terephthalamide) (PPD-T) is the preferred para-aramid for practice of this invention. By PPD-T is meant the homopolymer resulting from mole-for-mole polymerization of p-phenylene diamine and terephthaloyl chloride and, also, copolymers resulting from incorporation of small amounts of other diamines with the p-phenylene diamine and of small amounts of other diacid chlorides with the terephthaloyl chloride. As a general rule, other diamines and other diacid chlorides can be used in amounts up to as much as about 10 mole percent of the p-phenylene diamine or the terephthaloyl chloride, or perhaps slightly higher, provided only that the other diamines and diacid chlorides have no reactive groups which interfere with the polymerization reaction. PPD-T, also, means copolymers resulting from incorporation of other aromatic diamines and other aromatic diacid chlorides such as, for example, 2,6-naphthaloyl chloride or chloro- or dichloroterephthaloyl chloride; provided, only that the other aromatic diamines and aromatic diacid chlorides be present in amounts which permit preparation of anisotropic spin dopes. Preparation of PPD-T is described in U.S. Pat. Nos. 3,869,429; 4,308,374; and 4,698,414.
Examples of polymeric materials that can be used in the pulp of this invention include: para-aramids and copolymers as set out above, cycloaliphatic polyamides and aliphatic polyamides such as nylon 6 and nylon 66, poly(vinyl pyrrolidone), meta-aramids such as poly(m-phenylene isophthalamide) and copolymers, and the like.
The pulp used in this invention is, as stated, of high surface area; and that high surface area is achieved during the process wherein floc of fibers of the combination of polymers is refined to make a pulp. The fibers and the resulting pulp must be made from at least two component polymeric materials and the component polymeric materials must be mutually immiscible so that the polymeric materials will be present in the fibers in closely-mixed but separate solid phases. The fibers of closely-mixed but separate solid phases, when refined to a pulp, yield pulp particles with domains of two distinct polymeric materials;—one phase being the continuous, primary, polymer phase, usually the para-aramid polymer, and the other phase being the discontinuous, secondary, polymer phase, usually the other polymer component in the combination.
The primary polymer is, as stated, a continuous polymer phase in the fibers and in the fibrous pulp after refining. In the make-up of the pulp compositions, the primary polymer represents 65 to 97 weight percent of the total composition. The secondary polymer represents 3 to 35 weight percent of the total composition, is present as a discontinuous polymer phase in the fibers, and is concentrated at the outer surfaces of the fibrous pulp after refining.
In the refining process, wherein floc is ground or beaten to break individual fibers into pulp particles, the discontinuous, secondary, polymer is present as small domains of material running through the fibers and serving, in the refining process, as points of disruption in the fiber structure to promote ready and more complete refining into pulp. After the refining, a portion of the discontinuous, secondary, polymer from each disruption point is present on or at the surface of each pulp particle that results from the refining process.
Pulp refined from floc that is made from a single polymeric material or from a miscible blend of polymeric materials that does not have the domains of discontinuous secondary polymer, will not have such a high surface area or, if refined enough to have such a high surface area, will have it because the pulp particles are smaller with a lower aspect ratio and are, therefore, not as useful.
One important quality of the two-component pulp used in this invention, is the surface area or specific surface area of the pulp. As stated elsewhere herein, floc of fibers made from the two-component blend of polymeric materials is readily refined into high surface area pulp by virtue of fracture points provided by the presence of domains of the discontinuous second polymer. High surface area is important because the surface area provides an indication of the extent of fibrillation of the floc fibers. A large surface area (and, therefore, a high degree o
Prior David White
Truby Michael R.
Dixon Merrick
E. I. Du Pont de Nemours and Company
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