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US 7,740,741 B2Granted
Para-aramid pulp including meta-aramid fibrids and processes of making same
AssigneeE.I. du Pont de Nemours and Company
InventorsMikhail R. Levit, Achim Amma
Life of this patent
Estimating the term…
Abstract
The present invention relates to para-aramid pulp including meta-aramid fibrids for use as reinforcement material in products including for example friction materials, fluid sealing materials, and papers. The invention further relates to processes for making such pulp.
Claims11
A process for making a para-aramid pulp including meta-aramid fibrids for use as reinforcement material, comprising:
- (a) combining pulp ingredients including:
- (1) never-dried meta-aramid fibrids having an average maximum dimension of 0.2 to 1 mm, a ratio of maximum to minimum dimension of 5:1 to 10:1, and a thickness of no more than 2 micrometers, and being a 10 to 90 weight percent of the total solids in the ingredients;
- (2) para-aramid fiber being 10 to 90 weight percent of the total solids in the ingredients, and having an average length of no more than 10 cm;
- and
- (3) water being 95 to 99 weight percent of the total ingredients;
- (b) mixing the ingredients to a substantially uniform slurry, wherein random samples of the slurry contain the same wt % of the concentration of each of the starting ingredients as in the total ingredients in the combination step plus or minus 10 wt %
- (c) co-refining the slurry by simultaneously:
- (1) shearing and/or masticating the meta-aramid fibrids into fibril-free refined meta-aramid fibrids having an average maximum dimension of 0.1 to 0.5 mm;
- (2) fibrillating, cutting and masticating the para-aramid fiber to irregularly shaped fibrillated fibrous structures;
- and
- (3) dispersing all solids such that the refined slurry is substantially uniform;
- and
- (d) removing water from the refined slurry,
- thereby producing a meta- and para-aramid pulp with the para-aramid fibrous structures contacting and wrapped partially around at least some of the refined meta-aramid fibrids.
11 more elements
A process for making a para-aramid pulp including meta-aramid fibrids for use as reinforcement material, comprising:
- (a) combining ingredients including water and a first material of the group:
- (1) never-dried meta-aramid fibrids having an average maximum dimension of 0.2 to 1 mm, a ratio of maximum to minimum dimension of 5:1 to 10:1, and a thickness of no more than 2 micrometers and being 10 to 90 weight percent of the total solids in the pulp;
- and
- (2) para-aramid fiber being 10 to 90 weight percent of the total solids in the pulps, and having an average length of no more than 10 cm;
- (b) mixing the ingredients to a substantially uniform suspension, wherein random samples of the slurry contain the same wt % of the concentration of each of the starting ingredients as in the total ingredients in the combination step plus or minus 10 wt %;
- (c) refining the mixed suspension by:
- (1) shearing and/or masticating at least some of the meta-aramid fibrids;
- or
- (2) fibrillating, cutting and masticating at least some of the para-aramid fiber to irregularly shaped fibrillated fibrous structures;
- (d) combining ingredients including the refined suspension, the second material of the group of (a) (1 and 2), and water, if necessary, to increase the water concentration to 95-99 weight percent of the total ingredients;
- (e) mixing the ingredients, if necessary, to form a substantially uniform slurry;
- (f) co-refining the slurry by simultaneously:
- (1) shearing and/or masticating at least some of any remaining never-dried meta-aramid fibrids having an average maximum dimension of 0.2 to 1 mm, an aspect ratio of 5:1 to 10:1, and a thickness of no more than 2 micrometers, such that all or substantially all of the never-dried meta-aramid fibrids are size-reduced into fibril free, meta-aramid refined fibrids having an average maximum dimension of 0.1 to 0.5 mm and
- (2) fibrillating, cutting and masticating at least some of the para-aramid fiber such that all or substantially all of the para-aramid fiber is converted to irregularly shaped fibrillated fibrous structures;
- and
- (3) dispersing all solids such that the refined slurry is substantially uniform;
- and
- (g) removing water from the refined slurry,
- thereby producing a meta- and para-aramid pulp with the para-aramid fibrous structures contacting and wrapped partially around at least some of the meta-aramid refined fibrids.
16 more elements
Dependencies are inferred from the claim text.