U.S. patent application number 17/074769 was filed with the patent office on 2021-02-04 for bleaching and shive reduction for non-wood fibers.
The applicant listed for this patent is GPCP IP HOLDINGS LLC. Invention is credited to Jeffrey A. Lee, Alan Edward Wright.
Application Number | 20210032801 17/074769 |
Document ID | / |
Family ID | 1000005177315 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210032801 |
Kind Code |
A1 |
Lee; Jeffrey A. ; et
al. |
February 4, 2021 |
BLEACHING AND SHIVE REDUCTION FOR NON-WOOD FIBERS
Abstract
The present invention is directed to a method of increasing the
brightness of non-wood fibers and nonwoven fabric fabrics produced
by the method. In one aspect, the method includes forming a mixture
of non-wood fibers and exposing the mixture to a brightening agent
to produce brightened fibers. The brightening agent is oxygen gas,
peracetic acid, a peroxide compound, or a combination thereof. The
brightened fibers have a brightness greater than the fibers of the
mixture before exposure as measured by MacBeth UV-C standard.
Inventors: |
Lee; Jeffrey A.; (Neenah,
WI) ; Wright; Alan Edward; (Roswell, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GPCP IP HOLDINGS LLC |
Atlanta |
GA |
US |
|
|
Family ID: |
1000005177315 |
Appl. No.: |
17/074769 |
Filed: |
October 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14716153 |
May 19, 2015 |
10844538 |
|
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17074769 |
|
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62000825 |
May 20, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D04H 3/015 20130101;
D04H 1/4266 20130101; D10B 2201/08 20130101; D10B 2201/06 20130101;
D10B 2201/04 20130101; D21C 9/163 20130101; D04H 1/425 20130101;
D06L 4/60 20170101; D10B 2201/02 20130101 |
International
Class: |
D06L 4/60 20060101
D06L004/60; D04H 1/425 20060101 D04H001/425; D04H 1/4266 20060101
D04H001/4266; D04H 3/015 20060101 D04H003/015 |
Claims
1. An article, comprising: brightened bast fibers with a mean
length of about 5 to about 95 millimeters (mm) and a brightness
greater than or equal to 80 as measured by a TAPPI standard;
wherein the article is a yarn, a thread, a rope, a cord, or a
sliver.
2. The article of claim 1, wherein the brightened bast fibers are
flax fibers, hemp fibers, jute fibers, ramie fibers, nettle fibers,
Spanish broom fibers, kenaf plant fibers, or any combination
thereof.
3. The article of claim 1, further comprising a lubricant, a
finish, an antistatic agent, or a combination thereof.
4. The article of claim 1, wherein the article further comprises
synthetic fibers, polymeric fibers, thermoplastic fibers, staple
fibers, regenerated cellulose fibers, cotton fibers, wood pulp
fibers, or a combination thereof.
5. A fabric, comprising: brightened bast fibers with a mean length
of about 5 to about 95 millimeters (mm) a brightness greater than
or equal to 80 as measured by a TAPPI standard; wherein the fabric
is a woven fabric or a knit fabric.
6. The fabric of claim 6, wherein the fabric comprises a yarn, a
thread, a rope, or a combination thereof.
7. The fabric of claim 6, wherein the brightened bast fibers are
flax fibers, hemp fibers, jute fibers, ramie fibers, nettle fibers,
Spanish broom fibers, kenaf plant fibers, or any combination
thereof.
8. The fabric of claim 6, wherein the fabric further comprises
synthetic fibers, polymeric fibers, thermoplastic fibers, staple
fibers, regenerated cellulose fibers, natural fibers, or a
combination thereof.
9. The fabric of claim 10, wherein the natural fibers are cotton
fibers.
10. The fabric of claim 10, wherein the polymeric fibers are
polyester fibers.
11. The fabric of claim 6, wherein the fabric is a wet wiper, a dry
wiper, an impregnated wiper, a sorbent, a clean room wiper, a
medical supply product, a personal protective fabric, an automotive
protective covering, a personal care article, a fluid filtration
product, a home furnishing product, a thermal insulation product,
an acoustic insulation product, an agricultural application
product, a landscaping application product, or a geotextile
application product.
12. The fabric of claim 6, wherein the fabric is a baby wipe, a
cosmetic wipe, a perinea wipe, a washcloth, a kitchen wipe, a bath
wipe, a hard surface wipe, a glass wipe, a mirror wipe, a leather
wipe, an electronics wipe, a lens wipe, a polishing wipe, a medical
cleaning wipe, a disinfecting wipe, an industrial wipe, a food
service wipe, a surgical drape, a surgical gown, a wound care
product, a protective coverall, a sleeve protector, a diaper, a
feminine care article, a nursing pad, an air filter, a water
filter, an oil filter, a furniture backing, or a mask.
13. An article, comprising: brightened bast fibers having a mean
length of about 5 to about 95 millimeters (mm) and a brightness
greater than or equal to 80 as measured by a TAPPI standard;
wherein the article is an article of clothing or a home
furnishing.
14. The article of claim 15, wherein the article of clothing is a
shirt, a blouse, a sweater, a sweatshirt, a top, pants, trousers, a
tank top, a leotard, a sport specific clothing, a sock, an
undergarment, a hat, a belt, a jacket, a coat, a vest, a glove, a
dress, a skirt, a scarf, a bib, an apron, footware, or a
combination thereof.
15. The article of claim 15, wherein the home furnishing is a
drapery, a sheet, a blanket, a throw, a comforter, a bedspread, a
washcloth, a towel, a wall covering, a chair covering, a sofa
covering, a furniture upholstery, a seat cover, a table cloth, a
cushion covering, a pillow covering, or a combination thereof.
16. The article of claim 15, wherein the brightened bast fibers are
flax fibers, hemp fibers, jute fibers, ramie fibers, nettle fibers,
Spanish broom fibers, kenaf plant fibers, or any combination
thereof.
17. The article of claim 15, wherein the article further comprises
synthetic fibers, polymeric fibers, thermoplastic fibers, staple
fibers, regenerated cellulose fibers, natural fibers, or a
combination thereof.
18. The fabric of claim 20, wherein the natural fibers are cotton
fibers.
19. The fabric of claim 20, wherein the polymeric fibers are
polyester fibers.
20. A composite material comprising: brightened bast fibers having
a mean length of about 5 to about 95 millimeters (mm) and a
brightness greater than or equal to 80 as measured by TAPPI
standard; and a matrix material.
21. The composite material of claim 20, wherein the matrix material
comprises a thermoplastic material or a thermoset material.
22. The composite material of claim 21, wherein the thermoplastic
material is polypropylene, polyethylene, polystyrene, polyvinyl
chloride, poly(hydridocarbyne), polyhydroxybutyrate, or a
combination thereof.
23. The composite material of claim 21, wherein the thermoset
material is an epoxy resin, a phenolic resin, a polyurethane, a
polyester, a vinyl resin, an acrylate resin, or a combination
thereof.
24. The composite material of claim 20, wherein the brightened bast
fibers are randomly or substantially uniformly distributed
throughout the matrix material.
25. The composite material of claim 20, wherein the brightened bast
fibers are in the form of a nonwoven fabric or a woven fabric.
26. The composite material of claim 20, wherein the composite
material is an automobile part, an aviation part, a marine part, a
home furnishing, a building panel, or a combination thereof.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 14/716,153, filed May 19, 2015, which claims
benefit of U.S. Provisional Patent Application Ser. No. 62/000,825,
filed May 20, 2014, both of which are incorporated herein in their
entirety by reference.
TECHNICAL FIELD
[0002] The instant invention generally is related to methods for
fiber production. More specifically, the instant invention is
related to methods for non-wood fiber bleaching and shive
reduction.
BACKGROUND OF THE INVENTION
[0003] Plant fibers fall into three groups: seed fibers (e.g.,
cotton and kapok), stem fibers (bast fibers, e.g., flax and hemp),
and leaf fibers (e.g., sisal). Bast fibers occur as bundles of
fibers, which extend through the length of the plant stems, located
between the outer epidermal "skin" layers and the inner woody core
(cortex) of the plant. Therefore, bast fiber straw includes three
primary concentric layers: a bark-like skin covering layer, a bast
fiber layer, and an inner, woody core. The woody core has various
names, which depends on the particular plant type. For example, the
flax woody core is referred to as "shive." Thus, "shive" refers to
all woody-core materials contained in bast fiber plants.
[0004] The bundles of fibers are embedded in a matrix of pectins,
hemi-celluloses, and some lignin. The lignin must be degraded, for
example by "retting" (partial rotting) of the straw, for example by
enzymes produced by fungi (e.g., during dew-retting), or bacteria
(e.g., during water-retting). Decortication involves mechanically
bending and breaking the straw to separate the fiber bundles from
the shive and skin layers, and then removing the non-fiber
materials using a series of conventional mechanical cleaning
stages.
[0005] A substantial proportion of the pectin-containing material
that surrounds the individual bast fibers is pectin, with the
remaining portion being primarily various water-soluble
constituents. Pectin is a carbohydrate polymer, which includes
partially-methylated poly-galacturonic acid with free carboxylic
acid groups present as calcium salts. Pectin is generally insoluble
in water or acid, but may be broken down, or hydrolyzed, in an
alkaline solution, such as an aqueous solution of sodium
hydroxide.
[0006] Removal of the pectin-containing material, or gum, is
necessary in many instances to utilize the fiber for its intended
purposes. Various methods for pectin removal include degumming, or
removing, the pectin-containing substances from the individual bast
fiber. For example, U.S. Pat. No. 2,407,227 discloses a retting
process for the treatment of fibrous vegetable or plant material,
such as flax, ramie, and hemp. The retting process employs
micro-organisms and moisture to dissolve or rot away much of the
cellular tissues and pectins surrounding fiber bundles,
facilitating separation of the fiber bundles from the shive and
other non-fiber portions of the stem. Thus, the waxy, resinous, or
gummy binding substances present in the plant structure are removed
or broken down by means of fermentation.
[0007] Following retting, the stalks are broken, and then a series
of chemical and mechanical steps are performed to produce
individual or small bundles of cellulose fiber. However, a common
problem still occurring in non-wood fiber processes is the
occurrence of shives, which are undesirable particles in finished
paper products. Shives includes pieces of stems, "straw," dermal
tissue, epidermal tissue, and the like.
[0008] Shives are substantially resistant to defiberizing
processes, rendering their presence problematic. Even following
oxidative bleaching, shives continue to have deleterious effects on
the appearance, surface smoothness, ink receptivity, and brightness
of a finished paper product. Mechanical removal of shive to the
level required for a high value product involves the application of
significant mechanical energy, which results in fiber breakage and
generation of fines, or small cellulose particles. The fines are a
yield loss, increasing the production cost. Further, the broken
fibers reduce the overall fiber strength so they either cannot be
used in some manufacturing processes and/or result in weak textile
or paper products.
[0009] Thus, conventional methods of non-wood fiber processing are
not sufficiently robust to remove, decolorize, and break up the
residual shive present in the fibers. Thus, processed and finished
fibers can still include dark particles of shive, which are both
aesthetically unattractive and reduce the commercial value of the
fiber product. Furthermore, conventional bleaching processes are
not sufficiently robust to increase paper brightness to sufficient
levels required for commercial products.
[0010] Accordingly, there exists an on-going need for a method to
both adequately bleach and sufficiently reduce shive presence in
non-wood fibers, including plant-based fibers. Thus, the present
invention is directed to meeting this and other needs and solving
the problems described above.
SUMMARY OF THE INVENTION
[0011] The present invention is directed to methods of increasing
the brightness of non-wood fibers and nonwoven fabrics, tissues,
papers, textiles, and products produced by the methods. In one
aspect, the method comprises forming a mixture of non-wood fibers
and exposing the mixture to a brightening agent to produce
brightened fibers. The brightening agent is oxygen gas, peracetic
acid, a peroxide compound, or a combination thereof, to produce
brightened fibers. Such brightened fibers have a brightness greater
than the fibers of the mixture before exposure to the brightening
agent as measured by MacBeth UV-C standard.
[0012] In another aspect, a method of reducing the amount of
residual shive in non-wood fibers comprises forming a mixture of
non-wood fibers and exposing the mixture to a brightening agent to
produce low-shive fibers. The brightening agent is oxygen gas,
peracetic acid, a peroxide compound, or a combination thereof. Such
low-shive fibers have less visible shive content than the fibers of
the mixture before exposure to the brightening agent. Yet, in
another aspect, a nonwoven fabric made in accordance with this
method comprises brightened, non-wood fibers having a brightness
greater than about 65 as measured by MacBeth UV-C standard.
Nonwoven fabrics include air-laid, carded, spunbond, and
hydroentangled substrates.
[0013] It is to be understood that the phraseology and terminology
employed herein are for the purpose of description and should not
be regarded as limiting. As such, those skilled in the art will
appreciate that the conception, upon which this disclosure is
based, may readily be utilized as a basis for the designing of
other structures, methods, and systems for carrying out the present
invention. It is important, therefore, that the claims be regarded
as including such equivalent constructions insofar as they do not
depart from the spirit and scope of the present invention.
[0014] Other advantages and capabilities of the invention will
become apparent from the following description taken in conjunction
with the examples showing aspects of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention will be better understood and the above object
as well as other objects other than those set forth above will
become apparent when consideration is given to the following
detailed description thereof. Such description makes reference to
the annexed drawing wherein:
[0016] FIG. 1 is an illustration of a method for introducing oxygen
gas into a bleaching liquor using within a circulation pump to
dissolve the oxygen.
[0017] FIG. 2 is an illustration of a method for introducing oxygen
gas into a mixer after the circulation pump.
[0018] FIG. 3 is an illustration of a method for introducing oxygen
gas directly into the non-wood fibers.
[0019] FIG. 4 is an illustration of a method for exposing the
non-wood fibers to oxygen gas using an internal and external liquor
circulation system.
[0020] FIG. 5 is an illustration of a method for cooling the liquor
in the system of FIG. 4.
[0021] FIG. 6 is an illustration of a method for using gas to
displace the residual liquor from the fibers in the system of FIG.
4.
[0022] FIG. 7 is an illustration of another method for using gas to
displace the residual liquor from the fibers in the system of FIG.
4.
[0023] FIG. 8 is an illustration of a control system for oxygen
brightening of non-wood fibers.
[0024] FIG. 9 is a photomicrograph of control flax fibers which
were chemically treated to remove pectin and hydrogen peroxide
bleached.
[0025] FIG. 10 is a photomicrograph of the flax fibers of FIG. 9
after brightening using a quantum mixer and a peroxide bleaching
composition.
[0026] FIG. 11 is a photomicrograph of the flax fibers of FIG. 9
after bleaching using a quantum mixer and dissolved oxygen.
[0027] FIG. 12 is a photomicrograph of control flax fibers which
were only chemically treated to remove pectin.
[0028] FIG. 13 is a photomicrograph of the flax fibers of FIG. 12
after bleaching using a quantum mixer and dissolved oxygen.
DETAILED DESCRIPTION OF THE INVENTION
[0029] For a fuller understanding of the nature and desired objects
of this invention, reference should be made to the above and
following detailed description taken in connection with the
accompanying figures. When reference is made to the figures, like
reference numerals designate corresponding parts throughout the
several figures.
[0030] The following definitions and abbreviations are to be used
for the interpretation of the claims and the specification. As used
herein, the terms "comprises," "comprising," "includes,"
"including," "has," "having," "contains" or "containing," or any
other variation thereof, are intended to cover a non-exclusive
inclusion. For example, a composition, a mixture, process, method,
article, or apparatus that comprises a list of elements is not
necessarily limited to only those elements but can include other
elements not expressly listed or inherent to such composition,
mixture, process, method, article, or apparatus.
[0031] As used herein, the articles "a" and "an" preceding an
element or component are intended to be nonrestrictive regarding
the number of instances (i.e. occurrences) of the element or
component. Therefore, "a" or "an" should be read to include one or
at least one, and the singular word form of the element or
component also includes the plural unless the number is obviously
meant to be singular.
[0032] As used herein, the terms "invention" or "present invention"
are non-limiting terms and not intended to refer to any single
aspect of the particular invention but encompass all possible
aspects as described in the specification and the claims.
[0033] As used herein, the term "about" modifying the quantity of
an ingredient, component, or reactant of the invention employed
refers to variation in the numerical quantity that can occur, for
example, through typical measuring and liquid handling procedures
used for making concentrates or solutions in the real world.
Furthermore, variation can occur from inadvertent error in
measuring procedures, differences in the manufacture, source, or
purity of the ingredients employed to make the compositions or
carry out the methods, and the like. Whether or not modified by the
term "about," the claims include equivalents to the quantities. In
one aspect, the term "about" means within 10% of the reported
numerical value. In another aspect, "about" means within 5% of the
reported numerical value.
[0034] As used herein, the terms "percent by weight," "% by
weight," and "wt. %" mean the weight of a pure substance divided by
the total dry weight of a compound or composition, multiplied by
100. Typically, "weight" is measured in grams (g). For example, a
composition with a total weight of 100 grams, which includes 25
grams of substance A, will include substance A in 25% by
weight.
[0035] As used herein, the terms "nonwoven" means a web or fabric
having a structure of individual fibers which are randomly
interlaid, but not in an identifiable manner as is the case of a
knitted or woven fabric. The brightened fibers in accordance with
the present invention can be employed to prepare nonwoven
structures and textiles.
[0036] As used herein, the term "non-wood fibers" means fibers
produced by and extracted from a plant or animal, the exception
that such fibers do not include wood fibers, i.e., derived from a
tree, and man-made fibers formed from cellulose, e.g. viscose.
Non-limiting examples of suitable non-wood fibers are plant-based,
non-wood fibers, such as bast fibers. Bast fibers include, but are
not limited to, flax fibers, hemp fibers, jute fibers, ramie
fibers, nettle fibers, Spanish broom fibers, kenaf plant fibers, or
any combination thereof. Non-wood fibers include seed hair fibers,
for example, cotton fibers. Non-wood fibers can also include animal
fibers, for example, wool, goat hair, human hair, and the like.
[0037] As used herein, the term "kier" means a circular boiler or
vat used in processing, bleaching and/or scouring non-wood
fibers.
[0038] As used herein, the term "brightening agent" refers to
oxygen gas, peracetic acid, a peroxide compound, or a combination
thereof. In addition to oxygen gas, peracetic acid, and a peroxide
compound, other compounds and agents can be included in the
brightening agent. Non-limiting examples of additional compounds
include reducing agents and magnesium sulfate. The brightening
agent can further include other gases, for example nitrogen or
carbon dioxide. The oxygen gas can be present as a mixture with
other gases. In one example, the oxygen gas is present in the
brightening agent about or in any range between about 75, 80, 85,
90, 95, and 100%.
[0039] As used herein, the term "brightness" refers to the
whiteness of a composition of fibers. As discussed herein,
brightness is determined by the "MacBeth UV-C" test method,
utilizing a Macbeth 3100 spectrophotometer, commercially available
from X-Rite, Inc., Grand Rapids, Mich. UV-C is the illuminant
(lamp) used for brightness testing. As used herein, the term "gain"
means the increase in fiber brightness following a bleaching
process. Brightness and gain measurements of the fibers, before and
after exposure to the brightening agent, are conducted on thick
pads of the fiber. The fiber pads are prepared by diluting the
fibers to a consistency in a range between about 2% and about 10%
with water, mixing to separate the fibers, and then de-watering the
fibers, for example on a Buchner funnel with a filter paper, to
form the fiber pad. The fiber pad can be further dewatered by
pressing between blotters in a laboratory press and then dried on a
speed dryer to form a dry cake. The fiber pads can then be
air-dried for several days prior to brightness testing. Brightness
measurements also can be done on the fiber by: 1) drying the fiber
with hot air to less than 2-4% moisture, 2) carding the fiber to
straighten out and align the fibers into a mat, lap or sliver, and
3) measuring the brightness of the lap, mat or sliver. Brightness
and gain testing of the fibers according to the MacBeth UV-C
brightness standard is conducted before and after exposure to the
brightening agent, with the brightened fibers having a brightness
greater than the fibers before exposure. The MacBeth test measures
both TAPPI brightness and LAB whiteness. L* is the whiteness, and
a* and b* are the color (red-green and blue-yellow). A* and b*
values close to 0 indicate very low color/no color. The UV-C test
measures the illuminate, including the both the ultraviolet and
color components of the light.
[0040] As used herein, the term "consistency" means to the percent
(%) solid in a composition comprising a solid in a liquid carrier.
For example, the consistency of a fiber slurry/fiber mat/fiber
mass/fiber donut weighing 100 grams and comprising 50 grams of
fibers has a consistency of 50%.
[0041] As used herein, the terms "cellulose fibers," "cellulosic
fibers," and the like refer to any fibers comprising cellulose.
Cellulose fibers include secondary or recycled fibers, regenerated
fibers, or any combination thereof.
[0042] Conventional plant-based, non-wood fiber production involves
mechanical removal of non-fiber shive material, followed by
chemical removal of pectin and a mild oxidative bleaching step.
Plants, including flax, require an initial "retting" step before
mechanical removal of non-fiber material. The retting process
employs micro-organisms and moisture to dissolve or rot away much
of the cellular tissues and pectins surrounding fiber bundles, thus
facilitating separation of the fiber from the stem. Thus, waxy,
resinous, or gummy binding substances present in the plant
structure are removed or broken down by means of fermentation.
Pectin removal can be accomplished using an alkaline agent, such as
sodium hydroxide, at elevated temperatures. Enzymes and other
chemicals, such as detergents and wetting agents, also can be added
to enhance pectin detachment from the fibers. U.S. Pat. Nos.
8,603,802 and 8,591,701 and Canadian Patent No. CA 2,745,606
disclose methods for pectin removal using enzymes. Following the
pectin extraction step, the fibers are washed and treated with a
mixture of hydrogen peroxide and sodium hydroxide to increase the
brightness and whiteness of the finished fiber.
[0043] However, there are drawbacks to these conventional methods.
First, available pectin extraction and bleaching steps are not
robust enough to decolorize and/or break up residual shive in the
fiber. Second, the bleaching process also is not robust enough to
increase the brightness to levels required for high quality
commercial products. The result is finished fibers containing dark
shive particles, which is aesthetically unappealing and reduces the
commercial value of the fiber product. The shive also interferes
with the manufacturing processes which utilize the fiber. For
example, particles of shive can plug the filters on a
hydroentanglement system. The shive also has very low bonding
ability. Thus, any shive entrained in the finished product will
fall out and be unappealing to the end user. Further, residual
shive could also be a potential source of contamination when used,
for example, in food service wipes.
[0044] One commercially available solution to the shive problem is
to either increase the intensity of the mechanical shive removal
process or to add multiple mechanical removal stages so that the
residual shive content is low enough to be imperceptible in the
finished product. However, this solution has drawbacks. First,
additional mechanical processing increases the operating and
capital costs of production. Second, the additional mechanical
processing damages the fragile fibers, resulting in a product with
inferior tensile strength properties. Finally, additional
mechanical processing reduces the yield of the finished fiber
because of the generation of fines and long fiber losses due to the
inherent inefficiency of mechanical processing.
[0045] It was discovered that the addition of oxygen gas and/or
peracetic acid to the bleaching process both increases the fiber
brightness and reduces the residual shive to levels that
dramatically reduce the impact of shive on the appearance of the
finished fiber. Furthermore, and without being bound by theory, it
is believed that the brightening process disclosed herein reduces
the integrity of the shives so that they are more easily broken up
and removed in mechanical treatment. Reduced shive content after
exposure to the brightening agent can be assessed by visual
examination of the fibers.
[0046] Accordingly, the present disclosure is directed to a method
of increasing the brightness of natural fibers, in particular,
non-wood fibers. In one aspect of the present invention, the method
comprises forming a mixture of non-wood fibers and exposing the
mixture to a brightening agent to produce brightened fibers having
a brightness greater than the fibers of the mixture before exposure
as measured by MacBeth UV-C standard. The brightening agent
comprises oxygen gas, peracetic acid, a peroxide compound, or a
combination thereof. In another aspect, the present disclosure is
directed to a method of reducing the amount of residual shive in
non-wood fibers to provide low-shive fibers having less visible
shive content than the fibers of the mixture before exposure.
[0047] One category of non-wood fibers is bast fibers. Bast fibers
are found in the stalks of the flax, hemp, jute, ramie, nettle,
Spanish broom, and kenaf plants, to name only a few. Typically,
native state bast fibers are 1 to 4 meters in length. These long
native state fibers are comprised of bundles of straight individual
fibers that have lengths between 20-100 millimeters (mm). The
bundled individual fibers are glued together by pectins.
[0048] Bast fibers bundles can be used for both woven textiles and
cordage. An example of a woven textile produced with flax bast
fiber bundles is linen. More recently, as provided in U.S. Pat. No.
7,481,843, which is incorporated herein in its entirety by
reference, partially separated bast fiber is produced to form yarns
and threads for woven textiles. However, yarns and threads are not
suited for nonwoven fabrics.
[0049] In accordance with the present invention, any non-wood
fibers can be used. In one example, suitable fibers include cotton
fibers, bast fibers, or any combination thereof. Bast fibers can be
derived from a variety of raw materials. Non-limiting examples of
suitable bast fibers include, but are not limited to, flax fibers,
hemp fibers, jute fibers, ramie fibers, nettle fibers, Spanish
broom fibers, kenaf plant fibers, or any combination thereof.
Non-wood fibers can also include animal fibers, for example, wool,
goat hair, human hair, and the like.
[0050] Initially, pectin can be substantially removed from the
non-wood, plant-based fibers to form substantially individualized
fibers. Thus, the fibers are rendered substantially straight and
are substantially pectin-free. The fibers can be individualized, by
pectin removal, using mechanical or chemical means.
[0051] Enzymatic treatment is a non-limiting example of a chemical
treatment that can be used to substantially remove pectin. PCT
International Publication No. WO 2007/140578, which is incorporated
herein in its entirety by reference, describes a pectin removal
technology which produces individualized hemp and flax fiber for
application in the woven textile industry. The process to remove
pectin described in WO 2007/140578 can be employed.
[0052] The non-wood, plant-based fibers can have a mean length in a
range between about 1 and 100 mm depending on the characteristics
of the particular fibers and the cut length of the plant stalks
prior to chemical processing. In one aspect, the individualized
non-wood, plant-based fibers have a mean length of at least 10 mm,
at least 20 mm, at least 30 mm, and at least 40 mm. In another
aspect, the individualized non-wood, plant-based fibers have a mean
length greater than 50 mm. Still yet, in another aspect, the
non-wood, plant based fibers have a mean length about or in a range
between about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,
70, 75, 80, 85, 90, and 95 mm.
[0053] In addition to non-wood, plant-based fibers, the fiber
mixture can include fibers derived from one or more source,
including, but not limited to, cellulosic fibers, including staple
fibers, regenerated cellulose fibers, and thermoplastic fibers.
Optionally, the cellulosic fibers are secondary, recycled fibers.
Non-limiting examples of cellulosic fibers include, but are not
limited to, hardwood fibers, such as hardwood kraft fibers or
hardwood sulfite fibers; softwood fibers, such as softwood kraft
fibers or softwood sulfite fibers; or any combination thereof.
Non-limiting examples of regenerated cellulose include RAYON.RTM.,
lyocell, (e.g., TENCEL.RTM.), viscose, or any combination thereof.
TENCEL.RTM. and RAYON.RTM. are commercially available from Lenzing
Aktiengesellschaft, Lenzing, Austria.
[0054] In one aspect, the mixture of non-wood fibers includes
synthetic, polymeric, thermoplastic fibers, or any combination
thereof. Thermoplastic fibers include the conventional polymeric
fibers utilized in the nonwoven industry. Such fibers are formed
from polymers which include, but are not limited to, a polyester
such as polyethylene terephthalate; a nylon; a polyamide; a
polypropylene; a polyolefin such as polypropylene or polyethylene;
a blend of two or more of a polyester, a nylon, a polyamide, or a
polyolefin; a bi-component composite of any two of a polyester, a
nylon, a polyamide, or a polyolefin; and the like. An example of a
bi-component composite fiber includes, but is not limited to, a
fiber having a core of one polymer and a sheath comprising a
polymer different from the core polymer which completely,
substantially, or partially encloses the core.
[0055] Brightness measurements of the fibers, before and after
exposure to the brightening agent, can be conducted on thick pads
of the fiber. Brightness testing of the fibers according to the
MacBeth UV-C brightness standard, which measures TAPPI brightness,
is conducted before and after exposure to the brightening agent,
with the brightened fibers having a brightness greater than the
fibers before exposure. The brightened fibers of the present
invention can have a brightness in a range between about 65 and
about 90 as measured by MacBeth UV-C (TAPPI) standard. In one
aspect, the brightened fibers have a brightness in a range between
about 77 and about 90. In another aspect, the brightened fibers
have a brightness in a range between about 80 and about 95. Yet, in
another aspect, the brightened fibers have a brightness in a range
between about 65 and about 85. In some aspects, after oxygen
brightening and subsequent bleaching processes (e.g., one, two,
three or more), the brightened fibers have a brightness of at least
65, at least 66, at least 67, at least 68, at least 69, at least
70, at least 71, at least 72, at least 73, at least 74, at least
75, at least 76, at least 77, at least 78, at least 79, at least
80, at least 81, at least 82, at least 83, at least 84, at least
85, at least 86, at least 87, at least 88, at least 89, or at least
90. Still other aspects, the brightened fibers have a brightness
about or in any range between about 65, 66, 67, 67, 69, 70, 71, 72,
73, 74, 75, 76, 77, 78 ,79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89,
and 90 as measured by the MacBeth UV-C (TAPPI) standard.
[0056] The brightness gain, or increase in fiber brightness
following exposure to the brightening agent is in a range between
about 10 and about 60 as measured by MacBeth UV-C (TAPPI) standard.
In one aspect, the brightness gain is in a range between about 15
and about 30 as measured by MacBeth UV-C standard. In another
aspect, the brightness gain is in a range between about 45 and
about 55 as measured by MacBeth UV-C standard. Yet, in another
aspect, the brightness gain is about or in any range between about
10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 as measured by
MacBeth UV-C standard.
[0057] The brightened fibers of the present invention can be used
for any nonwoven fabric products or textiles, including air-laid,
carded, spunbonded, and hydroentangled substrates. In one aspect, a
nonwoven fabric comprises non-wood fibers having a brightness
greater than about 65 as measured by MacBeth UV-C (TAPPI) standard.
In another aspect, the nonwoven fabric includes bast fibers with a
brightness of at least 80 as measured by MacBeth UV-C (TAPPI)
standard.
[0058] Nonwood fiber brightening can be accomplished by 1) retting,
mechanical separation of bast fibers, scouring to remove
pectin+waxes+lignin, and one or two stage brightening as disclosed
herein; or 2) retting, mechanical separation of bast fibers,
scouring to remove pectin+waxes+lignin, conventional peroxide or
other bleaching/pre-bleaching, and one or two stage bleaching with
the disclosed process.
[0059] Then, the non-wood fibers (pre-bleached or unbleached) are
combined to form a mixture. Pectin removal by chemical methods can
be performed before or after forming the mixture. The mixture can
be formed into a fibrous mat, a fiber mat, a fiber pad, a thick
fiber pad, a wet cake, or a "donut" when used in a kier based
system. Optionally, the mixture can then be wetted before exposing
the mixture to the brightening agent. The mixture can be diluted to
any desired consistency, wetted, and/or combined with any desired
additives, non-limiting examples of which are mentioned below.
[0060] In the mixture before exposure to the brightening agent, the
fibers have a consistency in a range between about 1% and about
50%. In one aspect, the fibers in the mixture have a consistency in
a range between about 10% and about 30%. In another aspect, the
fibers in the mixture have a consistency in a range between about
15% and about 35%. Yet in another aspect, the fibers in the mixture
have a consistency in a range between about 20% and about 40%.
Still yet, in another aspect, the fibers in the mixture have a
consistency about or in any range between about 1, 2, 5, 7, 10, 12,
15, 17, 20, 22, 25, 27, 30, 32, 35, 37, 40, 42, 45, 47 and 50%.
[0061] To increase the brightness of the fibers, the mixture is
then exposed to a brightening agent, the brightening agent being
oxygen gas, peracetic acid, a peroxide compound, or a combination
thereof. Non-limiting exemplary methods for exposing the mixture to
the brightening agent are shown in FIGS. 1-8 (discussed in detail
below). However, the fiber mixture can be exposed to the
brightening agent by any suitable method. Pectin can be removed
from the fibers before exposure to the oxygen gas, peracetic acid,
and/or a peroxide compound.
[0062] Peracetic acid (CH.sub.3CO.sub.3H) can be produced by
autoxidizing acetaldehyde in the air. Alternatively, peracetic acid
can be produced by reacting acetic acid with hydrogen peroxide or
acetyl chloride with acetic anhydride. In addition, tetra acetyl
ethylene diamine (TAED) can be added to an alkaline hydrogen
peroxide solution to form peracetic acid. The resulting peracetic
acid provides an increased brightening effect compared to the
alkaline hydrogen peroxide alone.
[0063] TAED can be added to the brightening agent or the fibers to
increase the effective brightening on the fibers. In one aspect,
the brightening agent further comprises a peroxide compound and an
alkaline compound. In another aspect, the peroxide compound is
hydrogen peroxide and the alkaline compound is sodium hydroxide or
potassium hydroxide. Addition of the TAED produces peracetic acid.
Optionally, the fibers can be exposed to the peracetic acid before,
after, or during exposure to oxygen gas, as described in detail
below. As both peracetic acid and oxygen gas increase the
brightness of the fibers, they can be used alone or in combination.
The peracetic acid can be generated in situ with the fiber or can
be generated by pre-mixing the various chemicals and then added to
the fiber mixture. A peroxide compound, for example hydrogen
peroxide or another alkaline compound, can be present when either
oxygen gas or TAED is present in the brightening agent.
[0064] When TAED is used, it can be added in an amount in a range
between about 0.1 and about 1 wt. % based on the dry weight of the
fibers. In one aspect, the TAED is added in an amount in a range
between about 0.5 and about 5 wt. % based on the dry weight of the
fibers. In another aspect, the TAED is added in an amount in a
range between about 0.3 and about 3 wt. % based on the dry weight
of the fibers. Yet, in another aspect, the TAED is added in an
amount about or in any range between about 0.1, 0.2, 0.3, 0.5, 0.7,
1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 7.0,
8.0, 9.0, and 10.0 based on the dry weight of the fibers.
[0065] The peroxide compound of the brightening agent can be
hydrogen peroxide, sodium peroxide, or both hydrogen peroxide and
sodium peroxide. The brightening agent can include other additional
bleaching components, for example other peroxide compounds and an
alkaline compound. Non-limiting examples of suitable peroxide
compounds include hydrogen peroxide, sodium peroxide, or both
hydrogen peroxide and sodium peroxide. Suitable alkaline compounds
include, but are not limited to, sodium hydroxide, potassium
hydroxide, calcium hydroxide, monoethanolamine, ammonia, or any
combination thereof. After exposing the fibers to the brightening
agent, the fibers can be mixed or agitated. However, excessive
mixing can induce fiber tangling.
[0066] The brightening agent pH can be adjusted to an initial pH in
a range between about 9 and about 12. In one aspect, the initial pH
is in a range between about 10 and about 10.5. In another aspect,
the initial pH is in a range between about 9.5 and about 10.5. Yet
in another aspect, the initial pH is in a range about or in any
range between about 8, 8.5, 9, 9.5, 10, 10.5, and 11. Additional pH
buffering agents can be included to adjust the mixture to the
desired pH. Sodium hydroxide and/or magnesium hydroxide can be
used.
[0067] Turning now to the figures, FIG. 1 illustrates an exemplary
method 100 of exposing the fiber mixture to the brightening agent,
which includes oxygen gas alone, or in combination with peracetic
acid. Peracetic acid can be added or generated in situ in the
bleaching liquor 140 as described above. The non-wood fibers can be
disposed within a fiber processing Kier 120. The bleaching liquor
140, which can include additional components such as the peroxide
compound, peracetic acid, TAED, or the alkaline compound, can be
introduced and circulated through the system and the fibers with a
liquor circulation pump 130. The oxygen gas 110 is injected into
the bleaching liquor circulation pump 130, which acts to mix and
dissolve the oxygen gas 110 into the bleaching liquor 140. The
oxygen gas 110 can be injected until the desired system pressure or
partial oxygen pressure is achieved, or until the oxygen is
dissolved in the solution, forming a dissolved oxygen solution.
Alternatively, a low, continuous flow of oxygen gas 110 can be
maintained throughout the process.
[0068] FIG. 2 illustrates an exemplary method 200 of exposing the
fiber mixture to the brightening agent. As shown, the oxygen gas
110 can be introduced into a static or active mixing system 210
after the liquor circulation pump 130.
[0069] FIG. 3 illustrates an exemplary method 300 of exposing the
fiber mixture to the brightening agent. As shown, oxygen gas 110 is
directly introduced into top of the fiber processing Kier 120. As
such, the oxygen gas 110 permeates the fibers, which can be in the
form of a "fiber mat," to react with the chromophores and shive,
reducing the content of shive.
[0070] FIG. 4 illustrates an exemplary method 400 of exposing the
fiber mixture to the brightening agent. Method 400 has an
additional internal circulation system 410 in addition to the
external liquor circulation systems of methods 100, 200, and 300
using the liquor circulation pump 130. Oxygen gas 110 is injected
into the liquor feed line 420 after the liquor circulation pump 130
which goes directly into the intake of the internal pump 412. The
entrained oxygen gas 110 enters the impeller 414, which mixes and
dissolves the oxygen gas 110 in the bleaching liquor 140. The
bleaching liquor 140, along with the dissolved oxygen gas 110 then
enters the center shaft 416 of the basket and then travels and
circulates through the fiber mass within the fiber processing Kier
120.
[0071] FIG. 5 is an illustration of a method 500 for cooling the
liquor in the method 400 shown in FIG. 4. In method 500, employing
a cooling system 510, the bleaching liquor 140 from inside the
fiber processing Kier 120 is cooled below the flash temperature,
for example, less than about 100.degree. C., in a noncontact heat
exchanger 514 and then into a small liquor tank 516. A control
valve 512 controls the recirculation of the system and also holds
the pressure in the system. The cooled liquor 520 is then is pumped
back into the liquor circulation pump 130 of the external
circulation system. The cooling system 510 allows for addition of
chemicals without depressurizing and emptying the fiber processing
kier 120.
[0072] FIG. 6 is an illustration of a method 600 for using oxygen
gas to displace the residual liquor from the fibers in the method
400 shown in FIG. 4. In method 600, the bleaching liquor 140 is
drained from the fiber processing Kier 120 by using a drain valve
610. Then, oxygen gas 110 is injected directly into the center
shaft 416 of the basket and diffuses through the fibers in the
fiber processing Kier 130.
[0073] FIG. 7 is an illustration of another method 700 for using
oxygen gas 110 to displace the residual liquor from the fibers in
the method 400 shown in FIG. 4. In method 700, the bleaching liquor
140 is also drained from the fiber processing Kier 120 using a
drain valve 610. The fiber processing Kier 120 has an oxygen gas
connection with a check valve 710 at the top of the fiber
processing Kier 120, at the bottom of the fiber processing Kier
(not shown), or on the liquor circulation pump 130 (not shown).
Thus, oxygen gas can be injected, and vented, into the system using
check valve 710.
[0074] FIG. 8 is an illustration of a control system 800 for
brightening of non-wood fibers in any kier system. The control
system 800 has an oxygen tank or other oxygen source for injecting
oxygen gas 110. A pressure control device 810 controls the pressure
of oxygen gas 110 from the primary source. An oxygen flow control
device 820 then controls the flow of oxygen into the system. A
liquor flow control device 840 after the liquor circulation pump
130 controls the flow of bleaching liquor 140 into the system. A
pressure relief safety valve 830 limits the maximum safe pressure
within the fiber processing Kier 120. A Kier pressure control 850
also moderates the pressure within the fiber processing Kier
120.
[0075] In another aspect, the fiber mixture can be disposed within
any closed system, including a fiber processing Kier. The fiber
mixture is saturated with an alkaline peroxide bleaching liquor,
e.g., hydrogen peroxide and sodium hydroxide, and then the system
is drained and pressurized with oxygen. As a result, the oxygen
permeates the fiber mixture, or "fiber mat," to enhance the action
of the peroxide liquor. Thus, the brightness of the fibers is
increased compared to the fibers before exposure.
[0076] During oxygen gas exposure, the system can be maintained at
a temperature in a range between about 50 and about 150.degree. C.
In another aspect, the system can be maintained at a temperature in
a range between about 70 and about 140.degree. C. during oxygen
exposure. Yet, in another aspect, the system can be maintained at a
temperature in a range between about 70 and about 130.degree. C.
during oxygen exposure. Still yet, in another aspect, the system
can be maintained at a temperature about or in any range between
about 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115,
120, 125, 130, 135, 140, 145, and 150.degree. C.
[0077] The fibers can be exposed to the peracetic acid during or
after exposure to the oxygen gas by addition of peracetic acid or
by adding TAED to hydrogen peroxide to form peracetic acid. In one
aspect, the TAED is added at the end of the oxygen exposure stage,
for example after exposing the fibers to oxygen for about 30
minutes to about 60 minutes. In another aspect, the fibers are
exposed to TAED or peracetic acid after exposing the fibers to
oxygen for about 20 minutes to about 45 minutes. Yet, in another
aspect, the fibers are exposed to TAED or peracetic acid after
exposing the fibers to oxygen for about 40 minutes to about 60
minutes.
[0078] Optionally, TAED or peracetic acid can be added to the
fibers at temperatures lower than the oxygen exposure. For example,
the temperature of TAED or peracetic acid addition can be in a
range between about 60 and about 100.degree. C. In another aspect,
the temperature of TAED or peracetic acid addition to the fibers
can be in a range between about 70 and about 90.degree. C. Yet, in
another aspect, the temperature of TAED or peracetic acid addition
to the fibers can be in a range between about 70 and about
80.degree. C. Still yet, the temperature of TAED or peracetic acid
addition can be about or in any range between about 60, 65, 70, 75,
80, 85, 90, 95, and 100.degree. C.
[0079] Magnesium compounds can be added to the mixture of non-wood
fibers during exposure to the oxygen gas, peracetic acid, or
combination of oxygen gas and peracetic acid. In one aspect of the
present invention, magnesium sulfate functions as both a stabilizer
for oxidizing agents during bleaching/brightening process and as a
protecting agent for the cellulose within the fibers by reducing
oxidation. In another aspect, other magnesium compounds, for
example magnesium sulfate and magnesium hydroxide may provide both
alkalinity and a buffering capacity, which may be beneficial. Yet
in another aspect, other suitable magnesium compounds can be
included in the brightening agent and may include any magnesium
salts or compounds including magnesium. Non-limiting examples of
suitable magnesium compounds include magnesium hydroxide, magnesium
oxide, magnesium sulfate, magnesium glycinate, magnesium ascorbate,
magnesium chloride, magnesium orotate, magnesium citrate, magnesium
fumarate, magnesium malate, magnesium succinate, magnesium
tartrate, magnesium carbonate, or any combination thereof.
[0080] During the brightening process, the partial oxygen pressure
is in a range between about 0.5 and about 10 Bar. Maintaining the
system under pressure may promote oxygen dissolution in solution.
Further, the amount of oxygen available to the fibers during
brightening may promote brightening. For example, providing between
about 0.1% and about 2% on fiber oxygen in the system is a factor
in promoting increased brightening. For example, as shown in FIG.
8, flow control 820 can be a mass flow sensor that can be set to
control the total mass of oxygen added to the kier. Oxygen gas can
be added either very quickly at the beginning of the process, added
slowly throughout the process, added very quickly at the end of the
process, or any combination thereof In one aspect, the fibers are
exposed to at least about 0.1% on fiber oxygen during brightening.
In another aspect, the fibers are exposed to at least about 1% on
fiber oxygen during brightening. Yet, in another aspect, the fibers
are exposed to between about 0.1 and about 10.0% on fiber oxygen
during brightening. Still yet, in another aspect, the fibers are
exposed to at least about or between about 0.1, 0.2, 0.3, 0.4, 0.5,
0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.4, 1.6, 1.8, 2.0, 3.0, 4.0,
5.0, 6.0, 7.0, 8.0, 9.0, and 10.0% on fiber oxygen during
brightening.
[0081] The system may be maintained under pressure, for a time
sufficient to improve the brightness and reduce the shive content
of the fibers without damaging the fibers. In one aspect, the
system is maintained under pressure for a time in a range between
about 5 and about 60 minutes. In another aspect, the system is
maintained under pressure for a time in a range between about 10
and about 30 minutes. Yet, in another aspect, the system is
maintained under pressure for a time in a range between about 20
and about 50 minutes. Still yet, in another aspect, the system is
maintained under pressure for a time about or in any range between
about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 65,
80, 85, 90, 95, 100, 105, 110, 115, and 120 minutes.
[0082] Once the brightness of the fibers has been sufficiently
increased, and the shive content sufficiently reduced, the oxygen
pressure can then be relieved or the oxygen addition can be
stopped. Subsequently, the used bleaching components are removed
from the system, and water can be used to rinse the system and
remove residual bleaching components and dissolved compounds from
the fibers.
[0083] Subsequent to the oxygen gas, peracetic acid, and/or
peroxide compound exposure (first stage of brightening), the
brightened fibers, which have a brightness greater than the fibers
of the mixture before exposure, can be subjected to at least a
second stage of bleaching (without oxygen, second brightening
agent/second stage of brightening) to further increase the
brightness. The additional stages of brightness can include any
additional brightening agents. The additional brightening agent(s)
can be a peroxide compound, an alkaline compound, a reducing agent,
magnesium sulfate or a combination thereof.
[0084] Unexpectedly, exposure to oxygen gas during brightening
dramatically improved the performance of a subsequent reductive
bleaching stage. In contrast, reductive bleaching typically is
generally not effective on plant-based non-wood fibers in
conventional processes. Thus, only after an oxygen treatment in a
first stage of brightening is it possible to use reductive
bleaching in a second brightening stage effectively. This result is
a major commercial advantage because reductive bleaching is much
less expensive than oxidative bleaching.
[0085] In one aspect, a second stage of brightening/bleaching is
performed using a peroxide compound and an alkaline compound.
Subsequently, a reducing agent is used in a reductive bleaching
stage to further increase brightness. In another aspect, a reducing
agent is used in a second stage of brightening after initial
brightening with oxygen gas, peracetic acid, and/or a peroxide
compound. Non-limiting examples of suitable reducing agents include
sodium hydrosulfite, potassium hydrosulfite, sodium sulfite,
potassium sulfite, sodium sulfate, potassium sulfate, sodium
bisulfite, potassium bisulfite, sodium metasulfite, potassium
metasulfite, sodium borohydride, or any combination thereof.
[0086] The brightened fibers, e.g., brightened bast fibers, can be
used to form an article. Non-limiting examples of the article
include a yarn, a thread, a rope, a cord, or a sliver. According to
one or more aspects, the article is a yarn. According to other
aspects, the article is a thread. According to some aspects, the
article is a rope. In one or more aspects, the article is a cord.
In some aspects, the article is a sliver. The brightened bast
fibers can be used to form the articles. Methods for forming the
articles, such as yarns, thread, ropes, cords, and slivers, are
known in the art, and any suitable method or variation can be
used.
[0087] The article can include one or more additives. Non-limiting
examples of additives include a lubricant, a finish, an antistatic
agent, or a combination thereof.
[0088] In addition to bast fibers, the article can include other
types of fibers. Non-limiting examples of other types of fibers
include synthetic fibers, polymeric fibers, thermoplastic fibers,
staple fibers, regenerated cellulose fibers, natural fibers, or a
combination thereof. According to one or more aspects, the natural
fibers are cotton fibers. According to some aspects, the polymeric
fibers are polyester fibers.
[0089] The brightened fibers, e.g., brightened bast fibers, can be
used to make nonwoven fabrics and/or textiles according to
conventional processes known to those skilled in the art. The
nonwoven fabrics, textiles, and other products can include any
amount of the brightened fibers disclosed herein. The brightened
fibers can be used to make fabrics, such as woven fabrics and knit
fabrics. For example, nonwoven fabrics, textiles, woven fabrics,
and knit fabrics can include about or in any range between about 5,
10, 15, 20, 25, 30, 25, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,
95, and 100 wt. % of the brightened fibers. The fabrics, such as
woven fabrics and knit fabrics, can include the brightened fibers,
e.g., brightened bast fibers, in the form of a yarn, a thread, a
rope, or a combination thereof. The brightened bast fibers can be
woven or knit to form a woven or a knit fabric. Methods for
weaving, knitting, and like processes are known in the art, and any
suitable method or variation can be used to form the woven and knit
fabrics.
[0090] In addition to brightened bast fibers, the nonwoven fabrics,
textiles, knit fabrics, and woven fabrics can include other types
of fibers. Non-limiting examples of other types of fibers include
synthetic fibers, polymeric fibers, thermoplastic fibers, staple
fibers, regenerated cellulose fibers, natural fibers, or a
combination thereof. According to one or more aspects, the natural
fibers are cotton fibers. According to some aspects, the polymeric
fibers are polyester fibers.
[0091] The woven and knit fabrics can be or used in a variety of
applications. Non-limiting examples of applications include a wet
wiper, a dry wiper, an impregnated wiper, a sorbent, a clean room
wiper, a medical supply product, a personal protective fabric, an
automotive protective covering, a personal care article, a fluid
filtration product, a home furnishing product, a thermal insulation
product, an acoustic insulation product, an agricultural
application product, a landscaping application product, or a
geotextile application product.
[0092] Other non-limiting examples of products for the woven and
knit fabrics include a baby wipe, a cosmetic wipe, a perinea wipe,
a washcloth, a kitchen wipe, a bath wipe, a hard surface wipe, a
glass wipe, a mirror wipe, a leather wipe, an electronics wipe, a
lens wipe, a polishing wipe, a medical cleaning wipe, a
disinfecting wipe, an industrial wipe, a food service wipe, a
surgical drape, a surgical gown, a wound care product, a protective
coverall, a sleeve protector, a diaper, a feminine care article, a
nursing pad, an air filter, a water filter, an oil filter, a
furniture backing, or a mask (e.g., a surgical mask or other
personal protective mask).
[0093] The nonwoven fabric described herein can be incorporated
into a variety of textiles and products. Non-limiting examples of
products include wipers (or wipes), such as wet wipers, dry wipers,
or impregnated wipers, which include personal care wipers,
household cleaning wipers, and dusting wipers. Personal care wipers
can be impregnated with, e.g., emollients, humectants, fragrances,
and the like. Household cleaning wipers or hard surface cleaning
wipers can be impregnated with, e.g., surfactants (for example,
quaternary amines), peroxides, chlorine, solvents, chelating
agents, antimicrobials, fragrances, and the like. Dusting wipers
can be impregnated with, e.g., oils.
[0094] Non-limiting examples of wipers include baby wipes, cosmetic
wipes, perinea wipes, disposable washcloths, household cleaning
wipes, such as kitchen wipes, bath wipes, or hard surface wipes,
disinfecting and germ removal wipes, specialty cleaning wipes, such
as glass wipes, mirror wipes, leather wipes, electronics wipes,
lens wipes, and polishing wipes, medical cleaning wipes,
disinfecting wipes, and the like. Additional examples of products
include sorbents, medical supplies, such as surgical drapes, gowns,
and wound care products, personal protective products for
industrial applications, such as protective coveralls, sleeve
protectors, and the like, protective coverings for automotive
applications, and protective coverings for marine applications. The
nonwoven fabric can be incorporated into absorbent cores, liners,
outer-covers, or other components of personal care articles, such
as diapers (baby or adult), training pants, feminine care articles
(pads and tampons) and nursing pads. Further, the nonwoven fabric
can be incorporated into fluid filtration products, such air
filters, water filters, and oil filters, home furnishings, such as
furniture backing, thermal and acoustic insulation products,
agricultural application products, landscaping application
products, and geotextile application products.
[0095] According to some aspects, the brightened fibers, e.g.,
brightened bast fibers, are used to form an article, such as an
article of clothing. Non-limiting examples of articles of clothing
include a shirt, a blouse, a sweater, a sweatshirt, a top, pants,
trousers, a tank top, a leotard, a sport specific clothing, a sock,
an undergarment, a hat, a belt, a jacket, a coat, a vest, a glove,
a dress, a skirt, a scarf, a bib, an apron, footware, or a
combination thereof.
[0096] According to other aspects, the brightened fibers, e.g.,
brightened bast fibers, are used to form an article, such as home
furnishings. Non-limiting examples of home furnishings include a
drapery, a sheet, a blanket, a throw, a comforter, a bedspread, a
washcloth, a towel, a wall covering, a chair covering, a sofa
covering, a furniture upholstery, a seat cover, a table cloth, a
cushion covering, a pillow covering, or a combination thereof.
[0097] In addition to bast fibers, the articles, such as the
article of clothing or home furnishing, can include other types of
fibers. Non-limiting examples of other types of suitable fibers
include synthetic fibers, polymeric fibers, thermoplastic fibers,
staple fibers, regenerated cellulose fibers, natural fibers, or a
combination thereof. According to one or more aspects, the natural
fibers are cotton fibers. According to some aspects, the polymeric
fibers are polyester fibers.
[0098] The brightened bast fibers can be used to form a composite
material. The composite material includes the brightened fibers and
a matrix material. The brightened bast fibers can be randomly or
substantially uniformly distributed throughout the matrix material.
Brightened bast fibers and matrix material are combined to form
composite materials. Methods for forming composite materials are
known in the art, and any suitable method or variation can be
used.
[0099] The matrix material can be, for example, a thermoplastic
material or a thermoset material. Non-limiting examples of
thermoplastic materials include polypropylene, polyethylene,
polystyrene, polyvinyl chloride, poly(hydridocarbyne),
polyhydroxybutyrate, or a combination thereof. Non-limiting
examples of thermoset materials include an epoxy resin, a phenolic
resin, a polyurethane, a polyester, a vinyl resin, an acrylate
resin, or a combination thereof. The brightened bast fibers are in
the form of a nonwoven fabric or a woven fabric. The composite
material can be used in, for example, and not limited to, an
automobile part, an aviation part, a marine part, a home
furnishing, a building panel, or a combination thereof.
[0100] A nonwoven web of staple fibers can be formed by a
mechanical process known as carding as described in U.S. Pat. No.
797,749, which is incorporated herein in its entirety by reference.
The carding process can include an airstream component to randomize
the orientation of the staple fibers when they are collected on the
forming wire. A state of the art mechanical card, such as the
Triitzschler-Fliessner EWK-413 card, can run staple fibers having
significantly shorter length than the 38 mm noted above. Older card
designs may require longer fiber length to achieve good formation
and stable operation.
[0101] Another common dry web forming process is air-laid or
air-forming. This process employs only air flow, gravity, and
centripetal force to deposit a stream of fibers onto a moving
forming wire that conveys the fiber web to a web bonding process.
Air-laid processes are described in U.S. Pat. Nos. 4,014,635 and
4,640,810, both of which are incorporated herein in their entirety
by reference. Pulp-based air-formed nonwoven webs frequently
incorporate thermoplastic fibers that melt and bond the air-laid
web together when the air-formed web is passed through ovens.
[0102] Thermal bonding is also referred to as calendar bonding,
point bonding, or pattern bonding, can be used to bond a fiber web
to form a nonwoven fabric. Thermal bonding can also incorporate a
pattern into the fabric. Thermal bonding is described in PCT
International Publication No. WO/2005/025865, which is incorporated
herein by reference in its entirety. Thermal bonding requires
incorporation of thermoplastic fibers into the fiber web. Examples
of thermoplastic fibers are discussed above. In thermal bonding,
the fiber web is bonded under pressure by passing through heated
calendar rolls, which can be embossed with a pattern that transfers
to the surface of the fiber web. During thermal bonding, the
calendar rolls are heated to a temperature at least between the
glass transition temperature (T.sub.g) and the melting temperature
(T.sub.m) of the thermoplastic material.
[0103] Brightened fibers are formed into an unbounded web in the
wet or dry state. In one aspect, the web is formed by a method
employing a mechanical card. In another aspect, the web is formed
by a method employing a combination of a mechanical card and a
forced air stream. The dry web can be bonded by hydroentangling, or
hydroentanglement. In addition, the hydroentangled web can be
treated with an aqueous adhesive and exposed to heat to bond and
dry the web. Also, the dry web can be bonded by mechanical needle
punching and/or passing a heated air stream through the web.
Alternatively, the dry web can be bonded by applying an aqueous
adhesive to the unbounded web and exposing the web to heat.
[0104] Hydroentanglement, also known as spunlacing, or spunbonding,
to form non-woven fabrics and substrates is well-known in the art.
Non-limiting examples of the hydroentangling process are described
in Canadian Patent No. 841,938 and U.S. Pat. Nos. 3,485,706 and
5,958,186. U.S. Pat. Nos. 3,485,706 and 5,958,186, respectively,
are incorporated herein in their entirety. Hydroentangling involves
forming a fiber web, either wet-laid or dry-laid, and thereafter
entangling the fibers by employing very fine water jets under high
pressure. For example, a plurality of rows of waterjets is directed
towards the fiber web which is disposed on a moving support, such
as a wire (mesh). Hydroentangling of the fibers provides distinct
hydroemboss patterns, which can create low fiber count zones,
facilitate water dispersion, and provide a three dimensional
structure. The entangled web is then dried.
[0105] A nonwoven fiber web of brightened fibers can be wet-laid or
foam-formed in the presence of a dispersion agent. The dispersion
agent can either be directly added to the fibers in the form of a
so-called "fiber finish" or it can be added to the water system in
a wet-laying or foam-forming process. The addition of a suitable
dispersion agent assists in providing a good formation, i.e,
substantially uniform fiber dispersion, of brightend fibers. The
dispersion agent can be of many different types which provide a
suitable dispersion effect on the brightened fibers or any mixture
of such brightened fibers. A non-limiting example of a dispersion
agent is a mixture of 75% bis(hydrogeneratedtallowalkyl)dimethyl
ammonium chloride and 25% propyleneglycol. The addition ought to be
within the range of 0.01-0.1 weight %.
[0106] During foam-forming the fibers are dispersed in a foamed
liquid containing a foam-forming surfactant and water, whereafter
the fiber dispersion is dewatered on a support, e.g., a wire
(mesh), in the same way as with wet-laying. After the fiber web is
formed, the fiber web is subjected to hydroentanglement with an
energy flux of about 23,000 foot-pounds per square inch per second
or higher. The hydroentanglement is carried out using conventional
techniques and with equipment supplied by machine manufacturers.
After hydroentanglement, the material is pressed and dried and,
optionally, wound onto a roll. The ready material is then converted
in a known way to a suitable format and is packed.
[0107] The nonwoven fabric of the present invention can be
incorporated into a laminate comprising the nonwoven fabric and a
film. Laminates can be used in a wide variety of applications, such
outer-covers for personal care products and absorbent articles, for
example diapers, training paints, incontinence garments, feminine
hygiene products, wound dressings, bandages, and the like.
[0108] To form a laminate, an adhesive is applied to a support
surface of the nonwoven fabric or a surface of the film. Examples
of suitable adhesives include sprayable latex, polyalphaolefin,
(commercially available as Rextac 2730 and Rextac 2723 from
Huntsman Polymers, Houston, Tex.), and ethylene vinyl acetate.
Additional commercially available adhesives include, but are not
limited to, those available from Bostik Findley, Inc., Wauwatosa,
Wis. Then, a film is fed onto the forming wire on top of the
nonwoven fabric. Before application to the nonwoven fabric, the
film is stretched as desired. The nonwoven fabric and film are
combined and compressed in a nip to form the laminate. Although not
required for pressure sensitive adhesives, the nip can be
maintained at a desired adhesive bonding temperature suitable for
the adhesive employed, e.g. heat activated adhesions. The laminate
can be cut, directed to a winder, or directed to further
processing.
[0109] In addition to applying a film to the nonwoven fabric,
another fabric can be bonded to the nonwoven fabric, which can be,
for example another nonwoven fabric or a woven fabric. The nonwoven
fabric can be a nonwoven fabric made in accordance with the present
invention. An adhesive can be applied to either the nonwoven fabric
or the another fabric before nipping to form the laminate.
[0110] The films used in laminates can include, but are not limited
to, polyethylene polymers, polyethylene copolymers, polypropylene
polymers, polypropylene copolymers, polyurethane polymers,
polyurethane copolymers, styrenebutadiene copolymers, or linear low
density polyethylene. Optionally, a breathable film, e.g. a film
comprising calcium carbonate, can be employed to form the laminate.
Generally, a film is "breathable" if it has a water vapor
transmission rate of at least 100 grams/square meter/24 hours,
which can be measured, for example, by the test method described in
U.S. Pat. No. 5,695,868, which is incorporated herein in its
entirety by reference. Breathable films, however, are not limited
to films comprising calcium carbonate. Breathable films can include
any filler. As used herein, "filler" is meant to include
particulates and other forms of materials which will not chemically
interfere with or adversely affect the film, but will be
substantially uniformly dispersed throughout the film. Generally,
fillers are in particulate form and spherical in shape, with
average diameters in the range between about 0.1 micrometers to
about 7 micrometers. Fillers include, but are not limited to,
organic and inorganic fillers.
[0111] Optionally, the brightening agent or the fiber mixture
includes additives. Suitable additives include, but are not limited
to, chelants, magnesium sulfate, surfactants, wetting agents, pH
buffering agents, stabilizing additives, or any combination
thereof.
[0112] The optional one or more additives can be present in a range
between about 0.5 and about 5 wt. % based on the total weight of
the mixture of non-wood fibers. In another aspect, one or more
additives can be present in a range between about 1 and about 10
wt. %. Yet, in another aspect, one or more additives can be present
in a range between about 2 and about 6 wt. %. Still yet, in another
aspect, one or additives can be present in a range between about 3
and about 5 wt. %. In one aspect, the mixture of non-wood fibers
can include one or more additives about or in any range between
about 0.1, 0.2, 0.5, 0.7, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, and 20 wt. %.
[0113] Suitable chelants include any metal sequestrant.
Non-limiting examples of chelants include
ethylenediamine-N,N'-disuccinic acid (EDDS) or the alkali metal,
alkaline earth metal, ammonium, or substituted ammonium salts
thereof, or mixtures thereof. Suitable EDDS compounds include the
free acid form and the sodium or magnesium salt thereof. Examples
of sodium salts of EDDS include Na.sub.2EDDS and Na.sub.4EDDS.
Examples of such magnesium salts of EDDS include MgEDDS and
Mg.sub.2EDDS. Other chelants include the organic phosphonates,
including amino alkylene poly(alkylene phosphonate), alkali metal
ethane-1-hydroxy diphosphonates, nitrile-trimethylene phosphonates,
ethylene diamine tetra methylene phosphonates, and diethylene
triamine penta methylene phosphonates. The phosphonate compounds
can be present either in their acid form or as a complex of either
an alkali or alkaline metal ion, the molar ratio of the metal ion
to phosphonate compound being at least 1:1. Other suitable chelants
include amino polycarboxylate chelants such as EDTA.
[0114] Suitable wetting agents and/or cleaning agents include, but
are not limited to, detergents and nonionic, amphoteric, and
anionic surfactants, including amino acid-based surfactants. Amino
acid-based surfactant systems, such as those derived from amino
acids L-glutamic acid and other natural fatty acids, offer pH
compatibility to human skin and good cleansing power, while being
relatively safe and providing improved tactile and moisturization
properties compared to other anionic surfactants.
[0115] Suitable buffering systems include any agents buffering
agents that assist the buffering system in reducing pH changes.
Illustrative classes of buffering agents include, but are not
limited to, a salt of a Group IA metal including, for example, a
bicarbonate salt of a Group IA metal, a carbonate salt of a Group
IA metal, an alkaline or alkali earth metal buffering agent, an
aluminum buffering agent, a calcium buffering agent, a sodium
buffering agent, a magnesium buffering agent, or any combination
thereof. Suitable buffering agents include carbonates, phosphates,
bicarbonates, citrates, borates, acetates, phthalates, tartrates,
succinates of any of the foregoing, for example sodium or potassium
phosphate, citrate, borate, acetate, bicarbonate and carbonate, or
any combination thereof. Non-limiting examples of suitable
buffering agents include aluminum-magnesium hydroxide, aluminum
glycinate, calcium acetate, calcium bicarbonate, calcium borate,
calcium carbonate, calcium citrate, calcium gluconate, calcium
glycerophosphate, calcium hydroxide, calcium lactate, calcium
phthalate, calcium phosphate, calcium succinate, calcium tartrate,
dibasic sodium phosphate, dipotassium hydrogen phosphate,
dipotassium phosphate, disodium hydrogen phosphate, disodium
succinate, dry aluminum hydroxide gel, magnesium acetate, magnesium
aluminate, magnesium borate, magnesium bicarbonate, magnesium
carbonate, magnesium citrate, magnesium gluconate, magnesium
hydroxide, magnesium lactate, magnesium metasilicate aluminate,
magnesium oxide, magnesium phthalate, magnesium phosphate,
magnesium silicate, magnesium succinate, magnesium tartrate,
potassium acetate, potassium carbonate, potassium bicarbonate,
potassium borate, potassium citrate, potassium metaphosphate,
potassium phthalate, potassium phosphate, potassium polyphosphate,
potassium pyrophosphate, potassium succinate, potassium tartrate,
sodium acetate, sodium bicarbonate, sodium borate, sodium
carbonate, sodium citrate, sodium gluconate, sodium hydrogen
phosphate, sodium hydroxide, sodium lactate, sodium phthalate,
sodium phosphate, sodium polyphosphate, sodium pyrophosphate,
sodium sesquicarbonate, sodium succinate, sodium tartrate, sodium
tripolyphosphate, synthetic hydrotalcite, tetrapotassium
pyrophosphate, tetrasodium pyrophosphate, tripotassium phosphate,
trisodium phosphate, trometamol, or any combination thereof.
[0116] Optionally, one or more stabilizing additives can be added
during the bleaching or brightening process to prevent hydrogen
peroxide decomposition. Non-limiting examples of suitable
stabilizing additives include sodium silicate, magnesium sulfate,
diethylene triamine penta acetic acid (DTPA), DTPA salts, ethylene
diamine tetra acetic acid (EDTA), EDTA salts, or any combination
thereof.
[0117] The brightened fibers of the present invention can be used
for any paper or tissue product, including but not limited to,
tissue products made in a wet laid paper machine. In one aspect, a
tissue or a paper comprises non-wood fibers having a brightness
greater than about 65 as measured by MacBeth UV-C standard.
[0118] The tissue paper can include any additional papermaking
fibers, thermoplastic fibers, and/or synthetic fibers, and produced
according to the Conventional Wet Press (CWP) manufacturing method,
or by the Through Air Drying (TAD) manufacturing method, or any
alternative manufacturing method (e.g., Advanced Tissue Molding
System ATMOS of the company Voith, or Energy Efficient
Technologically Advanced Drying eTAD of the company
Georgia-Pacific). The web can be dried on a Yankee dryer and can be
creped or un-creped.
[0119] The tissue or paper can include any amount of the brightened
fibers disclosed herein. For example, tissues and papers can
include about or in any range between about 5, 10, 15, 20, 25, 30,
25, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100 wt. %
of the brightened fibers.
[0120] For example, conventional wet pressed tissues are prepared
by first preparing and mixing the raw fiber material in a vat to
produce a fiber slurry. Then, the fiber slurry is transferred
through a centrifugal pump to a headbox. From the headbox, the
fibrous mixture is deposited onto a moving foraminous wire, such as
Fourdrinier wire, to form a nascent web. Water can drain through
the wire by use of vacuum and/or drainage elements. The web can
then be dried by any suitable methods, including, but not limited
to, air-drying, through-air drying (TAD), or drying on a Yankee
dryer. For drying on a Yankee dryer, first an adhesive material is
sprayed onto the surface of the Yankee dryer. The nascent web is
transferred onto the hot Yankee dryer via one or two press rolls.
The web is dried on the Yankee dryer and then removed with a
creping doctor, which scrapes the web from the surface of the
Yankee dryer drum. Then, the dried web is wound into a roll at the
reel of the paper machine.
[0121] When used to form tissues or paper, the fiber slurry can
include any additional additives known in the art, including, but
not limited to, wet strength agents, debonders, surfactants, or any
combination thereof.
EXAMPLES
[0122] In the following examples, flax fibers (commercially
available from Crailar Technologies, Inc., Greensboro, N.C.) were
used to assess the impact of oxygen during the bleaching process on
shive content and brightness.
[0123] All brightness measurements were conducted on thick pads of
flax fiber. The pads were generated by diluting a sample of the
flax fibers to approximately 2% consistency with water. The flax
samples were gently hand mixed to separate the fibers as much as
possible and then dewatered on a Buchner funnel with a piece of
filter paper to form the fiber pad. During dewatering, the flax
fiber was manually distributed to form as uniform a pad as
possible. Then the pad was removed from the Buchner funnel and
pressed between blotters in a laboratory press machine for about 10
minutes under a maximum pressure of 3,000 PSI. The fiber pads were
then dried on a speed dryer until substantially dry. Care was taken
to avoid overheating the samples because any potential excess heat
induced yellowing. The fiber pads were air-dried for several days
prior to brightness testing. All brightness tests were conducted in
accordance with the MacBeth UV-C test method.
Examples 1-9
[0124] The initial starting (control) flax was commercially
available "finished flax" from Crailar Technologies, Inc. These
fibers were treated by the Crailar process, which included
mechanical treatment, chemical treatment to remove pectin, hydrogen
peroxide bleaching, and drying. As shown in Table 1 below (ID 1),
these flax fibers demonstrated a MacBeth UV-C brightness of 57.8.
FIG. 12 shows a photomicrograph of flax fibers, which have
substantial shive content.
TABLE-US-00001 TABLE 1 Compositions and properties for Examples 1-9
Brightness Chemicals % OP Physical MacBeth UV-C ID Peroxide Caustic
Oxygen TAED DTPA Silicate Method % TSS Temp F. Minutes Brightness
Gain 1 Start Sample - "Bleached" 57.8 2 1 1 0 0 0.1 0 Bath 12 190
120 76.4 18.6 3 2 2 0 0 0.0 0 Bath 12 190 120 77.4 19.6 4 4 3 0 0
0.1 0 Bath 12 190 120 75.8 18.0 5 2 2 0 0 0.1 0.2 Spinner 8 190 120
76.8 19.0 6 4 2 0 0 0.1 0.2 Spinner 8 190 120 78.7 20.9 7 4 2 0 0.5
0.1 0.2 Spinner 8 190 120 79.7 21.9 8 3 1 1 0 0.0 0.2 Q Mixer 12
190 180 84.4 26.6 9 3 1 0 0 0.1 0.2 Q Mixer 12 190 180 78.6 20.8
DTPA = diethylene triamine pentaacetic acid, a chelant; Caustic =
NaOH/sodium hydroxide; % TSS = percent Total suspended
solids/consistency
[0125] In Table 1, all the chemicals were % On Pulp (OP)=(weight of
the chemical/weight of the fiber)*100. All chemicals were
calculated on a 100% basis, i.e., the actual mass amount of the
chemical and not the amount of a solution of the chemical. In
Example 1, 30% hydrogen peroxide solution was used, but the data
was recited in terms of 100% hydrogen peroxide.
[0126] In Examples 1-3, control flax fibers (Example 1) were
bleached using the "bag" or "bath" method. Flax samples were placed
in a zip lock style plastic bag and maintained at a constant
temperature in a water bath for the bleaching process duration.
Thirty oven dry (OD) grams of fiber were diluted to a 12%
consistency using distilled water including the respective
chemicals (see Table 1). Additional mixing was performed at 30
minute intervals for the remaining retention time. The samples were
then removed from the water bath, and brightness pads of fibers
were prepared as detailed above. As shown in Table 1, brightness
gain ranged between about 18.0 and 19.6 according to the MacBeth
UV-C standard test.
[0127] Another method of bleaching at a lower consistency (8%), a
modified "spinner" method, was used in Examples 5-7. In this
method, 30 g OD fiber was added to a 4 L beaker. Distilled water
and the indicated chemicals were added to bring the pulp to an 8%
consistency. The beakers were then placed in a 190.degree. F. water
bath about 80% submerged. Instead of continuously agitating the
fibers with a motorized spinner, the samples were manually mixed
(using a spoon) at approximately 10 minute intervals throughout the
180 minute duration of bleaching. A small amount of sodium
silicate, 0.2 wt. % on pulp, was also added to the samples to help
stabilize hydrogen peroxide.
[0128] Examples 5 and 6 mirror the chemical application of Examples
3 and 4 and demonstrated a 19.0 and 20.9 brightness gain,
respectively. However, there was no significant difference in
brightness gain between the bag and spinner bleaching. Sodium
silicate also did not have any significant impact on the
results.
[0129] Example 7 used the same initial charge of Example 6 (also a
modified spinner method). This sample was allowed to peroxide
bleach for 90 minutes, and then a sample equal to 0.5 wt. % of TAED
granules was added to the pulp. The TAED was added to react with
residual hydrogen peroxide and sodium hydroxide to form peracetic
acid in situ. The addition of TAED resulted in a 1.0 higher
brightness gain compared to the baseline peroxide bleach.
[0130] In Example 8-9, a Quantum Mixer Mark III (Quantum
Technologies, Akron, Ohio) was used to test the addition of oxygen
gas to the peroxide bleach. The mixer was a variable speed, high
intensity mixer suitable for all bleaching stages, which allowed
the pulp and chemical to react under controlled conditions of time,
temperature and agitation with constant pH read out. The mixer was
run with the lowest possible level of mixing to minimize fiber
tangling in the final pulp mass. Examples 8 and 9 compare
brightness results with and without oxygen. Example 9 was run
without oxygen and achieved a 20.8 brightness gain, which is
comparable to the 19.0 and 20.9 gain for the spinner bleaches in
Examples 5 and 6. Example 8 was run with oxygen addition for the
first 60 minutes of the bleach. The mixer bowel was pressurized to
60 psig pressure with oxygen at the start of the bleach. After 15
minutes, the pressure was relieved and a second 60 psig charge was
added. After 60 minutes, the oxygen was vented, and the remaining
120 minutes of the retention was performed at atmospheric pressure.
This sample achieved a 26.6 brightness gain for a 84.4 final
brightness. Compared to Example 9, the oxygen increased the
brightness gain by 5.8. In addition, visual examination of the
handsheets showed a decreased visible shive content in the oxygen
Example 8 (see FIG. 11) compared the non-oxygen Example 9 (see FIG.
10).
[0131] As shown in Table 1, the fibers brightened without any
oxygen had a brightness between 75.8 and 79.7, while adding oxygen
provided a brightness of 84.8.
Example 10-17
[0132] In Examples 10-17 shown in Table 2, bleaching was performed
in the Quantum mixer to assess the impacts of oxygen and TAED on
brightness, as well as the effect of reductive bleaching. All
experiments were performed on a de-pectinified, unbleached flax
sample (Example 10). This control sample had a lower brightness,
27.9 and a higher level of shive contamination (see also FIG. 12 of
Example 24 below).
TABLE-US-00002 TABLE 2 Compositions and properties for Examples
10-17 Chemicals % OP Brightness Start Hydro- Physical MacBeth UV-C
ID Sample Peroxide Caustic Oxygen TAED DTPA Silicate sulfate Method
% TSS Temp F. Minutes Brightness Gain 10 Unbleached 27.9 11 10 4
1.5 1 0.1 0.5 Mixer 15 190 120 64.0 36.1 12 11 3 1.5 Mixer 15 180
120 82.6 54.7 13 10 4 1.5 1 0.5 0.1 Mixer 15 190 180 64.1 36.2 14
Unbleached 3 1.5 1 0.1 0.5 0.5 Mixer 15 190 180 83.6 55.7 15
Unbleached 3 1.5 1 0.1 0.5 1 Mixer 15 190 180 81.8 53.9 16
Unbleached 3 1.5 1 0.1 0.5 1.5 Mixer 15 190 180 82.2 54.3 17 1 2 1
1 0.1 0.5 Mixer 15 190 180 83.9 26.1
[0133] Example 11 utilized oxygen in the initial peroxide stage and
demonstrated a 64.0 brightness after 120 minutes of retention (the
first 60 minutes with oxygen as detailed above). As shown in FIG.
13, the fiber brightness pad demonstrated that the sample contained
long, dark fibers which have a different appearance than the shives
seen in the non-oxygen samples. Sample 11 was then washed on a
Buchner funnel using the procedure detailed above, returned to the
mixer, and then bleached with a hydrogen peroxide bleaching
mixture. The final brightness after the second stage of bleaching
was 82.6 (Example 12), compared to the final brightness of about 68
for the two-stage peroxide bleaching without oxygen (see Table 4).
The fiber pad also showed a significant reduction in the long, dark
fiber content and a very low level of shive.
[0134] Example 13 was performed similar to Example 11, except that
a quantity of TAED equal to about 0.5 wt. % on pulp was added after
60 minutes (after the oxygen was vented). The TAED was added to
form peracetic acid in situ from the residual peroxide and caustic.
After an additional 60 minutes of retention, the brightness was
measured and found to be 64.1.
[0135] Examples 14-16 were performed to assess the impact of
reductive bleaching on an oxygen-treated sample. The flax fibers
were peroxide bleached in the Quantum mixer analogously to Example
11, except with a lower peroxide charge (3% versus 4%). The pulp
was removed from the mixer, washed on a Buchner funnel and then
split into three portions. Each of the samples was reductively
bleached using a sodium hydrosulfite and the bag method. For the
reductive stage of bleaching, a 20 g OD portion of the pulp was
diluted to 8% consistency with distilled water and placed in a
zip-lock type bag. The samples were then placed in a sealed glove
box, and nitrogen was used to purge the oxygen. Nitrogen was purged
into the box for approximately 15 minutes. While under nitrogen
purge, the specified sodium hydrosulfite charge was prepared by
weighing the required hydrosulfite powder, adding 25 mL of
distilled water to dissolve the powder, and then adding the
composition to the flax sample. The bags were sealed and hand
kneaded to mix the sodium hydrosulfite. The sealed bags were then
removed from the glove box and placed in a 180.degree. F. water
bath for 60 minutes. Then, the bags were removed from the bath and
a brightness pad was prepared for each sample.
[0136] The final brightness for these samples was between 81.8 and
83.6, which is comparable to a 82.6 brightness for the two-stage
peroxide bleach Example 12. Table 4 below provides the brightness
and color data for these samples. As indicated, the hydrosulfite
bleached pulps (Examples 14-16) had less color than Example 12 (A*
and B*).
[0137] As shown in Table 2, using oxygen to brighten fibers
provided brightnesses between 81.8 and 83.9.
[0138] The MacBeth meter measures both TAPPI brightness and LAB
whiteness. L* is the whiteness, and a* and b* are the color
(red-green and blue-yellow). A* and b* values close to 0 indicate
very low color/no color. The b* values shown in Table 3 are
important because indicate a reduction in the yellow color of the
fiber. Natural flax fiber is very yellow and thus not desirable in
a wiper or tissue product. UV-C is the "C" illuminate, including
the ultraviolet component of the light. "UV Excl" is UV excluded
and does not include the ultraviolet light. The UV-C with UV may
provide the most realistic conditions under which consumers
perceive nonwovens.
TABLE-US-00003 TABLE 3 Brightness and color results for Examples
10-17 Brtness Color MB Color MB Color MB Brtness Color Color Color
UV Excl. UV Excl. UV Excl. UV Excl. MacBeth MacBeth MacBeth MacBeth
Whtness MacBeth A* B* L* UV-C L*UV C a*-UV C b*-UV C MacBeth ID %
Unitless Unitless Unitless % Unitless Unitless Unitless UV-C 10
28.8 0.9 8.7 65.5 27.9 64.6 1.0 8.5 -20.5 11 65.3 -1.0 10.3 90.4
64.0 89.7 -1.1 10.2 25.8 12 82.5 -1.0 5.4 95.8 82.6 95.7 -1.1 5.3
65.0 13 63.8 -1.2 10.5 89.7 64.1 90.1 -1.1 11.0 23.4 14 83.7 -0.8
4.7 95.9 83.6 95.8 -0.7 4.6 68.6 15 82.9 -0.7 4.8 95.6 81.8 95.4
-0.9 5.3 64.0 16 82.4 -0.8 5.0 95.4 82.2 95.2 -0.7 4.7 66.3 17 83.7
-0.8 4.4 95.7 83.9 95.8 -0.9 4.4 69.4
Examples 18-24
[0139] In Examples 18-24 (see Table 4), one and two-stage peroxide
bleach processes, without oxygen, were performed on de-pectinified,
unbleached flax (Example 24). FIG. 12 shows a photomicrograph of
the fibers in Example 24 (brightness of 57.8), which demonstrates
the higher level of shive contamination.
TABLE-US-00004 TABLE 4 Compositions and properties for Examples
18-24 Brightness Chemicals % OP Physical MacBeth UV-C ID Stage
Peroxide Caustic DTPA Silicate Method % TSS Temp F. Minutes
Brightness Stage Gain Total Gain 24 Start Sample - "Unbleached"
28.5 18 1 2 1 0.1 0.05 Spinner 8 190 180 60.2 31.7 19 2 3 1 0.05
Spinner 8 190 120 68.2 8.0 39.7 20 1 3 1 0.1 0.05 Spinner 8 190 180
59.2 30.7 21 2 3 1 0.05 Spinner 8 190 120 67.5 8.3 39.0 22 1 6 2
0.1 0.05 Spinner 8 190 180 60.0 31.5 23 2 3 1 0.05 Spinner 8 190
120 68.1 8.1 39.6
[0140] The modified "spinner" method was used for the bleaches.
After the first bleaching stage, the sample was diluted to
approximately 2 L with distilled water and de-watered on a Buchner
funnel. Two 1 L rinses were added to the de-watered pulp in the
Buchner funnel to remove any residual chemical. The pulp was then
split and one part used to make a pad for brightness testing. The
remaining pulp was then bleached in the spinner method for a second
peroxide stage. Finally, the brightness pad was made from the pulp
after the second bleaching stage was complete.
[0141] Example 1, the Crailar bleached flax (commercial bleaching
process by unknown bleaching methods), had a brightness of 57.8. In
comparison, Examples 18, 20, and 22 were single stage peroxide
bleached flax, which achieved brightness between 59.2 and 60.2. The
flat brightness response was independent of the amount of peroxide
used.
[0142] Each of the pulps was then second stage bleached as
described above (Examples 19, 21, and 23). An additional 8.0 to 8.3
brightness gain was seen in the second stage to provide a final
brightness between 67.5 and 68.3. Again, there was no difference in
brightness attributable to peroxide dose.
Examples 25-28
[0143] To determine the impact of reducing agents on the fiber
without prior oxygen treatment, a set of experiments was performed
on the unbleached (Example 10) and bleached (Example 1) flax
samples at neutral and acidic pH. Table 5 shows the brightness
gains and optical data for Examples 25-28.
TABLE-US-00005 TABLE 5 Brightness gains and optical data Start
Hydrosulfite Physical MacBeth UV-C ID Sample pH % OP Method % TSS
Temp F. Minutes Brightness Gain L* A* B* 1 Initial 59.1 87.34 -0.16
10.75 25 Bleached 7.03 1 Bag 8 180 60 61.1 2.0 87.5 -0.4 9.16 26
Bleached 3.36 1 Bag 8 180 60 61.0 2.0 87.54 -0.57 9.29 10 Initial
30.0 66.24 1.03 8.12 27 Unbleached 8.06 1 Bag 8 180 60 31.3 1.3
67.13 0.51 7.85 28 Unbleached 8.06 1 Bag 8 180 60 30.2 0.1 66.45
0.68 8.34
[0144] As shown in Table 5, single stage hydrosulfite bleaching on
both samples only showed up to 2 points of brightness gain and a
slight reduction in color. When this result is compared to the
reductive bleaching of oxygen-treated flax (Examples 14-16), it is
evident that oxygen-treated flax demonstrates a 15 to 20 point
brightness gain. Without being bound by theory, oxygen may be
acting as an activating agent to enhance the performance of a
subsequent reductive bleaching stage.
[0145] During hand-mixing of the samples (15 minute intervals
during the 60 minute retention), the unbleached samples
unexpectedly increased in brightness during visual observation. The
lower pH sample demonstrated the largest change and had a light tan
color, compared to the starting grey color. However, soon after the
fiber was exposed to air, the color reverted back to the dark grey
color, resulting in only a slight improvement in brightness over
the starting sample. The bleached flax sample may also have
displayed similar reversion, although, due to the higher initial
brightness, it was difficult to be sure how much reversion was
actually observed. This reversion was not observed in the oxygen
treated samples.
[0146] With respect to the above description then, it is to be
realized that the optimum dimensional relationships for the parts
of the invention, to include variations in size, materials, shape,
form, function, and manner of operation, assembly and use, are
deemed readily apparent and obvious to one skilled in the art, and
all equivalent relationships to those illustrated in the drawings
and described in the specification are intended to be encompassed
by the present invention.
[0147] Therefore, the foregoing is considered as illustrative only
of the principles of the invention. Further, various modifications
may be made of the invention without departing from the scope
thereof and it is desired, therefore, that only such limitations
shall be placed thereon as are imposed by the prior art and which
are set forth in the appended claims.
* * * * *