WO2020231887A1 - Compositions de fibres cellulosiques ayant des surfaces superhydrophobes et procédés écologiques pour leur production - Google Patents

Compositions de fibres cellulosiques ayant des surfaces superhydrophobes et procédés écologiques pour leur production Download PDF

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Publication number
WO2020231887A1
WO2020231887A1 PCT/US2020/032279 US2020032279W WO2020231887A1 WO 2020231887 A1 WO2020231887 A1 WO 2020231887A1 US 2020032279 W US2020032279 W US 2020032279W WO 2020231887 A1 WO2020231887 A1 WO 2020231887A1
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process according
particles
cellulosic fiber
fiber composition
superhydrophobic
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PCT/US2020/032279
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English (en)
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Anil N. Netravali
Namrata V. PATIL
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Cornell University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
    • C08L1/08—Cellulose derivatives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
    • C08L1/08—Cellulose derivatives
    • C08L1/10—Esters of organic acids, i.e. acylates

Definitions

  • the present invention generally provides, inter alia , environment-friendly superhydrophobic cellulosic fiber compositions, products made from the superhydrophobic cellulosic fiber compositions, and processes for their production.
  • Cotton fibers are made-up of cellulose, the most abundantly used natural polymer on earth. With worldwide efforts to curb the use of non-biodegradable petroleum-based products and replacing them with fully sustainable natural products, both government and industry have put increased emphasis on promoting the use of cellulosic products.
  • the present disclosure relates to, inter alia , environment-friendly processes based on‘green’ chemistry principles to render durable superhydrophobicity (water repellency) to cellulosic fiber compositions and products and materials containing the cellulosic fiber compositions.
  • the present disclosure relates to a process for preparing a cellulosic fiber composition having a superhydrophobic surface.
  • This process includes the steps of: (a) synthesizing anisotropic particles of different shapes and covalently attaching them to a non superhydrophobic cellulosic fiber, thereby yielding an intermediate cellulosic fiber composition having an altered surface; and (b) grafting long chain hydrocarbon lipids onto the altered surface of the intermediate cellulosic fiber composition, thereby lowering surface energy of the intermediate cellulosic fiber composition to yield a cellulosic fiber composition having a superhydrophobic surface.
  • the present disclosure relates to a cellulosic fiber composition having a superhydrophobic surface, with the cellulosic fiber composition being produced by the process of described herein.
  • the present disclosure relates to a product comprising a cellulosic fiber composition as described herein.
  • the present disclosure relates to a cellulosic material having improved hydrophobicity, with the cellulosic material comprising a cellulosic fiber composition as described herein.
  • Paragraph 1 A process for preparing a cellulosic fiber composition having a superhydrophobic surface, said process comprising:
  • Paragraph 2 The process according to Paragraph 1, wherein the cellulosic fiber composition has a water contact angle (WCA) selected from the group consisting of at least 150°, 151°, 152°, 153°, 154°, 155°, 156°, 157°, 158°, 159°, and 160°.
  • WCA water contact angle
  • Paragraph 3 The process according to Paragraph 1, wherein the cellulosic fiber composition has a durability characterized by a loss of water contact angle selected from the group consisting of less than 2 percent, less than 2.5 percent, less than 3 percent, less than 5 percent, less than 7 percent, and less than 8 percent, as confirmed by repeated standard laboratory laundry cycles.
  • Paragraph 4 The process according to Paragraph 3, wherein the repeated standard laboratory laundry cycles are selected from the group consisting of 2, 3, 4, 5, 6, 7, 8, 9, and 10 standard laboratory laundry cycles.
  • Paragraph 5 The process according to Paragraph 1, wherein the anisotropic particles are anisotropic silica particles.
  • Paragraph 6 The process according to Paragraph 1, wherein the anisotropic particles are selected from the group consisting of silicon oxides, silicon metal oxides, metal oxides, metal silicon oxides, halloysite nanotubes (HNTs), nanoclays, and polymers.
  • Paragraph 7 The process according to Paragraph 1, wherein the anisotropic particles are selected from the group consisting of nanoparticles and microparticles.
  • Paragraph 8 The process according to Paragraph 7, wherein the nanoparticles have a mean diameter in at least one dimension selected from the group consisting of between about 1 and 40 nanometers (nm), between about 40 and 100 nm, and between about 100 and 1000 nm.
  • Paragraph 9 The process according to Paragraph 7, wherein the microparticles have a mean diameter in at least one dimension selected from the group consisting of between about 1 and 2 microns (pm), between about 2 and 3 pm, and between about 3 and 4 pm.
  • Paragraph 10 The process according to Paragraph 1, wherein the anisotropic particles have a mean diameter in at least one dimension of between about 1 and 100 nm and in at least one other dimension of up to 2 pm.
  • Paragraph 11 The process according to Paragraph 1, wherein the anisotropic particles have different mean diameters in at least one dimension, said different mean diameters being selected from the group consisting of between about 40 nm and 100 nm, between about 100 nm and 2 pm, and between about 1 pm and 4 pm.
  • Paragraph 12 The process according to Paragraph 1, wherein the anisotropic particles are uniformly or substantially uniformly distributed on the superhydrophobic surface of the cellulosic fiber composition.
  • Paragraph 13 The process according to Paragraph 1, wherein the anisotropic particles cover a percentage of the superhydrophobic surface selected from the group consisting of at least 40 percent, at least 50 percent, at least 60 percent, at least 70 percent, at least 80 percent, and at least 90 percent.
  • Paragraph 14 The process according to Paragraph 1, wherein said anisotropic particles of different shapes comprise needle-shaped particles.
  • Paragraph 15 The process according to Paragraph 1, wherein said anisotropic particles of different shapes comprise cone-shaped particles.
  • Paragraph 16 The process according to Paragraph 15, wherein the cone-shaped particles have a mean or median an aspect ratio (length:diameter of base) selected from the group consisting of 2: 1, 5: 1, 10: 1, 20: 1, 40: 1, and 100: 1, or within ranges between any two choices from the group.
  • Paragraph 17 The process according to Paragraph 15, wherein the cone-shaped particles are oriented on the superhydrophobic surface vertex end upward, vertex end downward, or both vertex end upward and downward.
  • Paragraph 18 The process according to Paragraph 1, wherein said anisotropic particles of different shapes comprise spherical particles.
  • Paragraph 19 The process according to Paragraph 18, wherein said spherical particles have a diameter between about 40 nm and 4 pm.
  • Paragraph 20 The process according to Paragraph 1, wherein said anisotropic particles comprise a combination of needle-shaped particles, cone-shaped particles, and/or spherical particles.
  • Paragraph 21 The process according to Paragraph 1, wherein said anisotropic particles of different shapes comprise elongated particles having a first width at a first end and a second width at a second end, the first width being greater than the second width, and having a length greater than the first width.
  • Paragraph 22 The process according to Paragraph 21, wherein said first width is at least 1.2 times the second width.
  • Paragraph 23 The process according to Paragraph 21, wherein said first width is at least 1.5 times the second width.
  • Paragraph 24 The process according to Paragraph 21, wherein said first width is at least 2.0 times the second width.
  • Paragraph 25 The process according to Paragraph 21, wherein a shape of the anisotropic particles at the first end is at least substantially spherical.
  • Paragraph 26 The process according to Paragraph 21, wherein at least some of the anisotropic particles are stacked upon one another.
  • Paragraph 27 The process according to Paragraph 26 further comprising spherical particles arranged around and/or mixed with the stacked anisotropic particles.
  • Paragraph 28 The process according to Paragraph 1, wherein the lipids are fatty acids.
  • Paragraph 29 The process according to Paragraph 28, wherein the fatty acids are aliphatic fatty acids.
  • Paragraph 30 The process according to Paragraph 29, wherein the aliphatic fatty acids comprise aliphatic fatty acid molecules have fatty chains of uniform or different lengths.
  • Paragraph 31 The process according to Paragraph 30, wherein the length of the fatty chain comprises between about 3 and about 38 carbon atoms.
  • Paragraph 32 The process according to Paragraph 1, wherein the cellulosic fiber is from cotton.
  • Paragraph 33 The process according to Paragraph 1, wherein the cellulosic fiber is from a source selected from the group consisting of rayon, viscose rayon, liquid crystalline cellulose, lyocell fibers (e.g., TENCEL ® ), bacterial cellulose, and all plant based fibers such as wood pulp based microfibrils and jute, kenaf, ramie, sisal, flax, pineapple, banana, henequen, curaua, bagasse, bamboo, hemp, and fibrils derived from them.
  • a source selected from the group consisting of rayon, viscose rayon, liquid crystalline cellulose, lyocell fibers (e.g., TENCEL ® ), bacterial cellulose, and all plant based fibers such as wood pulp based microfibrils and jute, kenaf, ramie, sisal, flax, pineapple, banana, henequen, curaua, bagasse, bamboo, hemp, and fibrils
  • Paragraph 34 The process according to Paragraph 1, wherein the cellulosic fiber is in a form selected from the group consisting of fabric (woven, knitted, or nonwoven), yarn, fibers, filaments, microfibrils, and nanofibers.
  • Paragraph 35 The process according to Paragraph 1, wherein synthesizing the anisotropic particles comprises using a colloidal synthesis procedure with a surface stabilizer.
  • Paragraph 36 The process according to Paragraph 35, wherein the surface stabilizer comprises a mixture of one or more types of surface stabilizer of the same or different molecular weights.
  • Paragraph 37 The process according to Paragraph 35, wherein the surface stabilizer is an amphiphilic polymer having polar and non-polar sites.
  • Paragraph 38 The process according to Paragraph 35, wherein the amphiphilic polymer is a polyvinyl pyrrolidone (PVP) polymer.
  • PVP polyvinyl pyrrolidone
  • Paragraph 39 The process according to Paragraph 1, wherein covalently attaching the anisotropic particles to the non-superhydrophobic cellulosic fiber comprises a crosslinking procedure effective to increase durability of the cellulosic fiber composition having a superhydrophobic surface.
  • Paragraph 40 The process according to Paragraph 39, wherein the crosslinking procedures uses a crosslinker selected from the group consisting of 1,2,3,4-butanetetracarboxylic acid (BTCA), citric acid, maleic acid, and other polycarboxylic acids.
  • BTCA 1,2,3,4-butanetetracarboxylic acid
  • citric acid citric acid
  • maleic acid and other polycarboxylic acids.
  • Paragraph 41 The process according to Paragraph 39, wherein the crosslinking procedure is effective to produce crosslinking between the anisotropic particles and/or between the cellulosic fiber composition and the anisotropic particles.
  • Paragraph 42 The process according to Paragraph 39, wherein the crosslinking procedure further comprises crosslinking within cellulose molecules of the cellulosic fiber composition.
  • Paragraph 43 The process according to Paragraph 1, wherein the process is a fluorine-free process or a substantially fluorine-free process.
  • Paragraph 44 A cellulosic fiber composition having a superhydrophobic surface, said cellulosic fiber composition being produced by the process of any one of Paragraphs 1-43.
  • Paragraph 45 A product comprising a cellulosic fiber composition according to
  • Paragraph 46 The product according to Paragraph 45, wherein the cellulosic fiber composition is in a form selected from the group consisting of fabric (woven, knitted, or nonwoven), yarn, fibers, filaments, microfibrils, and nanofibers.
  • Paragraph 47 A cellulosic material having improved hydrophobicity, said cellulosic material comprising a cellulosic fiber composition according to Paragraph 44.
  • Paragraph 48 The cellulosic material according to Paragraph 47, wherein the cellulosic material is selected from the group consisting of viscose rayon, paper, liquid crystalline cellulose, cellulose acetate, lyocell fibers such as Tencel ® , bacterial cellulose and all plant based cellulosic fibers such as wood pulp based microfibrils and jute, kenaf, ramie, sisal, flax, pineapple, and banana, as well as yarns and fabrics made using them.
  • Figure l is a schematic representation of the colloidal synthesis of anisotropic
  • Figure 2 is a schematic of the chemical reaction between cellulose and heptanoic anhydride via esterification.
  • Figures 3A-3F are SEM images of cones ( Figures 3A-3C) and needles ( Figures 3A-3F).
  • Figures 4A-4D are cross-sectional TEM images of cones ( Figures 4A-4B) and needles ( Figures 4C-4D) at different magnifications.
  • Figures 5A-5B are ATR-FTIR spectra of cotton fabrics treated with (a) HA for
  • Figures 6A-6F are SEM images of (a) control ( Figure 6A); (b) HA ( Figure 6B),
  • Figures 7A-7D are SEM images of (a) PD-Si02(cones)-HA ( Figure 7A), (b)
  • Figures 8A-8B are graphs illustrating the effect of superhydrophobic treatment on
  • the present invention generally provides, inter alia , environment-friendly cellulosic compositions, products, and processes for their production.
  • the processes of the present invention involve the use of‘green’ chemistry principles to improve hydrophobicity and/or surface roughness of cellulosic materials, thereby yielding modified cellulosic
  • compositions having increased hydrophobicity and/or surface roughness are advantageous over prior art cellulosic compositions in that they are more durable in terms of their hydrophobicity and/or superhydrophobicity compared to cellulosic compositions not produced by the presently disclosed processes.
  • the present disclosure relates to a process for preparing a cellulosic fiber composition having a superhydrophobic surface.
  • this process includes the steps of: (a) synthesizing anisotropic particles of different shapes and covalently attaching them to a non-superhydrophobic cellulosic fiber, thereby yielding an intermediate cellulosic fiber composition having an altered surface; and (b) grafting long chain hydrocarbon lipids onto the altered surface of the intermediate cellulosic fiber composition, thereby lowering surface energy of the intermediate cellulosic fiber composition to yield a cellulosic fiber composition having a superhydrophobic surface.
  • This process is an improvement over existing processes at least in that it is a
  • the process of the present disclosure is a fluorine-free process or a substantially fluorine-free process.
  • synthesizing the anisotropic particles comprises using a colloidal synthesis procedure with a surface stabilizer.
  • a suitable surface stabilizer for use in this process can include, without limitation, a mixture of one or more types of surface stabilizer of the same or different molecular weights.
  • the surface stabilizer can include, without limitation, an amphiphilic polymer having polar and non-polar sites.
  • the amphiphilic polymer is a polyvinyl pyrrolidone (PVP) polymer.
  • covalently attaching the anisotropic particles to the non-superhydrophobic cellulosic fiber involves the use of a crosslinking procedure effective to increase durability of the cellulosic fiber composition having a
  • the crosslinking procedure is effective to produce crosslinking between the anisotropic particles and/or between the cellulosic fiber composition and the anisotropic particles.
  • the crosslinking procedure further involves crosslinking within cellulose molecules of the cellulosic fiber composition.
  • Non-limiting examples of crosslinkers that can be used in the crosslinking procedure of this process can include, without limitation, 1,2,3,4-butanetetracarboxylic acid (BTCA), citric acid, maleic acid, other polycarboxylic acids, and the like.
  • the present disclosure relates to a cellulosic fiber composition having a superhydrophobic surface, with the cellulosic fiber composition being produced by the process described herein.
  • the present disclosure provides a product comprising the cellulosic fiber composition as described herein.
  • the process of the present disclosure is effective to prepare a cellulosic fiber composition having a superhydrophobic surface.
  • the term “superhydrophobic” refers to a material having a water contact angle (WCA) of at least 150°.
  • WCA water contact angle
  • the term“superhydrophobic” is meant to also refer to a material that is “ultrahydrophobic.”
  • a cellulosic fiber composition having a superhydrophobic surface is one that has a water contact angle of at least 150°, 151°, 152°, 153°, 154°, 155°, 156°, 157°, 158°, 159°, and 160°.
  • non-superhydrophobic cellulosic fiber refers to any cellulosic fiber that does not have a water contact angle of at least 150°. More specifically, a “non-superhydrophobic cellulosic fiber” refers to a“hydrophilic cellulosic fiber.”
  • a cellulosic fiber composition prepared by the process of the present disclosure has a superhydrophobic surface.
  • the cellulosic fiber compositions prepared by the process of the present disclosure have increased hydrophobicity durability.
  • durability of the superhydrophobic properties of the cellulosic fiber compositions of the present disclosure can be measured by a laundering durability test, such as the American Association of Textile Chemists and Colorists (AATCC) test method 61-2003.
  • the cellulosic fiber composition prepared according to the process of the present disclosure has a durability characterized by a loss of water contact angle selected from the group consisting of less than 2 percent, less than 2.5 percent, less than 3 percent, less than 5 percent, less than 7 percent, and less than 8 percent, as confirmed by repeated standard laboratory laundry cycles.
  • a loss of water contact angle selected from the group consisting of less than 2 percent, less than 2.5 percent, less than 3 percent, less than 5 percent, less than 7 percent, and less than 8 percent, as confirmed by repeated standard laboratory laundry cycles.
  • one (1)“standard laboratory laundry cycle” corresponds to five (5) home washing cycles.
  • the repeated standard laboratory laundry cycles can include, without limitation, 2, 3, 4, 5, 6, 7, 8, 9, and 10 standard laboratory laundry cycles.
  • the anisotropic particles synthesized in accordance with the process of the present disclosure include, without limitation, anisotropic particles such as silicon oxides, silicon metal oxides, metal oxides, metal silicon oxides, halloysite nanotubes (HNTs), nanoclays, and polymers.
  • the anisotropic particles synthesized in accordance with the process of the present disclosure include, without limitation, anisotropic silica particles.
  • the anisotropic particles can include, without limitation, nanoparticles, microparticles, and/or mixtures thereof.
  • nanoparticles include particles having a mean diameter in at least one dimension selected from the group consisting of between about 1 and 40 nanometers (nm), between about 40 and 100 nm, and between about 100 and 1000 nm.
  • microparticles include particles having a mean diameter in at least one dimension selected from the group consisting of between about 1 and 2 microns (pm), between about 2 and 3 pm, and between about 3 and 4 pm.
  • the anisotropic particles can have, without limitation, a mean diameter in at least one dimension of between about 1 and 100 nm and in at least one other dimension of up to 2 pm.
  • the anisotropic particles can have, without limitation, different mean diameters in at least one dimension, with the different mean diameters being selected from the group consisting of between about 40 nm and 100 nm, between about 100 nm and 2 pm, and between about 1 pm and 4 pm.
  • the anisotropic particles can be, without limitation, uniformly or substantially uniformly distributed on the superhydrophobic surface of the cellulosic fiber composition.
  • the anisotropic particles cover a percentage of the superhydrophobic surface.
  • the anisotropic particles can cover at least 40 percent, at least 50 percent, at least 60 percent, at least 70 percent, at least 80 percent, or at least 90 percent of the superhydrophobic surface of the cellulosic fiber composition according to the present disclosure.
  • the anisotropic particles can be of different shapes.
  • the anisotropic particles are needle-shaped particles.
  • the anisotropic particles are cone-shaped particles.
  • the cone-shaped particles have a mean or median aspect ratio
  • the cone- shaped particles are oriented on the superhydrophobic surface with their vertex end upward or their vertex end downward. In certain embodiments, the cone-shaped particles are oriented on the superhydrophobic surface with some of the cone-shaped particles with their vertex end upward and some with their vertex end downward.
  • the anisotropic particles are spherical particles. In certain embodiments, the spherical particles have a diameter of between about 40 nm and 4 pm.
  • the anisotropic particles can include a combination of needle-shaped particles, cone-shaped particles, and/or spherical particles.
  • the anisotropic particles of different shapes can include, without limitation, elongated particles having a first width at a first end and a second width at a second end, the first width being greater than the second width, and having a length greater than the first width.
  • the first width is at least 1.2 times the second width.
  • the first width is at least 1.5 times the second width.
  • the first width is at least 2.0 times the second width.
  • the shape of the anisotropic particles at the first end is at least substantially spherical.
  • the anisotropic particles are stacked upon one another.
  • the anisotropic particles are stacked upon one another can further include spherical particles arranged around and/or mixed with the stacked anisotropic particles.
  • the lipids are fatty acids. More particularly, in certain embodiments, the fatty acids are aliphatic fatty acids. In certain embodiments, the aliphatic fatty acids can include aliphatic fatty acid molecules having fatty chains of uniform or different lengths.
  • the lengths of the fatty chains of the fatty acids can be of any known length, particular embodiments can include fatty chains that comprise between about 3 and about 38 carbon atoms in length. More particularly, the fatty chains can correspond to the following fatty acids: propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoic acid, heneicosanoic acid, docosanoic acid, tricosanoic acid, tetracosanoic acid, pentacosanoic acid,
  • tritriacontanoic acid tritriacontanoic acid, tetratriacontanoic acid, pentatriacontanoic acid, hexatriacontanoic acid, heptatriacontanoic acid, and octatriacontanoic acid.
  • the cellulosic fiber, cellulosic fiber composition, product comprising the cellulosic fiber composition, and/or cellulosic material comprising the cellulosic fiber composition can be in various forms known in the art with respect materials having a cellulosic surface. Suitable forms of the cellulosic fiber, cellulosic fiber composition, product comprising the cellulosic fiber composition, and/or cellulosic material comprising the cellulosic fiber composition of the present disclosure can include, without limitation, a form selected from the group consisting of fabric (woven, knitted, or nonwoven), yarn, fibers, filaments, microfibrils, and nanofibers.
  • the cellulosic fiber, cellulosic fiber composition, and/or cellulosic material is from cotton.
  • the cellulosic fiber, cellulosic fiber composition, and/or cellulosic material is from a source selected from the group consisting of rayon, viscose rayon, liquid crystalline cellulose, lyocell fibers (e.g., TENCEL ® ), bacterial cellulose, and all plant based fibers such as wood pulp based microfibrils and jute, kenaf, ramie, sisal, flax, pineapple, banana, henequen, curaua, bagasse, bamboo, hemp, and fibrils derived from them.
  • the product of the present invention can be any material or item that is used for protection, particularly as a water-repellant material.
  • suitable examples of such materials or items include, but are not limited to, any sort of apparel, outerwear, underwear, linens, blankets, coverings, banners, shoes, coats, jackets, sweaters, socks, headgear, tents, curtains, drapes, fabric, swimsuits, umbrellas, diapers, bandages for wounds, vehicle covers, awnings, and the like.
  • the present disclosure relates to, inter alia , a 'green' process for obtaining superhydrophobic cotton fabrics using anisotropic silica particles and lipids.
  • the present disclosure provides a 'green' sustainable two-step process to create superhydrophobic cotton fabrics.
  • the disclosed process includes: (i) a first step in which anisotropic silica particles of different shapes are synthesized and covalently attached to the cotton fabrics; and (ii) a second step in which long chain hydrocarbon lipids are grafted to lower the surface energy to obtain superhydrophobic characteristics.
  • the technology and processes of the present disclosure yield superior results over the current state of the art, including various improved properties of the processed cotton fabrics.
  • the loss of water contact angle (WCA) after laboratory laundry cycles (e.g., 6, 7, 8, etc.) or home washing (e.g., 30, 35, 40, etc.) is less than 2%, less than 2.5%, less than 3%, less than 5%, less than 7%, or less than 8%, etc.
  • the process is effective to yield cotton fabrics having a water contact angle of at least 156°, at least 157°, and at least 158°.
  • the process is effective to yield cotton fabrics exhibiting dramatic improvements over the state of the art.
  • the cotton fabrics produced according to the present disclosure exhibited much better resistance to wash due to the structural difference: cone shaped nanoparticle overlap with each other to form network with the round head of the cone protrude the surface of the fabric mimicking the lotus leaf structure vs. loose pure spherical nanoparticles covered the fabric.
  • the loss of WCA for the cotton fabrics of the present disclosure after 7 laundry cycle was only 2.55% (157° to 153°), while the loss of WCA for cotton fabrics made in accordance with other processes known in the art was shown to be almost 10%.
  • silica particles with different shapes were synthesized using water-in-alcohol emulsion and different molecular weights (MW) of polyvinyl pyrrolidone (PVP).
  • Low MW PVP resulted in a combination of spherical and cone-shaped particles while high MW PVP resulted in needle- shaped particles.
  • Particles were covalently bonded to the fabrics to create desired permanent surface roughness.
  • fabrics with altered-surfaces were grafted with fatty acid to lower the surface energy of fabrics. Covalent bonding of particles and grafting of fatty acids onto the fabrics was confirmed using ATR-FTIR. The combination of surface roughness obtained through silica particles and low surface energy of the fatty acid resulted in
  • an objective of the present disclosure was to create
  • the synthesized sphere + cone and needle-shaped silica particles were covalently bonded onto the cotton fabrics, separately, using a simple dip-cure method.
  • the covalent bonding of the particles permanently altered the surface topography of the fabrics and increased the durability of the treatment.
  • Seven-carbon aliphatic chains were then grafted on to the surface- altered fabrics using a simple dip-cure method via esterification as shown in the chemical reaction in Fig. 2.
  • hydrophobicity of other cellulose fibers such as viscose rayon, liquid crystalline cellulose, cellulose derivatives such as cellulose acetate, lyocell fibers such as Tencel ® , bacterial cellulose and all plant based cellulosic fibers such as jute, kenaf, ramie, sisal, flax, pineapple, banana, and many others as well as yams and fabrics made using them.
  • the ‘green’, fluorine-free process developed in this study can be easily scaled up for other cellulosic materials such as viscose rayon, paper, micro-fibrillated cellulose, etc., to expand their applications in self-cleaning surfaces, water-repellent protective coatings, packaging, polymer composites, electronics and others.
  • cellulosic materials such as viscose rayon, paper, micro-fibrillated cellulose, etc.
  • One aim of the research of this example was to create a fluorine-free and facile process to obtain superhydrophobic cotton fabrics that uses non-toxic and inexpensive materials and can be easily scaled up for industrial production.
  • Colloidal syntheses of different shapes (spheres + cones and needles) of silica (Si02) particles were carried out using two different molecular weights (MWs) of the emulsion stabilizer, polyvinyl pyrrolidone (PVP) as shown in the schematic representation in Fig. 1.
  • the synthesized sphere + cone and needle-shaped silica particles were covalently bonded onto the cotton fabrics, separately, using a simple dip-cure method for the first time.
  • the covalent bonding of the particles permanently altered the surface topography of the fabrics and increased the durability of the treatment.
  • Seven-carbon aliphatic chains were then grafted on to the surface-altered fabrics using a simple dip-cure method via esterification as shown in the chemical reaction in Fig. 2.
  • the presence of Si02 particles on the surface creates micro- structured pockets that act as air gaps at the interface between the fabric and the water droplet, enhancing the WCA of the fabrics.
  • the combined effects of surface roughness created by two different types of Si02 particles and the low surface energy caused by the aliphatic chains on the hydrophobicity of the fabrics were studied.
  • Polyvinylpyrrolidone) (PVP) with molecular weights (MWn) of 8000 and 40,000 were purchased from Sigma Aldrich, Allentown, PA.
  • 1-pentanol was purchased from Krackeler Scientific, Inc. Albany, NY.
  • Heptanoic anhydride (HA) was purchased from TCI America, Philadelphia, PA.
  • Ethanol >99.5% purity, absolute
  • sodium citrate sodium citrate
  • ammonium hydroxide ⁇ 28% NH4OH
  • BTCA butane tetra carboxylic acid
  • SHP sodium hypophosphite monohydrate
  • Milli-Q deionized water (resistivity, 18.2 MW.ah, Millipore RiOs and Elix water purification systems, Millipore Corporation, MA) was used for hydrolysis of TEOS and deionized (DI) water was used for the measurement of WCA.
  • TEOS and NH4OH, 300 m ⁇ and 500 m ⁇ , respectively, were added to the emulsions and left stirring at 300 rpm at room temperature for 18 h.
  • the emulsion was centrifuged at 20,000 rpm for 20 min and the supernatant was discarded.
  • the precipitate was dissolved in ethanol using vortex meter and centrifuged again at 20,000 rpm for 20 min. This process was repeated thrice to remove the surplus reactants.
  • S1O2 and Xlink-SiCk fabrics were grafted with low surface energy molecules, on the surface.
  • Cotton fabrics were dipped in HA and squeezed by hand to remove excess HA. They were further dipped and squeezed again and cured at 130°C in an air-circulating oven for required time. The fabrics were then rinsed with ethanol to remove the by-product, heptanoic acid and unreacted HA, if any. The fabrics were then dried at 50°C in an air-circulating oven to get rid of the treatment odor.
  • the cotton fabrics with physically deposited sphere + cone-shaped and needle-shaped S1O2 particles and treated with HA are termed as PD-Si02(cones)-HA fabrics and PD-Si02(needles)-HA fabrics, respectively.
  • the covalently bonded sphere + cone-shaped and needle-shaped S1O2 particles on cotton fabrics and further treated with HA are termed as Xlink- Si02(cones)-HA fabrics and Xlink-Si02(needles)-HA fabrics, respectively.
  • ATR-FTIR The ATR-FTIR spectra collected using Thermo Nicolet Magna-IR 560 spectrometer (Madison, WI) with a split pea accessory was used to confirm the grafting of both S1O2 particles as well the aliphatic fatty chains onto the cotton fabrics. Each scan was an average of 300 scans from 4000 cm 1 to 500 cm 1 wavenumbers.
  • Tensile properties Tensile strength of the fabrics was determined according to ASTM D5035 strip method. Fabrics having dimensions of 25 mm x 150 mm were cut and tested on Instron universal testing machine (model 5566, Canton, MA) at a gage length of 75 mm and crosshead speed of 300 mm/min (strain rate of 4mm 1 ). Six specimens each from different areas of the fabrics in both warp and weft directions were tested to obtain average values.
  • PVP has both polar and non polar binding sites and can act as an emulsion stabilizer by prohibiting the droplets from coalescing [29, 30]
  • water is added to the high concentrated PVP solution (in pentanol)
  • the water molecules bind to the PVP and water no longer acts only as a site for hydrolysis of TEOS, but also acts as a structure-directing agent due to bound PVP as shown earlier [31]
  • the ionic species induced after addition of sodium citrate creates inverse emulsion due to phase separation causing aqueous droplets to be dispersed in the pentanol-rich continuous phase
  • the silica precursor, TEOS when added to the emulsion, goes to the water phase and gets hydrolyzed [27] Ethanol facilitates the hydrolysis of TEOS.
  • Fig. 1 shows the SEM images of the particles made using 8K and 40K PVP at different reaction times.
  • the average diameter of the needle-shaped particles was found to be 189 nm and the average length to be 3.8 pm after 18 h of reaction. It was observed that the diameter of the particles decreased, and the length increased when higher MW PVP was used.
  • the 40K PVP has longer chain lengths and higher molecular entanglements as compared to 8K PVP. This may be a factor why 40K PVP resulted in smaller droplet size in the emulsion as shown the Fig. 1. As a result, the diameter of the needle-shaped particles was much lower as compared to that of cone shaped particles.
  • Fig. 4 shows TEM images of the cross sections of the sphere + cone and needle- shaped particles at different magnifications. From their cross-sectional views seen in these images it can be concluded that the synthesized particles are solid and not hollow, and no core shell structure exists.
  • FIG. 5A shows ATR-FTIR spectra of the cotton fabric and the cotton fabrics treated with HA for 10, 20, and 30 min at 130°C.
  • Control cotton fabrics show a broad peak between 3400 cm 1 and 3200 cm 1 which is due to the stretching of hydroxyl groups in cellulose as well as the absorbed moisture [34]
  • the peak at 2902 cm 1 is due to the symmetric C-H and C-H2 stretching vibrations and the peak around 1053 cm 1 and 1030 cm 1 is due to the C-O-C stretching absorption.
  • the degree of substitution of the hydroxyl groups from cellulose increases with increase in treatment time as seen from the increasing intensity of the peak at 1730 cm 1 in Fig. 5 A. While the control fabrics can be quickly and completely wetted by water, WCAs of the fabrics treated with HA were found to be 112°, 120° and 127° after 10, 20, and 30 min of treatment time, respectively.
  • the esterification results in the covalent attachment of the flexible seven-carbon planar zigzag aliphatic chains of HA which form a layer on the surface of the fibers in the fabric making it hydrophobic.
  • the surface polarity of the fabrics decreases as the hydroxyl groups from the cellulose are substituted by long aliphatic chains which have low surface energy.
  • Fig. 5B shows ATR-FTIR spectra of PD-S1O2 fabrics and Xlink-SiCk fabrics. As seen in Fig. 5B, an additional small peak is observed in both physically deposited and covalently bonded S1O2 cotton fabrics at 800 cm 1 .
  • This peak is the characteristic stretching vibration peak for Si-O-Si from the S1O2 particles [40]
  • the intensity of the peak at 1053 cm 1 is lower than the intensity of the peak at 1030 cm 1 for the control cotton fabrics.
  • the peak between 1015 cm 1 and 1060 cm 1 corresponds to C-0 stretch in cellulose.
  • the Si-O-Si asymmetric stretch overlaps with the C-0 stretch in cellulose [34]
  • the intensity of peak at 1053 cm 1 increases (Fig. 5B). This is due to the presence of Si-O-Si from the S1O2 particles.
  • An additional peak at 1722 cm 1 is observed in the Xlink-Si02 fabrics.
  • This peak is the result of the ester bonds formed by the co condensation of Si-OH from the particles and the -COOH from BTCA as well as the reaction between -OH from cellulose and the -COOH from BTCA.
  • Polycarboxylic acids such as BTCA are often used as heterogenous crosslinkers to improve the bonding between the inorganic- organic interfaces, especially between silica particles and cellulose [41-44]
  • BTCA has four carboxyl groups which can react with both, the S1O2 particles as well as the cellulose from the fabric and act as a crosslink (bridge) between the two. This covalent bonding between S1O2 particles and fabrics prevent these particles from leaving fabric during use and laundering and, thus, increases the washing durability.
  • Xlink-Si02(needles)-HA (40K PVP) fabrics was found to be 153°.
  • Fig. 6 shows the SEM images of the fibers taken from control and treated fabrics along with the digital photographs of the WCA test.
  • the surface of the control cotton fibers (Fig. 6A) is mostly smooth and flat with some convolutions and natural creases and does not change after the HA treatment (Fig. 6B).
  • the Xlink-Si02(cones)-HA and Xlink-Si02(needles)-HA fibers show that the surface of the fibers is coated with S1O2 cones and needles, respectively. This changes the surface topography of the fabrics and creates a desired surface roughness.
  • the concentration of the S1O2 particles used to treat the cotton fabrics was varied from 0.05% to 0.5%.
  • Supplementary material shows the effect of S1O2 concentration on WCA of the fabrics. It was observed that the WCA increased from 152° to 157° as the concentration of the sphere + cone shaped particles increased from 0.05% to 0.1%. However, further increasing the concentration of sphere + cone shaped particles to 0.3% or even 0.5% did not increase the WCA of the fabrics. Similar behavior was observed for the fabrics treated with needle shaped particles.
  • Supplementary material shows the SEM images of Xlink-0.5% Si02(cones)-HA and Xlink-0.5% Si02(needles)-HA. Some particle clusters can be observed at 0.5% S1O2
  • Table 1 shows the effect of laundering (up to 7 laboratory laundry cycles) on the durability of the superhydrophobic treatment. The washings were carried out according to the modified AATCC Test Method 61- 2003. Each laboratory laundry cycle, as mentioned earlier, corresponds to 5 home laundry washes. As can be seen from data in Table 1, WCA decreased slightly with the number of laundry cycles. The decrease in the WCA was higher for the physically deposited particles as compared to the crosslinked particles as could be expected.
  • Fig. 7 shows the SEM images of fibers after 7 laundry cycles. As seen in Fig. 7A and Fig. 7C, the surface of the physically deposited fibers is only partially covered with cone-shaped and needle-shaped particles, respectively as some of the particles are detached from the surface of the fibers during washing.
  • FIG. 8 shows the effect of superhydrophobic treatment on the tensile (fracture) stress and strain of the fabrics in both warp and weft directions.
  • the tensile stress values for control and the HA treated fabrics in the warp direction are 56.8 MPa and 55.5 MPa, respectively.
  • No change in the tensile stress was observed after grafting HA onto fabrics as it is simply a surface treatment and has no effect on the fiber morphology.
  • Fig. 8B shows the effect superhydrophobic treatment on the tensile strain of the fabrics in both warp and weft directions.
  • the tensile strain of the HA treated fabrics increased slightly from 6% for control to 7.1% for the HA treated fabrics in the warp direction.
  • the increase in the strain in the warp direction could be primarily due the relaxation of the built-up stress while weaving and finishing of the fabrics.
  • the tensile stress values of the PD-SiCk-HA and Xlink-SiCk-HA fabrics reduced to 50.2 MPa and 29 MPa, respectively.
  • the slight reduction in the tensile stress of the PD-SiCk-HA fabric could be due to the heat treatment.
  • the superhydrophobic fabrics obtained in accordance with the research of this example are durable to laundry washings and can find applications in various areas such as outerwear, protective clothing, medical apparel and others. Supplementary material show that water beads up on the treated fabrics without wetting the surface. Also, when held at an angle, the water simply flows down without wetting the fabric.
  • the superhydrophobic fabrics developed in this research support applications such as‘easy-cleaning’ fabrics and water- repellent clothing.
  • the treated fabrics are oil absorbent. Such materials can find applications in oil-absorbent wipes or even cleaning up oil-spills from oceans.
  • The‘green’ process developed in this research can be easily extended to other cellulose materials which can be used in developing biodegradable packaging films, microfluidic devices or oil-water separating membranes.
  • This study presents a bioinspired‘green’ process to create superhydrophobic cotton fabrics using S1O2 particles and HA.
  • Different molecular weights of PVP were used which acted as emulsion stabilizer as well as directing agents for the 1 dimensional growth of S1O2 particles.
  • Higher molecular weight PVP (40K) produced smaller droplets in the emulsion and gave needle-shaped longer particles as compared to the lower molecular weight PVP (8K).
  • Lower molecular weight PVP produced a mixture of spherical and cone-shaped particles.
  • Spherical + cone-shaped and needle-shaped particles were covalently bonded onto the cotton fabrics, separately, to create a desired and permanent surface roughness and then treated with HA to lower the surface energy of the fabrics to get superhydrophobic fabrics.
  • WCA of 157° was obtained using cone-shaped S1O2 particles.
  • Anisotropic S1O2 particles are crucial for creating desired dual size surface roughness or texture on the fabric surface which enhance their WCA as compared to spherical shaped particles which have been used to create surface roughness.
  • the facile approach for synthesizing anisotropic S1O2 particles used in this study is easily scalable for large scale commercial production.
  • grafting of nontoxic fatty acid to lower the surface energy of the fabrics used in this study, compared to the current use of expensive fluoropolymers which are toxic in nature creates a fully‘green’ process to obtain superhydrophobic cotton fabrics.
  • the ‘green’ process developed here can be easily scaled-up and applied to other cellulosic materials such as viscose rayon, paper and others to expand their applications for uses including self cleaning surfaces, water-repellent protective coatings, medical apparel, packaging, electronics, composites, and many others.

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  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
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  • Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
  • Chemical Or Physical Treatment Of Fibers (AREA)

Abstract

L'invention concerne un procédé pour la préparation d'une composition de fibre cellulosique ayant une surface superhydrophobe, comprenant : (a) la synthèse de particules anisotropes de différentes formes et la fixation de manière covalente de celles-ci à une fibre cellulosique non superhydrophobe, ce qui permet de produire une composition de fibre cellulosique intermédiaire ayant une surface modifiée ; et (b) le greffage de lipides hydrocarbonés à chaîne longue sur la surface modifiée de la composition de fibre cellulosique intermédiaire, ce qui permet d'abaisser l'énergie de surface de la composition de fibre cellulosique intermédiaire pour produire une composition de fibre cellulosique ayant une surface superhydrophobe. L'invention concerne également des compositions de fibres cellulosiques formées à partir de ce procédé et des produits contenant les compositions de fibres cellulosiques.
PCT/US2020/032279 2019-05-10 2020-05-10 Compositions de fibres cellulosiques ayant des surfaces superhydrophobes et procédés écologiques pour leur production WO2020231887A1 (fr)

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