WO2014049208A1

WO2014049208A1 - Hydrophobic material and method of producing the same

Info

Publication number: WO2014049208A1
Application number: PCT/FI2013/050936
Authority: WO
Inventors: Saila SEPPO
Original assignee: Greenbutton Oy
Priority date: 2012-09-25
Filing date: 2013-09-25
Publication date: 2014-04-03

Abstract

A method of manufacturing a hydrophobic material from a nanocellulose raw-material and a hydrophobic substance. The method comprises providing a fatty oil contacting the fatty oil with finely-divided nanocellulose raw-material, soaking the nanocellulose raw-material with the fatty oil, and forming said material into a composition of fatty oil containing nanocellulose material to obtain a hydrophobic material. The material produced can be used in anti-fouling of surfaces, filters,membranes, actuators, in packaging materials, in self-cleaning surfaces and dirt-repellent surfaces, as coatings for miniaturized sensors, in biochips, as plasticine, in decorations, in art work, electronics, shipbuilding and in the marine industry.

Description

Hydrophobic material and method of producing the same

Field of Invention The invention relates to a method for preparing flexible hydrophobic material, the material prepared by this method and the use of the material thus obtained.

Background There are two kinds of surfaces found in living organisms. One of them is

hydrophobic and the other one is hydrophilic. "Hydrophobic" means dislike of water or dispelling away from water. By contrast, hydrophilic means that the surface "likes" or is attracted to water. The differences between the properties can be attributed to differences in chemical structures or, more specifically, to differences in charges or polarity of the two surface.

It is well known that leaves of Lotus-plant have hydrophobic, self-cleaning surface.

Titanium dioxide pigments is treated after production with silicon compounds to render them hydrophobic so that they can be used in plastic industry.

Superhydrophobic coatings and liquid-repellent material are disclosed in previous patents publications, for example WO2004/113456 and WO2011/001036.

A fatty acid is a carboxylic acid with a long aliphatic chain. Fatty acids include for example stearic, palmitic or oleic acids.

Olive oil is a fat obtained from the olive, which is the fruit of Olea europaea. Olive oil contains saturated fats like palmitic acid (5.5- 0%), stearic acid (0.5-5.0%), and small amounts arachidic acid, behenic acid, myristic acid, and lignoseric acid. It contains monounsaturated fats like oleic acid (55-83%) and palmitoleic acid (0.3-

3.5%)), polyunsaturated fats like linoleic acid (3.5—21%) and a-linolenic acid (<1.0%).

Sunflower contains palmitic acid (4-9%), stearic acid (1-7%), oleic acid (14-40%), and linoleic acid (48-74%). Rape oil contains about 6% saturated fats, about 60% monounsaturated fats, about 22% linoleic acid and 11 % a-linolenic acid.

Cellulose (CeHioC^n is a long-chain β-D-glucose molecule, consisting of a

polysaccharide. The cellulose is not soluble in water or in oil. Wood contains 33 to 50 percent of cellulose. Cellulose is the most common organic compound on earth.

The term "nanocellulose" in this document includes, for example, products that are frequently called fine cellulose fibers, microfibrillated cellulose (MFC) fibers, cellulose nano fibers (NFC), microcellulose, micro crystalline cellulose and level-off DP (degree of polymerization) cellulose.

Nanocellulose has the same molecular formula as standard cellulose, but it differs in the characteristics. Nanocellulose can be obtained from wood, straw, sugar beet and potatoes.

Nanocellulose comprises of nanocellulose fibrelles, which have a substantially greater length than width (aspect ratio of at least 100 or more, more preferably 1000 or more). The small crystal and/or particle size means large specific surface area, high strength and biodegradability.

Nanocellulose manufacturing processes are, for example, illustrated in the following publications: WO2011128322, TW201030196, JP 2004204380, US 7381294, RU

2298562, CN 102182089, WO2011154600.

Nanocellulose is used as an additive in renewable and biodegradable composites, where it strengthens the structure. Plaster and cement industries utilize also the high strength of the nanocellulose by using it as an additive, cf. for example WO0228795.

In addition to the above, nanocellulose can be used, inter alia, to prevent the flow of oxygen between materials, as a flocculant and as a rheology modifier, and even in energy storage in modern forms of batteries. For example tunable oleophobicity have been obtained by structured porous aerogels produced from nanofibrillated cellulose. The aerogel was produced by freeze-drying method (cf. Aulin, Christian, Julia Netrval, Lars Wagberg and Tom Lindstrom, Soft Matter 2010, vol. 6, issue 14, p. 3298). Aerogels could be mechanically robust, but their production method needs several steps. As mentioned above, "nanocellulose" also includes microcellulose:

Microcellulose comprises of microcellulose fibrelles, which have a substantially greater length than width (aspect ratio of at least 100 or more, more preferably 1000 or more). The small crystal and/or particle size means large specific surface area, high strength and biodegradability.

Microcellulose is used as an additive in renewable and biodegradable composites, where it strengthens the system. Plaster and cement industries utilize also the high strength of the microcellulose by using it as an additive, cf. for example WO0228795.

Nano- and microcellulose have the same molecular formula than the standard cellulose, but it differs in the characteristics. Nano- and microcellulose could be obtained from wood, straw, sugar beet and potatoes. Manufacturing processes are, for example, illustrated in the following publications: WO2011128322, TW201030196, JP 2004204380, US 7381294, RU 2298562, CN 102182089, WO2011154600.

Earlier super-amphiphobic surfaces have been obtained by using surface modifiers on processed nanocellulose, cf. WO 2011/001036. There is a need for novel materials which have good hydrophobic properties, which can be easily formed and shaped and which can be produced at low cost on an industrial scale.

Summary of the Invention Based on the above, it is an aim of the present invention to solve at least a part of the problems of the art and to provide a novel material and methods of producing the same.

The present invention relates to a material, which is a composition of a nanocellulose raw- material and fatty oils, said material being hydrophobic. The present invention is based on the finding that nanocellulose is capable of sorbing oil and fatty acids when mechanically contacted, for example by mixing, with them and, furthermore, when soaked with oil or fatty acids up to saturation, the nanocellulose will retain the absorbed oil or fatty acid. The composition thus obtained exhibits hydrophobic properties but will not feel "oily" or "fatty" on the surface.

In particular, the material is hydrophobic also against hot water and it is repellent against solid fats. The composition material is gas-permeable. Thin and very thin layers of the material are flexible

Thus, the present invention relates to a method for manufacturing a material, wherein the method comprises the steps of

- providing a fatty oil selected from plant oils, like olive oil, sun flower oil and rape oil,

- contacting the fatty oil with a finely-divided nanocellulose raw-material,

- absorbing and preferably saturating the nanocellulose raw-material with the fatty oil, and

- forming said material into a composition of nanocellulose raw-material to obtain a hydrophobic material.

The present invention also relates to the use of said material in self-cleaning and dirt- repellent surfaces, in anti- fouling surfaces, filters, membranes, actuators, as plasticine, as gaspermeable carrier, and in gas extraction from liquids, as thermal insulator, in traffic, aeroplanes, decorative articles and objects, etc.

Hydrophobic materials has been made earlier by using nanocellulose, mainly

using surface treatment on an expensive aerogel. In connection with the present invention is has surprisingly been found that a hydrophobic material can be produced without any surface treatment or use of any adhesives, glues or resins.

More specifically, the method according to the present invention is mainly characterized by what is stated in the characterizing part of claim 1. The product produced is characterized by what is stated in the characterizing part of claim 12.

The uses according to the present invention are characterized by what is stated in claim 14.

The invention provides considerable advantages. The present material, which can be characterized as a "biomaterial" in the sense that it consists essentially of a material derived from a natural polysaccharide obtained from renewal sources, is produced easily by mixing two natural products (nanocellulose raw-material and oil or fatty acid).

The present material can be colored and modeled. It can have inside medical tablets or other particles. It can contain hydrophilic particles or subjects or rusting materials inside it. It can contain threads and it can hang in air or in water with those threads. It was surprisingly found that the novel material can be cut into thin slices. It is gas- permeable.

Quite surprisingly, the material reacts with hot water differently depending on the freshness of the material.

In one aspect, the present invention relates to aged materials, i.e. materials which have been preserved for more than 4 h, in particular more than 12 h, suitable more than 24 h after preparation. Description of Embodiments

The term "hydrophobic" denotes materials which - generally speaking - repel water and humidity. The term "finely-divided" stands for a material comprised of particles having particles sizes (average) in the range of less than 100 um. Preferably, the finely-divided material comprises substances formed by the particles which are at least partially loose and free flowing. Powders are particularly preferred. The term nanocellulose raw-material includes nanocellulose, fine cellulose fibers, microfibriUated cellulose (MFC) fibers, cellulose nano fibers (NFC), microcellulose, micro crystalline cellulose and level-off DP (degree of polymerization) cellulose. The nanocellulose raw-material preferably meets one or several of the following criteria:

- it has a crystal size of less than one micron,

- a particle size of less than 100 micrometers, preferably less than 50 micrometers,

- it is provided in the form of a powder having a bulk density of less than 500 grams per liter, preferably less than 100 grams per liter, and

- the dryness of the nanocellulose is more than 90 % by weight.

The terms "fatty acid" or "fatty acid or oil" is used in the following to denote fats, oils and fatty acids of various kinds, as will be explained in the following. The present invention is applicable to all kinds of, primarily, natural material ("hydrophobic agents") which are capable of rendering the polysaccharide hydrophobic. In addition to purely natural oils, acids and fats also various derivatives thereof can be used.

The fats or fatty acid or combination of fats and fatty acids, are selected from plant oils, such as from the group of olive oil, rape oil and sun flower oil and combinations thereof. Generally, fatty acids and fats suitable for the present invention are exemplified by coconut oil, palmseed oil, babassu oil, muscat butter oil, laurel seed oil, palm oil, cocoa butter, oleic and linoleic acids, tall oil, rapeseed and canola oil, olive oil, peanut oil, sesame oil, maize oil, sunflower oil, poppy seed oil, cottonseed oil and soy oil, perilla oil and hemp oil, rapeseed oil and mustard seed oil. Also derivatives of natural fats, including mono- or diglycerides of Cio to C28 fatty acids, can be employed.

In an advantageous embodiment, fatty acid or oil is added to a dry nanocellulose raw- material, for example a dry powder. The amount of fatty acid or oil added is at least essentially equal to the amount of such substance needed for thoroughly soaking the material, i.e. the amount of fatty acid or oil corresponds to the amount which the material is capable of taking up.

In the present context, the term "dry" when used in conjunction with the raw-material stands for a moisture content of less than 10 %, in particular less than 7.5 %, advantageously less than 5 %, suitably less than 2.5 % and preferably less than 1 % by total weight of the raw-material. Typically, commercial, dry nanocellulose raw-materials - as defined above - contain about 0.1 up to 10 % by weight of moisture. As discussed above, in the present invention, a hydrophobic material is produced from a nanocellulose raw-material and a hydrophobic substance. The method comprising the steps of

- contacting the fatty oil with finely-divided nanocellulose preferably in the form of a dry powder,

- soaking the nanocellulose with the fatty oil, and

- forming, for example by mechanically shaping, optionally kneading, said material into a composition of nanocellulose to obtain a hydrophobic material.

The contacting step comprises mechanically contacting finely-divided nanocellulose with fatty oil, and contacting is continued until a significant part of the nanocellulose is saturated with the fatty oil. Contrary to methods known in the art, there is typically no chemical reaction involved in the contacting step according to the present technology.

The addition of fatty oil (or other hydrophobic agent) can take place at ambient temperature (about 20 to 30 °C) and pressure. It is possible to operate at higher or lower temperatures preferably as long as the hydrophobic agent is in liquid form. To enhance absorption of water into the material, addition can be accompanied by agitation of the components.

In a preferred embodiment, nanocellulose is 60% moistened, more preferably 80% moistened and most preferable 100 % moistened with the fatty oil. Here the term

"moistened" is used interchangeably with "soaked" or "absorbed with" to designate that fatty oil or a similar hydrophobic agent is sorbed into the material which will retain it.

After the contacting step, the material is preferably left to settle for 5 hours, more preferably 10 hours, most preferably 24 hours or more. Any unabsorbed fatty oil is removed from the surface of the hydrophobic material thus obtained, for example by absorbing it to an absorbent, such as blotting paper.

Generally, the solid products obtained upon drying have a density of 50-800 kilograms per cubic meter, and they contain at least 1 % by weight up to about 90 % by weight, for example about 5 to 85 % by weight of hydrophobic agent (fatty oil etc.) calculated from the total weight of the composition.

As indicated above, the material can be used in various applications and for those purposes it can be shaped into various forms.

Generally, the hydrophobic material thus obtained is mechanically shaped, for example pressed to a disc or panel or plate, or produced to a ball or a bar or/and the material is coloured.

For the purpose of the present technology, the nanocellulose raw-material meets one or several of the following criteria:

- it has a has crystal size of less than one micron,

- a particle size of less than 100 micrometers, preferably less than 50 micrometers, - it is provided in the form of a powder having a bulk density of less than 500 grams per liter, preferably less than 100 grams per liter, and

- the dryness of the nanocellulose is more than 90 % by weight.

The novel materials thus produced can be applied in a number of uses. Examples include the following: anti-fouling of surfaces, filters, membranes, actuators, in packaging materials, in self-cleaning surfaces and dirt-repellent surfaces, as coatings for miniaturized sensors, in biochips, as plasticine, in decorations, in art work, in electronics, in

shipbuilding and in marine industry. Examples

The following non-limiting examples illustrate the invention. The examples described have bee carried out using household and kitchen utensils, devices and materials. That gives a good opportunity to use this invention very widely.

Microcellulose was employed in dried form. Two grades, M 0 and M90, supplied by J. RETTENMAIER & SOHNE GMBH+CO.KG, Germany, were employed.

Nanocellulose powder obtained from Aalto exhibited (in dry form) a weight per volume of less than 500 grams per liter, for example less than 150 grams per liter. The mean agglomerate size of the nanocellulose powder was 20-40 micrometer, measured by laser diffraction method. According to the electron microscope pictures the crystal size was about 100-300 nm.

The nanocellulose raw-material powder possesses preferably a weight per volume of less than 500 grams per liter, for example less than 150 grams per liter. Mean agglomerate size of nanocellulose powder was 20-40 micrometer measured by laser

diffraction method. According to the electron microscope pictures the crystal size is about 100-300 nm.

Example 1

A material was prepared by mixing olive oil to nanocellulose powder until the

nanocellulose was totally moistened. The material looked like a jelly, but it could be cut into thin slices like bread. The surface of the slices looked similar as it

were a spongy cake. The material was produced to a ball. It was easy to model it.

Then it was left to settle for a couple of days.

The material was placed in a bowl and water was added. The material was not

interfered with at all. Then water was poured off and acetic acid was added and the material was not interfered with at all. The material was not interfered with soda, neither with hot water. The material was treated with a solid shoe fat, and that fat was

removed with hot water. After this experiment the material was not interfered.

The material was at the same state and form as at the beginning of this

experiment. Example 2

The same experiments were made using instead of olive oil either rape oil or sun flower oil. The same results were obtained.

Example 3

A material was prepared by mixing olive oil to nanocellulose powder until the nanocellulose was totally moistened. The material was left to settle for two days. Then the material was produced to a ball. The ball was destroyed and built again.

A thread was placed inside and around the ball. The ball was pressed to a disc. The oil content of the material was diminished by blotting paper until all free oil was removed.

The material as a disc was hang in air. Then a water glass was arranged so that the disc was hang in the water. Later the water was removed and the material as a disc was hang in air for a week. The material disc was put into water and water spray was shooted against it. Bubbles of air arranged on the surface. The material disc was taken off from the water and it continued hanging in air.

Example 4

A material was prepared by mixing olive oil to nanocellulose powder until the nanocellulose was totally moistened. The material was left to settle for two days. Then it was produced to three small balls. Each of the balls was colored with oil colors. The material was in yellow, red, and blue balls. The balls were reshaped to letters and to rings etc. They were put under water and the water didn't interfere with them. Then the material was produced again to balls and then all the material in the balls with different colors were combined. The colors did not blend together, but shine individually. Example 5

A material was produced as was explained in Example 4 and colored with red oil color. The material was put into water. It was physically pressed with a rod on the surface of the material to produce letters on the surface. The water was taken away and the signs on the material surface were clearly seen. The material was reshaped to a ball and put again into water. The light ball acted like a football. Example 6

A material was prepared as in Example 4. It was produced to one ball, which was colored to brown with oil color. The material was put under water. Water was shooted by a water gun on it and it got signs on the surface. It would be easy to write on the surface, if the water spray were more precise and focused. After the water was removed all the signs were vanished. The solution is that oxygen layer on the surface produced the signs.

Example 7

A material was prepared as in Example 4. It was produced to one bar. The

material was cut into thin slices and after that all the slices were cut

rectangularly. Small pieces of the material were symmetrically on the plate. Then water was poured over the material, but slices were not interfered with the water flow. Water was taken off and the arrangement on the table was the same as before the water addiction.

Example 8 A material was prepared as in Example 4. It was produced to one bar and then modeled to a disc. It was put to cover the Vichy liquid bottle to check whether the material is gas-permeable. The bottle stayed overnight with the bottle cover made of the material. It was noticed that the gas escaped from the bottle through the material. The material seems to be gas-permeable. Example 9

A material was prepared as in Example 4. It was divided into several small

Minigrip pockets. It was easy to produce a thin layer of the material. After

several days it was found that the material was very flexible and hydrophobic.

Example 10 (comparative)

A material was prepared by mixing olive oil to nanocellulose powder until the nanocellulose was totally moistened. Then it was reshaped to a bar. And water was poured on it, but it did not interfere with it. Then hot water was poured over the material. The material became a gel with the hot water. After that it was

impossible to remove the material or nanocellulose from the gel.

Example 11 (comparative)

A material was prepared by mixing a solid shoe fat with nanocellulose powder.

The material was not at all flexible and it was more of a gel.

Example 12

A material was prepared by mixing olive oil to nanocellulose powder until the nanocellulose was totally moistened. Then it was produced to three small balls. Each of the balls was colored with acrylic colors. The material comprised in yellow, red, and blue balls.

The balls were left to settle for one week and extra oil was absorbed with blotting paper. The balls were weighted to 9 grams. They were put under water in the aquarium. They dropped instantly on the bottom. Fishes studied these blocks with bright colors, but the blocks didn't interfere with that. There was seen no oil drops in aquarium. Then the balls/blocks were taken out from the aquarium. They weighed 9 grams as before.

Thin slices were cut from the balls. The following clauses characterize embodiments of the invention: 1. A method for preparing hydrophobic material, wherein nanocellulose powder is mixed together with an organic liquid.

2. A method as defined in clause 1, wherein the organic liquid is a fatty acid or combination of fatty acids.

3. A method as defined in clause 2, wherein the fatty acid or combination of fatty acids as plant oil e.g. olive oil, rape oil or sun flower oil.

4. A method as defined in any of the preceding clauses, wherein nanocellulose is 60% moistened, more preferably 80% moistened and most preferable 100 % moistened.

5. A method as defined in any of the preceding clause, wherein the material is left to settle 5 hours, more preferably 10 hours, most preferably 24 hours or more.

6. A method as defined in any of the preceding clauses, wherein oil from the surface of the material has been removed e.g. by blotting paper.

7. A method as defined in any of the preceding clauses, wherein the material was pressed to a disc or produced to a ball or a bar or/and the material was colored.

8. A method as defined in any of the preceding clauses, wherein the nanocellulose has crystal size less than one micron and particle size less than 50 micrometers. The bulk density of the powder is less than 500 grams per liter, preferably less than 100 grams per liter. The dryness of the nanocellulose is more than 90%.

9. Hydrophobic material which contains a mixture of the nanocellulose and organic substance, the more preferably fatty acid or combination of fatty acids, most preferably plant oil e.g. olive oil, rape oil or sun flower oil.

10. Use of the material prepared as in any of clauses 1 to 8 in anti- fouling of

surfaces, filters, membranes, actuators, in packaging materials, in self-cleaning surfaces and dirt-repellent surfaces, as coatings for miniaturized sensors, in biochips, as plasticine, in decorations, in art work, in electronics, shipbuilding.

Claims

Claims:

1. A method of manufacturing a hydrophobic material from a nanocellulose raw-material and a hydrophobic substance, said method comprising the steps of

- contacting the fatty oil with finely-divided nanocellulose raw-material,

- soaking the nanocellulose raw-material with the fatty oil, and

- forming said material into a composition of fatty oil containing nanocellulose material to obtain a hydrophobic material.

2. The method according to claim 1, wherein the contacting comprises mechanically contacting finely-divided nanocellulose raw-material with fatty oil, and contacting is continued until a significant part of the nanocellulose raw-material is saturated with the fatty oil.

3. The method according to claim 1 or 2, wherein the nanocellulose raw-material is used in essentially dry powder form.

4. The method according to any of claims 1 to 3, wherein nanocellulose raw-material powder is mixed together with a fatty acid or combination of fatty acids.

5. The method according to any of the preceding claims, wherein the fatty acid or combination of fatty acids, is selected from plant oils, such as from the group of olive oil, rape oil and sun flower oil and combinations thereof.

6. The method according to any of the preceding claims, wherein nanocellulose is 60% moistened, more preferably 80%) moistened and most preferable 100 % moistened with the fatty oil.

7. The method according to any of the preceding claims, wherein the material is left to settle for 5 hours, more preferably 10 hours, most preferably 24 hours or more.

8. The method according to any of the preceding claims, wherein any unabsorbed fatty oil is removed from the surface of the hydrophobic material thus obtained, for example by absorbing it to an absorbent, such as blotting paper.

9. The method according to any of the preceding claims, wherein the hydrophobic material thus obtained is mechanically shaped, for example pressed to a disc or produced to a ball or a bar or/and the material is coloured.

10. The method according to any of the preceding claims, wherein the nanocellulose raw- material meets one or several of the following criteria:

- it has a has crystal size of less than one micron,

- a particle size of less than 100 micrometers, in particular less than 50 micrometers,

- the dryness of the nanocellulose is more than 90 % by weight.

11. The method according to any of the preceding claims, wherein the nanocellulose raw- material is selected from nanocellulose, fine cellulose fibers, microfibrillated cellulose fibers (MFC), cellulose nanofibers (NFC), microcellulose, micro crystalline cellulose and level-off DP (degree of polymerization) cellulose.

12. Hydrophobic material obtained by a method according to any of the preceding claims.

13. The material according to claim 12, characterized in that it contains a mixture of the nanocellulose and a fatty acid or combination of fatty acids, most preferably plant oil e.g. olive oil, rape oil or sun flower oil.

14. Use of a material prepared according to a method of any of claims 1 to 11 or according to claims 12 or 13, in anti-fouling of surfaces, filters, membranes, actuators, in packaging materials, in self-cleaning surfaces and dirt-repellent surfaces, as coatings for miniaturized sensors, in biochips, as plasticine, in decorations, in art work, electronics, shipbuilding and in the marine industry.