WO2019105576A1

WO2019105576A1 - Water-sensitive, edible, and biodegradable film

Info

Publication number: WO2019105576A1
Application number: PCT/EP2017/083571
Authority: WO
Inventors: Analia VAZQUEZ; Maria Jose RODRÍGUEZ BATILLER; Rocio GIMENES; Luciano LEONARDI; Mariana MELAJ; Victoria FERNÁNDEZ CORUJO
Original assignee: ROMANO, Marcela Adriana; Plásticos Romano S.A.; Consejo Nacional De Investigaciones Científicas Y Técnicas (Conicet); Universidad De Buenos Aires (Uba)
Priority date: 2016-12-22
Filing date: 2017-12-19
Publication date: 2019-06-06
Also published as: AR107134A1

Abstract

A water–sensitive, edible and soil biodegradable film comprising a mixture of the natural polymers starch and gelatin, a plasticizer selected from glycerol and sorbitol, and nano–reinforcements selected from MMT and nanocellulose. These films can be used as material for manufacturing containers or bags which may contain and transport products of various types. Since the film of the present invention comprises polymers which are water–sensitive and biodegradable in soil, the containers or bags made from these films can be used and buried without changing the conditions of the soil in which they are buried. Some of the possible uses of these films are: in the manufacture of containers or bags for containing and transporting hazardous agricultural products such as pesticides, herbicides, or any agrochemical, in the manufacture of bags for disposing of surgical material, in the manufacture of bags for domestic animal organic waste, in the manufacture of bags containing detergents or soap powder to be used in the cleaning of garments inside a container with hot water (washing machine), in the packaging of dry foods, in the manufacture of supermarket bags and/or rigid containers manufactured by thermoforming.

Description

WATER-SENSITIVE, EDIBLE, AND BIODEGRADABLE FILM

FIELD OF THE INVENTION

The present invention relates to water-sensitive, edible, and biodegradable films.

These films may be used as material for manufacturing containers or bags which may contain and transport products of various types, such as hazardous agricultural solid compositions such as pesticides, herbicides, or any agrochemical. In most cases, these agrochemicals are distributed in liquid form in plastic containers that are not biodegradable, since their polymers will not biodegrade for 200 years. In addition, these containers are contaminated with the liquid and cannot be recycled.

The film of the present invention comprises polymers which are water- sensitive and biodegradable on land, whereby they can be used and buried without changing the conditions of the soil in which they are buried. The containers or bags made from these films are not only useful for the handling of these toxic substances, but also solve the problems caused to the environment as a result of the disposal of said containers or bags.

In addition, the film may contain controlled release compounds, such as, for example, fertilizers within the film formulation, which would cause them to be gradually released when the firm disintegrates, dissolves or biodegrades.

A possible use of the film is in the packaging of dry foods, since these films are made of edible and heat-sealable elements that can be used for such purpose. These films would lengthen the period of use of these foods.

The film may also be used in the manufacture of bags for disposing of surgical material or in the manufacture of bags for organic domestic animal waste. Another possible use of the film is in the manufacture of bags containing detergents or powdered soap to be used in the cleaning of garments within a vessel with hot water (washing-machine).

Depending on the characteristics of the film, it may also be used in the manufacture of supermarket bags and/or rigid containers made by thermoforming.

BACKGROUND OF THE INVENTION

In the field of agrochemical bags, several patent applications are known in which polyvinyl alcohol (PVA) has been used as the main material.

AR6543A1 discloses a water-soluble bag design for transporting agrochemicals and the method for the manufacture thereof. The water-soluble film is comprised of multiple layers for manufacturing the bag so as to contain an agrochemical composition. The composition of the film disclosed in said patent is based on polyvinyl alcohol.

PVA is a biodegradable polymer in compost, and chemically has different structures according to its hydrolysis degree. PVA is obtained from the hydrolysis or saponification of polyvinyl acetate (PVAc), and the higher the hydrolysis degree, the more soluble it is. However, in published works it has been found that this polymer does not readily biodegrade in soil.

Then, in the publication by Pajak et al (2001 ) (“Poly(vinyl alcohol) - biodegradable vinyl material”; Jolanta PAJAK, Michat ZIEMSKI, Bozena NOWAK; Faculty of Biology and Environmental Protection, University of Silesia, Katowice; CHEMIK 2010, 64, 7-8, 523-530), reference is made to a work conducted by Chellini et at, showing that if PVA is incubated in soil only 8-9% of the film is degraded within 74 days. Similar results were obtained by Solaro et at, when PVA degradation with 88% hydrolysis degree was evaluated in soil for 120 days. Sawada has also conducted studies with PVA in various types of soil and ambient conditions. After two years of samples incubation, in spite of high microbiological activity of soil, no traces of material colonization by microorganisms was found and only slight decrement of foil mass (less than 10%) was observed.

US2013/0157031 discloses a method for forming a thermoplastic composition that contains a plasticized starch polymer. It discloses how to manufacture thermoplastic starch, with examples of the temperatures used in each part of the extruder. Examples of other polymers with which it may be mixed are also given. They are not water-soluble polymers, nor do they disintegrate; some may be biodegradable, whereby the present patent uses disintegrable or water- soluble materials, they are edible and biodegradable. In addition, the mechanical properties (tensile modulus) are superior to that of the previously described patent.

Patent CN 104893003 A comprises a film based on starch, gelatin, and other components such as chitosan, glucose, methyl cellulose, pectin, agar, polyalcohols, sorbic acid, paraffin, alginine, citric acid, sodium fumarate, L- aspartate, vitamin C, which are used to coat fruits as edible films, have a tensile modulus between 9 and 29 MPa, which is a very low value to be used as a container bag for solid material.

Rodriguez-Castellanos et al, “Extrusion blow molding of starch-gelatin polymer matrix reinforced with cellulose,” European Polymer Journal, 73 (2015) 335-343. In this reference cellulose has been used in order to decrease the viscosity of the starch-gelatin polymer mixture.

However, there is still a need to have a biodegradable film with the possibility of being edible and sensitive to water that overcomes the disadvantages presented by prior art films, i.e. biodegradation in percentage greater than PVA in soil within a time period of less than 74 days and having excellent mechanical properties, close to the commercial PVA bag. SUMMARY OF THE INVENTION

The present invention relates to biodegradable and water-sensitive films. Water sensitivity is interpreted as water absorption which causes the film to swell. The term “biodegradable” refers to material that is degraded by the action of microorganisms such as bacteria, fungi and algae, moisture, temperature or other environmental factors.

The term “disintegrable” refers to material that breaks down into increasingly smaller fragments of the same material.

The term“water- soluble" or“hydrosoluble" refers to material which, when immersed in water at a certain temperature, becomes a solution.

The components of the film are bio-polymers with mechanical properties which enable the bags or packages manufactured from said film to contain a solid product.

The invention relates to biodegradable polymers but these may not be soluble in water. The term“water-soluble” denotes a sensitivity of the polymer to water solvolysis. That is, the chains separate because the water breaks down the secondary bonds created by the hydrogen bridges, for example. To be defined as water-soluble, this effect must occur in at least 50% by weight of the total polymer at a temperature of not more than 60 °C (see U.S. Patent 5,108,807).

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a scanning electron microscopy (SEM) photo of untreated bacterial cellulose, wherein the nanometric size of the fibers and the micrometric length of the fibers are observed.

Figure 2 shows the photos of film numbers 111 and 112, 0 and 21 days after placing them in soil, and of film numbers 130 and 128, 8 days after placing them in soil. Disappearance of film pieces by biodegradation is observed therein. DETAILED DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a biodegradable, water- disintegratable or water-soluble film which enables to reduce the pollution produced in the environment by the use of non-biodegradable polymers.

Another object of the present invention is to provide a film which allows the manufacture of bags which, when dispersed in water, disperse particles contained in their matrix.

Another object of the present invention is to provide biodegradable, water- disintegrable or water-soluble films containing controlled-release products in their composition.

The film of the present invention comprises polymers selected from the group consisting of: starch, modified starch (acetylated or esterified, hydroxypropylated, etherified, pregelatinized, native, cationic, oxidized), gelatin (of various Bloom degrees from 100 to 270), modified gelatin, cellulose, micro or nanocellulose, nanoclay or montmoril Ionite (MMT) in all its possibilities (natural, sodium, calcium, organically modified).

Nanocellulose can be nanocellulose obtained from vegetable fibers, also called cellulose wiskers, or bacterial cellulose obtained from bacteria. Bacterial cellulose is obtained from an Acetobacter xilynium culture whose nutrients were based on corn mash and glycerol (50% by weight). The nanocellulose used had fermented for 7 days and was autoclaved (NCB) and treated with sodium hydroxide (2% for 1 hour) to remove traces of the fermentation process (NCB- treated). The NCB obtained has a non-woven blanket form of fibers of nanometric thickness and width. It is of a micrometric length. Therefore, this non-woven blanket (Figure 1 ) is processed by grinding in a processor. The nanometric size of the fibers allows to generate more specific surface that interacts with the starch and the gelatin, generating a greater reactive surface.

Another component is MMT, which acts as a reinforcement for gelatin- starch and which was not used in previous works for the mixture of starch-gelatin with cellulose.

The film of the present application comprises: starch between 20-70% by weight, gelatin of various Bloom degrees (between 100 and 270 Bloom degrees) between 15-85% by weight, MMT in a proportion between 2-10% by weight, nanocellulose between 0.5-10% by weight. Said film also comprises glycerol or sorbitol as a plasticizing agent, in a range of 7-40% by weight. Preferably, it comprises 65% by weight of starch, 16% by weight of gelatin of various Bloom degrees (between 100 and 270 Bloom degrees), 2.6% by weight of MMT, 0.3- 3.3% by weight of nanocellulose. Glycerol has also been used in a proportion of 13% by weight.

MMT, like nanocellulose, causes an increase in the film strength to breakage.

Glycerol or sorbitol allows the films to be flexibilized. The greater the proportion used, the greater the flexibility of the film obtained, and the greater the absorption of water and water-dissolving capacity. Glycerol may be soybean glycerol, analytical glycerol, biodiesel glycerol, etc.

The starch is gelatinized prior to the mixture in order to destructure the granules and to achieve thermoplastic starch. Depending on the type of starch (corn, wheat, yucca, potato, rice, cassava), the gelatinization temperature is different. The lowest gelatinization temperature is that of cassava starch, and the highest that of potato starch. This is due to the amylose and amylopectin composition of the starch. The gelatin may also be of bovine, porcine, or fish origin, and its Bloom degree indicates the degree of gel hardness. The higher the Bloom degree, the higher the gel degree. It is also required that the gelatin be hydrated prior to mixing.

The manufacturing process of the films is by casting of solvent evaporation, which in this case is water. Water evaporation from the films is on trays at a temperature ranging from 25 to 100 °C in a forced convection oven, preferably at a temperature between 40-80 °C. Another manufacturing process that may be used is by extrusion-blowing. This process does not require the addition of water in its formulation, and the mixing is produced by the shear stress to which the biopolymers are subjected in the device.

EXAMPLES

Different films have been prepared from the components forming the composition of the present invention in order to compare their mechanical properties, water sensitivity, and biodegradation time. Also, the examples allow to differentiate the composition of the film of the present invention from that of prior art films.

Water Sensitivity Measurement Method: Water sensitivity was measured by placing a 5 cm x 5 cm film (of about 1 g) in 150 mL of water and with stirring at 4000 rpm. The time after which said portion of the film is disintegrated and/or dissolved at temperatures of 20 °C and 60 °C was determined.

Percent by Weight of each Component: The percent by weight was calculated based on the entire formulation except water.

EXAMPLE 1 : Film No. 128: Oxidized starch with treated NCB + Gelatin with MMT

(Preparation of a film according to the present invention)

Materials:

Oxidized corn starch

150 Bloom gelatin

Montmorillonite (MMT)

NaOH-treated bacterial nanocellulose (NCB-treated)

Soybean glycerin (density = 1.69 g/cm³)

Composition of each solution

- Oxidized corn starch: 5 g

- Soybean glycerol: 0.756 g (0.6 mL )

- Nanocellulose: 0.025 g

- 150 Bloom gelatin: 5 g

- MMT: 0.8 g

- Glycerol: 0.756 g (0.6 mL )

Final Composition:

Oxidized corn starch: 3 g (67.5%)

150 Bloom gelatin: 0.75 g (16.9%)

MMT: 0.12 g (2.7%)

Treated nanocellulose (NCB treated) dry weight: 0.015 g (0.33%)

Soybean glycerol: 0.566 g (12.6%)

Water: 75 mL

Process:

Preparation of the Starch Solution:

30 grams of NaOH-treated nanocellulose blanket (containing 2 grams of nanocellulose per 100 grams of blanket) were weighed and 90 mL of distilled water were added to the blender, shaking at maximum speed for 30 seconds, leaving to rest for 15 seconds and repeating the procedure, performing the same four times.

5 mL of the system obtained were measured and 95 mL of distilled water were added. 5 g of corn starch were added. The sample was attempted to be dispersed under magnetic stirring (4000 rpm) at room temperature. After the starch was dispersed, it was heated to 85 °C (gelatinization temperature of corn starch) and once that temperature was reached, 0.6 mL of soybean glycerin was added. It was stirred keeping the heating at 85 °C until gelatinization.

Preparation of the Gelatin Solution:

100 mL of hot distilled water (70-80 °C) were measured in a beaker, and 5 grams of gelatin and 0.8 g of MMT were added under stirring, and 0.6 mL of soybean glycerin were added and stirred with stirrer to prevent bubble formation. Preparation of the Mixture:

80 mL of the starch solution were taken and 15 mL of the gelatin solution were added. It was shaken with a stirrer and dispensed in a Teflon-lined vessel and stoved at 40 °C to dryness.

Water Sensitivity of the Film

It was determined that at T = 20 °C it takes 1 minute to disintegrate, and at T = 60 °C it takes 15 seconds to disintegrate and takes 2 minutes to dissolve.

EXAMPLE 2:

Film No. 111 : Cationic corn starch with NCB + Gelatin with MMT (preparation of a film according to the present invention)

Materials:

Cationic corn starch

150 Bloom gelatin

Montmorillonite (MMT) Bacterial nanocellulose (NCB)

Soybean glycerin (density = 1.69 g/cm³)

Composition of each Solution

- Cationic corn starch: 5 g

- Soybean glycerol: 0.756 g (0.6 mL )

- Nanocellulose: 0.25 g

- Water volume: 100 mL

- 150 Bloom gelatin H40: 10 g

- MMT: 1.6 g

- Glycerol: 1.5 g (1.2 mL)

- Water volume: 200 mL

Final Composition:

Cationic corn starch: 4 g (65.5% by weight)

150 Bloom gelatin: 1 g (16.4% by weight)

MMT: 0.16 g (2.6% by weight)

Nanocellulose (NCB) dry weight 0.2 g (3.3% by weight)

Soybean glycerol: 0.75 g (12.1 % of the total polymer)

Water: 100 mL

Process:

Preparation of the Starch Dispersion:

50 grams of nanocellulose blanket (containing 2 grams of nanocellulose per 100 grams of blanket) were weighed and 150 mL of distilled water were added to the blender, shaking at maximum speed for 30 seconds, leaving to rest for 15 seconds and repeating the procedure, performing the same four times.

50 mL of the system obtained were measured and 50 mL of distilled water were added. 5 g of corn starch were added. The sample was attempted to be dispersed under magnetic stirring (4000 rpm) at room temperature. After the starch was dispersed, it was heated to 85 °C (gelatinization temperature of corn starch) and once that temperature was reached, 0.6 mL of soybean glycerin was added. It was stirred keeping the heating at 85 °C until gelatinization (8 minutes). Preparation of the Gelatin Dispersion:

200 mL of hot distilled water (70-80 °C) were measured in a beaker, and 10 grams of gelatin and 1.6 g of MMT were added under stirring, and 1.2 mL of soybean glycerin were added and stirred with stirrer to prevent bubble formation. Preparation of the Mixture:

80 mL of the starch dispersion were taken and 20 mL of the gelatin dispersion were added. It was shaken with a stirrer and dispensed in a flat vessel and stoved at 80 °C to dryness.

Water Sensitivity of the Film

It was determined that at T = 20 °C there is no disintegration after 2 hours and at T = 60 °C breakdown occurs at 3 minutes and disintegration at 60 minutes.

EXAMPLE 3:

Film No. 112: Oxidized starch with NCB + Gelatin with MMT (preparation of a film according to the present invention)

Materials

Oxidized corn starch

150 Bloom gelatin

Montmorillonite (MMT)

Bacterial nanocellulose (NCB)

Soybean glycerin (density = 1.69 g/cm³)

Composition of each Solution

- Oxidized corn starch: 5 g

- Soybean glycerol: 0.756 g (0.6 mL) - Nanocellulose: 0.25 g

- 150 Bloom gelatin H40: 10 g

- MMT: 1.6 g

- Soybean glycerol: 1.5 g (1.2 mL )

Final Composition:

Cationic com starch: 4 g (65.5% by weight)

150 Bloom gelatin H40: 1 g (16.4% by weight)

MMT: 0.16 g (2.6% by weight)

Nanocellulose (NCB) dry weight: 0.2 g (3.3% by weight)

Soybean glycerol: 0.75 g (12.3% by weight)

Water: 100 mL

Procedure:

Preparation of the Starch Dispersion:

Water Sensitivity of the Film

It was determined that at T = 20 °C and at T = 60 °C there is no disintegration after 2 hours. EXAMPLE 4:

Film No. 130: Cationic starch with treated NCB + Gelatin with MMT (preparation of a film according to the present invention)

Materials:

Cationic corn starch

150 Bloom gelatin

Montmorillonite (MMT)

Treated bacterial nanocellulose (NCB treated)

Soybean glycerin (density = 1.69 g/cm³)

Final Composition:

Cationic corn starch: 4 g (65.4%)

150 Bloom gelatin: 1 g (16.4%)

MMT: 0.16 g (2.6%)

Dry nanocellulose (NCB): 0.2 g (3.3%)

Soybean glycerol: 0.75 g (12.3%)

Water: 100 mL

Procedure:

Preparation of the Starch Solution: 50 grams of NaOH-treated nanocellulose blanket (containing 2 grams of nanocellulose per 100 grams of blanket) were weighed and 150 mL of distilled water were added to the blender, shaking at maximum speed for 30 seconds, leaving to rest for 15 seconds and repeating the procedure, performing the same four times.

50 mL of the system obtained were measured and 50 mL of distilled water were added. 5 g of corn starch were added. The sample was attempted to be dispersed under magnetic stirring (4000 rpm) at room temperature. After the starch was dispersed, it was heated to 85 °C (gelatinization temperature of corn starch) and once that temperature was reached, 0.6 mL of soybean glycerin was added. It was stirred keeping the heating at 85 °C until gelatinization.

Preparation of the Gelatin Solution:

80 mL of the starch solution were taken and 20 mL of the gelatin solution were added. It was shaken with a stirrer and dispensed in a Teflon-lined vessel and stoved at 80 °C to dryness.

Water Sensitivity of the Film

It was determined that at T = 20 °C it takes more than 17 minute to disintegrate, and at T = 60 °C it takes 10 minutes to disintegrate and does not dissolve for > 1 hour. Test of Tensile Mechanical Properties

The films were characterized by uniaxial tensile tests, and mechanical properties such as modulus, tensile strength and deformation at breakage were determined. The methodology followed for these determinations is described below.

Dumbbell test strips were cut from the films obtained following the recommendations of the ASTM D638 norm (geometry type IV). Uniaxial tensile tests were performed on an INSTRON dynamometer (Model 5985, 1 kN load cell). The dimensions of each strip (thickness and width of the reference area) were determined by a digital gauge before each test. Tests were performed at room temperature (16-18 °C) at a traverse velocity of 5 mm/min. A value of at least 4 strips per sample has been reported. The strips were conditioned at 65% relative humidity for 8 hours before testing. The Young modulus (E) was determined from the initial slope of the strain-deformation curve. The tensile strength was obtained as the value corresponding to the maximum tension supported by the strip. The percentage of strain at breakage was determined as the ratio between the maximum elongation of the strip (l-lo) and the initial reference length (lo), that is (l-lo/lo)%. The Young modulus (E), measured in MPa, the tensile strength (s), measured in MPa, and the percent deformation (s%) can be observed in Table 1. The thickness is also indicated in the table, as well as the references of the reported values.

3 o

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n H m b o₄

o

In Example 1 (Code No. 03), it can be seen that with a low percentage of NCB great deformation at breakage is obtained, but a modulus and resistance lower than the values of commercial PVA and those reported by Rodriguez-Castellanos. However, when the amount of NCB was increased to 3.3%, the tensile strength was higher than that obtained by Rodriguez-Castellanos, although the modulus and strength were lower. In Example 2 (Code 04) and Example 3 (Code 05), the effect of the type of starch can be observed. With oxidized corn starch (Example 3, Code 05) a higher modulus and higher strength to breakage were obtained, the latter ones being comparable to those of commercial PVA (Code 01 ), which is the material used for the manufacture of bags. In Example 4 (Code 06) it can be seen that, using cationic corn starch with 3.3% NCB, a very high modulus of 1470 MPa was obtained but with very low elongation, which would indicate a material that cannot be blown due to its fragility.

Biodegradation of Samples

The biodegradation of a material is defined as the degradation caused by biological activity which, by enzymatic action, causes significant changes in the chemical structure of said material. The degradation of polymers, as well as the microbial population, is conditioned by environmental factors, including humidity, temperature, pH, salinity, the presence or absence of oxygen, and the availability of certain nutrients.

The determination of the disintegration time for the films of the present invention, when exposed to a natural environment, was performed using a Molisol soil, which is a clayey slimy soil from the Province of Buenos Aires, Argentina, the characteristics of which are presented in Tables 2 and 3. Table 2. Characteristics of the Province of Buenos Aires site from where the sol! samples were extracted for the durability test

In 1.00-L beakers, 800 g of wet soil were weighed. Film pieces corresponding to Films Nos. 128, 111 , 112, and 130 of 3 cm x 4 cm were placed in the beakers, between the glass and the soil, following the breakdown through a photographic record. To calculate the durability of the film strips in the soil, the area of the films was measured in time, calculating the percentage of film that remained in the soil at the time point studied.

The results obtained are presented in Table 4. Table 5 compares the disintegration and dissolution times with the soil biodegradation times.

Table 4. Percentage of material tested remaining in the soil throughout the biodegradability test

Table 5: Disintegration and dissolution times at T=20 and 60 °C, soil degradation time

As for disintegration, the film that is most sensitive to water is Film 128 containing oxidized starch and 0.3% treated NCB, coinciding with the shortest biodegradation time in soil. The film that is most resistant to water is Film 112 containing oxidized starch and 3.3% untreated NCB, which is a storage advantage.

As for the type of starch, by comparing Films 112 and 111 containing the same amount of untreated NCB, the cationic starch is more water sensitive than the oxidized starch. Performance in soil is not similar to water sensitivity, since oxidized starch (Film 112) is more biodegradable in the composition of this invention than cationic starch (Film 111 ).

In all cases, biodegradation times are lower than crop change times.

Claims

1. A water-sensitive, edible and soil biodegradable film, characterized in that it comprises a mixture of the natural polymers starch and gelatin, a plasticizer selected from glycerol and sorbitol, and nano-reinforcements selected from MMT and nanocellulose.

2. A film according to claim 1 , characterized in that the ratio starch :gelatin is in the range of 1 :4 and 4:1 , with specific ratios of nanoreinforcements.

3. A film according to claim 1 , characterized in that the starch is selected from the group consisting of native starch, hydroxypropylated starch, oxidized starch, cationic starch, pregelatinized starch, starch from different sources: corn starch, rice starch, potato starch, and cassava starch.

4. A film according to claim 1 , characterized in that the gelatin is selected from bovine, porcine, and fish gelatin with a Bloom level between 100- 270.

5. A film according to claim 1 , characterized in that the bacterial cellulose is selected from bacterial cellulose obtained from a corn mash and glycerol means, untreated and treated with sodium hydroxide.

6. A film according to claim 1 , characterized in that it comprises:

20-70% by weight of starch,

15-85% by weight of gelatin of various Bloom degrees 100-270,

2-10% by weight of MMT,

0.3-10% by weight of nanocellulose,

7-40% by weight of glycerol.

7. A film according to claim 1 , characterized in that it comprises:

65-68% by weight of starch,

15-85% by weight of gelatin of various Bloom degrees 100-270,

2-10% by weight of MMT,

0.3-5% by weight of nanocellulose, -40% by weight of glycerol.

8. A film according to claim 1 , characterized in that it comprises:5% by weight of starch,

6% by weight of 150 Bloom degree gelatin,

.6% by weight of MMT,

.3% by weight of nanocellulose,

3% by weight of glycerol.