KR101766818B1

KR101766818B1 - Method for preparing biocomposite of Poly(vinyl Alcohol) (PVA) and lipid extracted algal biomass (LEA)

Info

Publication number: KR101766818B1
Application number: KR1020150146226A
Authority: KR
Inventors: 장용근; 양지원; 이현로; 진등순
Original assignee: 재단법인 탄소순환형 차세대 바이오매스 생산전환 기술연구단
Priority date: 2015-10-20
Filing date: 2015-10-20
Publication date: 2017-08-23
Also published as: KR20170045992A

Abstract

The present invention relates to a method for producing a biocomposite by mixing polyvinyl alcohol, which is one of conventional plastics, with biomass extracted from microalgae, and more particularly, to a method for producing biomaterials by mixing (a) lipid extracted microalgae biomass Preparing a lipid extracted microalgae biomass suspension from the raw material through a wet process; And (b) mixing the lipid extracted microalgae biomass suspension with polyvinyl alcohol and glycerol to produce a biocomposite material. According to the present invention, since a biocomposite material having a small particle size can be produced, it is possible to expect the effect of improving the physical properties and dispersion of the biocomposite material, and is useful for energy and time saving in the manufacturing process.

Description

TECHNICAL FIELD The present invention relates to a method for preparing a biocomposite by mixing polyvinyl alcohol and lipid extracted microalgae biomass.

The present invention relates to a method for producing a biocomposite material, and more particularly, to a method for producing a biocomposite material by extracting lipids from microalgae and dispersing the remaining biomass in an aqueous solution and mixing with polyvinyl alcohol, .

Biocomposite is a composite of biomass mixed with conventional plastics, and it is emerging as a material that can overcome limitations and economical problems of bioplastics at the same time. In fact, it has been found that starch is mixed with a thermoplastic material and is not much to commercialize. For example, GreenDat Company manufactures and sells Terratek SC 50, a biomaterial based on starch, as a commodity (http://www.greendotpure.com). (Avella, M. et al ., Materials , 2 (3)). In addition, research on the use of agricultural waste, chitosan, pectin, cellulose, gluten, gelatin, soy protein, : 911-925, 2009; Azizi, S. et al, Chinese J Polym Sci 32 (12):. 1620-1627, 2014; Chiellini, E. et al, Macromolecular bioscience 4 (3):. 218-231, 2004 ; Chiellini, E. et al, Biomacromolecules 2 (3):.. 1029-1037, 2001; Iannace, S. et al, Journal of Applied Polymer Science 73 (4): 583-592, 1999; Tang, XZ et al ., Critical reviews in food science and nutrition 52 (5): 426-442, 2012). Biocomposite materials can not replace all existing plastics, but can be used for disposable packaging bags, agricultural mulching films and water-soluble laundry pouches depending on their properties (Chiellini, E. et al ., Biomacromolecules 2 (3): 1029-1037 , 2001).

Up to now, large algae have been studied as a raw material for biomaterials, but there are very few cases of microalgae (Iannace, S. et al ., Journal of Applied Polymer Science 73 (4): 583-592, 1999 ; Shin, YJ et al ., Food Sci Biotechnol 20 (3): 703-707, 2011; Chiellini, et al ., Journal of Polymers and the Environment 21 (4): 944-951, E. et al ., Biomacromolecules 9 (3): 1007-1013, 2008). Microalgae accumulate large amounts of lipid, which has great potential in the biodiesel industry to replace petroleum, and the microalgae biodiesel market is steadily growing for economic and political reasons. Lipid extracted algal biomass (LEA) refers to the by-products of lipids extracted from microalgae. Currently, biologically extracted microalgae biomass is mostly used as animal feed or fertilizer, low in price, rich in carbohydrate and protein.

Conventionally, a biomass powder prepared by a conventional process has been used for biomaterials. The biomass is dried, crushed and sieved into powder form. However, in the conventional process, it is difficult to make particles less than 100 탆, the particle size is not constant, the mechanical properties are deteriorated, and it is difficult to have even dispersion throughout the entire portion. Moreover, the process of drying, grinding and sieving takes a lot of energy and time. If the particle size of microalgae can be applied to biomaterials as they are, the particle size of 5 ㎛ or less can be obtained, so that the improvement of physical properties and dispersion of biomaterials, energy and time can be expected.

Accordingly, the present inventors have made efforts to solve the problems of the prior art, and as a result, they have found that a lipid-extracted microalgae biomass suspension (LEA suspension) prepared from a lipid extracted microalgae biomass raw material in a wet form process It has been confirmed that a biocomposite material having improved physical properties and dispersibility can be produced when the biocomposite material is produced, and the present invention has been completed.

It is an object of the present invention to provide a method for producing a biocomposite material having improved physical properties and dispersibility.

In order to accomplish the above object, the present invention provides a method for producing a microalgae biomass suspension comprising: (a) preparing a microalgae biomass suspension from a lipid extracted microalgae biomass raw material through a wet process; (b) preparing a biocomposite by mixing the lipid-extracted microalgae biomass suspension, polyvinyl alcohol, and glycerol. The present invention also provides a method for producing a biocomposite material.

According to the present invention, since a biocomposite material having a small particle size can be produced, the physical properties and dispersion improving effect of the biocomposite material can be expected, and it is useful for energy and time saving in the manufacturing process.

1 is a conceptual diagram comparing a conventional process and a wet form process.
Figure 2 is a schematic diagram illustrating the preparation of a biocomposite material using a lipid-extracted microalgae biomass suspension (LEA suspension) through a wet process.
Figure 3 is an image of lipid extracted microalgae biomass and biocomposite film produced by traditional processes.
Figure 4 is an image of lipid extracted microalgae biomass and biocomposite film produced by the wetting process.
FIG. 5 is a graph showing the results of infrared spectroscopy (FI-IR spectra) of lipid extracted microalgae biomass, polyvinyl alcohol and a biocomposite film.
Figure 6 is a graph of the ultimate tensile strength (UTS) of a biocomposite material made from both traditional and wet processes.
FIG. 7 is a graph of elongation at break (EB) at break of a biocomposite material made from a conventional process and a wetting process, respectively.
8 is a Young's modulus (YM) graph of a biocomposite material made from a conventional process and a wet process, respectively.
9 is a graph of mechanical properties of a biocomposite material according to glycerol concentration.
10 is a thermogravimetric analysis graph of a biocomposite material produced according to various contents of lipid extracted microalgae biomass.
11 is a melting point and an enthalpy of fusion graph of a biocomposite prepared according to various contents of lipid extracted microalgae biomass.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

In the present invention, a lipid-extracted microalgae biomass suspension by a wet process was used to produce a biomaterial with improved dispersion and physical properties. The wetting process was a process of washing, dispersing, heating and neutralizing the biomass feedstock to produce a biomass suspension, and the biomass was maintained in an aqueous solution.

In one embodiment of the present invention, the lipid extracted microalgae raw material is centrifuged to wash the hexane and the sulfuric acid, and a suspension of the biomass which is neutralized to pH 7 with sodium hydroxide is prepared by making a highly dispersed suspension, And mixed with polyvinyl alcohol to prepare a biocomposite material.

In one aspect, the present invention provides a process for preparing a microalgae biomass suspension comprising: (a) preparing a microalgae biomass suspension lipid extracted from a lipid extracted microalgae biomass feedstock through a wet process; And (b) mixing the lipid-extracted microalgae biomass suspension with polyvinyl alcohol and glycerol to produce a biocomposite material.

In the present invention, the lipid extracted microalgae biomass feedstock relates to the biomass remaining after extracting lipids from organic alcohols and acids from microalgae.

In the present invention, the wetting step comprises i) washing the organic solvent and the acid by centrifugation; ii) dispersing in an aqueous solution state; iii) stirring and high temperature treatment; And iv) neutralizing with a base.

In the present invention, the particle size of the biocomposite material is about 500 nm to 10 m or less.

The reason why the particle size of the biocomposite material made according to the present invention is smaller than that of the conventional process is as follows. In the case of the wet process of the present invention, unlike the conventional process, there is no drying process, so that the particles do not aggregate and have a particle size of 5 μm or less. The particle size of the reduced biomass is maintained as it goes through the lipid extraction process, which is the previous step of the wetting process. The particle size is reduced by as much as 30 to 50% of the lipid is removed during the lipid extraction process, and is also reduced by the sulfuric acid treatment. The cell wall of the microalgae Nannochloropsis salina is connected to a dense polymer chain with high crystallinity and is surrounded by a hydrogen bond between lignin and hemicellulose, forming a very hard structure. The sulfuric acid solution hydrolyzes the lignocellulose constituting the Nannochloropsis salina , lowers the crystallinity of the cellulose, loosens the polymer chains, and breaks bonds with each other. Thus, the cell wall becomes fragile the particle size is small (Esteghlalian, A. et al, Bioresource technology 59 (2-3): 129-136, 1997; Mosier, N. et al, Bioresource technology 96 (6):.. 673 -86, 2005). The breakage of such a polymer chain becomes hydrophilic due to the expression of a hydrophilic group such as a hydroxyl group or a carboxyl group. Therefore, the particles of the lipid extracted microalgae biomass produced by the wetting process have a broad boundary area with the polyvinyl alcohol matrix, and the dispersing effect is also improved as the hydrophilic bond is increased.

The mechanical properties of the biocomposite material of the present invention are determined in the same manner in which the physical properties of the composite material are determined. In composite materials, physical properties are determined according to the physical and chemical structure at the interface between the reinforcing material and the matrix. In a solid-phase interface, a primary bond such as a covalent bond or an ionic bond or a secondary bond such as a hydrogen bond can be formed depending on the constituent material of the composite material, and the physical properties of the composite material are determined according to the bond . The bond energy of the secondary bond (8-16 kJ / mol) is smaller than the bond energy of the primary bond (40-400 kJ / mol) but has a large effect on the adhesion between the materials in the composite material (Zisman, WA, et al ., Industrial & Engineering Chemistry 55 (10): 18-38, 1963).

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The basis of the improved mechanical properties of the biocomposite material according to the present invention is as follows. The particle size of the lipid extracted microalgae biomass produced by the wetting process is much smaller than that of the conventional process and thus has a large surface area in contact with polyvinyl alcohol. Therefore, tensile force can be improved because it can form a greater number of bonds between polyvinyl alcohol and biomass (Pukanszky, B. et al ., Composites 21 (3): 255-262, 1990). Polyvinyl alcohol and biomass can form dipole-dipole bonds between polar molecules and induced dipole bonds between polar molecules and nonpolar molecules, including dispersion effects such as van der Waals forces. In addition, lipid extracted microalgae biomass can form intermolecular bonds such as hydroxyl groups and hydrogen bonds of polyvinyl alcohol because it has hydrophilic groups such as hydroxyl group, carboxy group and carbonyl group. In general, this increase in intermolecular force increases the wettability and adhesion between the matrix and the filter, thereby increasing the mechanical properties (Ehrburger, P. et al ., Philos TR Soc A 294 (1411): 495- +, 1980 ).

[ Example ]

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. It is to be understood by those skilled in the art that these embodiments are only for describing the present invention in more detail and that the scope of the present invention is not limited to these embodiments in accordance with the gist of the present invention.

Example 1: Elemental and elemental analysis of lipid extracted microalgae biomass feedstock

Lipid-extracted microalgae Biomass feedstocks contain carbohydrates, proteins, lipids and ashes that the microalgae themselves have. Carbohydrates were measured by phenol-sulfuric acid assay. The protein was analyzed by carbon, hydrogen, nitrogen, and sulfur using an element analyzer (FLASH 2000 series, Thermo Scientific, USA) at the KAIST Central Analysis Center, and the nitrogen- and the protein content was estimated by multiplying the total protein content by the protein-to-protein conversion factor for marine microalgae (Loureno, SO et al ., European Journal of Phycology 39 (1): 17-32, 2004). Total lipid analysis was performed using total lipid analysis using chloroform-methanol-water (Brown, MR et al ., J Exp Mar Biol Ecol 145 (1): 79-99, 1991 ). The remaining mass after heating up to 575 ° C in a furnace is determined by reference to the Determination of Ash in Biomass by Laboratory Analytical Procedure (LAP) by an experimental analysis procedure developed by the National Renewable Energy Laboratory Respectively. Calcium and phosphorus were analyzed using an Inductively Coupled Plasma Atomic Emission Spectrometer (OPTIMA 7300 DV, Perkin-Elmer, USA). As a result, 20.41% of carbohydrate, 26% of protein, 9.14% of total lipid and 21.72% of total lipid were contained in lipid extracted microalgae biomass (Table 1). In addition, the microalgae biomass contained 5.626% of nitrogen, 0.738% of nitrogen, 3.943% of sulfur, etc. in addition to organic matter (Table 2).

Main ingredient of biologically extracted microalgae ingredient carbohydrate protein Total lipid ashes Other Ratio (% content) 20.41 26.89 9.14 21.72 21.84

Elemental analysis of lipid extracted microalgae biomass element carbon Hydrogen nitrogen sulfur calcium sign Ratio (% content) 42.801 6.246 5.626 3.943 1.625 0.738 Standard Deviation 0.334 0.063 0.010 0.152 0.026 0.004

Example 2: Biomass suspension and biomaterials preparation of lipid extracted microalgae through wetting process

(1) Preparation of lipid extracted microalgae biomass suspension

A suspension was prepared from the lipid extracted microalgae by washing, dispersing, heating and neutralizing (Fig. 2). Hexane and sulfuric acid, which were used to extract lipids from microalgae, are present in slurry form in biomass feedstock immediately after lipid extraction. Hexane and sulfuric acid have been removed since biocomposite films can cause corrosion when they are made. That is, biomass pellets obtained by centrifuging the biomass raw material at 9000 rpm for 5 minutes and distilled water were mixed at a mass ratio of 3: 5, washed and centrifuged once more. The biomass pellet collected by centrifugation and distilled water were mixed at a mass ratio of 1: 3 to prepare a well-dispersed suspension in a mixer (hmf-995, Hanil Science Industrial, Republic of Korea). The suspension was treated at 90 DEG C and 400 rpm in a hot plate equipped with a stirrer to remove all the hexane. The bubbles existing between the polymers constituting the lipid extracted microalgae biomass were sufficiently removed by heating. The pH of the suspension was neutralized to pH 7 using 2N sodium hydroxide (NaOH) before mixing with polyvinyl alcohol and glycerol (FIG. 2).

(2) Manufacture and storage of biomaterials

The suspension prepared as described above was mixed with an aqueous polyvinyl alcohol solution prepared by dissolving in water at 80 ° C and glycerol, and the mixture was heated at 90 ° C and 300 rpm for 45 minutes. And then vacuum dried at room temperature for 3 to 4 hours to remove a small amount of air bubbles. The mixture was assembled on a glass plate using a knife coating device (KP-3000, Kobo Corporation) and a doctor blade (IMOTO 1117/150), and dried at room temperature for 24 hours or more (FIG. The dried film was stored in a sealed vessel with a saturated sodium bromide aqueous solution to meet the ASTM E-104-02 (ASTM E104-02) standard and maintained a relative humidity of 57.6% at 25 ° C.

Comparative Example 1: Production of biomass powder and biomaterial composite of lipid extracted microalgae through a conventional process

Biomass powder was obtained through the drying, grinding and sieving process of the conventional process. As in the wetting process, hexane and sulfuric acid present in the biomass feedstock were removed by centrifugation and washing. The biomass obtained by centrifugation was dried in a 70 ° C oven for 24 hours. The dried biomass was pulverized using a simple mill (SK-M2, Kyoritsu-Rikou, Japan). The pulverized powders were sieved using sieve bodies of 100, 200, 250, and 500 ㎛ in size, and powders smaller than 100 ㎛ were collected. (Fig. 1). The collected powders were mixed with a polyvinyl alcohol aqueous solution and glycerol to prepare a biocomposite material in the same manner as in Example 2 and stored under conditions of a temperature of 25 ° C and a relative humidity of 57.6%.

Example 3: Particle size and dispersion of Example 2 and Comparative Example 1

The particle size and the degree of dispersion of Example 2 and Comparative Example 1 were measured by inverted microscopy (Eclipse TS100, Nikon, Japan) and field-emission scanning electron microscopy (Sirion, FEI, Oregon, USA) (Figs. 3 and 4).

The biocomposite film used was a mixture of 80% polyvinyl alcohol and 20% lipid extracted microalgae biomass. When the upper surface of the biocomposite film was observed under an inverted microscope at a magnification of 20 times, in Comparative Example 1, particles having various sizes up to 200 μm or more were not uniformly dispersed as well as those having a size of 200 μm or less ). In Example 2, most of the particles were homogeneously dispersed, and all the particles had a size of 10 μm or less (FIG. 4 a). The cut surface of the biocomposite film was observed under a scanning electron microscope at a magnification of 5000 times. As a result, in Comparative Example 1, transparent polyvinyl alcohol and dark green particles were bounded to each other (Fig. 3B) Were homogeneously dispersed, and the whole was dark green (FIG. 4B). When Example 2 was observed at an enlarged magnification of 50000 times, it was observed that stick-shaped particles were uniformly dispersed while being smaller than 500 nm (Fig. 4C).

When the biomass particles of Comparative Example 1 were observed with a scanning electron microscope magnification of 2500 times, irregularly shaped particles of various sizes were observed between 2 and 200 탆 (FIGS. 3C and 3D). In the case of the biomass of Example 2, it was observed that the particle size was 10 탆 or less, and the shape and size of the particles were not constant, but they were roughly elliptical and rough (Fig. 4d).

Example 4: Mechanical properties of Example 2 and Comparative Example 1

The content of polyvinyl alcohol and lipid extracted microalgae biomass is 95% -5%, 90% -10%, 85% -15%, 80% -20%, 75% -25% and 70% -30% The maximum tensile strength, elongation at break and Young's modulus of the prepared biocomposite film were measured.

Ultimate tensile strength (UTS) decreased with increasing biomass content in both Example 2 and Comparative Example 1, but in Example 2 it did not change significantly with increasing biomass up to 25% At least 20 Mpa was maintained. Also, the biodegradability of the biomaterial was improved by more than twice as much as that of biomass over 15% (Fig. 6).

Elongation at break (EB) at break decreased in both Example 2 and Comparative Example 1 as the content of biomass increased, but the elongation at break of Example 2 was higher regardless of the content of biomass (Fig. 7).

Young's modulus (YM) is the ratio of tensile force to unidirectional strain. Young's modulus means large rigidity and low elasticity. The Young's modulus decreased with the increase of the biomass content of Comparative Example 1, but increased from Example 2, and was maintained from above 20% of the biomass (FIG. 8).

Example 5: Mechanical properties according to glycerol concentration in Example 2

Glycerol was added to improve the elongation at fracture of the biocomposite prepared only with polyvinyl alcohol and lipid extracted microalgae biomass. Glycerol is a typical plasticizer that enters between polymer chains to increase the free volume and increase the motion and deformability of the polymer chains. Biomaterials were prepared by changing the amount of biomass to 20% and changing the amount of glycerol to 0-30%. Mechanical properties were measured. The maximum tensile strength and Young 's modulus decreased with increasing glycerol concentration, but elongation at fracture increased. When the concentration of glycerol was 20% or more, the elongation at break was decreased (Fig. 9).

Example 6: Thermal properties according to various contents of polyvinyl alcohol and biomass of Example 2

The content of polyvinyl alcohol and lipid extracted microalgae biomass is 95% -5%, 90% -10%, 85% -15%, 80% -20%, 75% -25% and 70% -30% The thermogravimetric analysis, melting point, and heat of fusion of the prepared biocomposite film were measured. 100% polyvinyl alcohol film (100% -0%) was used as a control.

The mass change with temperature was measured using thermogravimetric analysis. The experimental conditions were set up to raise the temperature from 25 ° C to 700 ° C in 1 minute by 10 ° C in an environment with nitrogen gas. As a result, as the content of biomass increased, the thermal degradation temperature of the biomaterial increased (FIG. 10). The thermal decomposition temperature of the biocomposite material (P70L30) containing 70% -30% content was 323.04 ° C, which was about 70 ° C higher than that of 100% -0%.

For the melting point, the biocomposite film content of 95% -5% content was 223.75 ° C, which was higher than 198.58 ° C of 100% -0%. And, even if the content of biomass was increased, the temperature remained high.

In the case of enthalpy of fusion, the 95% -5% biocomposite film was increased by 40 J / g from 100% to 0%. As the content of biomass increased, it tended to decrease, but it was higher than that of 100% -0% polyvinyl alcohol (Fig. 11).

Example 7: FT-IR analysis of Example 2

Using FT-IR, the chemical bonds and functionalities on the surface of polyvinyl alcohol film, lipid extracted microalgae biomass suspension, and biocomposite film P80L20 (polyvinyl alcohol and biomass in a mass ratio of 8: 2) Respectively. Polyvinyl alcohol, lipid extracted microalgae biomass suspension, and biocomposite film P80L20 are shown in black, green, and blue, respectively (FIG. 5).

All specimens, including biocomposites in the wetting process, commonly contain a -OH stretching carboxylic band (3274 cm ^-1 ), CH stretching carboxylic / phenolic stretching bands (2918 cm ^-1 ) and a C-OH stretch (C-OH stretching (1089 cm ^-1 )). Biomass powder and biocomposite materials have many -OH stretch bands and C-OH stretch bands, so they are highly likely to form polar intermolecular bonds (eg, hydrogen bonds) with polyvinyl alcohol and glycerol.

OH bending (1421 cm ^-1 ) and CO stretching (CO stretching (921 cm ^-1 )) were higher in the polyvinyl alcohol than in the vinyl group (Prabhakaran, T. et al ., Smart Materials and Structures 21 (8): 085012, 2012). The biomass powders had inherent peaks at 2850 cm ^-1 , 1626 cm ^-1 and 1525 cm ^-1 . 2850 cm ^-1 represents a methyl group and a methylene group (Mayers, JJ et al ., Bioresource technology 148: 215-220, 2013). In addition, 1626 cm ^-1 and 1525 cm ^-1 indicate the presence of a secondary structure of the protein with amide I and amide II, respectively. Both amide I and amide II bands are major bands that appear in the protein infrared spectrum of proteins. Amides mainly exhibit C = O stretching vibration (70-85%), It is connected. Amides represent NH bending vibration (40-60%) and CN stretching vibration (18-40%). In particular, the stronger peak in amide means that there are many alpha-helical structures (Mayers, JJ et al ., Bioresource technology 148: 215-220, 2013; Pistorius, AM et al ., Biotechnology and bioengineering 103 : 123-129, 2009).

As a result of analyzing the dispersion, mechanical properties and thermal properties of the biocomposite material of the present invention, it was confirmed that the characteristics of the biocomposite film using the lipid extracted microalgae biomass suspension prepared through the wet process were improved.

Having described the measured portions of the present invention in detail, those skilled in the art will appreciate that these specific embodiments are merely preferred embodiments, and the scope of the present invention is not limited thereto Will be clear. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims

A method of making a biomaterial composite, comprising the steps of:
(a) separating the organic solvent and the acid by centrifugal separation from the biomass raw material extracted from the lipid extracted microalgae; Ii) dispersing the biomass raw material from which the organic solvent and the acid have been removed in an aqueous solution, and then treating the biomass raw material at 90 ° C; And iii) neutralizing with a base to produce a lipid extracted microalgae biomass suspension; And
(b) preparing a biocomposite by mixing the lipid extracted microalgae biomass suspension with polyvinyl alcohol and glycerol.

The method according to claim 1, wherein the (a) lipid extracted microalgae biomass raw material is biomass remaining after extracting lipids from organic alcohols and acids from microalgae.

The method of claim 1, wherein the (a) biomass raw material extracted from the lipid is in a slurry state.

The method for producing a biocomposite material according to claim 1, wherein the particle size of the biocomposite material is 500 nm to 10 탆 or less.