Method for producing a part from a particulate natural material and part obtained by such a method

Abstract

A method for producing a part in the form of a solid block from a natural material in particulate form containing scleroproteins. A phase of heating the natural material, under compression at a pressure greater than or equal to 30 MPa, to a temperature greater than or equal to the denaturation temperature of the scleroproteins contained in the material. A phase of cooling the material thus obtained to a temperature less than 100° C., while maintaining the compression during at least a part of the cooling phase.

Claims

1. A method for producing a part in a form of a solid block, from a natural material in a particulate form containing scleroproteins, comprising, carried out dry: a phase of heating the natural material under compression at a pressure greater than or equal to 30 MPa and at a temperature greater than or equal to a denaturation temperature of the scleroproteins to obtain a denatured material; and a phase of cooling the denatured material to a temperature less than 100° C., the compression at the pressure greater than or equal to 30 MPa being maintained for at least a part of the phase of cooling.

2. The method according to claim 1, wherein the phase of cooling the denatured material is carried out to a temperature less than a glass transition temperature of the denatured material.

3. The method according to claim 1, wherein the compression at the pressure greater than or equal to 30 MPa is maintained for at least half of the phase of cooling.

4. The method according to claim 3, wherein the compression at the pressure greater than or equal to 30 MPa is maintained for all of the phase of cooling.

5. The method according to claim 1, wherein the phase of heating the natural material is carried out by a spark plasma sintering.

6. The method according to claim 1, wherein the compression is carried out at a pressure between 30 and 100 MPa.

7. The method according to claim 1, wherein the phase of heating the natural material is for a duration between 1 and 45 minutes.

8. The method according to claim 1, wherein particles of the natural material in the particulate form have a diameter between 20 and 500 μm.

9. The method according to claim 1, further comprising grinding the natural material prior to the phase of heating.

10. The method according to claim 1, wherein the natural material in the particulate form containing scleroproteins has a humidity rate between 0 and 20% in conditions of 60% relative humidity of the air and a temperature of 20° C.

11. The method according to claim 1, wherein the scleroproteins are keratin proteins.

12. The method according to claim 1, wherein the natural material in the particulate form containing scleroproteins is of non-human animal origin.

13. The method according to claim 1, wherein the natural material in the particulate form containing scleroproteins is from a mammal horn.

14. The method according to claim 1, wherein the natural material in the particulate form containing scleroproteins is from a non-human animal leather.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The characteristics and advantages of the invention shall appear more clearly in light of the embodiments hereinafter, provided simply for illustrative purposes and in no way limiting to the invention, with the support of FIGS. 1 to 9B, wherein:

(2) FIG. 1 shows a graph that represents the denaturation temperature of the proteins contained in a sample of cow horn according to the humidity rate thereof, measured by differential scanning calorimetry;

(3) FIG. 2 shows a graph that represents the results of the dynamic mechanical analysis (Young's modulus and tan δ) according to the temperature, of a material obtained by high-pressure uniaxial molding of cow horn at 200° C. and 100 MPa;

(4) FIG. 3 shows a graph that represents, as a function of time, the temperature and the compression applied during the implementation of a spark plasma sintering method in accordance with the invention from cow horn powder, with the pressure being expressed in terms of displacement of the pistons of the spark plasma sintering device;

(5) FIG. 4 shows a photograph of a pellet obtained by a spark plasma sintering method in accordance with the invention from cow horn powder;

(6) FIG. 5 shows a graph that represents the water adsorption isotherms for untreated cow horn (“Untreated horn”), this cow horn after grinding (“Powder”), and the material obtained from this powder by a high-pressure thermoforming method in accordance with the invention (“HPHT”);

(7) FIG. 6 shows the spectra obtained by FTIR infrared spectroscopy for untreated cow horn (“Untreated horn”), this cow horn after grinding (“Powdered horn”), the material obtained from this powder by a spark plasma sintering method in accordance with the invention (“SPS”) and the material obtained from this powder by a high-pressure thermoforming method in accordance with the invention (“HPHT”);

(8) FIG. 7 shows a graph that represents, for untreated cow horn (“Untreated horn”), this cow horn after grinding (“Powder”), the material obtained from this powder by a spark plasma sintering method in accordance with the invention (“SPS”) and the material obtained from this powder by a high-pressure thermoforming method in accordance with the invention (“HPHT”), the variation in energy according to the temperature, measured by differential scanning calorimetry;

(9) FIG. 8 shows a diagram of X-ray diffraction obtained for untreated cow horn (“Horn”), the material obtained from this powder by a spark plasma sintering method in accordance with the invention (“SPS”) and the material obtained from this powder by a high-pressure thermoforming method in accordance with the invention (“HPHT”);

(10) FIG. 9A shows a photograph of a sample of non-human animal leather in particulate form; and

(11) FIG. 9B show a photograph of a part obtained from this sample by a spark plasma sintering method in accordance with the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A) IMPLEMENTATION OF THE METHOD ON COW HORN POWDER

(12) The examples hereinafter are implemented using Aubrac cow horn.

(13) The natural horn is subjected beforehand to a step of grinding, in order to form a horn powder of which the particles have a diameter comprised between 200 and 500 μm.

(14) The density of the untreated horn is 1.28±0.01 g/cm.sup.3.

(15) The curve that represents the denaturation temperature of the proteins contained in this cow horn powder, according to the humidity rate of the powder, is established by differential scanning calorimetry (DSC) using a DSC1 instrument (Mettler-Toledo), with steel capsules medium pressure of 80 μL, at 10° C./min.

(16) The result obtained is shown in FIG. 1.

(17) It is observed for example that at a humidity rate of 9.6% (this rate can be obtained after drying of the horn at 40° C.), the denaturation temperature of the proteins is about 185° C.

(18) Moreover, the glass transition temperature of the denatured proteins is determined by dynamic mechanical analysis (DMA), using a Tritec 2000 DMA apparatus (Triton Technology Ltd), single cantilever, 2° C./min.

(19) To this effect, the horn powder at a humidity rate of 11.7% is subjected to high-pressure uniaxial molding, at 200° C. and 100 MPa for 3 min, using a MAPA 50 instrument (Pinette Emidecau Industries), in a square mold of 5 cm each side.

(20) The glass transition temperature of the material (reconstituted horn) thus obtained is measured by dynamic mechanical analysis.

(21) The result obtained is shown in FIG. 2.

(22) It is measured that the glass transition temperature of the material, after denaturation of the proteins that it is formed of, is 95° C.

(23) The material implemented for the experiments hereinafter has a humidity rate of 11.7% at 60% relative humidity of the air and a temperature of 20° C. At this humidity rate, the denaturation temperature of proteins is 181° C. at an atmospheric pressure.

EXAMPLE 1

Method by Spark Plasma Sintering

(24) A method according to the invention is implemented for the production of a cylindrical part 160 mm in diameter and 22 mm high, from the horn powder.

(25) The tools used consist of a matrix and pistons made of graphite. The dimensions of the matrix are as follows: outer diameter: 230 mm inner diameter: 160 mm.

(26) The inner bore of the matrix is covered with a flexible graphite sheet, the function of which is to ensure the tightness of the assembly, and to prevent jamming between the matrix and the pistons. A graphite sheet is also positioned on the surfaces of the pistons in contact with the powder, in order to prevent the sintered material from sticking to the pistons.

(27) The quantity of desired powder is introduced into the matrix, which is then closed by the two pistons. The whole is then disposed in the chamber of the spark plasma sintering device (Sumitomo Sinter 2000), which is placed under reduced pressure, at 5-10 Pa. The device is then programmed to apply on the matrix containing the powder a compression at a pressure of 32 MPa in 4 min.

(28) Simultaneously, the whole is heated by the Joule effect by an electrical current passing through the pistons and passing through the walls of the graphite matrix. The whole is brought to 150° C. in 7 min. The control of the temperature is carried out with a thermocouple inserted on the outer wall of the matrix. At this temperature, at this reduced pressure, the proteins entering into the constitution of the powder undergo the phenomenon of denaturation.

(29) The temperature is maintained at 150° C. for 10 min, after which the heating is cut off. The compression is maintained until the temperature inside the matrix reaches a value of 70° C., less than the glass transition temperature of the denatured proteins. The device is then opened, and the formed part is removed from the matrix.

(30) FIG. 3 shows the temperature and compression profiles of the matrix that contains the material, which are applied as a function of time (with the compression profile expressed in terms of displacement of the pistons).

(31) It is observed that after 10 min of maintaining the temperature in the matrix at 150° C., the temperature progressively decreases. In parallel, the compression exerted on the matrix is substantially constant, the displacement of the pistons, by a few millimeters, being due to the changes in the state of the material inside the matrix.

(32) At the end of the method, a pellet of densified horn of the desired shape is obtained, of an intense black color. This part is shown in FIG. 4.

EXAMPLE 2

Method by High-Pressure Thermoforming (HPHT)

(33) The device used is a MAPA 50 instrument (Pinette Emidecau Industries).

(34) The powder is placed in a rectangular mold of dimensions 5×1 cm, at a temperature of 200° C., greater than the denaturation temperature of the proteins. It is then compressed, at this temperature, at a pressure of 100 MPa, for 5 min. The whole is then cooled to a temperature of 90° C., less than the glass transition temperature of the denatured proteins, still under compression, before demolding.

(35) The material obtained at the end of the method is dark, and denser than the initial untreated horn: the density of this material is 1.31±0.02 g/cm.sup.3.

EXAMPLE 3

Characterizations of the Materials

(36) Water Adsorption Isotherms

(37) The water adsorption isotherms are established by the dynamic vapor sorption technique (DVS), using a DVS Advantage instrument (Surface Measurements Systems), at 5% to 95% relative humidity, with an interval of 10% and at 25° C., for: untreated cow horn (piece of horn of about 300 mg), the same horn after grinding (particle diameter comprised between 200 and 500 μm), and the material obtained by an HPHT method in accordance with the invention in Example 2 hereinabove.

(38) The results obtained are shown in FIG. 5.

(39) An increase in the hygroscopy of the native horn after grinding is very clearly observed here. This is mainly linked to the increase in the specific surface of the material.

(40) Then after transformation by high-pressure thermoforming in accordance with the present invention, the opposite effect is observed. The denaturation of the scleroproteins has caused a clear decrease in the hygroscopy (3% adsorbed water at 60% relative humidity, compared to 7% for the natural untreated horn for example). This could be due to the deployment on the surface of more hydrophobic amino acids during the modification of the secondary structures of the scleroproteins induced by the method according to the invention.

(41) Infrared Spectroscopy

(42) A Fourier transform infrared spectroscopy analysis (FTIR) is conducted, using a Spectrum 65 instrument (PerkinElmer), for: untreated cow horn, the same horn after grinding, the material obtained by a method of spark plasma sintering (SPS) in accordance with the invention in Example 1 hereinabove and the material obtained by an HPHT method in accordance with the invention in Example 2 hereinabove.

(43) The results obtained are shown in FIG. 6.

(44) A modification in the vibration frequency of the amide I band is observed in this figure: 1633 cm.sup.−1 for the native horn and 1627 cm.sup.−1 for the horn after SPS treatment and 1628 cm.sup.−1 for the horn after HPHT treatment. This modification is characteristic of the modification of the secondary structure of the keratin during the implementation of the method according to the invention.

(45) The amide II band (about 1530 cm.sup.−1) is rather relative to the environment of the N—H groups, and the drop in the intensity observed at 1540 cm.sup.−1 could be relative to a decrease in the hydrogen bonds of these groups after transformation by the method according to the invention.

(46) DSC Analyses

(47) For each one of the following materials: untreated horn (in the form of a piece of about 20 mg), the same horn after grinding (particle diameter comprised between 200 and 500 μm), the material obtained by an SPS method in accordance with the invention in Example 1 hereinabove and the material obtained by an HPHT method in accordance with the invention in Example 2 hereinabove, a differential scanning calorimetry (DSC) analysis is conducted using a DSC1 instrument (Mettler-Toledo), with steel capsules medium pressure of 80 μL, at 10° C./min.

(48) For each material the curve representing the variation in energy according to the temperature shown in FIG. 7 is obtained.

(49) These results confirm that the peaks that materialize the endothermic phenomenon associated with the denaturation of the proteins, present on the curves for the samples of untreated horn (these peaks are indicated by arrows in the figure) do not appear on the curves of the samples obtained after treatment of the horn by a method according to the invention. This confirms that the proteins contained in the materials obtained by methods in accordance with the invention were indeed all denatured during the implementation of these methods.

(50) X-ray Diffraction Analysis

(51) For each one of the following materials: untreated horn (in the form of a piece of about 20 mg), the material obtained by an SPS method in accordance with the invention in Example 1 hereinabove and the material obtained by an HPHT method in accordance with the invention in Example 2 hereinabove, an X-ray diffraction (XRD) analysis is conducted using a Bruker D8 Advance instrument.

(52) For each material the diagram shown in FIG. 8 is obtained.

(53) The absence of diffraction peaks on these diagrams, and the sole presence of a diffusion signal linked to the particular structure of the horn, demonstrate that the final material obtained by the method according to the invention is mainly amorphous.

(54) Moreover, nitrogen absorption/desorption experiments show that the physical structure of the materials obtained by the SPS method as well as by the HPHT method, implemented in accordance with the invention, approach that of an elastic matrix with different networks of porosity (micro/meso/macroscopic) that communicate. The observation of these materials under the optical microscope and under the scanning electron microscope confirm this hypothesis.

EXAMPLE 4

Comparative Example

(55) Aubrac cow horn in the form of powder of which the particles have a diameter of 250 μm, having a humidity rate of 0%, is implemented in this example.

(56) The denaturation temperature of the proteins contained in this horn powder, measured by DSC, is greater than 240° C.

(57) The powder is subjected to a high-pressure thermoforming method, according to the conditions described in Example 2 hereinabove, but with a heating temperature of 220° C., 225° C. or 230° C., less than the denaturation temperature of the proteins.

(58) For each one of the temperatures tested, at the end of this method a block of compressed powder is obtained, of which the density is not greater than that of the initial powder and having a low degree of cohesion.

B) IMPLEMENTATION OF THE METHOD ON LEATHER

(59) These examples are implemented using leather coming from shaving, in the form of ground fiber of which the granulometry is located between 100 and 250 μm.

(60) FIG. 9A shows a photograph of the natural starting material.

EXAMPLE 5

(61) This material is subjected to a spark plasma sintering method in accordance with the invention. The operating protocol is similar to the one described in Example 1 hereinabove, except for the fact that the heating temperature is 140° C. In the conditions applied, the scleroproteins contained in the initial material are denatured.

(62) At the end of this method the part shown in FIG. 9B is obtained. This part has the aspect of natural leather, and properties that are improved with respect to the natural starting material.

EXAMPLE 6

(63) The humidity rate of the material implemented in this example is comprised between 15 and 20%. At such a humidity rate, the denaturation temperature of the scleroproteins is measured to be 140° C. The density of this powdery material is comprised between 0.1 and 0.5 g/cm.sup.3.

(64) The powder is subjected to a high-pressure thermoforming method, according to the conditions described in Example 2 hereinabove, but with a heating temperature of 65° C. or 110° C., less than the denaturation temperature of the proteins, or with a heating temperature of 150° C., greater than the denaturation temperature of the proteins.

(65) For the sample treated at 150° C., in accordance with the invention, a compact solid block that is denser than the initial natural material is obtained, more particularly of a density comprised between 1.1 and 1.3 g/cm.sup.3. The material obtained has good mechanical properties, in flexural as well as tensile terms. The flexural modulus thereof is for example comprised between 1,600 and 2,500 MPa.

(66) However, for each one of the temperatures of 65° C. and 110° C., at the end of this method, a block with low coherence is obtained, of which pieces are detached, and of which the mechanical properties are much lower than those of the part obtained in accordance with the invention. In particular, the value of the flexural modulus, which reflects the solidity and the rigidity of the part, is more than 4 times less than that obtained for the part treated in accordance with the invention (flexural modulus comprised between 350 and 450 MPa).

EXAMPLE 7

Comparative Example

(67) The powder with a humidity rate of 15% is placed in the high-pressure thermoforming device and treated at a temperature of 170° C., greater than the denaturation temperature of the proteins, under compression at a pressure of 81 MPa, for 5 min. The compression is then stopped, and the whole is cooled by dissipation to a temperature of 90° C., before demolding.

(68) A part is obtained of which the density is less than that of the initial material.

EXAMPLE 8

(69) This example is implemented using leather that has been subjected to a vegetable tanning, in the form of powder with a density of 0.2 g/cm.sup.3, of which the granulometry is comprised between 500 and 1,000 μm.

(70) The powder is placed in a mold at a temperature of 150° C., greater than the denaturation temperature of the proteins. It is compressed, at this temperature, at a pressure of 81 MPa, for 4 min. The whole is then cooled to a temperature of 90° C., less than the glass transition temperature of the denatured proteins, still under the same compression, before demolding.

(71) The material obtained is ground and analyzed by Fourier transform infrared spectroscopy using a spectrometer provided with an ATR (attenuated total reflectance) system with a diamond tip.

(72) With respect to the spectrum carried out in the same conditions for the initial material, a substantial decrease in the peak is observed at 1,661 cm.sup.−1, corresponding to the α helices in the characteristic zone of the amide I. This reflects a decrease in the quantity of α helices in the structure of the scleroproteins from 48% for the initial material to 12% for the final material, showing that the denaturation of the scleroproteins was indeed carried out.

(73) Furthermore no appearance of a new peak is observed on the spectrum obtained for the final material, with respect to the initial material, which demonstrates that there was no formation or appearance of any compound during the implementation of the method according to the invention: the treatment according to the invention indeed modified the secondary structure of the scleroproteins without degrading them.

(74) A DSC analysis of the material obtained furthermore shows that, with respect to the initial material, the area of the endothermic peak associated with the thermal denaturation of the scleroproteins has significantly decreased.

C) IMPLEMENTATION OF THE METHOD ON OTHER NATURAL MATERIALS

(75) In all of these examples, a high-pressure thermoforming device MAPA 50 (Pinette Emidecau Industries) is used. The natural material in granular form is placed in the device in a rectangular mold of dimensions 5×1 cm.

EXAMPLE 9

Split Horn

(76) 10 g of cow horn in the form of needles 2 to 4 cm long, containing α keratin as the main protein, with a humidity rate of 11% (denaturation temperature of the scleroproteins of 180° C.), are subjected to a high-pressure thermoforming method, at a temperature of 210° C., greater than the denaturation temperature of the proteins, under compression at a pressure of 92 MPa, for 210 s. The whole is then cooled to a temperature of 90° C., less than the glass transition temperature of the denatured proteins, still under compression, before demolding. The part obtained at the end of the method is denser than the initial material, it is compact and has a smooth surface.

EXAMPLE 10

Feather

(77) 8 g of pieces of duck feathers roughly cut in the form of pieces of 2 to 4 cm, containing keratin as the main protein (denaturation temperature of the scleroproteins of 180° C.), are subjected to a high-pressure thermoforming method, at a temperature of 210° C., greater than the denaturation temperature of the proteins, under compression at a pressure of 92 MPa, for 150 s. The whole is then cooled to a temperature of 90° C., less than the glass transition temperature of the denatured proteins, still under compression, before demolding. The part obtained at the end of the method is denser than the initial material, it is compact and has a smooth surface.

EXAMPLE 11

Cashmere

(78) 10 g of cashmere goat from 2 to 4 cm long, containing α keratin as the main protein, with a humidity rate of 70% (denaturation temperature of the scleroproteins of 110° C.) are subjected to a high-pressure thermoforming method, at a temperature of 150° C., greater than the denaturation temperature of the proteins, under compression at a pressure of 46 MPa, for 210 s. The whole is then cooled to a temperature of 90° C., less than the glass transition temperature of the denatured proteins, still under compression, before demolding. The part obtained at the end of the method is denser than the initial material, it is compact and has a smooth surface. A vitrification of the initial material has occurred.

EXAMPLE 12

Whole Silk

(79) 10 g of pieces of silk of 1 cm.sup.2, containing fibroin as the main protein, with a humidity rate of 60%, are subjected to a high-pressure thermoforming method, at a temperature of 230° C., greater than the denaturation temperature of the proteins, under compression at a pressure of 50 MPa, for 210 s. The whole is then cooled to a temperature of 90° C., less than the glass transition temperature of the denatured proteins, still under compression, before demolding. The part obtained at the end of the method is denser than the initial material, it is compact and has a smooth surface.

EXAMPLE 13

Defibered Silk

(80) 10 g of silk fibers from 2 to 4 cm long, with a humidity rate of 60%, are subjected to a high-pressure thermoforming method, at a temperature of 230° C., greater than the denaturation temperature of the proteins, under compression at a pressure of 59 MPa, for 210 s. The whole is then cooled to a temperature of 90° C., less than the glass transition temperature of the denatured proteins, still under compression, before demolding. The part obtained at the end of the method is much denser than the initial material, it is compact and has a smooth surface.

EXAMPLE 14

Wool

(81) 10 g of pieces of wool from 2 to 4 cm long, containing α keratin as the main protein, with a humidity rate of 11% (denaturation temperature of the scleroproteins of 130° C.) are subjected to a high-pressure thermoforming method, at a temperature of 150° C., greater than the denaturation temperature of the proteins, under compression at a pressure of 50 MPa, for 210 s. The whole is then cooled to a temperature of 90° C., less than the glass transition temperature of the denatured proteins, still under compression, before demolding. The part obtained at the end of the method is denser than the initial material, it is compact and has a smooth surface.