Densified Hygroscopic Materials And Products Made Thereof

Abstract

A method for densifying a hygroscopic material is disclosed. The method is for hygroscopic material which may be a natural hygroscopic material or woodThe method comprises the steps of providing the hygroscopic material to be densified; pre-conditioning of the hygroscopic material by adjusting the moisture content of the hygroscopic material to a value within a predefined moisture range, if required; simultaneously heating and pressing the gas-tight packed hygroscopic material under predefined temperature and pressure conditions, whereby the moisture content of the hygroscopic material is kept constant; and obtaining a densified material.

Claims

1.-57. (canceled)

58. A method for densifying a hygroscopic material comprising at least one of plant materials, natural fiber materials, synthetic fiber materials, mineral wool, animal wool, skin-based materials, chitin-based materials, chitosan-based materials and protein-based materials, the method comprising the steps of: a) providing the hygroscopic material to be densified; b) pre-conditioning the hygroscopic material by adjusting the moisture content of the hygroscopic material to a value within a predefined moisture range; c) simultaneously heating and pressing the hygroscopic material under predefined temperature and pressure conditions, whereby the moisture content of the hygroscopic material is kept constant; c1) pre-heating the hygroscopic material to a first temperature at a first pressure and maintaining the first temperature and the first pressure for a predefined first dwell time, wherein the first temperature is from 50-100 C., the first pressure is from 0 to 2 MPa and the first dwell time is about 1 min-10 hours; c2) raising the pressure, while keeping the first temperature, to a second pressure and maintaining the second pressure for a predefined second dwell time, wherein the second pressure is from 9-50 MPa and the second dwell time is about 1-45 min; c3) increasing the temperature, while keeping the second pressure, to a second temperature and kept for a predefined third dwell time, wherein the second temperature is from 100-220 C. and the third dwell time is about 1-120 min; c4) reducing the temperature to room temperature; c5) reducing the pressure to ambient pressure; and d) obtaining a densified material.

59. The method according to claim 58, wherein the step of pre-conditioning further comprises the step of gas-tight packaging the pre-conditioned hygroscopic material in a gas-tight casing before performing the step of simultaneously heating and pressing.

60. The method according to claim 58, wherein the hygroscopic material to be densified comprises wood.

61. The method according to claim 58, further comprising the steps of chemically treating a surface of the hygroscopic material to be densified before the step of pre-conditioning by impregnation with at least one of natural polymers, synthetic polymers, natural resins, synthetic resins, waxes, sulfur, and molten metals.

62. The method according to claim 58, wherein the step of pre-conditioning further comprises the step of adjusting the moisture content of the hygroscopic material to be densified to 5-30%.

63. The method according to claim 58, further comprising the step of customizing at least one of a surface structure and a surface texture of the hygroscopic material to be densified and/or of the densified material.

64. The method according to claim 63, wherein by the customization of the surface structure and/or of the surface texture an ultrahydrophobic surface is generated by micro- and/or nano-structuration.

65. The method according to claim 58, wherein the obtained densified material is a translucent material.

66. The method according to claim 58, wherein: in step a), the hygroscopic material to be densified is provided in the form of a stack comprising at least two layers, at least one layer is made of hygroscopic material, and all layers of the stack are densified together.

67. The method according to claim 66, wherein the stack furthermore comprises at least one layer of: (i) metals and/or metal alloys; and/or (ii) polymeric materials; and/or (iii) inorganic materials selected from ceramics, glass, stone, clay, metal-organic frameworks (MOF), zeolites, coal, char, carbon black and/or active coal.

68. The method according to any of claim 66, wherein the outermost layers in the stack are made from wood-based material.

69. The method according to claim 66, further comprising the steps of at least one of treating at least one of the layers of the stack with an adhesive and arranging at least one adhesive foil between the layers of the stack, such that all the layers of the stack are bonded together upon densification in order to produce a laminated structure.

70. The method according to claim 66, wherein the stack comprises at least one of an electronic functionality, a magnetic functionality, and an optical label.

71. The method according to claim 66, wherein: the stack comprises at least three layers, a thickness of the outermost layers of the at least three layers is larger than a thickness of the one or more layers located in between the outermost layers, and at least two layers of the stack are made of wood with different wood grain directions.

72. The method according to claim 66, wherein after step d) at least one of a recess and an engraving is produced at least in the outermost layer, and wherein at least one of: a further electronic functionality, a further magnetic functionality and/or a further optical label is placed in the recess; and the recess and/or the engraving is produced such that the layer lying directly under the outermost layer is exposed, whereby the layer lying directly under the outermost layer is a layer with a color different than the color of the outermost layer.

73. A method for producing a laminated structure comprising the steps of: a) densifying a layer of hygroscopic material or b) densifying a stack comprising at least two layers, the at least one layer being made of hygroscopic material, c) laminating at least one further layer, the at least one further layer comprising at least one of: (i) another layer of hygroscopic material that was densified with the method according to claim 58; (ii) plant-based material, animal-based material and/or wood-based material; (iii) metals and/or metal alloys; (iv) polymeric materials; and (v) inorganic materials selected from ceramics, glass, stone, clay, metal-organic frameworks, zeolites, coal, char, carbon black and/or active coal; or other porous or non-porous inorganic materials.

74. The method according to claim 73, further comprising the steps of placing, before laminating, at least one of an electronic functionality and a magnetic functionality in a recess of the layer of hygroscopic material or in the stack, such that upon lamination, the electronic functionality and/or the magnetic functionality is embedded within the laminated structure.

75. The method according to claim 74, wherein the laminated structure comprises: a) a backside made of a layer of a densified or non-densified wood veneer; b) a frontside made of a layer of a densified or non-densified wood veneer; c) optionally, one or more further layers of a densified or non-densified wood veneer, or any non-wood-based material, which are arranged between the backside layer and the frontside layer; d) an integrated circuit, a memory device, a tracking device, a sensing device, an antenna and/or an electromagnetic coil; e) optionally, a support layer made of cellulosic material, e.g. paper, densified wood, and/or fleece, which is arranged between the backside and the frontside, for carrying one or more of the integrated circuit, the memory device, the tracking device, the sensing device, the antenna and/or the electromagnetic coil; whereby the layers are laminated and at least one of the layers is made of densified wood veneer.

76. The method for producing a product comprising the steps of (i) densifying a hygroscopic material according to claim 58 and/or producing a laminated structure according to claim 73, and (ii) manufacturing the product at least partly from the densified material and/or the laminated structure obtained in step (i), whereby the product is a musical instrument or a part of it, a furniture, a door, a door handle, a floor covering, a wall covering, a revetment, an automotive part, a covering for a ceiling, a sports equipment, a load-bearing element, a card, an electronic device, or a casing for an electronic device, or a casing for a mobile phone.

77. The method according to claim 76, wherein the product is at least one of a payment card, a credit card, a debit card, an identity card, a member card and an access card.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0243] Further advantages, features, and details of the various embodiments of this disclosure will become apparent from the ensuring description of a preferred exemplary embodiment and with the aid of the drawings. The features and combinations of features recited below in the description, as well as the features and feature combination shown after that in the drawing description or in the drawings alone, may be used not only in the particular combination received, but also in other combinations on their own, without departing from the scope of the disclosure.

[0244] The drawings used to explain the embodiments show:

[0245] FIG. 1A laminated structure consisting of four rectangular layers of densified wood veneer whereby adjacent layers have different wood grain directions;

[0246] FIG. 2A top view onto a wooden credit card made of densified veneer with an integrated chip and engraved letters, numbers and logo on the outer surface;

[0247] FIG. 3A partial view of the cross-section along line A-A of the card of in FIG. 2;

[0248] FIG. 4 An exploded assembly drawing of another card with electronic functionality;

[0249] FIG. 5A perspective view of another card with electronic functionality;

[0250] FIG. 6 The structure of the central inlay layer of the card of FIG. 5;

[0251] FIG. 7A flow chart illustrating the production method for obtaining a card as shown in FIG. 5;

[0252] FIG. 8 An inlay sheet comprising a total of 24 metal antennas that are regularly spaced apart from each other on a sheet of paper.

[0253] In the figures, the same components are given the same reference symbols.

DETAILED DESCRIPTION OF THE INVENTION

[0254] As used throughout the present disclosure, unless specifically stated otherwise, the term or encompasses all possible combinations, except where infeasible. For example, the expression A or B shall mean A alone, B alone, or A and B together. If it is stated that a component includes A, B or C, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. Expressions such as at least one of do not necessarily modify an entirety of the following list and do not necessarily modify each member of the list, such that at least one of A, B, and C should not be understood as including only one of A, only one of B, only one of C, or any combination of A, B, and C.

[0255] In order to produce a densified wood veneer, the following process has been followed:

[0256] In a first step, a wood veneer specimen with a thickness of about 0.6 mm, e.g. of maple wood, was used as hygroscopic materials and pre-conditioned to a moisture content of about 12% wood moisture.

[0257] In a second step, the pre-conditioned wood veneer specimen was packed in a gas-tight manner in temperature resistant and moisture tight metal foil.

[0258] Subsequently, the foil-packed wood veneer specimen was pre-heated to about 70 C., in a mechanical press in contact mode with only 1 MPa pressure.

[0259] Then the pressure was raised to 10 MPa at a rate of 1 MPa/minute and kept for 25 minutes at the temperatures of 70 C. as set before.

[0260] Thereafter, without affecting the pressure set before, the temperature was raised to a temperature of about 150 C. at a rate of 6-8 K/minute and kept for 45 minutes. After this pressing and heating process, the temperature was cooled down actively to room temperature and the pressure was released.

[0261] As a result of this process, a densified wood veneer with a thickness of 0.3 mm, a density of 1250 kg/m.sup.3, and a tensile elastic modulus of 27500 MPa was obtained.

[0262] As it turned out, the densified wood veneer has a high color stability. Specifically, the surface color difference E (according to EN ISO 11664-4) after exposure to UV radiation (>500 W/m.sup.2, <400 nm) or simulated sunlight (>500 W/m2, wavelengths 190-850 nm) for 1-48 hours (initial radiation time), typically 24 hours, or natural sunlight for 6-300 hours is less than 4, when compared to the surface color before exposure to the UV radiation. After the initial radiation time (i.e. 1-48 hours) the surface color remains essentially stable.

[0263] According to another example, in order to produce a densified wood veneer, the following process has been followed:

[0264] In a first step, a wood veneer specimen with a thickness of about 0.6 mm, e.g. of maple wood, was used as hygroscopic materials and pre-conditioned to a moisture content of about 12-13% wood moisture.

[0265] In a second step, the pre-conditioned wood veneer specimen was packed in a gas-tight manner in temperature resistant and moisture tight metal foil.

[0266] Subsequently, the foil-packed wood veneer specimen with adjusted moisture content of 12-13% was pre-heated to about 70 C. in a mechanical press in contact mode with only 1 MPa pressure.

[0267] Then the pressure was raised to 30 MPa at a rate of 15 MPa/minute and kept for 0.5-5 minutes at the temperatures of 70 C. as set before.

[0268] Thereafter, without affecting the pressure set before, the temperature was raised to a temperature of about 170-185 C. at a rate of 10-20 K/minute and kept for 10 minutes. After this pressing and heating process, the temperature was cooled down actively to room temperature and the pressure was released.

[0269] FIG. 1 shows a laminated structure 10 which was produced by laminating four rectangular layers of densified wood veneer 11, 12, 13, 14 as obtained in the above described process. The structure was formed by bonding adjacent layers 11, 12, 13, 14 together with an adhesive, e.g. a polyurethane or any other adhesive.

[0270] As indicated by the arrows in FIG. 1, the wood grain direction of adjacent layers are perpendicular to each other. This gives a highly stable laminated structure with reduced flexibility.

[0271] A wooden electronic card 20 as shown in FIGS. 2 and 3 and having a size of 85.5 mm54 mm0.8 mm was produced by according to the following process:

[0272] An upper layer 21 (frontside of the card) and a lower layer 22 (backside of the card) each consisting of a densified wood veneer obtained according to the above described process were provided and cut to a size of about 90 mm60 mm with a computerized numerical control laser engraving and cutting machine (CNCL).

[0273] A middle layer 23 consisting of a support sheet (densified veneer) with an integrated/glued electromagnetic coil 27 was provided and cut to the same size as the upper and lower layers 21, 22.

[0274] In the upper layer 21 and the middle layer 23, using the CNCL, a rectangular opening 21.1, 23.1 for an integrated circuit chip 24 with electrical surface contacts 24.1 was cut. In the lower layer 22, a rectangular recess 22.1 (deepness of approximately 0.1 mm) was engraved to provide additional place for the chip 24.

[0275] A polyurethane foil or gelatin/protein-glue sheet (40-80 g/m.sup.2; area density depending on type of wood) was applied on the inside of the upper layer 21 and the lower layer 22 as an adhesive foil. Each layer 21, 22, 23 as well as the chip 24 were carefully positioned and assembled to obtain the basic structure of the card 20. The assembled basic structure was then placed in a vacuum bag, which was then evacuated in order to apply a pressure of approximately 1 MPa. The vacuum was maintained for 6 hours.

[0276] The electronic functionality, e.g. a contactless payment function, of the card was tested before the outer surface of the upper layer 21 was engraved using the CNCL. Thereby, a first engraving 25 consisting of a logo and a second engraving 26 consisting of characters and numbers were produced. Thereby, the moving speed and laser power were adjusted in order to avoid burning of the wooden surface. Further engravings were provided on the outer surface of the lower layer 22 (not shown in FIGS. 2 and 3).

[0277] Thereafter, the final shape of the card was cut using the CNCL (using a different set of moving speed and laser power).

[0278] Subsequently, the engravings 25, 26 were colored using a silver color pen. The drying time was about 2 hours.

[0279] Then the front side 21 as well as the backside 22 of the card 20 were sanded and polished with by using sanding papers with gradually increasing fineness (180, 240, 320 and 600 grit size)

[0280] After testing the card functionality, e.g. contactless and contact payment function, the card was ready for use.

[0281] As shown in the cross-section of the card 20 in FIG. 3, the chip 24 and the electromagnetic coil 27 are fully embedded within the card body. Cards with such a structure turned out to be fully functional as required by standard ISO/IEC 7810:2019.

[0282] FIG. 4 shows an exploded assembly drawing of another card 40 with electronic functionality. Card 40 comprises an upper part consisting of two laminated densified wood veneers 41a, 41b. The wood grain direction of the densified wood veneers 41a, 41b are perpendicular to each other. Both wood veneers 41a, 41b comprise a rectangular opening 41a.1, 41b.1 for receiving an integrated circuit chip 44. The outermost wood veneer 41a furthermore carries a printed logo 47 on the outer side.

[0283] A lower part of card 40 consists of two further laminated densified wood veneers 42a, 42b. Also in this case, the wood grain direction of the densified wood veneers 42a, 42b are perpendicular to each other.

[0284] In the middle of the card, there is an inlay 43 consisting of a wood veneer carrying an electromagnetic antenna 47 with contacts for chip 44. All of the layers 41a, 41b, 43, 42a, 43b of the card are adhesively bonded together in the final product.

[0285] Card 40 consists of five densified wood veneers whereby the wood grain direction of adjacent veneers are perpendicular to each other. Therefore, card 40 is especially robust from a mechanical point of view.

[0286] FIG. 5 shows a perspective view of another card 50 with electronic functionality. The card 50 is a laminated structure made from five layers of a hygroscopic material. Specifically, it comprises two top layers 51a, 52a of wood veneer, two thin mid layers 51b, 52b of wood veneer and an inlay layer 53 comprising a metal antenna 57 with contacts for a chip on a paper. The structure of the inlay layer 53 is shown in FIG. 6.

[0287] A thickness of each of the two top sheets 51a, 52a is for example 0.6 mm whereas a thickness of the two thin mid sheets 51b, 52b is for example 0.2 mm. The inlay layer 53 has for example a thickness of 0.1 mm.

[0288] Similar to card 40, card 50 comprises an opening or recess 51.1, respectively, for receiving an integrated circuit chip (not shown in FIG. 5). A symmetric setup as shown in FIG. 5 is suitable for direct connection or soldering, respectively, (TE-Connect), i.e. conductive glue, Asymmetric conductive foil (ACF), i.e. conductive gluing tape and Coil-on-Module, i.e. that belongs to group of Inductive-Coupling-chip-coupling technology. Also for the embedding of chip-coil-plug (the dual-interface chip and the antenna are on the same module/plug), the symmetric setup is suitable, as the card will not warp or deform beyond the requirements as defined in the ISO 7816.

[0289] FIG. 7 shows a flow chart 700 illustrating the production method for obtaining a card such as shown in FIG. 5. Specifically, in a first step 701, two top sheets 51a*, 52a* of wood veneer, two thin mid sheets 51b*, 52b* of wood veneer and an inlay sheet 53* are provided in undensified form (the undensified form is denoted with the *). The sheets are sized such that several cards as shown in FIG. 5 can be produced in parallel. For this, the sheets have a size of for example about 650 mm300 mm. FIG. 8 shows the inlay sheet 53* comprising a total of 24 metal antennas that are regularly spaced apart from each other on a sheet of paper (in other implementations, sheet 53* can be produced with another number of antennas, e.g. 316=48 antennas).

[0290] Subsequently, the two undensified thin mid sheets 51b*, 52b* are impregnated in step 702 with an adhesive. Thereby, the sheets 51b*, 52b* are impregnated with an adhesive dissolved in a suitable solvent (e.g. water, ethanol, or any other organic solvent or the mixtures thereof), via soaking, vacuum-impregnation or surface coating such as brushing, spraying, on-rolling. For protein-based adhesives a proportion of 20-40 g/m.sup.2 is used.

[0291] Then, the impregnated thin mid sheets 51b*, 52b* are layered on top of each other together with the other sheets in step 703 in order to obtain a stack 50* or sandwich structure, respectively, comprising the sheets in the following order: top sheet 51a*-impregnated mid sheet 51b*-inlay sheet 53*, impregnated mid sheet 52b*-top sheet 52a*. The wood grain direction of the mid sheets 51b*, 52b* is perpendicular to the wood grain direction of the top sheets 51a*, 52a*. Additionally, the top sheets are covered with a plastic foil or a layer of non-sticking material sheet/foil.

[0292] The so produced undensified stack 50* then is placed in a suitable press and densified in step 704. The pressure and time can be adjusted depending on the surface to densify, the required color and thickness. As a result of step 704, a laminated structure 50 # is obtained. To obtain a uniform pressure distribution in the press, the stack 50* to be densified can be placed in between a press insert such as steel plates and an elastic material, e.g. rubber of a thickness of a few millimeters. Thereby, the following layered structure is present: elastic material-steel plate-stack 50 #-steel plate-elastic material.

[0293] Subsequently, the laminated structure is cut 705 with laser cutting, knives, punch or other type of cutters to obtain several individual cards 50 as shown in FIG. 5. For finalizing the card, integrated circuit chip is placed and adhesively bonded in the recces 51.1 of the card 50.

[0294] While the densification process, laminated structure and wooden card described herein constitute preferred implementations and embodiments of this invention, it is to be understood that the invention is not limited to these embodiments, and that changes may be made therein without departing from the scope of the invention.

[0295] For example, the process as described above can be performed with other types of wood or with other hygroscopic materials, such as e.g. mentioned in the general description above. Also it is possible to perform the densification process with hygroscopic materials, especially solid wood, with a much higher thickness. Also, it is possible to replace the densified wood layer in the middle layer of the card with a paper sheet.

[0296] Also, additional process steps can be performed, e.g. the step of adding a chemical agent for treatment of the wood veneer before pre-conditioning or pressing.

[0297] Regarding the laminated structure 10 shown in FIG. 1, it is possible to replace one or more of the layers of densified veneer by a non-densified veneer and/or another material. However, at least one layer has to be of densified veneer. In principle, it is even possible to make use of layers of synthetic materials such as plastics, if desired. Of course, the number of layers may be changed to lower or higher numbers.

[0298] The wooden card 20 of FIGS. 2, 3 and 5 may be made of a different number of layers of wood veneer. Also it is possible to replace a layer of densified wood veneer with a non-densified wood veneer or another material. Of course, additional layers of synthetic materials and/or coatings may be added as well.

[0299] Furthermore, the process 700 shown in FIG. 7 can be replaced by another process in which individual cards are directly from sheets cut accordingly beforehand. Also it is possible densify the individual sheets 51a*51b*, 52a*, 52b*, 53* before forming a stack and then laminating the sheets together to obtain the laminated structure. This structure then can be further processed to obtain the individual cards.

[0300] Another method of adding an adhesive layer to the mid layer sheet is attaching a thin film/foil of the adhesive to one or both sides of the mid layer sheet.

[0301] In a further implementation, a structuring sheet, e.g. surface structured wood, plastics and/or metal, is placed on top of the top sheets 51a*, 52a* in the process 700. Such as structuring sheet serves as an embossing insert, that allows for structuring the outer surface of the top sheets.

[0302] For asymmetric conductive foil chip-coupling technology (ACF), unlike the setup shown in FIG. 5, an asymmetric construction, i.e. the inlay position closer to the top surface, is more suitable. Thereby, for example, a six layer construction can be realized with either six wood layers with a wood inlay as the second layer from the top or four wood layers and two paper layers with the top paper inlay layer. Thereby, as described above, the individual layers of anisotropic materials, i.e. wood, and the layers of isotropic materials, i.e. paper, fleece, PLA, Protein film etc., are provided with various thicknesses, e.g. ranging from 10 m to 420 m per layer, such that a card with high dimensional stability, suitable dimensions and proper positioning of antenna and chip module is obtained in which the anisotropic forces induced by environmental conditions are effectively compensated.

[0303] In summary, the present invention provides a highly beneficial process for densifying hygroscopic materials such as wood. This allows for producing very thin structures with a high dimension stability. Especially, the inventive process makes it possible to produce fully functional cards which are compatible with all kind of contactless and contact-based terminals known today.

[0304] Since the apparatus and its methods of manufacture are described in detail above are examples of embodiments, they can be modified to a wide extent by the skilled person in the usual manner without leaving the scope of the invention. In particular, the arrangements and the proportions of the individual elements with respect to each other are merely exemplary. Some preferred embodiments according to the invention have been disclosed above. The invention is not limited to the solutions explained above, but the innovative solutions can be applied in different ways within the limits set by the claims.