JP2019001008A - Method of producing composite material molded article of cellulose fiber resin - Google Patents

Abstract

To provide a method of producing a composite material molded article of cellulose fiber resin, the method being capable of increasing productivity of the composite material molded article of cellulose fiber resin by additive manufacturing technology using a 3D printer.SOLUTION: A method of producing a composite material molded article of cellulose fiber resin of this invention comprises: a first step of molding a porous body using a 3D printer from a molding material including at least thermoplastic resin; a second step of impregnating an impregnation liquid made of an aqueous dispersion liquid including at least cellulose fibers; a third step of dehydrating the porous body impregnated with the impregnation liquid; and a fourth step of impregnating liquid resin into the dehydrated porous body and curing the body.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a cellulose fiber resin composite material molded body using a 3D printer.

  In recent years, a manufacturing technique using a 3D printer has been put into practical use. 3D printer is a general term for devices that can reproduce various materials directly from 3D data into free shapes by adding materials to the platform. Unlike a cutting process, a series of techniques using a 3D printer is characterized by manufacturing while adding materials to a workpiece, and is also called an additional manufacturing technique.

  Various types of 3D printers have been proposed, but the main categories are binder injection method, directional energy deposition method, material extrusion method, material injection method, powder bed fusion method, sheet lamination method, A liquid tank photopolymerization method is known. Any of these methods is expected to have many benefits such as net shaping, on-demand production, and molding of complex shapes.

  By the way, cellulose nanofibers are made from general-purpose plant fibers such as pulp, and the plant fibers are loosened into ultrafine fibers. Cellulose nanofibers have unique properties such as high aspect ratio, high specific surface area and transparency due to their fineness, in addition to properties such as low linear expansion coefficient, high elastic modulus, high strength, good coloration and carbon neutral derived from cellulose. It has special properties. Thus, it is known that cellulose nanofibers have many properties that are useful as reinforcing materials for composite materials.

  Β-glucose, which is a structural unit of cellulose, has three hydroxyl groups in its molecule. For this reason, cellulose fibers tend to agglomerate due to hydrogen bonds when the dispersion medium (generally water) is lost. Paper is a paper that positively utilizes this agglomeration phenomenon. When cellulose nanofibers agglomerate in the same manner, coupled with the size of the surface area, especially when the dispersion medium (generally water) is lost, the cellulose nanofibers agglomerate strongly, and even when added, they are not easily dispersed again. This property is generally disadvantageous when kneaded into a thermoplastic resin and used as a reinforcing material. This is because, in order to obtain a high-strength composite material, it is important that the specific surface area and aspect ratio of the reinforcing material are large, and it is not preferable that the fibers aggregate to form a small lump.

  On the other hand, in Patent Document 1, in order to use cellulose nanofibers as a reinforcing material for a high-strength composite material, a chemical modification treatment is performed to disperse the hydroxyl group of cellulose with a functional group having a small dipole moment. There is disclosed a means for making a thermoplastic material which is improved and melt-mixed with a resin to be used for injection molding or the like. In Patent Document 2, as a method not involving chemical modification treatment, an aqueous dispersion of cellulose nanofibers is aggregated in advance as a network-like porous body having a large specific surface area and aspect ratio like paper (that is, paper making), A technique for immersing, laminating, and curing it in an adhesive such as resol is disclosed.

JP 2012-214563 A Japanese Unexamined Patent Publication No. 2016-113595

  Here, as described in Patent Document 1, as the cellulose nanofiber composite material is described, it is described that as the amount of cellulose is increased, the fluidity of the material becomes worse and it becomes difficult to mold a complex-shaped object. Has been. In addition, the cellulose nanofiber composite material is considered to be limited in the shape that can be formed by laying it up due to the poor followability (draping) of the paper-made cellulose nanofiber sheet (that is, paper) to the curved surface. . Thus, it can be said that the cellulose nanofiber composite material has a great potential as a material but has many restrictions on the shape that can be molded.

  On the other hand, in the additive manufacturing technology using a 3D printer, although the productivity of a molded body made of a synthetic resin is generally increased, it is said that the productivity is generally high for a high-strength material having a tensile strength exceeding 100 MPa. hard. For example, there are problems that the material is expensive, the molded product has no mechanical isotropy, and the post-treatment depends on manual work. As a result, the additive manufacturing technology using the 3D printer is expected to provide many benefits, but is impeded from being applied to consumer products that are required to be practical and inexpensive.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a cellulose fiber resin capable of improving the productivity of a molded product of a cellulose fiber resin composite material by an additive manufacturing technique using a 3D printer. It is providing the manufacturing method of a composite material molded object.

  In order to solve the above problems, according to the present invention, a first step of modeling a porous body from a modeling material containing at least a thermoplastic resin using a 3D printer, and an impregnation comprising an aqueous dispersion containing at least cellulose fibers A cellulose fiber resin composite comprising: a second step of impregnating the porous body with the liquid; a third step of drying the porous body impregnated with the impregnating liquid; and a fourth step of curing the porous body. A method for producing a molded material is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the productivity of the cellulose fiber resin composite material molded object by the addition manufacturing technique using 3D printer can be improved.

It is explanatory drawing which shows the process order of the manufacturing method of the cellulose nanofiber resin composite material molded object which concerns on this embodiment. It is a perspective view of the 3D model of the sphere which consists of a cellulose fiber resin composite material. It is a figure which shows the filling pattern in the middle of shape | molding the spherical body of FIG. 2 with the 3D printer of a material extrusion system. It is a schematic diagram of the manufacturing apparatus used for the manufacturing method of the cellulose nanofiber resin composite material molding which concerns on this embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

<< 1. Details of additive manufacturing technology >>
First, an example of an additive manufacturing technique for a high-strength material that has been proposed or put into practical use will be described.

  As a technique for additionally producing an isotropically high-strength molded body, there is an additive production technique for metal powder by a directional energy deposition method or a powder bed fusion bonding method. In this case, a material that is specially adapted for the composition and shape is used, and is often an expensive material. In addition, a solid laser oscillator or an electron beam oscillator used as a heat source has poor thermal efficiency or has a limit in increasing the output, and therefore the molding cycle time becomes long. Further, the molded body needs to be welded to the platform with an appropriate strength, and manual work is required each time the cutting work or the peeling work is performed.

  As another type of additional manufacturing technology, there is an additional manufacturing technology based on a material injection system or a liquid tank photopolymerization system. Cyanate ester prepolymers having excellent strength such that the tensile strength exceeds 100 MPa have been commercialized as materials used in the additive manufacturing technology by the material injection method or the liquid tank photopolymerization method. However, the material is generally expensive and cannot be said to be a practically versatile and inexpensive material. In addition to the support material cutting and peeling operations, there are a lot of complicated manual operations such as surface cleaning and treatment of the waste liquid that becomes industrial waste.

  As another type of additional manufacturing technology, there is an additional manufacturing technology based on a binder injection system. In the case of additive manufacturing technology using a binder injection method, molding is performed using wax powder as a material, and lost wax casting is performed using the molded body as a wax mold, thereby additionally manufacturing a strong metal in a two-stage method. Can do. However, in lost wax casting, many of the work processes are manual operations, and it is impossible to reproduce the elongated shape and hollow structure, and there are distortions in the molded product and casting holes that are unique to the cast product. Many new problems that may not have occurred.

  As another type of additive manufacturing technique, there is an additive manufacturing technique based on a powder bed fusion bonding system. In the additive manufacturing technique based on the powder bed fusion bonding method, a fiber reinforced resin can be additionally manufactured by using a mixture of carbon fiber or glass fiber powder and resin powder as a material. In order for any composite material to exhibit high strength, it is generally desirable that the aspect ratio and specific surface area of the reinforcing material be large. For this reason, it is desirable from the viewpoint of strength in the additive manufacturing technology using the powder bed fusion bonding method from the viewpoint of strength, but since the material powder has a particle size of several tens of microns, it is necessary to increase the aspect ratio. It is necessary to reduce the width of the fiber to submicron or nano size, which is not practical. When a reinforcing material having a small aspect ratio (for example, less than 5) such as a bead shape is used, high strength cannot be expected.

  Furthermore, in the case of an additive manufacturing technique using a powder bed fusion bonding method, the material is laminated one layer at a time so as to be pressed against the platform by rollers or blades, and therefore the fiber powder tends to be oriented only on the horizontal surface of the modeling platform. For this reason, the molded product is weak against the stress that splits or peels the stacked layers, and there is an example in which the tensile strength in the Z direction (the thickness direction of the layer) is lower than that of the base material alone. That is, a molded product obtained by an additive manufacturing technique based on a powder bed demand coupling method is not isotropic in mechanical properties. Furthermore, the fiber powder is irritating and may deteriorate the working environment.

  As another type of additive manufacturing technique, there is an additive manufacturing technique based on a material extrusion system. In the additive manufacturing technique using the material extrusion method, a fiber reinforced resin made of carbon long fibers can be additionally manufactured by injecting the carbon continuous fibers from the nozzle while roving them simultaneously with the thermoplastic resin. Dedicated 3D printers used in additive manufacturing technology by material extrusion are also in practical use. However, since the 3D printer can orient the fibers only on the horizontal surface of the modeling platform, the strength against the stress that splits or peels the stacked layers of molded products is only expected to be the same as that of the base material such as polyamide. Can not. That is, a molded product obtained by an additive manufacturing technique using a material extrusion method is not isotropic in mechanical properties. Furthermore, in the additive manufacturing technique using the material extrusion method, there is a possibility that the molding efficiency is low except in a case where there is a certain limit in the scanning speed of the nozzle and a large-scale extrusion apparatus is used.

  In addition, in the powder bed fusion bonding method or material extrusion method, after molding a material used in thermoplastic metal injection molding (MIM) as an additional production material, degreasing and sintering in a furnace By doing so, a metal high-strength molded product having a somewhat uniform structure can be obtained. However, in addition to the high unit price of such a material, a furnace for performing a degreasing process and a long-time sintering process is required. In addition, the material extrusion method has a certain limit in molding speed, and cannot be said to be an efficient device. Furthermore, in the degreasing process and the sintering process, it is necessary to adjust the temperature management program which varies depending on the shape and material. Further, the unsintered intermediate molded product after degreasing may be fragile, and if it fails in handling, it may be easily broken, resulting in a decrease in yield and consequently production efficiency. For example, from the viewpoint of the thermal efficiency of the furnace, it can be said that if a large furnace is used and heat treatment is carried out in large quantities together with similar shapes that can be fired under the same conditions and parameters, the production efficiency can be significantly increased. However, 3D printers are often originally intended for the production of many types of small lots, and as a result, there is a high possibility that only the disadvantages of 3D printers and MIM technology remain.

  As described above, there have been various attempts to apply 3D printers to produce high-strength material molded products using various additive molding techniques, all of which have yielded good results from the viewpoint of physical properties, production efficiency, and cost of the molded products. It can not be said.

<< 2. Cellulose fiber resin composite material production method >>
The manufacturing method of the cellulose fiber resin composite material molded body according to the present embodiment will be specifically described.

Drawing 1 is an explanatory view showing a process of a manufacturing method of a cellulose fiber resin compound material fabrication object concerning this embodiment. The manufacturing method according to the present embodiment includes the following four steps.
A step of forming a porous body from a mixed material containing at least a water-soluble substance and a water-insoluble substance using a -3D printer (hereinafter referred to as “first step”).
-A step of impregnating a porous body with an impregnation liquid comprising an aqueous dispersion containing at least cellulose fibers (hereinafter referred to as "second step").
-A step of drying the porous body impregnated with the impregnation liquid (hereinafter referred to as "third step").
A step of impregnating a dried porous body with a liquid resin and then curing (hereinafter referred to as “fourth step”).
Hereinafter, the manufacturing method according to the present embodiment will be described in detail for each process.

<2-1. First step>
The first step is a step of modeling a porous body from a mixed material containing at least a water-soluble substance and a water-insoluble substance using a 3D printer. In the first step, a porous body is formed from arbitrary 3D data using various 3D printers. The porous body modeled in the first step is a porous body having a plurality of voids spatially connected to each other, and is also referred to as “open-cell porous body”. The 3D printer system used is preferably a material extrusion system, a powder bed melt bonding system, or a paper lamination system, and among them, the resin powder bed melt bonding system is preferable because of its excellent productivity.

  In order to obtain a high-strength final molded product, it is important that the content of cellulose nanofibers, which are reinforcing materials, is large, and that a network in which cellulose nanofibers are connected by hydrogen bonds is formed. Therefore, it is desirable that the porosity of the porous body to be shaped is high. Furthermore, the resin used as the material of the porous body needs to have a certain hydrophilicity. Below, the selection of the material in the case of using the 3D printer by each system, and the point of modeling of a porous body are demonstrated.

(2-1-1. Material extrusion method)
A case where a material extrusion type 3D printer is used in the first step will be described. The material extrusion method is generally cheaper and can be used most easily. The material extrusion type 3D printer is rarely used originally for forming a dense body, and the inside of the model is drawn with a pattern with a hole. Therefore, a porous body having about 70% of the internal space of the 3D model can be created using commercially available or publicly available equipment and software. Various drawing patterns such as linear, honeycomb, lattice, or Voronoi have been put to practical use. In order to achieve this, it is preferable to use a lattice pattern in which a linear pattern is crossed for each layer from the viewpoint of ease of mounting. From the viewpoint of strength and isotropy, for example, in a certain coordinate space, the formula [sin (x) · cos (y) + sin (y) · cos (z) + sin (z) · cos (x) = [0] is preferably a method using a filling pattern in which a minimal periodic curved surface called a gyroid is expressed by a set of coordinate points (x, y, z) satisfying [0].

  A thermoplastic resin that can be used as a modeling material when the material extrusion method is used will be specifically described. Affinity (that is, a small contact angle) between the porous body to be formed and water is required. This is because when the impregnating liquid containing cellulose nanofibers impregnated in the second step is dried in the third step, a large number of separated ball-shaped impregnating liquids are formed when the affinity for the porous body is low. This is because the formation is not performed and a fine lump of cellulose nanofibers is formed. In that case, the structure of the molded product becomes non-uniform, or the aspect ratio of the cellulose nanofibers as the reinforcing material becomes small, so that the strength of the molded product does not appear.

  As a standard for measuring the hydrophilicity of a porous body formed using a modeling material containing a thermoplastic resin, a material having a contact angle with water of, for example, less than 65 degrees when the material is processed into a flat plate is used. It is preferable to do. Examples of such thermoplastic resins include polyamides, polylactic acid, polymethyl methacrylate, and novolak resin. For example, polyamide-based, polylactic acid, and polymethyl methacrylate wires are commercially available, and these materials can be used. However, the thermoplastic resin is not limited to the above example.

  In addition, after impregnating the impregnating liquid into the porous body in the second step, whether or not a network is formed when dried in the third step depends on impurities derived from cellulose raw materials, drying methods, etc. It is also influenced by other factors. As a result, network formation may not be observed during drying of the impregnating liquid. In such a case, the surface tension on the material side may be increased by kneading a hydrophilic component such as wood powder or cellulose into the modeling material forming the porous body, or a surfactant is added on the impregnating liquid side. By doing so, the surface tension may be lowered. Thereby, formation of a network can be promoted. Polylactic acid wires filled with wood flour are also commercially available and can be used.

  The modeling of a porous body having a porosity of 80% or more may be difficult in principle depending on the shape of the modeled object. In order to further increase the porosity, a material in which a water-soluble substance such as polyvinyl alcohol or sugar, a thermoplastic synthetic resin, and a fiber are mixed may be used. As such a material, for example, “Porollay” series of FormFutura can be used. In this case, when washed with water, about 50% of the mass is eluted and becomes voids, and thus a porous body having a maximum porosity of about 90% can be formed after washing.

  FIG. 2 is a perspective view of a 3D model 1 of a certain sphere, and FIG. 3 is a cross-sectional perspective view showing an internal pattern in the middle of modeling the 3D model 1. As shown in FIG. 3, according to the material extrusion method, a modeling material becomes a porous body without any particular effort by injecting a modeling material including at least a thermoplastic resin from a nozzle along a pattern. However, the finer the pores, the more uniform the structure and the dimensional accuracy of the modeled object. Therefore, it is preferable to form a finer porous using a nozzle having a smaller diameter.

  In this case, by selecting an appropriate material as the material to be used, it is possible to suppress a decrease in productivity due to the use of a small-diameter nozzle and to form a finer porous material as a whole. Can be made. For example, a modeling material in which a water-soluble substance such as sugar or polyvinyl alcohol, a fiber, and a synthetic resin are kneaded in advance in a thermoplastic resin can be used. A porous body having a fine open-cell porous structure can be efficiently modeled by washing with water and leaching after the modeling by the material extrusion method using such a material is completed.

  In addition, when mixing a water-soluble substance with modeling material, as a water-soluble substance, one or several mixtures, such as a scroll and polyethyleneglycol, can be used other than polyvinyl alcohol, for example. Moreover, when mixing a fiber with a modeling material, as a fiber, one or several mixtures of various cellulose derivatives, glass fiber, etc. other than wood powder and a cellulose can be used, for example. Moreover, when mixing a synthetic resin with modeling material, as a synthetic resin, one or several mixtures, for example among polyamides, polylactic acid, etc. can be used.

(2-1-2. Powder bed fusion bonding method)
An example in which a 3D printer using a resin powder bed fusion bonding method is used in the first step will be described. An apparatus with high productivity has already been put into practical use as a powder bed fusion bonding type 3D printer that handles thermoplastic resins. Such 3D printers are not limited to prototyping in the modeling of plastic products, but are widely applied to final products. By creating a 3D model having a large number of holes and outputting a modeling material containing at least a thermoplastic resin, a porous body can be modeled by a powder bed fusion bonding method.

  However, in the case of the powder bed fusion bonding method, in the porous 3D model having innumerable pores, the data size tends to be large, and the creation of the 3D model may not be easy. In the first place, when the resolution of the 3D printer is insufficient, it is possible that a sufficiently fine porous material cannot be formed. In addition, the larger the number of fine holes, the more difficult it is to remove excess powder after completion of modeling. For this reason, in this embodiment, when using a powder bed fusion bonding type 3D printer, from a modeling material in which a water-soluble substance powder and a water-insoluble substance powder are mixed in advance using non-porous 3D data. Build a 3D model. For example, the modeling material may be a modeling material in which salt, a thermoplastic resin powder, and a fibrous powder are mixed. After performing addition manufacture using such a modeling material, an open-cell porous body can be obtained by wash | cleaning a modeling thing. By using such a modeling material, a portion that is dense on the 3D data can be made porous and reproduced.

  Specifically, when using a powder bed fusion bonding type 3D printer, it is advantageous in terms of production cost to use a material that has already been generally used as a modeling material. For example, nylon 12 can be used. Moreover, although it is not a general material, the intensity | strength of a final molded product can be improved by utilizing the powder of a novolak resin. The novolac resin is an intermediate product when synthesizing the phenol resin and is thermoplastic. Although the novolak resin itself has a low degree of polymerization and a low utility value, it is polymerized as a phenol resin having a strong three-dimensional network by reacting with a crosslinking agent such as hexamine. Nylon 12 and novolak resin are both derived from functional groups such as amide bonds and hydroxyl groups in the molecular structure and are polar among synthetic resins, and the contact angle with water is about 60 degrees. It is preferable to use such nylon 12 or novolac resin by mixing a water-soluble substance such as salt, sugar, polyvinyl alcohol and the like.

  At this time, the volume ratio between the water-soluble substance and the mixed material of the water-insoluble synthetic resin is 8: 2 to 9.5: 0.5 from the viewpoint of increasing the filling rate of the cellulose nanofiber as the reinforcing material. Within the range is preferred. The term “volume” as used herein refers to the theoretical net volume of the material excluding voids, not the powder volume, but the mass of the powder material divided by the specific gravity. However, since the volume ratio may affect the moldability, such as the plasticity of the synthetic resin is poor and modeling becomes difficult, or the model is heavy and deforms under its own weight, so that the volume ratio is appropriate. It is preferable to adjust. Although it depends on the fluidity at the time of melting, surface tension, or specific gravity, when the proportion of synthetic resin is increased and the volume ratio of synthetic resin exceeds 50%, the water-soluble substance is spatially surrounded by synthetic resin during addition production. May begin to occur, resulting in defects in the final molded product. In this case, the strength of the final molded product decreases, and at the same time, the proportion of the reinforcing material in the final molded product decreases. Therefore, the volume ratio of the water-soluble substance to the water-insoluble synthetic resin mixed material is within the range of 9: 1 to 5: 5, the moldability is good, and the volume ratio of the water-soluble substance is as high as possible. It is preferable to set.

(2-1-4. Sheet lamination method)
A case where a sheet stacking type 3D printer is used in the first step will be described. If a model using paper as a material is used in the additive manufacturing by the sheet lamination method, a porous shaped article whose main component is paper can be obtained without any special effort. For example, it is possible to use a 3D printer that cuts out a paper layer and laminates it with an adhesive ink jet. For example, “Mcor Arke” from Mcor can be used. For example, about 50% of the inside of the porous body formed by the sheet lamination method is a void. Moreover, since the main component of a molded article is paper, ie, a cellulose, it is hydrophilic.

<2-2. Second step>
The second step is a step of impregnating the porous body with an impregnation liquid composed of an aqueous dispersion containing at least cellulose nanofibers. In this case, an adhesive may be added to the impregnating solution as needed in addition to the dispersion of cellulose nanofibers serving as a reinforcing material.

  In the second step, the impregnating liquid needs to have fluidity from the viewpoint of productivity. Moreover, it is preferable that the cellulose nanofiber in an impregnation liquid is a high concentration. Cellulose nanofibers have different viscosities even at the same concentration depending on the aspect ratio and the manufacturing method, and therefore the concentration range of the impregnating liquid needs to be appropriately adjusted. For example, in any production method, an aqueous dispersion of cellulose nanofibers containing 3% by mass or more of cellulose nanofibers often loses fluidity, and when it becomes 5% by mass, it becomes a texture like paper clay. In general, it is desirable that the impregnating liquid has a low viscosity in order to enhance the penetration into the pores. However, since the cellulose nanofiber aqueous dispersion is a pseudoplastic fluid, the cellulose nanofiber water is impregnated when impregnating the porous material. The fluidity is increased by the shearing force acting on the dispersion, and it becomes easy to enter the pores. For this reason, it is preferable to adjust the concentration of the impregnating liquid so as to be as high as possible within the range in which the fluidity of the impregnating liquid is recognized.

  When an adhesive is added to the impregnating liquid in the second step, the adhesive has a function of improving the adhesion between the fiber and the base material by the anchoring effect. The adhesive component is preferably one that can be copolymerized with the liquid resin that is impregnated and cured in the fourth step. As such an adhesive, for example, a water-soluble adhesive mainly composed of a prepolymer such as lignin, resol, urea resin, and methylolmelamine can be mentioned as a general-purpose and inexpensive adhesive. In particular, it is more preferable that the adhesive is lignin or resol because a material having a small amount of volatile components other than water (typically formaldehyde) is suitable from the viewpoint of the working environment during heat drying.

  The addition amount of the adhesive is preferably in the range of 1 to 20% when the mass of the cellulose nanofibers in the impregnating liquid is 100%. In this case, even if the added amount of the adhesive exceeds 20%, the effect of improving the strength is hardly exhibited, and the cost simply increases. In addition, when the liquid resin that is impregnated and cured in the fourth step uses a monomer liquid having a small molecule such as methyl methacrylate and a low viscosity, the impregnating solution used in the second step does not include an adhesive. Is preferred.

(2-3. Third step)
The third step is a step of drying the porous body impregnated with the impregnating liquid. In the third step, when the impregnating solution is dried, when moisture is positively heated and rapidly dried, a fluid-permeable three-dimensional network-shaped xerogel is formed. Therefore, the second step and the third step By repeating the above, high filling of cellulose nanofibers as a reinforcing material becomes possible. The reason for this is that only when water is rapidly boiled, a hole through which water vapor is ejected is formed in the cellulose and obstruction is obstructed. On the contrary, in a dry form close to evaporation where moisture is lost only from the surface of the impregnating liquid, a cellulose film is formed on the surface of the porous body, which closes the pores, which is inconvenient for molding.

  In the third step, if the porous body impregnated with the impregnating liquid is aerated to a high temperature to boil the moisture, the additionally produced porous body material may be softened and deformed. For this reason, the boiling point of water | moisture content is lowered | hung by heating in a pressure-reduced atmosphere, and a deformation | transformation of a porous body can be suppressed. For example, by heating a porous body impregnated with an impregnating liquid in a reduced pressure atmosphere of 0.01 MPa at a temperature within a range of 40 to 70 degrees Celsius, a resin having a melting point of less than 100 degrees Celsius such as a novolac resin Even so, it is possible to obtain a xerogel that does not lose its shape and is sufficiently fluid permeable.

  Examples of the drying method by heating include heat conduction or radiant heat by heating the whole decompression vessel, introduction of a small amount of warm air into the decompression vessel, or irradiation of infrared rays or microwaves into the decompression vessel. However, the heating means is not limited, and a plurality of means may be combined. In order to heat the porous body to the inside and boil it, microwave irradiation is preferred. The method of irradiating microwaves is excellent in heating efficiency and easy to increase the output, and therefore excellent in productivity.

(2-4. Fourth step)
The fourth step is a step of curing the porous body. In the example of this embodiment, the porous body dried by repeating the second step and the third step is partially or completely impregnated with a liquid resin and then cured. In the fourth step, the cavity of the porous body on which the three-dimensional network-like cellulose nanofiber xerogel is deposited is partially or completely impregnated with a liquid resin and cured. The liquid resin that can be used in the fourth step is compatible with the thermoplastic resin used in the first step and the second step in addition to the physical properties such as the viscosity of the liquid resin, the speed of curing, and the specific strength of the cured product. And selection based on copolymerization potential. For example, when polymethyl methacrylate or polyamide is used for forming a porous body, an acrylic impregnating agent generally used for the impregnation treatment can be suitably used because it has good adhesiveness.

  Alternatively, when the porous body is a novolak resin and lignin is added as an adhesive in the second step, it is also an intermediate product of a phenol resin, and is impregnated with a liquid resol resin having self-reactivity. A novolac resin and lignin can be copolymerized. Similarly, among melamine and benzoxazine-based resins, there are resins copolymerizable with phenols, and these resins can be used. In particular, benzoxazine-based resins are free of by-products (water, amine, formaldehyde, etc.) released during curing. In addition, since benzoxazine-based resin does not generate voids in the composite material, a dense and strong molded product can be obtained.

  When an adhesive is added to the impregnating liquid in the second step, the adhesive may be cured only in the fourth step without impregnating the liquid resin. Thereby, it can also be set as the lightweight molded product containing a space | gap.

<3. Configuration example of manufacturing equipment>
In regard to the impregnation apparatus and the dryer used in the second to third steps, when carrying out the method for producing a cellulose fiber resin composite material molded body according to the present embodiment with practical production efficiency, pressure reduction, pressurization, and micro It is preferable to use an apparatus that can continuously and automatically perform all of the wave irradiation. Thereby, the 2nd process-the 3rd process can be carried out in the same container (casing). Hereinafter, a configuration example of a manufacturing apparatus capable of continuously and automatically performing the second to third steps will be described.

  FIG. 4 is a schematic diagram illustrating a configuration example of the manufacturing apparatus 10. The illustrated manufacturing apparatus 10 includes a pressurization / decompression container 61 and a microwave heating apparatus 11 and is configured as a combined pressurization / depressurization / impregnation apparatus. The pressurizing / depressurizing container 61 is provided in the microwave heating apparatus 11. An electrical on-off valve 21 is connected to the pressurization / decompression container 61 through an intake pipe 31. The intake pipe 31 is opened and closed by driving the on-off valve 21. The humidity sensor 51 detects the humidity of the intake air supplied to the pressurized / depressurized container 61.

  A vacuum / pressurization pump 29 is connected to the pressurization / decompression container 61 through an exhaust pipe 33. By driving the vacuum / pressurization pump 29 as a vacuum pump, the air in the pressurization / decompression container 61 is sucked through the exhaust pipe 33 and is discharged from the exhaust port 43, and the inside of the pressurization / decompression container 61. Is depressurized. A liquid level sensor 55 is provided in the exhaust pipe 33, and the liquid level sensor 55 detects the liquid level of the impregnating liquid at the installation position of the liquid level sensor 55. The humidity sensor 53 detects the humidity of the air discharged from the pressurized / depressurized container 61. In addition, by driving the vacuum / pressurization pump 29 as a pressurization pump, air is sucked from the exhaust port 43 and is supplied into the pressurization / decompression container 61 through the exhaust pipe 33. The decompression container 61 is pressurized.

  Further, the impregnating liquid reservoir 13 is connected to the pressurizing / depressurizing container 61 through the impregnating liquid pipe 35. Both ends of the impregnating liquid pipe 35 are connected to the pressurized / depressurized container 61 and the bottom of the impregnating liquid reservoir 13, respectively. An impregnating solution 63 is stored in the impregnating solution reservoir 13. An electric on-off valve 23 is provided in the middle of the impregnating liquid pipe 35. The impregnating liquid pipe 35 is opened and closed by driving the on-off valve 23. An electrical on-off valve 25 is connected to the upper part of the impregnating liquid reservoir 13 through an exhaust pipe 37. A compressed air tank 15 is connected to the upper part of the impregnating liquid reservoir 13 via a compressed air supply pipe 39. An electric on-off valve 27 is provided in the middle of the compressed air supply pipe 39. The compressed air supply pipe 39 is opened and closed by driving the on-off valve 27.

  In FIG. 4, electrical components for control are omitted for simplicity, but the four on-off valves 21, 23, 25, 27, the vacuum / pressurization pump 29, and the microwave heating device 11 in FIG. Are connected to a power source, a control device, and a terminal, and are operated by the control device executing a program.

  In the second step and the third step described above, the porous body impregnated with the aqueous dispersion of cellulose nanofibers is put into the pressurized / decompressed container 61, and the reduced pressure step, the liquid injection step, the pressurized step, the drainage are performed. The liquid process and the heating process are repeated an appropriate number of times. In that case, the manufacturing apparatus 10 shown in FIG. 4 is used as follows.

(Decompression step)
In the depressurization step of depressurizing the inside of the pressurization / decompression container 61, the vacuum / pressurization pump 29 is driven as a vacuum pump with all the open / close valves 21, 23, 25, 27 closed. Thereby, the inside of the pressurized / depressurized container 61 is depressurized.

(Liquid injection process)
In the liquid injection process for supplying the impregnating liquid into the pressurized / depressurized container 61, the open / close valves 23 and 27 are opened while the vacuum / pressurized pump 29 is continuously driven as a vacuum pump. This state is maintained while the output of the liquid level sensor 55 is Low. At this time, it is possible to inject liquid only with the capability of the vacuum / pressurization pump 29 with only the opening / closing valve 23 opened, but only the atmospheric pressure to the impregnation liquid pipe 35 having a maximum diameter of about 10 mm where the microwave does not leak. In some cases, productive injection speed may not be obtained with the liquid injection and the pressure feeding. Therefore, the on-off valve 27 is opened to increase the pressure of the impregnating liquid. Thus, compressed air is supplied from the compressed air tank 15 to the impregnating liquid reservoir 13, and the impregnating liquid is pumped from the impregnating liquid reservoir 13 into the pressurized / depressurized container 61. Thereafter, the on-off valve 23 is closed when the impregnating liquid is supplied until the output of the liquid level sensor 55 becomes High. At the same time or thereafter, the on-off valve 27 is closed. In this way, the impregnating liquid is filled into the pressurized / depressurized container 61.

(Pressure process)
In the pressurizing step of pressurizing the inside of the pressurizing / depressurizing container 61, the vacuum / pressurizing pump 29 is driven as a pressurizing pump with all the open / close valves 21, 23, 25, 27 closed again. . As a result, the pressure in the pressurization / decompression container 61 increases while the pressurization / decompression container 61 filled with the porous body is filled with the impregnation liquid, and the impregnation liquid is impregnated into the porous body. .

(Drainage process)
In the draining process of discharging the impregnating liquid from the pressurized / depressurized container 61, the on-off valves 23 and 25 are opened while the vacuum / pressurized pump 29 is continuously driven as a pressurized pump. As a result, the impregnating liquid in the pressurized / depressurized container 61 is pumped to the impregnating liquid reservoir 13.

(Heating process)
In the heating step of heating the inside of the pressurized / depressurized container 61, the microwave heating device 11 is operated to heat the pressurized / depressurized container 61. At this time, the on-off valve 21 is opened, and the vacuum / pressurization pump 29 is again driven as a vacuum pump. As a result, air is supplied into the pressurized / depressurized container 61 through the intake pipe 31 and is exhausted through the exhaust pipe 33. A small amount of air supplied through the intake pipe 31 is sufficient for exhaust heat. When the difference between the humidity value detected by the humidity sensor 51 provided at the intake port 41 and the humidity value detected by the humidity sensor 53 provided at the exhaust port 43 falls within a predetermined range, preferably the difference When there is no more, the operation of the microwave heating device 11 is stopped, and the heating is finished.

  In addition, when a novolac resin is used for modeling of a porous body, the novolac resin has a property of absorbing microwaves. For this reason, it is possible to prevent overheating or fuming by introducing a small amount of air and cooling the container while decompressing the container.

  As described above, using the manufacturing apparatus 10, the decompression process, the liquid injection process, the pressurization process, the drainage process, and the heating process can be repeated continuously and automatically an appropriate number of times. Thereby, it is possible to fill the porous body with cellulose nanofibers as a reinforcing material while the porous body is being put into the pressurized / depressurized container 61. At this time, since a network is formed in which cellulose nanofibers geometrically enter the porous body, the strength against stress in all directions can be increased.

  Hereinafter, the Example of the manufacturing method of the cellulose fiber resin composite material molded object which concerns on this embodiment is demonstrated. In Example 1, an example will be described in which a molded body made of a polyamide / polymethyl methacrylate / cellulose nanofiber composite material is additionally manufactured using a powder bed melt-bonding 3D printer. In Example 2, an example in which a molded body made of a phenol / cellulose nanofiber composite material is additionally manufactured using a powder bed fusion-bonding 3D printer will be described. In addition, this invention is not limited to the 3D printer illustrated below or a material composition.

Example 1
In Example 1, a powder bed fusion bonding type 3D printer, a polyamide 12 as a porous modeling material, and polymethyl methacrylate as a liquid resin impregnated in the fourth step are used. First, salt having a particle diameter of 40 microns was mixed with the powder material of polyamide 12 so that the volume ratio of salt: polyamide of the mixed powder was 8: 2. The polyamide 12 powder is of a general grade adapted for the powder bed melt bonding system. A powder bed fusion bonded 3D printer “Sintratec S1 (manufactured by Sintratec)” was prepared, 1 kg of the above mixed material was set on the platform, and test pieces were additionally manufactured. At this time, equipment parameters were recommended by the manufacturer. Polyamide 12 is a basic material that can be handled by the 3D printer.

  After completion of modeling by the 3D printer, excess powder was removed, and the resulting model was ultrasonically washed in water to dissolve salt, and dried with a desiccator.

  Cellulose nanofiber wet powder (manufactured by Oji Paper Co., Ltd.) was procured to prepare 20 liters of an aqueous dispersion. At this time, the water content was adjusted so that the concentration of the cellulose nanofibers was 2% by mass.

  The impregnating liquid reservoir 13 of the manufacturing apparatus (compressed / depressurized / impregnated combined apparatus) 10 shown in FIG. 4 contains 1 liter of impregnating liquid, and a shaped porous body is put into the pressurized / depressurized container 61. . The pressure / depressurization container 61 was depressurized at 0.001 MPa or less, and then the impregnation liquid was poured into the pressurization / decompression container 61 and held for 2 minutes to impregnate the porous body with the impregnation liquid. Further, the pressure in the pressurized / depressurized container 61 was increased to 0.5 MPa and held for 3 minutes.

  After the impregnating solution was discharged from the pressurized / depressurized container 61, heating was started with a microwave having an output of 300 W while the pressurized / depressurized container 61 was depressurized to 0.02 MPa or less. In order to prevent overheating of the porous body, heat was exhausted while introducing a small amount of air into the container. The humidity in the air at the exhaust port 43 of the vacuum / pressurization pump 29 is measured by the humidity sensor 53, and the humidity becomes the same value as the humidity measured by the humidity sensor 51 provided at the intake port 41. The heating was stopped immediately.

  The above impregnation (second step) and heat drying (third step) were repeated 30 times, and the test piece of the porous body was filled with cellulose nanofibers.

  Thereafter, the shaped article was put into another pressure / decompression vessel, and impregnated with a two-component impregnation liquid “3D seal 4410” (manufactured by Chuo Inventors Co., Ltd.) mainly composed of methyl methacrylate monomer. This monomer liquid contains a radical polymerization initiator, and can be cured by boiling in water at 80 to 90 degrees Celsius.

  Next, the inside of the pressurized / depressurized container was held for 2 minutes in a state where the pressure was reduced to 0.001 MPa or less, and defoamed from the monomer solution. Next, in order to completely impregnate the shaped article with the monomer liquid, the inside of the pressurized / depressurized container was pressurized at 0.5 MPa and held for 10 minutes.

  The model was then removed from the pressurized / depressurized container and bathed in a pan for 20 minutes at 90 degrees Celsius to polymerize and cure the methyl methacrylate to complete the modeling.

(Example 2)
In Example 2, a powder bed fusion bonding type 3D printer and a phenol resin as a modeling material for a porous body are used. First, 200 g of novolak resin powder (manufactured by Meiwa Kasei Co., Ltd.), which is an intermediate product of a phenol resin, was prepared. The particle size of this powder is distributed around 40 microns, and is sieved to be 30 microns or more and 50 microns or less. Further, hexamine as a curing agent is mixed in advance. To this novolak resin powder, 800 g of sodium chloride having the same particle size distribution was mixed. A 3D printer of the same powder bed fusion bonding method as in Example 1 was prepared, 1 kg of the above mixed material was set on the platform, and a test piece was additionally manufactured. Since the melting point of the novolak resin was 95 degrees Celsius, the temperature in the 3D printer cabinet was set to 85 degrees Celsius and modeling was performed.

  After completion of modeling by the 3D printer, excess powder was removed, and the resulting model was ultrasonically washed in water to dissolve salt, and dried with a desiccator.

  Cellulose nanofiber wet powder (manufactured by Oji Paper Co., Ltd.) was procured to prepare 20 liters of an aqueous dispersion. At this time, the water content was adjusted so that the concentration of the cellulose nanofibers was 2% by mass. To this, 40 g of lignin as an adhesive was added and stirred to prepare an impregnation solution.

  In the same manner as in Example 1, after putting the shaped porous body into the pressurized / depressurized container 61 of the manufacturing apparatus (pressurized / depressurized / impregnated combined apparatus) 10 shown in FIG. The impregnating liquid was discharged and heating was started. When the humidity measured by the humidity sensor 53 provided at the exhaust port 43 of the vacuum / pressurization pump 29 and the humidity measured by the humidity sensor 53 provided at the intake port 41 become the same value, it is promptly performed. The heating was stopped. At this time, since the phenol resin absorbs microwaves and generates heat, a small amount of air was introduced to exhaust heat.

  The above impregnation (second step) and heat drying (third step) were repeated 30 times, and the test pieces of the porous body were filled with cellulose nanofibers and an adhesive.

  Thereafter, the shaped article was put into another pressure / decompression vessel and impregnated with a resole resin (Maywa Kasei Co., Ltd.) having a mass concentration of 70%. Next, the inside of the pressurized / depressurized container was held for 2 minutes in a state where the pressure was reduced to 0.001 MPa or less, and defoamed from the resole resin. Next, in order to completely impregnate the shaped article with the resole resin, the inside of the pressurized / depressurized container was pressurized at 0.5 MPa and held for 30 seconds.

  Next, the model was taken out from the pressurized / depressurized container, and the model was put into an oven preheated to 125 degrees Celsius and baked for 5 minutes to completely cure the novolak resin in the model. Furthermore, the oven was heated to 160 degrees Celsius and baked for 10 hours, and the resol resin in the molded article was completely cured to complete the modeling.

  According to Example 1 and Example 2, it is possible to produce an isotropically strong nanocellulose fiber resin composite material from any 3D data with high efficiency without depending on manual work. did it. The molded body has a structure in which a synthetic resin sponge-like porous body and a three-dimensional network-like cellulose nanofiber xerogel are three-dimensionally entangled and bonded by van der Waals force or hydrogen bond. . In the molded body, since the cellulose nanofibers as the reinforcing material are oriented in random directions, they exhibit mechanical isotropy macroscopically.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  By using a 3D printer, it is possible to easily manufacture a molded product having a complicated shape by cutting off unnecessary meat. For this reason, especially weight reduction can be achieved compared with the manufacturing method of the conventional fiber resin composite material molded article. Therefore, in the aerospace industry where weight reduction is important and there are few mass-produced parts, the present embodiment can be obtained if the cost of additional production with a fiber-reinforced resin material having a specific strength equivalent to that of metal can be reduced. It is thought that the applicability of the cellulose fiber resin composite molded body is expanded. Moreover, according to the cellulose fiber resin composite material molded body obtained by the present embodiment, it can be used for many consumer products that require lightness, strength, and low cost. As a specific example, with respect to a wide range of mobility such as automobiles, bicycles, wheelchairs, multicopters, and artificial limbs, by providing light and strong parts at low cost on demand, it is possible to improve the commercial value.

DESCRIPTION OF SYMBOLS 1 ... 3D model, 10 ... Manufacturing apparatus (compression, pressure reduction, impregnation compound apparatus), 11 ... Microwave heating apparatus, 13 ... Impregnation liquid reservoir, 15 ... Compressed air tank, 29 ... Vacuum / pressure pumps

Claims (6)

A first step of modeling a porous body from a modeling material containing at least a thermoplastic resin using a 3D printer;
A second step of impregnating the porous body with an impregnation liquid comprising an aqueous dispersion containing at least cellulose fibers;
A third step of drying the porous body impregnated with the impregnation liquid;
A fourth step of curing the porous body;
The manufacturing method of the cellulose fiber resin composite material molded object containing this. The modeling material includes a water-soluble substance,
The manufacturing method of the cellulose fiber resin composite material molding according to claim 1, wherein in the first step, the porous body is modeled by leaching the water-soluble substance in the modeled model with a solvent.   The method for producing a molded article of cellulose fiber resin composite material according to claim 1 or 2, wherein the second step and the third step are repeated a plurality of times.   The said 4th process WHEREIN: The said porous body is hardened after impregnating the said porous body dried at the said 3rd process partially or completely with liquid resin, Any one of Claims 1-3. Manufacturing method of cellulose fiber resin composite material.   The method for producing a cellulose fiber resin composite material molded body according to any one of claims 1 to 3, wherein when the impregnating liquid contains an adhesive in the second step, the adhesive is cured in the fourth step. . The cellulose fiber resin composite material molded body according to any one of claims 1 to 5, wherein the first step is performed using a 3D printer of any one of a powder bed fusion bonding method, a material extrusion method, and a sheet lamination method. Manufacturing method.

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