KR102200957B1 - Porous fiber reinforced composite material - Google Patents

Abstract

First fibrous particles; Second fibrous particles; And a binder for binding the first fibrous particles and the second fibrous particles, wherein the first fibrous particles and the second fibrous particles are bound by the binder to form an irregular network structure including pores, , The first fibrous particles are fibrillated natural fibers having nanofibril branches formed, the second fibrous particles include a first thermoplastic resin, the binder includes a second thermoplastic resin, and the first thermoplastic resin A porous fiber-reinforced composite with a melting point of higher than the melting point of the second thermoplastic resin is provided.

Description

Porous fiber reinforced composite material{POROUS FIBER REINFORCED COMPOSITE MATERIAL}

It relates to a porous fiber reinforced composite.

Conventional thermoplastic composite materials are composed of reinforcing fibers such as glass fibers or carbon fibers exhibiting high rigidity and a thermoplastic resin constituting the matrix. Since these thermoplastic composite materials exhibit higher mechanical properties than general thermoplastic resin products, they are widely used as materials for automobiles and buildings. The conventional method of manufacturing a thermoplastic composite material is a method of mixing reinforcing fibers with a thermoplastic resin and then molding through extrusion or mold press processes.In recent years, to improve strength and productivity, a dry needle punching process or a wet papermaking process is applied. First, a mat-shaped material containing reinforcing fibers is manufactured, and then a composite material is manufactured by impregnating the mat with a resin.

The composite material of the reinforcing fiber and the thermoplastic resin exhibits excellent mechanical strength because the reinforcing fiber serves as a reinforcing material compared to the thermoplastic resin. As a method of increasing the strength of the reinforcing fiber composite material, first, a method of increasing the stiffness of the reinforcing fiber itself or increasing the ratio of the reinforcing fiber, and a technology for improving the bonding strength between the reinforcing fiber and the thermoplastic resin are applied. However, when a process of manufacturing a reinforcing fiber mat through a wet or dry process is introduced, there is a limit to improving the strength through the reinforcing fiber modification.

One embodiment of the present invention provides a porous fiber-reinforced composite material capable of implementing mechanical strength, weight reduction, excellent moisture absorption resistance and sound absorption performance.

In one embodiment of the present invention,

First fibrous particles; Second fibrous particles; And a binder for binding the first fibrous particles and the second fibrous particles,

The first fibrous particles and the second fibrous particles are bound by the binder to form an irregular network structure including pores,

The first fibrous particles are fibrillated natural fibers in which nanofibril branches are formed,

The second fibrous particles include a first thermoplastic resin,

The binder includes a second thermoplastic resin,

The melting point of the first thermoplastic resin is higher than the melting point of the second thermoplastic resin

A porous fiber reinforced composite is provided.

The porous fiber-reinforced composite material has a low density, excellent moisture absorption resistance, and excellent sound absorbing and insulating properties while implementing high mechanical strength.

1 is a schematic schematic diagram of a porous fiber-reinforced composite according to an embodiment of the present invention.
Figure 2 schematically shows a fibrillated natural fiber in which nanofibrils branches are formed.
3 is a diagram illustrating that a porous fiber-reinforced composite according to another embodiment of the present invention is manufactured by applying heat and pressure to a reinforcing fiber and a two-component polymer by the method of manufacturing the porous fiber-reinforced composite.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

In one embodiment of the present invention,

First fibrous particles; Second fibrous particles; And a binder for binding the first fibrous particles and the second fibrous particles,

The first fibrous particles and the second fibrous particles are bound by the binder to form an irregular network structure including pores,

The first fibrous particles are fibrillated natural fibers in which nanofibril branches are formed,

The second fibrous particles include a first thermoplastic resin,

The binder includes a second thermoplastic resin,

It provides a porous fiber-reinforced composite with a melting point of the first thermoplastic resin higher than that of the second thermoplastic resin.

The first fibrous particles and the second fibrous particles are present in a state in which part or all of the binder components are coated. That is, the first fibrous particles and the second fibrous particles form a coating portion formed of the binder on the surface of each particle.

The coating portions of each of the first fibrous particles and the second fibrous particles are fused, so that the first fibrous particles and the second fibrous particles may be irregularly bound. The first fibrous particles and the second fibrous particles bound in this way can form an irregular network structure including pores.

1 is a schematic schematic diagram of a porous fiber-reinforced composite material 10 including a first fibrous particle 1, a second fibrous particle 2 and a binder 3 according to an embodiment of the present invention.

The porous fiber-reinforced composite material is a material that can realize high mechanical strength such as tensile, flexural, and impact strength, but has a low density, so that weight reduction can be realized.Therefore, the porous fiber-reinforced composite material can be usefully applied to automotive and construction materials requiring such properties. In addition, the porous fiber-reinforced composite may satisfy the excellent sound absorbing and insulating performance conditions required for such automobile and construction materials, and has excellent moisture absorption resistance.

Figure 2 schematically shows a fibrillated natural fiber in which nanofibrils branches are formed.

The surface of general natural fibers that do not form nanofibril branches, that is, are not fibrillated, is smooth. In contrast, in the fibrillated natural fiber in which the nanofibril branches are formed, the nanofibril branches are formed on the surface of the fiber.

Compared to the case where the surface of natural fibers is smooth, fibrillating fibers of the same weight increases the specific surface area in contact with the polymer matrix, and thus the strength of the composite material is further improved.

In addition, the interfacial adhesion between the first fibrous particles and the binder is improved by the nanofibril branches of the fibrillated natural fibers.

In addition, when the porous fiber-reinforced composite material receives sound energy from the outside, the sound-absorbing performance is expressed by fiber vibration. In the case of a composite material with fibrillated fiber, the degree of freedom and frequency of fiber vibration compared to when using general natural fiber. As is increased, the sound absorption performance can be improved. When the porous fiber-reinforced composite is applied to a product such as an automobile part, the strength of the part is improved and the sound-absorbing performance is improved.

In addition, the fibrillated natural fiber having the nanofibril branches formed thereon improves the moisture absorption resistance of the porous fiber-reinforced composite material by the lotus effect.

The diameter of the nanofibrils branch may be 1 nm to 800 nm, specifically, 1 nm to 400 nm, and more specifically 5 nm to 100 nm. When the diameter of the nanofibrils branch is within the above range, better strength and sound absorbing and insulating properties may be implemented.

The diameter of the nanofibrils branches in the porous fiber-reinforced composite may be formed by a method such as SEM image or TEM image analysis.

The porous fiber-reinforced composite may also be made of a sheet in which the first fibrous particles and the second fibrous particles have unidirectional orientation. As described above, if the sheet of the porous fiber-reinforced composite material is provided with unidirectional orientation, the sheet has high mechanical properties along the direction in which the orientation is imparted. Such a sheet is suitable for application as a material capable of withstanding a large force in a specific direction.

The porous fiber-reinforced composite material includes two types of reinforcing fibers, a first fibrous particle and a second fibrous particle. The porous fiber-reinforced composite material includes both the first fibrous particles and the second fibrous particles, and thus the type and content ratio thereof are controlled to be designed to exhibit excellent properties.

As the second fibrous particles, a thermoplastic fiber made of a thermoplastic resin may be used to improve strength while simultaneously imparting elasticity of the thermoplastic resin. Since the thermoplastic resin constituting the second fibrous particles uses a thermoplastic resin having a relatively high melting point, additional strength improvement can be expected compared to the case where only the first fibrous particles are present. In addition, since the thermoplastic fiber has excellent elasticity compared to the first fibrous particle, it is possible to effectively attenuate the impact energy against an external impact.

In addition, since the second thermoplastic resin included in the binder is a crystalline thermoplastic resin and has a relatively low melting point, the porous fiber-reinforced composite material has low-temperature moldability.

The second fibrous particles and the binder are prepared from a two-component polymer fiber including a core portion and a sheath portion as a raw material. That is, the core portion includes a first thermoplastic resin, the sheath portion includes a second thermoplastic resin, and the melting point of the first thermoplastic resin is higher than that of the second thermoplastic resin.

When the two-component polymer fibers are subjected to heat treatment, at least a part of the sheath portion is melted and fused with the first fibrous particles, thereby manufacturing the porous fiber-reinforced composite. The second thermoplastic resin remaining on the surface of the core portion and the second thermoplastic resin transferred to the surface of the first fibrous particles are the binder, and bind the first fibrous particles and the second fibrous particles in a fused state.

In one embodiment, the weight ratio of the sum of the content of the first fibrous particles to the content of the second fibrous particles and the binder in the porous fiber-reinforced composite is about 20: 80 to about 80: 20, specifically, about 40: 60 to about 60 : Can be 40. As the content of the first fibrous particles increases, the strength tends to be excellent, but the degree of improvement may decrease when the content is higher than a certain level. The content range is a content range suitable for obtaining an effect from the second fibrous particles while effectively securing an effect of improving strength according to an increase in the content of the first fibrous particles.

The porous fiber-reinforced composite may include about 40 parts by weight to about 250 parts by weight of the binder based on 100 parts by weight of the second fibrous particles. By controlling the content ratio of the second fibrous particles and the binder according to the content ratio, it is possible to appropriately impart binding force and elasticity while maintaining excellent dispersibility.

By adjusting the content ratio of the core portion and the sheath portion of the bicomponent polymer fiber, the content ratio of the second fibrous particle and the binder may be realized.

The first fibrous particles may have a cross-sectional diameter of about 20 μm to about 500 μm. The first fibrous particles having a thickness in the above range can appropriately impart strength and secure orientation and dispersibility. The porous fiber-reinforced composite material including the first fibrous particles having a thickness in the above range is resistant to external impact, and when the first fibrous particles are dispersed in an aqueous solution when manufactured according to the method of manufacturing the porous fiber-reinforced composite to be described later, It is possible to facilitate sheet formation by making it have an appropriate hydroentangle property.

The first fibrous particles may have a length of about 1 mm to about 50 mm. The first fibrous particles having a length in the above range can adequately impart strength while securing orientation and dispersibility, and also appropriately impart a bonding force between the fibrous particles so that the porous fiber-reinforced composite material has excellent strength. At the same time, if the fiber is too long, it is suitable for forming a sheet, preventing deterioration in dispersibility as the fibers are lumped together.

Specifically, the melting point of the first thermoplastic resin may be about 160°C or higher. More specifically, the melting point of the first thermoplastic resin may be about 200°C to about 400°C. By allowing the first thermoplastic resin to have a melting point within the above range, it is possible to maintain the fibrous shape even after the binder is melted during low temperature molding. When the melting point of the first thermoplastic resin is less than 160°C, the thermoforming temperature must be too low to maintain the fibrous shape, or the porous fiber-reinforced composite including the same may later deteriorate thermal stability, resulting in dimensional deformation or polymer deterioration. There is. In addition, since the temperature difference with the second thermoplastic resin may be excessively reduced, it may be difficult to control the molding temperature.

For example, the first thermoplastic resin may be polyethylene terephthalate.

In another embodiment, the specific gravity of the first thermoplastic resin is higher than about 1. According to the method of manufacturing a porous fiber-reinforced composite to be described later, the two-component polymer fibers are dispersed in an acidic aqueous solution, and a material having a specific gravity higher than 1, which is the specific gravity of water, should be used to improve dispersibility and easily form a network structure. Therefore, the core portion of the two-component polymer fiber may be a thermoplastic resin having a specific gravity higher than 1, such as polyester.

The first thermoplastic resin capable of forming the second fibrous particles is, for example, polyester, polypropylene (PP), polyethylene (PE), acrylic butadiene styrene (ABS), polycarbonate (PC), nylon (Nylon ), polyvinyl chloride (PVC), polystyrene (PS), polyurethane (PU), polymethyl methacrylate (PMMA), polylactic acid (PLA), Teflon (polytetrafluoroethylene), and combinations thereof It may include at least one. The first thermoplastic resin capable of forming the second fibrous particles may be, for example, polypropylene or polyester.

The second thermoplastic resin capable of forming the binder may include at least one selected from the group consisting of polyester, polyethylene terephthalate, polypropylene, polyethylene (PE), and combinations thereof.

The binder serves to bind the first fibrous particles and the second fibrous particles, and can be melted at a low temperature by allowing the second thermoplastic resin forming the binder to have a melting point within the above range. Can be secured. The binder may appropriately select a low melting point polyester, a low melting point polyethylene terephthalate, or polypropylene and polyethylene according to the molding temperature to be applied.

As described above, when selecting the first thermoplastic resin and the second thermoplastic resin as in the above example, the condition that the melting point of the first thermoplastic resin is higher than the melting point of the second thermoplastic resin must be satisfied. In addition, the first thermoplastic resin and the second thermoplastic resin may be selected so that the materials of the core portion and the sheath portion of the bicomponent polymer fiber used in the method of manufacturing a porous fiber-reinforced composite to be described later satisfy the above conditions.

The second fibrous particles may have a cross-sectional diameter of about 5 μm to about 50 μm. The second fibrous particles having a thickness in the above range can adequately impart strength and secure orientation and dispersibility. The porous fiber-reinforced composite material including the second fibrous particles having a thickness in the above range has excellent strength characteristics, and when the first fibrous particles are dispersed in an aqueous solution when prepared according to the method of manufacturing the porous fiber-reinforced composite to be described later, the aqueous solution It is possible to facilitate sheet formation by having an appropriate hydroentangle property within.

The second fibrous particles may have a length of about 1 mm to about 50 mm. The second fibrous particles having a length in the above range can adequately impart strength while securing orientation and dispersibility, and also appropriately impart a bonding force between the fibrous particles so that the porous fiber-reinforced composite material has excellent strength. At the same time, if the fibers are too long, the fibers are entangled to form a rope phase, preventing deterioration in dispersibility, and is suitable for forming a sheet.

The porosity of the porous fiber-reinforced composite may be about 40 to about 80% by volume. As described above, the porous fiber-reinforced composite material forms open pores while forming a network structure. The porous fiber-reinforced composite material having a porosity in the above range can achieve weight reduction while maintaining strength, and have excellent sound absorbing and insulating properties.

Since the sound waves entering through the open pores of the porous fiber-reinforced composite material are attenuated by the vibration of the fibers of the second fibrous particles, it can be applied as a sound absorbing and insulating material. The higher the porosity of the porous fiber-reinforced composite, the higher the content of the second fibrous particles, and the longer the length through which the sound waves pass, the better the energy attenuation effect. The length through which the sound wave passes is, for example, longer when the thickness of the material itself is large or the connection of the pores is good, even when they have the same porosity. The porous fiber-reinforced composite may be manufactured as a material having improved sound absorbing and insulating performance by controlling the content of the second fibrous particles while maintaining a certain degree of porosity, and also controlling the length through which the sound waves pass. . Particularly, since the second fibrous particles are more flexible than the hard first fibrous particles, the sound energy attenuating effect is high, and thus, the second fibrous particles effectively improve the sound absorbing and insulating performance.

The porous fiber-reinforced composite may be made of a plate having a density of about 0.2 g/cm ³ to about 1.6 g/cm ³ .

The plate may be manufactured by compressing the porous fiber-reinforced composite material to a predetermined level. For example, the plate material can be obtained by laminating several sheets of the porous fiber-reinforced composite material obtained as a single sheet by a wet papermaking process used in a method of manufacturing a porous fiber-reinforced composite to be described later, followed by press molding.

While the press molding is performed in a multi-stage process, by alternately performing the heat treatment process, the dispersibility of the binder may be improved. For example, after press molding the multi-layered porous fiber-reinforced composite sheet, then, after heating, the final plate may be obtained by press-forming again at room temperature. By performing the heat treatment process between press processes, heat transfer to the center of the plate material is easy, so that the binder is well melted and the distribution can be formed evenly. In this way, by evenly dispersing the binder, it is possible to obtain very even properties of the sheet material as a whole.

The press molding may be performed at a compression rate of 80 to 95%. By controlling the compressive density of the fiber by the press molding, it is possible to achieve excellent strength and sound-absorbing properties.

The plate material is formed including a pore structure. In general, a composite material prepared through a mold pressing process by mixing and extruding raw materials is difficult to form a pore structure, while the plate material forms a pore structure as it is manufactured using a porous fiber-reinforced composite.

Specifically, the plate material may have a porosity of about 40 to about 80 volumes. Since the porous fiber-reinforced composite plate is formed to have a porosity in the above range, the strength, impact resistance, and sound-absorbing properties of the plate of the porous fiber-reinforced composite can be excellent.

Since the porous fiber-reinforced composite plate material is in a compressed state, the structure of the porous fiber-reinforced composite material is merely compressed while maintaining the structure of the porous fiber-reinforced composite material of FIG. 1.

Specifically, the plate material may be manufactured by performing press molding so that the density of the plate material is about 0.2 g/cm ³ to about 1.6 g/cm ³ . The density of the plate is manufactured by pressing so as to be within the above range, so that excellent strength can be realized.

The plate material is a material that realizes high mechanical strength such as tensile, flexural, and impact strength, but has a low density and thus can realize weight reduction, and is a material that implements sound absorbing and insulating properties, so it is useful for use in automobiles and construction materials that require such properties. Can be applied. In addition, the plate may satisfy excellent sound absorbing and insulating performance conditions required for such automobile and construction materials.

The plate of the porous fiber-reinforced composite may also be prepared from a porous fiber-reinforced composite prepared by imparting unidirectional orientation to the fibrous particles as described above. The porous fiber-reinforced composite plate is first made of a composite sheet in which the first fibrous particles and the second fibrous particles are bound by the binder to form an irregular network structure including pores, and then a plurality of composite sheets are laminated. In this case, if the fibrous particles are given unidirectional orientation to the composite sheet, the composite sheet has high mechanical properties along the direction to which the orientation is imparted. The sheet of the porous fiber-reinforced composite obtained by laminating such a composite sheet in one direction and then press-molding can withstand a large force in a specific direction.

The sheet of the porous fiber-reinforced composite may be prepared to have a weight suitable for the intended use, for example, about 600 g/m ² to about 3000 g/m ² , for example, about 900 g/m ² To about 1400 g/m ² .

The composite porous fiber-reinforced composite plate may have a thickness of about 2mm to about 8mm.

The porous fiber-reinforced composite material is as described above that it is possible to achieve weight reduction, and specifically, its density may be about 0.2 g/cm ³ to about 1.6 g/cm ³ .

The porous fiber-reinforced composite may be manufactured in a form suitable for the intended application, and may be manufactured as a sheet through, for example, a wet papermaking process.

The sheet of the porous fiber-reinforced composite material may be prepared to have a weight suitable for the intended use, for example, may be prepared as a sheet having a weight of about 50 g / m ² to about 1200 g / m ² .

FIG. 3 shows that the porous fiber-reinforced composite material 20 is manufactured by applying heat and pressure to the fibrillated natural fiber 4 and the bi-component polymer fiber 5. Although the nanofibrils branch of the fibrillated natural fiber 4 is not shown in FIG. 4, it should be understood that the nanofibrils branches are formed as in FIG. 2.

The fibrillated natural fibers 4 may be the first fibrous particles described above. Therefore, the detailed description of the fibrillated natural fiber (4) is as described for the first fibrous particles.

The two-component polymer fiber 5 includes a core portion 5a and a sheath portion 5b, the core portion 5a contains a first thermoplastic resin, and the sheath portion is a second And a thermoplastic resin (5b).

The melting point of the first thermoplastic resin is higher than that of the second thermoplastic resin.

Detailed descriptions of the first thermoplastic resin and the second thermoplastic resin are as described above.

In the heat treatment and drying step, the second thermoplastic resin of the sheath portion is melted to bind the fibrillated natural fiber and the bi-component polymer fiber by thermal fusion, thereby forming an irregular network structure including pores.

The second thermoplastic resin of the sheath part is present in a state coated with the core part, and is melted in the heat treatment and drying step, and is transferred to the fibrillated natural fiber to coat part or all of the fibrillated natural fiber, and the molten state is As it solidifies, it acts as a binder for binding the core portion of the bicomponent polymer fiber and the fibrillated natural fiber.

As described above, since the sheath part acts as a binder, the method of manufacturing the porous fiber-reinforced composite may not additionally use a separate binder.

There is an advantage that low-temperature molding is possible by making the thermoplastic resin forming the sheath portion of the bicomponent polymer fiber have a relatively low melting point.

The porosity of the porous fiber-reinforced composite material, the degree of coating transferred to the fibrillated natural fiber, and the like can be controlled by changing the contents of the core part and the sheath part of the bicomponent polymer fiber.

For example, in the bi-component polymer fiber, the sheath portion may have a weight of about 40 parts by weight to about 250 parts by weight relative to 100 parts by weight of the core part.

The method of manufacturing the porous fiber-reinforced composite material consists of a two-component polymer fiber composed of a core part and a sheath part, although the two-component polymer fiber made of a chemically hydrophobic thermoplastic resin is dispersed in an aqueous acid solution. By increasing the specific gravity, excellent dispersibility can be made. As described above, when the specific gravity of the core portion of the bicomponent polymer fiber is greater than 1, the dispersion degree can be effectively improved during the stirring process in the aqueous solution.

Specifically, by silane treatment of the fibrillated natural fiber or bi-component polymer fiber with a surface treatment agent or coating agent that can be used in the manufacture of the fibrillated natural fiber and the bi-component polymer fiber, the bonding strength between fibers is improved or carbonization ( Carbonization) to improve heat resistance, hydrolysis to improve hydrophilicity, or oxidation (Oxidation) to improve water dispersion.

Examples of the surface treatment agent include fluorine-based waxes (eg, PFAO), hydrocarbon-based waxes, and silicone-based polymers.

Depending on the composition of the coating agent, properties such as hydrophilicity/hydrophobicity, water repellency, flame retardancy, non-flammability, heat resistance, acid resistance, alkali resistance, durability, and fouling resistance can be imparted. Specifically, as a coating agent, a water repellent such as a fluorine-based wax (eg, PFAO), a hydrocarbon-based wax, and a silicone-based polymer affinity agent (Compatibilizer) may be used.

According to the desired physical properties of the porous fiber-reinforced composite to be manufactured, the content ratio of the fibrillated natural fiber and the two-component polymer component can be adjusted.

For example, the weight ratio of the fibrillated natural fiber and the two-component polymer component may be about 20:80 to about 80:20, specifically, about 40:60 to about 60:40.

Specifically, as a method of manufacturing the porous fiber-reinforced composite, the fibrillated natural fiber and the bi-component polymer fiber are mixed with a dispersion medium to prepare a slurry solution, and after forming a web by a wet papermaking process, the formed The web can be prepared by heat treatment and drying.

The dispersion medium may be water or an alkali solvent.

It may further include the step of stirring the slurry solution. Dispersibility may be further improved by further performing the step of stirring the slurry solution.

In the method of manufacturing the porous fiber-reinforced composite, the heat treatment and drying of the formed web may be performed at a temperature lower than the melting temperature of about 30°C to about 30°C. The temperature range is determined based on the temperature at which the sheath portion of the bicomponent polymer fiber begins to soften or melt. If the temperature is lower than the above range, it is difficult to dry moisture, and the two-component polymer fiber (sheath part) does not sufficiently soften, so moisture remains after drying in a sheet shape, or it is difficult for the sheet to have fixed properties. Conversely, when the temperature is higher than the above range, the sheath portion of the bicomponent polymer fiber is completely melted, and it is difficult to uniformly transfer from the bicomponent polymer fiber to the fibrillated natural fiber. In addition, there is a fear that the sheath polymer of the bicomponent polymer fiber may deteriorate above the melting temperature.

By appropriately setting the cross-sectional diameter of the core portion of the bi-component polymer fiber, heat treatment and drying at an appropriate heat treatment temperature, the core of the bi-component polymer fiber is not melted and can be prepared so as to be included in a porous fiber-reinforced composite made of fibrous particles.

During the wet papermaking process, the fibers are evenly mixed in the aqueous solution of the slurry, and then a hydro-entangled web is formed while following the mesh moving along the conveyor belt. By imparting, the prepared composite sheet can have orientation. The sheet material of the porous fiber-reinforced composite material obtained by laminating the composite sheet having the orientation imparted as described above can further enhance the strength against the one direction by imparting orientation to the fiber component in one direction.

In this way, the sheet material of the porous fiber-reinforced composite material can be prepared so as to selectively impart orientation to the intended use.

For example, when fibers are transferred from a headbox to a conveyor belt and a composite sheet is formed, by giving an inclination to the portion where the composite sheet is formed (inclined web formation), the fibers are MD ( The process can be designed to lie well in the machine direction) direction. Directionality may be divided into a machine direction (MD) direction and a cross direction (CD) direction, and it is easier to give direction in the MD direction than in the CD direction.

The slurry solution may further include an additive such as a crosslinking agent or an additional binder.

The crosslinking agent acts to strengthen the chemical bonding strength between the fibrillated natural fiber and the two-component polymer fiber, and, for example, a silane-based compound, a maleic acid-based compound, or the like may be used.

The content of the crosslinking agent may be 0 to 5 parts by weight based on 100 parts by weight of the total fiber (sum of fibrillated natural fiber and bicomponent polymer fiber).

The additional binder may include water-soluble polymers such as starch, casein, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), and the like; Emulsions such as polyethylene, polypropylene, and polyamide; Cements, calcium sulfate-based clay, sodium silicate, alumina silicate, inorganic compounds of calcium silicate, and the like can be used.

The content of the additional binder may be from about 0 to about 5 parts by weight based on 100 parts by weight of the total fibers (sum of fibrillated natural fibers and bicomponent polymer fibers).

The sheet material of the porous single resin fiber composite material is formed by pressing at least two or more multiple sheets of the composite material, and specifically, it is possible to determine how many sheets to be stacked according to the desired weight per unit area of the final product. For example, if the weight per final unit area of the product for the composite sheet is 1200 g/m ² , approximately 2 to 12 sheets are stacked, and then heat press-molded by applying heat and pressure to produce a sheet of porous single resin fiber composite. can do.

The hot press molding may be performed at a temperature at which the sheath portion of the bicomponent polymer fiber can be melted and at a temperature at which the core portion is not melted. When performed in this temperature range, the sheath portion is melted and the interface between the composite sheets may be fused.

Specifically, the hot press molding may be performed by laminating the composite sheet by applying a pressure of about 1 to about 30 bar at a temperature of about 100 to about 180°C to manufacture a sheet of a porous single resin fiber composite.

The hot press molding may be performed so that a plate of a porous single resin fiber composite can be continuously manufactured by double belt press molding.

According to another embodiment, a plate of the porous single resin fiber composite material may be prepared as follows. First, fibrillated natural fibers and bi-component polymer fibers are blended, and the blended fibers are stirred in an aqueous solution containing an additive, and then transferred to a head box capable of forming a web. The slurry in the head box forms a wet web as it passes through the vacuum intake system, which is made into a sheet-like composite sheet while passing through the dryer. The weight of the composite sheet is set to be about 50 g to about 600 g per square meter for ease of subsequent thermoforming. The drying temperature is set at about 100° C. to about 180° C. depending on the sheath material so that the sheath portion of the bicomponent polymer fiber can serve as a binder. The prepared composite sheet is cut out and laminated according to the use, and a sheet of a porous single resin fiber composite material having a thickness of about 2 mm to about 8 mm in a plate shape is manufactured through a thermocompression press.

For example, the sheet material of the porous single resin fiber composite may be heated at about 200° C., transferred to a press at room temperature, and then press-molded to form a sheet having a thickness of 2 to 4 mm.

Hereinafter, examples and comparative examples of the present invention will be described. The following examples are only examples of the present invention, and the present invention is not limited to the following examples.

( Example )

Example One

First, natural fibers were prepared with kenaf yarn pellets having a length of 12 mm and a thickness of 1 mm to ensure aqueous dispersion. As for the two-component polymer fiber, a fiber having a length of 5 mm and a cross-sectional diameter of 20 μm was prepared in order to secure water-based dispersibility while having a weight ratio of 50:50 to the polyester core portion and the low-melting polyester sheath portion. 40 parts by weight of the natural fiber and 60 parts by weight of the bi-component polymer fiber were mixed, and the total fiber content of the natural fiber and the bi-component polymer fiber was 2 g per 1 liter of water. The kenaf fiber pellets were dissociated into fiber strands (filaments) with a fiber thickness of 100 μm through a stirring process through a high-speed impeller in a mixing tank. Then, while moving from the mixing tack to a pulper equipped with a grinder, a slurry having a ratio of 200 g of fibers per liter of water (sum of Kenaf fibers and bicomponent polymer fibers) was prepared. Subsequently, as the pulping process was performed at high speed, nanofibrillation was performed simultaneously with the refining process of the kenaf fibers. It was confirmed that the fibrillated kenaf fibers (fibrillated natural fibers) were formed in 5 nm to 50 nm as a result of measuring the diameter of the nanofibril branches by SEM image analysis.

A wet papermaking process was performed so that the aqueous slurry was formed into a web through a vacuum suction device in the head box. After the web was formed, the moisture was completely dried by passing through an oven dryer at 140°C to prepare a composite sheet. The dried composite sheet had a thickness of approximately 1.5 mm at 120 g/m ² . After 10 sheets of the composite sheet were stacked to be 1200 g/m ² , a hot press was performed at 170° C. and 5 bar to form a 1.5 mm thick composite preformed board. The composite preformed board thus prepared is expanded by preheating for 2 minutes at 200°C in an IR oven, transferred to a mold press at room temperature, and then subjected to mold pressing by applying 1 bar pressure to form a final mold having an average thickness of 2.0 mm. The molded product was completed.

Example 2

A composite sheet was prepared in the same manner as in Example 1, except that jute fibers were used instead of the kenaf fibers used in Example 1, and then the composite preformed board was molded in the same manner as in Example 1. Then, it was expanded through preheating at 200° C. for 2 minutes in an IR oven, transferred to a press at room temperature, and then pressure was applied to complete a final molded product having an average thickness of 2.0 mm.

Example 3

A composite sheet was manufactured in the same manner as in Example 1, except for the process of pulping the slurry having a ratio of 100 g of fibers per 1 liter of water in Example 1. It was confirmed that the fibrillated kenaf fibers (fibrillated natural fibers) were formed in 50 nm to 100 nm as a result of measuring the diameter of the nanofibril branches by SEM image analysis.

Subsequently, after the composite preformed board was molded in the same manner as in Example 2, it was expanded by preheating for 2 minutes at 200°C in an IR oven, transferred to a press at room temperature, and applied pressure to average 2.0 The final molded product formed in mm thickness was completed.

Comparative example One

A composite sheet was manufactured in the same manner as in Example 1, except for the process of pulping the slurry having a ratio of 400 g of fibers per 1 L of water in Example 1. It was confirmed that the fibrillated kenaf fibers (fibrillated natural fibers) were formed to be 1 μm to 20 μm as a result of measuring the diameter of the nanofibril branches by SEM image analysis.

Subsequently, after the composite preformed board was molded in the same manner as in Example 2, it was expanded by preheating for 2 minutes at 200°C in an IR oven, transferred to a press at room temperature, and applied pressure to average 2.0 The final molded product formed in mm thickness was completed.

Comparative example 2

In Example 1, except that the pulping process was not performed (the kenaf fibers were not fibrillated), After preparing a composite sheet in the same manner as in Example 1, then, after forming a composite preformed board in the same manner as in Example 2, it is expanded through preheating for 2 minutes at 200°C in an IR oven. Then, it was transferred to a press at room temperature, and then pressure was applied to complete a final molded product formed with an average thickness of 2.0 mm.

Comparative example 3

Except for using glass fibers instead of fibrillated kenaf fibers used in Example 1, the composite preformed board was molded in the same manner as in Example 1, and then again in an IR oven at 200°C for 2 minutes. During preheating, the product was expanded through preheating, transferred to a press at room temperature, and then pressure was applied to complete a final molded product having an average thickness of 2.0 mm.

evaluation

Experimental example One

For the final molded products prepared in Examples 1-3 and Comparative Examples 1-3, mechanical properties of flexural strength and flexural modulus were compared. The flexural strength was measured after the final molded products were allowed to stand at room temperature for 24 hours, respectively.

Flexural strength and flexural modulus were measured according to ASTM D790 for samples in which the final molded product had a thickness of 2 mm. The results are shown in Table 1.

division Flexural strength (MPa) Flexural modulus (GPa) Example 1 81 6.3 Example 2 65 5.7 Example 3 63 5.9 Comparative Example 1 57 5.1 Comparative Example 2 45 3.6 Comparative Example 3 37 2.8

Experimental example 2

For the final molded products prepared in Examples 1-3 and Comparative Examples 1-3, hygroscopic resistance was compared. For measurement, after leaving the final molded product at room temperature for 24 hours, a part of the sample was collected in a size of 150x150mm horizontally and vertically, immersed in water for 2 hours, and then maintained for 30 minutes at a temperature of 24℃ and 50% humidity. I did.

.

The results are shown in Table 2.

division Moisture absorption rate (%) Example 1 4 Example 2 5 Example 3 9 Comparative Example 1 29 Comparative Example 2 34 Comparative Example 3 3

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of the invention.

1: first fibrous particle
2: second fibrous particles
3: binding material
4: Fibrillated natural fiber
5: bicomponent polymer fiber
5a: core part
5b: sheath

Claims (12)

First fibrous particles; Second fibrous particles; And a binder for binding the first fibrous particles and the second fibrous particles,
The first fibrous particles and the second fibrous particles are bound by the binder to form an irregular network structure including pores,
The first fibrous particles are fibrillated natural fibers in which nanofibril branches are formed,
The first fibrous particles and the second fibrous particles are partially or entirely coated on the surface of each particle by the binder to form a coating portion, and the coating portions formed on each surface are fused to each other to be bonded,
The second fibrous particles include a first thermoplastic resin,
The binder includes a second thermoplastic resin,
The melting point of the first thermoplastic resin is higher than the melting point of the second thermoplastic resin
Porous fiber reinforced composite.
delete The method of claim 1,
The diameter of the nanofibrils branch is 1nm to 800nm
Porous fiber reinforced composite.
The method of claim 1,
The weight ratio of the sum of the content of the first fibrous particle to the content of the second fibrous particle and the binder is 20: 80 to 80: 20
Porous fiber reinforced composite.
The method of claim 1,
The weight of the binder is 40 to 250 parts by weight relative to 100 parts by weight of the second fibrous particles.
Porous fiber reinforced composite.
The method of claim 1,
The first fibrous particles have a cross-sectional diameter of 20 µm to 500 µm
Porous fiber reinforced composite.
The method of claim 1,
The first thermoplastic resin is polyester, polypropylene (PP), polyethylene (PE), acrylic butadiene styrene (ABS), polycarbonate (PC), nylon (Nylon), polyvinyl chloride (PVC), polystyrene (PS), Polyurethane (PU), polymethyl methacrylate (PMMA), polylactic acid (PLA), Teflon (polytetrafluoroethylene), including at least one selected from the group consisting of a combination thereof
Porous fiber reinforced composite.
The method of claim 1,
The second thermoplastic resin comprises at least one selected from the group consisting of polyester, polyethylene terephthalate, polypropylene, polyethylene (PE), and combinations thereof.
Porous fiber reinforced composite.
The method of claim 1,
The melting point of the first thermoplastic resin is 160 ℃ or more
Porous fiber reinforced composite.
The method of claim 1,
The specific gravity of the first thermoplastic resin is greater than 1
Porous fiber reinforced composite.
The method of claim 1,
The melting point of the second thermoplastic resin is less than 200 ℃
Porous fiber reinforced composite. The porous fiber-reinforced composite of any one of claims 1 and 3 to 11 is compressed to have a density of 0.2 g/cm3 to 1.6 g/cm3 and a thickness of 2mm to 8mm.
Plate.

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