KR102100679B1 - Underbody cover for automobiles and method for preparing the same - Google Patents

Abstract

It includes a porous composite material, the porous composite material includes a diffuse reflection surface structure on at least one surface, the porous composite material is a first fiber comprising a first thermoplastic resin; A second fiber comprising a second thermoplastic resin; And a binding material binding the first fiber and the second fiber, wherein the binding material includes a third thermoplastic resin, and the melting point of the first thermoplastic resin and the melting point of the second thermoplastic resin are respectively the third Provided is a vehicle underbody cover higher than the melting point of a thermoplastic resin and a method for manufacturing the same.

Description

A vehicle underbody cover and a method of manufacturing the same {UNDERBODY COVER FOR AUTOMOBILES AND METHOD FOR PREPARING THE SAME}

It relates to a cover material applied to the underbody of a vehicle and a specific method for manufacturing the cover material.

The underbody cover for a vehicle has an effect of protecting a vehicle body from impact from outside, damping noise, and smoothing air flow during driving to improve fuel efficiency. For this reason, since it has a good effect on characteristics that are prioritized in vehicles such as high fuel efficiency and quietness, its use has been expanded not only to commercial vehicles but also to passenger vehicles. Initially, the underbody cover for vehicles was made of steel for the main purpose of protecting the body, but was gradually replaced by thermoplastic injection products due to corrosion and heavy weight. However, compared to the strength required in a general vehicle underbody cover, thermoplastics have very low physical properties, and thus, a composite material in which reinforcing fibers such as glass fibers are blended with a thermoplastic resin has been recently used. However, since these reinforcing fiber composite materials are composed of high-density materials having no porosity, they have a relatively high weight and do not effectively block impact sounds from the ground, such as sand or gravel.

Conventional reinforcing fiber composite material manufacturing method is mainly a method of mixing the reinforcing fiber with a thermoplastic resin and then molding through an extrusion or mold press process. Recently, to improve strength and productivity, a dry needle punching process or a wet papermaking process is applied. Thus, first, a mat-shaped material containing reinforcing fibers is prepared, and then a composite material is manufactured by impregnating the resin with a mat.

An embodiment of the present invention provides an underbody cover for a vehicle, which is advantageous in mechanical strength and weight reduction, and at the same time has significantly improved sound absorption and heat insulation performance.

Another embodiment of the present invention provides a method for efficiently manufacturing the underbody cover for a vehicle having the aforementioned advantages.

In one embodiment of the present invention, a porous composite material is included, the porous composite material includes a diffuse reflection surface structure on at least one surface, and the porous composite material includes a first fiber including a first thermoplastic resin; A second fiber comprising a second thermoplastic resin; And a binding material binding the first fiber and the second fiber, wherein the binding material includes a third thermoplastic resin, and the melting point of the first thermoplastic resin and the melting point of the second thermoplastic resin are respectively the third It provides a vehicle underbody cover that is higher than the melting point of the thermoplastic resin.

In another embodiment of the present invention, (a) preparing a slurry solution by dispersing reinforcing fibers and bicomponent polymer fibers in an aqueous solution; (b) forming a web from the slurry solution by a wet papermaking process; (c) drying the web to produce a composite sheet; (d) press molding the composite sheet to produce a porous composite; And (e) pressure-molding the porous composite material by inserting it into a mold in which a reverse phase pattern of a diffuse reflection surface structure is imprinted, wherein the reinforcing fiber is a first fiber comprising a first thermoplastic resin, and the bicomponent polymer. The fiber includes a core portion including a second thermoplastic resin and a sheath portion including a third thermoplastic resin, and melting points of the first thermoplastic resin and the second thermoplastic resin are respectively the third thermoplastic resin It provides a method for manufacturing a vehicle underbody cover higher than the melting point of the.

The vehicle underbody cover is excellent in mechanical strength and light weight effect, but in particular, impact resistance, sound absorption performance and heat insulation performance can be improved significantly.

In addition, the underbody cover for a vehicle manufactured through the method for manufacturing the underbody cover for a vehicle can easily implement the above-described advantages.

1 schematically shows a cross-section of an underbody cover for a vehicle according to an embodiment of the present invention.
2 schematically shows the type of general reflection behavior.
3 is a schematic schematic diagram of a porous composite material of a vehicle underbody cover according to an embodiment of the present invention.
4 schematically illustrates a cross-section of a diffuse reflection surface structure of a vehicle underbody cover according to an embodiment of the present invention.
5 schematically illustrates a pattern of a diffuse reflection surface structure of an underbody cover for a vehicle according to an embodiment of the present invention.
Figure 6 schematically shows a part of the manufacturing process of the porous composite material of the underbody cover for a vehicle according to an embodiment of the present invention.
7 is a graph showing the change in the sound absorption curve pattern according to Experimental Example 2.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to embodiments described below. However, the present invention will not be limited to the embodiments disclosed below, but will be implemented in various different forms, Only the present embodiments are provided to make the disclosure of the present invention complete, and to provide those who have ordinary knowledge in the art to which the present invention pertains, to fully disclose the scope of the invention, and the present invention is defined by the scope of the claims. It just works.

In the drawings, thicknesses are enlarged to clearly represent various layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for convenience of description. The same reference numerals refer to the same components throughout the specification.

In one embodiment of the present invention, a porous composite material is provided, and the porous composite material provides a vehicle underbody cover including a diffuse reflection surface structure on at least one surface.

In the underbody cover for a vehicle, The porous composite material includes a first fiber comprising a first thermoplastic resin; A second fiber comprising a second thermoplastic resin; And a binding material binding the first fiber and the second fiber, wherein the binding material includes a third thermoplastic resin, and the melting point of the first thermoplastic resin and the melting point of the second thermoplastic resin are respectively the third It is higher than the melting point of the thermoplastic resin.

The underbody cover for the vehicle is applied to the lower portion of the vehicle body to smooth air flow, thereby improving fuel efficiency and protecting the vehicle body from external impact. On the other hand, in recent automobile materials, as demands for sound absorbing and insulating performance, insulation performance, and light weight have increased, it has become an important factor to secure various functionalities in addition to the essential functions described above in the case of a vehicle underbody cover.

The vehicle underbody cover according to an embodiment of the present invention, unlike a conventional plastic injection material or a vehicle underbody cover of a metal material, includes a porous structure composite material to obtain an advantage of securing sound absorption performance, heat insulation performance and light weight .

Furthermore, the vehicle underbody cover may further improve sound insulation performance and heat insulation performance by having a diffuse reflection surface structure on the surface.

1 schematically illustrates a cross-section of the underbody cover 100 for a vehicle according to an embodiment of the present invention. Referring to FIG. 1, the underbody cover 100 for a vehicle includes a porous composite material 10 and includes a diffuse reflection surface structure 20 on the surface.

Sound or heat has a waveform having a predetermined energy. When such a waveform is incident on the surface of the material, a part of the waveform is transmitted through the material and the rest is reflected. At this time, in order to realize the required sound absorption performance using only the principle of attenuating the sound and heat transmitted, the thickness and density of the material are increased in order to increase the input depth, thereby increasing the weight. In addition, when the thickness of the product is increased while maintaining the same weight, there is a problem that the strength is lowered.

Accordingly, the vehicle underbody cover 100 consumes sound and heat transmitted through the porous structure of the composite material 10, and at the same time reflects sound and heat through the diffuse reflection surface structure 20 to improve sound absorbing and insulating performance and Insulating performance can be achieved.

The reflection behavior of the waveform can be largely divided into specular reflection and diffuse reflection. As shown in FIG. 2, specular reflection occurs on a smooth surface, diffuse reflection occurs on a rough surface, and in the case of diffuse reflection, energy due to wave scattering Because of the large attenuation, it has better reflection characteristics than regular reflection.

Accordingly, the vehicle underbody cover 100 may implement an improved sound absorbing and insulating performance and an insulating performance by including a surface structure 20 using diffuse reflection.

3 schematically shows the structure of the porous composite material 10 of the underbody cover 100 for a vehicle according to an embodiment of the present invention. Referring to FIG. 3, the porous composite material 10 includes a first fiber 11 and a second fiber 12, and a binding that binds the first fiber 11 and the second fiber 12 Ash 13 is included.

At this time, the first fiber 11 includes a first thermoplastic resin, the second fiber 12 includes a second thermoplastic resin, and the binder 13 includes a third thermoplastic resin. In addition, the melting point of the first thermoplastic resin and the melting point of the second thermoplastic resin are higher than the melting point of the third thermoplastic resin, respectively.

The binding material 13 is present in a coated state on a part or the entire surface of each of the first fiber 11 and the second fiber 12. 3, as an example, shows the state in which the binder 13 is coated on the entire surface of each of the first fiber 11 and the second fiber 12. As described above, the coating portions formed on the surfaces of the first fiber 11 and the second fiber 12 by the binder 13 are fused to each other, so that the first fiber 11 and the second Between fibers 12; Between the plurality of first fibers 11; Alternatively, the plurality of the second fibers 12 may be irregularly bound. As a result, the composite preformed board 100 has an irregular three-dimensional network structure including pores, and a porous structure having a predetermined porosity.

The porous composite material 10 may have a porosity of about 5% by volume to about 80% by volume, for example, about 20% by volume to about 60% by volume. The porosity of the porous composite material 10 is comprehensively controlled by the process conditions during manufacture, the specific composition and content ratio of the first fiber 11, the second fiber 12 and the binder 13, and the like. It can be formed to satisfy the porosity of. Since the porosity of the composite preformed board 100 satisfies this range, heat insulation and sound absorption can be greatly improved.

The porous composite material 10 not only improves the physical properties of the underbody cover 100 for a vehicle by having such a structure, but also forms the diffuse reflection surface structure 20 in the process of manufacturing the underbody cover 100 for a vehicle. When you do it, you can realize excellent processability.

In the composite preform board 100, the first fiber 11 and the second fiber 12 may have different elongation. Specifically, the elongation of the first fiber 11 may be higher than the elongation of the second fiber 12.

For example, the first fiber 11 is an elongated fiber having an elongation of about 300% to about 600%, and the first fiber 12 is an elongated fiber having an elongation of less than 300%, or unstretched with an elongation of 0%. It can be a fiber.

The elongation of the first fiber 11 and the second fiber 12 is expressed as a percentage of the length of the maximum length that does not break with respect to the original length of the fiber, and each of these elongations satisfies the above range. The vehicle underbody cover 100 exhibits excellent mechanical strength and rigidity, and can minimize shrinkage during the thermoforming process. Furthermore, the first fiber 11 and the second fiber 12 have different elongation characteristics, thereby ensuring excellent impact resistance to external impact through mutual complementary action of elasticity.

The porous composite material 10, as the first fiber 11 and the second fiber 12, as described above, using a fiber made of a thermoplastic resin material, using an inorganic fiber such as glass fiber or carbon fiber I never do that.

For example, when applying carbon fiber, a high manufacturing cost is required and is not suitable as a consumable part. When applying glass fiber, despite low raw materials, glass fiber is exposed to the outside or scattered in the assembly, resulting in a human body. There is a problem that has a detrimental effect on. For this reason, when applying glass fiber, a finishing material such as a non-woven fabric or film is used separately. In this case, it may cause a cost increase, and has a disadvantage of being very vulnerable to recyclability, which is one of the issues due to environmentally friendly purposes in recent years. .

Therefore, the porous composite material 10 uses resin-made fibers as the first fiber 11 and the second fiber 12, thereby reducing production costs and obtaining an advantage of easy recycling. have.

In one embodiment, the porous composite material, based on 100 parts by weight of the first fiber 11, the total content of the second fiber 12 and the binder 13 may be about 30 parts by weight to about 50 parts by weight . Accordingly, it may be advantageous to simultaneously secure excellent strength according to the first fiber 11 and impact resistance according to the second fiber 12, and the first fiber 11 via the binder 13 The second fiber 12 is attached to the porous structure having a porosity suitable for securing sound absorption and heat insulation performance can be easily formed.

In addition, the binder 13 may be from about 40 parts by weight to about 250 parts by weight with respect to 100 parts by weight of the second fiber 12, for example, from about 40 parts by weight to about 150 parts by weight, eg For example, it may be about 80 parts by weight to about 120 parts by weight.

According to the manufacturing method of the underbody cover for a vehicle described later, the second fiber 12 and the binder 13 are derived from bicomponent polymer fibers, and the first fiber 11 is derived from reinforcing fibers. . Accordingly, in the manufacturing method described below, the content ratio of each component constituting the bicomponent polymer fiber and the content ratio of the reinforcing fiber and the bicomponent polymer fiber can be controlled to obtain a vehicle underbody cover 100 that satisfies the above conditions. .

In one embodiment, the first thermoplastic resin constituting the first fiber 11 and the second thermoplastic resin constituting the second fiber 12 may have a specific gravity greater than about 1, for example, about 1 to about 1.5. According to the manufacturing method of the underbody cover for a vehicle to be described later, the first fiber 11 corresponds to a reinforcing fiber, and the second fiber 12 corresponds to a core portion of a bicomponent polymer fiber. At this time, the reinforcing fiber and the bicomponent polymer fiber undergo a process of being dispersed in an aqueous solution. Considering that the specific gravity of water is about 1, the first thermoplastic resin included in the first fiber 11 and the agent 2 As the second thermoplastic resin included in the fiber 12, each resin having a specific gravity of greater than about 1 can be used to settle well without floating on the surface of the aqueous solution, to ensure excellent dispersibility, and as a result, for the vehicle The mechanical strength of the underbody cover 100 may be improved.

The first fiber 11 may have a diameter of a cross section perpendicular to the length direction of the fiber from about 5 μm to about 40 μm, and a length from about 1 mm to about 50 mm.

In addition, the diameter of the cross section perpendicular to the longitudinal direction of the second fiber 12 may be about 5 μm to about 30 μm, and the length may be about 1 mm to about 50 mm.

The thickness and length of the first fiber 11 and the second fiber 12 satisfy the above range, thereby achieving desired sound absorption and insulation performance as well as desired mechanical strength based on their proper physical weaving properties. It is possible to secure a porous structure suitable for securing.

When referring to the manufacturing method of the underbody cover for a vehicle, which will be described later, it can be seen that the binder 13 is derived from a sheath portion of a bicomponent polymer fiber having the second fiber 12 as a core. That is, the sheath portion of the bicomponent polymer fiber melts under a predetermined temperature condition, and a part thereof is transferred to the surface of the first fiber 11, and as the binder 13, the first fiber 11 and the second fiber It serves to bind (12). Therefore, the third thermoplastic resin constituting the binder 13 has a lower melting point than the first thermoplastic resin and the second thermoplastic resin constituting the first fiber 11 and the second fiber 12. .

In one embodiment, each of the first thermoplastic resin and the second thermoplastic resin may have a melting point of about 200 ° C to about 270 ° C. In addition, the melting point of the third thermoplastic resin may be less than about 200 ℃, for example, about 100 ℃ or more, may be less than about 200 ℃. The melting point of each thermoplastic resin can be measured using a thermogravimetric analysis (TGA) instrument.

The melting points of the first, second and third thermoplastic resins can be adjusted through the respective components constituting them, the chemical structure of the components, and the like.

Specifically, the first thermoplastic resin and the second thermoplastic resin are polyester, polypropylene, polyethylene, acrylo-butadiene-styrene, polycarbonate, nylon, polyvinyl chloride, polystyrene, polyurethane, and polymethyl methacrylate, respectively. , Polylactic acid, Teflon, and derivatives thereof.

In one embodiment, the first thermoplastic resin and the second thermoplastic resin may be polyester having a melting point of 200 ° C to 270 ° C, respectively.

The third thermoplastic resin constituting the binder 13 is polyester, polyethylene, polypropylene, polyethylene, acrylo-butadiene-styrene, polycarbonate, nylon, polyvinyl chloride, polystyrene, polyurethane, polymethyl methacrylate, It may include at least one selected from the group consisting of polylactic acid, Teflon and derivatives thereof.

In one embodiment, the third thermoplastic resin may be polyester having a melting point of less than 200 ° C, for example, 100 ° C or more and less than 200 ° C.

More specifically, the third thermoplastic resin may be a modified polyethylene terephthalate (modified-PET) resin.

The polyethylene terephthalate (PET) resin is a copolymer resin composed of an ethylene structural unit and a terephthalate structural unit, and the terephthalate structural unit is an ester-based structure in which two ester groups are bonded at 1,4- (para) positions of a benzene ring. It is a unit.

The modified polyethylene terephthalate (modified-PET) resin constituting the third thermoplastic resin, in one embodiment, combines some of the terephthalate structural units of the polyethylene terephthalate (PET) resin with two ester groups of the benzene ring The resin may be substituted with an isophthalate structural unit having a 1,3- (meta) position, or a phthalate structural unit having a 1,2- (ortho) position.

In this case, more specifically, more than about 0 mol% and less than about 50 mol% of the terephthalate structural units of the polyethylene terephthalate (PET) resin may be substituted, for example, about 20 mol% to about 40 mol % Can be substituted.

In another embodiment, the modified polyethylene terephthalate (modified-PET) resin constituting the third thermoplastic resin is a part of the ethylene structural unit of the polyethylene terephthalate (PET) resin C3 to C10 linear or branched alkylene, or C3 to C10 may include a resin substituted with an alicyclic alkylene structural unit.

In this case, more specifically, about 20 mol% to about 60 mol% of the ethylene structural units are substituted with one structural unit selected from the group consisting of cyclohexanedimethylene, trimethylene, 2-methyltrimethylene, and combinations thereof. Can be.

4 schematically illustrates a cross-section of a diffuse reflection surface structure 20 of a vehicle underbody cover 100 according to an embodiment of the present invention, and FIG. 5 illustrates the diffuse reflection surface structure observed in direction A of FIG. 1 ( 20) schematically shows an example of the pattern.

Referring to FIG. 4, the diffuse reflection surface structure 20 includes a fine concavo-convex pattern, and a height difference d between the concave portions 21 and the convex portions 22 of the fine concavo-convex patterns is about 0.1 mm to about 3.0 mm. It may be, for example, about 0.2mm to about 2.0mm. When the depth of the diffuse reflection surface structure 20 satisfies this range, reflection and scattering of sound and heat can occur effectively, and excellent processability is secured in forming the structure of this shape on the surface of the porous composite material 10 can do.

FIG. 5 schematically illustrates an example of a pattern of the diffuse reflection surface structure 20 of the underbody cover 100 for a vehicle observed in the direction A of FIG. 1.

Referring to FIG. 5, the diffuse reflection surface structure 20 includes a fine uneven pattern, and the fine uneven pattern may be a lattice pattern in which rhombuses are continuously arranged. At this time, the rhombus may have a length of two diagonals L1 and L2 of about 4 mm to about 15 mm, respectively, for example, about 5 mm to about 15 mm.

In one embodiment, the length of one diagonal (L1) of the rhombus is about 5mm to about 9mm, the length of the other diagonal (L2) may be about 10mm to about 15mm.

In another embodiment, the length of one diagonal (L1) of the rhombus may be from about 4mm to about 5mm, and the length of the other diagonal (L2) may be from about 7mm to about 8mm.

When the fine concavo-convex pattern is formed in such a lattice pattern, excellent workability can be realized in the formation of the diffuse reflection surface structure 20, and the diffuse reflection surface structure 20 of this pattern is formed on the surface of the porous composite material 10 It is possible to secure improved sound absorption and insulation performance by forming.

Referring to FIG. 5, in the fine concavo-convex pattern of the diffuse reflection surface structure 20, the total area of the concave portion 21 may be greater than the total area of the convex portion 22. Through such a structure, it is possible to realize excellent workability in the formation of the diffuse reflection surface structure, and it is possible to secure both insulating and sound absorbing and insulating performances according to reflection and transmission behaviors of sound and heat.

Specifically, the ratio of the total area of the concave portion 21 to the total area of the convex portion 22 may be about 2: 1 to about 10: 1, for example, about 2: 1 to about 4: 1 days You can.

The vehicle underbody cover 100 includes the diffuse reflection surface structure 20 on at least one surface of the porous composite material 10, and in one embodiment, the diffuse reflection surface structure only on one surface of the porous composite material 10 ( 20).

When the vehicle underbody cover 100 is applied to a vehicle body, the surface on which the diffuse reflection surface structure 20 of the porous composite material 10 is formed may be disposed to face the ground or the vehicle body.

When the underbody cover 100 for the vehicle is disposed such that the diffuse reflection surface structure 20 faces the ground, a role of blocking noise generated from the outside of the vehicle may be improved. In addition, when the underbody cover 100 for the vehicle is disposed such that the diffuse reflection surface structure 20 faces the vehicle body, a function of blocking noise and heat generated from an engine inside the vehicle may be improved.

In another embodiment of the present invention, a method of manufacturing an underbody cover for a vehicle is provided.

The method for manufacturing the underbody cover for a vehicle includes: (a) preparing a slurry solution by dispersing reinforcing fibers and bicomponent polymer fibers in an aqueous solution; (b) forming a web from the slurry solution by a wet papermaking process; (c) drying the web to produce a composite sheet; (d) press molding the composite sheet to produce a porous composite; And (e) pressure-molding the porous composite material by inserting the porous composite material into a mold engraved with an inverse pattern of a diffuse reflection surface structure.

In this case, the reinforcing fiber is a first fiber including a first thermoplastic resin, and the bicomponent polymer fiber includes a core portion including a second thermoplastic resin and a sheath portion including a third thermoplastic resin. And the melting points of the first thermoplastic resin and the second thermoplastic resin are higher than those of the third thermoplastic resin.

Matters related to the first thermoplastic resin, the second thermoplastic resin, and the third thermoplastic resin are all as described above.

In step (a), the slurry solution is prepared by dispersing the reinforcing fiber and the bicomponent polymer fiber in an aqueous solution.

At this time, the reinforcing fibers and the bicomponent polymer fibers may be surface-treated on each surface to improve dispersibility in an aqueous solution. For example, the surface treatment introduces functional groups such as a fluorine group, a hydroxyl group, a carboxyl group, an alkyl group, and a silane group on the outermost surfaces of the reinforcing fiber and the bicomponent polymer fiber, or the reinforcing fiber and the bicomponent polymer fiber The outermost surface of the carbonization (carbonization), hydrolysis (hydrolysis) or oxidation (oxidation) can be performed by a method.

In addition, when the surface of the reinforcing fiber and the bicomponent polymer fiber is surface-treated, depending on the coating agent, functionalities such as hydrophilicity / hydrophobicity, water repellency, flame retardancy, non-combustibility, heat resistance, acid resistance, alkali resistance, durability, and contamination resistance may also be provided. You can.

For example, the coating agent for the surface treatment may include a fluorine-based wax, a hydrocarbon-based wax, a silicone-based polymer, etc., and the fluorine-based wax or the hydrocarbon-based wax may act as a water repellent.

In the step (a) of preparing the slurry solution, the total content of the reinforcing fibers and the bicomponent polymer fibers per 1 L of the aqueous solution may be about 0.1 g to about 10 g. By controlling the total amount of the fibers for the aqueous solution to the content in the above range, excellent dispersibility can be secured, and a web of uniform thickness can be produced.

In addition, the pH of the aqueous solution may be from about 1 to about 8, for example, from about 3 to about 7. By adjusting the pH of the aqueous solution to the above range, charges are generated on the surfaces of the reinforcing fibers and the bicomponent polymer fibers to further improve dispersibility.

If necessary, the slurry solution may further include additives such as a crosslinking agent or an additional binder.

The crosslinking agent acts to strengthen the chemical bonding force between the reinforcing fiber and the bicomponent polymer fiber, and for example, a silane-based compound, a maleic acid-based compound, or the like can be used.

The content of the crosslinking agent may be from about 0 parts by weight to about 5 parts by weight based on 100 parts by weight of the sum of the reinforcing fibers and the bicomponent polymer fibers, for example, greater than about 0 parts by weight and less than or equal to about 1 part by weight.

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

The content of the additional binder may be from about 0 parts by weight to about 5 parts by weight based on 100 parts by weight of the sum of the reinforcing fibers and the bicomponent polymer fibers, for example, greater than about 0 parts by weight and less than about 3 parts by weight .

The slurry solution may include about 50 parts by weight to about 200 parts by weight of the bicomponent polymer fiber with respect to 100 parts by weight of the reinforcing fibers.

In addition, the bicomponent polymer fiber may include about 40 parts by weight to about 150 parts by weight of the sheath part, and about 80 parts by weight to about 120 parts by weight with respect to 100 parts by weight of the core part. have.

As a result, when the sheath portion of the bicomponent polymer fiber is melted and changed into a binding material for binding the core portion and the reinforcing fiber of the bicomponent polymer fiber, a structural change may occur such that a porous structure having an appropriate porosity is formed. , The final manufactured vehicle underbody cover can implement excellent sound absorption performance and heat insulation performance.

The manufacturing method of the underbody cover for a vehicle includes the step (b) of manufacturing a web using a wet papermaking process from the slurry solution.

6 schematically shows a process in which the web is manufactured. Referring to FIG. 6, the wet papermaking process uniformly mixes the reinforcing fibers and the bicomponent polymer fibers in the aqueous solution through an agitator 30 to prepare a slurry solution 40, and the prepared slurry solution 40 ) Is a process of manufacturing the wet web 60 while moving on the mesh along the conveyor belt 50.

Specifically, the wet web 60 may be manufactured by passing the slurry solution 40 through a vacuum intake system 70.

In one embodiment, the conveyor belt 50 may have a slope at a predetermined angle with respect to the ground. As a result, at least a portion of the reinforcing fibers and bicomponent polymer fibers of the slurry solution 40 may have orientation in the direction of movement of the conveyor belt 50, and in this case, high strength may be achieved with respect to the orientation direction.

Subsequently, the method for manufacturing the underbody cover for a vehicle includes the step (c) of manufacturing the composite sheet by drying the web.

The step of drying the web is performed at a lower temperature than the melting point of the third thermoplastic resin. That is, in step (c), the sheath portion of the bicomponent polymer fiber is not melted, and only the aqueous solution component of the slurry solution is evaporated.

For example, the step (c) may be performed at about 100 ℃ to about 150 ℃.

Subsequently, the method for manufacturing the underbody cover for a vehicle includes the step (d) of pressurizing the composite sheet to produce a porous composite material.

The step of press forming the composite sheet may be a step of laminating at least two sheets of the composite sheet and press forming using a double belt press method.

The single composite sheet may have a basis weight of about 250 g / m 2 to about 350 g / m 2 at a thickness of about 1 mm to about 5 mm, and the porous composite material may have a basis weight of about 700 g / m 2 to about 1600 g at a thickness of about 1 mm to about 5 mm. / M2. That is, the number of the composite sheet may be appropriately adjusted to satisfy the basis weight of the porous composite.

The press molding of step (d) is performed at a predetermined temperature condition, specifically, at a temperature higher than the melting point of the third thermoplastic resin and lower than the melting point of the first thermoplastic resin or the melting point of the second thermoplastic resin. Can be.

Thus, through the press molding, the sheath portion of the bicomponent polymer fiber in the composite sheet can be melted to serve as a binder, and at the same time, an appropriate pore structure is obtained by physically weaving the core portion of the reinforcing fiber and the bicomponent fiber. It is formed, and at the same time, it is possible to secure a desirable physical structure to form a diffuse reflection surface structure on the surface of the porous composite material, and at the same time, it is possible to implement excellent sound absorption performance and heat insulation performance.

The press molding of step (d) may be performed under a pressure of about 1 bar to about 30 bar. When the pressure is too high, the pore structure of the porous composite material cannot be properly formed, and when the pressure is too low, there is a fear that the interfacial adhesion between a plurality of the composite sheets is deteriorated.

The method for manufacturing the underbody cover for a vehicle includes the step (e) of pressurizing and molding the porous composite material by inserting it into a mold in which an inverse pattern of a diffuse reflection surface structure to be formed on at least one surface thereof is imprinted.

Features such as the shape of the diffuse reflection surface structure are as described above with respect to the vehicle underbody cover.

When the diffuse reflection surface structure is a fine concavo-convex pattern including concave and convex portions, the pattern imprinted on the mold is an opposite pattern between the diffuse reflection surface structure and concave and convex portions, and is pressed to form a diffuse reflection surface structure having a desired shape. can do.

The step (e) may be performed by preheating the porous composite material at about 140 ° C to about 220 ° C for about 1 minute to about 5 minutes, and then inserting it into the mold. As the porous composite material undergoes a preheating process under these conditions, the diffuse reflection surface structure may be more clearly formed on the surface.

In addition, in the step (e), the pressure on the porous composite material may be performed for about 50 seconds to about 120 seconds at a pressure of about 100 tons to about 400 tons. By pressurizing under such pressure and time conditions, while maintaining the pore structure of the porous composite material, the diffuse reflection surface structure is clearly formed, and the sound absorbing and insulating performance and heat insulation performance of the final undercarriage cover for the vehicle are desired. As can be easily implemented.

The method for manufacturing the underbody cover for a vehicle may further include a step (f) of detaching from the mold when the surface temperature of the pressure-molded porous composite material is normal temperature. Specifically, normal temperature means a temperature of about 20 ° C to about 50 ° C.

When the porous composite material having the diffuse reflection surface structure formed on the surface is removed from the mold by the pressure molding, when the surface is separated from a temperature higher than room temperature, there is a fear that the diffuse reflection surface structure is damaged, and in this case, the vehicle underbody cover is intended. This can be difficult to achieve.

Through the above-described manufacturing method, a first fiber 11 derived from the reinforcing fiber and a second fiber (12) derived from a core portion of the bicomponent polymer fiber including a diffuse reflection surface structure having a predetermined shape on the surface ), And is derived from the sheath portion of the bicomponent polymer fiber, the underbody cover for a vehicle made of a porous composite material including a binding material 13 binding the first fiber 11 and the second fiber 12. Can be produced.

That is, all matters related to the first fiber 11 and the second fiber 12 are as described above.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for specifically illustrating or describing the present invention, and the present invention is not limited thereto.

< Example  And Comparative example >

Example  One

A polyester core portion having a melting point of 260 ° C and an elongation of less than 300% and a polyester sheath portion having a melting point of 160 ° C have a weight ratio of 50:50, the length is 5 mm, and the diameter of the cross section perpendicular to the longitudinal direction is 20 μm. Phosphorous bicomponent polymer fibers were prepared. The cis part is composed of a modified polyethylene terephthalate (modified-PET) resin in which 30 mol% of the phthalate units among the constituent units of the polyethylene terephthalate are substituted with isophthalic units.

Subsequently, a polyester stretched yarn having a length of 13 mm, a cross-section perpendicular to the length direction of 13 µm, a melting point of 260 ° C., and an elongation of 300% was prepared as reinforcing fibers.

Based on 100 parts by weight of the reinforcing fibers, 40 parts by weight of the bicomponent polymer fibers were blended and stirred in an aqueous solution of hydrochloric acid (HCl) whose pH was adjusted to 2-7 for 1 hour to prepare a slurry solution. At this time, the reinforcing fiber and the bicomponent polymer fiber per 1 L of the aqueous solution were made to be 2 g.

Subsequently, the slurry solution was passed through a vacuum suction system while moving through a mesh moving on a conveyor belt to prepare a wet web. The wet web was completely dried by passing through an oven dryer at 140 ° C to prepare a composite sheet. The composite sheet had a thickness of 5 mm and a basis weight of 300 g / m 2. The composite sheet was stacked so that the total basis weight was 1200 g / m 2 and then pressed at 200 ° C. for 5 minutes by a double belt press method to prepare a porous composite material having a total thickness of 5 mm. After inserting the porous composite in a mold engraved with a lattice pattern, it was press-molded for 1 minute at a pressure of 200 ton to form a diffuse reflection surface structure on the surface. Subsequently, the porous composite material was removed from the mold at room temperature to prepare a vehicle underbody cover.

The diffuse reflection surface structure is a fine concavo-convex pattern with a difference in height between concave and convex parts of 0.5 mm, and the fine concavo-convex pattern has a rhombus having a diagonal length of 13.0 mm and another diagonal having a length of 7.0 mm. It is a lattice pattern and is formed in a structure in which the ratio of the area of the recesses to the area of the recesses is 2: 1.

Example  2

A vehicle underbody cover was manufactured in the same manner as in Example 1, except that a diffuse reflection surface structure was formed using a mold in which a grid pattern having a shape different from that of Example 1 was imprinted.

The diffuse reflection surface structure is a fine concavo-convex pattern with a difference in height between concave and convex parts of 0.5 mm, and the fine concavo-convex pattern has a rhombus with a diagonal length of 7.6 mm and a diagonal length of 4.3 mm. It is a lattice pattern and is formed in a structure in which the ratio of the area of the recesses to the area of the recesses is 3: 1.

Comparative example  One

In Example 1, a vehicle underbody cover was manufactured in the same manner, except that a non-reflective surface structure was not formed on the surface of the porous composite material.

<Evaluation>

Experimental example  1: thickness and Basis  Measure

For each of the vehicle underbody covers of Examples 1-2 and 1, the thickness and basis weight were measured using a thickness gauge (Mitutoyo, 547-321) and an electronic balance (Mettler Toledo, JP 1603CA). The results are shown in Table 1 below.

Thickness [mm] Basis weight [g / ㎡] waist Iron Example 1 3.0 2.5 1,200 Example 2 3.0 2.5 1,200 Comparative Example 1 3.0 1,200

Experimental example  2: Measurement of sound absorption coefficient

For each of the vehicle underbody covers of Examples 1-2 and Comparative Example 1, the sound absorption coefficient (α) at a frequency of 500 Hz to 6300 Hz was measured using an impedance tube sound absorption measurement equipment, and the average value of these was calculated. Table 2 below. In addition, analysis of changes in the sound absorption curve pattern is shown in FIG. 7.

Average value of sound absorption coefficient Example 1 0.39 Example 2 0.37 To comparison 1 0.33

Experimental example  2: Evaluation of insulation performance

For each of the vehicle underbody covers of Examples 1-2 and 1, a sample having a size of 250 mm × 250 mm was prepared, and heat transfer coefficients were measured using a thermal conductivity measuring equipment EKO Instruments (HC-074). Table 3 shows the results.

Heat transfer coefficient [W / mK] Example 1 0.28 Example 2 0.29 Comparative Example 1 0.30

When referring to the results of Tables 1 to 3, in the case of the underbody covers for vehicles of Examples 1 to 2 according to the embodiment of the present invention, the structure of the diffuse reflection surface of the specific structure and the porous structure of the specific component are mutually mutually By working, it can be seen that compared to the underbody cover for the vehicle of Comparative Example 1, excellent sound absorption performance and heat insulation performance are realized.

100: vehicle underbody cover
10: porous composite
11: first fiber
12: second fiber
13: binder
20: diffuse reflection surface structure
21: main part
22: iron
d: Difference in height of the main and convex parts
L1, L2: diagonal
30: agitator
40: slurry solution
50: conveyor belt
60: Web
70: vacuum intake system

Claims (15)

Comprising a porous composite,
The porous composite material includes a diffuse reflection surface structure on at least one surface,
The porous composite material includes a first fiber including a first thermoplastic resin; A second fiber comprising a second thermoplastic resin; And a binding material binding the first fiber and the second fiber,
The binder includes a third thermoplastic resin,
The melting point of the first thermoplastic resin and the melting point of the second thermoplastic resin are higher than the melting point of the third thermoplastic resin, respectively.
The diffuse reflection surface structure includes a fine concavo-convex pattern with a difference in height between concave and convex parts of 0.1 mm to 3.0 mm.
Vehicle underbody cover.
According to claim 1,
The first fiber and the second fiber form a coating part formed by coating part or all of the surface with the binder,
The coating parts are fused to each other and bound
Vehicle underbody cover.
According to claim 1,
The first fiber is a stretched fiber having an elongation of 300% to 600%,
The second fiber is an unstretched fiber having an elongation of 0%, or an elongated fiber having an elongation of less than 300%.
Vehicle underbody cover.
According to claim 1,
With respect to 100 parts by weight of the first fiber, the total content of the second fiber and the binder is 30 parts by weight to 50 parts by weight
Vehicle underbody cover.
According to claim 1,
The binder is 40 parts by weight to 250 parts by weight based on 100 parts by weight of the second fiber
Vehicle underbody cover.
According to claim 1,
The porosity of the porous composite material is 5% to 80% by volume
Vehicle underbody cover.
delete According to claim 1,
The fine concavo-convex pattern is a grid pattern in which rhombuses each having a length of two diagonals of 4 mm to 15 mm are continuously arranged.
Vehicle underbody cover.
According to claim 1,
In the fine concavo-convex pattern, the total area of the concave portions is larger than the total area of the convex portions.
Vehicle underbody cover.
(A) preparing a slurry solution by dispersing the reinforcing fibers and bicomponent polymer fibers in an aqueous solution;
(b) forming a web from the slurry solution by a wet papermaking process;
(c) drying the web to produce a composite sheet;
(d) press molding the composite sheet to produce a porous composite; And
(e) inserting the porous composite material into a mold in which an inverse pattern of a diffuse reflection surface structure is imprinted and pressure-molded;
The reinforcing fiber is a first fiber comprising a first thermoplastic resin,
The bicomponent polymer fiber includes a core portion including a second thermoplastic resin and a sheath portion including a third thermoplastic resin,
The melting points of the first thermoplastic resin and the second thermoplastic resin are higher than those of the third thermoplastic resin, respectively.
The diffuse reflection surface structure includes a fine concavo-convex pattern with a difference in height between concave and convex parts of 0.1 mm to 3.0 mm.
Method of manufacturing a vehicle underbody cover.
The method of claim 10,
The content of the two-component polymer fiber with respect to 100 parts by weight of the reinforcing fiber is 30 parts by weight to 50 parts by weight
Method of manufacturing a vehicle underbody cover.
The method of claim 10,
The total content of the reinforcing fibers and the bicomponent polymer fibers per 1L of the aqueous solution is 0.1g to 10g
Method of manufacturing a vehicle underbody cover.
The method of claim 10,
PH of the aqueous solution is 1 to 8
Method for manufacturing composite preform board.
The method of claim 10,
Step (c) is performed at a temperature lower than the melting point of the third thermoplastic resin.
Method of manufacturing a vehicle underbody cover.
The method of claim 10,
The step (d) is performed at a temperature higher than the melting point of the third thermoplastic resin, and lower than the melting point of the first thermoplastic resin or the melting point of the second thermoplastic resin.
Method of manufacturing a vehicle underbody cover.

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