KR102673286B1 - Molded object, sandwich panel using same, and method for manufacturing same - Google Patents

Abstract

The present invention relates to a molded body having a non-woven fiber aggregate structure containing polypropylene fibers, kenaf fibers, and maleic anhydride polypropylene, a sandwich panel using the same as a core layer, and a method of manufacturing the same.

Description

Molded body, sandwich panel using the same, and manufacturing method thereof {MOLDED OBJECT, SANDWICH PANEL USING SAME, AND METHOD FOR MANUFACTURING SAME}

The present invention relates to a molded body, a sandwich panel using the same, and a method of manufacturing the same.

Conventional sandwich panels have structural rigidity similar to metal panels while being effective in reducing weight, so they are used in various fields such as building materials.

These sandwich panels control the physical properties of the panel by forming a core layer (molded body) between skin layers made of aluminum, iron, etc. For example, the lightweight effect of the panel is increased by using a foamed resin material in the core layer, or the mechanical strength of the panel is increased by using general resin, composite material, or balsa wood material.

However, such sandwich panels have limitations in product application because they are not lightweight, have insufficient mechanical strength, and are not excellent in elongation. In addition, when forming a panel by applying an adhesive between the skin layer and the core layer, there is a problem of poor formability during processing due to weak bonding between the layers.

Background technology related to the present invention includes Republic of Korea Patent Publication No. 10-2017-0140111, which discloses a sandwich panel and its manufacturing method.

However, in the case of the above sandwich panel, although it has high density and secured physical properties such as high bending strength and tensile strength, there are problems with the shear rigidity of the panel, degree of deflection, bonding strength between different fibers, and lightweighting of the material to secure high mechanical properties compared to weight. there was.

(Patent Document 1) Republic of Korea Patent Publication No. 10-2017-0140111, Sandwich panel and manufacturing method thereof

In order to solve the above problem, the present inventors used maleic anhydride polypropylene (MAPP) in polypropylene (PP) fibers when manufacturing non-woven fabric (non-woven fiber aggregate) used as the core material of sandwich panels. The present invention was completed by studying the molded body manufactured by adding and mixing kenaf fibers, the sandwich panel using the same, and the manufacturing method thereof.

Therefore, the purpose of the present invention is to use Kenaf fiber material with high tensile properties due to a high proportion of cellulose, a crystalline polymer that affects the tensile properties of natural fibers, when manufacturing sandwich panels. The object of the present invention is to provide a sandwich panel and a manufacturing method thereof in which the mechanical strength of the core material is improved in density, while the adhesion between the core material and the skin layer is improved, thereby improving shear stiffness and the degree of deflection.

In addition, the purpose of the present invention is to secure high mechanical properties by increasing the contact area by adding maleic anhydride polypropylene along with polypropylene and kenaf fibers during the production of sandwich panels to improve the bonding force between different fibers. To provide sandwich panels and their manufacturing methods.

According to the first aspect of the present invention,

A molded body is provided, which is a non-woven fiber aggregate structure comprising polypropylene fibers, kenaf fibers, and maleic anhydride polypropylene.

In one embodiment of the present invention, the non-woven fiber aggregate structure includes 50 to 80% by weight of polypropylene fibers, based on the total weight of the non-woven fiber aggregate structure; 15 to 45% by weight of kenaf fiber and 0.1 to 14% by weight of maleic anhydride polypropylene.

In one embodiment of the present invention, the basis weight of the nonwoven fiber aggregate structure is 2700 to 3500 gsm.

In one embodiment of the present invention, the apparent density of the nonwoven fiber aggregate structure is 0.4 to 0.7 g/m ³ .

In one embodiment of the present invention, the modulus of the nonwoven fiber aggregate structure is 25 to 45 GPa, and the maximum load is 1500 to 3500 N.

In one embodiment of the present invention, the non-woven fiber aggregate structure is a structure in which two or more non-woven fiber aggregates are bonded, and the non-woven fiber aggregate is formed by bonding non-woven fibers in the form of a web or a sheet with an adhesive. , it was bonded using thermoplastic fibers.

According to the second aspect of the invention,

core layer; a skin layer laminated on one or more surfaces of the core layer; and an adhesive layer for adhering the core layer and the skin layer, wherein the core layer uses the molded body.

In one embodiment of the present invention, the skin layer is one or more selected from the group consisting of aluminum, iron, stainless steel (SUS), magnesium, and electrogalvanized steel sheet (EGI).

In one embodiment of the present invention, the adhesive layer includes one or more of an olefin-based adhesive, a urethane-based adhesive, an acrylic-based adhesive, and an epoxy-based adhesive.

According to the third aspect of the present invention,

a) mixing polypropylene fibers and maleic anhydride polypropylene to produce mixed fibers; b) adding kenaf fibers to the mixed fibers, heating and pressing to produce a non-woven fiber aggregate; c) manufacturing a core layer by performing a needle punching process on the nonwoven fiber aggregate at a number of punches of 300 to 1000 times per minute, a moving speed of 1 to 8 m/min, and a punching density of 100 to 500 punches/cm ² ; d) forming an adhesive layer on at least one side of the core layer; and e) forming a skin layer on the adhesive layer.

The sandwich panel according to the present invention is made by adding maleic anhydride polypropylene to polypropylene and then mixing it with kenaf fibers when manufacturing the non-woven fabric used as the core material of the sandwich panel, thereby improving the bonding strength between heterogeneous fibers even at low density. A molded body with improved strength is manufactured, and a sandwich panel with improved adhesion between the core material and the skin layer using the same is provided. Sandwich panels with the above effects are suitable for use in structural materials for home appliances (TV back covers, washing machine boards, etc.), interior and exterior boards for construction, interior and exterior materials for automobiles, interior and exterior materials for trains/ships/aircraft, various partition boards, and elevator structural materials. do.

Figure 1 is a schematic diagram of a sandwich panel according to the present invention.
Figure 2 is a photograph of the surface of the core layer of Example 3 according to the present invention.
Figure 3 is a photograph taken of the core layer surface of Comparative Example 1 according to the present invention.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. The present embodiments only serve to ensure that the disclosure of the present invention is complete and that common knowledge in the technical field to which the present invention pertains is not limited. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, the molded body and sandwich panel according to a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

As a result of the present inventors' experiments, in the case of the core material used in conventional sandwich panels, the bonding force between fibers is low due to the nature of the non-polar polypropylene fibers that have been used previously, so there is a manufacturing difficulty in improving the mechanical properties of the core material, so the bonding strength of the core material is reduced. There was a need for research to improve.

In addition, when manufacturing a non-woven fiber aggregate structure used as a core material, a mixture of polypropylene and kenaf fiber, a natural fiber based on cellulose, was used, but the bonding strength between the two fibers was low, which limited the improvement of mechanical properties. There was a problem.

In order to solve the above problems, the inventors of the present invention added maleic anhydride polypropylene and used it as a binder when manufacturing a non-woven fiber aggregate structure used as a core material, thereby forming a bond between polypropylene/kenaf fibers. By increasing the contact area and improving the bonding force, a sandwich panel with improved mechanical properties such as modulus and maximum load was produced.

molded body

The molded body according to the present invention is a non-woven fiber aggregate structure comprising polypropylene fibers, kenaf fibers and maleic anhydride polypropylene.

The non-woven fiber aggregate structure includes 50 to 80% by weight of polypropylene fibers, based on the total weight of the non-woven fiber aggregate structure; 15 to 45% by weight of kenaf fiber; and 0.1 to 14% by weight of maleic anhydride polypropylene.

In the present invention, 'non-woven fiber aggregate structure' is a structure in which two or more non-woven fiber aggregates are joined, and 'non-woven fiber aggregate' refers to non-woven fibers in the form of a web or sheet adhered with an adhesive or , refers to bonding using thermoplastic fibers. Since the molded body according to the present invention has a non-woven fiber aggregate in which fibers are entangled with each other, all or part of the kenaf fibers are fused by a binder, and therefore, in the molded body Natural pores are included, improving breathability and improving weight reduction. In other words, because the fibers have natural pores formed by entangling each other, unlike cases where pores are artificially formed by additives such as foaming agents, it is a non-foaming core, so manufacturing costs can be reduced and the foaming process can be omitted, thereby improving the manufacturing process. Efficiency can also be increased.

The molded body according to the present invention includes polypropylene fibers (PP). As the polypropylene fiber, those commonly used in the industry can be used. The average length of the polypropylene fiber is preferably 30 to 150 mm. If the average length of the fiber is less than 30 mm, it may be difficult to expect the effect of high elongation due to the short length of the fiber. On the other hand, if it exceeds 150 mm, the space occupied by the gap in the core layer may be reduced because the content of fibers entangled with each other increases. Additionally, if it exceeds 150 mm, the fibers may not be dispersed smoothly when manufacturing the core layer, and the physical properties of the core layer may deteriorate. In addition, the polypropylene (PP) fiber may have a tenacity of 3 or more and a fineness of 3 to 15 denier.

The nonwoven fiber aggregate structure is 50 to 80% by weight, preferably 55 to 75% by weight, preferably 55 to 70% by weight, especially more preferably 58 to 67% by weight, based on the total weight of the nonwoven fiber aggregate structure. May contain polypropylene fibers. When less than 50% by weight of polypropylene fibers are included, there is a problem that there is a limit to improving mechanical properties such as flexural strength due to insufficient binder content to bond the kenaf fibers. In addition, when more than 80% by weight of polypropylene fibers are included, there is a problem in that the fibers do not have a structure formed by entangling, and thus the elongation and strength of the fibers are not improved when used as a core material.

The molded body according to the present invention includes kenaf fiber. The kenaf fiber is a one-year-old subtropical plant that has a carbon dioxide decomposition ability more than 5 times that of existing plants and has a water purification effect, so it is a natural fiber material that has already been recognized for its use as an eco-friendly material. The density of the kenaf fiber may be 1.3 to 1.5 g/cm ³ . Additionally, the fineness of the kenaf fiber may be 2 to 25 denier. Additionally, the length of the fiber may be 0.5 to 200 mm. When the fineness of the kenaf fiber satisfies the above range, the dispersibility with the polypropylene fiber increases, which has the advantage of uniformly distributing inter-fiber bonds and increasing contact points between fibers, and when the length satisfies the above range. There is an advantage in that the contact points between homogeneous fibers are reduced and the contact points between heterogeneous fibers are increased.

The nonwoven fiber aggregate structure may include 15 to 45% by weight, preferably 20 to 40% by weight, and more preferably 25 to 35% by weight of kenaf fibers, based on the total weight of the nonwoven fiber aggregate structure. If the amount of kenaf fibers is less than 15% by weight, the structural complement of rigidity may be reduced, which may lower the flexural rigidity. If it exceeds 45% by weight, the binder content is small and the degree of bonding between fibers is reduced, thereby reducing the flexural rigidity and peel strength. Problems may arise.

The molded article according to the present invention includes maleic anhydride polypropylene. The maleic anhydride polypropylene can be used as a compatibilizer to increase compatibility between the kenaf fiber and the polypropylene fiber.

The nonwoven fiber aggregate structure is present in an amount of 0.1 to 14% by weight, preferably 1 to 14% by weight, more preferably 3 to 14% by weight, especially more preferably 3 to 7% by weight, based on the total weight of the nonwoven fiber aggregate structure. It may include maleic anhydride polypropylene. When the maleic anhydride polypropylene is less than 0.1% by weight, compatibility between kenaf fibers and polypropylene fibers may decrease and the effect of strengthening bonding strength due to an increase in contact area may decrease. If it exceeds 14% by weight, the formability of the molded body used as the core layer of the sandwich panel deteriorates, the degree of improvement in modulus and maximum load compared to the amount of maleic anhydride polypropylene input becomes insignificant, and the amount of kenaf fiber is relatively small. As the kenaf fibers are added, the structural supplementary effect of stiffness may be reduced.

The binder included in the core layer is not particularly limited as long as it has a structure that can bond non-woven fiber aggregates in the form of a web or a sheet, but may be polypropylene, maleic anhydride polypropylene, Preferably it may be maleic anhydride polypropylene.

All or part of the kenaf fibers included in the molded body according to the present invention are fused by the binder, and the binder may have a melting point of 170°C or higher.

The molded body having a non-woven fiber aggregate structure according to the present invention has an apparent density of 0.4 to 0.7 g/cm ³ . Since it satisfies the above density range, it can have sufficient mechanical strength to be used as packaging material for large cargo.

Since the molded body according to the present invention satisfies the mechanical strength as described above, it is included as a core layer in a sandwich panel, and is used as a structural material for home appliances (TV back cover, washing machine board, etc.), interior and exterior boards for construction, interior and exterior materials for automobiles, and trains. It can be used as interior and exterior materials for ships/aircraft (boards such as partitions), various partition boards, and elevator structural materials.

In addition, the molded body according to the present invention may further include fillers such as glass fiber, carbon fiber, polymer fiber, etc. Additionally, it may further contain a flame retardant such as a brominated organic flame retardant. In addition, additives such as impact modifiers and heat stabilizers may be further included.

Manufacturing method of molded body

The manufacturing method of the molded body according to the present invention can be manufactured by the following method.

The method for producing the molded body according to the present invention includes the steps of a) mixing polypropylene fibers and maleic anhydride polypropylene to produce mixed fibers; b) adding kenaf fibers to the mixed fibers, heating and pressing to produce a non-woven fiber aggregate; and c) manufacturing a core layer by subjecting the nonwoven fiber aggregate to a needle punching process at a number of punches of 300 to 1000 times per minute, a moving speed of 1 to 8 m/min, and a punching density of 100 to 500 punches/cm ² . do.

In step a), first, (A) polypropylene fiber and (B) maleic anhydride polypropylene can be prepared to produce polypropylene/maleic anhydride polypropylene mixed fiber. At this time, based on the total weight of the non-woven fiber aggregate structure (A) 50 to 80% by weight, preferably 55 to 75% by weight, preferably 55 to 70% by weight, particularly more preferably 58 to 67% by weight of poly. A mixture of propylene and (B) 0.1 to 14% by weight, preferably 1 to 14% by weight, more preferably 3 to 14% by weight, particularly more preferably 3 to 7% by weight of maleic anhydride polypropylene. You can use it. If the content of (A) polypropylene fiber and (B) maleic anhydride polypropylene does not satisfy the above range, there is a problem of reduced peel strength and bending rigidity due to insufficient bonding between fibers due to lack of binder.

In step b), kenaf fibers are added to the polypropylene/maleic anhydride polypropylene mixed fiber, and heated and pressed to produce a nonwoven fiber aggregate. At this time, based on the total weight of the nonwoven fiber aggregate structure, 15 to 45% by weight, preferably 20 to 40% by weight, and more preferably 25 to 35% by weight of kenaf fiber may be added.

In the present invention, it was explained that kenaf fibers were added to polypropylene/maleic anhydride polypropylene mixed fibers, but kenaf fibers were added in the process of mixing polypropylene and maleic anhydride polypropylene in step a). Addition is not ruled out.

Thereafter, in step c), the non-woven fiber aggregate is subjected to a needle punching process at a number of punches of 300 to 1000 times per minute, a moving speed of 1 to 8 m/min, and a punching density of 100 to 500 punches/cm ² to produce a molded product having a non-woven fiber aggregate structure. can be manufactured.

In the needle punching process, the number of punches per minute on the mixed nonwoven fiber aggregate is 300 to 1000, the moving speed of the nonwoven fiber aggregate is 1 to 8 m/min, and the punching density is 100 to 500 punches/cm ² , A needle punching process can be performed, and more preferably, the number of punches per minute on the non-woven fiber aggregate is 400 to 700, the moving speed of the non-woven fiber assembly is 1.5 to 6 m/min, and the punching density is 200 to 400 punches/cm. ² , the needle punching process can be performed.

If the number of punchings per minute is less than 300, there is a problem that the degree of bonding between non-woven fiber assemblies decreases, and if the number of punching times per minute is more than 1000, there is a problem that fracture of the non-woven fiber assemblies occurs. In addition, if the moving speed of the nonwoven fiber aggregate is slower than 1 m/min, there is a problem that the production speed is too slow, and if it is faster than 8 m/min, there is a problem that it is not easy to control the punching density. In addition, if the punching density is less than 100 punches/cm ^{2 ,} there is a problem that the degree of adhesion between non-woven fiber assemblies decreases, and if it is more than 500 punches/cm ² , there is a problem that fracture of the non-woven fiber assemblies occurs.

The needle punching process can be performed two or more times. If the needle punching process is performed two or more times, the cohesion of the interlayer fibers can be increased, which is effective in preventing interlayer delamination.

As the needle punching process in the above range is performed, the physical bonding force by needle punching is improved, and physical properties such as tensile strength of the molded body used as the core layer are improved, and through this, the shear stiffness strength and sagging of the final manufactured sandwich panel are improved. The degree can be improved.

Specifically, after adding and mixing maleic anhydride polypropylene to the polypropylene/kenaf fiber, carding was performed using a carding machine, and then a needle punching process was performed under the above conditions to obtain a basis weight of 2700 to 3500 gsm. Manufacture non-woven fiber aggregates (non-woven fabrics).

Afterwards, the prepared non-woven fiber aggregate (non-woven fabric) is mounted on a plurality of unwinding devices and then moved to a heating press. At this time, 1 to 10 sheets of the manufactured nonwoven fiber aggregate can be mounted on a plurality of unwinding devices according to the number, and then moved to a heating press for manufacturing the molded body. When a plurality of nonwoven fiber aggregates are used using a plurality of unwinding devices, the thickness of each nonwoven fiber assembly becomes thinner, so the length of the nonwoven fiber assembly wound on one unwinding device becomes longer. Therefore, there is an advantage in that the process can be simplified because the number of times the use of an opener to connect nonwoven fiber aggregates continuously introduced during a continuous process can be reduced.

Afterwards, the plurality of non-woven fiber aggregates (non-woven fabrics) moved to the heating press are heated and pressed at a temperature of 170 to 210° C. and a pressure of 1 to 10 MPa to produce a molded body having a non-woven fiber aggregate structure.

The heating press is not particularly limited as long as it is normally used in the industry, and a double belt press or the like can be used as a specific example.

In addition, the method for manufacturing the molded body according to the present invention,

After performing the needle punching process of step c), the method may further include preheating for 3 to 10 minutes at a temperature of 160 to 210°C.

sandwich panel

Referring to Figure 1, the sandwich panel according to the present invention includes a core layer (10); A skin layer 20 laminated on one or more surfaces of the core layer; and an adhesive layer (not shown) that adheres the core layer and the skin layer, and the core layer uses the molded body.

The core layer of the sandwich panel according to the present invention is composed of the molded body according to the present invention described above. The thickness of the core layer is preferably 0.1 to 10 mm. If the thickness is less than 0.1 mm, it is difficult to maintain excellent mechanical strength, and if the thickness exceeds 10 mm, there is a problem that formability is deteriorated when bending the sandwich panel or deep drawing.

The sandwich panel according to the present invention includes a skin layer laminated on one or more surfaces of the core layer.

The skin layer of the sandwich panel according to the present invention may be formed of a metal material, preferably at least one selected from the group consisting of aluminum, iron, stainless steel (SUS), magnesium, and electrogalvanized steel sheet (EGI). It can be included. For example, in order to have excellent formability and bending rigidity, a skin layer containing electrogalvanized steel sheet (EGI) can be applied to the sandwich panel. Additionally, a skin layer containing aluminum can be applied to the sandwich panel to reduce weight.

The thickness of the skin layer may be 6% or less compared to the thickness of the entire panel. The skin layer of the conventional sandwich panel had to be thick due to the poor mechanical strength of the core material, which had the problem of increasing the weight of the sandwich panel. However, the sandwich panel according to the present invention has a mechanical strength of the core material. As strength is improved, the thickness of the skin layer can be reduced to 6% or less compared to the thickness of the entire panel, thereby making it possible to reduce the weight.

The sandwich panel according to the present invention includes an adhesive layer that bonds the core layer and the skin layer.

The adhesive layer of the sandwich panel according to the present invention is applied between the core layer and the skin layer to adhere the core layer and the skin layer. The adhesive layer is preferably applied to a uniform thickness considering viscosity. In the present invention, a sandwich panel can be manufactured by laminating a core layer and a skin layer and then curing it, or by laminating a core layer and a skin layer and then heat-compressing them to manufacture a sandwich panel. At this time, as the adhesive penetrates into the core layer during the curing or heat compression process, the adhesion between the skin layer and the core layer is improved by not only chemical bonding with the components forming the core layer but also mechanical bonding. The chemical bond means that the adhesive forms a covalent bond, hydrogen bond, van der Waals bond, ionic bond, etc. with the upper and lower surfaces of the core layer.

The mechanical bond refers to a form in which the adhesive penetrates into the core layer and is physically hung like rings hanging from each other. This form is also called mechanical interlocking. Due to the natural pores contained in the core layer, the adhesive penetrates into the upper and lower surfaces of the core layer.

The adhesive forming the adhesive layer may include one or more of an olefin-based adhesive, a urethane-based adhesive, an acrylic-based adhesive, and an epoxy-based adhesive. The olefin-based adhesive may be one or more selected from the group consisting of polyethylene, polypropylene, and amorphous polyalphaolefin adhesive. The urethane-based adhesive can be used without limitation as long as it contains a urethane structure (-NH-CO-O-). The acrylic adhesive may include one or more of polymethyl methacrylate adhesive, hydroxy group-containing polyacrylate adhesive, and carboxyl group-containing polyacrylate adhesive. The epoxy adhesive is one or more of bisphenol-A type epoxy adhesive, bisphenol-F type epoxy adhesive, novolac epoxy adhesive, linear aliphatic epoxy resins, and cycloaliphatic epoxy resins. It can be included.

Additionally, the adhesive may include a photocurable adhesive, a hot melt adhesive, or a thermosetting adhesive, and either a photocuring method or a heat curing method may be used. For example, a sandwich panel can be manufactured by thermosetting a laminate containing a skin layer, a core layer, and an adhesive. The thermal curing may be performed for approximately 5 minutes to 2 hours at 50 to 110°C, which is the curing temperature of the epoxy resin, and may also be performed for approximately 1 to 10 hours at room temperature.

The adhesive layer may be applied to a thickness of approximately 20-300㎛, but is not limited thereto.

The adhesive layer may be applied to one surface of the skin layer using any one method selected from die coating, gravure coating, knife coating, or spray coating.

Another adhesive used in the adhesive layer may include a first adhesive layer containing high-density polyethylene (HDPE) and a second adhesive layer containing low-density polyethylene (LDPE).

The high-density polyethylene (HDPE) may have a density of 0.940 to 0.965 g/cm ³ , and the low-density polyethylene (LDPE) may have a density of 0.910 to 0.925 g/cm ³ .

The adhesive constituting the adhesive layer is not particularly limited as long as it can form a first adhesive layer containing high-density polyethylene (HDPE) and a second adhesive layer containing low-density polyethylene (LDPE), but is preferably co-extruded using a film extruder. It is manufactured.

The adhesive layer may be applied to a thickness of approximately 20 to 300 ㎛, and the first adhesive layer and the second adhesive layer may each have a thickness of 10 to 150 ㎛, but are not limited thereto. The thickness of the adhesive layer may be the same or different.

To form a skin layer on an adhesive layer, a sandwich panel can be manufactured by placing the skin layer on the adhesive layer and then heat-compressing the laminate containing the skin layer, core layer, and adhesive. The thermocompression may be performed at a pressure of 2 to 10 MPa at 150 to 200°C for approximately 3 to 10 minutes.

At this time, the core layer and the high-density polyethylene (HDPE) adhesive are adhered, and the skin layer and the low-density polyethylene (LDPE) adhesive are positioned so that they adhere to each other. In this way, LDPE adhesive is used for the skin layer so that it can be easily adhered even at relatively low heat, and for the core layer, HDPE adhesive is used to prevent the adhesive melted by heat from seeping into the core and failing to demonstrate adhesive strength. By doing so, the adhesion between each component can be improved.

Sandwich panel manufacturing method

The sandwich panel according to the present invention is formed by sequentially stacking the skin layer 20, the core layer 10, and the skin layer 20, and an adhesive layer is applied between the core layer 10 and the skin layer 20. It is manufactured. After the above components are laminated, curing and pressing steps may be performed, but are not limited thereto.

Specifically, the method for manufacturing a sandwich panel according to the present invention is,

a) mixing polypropylene fibers and maleic anhydride polypropylene to produce mixed fibers; b) adding kenaf fibers to the mixed fibers, heating and pressing to produce a non-woven fiber aggregate; c) manufacturing a core layer by performing a needle punching process on the nonwoven fiber aggregate at a number of punches of 300 to 1000 times per minute, a moving speed of 1 to 8 m/min, and a punching density of 100 to 500 punches/cm ² ; d) forming an adhesive layer on at least one side of the core layer; and e) forming a skin layer on the adhesive layer.

The core layer of the sandwich panel according to the present invention is composed of the molded body according to the present invention described above. Therefore, steps a), b), and c) are the same as the manufacturing method of the molded body discussed above.

Thereafter, in step d), an adhesive layer may be formed on one or more surfaces of the core layer.

The adhesive forming the adhesive layer may include one or more of an olefin-based adhesive, a urethane-based adhesive, an acrylic-based adhesive, and an epoxy-based adhesive. The olefin-based adhesive may be one or more selected from the group consisting of polyethylene, polypropylene, and amorphous polyalphaolefin adhesive. The urethane-based adhesive can be used without limitation as long as it contains a urethane structure (-NH-CO-O-). The acrylic adhesive may include one or more of polymethyl methacrylate adhesive, hydroxy group-containing polyacrylate adhesive, and carboxyl group-containing polyacrylate adhesive. The epoxy adhesive is one or more of bisphenol-A type epoxy adhesive, bisphenol-F type epoxy adhesive, novolac epoxy adhesive, linear aliphatic epoxy resins, and cycloaliphatic epoxy resins. It can be included.

Additionally, the adhesive may include a photocurable adhesive, a hot melt adhesive, or a thermosetting adhesive, and either a photocuring method or a heat curing method may be used. For example, a sandwich panel can be manufactured by thermosetting a laminate containing a skin layer, a core layer, and an adhesive. The thermal curing may be performed for approximately 5 minutes to 2 hours at 50 to 110°C, which is the curing temperature of the epoxy resin, and may also be performed for approximately 1 to 10 hours at room temperature.

The adhesive layer may be applied to a thickness of approximately 20-300㎛, but is not limited thereto.

The adhesive layer may be applied to one surface of the skin layer using any one method selected from die coating, gravure coating, knife coating, or spray coating.

Another adhesive used in the adhesive layer may include a first adhesive layer containing high-density polyethylene (HDPE) and a second adhesive layer containing low-density polyethylene (LDPE).

The high-density polyethylene (HDPE) may have a density of 0.940 to 0.965 g/cm ³ , and the low-density polyethylene (LDPE) may have a density of 0.910 to 0.925 g/cm ³ .

The adhesive constituting the adhesive layer is not particularly limited as long as it can form a first adhesive layer containing high-density polyethylene (HDPE) and a second adhesive layer containing low-density polyethylene (LDPE), but is preferably co-extruded using a film extruder. It is manufactured.

The adhesive layer may be formed to a thickness of approximately 20 to 300㎛, and the first adhesive layer and the second adhesive layer may each have a thickness of 10 to 150㎛, but are not limited thereto. The first adhesive layer and the second adhesive layer may have a thickness of approximately 10 to 150㎛. The thickness of the adhesive layer may be the same or different.

Thereafter, in step e), a skin layer can be formed on the adhesive layer.

The skin layer of the sandwich panel according to the present invention may be formed of a metal material, preferably at least one selected from the group consisting of aluminum, iron, stainless steel (SUS), magnesium, and electrogalvanized steel sheet (EGI). It can be included. For example, in order to have excellent formability and bending rigidity, a skin layer containing electrogalvanized steel sheet (EGI) can be applied to the sandwich panel. Additionally, a skin layer containing aluminum can be applied to the sandwich panel to reduce weight.

To form a skin layer on the adhesive layer, any one of a photocuring method, a heat curing method, and a heat compression method can be used. For example, a sandwich panel can be manufactured by thermosetting or thermocompressing a laminate containing a skin layer, a core layer, and an adhesive.

The thermal curing may be performed for approximately 5 minutes to 2 hours at 50 to 110°C, which is the curing temperature of the epoxy resin, and may also be performed for approximately 1 to 10 hours at room temperature.

When using an adhesive including a first adhesive layer containing high-density polyethylene (HDPE) and a second adhesive layer containing low-density polyethylene (LDPE), the heat compression is performed by placing a skin layer on the adhesive layer, and then attaching the skin layer, A sandwich panel can be manufactured by heat-compressing a laminate containing a core layer and an adhesive. The thermal compression may be performed at a pressure of 2 to 10 MPa at 150 to 200°C for approximately 3 to 10 minutes.

At this time, the core layer and the high-density polyethylene (HDPE) adhesive are adhered, and the skin layer and the low-density polyethylene (LDPE) adhesive are positioned so that they adhere to each other. In this way, LDPE adhesive is used for the skin layer so that it can be easily adhered even at relatively low heat, and for the core layer, HDPE adhesive is used to prevent the adhesive melted by heat from seeping into the core and failing to demonstrate adhesive strength. By doing so, the adhesion between each component can be improved.

As described above, the sandwich panel according to the present invention is lightweight and has excellent formability as well as mechanical strength by using a core layer with good mechanical properties. Specifically, in the sandwich panel, the core layer (molded body) having a non-woven fiber aggregate structure may have a modulus of 25 to 45 GPa and a maximum load of 1500 to 3500 N.

In addition, the shear stiffness, degree of deflection, bonding strength between different fibers, and material weight reduction issues of sandwich panels have been improved, making them suitable for use in structural materials for home appliances (TV back covers, washing machine boards, etc.), interior and exterior boards for construction, interior and exterior materials for automobiles, and trains/ships/ It is suitable for use as interior and exterior materials for aircraft (boards for partitions, etc.), various partition boards, and elevator structural materials.

Preferred examples are presented below to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that changes and modifications fall within the scope of the attached patent claims.

Example: Manufacturing of Sandwich Panels

Preparation of core layer (molded body): Preparation Examples 1 to 8

[Production Example 1]

After preparing polypropylene fiber (Jeonsantex, JT-RWH1576, tenacity 3.63g/de, elongation 125%) and maleic anhydride polypropylene (Hyundai EP, J720160), they were mixed at a weight ratio of 69.3:0.7. Afterwards, kenaf fiber (Soo industries, KenafA, moisture 12%, length 80 mm) was added to the polypropylene/maleic anhydride polypropylene mixed fiber at a weight ratio of 70:30 and mixed.

After mixing the fibers, carding is performed using a carding machine, and then a needle punching process in which the number of punches per minute is 500, the moving speed of the nonwoven fiber aggregate is 2 m/min, and the punching density is 297 punches/cm ^2. A non-woven fiber aggregate (non-woven fabric) with a basis weight of 3100 gsm was manufactured.

After mounting the non-woven fiber aggregate on two unwinding devices, the needle punching process is repeated with the number of punches per minute at 500, the moving speed of the non-woven fiber assembly at 2 m/min, and the punching density at 297 punches/cm ² . Physical rebonds were formed between the nonwoven fiber assemblies.

The nonwoven fiber aggregate joined by needle punching was entered into a preheating chamber with an internal temperature of 180°C and preheated for 3 minutes.

The nonwoven fiber aggregate was then transferred to a double belt press at a speed of 5 m/min. At this time, the heating temperature of the double belt press was 180°C and the pressure was 5MPa, and the core layer (molded body) of the nonwoven fiber aggregate structure was manufactured by heating/pressuring for 2 minutes.

Manufacturing example
One Manufacturing example
2 Manufacturing example
3 Manufacturing example
4 Manufacturing example
5 Manufacturing example
6 Manufacturing example
7 Manufacturing example
8 Kenaf 30 30 30 30 30 30 30 - PP 69.3 67.9 66.5 65.1 63.7 59.5 70 - MAPP 0.7 2.1 3.5 4.9 6.3 10.5 - - PET - - - - - - - 30 LMF - - - - - - - 70 total 100 100 100 100 100 100 100 100

(Unit: weight% based on the total weight of the non-woven fiber aggregate structure)

* PP: polypropylene, MAPP: maleic anhydride polypropylene, PET: polyethylene terephthalate, LMF (Low Melting Fiber): low melting point fiber

[Production Examples 2 to 6]

The core layer was manufactured in the same manner as Preparation Example 1, except that polypropylene fiber (PP) and maleic anhydride polypropylene (MAPP) were mixed at different weight ratios as shown in Table 1 above.

[Production Example 7]

As shown in Table 1, kenaf fibers and polypropylene fibers were mixed at a weight ratio of 30:70, and a core layer was prepared in the same manner as Preparation Example 1, except that maleic anhydride polypropylene was not added.

[Production Example 8]

Instead of polypropylene and kenaf fibers, polyethylene terephthalate fiber (Toray Chemical Co., Ltd., RPF, fineness 4 denier, fiber length 51 mm) and low melting fiber (EZBON-L, fineness 4 denier, fiber length 64mm) at a weight ratio of 30:70, without adding maleic anhydride polypropylene, and by setting the punching density to 270 punches/cm ² under needle punching process conditions to produce a nonwoven fabric with a basis weight of 3800gsm. Except, the core layer was manufactured in the same manner as Preparation Example 1.

Preparation of sandwich panels: Examples 1 to 6 and Comparative Examples 1 to 2

[Example 1]

After applying an epoxy adhesive (Kukdo Chemical) to both sides of the core layer prepared in Preparation Example 1, a skin layer made of electrogalvanized steel sheet was formed to a thickness of 0.4 mm, and then the laminated result was heat-cured at 100°C. A sandwich panel was manufactured.

[Examples 2 to 6]

A sandwich panel was manufactured in the same manner as Example 1, except that the core layer prepared in Preparation Examples 2 to 6 was used according to Table 2 below.

[Comparative Examples 1 to 2]

A sandwich panel was manufactured in the same manner as Example 1, except that the core layer prepared in Preparation Examples 7 to 8 was used according to Table 2 below.

Core layer used Example 1 Manufacturing Example 1 Example 2 Production example 2 Example 3 Production example 3 Example 4 Production example 4 Example 5 Production example 5 Example 6 Production example 6 Comparative Example 1 Production example 7 Comparative Example 2 Production example 8

Experimental example: Measurement of physical properties of sandwich panels

The basis weight and thickness of the core material used in the sandwich panels manufactured in Examples 1 to 6 and Comparative Examples 1 to 2 were measured. In addition, the mass and volume of the core material cut into horizontal (300 mm) and vertical (300 mm) sizes were measured, and the apparent density was calculated by dividing the mass of the core material by the volume.

Core weight (gsm) Thickness (mm) Apparent density (g/m ³ ) Example 1 3100 6.43 0.55 Example 2 3100 6.49 0.55 Example 3 3100 6.44 0.55 Example 4 3100 6.48 0.55 Example 5 3100 6.48 0.55 Example 6 3100 6.48 0.55 Comparative Example 1 3100 6.47 0.55 Comparative Example 2 3800 6.53 0.67

The sandwich panels prepared in Examples 1 to 6 and Comparative Examples 1 to 2 were made into specimens, and then the physical properties of the sandwich panels were measured by the following method.

(1) Modulus (GPa): The modulus of the sandwich panel was measured according to ASTM C393.

(2) Maximum load (N): Based on ASTM D790, the maximum load was measured at the maximum stress through strain hardening after the yield point where plastic deformation begins in the stress-strain relationship, and was measured three times.

Modulus (GPa) Maximum load (N) Example 1 29.13 1938 Example 2 33.77 2234 Example 3 41.55 2805 Example 4 42.29 2847 Example 5 43.84 2954 Example 6 44.12 2990 Comparative Example 1 19.82 1294 Comparative Example 2 31.97 2241

Referring to Table 4, compared to Comparative Example 1, although Examples 1 to 6 had the same basis weight of 3100 gsm, the bonding strength between kenaf fibers and polypropylene fibers was improved by the addition of maleic anhydride polypropylene (MAPP). , it was found that the modulus and maximum load increased. In addition, from Examples 5 and 6, it can be seen that although the modulus and maximum load are improved when maleic anhydride propylene is added in excess of 6.3% by weight based on the total weight of the nonwoven fiber aggregate structure, the degree of improvement gradually becomes insignificant. I was able to.

In addition, in Examples 2 to 6, compared to Comparative Example 2, which has a core weight of 3800 gsm, the core weight was reduced to 3100 gsm, but the modulus and maximum load were equal or equivalent due to the addition of maleic anhydride polypropylene (MAPP). It was confirmed that it had superior mechanical strength.

All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

10: core layer
20: skin layer

Claims (10)

A molded body having a non-woven fiber aggregate structure comprising polypropylene fibers, kenaf fibers, and maleic anhydride polypropylene, comprising:
The non-woven fiber aggregate structure is based on the total weight of the non-woven fiber aggregate structure,
55 to 75% by weight polypropylene fibers;
25 to 35% by weight of kenaf fiber; and
3 to 14% by weight of maleic anhydride polypropylene;
The basis weight of the nonwoven fiber aggregate structure is 2700 to 3500 gsm,
The apparent density of the nonwoven fiber aggregate structure is 0.4 to 0.7 g/m ³ ,
The modulus of the nonwoven fiber aggregate structure is 25 to 45 GPa, and the maximum load is 1500 to 3500 N.
delete delete delete delete According to claim 1,
The non-woven fiber aggregate structure is a structure in which two or more non-woven fiber aggregates are joined,
The non-woven fiber aggregate is a molded body made by bonding non-woven fibers in the form of a web or a sheet with an adhesive or using thermoplastic fibers.
core layer;
A skin layer laminated on one or more surfaces of the core layer; and
It includes an adhesive layer that adheres the core layer and the skin layer,
A sandwich panel wherein the core layer uses the molded body of claim 1.
According to claim 7,
A sandwich panel wherein the skin layer is at least one selected from the group consisting of aluminum, iron, stainless steel (SUS), magnesium, and electrogalvanized steel sheet (EGI).
According to claim 7,
The adhesive layer is a sandwich panel comprising one or more of an olefin-based adhesive, a urethane-based adhesive, an acrylic-based adhesive, and an epoxy-based adhesive.
a) mixing polypropylene fibers and maleic anhydride polypropylene to produce mixed fibers;
b) adding kenaf fibers to the mixed fibers, heating and pressing to produce a non-woven fiber aggregate;
c) manufacturing a core layer by performing a needle punching process on the nonwoven fiber aggregate at a number of punches of 300 to 1000 times per minute, a moving speed of 1 to 8 m/min, and a punching density of 100 to 500 punches/cm2;
d) forming an adhesive layer on at least one side of the core layer; and
e) forming a skin layer on the adhesive layer; the method of manufacturing the sandwich panel of claim 7, including.