KR102159081B1 - A method for manufacturing an article using an additive manufacturing - Google Patents

Abstract

One aspect of the present invention provides a method for manufacturing a molded article for laminating a composition comprising a thermoplastic resin and a microcapsule carrying a hydrocarbon-based physical foaming agent inside an expandable shell.

Description

Manufacturing method of molded products using additive manufacturing {A METHOD FOR MANUFACTURING AN ARTICLE USING AN ADDITIVE MANUFACTURING}

The present invention relates to a method of manufacturing a molded article using lamination processing.

Foam molding is a method of producing a product by creating bubbles during an injection molding or extrusion molding process and dispersing them uniformly in a polymer resin. Since the foamed molded product occupies a large part of the volume, the material cost can be significantly reduced, the weight can be reduced, and there is an advantage of obtaining thermal insulation or elasticity due to the foam.

In foam molding, a physical foaming agent or a chemical foaming agent is used. As the chemical blowing agent, low molecular weight organic compounds that decompose at critical temperatures and emit gases such as nitrogen, carbon dioxide, and carbon monoxide are used. As a physical blowing agent, gases such as carbon dioxide and nitrogen are used.

In general, in the foam injection molding, a resin, a foaming agent, and other additives are premixed for injection, or a foaming agent is injected into a suitable position of a barrel that melts the resin and uniformly dispersed in a polymer resin under high pressure before injection.

The mixture of the polymer resin and the foaming agent injected in this way is injected into the cavity, which is the molding space in the mold, and the generated gas expands and foams.

However, the method of manufacturing a porous body using such a conventional foam injection or foam extrusion method is suitable for manufacturing a simple porous body in large quantities, but manufacturing a porous body having a complex and various three-dimensional shape or a small amount of porous body. Not suitable for doing.

On the other hand, Korean Patent Registration No. 10-1823103 provides an apparatus capable of manufacturing a porous body having a complex and various 3D shapes or a small amount of porous bodies by 3D printing, and a 3D porous body printing method using the same. However, since the filament used as the 3D printing material contains a chemical foaming agent, it is difficult to control the foaming level, and accordingly, there is a limit to molding fine and sophisticated products.

The present invention is to solve the problems of the prior art described above, and an object of the present invention is to provide a method of manufacturing a molded article that is easy to control the foaming level and can uniformly form fine bubbles after foaming.

One aspect of the present invention provides a method for manufacturing a molded article for laminating a composition comprising a thermoplastic resin and a microcapsule carrying a hydrocarbon-based physical foaming agent inside an expandable shell.

In one embodiment, the content of the microcapsules may be 0.01 to 50 parts by weight based on 100 parts by weight of the thermoplastic resin.

In one embodiment, the lamination process comprises the steps of: (a) molding the composition into filaments and supplying the filaments to a nozzle; (b) heating the nozzle to a temperature higher than the melting point of the thermoplastic resin and the expansion start temperature of the microcapsules; And (c) discharging the filament through the nozzle while moving the nozzle and the stage horizontally and vertically.

In one embodiment, in the step (a), the filament may be heated to a temperature higher than the expansion start temperature of the microcapsules during the molding to expand the microcapsules.

In one embodiment, the thermoplastic resin is a soft or hard polyolefin elastomer, an ethylene copolymer, a styrenic copolymer, polyethylene, polypropylene, polyurethane, polyester, nylon, polybutylene terephthalate, polycarbonate, poly It is one selected from the group consisting of lactic acid, polymethyl methacrylate, polyoxymethylene, and combinations of two or more of them, and the hydrocarbon-based physical blowing agent may be one or more of C1 to C8 hydrocarbons.

The manufacturing method of a molded article according to an aspect of the present invention is easy to control the foaming level by laminating a composition containing a certain amount of thermally expandable microcapsules as a foaming agent, and the molded article manufactured by the above method is uniformly dispersed fine independent Since the air bubbles are included, mechanical properties such as tensile strength can be significantly improved compared to those manufactured using a conventional chemical foaming agent.

The effects of the present invention are not limited to the above effects, and should be understood to include all effects that can be deduced from the configuration of the invention described in the detailed description or claims of the present invention.

1 and 2 are diagrams illustrating the expansion behavior of microcapsules according to temperature according to an embodiment of the present invention;
3 is a schematic diagram of a molding method of a molded article according to an embodiment of the present invention;
4 and 5 are photographs of a filament for FDM and a foam manufactured therefrom according to an embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be implemented in various different forms, and therefore is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "indirectly connected" with another member interposed therebetween. . In addition, when a part "includes" a certain component, it means that other components may be further provided, rather than excluding other components unless specifically stated to the contrary.

One aspect of the present invention provides a method for manufacturing a molded article for laminating a composition comprising a thermoplastic resin and a microcapsule carrying a hydrocarbon-based physical foaming agent inside an expandable shell.

The thermoplastic resin is a soft or hard polyolefin elastomer, an ethylene copolymer, a styrene copolymer, polyethylene, polypropylene, polyurethane, polyester, nylon, polybutylene terephthalate, polycarbonate, polylactic acid, polymethylmethacrylic It may be one selected from the group consisting of rate, polyoxymethylene, and a combination of two or more of them.

In particular, the thermoplastic resin may be a thermoplastic elastomer, preferably, an ethylene-based copolymer. For example, the ethylene-based copolymer may be one selected from the group consisting of ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and combinations of two or more of them, and preferably, may be ethylene vinyl acetate, More preferably, the content of the vinyl acetate may be 10 to 20% by weight of ethylene vinyl acetate, but is not limited thereto.

1 and 2 are diagrams showing the expansion behavior of the microcapsules according to the temperature according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, the microcapsule 100 may have a hydrocarbon-based physical foaming agent 120 supported inside the expandable shell 110. The microcapsule contains a polymeric material shell 110 and a hydrocarbon-based physical foaming agent 120, and when the microcapsules are heated, the shell begins to soften first. At the same time, the enclosed hydrocarbon-based physical foaming agent begins to vaporize and the internal pressure increases, causing the microcapsules to expand. During expansion, the internal pressure and the tension of the shell, that is, the external pressure, are balanced to become a balloon state that maintains the expansion state, and when the heating state continues, the tension of the thinned shell increases, resulting in contraction.

The 3D printing material is made of a resin containing the microcapsules, and the microcapsules in the material may expand due to the heat supplied when it is manufactured into a molded article using an FDM and/or SLS type 3D printer, Accordingly, fine closed cells separated by the shell may be uniformly formed. That is, the microcapsules are not decomposed even after foaming and expansion by heating, but are expanded to a certain size to maintain their shape, and regular and fine closed cells of a certain size may be formed. The closed cells diversify the shape of the molded product and at the same time have excellent elasticity by itself, thereby contributing to the stability and mechanical properties of the molded product.

The microcapsules may be made of a thermoplastic resin obtained by polymerizing a monomer mixture containing a radical polymerizable monomer, and the expandable shell 110 may be formed by appropriately mixing an initiator in the monomer mixture.

Examples of the radical polymerizable monomer include nitrile-based monomers such as acrylonitrile, methacrylonitrile, α-chloracrylonitrile, α-ethoxyacrylonitrile, and fumaronitrile; Carboxyl group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid; Vinylidene chloride; Vinyl acetate; Methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isobornyl (meth) acrylate, cyclo (Meth)acrylic acid ester monomers such as hexyl (meth)acrylate, benzyl (meth)acrylate, and β-carboxyethyl acrylate; Styrene-based monomers such as styrene, α-methylstyrene, and chlorostyrene; Acrylamide monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; And maleimide-based monomers such as N-phenylmaleimide, N-(2-chlorophenyl)maleimide, N-cyclohexylmaleimide, and N-laurylmaleimide, but are not limited thereto. One type or two or more types can also be used together. For example, the expandable shell 110 may be made of a copolymer including 20 to 80% by weight of a nitrile-based monomer and 20 to 80% by weight of a carboxyl group-containing monomer.

The expansion initiation temperature of the microcapsules may be 150°C or less, preferably 140°C or less. When the expansion start temperature of the microcapsules exceeds 150°C, it is difficult to control the expansion or expansion rate at high temperature, that is, the expansion rate at high temperature cannot be uniformly generated, and thus the elasticity and mechanical properties of the manufactured molded article decrease. Can be.

In addition, the average particle diameter of the microcapsules may be 5 ~ 30㎛. If the average particle diameter of the microcapsules is less than 5 μm, the closed cells are not sufficiently formed to achieve the required level of foaming or expansion, and if the average particle diameter of the microcapsules is more than 30 μm, the size of the closed cells becomes excessively large, resulting in mechanical properties and surface texture of the final product. It can be degraded.

The composition, that is, the content of the microcapsules in the 3D printing material may be 0.01 to 50 parts by weight based on 100 parts by weight of the thermoplastic resin. If the content of the microcapsules is less than 0.01 parts by weight, the necessary level of foaming or expansion cannot be achieved, and if the content of the microcapsules is more than 50 parts by weight, workability is deteriorated and the cost increases, making it difficult to commercialize.

The hydrocarbon-based physical blowing agent may be one or more of C1 to C8 hydrocarbons, preferably, one or more of C1 to C6 hydrocarbons, but is not limited thereto.

The additive manufacturing is a method of 3D printing that stacks or combines raw materials in several layers to manufacture a three-dimensional object, that is, to manufacture a three-dimensional object by stacking raw materials in layers according to an electronic signal. Means the way. There is no need for an intermediate process such as making a mold at the stage of productization, and immediate correction is possible, increasing the efficiency of the product development cycle and cost.

The lamination process may be performed in a known manner such as fused deposition modeling (FDM) and selective laser sintering (SLS). It is necessary to pre-process the composition into an appropriate shape according to the above manner. For example, when the FDM method is adopted, the composition can be processed in the form of filaments, and when the SLS method is adopted, the composition can be processed in the form of powder or particles.

For example, the lamination process may include: (a) molding the composition into a filament and supplying the filament to a nozzle; (b) heating the nozzle to a temperature higher than the melting point of the thermoplastic resin and the expansion start temperature of the microcapsules; And (c) discharging the filament through the nozzle while moving the nozzle and the stage horizontally and vertically.

In the step (a), the microcapsules may be expanded by heating the filament to a temperature higher than the expansion start temperature of the microcapsules during the molding.

Referring to FIG. 3, when the 3D printing material is a filament for application to an FDM type 3D printer, the microcapsules among the filaments may exist in a state that is not foamed or expanded (non-foamed filament), as necessary. , It may exist in a foamed or expanded state (foam filament).

In the case of the unfoamed filament, the microcapsule expands while passing through a nozzle preheated to a temperature equal to or higher than the melting point of the thermoplastic resin and the expansion initiation temperature of the microcapsule, so that the specific gravity of the foam is lower than that of the unfoamed filament. It is advantageous in terms of physical properties.

In the case of the foamed filament, since the microcapsules pass through the nozzle in a state controlled in advance to a level required for foaming or expansion, the specific gravity does not substantially change during the molding process. At this time, since foaming or expansion can be controlled in advance, it is difficult to directly evaluate the impact on the weight reduction and mechanical properties of the molded article, but the specific gravity of the 3D printing material can be realized in the molded article as it is, resulting in advantageous effects in terms of productivity, reliability, and reproducibility. Can have.

4 and 5 are photographs of an unfoamed filament, a foamed filament, and a foam produced therefrom, respectively. Referring to Figures 4 and 5, the number and density of closed cells in the foam produced from the non-foamed filaments are larger and larger than those produced from the foamed filaments, respectively, so that the above-described effects by using the non-foamed and foamed filaments are variable. In addition, it is expected that it can be appropriately promoted in complementary ways.

Through the above manufacturing method, it is possible to mold a variety of products including shoes or parts thereof, clothing, household goods, etc., and in particular, shoes or parts thereof that require light weight, mechanical properties, and moldability at the same time can be efficiently manufactured. I can.

Hereinafter, embodiments of the present invention will be described in detail.

Example 1

For 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, 2 weight of the first microcapsules having an average particle diameter of 10 μm, an expansion initiation temperature of about 130° C., and a maximum expansion rate of about 3.0 (@160° C.) The parts were kneaded, extruded at 120° C., and then stretched to prepare an FDM 3D printing filament.

The prepared filament was mounted on a cartridge of an FDM 3D printer, and fed to a nozzle preheated at a temperature equal to or higher than the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsules to prepare a midsole specimen.

Example 2

For 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, 2 weight of second microcapsules having an average particle diameter of 30 μm, an expansion initiation temperature of about 120° C., and a maximum expansion rate of about 7.0 (@180° C.) The parts were kneaded, extruded at 120° C., and then stretched to prepare an FDM 3D printing filament.

The prepared filament was mounted on a cartridge of an FDM 3D printer, and fed to a nozzle preheated at a temperature equal to or higher than the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsules to prepare a midsole specimen.

Example 3

With respect to 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, 2.5 parts by weight of the first microcapsule and 2.5 parts by weight of the second microcapsule are kneaded, extruded at 120°C, and then stretched for FDM 3D printing The filaments were prepared.

The prepared filament was mounted on a cartridge of an FDM 3D printer, and fed to a nozzle preheated at a temperature equal to or higher than the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsules to prepare a midsole specimen.

Example 4

For 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, 2 weight of second microcapsules having an average particle diameter of 30 μm, an expansion initiation temperature of about 120° C., and a maximum expansion rate of about 7.0 (@180° C.) The part was kneaded, extruded at 190° C., and then stretched to prepare an FDM 3D printing filament. In the prepared filament, the second microcapsule is present in a foamed or expanded state.

The prepared filament was mounted on a cartridge of an FDM 3D printer, and fed to a nozzle preheated to a temperature equal to or higher than the melting point of ethylene vinyl acetate to prepare a midsole specimen.

Comparative Example 1

In the same manner as in Example 1, an FDM 3D printing filament composed of only ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate was prepared.

The prepared filament was mounted on a cartridge of an FDM 3D printer, and fed to a nozzle preheated at a temperature equal to or higher than the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsules to prepare a midsole specimen.

Comparative Example 2

For 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, 2 weight of the third microcapsule having an average particle diameter of 30 μm, an expansion initiation temperature of about 150°C, and a maximum expansion rate of about 8.0 (@190°C) The parts were kneaded, extruded at 120° C., and then stretched to prepare an FDM 3D printing filament.

The prepared filament was mounted on a cartridge of an FDM 3D printer, and fed to a nozzle preheated at a temperature equal to or higher than the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsules to prepare a midsole specimen.

Comparative Example 3

Based on 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, 3 parts by weight of zinc oxide, 1 part by weight of stearic acid, 2 parts by weight of dicumyl peroxide, 0.5 parts by weight of triallyl cyanurate, azodicarbon 3 parts by weight of amide was put into a kneader and kneaded at 80° C. for 10 minutes to prepare a pellet.

The pellets were first pressed at 90°C, 140kgf/cm ² for 8 minutes using a pouring foam molding method to form a sheet form, and then put them in a mold at 160°C, 150kgf/cm ² , for 15 minutes 2 After the primary press operation, a midsole specimen was prepared by cooling for 10 minutes in a cooling press.

Experimental Example: Evaluation of properties of midsole specimens

The physical properties of the midsole specimens prepared according to the Examples and Comparative Examples were evaluated, and the results are shown in Table 1 below. The evaluation method of each property is as follows.

-Specific gravity: Measured 5 times using an automatic specific gravity measuring device of Ueshima by KS M 6660 and expressed as an average value.

-Tensile strength: Measured using Zwick's universal testing machine according to KS M ISO 1798

-Resilience elasticity: Measured by using Daesung Science's resilient elasticity tester according to KS M ISO 8307

division unit Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Filament/pellet specific gravity g/cc 0.90 0.90 0.90 0.40 0.90 0.90 0.92 Specimen weight g/cc 0.71 0.65 0.52 0.40 0.90 0.48 0.2 Specimen rebound elasticity % 52 55 56 60 43 48 61 Specimen tensile strength MPa 33 21 17 14 43 15 15

Referring to the above table, the specific gravity of the midsole specimens prepared in Examples 1 to 3 is 0.50 g/cc or more, resilience is 50% or more, and tensile strength is 17 MPa or more.

Specifically, the tensile strength of the midsole specimens prepared in Examples 1 to 3 was about 17 MPa or more, and was measured to be about 18 MPa or more higher than the comparative example. The midsole specimen of Comparative Example 1, which did not undergo foaming, was measured to have a higher tensile strength than the Example, but the rebound elasticity was reduced by up to 13% to 50% or less. In addition, the rebound elasticity of the midsole specimens prepared in Examples 1 to 3 was measured at a level of 50 to 60%, and was found to be similar to the midsole specimen of Comparative Example 3 to which a conventional chemical blowing agent was applied.

On the other hand, the midsole specimen of Example 4 prepared using the foamed filament had the same specific gravity before and after the specimen was prepared, and relatively excellent resilience, while the tensile strength was slightly lowered.

As described above, when microcapsules carrying a hydrocarbon-based physical foaming agent are applied as a foaming agent, the number, size, density, and appearance, specific gravity, and mechanical properties of the molded product can be precisely and easily controlled. Therefore, it is possible to conveniently and efficiently manufacture a variety of products in response to the recent diversifying demand.

The above description of the present invention is for illustrative purposes only, and those of ordinary skill in the art to which the present invention pertains will be able to understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims to be described later, and all changes or modified forms derived from the meaning and scope of the claims and the concept of equivalents thereof should be construed as being included in the scope of the present invention.

100: microcapsules
110: expandable shell
120: physical blowing agent

Claims (5)

(a) molding a composition comprising microcapsules carrying a hydrocarbon-based physical foaming agent inside a thermoplastic resin and an expandable shell into a filament and supplying the filament to a nozzle;
(b) heating the nozzle to a temperature higher than the melting point of the thermoplastic resin and the expansion start temperature of the microcapsules; And
(C) discharging the filament through the nozzle while moving the nozzle and the stage horizontally and vertically,
The maximum expansion rate of the microcapsules is 3.0-7.0,
In the step (c), as the filament passes through the nozzle, the microcapsules expand,
The specific gravity of the shoe parts is 0.50g/cc or more, the repulsion elasticity is 50% or more, and the tensile strength is 17 MPa or more. The method of claim 1,
The amount of the microcapsule is 0.01 to 50 parts by weight based on 100 parts by weight of the thermoplastic resin. delete delete The method of claim 1,
The thermoplastic resin is a soft or hard polyolefin elastomer, ethylene-based copolymer, styrene-based copolymer, polyethylene, polypropylene, polyurethane, polyester, nylon, polybutylene terephthalate, polycarbonate, polylactic acid, polymethylmethacrylic It is one selected from the group consisting of rate, polyoxymethylene, and combinations of two or more of them,
The hydrocarbon-based physical foaming agent is a method of manufacturing a shoe part in which one or more of C1 to C8 hydrocarbons.

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