KR20200055830A - A method for manufacturing an article using an additive manufacturing - Google Patents

Abstract

The present invention relates to a manufacturing method of a molded product, which laminates a composition comprising: a thermoplastic resin; and a microcapsule supporting a hydrocarbon-based physical blowing agent inside an expandable shell and, more specifically, to a manufacturing method of a molded product, which can significantly improve mechanical properties such as tensile strength.

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 for manufacturing a molded article using additive manufacturing.

Foam molding is a method of manufacturing a product by generating bubbles during the injection molding or extrusion molding process and uniformly dispersing them in a polymer resin. Since the foamed part occupies a large portion of the bulk of the foamed material, it is possible to significantly reduce the material cost, reduce the weight, and also has the advantage of obtaining thermal insulation or elasticity due to the foam.

A physical foaming agent or a chemical foaming agent is used for foam molding. As a chemical blowing agent, a low-molecular-weight organic compound that decomposes at a critical temperature and releases gases such as nitrogen, carbon dioxide, and carbon monoxide is used. A gas such as carbon dioxide or nitrogen is used as the physical blowing agent.

In general, foam injection molding is performed by pre-injecting a resin, a blowing agent, and other additives, or by injecting a blowing agent at a suitable position in a barrel that melts the resin and uniformly dispersing it in a polymer resin under high pressure.

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

However, the conventional method of manufacturing a porous body by using a foam injection or foam extrusion method is suitable for manufacturing a simple form of a porous body in a large amount, but it produces a porous body having a complex and various three-dimensional shape, or a small amount of the porous body. It is not suitable for doing.

On the other hand, Korean Patent Registration No. 10-1823103 provides a device capable of manufacturing a porous body having a complex and diverse 3D shape, or a small amount of a porous body in a 3D printing method, and a 3D porous body printing method using the same. However, since the filament used as the 3D printing material includes a chemical blowing agent, it is difficult to control the foaming level, and accordingly, there is a limit to molding a fine and sophisticated product.

The present invention is to solve the problems of the prior art described above, the object of the present invention is to provide a method for 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 of manufacturing a molded article in which a composition including a microcapsule carrying a hydrocarbon-based physical foaming agent inside a thermoplastic resin and an expandable shell is laminated.

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

In one embodiment, the lamination process comprises: (a) forming the composition into a filament to supply the filament to a nozzle; (b) heating the nozzle to a temperature higher than the melting point of the thermoplastic resin and the initiation temperature of expansion of the microcapsule; And (c) discharging the filament through the nozzle while moving the nozzle and the stage in horizontal and vertical directions.

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

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

The method of manufacturing 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 a thermally expandable microcapsule as a foaming agent, and the molded article produced by the method is finely dispersed and uniformly dispersed. Since it contains air bubbles, mechanical properties such as tensile strength can be remarkably improved compared to those produced using a conventional chemical blowing agent.

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

1 and 2 is a diagram showing the expansion behavior according to the temperature of the microcapsules according to the embodiment of the present invention;
3 is a schematic diagram of a molding method for a molded article according to an embodiment of the present invention;
4 and 5 are photographs of FDM filaments and foams prepared 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 thus is not limited to the embodiments described herein. In addition, in order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and like reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "indirectly connected" with another member in between. . Also, when a part “includes” a certain component, this means that other components may be further provided instead of excluding other components, unless otherwise stated.

One aspect of the present invention provides a method of manufacturing a molded article in which a composition including a microcapsule carrying a hydrocarbon-based physical foaming agent inside a thermoplastic resin and an expandable shell is laminated.

The thermoplastic resin is soft or hard polyolefin elastomer, ethylene-based copolymer, styrene-based copolymer, polyethylene, polypropylene, polyurethane, polyester, nylon, polybutylene terephthalate, polycarbonate, polylactic acid, polymethyl methacryl Rate, polyoxymethylene, and combinations of two or more of these.

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, preferably, ethylene vinyl acetate, More preferably, the content of vinyl acetate may be ethylene vinyl acetate having 10 to 20% by weight, but is not limited thereto.

1 and 2 is a diagram showing the expansion behavior according to the temperature of the microcapsules according to an embodiment of the present invention.

1 and 2, the microcapsule 100 may be a hydrocarbon-based physical blowing agent 120 supported on the inside of the expandable shell 110. The microcapsule contains a shell made of a polymer material (110) and a hydrocarbon-based physical blowing agent 120, and when the microcapsule is heated, the shell begins to soften first. At the same time, the encapsulated hydrocarbon-based physical blowing agent starts to vaporize, and the internal pressure increases, causing the microcapsules to expand. When expanding, the internal pressure and the tension of the shell, that is, the external pressure is balanced, and thus the balloon is maintained in an inflated state. When the heated state is maintained, contraction occurs because the tension of the thinned shell is increased.

The 3D printing material is made of a resin containing the microcapsules, and the microcapsules in the material may expand due to heat supplied when it is manufactured into a molded product using a 3D printer of FDM and / or SLS method, Accordingly, fine independent bubbles separated by the shell may be uniformly formed. That is, the microcapsule does not decompose even after foaming and expansion by heating, and expands to a constant size to maintain a magnetic shape, and regular and fine independent closed cells of a constant size may be formed. The independent bubbles diversify the shape of the molded article and at the same time have excellent elasticity, thereby contributing to the stability and mechanical properties of the molded article.

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

Examples of the radically polymerizable monomers include nitrile 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-based monomers such as acrylamide, substituted acrylamide, methacrylamide and substituted methacrylamide; Maleimide-based monomers such as N-phenylmaleimide, N- (2-chlorophenyl) maleimide, N-cyclohexylmaleimide, and N-laurylmaleimide, but are not limited thereto. You may use together 1 type (s) or 2 or more types. For example, the expandable shell 110 may be made of a copolymer containing 20 to 80% by weight of a nitrile-based monomer and 20 to 80% by weight of a carboxyl group-containing monomer.

The expansion start temperature of the microcapsules may be 150 ° C or less, preferably 140 ° C or less. When the expansion start temperature of the microcapsule is greater than 150 ° C, foaming or expansion at a high temperature, that is, it is difficult to control a high-temperature expansion rate, so that independent bubbles cannot be uniformly generated, and accordingly, elasticity and mechanical properties of the molded article manufactured 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, independent bubbles are not sufficiently formed, and thus the necessary level of foaming or expansion cannot be achieved. It may degrade.

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

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

The additive manufacturing is a method in which 3D printing in which raw materials are stacked or combined in multiple layers to produce a 3D object is operated, that is, a 3D object is manufactured by stacking raw materials in layers according to an electronic signal. Means the way. There is no need for any intermediate process, such as manufacturing a mold in the commercialization stage, and it is possible to immediately modify it, thereby improving the product development cycle and cost efficiency.

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

For example, the lamination process may include: (a) forming the composition into a filament to supply 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 microcapsule; And (c) discharging the filament through the nozzle while moving the nozzle and the stage in horizontal and vertical directions.

In the step (a), the microcapsule may be expanded by heating the filament to a temperature higher than the expansion start temperature of the microcapsule during 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 foamed or unexpanded state (non-foamed filament), if necessary , May be in a foamed or expanded state (foamed filament).

In the case of the unfoamed filament, since the microcapsule expands while passing through a nozzle preheated to a temperature higher than the melting point of the thermoplastic resin and the expansion start temperature of the microcapsule, the specific gravity of the foam is lower than that of the unfoamed filament, thereby reducing the weight of the molded product and mechanically It is advantageous in terms of physical properties.

In the case of the foamed filament, since the microcapsule passes through the nozzle in a pre-controlled state at a level requiring foaming or expansion, the specific gravity does not substantially change during the molding process. At this time, since foaming or expansion can be pre-controlled, it is difficult to directly evaluate the impact on the weight and mechanical properties of the molded product, but since the specific gravity of the 3D printing material can be implemented in the molded product as it is, it has an advantageous effect in terms of productivity, reliability, and reproducibility. Can have

4 and 5 are photographs of unfoamed filaments, foamed filaments, and foams prepared therefrom, respectively. 4 and 5, the number and density of the independent bubbles in the foam produced from the unfoamed filaments is larger and larger than that produced from the foamed filaments, respectively, so the above-described effects of using the unfoamed and foamed filaments are variable. However, it is expected that they will be able to promote each other appropriately.

Through the above manufacturing method, it is possible to mold various products including shoes or its parts, clothing, household goods, etc. In particular, it is possible to efficiently manufacture shoes or parts that require light weight, mechanical properties, moldability, etc. at the same time. Can be.

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

Example 1

With respect to 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, the average particle size is 10㎛, the expansion start temperature is about 130 ℃ and the maximum expansion rate is about 3.0 (@ 160 ℃) 2 microcapsules 2 weight The parts were kneaded, extruded at 120 ° C., and then stretched to prepare FDM 3D printing filaments.

The manufactured filament was mounted on a cartridge of an FDM 3D printer, and a midsole specimen was prepared by feeding it to a nozzle preheated to a temperature above the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsule.

Example 2

With respect to 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, the average particle diameter is 30㎛, the expansion start temperature is about 120 ℃ and the maximum expansion rate is about 7.0 (@ 180 ℃) 2 microcapsules 2 weight The parts were kneaded, extruded at 120 ° C., and then stretched to prepare FDM 3D printing filaments.

The manufactured filament was mounted on a cartridge of an FDM 3D printer, and a midsole specimen was prepared by feeding it to a nozzle preheated to a temperature above the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsule.

Example 3

FDM 3D printing by mixing 2.5 parts by weight of the first microcapsule and 2.5 parts by weight of the second microcapsule, extruding at 120 ° C., and drawing with respect to 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate. Filaments were prepared.

The manufactured filament was mounted on a cartridge of an FDM 3D printer, and a midsole specimen was prepared by feeding it to a nozzle preheated to a temperature above the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsule.

Example 4

With respect to 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, the average particle diameter is 30㎛, the expansion start temperature is about 120 ℃ and the maximum expansion rate is about 7.0 (@ 180 ℃) 2 microcapsules 2 weight The parts were kneaded, extruded at 190 ° C., and then stretched to produce FDM 3D printing filaments. In the produced filaments, the second microcapsule is present in a foamed or expanded state.

The manufactured filament was mounted on a cartridge of an FDM 3D printer and fed to a nozzle preheated to a temperature above 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 10-20% by weight of vinyl acetate was prepared.

The manufactured filament was mounted on a cartridge of an FDM 3D printer, and a midsole specimen was prepared by feeding it to a nozzle preheated to a temperature above the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsule.

Comparative Example 2

With respect to 100 parts by weight of ethylene vinyl acetate containing 10 to 20% by weight of vinyl acetate, the average particle diameter is 30㎛, the expansion start temperature is about 150 ℃ and the maximum expansion rate is about 8.0 (@ 190 ℃) 2 of the third microcapsules The parts were kneaded, extruded at 120 ° C., and then stretched to prepare FDM 3D printing filaments.

The manufactured filament was mounted on a cartridge of an FDM 3D printer, and a midsole specimen was prepared by feeding it to a nozzle preheated to a temperature above the melting point of ethylene vinyl acetate and the expansion start temperature of the microcapsule.

Comparative Example 3

With respect to 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 added to a kneader and kneaded at 80 ° C for 10 minutes to prepare pellets.

After the pellets made of archways ring (pouring) the preform into a sheet form by the first ^{press-to-90 ℃, 140kgf / cm 2,} 8 minutes by the expandable criminal law was put into a mold 160 ℃, 150kgf / cm ^2, for 15 minutes 2 After the secondary press operation, the cooling press was cooled for 10 minutes to prepare a midsole specimen.

Experimental Example: Evaluation of physical 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 Uesima's automatic specific gravity measuring device according to KS M 6660 and expressed as an average value

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

-Rebound resilience: Measured by KS M ISO 8307 using Daesung Science's rebound resilience tester.

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, the rebound elasticity is 50% or more, and the 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 higher, which was higher than the comparative example by about 18 MPa or higher. The midsole specimen of Comparative Example 1, which had not undergone foaming, had a higher tensile strength than the example, but the rebound resilience was lowered by up to 13% to 50% or less. In addition, the rebound resilience of the midsole specimens prepared in Examples 1 to 3 was measured at a level of 50 to 60%, indicating that it was 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 foamed filaments had the same specific gravity before and after specimen preparation, and relatively excellent rebound resilience, while tensile strength was slightly lowered.

As described above, when a microcapsule carrying a hydrocarbon-based physical foaming agent is applied as a foaming agent, the number, size, and density of the independent bubbles present in the molded product and the appearance, specific gravity, mechanical properties, etc. of the molded product are precisely and easily controlled. Since it can be made, it is possible to easily and efficiently manufacture various products in response to the diversified demand.

The above description of the present invention is for illustration only, and a person having ordinary knowledge in the technical field to which the present invention pertains can understand that it can be easily modified to other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts should be interpreted to be included in the scope of the present invention.

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

Claims (5)

A method of manufacturing a molded article in which a composition comprising a microcapsule carrying a hydrocarbon-based physical foaming agent inside a thermoplastic resin and an expandable shell is laminated. According to claim 1,
The content of the microcapsules is a method of manufacturing a molded article that is 0.01 to 50 parts by weight relative to 100 parts by weight of the thermoplastic resin. According to claim 1,
The lamination process,
(A) forming the composition into a filament to supply the filament to the nozzle;
(b) heating the nozzle to a temperature higher than the melting point of the thermoplastic resin and the expansion start temperature of the microcapsule; And
(c) discharging the filament through the nozzle while moving the nozzle and the stage in the horizontal and vertical directions; According to claim 3,
In the step (a), a method of manufacturing a molded article in which the microcapsule is expanded by heating the filament to a temperature higher than the expansion start temperature of the microcapsule during the molding. According to 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, polymethyl methacryl Rate, polyoxymethylene, and combinations of two or more of these,
The hydrocarbon-based physical blowing agent is a method for producing a molded article of at least one of C1 ~ C8 hydrocarbons.

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