KR101768711B1 - Magnetorheological fluids containing ferro-magnetic compounds wrapped by foamed polymer and their preparation method - Google Patents

Magnetorheological fluids containing ferro-magnetic compounds wrapped by foamed polymer and their preparation method Download PDF

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KR101768711B1
KR101768711B1 KR1020140091887A KR20140091887A KR101768711B1 KR 101768711 B1 KR101768711 B1 KR 101768711B1 KR 1020140091887 A KR1020140091887 A KR 1020140091887A KR 20140091887 A KR20140091887 A KR 20140091887A KR 101768711 B1 KR101768711 B1 KR 101768711B1
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oil
magnetic particles
iron
particles
magnetic
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KR20160011276A (en
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서용석
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서울대학교산학협력단
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
    • H01F1/442—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids the magnetic component being a metal or alloy, e.g. Fe
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
    • H01F1/445—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids the magnetic component being a compound, e.g. Fe3O4
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
    • H02B1/00—Frameworks, boards, panels, desks, casings; Details of substations or switching arrangements
    • H02B1/54—Anti-seismic devices or installations

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  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Soft Magnetic Materials (AREA)
  • Lubricants (AREA)

Abstract

본 발명의 자기유변체는 강자성입자를 고분자로 둘러싸서 다층구조입자를 형성하게 되고 이 다층구조입자가 발포공정을 거침으로써 다공성을 갖게 되어 밀도를 줄이게 되고 안정성이 증가되어 침강속도를 현저히 줄일 수 있다. 이 자기유변체의 자기장에 대한 응답속도는 미리초(10-3 초) 수준으로 매우 빠르고 가역적인 동시에 안정성이 향상되었으므로 자기유변유체를 이용한 각종 장비개발에 널리 활용될 수 있을 것이다.In the magnetic oil variant of the present invention, the ferromagnetic particles are surrounded by a polymer to form multi-layered particles, and the multi-layered particles are subjected to a foaming process to have porosity so that the density is reduced and the stability is increased, . The response speed to the magnetic field of this magnetic oil variant is very fast and reversible at a level of 10 s (10 -3 sec) and at the same time, stability can be widely used in the development of various equipment using magnetorheological fluid.

Description

안정성이 우수한 발포고분자로 둘러싸인 자성입자를 함유하는 자기유변체 및 그 제조방법 {Magnetorheological fluids containing ferro-magnetic compounds wrapped by foamed polymer and their preparation method}TECHNICAL FIELD [0001] The present invention relates to a magnetic fluid containing magnetic particles surrounded by a foamed polymer having excellent stability, and a method for producing the same. [0002] Magnetorheological fluids containing ferro-

본 특허는 강자성입자를 고분자로 둘러싸서 다층구조입자를 형성하게 되고 이 다층구조입자가 발포공정을 거침으로써 다공성을 갖게 되어 밀도를 줄이게 되 감소되고 안정성이 증가된 자기유변체에 관한 것으로 자기장에 대한 응답속도는 미리초(10-3 초) 수준으로 매우 빠르고 가역적인 동시에 안정성이 향상되었다.The present patent relates to a magnetic oil variant in which ferromagnetic particles are surrounded by a polymer to form multi-layered particles, and the multi-layered particles have a porosity due to a foaming process, thereby reducing density and increasing stability. The response speed is very fast, reversible and stable at a very low level ( 10-3 seconds).

자기유변유체는 자기장의 변화에 대응하여 가역적으로 점도의 조절이 가능한스마트지능재료(smart intelligent material)의 하나이다. 자기유변유체는 지름이 0.1㎛ 보다 큰 강자성, 상자성 입자와 오일미디움으로 이루어져 있으며, 외부의 자기장이 가해지면 입자의 내부와 표면에 분극현상(polarization)에 의해서 입자들이 배열하고 섬유구조(fibril structure)를 형성하는데 (도 1), 이 섬유구조가 점도 향상과 유체의 흐름을 방해하는 역할을 한다. 이때의 항복응력(yield stress)은 자기장의 세기에 따라 증가하고, 가해진 전단응력(shear stress)이 유체의 항복응력보다 커지면 유체가 흐르게 된다. 자기장에 대한 자기유변유체의 응답속도는 미리초(10-3 초) 수준으로 매우 빠르며, 가역적이어서, 클러치, 엔진마운트, 진동제어장치, 고층건물 내진 장치, 로보틱 시스템(robotic system) 등에 응용된다.
A magnetorheological fluid is one of smart intelligent materials capable of reversibly controlling viscosity in response to changes in magnetic field. Magneto-rheological fluid consists of ferromagnetic, paramagnetic particles and oil medium with a diameter of more than 0.1 μm. When an external magnetic field is applied, particles are arranged by polarization on the inside and the surface of the particle, (Fig. 1), this fiber structure serves to improve viscosity and interfere with fluid flow. The yield stress increases with the magnetic field strength, and the fluid flows when the applied shear stress becomes larger than the yield stress of the fluid. Magnetic responsiveness of the rheological fluid for the magnetic field is very fast and the second (10 -3 second) level in advance, or the like is applied reversibly Then, clutch, engine mounts, vibration control device, high-rise buildings seismic devices, robotic systems (robotic system) .

대한민국 공개특허 2002-0064654Korean Patent Publication No. 2002-0064654 미국특허 제2,575,360호U.S. Patent No. 2,575,360 미국특허 제 5,645,752호U.S. Patent No. 5,645,752

"Electrorheological fluids : the non-aqueous suspensions" (2005) ELsevier Tian Hao"Electrorheological fluids: the non-aqueous suspensions" (2005) ELsevier Tian Hao

대한민국 공개특허 2002-0064654호에서 밝힌 바와같이 승용차, 트럭 등의 댐퍼(damper), 브레이크(brake)에 사용되는 효울적인 자기유변유체를 제조하기 위하여는, 무엇보다도 높은 항복응력(yield stress)을 가지는 자기유변유체의 제조가 필수적이며, 이를 위하여 자성입자의 부피분율을 높이거나 또는 강한 자기장을 부과하는 방법이 사용될 수 있으나, 자성입자의 부피분율을 높일 경우, 장비의 하중 및 구동전력 소모를 증가시키고, 강한 자기장을 부과할 경우, 자기장 무부하시의 점도를 증가시키는 단점을 안고 있기 때문에 바람 직하지 않다. 이에, 상기한 단점을 해결한 자기유변유체를 개발하여, 이를 효과적으로 적용하기 위한 노력이 계속되고 있다: 미국특허 제2,575,360호에서는 클러치와 브레이크에서 사용될 수 있는 토크 변환장치를 개시하고 있고, 이 장비에 사용될 수 있는 자기유변유체의 조성으로 자성입자(carbonyl iron)가 광윤활유(light lubricant oil)에 50%의 부피분율로 분산되어있는 유체를 개시하고 있다. 자기유변유체의 실제 응용시에 중요한 인자는 중력에 의한 침전문제로 인하여, 자기유변학적 거동이 큰 영향을 받는다는 점이다. 이 침전의 주요한 원인은 철자성입자(7.86g/cm3)와 연속상(silicon oil의 경우 0.95g/cm3)사이의 밀도의 차이에서 기인한 자기유변유체의 안정성 저하이다. 이를 극복하기 위하여, 지속적인 노력이 계속되고 있는데, 미국특허 제5,043,070호에서는 2가지층의 계면활성제를 자성입자에 코팅한 자성입자를 사용하여 자기유변유체의 안정화를 시도하였으나 효과는 만족스러운 수준에 이르지 못하였고, 미국특허 제 5,645,752호에서는 자기유변유체에 전단엷음첨가제를 혼합하여, 수소결합을 위한 틱소트로픽 가교(network)를 유도함으로써 자성입자의 침전을 최소화 하려고 시도하였으나, 역시 뚜렷한 안정성의 증가를 나타내지 못하였다. 따라서, 안정성이 향상된 자기유변유체를 개발하여야 할 필요성이 끊임없이 대두되었다.
As disclosed in Korean Patent Publication No. 2002-0064654, in order to produce a highly efficient magnetorheological fluid used in a damper and a brake of a passenger car, a truck, etc., it is required to have a high yield stress For this purpose, a method of increasing the volume fraction of the magnetic particles or imposing a strong magnetic field can be used. However, when the volume fraction of the magnetic particles is increased, the load of the equipment and the driving power consumption are increased , It is not desirable because it has the disadvantage of increasing the viscosity when the magnetic field is not loaded when a strong magnetic field is applied. Accordingly, efforts have been made to develop and effectively apply a magnetorheological fluid that solves the above disadvantages. U.S. Patent No. 2,575,360 discloses a torque converter that can be used in clutches and brakes. Discloses a fluid in which carbonyl iron is dispersed in a light lubricant oil in a volume fraction of 50% with the composition of a magnetorheological fluid that can be used. An important factor in the practical application of magnetorheological fluid is that the magnetorheological behavior is greatly affected by the precipitation problem due to gravity. The main cause of this precipitation is the poor stability of the magnetorheological fluid due to the difference in density between the spiral particles (7.86 g / cm 3 ) and the continuous phase (0.95 g / cm 3 for silicon oil). In order to overcome this, there is a continuing effort. In US Pat. No. 5,043,070, magnetic particles having two layers of surfactant coated on magnetic particles were used to stabilize the magnetorheological fluid, but the effect was satisfactory U.S. Patent No. 5,645,752 attempts to minimize precipitation of magnetic particles by mixing a shear thin additive in a magnetorheological fluid to induce a thixotropic network for hydrogen bonding, but also exhibits a pronounced increase in stability I did not. Therefore, there is a constant need to develop a magnetorheological fluid having improved stability.

본 발명에서는 안정성이 향상된 자기유변유체를 개발하고자 자성입체표면을 고분자로 둘러싸고 이 입자를 발포시켜 다공성 고분자 발포체로 둘러싸인 자성입체를 제조함으로써 침전에 대한 안정성이 우수한 자기유변유체를 제조할 수 있다. In order to develop a magnetorheological fluid having improved stability, a magnetorheological fluid having excellent stability against precipitation can be prepared by forming a magnetic solid surrounding a magnetic three-dimensional surface with a polymer and foaming the particles to form a magnetic solid surrounded by the porous polymer foam.

본 발명에 따라 제조된 자기유변체는 1주일이 지나도 90% 이상이 부유된 상태로 있으며 초기 제조된 항복응력을 그대로 유지함으로서 자기유변체를 이용한 각종 장비의 개발에 널리 활용할 수 있다.
The magnetic oil variant produced according to the present invention is in a state of being floated at 90% or more even after one week and can be widely used for the development of various equipments using the magnetic oil variant by maintaining the initial yield stress.

도 1은 자기유변체가 자장이 걸리기 전과 걸리고 난후 섬유구조를 형성하는 현미경 사진이다,
도2는 [A]본 발명으로 제조하고자 하는 다층구조 자성입자의 발포전과 발포후의 모식도이고 [B] 발포된 입자의 표면구조와 전자현미경사진 및 다공성을 보여주는 투과현미경 사진이다.
도3은 [A] 본 발명으로 제조된 자기유변체의 전단응력에 대한 반응으로서 전단율에 대한 변화이고 [B] 전단응력으로부터 얻어진 항복응력을 입력전압에 대한 함수로 도시한 그래프이다.
도4는 본 발명에서 제조한 다층구조 발포 자성입자로 제조된 자기유변체와 처리하지 않은 철자성입자로 제조된 자기유변체의 비교사진이다. 처음에는 둘 다 입자들이 미디움 내에 분산되어 있으나 1주일 후 (오른쪽 사진) 본 발명으로 제조한 입자는 대부분 부유되어 있는 반면 순수 철입자는 침강되어 가라앉았다. 1 is a photomicrograph showing the formation of a fiber structure before and after magnetic flux is applied to a magnetic oil variant.
FIG. 2 is a schematic view of the multilayered magnetic particles to be prepared according to the present invention before and after foaming, and FIG. 2 is a photograph of the surface structure, electron micrograph and porosity of foamed particles.
3 is a graph showing the change in shear rate as a reaction to the shear stress of the magnetic oil variant prepared according to the present invention and the yield stress obtained from the shear stress as a function of the input voltage.
4 is a comparative photograph of magnetic oil variants prepared from the multi-layered foamed magnetic particles prepared in the present invention and magnetic oil variants made from untreated sparse particles. Initially, both particles were dispersed in the medium, but after one week (right image), the particles prepared according to the present invention were mostly suspended while the pure iron particles were settled down.

본 발명의 자기유변유체의 제조방법은 자성입자의 표면에 폴리머를 중합시키는 공정, 폴리머로 둘러싸인 자성입자를 압축반응용기에 넣은후 초임계유체를 이용하여 발포 시키는 공정; 이후 발포된 고분자로 둘러쌓인 자성입자를 실리콘 오일이나 미네랄오일에 5 내지 50%의 무게분율로 분산시키는 공정을 포함한다. 이하, 본 발명의 자기유변유체의 제조방법을 보다 구체적으로 설명하기로 한다.
(i) 자성입자의 표면에 폴리머를 중합시키는 공정;
(ii) 폴리머로 둘러 쌓인 자성입자를 압축반응용기에 넣은후 초임계유체 (또는 아임계유체)를 이용하여 발포 시키는 공정공정; 및
(iii) 발포된 고분자로 둘러쌓인 자성입자를 실리콘 오일이나 미네랄오일에 5 내지 50%의 무게분율로 분산시키는 공정을 포함하는 자기유변유체의 제조방법을 제공한다.
본 발명의 자성입자를 둘러싸고 있는 고분자는 초임계 또는 아임계상태의 유체가 쉽게 침지될수 있는 비정형 또는 아주 낮은 반결정성고분자로 이루어진 것을 특징으로 하는 자기유변체 입자를 제공한다.
본 발명의 오일은 윤활유, 미네랄오일, 실리콘오일, 캐스터오일, 파라핀오일, 진공 오일, 콘 오일 및 탄화수소 오일로 구성된 그룹으로부터 선택되는 것을 특징으로 하는 자기유변유체의 제조방법을 제공한다.
본 발명의 자성입자는 철, 카보닐철, 철 합금체, 산화철, 질화철, 카바이드철, 저탄소강, 니켈, 코발트, 이들의 혼합물 및 이들의 합금으로 구성된 그룹으로부터 선택되는 것을 특징으로 하는 자기유변유체의 제조방법을 제공한다.
본 발명의 자성입자표면에 고분자 단량체 및 고분자가 잘 흡착 성장할 수 있도록 입자표면을 메타아크릴산, 폴리알콜, 글루코스, 솔비톨, 아미노알콜, 폴리에틸렌글리콜, 아미노옥사이드, 아민염, 4급암모늄염, 피리미딘염, 설포늄염, 포스포늄염,폴리에틸렌폴리아민, 카복실레이트, 설포네이트, 설페이트, 포스페이트, 포스포네이트, 아미노산, 베타인, 아미노설페이트, 설포베타인 및 이들의 혼합물로 전처리하는 것을 특징으로 하는 자기유변유체의 제조방법을 제공한다.
본 발명의 방법으로 제조된, 다층구조의 자성입자가 상기한 제3항의 연속상에 5 내지 50%의 부피분율로 분산되어 안정성이 향상된 자기유변유체를 제공한다.The method for producing a magnetorheological fluid according to the present invention comprises the steps of polymerizing a polymer on the surface of magnetic particles, placing magnetic particles surrounded by the polymer in a compression reaction vessel and foaming using a supercritical fluid; And then dispersing the magnetic particles surrounded by the foamed polymer in a weight fraction of 5 to 50% in silicone oil or mineral oil. Hereinafter, the method for producing the magnetorheic fluid of the present invention will be described in more detail.
(i) polymerizing the polymer on the surface of the magnetic particles;
(ii) a step of putting the magnetic particles surrounded by the polymer into a compression reaction vessel and foaming it using a supercritical fluid (or subcritical fluid); And
(iii) dispersing the magnetic particles surrounded by the foamed polymer in a weight fraction of 5 to 50% in silicone oil or mineral oil.
The polymer surrounding the magnetic particles of the present invention is characterized by being composed of an amorphous or very low semi-crystalline polymer capable of easily immersing a supercritical or subcritical fluid.
The oil of the present invention is selected from the group consisting of lubricating oil, mineral oil, silicone oil, castor oil, paraffin oil, vacuum oil, cone oil and hydrocarbon oil.
The magnetic particles of the present invention are selected from the group consisting of iron, carbonyl iron, iron alloys, iron oxides, iron nitrides, carbide iron, low carbon steels, nickel, cobalt, mixtures thereof and alloys thereof. Of the present invention.
The surface of the magnetic particles of the present invention may be coated on the surface of the magnetic particles with a binder such as methacrylic acid, polyalcohol, glucose, sorbitol, amino alcohol, polyethylene glycol, amino oxide, amine salt, quaternary ammonium salt, Characterized in that it is pretreated with a sulfonium salt, a phosphonium salt, a polyethylenepolyamine, a carboxylate, a sulfonate, a sulfate, a phosphate, a phosphonate, an amino acid, a betaine, an aminosulfate, a sulfobetaine and a mixture thereof And a manufacturing method thereof.
The magnetic particles produced by the method of the present invention are dispersed in a volume fraction of 5 to 50% in the continuous phase of the above-mentioned third claim to provide a magnetorheological fluid having improved stability.

제 1공정은 고분자로 코팅된 카보닐철 입자를 제조하는 공정으로서 철입자를 유화제등으로 전처리한 후 고분자 단량체를 함유하고 있는 용액에 첨가한후 여기에 개시제 및 안정제등을 투입하여 철입자표면에 고분자가 중합되면서 고분자로 둘러싸인 다층구조체를 이루게 된다. 제 2공정은 상기 공정에서 제조된 다층구조체를 고온가압반응기에 넣고 여기에 초임계 및 아임계유체를 주입하여 일정시간 후에 고분자층에 유체가 침지되면 반응기 출구를 열어 급격한 압력감소가 일어나면서 입자내에 흡수되어 있던 유체가 팽창하여 발포체를 이루어 철입자를 둘러싸고 있는 고분자가 다공성 고분자로 변하게 된다. 제3공정은 제조된 다공성고분자로 둘러싸인 철입자를 유체미디움 (실리콘오일, 미네랄오일, 윤활유등)에 분산시켜서 자기 유변체를 만들게 된다. 이하, 아래 실시예를 통하여 본 발명을 더욱 상세히 설명하기로 한다. 이들 실시예는 오로지 본 발명을 보다 구체적으로 설명하기 위한 것으로, 본 발명의 범위가 이들 실시예에 의해 제한되는 것은 아니다.The first step is a step of preparing carbonyl iron particles coated with a polymer, which comprises pretreating iron particles with an emulsifier or the like, adding the solution to a solution containing a polymer monomer, adding an initiator and a stabilizer thereto, Is polymerized to form a multi-layered structure surrounded by a polymer. In the second step, the multi-layered structure manufactured in the above step is put into a high-temperature pressurized reactor, supercritical and subcritical fluids are injected into the reactor, and when the fluid is immersed in the polymer layer after a certain time, the reactor outlet is opened, The absorbed fluid expands to form a foam, and the polymer surrounding the iron particles is transformed into a porous polymer. In the third step, iron particles surrounded by the porous polymer are dispersed in a fluid medium (silicone oil, mineral oil, lubricating oil, etc.) to form a magnetic oil variant. Hereinafter, the present invention will be described in more detail with reference to the following examples. These embodiments are only for describing the present invention more specifically, and the scope of the present invention is not limited by these examples.

다층구조체 제조 공정 : 제 1공정은 고분자로 코팅된 카보닐철 입자를 제조하는 공정으로서 철입자를 유화제등으로 전처리한 후 고분자 단량체를 함유하고 있는 용액에 첨가한후 여기에 개시제 및 안정제등을 투입하여 철입자표면에 고분자가 중합되면서 고분자로 둘러싸인 다층구조체를 제조하기 위하여 BASF의 철입자 (평균입자크기 4.25 마이크론미터, 밀도 7.91 g/cm3)위에 폴리스티렌을 중합하였다. 먼저 철입자와 유기코팅고분자(폴리스타이렌)와의 친화성을 부여하기위하여 철입자를 메탄올 100그램에 메타아크릴산 10g이 섞여 있는 용액에 초음파로 분산시킨후 혼합용액을 메탄올로 세척하여 과량의 메타아크릴산을 제거한다. 접합반응액으로 사용한 메타아크릴산은 카르복실그룹이 철입자 표면에 반응하며 붙게되고 아크릴 부분은 스타이렌단량체라디칼과 반응하여 철표면에 폴리스티렌 고분자가 생성되게한다. 메타아크릴산 처리된 철입자에 18g의 스타이렌 단량체를 첨가한다. 이 혼합물을 6.6g의 폴리비닐피리딘을 안정제로 함유하는 200g의 메탄올 용액에 넣는다. 개시제로 0.54g의 2,2'아조비스(아이소부티로나이트릴)을 반응기에 넣는다. 질소퍼징하며 반응기 온도를 55℃ 에서 24시간동안 450rpm으로 교반하며 반응시킨다. 반응이 끝나고 난후 최종 산물을 메탄올 용액에서 자석을 이용하여 분리한 후 60℃에서 24시간 동안 건조시킨다. Process for preparing a multi-layered structure: The first step is a step of preparing carbonyl iron particles coated with a polymer, wherein iron particles are pretreated with an emulsifier or the like and then added to a solution containing a polymer monomer, and then an initiator and a stabilizer are added thereto as the polymerizing polymer on the surface of the iron particles was polymerized polystyrene on top of BASF iron particles (having a mean particle size of 4.25 micron meters, density 7.91 g / cm 3) in order to produce a multilayer structure surrounded by the polymer. First, to give affinity between iron particles and organic coating polymer (polystyrene), iron particles were dispersed in 100 g of methanol in a solution containing 10 g of methacrylic acid by ultrasonic wave, and then the mixed solution was washed with methanol to remove excess methacrylic acid do. In the methacrylic acid used as the bonding reaction solution, the carboxyl group reacts with the surface of the iron particles and the acrylic moiety reacts with the styrene monomer radical to produce a polystyrene polymer on the iron surface. 18 g of styrene monomer is added to the iron-treated iron oxide particles. This mixture is added to 200 g of a methanol solution containing 6.6 g of polyvinylpyridine as a stabilizer. 0.54 g of 2,2 'azobis (isobutyronitrile) as initiator is placed in the reactor. Nitrogen is purged and the reactor temperature is allowed to react at 55 캜 for 24 hours with stirring at 450 rpm. After the reaction is finished, the final product is separated from the methanol solution using a magnet and dried at 60 ° C for 24 hours.

철 입자를 둘러싸고 있는 고분자를 발포시켜 다공성의 발포체로 둘러싸인 철입자 제조 공정 : 상기 실시예 1-1의 공정에서 제조된 다층구조체를 고온가압반응기에 넣고 여기에 초임계 및 아임계유체를 주입하여 일정시간이 지나서 고분자층에 유체가 침지되면 반응기 출구를 열어 급격한 압력감소가 일어나면서 입자내에 흡수되어 있던 유체가 팽창하여 발포체를 이루어 철입자를 둘러싸고 있는 고분자가 다공성 고분자로 변하게 된다. 초임계유체의 경우 일정 고온 고압의 한계를 넘어선 상태에 도달하여 액체와 기체가 구분 안되는 상태이나 본 특허에 사용된 상기한 고압유체는 발포시 사용되는 기체로써 그 상태가 초임계상태든 그 이하인 아임계 상태든 다 사용할 수 있다. 초임계유체의 경우 용해도 및 분산도가 매우 높고 일반유체와는 다른 특성을 나타낸다. 본 발명에서는 통상적인 압력용기 (오토클레이브)를 사용하여 여기에 가압된 유체를 첨가한다. 본 발명의 실시예에서는 환경친화적이고 비교적 다루기 쉬워 널리 사용되는 고압고온하의 이산화탄소 CO2를 사용하였으나 이외에도 물,암모니아등도 사용될 수 있다. 실시예 1-1에서 제조된 입자를 반응기 내에 넣고 여기에 고온고압 (83기압 60도 초임계 상태 (임계온도 27도 이상 임계압력 72.9기압 이상)에서 행하지만 실제로는 그보다 낮은 압력의 아임계 상태도 발포 가능하다.)의 CO2 유체를 주입한다. 일정시간 후에 배출구를 개방하면 급격한 압력감소가 일어나면서 입자내에 흡수되어 있던 유체가 팽창하여 발포체를 이루어 철입자를 둘러싸고 있는 고분자가 다공성 고분자로 변하게 되고 이로써 밀도가 급격히 낮아지게 된다 (도 2). Iron particle manufacturing process in which a polymer surrounding iron particles is foamed and surrounded by porous foam: The multi-layer structure manufactured in the process of Example 1-1 is put into a high-temperature autoclave, supercritical and subcritical fluids are injected into the high- When the fluid is immersed in the polymer layer after the elapse of time, the polymer layer surrounds the iron particles and becomes a porous polymer. In the case of supercritical fluid, the liquid and the gas are not distinguished from each other by reaching a state exceeding the limit of a certain high temperature and high pressure. However, the high-pressure fluid used in the patent is a gas used for foaming, Critical state can be used. Supercritical fluids have very high solubility and dispersibility and exhibit properties different from those of ordinary fluids. In the present invention, a pressurized fluid is added to a conventional pressure vessel (autoclave). In the embodiment of the present invention, carbon dioxide CO 2 under a high-pressure and high-temperature environment, which is environmentally friendly and relatively easy to handle and widely used, is used, but water and ammonia can also be used. The particles prepared in Example 1-1 were placed in a reactor and subjected to a high-temperature high-pressure (83 atm 60-degree supercritical state (a critical temperature of 27 degrees or more and a critical pressure of 72.9 atm or more) It is possible to foam.) CO 2 Fluid is injected. When the discharge port is opened after a certain period of time, a sudden pressure drop occurs, and the fluid absorbed in the particles expands to form a foam, and the polymer surrounding the iron particles is converted into a porous polymer, whereby the density is drastically lowered (FIG.

자기유변체 제조 공정 : 제조된 다공성고분자로 둘러싸인 철입자를 유체미디움 (실리콘오일, 미네랄오일, 윤활유등)에 분산시켜서 자기 유변체를 만들게 된다. Magnetostrictive body manufacturing process: The iron particles surrounded by the prepared porous polymer are dispersed in a fluid medium (silicone oil, mineral oil, lubricating oil, etc.) to form a magnetic oil variant.

자기장에 따른 자기유변유체의 전단응력 변화 : 실시예 1-3에서 제조한 자기유변체를 유변물성 측정기(자기장 발생기가 달려있는 회전레오미터 (Physica MC 300, Stuttgart, Germany))를 사용하여 전단응력을 측정하였다. 도 3은 각 자기장 영역하에서 자기유변유체의 전단응력 변화를 나타내는 그래프로서 전류를 변화시킴으로써 자기장의 세기가 변화되었다. 도 3에서 보듯이, 자기장이 0일 때에는 뉴토니언유체 거동을 나타내고, 자기장이 가해지면 빙햄유체의 거동을 나타내며, 전압증가에 따른 자기장의 크기가 증가할수록 전단응력이 증가함을 알 수 있었다.Change in Shear Stress of Magneto-Rheological Fluid According to Magnetic Field: The magnetic oil variant prepared in Example 1-3 was subjected to a shear stress test using a rheometer (a rotating rheometer equipped with a magnetic field generator (Physica MC 300, Stuttgart, Germany) Were measured. FIG. 3 is a graph showing the shear stress change of the magnetorheological fluid under each magnetic field region, and the intensity of the magnetic field was changed by changing the current. As shown in FIG. 3, when the magnetic field is 0, it shows Newtonian fluid behavior, and when the magnetic field is applied, it indicates the behavior of the Bingham fluid. As the magnitude of the magnetic field increases, the shear stress increases.

자성입자가 분산된 자기유변유체의 침강속도변화 : 실시예 1-3에서 제조된 자성입자를 분산시킨 자기유변체를 바이얼에 넣고 다층구조입자의 침강을 관찰하였다. 도 4-a 는 초기의 자기유변 유체이고 도 4-b는 1주일후의 상태다. 다층구조체의 경우 1주일후에도 전체입자의 90%가 그대로 부유되어 있는 것을 볼 수 있는 반면 순수 카보닐아이언의 경우는 대부분이 침전되어 깨끗한 용액이 된 것을 볼 수 있다.
Change in Sedimentation Velocity of Magneto-rheological Fluid in which Magnetic Particles are Dispersed: The magnetic oil variant in which the magnetic particles prepared in Example 1-3 were dispersed was put into a vial and the sedimentation of the multi-layer structure particles was observed. Figure 4-a is the initial magnetorheological fluid and Figure 4-b is the state after one week. In the case of the multi-layered structure, 90% of the whole particles are floating even after one week, while in the case of pure carbonyl irons, most of the particles are precipitated and become a clean solution.

본 발명에서 제조된 자기유변유체는 지름이 0.1㎛ 보다 큰 강자성, 상자성 입자와 오일미디움으로 이루어져 있으며, 외부의 자기장이 가해지면 입자의 내부와 표면에 분극현상(polarization)에 의해서 입자들이 배열하고 섬유구조(fibril structure)를 형성하여 점도 향상과 유체의 흐름을 방해함으로써 항복응력이 발생하게 되고 이때의 항복응력은 자기장의 세기에 따라 증가하고, 가해진 전단응력(shear stress)이 유체의 항복응력보다 커지면 유체가 흐르게 된다. 본 발명의 자기유변체는 강자성입자를 둘러싸고 있는 고분자가 발포공정을 거침으로써 다공성을 갖게되어 밀도를 줄일 수 있고 안정성이 증가되어 다층구조입자의 침강속도를 현저히 줄일 수 있다. 이 자기유변체의 자기장에 대한 응답속도는 미리초(10-3 초) 수준으로 매우 빠르고 가역적인 동시에 안정성이 향상되었으므로 자기유변유체를 이용한 클러치, 엔진마운트, 진동제어장치, 고층건물 내진 장치, 로보틱 시스템(robotic system) 등의 각종 장비개발에 널리 활용될 수 있을 것이다.
The magnetorheological fluid produced by the present invention is composed of ferromagnetic, paramagnetic particles and oil medium having a diameter of more than 0.1 탆. When an external magnetic field is applied, particles are arranged by polarization on the inside and the surface of the particles, When the shear stress is greater than the yield stress of the fluid, the shear stress increases with the strength of the magnetic field and the shear stress becomes larger than the yield stress of the fluid. Fluid flows. In the magnetic oil variant of the present invention, the polymer surrounding the ferromagnetic particles has a porosity through the foaming process, thereby reducing the density and increasing the stability, thereby significantly reducing the sedimentation rate of the multi-layer structure particles. Magnetic oil variants advance speed of response to the magnetic field of the second (10 -3 seconds) is very fast and reversible at the same time improves the reliability level because the clutch, the engine mount with a magnetorheological fluid, a vibration control device, high-rise buildings seismic device, Robo It can be widely used to develop various devices such as a robotic system.

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Claims (6)

(i) 자성입자의 표면을 접합반응액으로 메타아크릴산을 사용하여 반응시키는 단계;
(ii) 메타아크릴산으로 반응된 자성입자를 스타이렌 단량체 라디칼과 반응시켜 자성입자의 표면에 폴리스티렌 고분자를 생성시키는 단계;
(ii) 폴리스티렌 고분자로 둘러싸인 자성입자를 고온가압반응기에 넣은 후 고압고온하의 이산화탄소(CO2)를 사용하는 초임계유체 또는 아임계 유체를 이용하여 자성입자를 둘러싸고 있는 고분자를 발포시켜 다공성의 발포체로 둘러싸인 자성입자를 제조하는 단계; 및
(iii) 제조된 다공성의 발포체로 둘러싸인 자성입자를 오일 내에 5 내지 50 중량%로 분산시키는 것을 특징으로 하는 자기유변유체의 제조방법.(i) reacting the surface of the magnetic particles with methacrylic acid as a bonding reaction liquid;
(ii) reacting the magnetic particles reacted with methacrylic acid with a styrene monomer radical to form a polystyrene polymer on the surface of the magnetic particles;
(ii) magnetic particles surrounded by a polystyrene polymer are put into a high-temperature pressurized reactor, and a polymer surrounding the magnetic particles is foamed using a supercritical fluid or a subcritical fluid using carbon dioxide (CO 2 ) under high pressure and high temperature to form a porous foam Producing magnetic particles surrounded by the magnetic particles; And
(iii) 5 to 50% by weight of the magnetic particles surrounded by the prepared porous foam are dispersed in the oil. 삭제delete 청구항 1에 있어서,
상기 오일은 윤활유, 미네랄오일, 실리콘오일, 캐스터오일, 파라핀오일, 진공 오일, 콘 오일 및 탄화수소 오일로 구성된 그룹으로부터 선택되는 것을 특징으로 하는 자기유변유체의 제조방법.The method according to claim 1,
Wherein the oil is selected from the group consisting of lubricating oil, mineral oil, silicone oil, castor oil, paraffin oil, vacuum oil, cone oil and hydrocarbon oil. 청구항 1에 있어서,
상기 자성입자는 철, 카보닐철, 철 합금체, 산화철, 질화철, 카바이드철, 저탄소강, 니켈, 코발트, 이들의 혼합물 및 이들의 합금으로 구성된 그룹으로부터 선택되는 것을 특징으로 하는 자기유변유체의 제조방법.The method according to claim 1,
Wherein the magnetic particles are selected from the group consisting of iron, carbonyl iron, iron alloy, iron oxide, iron nitride, carbide iron, low carbon steel, nickel, cobalt, mixtures thereof and alloys thereof. Way. 삭제delete 삭제delete
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