JP2005053752A - Modified graphite particle and paint with which the modified graphite particle is compounded - Google Patents
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本発明は、黒鉛粒子の表面改質による分散性に優れた改質黒鉛粒子、並びにこの改質黒鉛粒子を配合してなる塗料に関するものである。 The present invention relates to modified graphite particles that are excellent in dispersibility due to surface modification of graphite particles, and a paint formed by blending the modified graphite particles.
黒鉛（Ｇｒａｐｈｉｔｅ）は、六方晶系の黒色鱗片状の光沢のある結晶からなる天然黒鉛、キッシュ黒鉛（溶けた銑鉄が溶銑予備処理等で温度低下するのに伴って析出する黒鉛）及び、例えばアチェソン法（コークスやカーボン等の炭素粉末をピッチ及び少量の砂と混ぜて加圧成形し、電気炉内で強熱して製造される）で製造される人造黒鉛等がある。これらの黒鉛は、電気の良導体であり、伝熱性、電気化学的安定性、層間を有する構造などに着目し、電気部品用導電塗料の媒質、リチウムイオン二次電池用負極材料、各種電極、導電接着剤、電波吸収材などのさまざまな用途に使用されている。そして、これら用途の多くの場合、黒鉛を媒体中に分散させて塗料状態にし、この塗料から塗膜状に形成されたものを使用している。 Graphite is natural graphite consisting of hexagonal black scale-like glossy crystals, quiche graphite (graphite that precipitates as the temperature of molten pig iron decreases during hot metal pretreatment, etc.) and, for example, Acheson Artificial graphite produced by a method (produced by mixing carbon powder such as coke and carbon with pitch and a small amount of sand, press-molding and igniting in an electric furnace). These graphites are good electrical conductors, paying attention to heat transfer, electrochemical stability, structure with layers, etc., and conductive paint media for electrical parts, negative electrode materials for lithium ion secondary batteries, various electrodes, conductive It is used for various applications such as adhesives and electromagnetic wave absorbers. In many cases of these uses, graphite is dispersed in a medium to form a paint, and a film formed from this paint is used.
一般に塗料として黒鉛を媒体中に均一に分散させるためには、カルボキシメチルセルロース、ヒドロキシメチルセルロースなどのセルロース系分散剤を使用したり、β−ナフタレンスルホン酸ソーダ、アルキルナフタレンスルホン酸ソーダ、リグニンスルホン酸ソーダなどの界面活性剤を用いることが多い。ところが、前述の分散剤や界面活性剤が塗膜中に残存することによって、塗膜の耐水性、耐溶剤性、電気化学的安定性などを阻害するおそれがある。この分散剤の悪影響を回避しようとして、分散剤や界面活性剤の添加量を減らすと、今度は均一な分散状態が得られず、分散不良による支障をきたすこととなり問題であった。 In general, in order to uniformly disperse graphite as a coating material in a medium, cellulose-based dispersants such as carboxymethyl cellulose and hydroxymethyl cellulose are used, β-naphthalene sulfonate sodium, alkyl naphthalene sulfonate sodium, lignin sulfonate sodium, etc. Often used is a surfactant. However, when the above-mentioned dispersant or surfactant remains in the coating film, water resistance, solvent resistance, electrochemical stability, etc. of the coating film may be impaired. In order to avoid the adverse effects of the dispersant, if the amount of the dispersant or the surfactant added is reduced, a uniform dispersion state cannot be obtained this time, causing problems due to poor dispersion.
一方、特許文献１によれば、扁平状粒子からなる無機質粉体をフィラーとし、コロイダルシリカ等をバインダーとして含む無機質塗料組成物から得られる塗膜は、前記扁平状粒子が被塗膜面に平行に配向し積層することによって、不燃性で、平滑度・光沢度・透水防止性・耐汚染性に優れ、建材の表面化粧に好適であることが開示されている。実施例７には、所望の扁平度からなる鱗片状黒鉛とコロイダルシリカと界面活性剤を配合した塗料組成物が記載されており、比較例３には、実施例７の鱗片状黒鉛に代えて人工球状黒鉛を用いた塗料組成物が記載されている。前記の各組成物を塗布した塗膜面について、実施例７の場合は非常に平滑であるが、比較例３については肌荒れが認められたことが記載されている（特許文献１第４頁）。前記の記載から、この発明は特定の扁平状粒子以外には適用が困難であり、範囲が限定される点において問題であった。
本発明は、黒鉛の形状に関係なく、あらゆる形状の黒鉛に対して表面改質を行うことで、界面活性剤乃至分散剤を添加せずに、又は添加量をできるだけ少なくして、塗料中の黒鉛の分散性、塗膜の平滑性を改善しようとするものであって、併せて、塗膜の耐水性・耐溶剤性などを向上させることを主たる目的とするものである。 In the present invention, surface modification is performed on graphite of any shape regardless of the shape of the graphite, so that a surfactant or a dispersant is not added or the addition amount is reduced as much as possible. The main purpose is to improve the dispersibility of graphite and the smoothness of the coating film, and to improve the water resistance and solvent resistance of the coating film.
本発明は、上記した課題を解決するために、黒鉛を媒体中に均一に分散させるためには、黒鉛の表面改質が重要であるとの見地に立ってなされたものである。即ち、本発明者らは、黒鉛の表面にメカノフィジカル的或いはメカノケミカル的にシリカ微粒子を修飾させて、溶媒中への分散時に、黒鉛微粒子に表面電荷を与え、黒鉛微粒子の凝集を抑えるとともに、シリカ微粒子の立体障害により凝集を抑えることを知見し、鋭意研究した結果、以下の発明を想到するに至ったものである。 In order to solve the above-described problems, the present invention has been made from the viewpoint that the surface modification of graphite is important in order to uniformly disperse graphite in a medium. That is, the inventors modified silica fine particles mechanophysically or mechanochemically on the surface of the graphite to give surface charge to the graphite fine particles when dispersed in the solvent, and suppress aggregation of the graphite fine particles, As a result of finding out that aggregation is suppressed by the steric hindrance of silica fine particles and earnestly researching it, the inventors have come up with the following invention.
即ち、前記の課題を解決するために、本発明は、塗料などの配合材として使用される黒鉛粒子において、該黒鉛粒子の表面にシリカ微粒子を修飾させて、該黒鉛粒子の表面電荷をゼータ電位にて−２〜−３０ｍVの範囲内にしてなることを特徴とする改質黒鉛粒子とする（請求項１）。 That is, in order to solve the above-described problems, the present invention provides a graphite particle used as a compounding material such as a paint, wherein the surface of the graphite particle is modified with silica fine particles, and the surface charge of the graphite particle is changed to a zeta potential. The modified graphite particles are characterized by being in the range of -2 to -30 mV.
また、前記の課題を解決するために、本発明は、前記シリカ微粒子がコロイダルシリカからなり、該シリカ微粒子の平均粒子径が５〜１００ｎｍの範囲内にあることを特徴とする前記の改質黒鉛粒子とすることが好ましい（請求項２）。 In order to solve the above problems, the present invention provides the modified graphite, wherein the silica fine particles are made of colloidal silica, and the average particle diameter of the silica fine particles is in the range of 5 to 100 nm. It is preferable to use particles (claim 2).
また、前記の課題を解決するために、本発明は、前記シリカ微粒子が疎水性シリカからなり、該シリカ微粒子の一次粒子径が５〜３０ｎｍの範囲内にあることを特徴とする前記の改質黒鉛粒子とすることが好ましい（請求項３）。 In order to solve the above problems, the present invention is characterized in that the silica fine particles are made of hydrophobic silica, and the primary particle diameter of the silica fine particles is in the range of 5 to 30 nm. It is preferable to use graphite particles.
また、前記の課題を解決するために、本発明は、前記黒鉛粒子は、天然黒鉛、メソフェーズピッチ系黒鉛、人造黒鉛及びキッシュ黒鉛から選ばれる少なくとも何れか一種からなることを特徴とする前記の改質黒鉛粒子とすることが好ましい（請求項４）。 In order to solve the above-described problems, the present invention provides the modified graphite, wherein the graphite particles comprise at least one selected from natural graphite, mesophase pitch-based graphite, artificial graphite, and quiche graphite. It is preferable to use graphite particles (claim 4).
また、前記の課題を解決するために、本発明は、前記の改質黒鉛粒子から選ばれる少なくとも何れか一種を配合してなることを特徴とする塗料とすることが好ましい（請求項５）。 In order to solve the above problems, the present invention is preferably a paint comprising at least one selected from the above-mentioned modified graphite particles (claim 5).
本発明の改質黒鉛粒子は、前記のように黒鉛粒子の表面にシリカ微粒子が修飾されていて、該黒鉛粒子の表面電荷がゼータ電位にて−２〜−３０ｍVの範囲内にあるため、極めて分散性が良好であり、且つ、長期安定性に優れている。また、係る改質黒鉛粒子を配合してなる塗料は、界面活性剤乃至分散剤を添加せずに、又は添加量を極力少なくしても、塗料中の改質黒鉛粒子は充分に均一に分散するので、この塗料から形成された塗膜は、平滑性、耐水性、耐溶剤性及び電気化学的安定性などの機能が保持されるという効果を奏する。また、改質黒鉛粒子が均一に分散する結果、黒鉛の添加量を軽減できる上、界面活性剤乃至分散剤を添加しないことによる経済的なメリットも期待できる。更に、前記改質黒鉛粒子は、所望のゼータ電位の範囲内において、黒鉛粒子の形状に無関係に分散性を向上でき、広く様々な塗料への応用が期待されるという利点がある。 Since the modified graphite particles of the present invention have silica fine particles modified on the surface of the graphite particles as described above and the surface charge of the graphite particles is in the range of −2 to −30 mV at zeta potential, Dispersibility is good and long-term stability is excellent. In addition, paints containing such modified graphite particles are sufficiently uniformly dispersed without adding surfactants or dispersants or even if the addition amount is minimized. Therefore, the coating film formed from this paint has an effect that functions such as smoothness, water resistance, solvent resistance, and electrochemical stability are maintained. Further, as a result of the uniform dispersion of the modified graphite particles, the amount of graphite added can be reduced, and an economic merit by not adding a surfactant or a dispersant can be expected. Furthermore, the modified graphite particles have the advantage that dispersibility can be improved within the desired zeta potential range regardless of the shape of the graphite particles, and application to a wide variety of paints is expected.
本発明を実施するための最良の形態について、以下に詳細に説明する。
本発明に係る改質黒鉛粒子は、黒鉛粒子の表面にシリカ微粒子が修飾されていて、且つ、該黒鉛粒子の表面電荷がゼータ電位にて−２〜−３０ｍVの範囲内にあることを特徴とする。特に限定されるものではないが、黒鉛粒子の表面にシリカ微粒子を修飾する方法について以下に説明する。先ず、水ないしアルコール中にシリカ微粒子を投入し、更に微粒子黒鉛を配合後、ボールミル、ビーズミル、振動ミル等の粉砕機にて分散混合処理を行う。その後、前記の分散混合物を乾燥させることによって、黒鉛粒子の表面にシリカ微粒子がメカノフィジカル的或いはメカノケミカル的に修飾された改質黒鉛粒子が得られる。ここで、「メカノフィジカル的或いはメカノケミカル的に修飾される」とは、黒鉛粒子がボールミル等の粉砕機によって機械的作用を受けて、二次凝集粒子が分離ないし粒子が破壊して生じた新生面にいわゆる活性点を生じ、ここに、例えば、ファンデルヴールス力や分子間力のような物理的或いは何らかの化学反応を伴って、シリカ微粒子が付着し、乾燥によって定着すると考えられる現象を意味する。
The best mode for carrying out the present invention will be described in detail below.
The modified graphite particles according to the present invention are characterized in that the silica particles are modified on the surface of the graphite particles, and the surface charge of the graphite particles is in the range of −2 to −30 mV at zeta potential. To do. Although not particularly limited, a method for modifying silica particles on the surface of graphite particles will be described below. First, silica fine particles are introduced into water or alcohol, and fine particle graphite is further blended, followed by dispersing and mixing with a pulverizer such as a ball mill, a bead mill, or a vibration mill. Thereafter, the dispersed mixture is dried to obtain modified graphite particles in which silica fine particles are mechanophysically or mechanochemically modified on the surface of the graphite particles. Here, “modified mechanophysically or mechanochemically” means that a new surface formed by separation or destruction of secondary agglomerated particles caused by mechanical action of graphite particles by a grinding machine such as a ball mill. This means a phenomenon that is considered to occur when silica fine particles adhere and are fixed by drying, accompanied by a physical or some chemical reaction such as van der Waals force or intermolecular force. .
前記で得られた改質黒鉛粒子を溶剤に分散して１質量％の分散液（塗料）を調整し、ゼータ電位を測定したところ、黒鉛表面が電荷を有しており、ゼータ電位が−２〜−３０ｍVの範囲で良好な分散性を示した。ゼータ電位が−２ｍV以下では、シリカ微粒子の修飾が少ないため、分散安定性が悪くなる。一方、表面改質に使用するシリカ微粒子量は、黒鉛に対して２０質量％を越えると、黒鉛本来の諸特性である導電性・伝熱性・電気化学的安定性・層間を有する構造に基づく特有の作用などが発揮され難くなる。このときのゼータ電位を測定したところ−３０ｍＶであったので、この値をゼータ電位の上限値としたのである。 The modified graphite particles obtained above were dispersed in a solvent to prepare a 1 mass% dispersion (paint), and the zeta potential was measured. The graphite surface was charged and the zeta potential was -2. Good dispersibility was exhibited in the range of -30 mV. When the zeta potential is −2 mV or less, the dispersion stability is deteriorated because the silica fine particles are not modified. On the other hand, if the amount of silica fine particles used for surface modification exceeds 20% by mass with respect to graphite, it is unique based on the inherent characteristics of graphite, such as conductivity, heat transfer, electrochemical stability, and a structure having an interlayer. It becomes difficult to exert the action of. Since the zeta potential at this time was measured and found to be −30 mV, this value was used as the upper limit value of the zeta potential.
ここで、液体中に分散している粒子の多くは、プラス乃至マイナスに帯電しているが、この粒子から充分離れた電気的に中性領域をゼロ点と定義づけ、このゼロ点を基準として、粒子の移動が起こる滑り面の電位をゼータ電位（ｚｅｔａ−ｐｏｔｅｎｔｉａｌ）と定義され、ゼータ電位の絶対値が増加すれば、粒子間の反発力が強くなり、粒子の安定性は高くなり、逆に、ゼータ電位がゼロに近くなると、粒子は凝集し易くなる。ゼータ電位の測定法として、例えば、分散液に交流電場を印加して音場を測定するＥＳＡ（Ｅｌｅｃｔｒｏｋｉｎｅｔｉｃ Ｓｏｎｉｃ Ａｍｐｌｉｔｕｄｅ）法やコロイド振動電流法などがあり、本発明におけるゼータ電位は、特に限定されるものではないが、ＥＳＡ法に基づく装置の一種である濃厚系ゼータ電位測定装置（ＥＳＡ−８０００）によって求めた値をもって表したものである。 Here, many of the particles dispersed in the liquid are positively or negatively charged. However, an electrically neutral region sufficiently separated from the particles is defined as a zero point, and the zero point is used as a reference. The potential of the sliding surface where particle movement occurs is defined as the zeta-potential, and if the absolute value of the zeta potential increases, the repulsive force between the particles increases, the stability of the particles increases, In addition, when the zeta potential is close to zero, particles tend to aggregate. Examples of the zeta potential measurement method include an ESA (Electrokinic Sonic Amplitude) method in which an AC electric field is applied to a dispersion to measure a sound field, and a colloid oscillating current method. The zeta potential in the present invention is particularly limited. Although it is not a thing, it represents with the value calculated | required with the dense system zeta potential measuring apparatus (ESA-8000) which is a kind of apparatus based on the ESA method.
平均粒子径が５〜１００ｎｍのコロイダルシリカからなるシリカ微粒子で修飾した本発明に係る改質黒鉛粒子は、シラノール基を有するシリカ微粒子が黒鉛表面に修飾されることで表面電荷を発生する。本発明に使用されるコロイダルシリカは、粒子径が５〜１００ｎｍの範囲にあるものが好ましく、このように粒子径が小さいコロイダルシリカは、黒鉛表面への付着力が向上する。 The modified graphite particles according to the present invention modified with silica fine particles made of colloidal silica having an average particle diameter of 5 to 100 nm generate surface charges when the silica fine particles having silanol groups are modified on the graphite surface. The colloidal silica used in the present invention preferably has a particle diameter in the range of 5 to 100 nm, and the colloidal silica having such a small particle diameter improves the adhesion to the graphite surface.
次に、一次粒子径が５〜３０ｎｍの疎水性シリカからなるシリカ微粒子で修飾された本発明に係る改質黒鉛粒子の場合、疎水性シリカは、表面官能基として、ハロゲン化シラン類、アルコキシシラン類、シラザン類、シロキサン類などとの反応で疎水化されたもの、例えば、ジメチルシリコーンオイルで表面処理したもの、オクチルシランで表面処理したもの、トリメチルシリル基で表面処理したものなどが挙げられる。このような疎水性シリカに使用されるシリカの例としては、例えば、デグサアクチエンゲゼルシャフト社製の火炎加水分解法で製造されるアエロジル（登録商標ａｅｒｏｓｉｌ）が好ましい。 Next, in the case of the modified graphite particles according to the present invention modified with silica fine particles composed of hydrophobic silica having a primary particle diameter of 5 to 30 nm, the hydrophobic silica has halogenated silanes, alkoxysilanes as surface functional groups. And those that have been hydrophobized by reaction with thiols, silazanes, siloxanes, etc., such as those that have been surface treated with dimethyl silicone oil, those that have been surface treated with octylsilane, and those that have been surface treated with trimethylsilyl groups. As an example of the silica used for such a hydrophobic silica, for example, Aerosil (registered trademark aerosil) manufactured by a flame hydrolysis method manufactured by Degussa Aktiengesellschaft.
前記の疎水性シリカは、親水性シリカに比較してシラノール基密度がより少ないが、化学処理して疎水性官能基を付加した疎水性シリカを黒鉛表面に修飾することによって表面電荷を発生できる。また、疎水性シリカは、粒子径５〜３０ｎｍの一次粒子が複数個凝集し、数μmの大きさからなるが、ボールミルなどを使用して黒鉛粒子の表面に均一に、且つ、メカノフィジカル的或いはメカノケミカル的に修飾することができる。これはシリカと黒鉛が共に疎水性であることに基づく疎水性相互作用が機能することにより、黒鉛粒子の全体に均一にシリカを修飾させることができると考えられ、疎水性シリカは親水性シリカと同様に黒鉛の表面改質剤として有効である。 The hydrophobic silica has a lower silanol group density than the hydrophilic silica, but surface charge can be generated by modifying the hydrophobic silica to which the hydrophobic functional group is added by chemical treatment on the graphite surface. Hydrophobic silica is composed of a plurality of primary particles having a particle size of 5 to 30 nm and a size of several μm. The surface is uniformly and mechanophysically on the surface of graphite particles using a ball mill or the like. It can be modified mechanochemically. This is thought to be because the hydrophobic interaction based on the hydrophobicity of both silica and graphite functions, so that the silica can be uniformly modified throughout the graphite particles. Similarly, it is effective as a surface modifier for graphite.
次に、修飾する黒鉛粒子として、天然黒鉛、メソフェーズピッチ系黒鉛、人造黒鉛、キッシュ黒鉛から選ばれる少なくとも何れか一種からなる本発明に係る改質黒鉛粒子において、これらの黒鉛は、黒鉛化度ないし結晶性は異なるが、六角網面炭素構造からなる黒鉛構造を有しており、前記のとおり粒子表面は疎水性である。本発明の場合、特許文献１記載の発明のように扁平状粒子に限定して適用されるものではなく、天然黒鉛の一種のリン状黒鉛やキッシュ黒鉛のような鱗片状のものは勿論、微小球状のメソカーボンマイクロビーズ（ＭＣＭＢ）にも適用でき、修飾される対象物の形状によって制限を受けないことが特徴の一つである。 Next, as the modified graphite particles, in the modified graphite particles according to the present invention consisting of at least one selected from natural graphite, mesophase pitch graphite, artificial graphite, and quiche graphite, these graphites have a graphitization degree or Although the crystallinity is different, it has a graphite structure composed of a hexagonal mesh surface carbon structure, and the particle surface is hydrophobic as described above. In the case of the present invention, the invention is not limited to flat particles as in the invention described in Patent Document 1, and is not limited to a kind of natural graphite, such as phosphorus-like graphite or quiche graphite, but is very small. One feature is that it can be applied to spherical mesocarbon microbeads (MCMB) and is not limited by the shape of the object to be modified.
また、一般にアスファルトやタールボトムを加熱すると、その中に含まれる多環式芳香族化合物が重縮合反応して成長し、コークスになる過程において、４００℃近辺で微小球状の炭素質が形成され、更にこれらが合体して均一な層状の異方性相を生ずる。この状態のピッチをメソフェーズピッチと称し、前記の過程において、微小球状が発生したピッチを冷却すると、微小球状が固化し、キノリン不溶分として分離される。この分離された微小球状粒子がメソカーボンマイクロビーズ（ＭＣＭＢ）である。一方、前記のアスファルトやタールボトムに代えて水添により分子量を低下させた原料から調製したメソフェーズピッチは、溶剤に可溶である。これらを黒鉛化した微粒子も本発明における黒鉛として使用可能であることは言うまでもない。 In general, when asphalt or tar bottom is heated, the polycyclic aromatic compound contained therein grows by polycondensation reaction, and in the process of becoming coke, a microspherical carbonaceous material is formed around 400 ° C., Furthermore, they combine to produce a uniform layered anisotropic phase. The pitch in this state is referred to as a mesophase pitch. When the pitch in which the fine spheres are generated is cooled in the above process, the fine spheres are solidified and separated as quinoline insolubles. The separated microspherical particles are mesocarbon microbeads (MCMB). On the other hand, mesophase pitch prepared from a raw material whose molecular weight is reduced by hydrogenation instead of the asphalt or tar bottom is soluble in a solvent. It goes without saying that fine particles obtained by graphitizing these can also be used as graphite in the present invention.
次に、前記の改質黒鉛粒子から選ばれる少なくとも何れか一種を配合してなる本発明に係る塗料は、前記の改質黒鉛粒子を媒体中に分散させて塗料状態にし、塗膜を形成できるものであって、およそ一般に塗料と称されるものを広く含むものである。前記の改質黒鉛粒子と共に他の無機系乃至有機系のフィラー等を媒体中に分散させてもよい。これらを水乃至溶剤等の媒体に分散させる方法は、特に限定されず、通常の塗料の調製手段によって分散混合することができる。また、本発明を実施するための最良の形態には、黒鉛粒子についてのみ記載したが、本発明は黒鉛以外にも、例えば金属粉その他の無機系粉体にも広く適用可能であると考えられる。以下に実施例を挙げて本発明を詳細に説明するが、本発明はこれらの実施例によって何ら限定されるものではない。 Next, the paint according to the present invention comprising at least one selected from the above modified graphite particles can form a coating film by dispersing the above modified graphite particles in a medium to form a paint state. And generally includes what is generally called a paint. Other inorganic or organic fillers may be dispersed in the medium together with the modified graphite particles. The method for dispersing these in a medium such as water or a solvent is not particularly limited, and can be dispersed and mixed by an ordinary paint preparation means. In the best mode for carrying out the present invention, only graphite particles have been described. However, the present invention can be widely applied to, for example, metal powders and other inorganic powders in addition to graphite. . EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
＜親水性シリカ（コロイダルシリカ）を用いた改質黒鉛粒子の調整＞
黒鉛微粒子９ｇ、水１０ｍｌをタングステンカーバイト製の容器に入れ、コロイダルシリカＡ〜Ｃ（いずれも固形分２０質量％）を黒鉛に対し１０質量％になるように調整して添加し、遊星ボールミルにて１時間、分散処理を行った。その後乾燥し、改質黒鉛粒子を調整した。
＜塗料の調整＞
改質黒鉛粒子１０ｇに対して、カルボキシメチルセルロース（ＣＭＣ）水溶液乃至エチルセルロース、スチレンブタジエンゴム（ＳＢＲ）エマルジョン（固形分３５質量％）乃至ポリビニルブチラール及び純水乃至イソプロピルアルコールをそれぞれ所定量加え、攪拌混合して塗料を調整した。
＜黒鉛粒子へのシリカ微粒子の修飾状態の確認＞
走査型電子顕微鏡で観察して確認した。
<Preparation of modified graphite particles using hydrophilic silica (colloidal silica)>
9 g of graphite fine particles and 10 ml of water are put in a container made of tungsten carbide, and colloidal silica A to C (all solid content 20% by mass) is adjusted so as to be 10% by mass with respect to graphite and added to the planetary ball mill. For 1 hour. Thereafter, drying was performed to prepare modified graphite particles.
<Adjustment of paint>
A predetermined amount of carboxymethyl cellulose (CMC) aqueous solution to ethyl cellulose, styrene butadiene rubber (SBR) emulsion (solid content 35 mass%) to polyvinyl butyral and pure water to isopropyl alcohol is added to 10 g of the modified graphite particles, followed by stirring and mixing. The paint was adjusted.
<Confirmation of modification of silica fine particles to graphite particles>
It confirmed by observing with a scanning electron microscope.
＜黒鉛分散液の分散安定性の評価＞
改質黒鉛粒子を水（溶媒）中に分散させ、５質量％の黒鉛分散液を調整した。これを室温で４８時間静置し、分散状態を目視観察により評価した。
＜ゼータ電位の測定＞
改質黒鉛粒子を水（溶媒）中に分散させ、１質量％黒鉛分散液を調整した。これをマテックアプライドサイエンス（Ｍａｔｅｃ Ａｐｐｌｉｅｄ Ｓｃｉｅｎｃｅ）社製の濃厚系ゼータ電位測定装置（ＥＳＡ−８０００）を用いてゼータ電位を測定した。
＜黒鉛塗膜の均一性の評価＞
銅箔上に前記にて調製した塗料を塗布後１２０℃で乾燥して得た黒鉛塗膜をスライドガラスで挟み、エポキシ樹脂で固定した後、表面を研磨し走査型電子顕微鏡で観察した。
＜評価結果＞
各検討試料における評価の結果を表１に示す。
<Evaluation of dispersion stability of graphite dispersion>
The modified graphite particles were dispersed in water (solvent) to prepare a 5 mass% graphite dispersion. This was left still at room temperature for 48 hours, and the dispersion state was evaluated by visual observation.
<Measurement of zeta potential>
The modified graphite particles were dispersed in water (solvent) to prepare a 1% by mass graphite dispersion. The zeta potential was measured using a dense zeta potential measuring device (ESA-8000) manufactured by Matec Applied Science.
<Evaluation of uniformity of graphite coating>
A graphite coating obtained by applying the above-prepared coating on copper foil and drying at 120 ° C. was sandwiched between glass slides and fixed with an epoxy resin, and then the surface was polished and observed with a scanning electron microscope.
<Evaluation results>
Table 1 shows the results of the evaluation for each sample examined.
表１において、実施例１〜３は、粒子径５〜１００ｎｍのコロイダルシリカを天然黒鉛粒子の表面に修飾させたものであり、実施例４及び５は、実施例１〜３の粒子径５〜１００ｎｍのコロイダルシリカに代えて粒子径５０ｎｍのコロイダルシリカを用い、天然黒鉛に代えてメソカーボンマイクロビーズ（ＭＣＭＢ）およびキッシュ黒鉛を用いた例である。比較例Ａはコロイダルシリカを配合することなく、天然黒鉛を水に分散させた例であり、比較例Ｂは粒子径５ｎｍのコロイダルシリカを加え、遊星ボールミルで分散処理後、乾燥工程を経ないで調製した例である。 In Table 1, Examples 1 to 3 are obtained by modifying the surface of natural graphite particles with colloidal silica having a particle size of 5 to 100 nm, and Examples 4 and 5 are examples of particle sizes 5 to 5 of Examples 1 to 3. In this example, colloidal silica having a particle diameter of 50 nm is used instead of 100 nm colloidal silica, and mesocarbon microbeads (MCMB) and quiche graphite are used instead of natural graphite. Comparative Example A is an example in which natural graphite is dispersed in water without blending colloidal silica, and Comparative Example B is a colloidal silica having a particle diameter of 5 nm added, dispersed in a planetary ball mill, and not subjected to a drying step. This is a prepared example.
表１に示すように、実施例１〜５に係る改質黒鉛粒子は、何れもシリカ微粒子が黒鉛粒子の表面に均一に修飾されており、これらの改質黒鉛粒子を水に分散させたときのゼータ電位は、−８．０ｍＶ〜−８．３ｍＶであった。このように改質された黒鉛粒子の表面には、表面電荷が発生しており、分散性・安定性の評価において、分散液は４８時間放置後も分離現象等の異常が全く認められず、分散性は極めて良好であった。これに対して、比較例Ａは、ゼータ電位が−０.６ｍＶと、黒鉛の表面にはほとんど電荷が認められず、分散状態も良くなかった。同様に、比較例Ｂは、ゼータ電位が−７ｍＶを示すものの、黒鉛エッジ面へのシリカの付着が少なく、分散性・安定性評価においては、４８時間放置後、分散液の上部に上澄みの分離現象が発生し、分散安定性が劣ることが分かった。これは、分散処理後に乾燥工程を省いたことに起因するものと考えられる。図１（ａ）は、未処理の黒鉛粒子の電子顕微鏡写真であり、図１（ｂ）は、コロイダルシリカで修飾した改質黒鉛粒子であって、黒鉛のエッジ面にもシリカが付着した状態の電子顕微鏡写真である。 As shown in Table 1, in the modified graphite particles according to Examples 1 to 5, the silica fine particles are uniformly modified on the surface of the graphite particles, and when these modified graphite particles are dispersed in water The zeta potential of was −8.0 mV to −8.3 mV. Surface charges are generated on the surface of the graphite particles thus modified, and in the evaluation of dispersibility / stability, the dispersion has no abnormality such as a separation phenomenon even after being left for 48 hours. Dispersibility was very good. On the other hand, Comparative Example A had a zeta potential of −0.6 mV, almost no charge was observed on the graphite surface, and the dispersion state was not good. Similarly, Comparative Example B shows a zeta potential of −7 mV, but the adhesion of silica to the graphite edge surface is small, and in the evaluation of dispersibility and stability, the supernatant is separated on the top of the dispersion after 48 hours. It was found that the phenomenon occurred and the dispersion stability was inferior. This is considered to be caused by omitting the drying step after the dispersion treatment. FIG. 1 (a) is an electron micrograph of untreated graphite particles, and FIG. 1 (b) is modified graphite particles modified with colloidal silica, with the silica adhering to the edge surface of graphite. It is an electron micrograph of.
次に、黒鉛粒子の表面を疎水性シリカで修飾した改質黒鉛粒子について説明する。
前記の親水性シリカを用いた改質黒鉛粒子の調整において、コロイダルシリカに代えて、疎水性シリカを用い、水に代えてエタノールを用いる以外は前記の親水性シリカを用いた場合と同様にして改質黒鉛粒子を調整した。また、前記の親水性シリカを用いた場合における、＜黒鉛分散液の分散安定性の評価＞及び＜ゼータ電位の測定＞中の、水（溶媒）に代えてエタノールを用いた以外は親水性シリカを用いた場合と同様である。その他の評価法等についても前記の親水性シリカを用いた場合と同様に行って、その評価の結果を表２に示す。
Next, the modified graphite particles obtained by modifying the surface of the graphite particles with hydrophobic silica will be described.
In the adjustment of the modified graphite particles using the hydrophilic silica, instead of colloidal silica, hydrophobic silica is used, except that ethanol is used instead of water, as in the case of using the hydrophilic silica. Modified graphite particles were prepared. Further, in the case of using the above-mentioned hydrophilic silica, hydrophilic silica other than using ethanol in place of water (solvent) in <Evaluation of dispersion stability of graphite dispersion> and <Measurement of zeta potential> It is the same as the case where is used. Other evaluation methods were performed in the same manner as in the case of using the above-mentioned hydrophilic silica, and the results of the evaluation are shown in Table 2.
表２において、実施例６〜８は、表面官能基の異なる粒径７ｎｍ、１２ｎｍの疎水性シリカ微粒子を黒鉛粒子の表面に修飾させた実施例であり、比較例Ｃは疎水性シリカを配合しない例であり、比較例Ｄは粒子径１２ｎｍの疎水性シリカを加え、遊星ボールミルで分散処理後、乾燥工程を経ていない例である。 In Table 2, Examples 6 to 8 are examples in which hydrophobic silica fine particles having a particle size of 7 nm and 12 nm having different surface functional groups were modified on the surface of graphite particles, and Comparative Example C does not contain hydrophobic silica. For example, Comparative Example D is an example in which hydrophobic silica having a particle diameter of 12 nm is added, and after a dispersion treatment using a planetary ball mill, a drying process is not performed.
表２に示すように、実施例６〜８に係る改質黒鉛粒子は、何れもシリカ微粒子が黒鉛粒子の表面に均一に修飾されており、これらの改質黒鉛粒子をエタノールに再分散させたときのゼータ電位は、−１４.７ｍＶ〜−２９.８ｍＶである。改質された黒鉛の表面には、表面電荷が発生しており、分散性・安定性の評価において、分散液は４８時間放置後も分散状態は良好なままであり、上澄みの分離現象も全く認められなかった。これに対して比較例は、前記の親水性シリカを用いた改質黒鉛粒子の場合と同様に分散状態が悪く、分散安定性も劣ることが分かった。 As shown in Table 2, in the modified graphite particles according to Examples 6 to 8, the silica fine particles were uniformly modified on the surface of the graphite particles, and these modified graphite particles were redispersed in ethanol. The zeta potential at the time is −14.7 mV to −29.8 mV. Surface charge is generated on the surface of the modified graphite, and in the evaluation of dispersibility and stability, the dispersion remains in a good state after being left for 48 hours, and the separation phenomenon of the supernatant is completely absent. I was not able to admit. In contrast, the comparative example was found to have a poor dispersion state and poor dispersion stability as in the case of the modified graphite particles using the hydrophilic silica.
次に、前記の実施例によって得られた改質黒鉛粒子を配合した塗料の塗膜特性を表３に示す。この実験例において、塗料をブレードコータで銅箔上に塗布後、１２０℃で約１０分間乾燥して得られた厚さ約６０μｍの塗膜を使用した。 Next, Table 3 shows the coating film characteristics of the paints containing the modified graphite particles obtained by the above-described Examples. In this experimental example, a coating film having a thickness of about 60 μm obtained by applying a coating material on a copper foil with a blade coater and drying at 120 ° C. for about 10 minutes was used.
表３において、実施例９は、親水性シリカを黒鉛表面に修飾した改質黒鉛粒子を用い、少量のカルボキシメチルセルロース、スチレンブタジエンエマルジョンを水で分散した塗料であり、実施例１０は、前記の実施例９において、分散剤のカルボキシメチルセルロースを添加しない例である。実施例１１は、前記の実施例９において、親水性シリカに代えて疎水性シリカを黒鉛粒子の表面に修飾した改質黒鉛粒子を、カルボキシメチルセルロースに代えてエチルセルロースを、水に代えてイソプロピルアルコールを、スチレンブタジエンエマルジョンに代えてポリビニルブチラールをそれぞれ用いて塗料化した例であり、実施例１２は、前記の実施例１１において、分散剤のエチルセルロースを添加しない例である。比較例Ｅは、前記の実施例９において、改質黒鉛粒子に代えて表面改質を行っていない天然黒鉛粒子を用い、カルボキシメチルセルロースの添加量を増やした以外は実施例９と同様にして調整した塗料である。 In Table 3, Example 9 is a paint in which a small amount of carboxymethyl cellulose and a styrene butadiene emulsion are dispersed in water using modified graphite particles obtained by modifying hydrophilic silica on the graphite surface. In Example 9, the carboxymethyl cellulose as a dispersant is not added. Example 11 is a modified graphite particle in which hydrophobic silica is modified on the surface of graphite particles in place of hydrophilic silica in Example 9 above, ethyl cellulose in place of carboxymethyl cellulose, and isopropyl alcohol in place of water. In this example, polyvinyl butyral was used in place of the styrene-butadiene emulsion, and Example 12 was an example in which ethyl cellulose as a dispersant was not added in Example 11 described above. Comparative Example E was prepared in the same manner as in Example 9 except that natural graphite particles not subjected to surface modification were used in place of the modified graphite particles and the amount of carboxymethyl cellulose was increased. Paint.
表３に示すように、実施例９及び１１は、従来の配合に比較して極端に分散剤の添加量を減らし、実施例１０及び１２は、分散剤を全く添加しないにもかかわらず、何れも塗膜中にクラックなどの欠陥がなく、塗膜面は平滑であった。一方、比較例Ｅは、分散剤を従来の配合量よりやや少な目に添加した（本実施例に比較すると５０倍以上添加）のであるが、塗膜中にクラックが発生し、分散が悪いため塗膜面も不均一であった。本実施例と比較例とでは、明らかに分散性において差が認められた。 As shown in Table 3, Examples 9 and 11 drastically reduce the amount of dispersant added compared to the conventional formulation, and Examples 10 and 12 have no added dispersants at all. There were no defects such as cracks in the coating film, and the coating film surface was smooth. On the other hand, in Comparative Example E, the dispersant was added in a slightly smaller amount than the conventional blending amount (added 50 times or more compared to this example), but the coating was generated because cracks occurred in the coating film and the dispersion was poor. The film surface was also uneven. There was a clear difference in dispersibility between this example and the comparative example.
本発明に係る改質黒鉛粒子及びこの改質黒鉛粒子を配合した塗料は、例えば、電気部品用導電塗料の媒質、リチウムイオン二次電池用負極材料、各種電極、導電接着剤、電波吸収材などのさまざまな用途に適用でき、極めて有用である。 Examples of the modified graphite particles according to the present invention and paints containing the modified graphite particles include, for example, conductive paint media for electrical parts, negative electrode materials for lithium ion secondary batteries, various electrodes, conductive adhesives, radio wave absorbers, and the like. It is applicable to various uses and is extremely useful.
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| US20090229987A1 (en) * | 2005-09-29 | 2009-09-17 | Dowa Metaltech Co., Ltd. | Method for producing composite plated product |
| JP2018123027A (en) * | 2017-02-01 | 2018-08-09 | 国立大学法人 名古屋工業大学 | Silica/graphite-based uncalcinated solidified body, and method for producing the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US20090229987A1 (en) * | 2005-09-29 | 2009-09-17 | Dowa Metaltech Co., Ltd. | Method for producing composite plated product |
| JP2008149600A (en) * | 2006-12-19 | 2008-07-03 | Furukawa Sky Kk | Resin-coated aluminum material, enclosure for electronic equipment or home appliance using resin-coated aluminum material and electronic equipment or home appliance using this enclosure |
| JP2018123027A (en) * | 2017-02-01 | 2018-08-09 | 国立大学法人 名古屋工業大学 | Silica/graphite-based uncalcinated solidified body, and method for producing the same |
| JP2019006670A (en) * | 2017-06-23 | 2019-01-17 | Ｊｆｅスチール株式会社 | Manufacturing method of graphite having metal oxide adhered to surface, graphite having metal oxide and water soluble resin adhered on surface, and manufacturing method of graphite-containing castable refractory |
| US20220056267A1 (en) * | 2018-12-17 | 2022-02-24 | Dupont Polymers, Inc. | Polymeric compositions with high dielectric constant and low dielectric loss |
| KR20210143863A (en) * | 2019-12-03 | 2021-11-29 | 컨템포러리 엠퍼렉스 테크놀로지 씨오., 리미티드 | Composite graphite material, secondary battery, device and manufacturing method |
| CN113207315A (en) * | 2019-12-03 | 2021-08-03 | 宁德时代新能源科技股份有限公司 | Composite graphite material, secondary battery, device and preparation method |
| WO2021108987A1 (en) * | 2019-12-03 | 2021-06-10 | 宁德时代新能源科技股份有限公司 | Composite graphite material, secondary battery, device, and preparation method |
| JP2022529586A (en) * | 2019-12-03 | 2022-06-23 | 寧徳時代新能源科技股▲分▼有限公司 | Composite graphite material, secondary battery, equipment and manufacturing method |
| JP7273182B2 (en) | 2019-12-03 | 2023-05-12 | 寧徳時代新能源科技股▲分▼有限公司 | Composite graphite material, secondary battery, device and manufacturing method |
| US11710822B2 (en) | 2019-12-03 | 2023-07-25 | Contemporary Amperex Technology Co., Limited | Composite graphite material, secondary battery, apparatus and preparation method thereof |
| KR102584121B1 (en) * | 2019-12-03 | 2023-10-04 | 컨템포러리 엠퍼렉스 테크놀로지 씨오., 리미티드 | Composite graphite material, secondary battery, device and manufacturing method |
| CN115626826A (en) * | 2022-11-11 | 2023-01-20 | 湖南大学 | Low-density wear-resistant carbon graphite material with independent micropores and preparation method thereof |
| CN115626826B (en) * | 2022-11-11 | 2023-09-05 | 湖南大学 | Low-density wear-resistant carbon graphite material with independent micropores and preparation method thereof |
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