詳解日本石墨纖維公司瀝青基碳纖維的發展歷程、關鍵技術與應用
The development, key technology and application of mesophase pitch-based carbon fiber (MPCF) in Japan graphite fiber companies
作者：錢鑫 | 中國科學院寧波材料技術與工程研究所 高性能碳纖維及其複合材料團隊（原中科院寧波材料所特種纖維事業部）
Author: Xin Qian | Carbon Fiber and Its Composite Group, Laboratory of Polymers and Composites of Ningbo Institute of Materials Technology & Engineering, CAS
1 日本石墨纖維公司發展歷程
Development History of Nippon Graphite Fiber Companies
日本石墨纖維公司通過利用煤焦油中所含的浸漬瀝青（中間相瀝青）生產瀝青基碳纖維，其中煤焦油是煤碳化過程中產生的副產物。
Nippon Graphite Fiber Corporation (NGF) produces pitch-based carbon fibers using impregnated pitch (mesophase pitch) contained in coal tar, which is a by-product of coal during the process of coal carbonization.
浸漬瀝青作為一種硬（重）瀝青，是通過對針狀焦所用的高純度瀝青進行熱處理，然後使輕質成分揮發而產生的。NGF生產瀝青基碳纖維所需的浸漬瀝青均來自於C-Chem Co., Ltd.公司（隸屬於新日鐵住金化學株式會社）。
Impregnated bitumen, as the hard (heavy) bitumen, is produced by heat-treating used in the high-purity bitumen for in needle coke and then volatilizing the light components. The impregnated bitumen used by NGF to produce pitch-based carbon fibers comes from C-Chem Co., Ltd. (affiliated to Nippon Steel & Sumikin Chemical).
1981年，日本鋼鐵行業巨頭新日本制鐵公司開展用於建築和機械行業的瀝青基碳纖維技術開發，其主要目的是促進煤碳化過程中產生的副產物再應用。1985年，在Hirohata建立工廠用於生產瀝青基碳纖維用高品質中間相瀝青。
In 1981, Nippon Steel, a giant in the Japanese steel industry, started the development of pitch-based carbon fiber technology for the construction and machinery with the main purpose of promoting the reuse of by-products produced during the process of coal carbonization. In 1985, a works was established in Hirohata for the production of high-quality mesophase pitch for pitch-based carbon fibers.
1995年，新日本制鐵公司和新日本石油株式會社（後者在航空航天，運動和休閒領域的碳纖維材料方面具有較強實力）整合了與碳纖維相關的業務成立NGF（日本石墨纖維公司，現為新日鐵材料株式會社集團公司）。此後，NGF為多元化和新興市場提供了高質量的瀝青基碳纖維。
In 1995, Nippon Steel & Nippon Oil Corporation (The latter has strong strength in carbon fiber materials in the fields of aerospace, sports and leisure) integrated the business related to carbon fiber and established NGF (Nippon Graphite Fiber) for the production of high-quality mesophase pitch-based carbon fibers for diversified and emerging markets.
雖然PAN基碳纖維在整個碳纖維市場佔據主導性地位，然而目前市場用PAN基碳纖維拉伸模量通常為240 GPa（航空用PAN基碳纖維模量為300 GPa左右），若要實現500 GPa或更高PAN基高模量碳纖維生產，則不可避免地需要更高的成本。
Although currently PAN-based carbon fiber plays a dominant role in the overall carbon fiber market, the tensile modulus of PAN-based carbon fiber in the market is usually 240 GPa (the modulus of aviation PAN-based carbon fiber is about 300 GPa). To achieve the production of PAN-based modulus carbon fiber with 500 GPa or higher will inevitably require higher costs.
對於基於瀝青的碳纖維，可以相對容易製備得到從50 GPa至900 GPa的模量的纖維。尤其是為了將瀝青基碳纖維與300 GPa級PAN基碳纖維產品加以區別，NGF公司開發低模量（通用級瀝青碳纖維）和高模量（中間相瀝青碳纖維）碳纖維，如下圖所示。
For pitch-based carbon fiber, it is relatively easy to prepare fibers with the modulus ranging from 50 GPa to 900 GPa. In particular, in order to distinguish pitch-based carbon fiber products from PAN-based carbon fiber products with 300 GPa, NGF develops carbon fibers with low modulus (general-purpose ptich-based carbon fibers) and high modulus (mesophase pitch-based carbon fibers), as shown in the figure below.
2 中間相瀝青基碳纖維關鍵技術
Key technology of mesophase pitch-based carbon fiber
製備瀝青基碳纖維關鍵是獲得高品質可紡性瀝青原料，為了將C-Chem公司生產的浸漬瀝青加工成具有可紡性的瀝青原料，NGF公司首先對原料進行氫化處理（又稱加氫催化處理）。
The key to producing pitch-based carbon fibers is to obtain high-quality spinnable pitch raw materials. In order to process the impregnated pitch produced by C-Chem into spinnable pitch raw materials, NGF first hydrogenates the raw materials (also known as hydrogenation treatment).
氫化處理可以將含有硫和氮元素的化合物去除，進而改變浸漬瀝青的分子結構，從而將其轉化為六元環碳結構。氫化處理後對原料進一步熱聚合加工，以及高精度蒸餾方法去除雜質，從而獲得性能優異、可紡性良好的瀝青原料（流程如下圖所示）。
By hydrogenation treatment, compounds containing sulfur and nitrogen can be removed, and then the molecular structure of impregnated pitch can be changed into six-membered cyclic carbon structure. After the hydrogenation treatment, the raw materials are further processed by thermal polymerization, and the impurities are removed by high-precision distillation, so as to obtain the pitch raw materials with excellent properties and good spinnability (the process is shown in the figure below).
由於瀝青屬於易石墨化碳，因此通過加熱可將瀝青內部的六元環碳轉化為石墨晶體，而隨著晶體的生長，其瀝青基碳纖維的拉伸強度和拉伸模量隨之增加。
As pitch is a kind of graphitized carbon, the six-membered cyclic carbon inside the pitch can be converted into graphite crystals by heating. As the crystals grow, the tensile strength and modulus of the pitch-based carbon fibers increase correspondingly.
如果採用各向同性瀝青原料，其內部結構無法充分轉化為石墨晶體，即使進行熱處理，也不會產生完善的石墨結構。但對於中間相瀝青（又稱各向異性瀝青）而言，即使在液態下，也可以通過加氫處理來調整中間相瀝青的分子結構，以製造規則取向的液晶分子結構。
If the isotropic pitch is used as raw material, its internal structure cannot be fully converted into graphitic crystals, and perfect graphite structure will not be produced even after heat treatment. But for mesophase pitch (also known as anisotropic pitch), its molecular structure can be adjusted by hydrotreating even in liquid state to produce regular-oriented liquid crystal molecular structure.
因此，各向同性瀝青原料只能用於加工低模量瀝青基碳纖維（即：通用級瀝青基碳纖維），而中間相瀝青可以製備高模量、高導熱瀝青基碳纖維（即：中間相瀝青基碳纖維），兩者纖維截面結構如下所示。
Therefore, the isotropic pitch raw materials can only be used to process low modulus pitch-based carbon fibers (i.e., general-purpose pitch-based carbon fibers), while mesophase pitch can produce pitch-based carbon fibers with high modulus and high thermal conductivity coefficient (i.e., mesophase pitch-based carbon fibers). The cross section structure of the two fibers is shown below.
在獲得可紡性瀝青原料的基礎上，通過紡絲、不融化、碳化、石墨化以及表面處理即可製備高性能瀝青基碳纖維，大致流程如下圖所示。
On the basis of obtaining spinnable pitch raw materials, high performance pitch-based carbon fibers can be prepared by a series of processes such as spinning, non-melting, carbonization, graphitization and surface treatment. The general process is shown in the figure below.
在瀝青紡絲過程中，瀝青原料經過紡絲製備得到直徑約10μm的纖維的瀝青纖維，在紡絲過程中通過噴絲孔配置和攪拌方法可實現結構取向排列；同時，通過控制晶體取向和層間排列等可以優化諸如模量和強度之類的物理性能（圖4）。
In the spinning process of pitch, the pitch fiber with diameter of about 10μm is prepared from pitch raw materials through spinning, and the structure-oriented arrangement can be realized through the configuration of spinneret holes and stirring method during spinning process. At the same time, physical properties such as modulus and strength can be optimized by controlling crystal orientation and interlaminar arrangement (Fig. 4).
目前世界上只有三家公司可以使用中間相瀝青作為紡絲材料來生產高性能碳纖維。但是只有NGF公司可以生產出晶體取向可控、不含缺陷結構（如下圖橫斷面斷裂缺陷）的高性能瀝青基碳纖維。
At present, only three companies in the world can use mesophase pitch as a spinning material to produce high-performance carbon fiber. But only NGF can produce high-performance pitch-based carbon fibers with controllable crystal orientation and free of defective structures. (as shown cross-sectional fracture defect).
對於絲束規格為12k即含有12,000根單絲的瀝青纖維而言，由於其具有較低的軟化點（300°C），當對纖維進行高溫熱處理時會導致熔融。為了實現瀝青纖維不熔不融，預先添加氧和其他元素以消除氫和其他雜質元素，同時通過精確控制用於提高軟化點的化學反應來提高分子鍵合能力。
For a 12k bituminous fiber with 12,000 single filaments, the low softening point (300°C) results in melting when the fiber is treated at very high temperatures. In order to achieve the non-melting of pitch fiber, oxygen and other elements are pre-added to eliminate hydrogen and other impure elements, and molecular bonding ability is improved by precise control of chemical reactions used to improve the softening point.
不熔化纖維經過無氧狀態的高溫處理，以除去碳以外的雜質和元素，並通過進一步提高熱處理溫度以改善模量和強度。表面處理主要用於提高碳纖維與樹脂界面結合能力。
The non-melted fiber is treated at high temperatures in an oxygen-free state to remove impurities and elements other than carbon, and the modulus and strength are improved by further increasing the heat treatment temperature. The surface treatment is mainly used to improve the bonding ability between carbon fiber and resin interface.
3 中間相瀝青基碳纖維應用
Application of metophase pitch-based carbon fiber
為了滿足各種應用，NGF公司提供了各種基於瀝青基碳纖維的原料，例如連續碳纖維（高性能）、短纖（低模量）、研磨碳纖維，以及通過浸漬熱固性樹脂製成的紗線，織物和預浸料（下圖所示）。
To meet a variety of applications, NGF offers a variety of pitch-based carbon fibers such as continuous carbon fiber (high performance), staple fiber (low modulus), ground carbon fiber, and yarn, fabrics, and prepregs made from impregnated thermosetting resins (as shown below).
目前NGF公司生產的通用級瀝青基碳纖維（拉伸模量50-150 GPa）越來越多的用於高爾夫球桿和魚竿領域。
NGF's general-purpose pitch-based carbon fibers (tensile modulus 50 - 150 GPa) are increasingly used in golf clubs and fishing rods.
生產難度相對較大的中間相瀝青基碳纖維（拉伸模量600 GPa或更高），目前已經用於液晶和半導體領域，以及各種印刷和成膜輥中零熱變形輥結構，此外在機器人部件和建築加固部件也獲得應用。而高模量瀝青基碳纖維在輕量化、高剛度需求的自行車賽車的車架上也實現應用。
Mesophase pitch-based carbon fibers (tensile modulus 600 GPa or higher), which are relatively difficult to produce, have been used in liquid crystal and semiconductor applications, as well as in zero-thermal deformation roller structures in various printing and film forming rollers, and in robot components and building reinforcement components. The high modulus pitch-based carbon fiber is also applied to the frame of lightweight and high stiffness racing bicycles.
大型機械工具機的長梁很重，由于振動會降低製造精度。因此，採用具有高減振能力的輕質碳纖維-增強複合材料可以有效降低工具機長梁的重量，並提高機械加工的精度（如下圖所示）。
The long arm of large mechanical machine tool is very heavy, and the vibration will reduce the manufacturing accuracy. Therefore, the use of lightweight carbon-fiber reinforced composite materials with high vibration reduction can effectively reduce the weight of the long arm of the machine tool and improve the machining accuracy (as shown in the picture below).
中間相瀝青基碳纖維具有高導熱性，加工成複合材料後，可以將其熱膨脹係數降至零，瀝青基碳纖維與其它材料熱導率、熱膨脹係數對比如下圖所示。
Mesophase pitch-based carbon fiber has high thermal conductivity. After being processed into composite materials, its thermal expansion coefficient can be reduced to zero. Comparisons between the thermal conductivity and thermal expansion coefficient of pitch-based carbon fiber and the thermal conductivity and thermal expansion coefficient of other materials are as shown in the figure below.
基於該特性，目前在溫度波動高達60％的太空中工作的電子設備、太陽能電池板部件以及人造衛星天線部件的熱輻射部件等均已採用中間相瀝青基碳纖維。
Based on this characteristic, the mesophase pitch-based carbon fibers are used in electronic equipment, solar panel components and thermal radiation components of satellite antenna components, which currently operate in space with temperature fluctuations of up to 60%.
由於中間相瀝青基碳纖維兼具了高模量（900 GPa）和高導熱（1000 W）等特性，因此為了促進瀝青基碳纖維的應用，NGF公司從兩個方向開拓市場。
In order to promote the application of mesophase pitch-based carbon fibers, NGF develops the market from two directions due to their characteristics such as high modulus (900 GPa) and high thermal conductivity (1000 W).
一是在工業領域逐漸用碳纖維替代金屬材料，具有高剛性的輕質瀝青基碳纖維可有助於減輕生產設備和裝置的重量；二是電子產品領域，隨著對電子設備裝置中更高功能性和更高密度的需求的增長，中間相瀝青基碳纖維的高散熱能力獲得青睞，因此可作為高導熱電子材料廣泛應用。
Firstly, carbon fiber is gradually used to replace metal materials in the industrial field. The lightweight pitch-based carbon fiber with high stiffness can help reduce the weight of production equipment and devices; Secondly, in the field of electronic products, with the increasing demand for higher functionality and density in electronic devices, mesophase pitch-based carbon fiber is favored by users because of its high heat dissipation capability, so it can be widely used as a high thermal conductivity electronic material.