油劑是PAN原絲生產(chǎn)過程中必不可少的助劑，對PAN原絲的親水性、集束性、加工毛絲率、抗靜電性、耐摩擦性，碳化過程中耐溫性（不熔融、不粘絲、不并絲和不燃燒）等有重要的影響。國內(nèi)PAN原絲油劑的研究發(fā)展相對滯后，同國外相比有很大差距，國內(nèi)碳纖維生產(chǎn)所用油劑只能依賴進口，進口的油劑品種單一，價格昂貴，配方保密，碳纖維生產(chǎn)企業(yè)缺乏自主調(diào)配的能力，由此造成我國碳纖維原絲的碳化工藝受制于國外油劑技術(shù)要求，生產(chǎn)成本居高不下，嚴重制約我國碳纖維技術(shù)創(chuàng)新與發(fā)展。目前國內(nèi)外碳纖維原絲油劑的研究工作主要集中在高校與碳纖維生產(chǎn)企業(yè)，多數(shù)企業(yè)重點關(guān)注的是上油工藝對碳纖維品質(zhì)的影響，而高校的研究方向多集中在進口油劑成分的反向分析以及功能型復(fù)合油劑的配方研究，由此總結(jié)出，***常用油劑成分為聚醚改性硅油、氨基改性硅油和環(huán)氧改性硅油。

聚醚改性硅油是一種兩親聚合物，既具有親油性，同時又具有親水性，加入到PAN原絲油劑中，可以起到表面活性劑的作用，降低油劑表面張力。

氨基改性硅油由于含有強極性的氨基，能與纖維表面的羥基、羧基等極性基團發(fā)生相互作用，從而定向吸附在纖維表面，降低纖維之間的摩擦因數(shù)，賦予織物柔軟和平滑的整理效果。但氨基改性硅油乳化需要添加大量乳化劑，整理后的織物會出現(xiàn)親水性差或是久置變黃的缺點。

環(huán)氧改性硅油可以提高碳纖維原絲的耐熱性，防止原絲在預(yù)氧化過程中發(fā)生軟化、黏連、并絲的現(xiàn)象，***終導(dǎo)致毛絲量大，降低碳纖維性能，甚至是不能順利完成生產(chǎn)過程。

此外，環(huán)氧改性硅油、氨基改性硅油和聚醚改性硅油及其它添加助劑如抗靜電劑、消泡劑等在親水-親油性能方面差異非常大，使用外乳化劑制備復(fù)配油劑乳液時，乳液膠束內(nèi)油劑組成很難控制相同，另外復(fù)配油劑乳液中各種組分在聚丙烯腈碳纖維原絲表面親和力差異非常大，由此導(dǎo)致聚丙烯腈碳纖維原絲生產(chǎn)過程中上油在原絲表面的油劑組成及剩留在油槽中油劑的組成不斷改變，導(dǎo)致上油不穩(wěn)定和不連續(xù)，由此嚴重影響原絲的連續(xù)穩(wěn)定化生產(chǎn)及碳化后碳纖維的連續(xù)穩(wěn)定化生產(chǎn)，是碳纖維企業(yè)不能連續(xù)穩(wěn)定化生產(chǎn)T700、 T800 或更高等級碳纖維原因之一。

與此同時，硅系油劑也存在著不足：首先，在高溫條件下，硅系油劑會發(fā)生交聯(lián)，從液態(tài)轉(zhuǎn)變成半固態(tài)的膠狀，不僅失去潤滑作用，還會導(dǎo)致纖維單絲之間出現(xiàn)粘結(jié)，同時造成纖維纏輥，對設(shè)備與生產(chǎn)造成影響；然后，碳纖維的生產(chǎn)過程中會有高溫加熱的過程，硅系油劑轉(zhuǎn)化的無機氧化硅等殘留在纖維內(nèi)部或表面，降低了碳纖維的含碳量，影響纖維性能；國外一些企業(yè)與實驗室正在進行著低硅或非硅油劑的研發(fā)如日本松本油脂株式會社的專利中提到，以酯類化合物和聚硅氧烷為主要成分的油劑，硅系油劑占比在10%_~50%之間，可用作碳纖維原絲油劑的酯類結(jié)構(gòu)如下圖1所示，三菱人造絲公司的專利中提到，芳香酯也可用作碳纖維原絲油劑的主要成分，芳香酯的結(jié)構(gòu)如下圖2所示。

圖1可用作碳纖維原絲油劑的高級酯（R¹_~R¹⁰為碳原子數(shù)在7_~21的烴基）

圖2 可用作碳纖維原絲油劑的芳香酯（R¹、R²為碳原子數(shù)在11_~17的烴基，A¹與A²為乙基或丙基，m、n為1或2）

CURRENT DEVELOPMENT SITUATION OF AN OIL AGENT FOR A POLYACRYLONITRILE CARBON FIBER PRECURSOR AT BOTH HOME AND ABROAD

DATE: 2022.01.14

    An oil agent/spin finish was applied to synthetic polyacrylonitrile （PAN ）carbon fiber precursor for ease of processing during manufacturing.  An oil agent has an important impact on the hydrophilicity, bundling, fluffing, antistatic properties, friction resistance and temperature resistance (non-melting, non-sticking, non-merging and non- combustion) in the carbonization process of the PAN carbon fiber precursor.  The research and development of the PAN carbon fiber precursor spin finish/oil agent in China falls behind when compared with foreign countries. The oil agent currently used in domestic carbon fiber production is reliant on imports. The imported oil agent is limited to one brand, is expensive and much is unknown about the formula due to confidentiality. Therefore, carbon fiber manufacturers lack the ability of independent formulation of the oil agent, resulting in the carbonization process of the PAN carbon fiber precursor in China being subject to the technical requirements of foreign oil agents. In addition, the high production costs seriously restrict the technological innovation and development of carbon fiber in China. Currently, the research work of a PAN carbon fiber precursor oil agent at home and abroad are mainly from colleges and carbon fiber manufacturing enterprises. Most enterprises focus on the impact of coating processes of the oil agent on carbon fiber quality, while the research direction of colleges mostly focuses on the reverse analysis of imported oiling agent composition and the formula research of functional composite oil agents. It is concluded that the most commonly used oil agent components are polyether modified silicone oil, amino modified silicone oil and epoxy modified silicone oil.

    Polyether modified silicone oil is an amphiphilic polymer, which has both lipophilic and hydrophilic properties. When compounded with other components into a PAN carbon fiber precursor oil agent, it can play the role of a surfactant and reduce the surface tension of the oil agent.

    Amino modified silicone oil contains strong polar amino groups which can interact with polar groups such as hydroxyl and carboxyl groups on the PAN carbon fiber precursor surface. As a result, it can be directionally adsorbed on the fiber surface, reduce the friction coefficient between fibers, and give the fabric a soft and smooth finishing effect. On the other hand, the amino modified silicone oil emulsification requires a large amount of emulsifier resulting in the finished fabric having disadvantages such as poor hydrophilicity or yellowing after long-term setting.

    Epoxy modified silicone oil can improve the heat resistance of the PAN carbon fiber precursor and prevent the problems from softening, adhesion and merging of the PAN carbon fiber precursor in the pre-oxidation process. These problems eventually lead to a large number of fluffs, reduce the performance of carbon fiber, and reduce the production performance. In addition, an epoxy modified silicone oil, an amino modified silicone oil, a polyether modified silicone oil and other additives such as antistatic agents and defoaming agents have very different hydrophilic- lipophilic properties.  When using external emulsifiers to prepare the compounding emulsion of the oil agent, the composition inside the micelles of the oil agent emulsion is difficult to control uniformly. Furthermore, the surface affinity and adhesion of various components in the compounding oil agent emulsion to the PAN carbon fiber precursor vary considerably. As a result, the constant change of the composition of the oil agent that is either coated on the fiber surface or remaining in the oil tank, during the extruded spinning process of the polyacrylonitrile carbon fiber precursor, results in unstable and undesirable properties of the PAN carbon fiber precursor that is coated by the oil agent. This further affects the continuous and stable carbonization of the PAN carbon fiber precursor to produce high quality carbon fiber. For the reasons stated, carbon fiber enterprises can not continuously stabilize the production of T700, T800 or higher grade carbon fiber.

    Another point that requires stating is that there are issues in silicon based oil agents. Firstly, under high temperature conditions, silicon based oil agents will have cross-linked reactions and change happening from a liquid to a semi-solid colloid. This will not only result in a loss of lubrication, but also will lead to a merge between fiber monofilaments which may result in fiber winding, ultimately affecting equipment and production. Secondly, there will be a high-temperature heating process in the production of carbon fiber, and the inorganic silicon oxide transformed by the silicon oil agent remains in the interior or surface of the fiber. This may reduce the carbon content of carbon fiber and affect the performance. Due to this, some foreign enterprises and laboratories are developing low silicon or non-silicon oil agents. For example, it is mentioned in the patent of Japan Matsumoto Grease Co., Ltd. that silicon oil agents consist of ester compounds and polysiloxane as the main components. the polysiloxane accounts for 10% _~ 50%. The ester structure that can be used as a PAN carbon fiber precursor oil agent is shown in Figure 1 above and mentioned in the patent of Mitsubishi Rayon.  an aromatic ester can also be used as the main component of carbon fiber precursor oil agent. The structure of aromatic ester is shown in Figure 2 avove.