【作者】 刘伟华；

【导师】 李英民；

【作者基本信息】 沈阳工业大学 ， 材料加工工程， 2009， 博士

【摘要】 铸造对于机械工业的作用举足轻重，针对铸造生产过程中产生污染的防治也越来越急迫。在铸造生产中，传统的冷芯盒工艺如三乙胺法、SO₂法采用了对人体和环境有毒、有害的气体作催化剂或固化剂，不利于环境保护，开发对人体无毒、对环境无害的新型铸造粘结材料及工艺具有重要的意义。本文新型CO₂硬化酚醛树脂粘结剂的制备技术以及硬化机理的研究就是为适应这一要求而研究开发的。该粘结剂由特别合成的甲阶酚醛树脂、分散剂、交联剂和增强剂等组分组成，本研究的工作分为以下几部分：首先对甲阶酚醛树脂的合成机理、影响因素进行了基本的分析和探讨,并对合成工艺进行了优化研究,确定了最佳的合成工艺：催化剂选用NaOH，NaOH/苯酚=0.06/l（摩尔比），甲醛／苯酚=2.5/l（摩尔比），采用分段升温、甲醛滴加的合成工艺，并根据物料粘度控制反应终点，从而得到具有较佳分子量分布、较高粘结强度的甲阶酚醛树脂，为下一步粘结剂的制备打好基础。CO₂气体硬化酚醛树脂粘结剂的制备是本文的重点，在制备过程中选择了KOH作为分散剂、硼砂作为交联剂、硅烷作为增强剂，以强度为主要考察指标，通过正交试验对粘结剂的各组分进行选择和优化，得出CO₂气体硬化酚醛树脂粘结剂优化的配比为甲阶酚醛树脂：KOH:硼砂：硅烷=100：45：16：1。通过在粘结剂中添加两种有机活性助剂A剂、B剂，大幅度地提高了粘结剂的强度，初强度可达1.8MPa以上，终强度值可达4.0MPa以上，其中有机活性助剂A剂加入量为5％,B剂加入量为15％。有机活性助剂A剂、B剂的成功添加是本文大幅度提高粘结剂粘结强度的技术关键。针对粘结剂吹气硬化机理的研究有助于我们认识其硬化的实质，提高研究的理论水平。本文通过核磁共振氢谱分析仪对甲阶酚醛树脂进行分析，确定了其结构以及结构中官能团-CH₂-与-CH₂-O-CH₂-数量的比值。主要通过红外光谱分析，结合电镜、pH的测量等方法对硬化酚醛树脂粘结剂的硬化机理进行了深入的分析。研究发现粘结剂在CO₂的作用下，随着体系pH值的不断降低，硼酸盐的负离子先后与甲阶酚醛树脂的羟甲基和酚羟基发生交联反应而硬化，而有机活性助剂在粘结剂中起到了重要的络合、交联作用。研究中发现混砂过程中添加一些粉状物质能有效地促进粘结剂硬化，因此特别地配制了一种CO₂硬化酚醛树脂粘结剂的粉状促硬剂，是由Ca（OH）₂、硅酸盐水泥以及ZnO、MgO复合混制而成，原料便宜易得。试验得出促硬剂的优化配比为：Ca（OH）₂：5.0、ZnO：2.0g、MgO：1.5g、42.5^#水泥：3.0g，促硬剂加入量占树脂量30％左右效果较佳。促硬剂的添加可增加酚醛树脂粘结剂CO₂气体硬化的敏感性，缩短吹气硬化时间，在吹气硬化后，大幅度地提高了粘结剂的工艺强度，当粘结剂加入量为3.O％时，添加适量的促硬剂，能够达到初强度>1．8MPa，终强度>5.2MPa的技术水平。粉状促硬剂的研制成功，在提高粘结强度方面有所突破，并为CO₂气硬酚醛树脂的推广应用创造了有利的条件。为了进一步降低酚醛树脂粘结剂的成本，本文还对其新型交联剂进行了系统研究，研究发现了一种硅酸盐-R很有粘结潜力。通过试验确定粘结剂的各组分优化配比为：甲阶酚醛树脂：NaOH：R：硅烷=100：15：45：1.6，吹气硬化后获得了较高的终强度。针对这种交联剂初强度低的不足，对酚醛树脂进行了改性，通过在酚醛树脂合成过程中添加一定数量丙烯酸或聚丙烯酸钠进行接枝共聚，并添加一定量的Ca（OH）₂，使其初强度大幅度提高，达到0.8MPa以上，终强度达到4.0MPa以上。硅酸盐R作为交联剂制备的粘结剂成本低廉、终强度高，特点明显，值得进一步深入研究。最后对CO₂气体硬化酚醛树脂的制备进行了中试、对气硬酚醛树脂砂的可使用时间、发气量、溃散性等工艺性能进行了系统的测定，并进行了现场生产验证。该CO₂硬化酚醛树脂粘结剂成功地被用来制造铝合金铸件、铸铁件、铸钢件的砂芯，制芯过程简便，制芯速度很快，芯子溃散性好，生产出来的铸件内腔光洁，完全能够满足铸造生产的要求。采用该CO₂硬化酚醛树脂粘结剂的制芯成本大大低于三乙胺冷芯盒工艺，具有很广的推广应用前景。更多还原

【Abstract】 Foundry is very important in the development of mechanical industry and it is urgent to prevent the heavy pollution from the production of foundry. The conventional cold-box process used in foundry such as tertiary-amine-set process, SO₂-set process,β-Set process with gaseous catalysts or hardeners are so poisonous or harmful that it is necessary to develop a new cold box process with harmless gas to human body and environment. Researching on the new producing technique and curing mechanism of CO₂-cured phenolic resin binder in this paper is developed to be meet the requirement.The new resin binder is composed of a resol phenolic resin、a dispersant an cross-linking agent and a intensifier etc. The synthetic process of resol phenol-aldehyde resin has been studied at first, the synthetic process parameters of phenolic resin is optimized as followed : NaOH is choosed as a catalyst, NaOH/phenol=0.06/l（mole-ratio）, phenol/formaldehyde=1/2.5（mole-ratio）, The reacting temperature is divided into two steps and the formaldehyde is added by dropping. The reaction time is controlled by the viscosity of resin to get a suitable molecular weight with a good binding strength. The synthesis is an important base for the next binder production.The producing technique of binder is a critical point in this paper. According to the affection on the strength of binder, the optimum results has been achieved by the experiments of orthogonal design about the amounts of phenolic resin、alkali、borax and silane to form a steady binder system with high strength. The proportion of above factors is as followed: the phenolic resin: KOH : borax: KH-550=100: 45: 16: 1, To add two kind of organic active agents into the binder can improve the strength of binder greatly, the original strength （σ₀） is above 1.8 MPa and final strength(σ₂₄) is above 4.0MPa with the organic active agent A 5% and B 15% to the binder. The successful addition of organic active agents is a technical key to the production of binder.The research on the mechanism of binder can reveal the essential of curing process and can raise the research level to a higher standard. The CO₂-cured mechanism of phenolic resin is analyzed by MRI、IR、SEM and pH measure. The binder which can be cured by carbon dioxide gas, consists of an alkaline aqueous solution of a resol of phenolic resin and an oxyanion capable of forming a stable complex with the resin and sufficient of alkali to substantially prevent stable complex formation between the resin and the oxyanion. While passing carbon dioxide gas through the sands ,the pH of alkaline aqueous solution becomes lower and lower and the hydroxymethyl and hydroxy of the phenolic resin are linked with the oxyanions to form a stable complex and thereby to cure the resin. With the bonding bridge fracture analyzed by SEM, the organic active agents is believed to play an important role in cross-linking of binder too.A cheap curing-promoter which consists of Ca（OH）₂、42.5^#cement and two kind of metal-oxide is specially prepared for the binder. The optimization of the proportion of each part is confirmed by orthogonal test: Ca（OH）₂:5.0 g、42.5^#cement:3.0 g、ZnO:2.0g、MgO:1.5g and the right addition of curing-promoter is about 30% to the amount of binder. The curing-promoter can increase the strength of binder greatly and shorten the time of gassing .The original strength （σ₀） is above 1.8MPa and final strength(σ₂₄) is above 5.2MPa with 3.0% binder . The curing-promoter can increase the strength of binder so successfully that it is quite helpful to the application of CO₂-cured phenolic resin binder.A new and potential cross-linking agent which is a kind of silicate called R is researched for the CO₂-cured phenolic resin to decrease the cost of binder further more. The proportion of main parts of this cross-linking system is as followed: phenolic resin: NaOH: R: silane=100: 15:45: 1 with a high final strength(σ₂₄). A certain amount of acrylic acid、sodium polyacrylate、Ca（OH）₂ is used to get a original strength（σ₀） 0.8MPa.The cross-linking system with a low cost and a high final strength(σ₂₄) 4.0MPa is worthy for a further research.Finally, research has been carried out on the phenolic resin binder industrial production and some performance index of phenolic resin sand have been tested. The CO₂-cured binder has been used successfully for making aluminium-alloy、iron and steel castings. Through the production test, the binder can meet the requirement of the foundry production.Compared with tertiary amine-set process,the cost of the binder is much lower for a beneficiai use in foundry.更多还原