【作者】 范东斌；

【导师】 常建民； 李建章；

【作者基本信息】 北京林业大学 ， 木材科学与技术， 2009， 博士

【摘要】 随着我国经济的快速发展,建筑、运输行业发展迅猛,室外用定向刨花板、木质水泥模板、集装箱底板、高速列车车厢底板等户外用木质人造板的需求快速增加。其中建筑用木质水泥模板的产量和使用量最大。2009年我国木质胶合板模板使用量为4.1亿平方米,约占全年建筑模板用量的70%,预计到2012年这一比例将达80%以上。在现浇混凝土结构工程中,模板工程一般占混凝土结构工程造价的20%～30%,其中模板的价格直接影响模板工程的造价。北京是我国年建筑总量位于前列的城市,每年需要使用大量的木质水泥模板。木质水泥模板用多层胶合板的制造常常使用性能优良的酚醛树脂。但是,由于石油资源的紧缺以及石化下游产品价格的不断升高,给以苯酚为主要原料的酚醛树脂生产带来了诸多不稳定因素,使酚醛树脂胶粘剂的价格长期以来居高不下,导致其胶接的木制品的价格相对较高。目前国内外在降低酚醛树脂成本方面的研究主要集中在利用尿素、快速热解生物油、单宁、木质素和苯酚液化产物作为苯酚的替代物。虽然使用这些苯酚的替代物可以制备价格相对较低的酚醛树脂,但是,目前合成工艺所制备的酚醛树脂的储存期较短,粘度较大,生产工艺复杂,固化速度慢,固化温度高,且树脂中苯酚替代物的使用量不高。因此,开发使用尿素、快速热解生物油等苯酚替代物制备低成本、高性能、低温快速固化酚醛树脂的新型合成工艺势在必行。本论文分别以尿素、生物油为原料部分替代苯酚,在保证酚醛树脂优良物理、化学性能的前提下,采用分子调控方法研发了新型的合成工艺,通过共缩聚反应分别制备了低成本、高性能、低温快速固化的苯酚—尿素—甲醛(PUF)系列树脂和苯酚—生物油—甲醛(POF)系列树脂。通过优化合成工艺和使用现代分析方法对PUF树脂与POF树脂的性能进行了分析,以期全面了解合成工艺对树脂结构、固化特性以及固化后树脂物理性能的影响,探讨不同结构与树脂物理性能之间的关系以及不同催化剂对两类树脂低温快速固化的促进作用,为调控树脂的化学结构,制备出低成本、高性能、环保型的低温快速固化酚醛树脂提供理论依据。采用本新型合成工艺制备的PUF树脂和POF树脂不仅能够用于定向刨花板、混凝土模板、集装箱底板、高速列车车厢底板等户外用木质人造板的生产,还可用于替代价格较昂贵的纯酚醛树脂生产实木复合地板。本PUF树脂和POF树脂的开发利用,不仅具有巨大的市场潜力,广阔的市场空间和前景,还具有重大的经济效益和社会效益。同时,本课题所获得的研究成果为实现产品的工业化提供了科学依据和可行的技术路线。本论文的主要成果及结论如下:1.首次研发了高尿素含量PUF树脂的新型合成工艺。当F/P摩尔比为3.3、尿素添加量为89.4%、采用合成方法二制备的PUF树脂具有较好的胶合强度和较低的甲醛释放量。最佳合成工艺下PUF树脂制备胶合板的合理热压温度为150℃,在此温度下制备胶合板的胶合强度为0.78 MPa,达到国家标准GB/T 9846.3-2004Ⅰ类胶合板的标准要求。研究表明,PUF树脂的粘度与pH值随着尿素添加量的增多,呈现出先增加后减小的趋势,而固体含量随着尿素添加量的增加而缓慢地增加;随着储存时间的增加,PUF树脂的粘度呈现出先缓慢增加后显著增加的趋势,而树脂的pH值不受储存时间的影响。PUF树脂的固化速度随着尿素添加量的增加而逐渐减小,而固化过程中放出的反应热则呈现出上升的趋势。2.PUF树脂结构与固化特性的研究表明,新型合成工艺能够提高尿素单元与苯酚结构单元的反应性,使尿素单元很好地嵌入到PUF树脂的分子体系中。在树脂反应后期添加的尿素也可以参与PUF树脂的进一步缩聚反应,且随着尿素添加量的增加,树脂中共缩聚亚甲基的含量也随之相应地增加,同时也会提高树脂中低分子取代脲的含量;PUF树脂中低分子取代脲影响树脂的固化温度、反应热及固化速度等固化特性。3.本PUF树脂的合成原理大致分为两个阶段:1)加成反应,尿素与甲醛在碱性条件下进行加成反应生成多羟甲基脲;2)羟甲基脲上的空位氢、羟甲基与苯酚环上的羟甲基、活性空位(邻位或对位)发生共缩聚反应,同时,羟甲基脲彼此之间也发生了自缩聚反应。4.首次通过改变化学结构实现了PUF树脂的低温快速固化。研究表明,在PUF树脂的合成过程中加入Na2CO3、Ca(OH)2、MgO、ZnO等金属化合物,促进了树脂的合成反应,其中MgO的催化促进作用最为显著,而且使树脂增加了酚羟甲基之间的自身缩聚这一反应类型,同时也提高了树脂中共缩聚亚甲基的含量、对位酚羟甲基/邻位酚羟甲基的比例,降低了低分子取代脲含量,实现了PUF树脂的低温快速固化。金属化合物催化作用下PUF树脂的ΔH值均比NaOH催化作用的PUF0树脂高,说明复合催化剂下PUF树脂的固化反应比PUF0树脂剧烈、彻底。5.首次研发了高生物油替代率POF树脂的新型合成工艺,得出POF树脂的最佳合成工艺条件:F/P摩尔比为1.8,生物油替代率为50%,NaOH/P摩尔比为0.35,反应时间为60min。最佳合成工艺下POF树脂胶接胶合板的胶合强度可达Ⅰ类胶合板国家标准(不小于0.70 MPa)要求,甲醛释放量满足国家E0级(不大于0.5 mg/L)标准要求。研究表明,甲醛/苯酚(F/P)摩尔比、氢氧化钠用量(NaOH/P摩尔比)、生物油替代率、反应时间等合成工艺对POF树脂的pH值、固体含量、贮存期以及水混合性等性能指标的影响不大,而对树脂的粘度、游离酚含量、胶合板的胶合强度及其甲醛释放量的影响较大。新型合成工艺能够使生物油中多元酚组分很好地嵌入整个POF树脂体系。6.POF树脂结构的研究表明,固化后POF树脂的断面出现了大量蜂窝状且尺寸不等的近似圆形孔隙。POF树脂与酚醛树脂具有相似的结构和成分组成;生物油中多元酚类化合物能够与甲醛反应生成多元酚羟甲基,这些多元酚羟甲基可通过自身缩聚或与苯酚结构单元的活性羟甲基发生共缩聚反应生成亚甲基键。7.POF树脂低温快速固化的研究表明,MgO、Na2CO3及尿素催化作用的3种POF树脂可以实现低温快速固化,其中Na2CO3对树脂低温快速固化的促进作用最为显著。Na2CO3、尿素催化作用下POF树脂的固化反应比较剧烈,尤其是尿素催化作用的POF树脂由于尿素结构单元参与了固化,使固化反应变得更为复杂、剧烈。更多还原

【Abstract】 With the rapid development of construction and transport industry in china, exterior quality wood composite materials such as oriented strandboard, wood based cement template, container flooring, etc, have been greatly used for meeting the consumption demand. Especially, wood based cement template has the relatively large production and consumption. In 2009, about 410 million square meters of plywood panel template were used, which takes up 70% of building template dosage, and the proportion will reach more than 80% in 2012. The cement template usually influences the cost of the concrete construction, in which the cost of cement template accounts for 20%～30%. Building scale in Beijing lies at the forefront of all the china’s cities and lots of wood based cement template are used every year. The plywood panel for producing cement template usually use phenol formaldehyde (PF) resin as adhesive. However, the increasing cost of phenol due to the increase of oil cost has increased the cost of PF resins, which also makes the wood bonding products the relatively high cost. Considerable amount of research on the low-cost PF resins mainly focus on the Urea, fast pyrolysis bio-oil, tannin, lignin, and phenol liquefied products as substitutes for phenol in the synthesis at home and abroad. Although low-cost PF resins can be prepared by using these alternatives, these PF resins with current synthesis procedure have shorter storage time, higher viscosity and cuing temperature, slower curing rate and more complicated synthesis procedure, especially lower substitution proportion for phenol. Therefore, the development of the new synthesis procedure for manufacturing low-cost and high performance fast cuing PF resin based on the urea, fast pyrolysis bio-oil, etc, has become very imperative.In this dissertation, low-cost, well performance and fast curing phenol-urea-formaldehyde (PUF) resins and phenol-biomass oil-formaldehyde (POF) resins were respectively prepared by using urea and bio-oil as partial substitution of bio-oil via new type of synthetic method. Effect of the synthesis process parameters on structure, curing characteristics, and physical properties of PUF and POF resins were comprehensively discussed by optimizing the synthesis procedure and using modern analytical methods. The relationships between different structures and physical properties of resin and the accelerating effects of catalysts on the cure reaction of resins were also studied for provides a theoretical basis on the preparation of low-cost, high -performance and environmentally friendly fast-curing PF resins. In this dissertation, PUF and POF resins prepared by new synthesis procedure are applied for not only producing exterior quality wood composite materials such as oriented strandboard, wood based cement template, container flooring, etc, but also replacing expensive neat PF resins to produce wood composite floorings. The developed PUF and POF resins not only have huge market potential and broad prospects, but also bring significant economic and social benefits. The Obtained research results provide a scientific basis for industrialization of products and feasible technology routes. The main results from this study can be summarized as follows:1. A new type of synthetic method of PUF resins with high urea content was firstly developed. When the F / P molar ratio was 3.3 and urea addition level was 89.4%, PUF resin prepared by synthesis methodⅡpossessed good bonding strength and low formaldehyde emission. When the pressing temperature reached 150℃, the wet strength of plywood bonded by PUF resin was 0.78 MPa, which can pass the requirements of China Industry Standard for the exterior grade of structural plywood. When urea content in the PUF resins increased, the viscosity and pH value of resins presented first increasing and then decreasing trend, however, the solid content of resins increased. With the increase of storage time, the viscosity of PUF resins presented first slowly and then significantly increasing trend, however, the solid content of resins presented first significantly increasing and then unchanged trend, and the pH value was not nearly influenced. The curing enthalpy value gradually increased, however, the curing rate gradually decreased when urea content in PUF resins increased.2. The new synthetic method of PUF resins can improve the reactivity of urea with phenolic units and made methylolureas be well converted into cocondensed methylene groups between phenolic ring and methylolureas. Urea added at the end of the condensation reaction can also take part in the condensation reaction of PUF resins and furthermore, with the increase of urea addition content, the amount of cocondensed methylene and low molecule substituted urea gradually increased. Low molecule substituted urea in PUF resins influenced curing temperature, curing enthalpy value, and curing rate of resins.3. The synthetic principle of PUF resin by new synthetic method included two processes: 1) Addition reaction, namely, a mixture of methylolureas was synthesized in the reaction between urea and formaldehyde under the alkaline condition; 2) The cocondensed reaction of urea units including methylolureas and free urea with phenolic units took place, and self-condensation of methylolureas also existed.4. The fast cure of PUF resins under low temperature was firstly achieved by changing the chemical structure of resin. Sodium carbonate(Na2CO3), calcium hydroxide(Ca(OH)2), magnesium oxide(MgO), and zinc oxide (ZnO) added to reaction system can promote synthesis reaction of PUF resin especially the most significant promotion of MgO, increase the amount of cocondensed methylene groups and the ratio of para- and ortho- methylol group, and decrease the amount of low molecule substituted urea. Curing enthalpy value of PUF resins catalyzed by metal compounds were higher than PUF resin catalyzed by sodium hydroxide (NaOH), which indicated that the former possessed much stronger curing reaction than the latter.5. A new type of synthetic method of POF resin with high biomass oil replacement ratio was firstly developed. The optimum synthesis conditions were obtained: F / P molar ratio was 1.8, bio-oil substitution proportion was 50%, NaOH / P molar ratio was 0.35 and the reaction time was 60min. PUF resin with the optimum synthesis procedure can produceⅠlevel (≥0.70 MPa) of plywood and its formaldehyde emission level reached E0 (≤0.5 mg / L). The effect of F/P molar ratio, NaOH/P molar ratio, biomass oil replacement ratio, and reaction time on the pH value, solid content, storage time, and water-soluble property of POF resins were not obvious, but on the viscosity, free phenol content, and wet strength and formaldehyde emission of plywood were remarkable. The new synthetic method of POF can make polyhydric phenol in biomass oil be embedded into the molecular system of resin.6. There were lots of holes distribute around surface of cured POF resin. POF resins had similar chemical structure with pure PF resin and polyhydric phenol in biomass oil can react with formaldehyde to form polyhydric phenol methylols which reacted with each other to form self-condensation methylene or with phenolic units to form cocondensed methylene. Different kinds of aliphatic compounds and carbohydrate compounds in biomass oil can also take part in the condensation reaction of POF resins.7. Na2CO3, MgO, and urea added to reaction system can promote the fast cure of POF resin under low temperature, especially the most significant promotion of Na2CO3. Curing enthalpy value of POF resins catalyzed by Na2CO3, MgO, and urea were higher than POF resin catalyzed by NaOH, especially the most significant promotion of urea, which indicated that the resin catalyzed by urea had strongest curing reaction.更多还原