【作者】 张震；

【导师】 王仕峰；

【作者基本信息】 上海交通大学 ， 化学， 2022， 博士

【摘要】 我国已迅速发展成为全球第一的橡胶制造和消费大国,由此产生的大量废旧橡胶给生态环境造成了巨大压力。废旧橡胶的再生利用既能减轻生态环境污染,又可补充我国相对短缺的橡胶资源。目前,工业再生技术通常在隔氧下进行,化学键的断裂基本上只发生在交联键上,而主链断裂较少。制备的再生胶的解交联程度低（约20%溶胶）,其尺寸在几十微米,主要作为填料使用。此外,再生胶生产的高能耗（约800 k W?h/t）,有害脱硫助剂带来的“二次污染”和再生胶的门尼反弹等问题也成为行业发展的掣肘。因此,在“双碳”背景下,发展绿色、高效的废旧橡胶再生方法迫在眉睫。本文选用典型轮胎橡胶天然橡胶（NR）和丁苯橡胶（SBR）为研究对象,基于其主链和交联硫键均易发生热氧化反应的特点,发展了轮胎橡胶的热氧高效解交联方法。通过调控热氧反应条件使主链和交联硫键均发生断裂,制备深度解交联（溶胶含量>40%）的再生胶。然后,研究了轮胎橡胶热氧反应的内在（橡胶交联网络的结构、反应位点等）和外在（温度、油份、气氛和引发剂等）因素对解交联的影响,为轮胎橡胶热氧解交联的工业化提供理论基础。最后,利用热氧解交联的再生胶制备橡胶制品和道路沥青等复合材料,并评价了其应用性能。首先,研究了NR和SBR硫化胶的热氧解交联过程。在空气氛围下,NR硫化胶的失重速率和其产物的溶胶含量较氮气气氛下均增加。240℃反应约7.5 min时为热氧解交联的转折点。在热氧降解后,溶胶的含量明显增加,其分子量降低而且分布变窄。在降解过程中,先后释放出二氧化硫（SO₂）与含碳的氧化物气体,表明交联键和主链先后发生了氧化断裂,并导致交联网络快速破坏。不同于NR硫化胶,SBR硫化胶在240℃下发生明显热氧炭化现象;在150℃和210℃下的SBR硫化胶热氧反应初期溶胶含量逐渐增加,达到最大值后开始下降,表明SBR硫化胶先解交联后发生二次交联反应。其次,研究了典型载重轮胎胶粉（NR为主）的热氧解交联过程。在空气氛围下,随温度的升高轮胎胶粉失重和溶胶含量而增大,且溶胶分子量逐渐降低。在240℃下胶粉热氧反应10 min时,产物中溶胶含量达55.9%,其中含有羰基和亚砜基官能团,同时有H₂O和CO₂等气体生成,表现出类似NR硫化胶热氧降解行为。采用改进的Friedman等变分法计算胶粉复杂的热氧解交联反应活化能,得出结果符合橡胶的自催化氧化反应。然后,针对SBR硫化胶热氧反应过程中容易二次交联的难题,研究了其经大豆油溶胀和过氧化氢（H₂O₂）作用下的热氧解交联。随着大豆油的增加,在150℃下SBR硫化胶解交联后的溶胶含量增加可至47.8%,而且溶胶分子量降低;凝胶中含有羟基和羰基官能团,且其交联密度明显下降。在H₂O₂作用下,SBR硫化胶发生低温氧化解交联。随着H₂O₂的用量增加,在100℃下SBR硫化胶解交联产物中溶胶含量增加且最高可达100%,凝胶中的氧化官能团数量随时间增加而增加。动力学分析表明H₂O₂降低了SBR硫化胶解交联初期反应活化能。最后,研究了热氧再生胶在橡胶制品和道路沥青材料中的应用。将旧卡车轮胎橡胶胶粉通过氧化法制备得到热氧再生胶,将其低比例应用于轮胎胎面胶和高比例应用于输送带的不同粘合层。在轿车轮胎胎面胶的应用结果表明,加入了热氧再生胶的混炼胶比加入传统再生胶的正硫化时间缩短,硫化胶的静态力学性能、热稳定性和耐溶剂抽出性能更好,在动态力学性能方面其60℃的损耗因子tanδ降低;将热氧再生胶高比例应用于输送带中力学性能和粘合性能能够满足使用标准,热氧再生胶储存时相比于传统再生胶门尼反弹较低。另外,热氧再生胶作为高性能改性剂和沥青组分,被用于制备高粘弹复合改性沥青和高掺量改性沥青,研究发现高粘弹复合改性沥青的高温稳定性和低温应力敏感性等性能相对SBS（苯乙烯-丁二烯-苯乙烯嵌段共聚物）改性沥青有所提高,其制备的沥青混合料水稳性能、抗车辙性能和低温弯曲性能等性能比SBS改性沥青混合料优异;高掺量热氧再生胶制备的改性沥青及其混合料具有良好的水稳定性能和高低温性能。综上,本研究摈弃传统再生法中仅断裂交联键的思路,发展了既断交联键又适当断主链的高效热氧解交联法,制备了高溶胶含量、微纳分散的再生胶,为再生胶产业的降本增效提供了理论基础。该再生胶以不同比例添加橡胶制品和改性沥青等复合材料实现高值化应用。此外,该研究也针对日益增多的SBR为主的轿车废旧轮胎,提出SBR硫化胶的高效热氧解交联反应策略,为轿车轮胎再生利用提供参考。更多还原

【Abstract】 China has rapidly developed into the largest rubber manufacturing and consuming country,resulting in a large amount of waste rubber.If these waste rubbers are improperly treated,they will have a bad impact on the environment.Recycling the waste rubbers into new materials not only helps protect the environment,but also alleviates the shortage of resources in our country.The traditional recycling method of waste rubber is to break only the cross-linked bonds in the rubber network under an inert atmosphere,but keep the main chain intact.The reclaimed rubber is still a filler with dozens of microns due to the low degree of reclamation.However,the industrial production by the traditional recycling methods is often accompanied by serious“secondary pollution”and high energy consumption process（～800 k W?h/t）,which seriously restricts the development of these recycling method.Therefore,it is of great significance to develop green and efficient recycling methods for waste rubber to achieve carbon peak and neutrality goals.In this paper,the typical tire rubber natural rubber（NR）and styrene butadiene rubber（SBR）were selected as the research objects.Based on the main chain and cross-linked sulfur bond prone to thermo-oxidative reaction,a high-efficiency thermo-oxidative reclaiming method of waste tire rubber was developed.The main chain and cross-linked sulfur bond were broken by adjusting the thermo-oxidative reaction conditions to prepare deep reclaimed rubber（sol content>40%）.Then,the internal（structure of rubber network,reaction sites,etc.）and external factors of thermal oxygen reaction of tire rubber were studied.The effects of temperature,oil,atmosphere and initiator on the reclaiming were explored.Finally,the reclaimed rubber was used to prepare rubber products and road asphalt,and its application performance was evaluated.Firstly,natural rubber（NR）and styrene butadiene rubber（SBR）were token as the research objects,which were the main component of tire rubber.The weight loss rate and the sol content of NR vulcanizate increased in air atmosphere compared with nitrogen atmosphere.The turning point of thermo-oxidative reclamation was obtained when the reaction time was about 7.5 min at 240℃.After thermo-oxidative reclamation,the sol content of NR vulcanizates significantly increased,its molecular weight decreased and its distribution became narrow,accompanied by the release of sulfur dioxide（SO₂）and carbon containing oxide gases.It indicated that the oxidative breakdown of the crosslinks and main chain successively occurred,leading to the rapid destruction of the crosslinked network.Different from NR vulcanizates,SBR vulcanizates has obvious carbonization phenomenon at 240℃.At 150℃and 210℃,the sol content of SBR vulcanizates gradually increased at the initial stage of thermo-oxidative reclamation,and then decreased after reaching the maximum value,indicating that the network of SBR vulcanizates degraded and then re-crosslinking reaction occurred.Secondly,the oxidative reaction of tire rubber powder at different temperatures was studied.Under aerobic condition,the weight loss and sol content of tire rubber powder increased with the increase of temperature,and the molecular weight of the sol decreased gradually.The sol content reached 55.9%after 10 min of de-crosslinking under aerobic condition.Carbonyl and sulfoxide functional groups were found in the products accompanied by the formation of H₂O and CO₂.The sol content increased as the generation of gas,indicating that the main chain and crosslinking bonds of rubber were effectively broken.According to the modified Friedman method,the activation energy of the complex oxygen reaction of rubber powder was calculated and the results showed that the reation followed autocatalytic oxidation mechanism.Thirdly,the oxidative reaction of SBR vulcanizates in the presence of soybean oil and hydrogen peroxide（H₂O₂）was studied because SBR vulcanizates are difficult to be degraded and recycle.With the increase of soybean oil,the content of SBR vulcanized sol increased to 47.8%at 150℃,and the molecular weight of the sol decreased.The gel products contained hydroxyl and carbonyl functional groups,and crosslinking density of the gel obviously decreases.On this basis of the above results,the oxygen reaction of SBR vulcanizates induced by H₂O₂ under low temperature was studied.With the increase of H₂O₂,the content of sol in the crosslinking product of SBR vulcanizate increased and reached up to 100%at 100℃and molecular weight of the sol decreased,and the carbonyl groups in the gel increased with time.In addition,the kinetic analysis showed that the addition of H₂O₂ reduced the initial reaction activation energy of the oxidative reaction of SBR vulcanizates.The addition of H₂O₂ and soybean oil can improve the degree of breakdown of SBR vulcanizate and reduce the re-crosslinking reaction.Finally,the application of the reclaimed rubber in rubber products and road asphalt materials was studied.Reclaimed rubber was prepared by oxidative reclamation.A small amount of the reclaimed rubber was applied to the tire tread rubber and a high proportion of the rubber was added to prepare different adhesive layers of conveyor belt.The results showed that the vulcanized rubber containing the reclaimed rubber has shorter curing time,better static mechanical properties,thermal stability and solvent extraction resistance compared with conventional reclaimed rubber.In addition,the reclaimed rubber,as a high-performance modifier and asphalt component,was used to prepare high viscoelastic modified asphalt and modified asphalt with high addition.It was found that the high temperature and low temperature properties of high viscoelastic modified asphalt were better compared with SBS modified asphalt.The water stability,rutting resistance and low temperature performance of the asphalt mixture with the reclaimed rubber were better than those of SBS modified asphalt mixture.The modified asphalt and its mixture prepared with high content of the reclaimed rubber had good water stability and high and low temperature performance.This paper abandoned the traditional recycling methods（only breaking the crosslinking bond）and developed a thermo-oxidative reclamation（both breaking the crosslinking bond and breaking the main chain）.The reclaimed rubber was prepared the with high sol content,which provided a theoretical basis and reference for the industrialization of rubber recycling to reduce energy consumption and cost.The reclaimed rubber was applied for rubber products and modified asphalt in different proportions,and its high value-added applications were initially promoted.In view of the increasing number of used car tires（mainly SBR）,the degradation degree and temperature of vulcanized SBR rubber were improved and the temperature was reduced,which provided reference for the recycling of car tires.更多还原