CN115386032A

Movatterモバイル変換

Info

Publication number: CN115386032A
Application number: CN202211129619.3A
Authority: CN
Inventors: 李羽航; 林兴旺; 赵新新; 盖婷婷; 许红丽
Original assignee: Shandong Haike Innovation Research Institute Co Ltd
Current assignee: Shandong Haike Innovation Research Institute Co Ltd
Priority date: 2022-09-15
Filing date: 2022-09-15
Publication date: 2022-11-25

Abstract

The invention provides a preparation method and a reaction device of polyethylene-vinyl alcohol resin, belongs to the technical field of preparation processes of high-molecular copolymers, and can solve the technical problems of low production efficiency, unstable reaction and low monomer conversion rate of the traditional polymerization method of EVOH resin. The technical scheme comprises the following steps: injecting vinyl acetate, an initiator and a reaction solvent into a high-pressure mixer, and fully mixing to obtain a mixture; injecting the mixture into a first reaction kettle, and adjusting the pressure and temperature of the first reaction kettle to obtain a first-stage reaction polymerization solution; injecting the first-stage reaction polymerization liquid into a second reaction kettle, adjusting the pressure and the temperature of the second reaction kettle, and intermittently adding an initiator and a reaction solvent to obtain a second-stage reaction polymerization liquid; stopping the reaction, cooling, collecting the polymerization solution, and performing reduced pressure distillation, saponification, precipitation and cleaning to obtain the polyethylene-vinyl alcohol resin finished product. The invention can be applied to the preparation of polyethylene-vinyl alcohol resin.

Description

Translated fromChinese

聚乙烯-乙烯醇树脂的制备方法及反应装置Preparation method and reaction device of polyethylene-vinyl alcohol resin

技术领域technical field

本发明属于高分子共聚物的制备工艺技术领域，尤其涉及一种聚乙烯-乙烯醇树脂的制备方法及反应装置。The invention belongs to the technical field of preparation technology of polymer copolymers, and in particular relates to a preparation method and reaction device of polyethylene-vinyl alcohol resin.

背景技术Background technique

聚乙烯-乙烯醇树脂(简称“EVOH树脂”，别名乙烯-乙烯醇聚合物，英文名Ethylenevinyl alcohol copolymer)。EVOH树脂是一种应用广泛、性能优良的高阻隔性材料，主要应用于食品、医药、化妆品、油箱等的包装。EVOH树脂的显著特点是对气体具有优异的阻隔性和良好加工性，而且其制品呈现出优异的透明性、光泽性、耐磨性和耐寒性能。EVOH的阻隔性能和加工性能主要取决于乙烯在聚合物中所占比例，乙烯所占比例增加会增强加工性能，同时也会使气体阻隔性下降。因为EVOH的阻隔性能和加工性能主要取决于乙烯在聚合物中所占比例，所以不同乙烯含量的聚合物其性质存在较大的差异性，同样也会在后期加工过程出现黄变或晶点等问题。在连续聚合生产工艺中控制聚合物中乙烯含量和分子量分布的一直是困扰其生产的重点和难点。Polyethylene-vinyl alcohol resin (referred to as "EVOH resin", alias ethylene-vinyl alcohol polymer, English name Ethylenevinyl alcohol copolymer). EVOH resin is a high barrier material with wide application and excellent performance. It is mainly used in the packaging of food, medicine, cosmetics, fuel tanks, etc. The remarkable feature of EVOH resin is that it has excellent gas barrier and good processability, and its products show excellent transparency, gloss, wear resistance and cold resistance. The barrier performance and processing performance of EVOH mainly depend on the proportion of ethylene in the polymer. An increase in the proportion of ethylene will enhance the processing performance and decrease the gas barrier performance. Because the barrier properties and processing properties of EVOH mainly depend on the proportion of ethylene in the polymer, the properties of polymers with different ethylene content are quite different, and yellowing or crystal points will also appear in the later processing process. question. Controlling the ethylene content and molecular weight distribution in the polymer in the continuous polymerization production process has always been the focus and difficulty of its production.

虽然经过几十年的发展，EVOH共聚物的合成技术已取得较大进展，但主要技术依然面临着相关国家企业的技术封锁。目前，仅有日本可乐丽公司的产品稳定性和加工性能最好，市场占有率也最高，其他厂家虽然液生产相应的产品，但其质量和性能仍有一定的差距，国内企业已开展EVOH研究多年，但是至今还未实现工业化。EVOH树脂的制备主要包含聚合和再皂化过程，但聚合反应过程中存在生产效率低，反应不稳定，导致后期单体、溶剂回收处理耗能大，生产工艺总成本高等问题。Although after decades of development, the synthesis technology of EVOH copolymer has made great progress, but the main technology still faces the technical blockade of relevant national enterprises. At present, only Japanese company Kuraray has the best product stability and processing performance, and the highest market share. Although other manufacturers produce corresponding products, there is still a certain gap in quality and performance. Domestic companies have carried out EVOH research For many years, but has not yet achieved industrialization. The preparation of EVOH resin mainly includes the process of polymerization and re-saponification, but there are problems such as low production efficiency and unstable reaction during the polymerization process, resulting in high energy consumption for monomer and solvent recovery and treatment in the later stage, and high total cost of the production process.

由此可见，研发一种生产效率高、聚合物生产更加稳定、单体转化率更高、溶剂回收处理量降低且成本可控制的聚乙烯-乙烯醇树脂的制备方法是解决上述问题的关键。It can be seen that developing a polyethylene-vinyl alcohol resin preparation method with high production efficiency, more stable polymer production, higher monomer conversion rate, reduced solvent recovery and controllable cost is the key to solving the above problems.

发明内容Contents of the invention

本发明针对EVOH树脂传统聚合方法存在生产效率低，反应不稳定、单体转化率低的技术问题，提出一种聚乙烯-乙烯醇树脂的制备方法及反应装置，其中该方法采用两个分级串联的反应釜聚合反应装置进行，通过控制不同反应釜内的聚合条件，对聚合反应提供了更大的缓冲空间，使聚合物生产更加稳定，单体转化率更高，溶剂回收处理量降低，有效的降低了生产成本。本发明对国内聚乙烯-乙烯醇树脂的研发和生产会具有很大的促进作用。Aiming at the technical problems of low production efficiency, unstable reaction and low monomer conversion rate in the traditional polymerization method of EVOH resin, the present invention proposes a preparation method and reaction device of polyethylene-vinyl alcohol resin, wherein the method adopts two stages in series By controlling the polymerization conditions in different reactors, a larger buffer space is provided for the polymerization reaction, which makes the production of polymers more stable, the conversion rate of monomers is higher, and the amount of solvent recovery and treatment is reduced, effectively reduced production costs. The invention will greatly promote the development and production of domestic polyethylene-vinyl alcohol resins.

为了达到上述目的，本发明采用的技术方案为：In order to achieve the above object, the technical scheme adopted in the present invention is:

聚乙烯-乙烯醇树脂的制备方法，采用两个分级串联的反应釜聚合反应装置进行，包括以下步骤：The preparation method of polyethylene-vinyl alcohol resin is carried out by adopting two graded series reactor polymerization reaction devices, comprising the following steps:

向高压混料器、第一反应釜和第二反应釜中注入乙烯气体；Inject ethylene gas into the high pressure mixer, the first reactor and the second reactor;

将醋酸乙烯酯、引发剂和反应溶剂注入所述高压混料器中充分混合，得到混合物；Inject vinyl acetate, initiator and reaction solvent into the high-pressure mixer and mix thoroughly to obtain a mixture;

将所述混合物注入第一反应釜中，调节所述第一反应釜的压力和温度，控制醋酸乙烯酯单体转化率为10-50％，得到一段反应聚合液；injecting the mixture into a first reaction kettle, adjusting the pressure and temperature of the first reaction kettle, controlling the conversion rate of vinyl acetate monomer to 10-50%, and obtaining a first-stage reaction polymerization liquid;

将所述一段反应聚合液注入第二反应釜中，调节所述第二反应釜的压力和温度，并间歇加入引发剂和反应溶剂，控制醋酸乙烯酯单体转化率为30-90％，得到二段反应聚合液；Inject the polymerization solution of the first stage of reaction into a second reaction kettle, adjust the pressure and temperature of the second reaction kettle, and intermittently add an initiator and a reaction solvent to control the conversion rate of vinyl acetate monomer to 30-90%, and obtain Two-stage reaction polymerization solution;

向所述二段反应聚合液中加入阻聚剂终止反应，降温收集聚合液；Adding a polymerization inhibitor to the polymerization solution of the second stage reaction to terminate the reaction, cooling down to collect the polymerization solution;

所述聚合液依次经过减压蒸馏、皂化反应以及析出清洗处理后，制备得到所述聚乙烯-乙烯醇树脂成品。After the polymerization solution is subjected to vacuum distillation, saponification reaction and precipitation cleaning in sequence, the finished product of polyethylene-vinyl alcohol resin is prepared.

在一实施方式中，所述第一反应釜和第二反应釜均为全混流反应釜，所述第一反应釜和第二反应釜上均安装有减压阀。In one embodiment, both the first reactor and the second reactor are fully mixed flow reactors, and pressure reducing valves are installed on the first reactor and the second reactor.

在一实施方式中，所述第一反应釜和第二反应釜的加料方式均为连续添加，所述高压混料器的压力为2-8Mpa。In one embodiment, the feeding method of the first reactor and the second reactor is continuous addition, and the pressure of the high pressure mixer is 2-8Mpa.

在一实施方式中，所述第一反应釜的压力为2-8MPa，温度为50-90℃，停留时间为0.5-5h；所述第二反应釜的压力为1-7MPa，温度为40-100℃，停留时间为1-5h。In one embodiment, the pressure of the first reactor is 2-8MPa, the temperature is 50-90°C, and the residence time is 0.5-5h; the pressure of the second reactor is 1-7MPa, and the temperature is 40-90°C. 100°C, the residence time is 1-5h.

在一实施方式中，所述第一反应釜的压力为3-7MPa，温度为50-80℃，停留时间为0.5-3h；所述第二反应釜的压力为2-6MPa，温度为50-80℃，停留时间为1-3h。In one embodiment, the pressure of the first reactor is 3-7MPa, the temperature is 50-80°C, and the residence time is 0.5-3h; the pressure of the second reactor is 2-6MPa, and the temperature is 50-80°C. 80°C, the residence time is 1-3h.

在一实施方式中，所述引发剂选自偶氮类引发剂或过氧化物引发剂，所述反应溶剂为甲醇或甲醇与2-4碳原子数醇溶剂的混合物，其中，所述混合物中甲醇占比50-98％，2-4碳原子数醇溶剂占比2-50％。In one embodiment, the initiator is selected from azo initiators or peroxide initiators, and the reaction solvent is methanol or a mixture of methanol and an alcohol solvent with 2-4 carbon atoms, wherein in the mixture Methanol accounts for 50-98%, and alcohol solvent with 2-4 carbon atoms accounts for 2-50%.

在一实施方式中，在反应开始前，先用甲醇清洗所述第一反应釜和第二反应釜1-3次，再用氮气吹扫5-15min第一反应釜和第二反应釜置换后，抽真空至第一反应釜和第二反应釜的压力-0.08～-0.1MPa，最后用乙烯气体置换1-2次。In one embodiment, before the reaction starts, the first reactor and the second reactor are cleaned with methanol for 1-3 times, and then purged with nitrogen for 5-15min after the replacement of the first reactor and the second reactor , evacuated to the pressure of the first reactor and the second reactor -0.08 ~ -0.1MPa, and finally replaced with ethylene gas 1-2 times.

在一实施方式中，所述终止反应为：先将所述二段反应聚合液输入缓存槽中，再启动高压泵向二段反应聚合液注入阻聚剂溶液并计量进液质量，终止反应，待缓存槽温度降为25℃以下，缓慢调节减压阀至有气体排出，梯度调节减压阀至缓存槽压力为0Mpa，并收集聚合液。In one embodiment, the termination reaction is as follows: firstly input the second-stage reaction polymerization solution into the buffer tank, then start the high-pressure pump to inject the polymerization inhibitor solution into the second-stage reaction polymerization solution and measure the quality of the liquid to terminate the reaction, When the temperature of the buffer tank drops below 25°C, slowly adjust the pressure reducing valve until the gas is discharged, adjust the pressure reducing valve gradually until the pressure of the buffer tank is 0 MPa, and collect the polymerization liquid.

在一实施方式中，所述减压蒸馏为：向所述聚合液中不断加入甲醇或甲醇蒸汽除去未反应的醋酸乙烯酯单体，保证聚合物中醋酸乙烯酯含量低于100ppm；In one embodiment, the vacuum distillation is: continuously adding methanol or methanol vapor to the polymerization liquid to remove unreacted vinyl acetate monomer, so as to ensure that the vinyl acetate content in the polymer is lower than 100ppm;

所述皂化反应为：将1-20％的碱性甲醇溶液加入到5-35％固含率的聚合液中，并不断加入甲醇或甲醇蒸汽，将产生的醋酸甲酯及时排出，反应结束向反应体系中加入一定量乙酸将溶液pH调节至5，得到醇解液；The saponification reaction is as follows: adding 1-20% alkaline methanol solution to the polymerization solution with 5-35% solid content, and continuously adding methanol or methanol steam, discharging the produced methyl acetate in time, and sending the reaction to A certain amount of acetic acid is added to the reaction system to adjust the pH of the solution to 5 to obtain an alcoholysis solution;

析出清洗处理为：将所述醇解液在4-12倍冷水中析出后，再用同析出相同量的水清洗2-3次，将清洗后的聚合物置于60-100℃真空烘箱中干燥2-8h，得到所述聚乙烯-乙烯醇树脂成品。Precipitation and cleaning treatment is as follows: after the alcoholysis solution is precipitated in 4-12 times cold water, and then washed with the same amount of water as the precipitation for 2-3 times, the cleaned polymer is placed in a vacuum oven at 60-100°C to dry 2-8h to obtain the finished polyethylene-vinyl alcohol resin.

本发明还提供了一种用于制备上述任一实施方式所述的聚乙烯-乙烯醇树脂的聚合反应装置，包括：The present invention also provides a polymerization reaction device for preparing the polyethylene-vinyl alcohol resin described in any one of the above embodiments, including:

高压混料器，用于将醋酸乙烯酯、引发剂和反应溶剂混合均匀，High-pressure mixer for uniform mixing of vinyl acetate, initiator and reaction solvent,

第一反应釜，其进料口连接所述高压混料器的出料口，用于制备一段反应聚合液，The first reaction kettle, its feed port is connected to the discharge port of the high-pressure mixer, and is used to prepare a stage of reaction polymerization liquid,

第二反应釜，其进料口连接所述第一反应釜的出料口，制备二段反应聚合液，及A second reaction kettle, the feed port of which is connected to the discharge port of the first reaction kettle to prepare a two-stage reaction polymerization liquid, and

缓存槽，其进料口连接所述第二反应釜底部的出料口，用于对所述二段反应聚合液进行终止反应；A buffer tank, the feed port of which is connected to the discharge port at the bottom of the second reaction kettle, for terminating the reaction of the second-stage reaction polymerization liquid;

其中，所述第一反应釜和第二反应釜上安装有减压阀，所述第一反应釜出料口与所述第二反应釜之间的管路上设有高压泵。Wherein, a pressure reducing valve is installed on the first reactor and the second reactor, and a high-pressure pump is arranged on the pipeline between the discharge port of the first reactor and the second reactor.

与现有技术相比，本发明的优点和积极效果在于：Compared with prior art, advantage and positive effect of the present invention are:

1、本发明提出的聚乙烯-乙烯醇树脂的制备方法及反应装置，该方法采用两个分级串联的反应釜聚合反应装置进行，通过控制不同反应釜内的聚合条件，对聚合反应提供了更大的缓冲空间，使聚合物生产更加稳定，单体转化率更高，溶剂回收处理量降低，有效的降低了生产成本；1. The preparation method and reaction device of the polyethylene-vinyl alcohol resin proposed by the present invention, the method adopts two graded series reactor polymerization reaction devices to carry out, by controlling the polymerization conditions in different reactors, the polymerization reaction is provided more Large buffer space makes polymer production more stable, monomer conversion rate is higher, solvent recovery treatment volume is reduced, and production cost is effectively reduced;

2、本发明提出的聚乙烯-乙烯醇树脂的制备方法能够有效的控制反应速率，避免了单个反应釜聚合后期转化率高引起的聚合速率难控制、分子量分布宽等问题，使聚合物生产更加稳定，单体转化率更高，溶剂回收处理量降低，有效的降低了生产成本，提高了生产效率，减少单体和引发剂残留，从而降低生产成本。2. The preparation method of polyethylene-vinyl alcohol resin proposed by the present invention can effectively control the reaction rate, avoiding the problems of difficult control of the polymerization rate and wide molecular weight distribution caused by the high conversion rate in the later stage of polymerization in a single reactor, and making polymer production more efficient. Stable, higher conversion rate of monomers, reduced solvent recovery and treatment, effectively reducing production costs, improving production efficiency, reducing monomer and initiator residues, thereby reducing production costs.

附图说明Description of drawings

图1为本发明实施例所提供的用于制备聚乙烯-乙烯醇树脂的聚合反应装置结构示意图。Fig. 1 is a schematic structural diagram of a polymerization reaction device for preparing polyethylene-vinyl alcohol resin provided by an embodiment of the present invention.

上图中：In the picture above:

1、高压混料器；2、第一反应釜；3、第二反应釜；4、减压阀；5、高压泵；6、缓存槽。1. High-pressure mixer; 2. First reactor; 3. Second reactor; 4. Pressure reducing valve; 5. High-pressure pump; 6. Buffer tank.

具体实施方式Detailed ways

下面将对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

本发明实施例提供了一种聚乙烯-乙烯醇树脂的制备方法，采用两个分级串联的反应釜聚合反应装置进行，包括以下步骤：The embodiment of the present invention provides a preparation method of polyethylene-vinyl alcohol resin, which is carried out by adopting two graded series reactor polymerization reaction devices, including the following steps:

S1、向高压混料器、第一反应釜和第二反应釜中注入乙烯气体；S1, inject ethylene gas into the high pressure mixer, the first reactor and the second reactor;

在上述S1步骤正式向各反应装置中注入乙烯气体之前还包括前处理过程，即在反应开始前，先用甲醇清洗所述第一反应釜和第二反应釜1-3次，再用氮气吹扫5-15min第一反应釜和第二反应釜置换后，抽真空至第一反应釜和第二反应釜的压力-0.1Mpa，最后用乙烯气体置换1-2次。Before the above-mentioned S1 step officially injects ethylene gas into each reaction device, it also includes a pretreatment process, that is, before the reaction starts, the first reactor and the second reactor are cleaned with methanol for 1-3 times, and then blown with nitrogen. After sweeping for 5-15 minutes, the first reactor and the second reactor were replaced, and then vacuumed to the pressure of the first reactor and the second reactor -0.1Mpa, and finally replaced with ethylene gas for 1-2 times.

S2、将醋酸乙烯酯、引发剂和反应溶剂注入所述高压混料器中充分混合，得到混合物；S2. Inject vinyl acetate, initiator and reaction solvent into the high-pressure mixer and mix thoroughly to obtain a mixture;

在上述S2步骤中，所用的引发剂选自偶氮类引发剂或过氧化物引发剂，优选偶氮类引发剂，所用的反应溶剂为甲醇或甲醇与2-4碳原子数醇溶剂的混合物，其中，所述混合物中甲醇占比50-98％，2-4碳原子数醇溶剂占比2-50％。In above-mentioned S2 step, used initiator is selected from azo initiator or peroxide initiator, preferred azo initiator, used reaction solvent is the mixture of methanol or methyl alcohol and 2-4 carbon number alcohol solvent , wherein, in the mixture, methanol accounts for 50-98%, and alcohol solvent with 2-4 carbon atoms accounts for 2-50%.

S3、将所述混合物注入第一反应釜中，调节所述第一反应釜的压力和温度，控制醋酸乙烯酯单体转化率为10-50％，得到一段反应聚合液；S3. Pour the mixture into the first reactor, adjust the pressure and temperature of the first reactor, and control the conversion rate of vinyl acetate monomer to 10-50%, to obtain a first-stage reaction polymerization solution;

在上述S3步骤中，通过控制第一反应釜的温度、压力等参数，使得一段反应中醋酸乙烯酯单体转化率控制在10-50％，得到的一段反应聚合液直接进入第二反应釜中进行后续反应。In the above S3 step, by controlling the temperature, pressure and other parameters of the first reaction tank, the conversion rate of vinyl acetate monomer in the first-stage reaction is controlled at 10-50%, and the obtained first-stage reaction polymerization liquid directly enters the second reaction tank for follow-up reactions.

S4、将所述一段反应聚合液注入第二反应釜中，调节所述第二反应釜的压力和温度，并间歇加入引发剂和反应溶剂，控制醋酸乙烯酯单体转化率为30-90％，得到二段反应聚合液；S4. Inject the first-stage reaction polymerization liquid into the second reactor, adjust the pressure and temperature of the second reactor, and intermittently add initiator and reaction solvent to control the conversion rate of vinyl acetate monomer to 30-90% , to obtain the two-stage reaction polymerization solution;

在上述S4步骤中，通过控制第二反应釜的温度、压力等技术参数，使得二段反应中醋酸乙烯酯单体转化率控制在30-90％，能够显著提高生产效率和单体转化率，单体转化率可达到80％以上，有效降低了后期脱单体和回收处理的成本。In the above S4 step, by controlling the technical parameters such as the temperature and pressure of the second reactor, the vinyl acetate monomer conversion rate in the second stage reaction is controlled at 30-90%, which can significantly improve the production efficiency and the monomer conversion rate, The monomer conversion rate can reach more than 80%, which effectively reduces the cost of monomer removal and recycling in the later stage.

S5、向所述二段反应聚合液中加入阻聚剂终止反应，降温收集聚合液；S5, adding a polymerization inhibitor to the polymerization solution of the second stage reaction to terminate the reaction, cooling down to collect the polymerization solution;

在上述S5步骤中，所述的终止反应为：先将二段反应聚合液输入缓存槽中，再启动高压泵向二段反应聚合液注入阻聚剂溶液并计量进液质量，终止反应，待缓存槽温度降为25℃以下，缓慢调节减压阀至有气体排出，梯度调节减压阀至缓存槽压力为0Mpa，并收集聚合液。此外，考虑到本发明终止反应中用到的阻聚剂为化工领域常见的化学试剂，所以本发明并未对阻聚剂的具体类型做明确限定，本领域技术人员可根据试剂需要进行选择。此外，此处需要说明的是，此外，在本发明中的第一反应釜和第二反应釜是一个连续的反应体系，该S5步骤中加入阻聚剂并非在第二反应釜中进行，而是将所述二段反应聚合液输入另一专门的缓存槽中进行，加入阻聚剂后终止反应，降温收集聚合液。In the above step S5, the termination reaction is as follows: firstly input the second-stage reaction polymerization liquid into the buffer tank, then start the high-pressure pump to inject the polymerization inhibitor solution into the second-stage reaction polymerization liquid and measure the quality of the incoming liquid, terminate the reaction, wait When the temperature of the buffer tank drops below 25°C, slowly adjust the pressure reducing valve until the gas is discharged, adjust the pressure reducing valve gradually until the pressure of the buffer tank is 0Mpa, and collect the polymerization liquid. In addition, considering that the polymerization inhibitor used in the termination reaction of the present invention is a common chemical reagent in the chemical industry, the present invention does not clearly limit the specific type of the polymerization inhibitor, and those skilled in the art can choose according to the needs of the reagent. In addition, it needs to be explained here that, in addition, the first reactor and the second reactor in the present invention are a continuous reaction system, adding the polymerization inhibitor in the S5 step is not carried out in the second reactor, but The second-stage reaction polymerization solution is input into another special buffer tank, the reaction is terminated after adding a polymerization inhibitor, and the temperature is lowered to collect the polymerization solution.

S6、所述聚合液依次经过减压蒸馏、皂化反应以及析出清洗处理后，制备得到所述聚乙烯-乙烯醇树脂成品。S6. After the polymerization solution is sequentially subjected to vacuum distillation, saponification and precipitation cleaning, the finished product of polyethylene-vinyl alcohol resin is prepared.

在上述S6步骤中，所述减压蒸馏为：向所述聚合液中不断加入甲醇或甲醇蒸汽除去未反应的醋酸乙烯酯单体，保证聚合物中醋酸乙烯酯含量低于100ppm；In the above step S6, the vacuum distillation is: continuously adding methanol or methanol vapor to the polymerization liquid to remove unreacted vinyl acetate monomer, so as to ensure that the vinyl acetate content in the polymer is lower than 100ppm;

所述析出清洗处理为：将所述醇解液在4-12倍冷水中析出后，再用同析出相同量的水清洗2-3次，将清洗后的聚合物置于60-100℃真空烘箱中干燥2-8h，得到所述聚乙烯-乙烯醇树脂成品。The precipitation cleaning treatment is as follows: after the alcoholysis solution is precipitated in 4-12 times cold water, it is washed 2-3 times with the same amount of water as the precipitation, and the cleaned polymer is placed in a vacuum oven at 60-100°C drying in medium temperature for 2-8 hours to obtain the finished product of polyethylene-vinyl alcohol resin.

在一具体实施方式中，所述第一反应釜和第二反应釜均为全混流反应釜，所述第一反应釜和第二反应釜上均安装有减压阀。In a specific embodiment, both the first reactor and the second reactor are fully mixed flow reactors, and pressure reducing valves are installed on the first reactor and the second reactor.

在一具体实施方式中，所述第一反应釜和第二反应釜的加料方式均为连续添加，所述高压混料器的压力为2-8Mpa。In a specific embodiment, the feeding method of the first reactor and the second reactor is continuous addition, and the pressure of the high pressure mixer is 2-8Mpa.

在上述实施方式中，高压混料器的压力可选择2Mpa、3Mpa、4Mpa、5Mpa、6Mpa、7Mpa、8Mpa或根据实际需要选择上述限定范围内的任一数值均落在本发明的保护范围之内。In the above embodiment, the pressure of the high-pressure mixer can be selected from 2Mpa, 3Mpa, 4Mpa, 5Mpa, 6Mpa, 7Mpa, 8Mpa or any value within the above-mentioned limited range according to actual needs, which falls within the protection scope of the present invention .

在一具体实施方式中，所述第一反应釜的压力为2-8MPa，优选3-7MPa，温度为50-90℃，优选50-80℃，停留时间为0.5-5h，优选0.5-3h；所述第二反应釜的压力为1-7MPa，优选2-6MPa，温度为40-100℃，优选50-80℃，停留时间为1-5h，优选1-3h。In a specific embodiment, the pressure of the first reactor is 2-8MPa, preferably 3-7MPa, the temperature is 50-90°C, preferably 50-80°C, and the residence time is 0.5-5h, preferably 0.5-3h; The pressure of the second reactor is 1-7MPa, preferably 2-6MPa, the temperature is 40-100°C, preferably 50-80°C, and the residence time is 1-5h, preferably 1-3h.

在上述实施方式中，第一反应釜的压力具体可选择2Mpa、3Mpa、4Mpa、5Mpa、6Mpa、7Mpa、8Mpa或根据实际需要选择上述限定范围内的任一数值均落在本发明的保护范围之内，温度可选择50℃、60℃、70℃、80℃、90℃或根据实际需要选择上述限定范围内的任一数值均落在本发明的保护范围之内，停留时间可选择0.5h、1h、1.5h、2h、2.5h、3h、3.5h、4h、4.5h、5h或根据实际需要选择上述限定范围内的任一数值均落在本发明的保护范围之内；第二反应釜的压力可选择1Mpa、2Mpa、3Mpa、4Mpa、5Mpa、6Mpa、7Mpa或根据实际需要选择上述限定范围内的任一数值均落在本发明的保护范围之内，温度可选择40℃、50℃、60℃、70℃、80℃、90℃、100℃或根据实际需要选择上述限定范围内的任一数值均落在本发明的保护范围之内，停留时间可选择1h、2h、3h、4h、5h或根据实际需要选择上述限定范围内的任一数值均落在本发明的保护范围之内。In the above-mentioned embodiment, the pressure of the first reactor can be specifically selected from 2Mpa, 3Mpa, 4Mpa, 5Mpa, 6Mpa, 7Mpa, 8Mpa or any value within the above-mentioned limited range according to actual needs, which falls within the protection scope of the present invention Within the range, the temperature can be selected from 50°C, 60°C, 70°C, 80°C, 90°C, or any value within the above-mentioned limited range can be selected according to actual needs, which falls within the protection scope of the present invention, and the residence time can be selected from 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or select any value within the above-mentioned limited range according to actual needs and all fall within the protection scope of the present invention; The pressure can be selected from 1Mpa, 2Mpa, 3Mpa, 4Mpa, 5Mpa, 6Mpa, 7Mpa, or any value within the above-mentioned limited range can be selected according to actual needs, which falls within the protection scope of the present invention, and the temperature can be selected from 40°C, 50°C, 60°C °C, 70 °C, 80 °C, 90 °C, 100 °C or any value within the above-mentioned limited range selected according to actual needs falls within the protection scope of the present invention, and the residence time can be selected from 1h, 2h, 3h, 4h, 5h Or select any value within the above limited range according to actual needs, all fall within the protection scope of the present invention.

高压混料器1，用于将醋酸乙烯酯、引发剂和反应溶剂混合均匀，High-pressure mixer 1, is used for vinyl acetate, initiator and reaction solvent are mixed homogeneously,

第一反应釜2，其进料口连接所述高压混料器1的出料口，用于制备一段反应聚合液，Thefirst reaction kettle 2, its feed port is connected to the discharge port of the high-pressure mixer 1, and is used to prepare a section of reaction polymerization liquid,

第二反应釜3，其进料口连接所述第一反应釜2的出料口，制备二段反应聚合液，及Thesecond reaction kettle 3, its feed port is connected to the discharge port of thefirst reaction kettle 2 to prepare the second-stage reaction polymerization liquid, and

缓存槽6，其进料口连接所述第二反应釜3底部的出料口，用于对所述二段反应聚合液进行终止反应；Buffer tank 6, the feed port of which is connected to the discharge port at the bottom of thesecond reaction kettle 3, for terminating the reaction of the second-stage reaction polymerization liquid;

其中，所述第一反应釜2和第二反应釜3上安装有减压阀4，所述第一反应釜2出料口与所述第二反应釜3之间的管路上设有高压泵5。Wherein, thefirst reactor 2 and thesecond reactor 3 are equipped with apressure reducing valve 4, and the pipeline between the outlet of thefirst reactor 2 and thesecond reactor 3 is provided with a high-pressure pump 5.

为了更清楚详细地介绍本发明实施例所提供的聚乙烯-乙烯醇树脂的制备方法，下面将结合具体实施例进行描述。In order to describe the preparation method of the polyethylene-vinyl alcohol resin provided by the embodiments of the present invention in more detail, the following will be described in conjunction with specific examples.

实施例1Example 1

本实施例提供了一种聚乙烯-乙烯醇树脂的制备方法，具体为：The present embodiment provides a kind of preparation method of polyethylene-vinyl alcohol resin, specifically:

(1)反应釜清洗和除氧置换：用甲醇清洗反应釜3次，再用氮气吹扫9min反应釜置换后，抽真空至反应釜压力-0.1Mpa，最后用乙烯气体置换2次；(1) Reactor cleaning and deoxygenation replacement: wash the reactor with methanol for 3 times, then purge the reactor with nitrogen for 9 minutes and replace it, then vacuumize the reactor to -0.1Mpa, and finally replace it with ethylene gas twice;

(2)进料反应：启动气动增压泵往高压混料器1、第一反应釜2和第二反应釜3内注入乙烯气体，控制第一反应釜2压力为3.4MPa，并设定自动控制，启动高压泵5将0.2份偶氮二异丁腈、110份甲醇、10份乙醇和400份醋酸乙烯酯注入高压混料器1充分溶解，再进入第一反应釜2，调节反应釜温度为72℃，反应停留时间为1.5h，醋酸乙烯酯单体转化率为35％，得到一段反应聚合液；(2) Feed reaction: start the pneumatic booster pump to inject ethylene gas into thehigh pressure mixer 1, thefirst reactor 2 and thesecond reactor 3, control the pressure of thefirst reactor 2 to 3.4MPa, and set the automatic Control, start the high-pressure pump 5 and inject 0.2 parts of azobisisobutyronitrile, 110 parts of methanol, 10 parts of ethanol and 400 parts of vinyl acetate into the high-pressure mixer 1 to fully dissolve, then enter thefirst reactor 2, and adjust the temperature of the reactor The temperature is 72°C, the reaction residence time is 1.5h, the conversion rate of vinyl acetate monomer is 35%, and a reaction polymerization solution is obtained;

经高压泵5将一段反应聚合液打入第二反应釜3，控制第二反应釜3压力为3.1MPa，调节反应釜温度为65℃，并间歇加入0.05份偶氮二异丁腈和20份甲醇溶液，停留时间3.5h，醋酸乙烯酯单体转化率为75％，得到二段反应聚合液；A section of the reaction polymerization liquid is pumped into thesecond reactor 3 through the high-pressure pump 5, the pressure of thesecond reactor 3 is controlled to 3.1MPa, the temperature of the reactor is adjusted to 65°C, and 0.05 parts of azobisisobutyronitrile and 20 parts of Methanol solution, residence time 3.5h, conversion rate of vinyl acetate monomer is 75%, to obtain two-stage reaction polymerization liquid;

(3)反应结束：将步骤(2)得到的二段反应聚合液输入缓存槽6中，再向二段反应聚合液中注入0.5份对苯二酚阻聚剂溶液，终止反应，待聚合液温度降为25℃以下，缓慢调节减压阀至有乙烯气体排出，梯度调节减压阀至缓存槽6压力为0Mpa，收集聚合液；(3) The reaction ends: the second-stage reaction polymerization solution obtained in step (2) is input into thebuffer tank 6, and then 0.5 parts of hydroquinone inhibitor solution are injected into the second-stage reaction polymerization solution to terminate the reaction. When the temperature drops below 25°C, slowly adjust the pressure reducing valve until ethylene gas is discharged, and adjust the pressure reducing valve tobuffer tank 6 with a pressure of 0 Mpa to collect the polymerization liquid;

(4)脱除醋酸乙烯酯单体：用减压蒸馏的方式不断加入甲醇蒸汽除去未反应的醋酸乙烯酯单体，保证聚合物中醋酸乙烯酯单体含量低于100ppm；(4) Remove vinyl acetate monomer: constantly add methanol steam to remove unreacted vinyl acetate monomer by means of vacuum distillation to ensure that the content of vinyl acetate monomer in the polymer is lower than 100ppm;

(5)皂化反应：将8％氢氧化钠(相对醋酸乙烯酯摩尔量)甲醇溶液加入到30％固含率的聚合液中，并不断加入甲醇，将产生的醋酸甲酯及时排出；反应结束向反应体系中加入一定量乙酸中和至PH≈5；(5) saponification reaction: 8% sodium hydroxide (relative to vinyl acetate molar weight) methanol solution is added in the polymerization liquid of 30% solid content rate, and constantly add methyl alcohol, the methyl acetate that will produce is discharged in time; Reaction ends Add a certain amount of acetic acid to the reaction system to neutralize to PH≈5;

(6)析出清洗：将醇解液在8倍水中析出后，再用同析出相同量的水清洗3次；将清洗后的聚合物在85℃真空烘箱中干燥6h，得到EVOH树脂成品，产品参数见表1。(6) Precipitation and cleaning: after precipitating the alcoholysis solution in 8 times of water, wash it three times with the same amount of water as that of precipitating; dry the cleaned polymer in a vacuum oven at 85°C for 6 hours to obtain the finished product of EVOH resin, the product The parameters are shown in Table 1.

实施例2Example 2

(1)反应釜清洗和除氧置换：用甲醇清洗反应釜3次，再用氮气吹扫10min反应釜置换后，抽真空至反应釜压力-0.09Mpa，最后用乙烯气体置换2次；(1) Reactor cleaning and deoxygenation replacement: wash the reactor with methanol for 3 times, then purge the reactor with nitrogen for 10 minutes and replace it, then vacuumize the reactor to -0.09Mpa, and finally replace it with ethylene gas twice;

(2)进料反应：启动气动增压泵往高压混料器1、第一反应釜2和第二反应釜3内注入乙烯气体，控制第一反应釜2压力为5.5MPa，并设定自动控制，启动高压泵5将0.3份偶氮二异丁腈、120份甲醇、40份叔丁醇和450份醋酸乙烯酯混合溶液注入高压混料器1充分溶解，再进入第一反应釜2，调节反应釜温度为68℃，反应停留时间为3.5h，醋酸乙烯酯单体转化率为30％，得到一段反应聚合液；(2) Feed reaction: Start the pneumatic booster pump to inject ethylene gas into thehigh pressure mixer 1, thefirst reactor 2 and thesecond reactor 3, control the pressure of thefirst reactor 2 to 5.5MPa, and set the automatic Control, start the high-pressure pump 5 and inject 0.3 parts of azobisisobutyronitrile, 120 parts of methanol, 40 parts of tert-butanol and 450 parts of vinyl acetate mixed solution into the high-pressure mixer 1 to fully dissolve, then enter thefirst reaction kettle 2, adjust The temperature of the reaction kettle is 68°C, the reaction residence time is 3.5 hours, the conversion rate of vinyl acetate monomer is 30%, and a first-stage reaction polymerization solution is obtained;

经高压泵5将一段反应聚合液打入第二反应釜3，控制第二反应釜3压力为5.0MPa，调节反应釜温度为66℃，并间歇加入0.05份偶氮二异丁腈和30份甲醇溶液，反应停留时间4.0h，醋酸乙烯酯单体转化率为80％，得到二段反应聚合液；A section of the reaction polymerization liquid is poured into thesecond reactor 3 through the high-pressure pump 5, the pressure of thesecond reactor 3 is controlled to 5.0 MPa, the temperature of the reactor is adjusted to 66°C, and 0.05 parts of azobisisobutyronitrile and 30 parts of Methanol solution, the reaction residence time is 4.0h, the conversion rate of vinyl acetate monomer is 80%, and the two-stage reaction polymerization liquid is obtained;

(3)反应结束：将步骤(2)得到的二段反应聚合液输入缓存槽6中，再启动高压泵5向二段反应聚合液中注入0.6份对苯二酚阻聚剂溶液，终止反应；待聚合液温度降为25℃以下，缓慢调节减压阀至有乙烯气体排出，梯度调节减压阀至缓存槽6压力为0Mpa，收集聚合液；(3) End of reaction: the second-stage reaction polymerization solution obtained in step (2) is input into thebuffer tank 6, and then the high-pressure pump 5 is started to inject 0.6 parts of hydroquinone inhibitor solution into the second-stage reaction polymerization solution to terminate the reaction ;When the temperature of the polymerization solution drops below 25°C, slowly adjust the pressure reducing valve until ethylene gas is discharged, and adjust the pressure reducing valve tobuffer tank 6 with a pressure of 0 MPa, and collect the polymerization solution;

(4)脱除醋酸乙烯酯单体：用减压蒸馏的方式不断加入甲醇或甲醇蒸汽除去未反应的醋酸乙烯酯单体，保证聚合物中醋酸乙烯酯单体含量低于100ppm；(4) Remove vinyl acetate monomer: continuously add methanol or methanol steam to remove unreacted vinyl acetate monomer by means of vacuum distillation to ensure that the content of vinyl acetate monomer in the polymer is lower than 100ppm;

(5)皂化反应：将8％氢氧化钠(相对醋酸乙烯酯摩尔量)甲醇溶液加入到30％固含率的聚合液中，并不断加入甲醇，将产生的醋酸甲酯及时排出；反应结束向反应体系中加入一定量乙酸中和至PH≈5。(5) saponification reaction: 8% sodium hydroxide (relative to vinyl acetate molar weight) methanol solution is added in the polymerization liquid of 30% solid content rate, and constantly add methyl alcohol, the methyl acetate that will produce is discharged in time; Reaction ends A certain amount of acetic acid was added to the reaction system to neutralize to PH≈5.

(6)析出清洗：将醇解液在10倍水中析出后，再用相同量的去离子水清洗2次；将清洗后的聚合物在85℃真空烘箱中干燥6h，得到EVOH树脂成品，产品参数见表1。(6) Precipitation and cleaning: After the alcoholysis solution is precipitated in 10 times of water, it is washed twice with the same amount of deionized water; the cleaned polymer is dried in a vacuum oven at 85°C for 6 hours to obtain the finished product of EVOH resin, the product The parameters are shown in Table 1.

实施例3Example 3

(1)反应釜清洗和除氧置换：用甲醇清洗反应釜3次，再用氮气吹扫10min反应釜置换后，抽真空至反应釜压力-0.1Mpa，最后用乙烯气体置换2次；(1) Reactor cleaning and deoxygenation replacement: wash the reactor with methanol for 3 times, then purge the reactor with nitrogen for 10 minutes and replace it, then vacuumize the reactor to -0.1Mpa, and finally replace it with ethylene gas twice;

(2)进料反应：启动气动增压泵往高压混料器1、第一反应釜2和第二反应釜3内注入乙烯气体，控制第一反应釜压力为5.0MPa，启动高压泵5将0.2份偶氮二异庚腈、90份甲醇、30份叔丁醇和350份醋酸乙烯酯注入高压混料器1充分溶解，再进入第一反应釜2，调节反应釜温度为56℃，待压力稳定后关闭乙烯进气阀门，反应时间为2.0h，醋酸乙烯酯单体转化率为45％，得到一段反应聚合液；(2) Feed reaction: start the pneumatic booster pump and inject ethylene gas into the high-pressure mixer 1, thefirst reactor 2 and thesecond reactor 3, control the first reactor pressure to be 5.0MPa, start the high-pressure pump 5 to 0.2 parts of azobisisoheptanonitrile, 90 parts of methanol, 30 parts of tert-butanol and 350 parts of vinyl acetate are injected into the high-pressure mixer 1 to fully dissolve, and then enter thefirst reaction kettle 2, and adjust the temperature of the reaction kettle to 56°C. After stabilization, close the ethylene inlet valve, the reaction time is 2.0 h, the conversion rate of vinyl acetate monomer is 45%, and a reaction polymerization solution is obtained;

经高压泵5将一段反应聚合液打入第二反应釜3，控制第二反应釜3压力为4.6MPa，调节反应釜温度为53℃，待压力稳定后关闭乙烯进气阀门，并加入0.05份偶氮二异庚腈和40份甲醇溶液，反应时间3.5h，醋酸乙烯酯单体转化率为85％，得到二段反应聚合液；A section of the reaction polymerization solution is pumped into thesecond reactor 3 through the high-pressure pump 5, the pressure of thesecond reactor 3 is controlled to 4.6MPa, the temperature of the reactor is adjusted to 53°C, and the ethylene inlet valve is closed after the pressure is stabilized, and 0.05 parts of Azobisisoheptanonitrile and 40 parts of methanol solution, the reaction time is 3.5h, the conversion rate of vinyl acetate monomer is 85%, and the second-stage reaction polymerization liquid is obtained;

(5)皂化反应：将10％氢氧化钠(相对醋酸乙烯酯摩尔量)甲醇溶液加入到30％固含率的聚合液中，并不断加入甲醇，将产生的醋酸甲酯及时排出；反应结束向反应体系中加入一定量乙酸中和至PH≈5；(5) saponification reaction: 10% sodium hydroxide (relative to vinyl acetate molar weight) methanol solution is added in the polymerization liquid of 30% solid content rate, and constantly add methyl alcohol, the methyl acetate that will produce is discharged in time; Reaction ends Add a certain amount of acetic acid to the reaction system to neutralize to PH≈5;

(6)析出清洗：将醇解液在8倍水中析出后，再用相同量的去离子水清洗2次；将清洗后的聚合物在85℃真空烘箱中干燥6h，得到EVOH树脂成品，产品参数见表1。(6) Precipitation and cleaning: After precipitating the alcoholysis solution in 8 times of water, wash it twice with the same amount of deionized water; dry the cleaned polymer in a vacuum oven at 85°C for 6 hours to obtain the finished product of EVOH resin, the product The parameters are shown in Table 1.

实施例4Example 4

(2)进料反应：启动气动增压泵往高压混料器1、第一反应釜2和第二反应釜3内注入乙烯气体，控制第一反应釜2压力为3.8MPa，启动高压泵5将0.25份偶氮二异丁腈、100份甲醇、10份乙醇和350份醋酸乙烯酯注入高压混料器1充分溶解，再进入第一反应釜2，调节反应釜温度为63℃，待压力稳定后关闭乙烯进气阀门，反应停留时间为3.5h，醋酸乙烯酯单体转化率为42％，，得到一段反应聚合液；(2) Feed reaction: start the pneumatic booster pump to inject ethylene gas into the high-pressure mixer 1, thefirst reactor 2 and thesecond reactor 3, control the pressure of thefirst reactor 2 to 3.8MPa, and start the high-pressure pump 5 Inject 0.25 parts of azobisisobutyronitrile, 100 parts of methanol, 10 parts of ethanol and 350 parts of vinyl acetate into the high-pressure mixer 1 to fully dissolve, and then enter thefirst reaction kettle 2. Adjust the temperature of the reaction kettle to 63°C. After stabilization, close the ethylene inlet valve, the reaction residence time is 3.5h, the conversion rate of vinyl acetate monomer is 42%, and a reaction polymerization solution is obtained;

经高压泵5将一段反应聚合液打入第二反应釜3，控制第二反应釜3压力为4.6MPa，调节反应釜温度为67℃，待压力稳定后关闭乙烯进气阀门，并加入0.05份偶氮二异丁腈和30份甲醇溶液，停留时间4.5h，醋酸乙烯酯单体转化率为87％，得到二段反应聚合液；A section of the reaction polymerization solution is poured into thesecond reactor 3 through the high-pressure pump 5, the pressure of thesecond reactor 3 is controlled to 4.6MPa, the temperature of the reactor is adjusted to 67°C, and the ethylene inlet valve is closed after the pressure is stabilized, and 0.05 parts of Azobisisobutyronitrile and 30 parts of methanol solution, the residence time is 4.5h, the conversion rate of vinyl acetate monomer is 87%, and the second-stage reaction polymerization liquid is obtained;

(3)反应结束：将步骤(2)得到的二段反应聚合液输入缓存槽6中，再启动高压泵5向二段反应聚合液中注入0.8份对苯二酚阻聚剂溶液，终止反应；待反应釜温度降为25℃以下，缓慢调节减压阀至有乙烯气体排出，梯度调节减压阀至缓存槽6压力为0Mpa，收集聚合液；(3) End of reaction: the second-stage reaction polymerization solution obtained in step (2) is input in thebuffer tank 6, and then the high-pressure pump 5 is started to inject 0.8 parts of hydroquinone inhibitor solution into the second-stage reaction polymerization solution to terminate the reaction ;When the temperature of the reactor drops below 25°C, slowly adjust the pressure reducing valve until ethylene gas is discharged, and adjust the pressure reducing valve tobuffer tank 6 with a pressure of 0 MPa, and collect the polymerization liquid;

(5)皂化反应：将10％氢氧化钠(相对醋酸乙烯酯摩尔量)甲醇溶液加入到30％固含率的聚合液中，并不断加入甲醇，将产生的醋酸甲酯及时排出；反应结束向反应体系中加入一定量乙酸中和至PH＝5；(5) saponification reaction: 10% sodium hydroxide (relative to vinyl acetate molar weight) methanol solution is added in the polymerization liquid of 30% solid content rate, and constantly add methyl alcohol, the methyl acetate that will produce is discharged in time; Reaction ends Add a certain amount of acetic acid to the reaction system to neutralize to PH=5;

(6)析出清洗：将醇解液在8倍水中析出后，再用相同量的去离子水清洗2次；将清洗后的聚合物在90℃真空烘箱中干燥7h，得到EVOH树脂成品，产品参数见表1。(6) Precipitation and cleaning: After the alcoholysis solution is precipitated in 8 times of water, it is washed twice with the same amount of deionized water; the cleaned polymer is dried in a vacuum oven at 90°C for 7 hours to obtain the finished product of EVOH resin, the product The parameters are shown in Table 1.

实施例5Example 5

(2)进料反应：启动气动增压泵往高压混料器1、第一反应釜2和第二反应釜3内注入乙烯气体，控制第一反应釜2压力为3.2MPa，并设定自动控制，启动高压泵5连续往高压混料器中注入反应溶液(0.2份偶氮二异丁腈、120份甲醇和400份醋酸乙烯酯混合溶液)，待充分溶解后再进入第一反应釜2，调节反应釜温度为58℃，反应停留时间为3h，醋酸乙烯酯单体转化率为35％，得到一段反应聚合液；(2) Feed reaction: Start the pneumatic booster pump to inject ethylene gas into thehigh pressure mixer 1, thefirst reactor 2 and thesecond reactor 3, control the pressure of thefirst reactor 2 to 3.2MPa, and set the automatic Control, start the high-pressure pump 5 to continuously inject the reaction solution (0.2 parts of azobisisobutyronitrile, 120 parts of methanol and 400 parts of vinyl acetate mixed solution) into the high-pressure mixer, and enter thefirst reaction kettle 2 after fully dissolving , adjust the temperature of the reactor to be 58°C, the reaction residence time is 3h, the conversion rate of vinyl acetate monomer is 35%, and a reaction polymerization solution is obtained;

经高压泵5将一段反应聚合液连续打入第二反应釜3，控制第二反应釜3压力为3.0MPa，调节反应釜温度为65℃，并连续加入0.05份偶氮二异丁腈和20份甲醇溶液，停留时间3.5h，醋酸乙烯酯单体转化率为75％，得到二段反应聚合液；Through the high-pressure pump 5, a section of the reaction polymerization liquid is continuously poured into thesecond reactor 3, the pressure of thesecond reactor 3 is controlled to 3.0MPa, the temperature of the reactor is adjusted to 65°C, and 0.05 parts of azobisisobutyronitrile and 20 Part methanol solution, residence time 3.5h, vinyl acetate monomer conversion rate is 75%, obtains two-stage reaction polymerization liquid;

(3)反应结束：将步骤(2)得到的二段反应聚合液输入缓存槽6中，再启动高压泵5向二段反应聚合液中注入0.5份对苯二酚阻聚剂，终止反应；待聚合液温度降为25℃以下，缓慢调节减压阀至有乙烯气体排出，梯度调节减压阀至缓存槽6压力为0Mpa，收集聚合液；(3) end of reaction: the second-stage reaction polymerization liquid that step (2) obtains is imported in thebuffer tank 6, and then the high-pressure pump 5 is injected into the second-stage reaction polymerization liquid into 0.5 parts of hydroquinone polymerization inhibitor, and the reaction is terminated; When the temperature of the polymerization liquid drops below 25°C, slowly adjust the pressure reducing valve until ethylene gas is discharged, and adjust the pressure reducing valve tobuffer tank 6 with a pressure of 0 MPa, and collect the polymerization liquid;

(6)析出清洗：将醇解液在6倍水中析出后，再用同析出相同量的水清洗2次；将清洗后的聚合物在75℃真空烘箱中干燥10h，得到EVOH树脂成品，产品参数见表1。(6) Precipitation cleaning: Precipitate the alcoholysis solution in 6 times of water, and then wash it twice with the same amount of water as the precipitation; dry the cleaned polymer in a vacuum oven at 75°C for 10 hours to obtain the finished EVOH resin, the product The parameters are shown in Table 1.

实施例6Example 6

(2)进料反应：启动气动增压泵往高压混料器1、第一反应釜2和第二反应釜3内注入乙烯气体，控制第一反应釜2压力为5.0MPa，并设定自动控制，启动高压泵5连续往高压混料器1中注入反应溶液(0.35份偶氮二异丁腈、120份甲醇、10份叔丁醇和300份醋酸乙烯酯混合溶液)，待充分溶解后再注入第一反应釜2，调节反应釜温度为67℃，反应停留时间为3.0h，醋酸乙烯酯单体转化率为50％，得到一段反应聚合液；(2) Feed reaction: Start the pneumatic booster pump to inject ethylene gas into thehigh pressure mixer 1, thefirst reactor 2 and thesecond reactor 3, control the pressure of thefirst reactor 2 to 5.0MPa, and set the automatic Control, start the high-pressure pump 5 to continuously inject the reaction solution (0.35 parts of azobisisobutyronitrile, 120 parts of methanol, 10 parts of tert-butanol and 300 parts of vinyl acetate mixed solution) into the high-pressure mixer 1, and then Inject into thefirst reaction kettle 2, adjust the temperature of the reaction kettle to 67°C, the reaction residence time to 3.0h, and the conversion rate of vinyl acetate monomer to 50%, to obtain a first-stage reaction polymerization solution;

经高压泵5将一段反应聚合液连续打入第二反应釜3，控制第二反应釜3压力为5.6MPa，调节反应釜温度为72℃，并连续加入0.07份偶氮二异丁腈和30份甲醇溶液，停留时间1.5h，醋酸乙烯酯单体转化率为83％，得到二段反应聚合液；Through the high-pressure pump 5, a section of the reaction polymerization liquid is continuously pumped into thesecond reactor 3, the pressure of thesecond reactor 3 is controlled to 5.6MPa, the temperature of the reactor is adjusted to 72°C, and 0.07 parts of azobisisobutyronitrile and 30 Part methanol solution, residence time 1.5h, vinyl acetate monomer conversion rate is 83%, obtains two-stage reaction polymerization liquid;

(6)析出清洗：将醇解液在10倍水中析出后，再用同析出相同量的水清洗2次；将清洗后的聚合物在85℃真空烘箱中干燥7h，得到EVOH树脂成品，产品参数见表1。(6) Precipitation cleaning: after precipitating the alcoholysis solution in 10 times of water, wash twice with the same amount of water as precipitating; dry the cleaned polymer in a vacuum oven at 85°C for 7 hours to obtain the finished product of EVOH resin, the product The parameters are shown in Table 1.

性能测试Performance Testing

本发明还对各实施例制备得到的EVOH树脂成品进行了各项性能测试，具体测试方法及测试结果如下：The present invention has also carried out various performance tests to the EVOH resin finished product that each embodiment prepares, and concrete test method and test result are as follows:

测试方法：乙烯含量测试采用H-NMR法测试后计算所得，分子量测试采用液相凝胶色谱仪测试，色度采用分光测色仪直接测试，熔指使用熔体流动速率仪测试；Test method: Ethylene content test is calculated by H-NMR method, molecular weight is tested by liquid gel chromatography, color is directly tested by spectrophotometer, melt index is tested by melt flow rate meter;

测试结果：见表1。Test results: see Table 1.

表1实施例1-6所得EVOH树脂成品的产品参数The product parameter of table 1 embodiment 1-6 gained EVOH resin finished product

通过分析表1数据可知，本发明采用两个分级串联的反应釜聚合反应装置进行，通过控制不同反应釜内的聚合条件，对聚合反应提供了更大的缓冲空间，使聚合物生产更加稳定，单体转化率更高，溶剂回收处理量降低，有效的降低了生产成本。本发明对国内聚乙烯-乙烯醇树脂的研发和生产会具有很大的促进作用。本发明通过控制不同聚合条件可得到不同组成和分子量的EVOH样品，且分子量分布均匀，树脂色度低加工性能优异。By analyzing the data in Table 1, it can be seen that the present invention adopts two graded series reactor polymerization reaction devices to carry out, and by controlling the polymerization conditions in different reactors, a larger buffer space is provided for the polymerization reaction, so that the polymer production is more stable. The monomer conversion rate is higher, the amount of solvent recovery and treatment is reduced, and the production cost is effectively reduced. The invention will greatly promote the development and production of domestic polyethylene-vinyl alcohol resins. In the invention, EVOH samples with different compositions and molecular weights can be obtained by controlling different polymerization conditions, and the molecular weight distribution is uniform, and the resin chromaticity is low and the processability is excellent.

Claims

1. The preparation method of the polyethylene-vinyl alcohol resin is characterized by adopting two reaction kettle polymerization reaction devices which are connected in series in a grading way, and comprises the following steps:

injecting ethylene gas into the high-pressure mixer, the first reaction kettle and the second reaction kettle;

injecting vinyl acetate, an initiator and a reaction solvent into the high-pressure mixer, and fully mixing to obtain a mixture;

injecting the mixture into a first reaction kettle, adjusting the pressure and the temperature of the first reaction kettle, and controlling the conversion rate of vinyl acetate monomer to be 10-50% to obtain a first-stage reaction polymerization liquid;

injecting the first-stage reaction polymerization liquid into a second reaction kettle, adjusting the pressure and the temperature of the second reaction kettle, intermittently adding an initiator and a reaction solvent, and controlling the conversion rate of a vinyl acetate monomer to be 30-90% to obtain a second-stage reaction polymerization liquid;

adding a polymerization inhibitor into the second-stage reaction polymerization liquid to terminate the reaction, and cooling and collecting the polymerization liquid;

and (3) carrying out reduced pressure distillation, saponification reaction and precipitation and cleaning treatment on the polymerization solution in sequence to obtain the finished product of the polyethylene-vinyl alcohol resin.

2. The method for preparing a polyethylene-vinyl alcohol resin according to claim 1, wherein the first reaction vessel and the second reaction vessel are both fully mixed flow reaction vessels, and a pressure reducing valve is installed on each of the first reaction vessel and the second reaction vessel.

3. The method for preparing a polyethylene-vinyl alcohol resin according to claim 1, wherein the first reaction vessel and the second reaction vessel are continuously fed, and the pressure of the high-pressure mixer is 2 to 8Mpa.

4. The method for preparing polyethylene-vinyl alcohol resin according to claim 1, wherein the pressure of the first reaction vessel is 2 to 8MPa, the temperature is 50 to 90 ℃, and the residence time is 0.5 to 5 hours; the pressure of the second reaction kettle is 1-7MPa, the temperature is 40-100 ℃, and the retention time is 1-5h.

5. The method for preparing a polyethylene-vinyl alcohol resin according to claim 4, wherein the pressure of the first reaction vessel is 3 to 7MPa, the temperature is 50 to 80 ℃, and the residence time is 0.5 to 3 hours; the pressure of the second reaction kettle is 2-6MPa, the temperature is 50-80 ℃, and the retention time is 1-3h.

6. The method for preparing a polyethylene-vinyl alcohol resin according to claim 1, wherein the initiator is selected from azo initiators or peroxide initiators, and the reaction solvent is methanol or a mixture of methanol and an alcohol solvent having 2 to 4 carbon atoms, wherein the mixture contains 50 to 98% of methanol and 2 to 50% of an alcohol solvent having 2 to 4 carbon atoms.

7. The method for preparing polyethylene-vinyl alcohol resin according to claim 1, wherein the first reaction vessel and the second reaction vessel are washed with methanol 1-3 times before the start of the reaction, then purged with nitrogen for 5-15min, and then vacuum-pumped to the pressure of-0.08 to-0.1 MPa in the first reaction vessel and the second reaction vessel, and finally replaced with ethylene gas 1-2 times.

8. The method for producing a polyethylene-vinyl alcohol resin according to claim 1, wherein the termination reaction is: inputting the second-stage reaction polymerization liquid into a buffer tank, starting a high-pressure pump to inject a polymerization inhibitor solution into the second-stage reaction polymerization liquid, metering the mass of the liquid inlet, stopping the reaction, slowly adjusting a pressure reducing valve until gas is discharged when the temperature of the buffer tank is reduced to below 25 ℃, adjusting the pressure reducing valve in a gradient manner until the pressure of the buffer tank is 0Mpa, and collecting the polymerization liquid.

9. The method for producing a polyethylene-vinyl alcohol resin according to claim 1, wherein the distillation under reduced pressure is: continuously adding methanol or methanol steam into the polymerization solution to remove unreacted vinyl acetate monomer, and ensuring that the content of vinyl acetate in the polymer is lower than 100ppm;

the saponification reaction comprises the following steps: adding 1-20% alkaline methanol solution into 5-35% solid content polymer solution, continuously adding methanol or methanol vapor, timely discharging generated methyl acetate, and adding a certain amount of acetic acid into a reaction system after the reaction is finished to adjust the pH of the solution to 5 to obtain an alcoholysis solution;

the precipitation cleaning treatment comprises the following steps: and (3) separating out the alcoholysis solution in 4-12 times of cold water, then washing for 2-3 times by using the same amount of water separated out, and drying the washed polymer in a vacuum oven at 60-100 ℃ for 2-8h to obtain the polyethylene-vinyl alcohol resin finished product.

10. A polymerization apparatus for preparing the polyethylene vinyl alcohol resin according to any one of claims 1 to 9, comprising:

a high-pressure mixer used for uniformly mixing the vinyl acetate, the initiator and the reaction solvent,

a feed inlet of the first reaction kettle is connected with a discharge outlet of the high-pressure mixer and is used for preparing first-stage reaction polymerization liquid,

a second reaction vessel having a feed inlet connected to the discharge outlet of the first reaction vessel for preparing a second-stage reaction polymerization solution, and

a feed inlet of the buffer tank is connected with a discharge outlet at the bottom of the second reaction kettle and is used for carrying out termination reaction on the second-stage reaction polymerization liquid;

the pressure reducing valves are installed on the first reaction kettle and the second reaction kettle, and a high-pressure pump is arranged on a pipeline between the discharge port of the first reaction kettle and the second reaction kettle.