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Three major problems that may exist in low temperature and low pressure technology of domestic paperboard

最近,国内纸板行业正悄然流行“低温低压”技术,该技术的发展成熟将给国内纸板企业的生产力带来又一技术性革命。目前,国内部分纸板企业充当先锋勇于尝试,将“低温低压”技术率先应用在日常生产中。那么,究竟什么才是“低温低压”技术?另外,纸板生产中,配置多少蒸汽压力才算符合“低压”技术呢? 现状:国内低温低压技术应用情况并不乐观 曾有业内专家走访了国内数家运用“低温低压”技术较为成功的纸板企业,但明显发现“低温低压”技术实际运用情况并不乐观,如瓦线设计和实际生产情况均不乐观,致使产品质量也不稳定。此外,还发现当瓦线运行一段时间后,蒸汽压力又要恢复到以往的高压才能生产。 与欧美相比,我国低温低压技术上可能存在3大问题 该专家就低温低压技术,专门参观访问了欧洲发达国家多家纸板企业。通过交流和学习,基本了解了目前国外纸板企业所掌握的高新技术,与我国国内纸板企业所提出的“低温低压”概念,还是有偏差的,是值得商榷的。为此,笔者就以下几点心得与业内同仁分享: 控制各层纸和纸板的温度,控制低材质和高材质的温度 国内高速瓦线普遍采用“防弯翘系统”程序,通过检测和控制瓦线各关键点的纸板温度,确保纸板出驱动轮后的温度控制在合理的范围,致使纸板平整而不易变形。因此,我们需要控制各层纸和纸板的温度,控制低材质和高材质的温度。 在此提醒的是三层和五层纸板对热量的需求是不同的,如若采用统一的“低压”值生产纸板,那么瓦线供给的热量是无法满足纸板生产的热量需求 各部位的蒸汽压力并不是采用统一的“低压”值 笔者从国外提供的瓦线看其各部位配置的蒸汽压力情况,发现其蒸汽压力的分配也是有侧重点的。如一条幅宽2500mm,车速350m/min的瓦线,其蒸汽主管道蒸汽压力14kgf/cm².其压力分配大致如下:   (1)高定量纸板,双面机热板压力10-12 kgf/ cm².瓦楞棍压力8 kgf/cm².预热缸4-6 kgf/cm (2)低定量纸板,双面机热板压力6-8 kgf/ cm².瓦楞棍压力6 kgf/cm². 预热缸2-4 kgf/cm 从压力分配表中,我们可以看出,纸板定量不同,蒸汽供给压力量也是不同的。所以在瓦线生产过程中,各部位的蒸汽压力并不是采用统一的“低压”值。尤其是需要“高压”的瓦线部位,还是要采用“高压”生产,唯有如此才能确保瓦线的高效生产和纸板品质。 不能盲目跟学国外经验 从某种程度上看,对于300m/min车速的高速瓦线,如此蒸汽压力供给确实对我们来说算是一种“低压”了,但我们并不能盲目跟学。 笔者分析其主要原因如下:   <1>国外高速瓦线所配置的瓦辊和双面机热板,均是周边加热型的,相对于我们国内腔式加热容器,其热效能高,温度转换快,是我们无法效仿的。 <2>国外瓦线各加热容器为满足纸板加热温度,均实施了蒸汽压力自动调整。同时在关键部位加装了很多弧形加热器进行热量补偿,这是我们容易忽略的。 <3>国外纸板厂粘合剂工艺和使用的原料,也与我们有较大的差异。他们采用的是小麦淀粉,糊化温度一般控制在53摄氏度左右,而我们一般用的是玉米粉或木薯粉,糊化温度在56-60摄氏度之间。

2022

01-18

Why does the packaging carton factory not advocate large-scale watermark printing?

Carton customers often hear this kind of words, "do not recommend large area printing" or "can not do large area printing", this is why? First, large-area printing will increase production costs. First, the amount of printing plates and ink will increase, which directly increases production costs. Second, the scrap rate will increase, indirectly increasing costs. Second, the requirements for cardboard are relatively high, and the raw material levels of cardboard factories are different, resulting in cardboard transparent, hard and soft, which will affect the printing of cardboard. Then can't choose a better cardboard? I have learned that the cardboard is affected by the weather and humidity, and the amount of glue applied is more or less, and the cardboard will be uneven, and the cardboard factory will not return it. Third, the requirements for printing presses are strict. In this way, the printing machinery of the general carton factory is about 200000. It takes about 8 million or so to make a good large-area printing press. So if there is no way to print a large area? The answer is that there is a way to choose a carton factory with cardboard lines, which can directly intervene in the production of cardboard. Of course, such units have minimum order requirements. Like Shunfeng is the way to go. What if the amount is not so large? That can only choose ink printing, because ink printing is the first pattern printed on a piece of paper, in the paper on the corrugated, so as to avoid the impact of corrugated printing. Of course, this will increase the price of cartons. If the watermark is printed directly on the paper, is it OK to stick corrugated? In theory, this is the past, but it is still the problem of watermark machinery. General watermark machinery cannot be printed on paper, and the paper is too thin.

2022

01-18

What are the factors that affect the stiffness of paper board? Test method for stiffness of paper board

The importance of paper board stiffness: for box board paper and white board paper, stiffness is a basic performance index. Paper stiffness is a very important indicator, which directly affects the size of the crease stiffness (another influencing factor is die-cutting pressure), thus affecting the finished product forming. The stiffness is small, the finished product is easy to crush and warp; the stiffness is large, and the finished product is difficult to form. Packaging paper has requirements for stiffness. Different quantitative paper stiffness is different, generally proportional to the square of thickness. The thicker the cardboard, the higher the stiffness. Factors affecting bending stiffness There are many factors that affect stiffness. The thickness and elastic modulus of the paperboard are the most basic factors affecting the stiffness of the paperboard or paper. When the thickness is constant, the stiffness increases with the increase of tightness. When the weight is constant, it increases slightly with the increase of tightness and then decreases slightly, but the general trend is a net increase. Test method for stiffness of paper and board The measurement method of stiffness includes the bending strength of the fixed and unfixed angle test sample, and the strength change of the sample is measured by free bending. Some test methods have both. Clark and Graml are commonly used to measure the stiffness of paper.

2022

01-18

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