1. uneven coating
The thickness of the paint coated on the surface of the tinplate is different, and it is dried at the same temperature and speed. It is very easy to have insufficient hardening of the thick coating film and excessive hardening of the thin coating film. As a result, the adhesion, hardness, and durability of the coating film Corrosion, bending resistance, impact resistance, etc. will decrease, and for colored coatings, the color of the coating film will vary in shades. Factors affecting uneven coating are as follows.
(1) The gap between the two ends of the roller and the roller is different. When the gap between the rubber roller and the pressure coating roller, the feed roller and the rubber roller, the feed roller and the transfer roller, the feed roller and the transfer roller are four groups of rollers, and the gap adjustment between the rollers is inconsistent, it will often cause tinplate feed The thickness of the coating on the left and right is different in the direction.
Treatment method: When the thickness of the coating film is different, first use a plug gauge to check whether the gap between the two ends of the feed roller and the transfer roller is consistent, and then check whether the gap between the two ends of the feed roller and the transfer roller is consistent. When parallel, adjust the gap between the rubber roller and the pressure coating roller, the glazing head and the rubber roller so that the three rollers and the two rollers are parallel to each other.
(2) The coating drill degree is too large. The cohesive force between the resin polymers is too large. When the cohesive force is greater than the private adhesion of the resin on the surface of the tinplate, the coating cannot spread evenly on the tinplate, and the higher the speed of the coating machine, the easier it is to cause damage to the surface of the tinplate. Random coating is uneven.
Treatment method: Properly reduce the thickness of the coating, or use a solvent with low surface tension as a diluent. The purpose is to reduce the cohesion between the resin polymers so that the coating can spread evenly on the surface of the tinplate. And slow down the coating speed so that the coating has Enough time to spread evenly on the tinplate surface.
(3) The oil content on the surface of the tinplate is high. The oil film on the surface of the tinplate is mainly to protect the tinplate from oxidation and corrosion before coating. The thicker the oil film, the worse the wettability of the coating resin polymer on the surface of the tinplate, so that the coating cannot be uniformly attached to the surface of the tinplate.
Treatment method: When the oil content of the tinplate is high, the drilling degree of the coating can be appropriately reduced. For tinplate with too high oil content, it can only be degreased by high temperature baking.
(4) The quality of the paint is not good. The paint is mixed with impurities or stored for a long time and layered. As a result, some resin polymers of the paint have undergone polymerization before coating. Although the paint has been fully stirred before coating, it is easy to appear mottled uneven coating when the polymerized polymer chemical bonds cannot be broken.
Treatment method: replace the paint.
(5) The choice of diluent is wrong. When diluting the paint, the wrong diluent is used to cause the resin and the diluent to be incompatible. After the paint is separated and precipitated, the coating film is prone to linearization and poor flow.
Treatment method: Correctly choose the thinner, it is better to use the supporting solvent provided by the paint supplier.
(6) Rubber rollers are not concentric. After the eccentric coating rubber roller is installed on the coating machine, the contact pressure between the different circumferential positions of the surface and the tinplate and the pressure coating roller is different. As a result, the thickness of the coating film on the surface of the tinplate in the feeding direction is different. one. Colored coatings appear from light to dark or from dark to light film color gradient.
Treatment method Re-grind the rubber roller.
2. Dirty back
(1) Back dirty caused by scraper wear. After the paint is rolled on the surface of the tinplate, there is a small amount of regular linear paint dirt on the back, which is mainly due to the sand particles in the paint causing the scraper to be defective, which in turn causes the paint on the press roller to not be scraped off by the scraper.
Solution: Regrind the scraper to solve it. It is worth mentioning that due to the flaws of the sharpening wheel, there are still small burrs or nicks in the seemingly smooth blade. Therefore, after the newly ground blade is installed, it is better to put a certain amount of white magnetic oil paint in the scraper groove to make the scraper and the pressure coating roller grind each other until there is no white line on the roller. After installing the knife, pay attention to adjusting the contact pressure between the blade and the pressure coating roller. The left and right ends need to be adjusted evenly. Before starting the machine, make sure that the overflow of the scraper groove has paint flowing out. If the surface of the roller is slightly damaged due to the frequent contact between the tinplate and the surface of the pressure coating roller, only the pressure coating roller with a higher surface hardness should be replaced.
(2) Back dirty caused by conveying device. The tinplate surface with the coating film is in contact with the conveyor belt. It is very easy to cause slight shedding of the coating film and is continuously absorbed and accumulated by the belt. When other tinplate products are coated, the shedding accumulated on the belt is easily absorbed by the back of the tinplate Belt traces are formed on the back; in addition, the drill degree of the paint is too thin, and the private adhesion on the roll and roller is small. When the coating machine is running at high speed, the paint is easy to splash, resulting in irregular dirt on the back of the tinplate.
Remedy: Wipe the conveying device clean. If the back is dirty due to paint splashing, treat it as a splash fault.
(3) The back of the adhesive sheet is dirty. Insufficient baking temperature or insufficient cooling of the furnace outlet. When the tinplate is piled up at a high temperature, the tinplate and the tinplate will stick together. The coating film coated on the surface of the tinplate is absorbed by the back of the tinplate stacked on it, forming back dirt. It is generally required that the surface temperature of the tinplate after cooling is at most 10°C higher than the room temperature. If the cooling is not proper, the coating film will not harden completely. Treatment method: Properly increase the baking temperature, so that the coating coated on the tinplate can fully polymerize the conjunctiva. Increase the cooling air volume to fully harden the coating film. Sometimes reducing the coating speed can also prevent sticking and soiling.
3. Scratch
During the production process of the tinplate surface coating film, due to mechanical reasons or the defects of the tinplate itself, the surface of the coating film is scratched, and the scratches on the inner coating film of the food can will greatly reduce the corrosion resistance of the inner coating film.
(1) Conveying device. Through the coordinated action of the iron suction nozzle and the iron feeding nozzle, the tinplate is sent to the coating machine. If the separation between the tinplate to be separated and the next tinplate is not effective, and the cutting edge of the tinplate trailing edge is facing downward, it is easy When the air nozzle is feeding, the edge of the last tinplate scratches the coating film on the surface of the next tinplate: if the surface of the conveying trough for conveying tinplate is not smooth, it will also cause scratches on the coating film on the back of the tinplate.
Treatment method: When the next surface of the tinplate is scratched, adjust the actions of the iron suction nozzle and the iron delivery nozzle to make them cooperate tacitly. At the same time, adjust the position of the surrounding magnets and the direction, position and wind t of the blowing nozzle so that the upper and lower sides When the tinplate is separated, there is a certain gap between each other; in addition, turning the tinplate and applying white magnetic oil so that the cutting edge of the trailing edge is facing upward can also prevent the cutting edge of the tinplate trailing edge from scratching the printing ink layer during printing. Of course, the tinplate trailing edge When the cutting edge of the side is upward, the printing blanket will be damaged during printing; when the back of the tinplate is scratched, check whether the surface of the conveying trough is smooth. If possible, several sets of rollers can be installed next to the conveying guide rail to allow the tinplate to roll through during conveying .
(2) flower iron frame device. The surface of the flower iron frame is not smooth. The driving of the flower iron frame is not stable when the tinplate is conveyed. There is intermittent vibration, which can easily cause scratches on the coating film on the back of the tinplate in the drying room; when the tinplate is coated and enters the drying room, it rotates with the flower iron frame Not synchronous. It is also very easy to cause scratches on the coating film coated on the back of the tinplate. The faster the coating speed, the more serious the scratches.
Treatment method: replace the non-smooth flower iron frame in time: regularly check whether the supporting rollers that drive the flower iron frame are worn out: adjust the time for the tinplate to enter the drying room so that the tinplate enters the drying room just to be supported by the flower iron frame to prevent the tinplate from entering the drying room From time to time, rub and scratch flowers on the flower iron frame.
(3) Receiving device. The accumulated tinplate can easily cause friction between the last tinplate and the previous tinplate when the blowing wind is not enough, so that the scratches on the back of the previous tinplate are especially obvious when the cutting edge at the tip of the tinplate is upward. In addition, the rough surface of the receiving trough is also an important factor causing scratches.
Treatment method: The scratches caused by the rough surface of the receiving chute are generally fixed in a certain position.
And this position is generally supported by a seemingly smooth support iron. It is enough to find burrs on the surface and polish it: the friction and scratches caused by insufficient air volume are generally irregular. It can be solved by adjusting the blowing volume. The amount of blowing is determined by the weight of the tinplate.
(4) Baking temperature. When the coating film is baked at a low temperature, it is easy to cause the coating film on the surface of the tinplate to be poorly polymerized and conjunctival, and the polymerization force between the resin polymers in the coating film is poor. It is easy to cause scratches during production. If the baking temperature is too high, it is easy to cause embrittlement of the coating film. It is easy to be scratched after mechanical processing in the next process.
Treatment method: Strictly control the coating temperature and baking time to make the coating film polymerized firmly. And regularly check the temperature in the drying room, and control the error between the actual measured temperature value in the drying room and the temperature value of the drying room temperature display instrument within ±3°C.
(5) Manually move the tinplate. In the process of printing or coating, in order to check the effect of tinplate coating or printing, the relevant quality is often checked by sampling. If you do not pay attention, it is easy to cause scratches on the sample. In addition, when there is a quality problem in printing or coating, it is necessary to sort out waste or defective products. It is necessary to move the tinplate to cause scratches.
Handling method: When handling tinplate by hand, it should be handled with care: if there are quality problems such as printed graphics, it is better not to pick up tinplate before making cans, especially those tinplate products with inner coating film. Moving the tinplate in pieces can easily cause scratches on the inner and outer surfaces of the whole product. In severe cases, the food cans are easily corroded or even perforated.
4. Bar stripe failure
(1) Gear wear. Due to wear and tear, the gears of the coating machine are not well meshed. They cannot rotate smoothly, resulting in uneven coating film and bar-shaped spots.
Solution: replace the gear.
(2) There is hard dirt between the gears. The hard dirt between the dry gears causes the beating between the roller and the roller during coating, forming bar-shaped stripes.
Treatment method: clean the gear
5. sticky sheet
Sticking refers to the phenomenon that when the baking temperature is insufficient or the cooling of the furnace outlet is insufficient, the tinplate sticks together when the tinplate is piled up at a high temperature. If one piece is peeled off, it will make a sound. Sometimes it is accompanied by the phenomenon of dirt on the back of the tinplate. After a long time of accumulation, the dirt on the back is especially serious. In addition, when the coating thickness is too thick, the organic solvent in the coating near the tin layer is not completely volatilized, and it is also very easy to stick when it cannot be firmly adsorbed and stacked with the tin layer.
Treatment method: Use high-temperature baking within the satisfactory baking temperature range of the paint to fully polymerize the conjunctiva on the surface of the tinplate. If the problem cannot be solved by increasing the temperature, the problem can be solved by reducing the coating speed to prolong the cooling time after the tinplate is out of the furnace or increasing the cooling air volume (replacing with a high-power fan). If the coated tinplate has stickiness, it can be eliminated by baking once at a high temperature within the satisfactory baking temperature range of the coating. When it is necessary to coat a thick coating film, two coatings should be used to prevent sticking, so as to improve the adhesion between the coating film and the tinplate.
6. Orange peel
Refers to the uneven coating film after baking, which becomes a wrinkled surface like orange peel.
（1）背面起脏。涂在马口铁表面的涂料中堆积期间发生背面起脏.造成马口铁背面涂布其他涂料时发生涂膜桔皮现象这主要是内外两种涂料互相排斥的原因。先上光或先涂银色涂料的马口铁如果堆积时间长或烘烤温度不够.在其背面涂布其他涂料时极易出现此问题主要是因为光油中的润滑剂成分、银色涂料中的铝成分极易引起背脏。
处理方法:堆积时间不易太长如出现桔皮除洗或擦背面以外别无他法
(2)涂料的钻度过高。涂料钻度过高,树脂高分子间的内聚力很强,涂布在马口铁上的涂料树脂高分子受内聚力的影响,易出现流展不均匀.造成涂料涂布在马口铁表面流展性差。
处理方法:降低涂料钻度。
(3)稀释剂选择不当。稀释涂料或清洗涂布机时如果稀释剂或清洗剂选用不当极易造成树脂高分子内聚成团,减弱了树脂高分子在马口铁表面的吸附,造成涂布流展不均匀。
处理方法:正确地选用涂料供应商提供的稀释剂和清洗剂.特别在涂布有色涂料或前后工序涂布的涂料树脂类型不一样时.一定要将涂布机清洗干净避免上工序涂料脏污下工序涂料,涂膜烘烤后出现桔皮现象.
7.眼孔
也叫针孔涂膜涂布干燥后表面有针刺状的小孔小孔处有时有很薄的涂膜,有时没有.甚至露出马口铁。出现眼孔的原因有以下几方面。
(1)胶辘滚筒上有洞。胶辘滚筒上有洞眼,滚涂时洞眼处无涂料转移到马口铁表面造成眼孔。一般因胶辘滚筒造成的眼孔有规律前后马口铁上的眼孔位置一致,大小一定。处理方法:更换胶辘滚筒或用胶水修补洞眼。
(2)马口铁面上有油或露珠。由于马口铁上的细小颗粒油或水珠与涂料树脂相排斥,在有颗粒油或露珠的表面.涂料不能均匀涂布。处理方法:用200℃左右温度烘烤马口铁;也可降低涂料钻度,增大湿状涂膜量。
(3)涂料、马口铁上有脏污。眼孔特别细小。处理方法:先用无脏污的马口铁试涂涂料如无问题则擦洗马口铁上的脏污即可解决。否则更换涂料,同时注意正确选用稀释剂。此外马口铁表面有灰尘也易产生眼孔。
(4)马口铁表面带静电。马口铁表面有静电也会使涂料不能在其表面均匀覆盖而出现眼孔。处理方法:提高涂料钻度,或擦洗输送带消除静电。
8.飞料
类似印刷“飞墨”,涂布机的转速变快在两个辊面上涂料层被一分为二时.拉丝断裂成数段但有时也会产生许多飘浮在空中的极小颗粒,这些微粒由于离心力而飞散。造成输送装置及涂布机污染,特别在有留空涂布时造成留空处脏污.影响成罐焊接。一般来说“黏性”大的涂料这种倾向大。
处理方法:提高钻度或添加表面活性剂降低表面张力,降低涂布速度也有效。如果是白色涂料.提高颜料浓度或含量。降低湿状态涂膜的厚度,也可以防止飞料。
9.斑马条纹
出现像席子条状的条纹。涂料从胶辗滚筒转移到马口铁上后.在马口铁表面不能平滑延展.呈山状,多起因于钻度高或溶剂挥发快.不相溶的涂料混入也可引起此故障。
处理方法:需要清洗干净涂布装置。再使用挥发慢的溶剂试验降低钻度。冬季或休假结束等情况下涂料过于变凉时,也容易发生此故障因此应充分搅拌涂料,涂料液温稍微升高即可解决。胶辘滚筒表面硬度过高,也易发生此现象,换用硬度较低的胶辘滚筒即可解决。有时因上工序的涂料残留在涂布机的送料管道而造成下工序涂料不相溶而出条纹.此时只有更换涂料。
10.爬纹
冬季气温低时炉内急速被加热的部分(热风吹出附近)周围形成较厚涂料膜圆形。这是因为低温涂料中分子的运动处于缓慢状态,急速处于高温中低沸点的溶剂立刻蒸发而树脂中的高分子溶剂原封不动处于不易蒸发状态而残留。如果进一步被加热呈熔融.由于表面张力而发生凝聚.在这种状态下干燥,会形成回形爬纹。
处理方法:降低涂布速度,并充分搅拌涂料使其液温升高.同时使用稀释剂时尽量采用高沸点、表面张力与涂料的表面张力接近的溶剂。
11.幻影
烘烤时.马口铁表面出现朦胧可见的涂膜颜色变淡的形状.这是因为热风被花铁架吸收.此部分烘烤不足,溶剂蒸发变慢,加之受表面张力拉引,涂膜变薄、颜色变浅。涂膜量越大这种现象越容易出现。涂料钻度过低,也易出现此故障。特别是冬天高速涂布时此现象尤其明显。
处理方法：一般可降低涂布速度延长预热时间,同时在工艺允许的条件下减小涂膜量。另外要注意使用蒸发快的稀释剂且钻度不宜过低。
12.花铁架斑纹马口铁上的涂料在未干燥期间.与前面的花铁架相接触,产生花铁架的痕迹。
处理方法:如果是马口铁弯曲变形造成斑纹一般应更换马口铁。否则应检查热风是否太强,马口铁在花铁架上是否跳起,或花铁架的驱动是否平稳。
13.重皮
胶辘滚筒有横向留空时,在横向留空的切口处积聚的涂料过多,切口部形成涂料“滴垂”,尤其是白磁油涂料容易发生重皮。
（1)胶辘滚筒橡胶硬化。留空槽处的橡胶变硬,在此位置处易吸附过多的涂料,造成横向留空切口处上下涂膜厚度过厚。处理方法:更换新辊。
(2)钻度过低。因为钻度过低涂料的流动性比较大.极易在横向切口处形成涂料堆积。处理方法:提高涂料的涂布钻度或在降低涂料的钻度时,使用挥发性强的稀释剂比较好。
(3)涂膜量多。涂膜量增大时,切口槽处涂料容易积存出现重皮。处理方法:在满足产品工艺质量的条件下尽量减小涂膜贵,这样既可降低生产成本.又可避免重皮。
14.起皱
马口铁涂布后湿膜均匀平滑,但烘烤后一部分涂膜光泽消失,形成皱面出现裂纹模样.主要是由于马口铁涂布后经烘房的预热区时间过短.涂料中的大部分溶剂在烘房预热区未挥发.进入恒温区时高沸点的溶剂匆忙逃离涂膜表面.造成起皱。另外烘房口排风存在缺陷,炉内有冷空气热风不能充分流动时也会发生起皱。皱纹的模样有蜘蛛巢状、星星点点状、降霜状等。这种现象在阴湿的冬天比较明显。
处理方法:确保炉内充分进行排气通风.降低涂布速度,延长预热时间让涂料中的溶剂在预热区慢慢地挥发掉。生产中调整涂料钻度时采用低沸点的溶剂。减薄涂布厚度也能避免此类外观问题出现。
15.熔锡马口铁涂布涂料经高温烘烤时,其表面出现锡层熔化,形成锡斑。一般发生熔锡是由于马口铁表面性能存在缺陷但也不能排除马口铁在烘炉中某一部位温度过高,出现熔锡。
处理方法:先检查马口铁的四个角及其中心处在烘炉中其表面温度曲线是否一致,如不一致,则需调整从燃烧器向不一致处送热风的送风量或送风方向。一般在不影响涂料在马口铁聚合结膜的条件下.适当降低烘烤温度能防止熔锡的发生
16.漏涂
(1)油污漏涂。马口铁输送装置、花铁架传送装置及收料装置均需润滑加油极易造成加油过多而漏油马口铁经过时背面易带油污当马口铁背面涂布时.有油污处涂料无法吸附在其表面。
处理方法:检查马口铁输送装置、花铁架传送装置、收料装置是否有漏油发生。如是油污漏涂则用汽油擦洗油污即可。另外.由于手上有油脂.搬拿马口铁时手上油脂易沾污马口铁.造成下工序涂布漏涂。
(2)露点漏涂。马口铁包装差,在运输途中受潮湿空气影响表面易出现露点。尤其是南方湿气较重的春天.马口铁裸露在空气中表面很快结露。
处理方法:干烘马口铁后即可涂布。若因湿气出现露点情况更好是开涂时再打开包装。
(3)马口铁。马口铁生产厂家在进行表面处理时出现表面性能不一的问题从而使涂布在马口铁表面的涂料表面张力不一致造成漏涂。另外马口铁表面涂保护油时不均匀或过多.也易造成漏涂。
处理方法:如因马口铁表面性能不一造成漏涂,只能更换马口铁;如因保护油过多或不均一般采用高温205℃烘烤除油有时则需用汽油擦洗漏涂部位后再涂布才能消除漏涂。
17.脏污
(1)生产环境欠佳。工作环境尘埃太多.生产时尘埃混入涂料中既影响涂膜外观.又影响涂膜的理化性能。处理方法:马口铁送到生产车间前应清除其外包装上的尘埃经常清洁车间环境。
(2)烘房中有炉灰。涂料中的溶剂或燃气在燃烧炉中不完全燃烧.产生颗粒状炭灰.当涂布的马口铁经过时炭灰被湿的涂层吸附。处理方法:确保燃气在燃烧炉中的火呈蓝色定期对烘房进行清洁,一般采用废马口铁在其表面涂布一层废涂料,在低温烘烤的条件下,把烘房中的炭灰吸尽;降低涂料钻度时尽量不采用高燃点的大分子溶剂作稀释剂。
(3)花铁架上的残留物脱落。支承马口铁的花铁架在长时间生产中与挥发的溶剂分子接触.表面积聚一层金黄色的残留物,这层残留物积聚到一定的厚度极易脱落,特别在停产后再开机生产时.残留物受热更易脱落。处理方法:定期进行花铁架的除残清洗.
(4)涂料中有脏污。涂料生产厂家的生产控制不严混有脏物;涂布生产时换用涂料清洗涂布装置不有效,造成后一工序涂料污染,特别是在前一工序涂布有色涂料、后工序涂布无色涂料时尤其明显。处理方法:涂料中有颗粒尘埃时采用细滤网过滤或退货:生产中更换涂料时尽量洗净涂布装置,避免前一工序的涂料污脏。
18.白磁面泛黄
(1)涂布光油。马口铁多色套印后还要在油墨表面涂布一层光油。涂布的光油不仅能增加马口铁图文外观的光泽度同时也增强了墨层表面的柔韧性、耐冲击强度、耐磨性及其他物理化学性能。但实际生产中,不同种类树脂的光油涂布印刷面均会造成其表面泛黄。相对而言,丙烯酸树脂光油高温烘烤不易泛黄,氮基聚醋类树脂与醉酸树脂类光油次之环氧树脂类光油最易泛黄。
处理方法:选择合适的上光油特别是对于冷相白磁底的印刷品上光时不宜使用环氧树脂类光油。
(2)烘烤温度。烘烤温度过高也是造成白磁面泛黄的原因之一。
处理方法:保持合适的烘烤温度必要时降低烘烤温度有利于防止白磁面发黄。
19.印刷油墨变色
马口铁印刷中,印刷好的产品经上光后往往会发生印刷图案在上光前后色相不一的问题。特别是印刷专色图案由于专色油墨是几种油墨配色而成印刷上光时变色尤其明显。
处理方法:印刷专色前进行试上光。先在马口铁表面印刷一定厚度的专色,烘干后进行上光对比上光烘干样的色相与客户要求的色相是否一致。
20.光泽度差
马口铁印刷面多次印刷后均须涂布一层光油,以保护印刷面的油墨在机械加工时不受损伤但生产时往往会出现上光后印刷面图案失去光泽特别是需要高温蒸煮的产品易出现蒸煮后失光。影响马口铁印刷品外观光泽的原因很多。
(1)湿罩湿上光。采用湿罩湿上光的产品极易出现蒸煮后马口铁印刷面图文失光.特别是光油罩在未干燥的红色、黑色油墨上蒸煮后,有红色、黑色图案的部分用手摸有粗糙的感觉。处理方法:对于需高温蒸煮的产品采用湿罩湿上光时需要先检测试涂片的高温蒸煮性,只有确保无问题才能正式生产。否则应采用湿罩干即印刷油墨干燥后再罩光油。
(2)光油的粘度。光油的钻度过低极易出现光油烘烤结膜表面不光滑印涂膜无光泽.处理方法:私度不易太低,且不能用错稀释剂。使用高沸点稀释剂流动性好,涂膜的光泽好但过多加入溶剂干燥速度会变慢。
(3)光油的种类。不同种类的树脂光油,其罩光后的光泽度不一样。一般认为环氧树脂的罩光性很好。处理方法:换用其他种类的光油。
(4)光油中有脏污。光油中如混入其他种类的涂料直接影响光油的涂布性能。处理方法:上光前一定清洗净涂布装置。
（5）涂膜太薄。涂布时涂料不能在马口铁表面均匀流展形成均一的表面.易造成涂膜面无光泽。处理方法控制好一定的涂膜厚度。在涂料供给量一定的情况下控制好涂料钻度。
（6）印刷油墨。印刷有专色图案的马口铁产品时需要配墨但配墨时如采用不同生产厂家的树脂油墨极易造成上光蒸煮后,图文失去光泽。处理方法;对于需蒸煮的制罐产品,印刷专色配墨时更好使用同一生产厂家的同类树脂油墨。
(7)烘炉口排气。当烘房口的排气不流畅时.烘房内热空气循环受阻涂料中的溶剂不能在预热区充分挥发造成涂膜面失光。这种现象在阴天湿度高的情况下尤为明显。处理方法:调整涂料钻度时,采用低沸点的溶剂作稀释剂并降低涂布速度。
21.白磁涂膜的色相差
影响马口铁表面白磁色相的因素主要有白磁膜的厚度、颜料及增色剂的含量、马口铁表面的镀锡量。同一种白磁油涂布在同一种马口铁上涂布愈厚.色相愈深;马口铁镀锡量越高,白磁涂膜厚度相同色相越深涂布相同色相时要求的白磁越少。
处理方法:同一种马口铁涂布白磁时在涂料供给量一定时,要控制好涂布毅度使涂布在马口铁表面的白磁厚度一致.消除色差。对于不同的马口铁.一般可调节供料量.改变白磁的涂布厚度从而消除色差
22.留空涂布走位
需要边缝焊接的马口铁容器罐边缝焊接部位不能涂布涂料.因此涂布前应According to容器的大小在胶辘滚筒上开槽留空一般胶辘滚筒上的开槽留空比容器边缝焊接部位露铁宽度大1一Zmm。影响留空走位的主要因素有:
(1)马口铁。马口铁弯曲变形易造成马口铁到达叼牙位时.叼牙无法叼住马口铁致使定位失败.留空走位;马口铁规格大小不一时,推规、侧规无法定位也会出现走位。处理方法:如因马口铁弯曲变形造成马口铁不能被叼牙叼住走位一般可采取在输送槽的支撑板下加磁铁的办法解决:如因马口铁规格不一长宽误差在2一3mm可适当减小侧规及推规的推力,但对于梯形马口铁,则只有更换马口铁.
(2)涂布机叼口挡板位置。两个定位叼牙前挡板如不在一条直线上时马口铁纵向长度有误差极易出现留空走位.处理方法:调整前规挡板位置使其在一条直线上同时注意叼牙的叼力需要合适否则易损坏马口铁。
(3)侧规。侧规的工作时间与叼牙的工作时间不同步。处理方法:调整侧规工作时间使叼牙叼住马口铁时侧规正好到位同时要调节好弹性侧规的弹力。当马口铁两面均需留空涂布时,为减小因马口铁大小不一而造成内外留孔走位可更换马口铁进料的方向,即不改变固定侧规与弹性侧规的工作位,而把第一次外涂的马口铁叼口边换成第二次背面涂布时的拖梢边二也可不改变进料方向.而更换固定侧规与弹性侧规的工作位。(4)推规。推规的工作时间与叼牙的工作时间不同步。处理方法:调整推规与叼牙的工作时间,使叼牙叼住马口铁时.推规对马口铁有一定的推力.一般使马口铁拖梢处向上微弯曲,就能防止马口铁发生留空走位
23.留空槽处涂膜变浅
胶辘滚筒留空槽太宽为了达到涂布工艺要求的涂布留空宽度.往往加大胶辘滚筒与压涂滚筒之间的压力这样会造成留空槽处涂膜变浅.严重时出现变浅后又在留空处出现两条深的涂料压线;另外.着料辊与胶辘滚筒间的压力过大时当完成胶辘滚筒上的着涂料后,胶辘滚筒的压缩弹力恢复,涂料在胶辘滚筒表面张力的作用会使胶辘滚筒留空槽处的涂膜量减小.从而造成转涂到马口铁上留空处的涂膜变薄。
处理方法:调整好胶辘滚筒与压涂滚筒、着涂辊与胶辘滚筒间的压力,特别是对于有色涂料一般选择其称心涂布钻度的最大值开涂如留空槽太宽应更换胶辘滚筒。
24.气泡
Coatings are generally colloidal solutions made of resins, solvents, colorants and additives. After a period of storage, there will be a phenomenon of upper and lower layers. Generally, colorants and resins are deposited in the lower layer, while solvents and additives float in the upper layer. Especially if the colored paint is stored for a long time, this phenomenon is more obvious. If the coating is extracted in time for construction, it will be found that the coating has a low degree of penetration. Even if it can be produced, the color, thickness and performance of the coating film will be inconsistent. Only by fully stirring the paint so that the pigments, resins, solvents, and additives in the whole bucket of paint are uniformly mixed can the paint maintain good and stable performance in production. Bubbles are inevitably mixed in the coating when stirring. If it is applied immediately, the air bubbles will often be transferred to the surface of the tinplate during coating to make the coating film have air bubbles.
Treatment method: The stirred paint should be allowed to stand for a period of time, so that the air bubbles in the paint can be fully discharged from the paint. When coating, try to ensure that the paint does not bubble when it is input from the paint tank to the gap between the feed roller and the transfer roller. Coating drill degree should not be too high under the permitted conditions. Reducing the drill degree is beneficial to eliminate air bubbles
25. Rust
If the tinplate is exposed to the air for too long, the water vapor in the air will easily form a dew point on the surface and edge of the cold-phase tinplate to form a primary battery, which will accelerate the corrosion of its surface and edge. Especially in the spring with heavy humidity in the south. After opening the package, dew points will accumulate on the surface of the tinplate. The longer the time, the more likely the tinplate will condense, which will undoubtedly affect the coating of the coating.
Treatment method: Try to shorten the time that the tinplate is exposed in the air. After opening the package, it is coated, and the finished product is packaged with moisture-proof packaging. If there is a dew point on the surface of the tinplate due to carelessness, it should be dried at a baking temperature not higher than 40°C to avoid the formation of the dew point. The primary battery reacts intensified at high temperature and forms white spots.
