復合包裝袋的白點和氣泡是怎么回事？

來源：http://bjtdacyu.cn/ 日期：2023-12-08

復合包裝袋的白點、氣泡形狀各異，人們對氣泡和白點的概念不盡相同。雖然都叫白點和氣泡，但細究起來大多數(shù)不是同一現(xiàn)象，形成機理更是千差萬別。所以白點和氣泡是個籠統(tǒng)的名稱，值得分類探討和研究?，F(xiàn)在把白點、氣泡形成的原因分列如下：

The white dots and bubble shapes of composite packaging bags vary, and people have different concepts of bubbles and white dots. Although they are both called white dots and bubbles, upon closer examination, most of them are not the same phenomenon, and their formation mechanisms vary greatly. So white dots and bubbles are a vague name that is worth categorizing, exploring, and researching. Now, the reasons for the formation of white spots and bubbles are listed as follows:

白點氣泡：①干燥不充分

White dot bubbles: ① Insufficient drying

②上膠量不足：督辦、復溶性差、轉(zhuǎn)移率下降。。  薄膜太厚

② Insufficient glue application: supervision, poor solubility, and decreased transfer rate.. Thin film too thick

③復合后膠未流平：膠分子量大、熟化不夠，復合熱輥溫度太低、氣溫較低而預熱輥沒用

③ The composite glue is not leveled: the molecular weight of the glue is high, the curing is not enough, the temperature of the composite hot roller is too low, the temperature is too low, and the preheating roller is useless

一、鍍鋁膜復合印刷基材，如產(chǎn)生氣泡，在印刷膜淺色部分看起來是白點。氣泡部分兩層基材未密切貼合，不一定是圓鼓鼓地凸起狀。但嚴重的干燥不良形成的氣泡倒是鼓起的，大的像芝麻粒。產(chǎn)生這類氣泡的原因有的是膠黏劑未干透，有的是油墨溶劑干燥不充分造成，經(jīng)常出現(xiàn)在大面積跌印部分。某些小印刷機還在使用紅外線干燥箱。輕微的干燥不良雖然沒有鼓起大氣泡，只足夠小事，能透過某些薄膜釋放溶劑。如同樣的工藝條件，PET復鋁箔有氣泡，而BOPP復鋁箔熱化后氣泡會消失。

1、 Aluminum coated composite printing substrate, if bubbles are generated, appears as white dots in the light colored part of the printing film. The two layers of substrate in the bubble part are not closely adhered, and may not necessarily be bulging. But the bubbles formed by severe poor drying are bulging, big like sesame seeds. The reasons for producing such bubbles are either due to the adhesive not drying completely, or due to insufficient drying of the ink solvent, which often occurs in large areas of drop printing. Some small printing machines are still using infrared drying boxes. Mild dryness, although not accompanied by large bubbles, is only a minor issue that can release solvents through certain thin films. Under the same process conditions, PET composite aluminum foil has bubbles, while BOPP composite aluminum foil will disappear after heating.

二、干燥不良形成的小氣泡和上膠量不足產(chǎn)生的氣泡用放大鏡觀察區(qū)別不大，這時需要作理性分析。任何看起來很光滑的表面，用放大鏡觀察都是凹凸不平的。膠黏劑把表面抹平需要一定厚度——也就是上膠量。普通透明復合膜用低粘度膠黏劑。印刷膜涂膠要厚點，如白膜，色塊下托白膜厚度就更大。里印復合墨樹脂含量少于表印白膜，所以復合白墨表面比較粗糙。粗糙苯類是復合白墨的優(yōu)點，有利于膠黏劑滲透產(chǎn)生足夠的剝離強度，反過來卻需要較多的上膠量。為了保證油墨部分有足夠的膠黏劑厚度，上膠量需3-3.5G，少于這標準也是上膠量不足。因堵版造成上膠量不足容易理解。堵版分2種：一時突發(fā)性的，因涂料復溶性差和操作中轉(zhuǎn)移率不斷下降造成。這類堵版如未找出原因及時排除，僅靠停車擦版只能維持一時。另一種堵版是漸變型的，嚴格地說不能算故障，因為每次復合后不可能把網(wǎng)紋輥中的殘膠完全清洗干凈，殘膠日復一日地在網(wǎng)孔底部沉積固化。上膠量慢慢變小、小氣泡也漸漸產(chǎn)生、由少變多、由小變大。終因某做要求高的產(chǎn)品和復合較厚的膜，小氣泡變得不可容忍。這時要用專門的洗版液。問題是解決了，卻不是一種好的生產(chǎn)習慣，因為之前有大量介于合格與不合格之間的產(chǎn)品被生產(chǎn)出來。我們提倡定期測量上膠量，當上膠量遞減預定值時就清洗。

2、 There is not much difference between the small bubbles formed by poor drying and the bubbles generated by insufficient glue application when observed with a magnifying glass. In this case, a rational analysis is needed. Any surface that appears smooth is uneven when viewed with a magnifying glass. The adhesive needs a certain thickness to smooth the surface - that is, the amount of adhesive applied. Low viscosity adhesive for ordinary transparent composite films. The coating of printing film should be thicker, such as white film, and the thickness of the white film under the color block is even greater. The resin content of the inner printed composite ink is less than that of the surface printed white film, so the surface of the composite white ink is relatively rough. Rough benzene is an advantage of composite white ink, which is beneficial for the penetration of adhesive to produce sufficient peel strength, but in turn requires a higher amount of adhesive application. In order to ensure sufficient adhesive thickness for the ink part, the amount of glue applied needs to be 3-3.5G, which is also insufficient. It is easy to understand that insufficient glue application is caused by blocking the plate. There are two types of blockage: temporary and sudden, caused by poor paint re solubility and continuous decrease in transfer rate during operation. If the cause of this type of blockage is not identified and eliminated in a timely manner, relying solely on parking and wiping the plate can only maintain it for a while. Another type of blockage is a gradient type, strictly speaking, it cannot be considered a malfunction because it is impossible to completely clean the residual glue in the mesh roller after each composite, and the residual glue accumulates and solidifies at the bottom of the mesh hole day after day. The amount of glue applied gradually decreases, and small bubbles gradually appear, increasing from less to more and from small to large. Eventually, due to one day producing high demand products and thick composite films, small bubbles became intolerable. At this point, specialized plate washing solution should be used. The problem has been solved, but it is not a good production habit because there were a large number of products that were previously produced between qualified and unqualified. We advocate regularly measuring the amount of glue applied, and cleaning when the amount of glue decreases to the predetermined value.

三、有時候干燥很充分，上膠量也不少，剛下機的復合膜還是有氣泡。其實剛復合好的產(chǎn)品沒有一點氣泡是不太可能的。小的氣泡經(jīng)過熟化能，因為不含溶劑但沒喲充分固化的聚氨酯膠黏劑有一定的流動性。

3、 Sometimes the drying is sufficient, and the amount of glue applied is also considerable. The composite film that has just been removed from the machine still has bubbles. It's actually unlikely that a newly compounded product doesn't have any bubbles. Small bubbles can be eliminated through maturation because polyurethane adhesives that do not contain solvents but have not fully cured have a certain degree of fluidity.

溫度越高流動越大，分子量越大流動性越小，固化的實質(zhì)就是分子量不斷增大的過程。熟化室中的復合膜，膠黏劑在溫度的作用下緩慢流平，大氣泡縮小，小氣泡消失，直膠黏劑的分子量增大到膠不能流動為止。有經(jīng)驗的操作工看得出多大的白點能消失，如沒有把握好先把樣品放進80度烘箱中30分鐘，檢查氣泡是否去除。同樣大小的氣泡，低粘度的膠能，而高粘度膠可能不行，這是因為50%高粘度膠分子量大，流平性差。

The higher the temperature, the greater the flow, the larger the molecular weight, and the smaller the fluidity. The essence of solidification is the process of continuously increasing molecular weight. The composite film in the curing room is slowly leveled by the adhesive under the action of temperature, with large bubbles shrinking and small bubbles disappearing until the molecular weight of the adhesive increases to the point where the adhesive cannot flow. Experienced operators can see how big the white spots can disappear. If they are not sure, first place the sample in an 80 degree oven for 30 minutes and check if the bubbles are removed. Bubbles of the same size can be eliminated with low viscosity glue, while high viscosity glue may not be able to. This is because 50% of high viscosity glue has a large molecular weight and poor leveling performance.