Related “packaging aluminum tubes”, you may feel strange, but just look around the house and stores, it is easy to find the existence of packaging aluminum tubes with different cap and specifications, such as hair dye, hand cream, ointment, toothpaste, glue, children’s color ink pens, etc., many are packaged with aluminum tubes. Packaging aluminum tubes are usually used to fill cream products, widely used in the skincare and cosmetics industry, pharmaceutical industry, household products, chemical products, etc. The capacity of the paste products for end consumers is generally small, between 3ml and 200ml, which is convenient to use, easy to carry, and easy to store.
Unlike plastic tubes, aluminum laminated tubes, aluminum tubes are packaging containers produced from more than 99.5% pure aluminum, aluminum is a metal material, its own properties are stable, but inevitably some products may have a chemical reaction with aluminum, so there must be a substance to isolate the filler to protect the aluminum tube.
Except for curious children, probably not many people will cut open the packaging aluminum tube to explore its interior. You may not have thought that the aluminum tube can provide excellent packaging and protection because of the application of a special process, and “internal coating” is a common procedure for the production of high-quality packaging aluminum tube.
One of the major advantages of aluminum tubes is to protect the cream products, isolated from the external environment of air, moisture, moisture, light, ultraviolet light, bacteria and other substances, reducing the chance of creams being contaminated and spoilage, spoilage. However, even if the aluminum has good chemical stability, if it encounters a slightly corrosive paste, there is a possibility of chemical reaction, resulting in corrosion of the tube wall or deterioration of the paste. Therefore, the correct internal coating needs to be used.
The process of spraying is to spray a layer of modified epoxy phenolic resin with high resistance on the inner wall of the aluminum hose. This resin is transparent with a slight brown (beige) or golden color. It effectively isolates acids, alkalis, water vapor and solvents, and avoids chemical reactions due to contact between the paste and the aluminum. Products that are susceptible to oxygen and moisture, such as moisture-hardening silicone adhesives, have an extended shelf life when filled in sprayed packaging aluminum tubes. In addition, if the filled paste is slightly corrosive, such as hair dye, the inner wall of the packaging aluminum tube must be sprayed first.
How many kinds of internal spraying are there on the market?
There are six options for internal coating for flexible aluminum tubes
1. No internal lacquer
As the name implies, it is not coated inside the aluminum tube with internal spraying, for glue and some other inexpensive products, because the glue will not produce chemical reactions with aluminum, so not spraying internal spraying can also save costs, especially for small capacity glue tubes, such as 1ML – 5ML glue tubes, because the demand is large, so it is more necessary to save costs and reduce prices, not internal spraying is a very good choice.
2. Golden epoxy resin
This is the most popular and common kind of internal coating, used for pharmaceutical ointment, hand cream, shaving cream, toothpaste, hair dye and other daily using and chemical products, as well as glue, sealants, sticky seam agent, etc.
3. Beige epoxy resin
For some hair dyes that are more alkaline, we choose to use the beige inner coating, especially in the Brazilian market, many hair dyes use this beige inner coating.
4. Transparent inner coating
Some products have high requirements for the inner coating, especially for open tubes. It is easy to spatter the golden inner coating on the tube body during the production process, it affect the printing process, making the product unusable. So clear internal lacquer can help to solve the problem.
The transparent inner coating is generally used for products that require a high-quality appearance such as hand creams.
5. A plastic bag inside the aluminum tube
some hair dyes with heavier alkaline will use a plastic bag of about 0.5MM thickness inside the aluminum tube, so as to better isolate the direct contact between the hair dye and the aluminum tube, this is generally a 2-dose product in the hair dye, while the 1-dose product generally still uses the golden inner coating.
6. Food grade internal lacquer
There is also a senior internal coating is used in food and other products with high product requirements, because of direct contact with the human body, must ensure that this internal coating non-toxic safety, and this internal coating does not contain bisphenol amines so it is also of great concern to customers, so that consumer safety is more secure, of course, the price will also be more expensive.
So the quality of the inner coating is very critical in the quality of the collapsible aluminum tube, we have been using the top quality of the inner coating to produce products.
What kind of testing standards are there for the internal lacquer?
1. Continuity test of the inner coating
As shown in the picture of the instrument, coated with a layer of aluminium tube filled with experimental liquid containing copper sulfate, a sliding electrode immersed in the experimental liquid, the aluminum tube itself and a wipe V-groove base electrode contact, and then applied 5V +- 0.5V DC voltage between the sliding electrode and the aluminum tube, the flow of current and the aluminum tube is not covered by the surface area of the inner coating is proportional, if the coating is not continuous, there will be copper precipitation phenomenon.
2. Inner coating chemical stability test
The aluminum tube body is cut longitudinally and leveled, and the inner coating is lightly rubbed with skimmed cotton dipped in acetone 30 times to observe whether the coating comes off on the skimmed cotton.
3. Coating flexibility and adhesion test
Put the aluminum collapsible tube for test on the rod as shown in the figure below, make the tail of the tube set on a step corresponding to the specifications of the aluminum tube, and let the rod stick out from the mouth of the tube. The aluminum tube should remain vertical to the base throughout the test.
Put the top platen over the extended bar and let it rest gently on the top of the nozzle, apply uniform pressure on the platen and squeeze the aluminum tube rapidly downward. The squeezed aluminum tube takes on an evenly folded “accordion” appearance.
Remove the pressed tube from the bar, stretch it as close to its original length as possible, cut it open lengthwise, and observe the inner and outer coating surfaces for cracks and peeling.
We ( Beauty Sky Packaging) all have a strict quality inspection during the production process, every 30 minutes we will take 5 – 10 aluminum collapsible tubes from the production line to test and make recorders, in order to be traceable and ensure quality.
It is very important to choose a good and experienced aluminum collapsible tube factory. And the control of quality determines how far a factory can go. We have been established for 13 years in 2022, and we will continue to work hard to win-win with our customers under the premise of quality assurance. Free stock samples are available to send for testing.
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