Green high barrier packaging material

First, the development trend of high barrier packaging materials

Currently, high barrier packaging materials in the market mainly include polyvinylidene chloride ( PVDC ), ethylene-vinyl alcohol copolymer ( EVOH ) and polyvinyl alcohol ( PVA ). With the increase of the market packaging function and the improvement of environmental awareness, the cost performance of the product cost becomes more and more important. However, PVDC contains chlorine ions. During the process of processing and waste disposal, HCl gas is generated, air is contaminated, and articles are packaged. Europe and the United States and other regions have begun to restrict and stop their use. The water resistance and weather resistance of EVOH have not been solved yet, and the price is high. No less than that, the entire packaging market is daunting for high barrier multi-layer co-extruded films. The market's expected price/performance ratio is more reasonable, and it can be an inevitable trend to replace the water-resistant modified PVA coating film of PVDC and EVOH .
First of all, in nature, the water-resistant modified PVA coating film is a product with high technological content and high added value. Whether it is the selection of raw materials, or the processing and consumption process, there is no or no release of any toxic and harmful substances, which is conducive to environmental protection and realization. Green consumption is an environmentally friendly product.
Secondly, on the dosage: As China's accession to the WTO , China's economy will usher in a new round of accelerated development, the packaging industry will continue to increase the use of PVA high barrier membrane, the domestic high barrier packaging materials in the total amount of flexible packaging materials The proportion does not exceed 10 %, far below the 40 % of Japan and the United States , so there is still huge room for potential demand growth in the market.
Again, the benefits: Water-resistant modified PVA main components are PVA resin and water, raw materials can be purchased in the domestic market. The product is superior to the current EVOH co-extruded film and PVDC coating film both in terms of performance and price, and is an ideal substitute for PVDC coating film.
Finally, the policy: State Economic and Trade Commission in June 2001 published "15 Plan" that: focus on the development of various packaging materials in food, beverage, pharmaceutical and other packaging to enhance the protection, extend the shelf life of high-barrier packaging materials, Hot-filling packaging materials, fresh-keeping materials, grain storage and transportation of mold and pest control materials. September 28, 2002 the State Economic and Trade Commission issued the "recent development-oriented industries" (Guo Jing Mao Industry [2002] No. 716) that "the development of high barrier containers, packaging material, multi-function film, water-soluble and biodegradable film Material technology and equipment." Therefore, the water-resistant modified PVA coating film conforms to the development direction of the national industrial policy.
In short, the water-resistant modified PVA high-barrier coating film is a green environmental protection, oxygen barrier performance, cost-effective packaging materials, the project product line with the development direction of the national industrial policy, the outlook is optimistic.
Second, the current market in the modified PVA coating film problems
(1) Water resistant
Many manufacturers who apply PVDC are disgusted with the modified PVA on the market. They are not interested in the modified PVA. Instead, they are not satisfied with the water-resistant performance of the product and will be rejected. According to research, there are indeed such products on the market. According to the experimental analysis, the so-called modification of this type of product is that only a few hydroxyl groups of polyvinyl alcohol are cross-linked and blocked with a modifier, and most of the hydroxyl groups are also exposed on the outside. These exposed hydroxyl groups have strong hydrophilicity. Sex, macroscopically, the PVA coating is not water resistant.
(2) Color is not transparent
At present, the modified PVA glue liquid on the market is yellow, opaque, and the diameter of the rolled-back end of the coated substrate is also obviously yellow, and the color changes from yellow to reddish-brown with the extension of time. As a packaging material, this product seriously affects the natural appearance of the packaged product.
(3) poor glue stability
Through the understanding of PVA coating film manufacturers, the existing modified PVA glue on the market is greatly affected by temperature, time and pH. The main performance is that the lower the temperature, the longer the time, the smaller the PH value, the easier the modified PVA glue gel.
Third, the advantages of water-resistant modified PVA coating film
(1) Performance advantages
Water-resistant modified polyvinyl alcohol ( PVA ) high-barrier diaphragm is a patented product of China Aerospace Engineering Group's 8511 Institute (Nanjing Institute of Electronic Equipment) (patent number: ZL 95112745.4 ), which is a modified polyvinyl alcohol. The aqueous solution is coated and dried. Due to the use of chemical modifiers to block the hydrophilic hydroxyl groups of polyvinyl alcohol, the product has good resistance to oxygen and good water resistance, and the coating does not produce under water or high humidity conditions. Back-adhesion and swelling phenomenon, coated base materials such as PE and CPP can be used directly as high-barrier packaging materials, and the coating has good printing and composite adaptability and can satisfy various requirements. Composite structure requirements.
Table 1 Comparison of Performance of Water-resistant Modified PVA Coating Film and PVDC Coating Film

project
Water-resistant modified PVA coating film
PVDC coating film
Dry coating weight /g/m2
0.6
3
Oxygen permeation / cm3/(m2 ·24h·0.1MPa)
2
15
Moisture resistance
Suboptimal
excellent
Pre-coating (bottom glue)
Need not
need
Coating times
1
2
Equipment investment
low
high
Green
excellent
difference
Compared with PVDC coated film, the comprehensive performance of water-resistant modified PVA coating film is more advantageous. From Table 1, it can be seen that the dry weight of the water-resistant modified PVA coating is 0.6 g/m2 , while the dry weight of the PVDC coated is 3 g/m2 , which is five times that of the former, and apparently the same coating substrate, by weight of the same coating products, which use much less area than the former; in oxygen barrier properties, water-modified PVA coating film an average oxygen transmission rate 2 cm3 / (m2 · 24h · 0.1MPa), the minimum value of the test It is 0.27cm3/(m2·24h·0.1MPa), while the oxygen permeability of the PVDC coating film coated twice is about 15 cm3/(m2 ·24h·0.1MPa), and the former has much better oxygen barrier performance than the latter. ; in moisture barrier, which is slightly inferior former; modified PVA coating film because the water production process is simple, only 1 is applied, and not pre-coated, the oxygen barrier property and adhesion fastness is very good, so the coating The equipment requirements for water-resistant modified PVA are lower than that for coating PVDC ; finally, the water-resistant modified PVA is green and environmentally friendly, and developed countries have used it in large quantities, while PVDC contains chlorine ions, which generates a large amount of HCl gas during waste treatment. Contamination of the environment, Europe and the United States and other regions have begun to limit and stop using.
(2) price advantage
Taking PET with a thickness of 12 μm as an example, the width is 1m , the weight is 1t , the density is 1.41 × 103kg/m3 , the area is 60000 m2, and the tonnage price of the substrate is 13,000 yuan/t. At present, the ton price of PET/PVDC coating film on the market is 21,000 yuan/t, and the ton price of our PET/PVA coating film is 23,000 yuan/t. On the surface, the ton price of PET/PVA coating film is higher than PET/PVDC coating. The high price of membranes is actually not the case. After PVDC coating, the dry weight is 3g/m2. After 1tPET is coated, the weight is 1.18t and the weight gain is 180kg. After the PVA is coated, the dry weight is 0.6g/m2. After the 1tPET is coated, the weight is 1.036t and the weight gain is 36kg. . It can be seen that the weight gain of the PET/PVDC coating film is 5 times that of the PET/PVA coating film weight; the gram weight of the PET/PVDC coating film is 19.7 g/m2, and the PET/PVA coating film Weight is 17 .3g/m2; 1tPET/PVDC coating film area is 50761m2, 1tPET/PVA coating film area is 57803m2; PET/PVDC coating film square price is 0.41 yuan/m2, PET/PVA The square unit price of the coating film is 0.40 yuan/m2; the coating cost of the PET/PVDC coating film is 0.20 yuan/m2, and the coating cost of the PET/PVA coating film is 0.18 yuan/m2. In other words, the area of ​​the 1tPET/PVDC coating film is 7042 m2 less than that of the 1tPET/PVA coating film; the ton price of the PET/PVA coating film on the surface is higher than the ton price of the PET/PVDC coating film, actually PET/ The coating cost of the PVA coating film is lower than the coating cost of the PET/PVDC coating film. Specific data are shown in Table 1.
Table 1 Comparison of PET/PVA Coating Films and PET/PVDC Coating Films

project
Ton price (yuan/t)
Weight (g/m2)
Ton area (m2/t)
Square unit price (yuan/m2)
Coating cost (yuan/m2)
PET/PVDC
21000
19.7
50761
0.41
0.20
PET/PVA
23000
17.3
57803
0.40
0.18

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