Status and Prospects of PVA Water-Soluble Films

  • Introduction

PVA water-soluble film, as a novel packaging material, is widely used in the packaging of products used with water in countries such as Europe, the United States, and Japan. These products include pesticides, fertilizers, pigments, dyes, detergents, water treatment agents, mineral additives, concrete additives, chemical reagents for photography, and chemical reagents for horticultural care. Its main characteristics are as follows:

1. Environmentally safe, completely biodegradable (up to 100%), with the final degradation products being carbon dioxide and water, which can effectively solve the problem of packaging waste disposal.

2. Convenient and safe to use, avoiding direct contact between the user and the packaged product, making it suitable for packaging hazardous substances.

3. Precise measurement, preventing waste.

4. Good mechanical properties and the ability to be heat-sealed with high strength.

5. Anti-counterfeiting features, serving as an effective tool to extend the lifespan of high-quality products.

Major producers and sellers of these products are Japan, the United States, France, China,  including companies like W.T.P in the United States, C.C.L.P, GRENSOL in France, and synthetic chemical companies in Japan. In China, with the support of the Technology Department of the China Packaging Corporation, few company jointly developed high-tech water-soluble films and their production equipment, which are now in production, filling the domestic gap and entering the market. This article introduces the composition of water-soluble plastic films, the production process, and their application prospects in a systematic manner.

 

  • Production Process:

PVA water-soluble film is mainly made from polyvinyl alcohol and starch as the primary raw materials, with various additives such as surfactants, plasticizers, anti-adhesive agents, and more. Its production process is different from traditional plastic film forming. The process involves turning the raw materials into a water-soluble gel with a solid content of 18-20%. This gel is then coated onto a mirror-finished stainless steel belt, dried to form a film, peeled off from the steel belt, and then dried in a drying chamber to the specified moisture content before being cut and wound into the final product.

 

  • Chemical Composition:

The main raw materials of water-soluble packaging films are low alcohol-soluble polyethylene and starch, with various additives. These additives consist of C, H, and O compounds, and are non-toxic and compatible with polyethylene. They improve the physical properties, mechanical properties, processing properties, and water solubility of polyethylene, but do not undergo chemical reactions, preserving its chemical properties. The primary chemical components are C, H, and O.

 

  • Environmental Characteristics:

PVA water-soluble film products are considered green and environmentally friendly packaging materials and have received recognition from environmental authorities in countries like Europe, the United States, and Japan. Currently, both domestically and abroad, the biological oxygen demand (BOD) and chemical oxygen demand (COD) are used as environmental indicators. Studies in Japan have shown that the BOD of polyvinyl alcohol is significantly lower than that of starch, and in the United States, Airvol PVA products from Air Products and Chemicals, Inc. exhibited a BOD reduction to less than 1% of the initial BOD after 5 days of biodegradation. Biodegradation experiments have indicated that polyvinyl alcohol is non-toxic and does not affect waste treatment or environmental hygiene. Microbial degradation studies have shown that polyvinyl alcohol is nearly completely decomposed, resulting in very low COD levels.

 

Regarding the degradation mechanism, polyvinyl alcohol has both water and biological degradation properties. It first dissolves in water to form a gel that infiltrates the soil, improving soil aggregation, aeration, and water retention, making it suitable for sandy soil improvement. In the soil, PVA can be decomposed by strains of bacteria, particularly Pseudomonas species. At least two bacterial strains are required for the decomposition of polyvinyl alcohol: one is an active strain of polyvinyl alcohol, and the other produces the substances needed for PVA metabolism. Enzymes catalyze the oxidation of secondary alcohols, followed by hydrolysis of oxidized PVA chains, further degradation, ultimately reducing it to carbon dioxide and water.

 

  • Key Properties:

 

  1. Moisture Content

Rolled water-soluble films are typically packaged in PE plastic to maintain their specific moisture content. When water-soluble films are removed from PE packaging, their moisture content changes with environmental temperature, which affects their performance until they reach equilibrium.

 

       2. Anti-static Properties

Water-soluble films are anti-static and different from other plastic films; they possess excellent anti-static properties. Using water-soluble film for product packaging does not lead to reduced plasticity or static dust due to static electricity.

 

    3. Water and Gas Permeability

Water-soluble films exhibit strong permeability to water and oxygen but excellent barrier properties against oxygen, nitrogen, hydrogen, and carbon dioxide gases. This characteristic allows them to maintain the composition and odor of the packaged products.

 

   4.Heat Sealing

Water-soluble packaging films have excellent heat-sealing properties suitable for resistance sealing, high-frequency sealing, and heat-sealing strength, which depends on factors like temperature, humidity, pressure, and time, typically ranging from 100 to 200 g/cm.

 

   5. Printing Performance

Water-soluble films can be easily printed using standard printing methods, providing good printing quality.

 

   6. Oil and Chemical Resistance

Water-soluble packaging films show good resistance to oils (vegetable, animal, mineral), fats, organic solvents, and carbohydrates. However, they are not recommended for packaging with strong bases, strong acids, chlorine radicals, and other substances that react chemically with PVA, such as borax, boric acid, and certain dyes.

 

   7. Water Solubility

The water solubility of water-soluble films depends on their thickness and temperature. There are cold water-soluble, medium-temperature water-soluble, and high-temperature water-soluble films. Generally, they can completely dissolve in water at a specific temperature, with dissolution times ranging from 10 seconds to 5 minutes, depending on the process. The thickness can range from 17 to 100 micrometers depending on the process.

 

Prospects:

Water-soluble films have a wide range of applications and a vast market due to their eco-friendly nature. They are gaining significant attention in developed countries worldwide. For example, Japan, the United States, France, and other countries have already produced and sold a large number of such products. Companies like W.T.P, C.C.L.P, GREENSOL, and synthetic chemical companies have also started using water-soluble films for their products. In the domestic market, the water-soluble film market is growing, and according to relevant statistics, currently, the annual demand for packaging films accounts for 20% of plastic products, or approximately 309,000 tons. Even with a 5% market share, the annual demand would be 15,000 tons. The main applications include:

 

Packaging for products used with water, such as pesticides, fertilizers, pigments, dyes, detergents, water treatment agents, mineral additives, concrete additives, chemical reagents for photography, and chemical reagents for horticultural care.

Water transfer printing for applying logos and patterns on ceramic and irregularly shaped electrical enclosures.

High-temperature water-soluble films (not soluble below 40°C), suitable for packaging clothing, textiles, and food preservation films, especially for export products.

Used for seed bags, agricultural seedlings, embroidery, etc.

Furthermore, since the main raw material of water-soluble films is polyvinyl alcohol, and China is a major producer of this material, it has favorable market prospects for the application of high-tech water-soluble packaging films. As society develops and people become increasingly concerned about preserving the environment, the demand for eco-friendly packaging is growing. Therefore, the prospects for water-soluble films are undoubtedly vast.

 

 

 

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