VAE (vinyl acetate-ethylene copolymer emulsion) is a high-performance emulsion polymer. Due to its excellent comprehensive properties, it is widely used in building materials, textile printing and dyeing, papermaking, coatings, adhesives, labels, and sealing materials. It is an indispensable green fine chemical product that can be seen everywhere in life.
VAE is a polymer compound made of vinyl acetate and ethylene as the main raw materials and other excipients through emulsion polymerization process. It has significant environmental protection properties and good bonding properties.
EVA (ethylene-vinyl acetate copolymer resin) and VAE are different types of ethylene and vinyl acetate copolymers. EVA resin is flexible when the vinyl acetate content is less than 40%; EVM (ethylene-vinyl acetate elastomer) is elastic when the vinyl acetate content is 40% to 70%; VAE emulsion when the vinyl acetate content is 70% to 95%, and the appearance is milky white.
Vinyl acetate-ethylene copolymer emulsions (VAE) are a relatively young member of the emulsion polymer family. In the 1950s, researchers first tried to introduce ethylene as a monomer into emulsion polymerization, and VAE emulsions achieved commercial mass production in the late 1960s. After years of development, this new type of copolymer emulsion has gradually broken through the limitations of niche markets and achieved success on a global scale.
Since the 1990s, VAE emulsions have entered a period of rapid growth and have become one of the fastest growing segments in the emulsion sector. The growth of the VAE emulsions market is mainly driven by two factors: one is the shift of manufacturing to Asia and other emerging regions at that time, where the construction industry is booming; the second is the increasing environmental awareness of local consumers. The construction and other industries are moving towards a green transformation, and it has become a trend for water-based systems to gradually replace solvent-based systems. In the application of low-emission or even zero-volatile organic compound (VOC) formulations, VAE emulsions continue to expand their market share due to their environmental advantages.
Between 1995 and 2010, a series of mergers and acquisitions led to the creation of today's two global leaders: in 2008, Wacker Chemie acquired its emulsions business after running two joint ventures with Air Products for a decade; Celanese took over Hearst's legacy VAE emulsions business from Clariant and integrated it with Imperial Chemical Industries' (ICI) emulsions business in 2005.
In addition to the market dominance of Wacker Chemical and Celanese, there are also Formosa Plastics Group, as well as the domestic Chuanwei Chemical and Wanwei Group. At present, the overall domestic market capacity in China is about 1 million tons.
In addition, the transportation cost of end point products also accounts for a considerable proportion of the total cost - all emulsion products contain up to 50% moisture, and a large amount of moisture is actually transported over long distances during transportation, which undoubtedly drives up logistics costs.
In recent years, the growth of VAE emulsions has encountered bottlenecks in some existing application fields, such as engineering fabrics, paper and packaging adhesives. The main reasons are the slow growth rate of the application field itself, or the competition from non-congeneric products. At present, VAE emulsions still maintain unique advantages in only a few sub-sectors, and most bulk products have been reduced to commodities, and profit margins are under pressure.
With its outstanding combination of material properties, VAE emulsions have achieved significant commercial success in the following areas:
The demand for these four application fields accounts for about 70% -80% of the total global VAE emulsion production.
In water-based adhesives for paper and packaging, VAE emulsions are used without the addition of low-molecular-weight plasticizers - these plasticizers are already under strict regulatory pressure due to migration risks and potential toxicological issues. Adhesives prepared from VAE can meet relevant regulatory requirements for indirect and even direct food contact.
In the production process, two key points need to be controlled: one is to ensure that the polymer reaches a sufficiently high molecular weight; the other is to balance the adhesive's adhesion to low surface energy/low polarity surfaces with its own sufficient cohesion strength through the introduction of ethylene units.
As the packaging industry continues to innovate, VAE suppliers need to develop adhesives that meet the following requirements:
The material properties of VAE make it a significant advantage in polymer-modified construction adhesives (such as ceramic tile adhesives, mortars, putty, etc.). Redispersible latex powder based on VAE emulsion has the characteristics of high adhesion, high flexibility and high saponification resistance. VAE used for redispersible latex powder in the construction field is usually stabilized by PVOH in standard application scenarios without functional modification; for applications with higher quality requirements.
VAE emulsions, with their unique material properties, are used as adhesives in nonwovens and exhibit excellent application characteristics, including: a good balance of rigidity and high tensile strength; a soft feel and excellent toxicological properties.
With the increasing awareness of environmental protection among consumers and the introduction of relevant indoor emission regulations, the market share of VAE emulsions in the field of decorative coatings (especially for indoor applications) has gradually expanded.
The core advantage of VAE emulsions for the field of coatings and coatings is the "water plasticizing effect": VAE is formed by the copolymerization of hydrophilic VAM and hydrophobic ethylene, and water acts as a film-forming aid in the system. Based on this characteristic, low-emission, high-scrub-resistant coatings can be formulated without the addition of organic solvents as film-forming aids; the minimum film-forming temperature of these coatings is less than 5 ° C, and it can still be applied at lower ambient temperatures.
The choice of functional comonomers and stabilizers in VAE coating formulations varies by region and specific application scenarios. For example, vinyl alkoxysilane or glycidyl methacrylate (GMA) are often used as functional comonomers in VAE emulsions to enhance cross-linking with inorganic surfaces.
Although VAE emulsions have many advantages, their application scope is still limited due to their physical and chemical properties. For example, commercial monomers that can easily access the backbone of VAE polymers are limited in variety and diversity; most commercial functional monomers are based on acrylic or methacrylic acid structures, and have poor copolymerization characteristics with VAM and ethylene;
VAE technology also faces production-level challenges: it is necessary to ensure the safe handling of ethylene and the standardized operation of pressure equipment. The pressure level of the equipment determines the ethylene that can be introduced into the VAE within the economically feasible batch operation reaction time, which increases the capital cost of new investments, resulting in relatively low profitability in the early stage of VAE technology.
The glass transition temperature range of VAE is - 20 ° C to 20 ° C, and there are also specific ranges in terms of hydrophobic-hydrophilic equilibrium and bond-cohesion properties.
"VAE limitations" within the current boundaries have been fully explored. New products are often adaptations of existing products to changing application scenarios or new markets, or incremental improvements in certain performance indicators. Further innovations have been achieved. VAE enterprise capacity continues to increase, and market competition will become more intense. Continuously improve production technology, reduce costs, and develop high-end and high-performance products.
The increasing awareness of environmental protection around the world and the increasingly strict regulations on VOCs and other fields related to people's lives in various regions are expected to create many innovative opportunities with new material properties. VAE emulsions provide green development momentum for industries such as adhesives.
