Isocyanate emulsion-polymer

An emulsion polymer-isocyanate adhesive, a crosslinked polyvinyl acetate adhesive, a resorcinol-formaldehyde adhesive, a phenol-resorcinol-formalde-hyde adhesive, and an acid-catalyzed phenolic-formaldehyde adhesive developed bonds of high shear strength and wood failure at all levels of acetylation in the dry condition. A neoprene contact bond adhesive and a moisture-curing polyurethane hot-melt adhesive performed as well on acetylated wood as untreated wood in tests of dry strength. Only a cold-setting resorcinol-formal-... 

Wood was soaked or impregnated with chemicals. After that they were set in a hot press and pressed at 160 iC/0.5-2MPa for 5-30min. [Heat-Pressed Treatment]. Comparison specimens were set in a hot oven and dried at 160 °C for 2-6hrs. [Heat-Dried Treatment]. Heat pressed material was put on top of each other or untreated material with emulsion polymer-isocyanate adhesives to make a laminated board. 

Isoset . [Ashland/Foundry Prods.] Emulsion polymer/isocyanate adhesive resins found core binders. 

Adhesive abbreviations are as follows EP, amine-cured epoxy P, polysulfide rubber flexibilizers EP/20P, EP/ 40P, and EP/60P, amine-cured epoxy with 20, 40, and 60 parts polysulfide flexibilizer EPI, emulsion polymer isocyanate ISO, isocyanate MF, melamine-formaldehyde PF, phenol-formaldehyde PF/PVA, phenol-formaldehyde flexibilized with poly(vinyl acetate) PVA, poly(vinyl acetate) PRF, phenol/resordnol-formaldehyde RF, resorcinol-formaldehyde UF, urea-formaldehyde UF/filler, UF with wheat flour UF/MF/fiUer, UF/MF copolymer with wheat flour. 

Emulsion Polymer Isocyanates as Wood Adhesive A Review... 

EPI, Emulsion Polymer Isocyanate, MDI, pMDI, wood adhesives, solid wood panel, parquet, window frame, furniture, plywood, finger joint, glulam beam, I-betim, cross-laminated timber... 

Emulsion Polymer Isocyanate (EPI) adhesives are two-component adhesive systems consisting of water-based emulsions cured with an isocyanate cross-linker. The first EPI adhesives were developed in Japan in the early I970 s and this adhesive type has been extensively used in Japan since then [1-3]. 

Water-based Polymer Isocyanate (JIS name [7]) or Emulsion Polymer Isocyanate (EPI) adhesives were developed in Japan by Kuraray Co., Ltd, Koyo Sango Co., Ltd and Asahi Plywood Co., Ltd in the early 1970 s [8]. The driving forces were to establish new markets for poly(vinyl alcohol) (PVA) and to develop alternatives to formaldehyde-based wood adhesives. The technology was patented [9], and thereafter licensed to different companies worldwide [8]. The licenses led to introduction of EPI adhesives into Europe, North America and Oceania. Since the EPI adhesives are of Japanese origin, their popularity is naturally concentrated in the Asian markets. Non-Asian consumption is growing, but the market for this adhesive type is still limited. 

EPI adhesives are two-component systems. In the following the emulsion/polymer based component (the adhesive component) and the isocyanate based cross-linker component will be discussed separately. 

The main source of hydroxyl groups in the adhesive is usually the PVA, but hydroxyl and other functional groups such as carboxyl groups and amines on the emulsion polymer chain can also react with the isocyanate, provided that they are physically available. In addition, the hydroxyl groups in the wood may take part in... 

Emulsion Polymer Isocyanate (EPI) adhesives appeared 2 years ago in Europe for the manufacture of glulam beams because of environmental issues. These adhesives are still not covered by a European standard but must meet the performance requirements specified by the CEN TC193/SC1 Committee in a draft that will be... 

Last, but not least, a serious interest is to reduce formaldehyde emissions coming from all types of glued products. This is the reason for development of new formaldehyde-free products such as polyurethane adhesives and emulsion polymer isocyanate (EPI) adhesives for load bearing structures. 

Emulsion-polymer isocyanates (EPI s) were introduced by Ashland Chemical Co. as better performing wood adhesives (101). EPI s are equivalent to phenol-resorcinol and cross-linkable polyvinyl acetate adhesives. EPI s are more advantageous than others because they have shorter press times, no chalking temperature, a low-temperature curing, no formaldehyde emission, better resistance to high temperatures and accelerated aging, environmental attractiveness, an ability to determine performance by adjusting hardener level, and more tolerance to variations in process conditions. 

Anionic coatings systems for water-borne topcoats are emulsion polymers, miniemulsion polymers, polyurethane dispersions, different types of dispersions of acrylic resins in water and amino resins, water-borne polyesters, polyurethanes. Many of the polymers are hydroxyl containing and cured with various melamines and blocked isocyanates. The polymers are mainly stabilized in the water phase by neutralization of anionic groups with volatile amines (2-amino-2-methyl-l-propanol). Cross-linkers like aminoplast resins, alkoxy silanes, blocked epoxy resins, carbodi-imides can be used. 

Both aqueous polymer-based systems (latex), made by emulsion or dispersion polymerization, and oil-modified alkyd resin-based systems are still in wide use [781], Table 12.2 shows the composition of a typical water-based emulsion paint. There is a wide variety of coatings, ranging from broad applicability to highly specialized, including latexes, amino resins, isocyanates, epoxy resins, acrylic resins, polyester... 

The first step in all interfacial polymerization processes for encapsulation is to form an emulsion. This is followed by initiation of a polymerization process to form the capsule wall. Most commercial products based on interfacial or in situ polymerization employ water-immiscible liquids. For encapsulation of a water-immiscible oil, an oil-in-water emulsion is first formed. Four processes are schematically illustrated in Figure 5.82. In Figure 5.82(a), reactants in two immiscible phases react at the interface forming the polymer capsule wall. For example, to encapsulate a water-immiscible solvent, multifunctional acid chlorides or isocyanates are dissolved in the solvent and the solution is dispersed in water with the aid of a polymeric emulsifier, e.g., poly(vinyl alcohol). When a polyfunctional water-soluble amine is then added with stirring to the aqueous phase, it diffuses to the solvent-water interfece where it reacts with acid chlorides or isocyanates forming the insoluble polymer capsule wall. Normally some reactants with more than two functional groups are used to minimize a regation due to the formation of sticky walls. 

Originally the adhesive system consisted of an aqueous poly(vinyl alcohol) solution with an isocyanate cross-linker. At this stage the common name was Aqueous Polymer Isocyanate (API) [3]. Further developments including use of different types of polymer emulsions, like poly(vinyl alcohol) (PVA), ethyl(vinyl acetate) (EVAc), styrene butadiene rubber (SBR) or acrylic-styrene (AcSt) emulsion, led to adhesives systems with improved performance, hence today the common abbreviation is EPI [4, 8]. The isocyanate cross-linking agent has also been further developed to improve the compatibility and the reactivity with the water-based component, thus several different types are now available for use in EPI adhesives. 

Since the EPI adhesives are emulsion based but cross-linked with isocyanate, they share characteristics with both thermosetting and thermoplastic adhesives. The adhesives are multi-phase systems comprising emulsion particles, polymer solution, cross-linker droplets and filler particles. Just as for other emulsion adhesives, the coalescence of the emulsion particles [18, 19] and the distribution of these in the glue film is important for the bond quality. The cross-linking in the adhesive film is also of great importance for the bond quality as well as for the moisture resistance and heat resistance of the adhesive. 

Prepolymer ionomers with isocyanate end-groups and of sufficiently low molecular weight can be mixed with water in the presence of hydrophobic organic solvents, such as methylene chloride or toluene, or, in the case of sufficiently low viscosities, even without solvent. The prepolymers form emulsions, which in turn form polymer dispersion after chain extension by reaction of the isocyanate. Such a process requires powerful high-shear mixing equipment in the presence or absence of solvents. Solutions of ionomers in hydrophilic solvents form emulsions spontaneously in the presence of water. The formation of the emulsion must be... 

The condensation route to wall polymers is the best method for pesticide encapsulation. In this process the two reactive monomers, one dissolved in each of the two phases (of the emulsified oil/pesticide in water), polymerize at the interface and generate the wall material. Typically, the oil-phase monomers are polyfunctional isocyanates (A) or acid chlorides (B) and the water-phase reactants are polyalcohols or amines. Compounds sufficiently reactive are chosen such that when they meet at the interface the condensation polymer forms the capsule wall (Fig. 4). Alternatively, the two reactants (a diol and a diisocyanate) and a low boiling solvent make up the oil phase of the emulsion along with the pesticide. When heated the solvent evaporates bringing the monomers together at the droplet surface to form the capsule wall (27). 

Water (Isopropyl alcohol can also be used) Wax, silicone and nonionic surface active agent are used as anti foaming agents. Acrylic polymer Emulsion of acrylic polymer Ethylene oxide polymer Hydroxyl ethyl Cellulose Methyl cellulose Polyvinyl alcohol Isocyanate Wax wetting agent Aqueous urethane. Salt of methacrylic acid copolymer Wax emulsion Emulsion of ethylene-vinyl acetate eopolviner ... 

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