Emulsion polymerization typical recipe

If a linear mbber is used as a feedstock for the mass process (85), the mbber becomes insoluble in the mixture of monomers and SAN polymer which is formed in the reactors, and discrete mbber particles are formed. This is referred to as phase inversion since the continuous phase shifts from mbber to SAN. Grafting of some of the SAN onto the mbber particles occurs as in the emulsion process. Typically, the mass-produced mbber particles are larger (0.5 to 5 llm) than those of emulsion-based ABS (0.1 to 1 llm) and contain much larger internal occlusions of SAN polymer. The reaction recipe can include polymerization initiators, chain-transfer agents, and other additives. Diluents are sometimes used to reduce the viscosity of the monomer and polymer mixture to faciUtate processing at high conversion. The product from the reactor system is devolatilized to remove the unreacted monomers and is then pelletized. Equipment used for devolatilization includes single- and twin-screw extmders, and flash and thin film evaporators. Unreacted monomers are recovered for recycle to the reactors to improve the process yield. 

A typical recipe for batch emulsion polymerization is shown in Table 13. A reaction time of 7—8 h at 30°C is requited for 95—98% conversion. A latex is produced with an average particle diameter of 100—150 nm. Other modifying ingredients may be present, eg, other colloidal protective agents such as gelatin or carboxymethylcellulose, initiator activators such as redox types, chelates, plasticizers, stabilizers, and chain-transfer agents. 

Simplified nitrile mbber polymerization recipes are shown in Table 2 for "cold" and "hot" polymerization. Typically, cold polymerization is carried out at 5°C and hot at 30°C. The original technology for emulsion polymerization was similar to the 30°C recipe, and the redox initiator system that allowed polymerization at lower temperature was developed shortiy after World War II. The latter uses a reducing agent to activate the hydroperoxide initiator and soluble iron to reactivate the system by a reduction—oxidation mechanism as the iron cycles between its ferrous and ferric states. 

The polymerization reaction is conducted at the desired temperature with a slow stirring regime for a certain period. A typical recipe for the emulsion polymerization of styrene is exemplified in Table 1 [40]. As seen here, potassium persulfate and sodium dodecyl sulfate were used as the initiator and the stabilizer, respectively. This recipe provides uniform polystyrene particles 0.22 /Lim in size. 

Table 1 A Typical Recipe for the Emulsion Polymerization of Styrene [40]...

The physical picture of emulsion polymerization is based on the original qualitative picture of Harkins [1947] and the quantitative treatment of Smith and Ewart [1948] with subsequent contributions by other workers [Blackley, 1975 Casey et al., 1990 Gao and Penlidis, 2002 Gardon, 1977 Gilbert, 1995, 2003 Hawkett et al., 1977 Piirma, 1982 Poehlein, 1986 Ugelstad and Hansen, 1976]. Table 4-1 shows a typical recipe for an emulsion polymerization [Vandenberg and Hulse, 1948]. This formulation, one of the early ones employed for the production of styrene-1,3-butadiene rubber (trade name GR-S), is typical of all emulsion polymerization systems. The main components are the monomer(s), dispersing medium, emulsifier, and water-soluble initiator. The dispersing medium is the liquid, usually water,... 

Typical emulsion polymerization recipes involve a large variety of ingredients. Therefore, the possibilities of variations are many. Among the variables to be considered are the nature of the monomer or monomers, the nature and concentration of surfactants, the nature of the initiating system, protective colloids and other stabilizing systems, cosolvents, chain-tranfer agents, buffer systems, short stops, and other additives for the modification of latex properties to achieve the desired end properties of the product. 

Free-Radical Polymerization. The best method for polymerizing isoprene by a free-radical process is emulsion polymerization. Using potassium persulfate [7727-21-1] as initiator at 50°C, a 75% conversion to polyisoprene in 15 h was obtained (76). A typical emulsion polymerization recipe is given as follows (77). 

Emulsion Polymerization A typical recipe is give in Table I. Emulsion polymerization was carried out at 60°C under a nitrogen atmosphere using a batch process. Theoretical solids content in all the formulations was 25%, and generally the conversions were better than 98%. A polyvinyl acetate homopolymer and two poly (vinyl acetate-butyl acrylate) copolymers having VA/BA composition of 85/15 and 70/30 were prepared according to the above procedure. 

The most common continuous emulsion polymerization systems require isothermal reaction conditions and provide for conversion control through manipulation of initiator feed rates. Typically, as shown in Figure 1, flow rates of monomer, water, and emulsifier solutions into the first reactor of the series are controlled at levels prescribed by the particular recipe being made and reaction temperature is controlled by changing the temperature of the coolant in the reactor jacket. Manipulation of the initiator feed rate to the reactor is then used to control reaction rate and, subsequently, exit conversion. An aspect of this control strategy which has not been considered in the literature is the complication presented by the apparent dead-time which exists between the point of addition of initiator and the point where conversion is measured. In many systems this dead-time is of the order of several hours, presenting a problem which conventional control systems are incapable of solving. This apparent dead-time often encountered in initiation of polymerization. 

In Fig. 8 the calorimetric curve of a typical miniemulsion polymerization for 100-nm droplets consisting of styrene as monomer and hexadecane as hydrophobe with initiation from the water phase is shown. Three distinguished intervals can be identified throughout the course of miniemulsion polymerization. According to Harkins definition for emulsion polymerization [59-61], only intervals I and III are found in the miniemulsion process. Additionally, interval IV describes a pronounced gel effect, the occurrence of which depends on the particle size. Similarly to microemulsions and some emulsion polymerization recipes [62], there is no interval II of constant reaction rate. This points to the fact that diffusion of monomer is in no phase of the reaction the rate-determining step. 

The essential ingredients in an emulsion polymerization are the water, a monomer which is not miscible with water, an oil-in-water emulsifier, and a compound or compounds which release free radicals in the aqueous phase. Other ingredients which may be used in practical recipes are mentioned briefly later. Typical proportions (by weight) are monomers 100, water 150, emulsifier 2-5, and initiator 0.5, although these ratios may vary over a wide range. 

A typical emulsion polymerization recipe includes specific proportions of the added ingredients, e.g. (in wt%) monomer, 100 water, 150 initiator, 0.5 surfactant, 5. Because the monomer has low water solubility, it is clear that there will be two separate phases referred to as the monomer phase and the aqueous phase. The aqueous phase, containing the surfactant in the form of micelles, can be considered as consisting of two phases, the micellar phase and the true aqueous phase. The emulsifier helps disperse the monomer in the aqueous phase with droplets in the order of a few micrometers in size. The hydrophobic interior of the micelles contains solubilized monomer, which is apportioned by diffusion out of the emulsified monomer droplets and through the aqueous phase. 

A simple recipe for emulsion polymerization would be comprised of hydrophobic monomers (AO to 60 volume percent), a continuous aqueous phase (AO to 60 volume percent), a water-soluble initiator, and an emulsifier or stabilizer. Other minor ingredients such as chain transfer agents, inhibitors or retarders, and buffers may also be present. Emulsion polymerization is characterized by a large number of reaction sites (the polymer particles) that contain a small number of free radicals. These free radicals are isolated because of the water phase between the particles. Typical polymer... 

A series of latex copolymers were prepared using a typical emulsion polymerization recipe and procedure only the monomer composition was varied. The control composition (80/20 vinyl acetate/butyl acrylate) is similar to that used for interior latex paint. Table V lists the compositions and properties of the latexes. Percent solids, pH, and particle size are similar for all the latexes. Viscosity varies somewhat, but is within limits for this type of latex. The only unreacted monomer detected was the vinyl acetate. Thus, the incorporation of VEC into the emulsion polymerization via the monomer mixture did not affect the latex synthesis. The Tg and minimum film formation temperature (MFFT) of the latexes increase with increasing VEC content, which is expected based on the previous results. 

Typical Emulsion Polymerization Recipes, Prod. Bull. F-40039B. Carbide and Carbon Chem. Co., New York, 1956. 

A typical recipe for emulsion polymerization in parts by weight consists of 180 parts of water, 100 parts of monomer, 5 parts of fatty acid soap (emulsifying agent), and 0.5 parts of potassium persulfate (water-soluble initiator). The question, of course, is how these eomponents are distributed within the system. By definition, soaps are sodium or potassium salts of oiganic acids, for example, sodium stearate ... 

In emulsion polymerization, the rate of generation of free radicals is about lO Vm-s while the number of monomer-polymer particles for typical recipes, N, is in the range 10 to 10 particles/ml of the aqueous phase. Consequently, if all the initiator radicals are captured by the monomer-qxilymer particles, each particle will acquire, at the most, a radical every 1 to 100 s. It can be shown that if a particle contains two radicals, mutual annihilation of radical activity will occur within a time span of the order... 

A typical emulsion polymerization recipe consists of 180 g water, 100 g monomer, 5 g soap, and 0.5 g potassium persulfate. Estimate the ratio of the total surface area of micelles to that of monomer droplets. Assume that the relative volume of micelle to a droplet is equal to the ratio of their volumes in the polymerization recipe. The density of a micelle is 0.2 g/cc and that of a droplet is 0.8 g/cc. 

A typical recipe of the materials used for emulsion polymerization is given in Table These materials are charged in a reactor under... 

Table 3.1 Typical Recipe of Materials for Emulsion Polymerization. ( 1991, American Concrete Institute, Reprinted witii permission.)...

Chloroprene is polymerized commercially by free-radical emulsion polymerization. The reaction is carried out at 40 °C to a 90% conversion. A typical recipe for such an emulsion polymerization is as follows ... 

Table 5.10. Typical Recipes fcjr Preparation of Butadiene-Styrene Rubbers by Emulsion Polymerization...

It is a matter of significant interest that many commercial ABS plastics made via an emulsion polymerization route are actually semi-I IPNs. A typical recipe for polymer I is as follows ... 

There are numerous examples of typical industrial emulsion polymerization recipes available in the open literature (111,112). A process for the synthesis of a polymer with a 50% methyl methacrylate, 49% butyl acrylate, and 1% methacrylic acid terpolymer at a solids content of 45% is described below ... 

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