Seed latexes

Emulsion polymeriza tion of ABS (241) gives a mbber-phase particle morphology which is mostly deterrnined by the mbbet-seed latex. Since the mbber particle size, polydispersity, and cross-linking ate estabhshed before the preparation, the main variables relate to grafting, molecular weight... 

A new process, from Norway, has filled the size gap between emulsion and suspension polymerization techniques [7,8]. This novel polymerization method, the so-called swollen emulsion polymerization has been developed by Ugelstad for producing uniform polymeric particles in the size range of 2-100 /nm. This process comprises successive swelling steps and repolymerizations for increasing the particle size of seed polymer particles by keeping the monodispersity of the seed latex. 

Method Seed latex Comonomers Functional group Reference... 

Figure 19 The scanning electron micrographs of the polystyrene seed latex and the copolymer latices carrying carboxyl, hydroxyl and amine functional groups, (a) PS/PAA, (b) PS HEMA, (c) PS/PDMAEM. The original SEM photographs were taken with 10,000 x magnification and reduced at a proper ratio to place the figure. (From Ref. 93. Reproduced with the permission of John Wiley Sons, Inc.)...

A modified latex composition contains a phosphorus surface group. Such a latex is formed by emulsion polymerization of unsaturated synthetic monomers in the presence of a phosponate or a phosphate which is intimately bound to the surface of the latex. Thus, a modified latex containing 46% solids was prepared by emulsion polymerization of butadiene, styrene, acrylic acid-styrene seed latex, and a phosphonate comonomer in H20 in the presence of phosphated alkylphenol ethoxylate at 90°C. The modified latex is useful as a coating for substrates and as a binder in aqueous systems containing inorganic fillers employed in paper coatings, carpet backings, and wallboards [119]. 

Composite core-shell type microspheres were prepared by in situ heterogeneous polymerization on monodispersed seed latex particles suspended in an aqueous magnetite dispersion stabilized with sodium oleate (58). 

Raise and maintain the temperature to 75°C for 15 min to form the seed latex. (Note any change in the appearance of the reacting mixture.)... 

A seed latex consisting of styrene and a-methylstyrene was prepared by Mestach et al. (4) and used to polymerize styrene and methylacrylate. 

If one provides the system with preformed nuclei, for example in the form of "seed" latex particles, monomer droplets (in sufficient number), dust, or monomer-swollen soap micelles, the AG will have been provided and the system progresses on a downward slope (dashed curve in Figure 1) from the beginning. This constitutes heterogeneous nucleation. Since it is energetically favored, it will tend to occur whenever such conditions obtain. 

The polymerization was conducted in a 50-gal. pilot plant reactor using the charge procedure described by Jones and Schaefer. (A) The polymerization was seeded with a PVC seed latex produced in a separate polymerization. During the... 

The polystyrene seed latex was monodispersed. Even after several grow-ups (polymerizations) the final 1650 A latex was monodispersed. Hydrodynamic chromatography on the 1650 A latex gave a mean diameter of 1660 a with a size variance as small as for normal polystyrene latex standards (typical standard of 1760 8 with a standard deviation of 23 a). The final latex particle size could be accurately predicted from the initial particle size and the total amounts of monomer and polymer used. 

Utilizing the seed latex polymerization method to avoid the occurance of new particle formation, the kinetic treatment of an emulsion polymerization is quite straight forward. Assuming that all the particles are the same size, the rate of polymerization,... 

Figure 3, Conversion profiles for styrene seed latex polymerization at 50°C. Solid curves are theoretical predictions and data points are experimental results (( 3) < o = 0.0076 (A) a0 = 0.0393 (O )a0 = 0.458 (X) o = 137).

The seed latex was prepared by emulsion polymerization at 50°C using distilled water, 4 dnrr SDS, 50g PPS, 5g and distilled styrene, 440g. Two batches were prepared, one in U.S.A. and one in Japan with same recipe. 

Electron microscopy of the final latex of the experiments given in Table I showed almost no new nucleation. The particle size distributions were narrow and indicated no noticeable coagulation as well. New nucleation would lead to increased rates whereas coagulation would have the opposite effect. Any decrease in the rate therefore must be due to a decrease in [m], if we assume n to be constant. We therefore determined the tofuene/polymer ratio in the seed latex in the absence and presence of the various additives. Toluene was chosen as the solvent, because it is similar to styrene and allows the measurement of equilibrium solubilities without the risk of polymerization. Table II gives the experimental values of the toluene solubility in the seed as a function of time. The results indicate that the swelling is nearly complete within 5 to 10 min. 

The swelling of the seed latex in the presence of water-insoluble, low molecular weight compounds in the monomer phase may be quantitatively expressed by (3, 7-18),... 

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