Polymers small-volume specialty

A large number of compounds related to styrene have been reported in the literature, Those having the vinyl group CH2=CH—attached to the aromatic ring are referred to as styienic monomers, Several of them have been used for manufacturing small-volume specialty polymers. The specialty styreme monomers that arc manufactured in commercial quantities arc vinyl toluene, /r, -methylstyrene, or-methylstyrene. and divinylbenzene. In addition, 4-fert-butylstyrene (TBS) is a specialty monomer that is superior to vinyltoluene and pnra-methylstyrene in many applications. Other styrenic monomers produced in small quantities include chlorostyrene and vinylbenzene chloride. With the exception of a-methylstyrene, which is a by-product of the phenol-acetone process, these specialty monomers are more difficult and expensive to manufacture than styrene... 

Product type Small volume specialty polymers heterogeneous polymerization system (e.g., emulsion, suspension, precipitation) Small volume specialty polymers copolymers Large volume commodity polymers engineering polymers... 

Industrial production of perfluorinated ionomers, Nafion membranes, and all perfluorinated membranes is costly due to several factors first, the monomers used are expensive to manufacture, since the synthesis requires a large number of steps and the monomers are dangerous to handle. The precautions for safe handling are considerable and costly. Secondly, the PSEPVE monomer is not used for other applications, which limits the volume of production. The most significant cost driver is the scale of production. Today, the volume of the Nafion market for chlor-aUcali electrolysis (150,000 m year ) and fuel cells (150,000 m year ) is about 300,000 m year resulting in a production capacity of 65,000 kg year. When compared to large-scale production of polymers like Nylon (1.2 x 10 m year ), the perfluorinated ionomer membrane is a specialty polymer produced in small volumes. 

Batch polymerization reactors are ideal to manufacture small volume polymers, specialty polymers, and polymers that are difficult to make in continuous reactors. Emulsion polymers, suspension polymers, and precipitation polymers are mostly made by batch polymerization processes. One of the disadvantages of a batch reactor is that the ratio of heat transfer surface area to reactor volume decreases as the reactor size is increased. For many polymer products made in batch reactors, the process economy improves with an increase in reactor size. Therefore, effective heat removal becomes a critical factor in designing and controlling a large-scale batch polymerization reactor. 

The specialty resins are expensive, produced in relatively small volumes either for a specific application or looking for a market niche. Their Tg > 200°C and modulus > 3 GPa. In 1991 the total world consumption of polysulfones (PSE) and polyethersulfones (PES) was 8.5 kton. Blends of the following polymers are known polyfluorocarbons, polysiloxanes, sulfur-containing polymers (PPS, PPSS, PES, and PSF), polyetherk-etones (PEK, PEEK, PEKK), polyimides (PI, PEI, and PAI), PAr, COPO, polyphosphazene (PHZ) and LCP. 

X10 m year ), the perfluorinated ionomer membrane is a specialty polymer produced in small volumes. 

Batch vs. Continuous. Some nitrile rubber producers use a batch process. The batch process has the advantage of making small amounts of many different products, thus enabling the producer to tailor-make polymers for relatively low-volume specialty applications. Obviously, however, the disadvantage is the relatively high changeover costs. On the other hand, some nitrile rubber producers use a continuous process. This process is relatively low cost but limits the number of products that can be economically produced since minimum run quantities are relatively large. 

All those examples elucidate that polymer dispersions are used in both big volume and small volume applications. They are both commodities and specialties. And the use of polymer dispersions is increasing worldwide. The main reasons for this are the variety of polymer properties achievable by emulsion polymerization is virtually unlimited, emulsion polymerization is an inexpensive production process for these products, the fluid form of polymer dispersions is easy to handle, and water is environmentally friendly. 

In Table 1.1 the usage of polymers in three major categories is summarized for two decades. Of course, in every category there are some specialty polymers that go into specific niche markets representing areas of growth and profit. The commodity polymers may dominate the statistics, but they do not always represent the items of greatest value to a particular company. For example, biodegradable sutures, contact lenses, and adhesives for microchips all use small volumes of expensive, special polymers. 

An abbreviated list of medical applications for commodity polymers (Table 13.6) is an indication of the wide scope of both materials and their uses. Since many of these uses require small volumes of premium materials, it is often feasible to supplement commodity plastics by developing specialty polymers that would not otherwise be justified on an economic basis. In the examples that follow, one encounters both commodity polymers such as ultrahigh-molecular-weight polyethylene (UHMWPE) and poly(tetrafluoroethylene) (PTFE), and specialty polymers such as the polyanhydrides and poly(glycolic acid). 

The work discussed in the various chapters clearly shows that great opportunities exist for research and development on new monomers and polymers. In addition, the work done at Mobil on poly(p-methylstyrene) decisively illustrates that great opportunities still exist for finding routes to new monomers that need not be tied to small specialty markets. After all, in a few years p-methylstyrene could become a fairly high volume commodity chemical and its homopolymer and copolymers could make a very large market Impact (W.W. Kaeding, L.B. Young, and A.G, Propas,... 

This trend will continue and grow. This is clear when you realize that when the modified work horses are not adequate, a stable of new specialty polymers is waiting in the wings (Fig. 4). While volume of these specialties is small today, it is growing rapidly and even more rapid growth In the 90 s Is expected. 

One of our problems that we have in art restoration is that relatively small amounts of materials, varnishes, glues, of very specific characteristics are needed. Ideally speaking it would be nice to have available one type of material for each type of painting and each period. From the commercial point of view, it is not justifyable to produce many types of small amounts of material. Consequently, the cooperation of industry for the preparation of these specialty polymers, polymers that would in most cases have to be tailor made, is limited. In the case of polymeric materials for electronic applications, it is much easier to arouse interest for polymers with low volume but with larger returns. It is one of the objectives of this discussion to call attention to the need of specific materials in art restoration and preservation and to alert the scientists and restorers to the importance of a bridge of knowledge in this field and for industry to become aware of the opportunities. 

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