Terpene monomers

I.4. Polyterpene resins. Terpene resins are obtained from natural terpene monomers obtained from naval stores, paper pulp production, and citrus juice production. Terpenes are found in almost all living plants, and the turpentine oil from pine trees is the most important source. 

Polyterpenes. Polyterpenes is one of the first classes of non-polar tack-ifiers to be developed. Terpene monomers are a by-product in the extraction of rosin from wood stumps or tree sap, and from the extraction of oils from citrus fruits. The latter is the dominant source. As such, polyterpene prices generally mirror those of citrus fruits, which fluctuate substantially from one growing season to the next. Terpenes like rosin are cyclic, see Fig. 6, which is partly responsible for their excellent solvent properties. 

Terpene monomers are another class of interesting natural monomers because they give, on polymerization, hydrocarbon therplastic resins that exhibit a high degree of tackiness useful in pressure sensitive tapes [25]. They are also used for sizing paper and textile materials. Terpene-phenol resins are effective heat stabilizers for high-density polyethylene. 

The most widespread use of limonene has been as a raw material for the manufacture of adhesives, such as the glue on labels and envelopes. Terpene monomers used for resin production are pinene, dipentene from turpentine and rf-limonene. Waterless hand cleaners produced from d-limonene were among the first to replace solvents such as mineral spirits. Although ri-limoncnc is more expensive than mineral spirits and kerosene, the former is used because of the pleasant citrus aroma and its claimed biodegradability (Coleman, 1975 Kutty et al., 1994). Many flavor chemicals... 

To illustrate another component of the forest products industry it may be instructive to take a brief look at the pine chemicals industry. The pine chemicals industry is not a new industry, but it is a very small portion of what is now known as the specialty chemicals industry, despite the fact that pine chemicals have been in active use for longer than the modern chemical industry era that arose in the early part of the 20th century. The pine chemicals industry has been extracting useful products such as turpentine and other simple materials for literally hundreds of years. With the rise of the pulp and paper industry, chemicals have in the majority been extracted from two waste streams crude tall oil and crude sulfate turpentine. Crude tall oil can be further separated into a fatty acid fraction, a tall oil fraction, a tail oil rosin fraction, and a tall oil pitch fraction. The crude sulfate fraction is separated into a variety of terpene monomers that can be further transformed into a variety of terpene resins. AH of these streams can be used as raw materials for coatings, various oil applications, surfactants, adhesives, inks, etc. [50]. 

TRs have been drawn from some natural products. Compounds thus produced were diversified either by chemical modification or by copolymerization of terpenic monomers with monomers of petrochemical origin [4,5]. 

Polymerization of a-pinene and 3-carene is a reaction occurring in the synthesis of hydrocarbon resins from terpene monomers under the action of Lewis adds [2]. 

In this pyrolysis, sub atmospheric partial pressures are achieved by employing a diluent such as steam. Because of the corrosive nature of the acids (HE and HCl) formed, the reactor design should include a platinum-lined tubular reactor made of nickel to allow atmospheric pressure reactions to be mn in the presence of a diluent. Because the pyrolysate contains numerous by-products that adversely affect polymerization, the TFE must be purified. Refinement of TFE is an extremely complex process, which contributes to the high cost of the monomer. Inhibitors are added to the purified monomer to avoid polymerization during storage terpenes such as t7-limonene and terpene B are effective (10). 

Hydrocarbon resin is a broad term that is usually used to describe a low molecular weight thermoplastic polymer synthesized via the thermal or catalytic polymerization of coal-tar fractions, cracked petroleum distillates, terpenes, or pure olefinic monomers. These resins are used extensively as modifiers in the hot melt and pressure sensitive adhesive industries. They are also used in numerous other appHcations such as sealants, printing inks, paints, plastics, road marking, carpet backing, flooring, and oil field appHcations. They are rarely used alone. 

Terpenes, specifically monoterpenes, are naturally occurring monomers that are usually obtained as by-products of the paper and citms industries. Monoterpenes that are typically employed in hydrocarbon resins are shown in Figure 2. Optically active tf-limonene is obtained from various natural oils, particularly citms oils (81). a and P-pinenes are obtained from sulfate turpentine produced in the kraft (sulfate) pulping process. Southeastern U.S. sulfate turpentine contains approximately 60—70 wt % a-pinene and 20—25 wt % P-pinene (see Terpenoids). Dipentene, which is a complex mixture of if,/-Hmonene, a- and P-pheUandrene, a- and y-terpinene, and terpinolene, is also obtained from the processing of sulfate Hquor (82). 

Terpene Copolymers. Terpenes are routinely polymerized with other terpenes or with nonterpene-type monomers (97—102). The AlCl catalyzed polymerization of P-pinene, dipentene, and terpene oligomers (oily dimers and trimers) has been found to yield resins with softening points ranging from 0—40°C (103). 

Selected physical properties of chloroprene are Hsted in Table 1. When pure, the monomer is a colorless, mobile Hquid with slight odor, but the presence of small traces of dimer usually give a much stronger, distinctive odor similar to terpenes and inhibited monomer may be colored from the stabilizers used. Ir and Raman spectroscopy of chloroprene (4) have been used to estimate vibrational characteristics and rotational isomerization. 

Other natural product-based resins also became widely used, such as the light colored Lewis acid oligomerized products of terpenes such as a-pinene, p-pinene, and limonene. These natural product resins are relatively expensive, however, and formulators now often use the newer, less expensive synthetic resins in present day natural rubber PSAs. These are termed the aliphatic or C-5 resins and are Lewis acid oligomerized streams of predominately C-5 unsaturated monomers like cis- and /rawi-piperylene and 2-methyl-2-butenc [37]. These resins are generally low color products with compatibility and softening points similar to the natural product resins. Representative products in the marketplace would be Escorez 1304 and Wingtack 95. In most natural rubber PSA formulations, rubber constitutes about 100 parts and the tackifier about 75-150 parts. 

The other class of acrylic compatible tackifiers includes those based on ter-penes. Terpenes are monomers obtained by wood extraction or directly from pine tree sap. To make the polyterpene tackifiers, the monomers have to be polymerized under cationic conditions, typically with Lewis acid catalysis. To adjust properties such as solubility parameter and softening point, other materials such as styrene, phenol, limonene (derived from citrus peels), and others may be copolymerized with the terpenes. 

Resins from pure monomers. Some colourless resins can be produced from pure unsaturated monomers, such as styrene, oi-methylstyrene and vinyl-toluenes (Fig. 19). These monomers are used individually or as blends with terpenes or unsaturated aliphatics. 

Aliphatic/aromatic. Copolymerization of aliphatic monomers (terpenes, cyclic C5, and acyclic C5) with the aromatic C9 petroleum stream is used to produce... 

Emission of volatile noxious chemicals from wood-based panels during their production can be caused by chemicals inherent to wood itself, like terpenes or free acids, as well as by volatile compounds and residual monomers of the adhesive. The emission of formaldehyde as well as free phenol effluents is a matter of concern. 

A terpene inhibitor is usually added to the monomer to prevent spontaneous polymerisation, and in its absence, the monomer will spontaneously explode at pressures above 2.7 bar. The inhibited monomer will explode if ignited [1]. Explosion under thermal initiation is now held to be a disproportionation, that to tetrafluo-romethane and carbon gives 3.2 kJ/g, the same energy as black powder [3], Liquid tetrafluoroethylene, being collected in a liquid nitrogen-cooled trap open to air, formed a peroxidic polymer which exploded [2]. 

Conventionally, central and special metabolic pathways are distinguished. Central pathways are common to the decomposition and synthesis of major macromolecules. Actually, they are much alike in all representatives of the living world. Special cycles are characteristic of the synthesis and decomposition of individual monomers, macromolecules, cofactors, etc. Special cycles are extremely diversified, especially in the plant kingdom. For this reason, the plant metabolism is conventionally classified into primary and secondary metabolisms. The primary metabolism includes the classical processes of synthesis and deeradation of major macromolecules (proteins, carbohydrates, lipids, nucleic acids, etc.), while the secondary metabolism ensuing from the primary one includes the conversions of special biomolecules (for example, alkaloids, terpenes, etc.) that perform regulatory or other functions, or simply are metabolic end byproducts. 

Recently it was shown by radiolabeling studies that the formation of the serrulatane skeleton is catalyzed by the pseudopterosin diterpene cyclase, which can be considered as a key enzyme in terpene biosynthetic pathways (Scheme 2). The elisabethatriene cyclase is a monomer with a molecular mass of47kDa [25]. 

These processes are both natural and manmade. In fact, the Los Angeles basin was called by the early Native American inhabitants the land of the smokes, and salt spray from oceans is a major source of Cl in the atmosphere. In many situations people have only exaggerated the natural chemicals and reactions that were present before we and our technology arrived. The Smoky Mountains are an example of natural smog caused by chemicals such as isoprene (the natural mbber monomer) and terpenes, which are emitted by trees. 

VOCs responsible for the smell of brand new cars alkanes, aromatic hydrocarbons, carbonyl compounds, residual monomers, alcohols, esters, ethers, halo-genated hydrocarbons, terpenes, nitrogen and sulfur compounds ... 

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