Rosin (/ˈrɒzɪn/), also known ascolophony orGreek pitch (Latin:pix graeca), is aresinous material obtained frompine trees and otherplants, mostlyconifers. The primary components of rosin arediterpenoids, i.e., C20carboxylic acids. Rosin consists mainly ofresin acids, especiallyabietic acid.[1] Rosin often appears as a semi-transparent, brittle substance that ranges in color from yellow to black and melts at stove-top temperatures.
In addition to industrial applications such as in varnishes, adhesives, and sealing wax, rosin is used withstring instruments on thebow hair to enhance its ability to grip and sound the strings, and it provides grip in various sports and activities. Rosin also serves as an ingredient in medicinal and pharmaceutical formulations and can causecontact dermatitis oroccupational asthma in sensitive individuals. It is anFDA approved food additive.[2]
The name "colophony" originates fromcolophonia resina, Latin for "resin fromColophon" (Ancient Greek:Κολοφωνία ῥητίνη,romanized: Kolophōnía rhētínē),[3][4] an ancientIonic city.[5]
Rosin isbrittle andfriable, with a faint pine odor. It is typically aglassy solid, though some rosins willcrystallize, especially when brought into solution.[6] The practical melting point is variable, some being semi-fluid at the temperature of boiling water, others melting at 100 to 120 °C (212 to 248 °F). It is flammable, burning with a smoky flame. It is soluble inalcohol,ether,benzene andchloroform.
Rosin, consisting mainly ofabietic acid, combines with causticalkalis to form salts (rosinates orpinates) that are known asrosin soaps. They are used insoap making.
Rosin is extensively used for itsfriction-increasing capacity in several fields:
Other uses that are not based on friction:
Rosin and its derivatives also exhibit wide-ranging pharmaceutical applications. Rosin derivatives show excellent film forming and coating properties.[11] They are also used for tablet film and enteric coating purpose. Rosins have also been used to formulate microcapsules and nanoparticles.[12][13]
Glycerol,sorbitol, andmannitol esters of rosin are used aschewing gum bases for medicinal applications. The degradation andbiocompatibility of rosin and rosin-based biomaterials has been examinedin vitro andex vivo.
Treatment of rosin with sodium hydroxide or sodium carbonate converts the abietic acid into its sodium salt, which is known as a soap. Whereas most domestic soaps are sodium salts of straight-chain fatty acids, the rosin soaps have the branched and cyclic backbone associated with abietic acid. Rosin soaps, also called rosinates, are used to "size" paper, a process that gives paper a desirable hydrophobic texture.[1]
The conversion of abietic acid to esters is also practiced commercially. Ester of glycerol and methanol are both of interest. These materials are colorless syrups. They are compounded with polymers astackifiers.[1]
Players ofbowed string instruments rub cakes or blocks of rosin on their bow hair so it can grip the strings and make them "speak", or vibrate clearly.[14] Occasionally, substances such asbeeswax,gold,silver,tin, ormeteoric iron[15] are added to the rosin to modify itsstiction/friction properties and the tone that can be produced.[16] Powdered rosin can be applied to new hair, for example with a felt pad or cloth, to reduce the time taken in getting sufficient rosin onto the hair. Rosin is often reapplied immediately before playing the instrument. Lighter rosin is generally preferred for violins and violas, and in high-humidity climates, while darker rosins are preferred for cellos, and for players in cool, dry areas.[17] There are also specific, distinguishing types forbasses.
The type of rosin used with bowed string instruments is determined by the diameter of the strings. Generally this means that the larger the instrument is, the softer the rosin should be. For instance,double bass rosin is generally soft enough to bepliable with slow movements. A cake of bass rosin left in a single position for several months will show evidence of flow, especially in warmer weather.
Three methods are used to collect rosin. Rosin exudates are collected from gashes in the bark of living pine trees. Alternatively (see below) rosin isextracted from stumps. Yet another source is pulp mills that use theKraft process.Tall oil rosin is produced during the distillation of crude tall oil, a by-product of thekraft paper making process. The collection and processing of rosin is called Naval Stores.[1]
The separation of the oleo-resin into theessential oil (spirit of turpentine) and common rosin is accomplished bydistillation in large copperstills. The essential oil is carried off at a temperature of between 100 °C (212 °F)° and 160 °C (320 °F), leaving fluid rosin, which is run off through a tap at the bottom of the still, and purified by passing through straining wadding. Rosin varies in color, according to the age of the tree from which the turpentine is drawn and the degree of heat applied in distillation, from anopaque, almost pitch-black substance through grades of brown and yellow to an almost perfectly transparent colorless glassy mass. The commercial grades are numerous, ranging by letters from A (the darkest) to N (extra pale), superior to which are W (window glass) and WW (water-white) varieties, the latter having about three times the value of the common qualities.
When pine trees are harvested "the resinous portions of fallen or felled trees like longleaf and slash pines, when allowed to remain upon the ground, resist decay indefinitely."[18] This "stump waste", through the use ofdestructive distillation or solvent processes, can be used to obtain rosin. This type of rosin is typically calledwood rosin.
Because the turpentine and pine oil from destructive distillation "become somewhat contaminated with other distillation products",[18] solvent processes are commonly used. In this process, stumps and roots are chipped and soaked in the light end of the heavynaphtha fraction (boiling between 90 and 115 °C (194 and 239 °F)). Multi-stage counter-currentextraction is commonly used. In this process, fresh naphtha first contacts wood leached in intermediate stages, and naphtha laden with rosin from intermediate stages contacts unleached wood beforevacuum distillation to recover naphtha from the rosin, along withfatty acids, turpentine, and other constituents later separated throughsteam distillation. Leached wood is steamed for additional naphtha recovery prior to burning for energy recovery.[19] After the solvent has been recovered, "the terpene oils are separated byfractional distillation and recovered mainly as refined turpentine, dipentene, and pine oil. The nonvolatile residue from the extract is wood rosin of rather dark color. Upgrading of the rosin is carried out by clarification methods that generally may include bed-filtering orfurfural-treatment of rosin-solvent solution."[18]
On a large scale, rosin is treated by destructive distillation for the production of rosin spirit, pinoline androsin oil. The last enters into the composition of some of the solid lubricatinggreases, and is also used as anadulterant of other oils.
The chief region ofrosin production includesIndonesia, southernChina (such asGuangdong,Guangxi,Fujian,Yunnan andJiangxi), and the northern part ofVietnam. Chinese rosin is obtained mainly from theturpentine ofMasson's pinePinus massoniana andslash pineP. elliottii.[citation needed] The latter species is native to the southeastern U.S., but is now widely planted in tree plantations in China.
TheSouth Atlantic and easternGulf states of theUnited States is a second chief region of production. American rosin is obtained from the turpentine oflongleaf pinePinus palustris andloblolly pineP. taeda. InMexico, most of the rosin is derived from live tapping of several species ofpine trees, but mostlyPinus oocarpa,Pinus leiophylla,Pinus devoniana andPinus montezumae. Most production is concentrated in the west-central state ofMichoacán.[citation needed]
The main source of supply inEurope is theFrench district ofLandes, in thedepartments ofGironde andLandes, where themaritime pineP. pinaster is extensively cultivated. In the north of Europe, rosin is obtained from theScots pineP. sylvestris, and throughout European countries local supplies are obtained from other species of pine, withAleppo pineP. halepensis being particularly important in theMediterranean region.[citation needed]
Prolonged exposure to rosin fumes released during soldering can causeoccupational asthma (formerly calledcolophony disease[20] in this context) in sensitive individuals, although it is not known which component of the fumes causes the problem.[21] The symptoms also includedesquamation ofbronchialepithelium.[22]
Prolonged exposure to rosin, by handling rosin-coated products, such aslaser printer or photocopying paper, can give rise to a form of industrialcontact dermatitis.[23]
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