Hard resins

A varnish is often appHed on top of the paint layers. A varnish serves two purposes as a protective coating and also for an optical effect that enriches the colors of the painting. A traditional varnish consists of a natural plant resin dissolved or fused in a Hquid for appHcation to the surface (see Resins, natural). There are two types of varnish resins hard ones, the most important of which is copal, and soft ones, notably dammar and mastic. The hard resins are fossil, and to convert these to a fluid state, they are fused in oil at high temperature. The soft resins dissolve in organic solvents, eg, turpentine. The natural resin varnishes discolor over time and also become less soluble, making removal in case of failure more difficult (see Paint and FINNISH removers). Thus the use of more stable synthetic resins, such as certain methacrylates and cycHc ketone resins, has become quite common, especially in conservation practice. 

Polymerizations are typically quenched with water, alcohol, or base. The resulting polymerizates are then distilled and steam and/or vacuum stripped to yield hard resin. Hydrocarbon resins may also be precipitated by the addition of the quenched reaction mixture to an excess of an appropriate poor solvent. As an example, aUphatic C-5 resins are readily precipitated in acetone, while a more polar solvent such as methanol is better suited for aromatic C-9 resins. 

Water-based flexo inks can be formulated with either a soluble toner or with the Day-Glo EPX Series which is a tme pigment and can be formulated like a conventional pigment dispersion. The Radiant Aquabest or the Day-Glo WST can be formulated in an alkaline water-soluble system to yield strong inks. They have limited shelf life and inferior fade, but do not necessarily requite additional binder. Day-Glo EPX must be formulated with a binder such as a hard resin or can be used with one of the soluble toners such as WST. The EPX Series has several advantages over soluble toners such as much superior fade, exceUent ink stabiHty, and some hiding power over kraft-type papers. A disadvantage of the EPX is its lower tinctorial strength than other fluorescent toners. 

Many lens casters use the term hard-resin lenses for DADC products companies and trade names include American Optical (Aoflte ), Cobum (Supremacy I), Optical Radiation (Orcoflte), and Silor Optical (Orma 1000). Additional information can be obtained from the Optical Manufacturers Association, Falls Church, Va. Cast sheets of homopolymer and copolymers are suppHed by the SGL Homalite Company, Foster Grant, and others. 

Sandarac. This resin, which originates in Morocco, is a polar, acidic, hard resin with a softening point of 100—130°C, an acid number of 117—155, and a saponification number of 145—157. Sandarac [9000-57-1] is soluble in alcohols and insoluble in aryl and aUphatic hydrocarbons. It is used in varnishes and lacquers for coating paper, wood, and metal. 

The polysulphides used are relatively mobile liquids with viscosities of about 10 poise and are thus useful as reactive diluents. They may be employed in any ratio with epoxide and produets will range from soft rubbers, where only polysulphides are employed, to hard resins using only epoxide. 

Rosin is an organic flux that has long been used for soldering. It is a yellow, transparent, and relatively hard resin secreted from wounds in the trunks of coniferous trees. Rosin is insoluble in water, and its exact composition and structure are as yet unknown. 

The extreme hazards involved in handling this highly reactive material are stressed. Freshly distilled material rapidly polymerises at ambient temperature to produce a gel and then a hard resin. These products can neither be distilled nor manipulated without explosions ranging from rapid decomposition to violent detonation. The hydrocarbon should be stored in the mixture with catalyst used to prepare it, and distilled out as required [1], The dangerously explosive gel is a peroxidic species not formed in absence of air, when some l,2-di(3-buten-l-ynyl)cyclobutane is produced by polymerisation [2], The dienyne reacts readily with atmospheric oxygen, forming an explosively unstable polymeric peroxide. Equipment used with it should be rinsed with a dilute solution of a polymerisation inhibitor to prevent formation of unstable residual films. Adequate shielding of operations is essential [3],... 

Shellac is a complex mixture made of mono- and polyesters of hydroxy-aliphatic and sesquiterpene acids, which can be separated into two fractions the soft resin, soluble in ether, mainly consisting of monoesters [134], constituting about 30% of the total resin and the hard resin, ether insoluble, which has quite a complex polyester composition, and... 

R.G. Khurana, A.N. Singh, A.B. Upadhye, V.V. Mhaskar, Stikh Dev, Chemistry of lac resin III. An integrated procedure for their isolation from hard resin chromatography characteristics and quantitative determination, Tetrahedron, 26, 4167 4175 (1970). 

A hard resinous thermoplastic substance of the same chemical composition as rubber hydrocarbon but having the ftvms-structure. See Cis-trans Isomerism. Formerly extensively used for the insulation of submarine cables (now superseded by polyethylene) and in the early manufacture of golf balls (now superseded by... 

Both acrylic acid and methacrylic acid polymerise to give water soluble hard resins. The viscous solutions so formed have been used as emulsifying agents, adhesives and as thickening agents for inks and dyes. Polymers of esters of these acids are of greater commercial importance. Esters can be prepared from cyanhydrins by reaction with an alcohol ... 

Particular difficulties similar to those associated with specific surface area determinations (Sec. 1.5.1) also accompany particle size distribution studies on surface coated organic pigments. The identity of the additive, be it an amine, a hard resin, or some other material, is less of a concern than the question of its concentration There is no information on the concentration limits above which an additive may distort the measurements but one can expect this value to be defined largely by the specific surface area and the average particle size of each individual pigment. For pretreated surfaces, sizing the pigment particles by electron mi-... 

Surface treatments with hard resins are also used. 

The leaves of Beyeria brevifolia, from western Australia, have a hard resin coating. Dlterpenols and dlterpenolc acids... 

Industrial plants are working at 300 to 350 bar and 40 to 65°C. Under these conditions all the hop bitter-principles are extracted quantitatively. The content of total resins in the extract is about 90% and a part of the hard resins is extracted, which is not the case with subcritical conditions. 

Above 400 bar, most of the hard resins are extracted. At 300 bar and 80°C the solubility of hops-extract in C02 is around 3.2%wt. The supercritical extraction has many advantages compared to the subcritical extraction, so that even though the investment costs are higher, all new plants have been built for supercritical extraction. 

Resins are separated into several classes. Many of the resins contain almost no volatile oil and are hard, without taste or odor. These are the varnish or hard resins. Other resins, when removed from the plant in which they arc formed, and dissolved in volatile oils, form a thick semi-solid mass these are the oleoresins. In still other cases the tesin occurs in combination with a gum, forming a gum resin. 

One of die commonest and most important of the hard resins is rosin, obtained by distilling the pitch, or turpentine, which is a product of several of the native pines of the southeastern United States. This rosin, also known as colophony, is a very important product of that region. Originally the turpentine was obtained by chopping a deep hollow in the base of the trunk of the tree and allowing it to fill up with the turpentine, which was then scooped out. This method was very destructive and wasteful, since much of the oleoresin, turpentine, was lost during the process. The weakened trees were easily blown down. 

Mastic is a hard resin exuding from the branches of one of the Pistachio trees, Pistncin lentiscus, native of Mediterranean F.nrope and southern Asia. Formerly, it was extensively used medicinally, for stomach troubles and dysentery, as well as other ailments.. Now it is used in making varnishes and in lithographic work. Natives of the region in which it is found chew mastic, which has a pleasant taste. 

Since turpentine is a mixture of a volatile substance, spirits of turpentine and a hard resin, il is one of the ole ore sins. 

Coumarone Indene Resins, These are thermoplastic resins of relatively low mw, varying from fairly viscous liqs to hard resins. Their color varies from pale yel to nearly black. They are obtd by heating mixts of coumarone indene with H2SC>4 so as to cause polymerization. Coumarone indene resins are one of the oldest types of synthetic resins, having been produced in Germany as early as 1900. The manuf props are described in Ref 2... 

Cyclisation of unsaturated elastomers has been the subject of interesting research. Cyclisation yields hard resinous products which have commercial importance and are designated as cyclised rubber [49, 50]. Cyclisation can be carried out with cationic, radiation induced, photo-induced or by thermal methods. Among all these methods cationic cyclisation has been extensively reported probably because there are less side reactions. The generally accepted mechanism of cyclisation of 1,3 diene elastomers is shown in Scheme 4.3a. 

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