Microencapsulation carbonless copying paper

Carbonless Copy Paper. In carbonless copy paper, also referred to as pressure-sensitive record sheet, an acid-sensitive dye precursor, such as crystal violet lactone or /V-hen2oy11eucomethy1ene blue, is microencapsulated with a high boiling solvent or oil within a cross-linked gelatin (76,83,84) or in synthetic mononuclear microcapsules. Microcapsules that have a starch binder are coated onto the back of the top sheet. This is referred to as a coated-back (CB) sheet. The sheet intended to receive the image is treated on the front (coated-front (CF)) with an acid. When the top sheet is mechanically impacted, the dye capsules mpture and the dye solution is transferred to the receiving sheet where the acid developer activates the dye. 

Another important apphcation for 4-/ f2 -octylphenol is ia the production of phenoHc resias. Novolak resias based oa 4-/ f2 -octylpheaol are widely used ia the tire iadustry as tackifiers. The tackiaess of these resias biads the many parts of an automobile tire prior to final vulcanization. A specialty use for novolak resias based oa 4-/ f2 -octylpheaol is the productioa of a ziacated resia, which is formulated as a dispersioa ia water and coated onto paper ia combination with eacapsulated leuco dyes to yield carbonless copy paper (see Microencapsulation). Pressure from writing bursts the encapsulated leuco dye, which is converted from its colorless form to its colored form by the ncated resin (53). Novolak resias based oa 4-/ f2 -octylpheaol are also used ia the productioa of specialty printing inks. 

Microencapsulation is a revolutionary technology enabling liquids to be treated as solids. The technology was first used to produce carbonless copying paper, but today it is widely used in a number of industrial fields such as medicine, agricultural chemicals, thermochromic materials, cosmetics, and toiletries. 

Microencapsulation technology has been used from 1930s in packaging flavors and vitamins. Since the first commercial product was introduced for the carbonless copying paper, the technology has advanced to a new level. Various microencapsulation techniques are available nowadays, and the microencapsulated products are widely used in pharmaceutical, biomedical, agricultural, food, consumer products, and cosmetic industries. Representative applications of microparticles in the pharmaceutical and biomedical industries include ... 

Applications of microencapsulation in other industries are numerous. The best known microencapsulated products are carbonless copying paper, photosensitive paper, microencapsulated fragrances, such as scent-strips (also known as snap-n-burst ), and microencapsulated aromas ( scratch-n-sniff ). All of these products are usually prepared by gelatin-acacia complex coacer-vation. Scratch-n-sniff has been used in children s books and food and cosmetic aroma advertising. Microcapsules are also extensively used as diagnostics, for example, temperature-sensitive microcapsules for thermographic detection of tumors. ... 

Many processes for making microencapsulated product have been reported in the literature. They encompass a broad range of scientific and engineering disciplines. Some are used in high volume applications as in carbonless copy paper, others are in low volume specialty applications many are used in pilot plant scale. 

The development of early encapsulation technology and preparation of microcapsules dates back to 1950s when Green and coworkers produced microencapsulated dyes by complex coacervation of gelatin and gum Arabic, for the manufacture of carbonless copying paper. The technologies developed for carbonless copy paper have led to the development of various microcapsule products in later years. 

Polymer coacervation is one of the earliest microencapsulation techniques. The first commercial application of encapsulation with coacervation was to the development of carbonless copy paper by the National Cash Register Company, which resulted from patents by Barrett K. Green and Lowell Schleicher in the late 1950s. Since then, coacervation has been used for various applications. 

Since the first commercial application to carbonless copy paper in the 1950s, microencapsulation with coacervation technology has been successfully applied to many other areas, such as food, pharmaceuticals, cosmetics, biotechnology, and agrochemicals. The capsules provide such functions as controlled release, taste masking, improved heat and oxidative stability, reduced volatility/ flammability/toxicity, separation of reactive incompatibles, improved shelf-life, conversion of liquids to solids, and improved flowability as well as material handling. Among various coacervation processes, complex coacervation is most prevalent. 

Microencapsulation. Microencapsulation (qv) has now been commercially practiced for more than 30 years, following the first application of the technology to carbonless copying paper. Pesticide formulations based on microcapsules appeared in 1974 with the product Penncap-M containing the insecticide methyl parathion (4). Since then many microcapsule suspension formulations have been introduced and form the major group of CRF. 

The earliest commercial application of coacervation was for the development of carbonless carbon copy paper by the National Cash Register Company in the late 1950s. More recently, the field of polymer coacervation has developed steadily so that a more refined and complete classification of coacervation systems can be proposed here (Table 1). Other classification schemes and related principles of coacervation for microencapsulation are available in the literature with illustrated examples. " ... 

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