Contents

Introduction
The Technology of CCP
Exposure
Health Effects
Summary and Conclusions
Recommendations
References
Other Publications Examined

The Technology of CCP

2.1 How CCP Works

Athree-part business form (Figure 2-1) illustrates the concept of how CCP works. The first sheet in this three-part example is a coated-back (CB) sheet, the second is a coated-front and -back (CFB) sheet, and the third is a coated-front (CF) sheet. The bottom surfaces of the top and the second sheet are coated with a layer of microcapsules that have a diameter of 3 to 6
m. The coating includes inert spacer particles ("stilts," such as floc, uncooked arrowroot, and/or wheat starch particles) that are larger than the microcapsules and are added to protect the microcapsules from premature rupture. The microcapsules (filled with a colorless solution of 2% to 6% dye dissolved in a high-boiling-point-organic solvent) rupture under pressures encountered in normal handwriting or impact printing. For example, in a three-part form, the released dye solution is transferred from the bottom surfaces of the first and second sheets to the top surfaces of the second and third sheets, respectively, where it reacts with the clay or resin coating to form an image. The capsules and reactive coating can be coated onto the same paper surface. In this case, the product is called self-contained CCP.

2.2 CCP Production

The principles of the CCP production process are similar throughout the industry, but many components are variable and complex. During CCP production, an acid-sensitive dye precursor such as crystal violet lactone (CVL) or N-benzoylleucomethylene blue (N-BLMB) is microencapsulated with a high-boiling-point solvent or oil within a cross-linked gelatin or in synthetic mononuclear microcapsules, including polyamides, polyesters, or polyurethanes. From the origination of NCR paper until 1970, the main solvent for the dyes was polychlorinated biphenyls (PCBs [Arochlor]). Examples of solvents that have replaced PCBs are hydrogenated terphenyls, diarylethanes, alkylnaphthalenes, cyclohexane, and dibutylphthalate (more detailed information about solvent composition, technical requirements, and admixtures is given later in this section). These materials are often diluted with odorless kerosene [Calnan 1979].

CCP production consumes thousands of tons of microcapsules annually. During CCP manufacturing, microcapsules are coated onto the back of the top sheet (referred to as a CB sheet) at a density of several million per cm2 with a binder or suitable adhesive [Certin and Zissu 1983]. Since paper is the usual support, the binders or adhesives are principally paper-coating agents such as the following [Murray 1991; Mathiaparanam 1992]:

• Gum arabic
• Hydroxymethyl cellulose
• Casein
• Methyl cellulose
• Dextrin
• Starch or starch derivatives (wheat or corn) or polymer lattices (e.g., butadiene/styrene copolymers or acrylic homopolymers or copolymers)
• Vinyl acetate and water soluble polymers such as carboxymethyl cellulose
• Polyvinylacetate
• Gelatin
• Polyacrylates
• Polystyrene
• Polyvinyl alcohol

The paper employed comprises not only normal paper made from cellulose fibers, but also paper in which cellulose fibers are replaced (partially or completely) by synthetic polymers [Bedekovic and Fletcher 1986]. (Please refer to Section 2.8 for a listing of brand names and trademarks of CCP.)

The sheet intended to receive the image, the CF sheet, is treated on the front with a clay or resin that is alkaline on the surface but acidic inside, or with an alternative reactive coating [Calnan 1979]. In Europe, the color developer system is typically based on clays, whereas phenolic resins are most commonly used in the United States and Japan [Murray 1991]. The coating is spread in a mixture, dried, and adhered with a styrene-butadiene-latex or one of the binders listed above. When the top sheet is mechanically impacted, the dye capsules rupture and the dye solution is transferred to the receiving sheet, where the acid developer activates the dye as a result of a change in pH or oxidation.

2.3 Microcapsule Production

Three processes can be used to microencapsulize the dyes for the size requirements of CCP: complex coacervation, interfacial polymerization, or in situ polymerization [Kroschwitz and Howe-Grant 1979, 1995; Sliwka 1975]. The complex coacervation process produces a shell material of gelatin and gum arabic (treated with glutaraldehyde); the chemical class is a protein-polysaccharide complex. Interfacial polymerization produces a shell of polyurea or polyamide and is chemically classed as a cross-linked polymer. The in situ process results in a shell material of aminoplasts and is also considered to be in the cross-linked polymer chemical class. Microcapsules have a wide range of geometries and structures. These range from a continuous core shell that surrounds the core material to a multinuclear capsule in which a number of cells of core material are distributed uniformly throughout the matrix of shell material and a continuous core capsule with two different shells. Examples of other synthetic resins used for the microencapsulation process are urea-formaldehyde, melamine-formaldehyde, polyamide, and polyurethane resins [Asano et al. 1983]. Maggio et al. [1978] stated that urea-formaldehyde capsules are more resistant to pressure than those made of gelatin.

2.4 CCP Production Process

Apol and Thoburn [1986] described the process of CCP manufacturing. The plant they investigated made paper from pulp and then applied the appropriate coatings to the paper to make CCP. The paper itself is usually produced in a continuous sheet from a pulp slurry to form a wet web of paper as it exits on a screen, such as in a Fourdrinier paper machine. Apol and Thoburn [1986] describe a process in which the CF and CB coatings are applied to the wet web. The CF coating can also be applied as the paper exits from the paper machine. As the coating is applied, the paper passes through a dryer and is wound on a roll. The CB coating may be applied in a separate plant area to the paper as it passes through a series of dryers and is rewound on a roll.

The CF and CB coatings are prepared in the coater preparation area. The phenolic resins (1- to 10-
mor 1- to3-
msize range is preferred [Mathiaparanam 1992]) may be prepared by grinding the resins to specific-size particles, or they may be purchased already prepared. The already prepared resin reduces exposure to phenol among workers who handle the coating preparation and is the preferred option for today's technology.

A typical coating composition for the CF component is shown in Table 2-1. The CF is dried in a high-velocity air oven at 93 °C [Kroschwitz and Howe-Grant 1995]. Miller and Phillips [1972] stated that suitable amounts of the various materials per unit of paper are as follows: chromogenic dyes, 0.03 to 0.075 lb/ream (one ream is 500 sheets of 25- × 38-in. paper totaling 3,300 ft2), with the preferred amount being 0.05 lb/ream; solvent, 1 to 3 lb/ream; polymer, 0.5 to 3 lb/ream.

CF, CB, and CFB coated papers are produced in large rolls weighing up to several tons. These are subsequently cut down by machines to a variety of smaller reel and sheet sizes. This cutting means that the contents of the microcapsules will be ruptured and released. Although many of the sheeting, reeling, and packing operations are automated, some of the paper still needs to be hand-sorted. The workers who hand sort these papers are potentially exposed to the components, particularly the contents of the ruptured capsules that have been cut in previous mechanical operations. Some of these workers sort paper at the rate of 90 kg/hr (or more than 2 tons/week [600,000 sheets]) [AEMCP 1985].

2.5 Forms Production

CCP is converted into forms for a variety of applications-for example, business forms, invoices, computer paper, and Telex rolls. This process is normally performed by printers with appropriate forms design using conventional printing inks as well as specialized desensitizing inks. The latter are applied to the CF surface to prevent the color former from developing into an image on certain areas of the paper [AEMCP 1985].

CCP may be collated into business form sets that are glued along one edge. The glues (called edge-padding, edge-tipping, or "fanapart" glues) are similar to those used for ordinary paper writing pads. Manifold forms using pressure-sensitive CCP are produced using conventional printing press techniques. For some applications, the production of the multipart form by photocopying or laser printer operations is preferred-especially in short-run for production, emergencies, and experimental or individualized forms. The manifold forms are bound with an adhesive containing gum resins such as abietic acid. More recently, Moore Business Forms, Inc., was granted a patent [McIntyre and Greig 1989] for the use of a repositionable adhesive pad on the CF (such as is found on money wrappers). Bodmer and Peters [1984] and Bodmer and Miller [1985, 1986] noted that CF coating components can accumulate on the heated fuser roll of the copier or the laser printer, which becomes tacky and can lead to poor copy quality. A phenolic polymeric film material, diolefinic alkylated or alkenylated cyclic hydrocarbons (cyclic terpene derivatives such as limonene), and/or an oil-soluble metallic salt (primarily zinc) of a phenol- formaldehyde novolak resin can be used to overcome the fuser roll contamination problem, which may or may not result in slower print speeds.

2.6 Other Forms and Variations of CCP Technology

Forms sometimes combine CCP with carbon paper to become a "two-write" system [Mead Corporation 1992]. The Branch Safety Council for Offices and Administrations [1988] also reported on another type of CCP that is pressure sensitive and is called "mechanical" paper. The CB sheet is coated with zinc chloride and covered by a thin layer of wax. Pressure created on the top side of the form causes the zinc chloride to break through the wax and adhere to the sheet below that is coated with an absorbing layer of color generators, polyvinyl acetate, and clay. The Mead Corporation was granted a patent that incorporated a microencapsulated, photosensitive material that cured to a stable image when heat-activated in the presence of a developer such as an organic peroxide [Sanders 1984]. The Mead Corporation was also granted a patent on a novel system that uses a self-contained imaging sheet to produce images on plain paper using a photosensitive *, photocurable, image-forming agent and a developer material on the surface of the paper support [Feldman et al. 1994].

The NCR Corporation (formerly the National Cash Register Company) was granted a patent [Marinelli 1985] for the addition of an aqueous wax emulsion to the CB coating to act as a barrier between the reactants in the CB coating and in the CF coating in multiple-copy printing operations. The technology prevents precolor formation caused by reactants seeping into the CF and can withstand on-press CF coating (presumably with desensitizing inks). Formulations included the use of JonwaxT 120 (an emulsion of polyethylene and paraffin wax), Jonwax 26 (a wax emulsion of polythene wax), and Jonwax 22 (a water-based wax compound). The wax emulsion also replaces some of the microcapsules on the substrate. (JonwaxT is a registered trademark of S.C. Johnson and Son, Inc., of Racine, Wisconsin.) According to Graves and Tardiff [1999], this process was never commercialized.

2.7 Desensitizing Inks

Frequently, information entered on the top form must be unreadable on certain sections of the form or forms beneath. If the areas on the forms beneath are not needed for other data, two types of obscuring methods can be used. The most common is the "masking" blockout, which entails the printing of a solid block of blue ink over the appropriate areas. The second type of blockout method calls for printing a dense pattern of random lines and blotches suggestive of Chinese characters ("Chinese blockout"). Both methods use the same color ink as the carbonless image color. When the blocked-out areas must remain clear to allow data entry on lower plies, the manufacturer must print a special clear "desensitizing" ink on that area. This desensitizing ink deactivates the carbonless imaging system by not allowing the CF side to react with the color former encapsulated on the CB surface [Mead Corporation 1993]. Desensitizing inks may contain a variety of solvents such as white spirits, kerosene, toluene, alcohols, glycols, ketones, and plasticizers such as dibutyl phthalate, etc. [AEMCP 1985]. Desensitizing inks are sold to industrial printers much like other printing inks [Graves and Tardiff 1999].

Chang [1978] described a patented method of desensitizing CCP when the color developer is a combination of acid clay, phenolic novolac resin, and metal salt of an organic carboxylic acid coated with 10 to 35 parts N-vinylpyrrolidone and about 65 to 90 parts of a free-radical, co-polymerizable compound of a photoinitiator having at least one terminal ethylenic group per molecule. The paper is then subjected to ultraviolet radiation.

Some CCP originates from printing shops that may use different manufacturing sources of CCP in the same manifold. Thus it is extremely difficult to trace the origin of a particular paper. For example, the CF sheet could come from one manufacturer and the remainder of the form from another supplier or manufacturer. In addition, the printer can apply the desensitizing inks to the form [Danish Branch Safety Council for Offices and Administration 1988].

2.8 Summary of Chemical Components of CCP

This section lists the known components of CCP classified as to the microcapsule, color developer, CF coating, etc. The compilation was taken from the scientific literature, patent applications, and manufacturers' submissions.

Adhesives for Binding the Various Coatings to the paper

Color Developers for Dye-Formers on CF and other Associated Agents

Agents Connected with the Coatings on the CB

2.9 Brand Names or Trademarks for CCP

Brand names or trademarks for CCP were obtained from the following sources: Calnan [1979], CHIP [1988], Levy and Hanoa [1982], Olsen and Mørck [1985], Paper Europe [1993], and Dady [1998]. The brand names or trademarks are listed as follows:

Introduction

Exposure