Paper makers use many different synthetic and natural chemical additives for a variety of different reasons during the wet formation process. They are used to influence the efficiency of the formation process or to impart specific sheet properties. They are usually added (with the exception of pigments) at a level of around 0-5% by weight of the other components of the furnish and, because of their relatively high cost, they often represent a significant proportion of the total raw material costs - particularly for recycled grades where the fibre costs may be very low. When it is necessary to modify bulk sheet properties, as in the control of aqueous fluid penetration (internal sizing), the chemicals have to be added to the wet fibre suspension so that they become well distributed throughout the z-direction of the sheet. Chemicals which are added as a surface treatment to the dry sheet are usually only able to influence surface properties.
The size distribution of the microporous structure of fibers derived from wood for use in interactive paper is discussed in terms of wood sources, pulping methods and conditions. The merits and demerits of the various procedures for the placement of both organic and inorganic chemicals within the cell wall pores are reviewed.
When we move our considerations of the components of paper, through the manufacture of paper, to the use of paper, we are analyzing the fundamental properties of paper related to its end uses. Paper as a product has a lot of possible uses and they are increasing, nevertheless it is very important in secondary products like corrugated board, etc. Every year the paper world production has an increase of approximately 1.6%. For the year 1994 it was 268,772,000 tons and during 1995 this production was 277,791,000 t. In Mexico for instance in 1994/2,860,162 tons and 1995/3,047,153 tons plus paper importation is possible to reach a per capita consumption of 35.8 kg. All paper quality kinds demand some special paper properties, which require technology, human resources and fibers properties. Surely there are fields to investigate by comparing the fundamental properties of paper and board with those of other materials, that is the reason why research must be done, despite the recent difficult times. In hard times its done distinction on switch of founds from fundamental to applied research and research for immediate development, this is understandable. Nevertheless, to study the relation between fibers and end use performance could well capture and even create a yet unknown market. Rather than adopt the attitude that 'here is paper, let us find markets for it' such research into the fundamental properties of the product will give one a clearer understanding of how it can satisfy future demands and meet possible future specifications. Because it is in meeting these specifications that the future of the industry must depend, it must be clear that money spent in this way now may not produce immediate quantifiable benefits, but it will produce the essential reserves that will in future be turned to good account by the industry.
Organic guests such as aniline, pyrrole and thiophene polymerize on the surface and in the intergallery regions of smectite clays which contain exchangeable transition metal cations such as Cu2+ and Fe3+. We monitor these reactions in thin films of smectite clays using electron spin resonance (ESR) and impedance spectroscopies. Polymers that form on the surface and in the interlayer region are studied by scanning force microscopy (SFM). ESR studies have shown that the transition metal ions are reduced during the polymerization process. Impedance measurements indicate that the formation of conducting polymer in the interlayer region of dry, Cu2+ exchanged hectorite thin films results in a dramatic reduction in observed impedance. SFM scans indicate that the conducting polymers can adopt a variety of morphologies on the surfaces of the films and within the intergalleries of the host framework. These studies have applications in the development of advanced materials including microsensors and novel nanocomposites.
Manufacturing technologies for making interactive paper have been steadily improving and have satisfied most present-day requirements of printers and other consumers. Features such as paper composition, color, texture, strength and chemical stability have been optimized through increased understanding of the chemical interactions between the raw material and additives. However, next generation higher-speed printing machines, the public's desire to read higher resolution print, and the need for better security papers are challenging chemists to develop new fillers for inks and paper. The latter are often dispersions of fine particles in a liquid or cellulose matrix. This presentation summarizes advances being made in the author's laboratory for preparing new and unique colloidal and coated particles having potential use by the paper and printing industry.
Ink jet printability is rapidly becoming a requirement for all multipurpose office papers. These papers must have an optimized balance of properties so they can perform equally well under various printing methods such as xerography, ink jet, and thermal imaging. The office paper of today truly must be a multipurpose copy paper capable of providing good toner adhesion as well as controlled absorption of aqueous ink jet solutions. The demand for ink jet paper is increasing rapidly. The global market for cut-size ink jet papers will expand to nearly 1.4 million tons by the year 2000. By that time the global market for all cut-size multipurpose plain printing papers will grow to nearly twenty million tons. The ink jet printing process places a large volume of aqueous ink on the surface of a substrate. The manner in which the substrate handles that volume of ink determines in large part the quality of the print. Multipurpose office papers are composed chiefly of cellulose fibers, inorganic fillers, and chemical additives. All of these components affect the quality of the sheet as an ink jet substrate. The particle morphology, surface area, and surface treatment of PCC fillers affect the ink jet printability of multipurpose office papers. This paper focuses on results from pilot paper machine and commercial trials performed in an effort to turn 'plain' office papers into high quality multipurpose papers capable of meeting or exceeding ink jet print quality specifications.
Swelling clays are known for their ability to intercalate organic and inorganic species in their interlamellar space. For example, Montmorillonite and Vermiculite interact strongly with organic and inorganic guests, which provoke dimensional changes upon intercalation. Unlike other minerals like zeolites, clays present geometrical changes at the molecular scale by penetration of polar species of suitable size into the layers. The anionic charge of swelling clays attract positive ions which remain fixed on the flakes surface until other ions exchange. The intermediate charge densities, i.e. 57 - 100 square angstroms of interlayer surface per unit charge, which are typical of vermiculites and smectites that swell easily, are different to the high surface charges of about 12 - 30 square angstroms per unit charge that are typical for non swelling micas like Muscovite. In Ca- Monmorillonite, the basal spacing d(100) expands proportionally to the carbon number of monohydric alcohols. One and two layer complexes having the organic molecules parallel to the basal surfaces were reported for the polyethyleneglicol ester of the oleic acids in Na-, Ca- and Mg-montmorillonite. This has proved that intercalation of high molecular weight materials can readily occur from aqueous solutions. In addition, smectites form colored complexes with a number of bases, i.e. Pyridine, which are adsorbed into well outgassed natural montmorillonites, giving rise to blue complexes which become gray upon humidification with water steam. Also, glycine and its peptides, as well as a variety of other aminoacids are sorbed by Na-, Ca- and H-Montmorillonites from aqueous solutions. Also, photochromic molecules were reported to intercalate readily in montmorillonite type clays. On the other hand, spiropyrans are molecules with long alkyl chains and their use as 3-D memory devices has been proposed. The molecules are formed by two (pi) -moieties which are set orthogonally to each other, exhibiting the individual absorption spectra rather than the conjugated spectrum. In this view, swelling clays may be used to host reactive molecules for optical, thermal or electrical recording in paper. Most of the clays that are introduced already into the composition of paper, i.e. kaolin paper clays, can host molecules externally and are potentially useful for the design of interactive papers. In this work, the interaction of dyes and clays was investigated, based on the reactive forms of spiropyrans, which are sensitive materials for recording optical and electrical signals.
A brief review is given of the fundamental features determining the behavior of amorphous PEO-based networks as polymer electrolytes containing ionic moieties in terms of two basic issues affecting the ultimate optimum ionic conductivity, viz. the factors determining the extent of ionic dissociation and those influencing the ionic mobility. These generalizations deduced from previous studies on a variety of systems allowed the elaboration of a new family of structures based on polysaccharides cross-linked with PEO and grafted with polyether chains. The preliminary results described in this paper are promising in view of the application of these materials in solid-state batteries because of their good electrochemical properties combined with mechanical strength and film-forming aptitude.
The purpose of this article is to discuss one comparatively simple way for modification of papers, on which can be developed many new and attractive sensor systems. Variation of the sensitivity of the papers toward different kind of radiation, temperature, electricity, toxic chemicals can be developed on the base of polymer/dye systems. The active part of the high sensitive papers doped with the composition is the polymer/dye system. The result of the interaction -- change of color can be produced on the surface or into the paper by the scheme: a/ action plus polymer yields polymer product plus dye yields polymer/dye product. The polymer is active part in the process. b/ action plus dye yields dye product. The polymer is inactive part of the composition.
The analysis of available data about properties and possibilities of the CycolorTM reproduction technology for preparing color images using the nonsilver light-sensitive media containing microcapsules with photopolymerizable compositions is carried out. The results of our own investigations in the field of the peculiarities of polymerization processes, the method of preparation for microcapsules based on modified liposomes, and compositions for receiver sheet are discussed.
New aspects of cellulosic material science and application are related to the lyotropic liquid crystalline properties of this classical natural polymer. In this work the preparation of anisotropic polymer networks based on (hydroxypropyl) cellulose and its derivatives as well as their properties are discussed. Cellulose derivatives form liquid crystalline solutions also in polymerizable solvents, e.g. acrylic acid thus anisotropic polymeric networks can be fixed by photopolymerization. These films have been investigated with regard to their orientation birefringence and thermal stability. Some possible applications of these interesting systems are briefly shown.
Photofabrication of surface relief gratings on various polymer films containing azobenzene groups was demonstrated. Large surface modulation (greater than 6000 angstrom) and high diffraction efficiency (greater than 40%) could be obtained under optimal recording conditions. Formation of the surface gratings was observed in both organic and water-soluble azo polymers. We demonstrated the formation of various multiple gratings in a two dimensional format on the same spot by simply controlling the writing wavelength and the writing angle. The resulting surface pattern was a simple superposition of all the interference recording beams regardless of the sequence of the recording. Large surface grating could be created in the polymer film coated on various paper based flexible substrates.
The composition of photographic color negative papers is reviewed. Information is presented on the potential detrimental effect of the polyethylene resin-coated (RC) paper support on the thermal stability of the silver halide element. Evidence is provided for the major role that the pH of the dry paper stock has in this effect. A mechanism for the detrimental photographic performance involving both the RC and the paper stock is proposed.
Optical processing and computing applications require practical recording materials with certain advantages such as real-time capability high-resolution and stability against environmental changes. Organic materials are one class of recording materials well suited for information storage. This presentation gives an historical review of holographic materials used to record holograms. Some basic aspects of holography also are given to complete the presentation. Some discussions of the photophysics and the photochemistry involved during the recording of light patterns are also presented. Finally, some applications in the fields of dynamic holography, write-once holography and optical data storage are presented.
2H-1-Benzopyrans (or 2H-Chromenes) are an important family of oxygenated heterocycles particularly attractive because of their photochromic properties. Indeed, 2H-Chromenes undergo a reversible ring opening of the pyran cycle. The Csp3-O-bond is cleaved by UV irradiation leading to opened colored forms (generally called 'photomerocyanines'). The opened isomer reverts to its original form via a thermal pathway. The first described chromenes, 2,2-dimethyl [2H]-chromenes and their benzo annulated derivatives (naphthopyrans) showed photochromic behavior only at low temperatures and, moreover led to undesirable by-products. Interest in research in this field was developed only recently because of the industrial applications of materials undergoing variable optical transmission of light. For this purpose the desirable properties could be summarized as follows: light efficiency for coloring in the near ultra violet region, low quantum yield for bleaching with visible light and fast thermal fading at ambient temperatures. Another important criterium concerns the good resistance to the fatigue under continuous irradiation. These kinds of requirements have led to several structural modifications in the chromene series. Particularly, improvement of photochromic properties ('colorability') was obtained by the annulation of the chromene ring in the 7,8 positions, by appropriate substitution of the naphthopyran cycle replacing the alkyl groups on the Csp3 carbon atom by cyclopropyl groups, spiro adamantyl groups, and overall, by aryl groups. This last kind of substitution is nearly indespensible for showing good photochromic properties. Our interest in benzopyran chemistry has been focused on the design and study of heterocyclo-fused analogues, in order to modify the photochromic parameters. So we have introduced five-ringed and six-ringed heterocyclic systems involving oxygen, sulphur and nitrogen heteroatoms, particularly with an annulation in 5,6 positions. The general methods (A and B) have been used for the synthesis, they are briefly described.
Thermal coloration of spiropyrans and spiroxazines at or above their melting point is well known to photochromists. The erasure of the color developed by exposure of photochromic paper by radiations of certain wavelengths in the visible region is little known. Six-nitrospirobenzopyran and 8- nitrospirobenzopyran, 8-methoxy-6-nitrospirobenzo-pyran, 6- methoxy-8-nitrospirobenzopyran, and 6,8-dinitrospirobenzopyran have been studied. The medium in which these photochromic dyes were dissolved or incorporated was limited to cellulose derivatives such as cellulose acetate, cellulose acetate- butyrate, and cellulose trinitrate. Paper coated with 6- nitrospirobenzopyran dissolved in an ethyl acetate solution of cellulose trinitrate readily colored on exposure to UV light or IR radiation and faded on exposure to light in the visible range. This unusual phenomenon, although not fully understood, is believed to be a selective light sensitizing ability of nitro groups. The applications of photoerasing paper and thermally colorable films are numerous, such as in polaroid type photography, in copy machines, and in thermally stable photochromic ophthalmic lenses.
Microlithographic techniques have been developed to generate conducting patterns, at the micron scale, in nonconducting polybutadiene films. The conducting patterns thus produced are colored and show strong fluorescence emission, and are of promise for various practical applications including fabrication of devices for optical and electrical addressing and retrieval.
Scientists at the NCR Corporation in Dayton, Ohio laboratories invented the basic technology used in direct thermal imaging in the early 1960's. Direct thermal is differentiated from thermal transfer and dye sublimation technologies in that images are generated directly on the substrate which contains the active components. Thermal transfer and dye sublimation are characterized by mass transfer from a substrate sheet containing the image forming components to a receiver sheet that holds the final image. Direct thermal coated paper products became commercially available in 1964. The thermal coating components of these early papers had low heat sensitivities, but were well matched to what today would be described as crude and bulky high temperature thermal printheads. The first product, called Miniprint Bond had utility in military applications. Rapid expansion of direct thermal applications began in the l 970's as thermally sensitive papers found uses in chart recorders, calculators, and printers. Direct thermal product developments in the 1980's were characterized by the introduction of facsimile and barcode label papers. More recent developments target specialty applications such as infrared scannable labels, products with colored backgrounds for point of sale (POS) tags/signage, and application of thermal coatings to synthetic substrates for use in medical chart recorders. From the perspective of customer value, direct thermal imaging technology offers several major benefits. For instance, since they have few moving parts the imaging devices require minimal maintenance. This attribute is important in remote locations such as automated teller machines (ATM's) where frequency of use and minimal hardware service are the norm. Another benefit is that direct thermal products are self-contained; the image forming components are on one substrate eliminating the need for transfer ribbons or receiver sheets. Also, speed of printing is important to users, virtually instantaneous imaging is possible with modem printheads and direct thermal papers. Currently, direct thermal products are thought of in terms of two broad product categories: facsimile and label/tag applications. Driving the evolution of facsimile products is the need for cost reduction and increasing image sensitivity. This results from the development of low energy printheads which have longer life and higher facsimile transmission rates. Another concern in facsimile grades is the archivability of imaged sheets for office file storage since the direct thermal image, made by the formation of a chemical complex, may be reversible under certain conditions. Label products, on the other hand, must withstand image erasure due to exposure to a variety of environmental stresses not found in office environments, they include exposure to oils, blood, alcohol, plasticizers as well as wide swings in temperature and relative humidity. The diverse environments in which they find utility result in direct thermal products of increasing complexity with regard to composition and processing of the thermal coatings, as well as place increasing demands on the coating substrate. As a result of technical developments in the areas of hardware and thermal coating design, along with aggressive market development, the world demand for direct thermal products is currently over 400,000 tons per year. Total market growth rate is expected to be over 7% per year for the next several years (Appleton Papers Inc. estimate). The predominant manufacturers of direct thermal products include Appleton Papers Inc., which acquired the thermal assets of the NCR Company in 1978, New Oji/Kanz.aki, Mitsubishi, Ricoh, Koehler, Stora and Nippon/Jujo.
Uncontrolled growth of bacteria and fungi in the papermaking process adversely affects machine runability. How this growth influences factors in the finished sheet and sheet print properties is often overlooked, even though it can have a profound effect on printing characteristics. Many of the materials used in making paper coatings are excellent microbial nutrients. In addition to being nutrients, these compounds are critical to performance. For example, coatings made of poorly preserved clays can form a surface that has fine scratches caused by microagglomeration of the clay particles. This may be caused by microbial degradation of the dispersants in the clays. This paper explores these issues and discusses steps that can be taken to minimize these problems.
From the chemical point of view paper coatings are mainly polymer dispersions. Polymer dispersions are constituted in multitude fields, for example as dispersion coatings or adhesives. As far as no additional treatment is done, polymer materials as well as polymer agents contain non polymer, volatile organic components that may arise from: (1) incomplete polymerization of the applied monomers, (2) primary materials containing non polymerizable components, (3) undesirable side reactions during the synthesis. Requirements for the removal of volatile substances from polymer dispersion are given by several reasons: (1) low molecular substances deteriorate the product characteristics (viscosity, thermal stability and others), (2) in order to comply with legislative standards, volatile organic compounds have to be removed from dispersions, especially when applied to large surfaces (e.g. in surface refining in paper and leather industries as well as on coating). The removal of volatile organic compounds (deodorization) can be realized in continuous or discontinuous processes. In contrast to highly developed process technology, the process itself is not well understood, especially mass transport phenomena between the gas phase and the aqueous polymer dispersion are insufficiently and controversially discussed in the literature. Two processes, their advantages and disadvantages and the description by mathematical- mechanistic models are presented in this paper.
Various organic conjugated materials, e.g. conjugated polymers and short conjugated oligomers, have been up to now proposed as active semiconducting layers in organic-base devices, such as thin film transistors, TFTs, or light emitting diodes. The mode of operation of TFTs shows that a high carrier mobility together with a low conductivity are required for their figure of merit. Experimental results from literature indicate that, whereas conjugated polymers exhibit a low carrier mobility, of the order of 10-4 to 10-5 cm2V-1s-1, conjugated oligomers appear much more promising. It is thus shown that carrier mobility is directly related to the long range structural order in conjugated oligomer films, i.e. to the decrease of grain boundaries, leading to values of the order of 10-1 cm-2V-1s-1, comparable to that of amorphous hydrogenated silicon. Conjugated oligomers are well defined materials, offering various physical and chemical ways for control of the structural organization of thin films made from them. Besides, conductivity in thin films of conjugated oligomers is mainly determined by the purity of the materials, allowing values lower than 10-7 Scm-1, with a high on/off ratio. The low melting and evaporation temperatures of conjugated oligomers, together with the solubility of some of these materials, allows the construction of TFTs by the use of room temperature techniques, following a process compatible with paper technology.
The fibers and additives found in paper have intrinsic properties which can be combined to perform important functions heretofore taking place on the surface of the substrate. These unique properties can be used to different ends such as (1) storing information transmitted photonically, electrically, thermally or magnetically; (2) generating contrast (imaging); (3) acting as a sensor for light, electric or magnetic fields, humidity, pressure, chemicals; (4) performing mathematical functions, etc. The fibers of paper are tube-like elongated bodies made of a hollow part and a wall which has its own structure. The hollow part can be the recipient of chemicals species which promote a reaction by release of an active component through the wall or be part of a physical reaction inside the fiber. The role of the fiber in such instance would be to protect the specie from the environment (oxygen, humidity, chemical pollutants, etc.) and thereby increasing its lifetime. The roles of the wall can be multiple. They can contribute to the controlled release of the chemical (or chemicals) stored in the fiber to an outside medium. This release is initiated by a physical process acting on the structure of the wall (mechanical, thermal, photonic, electric or magnetic). We can also use the surface properties of the inside-wall or the outside-wall interfaces. The chemical structure of the wall provides radicals on each interface which can be made to establish bonds with the chemical stored in the fiber or with a chemical composition outside the fiber. Simple examples are shown. Charges in the paper making process have been introduced as components for different reasons: mechanical, chemical, optical or electrical but apart from this intended function the charges have other properties of which we can take advantage for other functions created for that component or in combination with other components.
The threat of counterfeiting Bank Notes and other security documents is steadily increasing with the continuous improvement of printing and copying technologies. The perfect reproduction of a document is indeed reachable with the right combination of technique and economics. Our only protection is to make it difficult by introducing artifacts which appear only through the counterfeiting process or reduce significantly the efficiency of that process. A number of methods are available to defeat counterfeiting none of which are completely satisfactory. The difficulty is not as much the prevention of the duplication than doing it while safeguarding the intrinsic properties (durability) of the documents as far as permanent readability, resistance to wear, etc. Basic approaches are: (1) The light switch: a transparent coating which becomes opaque during any attempt of duplication. (2) An alternative to this first approach is an ink which becomes transparent at the time of duplication. (3) The use of a substrate (paper stock) whose optical density will rise to that of the printed graphic on the bill at the time of copying. This would be a true interactive paper. (4) Luminescent materials that would blind the photoreceptor during exposure. Such material could be in the substrate or in the printing ink. (5) Introduction of an artefact in the printed copy through a hologram hidden in a transparent coating or embossed in the substrate. All approaches have been investigated to a certain extent with variable success. We report hereafter the results of investigations made by the author on alternatives (1) and (2) in this laboratory and at the University of Texas at El Paso under contract from the National Bank of Belgium and with the collaboration of the CNRS in Paris and the University of Marseille France.