Background of the Invention

One of the most important factors in the progress of civilization has been the introduction and improved manufacture of paper, a semisynthetic product comprised of closely matted fibers obtained by chemical or mechanical processing of cellulosic fibers. While originally made from vegetable fibers reclaimed from rags, the increased demand for paper has led to the utilization of material which could be obtained in much greater quantities. A wide variety of sources have been utilized (i.e. flax, bagasse, esparto, straw, papyrus, bamboo, and jute), but by far the largest quantity is made from softwood trees (coniferous trees) such as spruce, hemlock. pine. etc.. Additional sources include such hardwood trees as poplar and oak. as well as from synthetic fiber.

Pulp is the product of the separation of the fibers in wood or other plant fiber material and is an intermediate product in the manufacture of paper and paperboard. Pulping is achieved by chemical or mechanical means or combinations thereof. In mechanical pulping, the original chemical constituents of the fibrous material are unchanged except for the removal of water-solubles. Chemical pulping has as its purpose the selective removal of the fiber-bonding lignin to a varying degree, with a minimum solution of the hemicelluloses and celluloses. This purification step can be continued in a bleaching step. The properties of the end products, the papers and paperboards, will depend on the properties of the pulps used in their manufacture. These in turn will vary with the wood species or non-wood plant fiber used and the pulping process employed. Wood-derived mechanical pulps -which are merely finely divided wood without purification- are useful in the production of newsprint, cheap manila papers and non- permanent tissue, while chemical pulps of wood have much more extensive uses.

The ever-increasing need for new wood supplies for production of pulp and paper products has led to an increasing concern over the apparent abuse of our resources. In the developing world, the opening of tropical forests and the selective extraction of high-value logs for pulping has led to harmful land-use practices. Thus. there is a need to create pulps from non-traditional sources.

Summary of the Invention

This invention pertains to algal pulps and pre-pulps generated from members of the order Cladophorales, for use in making papers and paper products and to the paper and paper products made from these pulps. The invention also pertains to methods of forming algal pre-pulps, pulps and paper and paper products.

The algal pulps, paper and paper product are made from filamentous green algae of the Division Chlorophyta, Class Chlorophycaeae, and Order Cladophorales, and include at least the following genera: Cladophora, Chaetomorpha, Rhizoclonium, Pithophora, Valonia, Valoniopsis, Cladophoropsis, Boergesenia, Anadyomene, Microdictyon, Boodlea, Chamaedoris, and Dictyosphaeria.

The algal pulps of this invention can be generated by mechanical, chemical, or biological pulping processes, or combinations thereof. These pulping processes can be utilized to control the hemicellulose levels in the pulp as well as to control the fiber length in the pulp. Examples of chemical processes useful in the present invention for pulping of cladophoralean algae include alkaline sulfite, acid sulfite, neutral sulfite, sulfate (Kraft and Green Liquor), bisulfite, and polysulfide, caustic soda (such as cold soda), soda-AQ (sodium hydroxide and anthraquinone), sodium bicarbonate, and soda-oxygen reactions. Bleaching of the algal pulp can be accomplished either by chemical bleaching, photo-bleaching or both. Useful chemical bleaching agents comprise oxidizing or reducing agents such as chlorine dioxide, hypochlorites (such as calcium hypochlorite and sodium hypochlorite). bisulfite, dithionite, peroxides (such as sodium peroxide and hydrogen peroxide), hyperchlorous acid, sodium chlorite, sodium borohydride, and thioglycolic acid.

Photo-bleaching can involve the subjection of an algae to optical energy and to controlled conditions adverse to photosynthesis and cell growth. For instance, an algal mass can be isolated in which at least a predetermined fraction of the harvested algae has achieved maximal growth and has entered a senescent stage of cell growth concomitant with chloroplast autolysis and susceptibility of the chlorophyll component to photo-degradation. The algal mass is slowly dried and exposed to optical energy sufficient to bleach the chlorophyll component to a substantially colorless state so as to create a bleached pre-pulp.

The pulps and paper products of the present invention provide unique advantages. For instance, in terms of resource conservation, the use of algae in papermaking can lead to a decreased use of trees in the production of pulps. The lack of any need to delignify the pulps of the present invention allows faster, cheaper production of high grade pulps. This characteristic can also lead to reduction in the

use of environmentally hazardous chemicals. Likewise, photo-bleaching of the algae to form the photo-bleached pre-pulps of the present invention can also lead to a reduction in the environmentally damaging chemicals generally required to bleach pulps. Additionally, the photo-bleaching step can result in longer cellulosic fibers in the pulp, whereas chemical bleaching can cause significant fiber shortening.

The pulps and pre-pulps of the present invention can be used alone to generate papers and paper products, or can be mixed with other virgin or recycled pulp sources. For instance, when mixed with recycled pulps, the length of the cellulosic fibers of the algal pulps of the present invention can provide greater strength to the recycled pulps which often have undergone significant fiber shortening during processing.

Detailed Description of the Invention

The organisms specified for use for the purposes set forth in this patent application are filamentous green algae of the Division Chlorophyta, Class Chlorophycaeae, and Order Cladophorales.

The systematics of the order Cladophorales is summarized as follows. Cladophoraleans are straight chain and branched filamentous plants composed of multinucleate cells. The filaments are attached to the substrate by rhizomes or are free floating. The cells contain numerous discoid angular chloroplasts forming a parietal reticulum, but they may extend into the internal meshes of the protoplasmic foam. The main wall polysaccharide is a highly crystalline cellulose I, forming numerous lamellae of microfibrils in a crossed fibrillar pattern. In at least one species, the outer walls and cross walls contain chitin as well as cellulose I. One or more species may contain silica in their outer cell walls. Reproduction can be by either sexual or asexual means.

The extremely complex and exact system of wall formation in the Cladophorales suggests that deposition is under very precise control and that the production and orientation of microfibrils is a function of the outermost layer of cytoplasm. The set of microfibrils are deposited in the sporeling cells with the first to be deposited making a small angle to the transverse axis, followed by the second at a greater angle, and finally the third, when present. The rhythm of deposition is retained by the daughter cells through several cell divisions so that adjacent cells in a filament have the innermost lamellae lying in the same direction.

Microfibrils normally are synthesized through the formation of terminal synthesizing complexes (TC). containing enzymes and other factors at their growing tip. TC structure determines final microfibrillar assembly in the cell walls of algae.

There are two basic forms of these TC\'s; rosettes and linear. Unlike the herbaceous and woody higher plants which all have the rosette form, linear TC\'s are found in the Cladophorales, making them distinctive in this regard from all other current paper producing substances.

The interactions of the chemical and physical properties of the cell walls of filamentous green algae provide form, strength and stability. These properties include:

1. Microfibrillar lamellae composed of cellulose I.

2. An amorphous matrix composed of polysaccharides, between the inner and outer walls or the filaments, which surrounds the microfibrillar lamellae.

3. Hemicelluloses concentrated on the outer surfaces of the microfibrils.

4. Chitin and chitosan in the outer and cross walls of some species.

5. Silica in the outer wall of some species.

6. Proteins, glycoproteins and heteropolysaccharides.

In general, the filaments of the cladophoralean algae are composed of cells enclosed by a double cell wall. The inner wall encloses individual cells, while the thinner outer wall ensheathes the whole filament. The mass of the cell wall is made up mostly of microfibrillar elements which provide rigidity and strength. The most common component of the microfibrils is the polysaccharide, cellulose. In the Cladophorales. a highly crystallized form of cellulose, cellulose I (or native cellulose) is present in all the species of the genera Cladophora, Chaetomorpha, Pithophora and Rhizoclonium, whereas it is replaced by cellulose II (a less polymerized form of cellulose with irregularly disposed molecules) in all Spongomorpha spp. The percentage of microfibrillar material in the genus Cladophora is about 28.5%, and in the genus Chaetomorpha is in the range of 36.5-41%.

In the cell wall, cellulose is usually laid down in the form of lamellae running in two directions, in steep or slow spirals, almost at right angles or with a third lamellae, if present, as in some species of Cladophora, Chaetomorpha and Valonia. in which the fibrils run in the obtuse angle between the other two. The third spiral is not always present, in which case the cell wall is a two lamellae repeat. Uniquely, microfibrils are interwoven between different bands of lamellae. The microfibrils of the side walls are continuous with those of the cross wall. The microfibrillar lamellae

are in general surrounded by a water soluble amorphous material also composed of polysaccharides.

The polysaccharide composition of cladophoralean cell walls is, in general, as follows:

Cellulose microfibrils - Glucose, galactose, arabinose and xylose.

Water soluble fraction - Uronic Acid, galactose, glucose, arabinose, xylose.

Hemicellulose fraction - Galactoglucomannan. arabinoglucuronoxylan.

Other sugars represent the constituents of glycoproteins and heteropolysaccharide fragments that are linked to each other or to cellulose. Protein related in structure to collagen are also found. In addition, silica is also found to a small extent in the cell walls of the cotton- mat algae.

The order Cladophorales is defined here to include at least the following genera: Cladophora, Chaetomorpha, Rhizoclonium, Pithophora, Valonia, Valoniopsis, Cladophoropsis, Boergesenia, Anadyomene, Microdictyon, Boodlea, Chamaedoris, and Dictvosphaeria. Because of the taxonomic state of flux, the order Cladophorales is further defined to include any filamentous green alga of the class Chlorophyceae with the cell wall characteristics, general chemical and physical composition, and structure and function as described above. The preferred species with reference to this invention are Cladophora spp.. especially Cladophora glomerata Kuetzing. Chaetomorpha spp.. Pithophora spp.. and Rhizoclonium spp.

The species of preference to be harvested under current world conditions of pollution eutrophication is Cladophora glomerata Kuetzing. Worldwide, this species has the widest distribution and greatest biomass of all the filamentous green algae. In addition, this species is of the genus having the second highest proportion of cellulose I microfibrils in its cell walls. However, it will be appreciated by those skilled in the art that other Cladophora spp., Chaetomorpha spp., Pithorphora spp., and Rhizoclonium spp.. all contain cellulose I in their cell walls and can be utilized for the various formulations and applications described below.

For culturing. Cladophora glomerata Kuetzing. Chaetomorpha spp. , Pithorphora spp.. and Rhizoclonium spp. will be used preferentiall)\'. Ultimately, however, whichever cladophoralean species is most amenable to being bred or biologically engineered to provide the highest yields of the best quality cellulose and related hydrogen bond-inducing polysaccharides will be used. Strain improvement can be carried out by breeding under standard laboratory conditions of monoalsal

culture, or by introducing genes using recombinant manipulation of the genome.

While pulping and fiber preparation used in wood and nonwood-fiber processes (see for example Pulp and Paper Chemistry and Chemical Technology vol l ed. James Casey (1980) Wiley & Sons, NY; Papermaking ed. Francis Bolam (1965) Clowes & Sons, London, chapters 4 and 5; Chemical and Mechanical Pulping ed. James Casey (1984) Marcel Dekker, NY; and Joint Textbook Committee of the Paper Industry ed. T. Grace and E. Malcolm (1989) TAPPI, Atlanta, incorporated by reference herein) are generally applicable in making the cladophoralean pulps of the present invention, milder chemical reactions can be used due to the lack of any need to delignify the cladophoralean pulps. The advantage of these cladophoralean pulps over wood and other non-algal plant fiber pulps is that they are entirely lacking in lignin. This characteristic allows faster, cheaper production of high grade pulps. The selective chemical extraction procedures most useful in the present invention are not designed to remove lignin. but rather to differentially extract hemicelluloses. sugars. and other components to create the ideal pulp for specific uses. Cladophoralean pulps can be produced by gentle chemical action and selective extraction, by mechanical pulping, by biological pulping, or combinations thereof. The pulping method selected should 1) retain or create the optimum fiber length for the application, and 2) differentially select the hemicelluloses and other sugar polymers so as to promote optimum hydrogen bonding capacity or to increase the fold strength by altering the networking and proximity of the cellulose fiber, or by increasing the total proportion of cellulose in the mix.

In addition, the method selected for preparation of the pulp from cladophoralean algae will depend on the type of paper required. Generally, the operation will consist essentially of separating the ultimate fibers and then purifying them to an extent depending on the quality required for the final product. When the ultimate fibers of the raw algal pulp are long (i.e. over 7mm), they can be shortened with advantage during their separation. On the other hand, if they are already short (i.e. less than 4mm), care can be taken to preserve the length, and any further shortening that may be needed can be obtained during a beating stage. In addition, the choice of a pulp bleaching process can also effect the type of pulping process to be used.

The nature of the fiber purification is also governed by the types of impurities to be removed. These may consist of dirt and other foreign matter soluble in water. or be intimately associated with the cellulose, such as hemicelluloses. With regard to the pulping of cladophoralean algae, as the main goal is the selective extraction or modification of non-cellulosic materials rather than the removal of lignin. the most useful pulping processes are generally semi-chemical (chemimechanical) and do not

require as harsh conditions as necessary in wood pulping. These processes depend in general on a relatively mild digestion under alkaline conditions, followed by mechanical treatment to break up the plant structure.

Examples of chemical processes useful in the present invention for pulping of cladophoralean algae include alkaline sulfite, acid sulfite, neutral sulfite, sulfate

(Kraft and Green Liquor), bisulfite, and polysufide. In addition, non-sulfer chemical pulping processes include caustic soda (such as cold soda), soda-AQ (sodium hydroxide and anthraquinone), sodium bicarbonate, and soda-oxygen reactions.

These chemical processes can be combined with mechanical fiberizing or pulp disintegrating steps, such as disc refining or beating, to yield chemimechanical pulping processes. For instance, the algal mass can be soaked in cold sodium hydroxide solution, or treated by an alternate chemical method, for shorter periods of time and/or with smaller proportions of chemicals. The partially pulped algae is then subjected to a mechanical fiberizing step to produce a finer more dispersed pulp. Thermomechanical or chemithermomechanical pulping processes can also be used which involve the application of thermal energy in conjunction with mechanical force to the algal mass as a principal pulping means. In the instance of thermomechanical pulping, the pulp produced will generally be of higher fiber length and hemicellulose levels than produced by most chemical and chemi-mechanical pulping techniques.

Further, biological pulping processes comprising the liberation of cellulosic fibrils by enzymatic digestion of the algae can be used to produce the algal pulp. These processes can be utilized to digest non-cellulosic components of the algae, as well as to alter the characteristics of the cellulosic fibers themselves. For example, biological pulping can be carried out by the use of purified or semi-purified enzymes, or alternatively, by treatment with whole organism (both naturally-occurring and engineered) which act to digest components of the algae in the pulp formation process.

After the digestion stage by any of the above processes, it may be desirable to remove from the pulp certain material, such as dirt and non-pulped clumps of plant material as well as air. Techniques for such mechanical purification are well known in the art of pulp and papermaking. For example, various screening techniques can be employed to remove particles larger in size than the preferred fiber length of a given pulp. In addition, many types of centrifugal cleaners are known for the removal of fines (those particles smaller than the desired fiber). While air in pulp stock is not usually included in the list of materials which constitutes dirt or contribute to the contamination of stock, it can be an unwanted component. Deaeration equipment is well-known for the removal of air from pulp stock and will

generally be usable with algal pulps.

The presence of chlorophyll and other pigmentary molecules in the algae can require a bleaching process in those instances where the coloration of the final paper product is of importance. Chemical bleaching of the algal pulp can be carried out using many of the same processes found in the bleaching of wood and nonwood-fiber pulps. The actual bleaching process will depend in part upon the pulping process utilized as well as the desired brightness of the final paper product. Chlorine dioxide, hypochlorites (such as calcium hypochlorite and sodium hypochlorite), bisulfite, dithionite, peroxides (such as sodium peroxide and hydrogen peroxide), hyperchlorous acid, sodium chlorite, ozone, sodium borohydride, and thioglycolic acid are examples of strongly oxidizing or reducing agents useful in bleaching processes for this invention.

In addition to, or instead of, the chemical bleaching steps above, a bleached pre-pulp can be obtained by photo-bleaching. The algae are subjected to conditions which are adverse to photosynthesis and cell-growth so as to cause autolysis of chlorophyll-containing chloroplasts. In the presence of optical energy, the algal mass can then be photo-bleached with a large degree of coloration removed. Depending on the brightness sought for the desired paper product, it may be desirable to carry out both photo-bleaching to form an algal pre-pulp, followed by a chemical bleaching step of the algal pulp. However, any further chemical bleaching (if even necessary) of the photo-bleached pre-pulps can be carried out under milder conditions than chemical bleaching alone. The optical energy used for photo-bleaching can be natural sunlight, or alternatively, artificial light of a wavelength suitable to bring about bleaching of the chlorophyll. To carry out the in situ bleaching (photo-bleaching) of cladophoraleans for the production of pulps, cladophoralean algae, under prevailing natural or artificially simulated conditions, can be harvested when at least a certain fraction of the harvested population have reached maximum growth and their physiological processes have induced the autolysis of chloroplasts as indicated by the reduction of chlorophyll. It is important to note that algae, which are of the kingdom Protista, are unicellular organisms distinguished from, for example, grasses in that they have no true root, stem or leaf. The present method of generated photo-bleached pre-pulps makes use of the retention of the organism\'s own physiologically responsive mechanism necessary to facilitate self-digestion of the chloroplasts. and therefore requires some degree of integrity of the algae during this process. It is emphasized that mere exposure of the algae to optical energy is not. in and of itself, sufficient for suitable photo-bleaching of the algae. As set forth below in Examples 1 and 2. algal samples that were not subjected to conditions which induce chloroplast autolysis did

not bleach well and remained a deep green even after exposure to sunlight. The percentage of the population needed to attain this growth state before harvesting can be determined based on the particular strain employed as well as end-product needs. For example, this fraction can range from 30-percent to 70-percent of the harvest population.

Once harvested, the cladophoraleans can be allowed to slowly dry out while exposed to the optical energy necessary for photo-bleaching. Sprinklers can used to control the drying process by keeping the cladophoraleans moist enough to allow physiological processes such as the degradation of the chloroplasts to be maintained. The need for wetting can be determined by the rate of drying, which can be a function of ambient meteorological conditions and the intensity of the sun. The drying process should progress to the point that the algal mass is fully dry, or until autolysis of the chloroplasts is complete as indicated by the loss of green color. If the photo-bleaching of the algal mass is sufficient, the drying step can be suspended and the moist photo-bleached pre-pulp used directly in the pulping stage if desired.

In some instances it may be preferable to harvest the algae and mechanically express the water (i.e. by the use of heat, pressure, or combinations thereof) and transport the material to a processing site. At the processing site, the dried algae can then be photo-bleached with artificial or natural light, either before or after mechanical pulping. The key is to harvest the cladophoraleans at the growth stage, or to provide a physiological stimulus to trigger, or make susceptible to autolysis, the chloroplast bodies.

The moisture content of wood is definitely related to the strength of pulp made from it (rewetting does not restore strength). Wood which has less than 40-percent moisture makes weaker pulp. Likewise, as can be determined by the strength of an algal pulp, the pre-bleaching/drying process can be controlled to yield material with a moisture content appropriate to yield a pulp having a strength no less than a desired value.

Beating and refining can be defined as the mechanical treatment of pulp. Often these processes are carried out in the presence of water usually by passing the suspension of pulp fibers through a relatively narrow gap between a revolving rotor and a stationary stator, both of which carry bars or knives aligned more or less across the line of flow of the stock. The term "beating" is usually applied to the batch treatment of stock, for instance in a Hollander beater or one of its modifications. The term "refining" is used when stock is passed continuously through one or more refiners in series or in parallel. Examples of refiners useful in the present invention include the disk, conical, or wide-angle types.

Beating or refining is carried out primarily because of its effects on the physical properties of the finished sheet of paper. The sheet properties are modified by beating or refining in such a way as to make the sheet more suitable for the use to which it is to be put. For example, beating can improve the bursting strength and the formation of the sheet. Beating and refining may also have undesirable effects such as reduction in the tearing strength or an increase in the expansion when the sheet is exposed to high humidity. Another reason for carrying out beating and refining is to facilitate sheet formation, for example, to control drainage rate on the paper machine. It will be appreciated by those skilled in the art that beating and refining may not produce the same effects on chemically or biologically pulped stock as with mechanically pulped stocks due to potential differences in cellulosic fiber characteristics between the processes.

Paper made from unbeaten fibers is often lower in strength, more porous, not as well bonded, and wild in formation relative to paper made from beaten and refined stock.

One major effect of beating and refining is to produce an increase in the specific surface of the pulp fibers. The sizing of paper pulp is a surface phenomenon as is retention of fillers. Dyeing by some types of dyes such as direct dyes can be dependent of characteristics of the pulp fibers. The effect of beating and refining on sheet density and consequently on optical properties, particularly opacity and brightness, can have a marked effect on the appearance of the sheet.

In addition to mechanical beating processes, ultrasonic treatment of the pulp, using high-intensity sound waves to transfer energy to the pulp fibers, can be utilized for beating. Hand sheets can be made from the beaten or refined stock and tested for the properties in which the papermaker is interested. The method of making hand sheets for test purposes is specified in a number of standard procedures. The best known and most widely used is the TAPPI standard T205 which is based on the report of the Pulp Evaluation Committee of the British Paper and Board Makers Association (see Anon., Forming Handsheets for Physical Tests of Pulp T205 os-71, TAPPI Testing Procedures. Technical Association of the Pulp and Paper Industry, Atlanta. GA 1971, incorporated by reference herein). Breaking lengths calculated for handsheets formed from algal pulps will herein be defined relative to TAPPI standard T205. The particular algal species utilized, as well as factors such as the pulping processes and bleaching processes used to make the pulp, can effect the breaking length. For instance, the paper handsheets made from the algal pulps described herein can have breaking lengths exceeding values such as 4000 meters, or 8800 meters. For instance. Example 2 describes in further detail paper handsheets made from an algal

pulp which have breaking lengths of about 15 kilometers.

In some instances, it can be desirable to blend pulps from different sources. For example, blended pulps can comprise inter-algae pulps, algae-wood (or other fiber derived from non-algal plant sources) pulps, or any combination of algae and appropriate fiber pulps useful for making a desired paper product. In addition, synthetic fiber pulps can also be useful in the blended pulps. The pulps can be blended either at a post-beating stage, or prior to a beating stage of the processing.

At some point during the stock preparation period, it can be desirable to add sizing agents, resins to contribute wet or dry strength, starches, mineral fillers, retention aids, microbocides, dyes, or similar materials to the fibrous furnish in order to develop special properties in the particular grade of paper desired.

The process of adding mineral matter to pulp stocks is well known in the art. Depending on the ultimate paper product desired, fillers can be added to the pulp to improve such characteristics as the printing surface and the absorption of printing ink, to give a higher finish, greater opacity, improved brightness, a close and even appearance, flatness, softness of handle, and to improve dimensional stability in changing atmospheric conditions. A large number of fillers are available to the paper chemist. Examples of fillers useful in the present invention include china clay (kaolin), calcium sulfate, titanium dioxide, barium sulfate, magnesium silicates (i.e. talc, agalite, french chalk, asbestine), calcium carbonate, diatomaceous silica, and zinc sulfide. Colored pigments can be used as well. In general, for use with bleached pulps, the fillers should have a high degree of whiteness, a high index of refraction, small particle size, low solubility in water, and be chemically inert with regard to reacting with other components of the pulp. In addition to the use of fillers, to impart resistance to the penetration of liquids to the ultimate paper or paperboard product of the algal pulp internal sizing components can be added to the pulp. When the ultimate paper product of an algal pulp is designed for use in writing, printing, wrapping, packaging or construction applications it may be desirable to use sizing agents. These products can be characterized as strongly (hard) sized or weakly (slack) sized, depending on the rigor of the end use as well as the natural fluid impermeability imparted by the algal matter. Products such as tissue, toweling, blotters, and sanitary grades are designed for rapid absorption of aqueous fluids and generally will lack any added sizing agents. Examples of sizing agents useful in the present invention include rosin sizings. synthetic sizings (such as alkyl ketene dimers. stearic anhydride, and alkenyl succinic anhydrides), wax emulsions, and petroleum resins.

The pulps of the present invention can be formed into paper products in a substantially similar manner as wood pulps are. For example, the pulps of the

present invention can be used with such high speed, integrated paper machines as Fourdrinier machines, multi-wire machines, tissue machines, and multiply machines. The paper products can be subjected to calendering and finishing processes. In addition, the paper products can be used with corrugating machines to produce corrugated board.

Example 1

A photo-bleached pre-pulp of cladophoralean algae was made in which the chloroplasts containing green chlorophyll were self-digested by the algae, and the chlorophyll photo-bleached. The propensity of the algae to autolyze its own chloroplasts appears to be a function of a number of physiologic parameters, including age, stress caused by nutritional factors, gradual stranding of the Cladophoralean by dropping water level, and temperature. Samples of young, vigorously growing Cladophora glomerata from a cold river were compared to early senescent C. glomerata from a warm creek. Microscopic examination demonstrated that, when compared to the young C glomerata, the number of chloroplasts in the cells of the early senescent C glomerata were greatly reduced or entirely absent. The algal samples were placed on wire-meshed screens inclined at an angle facing the sun and were kept thoroughly wet to maintain physiological activity as the drying process began. The C glomerata samples were allowed to slowly dry. At the end of the drying process, 80-90 % of the mass of the samples of senescent C glomerata had bleached to an off-white color. The dried samples of young C glomerata remained a deep green color. Intermediate stages of bleaching were obtained from samples of older, not yet senescent C glomerata.

Example 2

Samples of senescent C glomerata were also dried in the dark. These dried samples were observed to retain their yellow-green color until placed in sunlight. This subsequent exposure to sunlight bleached the yellowish color and the already dried samples turned the same white as the samples dried under constant exposure to sunlight. The pre-pulp made from the senescent samples of C. glomerata thus lacks the principal green pigmentation of the native plant while retaining the characteristics desired for high value pulps. The samples of young C. glomerata which were dried in the dark remained green after exposure to sunlight.

Example 3

Chemical pulps were made from sun-dried samples of C glomerata Kuetzing (collected from the Russian River, Sonoma, CA). The pulp was produced by boiling dried algal material in dilute caustic soda. The pulps were shown to have a low kappa number (see TAPPI method T236; and Pulp Technology and Treatment for Paper, Clark, J d\'A (1985) Miller FreemamSan Francisco) indicative of a material low in lignin or lignin-like proteins. These pulps were high in hemicellulose and cellulose, and readily formed paper handsheets. Paper handsheets, formed from the pulp of C glomerata by the T205 procedure, had a tensile strength of about 15 kilometers. The paper handsheets of C. glomerata had a distinctive rattle indicative of heavily hydrogen bonded pulps, which are high in starch and hemicelluloses. The pulp fibers, when viewed by scanning electron microscopy were found to be 20 micrometers thick, the size as measured in native Cladophorales.

Example 4

Algal pulps were also made from C. glomerata samples by soaking the algae in water. For example, 100 grams (dry weight) of algae was soaked in 1 liter of water at either room temperature or hot (e.g. 65-95°C) for 45 hours, then subsequently mechanically expressed. The algae was then gently refined with a disk refiner, with a clearance setting of 0.1mm for the initial pass of the fibers, and a setting of 0.05mm clearance for the final pass of the algal fibers through the refiner. The fibers coming out of the refiner were collected on 100-150 mesh screen, and then resuspended in water to form handsheets. The resulting handsheets had certain physical characteristics which were at least comparable to those obtained by alkaline pulping processes (see Example 3). Such a pulping process could be particularly advantageous due to the virtual absence of environmentally harmful chemicals, especially if combined with the photo-bleached pre-pulping process.

Example 5

A pulp can be derived from cladophoraleans by gentle mechanical or weak alkali pulping, optionally followed by extraction of between 10-50 percent of hemicellulose and starch-like material, such that the cellulose fiber are concentrated without compromising their length. Under these conditions, a cladophoralean pulp can be made to retain maximum fiber length due to the hemicellulose and other sugar polymers that promote optimum hydrogen bonding capacity to capture and

chemically bond short recycled fibers.

Thus, a pulp made in this manner can be used in the manufacture of recycled paper goods, including prolonging the recycling life of, and improving the quality of recycled paper pulps by blending the algal pulp with recycled pulps. For instance, the pulp can be mixed with recycled pulp to bring up the concentration of long fibers in the mix, and to allow enough hemicellulose to preserve high tensile strength and bonding while at the same time not impairing tear strength. The long cladophoralean fibers can come in intimate contact with the recycled pulp fibers and form strong transverse bonding upon drying, thus improving the quality and effective recovery of the recycling process. The amount of cladophoralean pulp added can be between 5- percent and 80-percent, depending up the qualities desired in the final product.

The length of the cladophoralean cellulose fiber can provide a network that improves the strength and quality of the final product. Generally, the number of times paper products can be recycled is limited due to the shortening of cellulose fibers during the recycling process. Cladophoralean pulp can both extend the number of times paper products can be recycled and improve the quality of the material above the recycled fiber alone.

To illustrate, two batches of 250 grams each (dry weight) of Cladophora glomerata were agitated in water, and algal fibers transferred to a holding container using a wire mesh. A portion of these fibers were then cooked in an alkali solution by first mechanically expressing water from the wet fibers, then placing the fibers (approximately lOOOmL in volume) into 1% NaOH at 65 °C. The fibers were incubated in the alkaline solution at this temperature for a period of two hours, occasionally being agitated. The resulting alkaline pulp was then rinsed with water. Both batches of fibers (NaOH-treated and water-treated) were refined with a disk refiner, with a clearance setting of 0.01 for the initial passes of the fibers, and a setting of 0.05 for the final pass of the algal fibers through the refiner. The resulting pulps for each of the NaOH and ^O-alone samples were added to a base recycling pulp (e.g. a typical pulp comprising paper made from previously virgin wood pulps) at concentrations ranging from zero to 20-percent. Handsheets of the resulting pulp mixture were generated by TAPPI standards, and mechanical properties of the handsheets measured and compared. In even\' instance, the handsheets made from the recycled pulps containing algal pulp supplements were of better strength than the base recycled pulp alone. Each of the handsheets made from algae-containing pulps displayed greater tensile, burst and tear strengths relative to the base recycled pulp handsheets. Also, in each instance the strengths were increased as the amount of algal pulp was increased, with the handsheets made from pulp containing 20-percent of the NaOH prepared samples having tensile strengths, burst strengths, and tear

strengths in the range of 150-percent, 250-percent, and 165-percent (respectively) greater than the handsheets made from the base pulp alone. Moreover, the percent elongation factor decreased as the amount of algal pulp was added to the recycled pulp.

Example 6

A cladophoralean pulp can be derived which is useful, when used alone or with wood pulps, for fine applications such as in the production of fine papers. These pulp can be formed by eliminating some or all of the adjunctive polysaccharide materials from the cellulose fibers and mechanically shortening the cellulose fiber length. This can act to allow the fibers to lay closely together and in a network that diffuses shock and optimizes foldability while losing only a modicum of tensile- strength. Depending on the application of the pulp, differential extraction of the other chemical components of the pulp can be carried out. For example, the degree of sizing or bonding desired can depend on the pectins, starches, pentosans and other hemicelluloses, silica and chitin (if present) and these constituents can be selectively extracted depending on the desired end-use of the pulp.

Example 7

A cladophoralean pulp can also be derived from other genre of algae. For example, the present method was used to form paper from algal pulps derived from Pithophora, an alga having high glucosamine and galactosamine content. For instance, sample of the dried Pithophora were soaked (and cleaned) in water for two days prior to use, The rehydrated algae was processed in a Sprout- Waldron 12 inch disc refiner. Hot water (e.g. 95°C) was used throughout the processing of the fibers as it tends to swell fibers and minimize "balling" of the fibers in the refiner. The algae was passed through the refiner twice at a clearance of 0.005 inches, then once at 0.003 inches, then a final pass at 0.002 inches. The refined pulp was then placed into a Nalley vibrator equipped with a 5 cut plate -a .25 inch thick brass plate into which were cut 2 columns of 0.005 inch slits each separated by a quarter of an inch. The "accepts" (those fibers of appropriate length) passed though the slits and were deposited on a 200 mesh screen, while the rejects (excessively long fibers, debris) remained on top of the plate.

The resulting pulp was then diluted to 1.2-percent, and processed for 10 minutes in a three-blade disintegrator running at 3000 rpm. to separate and partially beat the fibers in order to bring about further swelling of the fibers. The disintegrated

pulp was further diluted to a consistency of 0.3-percent for making handsheets Based on experience with both wood and algal pulps, the Pithophora pulps had very ⁷ good mechanical properties. The results of handsheet tests further indicated that paper of good quality can be made with Pithophora by mechanical refining alone (e.g. no chemical pulping).

Equivalents

Although particular embodiments of this invention have been described herein, it is recognized that modifications and variations may readily occur to those skilled in the art. Consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

What is claimed is: