FI67417B - FOERFARANDE FOER FRAMSTAELLNING AV PAPPER KARTONG ELLER PAPP SOM INNEHAOLLER STAERKELSEFIBRER - Google Patents

Description

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Patent and Register 7 AmMmi uthgd odi utLskrtfun p «biicar * d 30.11.84 (32) (33) (31) ryydtttjr« cuoikw * —toglrd prtorkat 25.03.76 USA (US) 670360 (71) National Starch and Chemical Corporation, 10 Finderne Avenue, Bridgewater, New Jersey 08876, USA (72) Henry R. Hernandez, Somerville, New Jersey, Albert N. Barna, Plain Field, New Jersey, Donald S. Greif, Bound Brook, New Jersey,

The present invention relates to paper, paperboard and paperboard. The present invention relates to paper and board, and to paperboard, paperboard or paperboard, and to paperboard, paperboard or paperboard. "or a method of making cardboard in which an aqueous slurry of fibrous pulp is passed over a wire in such a way that the water is removed and the compacted fibers form a sheet from which, by pressing and drying, the final paper product is obtained.

Various natural fibers (other than cellulose) as well as various synthetic fibers have been used in the manufacture of paper. However, none of these substitutes have succeeded in producing a commercially viable cellulose substitute 6741 7 2 due to their cost, poor bonding properties, chemical incompatibilities, difficulty in processing in papermaking systems, etc. Although , and paper is still made almost exclusively from wood-based cellulosic materials - whose reserves are rapidly depleting.

It is obvious that in aqueous systems normally used in papermaking operations, the pulp fibers must be so water resistant that they can be used in all parts of the manufacturing process over a relatively wide pH range without losing their integrity. In this regard, in the few references that have proposed replacing cellulosic fibers with starch fibers (e.g., U.S. Patent 1,682,293), starch must be chemically modified to radically alter its naturally occurring properties prior to fiber formation to provide the necessary water resistance in the papermaking process. Alternatively, in other references (e.g., U.S. Patent 2,570,449), the papermaking process itself must be modified by replacing the normally used aqueous system with an alcohol-insoluble solvent. The use of such methods is understandably both impractical and uneconomical when used on a commercial basis.

Another aspect of papermaking is that additives often have to be added to the pulp to provide certain end properties. Additives such as pigments, latexes, synthetic microspheres, flame retardants, dyes, perfumes, etc. are often used in papermaking. Effective retention of these additives at the wet end of the paper machine presents difficulties for the manufacturer, as not retaining not only causes economic losses but also significant losses. if it becomes part of the plant effluent. In addition, such additives are also added by coating or impregnation processes well known in the art. These methods usually require excess heating energy to pre-dry the paper after coating. In addition, in some cases, coating systems must be solvent-based, which results in very high capital costs and requires the organization of volatile matter recovery.

3,67417

The object of the invention is to avoid the above-mentioned drawbacks and to provide a practical papermaking in which cellulose is partially or completely replaced by starch fiber. The method has enhanced the retention and addition of additives, especially those associated with water-insoluble towers encapsulated in the paper fibers, in papermaking.

It is a further object of the invention to provide an efficient and economical method for bonding synthetic and / or natural fibers to a non-woven web form.

These and other related objects are achieved by a method according to the invention, the features of which are set out in claim 1. Claims 1 to 10 set out some preferred embodiments of the invention.

In accordance with the present invention, it has been found that said and related objects are achieved when water-resistant starch fibers prepared by precipitating a colloidal dispersion of starch in a coagulation salt solution are partially or completely replaced by cellulose and similar fibers in normal paper and board manufacturing operations. The fibers can be used as a pulp extension, as a means of adding an additive to a paper product, as a binder for bonding fibers to non-woven webs, or any combination thereof.

As used herein, the term "paper and board" encompasses sheet-like pulps and extrudates made from fibrous cellulosic materials as well as such fibrous materials which may be derived from synthetic materials (such as polyamide, polyester, rayon and polyacrylic resin), mineral fiber, and the like.

As used herein, the term "normal papermaking operation" means a process in which wood pulp fibers (which have been ground in the Netherlands or ground to a certain degree of hydration of the fibers and to which many functional additives may be added (an aqueous slurry is passed over a wire or similar device)) that water is removed to form a sheet of compacted fibers which, by compression and drying, can be made into a dry roll or sheet.This expression also includes conventional methods for making wet- and dry-deposited non-woven materials.

In one aspect, the present invention provides a feasible, efficient, and economical method for extending existing raw material sources. In addition, it gives the papermaker much more flexibility in its operations: It can obtain starch fibers in a dry or wet layer form and can store them for later use, or it can integrate the starch fiber manufacturing process into its plant as an integrated stage of its pulp and / or papermaking operations.

The present invention further provides the manufacturer with a new means of adding additives to paper products while increasing their retention and thus reducing economic losses and pollution problems. As mentioned earlier, it is common practice in papermaking to add additives to the fibers used in the pulp. Such additives are added to impart certain properties to the paper other than those provided by the fiber alone. Such additives include substances that act as pigments (e.g., titanium dioxide) as well as other substances that are added to paper to achieve properties such as better whiteness, capacity, smoothness, ink absorption, flame retardant, water resistance, larger size, etc. As a further embodiment of the present invention, it is found that starch fibers are prepared to contain a variety of functional additives, and when such fibers are subsequently used in an aqueous papermaking process, the retention of the additives is greatly increased compared to that achieved using current methods. In addition to greater retention, such an addition of additives has the added advantage of not having to rely on a delicate charge balance between the cellulosic fiber additive and flocculation (e.g., alum) or other retention aids. In fact, the flocculation or retention aid need not be used with the starch fibers used in this invention.

6741 7 5

It has further been found that according to the present invention, non-woven webs can be made in wet or dry deposited form when starch fibers are added inside the web where they act as web binders. The starch fibers can be left in the finished web or, if the base fiber used in the web is non-combustible, they can be removed depending on the desired use.

In particular, the present invention relates to an improvement in a paper and board manufacturing process in which an aqueous slurry of fibrous pulp material is passed over a wire in such a way as to remove water and form a sheet of compacted fibers which, when pressed and dried, yields a final paper product. The method comprises the step of using 1 to 100% by weight of pulp as starch fibers having a diameter of 10 to 500 microns and prepared by extruding a colloidal dispersion of starch having a dry matter content of 5 to 40% by weight into a wire stream in a mobile coagulation bath which is a coagulation bath of selected from the group consisting of ammonium sulfate, ammonium sulfamate, monobasic ammonium phosphate, dibasic ammonium phosphate, and mixtures thereof, an aqueous solution containing at least enough coagulation salt to coagulate the starch.

The process of the present invention can be readily made to be used in any conventional papermaking equipment using the normal procedures of a particular plant, the only difference being that the cellulosic pulp is completely or partially replaced by starch fibers.

The starch fibers used can be made in various variations. The only requirement is that the water-resistant fibers be 10 to 500 microns in diameter and that they be precipitated by extruding a colloidal dispersion of starch with a dry matter content of 5 to 40% by weight into a suitable mobile coagulation salt solution.

Useful are fibers made from any naturally occurring or fractionated starch. Thus, cereal starch, waxy corn, rice, tapioca, wheat, potato, amylose-rich cereal starch, 6,674,17 commercial amylose powder, etc. can be used. Natural cereal starch, tapioca and waxy corn are preferred due to their economy and availability.

The concentration of starch-dry matter in the dispersion should be about 5-40% by weight. Although higher starch dry matter concentrations can be used, the resulting dispersions become very viscous and require special equipment to handle them. However, the concentrations used in the dispersions affect the properties of the finished fiber and the desired end use. For example, starch fibers made from a 5% dry matter dispersion have been found to be particularly useful in the manufacture of glassine papers or greaseproof paper, while starch fibers made from 15% dry matter dispersions have been found to be more suitable. papers such as filter paper.

The starch used in each case must be used as a colloidal dispersion. For purposes of this invention, the term "colloidal dispersion" means a dispersion of starch that is substantially granular and that, when standing at the temperature at which it is to be used, shows little evidence of gelation or precipitation. This dispersion state can be achieved using many different methods depending on the particular starch base used, the desired end use, and the equipment available.

When using natural starches that are very rich in amylopectin, such as waxy corn, a suitable colloidal dispersion can be prepared simply by cooking the starch well in water without the need for any chemical additives or modifications. In most cases, when using starch containing less than about 95% amylopectin, it is desirable to chemically derivatize or modify the starch to ensure its colloidal dispersion prior to addition to the aqueous system. The derivatization or modification is performed to the extent necessary to ensure the formation of the desired colloidal dispersion without affecting the ability of the starch to subsequently precipitate. Alternatively, if there are no obstacles to the presence of lye in the system, these starches can be dispersed in aqueous sodium hydroxide, potassium hydroxide or other conventional alkali. Alternatively, the starch bases may also be dispersed in a minor amount of an organic solvent such as dimethyl sulfoxide and then added to water or the starch may be dispersed together with a chemical additive such as urea and / or paraformaldehyde. In cases where causticization is used, the amount of alkali used must be sufficient to disperse the starch sufficiently. Typical amounts of alkali when using sodium hydroxide are 15 to 40% by weight based on the weight of the starch.

In preparing the starch dispersion, the starch is added to the dispersant and mixed vigorously until a state of colloidal dispersion is reached. In the case of dilute starch dispersions (i.e. 5-10% by weight of starch powder), this takes about 45 minutes. More concentrated starch dispersions or certain chemically modified starch bases require longer times and / or reasonable heat.

Most starch dispersions, including waxy corn dispersions and most chemically modified starch dispersions, can be cooled to room temperature before being added to the coadjulation bath. In the case of a few, less chemically modified starches, it is advisable to use the dispersions at approximately the elevated temperatures at which they are prepared so as to maintain the necessary colloidal dispersion and ensure efficient fiber production.

The coagulation bath used in preparing the starch fibers according to the present invention is an aqueous solution containing certain ammonium salts selected from the group consisting of ammonium sulfate, ammonium sulfamate, monobasic or dibasic ammonium phosphate, and mixtures thereof. It is also possible to combine the above-mentioned functional salts with other compatible salts which form a starch precipitate, thus providing satisfactory coagulation and a fibrous product. Salts suitable for this purpose include e.g. ammonium persulfate, ammonium carbonate, ammonium bromide, ammonium bisulfite, ammonium nitrite, ammonium nitrate, ammonium bicarbonate, ammonium oxalate, sodium and potassium chloride, sodium and potassium sulfate. In general, the use of these additional salts has no advantage, however, in order to achieve coagulation, a corresponding minimum amount of ammonium sulfate, sulfamate, or ti- or phosphate salts must be present. The only time it may be desirable to include substantial amounts of other salts is to use a recycled coagulation bath with salts formed in situ, as described below.

The minimum salt concentration required to effect coagulation, as well as the recommended salt or salt mixture, will depend on the starch base used. For example, in the case of waxy maize starch, it is necessary that at least 35% by weight of ammonium sulphate be present in the total solution, ammonium sulphamate 72% (saturated), dibasic ammonium phosphate 37% and monobasic ammonium phosphate 40%. In the case of wheat starch or similar starches containing about 64 to 80% amylopectin, less salt may be used. Ammonium sulphate is required 20%, ammonium sulphamate 50%, monobasic ammonium phosphate 25% and dibasic ammonium phosphate 30%. In the case of hybrid cereal starches containing less than about 50% amylopectin, at least 15% ammonium sulfate, 40% ammonium sulfamate, 25% dibasic ammonium phosphate, and 20% monobasic ammonium phosphate must be present.

It should be noted that alkali salts are formed in the coagulation bath when causticized starch dispersions are used. Satisfactory formation of the desired starch fibers continues until the amount of salt formed is relatively high. The tolerance limit of the salt formed above which fiber formation becomes inefficient varies depending on factors such as the salt used, the total amount of salt dry matter used, the starch dry matter concentration in the dispersion, the amount of amylopectin in the starch base, etc. After this salt is equilibrated, the system can be achieved at this maximum level (or lower) by the intermittent but continuous addition of ammonium sulfate. For example, when sodium hydroxide is used as the dispersing medium and the starch mixture is extruded into an ammonium sulfate coagulation bath, sodium sulfate is formed. In this case, it has been found that the formation of cereal starch fibers (13% dry matter content of the dispersion) continues at a satisfactory level until the bath contains no more than about 70 parts of sodium sulfate per 30 parts of ammonium sulfate (44% dry matter content of the solution). Above this level, the formation of starch fibers becomes less efficient, and the resulting fibers tend to lose their individual integrity. However, the amount of salt formed in the system can be considerably increased before the fiber formation deteriorates considerably by adding a small amount of inorganic acid to the original coagulation bath or bath during fiber formation. In the example described above, the addition of as little as 3 parts of sulfuric acid per 100 parts of salt in the initially used coagulation bath thus results in a tolerance limit of 90 parts of sodium sulfate per 10 parts of ammonium sulfate, which increases the age of the coagulation bath.

The brine used in the fiber formation process can apparently be recycled and reused after fiber removal. However, maintaining the salt concentration is important, especially when the amount of salt is reduced by a chemical reaction associated with increasing the starch dispersion. Starch-free starch dispersions do not present much difficulty in recycling in this respect except that the dry matter concentration of the salt must be maintained. However, in cases where causticized starch dispersions are used, chemical reactions with the coagulation solution occur. For example, if ammonium sulfate is used, the reaction will result in the formation of ammonia gas and sodium sulfate. The recycling of such a system can be extended by recovering ammonia in an acid scrubber and returning it to the system as ammonium sulfate. The sodium sulphate formed can be used in a coagulation bath as part of a salt mixture until the tolerance limits discussed above are reached, or they can be used as a raw material in other parts of pulp or paper production, for example in the production of sulphate cellulose as a source of "salt cake".

Starch fibers can be prepared at any temperature at which the starch dispersion can be treated. Generally speaking, the coagulation bath is maintained at approximately room temperature (20 ° C) during the preparation of the fibers, however, temperatures as high as about 70 ° C may be used. Under certain conditions, even these higher temperatures can be used because they increase the solubility of the salt in the coagulation bath, resulting in more concentrated solutions. Thus, when it is desired to prepare fibers from waxy corn using monobasic ammonium phosphate as a coagulant, it is desirable to raise the temperature of the bath to a salt concentration of about 40% (saturation limit for monobasic ammonium phosphate at 20 ° C is 28%).

10 6741 7

In preparing the starch fibers used in the invention, the starch dispersion is added continuously or in batches in a wire stream to the moving coagulation salt solution. This addition can be performed either above or below the saline solution using any conventional technique. The dispersion can be extruded through a device that includes at least one hole, such as a spinneret, a plunger, or a diuretic delivery tube. Alternatively, the dispersion may be removed from a pressurized tube or hose containing a plurality of holes in an enclosed space, for example a concentric tube containing a mobile coagulation solution. Various modifications of the above and similar methods can be used, and the fibers can thus be produced either batchwise or continuously.

According to both embodiments, the aqueous salt coagulation solution should move to the starch dispersion. The direction of both flows can be utilized to adjust the lengths and diameters or widths of the fibers. If the brine moves generally downstream with the starch dispersion stream, rounder fibers are formed; if the starch dispersion is added at an angle of about 90 ° to the brine flow, relatively flatter fibers are formed. In general, holes with a diameter of 10 to 500 microns are recommended to produce fibers of the size required in this context. The starch fibers used in this invention have a diameter (width) of 10 to 500 microns and are generally 0.1 to 3.0 mm in length if they are to be used as substitutes for cellulosic pulp in paper. Longer fibers can be used in non-woven applications.

It should be noted that the length, cross-sectional size, and configuration of the resulting fibers depend on many interdependent parameters in addition to those described above. The viscosity of the starch dispersion, the dry matter content and the components used in the coagulation solution and / or starch dispersion and their relative flow viscosities are additional factors that can be used to control the dimensions of the fiber obtained with the parameters considered with LED.

This and similar coagulation processes for producing starch fibers useful herein are described in our co-pending patent application 770869, filed the same day as the accompanying application 6741 7 11, which is incorporated herein by reference, and U.S. Patent 2,902,336. Various variations of the methods can also be used if the final fiber is so water resistant that it can be used in papermaking.

The resulting aqueous slurry or suspension of starch fibers can be used directly by passing it into a pulp stream, whereby the fibers and paper web can be produced in an "in-line" paper mill.

If this embodiment is to be used, it is generally recommended to first wash the fibers free of coagulation salt before passing the slurry to a papermaking operation. Alternatively, the fibers can be recovered in a dry state by collecting water from a wire or similar device. It is then recommended to resuspend the fibers in a non-aqueous solvent such as methanol, ethanol, isopropanol, acetone or the like in which the fibers are insoluble. The fibers are then recovered, for example by filtration, in a solvent and dried. Other methods such as centrifugation, flash drying or spray drying can also be used to remove water. After drying, the fibers can be re-added to the aqueous medium, giving them excellent redispersibility and retaining their distinct, discontinuous structure. Alternatively, the fibers can be recovered from the slurry, for example by filtration, washed and added to water to dry matter contents of up to about 50% and formed into "wet sheets" for later use.

It should further be noted that the starch used may be chemically treated to alter the properties of the fiber formed or to aid in the formation of a colloidal dispersion. Alternatively, the starch fibers can be treated after formation to give them certain functional properties. The starch can be treated chemically, for example by aminoethylation, to make the starch rapidly dispersible in the dispersion.

This treatment also results in the formation of a fiber having a cationic charge when used in an aqueous medium. Similarly, starch modified to contain anionic groups and stable in dispersion can be used to produce a fiber having anionic properties after regeneration. The fibers can also be modified after formation to provide certain functional properties. Thus, better anionic 6741 7 12 functionality can be obtained by bleaching the fibers after precipitation, provided that the conditions are not so severe as to destroy the fibers. The properties of the fibers can also be adjusted by using mixtures of modified and unmodified starches or by adding other functional agents, such as polyacrylic acid, so as to obtain exactly the desired properties.

One of the advantages of the method according to the present invention is that it can be used in many ways to improve paper products by means of properties which are either inherent in the starch fiber or which can be imparted to it. An example of such improved properties is the production of various specialty papers such as glassine paper and filter paper, which requires special treatment when conventionally prepared.

Glassine paper is made from pulps where the quality of the fiber allows for abundant hydration. Mechanical treatment of the pulp suspended in water results in clear grease-retaining properties. The fibers are fiberized and swollen to an almost gelatinous state. When the hydrated fibers are made into paper, a dense non-porous sheet is formed on the wire. The resulting sheet is resistant to the penetration of fats and oil, as it consists almost entirely of well-hydrated cellulose. Bringing cellulose into this well-hydrated form requires a considerable amount of energy. The production of glassine paper has to grind its raw material for long periods of time or increase the number of refiners through which the raw material must pass. Once the raw material is hydrated and passed to the wire, it dries by running very slowly. As a result, paper machine speeds are limited to 45 to 152 m / min. depending somewhat on the basis weight of the paper. The temperature of the raw material may need to be raised with steam to allow the water to drain faster with the wire. Attempts by glassine paper manufacturers to use cationic polyelectrolytes to improve runoff have been limited. Flocculation of the fibers can improve runoff, but this breakage of the formation can cause holes that reduce the oil and grease resistance properties of the product.

We have now found that when starch fibers are combined with cellulosic fibers ground in the Netherlands below the level that would be required in conventional glassine paper making, the resulting mixture has a significantly higher free-ness and drains at lower temperatures for about one third of the time required. at the elevated temperatures currently used, and the wet mat dry matter content of the mixture is higher after compression and has a better drying efficiency compared with the conventional glassine raw material. In addition, the sheet properties obtained of this new paper include better internal strength (Z-direction strength), better oil retention properties, and higher resistance to air flow than conventional glassine paper. It is apparent that reducing cellulose grinding requirements can result in significant energy savings because the temperature of the fiber blend does not need to be raised to achieve acceptable dewatering rates, as is commonly done in conventional glassine paper manufacturing.

Starch fibers can also be used to give a more porous sheet.

This feature may be desirable in papers such as filter grades and impregnable grades. In previous methods in the art, less grinding of cellulose has been found to aid in the development of this property, but this is only at the expense of lower web strength. The addition of the starch fibers of this invention together with the cellulose can result in a more porous sheet structure, while maintaining and often improving the required strength properties.

As a feature of the present invention, it is possible to add some hydrocolloids to the dispersing medium and co-compress the hydrocolloids with the starch to obtain a starch hydrocolloid fiber that can be used in the papermaking process of the present invention. To obtain this fiber mixture, the hydrocolloid (a smaller amount, i.e. less than 50% of the total weight of the dry matter) only needs to be brought into a colloidal dispersion state together with the starch part before contact with the coagulation bath. In the case of water-dispersible hydrocolloids such as polyvinyl alcohol, carboxymethylcellulose, hydroxyethylcellulose, etc., the hydrocolloid need only be added to the water in which the starch is dispersed. In the case of other hydro-colloids, such as casein, the dispersion must be causticized to obtain the desired colloidal dispersion.

In an alternative embodiment of the present invention, water-insoluble additives can be uniformly mixed into the starch dispersion and then encapsulated within the resulting starch fiber.

6741 7 14

The starch fibers of the invention can be encapsulated with water-insoluble additives including pigments, metal powders, latexes, oils, plasticizers, microspheres (glass beads * foamed silica or other low density materials) in the form of blown or unbleached fibers, either in blown or blown form. latexes such as polyvinyl acetate, polyacrylonitrile, polystyrene, etc. It should also be noted that the density of the starch fibers can be changed by adding air or other gases to the starch dispersion before it is introduced into the coagulation bath. It should further be noted that certain water-soluble solid additives may also be co-extruded with starch fibers. In such cases, the additive is dissolved in an aqueous starch dispersion and the coagulation bath used to form the starch fibers is adjusted by adding a sufficient amount of a compatible salt capable of precipitating the additive. For example, a commercial resin adhesive can be added to the starch dispersion and extruded into a coagulation bath containing a functional starch coagulating salt and a sufficient amount of aluminum sulfate to precipitate the resin to form a co-precipitated starch-aluminum resin fiber.

The water insolubility of the starch fibers of the present invention can be further enhanced by adding conventional crosslinking agents such as urea-formaldehyde, glyoxal, urea-melamine-formaldehyde, Kymene (registered trademark, Hercules, Inc., Wilmington, Delaware), etc. These crosslinkers can be added. before extrusion or may be added to the starch fiber afterwards.

The particular additive selected for addition, as well as the amount used in any of the embodiments described above, will depend on the properties desired to be obtained in the final fiber. The pigmented fibers thus have a better opacity and can be added to the fibrous web by normal methods, whereby the retention of the pigment as a whole is better than simply by adding the pigment to the paper stock. The substrate can be imparted flame retardant properties by adding polyvinyl chloride powder and antimony trioxide or other flame retardant chemicals to the starch fiber. Starch fibers containing microspheres 15 6741 7 can be added to the paper webs so that the retention is very good. The retention of such spheres makes it possible to produce sheets with a large size and a low weight compared to cellulose sheets of the same weight. In conventional sheets containing microspheres, the presence of microspheres between the fibers has a fiber-releasing effect, resulting in a sheet of poor strength. On the contrary, the sheet according to the present invention has excellent strength properties because the spheres are encapsulated inside the starch fibers, whereby the effect of deteriorating the bonding of the spheres is as small as possible. The density of the starch fibers and the resulting paper can also be varied by adding air or other gases to the starch dispersion before passing it to the coagulation bath.

By using the fibers encapsulating the additive, it is also possible to obtain new properties for the paper itself, in addition to being a new method for adding additives to the paper. For example, there are papermaking machines that produce a finished web formed from individual, compressed layers. Such devices may be referred to as cylinder machines or Fourdrinier paper machines with a second, downstream pressure box or multiple pressure boxes. In this type of machine, lower quality fibers are usually used in the inner layers and a good quality pulp as the surface layer. By using pigmented starch fiber in the surface layer, it is possible to produce a paper web having the surface properties of coated paperboard. Coated board could be made by the wet end method because of the high concentrations of starch and pigment on the substrate surfaces. Alternatively, decorative or patterned special paper could be made, the sides of which would be of different colors. The fiber could be made in different colors and fed into two different stage boxes. Such paper of different colors on both sides is nowadays produced, but surface application must be used during the production.

One advantage of using water-insoluble synthetic polymers encapsulated within a starch fiber is that it allows good retention of synthetic fibers (such as rayon, acrylic fibers, polyester, nylon, or polypropylene) in paper webs or paper-like webs. Most of these fibers have a very low surface charge, and thus their retention is poor in commonly used latex binder systems based on precipitation and fiber deposition techniques. Such poor retention ring 6741 7 16 results in low binder efficiency and causes problems with polymer foaming, sticking, and accumulation in the system. The starch fiber surrounding the resin ensures effective retention and gives the sheet the desired final properties.

A further feature of the present invention is that starch fibers can also be used in the manufacture of dry-laid non-woven materials from synthetic fibers. In such applications, the web is made using air as the medium to deposit the fibers on the moving metal fabric. Because such synthetic fibers are not hydrated, binding is inhibited and relatively weak and soft structures are formed. In order for the web to be complete, a binder must be sprayed onto its surface. According to the present invention, it is possible to mix dry starch fibers with synthetic fibers. Such a method is particularly advantageous in disposable non-woven materials where the biodegradable properties of the starch fiber are superior to the properties obtained with the synthetic fiber binders currently in use. Fibers that are particularly rich in amylopectin are preferred binders. It should be noted that the starch fiber may be retained in the final non-woven web or may be removed therefrom if desired. If the starch fiber is to be removed, such as from a ceramic web, a suitable means of removing it is to keep the web under conditions sufficient to burn the starch fibers.

Starch fibers, whether filled or unfilled, can be successfully used alone to form a paper product made entirely of starch, or can be used in combination with all types of cellulosic or non-cellulosic fibers. Softwood or hardwood cellulose fibers that may be used include bleached and unbleached sulphate fiber (kraft paper fiber), bleached and unbleached sulphite fiber, bleached and unbleached soda ash fiber, neutral sulphite fiber, semi-chemical ground fiber fiber, man-made fiber fiber and all of these. These designations refer to wood pulp fibers made by a variety of methods normally used in the pulp and paper industry. In addition, synthetic cellulosic fibers of the viscose rayon or regenerated cellulose type as well as recycled waste papers from various sources can be used. Similarly, ceramic fibers, glass, asbestos or other inorganic fibrous materials can be used with the starch fibers of the invention 17 6741 7.

Due to the water-resistant nature of the starch fibers used in this context, the fibers are easily dispersed to form durable dispersions that can be used without the addition of surfactants in conventional papermaking operations. This allows the fibers to be used in papermaking operations and equipment without having to modify normal processing conditions. The fibers can thus be added to a grinder or mixing box, a pressure box, a Fourdrinier wire, and from there the sheet can be passed through drying rollers, calenders to an oriental press and wound into a sheet without substantially altering the normal operating values of machines used to make cellulosic paper. It should be noted that in the case of paper made entirely of starch fibers, it may be desirable to place the web between nylon nets or to dry the web drier than normally in papermaking to prevent the fibers from sticking to the dryer.

In addition, papermaking can be integrated into the production of starch fiber using a slurry containing precipitating fibers. It is also possible to mold articles directly from thick fiber slurries by slurry molding into patterns or molds.

It will be apparent to those skilled in the art that the starch used and the amount of starch used will vary depending on the desired quality of the paper. By choosing the right type of starch, it is possible to achieve the desired sheet properties, which in the past have only been achieved by hydrating and defibering the wood pulp to different degrees of grinding. More specifically, it has been necessary to grind the pulp a little (650 ml, CSF = Canadian standard grinding rate) in applications using unbleached cellulose as a liner to ensure rapid water removal while maintaining high processing speeds.

The internal bond strength of the product to be manufactured also adjusts the degree of grinding. The addition of starch fiber allows rapid removal of water and maintenance of the production rate, but still ensures the development of internal bond strength. Glassine papers are often made from finely ground pulp (less than 50 ml, CSF). It has now been found that glassine-type papers can be made by halving the grinding of cellulose with the addition of as little as 15% starch fiber. Alternatively, in papers where the opacity and porosity must be even lower, it is recommended to use higher amounts of starch fibers, i. about 50% or more.

The starch fiber-containing papers of the present invention may be prepared in combination with any commonly used internal additives such as adhesives, wet and dry strength agents, etc., or their surface may be treated by coating, spraying or impregnation as is commonly used in the art.

The starch fiber-containing paper of the present invention can be reslurried and recovered. The ability of the starch fiber to maintain its fiber integrity during reslurry is affected by the type of starch fiber (starches containing more amylose are more easily slurried) and the slurry conditions applied to them. In general, the less basic chemicals and elevated temperatures are used during reslurrying, the more advantageous it is to recycle starch fiber.

The following examples further illustrate various aspects and embodiments of the present invention. In the examples, all parts are by weight unless otherwise indicated.

Example 1

A slurry was prepared by mixing naturally occurring unmodified starch containing 70% amylose and 30% amylopectin with water at 5% by weight of solid starch. A solution of 25% sodium hydroxide in the dry matter was then added with stirring that the mixture contained 40% lye based on the dry weight of the starch. This mixture was stirred until a dispersion of starch granules was obtained.

The resulting dispersion was passed through a spinneret containing 100 holes, each 70.2 microns in diameter, in a coagulation bath containing ammonium sulfate at a 90 ° angle to 90 ° g / cm of mobile salt solution in a stirred coagulation bath. The resulting fibers were collected on a wire rod, washed desalted and recovered again. The fibers had an average diameter of 65 microns, an average length of about 4 mm 6741 7 19 and a final dry matter content of 23.5% by weight.

In the Noble and Wood sheet mold, a series of hand sheets were made using different amounts of bleached softwood pulp (BSWK) in combination with the fibers prepared above. The sheets were dried in a Noble and Wood dryer at a drum temperature of 121 ° C and allowed to equilibrate for 24 hours at a constant temperature of 22 ° G and 55% relative humidity.

Table I summarizes the sheet manufacturing conditions and test values.

Table I

Fiber mixture_ Square- Grinding degree Scheffield- Strength Z-

RqwK Starch meter position Canadian porous directional fiber no g / nr standard oral (2) „(3) .___ (ml) t!) 100 O 78.1 544 218 596 90 10 82.6 540 192 630 75 25 80.4 475 74 846 50 50 77.9 367 28 1050+ 25 75 77.1 250 16 1050+ (1) Measure the flow of water from the mass through the wire rod. The degree of grinding of unground pulps is high compared to the low degree of grinding of well ground pulps. TAPPI test T227-M-58.

(2) This test measures the paper's ability to resist airflow. More specifically, it measures the volume of air that can be passed through a given sample area at a given pressure and time. The higher the value, the more porous the sheet (the inside diameter of the tire used and 7.62 cm; the values are unitless).

(3) The Scott Internal Bond Tester measures the strength of the paper in the Z direction. This method is designed for the average force in joules per square meter required to separate a paper sample. TAPPI RC-305.

The results in the table show that as the amount of this particular starch fiber prepared as a dispersion containing 5% dry matter increases, the water retention capacities of the fiber mixture increase and 20 6741 7 sheets with a lower porosity and a Z-strength greater than 100% cellulosic sheet.

Example 2 Starch fibers were prepared using the materials and method of Example 1. However, after the last wash, the fibers were dispersed in ethanol solution, recovered and allowed to dry. The fibers were then combined with cellulose and hand sheets were prepared according to Example 1. Experiments with these hand sheets showed that the properties provided by the dried fiber were comparable to those obtained using the wet fiber products of Example 1.

Example 3 Starch fibers were prepared using the materials and methods of Example 1. However, the starch dry matter concentration of the starch dispersion was 20% and the final dry matter content of the fiber was 38%. The hand sheets were prepared and tested as in Example 1. The results are shown in Table II.

Table II

Fiber mixture__ Square- Grinding degree Scheffield- Strength Z- ς Starch- metric-position Canadian porous directional fiber no g / m ^ standard oral (2) sa (3) _ (ml) u '100 0 86.2 505 158 538 90 10 82.9 545 333 527 75 25 82.9 595 1215 565 50 50 79.7 676 8645 647 25 75 79.7 814 50496 1035+

As shown in Table II, the use of starch fibers made from a dispersion with a higher dry matter content increased the water yield of the raw material (i.e., grinding precipitation) and produced a more porous sheet with a porosity and strength in the Z direction greater than 100% cellulose. Sheet. It should be noted that this level of starch solids produces clearly different grinding degree and porosity values than those obtained in Example 1, where a 5% level of starch solids was used to make 21,641 7 fibers. This comparison illustrates the applicability of the method of the present invention to impart different properties to the finished paper product (e.g., the required porosity in the glassine feedstock). It should further be noted that the use of starch fibers improved the strength of the paper in both Examples 1 and 3.

Example 4 Starch fibers were prepared using a 20% starch-dry matter dispersion as in Example 3, but after washing they were reslurried in ethanol, recovered and dried. The hand sheets were prepared and tested, and it was found that the properties given by the dried fiber were comparable to those obtained using the wet fiber product of Example 3.

Example 5 This example illustrates the use of fibers formed from different starch bases in the manufacture of the paper of the present invention.

Starch fibers were prepared and combined with cellulose by the methods described in Example 1. The cellulose portion was ground before mixing with the starch fibers to a degree of grinding of 645 ml (Canadian standard). The basis weight of the hand sheets was considered to be 97.5 g / m2.

v

Table III

22 6741 7

Fiber blend 2 4

BS Starch- Starch Fiber- Tensile- Mullen Strength Z- MIT

flax fiber base strength g / cm ^ directional fold _tu_____ g / Oin_ sa _amount_ 100 0 - 1040.55 4429.40 145 552 90 10 Aminoethyl 1462.4 6679.26 903 1210 grain 70 30 "1476.46 5624 , 64 1050+ 1280 90 10 Waxy 1525.68 6679.26 853 1670 Maize 70 30 "1413.19 5062.17 1050+ 1125 90 10 Modified 1553.80 5484/02 567 1340 tonnes of cereals 70 30" 1293.66 3445 , 09 1050+ 1245 90 10 Hybrid cereals, 1659.26 5273.10 622 1420 containing 70% amylose 70 30 "1652.23 4148.17 1050+ 1390 90 10 Amylose 1545.99 5413.71 683 1433 70 30" 1652, 23 4780.94 1050+ 1395 ^ TAPPI Method T404-5s-66 - Determines the tensile strength in pounds per inch (converted to metric units).

2 TAPPI Method T403-ts-63 - Hydrostatic pressure in pounds per square inch (converted) required to break paper when the adjusted, increasing pressure is applied through a rubber film to a circular surface 3048 cm in diameter.

3 Defined as in Example 1.

4 TAPPI method T423M-50. The number of folds a specimen can withstand before rupture when using a type of refractor developed at MIT (Massachusetts Institute of Technology).

As shown in Table III, the addition of any of a variety of starch fibers can be used to improve those strength properties of the paper compared to a 100% cellulosic fibrous sheet.

Example 6 6741 7 23 This example illustrates two methods for making 100% starch fiber sheets.

Method A. 6 g of unmodified cereal starch fiber was slurried in 1 liter of water. The fibers were mixed with a paddle mixer until a uniform mixture was obtained. A hand sheet was made in a Noble and Wood sheet forming machine fitted with a 100 mesh steel wire cloth. The obtained fibrous web was removed from the wire and the suction sheets and compressed as follows: 3 presses at a pressure of 7030.8 g'cm 2 and 3 presses at a pressure of 28123.2 g / cm, whereby the suction sheets were switched between presses. The resulting mat had a dry matter content of 70%.

The web was then placed between the suction plates and dried in a Noble and Wood dryer at 120.1 ° C. The resulting rigid unreinforced paper product had a basis weight of 145 g / cm 2.

Method B. The starch fibers were treated as in Method A, and the resulting web mat was pressed as follows: 2 presses at 2 7030.8 g / cm 2 and 2 presses at 14061.6 g / cm, with the suction sheets being switched between presses. The resulting wet mat had a dry matter content of 50%. The web was placed between two nylon wires and passed through a Noble and Wood dryer at 120.1 ° C. The resulting rigid unreinforced paper web had a basis weight of 145 g / m 2.

Example 7 Hand sheets were prepared by the method of Example 1, but a commercial, unmodified ground glassine raw material was combined with cereal starch fibers using two different milling steps. The cellulose pulp was obtained from two different grinding points, the second part having a Schopper Reigler degree of grinding of 350 ml, while the degree of grinding of the completely ground part was 160 ml. 20% of the cellulosic fibers were replaced with starch fibers and all hand sheets were made 2 so that the basis weight was 48.8 g / m 2. The surface of the sheets was then glued in a laboratory-scale size press equipped with rubber rollers using a polyvinyl acetate solution having a dry matter content of 1% maintained at 60 ° C (available under the trademark Vinol 165 from Air Products and Chemicals). The residue of polyvinyl acetate was 1%. The sheets were then equilibrated at a constant temperature of 20 ° C and 55% room humidity for 24 hours before their turpentine resistance was tested using the TAPPI standard T454-ts-66. The results of turpentine testing are shown in Table IV.

Table IV

Cellulose Star Sheet Mold Raw Material Turpentine SR Grinding Leakage Heating Degree * _Canop fiber a »ika_ pot Sat ° C ______ 350 ml 100 - 21.3 s 24 855 s 350 ml 80 20 19 , 9 s 24 1800+ s 160 ml 100 - - 62.1 s 60 1800+ sv

Schopper-Riegler Freeness Tester, manufactured by Testing Machines, Inc.

The use of starch fiber together with the partially ground pulp increased the turpentine resistance of the cellulose and corresponded completely to the resistance of the ground glassine raw material. In addition, the reduction in grinding made it possible to reduce the flow time to almost a third at significantly lower temperatures. Thus, although the temperature of the conventional raw material must be raised to about 60 ° C to give a flow time of 62 seconds, a flow time of about 20 seconds can be achieved at 24 ° C without losing the desired properties using the method of the present invention. This better run-off can lead to faster machine speeds and increase production efficiency while allowing significant energy savings due to lower grinding and raw material temperatures.

Example 8 This example illustrates the improvement in properties that can be achieved by adding starch fibers containing polymeric microspheres to the cellulose pulp.

Starch fibers were prepared by the method of Example 1, but 8.5% microspheres (available from Dow Chemical under the name XD 6850) were added to the starch dispersion prior to fiber formation. The fibers were then hand-combined in combination with cellulosic pulp using the method described in Example 1. In all cases, the grinding degree of the Canadian standard for the cellulose component was 730 ml. The results of the testing are shown in Table V. For comparison, samples were also prepared in which the microspheres were added directly to the pulp in the manner normally used in industry.

Table V

2

Fiber mixture Spheres,% Square-ι Potassium Taber Strength Z- BSWK Starch-metered perpendicular slip barx lx10-3 cm size 100 O 0 O 97.6 18.79 3.7 111 100 O 0 0 130.1 24.38 6.3 137 100 0 1.8, 86 97.6 24.39 6.6 103 100 O 2.0 1.0 97.6 25.40 7.1 90 95 5, 43, 43 97.6 23.11 5.0 168 90 10, 86, 86 97.6 26.16 6.3 206 85 15 1.29 1.29 97.6 28.45 7.5 237 ^ Paper thickness in centimeters per centimeter 2TAPPI method T451-M-60 3 Defined as in Example 1.

As shown in Table V, the addition of microspheres by both methods substantially improved the caliber and stiffness of the paper product. In this respect, by adding microspheres, it was possible 2 to obtain a product with a basis weight of 130 g / m, a caliber of 2 and a stiffness of only 97.6 g / m 2. The importance of weight savings, both in terms of the amount of fiber required and the post-papermaking costs (e.g. in mailing), is easily understood.

When comparing the other properties of the sheets containing microspheres, it was found that the retention of the separately added beads was about 50% of the amount initially added, while the retention was about 100% of the beads added encapsulated in the fibers. In addition, in the case of separately added spheres, the strength decreased and there were indications that the spheres were not evenly distributed (the concentration was higher above), whereas these factors were not present in the spheres encapsulated in starch. The observed 26 6741 7 increase in caliber and stiffness obtained using normal extracellular addition was achieved only at the expense of lower internal bond strength of the paper, while the addition of spheres within the starch fiber ensured their retention in the sheet while increasing internal bond strength and desired stiffness and caliber.

Example 9 This example illustrates the results obtained using three kaolin addition methods in papermaking.

The hand sheets were prepared using similar methods as in Example 1. The hand sheets were prepared by adding coating kaolin No. 2 to the finished sheet during the forming operation. The addition of kaolin to the hand sheets was performed in three different ways: (1) by conventionally slurrying the pigment into pulp fibers; starch fibers containing 80% kaolin and 20% starch, and (3) using a combination of methods (1) and (2). In all cases, the basis weight of the sheet was 97.6 g / m 2.

The physical and optical properties of the resulting paper sheets are shown in Table VI.

Table VI

Conventional addition Starch fiber

Pulp- Kao- TiO-, Starch- Kao- Opa- Tensile- Strength Z- loose, line, 2 * J11 "1 'Vj' <2> ^ ^ ΐ ό t * l J NEW Sa 100 0 0 0 0 85, 9,991.34 302 87.2 12.8 O 00 92.0 625.74 113 75.2 0 O 5.0 19.8 88.9 1371.00 351 68.4 6.8 0 5.0 19.8 90.5 864.79 256 72.1 0 4.5 4.7 18.7 94.1 850.73 233 (1) TAPPX method T425-m-60 Expressed as a percentage and equal to 100 times the number of samples taken behind the a blank with a reflectance of not more than 0.005, the ratio of the scattered reflectance to the same sample, behind which is a white body with an absolute reflectance of 0.89, the higher the value, the more opaque the paper.

(2) 6741 7 27 Defined in Example 5.

(3) Defined in Example 1.

As can be seen from Table VI, by adding pigment inside the starch fiber, more pigment can be used and better strength properties can be obtained compared with the conventional pigment addition technique.

When 12.8% of kaolin was added to the cellulose pulp by a conventional technique, the tensile strength and the strength in the Z direction decreased. In contrast, when kaolin was added as 19.8% encapsulated starch fibers (total addition rate 24.8%), the tensile strength and strength in the Z direction increased. It was further shown that the decrease in opacity that occurred when filling the fiber encapsulated with kaolin could be compensated for by separately adding a small amount of kaolin or titanium dioxide.

Example 10 This example illustrates the superior retention of the starch fibers used in the process of the present invention.

The bleached softwood pulp was ground to a 500 ml grind (Canadian standard) and divided into three portions. Coating kaolin No. 2 was added to one portion and the resulting mixture was mixed until the pigment was evenly distributed in the pulp fibers. The second portion was treated in the same manner, but Natron 86 (trademark, National Starch and Chemical Corporation) was added as a retention aid. To the remaining part, starch fibers containing kaolin encapsulated (50% starch and 50% kaolin) were added, and the fiber mixture was mixed until the distribution was uniform. The hand sheets were prepared by the method of Example 1 and the kaolin content and retention percentages of the sheets were evaluated. The results are shown in Table VII.

28 6741 7

Table VII ^ ''

Fiber blend BSWK starch— fiber (50% Retention- Kaolin retention-_kolin) _Kaolin_adjuvant_tyrni ne n,% __ 90 0 10 0 11 90 O 10 0.02% 35 80 20 0 0 97

Table VII shows that kaolin retention was highest when kaolin was encapsulated in starch fiber in accordance with the present invention.

Example 11

The following example illustrates the use of starch fibers based on their bonding properties in the manufacture of a multilayer sheet.

In the Noble and Wood sheeting machine, double-layer hand sheets were made from bleached softwood cellulose ground to a degree of grinding of 500 ml (Canadian standard). To give a final basis weight of 146 g / m 2, two o layers (each weighing about 73 g / m 2) were prepared and pressed together before drying in a Noble and Wood dryer at 121 ° C. The control hand sheet contained 100% cellulose in both layers, while the test hand sheet had replaced 20% of the cellulose with starch fibers. The bond between the layers was tested using a Scott Internal Bond tester. The results are shown in Table VIII.

Table Vili

The fiber mixture

Strength Z-direction

Base Layer - Top Layer - 100% Cellulose - 100% Cellulose 119.7 100% Cellulose - 80% Cellulose and 2% Starch Fiber 197.4 ^ As defined in Example 1.

6741 7 29 The presence of starch fiber increases the bond strength between the finished sheet layers according to Table VIII.

Example 12 This example illustrates the preparation of paper containing various additives added using encapsulated starch fibers containing additives.

The additives were encapsulated within the starch fibers as described in Example 8. They were formed into hand sheets containing the percentages shown in Table 9 for starch fibers.

Table IX

Additive Additive Added to the mass of starch fiber in the __________ fiber,% _ amount,%

TiO2 25 20

CaCO 3 25 20

Ai powder 25 20

Carbon black 25 20

Fibran 68 5 10 (Trademark for Adhesive, National Starch and Chemical Corporation)

Pexol 200 5 10 (Trade mark for adhesives,

Hercules Powder Co.)

1: 1 mixture of antimony trioxide and vinyl chloride (flame retardant)

Tres-dichloropropyl 57 40 phosphate (flame retardant)

In all cases, the additives adhered well to the finished paper product and gave it its characteristic properties.

Example 13 This example illustrates the use of starch fibers as a way to add latex binders to a non-woven web made of synthetic fibers.

A dispersion of rayon fibers (0.635 cm, 1.5 denier) and polyester fibers (0.635 cm, 1.5 denier) was prepared in separate containers to a dry matter content of 0.1%.

100% starch fiber product as well as starch fiber containing 20% by weight of encapsulated latex, vinyl acetate / butyl acrylate copolymer, were added as a binder in such an amount that the final fiber mixture contained 25% starch fiber products. In the Noble and Wood sheeting machine, hand sheets 2 with a basis weight of 65 g / m 2 were prepared using the methods described in Example 1. The webs were determined to improve their tensile strength. The results are summarized in Table X.

Table X

Starch fiber Binder-> Synthetic- Tensile strength ^ fiber (g / cm2) _________ amount _____________

No (comparison) - Raion *

No (comparison) - Polyester * 100% starch 25% Rayon 710.11 100% starch 25% Polyester 217.95 80% starch - 20% latex 25% Rayon 984.31 80% starch - 20% latex 25% Polyester 135, 69

The density of the sheet was not sufficient to measure the tensile strength ^ Defined in Example 5.

As shown in Table X, the tensile strengths of the webs made using both starch fibers and starch-latex fibers as binders were superior. In contrast, control webs made from 100% synthetic fiber were not even so intact that they could be tested. It should be noted that the latex used increased the tensile strength of the rayon web, while it reduced the strength of the polyester web compared to 100% starch fiber. This shows how important it is to choose the right latex for the synthetic fiber being treated.

Example 14 This example illustrates the use of starch fibers as a binder in ceramic fibers. This example also shows that starch fiber binders can be removed after forming the web to give a 100% ceramic fiber sheet.

A 3% dry solids slurry was prepared in a Waring Blender, to which 0.2% sodium hydroxide (based on the dry weight of the fiber) was added as a dispersant, followed by stirring for 1 minute. The fiber mixture was then transferred to a tank equipped with a paddle stirrer and a predetermined amount of starch fiber from the mixture / having a dry matter content of 1% was added. The mixture was stirred for 5 minutes, then

Pre-sheets with a basis weight of 407 g / m 2 were made from the Noble and Wood sheet making machine. For comparison, a ceramic sheet was made without adding any starch fibers. The strengths of all sheets were determined and the results are shown in Table XI.

Table XI

Starch fiber Weight per square meter Tensile strength ^ _____________ g / m2 _g / cm2 0 407.5 - * 5% 407.5 3.52 10% 407.5 20.39 ajx

The sheet density was not sufficient to measure the tensile strength ^ As defined in Example 5.

The sheets containing starch fibers were then placed in an oven maintained at such a high temperature that the starch fibers burned and the ceramic fibers melted. In this way, a well-bonded ceramic web was obtained.

Example 15

Double-layer hand sheets were prepared containing 10% 2 of titanium dioxide by weight of the final sheet, which was about 145 g / m 2. Titanium dioxide was added to the control hand sheets in the usual manner by dispersing the pigment with unbleached cellulose fibers. This formed the top layer. In other hand sheets, so much starch fiber containing 20% by weight of titanium dioxide encapsulated was added to the top layer that 10% of the weight of the finished sheet was titanium dioxide.

32 6741 7

The final sheet was formed from two layers made separately in a Noble and Wood sheet mold with a basis weight of 2 of 82.5 g / m 2. The sheets were removed from the wire and pressed together as 2 wet mats at 14061 g / cm. The sheets were then dried in a Noble and Wood dryer at 121 ° C. Difficulty readings were then taken from the top layer according to TAPPI R452-M-58. The results are shown in Table XII.

Table XII

Sample sheet_Whiteness of the top layer

Comparison 26.2 Starch fiber 30.1

The results in Table XII show that the properties of hand sheets made from used TiO 2 -encapsulated starch fibers were much better than those of sheets made by conventional methods.

Following the preferred embodiments of the present invention described above, various variations and improvements will be apparent to those skilled in the art. The spirit and scope of the present invention are not limited to the above description, but only the claims limit the invention.

Claims (10)

1. A process for making paper, paperboard or paff, wherein a fibrous mass of water sludge is guided on top of a wire in such a way that the water is removed and the concentrated fibers produce a sheet from which the final paper product is obtained by pressing and drying. thereof, that from 1 to 100% by weight of the pulp are water-resistant starch fibers having a diameter of 10 - 500 µm, which fibers are produced by spray-pressing a tree-like stream of a colloidal dispersion of starch, the dry matter content of which is 5 - 40% by weight, into a moving coagulation bath, which comprises an aqueous solution of a coagulating salt, wherein the salt is ammonium sulphate, ammonium sulphamate, mono- or bi-basic ammonium phosphate or a mixture thereof, which aqueous solution contains coagulating salt At least so much that it is sufficient for coagulation of the starch. Method according to claim 1, characterized in that starch fibers made from corn or corn starch are used. 3. A process according to claim 1, characterized in that starch fibers made from starch containing amylose are used. Method according to claim 1, characterized in that starch fibers made from cationically modified starch are used. 5. A process according to claim 1 or 4, characterized in that starch fibers made from starch ether or ester derivatives are used. Method according to any of claims 1-5, characterized in that the length of the starch spheres is 0.1 - 3.0 mm. Process according to any of the preceding claims, characterized in that the colloidal starch dispersion contains a dispersed, water-insoluble additive not exceeding 80% by weight of the starch. Process according to any of the preceding claims, characterized in that the colloidal starch dispersion contains dispersed hydrocolloid below 50% by weight of the starch. 9. A process according to any one of claims 1-8, characterized in that the remaining fibrous pulp material is essentially wood cellulose. Method according to any of claims 1-8, characterized in that the remaining fibrous pulp material is essentially polyester fiber, rayon fiber, ceramic fiber, glass fiber or asbestos fiber.