NO140193B - ENGINE FUEL MIXTURE. - Google Patents

Description

Process for producing water-deposited products from synthetic, partially degraded fibres.

This invention relates to the production of products deposited from aqueous suspensions of synthetic fibers of organic ones

substances, such as cellulose or nylon.

The physical properties such as strength,

tear strength and burst strength of fibrous objects, e.g. nonwoven structures and

water-deposited sheets or plates, depends i

large extent of an entanglement of

the fibers and fibrils on the fibers and of fiber-to-fiber bonds. The most used material, which can be attributed to the group of non-woven structures, is paper, as usual

is produced from a feed containing the dispersed and fibrillated fibres.

It is common knowledge that natural cellulose fibers, e.g. wood pulp, cotton linters

and the like when treated with water i

Dutch assumes a fibrillated state. This

"fibrillation" that is used

papermaking, is mainly achieved by

to beat or grind the fibers in a large excess of water. The fibrillation signifies what one

could call a microscopic and sub-microscopic progressive release of individual fibrils along the surface and

at the ends of the fiber bundles, and this virk-1

ning is achieved without the fibers undergoing any

chemical change. The cell walls of these natural cellulose fibers are composed of

fibrils, and these are displaced by exposure

for paint in water. It is common knowledge

that the fibrillation is an inherent property of

the naturally occurring cellulose fibers,

like for example. wood fibers, and that each fibril

have a diameter of the order of 150 A or less.

Synthetic organic fibers usually do not have the fibril-stable structure that natural fibers have and therefore do not undergo "fibrillation" when they are ground and mixed in a large excess of water such as in a Dutcher. When attempting to form water-deposited sheets or plates, the lack of fibrils or fibril elements will therefore preclude an intimate entanglement of the fibers, and very little, if any, fiber-to-fiber bonding occurs. Similarly, if the unfibrillated synthetic fibers are formed into a sheet or web by a dry system, e.g. by air blowing or during a carding operation, and the sheets are then moistened with water, very little, if any, fiber-to-fiber bonding will develop upon subsequent drying of the sheet. Also, certain classes of synthetic organic fibers are difficult to disperse in water. Still, synthetic organic fibers would be the highest

desirable for the production of water deposits

sheets or webs, because it is possible to obtain fibers of any desired exact diameter and length, while the natural fibers must be used as they are from nature, and they vary both in diameter and length. They usually have a length of approx. 0.5 mm to 4 mm. Lack of a fibrillation property

and strong fiber-to-fiber bonding have limited the use of conventional synthetic organic fibers in the manufacture of water-deposited webs for special types of specialty papers.

In the production of special paper from synthetic fibres, it is sometimes necessary to use a binder which is incorporated into the paper by adding this to the pulp before it is fed to the screen or by adding it to the water-deposited web, before the web is removed from the screen or wire. An alternative is that at least some of the fibers can be made of a thermoplastic material, and that the web deposited in water is subjected to heating and pressure before it is removed from the wire. Non-woven structures made from synthetic fibers by dry methods also require binders to increase the strength properties, and the binders can be incorporated into the structure when the fibers are to be deposited or collected, or by the binder being impregnated into the mass of collected fibers. When using fibrillated synthetic organic fibres, the required amount of binder can be greatly reduced, and in some cases even omitted due to the binding that results from the presence of the fibrils.

One of the earliest and widely used synthetic organic fiber materials that illustrates the general properties of the synthetic organic fibers as a class with regard to the production of water-deposited webs is regenerated cellulose. Regardless of the production method, regenerated cellulose fibers have the same properties from the paper manufacturers' point of view. With the viscose process, it is thus possible to produce fibers with a diameter of approx. 2-3 microns (0.002-0.003 mm) to any desired diameter and length, and therefore all fibers can be the same size. As is also known, the physical properties, e.g. strength, elongation, etc., of the synthetic fibers are varied over a wide range, and they can be carefully regulated by adjusting the spinning conditions. But it is extremely difficult to disperse the fibers in water without using a dispersant. Even with prolonged painting, the fibers will not form the necessary fibrils so that a web deposited in water is obtained with sufficient entanglement of fibre-to-fibre bonding to give the web such great wet web strength that it can be removed from the collection wire. Other synthetic fibers, e.g. those made from cellulose acetate, nylon, polyesters, etc., are similar to fibers made from regenerated cellulose in that they do not fibrillate and do not form fiber-to-fiber bonding when a wet sheet is dried.

A method for treating synthetic fibers to make them fibrillable is discussed in the patent holder's French patent no. 1 245 863. This method involves a carefully regulated hydrolysis treatment which reduces the average degree of polymerization of the fibre's cellulose, without significantly reducing the fibre's weight.

Although this method is highly effective, the individual fibrils that are formed by

stir the treated fibers in excess of

water, as in a Dutchman, not of an order of magnitude approaching the order of magnitude of the fibrils which form on natural fibers of cellulose. When one examines the fibrils under an electron microscope with a magnification of about 25,000, it turns out that the fibrils on these treated fibers have an appearance similar to tiles or shavings and have a diameter of the order of 7,500 Å. Nevertheless, these fibrillable fibers are treated in a similar manner to natural papermaking fibers to produce water-laid sheets with a tensile strength, expressed as breaking length, of at least 400 m and a tear factor of at least 50.

According to the present invention, synthetic organic fibres, which are referred to here as hybrid fibres, are subjected to a weak, carefully regulated degradation treatment followed by mechanical stirring of the treated fibers in a large excess of an aqueous medium to cause fibrillation of the fibres, after which the fibrillated fibers are separated from the aqueous medium . The hybrid fibers are composed of an organic fiber-forming base material and a hybrid-forming material or foreign material that is dispersed intimately throughout the entire fiber mass.

With the help of the invention, a method is thus obtained for the production of products deposited from aqueous suspensions, preferably paper, from synthetic, organic partially degraded fibers with a fine structure comprising crystalline and amorphous parts, which method is distinguished by the fact that a spinning liquid containing a fiber-forming polymer , such as regenerated cellulose or nylon, with thorough stirring, at least one polymer is added which is chemically different from the fiber-forming polymer, and which can break the amorphous part of the polymer suitable for fiber formation, after which it is spun in a manner known per se mixture obtained and by acid hydrolysis, the amorphous parts of the fiber-forming polymer break up to an extent which is insufficient to reduce the fiber weight but which gives fibrillable places on the fibers, and that by subjecting the fibers to impact in water, fibrils with a diameter of the order of from 50 to 7500 Å, after which one on in a manner known per se, they convert the fibrillated fibers into products deposited from aqueous suspensions.

It has thus been shown that a very significant reduction in the size of fibrils formed on synthetic organic fibers can be achieved when the continuity of the fine structure is broken by the presence of a foreign material during fiber formation. A variety of materials can be incorporated into the fiber-forming liquid, which can be either a solution or a melt of the fiber-forming material, to cause the disruption of the fine structure during fiber formation. These materials are usually amorphous materials which are preferably miscible with or dispersible or soluble in the fiber-forming liquid. The materials must be able to change to a solid state under the conditions under which the fibers are formed, and must be retained in the fibers during subsequent treatments. These materials are amorphous materials and are preferably hydrophilic, although they may contain substituent groups which reduce the hydrophilic character of the substituted materials compared to the hydrophilic character of the material itself. The hybrid-forming material need not itself be a fiber-forming material.

The special hybrid-forming material or foreign material is thoroughly and intimately mixed with the fiber-forming spinning liquid, so that a homogeneous distribution of the material occurs throughout the liquid. The "hybrid-forming material" can be a mixture of two or more materials, so that not only the fine structure of the fiber-forming material is broken, while the fibers are also given desired properties. The spinning liquid is processed and spun into filaments, and these are processed in a conventional manner, depending on the fiber-forming material and on the mixture of the fiber-forming material and the hybrid-forming material. The hybrid-forming material or the foreign material can be added to the fiber-forming liquid in amounts from approx. 0.5 percent to as much as 90 percent and 95 percent, preferably in amounts between about 25 percent and approx. 75 percent of the hybrid-forming material, calculated on the weight of the organic fiber-forming material.

A mild and regulated degradation step is then used as a pre-treatment of the hybrid fibres, so that they can be fibrillated by a subsequent mechanical treatment in an aqueous medium. The specific degradation conditions, e.g. where acid hydrolysis is used as the dividing step, the acid concentration, the temperature of the aqueous, acidic solution and the treatment time will depend on the special fine structure of the hybrid material and will be chosen so that a regulated cutting or detachment of the unoriented or amorphous chains which are present in the fine structure of the hybrid material. The degradation conditions are such that they cause a regulated truncation of these chains without producing any significant weight loss. When the desired demotion has been achieved, the demotion conditions are lifted immediately. If the hybrid fibers are subjected to the effect of e.g. an acid, the treated fibers will thus be washed to free them from the acid.

After the regulated, partial degradation, the fibers are easily fibrillated by mechanical stirring, such as in a conventional Dutchman. If the fibers are to be used to form water-deposited products at a place other than the production site, the dried fibers will be subjected to the same treatment and painting as is used for ordinary fibers for the production of paper, such as wood pulp. The fibrils formed during Dutch painting can have diameters of the same order of magnitude as natural wood pulp fibres, namely diameters of the order of 500-50 Å. However, the fibrils differ from natural cellulose fibers by a much greater length. To the best of our knowledge, this is the first method to produce artificial fibers that exhibit fibrils of the same order of magnitude as or smaller than those produced from natural cellulose fibers, when the artificial fibers are milled in a conventional Dutcher or subjected to equivalent stirring in water.

With the help of the present invention, it is thus possible not only to fine-tune the diameter and length of the fibers as well as their physical properties, but also to regulate and adjust the size of the fibrils formed on the fibers when they are ground in an aqueous medium. The possibility of obtaining fibers with any desired properties and with diameters within the mentioned range entails a precise matching of the properties of fibrous structures that vary from thin tissue-like paper to thick felt-like non-woven webs.

Referring again to regenerated cellulosic fibers only as an example of the characteristic properties of synthetic organic fibers as a class, hybrid fibers can be made from a mixture of viscose and a hybrid-forming material or foreign material, e.g. an alkali solution, water-insoluble hydroxyethylcellulose. It is known that regenerated cellulose fibers do not fibrillate, but if they are subjected to a mild hydrolysis treatment, so that the average degree of polymerization of the cellulose is reduced to a value within the range from 20 to 75 percent of the original average degree of polymerization of the cellulose, then they will form fibrils when they is ground in water, and these fibrils have a tile-like shape and have diameters of the order of 7500 Å. The size of these fibrils will not change either by strong hydrolysis or by prolonged grinding of the fibers in water. Fibers which are composed of hydroxyethylcellulose with an average degree of substitution of e.g. about. 0.20, will not fibrillate, and a similarly mild hydrolysis treatment will not render them fibrillable.

Hybrid fibers were produced from a mixture of viscose and hydroxyethyl cellulose with an average degree of substitution of approx. 0.20. Viscose was prepared in the conventional manner, which viscose contained 7% cellulose, 6% caustic soda and 30% carbon disulfide by weight of the cellulose, and the hydroxyethyl cellulose was dissolved in a 6% solution of caustic soda to form a solution which contained 7 percent hydroxyethylcellulose, which contained 7 percent hydroxyethylcellulose. The two solutions were mixed to obtain equal amounts of cellulose and hydroxyethyl cellulose. The solution was spun into a spinning bath containing 12% sulfuric acid, 5% zinc sulphate and 20% sodium sulphate, the bath being kept at a temperature of approx. 50°C. From the spinning bath, the filaments were then passed through a warm, watery bath (85°C) containing approx. 4 per cent sulfuric acid, 0.75 per cent zinc sulphate and 3 per cent sodium sulphate, and while passing through this bath they were stretched approx. 50 per cent. The filaments were then collected and subjected to the finishing treatments that are usually used in the production of viscose rayon, and then dried.

The diameter of the hybrid filaments was approx. 12-15 microns, and they were cut into hybrid fibers of approx. 6 mm length. These hybrid fibers were now pre-treated to partially degrade the hybrid material by exposing them to the action of a 5% sulfuric acid solution at room temperature for approx. 16 hours. After careful washing to free the pretreated fibers from the acid, they were placed in a mortar and pounded lightly, then placed in a standard Waring Blender (y 4 size), ground for 15 minutes, then again pounded in a mortar and finally processed in said "Waring Blendor" for another 15 minutes. Pounding in the mortar was done only to accelerate the fibrillation of the fibers. Essentially the same fibrillation takes place when the fibers are milled for 2 hours in a standard Walley paper laboratory disintegrator. Smaller samples of fibers should rather be processed in a "Warring Blendor" than in a "Valley" disintegrator, as the required processing time is then considerably shorter.

When, after the mechanical treatment of the hybrid fibers in water, they were examined under an electron microscope, it turned out that the fibers showed an extremely large degree of fibrillation, and that the fibrils had diameters of the same order of magnitude as the natural cellulose fibers, as most fibrils turned out to have diameters that were not larger than approx. 150 Å. With smaller amounts of foreign materials, such as hydroxyethylcellulose, fibrils with a larger diameter are obtained, but by increasing the amount of the foreign material or hybrid material, fibrils with smaller diameters are obtained.

During the preparation of the fibers described above, the viscose is first coagulated

the spinning bath, after which the cellulose is regenerated from the viscose. Part of the regeneration can take place in the spinning bath, while a

the greater part of the regeneration takes place in the warm diluted acid bath. At the same time, the foreign material is precipitated, in this case hydroxyethyl cellulose, and it is enclosed in the extruded filament and thus interrupts the regenerated cellulose's crystallization process and gives rise to a greater discontinuity between the crystalline and the amorphous parts of the regenerated cellulose than that which exists in a filament consisting exclusively of regenerated cellulose. It is assumed that the pre-treatment acid or other degradation medium at these points of discontinuity will be able to cause such a breaking of the available 1,4-glycosidic bonds in the cellulose chains that, after subsequent mechanical stirring in water, points of discontinuity arise from which fibrillation can be initiated. Alternatively, the regulated partial degradation of hybrid fibers can be regarded as a receptive treatment whereby discontinuity points and areas are made receptive so that they are hydrated and partially torn up by painting in water, so that fibrils are formed in a similar way to development of fibrils on natural cellulose fibers. This illustrates the control that can be maintained with the diameters of the fibrils formed on synthetic organic hybrid fibers.

Regulation of the fiber properties and fibril diameters can also be accompanied by regulation of the length of the fibrils. For example, polyacrylates are another hybrid-forming material that can be used in the production of regenerated cellulose fibres. A commercial polyacrylamide marketed by the American Cyanamid Company under the name "Polyacrylamide-100"

(molecular weight approx. 1,000,000) was added to a 6% sodium hydroxide solution in an amount which led to a solids content of 9% and this solution was allowed to hydrolyse to convert the acrylamide groups into sodium acrylate groups, which are stable in the sodium hydroxide solution. Various amounts of the solution were then added to a viscose solution as previously explained, and the mixture was spun under essentially the same conditions as discussed in connection with the production of the hybrid fibers using hydroxyethyl cellulose. It is known that polyacrylate fibers produced from this polyacrylamide will not fibrillate when milled in water. After regulated partial degradation, carried out e.g. by exposing the fibers to the effect of a 5% sulfuric acid solution at room temperature for approx. 16 hours and then milled in water, the hybrid fibers exhibit fibrillation properties similar to those described above. For such a hybrid fiber consisting of approx. 5 per cent of the polyacrylate, calculated on the weight of the cellulose, when examining the fibers after cutting, partial degradation and fibrillation was regulated, an average fiber length of 6,000 microns was demonstrated, and the average number of fibrils per 6000 micron length was 12. The average length of the fibrils was about 35 microns. For another hybrid containing 15 percent polyacrylate, based on the weight of the cellulose, the fibrillated fibers were found to have an average number of fibrils of 7, and the average length of these fibrils was approximately 105 microns.

It will therefore be clear from the preceding discussion that the invention provides a means to regulate all the characteristic properties of a fibrillarable synthetic organic fibre, i.e. that the physical properties of the fibres, the number of fibrils per length unit as well as the diameters of the fibrils and their length can be regulated. It is well known that the corresponding characteristics and properties of natural cellulose fibers cannot be regulated and the greatest regulation that is possible lies in the choice of natural fiber and in regulation of its treatment, but the characteristic properties of the fibers are established during plant growth. As far as is known, there is no method by which all the characteristic properties of a natural, fibrillarable fiber have been subject to precise regulation.

In addition to the precise regulation of the fibers' size and their physical properties, it is also possible to give the fibers other properties that are completely foreign to natural cellulose fibers. While fibers of thermoplastic materials can be made fibrillable in accordance with the present invention, it is also possible to form hybrid fibers which possess a sufficient thermoplastic property to form a heat-sealable paper, although the fiber base is a non-thermoplastic material. Regenerated cellulose, for example, is not a thermoplastic material, and hybrid fibers with regenerated cellulose as a base and a hybrid-forming material e-rial, e.g. hydroxylethyl cellulose as described above is not thermoplastic. Paper made from such hybrid fibers would not be heat sealable. Methyl and ethyl esters of cellulose, which are soluble in alkali solutions, are. on the other hand, thermoplastic, and when used as the hybrid-forming agent in the manufacture of regenerated cellulosic fibers, will cause them to become sufficiently thermoplastic to render paper made from such fibers heat-sealable. When there e.g. form hybrid fibers consisting of approximately equal parts by weight of alkali-soluble methyl cellulose or ethyl cellulose and regenerated cellulose, the fibers when subjected to a controlled partial degradation with subsequent mechanical treatment in water as described for regenerated cellulose hydroxyl ethyl cellulose fibers will fibrillate in approximately the same way as the regenerated cellulose-hydroxy-ethylcellulose hybrid fibers. When the fibers are processed in accordance with common methods conventional in the paper industry, they will form a heat-sealable paper.

It is clear that a large number of materials can be used as the hybrid-forming material, so that fibrillable fibers are formed which, after a regulated partial degradation, will form fibrils with desired diameters within the above-mentioned range. When producing e.g. cellulose fibers on the basis of regenerated cellulose, a large variety of materials that can be put in the class of natural hydrocolloids can be satisfactory. These hydrocolloids can be illustrated by starches, the straight-chain components of starches which are usually referred to as amylose, and especially the material known under the trade name "Superlose", the branched components of starch which are usually referred to as amylopectin, e.g. the material known under the trademark "Ramalin", partially acetylated starch, guar gum, dextran, chitin and other soluble and dispersible materials of this class. Similarly, a large number of synthetic materials are satisfactory, e.g. methylcellulose and ethylcellulose with a low degree of substitution, alkali-soluble, water-insoluble carboxymethylcellulose, hydroxypropylcellulose and carboxypropylcellulose, polyacrylates, polymethacrylates, polyvinylpyrrolidone, carboxymethyloxyd, polyvinyl alcohol and the like.

As pointed out above, the invention is not limited to hybrid fibers based on regenerated cellulose, but is equally applicable to other artificial fibers. Thus, easily fiberizable organic hybrid fibers can be produced from other synthetic fibers, e.g. fibers made from mixtures of nylon, polyesters or polytetrafluoroethylene with various acrylic materials, e.g. polyacrylonitrile and common copolymers, e.g. those that go under the brand name 'Acrilan' and 'Orlon', or of mixtures of polyolefins and nylon. The physical properties of the fibers can be regulated by varying the spinning conditions, and the size, length and diameter of the fibrils can be regulated by varying the amounts of hybrid-forming materials in the same way as described in connection with regenerated cellulose fibres.

For different products, the properties and characteristics of fibrous structures, such as water-deposited sheets, vary within a wide range, depending on the intended use of the different products. The composition of a given fibre, and the fibrillation properties of this fibre, will depend on the final product's intended use. For certain purposes, the product can consist entirely of the fibrillable product, while for other purposes, the fibrillable fibers according to the invention will be mixed with other fibers, either with natural or with synthetic fibers, e.g. cotton, rayon, glass fibers, wool fibers and natural papermaking fibers. Adhesives, fillers, materials suitable for improving wet strength, and other desired materials normally used in the paper and cellulose industry and in the manufacture of nonwoven products can be incorporated into the fiber suspension, or they can be incorporated into the water-deposited webs or into the collected fiber mass . For certain purposes, calendering of the water-deposited web during or after drying can be done in the same way as in the paper and wood pulp industry, or a fibrous structure produced by a dry process can be calendered in the same way as that used in manufacturing of non-woven products. As will be known, calendering of paper will improve the strength properties and have the same effect when used for webs which are deposited in water and which contain the fibrillable fibers of the present invention. Various synthetic resins, e.g. polyolefins, urea-formaldehyde resins, melamine-formaldehyde resins, etc. may be used at any suitable step in the preparation of the fibrous structures. Thus, melamine-formaldehyde resins can be used to improve the wet strength of the fibrous structure.

When determining the fibrillation properties of fibers produced in accordance with the present invention, standard paper laboratory methods can be used, e.g. a 2 hour grind in a standard Valley defibrator. For the purposes of the present invention, a 20 minute grind in a standard (y4 size) Waring Blendor is preferred, because it enables the use of smaller samples and shorter working time and has been found to be equivalent to 2 hours of grind in a Valley defibrator. With these provisions, the fibers are cut into lengths of 6 mm and subjected to a consistency of 1.2 percent paint in a Waring Blendor. Water-deposited webs or hand sheets are produced from the pulp on a standard "Noble and Wood" screen, and the hand-made sheets are dried without calendering. The degree of fibrillation and the approximate dimensions of the fibrils can be determined by examining the fiber samples under a microscope after the vigorous mechanical treatment in water. The effectiveness of the fiber ring is evident from the physical properties of handmade sheets, particularly the tensile strength, burst factor and tear factor.

Common synthetic organic fibers such as nylon, rayon and the like will not exhibit fibrillation when exposed to the above mentioned paint. Handmade sheets made from these fibers in the aforementioned manner have no measurable tensile strength and no measurable tear factor. Hybrid fibers alone do not fibrillate without the controlled partial degradation treatment, although in many cases the hybrid-forming material present in the fibers can induce a very weak bond in sheets deposited in water. This property can be illustrated by reference to the hybrid fibers described above which comprise regenerated cellulose and a polyacrylate. The fibers had diameters of 12-13 microns. Samples of such hybrid fibers containing 5%, 15% and 25% polyacrylate, which were cut into 6 mm lengths, did not undergo fibrillation when milled in water. Handmade sheets produced from a dispersion of these fiber samples showed relatively poor physical properties. In the wet state, the handmade sheets fell apart when handled in an attempt to measure the tensile strength, tear factor and burst factor. When the same fibers were subjected to controlled partial degradation, such as treatment with a 5% sulfuric acid solution at room temperature for 16 hours and then washed, they exhibited fibrillation when ground at a 1.25% consistency in a Waring Blender for 20 minutes. Handmade sheets of these ground fiber masses clearly showed improvements in the physical properties. In the wet state, the sheets fell apart when handled in attempts to measure the tear factor and burst factor. Table I below lists the properties of handmade sheets of the hybrid fibers as such and of the partially degraded ground fibers.

In the table, (pounds) denotes the calculated weight of a rice (500 sheets) of size 101.6 x 63.5 cm. The tensile strength is expressed as breaking length in meters (calculated on a 15 mm strip and is equal to

where p is the breaking load for a 15 mm strip in kg.

Different hybrid-forming materials will lead to different properties of the final products, although the fiber-forming base material may be the same. This is evident from the data listed in Table 2. In the production of the hybrid fibres, from which the hand sheets were made, approximately equal amounts by weight of regenerated cellulose and hybrid material were used. The fibers were prepared by mixing the hybrid-forming material with viscose and spinning the mixture into an acid spinning bath under the conditions described above. The dry fibers had diameters of 17-18 microns. The fibers were produced by cutting filaments of 6 mm lengths, and the fibers were subjected to controlled degradation, namely a 5 percent sulfuric acid solution at room temperature for approx. 16 hours. After washing to free the fibers from acid, they were ground in a Waring Blendor at a 1.2% consistency for 20 minutes. Handmade sheets were produced using standard paper laboratory methods.

The listed data for samples D, E and F show that the fibrillable fibers according to the present invention follow the same general principles that apply to natural cellulose fibers. When the painting time is increased, the tensile strength and tear factor increase. However, prolonged painting reduces the blast factor as a result of breaking fibrils and removing some of the fibrils from the fibres.

Although the examples used here have been more or less limited to regenerated cellulose as base material or fiber-forming material, the principles are applicable to all fiber-forming and film-forming high polymers. It is generally known and established that all high-polymers and high-polymer materials that can form fibers and films have a fine structure that includes varying orientation of the long-chain molecular constituents, as there are crystalline and amorphous areas that are connected to each other through the fibers or the film. Parts with a high degree of orientation are usually referred to as a crystalline part, while parts with a small degree of orientation are usually referred to as an amorphous part. The physical properties of the filaments and fibers produced from high polymers are regulated, as is known, by the size of the crystalline parts and by the total amount of the crystalline parts as well as by the size and the total amount of the amorphous parts.

The fine structure of fiber-forming polymers is shown schematically in the drawings' fig. 1. All synthetic organic fibers, including fibers such as regenerated cellulose, nylon, polyesters and the like, have a continuous network structure comprising crystalline regions or parts with a high degree of orientation (1) connected to each other in much the same way as a fishing net with amorphous parts or parts with a small degree of orientation (2).

A number of methods, e.g. acid hydrolysis, pyrolysis, bacterial degradation, photolysis and other degradation methods can be used under regulated conditions. A partial degradation thereby occurs which works to defragment molecules in the amorphous parts that connect the crystalline parts. A severe degradation, e.g. a strict hydrolysis treatment would naturally remove all the amorphous material and lead only to a skeleton consisting of the crystalline material. The degraded fiber, from which the amorphous material has been removed, is extremely fragile and will be reduced to fine particles by weak grinding in water. This powerful treatment is generally used when examining the fine structure of various high polymers, e.g. cellulose.

According to the previously mentioned French patent no. 1 245 863, regenerated cellulose fibers are subjected to a partial degradation which is believed to separate from each other some of the polymer chains in the amorphous parts as shown in fig. 2. In the case of the regulated degradation, e.g. when using acid hydrolysis of regenerated cellulose, the crystalline areas (1) remain essentially unchanged. Some of the molecular connection chains in the amorphous parts (2) are made vulnerable or interrupted as shown in 3. This impact or breaking of some of the molecular chains in the connecting amorphous parts weakens these parts, and there are places where fibrils are formed as a result -the mechanical treatment in a liquid medium, e.g. in water. For purposes of illustration, amorphous parts are shown containing chains that have been separated or interrupted at 3, but it has not been proven for sure whether these chains have really been interrupted or whether they have only been made vulnerable.

The quantity, size and distribution of both the crystalline and the amorphous parts of the fiber-forming polymer is determined by the special method and under the special conditions used in the production of the fibers. These properties are thus fixed for any given fiber produced under given conditions. It is known that for a given polymer there are certain limitations with regard to the quantity, size and distribution of crystalline and amorphous fiber parts. In accordance with the present invention, one or more hybrid materials are incorporated into the spinning liquid containing the fiber-forming material. The hybrid-forming material is a chemically different kind of polymer, which can burst or interrupt the fine structure of the fiber-forming material during the fiber's formation. The hybrid-forming materials effect a regulation of the quantity, size and distribution of the crystalline and amorphous parts within the fiber's fine structure beyond the regulation that is possible by using only the fiber-forming material.

Fig. 3 schematically shows the fine structure of a hybrid fiber, in which hybrid fiber the fiber-forming polymer is indicated by 4 and the hybrid-forming material is indicated by 5. The presence of the hybrid-forming material modifies the crystallization phenomenon that takes place. The fiber-forming polymer's parts with a high degree of orientation or crystalline parts 6 and its parts with a low degree of orientation or amorphous parts 7 are usually of a smaller size, although they

total amounts may be substantially the same as in a fiber made entirely from the fiber-forming polymer. The hybrid-forming material also transitions into a solid state and forms so-called crystalline parts 8 which are separated but connected through amorphous parts 9. When the fiber is produced in its entirety from the fiber-forming polymer, and there is no hybrid-forming material , the chains of the homogeneous polymer mixture are free and can form aggregates and crystallize in a preferred thermodynamic arrangement for the given polymer mixture. By introducing one or more hybrid-forming materials, it is possible to intervene in the normal crystallization mechanism, and the size and distribution of the crystalline and amorphous parts are then completely changed.

This intervention of the hybrid-forming material in the normal crystallization mechanism is reflected in a greater vulnerability of the fine structure of the fiber-forming polymer as regards the action of a degrading agent. Due to the smaller size of the crystalline and amorphous parts, the points or areas where the degrading agent can indicate the amorphous parts are far more numerous than corresponding areas where the fiber consists exclusively of the fiber-forming polymer. As fig. 4 shows, some of the molecular connection chains in the amorphous parts 7 are made vulnerable or interrupted as shown at 10. Because these areas or parts are smaller than corresponding parts where the fiber is made up only of the fiber-forming polymer, a much larger number of areas made vulnerable or interrupted, so that places are formed from which fibrils are formed, and the fibrils will also be smaller in size. As a result of the interruption of the crystallization mechanism in question, the partially degraded fiber has far more parts or places from which the fibrils are formed, and the fibrils get smaller dimensions when the fiber is subjected to the mechanical treatment in the liquid medium.

Although some synthetic organic fibers are difficult to disperse uniformly in water, the fibrillable fibers of the present invention excel in that they can be dispersed in water in substantially the same manner as natural papermaking fibers, such as cellulose fibers. For example, commercial grades of viscose rayon with a diameter of the order of 12 microns and a . length of approx. 13 mm agglomerates when placed in a TAPPI standard disintegrator at a consistency of 0.6 per cent, and it is not possible to produce handmade sheets of such viscose rayon fibres. Partially degraded hybrid fibers consisting of regenerated

rated cellulose and a hybrid-forming ma-

terial as described above, and which have essentially the same diameter and length,

can be very easily dispersed in water under the same conditions and can form satisfactory handmade sheets with measurable tensile strength, tear factor and burst factor. Fi-

The fibers according to the present invention can also be mixed with other fibers in an ordinary Dutchman and can constitute any desired proportion of the total fiber content.

hold.

The possibility of obtaining fibrillated hybrid fibers of any desired diameter and any desired length provides a mid-

part to produce sheets by deposition in water or by a dry process, which sheets can be varied within an exceptionally large range

advise with regard to tensile strength, tear factor and burst factor. These product properties can be regulated separately for the manufacture of products for specific purposes. water hub

set products turn out to have an unusual

uniform nature, regardless of whether the fiber consists exclusively of the fibrillated hybrid

fibers or present in a mixture with other synthetic fibers or with any natural fibers. The wet strengths for water de-

set sheets, such as mainly be-

made of natural papermaking fibers,

can be increased considerably by adding a few percent of the fibrillated hybrid

fibers with lengths of 12 mm or more.

By adding to cellulose as little as 10 per cent.

of the fibrillated hybrid fibres, the tear factor of the sheet can be increased by 30 to 40 per cent without mentioning

worthy change in the blast factor and tensile

the strength. Larger amounts of the fibrillable hybrid fibers can be added to cellulose to further improve the tear factor without significant change in the burst factor and with a small increase in tensile strength. In general, the use of fibrillated hybrid fibers of smaller diameters will result in an increase of the tensile strength, tear factor and burst factor. Similar results up-

is achieved when dry spinning is used to produce a fibrous web which is then

treated with water and finally dried.

Although by the above reason-

making for the invention in particular the production of sheets or web-like pro-

ducts, it is clear that collection over-

the surface can have any desired shape and that the collecting web in terms of thickness can vary from a paper-like web to a thick f Compensating web. Although the path can be collected as a sheet, it can be transferred

into a desired shape and finished by pressing or heating or by pressing and drying to produce an object of the desired shape.

In the description and the claims, the term "regulated degradation" denotes a partial

or degradation of the fiber-forming polymer's fine structure to make the network structure vulnerable or to break it without causing significant weight loss. Degradants for high polymer materials are known in the art. In connection with the drawings, reference is made above to the treatment of hybrid fibers with base fibers of regenerated cellulose with a 5 percent solution of svo-

velacid at room temperature for 16 hours. An-

other means and conditions can be used instead of those mentioned here. Thus, a 2.5

wt. hydrochloric acid solution essentially as good as the aforementioned sulfuric acid solution.

The time can be reduced by increasing the temperature

pure. At 80° C, the treatment time can be reduced

seen to approx. 5 minutes. It is clear that the degradation agent used will depend on the hybrid fiber used and can be chosen according to what is to be achieved in each case. The term "hybrid" denotes a fiber-forming mixture that contains a fiber-forming and/or film-forming high-polymer material and one or more chemically different polymer types that can change into solid form

where the conditions under which the fiber

is set and which is capable of interrupting the fine structure of the fiber-forming polymer during the production of the fiber or filament

intended.

Claims (3)

1. Process for the production of products deposited from aqueous suspensions, preferably paper, from synthetic, organic, partially degraded fibers with a fine structure comprising crystalline and amorphous parts, characterized by adding to a spinning liquid containing a fiber-forming polymer, such as regenerated cellulose or nylon, with thorough stirring, at least one polymer that is chemically different from the fiber-forming polymer, and which can breaking up the amorphous part of the polymer that is suitable for fiber formation, after which the obtained mixture is spun in a manner known per se and by acid hydrolysis the amorphous parts of the fiber-forming polymer are broken up to an extent that is insufficient to reduce the fiber weight but which produces fibrillable sites on the fibres, and that by subjecting the fibers to impact in water, fibrils with diameters of the order of magnitude from 50 to 7500 Å are formed, after which the fibrillated fibers are converted in a manner known per se into products deposited from aqueous suspensions . 2. Process according to claim 1 using regenerated cellulose as the fiber-forming polymer, characterized in that alkali-soluble, water-insoluble hydroxyethyl-, hydroxypropyl- or carboxyethyl cellulose is used as the polymer which is chemically different from the fiber-forming polymer in the spinning bath . 3. Method according to claim 1 using regenerated cellulose as the fiber-forming polymer, characterized in that polyacrylate is used as the polymer which is chemically different from the fiber-forming polymer.