FI79580B - FOERFARANDE FOER FRAMSTAELLNING AV FOERPACKNINGSPAPPER. - Google Patents

Abstract

New process for preparing a fiber sheet by using paper techniques, with a pH comprised between 6.2 and 9.5, from fibers, an organic polymer binder, an organic cationic flocculant and an agent reducing the adherence of the sheet to the wet presses during the formation of the sheet. The sheet obtained according to said method, of which the pH of the aqueous extract is higher than 7, and which exhibits improved mechanical properties particularly as to the tensile strength, the bursting resistance, the impact resistance, the rupture energy and the machinability, is useful in the packaging field and particularly for paper bags.

Description

79580

The present invention relates to a new process for the production of a fibrous web by papermaking techniques from a source of fibers, a binder, a flocculant and a special additive, said web having small, medium and large paper bags or sacks. The invention also relates to a paper obtained by this method as a new industrial product.

It is known that manufacturers and processors of kraft paper for packaging have to compete with a number of forms of packaging, such as plastic bags and packages designed for bulk or semi-bulk deliveries. Similarly, papermakers and processors have had to develop more technical products that weigh less than traditional materials (reducing the weight of paper or reducing the number of folds of bags, 20) that fully meet end-user qualitative requirements for automatic packaging stressors in a wide range of industries. may be, depending on the specialty of the professional: 25 a) building materials: cement, mortar, water-curable mortar, coatings, floor coverings, insulation materials, sealants; (b) mineral products: raw clays, kaolins, ceramics, refractory products based on clay or asbes-30, lava, marble, ground silicon, barites, precipitated lime and precipitated gypsum, okra, talc, silicate products and silicas, bentonites, activated carbons , salt; (c) human consumption: 35 bread and pastry flour, sugars, milk powder, pasta, potatoes, fruit and vegetables, dried foods; 2 79580 (d) animal nutrition: feed, meat and fish feed, molasses, livestock concentrates, wheat, alpha meal, pulps, mineral concentrates, pet food, milk powder; 5 e) chemicals: aluminum, sodium, sulfur and combinations, washing powders, detergent soaps, polymers as derivatives of petrochemicals and carbon chemistry, insecticides, pesticides, synthetic resins, cellulose or starch derivatives, dyes, pigments; (f) fertilizers: nitrogen and phosphate fertilizers, calcium nitrate, potash, fertilizer combinations, phosphorus or potassium slags; and (g) other products: 15 seeds, sawdust, bitumen, charcoal, etc.

Depending on the different uses, a paper bag or sack, either with a valve or with an open one, must meet a number of qualitative requirements: it must be shaped to a certain volume of product; the bag or sack must be suitable for the purposes of the processor (runnability and printability), modern packaging technology and rapid and automatic mechanization; it must be able to withstand packaging stresses and shocks at various stages of handling, as well as excessive compression; it must protect the contents against physico-25 chemical effects and organoleptic deterioration; it must also be arranged to be stacked on a pallet so that it cannot slip.

For years, it has been necessary for kraft paper manufacturers to determine the main characteristics of the paper, firstly so that the processor can properly drive the paper and secondly so that the bag or sack meets the above requirements. Related studies show that the breaking energy of paper, which is mainly related to elongation at break, especially in the machine direction, is a basic property in terms of the final strength of 35 bags or sacks.

Many 3 79580 * technical solutions are known to be recommended for such problems. One particularly known solution, called "high-consistency processing of cellulosic pulp", cf. in particular WCWEST, Pin _47 (6), 313 (1964), French patent 1,453,803 and its li-5 patents 91,978 and 91,979, generally make it possible, starting from 20-35% of the cellulose content, to improve the tear strength and elongation at break 5- 10%, but its major drawback is the high energy consumption compared to conventional processing methods.

10 A solution called "fluidized bed" is also known; this has the advantage of limited traction during papermaking and thus improved fracture energy, but has the following disadvantages: high investment costs, very high energy costs and irregularities in the transverse direction, the machine equipped with this solution being unable to produce more conventional paper products unless fracturing energy is set. .

A solution called "creped kraft" is also known, cf. in particular French Patent 1,261,100; This provides at least 7-8% elongation at break in the machine direction, but is too flexible and runnable for both the processor and the bag or sack filler, especially due to the substantial development of bagging and bagging line automation.

25 It is known that due to the serious disadvantages associated with creped paper, another stretchable solution has been proposed, known in particular as the "CLUPAK" method (trademark of GLUPAK INC.), For the production of stretchable or semi-stretchable kraft paper, cf. in particular U.S. Patent 2,624,245 and FR Patents 1,439,100, 1,442,574 and 1,550,049; this method involves pressing the paper still wet between the rubber belt press and the drying roll, the rubber belt retracting to provide compression forces in the machine direction and causing local compression, providing a certain degree of elongation in the paper, the desired elongation being obtained mainly by adjusting speed differences at 4,79580

In this context, this solution is one that offers the best compromise between quality and price. However, the amount to which it can allow the weight of the bags or sacks to be reduced is still limited. In fact, the elongation levels in the breaking of semi-stretchable kraft paper are generally of the order of 5-10% in the machine direction, and in particular 5-7%, because above this threshold the already mentioned main disadvantages of creped paper flexibility and therefore runnability occur. Under these conditions, even this solution has a limitation in terms of fracture energy. It is also very important to emphasize, however, that the mechanical event of elongation, which favors the elongation properties of the paper, has a very opposite effect, in the order of 15-30%, on the tensile strength of the paper.

In addition, so-called standard kraft paper for making small, medium or large sacks or bags, so-called semi-stretchable, stretchable or crimped paper according to the latter two solutions is obtained by using a fiber suspension consisting mainly of unbleached or bleached softwood fibers. depending on), and containing agents to make the cellulose water-repellent, commonly referred to as "sizing agents", to reduce the water sensitivity of the paper.

These sizing agents are usually prepared from rosins comprising various resin acids (especially abietic, neoabietic and palustric acids). These are either rosin adhesives, most commonly saponified with sodium hydroxide, sodium carbonate, potassium hydroxide, aqueous ammonia or organic bases, or reconstituted rosin emulsions, i.e. emulsions consisting of a modified disinfectant or emulsified resin. being. However, it is now the case that these adhesives must always be used in a toothed medium, i.e. at a pH between 4-6 and the most common »- 5 79580 min 4-5. This acidity is generally achieved by the use of aluminum sulfate alone or in combination with sulfuric acid. Aluminum sulfate acts as a flocculant and as an adhesive for adhesive resin particles to the fibers.

The presence of aluminum ions is also necessary in the prior art for the precipitation and attachment of residual resin particles in the pulp after the conifer has been cooked by the kraft process to the fibers. In the absence of aluminum ions, these deposits or resins cause very significant disturbances to the manufacturing conditions: staining of the wire and felts and excessive dusting in the wet presses, which regularly results in web breaks in the machine. The addition of aluminum sulphate, which facilitates production conditions, impairs the general mechanical properties of the paper under the conditions of use according to the invention.

To clarify the situation, it should be noted that a high degree of grinding of the fibers (the degree of SR freeness must be greater than 35 and practically greater than or equal to 50) promotes the formation of paper in the paper machine. On the other hand, when low pulverization (SR-freenees less than or equal to 35) cellulosic fibers are used, difficulties arise: (i) fibers with a low degree of grinding have sticky ingredients that tend to precipitate in the press rolls, causing heavy dusting and consequent mouth On the other hand, when a high degree of grinding in an alkaline medium affects the good internal adhesion or cohesion of the sheet, a low degree of grinding is unfavorable for internal adhesion.

These difficulties explain why the technique, known as "neutral medium sizing" (pH range 6.5-8.5), and described in DE patent application 3,000,367, FR patent 1,005,346 and FR patent 1,218,904, very high degree of grinding fibers (SR freeness grade 50) are used to avoid interruptions and to promote internal cohesion.

In addition, DE patent application 2,809,422 discloses a process for the production of packaging paper 6 79580, in which 0.01 to 0.3% by weight, relative to the weight of the final dry paper, of a composition comprising 2 to 15% by weight is added upstream of the headbox. % anti-adhesion agent and 98-85% by weight of synthetic rubber or synthetic resin. For the reasons given above, this method is used from fibers with a very high degree of grinding (SR freeness degree 68-70).

According to the invention, a completely different technical ankle is used. In order to save energy, fibers with a low degree of grinding are used, and in order to compensate for the disadvantages associated with the use of these fibers, it is recommended to add a number of ingredients according to specific alternatives.

This technique, which is particularly advantageous for so-called integrated paper mills, which produce pulp and paper as a continuous process, makes it possible to produce kraft paper for the purpose of making packaging bags or sacks.

According to the invention, a new technical solution 20 is proposed which makes it possible to eliminate the above drawbacks and, on the one hand, offers the advantage of providing fibrous paper with improved mechanical properties such as impact strength, breaking energy and runnability on the one hand, and energy savings and raw material savings on the other. fibers, and during the manufacture of bags or sacks, an adhesive for gluing fibrous paper.

According to the invention, the cellulose savings associated with the reduction in the amount and / or weight of paper from which the bag or sack is made can be, by way of example, between 5 and 35% and in particular 10-15%, depending on the use; for adhesives, this saving can be in the order of 10-20%.

A method of making a fibrous web according to the invention by papermaking from an aqueous suspension containing fibers, a binder, a flocculant and an agent that reduces dust and adhesion of the web to the wet end presses of 7,79580 machines. to prepare an aqueous suspension having a pH of 6.2 to 9.5 and containing (a) 100 parts by dry weight of fibers selected from the group consisting of: (i) cellulose-based fibers having an SR freeness degree of 16-35, and (ii) combinations of cellulose-based fibers having a degree of SR freeness of 16-35 in combination with non-cellulose-based fibers, wherein the weight ratio of non-cellulose-based fibers to cellulose-based fibers is 0.1 or less, (b) 0 .05-1 parts by dry weight of organic cationic flocculant, (c) 0.2-5 parts by dry weight of organic polymeric binder and 0.01-1 parts by dry weight of ai which reduces dusting of the web 15 and adhesion to the wet end presses of the machine during its formation.

It is important that the pH be substantially neutral or alkaline in the stern piping and headbox. The pH used is between 6.2 and 9.5, preferably between 6.7 and 8.5 and preferably greater than 7 and less than or equal to 8.5.

The amount of the agent which reduces dusting and adhesion of the web to the wet end presses of the machine is preferably between 0.01 and 1 dry weight part per 100 dry weight parts per fiber 25.

All cellulose-based fibers are suitable, for example, chemical, semi-chemical, mechanical and mechanochemical fibers, softwood fibers, hardwood fibers, annual plant fibers, fibers recovered from waste paper, and mixtures thereof. It is recommended to use unbleached, semi-bleached or bleached cellulose-based fibers obtained by a chemical sulphate process known as the kraft process. These fibers are selected in particular from softwood kraft fibers, either singly or in combination with hardwood kraft fibers. For certain uses, it is possible to use softwood kraft β 79580 fibers if they are suitably mixed with hardwood kraft fibers, together with fibers from recovered waste paper or, alternatively, with fibers obtained by methods other than the kraft method. It is also possible to mix cellulose-based fibers with synthetic organic fibers (polyamides, polyesters, polyalkylenes such as polyethylene or polypropylene) and / or mineral fibers (glass, calcium sulphate, rock wool).

The fibers performed are preferably selected from the group consisting of: A) unbleached softwood kraft fibers, bleached softwood kraft fibers, or mixtures thereof; B) fiber combinations comprising, on the one hand, 60 to 90% by weight of fibers belonging to the group comprising unbleached softwood kraft fibers, bleached softwood kraft fibers and mixtures thereof, and, on the other hand, 40 to 10% by weight of fibers belonging to the group comprising unbleached hardwood kraft fibers, bleached hardwood kraft fibers and mixtures thereof; C) fiber combinations comprising, on the one hand, 40 to 90% by weight * of fibers belonging to the group comprising unbleached softwood kraft fibers, bleached softwood kraft fibers and mixtures thereof, and, on the other hand, 60 to 10% by weight of waste paper recovered and fibers; D) fiber combinations comprising, on the one hand, 30 to 90% by weight * of fibers belonging to the group comprising unbleached softwood kraft fibers, bleached softwood kraft fibers and mixtures thereof, and, on the other hand, 7 to 10% by weight of fibers derived from other cellulose-based pulps manufacturing method than the kraft method.

In addition, if non-cellulose-based fibers are used with low cellulose-based fibers, the weight ratio of non-cellulose-based fibers to cellulose fibers is less than or equal to 0.1.

It is important that the cellulosic fibers be ground in a controlled manner (i.e., per tonne of milling power produced, 9,79580 which is about 20-50% less than conventional methods, for example using 125-350 kWh, preferably 125-250 kWh according to the invention. Instead of 450 kWh, produced per tonne of paper for 5 SR-freenees between 16 and 35).

The flocculant is selected from organic cationic Flocculants such as resins of the type which are synthetic organic cationic products such as polyamide / epichlorohydrin type resins, polyamide / polyamine / epi-10 polyethylene / polyethylene modylene resin, polyamine resins such as polyethylene resins polyamide resins, glyoxal, quaternary ammonium derivatives such as chlorohydroxypropyltrimethylammonium derivatives, and modified polyacrylamides. Poly-15 ethyleneimine, polyamidamine and crosslinked polyalkylamine resins are used as an aqueous solution and in various concentrations, generally between 5-30% w / v. The amount of flocculant to be used is preferably between 0.05 and 1 part by dry weight per 100 parts by dry weight per fiber.

Suitable binders are those commonly used in the paper industry, such as natural starches with a straight or branched chain, or starches modified by chemical, enzymatic or thermal methods, dextrins, polyvinyl alcohols, casein, animal protein glue, animal glue, such as carboxymethylcellulose, alginates and mixtures of far-reaching synthetic polymers in the form of 300-600 g / liter of aqueous dispersions, containing: 87-90 parts by weight of ethyl acrylate units, 1-8 parts by weight of 30 acrylonitrile units, 1-6 parts by weight of parts of N-methylolacrylamide units and 1 to 6 parts by weight of acrylic acid units, or - 60 to 75 parts by weight of ethyl acrylate units, 5.15 parts by weight of acrylonitrile units, 10 to 20 parts by weight of butyl acrylate units and 1 to 6 parts by weight of N -methylolacrylamide units, or - 60-65 parts by weight of butadiene units, 35-40 parts by weight of ac-79580 rylonitrile units and 1-7 parts by weight of methacrylic acid units, or - 38 to 50 parts by weight of styrene units, 47 to 59 parts by weight of butadiene units and 1 to 6 parts by weight of methylacrylamide units, or - 53 to 65 parts by weight of styrene units, 32 to 44 parts by weight. parts of Buta diene units and 1-6 parts by weight of methylacrylamide units.

It is recommended to choose natural starches with a straight or branched chain (in the straight or amylose moiety with glucose units linked together by alpha 1-4 bonds, where the degree of polymerization may be between 100-3000, and in the branched or Amy lopectin moiety with alpha 1-4 and alpha 1-6 bonds and a degree of polymerization between 200-2000), cold-soluble and chemically modified starches, and aqueous dispersions of the synthetic polymer such as carboxylated and / or non-carboxylated styrene / butadiene latexes and acrylic latexes.

The amount of binder to be used is preferably in the range of 0. 2 to 5 parts by dry weight per 100 parts by dry weight per fiber.

The agent which reduces dusting and adhesion to the wet end presses of the machine is selected in particular from the group consisting of (i) amino fatty acids, (ii) amino fatty acids obtained by condensation with at least one polyfunctional compound (such as in particular epichlorohydrin, polyamines and epichlorohydrin or diamine / diamine / diamine) alkylene oxide / diamine type mixtures and precondensates, the alkylene oxide being ethylene oxide or propylene oxide), (iii) textile softeners and (iv) mixtures thereof.

In addition to fibers, a binder, a flocculant, and a substance that reduces the adhesion of the web to the wet end presses of the machine, various excipients commonly used in paper mills, such as those listed below, can be used as needed.

1. An adhesive, also called a water repellent 11,79580, used in a neutral medium to reduce the water sensitivity of the web. Water repellents are solutions of dimeric alkyl ketene with weight / volume concentrations between 5-12%, mixtures of styrene / maleic anhydride-5 dicopolymer (50:50) ammonium salt and acrylonitrile / acrylic acid copolymer 20-60% (w / v). volume) as a solution or dispersion, ammonium salts of a diisobutylene / maleic anhydride / maleic acid copolymer 20-60% (w / v) solution or dispersion, styrene / acrylic acid / ammonium salts of a maleic acid copolymer 20-60% (w / v) paraffin wax 30-50% emulsions.

The amounts of water gelling agents can obviously vary depending on the nature of the products to be manufactured and the qualitative application, but in general this amount varies from 0.05 to 2 parts by dry weight per 100 parts by weight of fibers.

2. Possibly a dye and tinting agent.

3. Possibly antifoam.

20 4. Possibly fungicides and bactericides.

5. Possibly one or more special additives to give the material certain specific properties, such as: - grease resistance - plasticity (with plasticizer) - insect resistance - anti-slip properties - anti-adhesive properties 6. Possibly conventional inorganic filler, such as talc, kaolin or CaCO 3.

Firstly, in order to achieve improved mechanical properties and secondly, in order to achieve energy and raw material savings, it is recommended in practice to carry out the following measures at a pH between 6.2 and 9.5 and between pH 6.7 and 8.5. (a) preparing aqueous suspensions containing 20 to 100 12 79580 g / liter of fibers selected from the preceding group of fibers AE; b) 0.05-1 parts by dry weight of organic cationic flocculant per 100 parts by weight of fibers are added to the aqueous suspension thus obtained, with a solids content of 20-80 g / liter of the resulting aqueous medium, c) 0.2-5 dry weight is added to the resulting aqueous medium. a portion of an organic polymeric binder per 100 parts by weight of fibers, the solids content of the aqueous medium thus obtained having a solids content of 15 to 50 g / liter; d) 0.01-1 parts by weight of dry weight of a substance which reduces dusting and adhesion of the web to the wet end presses of the machine during its formation is added to the resulting aqueous medium, 100 parts by weight per fiber having a solids content of 2-30 g / liter ; and e) forming a web to be pressed at the wet end of the machine using a press apparatus having a Shore hardness of the sheath greater than or equal to 60 °, and drying.

If necessary, an inorganic filler may be added to the fibrous aqueous suspension in step a), the weight ratio of inorganic filler to fibers being less than or equal to 0.1.

The sizing agent used in the neutral medium can be added either after step c) and before step d) or alternatively after step b) and before step c).

The fibrous dough obtained by the method of the invention can advantageously be subjected to a mechanical stretching treatment in the machine direction, which takes place while the web is still wet.

This stretch treatment can be performed by (i) creping or (ii) pressing between the elastic belt and the heated roll.

35 The propagation times are as follows; - for the flocculant - in step b) - from 15 seconds to 30 minutes - I: 13 79580 and in particular from 15 seconds to 10 minutes, - for the binder - in step c) - from 15 seconds to 30 minutes and in particular from 15 seconds to 10 minutes, - for a substance which reduces dusting and adhesion to the wet end presses of the machine 5 - in step c) - from 15 seconds to 20 minutes and in particular from 15 seconds to 10 minutes, and - from the adhesive from 15 seconds to 20 minutes and in particular from 15 seconds to 10 minutes.

When using a continuous process, the addition times are generally between 10 seconds and 2 minutes.

The best embodiment of the process according to the invention is as follows: 1. - The fibers in aqueous suspension, already obtained by grinding in a pulper (non-integrated mill) or directly from a pulp mill (integrated mill), are stored in a vat, with mixing.

The pulp is milled in a line of plate and cone refiners combined with conventional paper consistency with a grinding power that is 20-50% lower than that used in the known method for producing unbleached or bleached kraft paper for bag or bag production. The recommended degree of grinding of the pulp, expressed as Schöpper-Riegler freeness, is between 16 and 35, and in particular between 17 and 25. At this stage, the pH of the fiber suspension is between 6.2 and 9.5 and the concentration is 20-100 g / liter.

2. - The flocculant is added to the fiber suspension in a batch or continuous process. At this stage, the concentration of the resulting suspension is between 20 and 80 g / liter and in particular between 20 and 60 g / liter. This flocculant is used as an aqueous solution in a dose of 0.05 to 1 parts by dry weight, preferably 0.05 to 0.8 parts by dry weight per 100 parts by weight of fibers.

The exact amount to be used depends on: - the concentration of the synthetic organic product in the aqueous solution and its cationic strength; - the amount of organic binder; and 14,79580 - the final properties desired for the web material, and in particular its wet strength properties.

3. - The organic binder is added, preferably as a continuous process, to the resulting suspension containing fibers and a flocculant, the organic binder being introduced in ready-to-use form if it is a synthetic polymer in an aqueous dispersion with a concentration of 300-600 g / liter, or after dissolution if it is especially natural or modified starch. The latter is usually sold as aqueous compositions of 20-200 g / lit-10 ran.

The concentration of the suspension formed at this stage is between 15 and 50 g / liter and usually between 15 and 30 g / liter. The amount of binder used is between 0.2 and 5 parts by dry weight, and in particular between 0.2 and 3 parts by dry weight per 100 parts by weight of fibers.

4. - Other additional additives to impart final properties to the web material, such as in particular an adhesive, can be added either to the pulp storage tank or continuously to the headbox piping.

5. - A substance which reduces the adhesion to the wet end presses of the machine, said substance having been pre-diluted by a factor of 1 to 10, is continuously added (using a feed pump) to the headbox piping of the paper machine at a concentration of 2-30 g / liter and 25 in particular between 2 and 20 g / liter.

The amount of the agent which reduces the adhesion to the wet end presses of the machine may be between 0.01 and 1 part by dry weight per 100 parts by weight of the fibers, and in particular between 0.01 and 0.5 parts by dry weight per 100 parts by weight of the fibers.

6. The resulting suspension with a pH between 6.2 and 9.5 is transferred to a paper machine wire to form a material in web form, taking into account certain conditions imposed by wet pressing and drawing at the wet end of the machine and in the drying section.

35 Selected wet press parts have feasible coatings with a minimum Shore hardness of 60 °.

15 79580

Dry and wet draw ratios are as low as possible to increase web elasticity and fracture energy as much as possible.

The mechanical properties of the fibrous web obtained according to the invention are improved and the pH of its aqueous extract is higher than 7, according to French standard 003-005 (norme francaise, NF) (where after extracting 2 g of the sample for 1 hour in 100 ml). distilled or deionized water with a conductivity of less than or equal to 10 mS / m, the pH of the extract is measured at a temperature of 20-25 ° C).

The fibrous web according to the invention can be produced on a paper machine with a conventional single- or multi-ply wire, horizontal, vertical or inclined, for the production of unbleached or bleached kraft paper for the packaging industry and in particular for small, medium and large bags. or sack manufacturers. Such paper machines are usually equipped with drying rollers.

The material forming the subject of the invention can also be produced in a machine equipped with a tunnel for fluid drying the web to further improve the mechanical properties of the material, but as already mentioned, such production conditions are much less economically advantageous due to the high energy consumption required for fluidized bed drying.

According to the invention, the fibrous web can be produced on a paper machine lined with conventional drying sections and preferably on drying sections involving a known mechanical method of stretching in the machine direction and increasing fracture energy, such as the above-mentioned creping methods or "CLUPAK" type methods for making a semi-flowable or stretchable kraft paper. has the great advantage of eliminating the disadvantages of the above-mentioned methods involving the extensibility of the paper, while taking advantage of the known advantages of these methods, thus combining unbleached or bleached web material with mechanical properties and runnability or processing properties are superior to those of known materials intended for the packaging industry, and in particular for small, medium and large bags or sacks; manufacturers.

The material according to the invention can be used as such or in combination with other substances, such as cellulose or its derivatives, fashion or aluminum.

It may be coated in a conventional manner with preparations in an aqueous medium, a solvent medium or a hot-melt medium and based on an organic, vegetable, animal or synthetic binder, which may optionally contain conventional additives used in the processing industry, such as inorganic and / or organic fillers. , plasticizers, dyes, antioxidants, lubricants, special resins, etc.

If desired, the web of the invention can also be sharpened, foam coated, pasted, extruded, machine polished, calendered, roughened, friction polished or polished.

The material according to the invention may also be suitable for pin-25 back-processing and / or coating operations in or separately from papermaking by conventional means such as glue press, champion scraper, blade scraper, drag scraper or air knife to obtain certain special properties or their properties. grease resistance - water repellency - insect resistance - resistance to organic decomposition 35 - fire resistance - anti-slip properties 17 79580 - improved bending resistance - protection against certain chemicals or solvents.

The material may also be suitable for use in conventional monochrome or monochrome printing methods, such as flex printing, offset printing or gravure printing.

More specifically, in connection with the manufacture of bags or sacks, the material according to the invention is suitable for folding, corrugating, gluing, sewing and perforating. Various surfactants such as colloidal silica derivatives as an aqueous emulsion can also be added to it to add anti-slip properties to the final pouch or sack and thus to facilitate stacking.

The reduction in the number of folds in small, medium and large bags or sacks due to the advantageous mechanical properties of the material according to the invention is also very advantageous in terms of rapid deaeration of the bags or sacks after packaging and thus piano and loading operations before shipment.

Other advantages and features will become more apparent from the following description of non-limiting examples, which is provided to illustrate the invention.

For comparison, the first set of packaging kraft paper (Examples A-1 to A-8) was prepared by known and conventional methods, with or without mechanical stretching devices ("CLUPAK" or creping type). The resulting material was tested (results related to mechanical properties are shown in Table I) and used to make small, medium and large bags or sacks.

Example A-1

Unbleached softwood kraft fibers are ground in a line formed by plate mills and cone mills. The grinding energy is 300-350 kWh per tonne of paper produced. The degree of infiltration of the pulp-35 lodge, which is controlled by Schöpper-Riegler’s freeness number, is between 16 and 30. A conventional adhesive based on saponified rosin 18 79580 is added to a fiber suspension having a concentration of between 20 and 60 g / liter, and the cloth is precipitated and fixed to the cellulose with aluminum sulfate. At this stage, a suspension with a solids content of between 5 and 20 g / liter and a pH between 4.5 and 5 is transferred to a conventional paper machine with a horizontal single-layer flat wire (wet press, drying rolls) to produce bag or sack kraft paper. This machine was not equipped with a web stretching system ("CLUPAK" or creping spoon-10 only type).

2

The basis weight of the web to be produced is 70 g / m 2.

Example A-2

According to a modified version of Example A-1, kraft paper with a basis weight of the order of 90 g / m 2 is prepared.

15 Example A-3

According to a modified version of Example A-1, kraft paper with a basis weight of 100 g / m 2 is produced.

Example A-4

The fiber suspension of Example A-1 contains the conventional urea / formaldehyde resin used in the final manufacture of paper at a dose of 0.6 parts by dry weight per 100 parts by weight of cellulose to improve the mechanical properties when wet.

All other modified procedures are as described in Example 2-A-1. The basis weight of the web to be produced is 70 g / m 2.

25 Example A-5

The fiber suspension of Example A-1 contains urea / formaldehyde resin and cationic starch, which are added to the pulp by conventional papermaking techniques in doses of 0.6 parts by dry weight and 0.3 parts by dry weight to 30 parts by weight per 100 parts by weight of cellulose, respectively. These excipients are used to improve the strength properties of the web when dry and wet. All other conditions are as defined in Example 2 A-1; the basis weight of the web to be produced is 70 g / m 2. Example A-6 The preparation conditions are as in Example A-1, but the web weighing 90 g / m 2 is pressed by the "CLUPAK" -1979580 technique. The target elongation at break in the machine direction is 4-6%.

2

The basis weight of the web to be produced is 90 g / m 2.

Example A-7

The modified procedures are as in Example A-1, but the web with a basis weight of 90 g / m 2 is pressed by the "CLUPAK" technique. The target elongation at break in the machine direction is 8-10%.

The basis weight of the web to be produced is 90 g / m 2.

Example A-8 2 The web obtained in Example A-1, having a basis weight of 70 g / m 2, is extruded with polyethylene (the amount of low-density polyethylene 2 used is 15 g / m 2) to improve the moisture protection properties of the paper.

For comparison, another set (pre-15 marks A-9 to A-14) of commercial materials commonly used in the manufacture of 50 or 25 kg sacks for a wide range of industries (building materials, human or animal feed, fertilizers, etc.) was prepared. . These materials were tested (results related to mechanical properties are shown in Table II) and used to make sacks.

Example A-9

Stretchy unbleached kraft paper, 75 basis weight 75 g / m, obtained by standard "CLUPAK" technique. The fibers of this paper are exclusively unbleached softwood kraft fibers, and this paper contains a urea / formaldehyde-based resin to increase wet strength.

Example A-10 2

90 g / m 2 stretch basis kraft paper, made according to Example A-9.

Example A-11

Semi-stretch unbleached kraft paper, weighing 2,100 g / m, obtained by standard "CLUPAK" technique. The fibers of this pepri are exclusively unbleached softwood kraft-35 fibers.

20 79580

Example A-12

Creped unbleached kraft paper, basis weight 95 g / 2 m, obtained by conventional papermaking techniques. The fibers in this paper are exclusively unbleached coniferous fibers.

Example A-13 2

Bleached standard kraft paper, basis weight 75 g / m. This wrapping paper is made from bleached softwood fibers on a conventional paper machine with a horizontal 10-ply straight single-ply wire and not equipped with a web-stretching system.

Example A-14

The web is made from the fibers recovered from the waste paper by a conventional machine with a horizontal YK-15 multi-layer fabric and equipped with a "CLUPAK" stretching system, with a target basis weight of 90 g / m 2.

All the products of Examples A-1 to A-14 are obtained from a fiber suspension in an acidic medium, i.e. between pH 4-6 and most often between 4-5.

In the third series, the fibrous material according to the invention was prepared, tested (the results related to the mechanical properties are shown in Table III) and used for the production of paper bags or sacks.

Example 1: 25 Unbleached softwood kraft fibers are ground in a line formed by plate mills and cone mills of the type used in Example A-1. The grinding energy is 160-180 kWh per tonne of paper produced. The level of cellulose infiltration, controlled by the Schöpper-Riegler freeness number, is between 30 and 16-30. At this point, the pH of the fiber suspension is between 6.7 and 9.5. The following ingredients are added to an aqueous suspension containing 20-60 g / liter of fibers: 0.2 parts by dry weight of flocculant (polyamide / polyamine / epichlorohydrin resin in aqueous solution) per 100 parts by weight of fibers; - 1.5 parts by dry weight of binder per 100 parts by weight of fiber, 21 79580 parts by weight, the binder consisting of an aqueous dispersion of polymer containing 90 parts by weight of ethyl acrylate units, 1-8 parts by weight of acrylonitrile units, 1-6 parts by weight N-methylolacrylamide units and 1-6 parts by weight of acrylic-5 acid units; - 0.15 parts by dry weight of dimeric alkyl ketene per 100 parts by weight of fibers; and - 0.05 parts by dry weight of a substance which reduces dust and adhesion of the web in the wet end presses of the machine, 10 100 parts by weight per fiber, said substance being a derivative of aminostearic acid (oxyethylenediamine-modified aminostearic acid then soluble in acetic acid).

At this point, the pH of the resulting aqueous suspension is between 6.7 and 9.5.

The web formation is performed in a machine with a horizontal single-layer wire and conventional drying rollers without a web stretching system, taking into account the conditions determined according to the preferred embodiment.

o 20 The target basis weight of the web is 90 g / m.

Example 2:

A web is prepared according to a modified version of Example 1, with the organic binder being natural starch with a degree of polymerization between 100 and 3000. This binder 25 is used in a ratio of 2 parts by dry weight to 100 parts by weight of fibers.

2

The target basis weight of the web is 70 g / m.

Example 3:

The method is performed according to the modified procedure 2 of Example 2, with a target web basis weight of 85 g / m 2. Example 4;

The process is carried out according to the modified procedure 2 of Example 2, with a target web basis weight of 90 g / m 2. Example 5; The process is carried out according to the modified procedure 2 of Example 2, with a target web basis weight of 100 g / m 2.

22 79580

Example 6:

The process is carried out according to the modified procedure of Example 2, with a target weight of 120 g / m 2. Example 7: The process is carried out according to the modified procedure of Example 1, starting from a mixture of 80 parts by weight of unbleached softwood kraft fibers and 20 parts by weight of unbleached hardwood kraft fibers (eucalyptus) in the presence of 100 parts by weight of unbleached softwood kraft fibers. possibly necessary to improve web formation.

2

The target basis weight is 90 g / m 2.

Example 8: A web is made according to the modified version of Example 1 starting from a fiber suspension consisting of a mixture of 80 parts by weight of unbleached softwood kraft fibers and 20 parts by weight of waste paper fibers derived from substantially recovered packaging kraft paper, 20 waste paper fibers necessary to reduce material costs.

2

The target basis weight is 70 g / m.

Example 9: A web is prepared according to Example 1, but the fiber suspension consists of bleached softwood kraft fibers. The flocculant is a modified polyamine / polyethyleneimine resin used in a proportion of 0.4 parts by dry weight per 100 parts by weight of fibers.

An organic binder is a polymer dispersion containing 60 to 75 parts by weight of ethyl acrylate units, 5 to 15 parts by weight of acrylonitrile units, 10 to 20 parts by weight of butyl acrylate units and 1 to 6 parts by weight of N-methylol acrylamide units. This binder is added to the resulting suspension in a proportion of 1.5 parts by dry weight per 100 parts by weight of fibers.

Other excipients and modified procedures are in accordance with Example 23 79580 I.

2

The target in Ukraine is 70 g / m.

Example 10:

A paper web is prepared according to the modified version of Example 2, but the material is processed into a web in a machine with a horizontal single-ply wire, conventional drying rollers, and equipped with a "CLUPAK" type paper stretching system. The target elongation at break in the machine direction is 5-6%.

2 10 The basis weight of the web to be produced is 90 g / m 2.

Example 11:

The method is carried out according to the modified procedure of Example 2, but the material is processed into web form in a machine with a horizontal single-layer wire, conventional drying rollers, and equipped with a "CLUPAK" type paper stretching system. The target elongation at break in the machine direction is 6-7%.

2

The basis weight of the web to be produced is 90 g / m 2.

Example 12: 20 The material according to the invention is prepared according to a modified version of Example II, but the target elongation at break in the machine direction is 9-10%.

Example 13:

A fibrous web is prepared according to the modified version 2 of Example 1, but with a target web basis weight of 60 g / m 2. Example 14:

The procedure is carried out according to the modified procedure of Example 1, but after grinding and before adding the flocculant to the fiber suspension, bis (2-N-ethyl-30 (perfluorooctane-1-sulfonamidoethyl)] ammonium orthophosphate-type fat repellent is added in a proportion of 0.3% by dry weight. parts per 100 parts by weight per fiber to provide grease penetration resistance to the web.

The target basis weight of the web is 60 g / m.

35 Example 15:

A web is prepared according to the modified version of Example 9, followed by unilateral treatment on a paper machine to improve its surface properties. A surface treatment bath of the type commonly used for printing or writing has the following composition: - kaolin 80 parts by dry weight; - calcium carbonate in 20 parts by dry weight (wherein these inorganic fillers are pre-dispersed in an alkaline medium (pH 8-8.5) at a concentration of 10,500-650 g / liter); - 10 parts by dry weight of oxidized starch (used after dissolution at 90 ° C); - styrene / butadiene latex (aqueous dispersion) 20 parts by dry weight; and 15 - a dry weight portion of a calcium stearate-based lubricant 1.

The amount of solids precipitated on one side is in the order of 10-12 g / m2.

The web thus obtained is lightly polished (40 kg / cm) at the end of the pa-20 machine. The final target basis weight of the web is 75 g / m2.

Example 16:

A web is made according to the modified procedure of Example 10, starting from fibers taken from waste paper instead of unbleached softwood kraft fibers, 2 with a target basis weight of 90 g / m 2.

Example 16 bis

A web is prepared according to the modified procedure of Example 2 starting from a fiber composition of 30 to 70 parts by weight of unbleached softwood kraft fibers and 30 parts by weight of waste paper fibers containing long fibers, short fibers and inorganic filler (talc), all other ingredients being as in Example 2. is produced on a paper machine using a press-35 with a target basis weight of 70 g / m 2. The ash content of this web is between 5 and 8% by weight relative to the weight of said dried web (this ash content corresponds to a weight ratio of inorganic filler / fibers of less than 0.1). Examples 17-19:

A web is prepared according to the modified procedure 5 of Example 10 starting from fibers B, C and D, respectively, instead of unbleached softwood kraft fibers, with a target basis weight of 2 g / m 2.

Without departing from the scope of the invention, it is possible to produce lower weights, in the order of 40-60 g / m 2, or higher weights, in the order of 100-200 g / m 2 or even more than 200 g / m 2, by following the modified procedures described above, in particular Example 10. ^.

In addition, the dust and anti-adhesive agent used in Examples 1-16, 16 bis and 17-19 can be replaced by an amino derivative of a fatty acid (wherein the fatty acid group contains 12-24 carbon atoms), for example a lubricant such as ammonium stearate, stearoylaminopropyleneamine and lauroylaminopropyleneamine necessary 2-22 and especially 7 molecules of ethylene oxide per amine-20 molecule) and aminopropylene aminostearic, aminopropylene amino oil and aminopropylene aminolauric and aminostearic, amino oil and aminolauric acids ethoxylated if necessary with 2-22 molecules of ethylene.

The results of the comparative tests in Tables I, II and III with the prior art products (A-1 to A-14) and the products of the invention (Example 1 to Example 16) were obtained by conditioning at 65% RF and 20 ° C, and under the following conditions: - air permeability

The absolute porosity is the cm volume of its air, 2 30 which passes through 1 cm of paper in 1 second at a pressure difference of 1 millibar (French standard NF Q 03-001).

AFNOR porosity is the product of the absolute porosity and the basis weight of the paper, expressed in g / m.

- breaking load

35 Breaking load (as determined by the NF

Q 03-004) is expressed as the breaking length according to the following formula 26 79580: „,, 1 TS 106 L (m) 9,81 XW x 15 where TS = average tensile strength expressed in newtons for a 15 mm test piece 5 L = average breaking length in m, 2 W = weighted basis weight in g / m.

- puncture resistance

The puncture resistance is expressed in kilopascals and is determined in accordance with French standards NF Q 03-053 and Q 03-054.

- tear strength

The stem strength is expressed in millinewtons and is determined according to the French standard NF Q 0-3011.

- dynamic punching 15 The test piece is impacted by a punching head (French standard NF Q 03-034) attached to the pendulum, the drop height of which corresponds to the known potential energy.

The work absorbed in the piercing of the test material is expressed in decijoules (dJ).

2 0 - Kodak stiffness

The test piece attached at one end is allowed to oscillate in resonance with a known frequency by adjusting its free length. The stiffness is calculated from the basis weight and the free resonance length according to the following formula: o = 20 (L) 4 _M_ 100 100 25 where -3 S = Kodak stiffness in 10 mN, L = length in mm 2 M = basis weight in g / m.

Tables I, II and II now show the results of the study-30 and a comparison of the properties of the products.

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- A comparison of Example A-1 with Examples A-4 and A-5 shows that the addition of urea / formaldehyde resin to the pulp with or without cationic starch in acidic medium 5 mainly affects the improvement of properties in the wet state (+ 60-70%); while tensile strength, puncture resistance and fracture energy increase only by 5-7%, 3-7% and 7-15%, respectively. Under these conditions, the effect on tear strength is on average 20%. The resulting web is more fat sensitive.

10 - A comparison of Example A-2 with Examples A-6 and A-7 shows that, as previously mentioned, the "CLUPAK" type web stretching technique makes it possible to improve the breaking energy by 50% for a machine direction elongation of 5-6% and 70% for 8-9% machine direction elongation, but tensile strength can be reduced by 25-30%. It should also be emphasized that excessive compression of the web (elongation in the machine direction by more than 8%) has the opposite effect on the runnability properties of the final product. Notes related to Table II.

- The properties measured for the various materials mainly used for the production of small, medium and large bags or sacks again show (Examples A-9, A-10 and A-11) the value of the "CLUPAK" system in terms of breaking energy, but the tensile strength values measured for these papers remain at a relatively low level (break length - average of machine direction 25 and transverse direction - 5000-5500 m).

As soon as this technique, which is very common in paper machines producing unbleached or bleached sack kraft paper, is combined with a urea / formaldehyde or melamine / formaldehyde type treatment of the cellulosic pulp in an acidic medium to improve the wet properties of the paper, the tear strength decreases by 10-15. and the cut length remain substantially the same (comparison of Examples A-6 and A-7 to Example A-10).

- Example A-12 shows the favorable effect of creping on the fracture energy and tear strength 35, but this technique does not work well at all considering the tensile strength and stiffness.

36 79580

Notes related to Table III.

- The results shown in Table III show the surprising and unexpected nature of the mechanical properties of the products obtained according to the invention compared to the prior art embodiments.

Firstly, if the mechanical properties of the materials obtained at basis weights of 70, 90 and 100 g / m, respectively, by the process of the invention (Examples 2, 4 and 5, respectively) on a paper machine without a stretching system are compared with the prior art also on a paper machine is not equipped with a stretching system, to the corresponding materials made (products A-1, A-2 and A-3, respectively), the improvements obtained by the invention are shown in Table IV below.

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40 79580 - Thirdly, if the mechanical properties of the materials obtained by the method of the invention on a paper machine equipped with a stretching system are compared with those of standard papers made by the prior art commonly used by packaging paper manufacturers, including a paper machine equipped with a stretching device, improvements, especially for paper with a basis weight of 90 g / m, as shown in Table VI.

41 79580

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The following use examples illustrate in particular the material savings that can be achieved with the products of the invention. Examples of Use These examples were selected from the packaging industry, where the invention has a very important application: paper bags and sacks.

Sacks and bags are divided into three main categories.

Sack or bag class_size_type_ small <1.5 kg large type range depending on use medium 1.5-10 kg - "SOS" sack or bag: self-opening square based, reinforced; - flat sack or bag: self-opening, reinforced; -cornless sack or bag: self-opening, without reinforcements large 10-50 kg valve bag open sack (sewn or glued base)

Example 20 - small bags 1 kg flour bag 10 - A standard bag is generally made of a single ply bleached kraft paper with a basis weight of 75 g / m 2 (according to Example A-13).

- The new bag consists of simple bleached kraft paper obtained according to the method of the invention and weighing 70 g / m 2.

Cellulose savings 7-8%.

Example 21 - medium sacks or bags 5 kg SOS sack for animal feed - A standard sack is usually made: 20. simple bleached kraft paper, basis weight 75 g / m (from Example A-13),. simple unbleached Kraft Paper, 2 basis weight 70 g / m 2 (from Example A-1).

- A new sack is formed:. from simple bleached Kraft Paper, basis weight 2 70 g / m (according to Example 9), 43 79580. from a simple unbleached Kraft Paper, 2 basis weight 60 g / m 2 (according to Example 13), obtained by the process forming part of the invention. Cellulose savings> 10-11%.

5 The area of use of large sacks, which is very important, formed the subject of a more complete comparative study. Example 22 - 50 kg valve bag for cement. The standard sack consists of double semi-stretch unbleached Kraft Paper, basis weight 100 2 10 g / m, of the type of Example A-11.

. The new sack is made of double unbleached Kraft Paper obtained according to Example 4.

Cellulose savings of 10-12%.

Lightweight sacks made of the fibrous material according to the invention behave very well in a fast bagging machine, e.g. a turbine type with 4 nozzles (25-40 sacks per minute). The amount of breakage recorded on the package and during the various handling operations 20: dropping on the conveyor belts, stacking, loading, etc., is less than 3 sacks per thousand, while the usual amount is 5-8 sacks per thousand.

The new sacks are stiffer, which makes it easier to open the valve, and thus makes it easier to place the sack on the nozzle of the packaging machine. For this purpose, it is also possible to consider the use of a double sack of the type of material of Examples 10, 11 or 12, but with a basis weight of 80 g / m 2.

Example 23 - 40 kg valve bag for mortar 30. The standard sack generally consists of triple stretchable Kraft Paper, 75 g / m 2, of the type of Example A-19.

. The new sack is made of either triple bleached kraft paper with a basis weight of 70 g / m according to Example 2 (cellulose saving 8%) or double bleached paper with a basis weight of 90 g / m 44 79580 according to Example 1. Kraft paper (cellulose savings 14-15%) and is filled in a 4-nozzle turbine-type bagging machine at a bagging speed of 1300-1500 bags per hour.

The breakage rates during packaging and handling operations are as follows:

Triple standard sack 2.3 / 1000 sacks

Triple new sack 1.3 / 1000 sacks

Double new sack 2.2 / 1000 sacks

Example 24 - 50 kg open flour bag 10. The standard sack usually consists of three times the stretchable Kraft Paper, 75 g / m 2, obtained according to A-9.

. The new sack is made of either triple unbleached Kraft Paper obtained according to Example 2 2 15, 70 g / m 2 (cellulose saving 8%), or double unbleached Kraft Paper obtained according to Examples 10, 11 or 12 (cellulose saving 14-15%) .

With a packaging machine with 6 feed chutes, 3 lateral-20 vibrating conveyors (packing speed e.g. 600-800 sacks per hour) and automatic shaping and sewing, the results obtained with the new lightweight sacks show particularly good performance compared to standard stretch kraft paper sacks.

A sack which is three-layered and obtained according to Example 12, but which has a target weight of 60 g / m 2, is suitable.

Example 25 - 50 kg open sack for fertilizers. The standard sack is generally formed of triple unbleached Kraft Paper, basis weight 70 g / m 3 (Example A-1), and one layer of polyethylene coated unbleached kraft paper, basis weight 70 g / m 2 (Example A-8).

. The new sack is made of the double unbleached Kraft Paper of Example 2, basis weight 2 35 70 g / m, together with the polyethylene coated simple 2 unbleached kraft paper, basis weight 70 g / m, 45 79580 (type A-8 of Example).

Cellulose savings of 25%.

Example 26 - Large garbage bag. Depending on the use, a conventional sack is made of either simple stretchable unbleached kraft paper, 100 g / m 2 (according to Example A-11), or double standard kraft paper, 2 g / m 2 (according to Example A-1).

. The following combinations are used with the fibrous materials 10 according to the invention: 2. A simple 100 g / m sack is replaced by a new sack consisting of a simple 90 g / m material (according to Example 8).

2. A double sack 15 with a basis weight of 70 g / m 2 shall be replaced by either a new sack which is simple,

In the horn 120 g / m (according to Example 6), or in a sack 2 double, the basis weight is 60 g / m (according to Example 13).

Cellulose savings are between 10-15%.

20 Example 27 - 25 kg open sack for milk powder. A conventional sack is generally made of a simple bleached kraft paper having a basis weight of 75 g / m 2, a double bleached kraft paper having a basis weight of 2 70 g / m 2, type 25 of Example A-1, and a polyethylene sheath.

. The new sack is made from one layer with a basis weight of 75 2 g / m 2, according to Example 15, from one layer with a basis weight of 70 g / m 2, according to Example 2, and a polyethylene jacket.

30 Cellulose savings of more than 30%.

Example 28 - 10 kg sack for dog food

The fat content of dog food bags is generally high (on the order of 10-12% by weight). For this purpose, when one layer of grease-35 resistant unbleached kraft paper has to be used, the composition of the sack is as follows: 46 79580 - 1 outer layer of bleached kraft paper according to Example 15 together with 1 inner layer of Example 14 square pulp-2 obtained with 60 g / m unbleached kraft paper .

In this application, the cellulose savings are always at least 5%.

In these use examples, only cellulose savings are mentioned, which are easy to quantify, but it is clear that a double sack requires less glue than a triple and is easier to manufacture 10 (reduction of production costs - less waste and processing steps). In addition, transportation costs are also lower.

Claims (11)

47 79580 A method of making a fibrous web by a papermaking technique starting from an aqueous suspension containing fibers, a binder, a flocculant and a substance that reduces dusting and adhesion of the web to the wet end presses of the machine, the suspension being having a pH of 6.2 to 9.5 and comprising (a) 100 parts by dry weight of fibers selected from the group consisting of: (i) cellulose-based fibers having an SR freeness of 16 to 35, and (ii) combinations of cellulose-based fibers having an SR freeness of 16 to 35 in combination with non-cellulose-based fibers, wherein the weight ratio of non-cellulose-based fibers to cellulose-based fibers is 0.1 or less, (b) 0.05-1 a dry weight portion of an organic cationic flocculant, (c) 0.2-5 a dry weight portion of an organic polymeric binder and 0.01-1 a dry weight portion of a web reducing agent. dusting and sticking to the wet end presses of the machine during its formation. Method according to Claim 1, characterized in that the pH of the aqueous suspension in the stern piping and headbox of the paper machine is 6.7 to 8.5. Process according to Claim 1, characterized in that, at a pH of 6.7 to 8.5: 1 °), an aqueous suspension containing 20 to 100 g / liter of cellulose fibers with a low degree of grinding and an SR freeness is prepared. degree of 16 to 35 and selected from the group consisting of A) unbleached softwood kraft fibers, bleached softwood kraft fibers or mixtures thereof; B) fiber combinations comprising, on the one hand, 60 to 90% by weight of fibers belonging to the group comprising unbleached softwood kraft fibers, bleached softwood kraft fibers and mixtures thereof, and, on the other hand, 40 to 10% by weight of fibers belonging to the group comprising unbleached hardwood kraft fibers, bleached hardwood kraft fibers and mixtures thereof; C) fiber combinations comprising, on the one hand, 40 to 90% by weight of fibers belonging to the group comprising unbleached softwood kraft fibers, bleached softwood kraft fibers and mixtures thereof, and, on the other hand, 60 to 10% by weight of fibers recovered from waste paper; D) fiber combinations comprising, on the one hand, 30 to 90% by weight of fibers belonging to the group comprising unbleached softwood kraft fibers, bleached softwood kraft fibers and mixtures thereof, and, on the other hand, 70 to 10% by weight of fibers derived from a process for making cellulose-based pulps other than kraft ; and 2 °) an organic cationic flocculant is added to the aqueous suspension thus obtained, the solids content of the resulting aqueous medium being 20 to 80 g / liter; 3 °) to the resulting aqueous medium is added organic poly-. a sea binder, the aqueous medium thus obtained having a solids content of 15 to 50 g / liter; 4 °) a substance which reduces the dusting and adhesion of the web to the presses of the wet end of the machine during its formation is added to the resulting aqueous medium, the water thus obtained - having a solids content of 2-30 g / liter; and 5 °) to form a web which is pressed at the wet end of the machine using a press apparatus having a Shore hardness of 60 ° or greater in the press coating and dried. Process according to Claim 3, characterized in that, after step 3 °), 0.05 to 2 parts by dry weight of water-repellent substance per 100 parts by weight of fibers are added. Process according to Claim 3, characterized in that 0.05 to 2 parts by dry weight of water-repellent substance per 100 parts by weight of fibers are added before step 3 °. 49 79580 Method according to Claim 1 or 3, characterized in that, after the web has been formed, it is subjected to a stretching treatment in the machine direction while it is still wet. A method according to claim 6, characterized in that the stretching treatment is performed by pressing between an elastic belt and a heated roll. Method according to Claim 6, characterized in that the stretching treatment is carried out by creping. Process according to Claim 3, characterized in that the following are added successively to an aqueous suspension of 100 parts by weight of fibers selected from the group consisting of unbleached softwood kraft fibers with an SR freeness of 16 to 30: 0.3 dry weight parts by weight of organic cationic flocculant, - 2 parts by dry weight of starch, - 0,15 parts by dry weight of dimeric alkyl ketene as a water repellent, and - 0,05 part by weight of a substance which reduces web dust and adhesion to the wet end presses of the machine during its formation. Process according to Claim 3, characterized in that an inorganic filler is added to the aqueous suspension of fibers obtained from step 1 °), the weight ratio of inorganic filler to fibers being 0.1 or less. A method according to claim 1, characterized in that the agent which reduces dusting and adhesion to the wet end presses of the machine is selected from the group consisting of (i) amino fatty acids, (ii) amino fatty acids condensed with at least one polyfunctional compound, (iii) textile plasticizers and (iv) mixtures thereof. 50 7 9 5 8 0