FI56998C - AV STRAO FRAMSTAELLT HAOLLFAST OMSLAGSPAPPER OCH FOERFARANDE FOER FRAMSTAELLNING AV DETSAMMA - Google Patents

Description

»I r-1 ANNOUNCEMENT _ΛΛΛ TOSTa ^ (11) UTLÄGGNINGSSKRIFT S6 99 8 C (45) Patent granted 12 05 1930 Patent meddelat '(51) Kv.lk.VInt.CI. * D 21 H 5/14 213U / 73 ENGLISH —FINLAND (21) PM * nttlh »k« nu * - Patantansökning (22) HakemitpUvi - AntBknlngtdag 03 · 07 · 73 (23) AlkupUvi —GiMghttsdag 03-07 * 73 (41) Tullut luikikuksi - Blivlt offuntllg 0U. 01.7 ^

Patent and Registration Administrators,. , _,, (44) Date of Nihtivikslpwon and moon | - is m An

Patents and Registration of the United States of America (32) (33) (31) Requested Priority — Begird Priority 03-07-72 USA (US) 268508 (71) Clupak, Iiic., 530 Fifth Avenue, New York, NY 10036, USA (US) (72) James Wade Emerson, Hazlet, New Jersey, USA (US) (7 * 0 Berggren Oy Ab. (5 * 0 Strong, straw wrapping paper and method for its production -Av strä framställt h & llfast omslagspapper och förfarande för fram-ställning av detsamma

The present invention relates to straw paper and a method for producing straw paper having good energy absorption capacity and good tear resistance. More specifically, the invention relates to straw paper containing straw fibers and softwood fibers suitable for use as a high strength wrapping paper and for making high strength, multi-ply paper bags in which most of the straw fibers are 0.70-4.00 mm in length, the straw fibers being arbitrarily blended a method of making this straw paper in which the cut straw is fed to a digester, the broth is dispensed into the straw, the straw solution is boiled under pressure and in the presence of superheated steam, the straw is pushed, the waste solution is removed, the softwood pulp is blended into .

Straw paper has been known for centuries and has been used in a wide variety of commercial applications. Straw papers are usually grouped into two main categories. The second category is paper made from hay straw. The second category, on the other hand, is paper made from grain straw such as wheat, rice and rye straw. This description is limited to cereal straw, although many of the process steps described 2 5 G 39 ε can be applied to other types of straw used in papermaking.

Paper made from grain straw such as wheat and rice straw is used to make corrugated board, egg mass, decorative wrappers, and bleached is used on high quality white papers such as writing and printing papers. However, straw paper is not considered suitable as sack or bag paper because straw fiber papers are unsuitable for applications where good tear resistance is required. Thus, although straw wrapper is used to make some low strength decorative wrapping paper, high quality packaging and sack papers containing straw fibers as an essential ingredient have not been made to date. It is quite clear that straw fiber paper with toughness and tear resistance is a quite desirable product. According to the present invention, there is provided such a product and a method for its preparation, and the features thereof are apparent from the appended claims 1 and 3.

In addition, according to the invention, it is possible to produce heavy straw paper by surface area, instead of the hitherto, due to the slow removal of water from the straw fibers, it has been difficult to produce heavy straw paper.

According to the present invention, there is provided a method for producing a novel straw fiber paper having a high tear resistance and a high energy absorption capacity. Thus, this new type of paper is particularly well suited for commercial uses for which straw paper could not previously be used. The paper according to the invention can be used for packaging and wrapping, especially when tear resistance and toughness are required.

This new product is made by a process that involves dissolving straw fibers, washing the dissolved straw, adding a certain amount of some other pulp such as softwood pulp to a thoroughly blended pulp slurry containing about 50-80% straw fibers, adding resin glue if necessary, passing the pulp slurry to a web , sealing the web with a wire by suction, further compacting and partially drying the web, and then, at a certain moisture content, pushing the web fibers generally at the web plane to further solidify the web by causing the fibers to penetrate and the straw fibers and other fibers to entangle, and then complete drying of the web.

According to the invention, the threshing of the fibers of the web can be carried out either in only one direction or, alternatively, by forces acting in mutually transverse directions, either simultaneously or in succession.

The product of the invention is empirically recognizable by the inherent intertwining of the fibers, by the fact that straw fibers contain about 50-80% of the total weight of the product, and by the presence of other fibers such as softwood fibers, and under test conditions of 5G9S6. with a typical straw paper of similar composition not made in accordance with the present invention.

The embossing step of the method of the invention can be performed in many ways, but, as will be explained in more detail below, the embossing is preferably performed in a press nip to which the web is fed in a tensioned manner and having a moisture content of less than about 50%.

The object of the invention is to provide an even better straw paper.

It is a further object of the invention to provide a method of making straw paper suitable for wrapping and packaging purposes.

It is a further object of the invention to provide heavy straw papers with their surface pressures.

It is a further object of the invention to provide a method for producing heavy surface area straw papers.

In addition, the aim is to provide a straw paper with a heavy surface weight and good tear resistance and toughness.

In order to achieve the above-mentioned and other objects of the present invention, the invention comprises the features described below, which are set out in particular in the claims, while the description sets forth in detail some embodiments illustrating the invention. These embodiments are presented to illustrate some uses of the principles of the invention.

For a more complete understanding of the invention, reference will be made to the accompanying drawing, which shows a device suitable for carrying out the method according to the invention and for manufacturing the product according to the invention. The drawing is to be regarded as more or less in the nature of a diagram and is presented for the purpose of illustrating the invention only.

The present invention will now be described in connection with a specific device which can be used to manufacture a product according to the invention. It is clear that the various principles set out below can be applied to other types of equipment.

When the term treated paper is used in the following, it means paper produced by the method described in this specification.

The following explanation is given in connection with the accompanying drawing, which shows the various devices used to make this new straw paper. At the beginning of the process, the straw used to make the new product must first be cut into pieces of suitable length. It is desirable that the straw be cut so that most of the pieces are between 2.5 and 7.6 cm in length. The pieces should preferably be cut 4 5 G 9 9 8 so that their length is fairly uniform, in order to facilitate their handling.

Cut straw chips typically contain a lot of small loose fibers and dust particles as well as seeds and mold. These contaminants must be removed. The initial cleaning can be performed by passing the shredder through a vortex separator, which removes dust and loose fibers. This delivery is followed by mechanical rolling, i.e. compression, to crush the straw and partially separate the fiber from each other. Rolling and pressing promotes the penetration of cooking liquid at a later stage in the process.

As shown in the drawing, the shredded and cleaned straw is conveyed to a solvent, i.e. a "digester", generally designated 10, by a conveyor 11. The straw is dispensed into the digester by a dispensing system 12. Excess straw is conveyed away by another conveyor 13. and the dry matter content must be fairly uniform. Wet washing can be used to harmonize the moisture content. Cutting, cleaning and moisture setting are explained above as separate steps. However, all three steps can be performed simultaneously in the pulper by means known in the art.

The straw shredder, which is now clean, uniform in moisture and cut, is typically sprayed with a metered amount of cooking liquid in a stirrer 14. In a stirrer, the cooking chemicals are thoroughly mixed with the straw. The cooking liquid usually contains sodium hydroxide and sodium sulfide. When only the former is used, the process is said to be a sood process, and when the latter is also used, the process is said to be a sulfate process. Which of these processes is used is usually determined by the availability of chemicals. Cooking liquid recipes have long been known. The sulfate process is likely to be more advantageous unless the pulp is bleached. When aiming for strong paper, it is not usually required to be whiteness.

The chemicals are thoroughly mixed with the straw, and the straw is forced into the compactor 15 and from there with a spiral feeder into the pressure cookers 16 and 17 · In the cookers, the mixture of straw and chemicals is boiled with direct steam. There are usually several of these tubes in series, although for clarity only two are shown in the drawing. In the horizontal tubes of the digester, the consistency of the mixture is about 10-12% straw.

c SG998

At the outlet end of the last digester tube, the mixture of straw and liquid is suddenly forced into the tank 20, whereby the "defibering" of the straw takes place. This sudden release of straw into the tank is called a butt and its job is to break up the straw pieces into fibers. The fiber length is preferably about 0.70-4.00 mm. Thus, the butt continues the work that has begun in the digester. The straw is now ready for grinding and mixing, except that it contains cooking chemicals that need to be thoroughly removed. The removal of chemicals can be accomplished in a scrubber by adding a substantial amount of pure water to the mixture of straw and chemicals to a consistency of about 3.5% - In this consistency, the chemicals are washed away from the straw mass, typically with multi-stage vacuum filters and centrifugal cleaners. When the purification is completed, the water is squeezed out of the pulp so that the consistency becomes about 12%.

The pulp is then ground and mixed with other pulp, such as softwood pulp, in a mixer 21. At the same time, additives such as resin glue can be added to it when the end use of the paper so requires. After mixing, these different ingredients are thoroughly dispersed in the pulp slurry, which consists mainly of cellulose fibers released into natural cellulosic pulp. The consistency of the pulp slurry is about 0.2-1.4% and it is at this consistency that the pulp slurry is fed to the headbox 23 and the web wire 24 passing therefrom.

The drawing shows the suction box 25, the register rollers 26, the felting roller 27, the tensioning roller 28 and four idler rollers, all of which are marked with the number 29. These members together with the headbox and the flat wire form the wet end of the device.

On the wire, the pulp slurry forms a wet web when water is removed from it. Suction is applied to the web from a device 25 which sucks water from the web as it travels with the wire. The surface tension of the water absorbed from the web, the natural bonding of the fibers to each other, and the bonding caused by the additives all together at this stage of manufacture initiate the actual formation of the paper web by solidifying the fiber structure.

The web is further solidified in a press section of a paper machine, generally designated 30. The press section consists of a plurality of drying cylinders 31 over which the web W is passed. The drying cylinders are associated with an upper blanket 32 and a lower blanket 33 with different tensioning and guide rollers for each felt, i.e. the fabric. The purpose of the blankets is to hold the web against the cylinders. Due to the fact that the straw webs have quite a lot of zero mass and broken fibers, the felts must be of the open type with a high porosity. They must also be equipped with some kind of device for continuous cleaning to prevent the blankets from clogging and thus slow down the drainage of water from the web. Press rolls can also be used to squeeze water from the web and help solidify the web in the press section of the paper machine.

The ratio of water to fibrous material in the web as it leaves the wire is approximately 4: 1. The moisture content must be reduced from this before the next main step of solidifying the web is performed. This next step is the filling of the fibers of the breast and must be carried out with a moisture content of the web of approximately 30-50% by weight. SL The most suitable moisture content is considered to be about 37% ·

The solidification of the web by pushing the fibers is carried out under the action of forces which are generally applied to the web parallel to its surfaces, while forces perpendicular to the surface of the web are also acting. The result is that the private fibers constrict and curl together, bending twice in the direction of the web surfaces and completely between the web surfaces.

This step is best understood by explaining a device that can be used to effect the pushing of the private fibers of the web. Generally speaking, the device most suitably used for this purpose comprises a soft-surfaced roll or belt which is forced against a hard, slippery surface. The soft surface is made to resilient when it is hard against the surface. When the straw fiber web is in the nip formed by the two surfaces, this resilience causes the different fibers of the web to move generally randomly in the space between the surfaces of the web. More specifically, the device includes a thick elastomeric belt 40 that passes over three idler rolls 41, 42 and 43. The idler rollers hold this belt against the large drum 44 on a portion of the drum circumference. The function of the rod 45 is to press the belt against the surface of the drum to form a local nip in the axial direction over the surface of the drum. The extent to which the belt is wrapped around the drum is adjustable, as is the compression pressure of the nip bar. Various layout devices are not shown as they are already known. As the curvature of the belt 40 changes direction as the belt passes over the nip bar 45, the drum-side surface of the thick belt shortens, and thus moves more slowly than the surface of the drum.

This difference in surface speeds causes the fibers of the web to compress, while the nip bar applies sufficient pressure to the web to prevent it from buckling as a whole.

The belt is not operated independently by means of its own support rollers, but instead passes through its contact with a drum which is driven by a drive device not shown in the drawing. The length of the belt arc must therefore be large enough to provide traction on the belt. Since the amount of fiberization depends on the length of the belt contact arc, i.e. the coverage length, as one important parameter, the arc must be long enough to achieve the desired results.

Alternatively, the device may consist of a pair of rollers, one roll having an elastomeric surface and the other roll having a hard surface. The hard-surfaced roll is forced-operated, while the elastomer-surfaced roller is braked. This fit provides the necessary resilience of the elastomer over the entire width of the hard surface, and the pressure that forces the two rollers into contact with each other prevents the web from buckling. Both in this device and in the device described above, the web must be introduced from the press section into the press nip of the tamping device by tightening.

It should be remembered that straw pulp and other types or types of pulps must be well mixed together in order for softwood fibers, etc., to promote interfiber bonding, which is enhanced by web tamping, i.e. mechanical solidification.

When it is desired to produce paper with a heavy basis weight p (basis weight over 147 g / m 2), the treatment according to the present invention makes it possible to produce heavier paper than could be produced with a paper machine of the same capacity.

This is because solidifying the web in the tamp nip increases the weight of the paper by about 10% at the dry end of the machine. Thus, a smaller amount of solids can be used in the wet pulp slurry applied to the wire to achieve the same basis weight at the dry end of the machine 2. For example, to make 180 g / m paper, only 164 g / m need to be run on the wire. The net effect is that the present invention increases the production capacity of the paper machine by acting in the opposite direction to the slow drainage of the straw fibers from the straw fibers.

From the solidification nip, the paper is finally directed to a drying group where the drying and ironing of the web is performed. In some cases, it may be advantageous to use a smooth surface drying cylinder or calender roll if a hard or shiny surface is desired.

8 56998

As an illustrative experiment of the invention, sheets were prepared according to the invention and then compared. Unbleached straw pulp was used in combination with long-fiber, unbleached sulphate wood pulp. The Freeness of straw pulp was 74 seconds (Williams) and the Freeness of wood pulp was 29 seconds (Williams). The wire speed was 7.5 m / min and a vacuum of 25.4 cm Hg was used at the wet end. The sheets were placed in a mechanical hardener at 37% humidity and thinned so that the length of the sheet was reduced by about 12%.

The sheets were run at varying ratios of straw pulp to wood pulp, and the sheets were determined for quantities such as TEA (tensile energy absorption), elongation, edge tear resistance, and tensile strength. The treated papers were compared to a standard type of untreated high quality multipack paper made from 100% pine sulfate distillate. The experimental results showed that the treated paper with up to as much as 80% straw pulp had a higher edge tear resistance, a higher TEA and a higher% elongation. However, the final tensile strength of the straw paper was somewhat lower. Paper made from 100% straw pulp had a higher TEA after treatment than a standard multiple sheet, and was competitive in tear resistance and elongation. Comparative results. 2 are shown in Table I. All figures are reduced to 100 g / m 2 for basis of comparison.

Table I

% Strain Tensile strength% TEA 2 Edge end (kg / 15 mm) Elongation (cm kg / 100 cin) depth resistance, g 30 2.25 9.6 10.4 6855 40 4.20 14.5 26.3 4086 50 3, 64 11.9 20.5 3405 60 3.42 10.1 16.5 3587 70 2.95 7.9 11.7 3223 80 3.18 8.8 13.8 3677 90 4.80 11.3 24, 8,225,100 4.04 9.8 19.6 1725

Reference 5.23 2.4 6.5 3360 paper

The invention has been described above with reference to a specific device and certain specific method steps; however, it should be noted that a variety of changes can be made to both of these. For example, the private features of the invention may be utilized independently, and in place of various method steps

Claims (4)

9. G 9 9 G may use their equivalents within the scope of the invention as defined in the claims. Straw paper containing straw fibers and softwood fibers, suitable for use as high-strength packaging paper and for the production of high-strength, multi-ply paper sacks, in which most of the straw fibers are 0.70 to .00 mm in length, the straw fibers being arbitrarily and substantially uniformly blended that it contains about 50 to 80% by weight of straw fibers and the remaining softwood fibers, that it has a basis weight of more than 90 g / m 2 and that substantially all of its fibers are locally curled and intertwined so that the straw paper has a much greater permanent extensibility as untreated on the same paper and that it has approximately the same or higher tensile energy absorption and edge-end resistance as packaging paper of the same weight made from 100% sulphate softwood pulp. Straw paper according to Claim 1, characterized in. 2 that at a basis weight of 100 g / m the percentage elongation is 2 about 7.9 to 11.9, the tensile energy absorption is about 11.7 to 20.5 cm kg / 100 cm and the edge tear resistance is about 3223 to 3677 g · A method of making straw paper according to claim 1, wherein the cut straw is fed to a digester, the digestion solution is dispensed into the straw, the straw solution is boiled under pressure and in the presence of superheated steam, the straw is pushed, the waste solution is removed, the pulp is mixed conveyed by the web under suction, characterized in that the pulp contains about 50-8% by weight of straw with the rest being softwood fiber, that the surface weight of the paper on the wire 2 is at least 90 g / m, that the web is dried to a moisture content of about 30-50% by weight, that the web is pressed by passing a partially dry web through a compression nip so that the fibers of the web are compressed in the plane of the web surface to increase the density of the web to a value higher than before the compression of the fibers, the compressive compression of the fibers being performed by forces generally acting in parallel with the web surfaces while acting on other forces perpendicular to the web surface, causing the individual fibers to constrict, curl and bend over each other in a direction parallel to the web surfaces and completely inside the web surfaces, after which the web is transferred to drying rollers for complete drying . A method according to claim 3, characterized in that the pressing step increases the density of the web to approximately 10% higher compared to the space before the pressing step, that the dried straw paper has a significantly higher permanent elongation than the untreated paper web and that the straw paper has a surface weight of 100 g / m has a percentage elongation between 7.9 and 11.9 »tensile energy absorption value between 11.7 and 20.5 cm kg / 100 cm and an edge tear depth between 3223 and 3677 g.