BG63849B1 - Method for the production of kraft paper and bag with ventilation propeties made by the said method - Google Patents

Abstract

The method and the bag find broad application in civil engineering for filling of bags with cement and other bulk materials. They improve the characteristics of extension and porosity, and reduced production costs. The method for making kraft paper weighing from 50 to 140 g/m2 and absorption index of energy of extension of 2.3 to 3.5 J/g in porosity of Gurley less than 7 s, includes steps of substrating sulphate pulp only of highly consistent refining or combined effect of consistent refining and low consistence splitting. Then acceleration agent is added, in particular filled polymer such as starch, to the treated material. This addition is made before the material is fed to the paper machine. The high consistence refining is effected by maintaining energy supply of no less than 150 kWh per ton of paper, calculated for 100% dry paper. The acceleration agent is added to the treated material in two or more steps, and in the first and second step no less than 5 kg have to be added per ton dry paper. 20 claims, 2 figures

Description

(54) METHOD FOR THE PRODUCTION OF KRAFTHART AND THE BAG WITH VALVE PROPERTIES PRODUCED BY THE METHOD

Technical field

The invention relates to a method for producing kraft paper and a sack produced by the method which are used in the construction of cement sacks and other materials.

BACKGROUND OF THE INVENTION

Kraft paper production methods are known in which the pulp intended for the manufacture of kraft paper is subjected to a preliminary first fiber treatment in order to optimize the performance of the paper. In this type of treatment, energy is supplied to the fibers when the fiber suspension has a high consistency, totaling more than 15% by weight. This process is highly consistent refining - HC-refining. Thereafter, a second burst is performed with energy delivered at a low fiber consistency of about 4% by weight. This process is called low consistency breakdown - LC breakdown. The energy supplied in connection therewith is at least 100 kWh per tonne of paper. HC-refining is an operation that ensures the blending of the fibers into one another and the microcompression of the fibers, which imparts good fiber-elasticity properties. LC-breaking provides fragmentation of the fiber wall, improving its tensile strength.

In order to improve the tensile strength, starch is added to the starting material resulting from the fracture before it is fed into the paper machine as a reinforcing agent. The total amount of amplifying agent fed is up to about 6 kg per tonne of paper in order to maintain satisfactory porosity in the finished product.

Closest to the proposed method is the method of producing paper for bags with valve properties, such as cement bags described in US 4279694. It produces kraft paper with a weight of 50 to 140 g / m ² and an absorption index of tensile energy 2.3 to 3.5 J / g with a Gurley porosity of less than 7 s. The method involves the steps of subjecting the sulphate pulp to HC refining alone or to the combined effect of consistent refining and LC digestion. A reinforcing agent, in particular a filled polymer such as starch, is then added to the material to be treated. This addition occurs before the material is fed to the paper machine.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method for producing kraft paper with combined indices of absorption energy index of tensile and porosity, reducing production costs and reducing environmental pollution.

The task also involves creating a bag with valve properties that has good air permeability so that no perforations are required. This means fewer operations to produce the bag itself and a better working environment for the bag to fill and process.

The problem was solved by a method for producing kraft paper with a weight of 50 to 140 g / m ² and an absorption energy index of tensile strength of 2.3 to 3.5 J / g with a Gurley porosity of less than 7 s, -specially paper for bags with valve properties, such as cement bags, which method involves the steps of subjecting the sulphate pulp to HC refining alone or to the combined effect of consistent refining and LC-breaking. A reinforcing agent, in particular a filled polymer such as starch, is then added to the material to be treated. This addition occurs before the material is fed to the paper machine. According to the invention, high consistent refining is effected by maintaining an energy supply of not less than 150 kWh per tonne of paper calculated for 100% dry paper. Said enhancer is added to the material to be treated in two or more steps, adding not less than 5 kg in the first and second steps, per tonne of 100% dry paper.

According to a preferred embodiment of the method, the first addition of the enhancing agent is carried out in the machine chamber of the paper machine.

The second addition of the booster is carried out in the mixing pump of the paper machine, and in particular in its suction portion.

High consistency refining is carried out at a fiber suspension consistency of more than 15 to 40% by weight.

High consistency refining is accomplished by maintaining a consistency of 28 to 40% by weight.

The low consistency breakdown takes place at a fiber suspension consistency in the range of 2 to 10% by weight.

High refining consistency and low consistency breaking can be performed in a refiner.

Maintaining energy supply at low consistency breakdowns does not exceed 30 kWh.

High power refining energy is 200 to 300 kWh per ton of 100% dry paper.

The addition of said enhancer is a maximum of 20 kg per tonne of paper.

The enhancer added at the first stage is in the range of 5 to 8 kg per tonne of paper.

The enhancer added in the second step is in the range of 5 to 8 kg per tonne of paper.

In both steps, equal amounts of said enhancer agent may be added.

A maximum of 6 kg of said enhancing agent is added in the first stage and more than 6 kg in the second.

After drying the paper and leaving it on the paper machine, the sheet is pressed using a press bar.

The pressing rod moves faster or slower than the paper sheet.

The absorption index of the tensile energy is 3 J / g at a Gurley porosity of about 5 s.

The problem is also solved with a bag of valve properties composed of one or more layers of kraft paper, the bag being filled with smooth surfaces according to the invention.

Each of the layers of kraft paper has a maximum weight of 70 g / m ² .

The bag can be made from a single layer of kraft paper with a maximum weight of 120 g / m ² .

The advantages of the invention are that the LC breakdown is performed at a significantly lower power supply. The method produces kraft paper, which has good tensile strength and porosity, which allows it to be used for making single-layer bags. Crafted paper makes it possible to increase the flow rate of bag making machines as they are driven at a high speed. If the paper is of poor quality, it is pulled from one side, which impedes the machine's flow. In this case, the paper produced has good tensile strength with appropriate weight.

The bags made by the method have valve properties and good air permeability, without having to perform perforations on them.

The use of shallow pressing reduces the weight of manufactured paper used by the user, making the pressing itself redistributes the tension in the paper and makes it less stretchable.

The crafted paper can be colored or discolored, mainly made of sulphate pulp - kraft pulp, and in this context can also be unbleached sulphate pulp of softwood.

Description of the attached figures

Exemplary embodiments of the invention are shown in the accompanying drawings, of which:

Figure 1 is a flow chart with respect to the breaking and adding of an enhancing agent, as well as to the feeding of paper to a paper machine;

Figure 2 is a block diagram of a shallow compression device.

Examples of carrying out the invention

With arrow 1 in FIG. 1 shows the flow direction of the sulphate pulp in the HC tower 2, where the pulp is stored before being fed into the HC press 3 to adjust its density to the desired value. From the press 3, the pulp moves to the HC refiner 4 for high consistency purification. Then, through the buffer bath 5, the slurry slurry is transferred to a first set of HC refiners 6 in which the first LC shattering is performed. The second buffer tank 7 is followed by a new LC breakdown into a second set of LC refiners 8. The stay of the pulp in the buffer tanks 5 and 7 results in a smoothing of the fluctuations of the flow from the previous stages of the process.

The broken pulp leaves the second set of LC refiners and goes to a machine chamber 9 in which it is mixed with starch added in the direction of the arrow 10. Sulfuric acid is also added to the machine chamber 9 to adjust the pH according to the technological requirements. By means of pump 11, weighing box 12 and centrifugal cleaner 13, the pulp is passed to a mixing pump 14, into which the suction portion is further added with starch, indicated by arrow 15. By arrow 17, the mixture is fed to the paper machine, which is a machine. of the conventional type, for example for bags. The figure also shows the addition of conventional additives such as alum - arrow 19 and moisture resistant agent - arrow 20.

The shallow pressing apparatus shown in FIG. 2, includes a press roller 21 with a corresponding press rod 22. The machine also includes a number of drying cylinders 23 included in the drying section of the paper machine. Through them, the drying wire 24 and the paper strip 25 remain on them during their travel.

The press rod 22 moves independently with respect to the paper strip 25 at a speed different from that of the tape.

Paper is calibrated to the specified size in the shallow press.

The method according to the present invention is a method for producing kraft paper, comprising the steps of subjecting the sulfate or kraft pulp to HC refining alone or refining in combination with LC-breaking. If a low consistency breakdown is used, the energy supply shall be kept below 80 kWh per tonne of finished paper calculated on 100% dry paper and the addition of a reinforcing agent to the material processed in this connection in one or more individual points of the process. The total amount of enhancer to be added must be at least 80 kg per tonne of paper.

LC decomposition is performed at a significantly lower power supply, and the addition of the enhancing agent is in an amount substantially higher than known methods.

The process of the invention produces kraft paper with a weight of 50-140 g / m ² . How much the manufacturer will decide depends on the particular paper application.

Additional steps are included in the method, such as the use of micro-fastening equipment to increase the stretchability of the paper, resulting in more than 4% stretchability.

According to an alternative of the invention, the sulphate pulp, which forms the initial stage, is subjected only to HC refining, which is generally carried out at an energy supply in the range of 150 to 400 kWh per tonne of the final kraft paper, which is calculated at 100% dry paper. In particular, the preferred range is 200 to 300 kWh.

HC refining is generally carried out at a fiber suspension consistency in excess of 15% by weight. and generally at the upper limit of 40% by weight. The preferred consistency of the fiber suspension in relation to HC refining is from 28 to 40% by weight, most preferably 30-34% by weight.

According to one variant of the method, HC refining can be combined with LC-splitting, whereby the energy supply is 80 kWh per tonne of paper. Preferably, the LC breakdown can be achieved with a maximum power supply of 50, 30 or 20 kWh per tonne of finished paper. In this case, the LC breakdown was carried out at a fiber structure consistency of about 4% by weight.

The HC refining and LC shaking can be carried out independently by conventional grinding and refining devices such as refiners. In this embodiment of the method, operations are performed in a refiner.

By the method, a reinforcing agent is added in the specified minimum amount before the workpiece is fed into the paper machine. The term starch is widely interpreted to mean all perceived types or fractions of starch. The choice of this type of enhancing agent is made between the filled polymers in accordance with customary practice.

In principle, the addition of an enhancer can be accomplished at any point in the process from the time of the last refining or shaking until it is fed to the paper machine. The process may be performed in one or more steps, it being found that the steps are preferably two. The first addition is carried out in the machine chamber 9 and the second in the stirring pump 11, preferably in its suction portion. In this context, the function of the enhancing agent in the last step not only enhances the enhancement of the agent in question, but also serves to retain and finely distribute the material on the sheet.

The minimum amount of paper tonic enhancer is 8 kg and the maximum is 20 kg, calculated on the basis of starch with DS 0,035.

In one preferred embodiment, the amounts of booster added in the two steps are the same from 5 to 8 kg per tonne of paper.

Another embodiment of the method involves adding a maximum of 6 kg of enhancer agent for the first stage and more than 6 kg for the second, more precisely increasing the amount of agent for the second addition than for the first. The preferred amounts are 5-6 kg for the first addition and up to 8 kg for the second.

The porosity of the paper produced is indicated in Gurley units, defined as the time required for 100 ml of air to pass through a sample circle of 28.7 mm diameter.

The method combines the following combination of tensile energy absorption index value and porous tensile energy absorption index: 2.7-3.5 J / g and a Gurley porosity of less than 10 s, preferably 7 s. A Gurley value of 5 s produces paper with an energy absorption index for stretching 3.1 longitudinally and 3.0 transversely.

According to a preferred embodiment of the invention, the shallow-pressed rod is driven separately with respect to the paper roll, the rod being driven faster or slower than the paper roll.

Pressing the rod against the paper during shallow pressing affects the paper in caliber. In this case, the paper lies against a soft sublayer, which means that the caliber pressed against the paper serves to increase its thickness. This allows the caliber to redistribute the stresses in the paper and make it more unstretchable.

Crafted paper is characterized by the following physical characteristics:

Tensile energy absorption index 2.5-3.5 J / g with a Gurley porosity of 7 s. For unbleached paper, the absorption index of 5 is the tensile energy in the range of 2.7-3.5 J / g.

The most preferred values are the absorption energy index for stretching 2.7-3.5 J / g at a Gurley porosity of about 5 s.

The tensile energy absorption index is about 10% lower for bleached paper than for unbleached paper.

The fabricated bag is filled with one or more layers of kraft paper and is filled completely without perforations. Such a bag can hold about 501¾ cement. The bag has a weight not exceeding 70 g / m ² .

The bag can also be made of one layer of kraft paper, with a weight of no more than 120 g / m ² .

Three tests - Nos. 4, 5 and 6, and three comparisons - Nos. 1, 2 and 3, were performed by the method of the invention. the invention, and with the various addition of a boosting agent. Table 2 summarizes the test results. These characteristics were measured according to the methods on the right-hand column of the table.

Table 2 shows that the paper produced by the method has unique combinations of the Tensile Absorption Index and the Gurley value of the comparative examples. The reduction of the Gurley value from 18 s to 5 s at comparable or slightly increased values of the tensile energy absorption index is a step forward in the art.

Table 1

TecrN

NS-shelf (4) 2 3 4 5 e «Ner kWM % weight 220 30 230 30 230 X 240 X 220 31 210 X LOput BMI (6) 4 50 ze 55 4 0 4 0 4 0 4 kWM % ΓΟΓΛΟ βο L & pm6mmh> (7) 35 4 40 3.9 40 4 36 4 20 4 0 33 kWM % weight Mourning (9) kDospe 20 25 0 7.0 5 5 Starch (15) kgAome 4.0 43 43 5.0 7.0 «L.

Table 2

Characteristics A unit Test N Method 1 2 3 4 5 6 Weight loss d / t ² 60 70 80 60 66 70 ISO 536 Tensile index NnVg L 76 70 72 79 79 79 IS01924 / 2 T 60 60 60 66 64 60 Stretching % L 7.0 7.0 7.0 7.6 7.7 7.4 IS01924 / 2 T 8.2 7.8 7.4 8.0 7.5 8.4 Tensile energy absorption index. J / y L 3.0 2.9 2.9 3.3 3.1 3.0 IS01924 / 2 T 3.0 2.8 2.8 3.1 2.9 2.9 Break Index mlW / q L 11 13 13 13 13 14 ISO 1974 T 12 13 14 14 13 13 Cobb 60S g / m ² TS 30 29 29 29 30 29 ISO 535 Moisture content * 7.0 7.0 7.0 7.0 7.0 7.0 7.0 ISO 287 Gurley value S 20 16 18 5.7 4.8 4.7 ISO 5636/5 Static coefficient. on friction WS 0.6 0.7 0.7 0.6 0.7 0.6 Tappl T 815

L = Machine direction; T = Transverse direction; TS = TopHa side; WS = Rod side

Conditioning and testing atmosphere 50% RH, 23 ° C

Claims (20)

Claims 1. A method for producing kraft paper having a weight of 50 to 140 g / w ² and an absorption energy index of tensile strength of 2.3 to 3.5 J / g for a Gurley porosity of less than 7 s, in particular 30 paper for bags with valve properties, such as cement bags, which method involves the steps of subjecting the sulphate pulp to only high-grade refining - HC-refining - or to the combined effect of consistent refining, and 3 low consistency breakdown - LC breakdown - and the addition of a reinforcing agent, in particular a filled polymer such as starch, to the material to be processed, before the material is fed to the paper machine, characterized in that high consistent refining is effected by maintaining energy supply of not less than 150 kWh per tonne of paper, calculated on 100% dry paper, and said enhancing agent being added to the material to be processed in two or more stages, with no more than one step in the first and second ^ 5 steps. less than 5 kg, he believes o tonne 100% dry paper. 2. The method of claim 1, wherein the first addition of said The 50th enhancing agent is carried out in the machine chamber (9) of the paper machine. Method according to claims 1 and 2, characterized in that the second addition of said amplifying agent is carried out in a mixing pump (14) of the paper machine and, in particular, in its suction portion. A method according to any one of the preceding claims, characterized in that the high consistency refining is carried out at a fiber suspension consistency of more than 15 to 40% by weight. A method according to claim 4, characterized in that the high consistent refining is carried out by maintaining a consistency of 28 to 40% by weight. Method according to any one of the preceding claims, characterized in that the low consistency breakdown is carried out at a fiber suspension consistency in the range of 2 to 10% by weight. Method according to any one of the preceding claims, characterized in that the performance of the high consistency refining and the low consistency breaking is carried out in a refiner (6, 8). A method according to any one of the preceding claims, characterized in that the maintenance of the energy supply at the low consistency breakdown does not exceed 30 kWh. Method according to any one of the preceding claims, characterized in that the energy supply at high refining consistency is from 200 to 300 kWh per tonne of 100% dry paper. A method according to any one of the preceding claims, characterized in that the addition of said enhancer is a maximum of 20 kg per tonne of paper. Method according to any one of the preceding claims, characterized in that the amplifying agent added in the first stage is from 5 to 8 kg per tonne of paper. Method according to any one of the preceding claims, characterized in that the enhancer added in the second step is from 5 to 8 kg per tonne of paper. A method according to any one of the preceding claims, characterized in that equal amounts by weight of said enhancing agent are added in the two steps. A method according to claims 1 to 12, characterized in that a maximum of 6 kg of said enhancing agent is added in the first step and more than 6 kg in the second step. A method according to any one of the preceding claims, characterized in that after drying the paper and leaving it on the paper machine, the sheet is pressed by means of a pressing rod. 5 A method according to claim 15, characterized in that the pressing rod moves faster or slower than the paper sheet. A method according to any one of the preceding claims, characterized in that The 10 tensile energy index is 3 J / g at a Gurley porosity of about 5 s. A bag with valve properties according to claims 1 to 17, comprising one or more layers of kraft paper, characterized in that 15 that it is filled with smooth surfaces. A bag according to claim 18, characterized in that each of the layers of kraft paper has a maximum weight of 70 g / m ² . 20. Bag according to claim 19, characterized in that it is made of a single layer of kraft paper with a maximum weight of 120 g / m ² . Attachment: 2 figures Publication of the Patent Office of the Republic of Bulgaria 1113 Sofia, ”Dr.” Blvd. M. Dimitrov ”52-B