Bag paper and method for making bag paper

IPC classes for russian patent Bag paper and method for making bag paper (RU 2345188):

D21H27/10 - Packing paper (packaging materials of special type or form B65D0065380000)

D21H27 - Special paper not otherwise provided for, e.g. made by multi-step processes

D21H21/10 - Retention agents or drainage improvers

D21H17/45 - Nitrogen-containing groups

D21F11 - Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibreboard production, on paper-making machines

Another patents in same IPC classes:

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Fibrous filtering material / 2331726

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Water-soluble polymer dispersion and method of obtaining water-soluble polimer dispersion / 2336281

Invention relates to water-soluble polymer dispersion and method of its obtaining, its application, method of paper production from water suspension. Dispersion includes following components: dispersed polymer, consisting of water-soluble monomer A and water-soluble cationic monomer B, at least one polymeric stabiliser C in amount approximately from 0.05 to approximately 10% wt and co-stabiliser D cationic polyelectrolyte in amount approximately from 1 to approximately 25% wt relative to total dispersion weight. In polymer dispersion there are no essential amounts of salts of inorganic multivalent anion. Dispersed polymer consists of: a) approximately from 50 to approximately 99% molar monomer A, which represents compound of general formula I , where R₁=H or methyl, R₂=H, methyl, ethyl, isopropyl, metiloil, hydroxyethyl or 2-hydroxypropyl, and b) approximately from 1 to approximately 50% molar monomer B, representing compound of general formula II , where R₁ = H or methyl, R₃, R₄, R₅ - independently on each other H, alkyl(C₁-C₈), benzyl or alkylbenzyl , A=NH, O, B=alkyl(C₁-C₁₀) or hydroxyalkyl(C₁-C₁₀), X^-=anionic counter-ion. Polymer stabiliser C represents copolymer, which contains at least, one monomer, selected from group, including diallyldimethylammonium chloride (DADMAC), vinylpyridonium chloride, N-vinylimidazoline chloride, vinylbenzyltrimethylammonium chloride and their mixture, and/or compound of general formula II and one of compounds of general formula III, IV and V. Compound of general formula III represents polyether with one functional end allyl group , where R₁=H or methyl, R₆ = independently on each other H, methyl or ethyl, n=1 or 3, x = from 5 to 50 and y = from 5 to 50. Compound of general formula IV is macroinitiator , where R₁=H or methyl, R₆ = independently on each other H, methyl or ethyl, R₇, R₈ = independently on each other alkyl, cyanoalkyl, carbalcoxyalkyl, (C₁-C₈), n=1 or 3 and x = from 5 to 100. Compound of general formula V represents polyether with one functional end vinyl group , where R₁=H or methyl, R₆=H, methyl or ethyl, n = 1 or 3 and x = from 5 to 50. Weight ratio of stabilisers and co-stabilisers to dispersed polymer is C+D/ A+B<1. Method of obtaining dispersion is in polymerisation of said above components in one stage. Dispersion is used as additive for improvement of retention in production of paper, as thickener and/or as additive for improvement of dirt-repellent properties. Method of paper production from water suspension, which contains cellulose fibres and non-obligatory fillers, lies in addition to suspension of said above water-soluble polymer dispersion. Then forming is carried out and suspension is dried on net.

FIELD: textiles, paper.

SUBSTANCE: method refers to pulp-and-paper industry, specifically to method for making bag paper, as well as to bag paper with improved service properties. Method for making bag paper involves pulp beating stage at fibre concentration 28-40% and thereafter at fibre concentration 3-6%. It is followed by two-staged addition of reinforcing and at once flocculating agent to pulp. Then paper web is casted and dried. Further beating stage at fibre concentration 3-6% requires power consumption within 20-60 kWt/h per paper ton. The second stage of addition is followed with the third stage of addition implying flocculating agent preceding headbox. Herewith at the first stage, reinforcing and at once flocculating agent is cationic starch of fractional substitutionality 0.040-0.150 in amount 0.1-1.2% of absolutely dry fibre weight, or polyacrylamide in amount 0.1-0.5% of absolutely dry fibre weight. Specified agent is added to pulp, 5-120 minutes prior to paper web casting. At the second stage reinforcing and at once flocculating agent is added in amount 0.005-0.400% of absolutely dry fibre weight. Specified agent is added to pulp, 20-120 seconds prior to paper web casting. At the third stage flocculating agent is anionic montmorillonite microparticle dispersion. Specified agent is added to pulp in amount 0.05-0.50 % of absolutely dry fibre weight. Bag paper is made under the offered method.

EFFECT: lower consumption of reinforcing and flocculating polymers, improved pulp water yield on papermaking machine grid and enhanced consumer paper properties including paper air permeability.

4 cl, 1 tbl, 3 ex

The invention relates to the pulp and paper industry, in particular, to methods for producing paper sack, and the sack paper with improved performance characteristics.

Sack paper must have certain properties associated with its contact with various Packed in bag materials and the need to ensure strength, water absorption and other characteristics of the paper, providing good performance properties.

There is a method of making paper or paperboard comprising preparing a pulp suspension, flocculation of the suspension, draining the suspension on the grid casting sheet and subsequent drying (patent RU №2246566).

The disadvantage of this method and made of paper and cardboard is the insufficient mechanical strength of paper and paperboard using them to manufacture the bags.

The closest analogue is the method of manufacture of Kraft paper, including the processing of pulp by grinding at a concentration of mass 28-40% and subsequent grinding at a concentration of mass 3-6%, introduction to fiber strengthening and at the same time flocculating substances in two stages, the first of which is realized by the introduction of the specified substance in the machine pool, and the second carried out by the introduction of this substance into the mixing the pump, subsequent outflow of the paper web and drying. In accordance with this method are made sack paper (patent RU №2208079).

In the patent RU No. 2208079 high porosity is achieved primarily by reducing the intensity of grinding at the stage of low concentration. This leads to reduced mechanical strength and TEA (energy consumed when the elongation of the sample), which is particularly unacceptable in the manufacture of paper of a small mass. In addition, in this patent the second stage provides too much flocculation and hardening of the polymer, and the absence of the third stage eliminates the possibility macroglobulinaemia mass with good yield and retention.

Of hardening substances in the descriptive part of the patent RU №2208079 negotiated only starch with a degree of substitution 0,035, but not even specified what type of substituent selected cationic or anionic, and in the formula as a hardening substance shows only the word "starch". At the same time indicated a preferential point of the first and second dosages: machine pool and directly into the mixing pump.

The authors of the patent lead experimental comparative data in the table, which in General follows that if you follow the patent, you can get a sack paper with high strength and very high air what pronitsaemosti, dramatically reducing energy consumption during grinding low concentrations, but increased about 2 times the consumption of starch in the machine pool, and mixing pump.

High porosity allows not only to reduce the proportion of fine fraction of fibers, clogging of the pore space in the formation, but also to maintain boyhoodparadise fibers longer. This long staple laboratoty the paper weight is less sensitive to flocculation polymer flocculants than the mass, containing a lot of detail, and, on the other hand, it forms less durable canvas with worse lumen and, accordingly, with large pores. Therefore, 5-7 kg/t of starch in the machine pool is a compensation for the loss of strength due to "disable" dilute grinding. Starch is also supplied to the mixing pump, performs the role of a "wiper"that collect free coins on large fibers.

It is clear that the use of grinding low concentration is not only increasing the mechanical strength of the paper sack. Some shortening of the fibers leads to increased small-scale uniformity of the paper web by reducing the ability of long fibers spontaneously form large clumps-flocculi. It is also clear that the ability dlinnovoloknistoy mass to spontaneous flocculation is which is the journey towards weight paper. Therefore, the actual failure from grinding at low concentration is a big disadvantage of this patent. In addition, in this patent there are too large costs of hardening substances. High consumption of starch greatly increases the cost of the finished product. Moreover, if it is anionic starch, it is necessary to introduce aluminum sulfate and lead the process of paper production in weakly acidic medium at a pH not higher than 5,0 and to impart hydrophobicity to use the agents for acidic sizing. If this is not the starch, and, for example, cationic polyacrylamide, which, as you know, refers to the widespread hardening substance, even at the lowest doses according to the patent the total flow of the hardening agent should be 1% of the mass of absolutely dry matter. This is a very expensive option, not to mention the fact that he almost never acceptable.

From the point of view of the authors to obtain a strong highly porous paper or paperboard more promising solution, which combines three factors impact on pulp: strengthening flocculation polymer used in the first stage, dosing, and strengths flocculation polymer used in the second stage, dispensing, and anionic dispersion of microparticles in the third stage.

However, despite the claims of the authors of the patent RU 2208079, us is tableno experimentally, when using this technology, the choice of hardening polymer for dosing, for example, in machine pool in the first stage is important both from the point of view of the cost of the finished product, and from the point of view of its consumer properties. Hardening the polymer has high molecular weight and accordingly the viscosity. And in the second stage of dispensing unlike patent RU 2208079 we used the polymer, providing additional flocculation.

The authors found that if you enter in a dense fibrous mass of circulating water to remove the fibrous fraction, the subsequent processing of the received paper microparticles allows you to more stably obtain the necessary consumer properties, including permeability. It was also found that for a fast exit on the equilibrium technology parameters in the second stage it is better to use linear type polymer of polyacrylamide.

This technical result is achieved in that in the method of manufacturing a paper sack, including the processing of pulp by grinding at a concentration of mass 28-40% and subsequent grinding at a concentration of mass 3-6%, introduction to fiber strengthening and at the same time flocculating substances in two stages, the first of which is realized by the introduction of this ve is esta machine in the pool, and the second carried out by the introduction of this substance into the mixing pump, the subsequent outflow of the paper web and drying, according to the invention subsequent grinding at a concentration of 3-6% is carried out at a consumption average of 20-60 kW/h per ton of paper, and after the second stage of the introduction of carry out the third stage of the introduction, which is carried out by introducing one flocculating substances before discharge box, with the first stage as a hardening and at the same time flocculating agent used cationic starch with a degree of substitution 0,040-0,150 in an amount of 0.1 to 1.2% by weight of the absolutely dry fiber or polyacrylamide in an amount of 0.1 to 0.5% from the mass of absolutely dry fiber and a specified substance is injected into the fibre mass for 5-120mm minutes before low tide of the paper web, and the second stage is injected hardening and simultaneously flocculation agent in the amount of 0.005-0,400% by weight of the absolutely dry fiber and a specified substance is injected into the fibre mass for 20-120 seconds before the tint of the paper web, and in the third stage as a flocculating agent used anionic dispersion of microparticles of montmorillonite clay and a specified substance is injected into the fibre mass in the amount of from 0.05 to 0.50% by weight of the absolutely dry fiber.

Before the second stage in the fibrous weight enter the circulating water, which has preliminarily the removed fibrous fraction.

As a hardening and simultaneously flocculation substance in the second stage of the introduction of the specified substance use cationic or anionic polyacrylamide.

Sack paper produced according to this method.

The invention is illustrated by the following examples.

Example 1.

Sack paper is produced as follows: process a fibrous mass by grinding in a mill high concentration when the concentration of its 28%, then perform the subsequent grinding disk mill at a concentration of mass 4% and the energy consumption of 20 kWh per tonne of paper. Then in the machine pool in the fibrous mass is injected hardening and simultaneously flocculation substance, which is used as a cationic starch with a degree of substitution 0,040 in the amount of 1.2% by weight of absolutely dry fiber 5 minutes before low tide of the paper web. This is the first stage of introduction of the specified substances. Then carry out the second stage of the introduction of the specified substance in the mixing pump. Cationic starch is taken with a degree of substitution of 0.05 in the amount of 0.2% by weight of absolutely dry fiber for 30 seconds before the tint of the paper web. Then carry out the third stage injection, which is administered before discharge box flocculation substance - anionic dispersion of microparticles of montmorillonite clays is (bentonite) in the amount of 0.3% by weight of absolutely dry fiber. Then produce the sheen of the paper web and drying by conventional technology with getting paper sack.

Example 2.

The method is carried out analogously to example 1, but the grinding is subjected to a mass concentration of 40%, the subsequent grinding is carried out at concentrations of 3% and the power consumption at this stage 40 kW/h per ton of paper. In the first stage as a hardening and at the same time flocculating substances injected cationic polyacrylamide in an amount of 0.1% by weight of absolutely dry fiber 30 minutes before low tide of the paper web. In the second stage, introducing cationic polyacrylamide in the number 0,400% by weight of absolutely dry fiber for 120 seconds before the tint of the paper web, and in the third stage, introducing a dispersion of microparticles of montmorillonite clay (bentonite) in an amount of 0.05% by weight of absolutely dry fiber.

Example 3.

The method is carried out analogously to example 1, but the grinding is subjected to the mass concentration of 30%, the subsequent grinding is carried out at concentrations of 6% and a power consumption of 60 kWh per tonne of paper. In the first stage as a hardening and at the same time flocculating substances injected cationic starch with a degree of substitution 0,150 in the amount of 0.2% by weight of absolutely dry fiber 120 minutes to tint the paper web. Before the second stage in the fibrous mass is injected recycled water, from to the th pre-remove fibrous fraction. In the second stage, introducing anionic polyacrylamide in an amount of 0.005% by weight of absolutely dry fiber for 20 seconds before the tint of the paper web, and in the third stage, introducing a dispersion of microparticles of montmorillonite clay (bentonite) in the amount of 0.5% by weight of absolutely dry fiber.

Table
Technology parameters and properties of paper	The patent RU No. 2208079	1	2	3
1. The flow rate of hardening and flocculation agent in stage 1	0,65	1,2	0,1	0,2
2. The flow rate of hardening and flocculation agent in stage 2	0,5	0,4	0,4	0,005
3. Consumption of microparticles in stage 3	-	0,3	0,05	0,5
4. The energy consumption in grinding at low concentration, kWh/t	0	40	40	60
5. The concentration of circulating water %	0,015	0,02	0,021	0,001
6. Yield weight	25	18	20	15
Properties of paper
7. Paper weight, g/m²	60	60	60	60
8. Breathability in Garli,	the 4.7	4,5	4,3	4,2
9. The absorption of energy by spreading, TEA, j/g	3,0	3,2	3,1	3,3

The use of this invention allows to obtain the following positive results in the production of sack paper:

- lower consumption of hardening and flocculation of the polymer in the second stage;

the best yield of the mass on the grid paper machine due to the introduction of the third stage;

the best yield weight and air permeability of the paper due to the purification of the circulating water from suspended fibers.

1. A method of manufacturing a paper sack, including the processing of pulp by grinding at a concentration of mass 28-40% and subsequent grinding at a concentration of mass 3-6%, introduction to fiber strengthening and at the same time flocculating substances in two stages, the first of which is realized by the introduction of the specified substance in the machine pool, and the second carried out by the introduction of this substance into the mixing pump, the subsequent outflow of the paper web and e is about drying, characterized in that subsequent grinding at a concentration of 3-6% is carried out at a consumption average of 20-60 kW/h per ton of paper, and after the second stage of the introduction of carry out the third stage of the introduction, which is carried out by introducing one flocculating substances before discharge box, with the first stage as a hardening and at the same time flocculating agent used cationic starch with a degree of substitution 0,040-0,150 in an amount of 0.1 to 1.2% by weight of the absolutely dry fiber or polyacrylamide in an amount of 0.1 to 0.5% by weight of the absolutely dry fiber and a specified substance is injected into the fibre mass per min to 5-120mm the tint of the paper web, and the second stage is injected hardening and simultaneously flocculation agent in the amount of 0.005-0,400% by weight of the absolutely dry fiber and a specified substance is injected into the fibre mass for 20-120 seconds before the tint of the paper web, and in the third stage as a flocculating agent used anionic dispersion of microparticles of montmorillonite clay and a specified substance is injected into the fibre mass in the amount of from 0.05 to 0.50% by weight of the absolutely dry fiber.

2. The method according to claim 1, characterized in that before the second stage in the fibrous mass is injected recycled water, from which previously removed fibrous fraction.

3. The method according to claim 1, characterized in that as UPRONA the future and at the same time flocculating substance in the second stage of the introduction of the specified substance use cationic or anionic polyacrylamide.

4. Sack paper, manufactured according to the method according to any one of claims 1 to 3.