JPS6017192A - Dehydration speed increasing method of pulp liquid - Google Patents

Abstract

A process for increasing rate of dewatering in the manufacture of paper from an aqueous furnish which comprises at least 40% by weight of mechanical wood pulp, thermomechanical wood pulp, or mixtures thereof, by addition thereto of an aluminum salt, e.g., alum, and a water-soluble copolymer containing from about 2 to about 30 mole percent repeating units derived from 2-acrylamido-2-methylpropane sulfonic acid, from 0 to about 25 mole percent repeating unit derived from acrylic acid, and from about 45 to about 98 mole percent repeating units derived from acrylamide, while maintaining pH of the furnish in the range of from about 3.5 to about 6.5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to the use of fu
The present invention relates to a method for increasing the dewatering rate of pulp (rnish), in particular when the pulp component of the pulp liquor contains a high content of mechanical pulp and/or thermomechanical pulp.

In a common embodiment of papermaking, an aqueous suspension of Nosolde 8, i.e. 1.! of cellulose fibers obtained by pulping raw wood, is used. The Rude liquor is conveyed hydraulically and mechanically to a moving wire grid or screen to produce a wet web of cellulose fibers. This wet fibrous web is dewatered in a drainage stage on the screen and It is then subjected to further processing, drying, calendering, and any additional processing desired.

In a typical embodiment, the pulp liquor communicating with the wire base (wet web forming means) contains a number of additives. These additives may include processing aids to improve the operation of papermaking machinery systems and chemicals to improve the properties of the final paper product. Suitable process aids include retention aids to retain fillers in and on the web being formed and to reduce runoff of paper pulp fines from the Noyalde liquor during the dewatering step; and drainage aids to increase the rate of dewatering of the liquid on the web forming means. Other additives include forming aids, flocculants, defoamers, wet and dry strength aids, pitch control agents, slime inhibitors, crepe aids, etc., which are well known to those skilled in the art. It can be done.

Functional additives may include fillers, sizing aids, reinforcing additives, etc. as described above. Fillers may include brighteners, opacifiers and pigments. Sizing agents are used to obtain paper products that resist wetting by liquids such as ink and water, and pine and wax are typically used for this purpose.

Considering efficiency and ease of process, NO! It is desirable to add drainage aids to the Rude liquor to increase production capacity, ie, papermaking speed, in papermaking processes in systems where dewatering or drainage is a rate-limiting step in the process.

In papermaking systems, it is desirable to maximize drainage rates, but activity is reduced when used in newsprint pulp liquors made under conditions conventionally used for this purpose. Such additives include conventional drainage aids containing -COOE groups as anionic substituents, and copolymer additives containing -5O3H groups.

As used herein, the term 1 newsprint and liquid 1 refers to paper and cardboard, especially newsprint, raw 1-+ coated grade (co
ating raw 5tock grade) and fine paper grades
) of at least 40 wood pulps containing fine fibers and fillers, produced under acidic conditions and selected from the group consisting of mechanical wood pulps, thermomechanical wood pulps and mixtures thereof. Contains weight%! It has a rusty component and has a warm taste.

Therefore, there is an inherent need for improved drainage additives for newsprint pulp fluids that are characterized by stability and high activity.

Shitakatsu 1, low p 11 similar to newsprint and liquid liquid
It is one of the goals of the present invention to present a method of increasing the dewatering rate of newsprint pulp liquor under certain conditions.

The present invention provides: (α) Prior to the dehydration step, (1
) from about 0.5 to about 5% by weight aluminum salt, based on the weight of cellulose fibers in the pulp liquor;
) from about 0.1 to about 0.5% by weight of 2-acrylamide based on the weight of cellulose fibers in the pulp liquor;
from about 2 to about 25 mole percent of repeating units derived from 2-methylderonozinsulfonic acid, from 0 to about 25 mole percent of repeating units derived from acrylic acid, and from about 45 to about 98 mole percent of repeating units derived from acrylamide. (b) bring the pH of the liquid to a range of from about 3.5 to about 6.5 during step (α) and through the dehydration step; A wood selected from the group consisting of mechanical wood ! !, thermomechanical wood ! 5 and mixtures thereof, comprising a pulp component containing at least 40% by weight of wood sap. This invention relates to a method for increasing the dewatering rate when producing paper from.

In the context of the present invention, from about 2 to about 30 molar succent repeat units derived from 2-acrylamido-2-methylpropanesulfonic acid (hereinafter referred to as "AMps");
0 to about 25 mole percent repeating units derived from acrylic acid, and 7'c repeating units derived from acrylamide.
A water-soluble copolymer containing from about 45 to about 98 mole percent repeating units, in the form of an aluminum salt such as alum sulfate, aluminum chloride, or aluminum nitrate, is added in total from about 3.5 to 6.5 mole percent. After one use under conditions of low PLJ, J41 wood pulp containing at least 40% by weight of a wood pulp selected from the group consisting of mechanical wood pulp, thermomechanical wood pulp and mixtures thereof. It has ingredients! The fact that the dehydration rate of Rude's liquid had a remarkable effect on increasing the rate of dehydration was something that Saki should have expected and could not have predicted.

By the method of the present invention, high speed 6 degree drainage of newsprint liquids is achieved under highly acidic conditions where conventional anionic or cationic polymers are ineffective. As mentioned above, conventional drainage aids containing carboxylic acid groups (even those containing all sulfonic acid groups) are ineffective under these acidic conditions; does not create conditions for its effectiveness. AMPSM conjugates and copolymers have been described in the prior art, for example in West German Open
fftJn) f:NKlegungsschrift
) No. 2,248.752, the present invention contemplates that experience has shown that hard water/softwood kraft pulp is not effective as a drainage aid under low P11 conditions, along with alum. It was previously unknown that such additives could be used in newsprint-type pulp fluids. Observe the fact that most of the additives which have satisfactory efficacy in promoting drainage in neutral and alkaline pulp liquor media and in kraft pulps exhibit very poor performance in highly acidic newsprint pulp liquors. For example, it was truly unexpected that the method described in the present invention could be effectively used to achieve high water drainage.

The AMPS copolymer used in the present invention is AMpS
from about 2 to about 30 moles of repeating units derived from! - cents, 0 to about 2 repeating units derived from acrylic acid
5 mole percent and about 45 to about 98 moles of repeating units derived from acrylamide. The term AMPS used here is broadly 2-
It is also intended to refer to acrylamido-2-methylpropanesulfonic acid and any suitable salts thereof.

Suitable AMPS# shield conjugates include, for example, about 2 to about 20 molar f-cents of repeating units derived from AMPS and about 80 molar f-cents of repeating units derived from acrylamide.
Also included are those containing from about 98 mole percent.

As used herein, the term "acrylamide 9" is intended broadly to include acrylamide itself and acrylamide@conductors such as substituted acrylamides. Compositions of such copolymers are The addition of aluminum salts in weight percentages of this order advantageously lowers the pH of the pulp liquor to about 2.0 mm based on the weight of the cellulose fibers. is maintained in the range of about 4.1 to about 6.5 during the addition of W i and throughout the dehydration stage Wi of the pulp liquor.

In the process of the present invention, aluminum* is used as a co-source of polyvalent metal ions to enhance the effectiveness of the AMPS copolymer, and the specific amount of aluminum salt required in any particular system is A simple test without unsuitable experimentation, such as the Canadian Standard Reactor Water K (Ca
nadiansta3dardfrttengss
(CS p ) method or the Britt jar effluent measurement method (CS p ) method for the liquid to be treated.
drainagttdtttttrmination
) can be easily determined.

A preferred aluminum salt is aluminum sulfate (alum).

The AMPS/acrylamide copolymer described above is used with the addition of an aluminum salt to the pulp liquor in an amount of about 0.5 to about 2 weight percent, based on the weight of cellulose fibers in the pulp liquor. 4.8 to about 6
．． 5 is desirable to achieve the best performance of the drainage aid.

Among the broad embodiments of the invention, particularly preferred are AM
AMPS containing about 2 to about 30 mole percent repeating units derived from PS, about 5 to about 25 mole percent repeating units derived from acrylic acid, and about 45 to about 9 mole percent repeating units derived from acrylamide. It is a polymer. Such terpolymer systems ensure that the temperature of the Nocelde liquor is maintained in the range of about 20 to about 60° C. during the addition of the terpolymer/aluminum salt and throughout the dehydration step, as discussed in more detail below. It has been found that it particularly provides improved drainage characteristics when dripping. Most preferably, it has been found that this improved property is particularly improved at elevated temperatures in the range of about 40 to about 60°C.

The above terpolymer composition has a special effect when the pH of the pulp liquid is 3.

In papermaking systems using the preferred aluminium salt, sulfurized aluminum (alum), the amount of alum used for best drainage promotion by the terpolymer is 4'/4' the weight of cellulose fibers in the liquor. About 2 to about 4
The pH of the nosolde solution should be maintained in the range of about 4.5 to about 6.3 throughout the terpolymer/alum addition and dehydration steps. is desirable.

When a smaller amount of alum addition, for example in the range of about 0.5 to about 2 weight cents based on the weight of cellulose fibers in the pulp liquor, is most effective, The pH therein is desirably maintained in the range of about 4.5 to about 5.6 during the addition of the terpolymer/alum and throughout the dehydration step. These relationships may vary slightly depending on the type of pR, temperature conditions, and the presence or absence of a circulation path in the papermaking system.6 In practice, the optimal pR conditions can be determined by testing in an actual factory without conducting inappropriate experiments. can be determined accurately.

As indicated above, the method of the present invention is particularly effective when applied to newsprint-type pulp liquors where the pulp component is mechanical wood pulp and thermomechanical wood pulp. The method can be applied to the stone crushing machine Zurde to achieve special effects.

The most preferred copolymer is, for example, 0.33 MN at 25°C.
Standard Brookfield mucus (Standa
rd Brookfield visco-8zety)
has.

In a preferred embodiment, the present invention provides AMp S,
Instead of the alum component, it is also possible to use other ion sources, such as cationic metal (aluminum) sols that have the ability to bind sulfonic or carboxylic acid groups. Other aluminum salts that may be effective in combination with AMPS copolymers under low pH conditions include aluminum chloride and aluminum nitrate.

As already mentioned, AMpS copolymer/Miyorho is used to maintain a constant elevated temperature throughout the addition and dehydration steps. Heating the Luso liquid medium also causes
Presumably, more of the necessary cationic alumina complex is formed by converting the aluminum hydroxide groups to the At''-0-At type structure, which is formed at low pE and prevails at disordered feedstock temperatures. This improves the dehydration properties of Selde's liquid.

It is of utmost importance in the construction of newsprint to promote drainage or dewatering and to minimize any pitch deposition problems. These two challenges can be overcome by using an appropriate drainage aid that allows groundwood fine fibers to aggregate under the strongly acidic conditions characteristic of newsprint liquids and to retain pitch particles on the fibers. It can be reduced.

Typically, the newsprint pulp fluid is about 25% long fiber chemical pulp, such as bleached sulfite #7' pulp, or 7'C is bleached kraft iJI pulp and 75% high yield mechanical pulp, such as stone crushed wood pulp. (GF)'' or stone crushed wood pulp and thermomechanical pulp (TMP). In forming paper (wet web) on a commercial high speed paper machine,
Many of the fine fibers, consisting primarily of fine fragments of GJF' or TMP pulp components, pass through the paper machine wire, resulting in a characteristically low first pass retention in such systems, around 50
On the order of ~60%, such fine fibers are therefore depleted into the wet web forming part of the papermaking system by recycling the tray water. By this means, most of the fine fibers in the initial solution are ultimately retained in the paper layer after several circulations.

High speed paper machines are generally very sensitive to any changes in drainage rate. Agglomeration of fine fibers and pitch particles onto long fibers is extremely important as it minimizes pitch deposition problems and increases dewatering rates. High-quality paper(
Fine paper 1 grade, mildly acting drainage aids generally do not produce significantly beneficial results in newsprint pulp fluids. Such ineffectiveness is due to the fact that high-yield pulps have a large surface area (due to their fine fiber content) and the binding capacity of polymeric additives attached to the lignin-rich fiber surfaces of mechanical pulps is considerably reduced. This is probably because it is suppressed.

Characteristic properties of retention aids (as described in the above-mentioned West German publication specification (0)
No. 2,248,572) could not be transferred to a pulp liquor containing a high proportion of high-yield pulp. Accordingly, the present invention provides a pulp liquor treatment agent (9) which surprisingly and quite unexpectedly improves the dewatering rate of pulp liquors containing significant amounts of mechanical wood pulp and/or thermomechanical wood pulp. liquid additives) and represent considerable progress in the industry.

The following specific examples illustrate specific embodiments of the invention. These examples are presented for illustrative purposes only and are not to be understood as limiting the scope of the invention, except as provided in the claims. In all examples presented below, parts and cents are parts by weight and cents by weight, unless otherwise specified.

did. It is generally extremely difficult to accurately measure changes in the amount of drained liquid since 9-rude containing a high content of Ishikanki Zorup has the characteristic of slow drainage.

As previously indicated, the composition of a typical commercially available newsprint pulp liquor is approximately 75:1% by weight of ground wood and 25% by weight of long fiber chemical pulp. In the measurements carried out in the following examples, the pulp liquid contained side fiber components, that is, crushed wood and long fibers in a ratio of 50:50.
tl1%-cent. The long fiber pulp part of the pulp liquid consists of equally coarse parts of bleached soft wood kraft and bleached hard water kraft beaten to about 4500 SF. Is the ground wood pulp part of this pulp solution for Jitsun made from typical stone crushed wood? -Bowatgrs paper C
Company.

It is for newsprint manufactured by Calhoun, Tennesse l, pH 4,'l, and contains about 1% alum by weight, based on the weight of the fibers, the alum being:
To reduce pitch deposition in subsequent papermaking operations,
It is added during the production of groundwood pulp.

In each test described below, a 50:50 (by weight) 9-cent mixture of long fiber chemical pulp and ground wood pulp was diluted to a fiber a content of 0.5 percent, treated with alum addition, and diluted with sodium hydroxide. A solution is added to the Sölde liquor to adjust the p 11 f of the pulp liquor and carry out the method according to the invention.

A 0.1% solution of a specific polymer or copolymer or wastewater additive is added to the pulp liquid raw material prepared as described above, and the actual amount of the polymer is 0.025% based on the total fiber weight. Add at a level such that

The pulp liquid is then mixed by transferring it from one container to another and repeating the process six times. A 500d fraction of this treated pulp liquor is then transferred to a drain tube fitted with paper machine wire at the lower end. This pulp liquid is drained for 15 seconds, and the p liquid that has grown during the above period is quantified. A large increase in fF fluid volume in a run compared to a control pulp liquor containing no drainage aid indicates a significant improvement in dewatering or drainage during web formation.

In each experiment in the following examples, a blank test was conducted using a pulp liquid containing additives other than alum. An increase or decrease in the amount of P solution collected compared to that of the blank test indicates an increase or decrease in the drainage rate of Norde solution, respectively.

For comparison purposes, a typical cationic polyacrylic binder and a typical anionic polyacrylamide retention group/drainage aid 1 were evaluated when the method of the present invention was applied to newsprint paper making. A dilution was added for each drainage trial. These conventional cationic and anionic polyacrylamide additives had molecular weights ranging from 4 to 15X10'.

Example ■ Figure 1 shows the change in drainage volume, that is, the drainage volume with pulp liquor containing various drainage aids, when the amount of alum added to the pulp liquor was 3%, and with no drainage additives. FIG. 2 is a graph showing the amount of change compared to the value for J/Lude liquid (blank test) as a function of the pH of the pulp liquid, expressed as -. In FIG. 1, curve A is the drainage curve for the above-mentioned Selde solution containing a copolymer containing 15% by weight AMPS and 85% by weight acrylamide (AM) as a drainage aid. .

Curve B is the drainage curve for a pulp liquor with total addition of a terpolymer containing 5% by weight A, MPS, acrylic acid (AA) and 85% AMf by weight. . Curve C shows the drainage characteristics of the pulp liquor containing the above-mentioned conventional anionic polyacrylamide drainage/retention aid? The curves shown are characteristic curves for pulps containing conventional cationic polyacrylamide drainage/retention aids as previously described.

As can be seen from Figure 1, the change in pH was significant for all pulp liquid compositions tested, especially for
Pulp liquor with copolymer added (curves A and B) and anionic polyacrylamide added! dramatically affects the properties of Rude's solution (curve C). 15/8.5 AM
The P/A, 'd# polymer ([li!, 4) exhibited the best drainage rate in the pH range of 43 to 5.7 for all pulp liquors tested, while the anionic (containing cardegyl groups) The pH changes within the range of polyacrylamide gel have relatively little effect. Cationic polyacrylamide (aDI) has a mild effect in this pH range.

Such pH range and alum usage @ (3 wt.)
is a general representation of the process conditions in many newsprint mills. AMPS copolymer of curve A and song #i! B
Both AMPS terpolymers should be partially neutralized in the alum added to the pulp liquor, ie in the form of cationic alumina polymers. As indicated above, the best compositions are a combination of the type of copolymerization represented by curve A and the type of copolymerization represented by curve B, since agglomeration of toughness may be undesirable for a particular application. It is intermediate between the terpolymer and can be determined by actual factory trials. Nevertheless, as clearly shown in the graph, both types of AMPS-containing polymers are more effective than the cationic polyacrylamide (curve D), which has traditionally been used as a drainage/retention aid. It is effective for

The aionic II'2 lyacrylamide of curve C is highly active only at high pE's where the polymer is structurally stretched.

However, high pE conditions are not attractive for newspaper production due to the attendant problems of pitch deposition. Ability, 73B”
If f: is lowered to extremely low levels, in the region below 4.0, AMpS-containing polymers are likely to have an adequate amount of cationic alumina, which would provide all of the active bonding sites for such polymers. Once d) is no longer present, the efficacy is clearly reduced.

Example m Figure 2 shows the change in drainage volume (1) as a function of pB in a system in which 1 weight cent alum was added to the pulp liquid.
me). Each curve corresponds to the same liquid silk composition and drainage aid as the correspondingly labeled curve in FIG.

As can be seen from this graph, when the AMPS-containing copolymer is raised to the point (approximately 5 to 5.5) at which a sufficient amount of cationic polymer-like lumina is produced, Highly effective. The difference in optimum pH seen compared to the results of Example ■ is probably due to the lower level of alum usage here compared to Example ■, which reduces the effective concentration of active cationic alumina. Probably for a reason. The results shown in Figure 2 indicate that the optimum operating pH is
This shows that it is a function of the amount of t ions.

EXAMPLE 1 FIG. 3 is a graph of the change in the amount of drained liquid (ml) as a function of the amount of alum added at pH 4 and 5.

Curve A is 1.5-coulometric percent/85 as a drainage aid.
Lightning 11'A-St's AMPlAM common nail combination is related to the shared combination/Zorude, and the song a! B is 5:1.
5: So sentient percentage A JfP S /
A A / A Jf D This relates to a pulp liquid containing a terpolymer, and curve C is a liquid containing 3Q as a drainage aid.
This invention relates to a Norde solution using an anionic polyacrylamide containing a free cardoxyl group of z#-cent.

In this experiment, 1 liter dose of alum was mixed with 0.5 to 2. O
Jf quantity no! -cent and the pH was adjusted to 4.5. The results obtained are the same as those shown in Example
When the weight is 0%), the polymer is 4! In fact, all indications are to convey drainage. In this pulp liquid system, ri, A
, a minimum of 1.5 = 2.0 wt...''% appears to be essential for proper /r activation of VPS-containing polymers. Shadow I# due to changes in alum content
I don't receive it.

EXAMPLE V FIG. 4 is a graph of the effluent change (me) as a function of dpE, showing the effect of changes in alum addition level and temperature rise as a crameter.

The effect of temperature on drainage rate is determined by whether heat affects the chemical behavior of the alum, since oxated alumina (polymeric) alumina is more likely to form at elevated temperatures.

Alum concentration and temperature conditions as parameters are shown on the figure. Drainage aid used in all cases: 5/15/80 weight neutral AMPS/AA
/AAi terpolymer.

In each trial, the Norep solution is adjusted to a specific temperature by warming the stainless steel beaker containing the Solde solution in a steam bath. After the conductivity conditions as a 9-meter have been established, Notalde 7 (treated with L'c alum, neutralized with an appropriate amount of sodium hydroxide,
Allow to equilibrate for 5 minutes.

[Brief explanation of the drawing]

Figure 1 is based on a pulp liquor that does not contain drainage aids)
(This is a graph of the change (-) in the drainage volume of the pulp liquid, plotted as a function of -pE of the pulp liquid.3% alumina sulfate was added to the pulp liquid.) 8i42 Figure Q↓Alum f3: l''10 It is rough to express the change (-) in the added lifting platform cb effluent M as a function of pH. 4 is a graph of the change (pain) in the effluent l as a function of the amount of addition of A7. The fourth M is a graph of the change (-) in the effluent l as a function of pH; Volume and temperature shadow W
It is shown as e-ceramator. Patent Applicant: American Sairyonamido Kang Guni
pH Fig, 3 0 0.5 1.0 1.5 2.0 Water #, internally changed aluminum 3rd grade / to °1 and 7° Procedural amendment (method) August 3, 1980 Manabu Shiga, Commissioner of the Patent Office1, Indication of the case Patent Application No. 119232/19832, Name of the invention Method for increasing the dehydration rate of pulp liquid3 Nagisa making amendments Relationship with H 4th Patent Applicant Agent Address: 107

Claims (1)

[Scope of Claims] 1. (α) In the pulp liquid before dehydration, (1) about 0.5 to about 5 weight percent of aluminum salt based on the weight of cellulose fibers in the pulp liquid and (2J from about 0.01 to about 0.5 weight percent of 2-acrylamide-2 based on the weight of cellulose fibers in the pulp liquor.
- from about 2 to about 30 mole percent of repeating units derived from methylpropanesulfonic acid, from 0 to about 25 mole percent of repeating units derived from acrylic acid, and from about 45 to about 98 mole percent of repeating units derived from acrylamide; (a) and maintaining the pH of the feedstock in the range of about &5 to about 6.5 during step (α) and throughout the dehydration step. Wood selected from the group consisting of lumber, thermomechanical wood pulp, and mixtures thereof.Increasing the dewatering rate during paper production from lude liquor containing a small amount of lude and Φ 40 multiphase poles. Method 2. The copolymer comprises about 2 to about 20 mole percent of repeat units derived from 2-acrylamido-2-methylpropanesulfonic acid and about 80 to about 98 mole percent of repeat units derived from acrylamide. The method according to claim 1, characterized in that the aluminum salt is added to the pulp liquid based on the weight of cellulose fibers in the pulp liquid. Approximately 2
A method according to claim 2, characterized in that it is carried out in an amount of from about 4% by weight. 4. The method of claim 3, wherein the pH of the pulp liquor is maintained in the range of about 4.1 to about 6.5 during step (a) and throughout the dehydration step. A patent claim characterized in that the aluminum salt is added to the pulp liquid in an amount of about 0.5 to about 2% by weight based on the weight of cellulose fibers in the pulp liquid. The method according to item 2 within the scope of 6. The pH of the pulp liquid is maintained in the range of about 4.8 to about 6.5 during stage (Z) and throughout the dehydration stage. Method. 7. The copolymer has about 2 to about 30 mole percent of 2.
- from about 5 to about 25 mole percent of repeating units derived from acrylic acid and about 4
2. The method of claim 1, wherein the acrylamide-derived repeating unit contains from 5 to about 93 molar cents. & A method according to claim 6, characterized in that the pH of the pulp liquor is maintained in the range of about 4 to about 5 during stage (Z) and throughout the dewatering stage. 9. The method of claim 1, wherein the temperature of the pulp liquor is maintained in the range of about 20 to about 60° C. throughout the opening of step (α) and the dehydration step. 7. A process according to claim 6, characterized in that the temperature of the Rude liquor is maintained in the range of about 40 to about 60° C. during step (α) and throughout the dehydration step.