JPH02504049A - Paper and paperboard manufacturing methods - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Method of manufacturing boards and paperboard Paper and paperboard are prepared by passing an aqueous cellulose suspension through a screen to drain the water. The sheet is manufactured by forming a sheet and then drying the sheet. The suspension contains substantially filler (f filter) or may contain a substantial amount of filler.

In either method, retention, formation n) and drainage IJ must be balanced. Ru.

If the amount of fines II miscellaneous and filler discharged through the screen is minimal, the yield is optimal. Macro scale (e.g. in the width direction of the sheet) and micro scale m and plate with uniform density and thickness even at scale (e.g. at any particular point) For paper, the texture is optimal. Suspended S liquid water drains very quickly through the screen If so, a colander is best. Water is generally used when the paper or paperboard structure is open. Cutting is optimal, and in such cases, the formation and yield are often poor.

What is usually done to modify these properties is to include water-soluble polymeric materials. It is important to achieve the right balance of these properties through material selection. can be done. For most purposes, materials containing relatively high molecular weight polymers are recommended. Zeru.

This has the effect of causing agglomeration of the T&fibers and any fillers present. .

If the flocs are very large, even if the yield and drainage are good, the formation may not be good. There is a tendency not to. If the flocs are small, the formation is quite good, but other properties is adversely affected.

The properties of flocs depend in particular on the molecular weight of the polymeric flocculant; It is known that the size of flocs increases with increasing amount of flocs. Since such flocs are expected to cause very poor formation, the molecules of the retention aid It is well known in the art that the amount should not be too high.

When the polymer retention agent is cationic, the intrinsic viscosity is approximately 10 cLi. ! It typically has an intrinsic viscosity of up to 7 g/g, although some can reach up to 7 g/g. Departure To the best of Akira et al.'s knowledge, there are no practical studies using cationic retention agents with high intrinsic viscosity. There is no industrial process for producing paper or paperboard that is currently in operation.

Applying shear force to a flocculated suspension reduces floc size, regardless of molecular weight (although it may theoretically provide some improvement in the ground), The application of shear is usually undesirable at the expense of very poor yields. It is well known that there is no. Suspension with minimal agitation to minimize shear Retention aids are mixed in the headbox, often after a high shear parking point. The suspension is then run from the headbox onto a screen through which it drains. However, normally no shear force is applied during this time.

Many studies have been conducted on the effect of shear on flocs, and it is generally It is usually best to allow relatively small flocs to form and avoid further breakage. It is.

In European Patent No. 0202780, a slightly cross-linked reverse phase dispersion polymer is used to increase the floc size. The beneficial effects on floc size and floc strength have been described; Not directly related to the problem, especially the use of even slightly insoluble polymers, It is strictly considered a tab. Do not use the pot as it may leave an insoluble residue on the paper and board. Remer retention agents usually must be highly soluble.

In European Patent No. 0235893, the inventors describe a specific method, namely The polymer is added at a relatively early stage, the resulting suspension is subjected to shear, and then drained. Add 1 j pentoite (generally to give rough shear) before stripping. I'm confused about the method.

Although this method gave very good results, bentonite was removed at a later stage. This requires the addition of It is normal to apply shear in the middle of this floc. Although not a legal method, subsequent addition of bentonite can reduce sheared flocs. This has the effect of converting it into a so-called very large aggregated structure. This final structure It is preferable to leave it so that it does not substantially disintegrate.

As a general rule, all methods that do not add ben-1-nite later result in a relatively hard structure. Avoid applying any shear and select the polymer to obtain a uniform floc. selected to withstand later processing conditions.

As mentioned above, in the case of cationic molecules (although cationic molecules are usually preferred), the polymer step The intrinsic viscosity of the retention improver is approximately 10dj! The current situation is to use up to /g. . Some literature simply speculates that higher molecular weights may be useful. ing. For example, Yoneda Patent No. 3,901,857 describes the hardening of cationic retention improvers. Viscosity is 12-25clj! There is a description of /9. However, this actually It has not been proven that such a product was used commercially or industrially. We don't even know that it happened. The reason for this is that polymers in dilute aqueous solutions Preparation by polymerization and retention in solution form rather makes this method economically disadvantageous. Probably for the purpose of doing so. This is because most paper mills use reverse phase dispersions or powdered polymers. This is because it requires・In European Patent No. 277728-A, cation The retention improver is defined by its specific viscosity, but what is its molecular weight? It is unclear whether The loss of cationic polymer retention improvers occurs as the molecular weight increases. The solubility of polymers tends to deteriorate, and it is true that in 1975 Polymer technology is based on solid grains with an intrinsic viscosity of 25 and appropriate solubility. It has not been possible to produce a retention aid for a board (reverse phase dispersion or powder).

It is absolutely essential that the polymer dissolves completely, otherwise it will become insoluble. This is because the particles remain on the paper and this is unacceptable.

Other potential problems when using such high molecular weight polymers are that these Polymers necessarily give very large flocs, making them difficult to use on today's conventional paper machines (PAP). (er-making machine) is to make the condition very bad.

A paper machine screen runs along the flow of cellulose suspension or be forced to do so. Until recently, the maximum screen speed was approximately 800 meters per minute. It was. The contact between this screen and the suspension essentially causes an acceleration of the suspension; This imparts shear to the suspension. Intrinsic viscosity 7 to 10clj! Cations up to /9 The retention agent provides a satisfactory floc under these conditions.

However, recently, especially in the United States, with much faster screen speeds, Paper making machines now operate at speeds of more than 950 meters per minute, and The shear applied to the suspension is now increased. Also high speed operation (therefore, In order to use suspended Si at high speed, it is necessary to mix the suspension components to be drained at high speed. sexuality is increasing. Therefore, before draining, make sure to add cellulose to make the suspension uniform. tend to impart significant shear to mixtures of suspensions, retention aids and fillers. ing.

These new high-speed, high-density paper machines increase throughput and provide satisfactory paper formation. However, on the other hand, the solid content in the drained water is Undesirably high results and yields tend to be more unsatisfactory .

Therefore, it is possible to apply shear, especially when operated with modern ultra-high speed machines. can achieve better yield and formation performance, or It is highly desirable to be able to save on retention aid while obtaining equal yields. .

Surprisingly, as a way to achieve these objectives, the market (industrial) A different type of cationic retention aid known from the The use of retention aids that give Destroys flocs and improves formation by applying shear or other shears We have discovered that giving.

In the present invention, paperboard; Cellulose containing a water-soluble cationic retention agent prepared from a nomer blend prepared by draining an aqueous suspension through a screen. The poly used here The polymer retention agent has an intrinsic viscosity of at least about 124/'J and Even if shear is applied to the suspension during draining, the yield will not deteriorate substantially. The formation of paper and paperboard is improved.

In addition, in this process, the polymer is slag (l) per gram as defined below. UmD) has a solubility of less than 25 and a powder or a reverse phase suspension of this polymer The polymer is introduced into the suspension as a solution of W4 by dissolving it in water. Ru.

Solubility, as defined here, means that the polymer is in true solution and the desired This is an indicator that no polymer precipitates are left behind.

The test is carried out as follows: 17 drops of polymer are placed in a needle threaded jar. 5d's Wet the polymer by adding acetone.

Add 95 d of deionized water to the jar and place the sealed jar on a laboratory shaker for 2 minutes. Shake to ensure maximum dissolution. 150p stainless steel screen Moisten the sieve and pour the resulting polymer solution into the sieve. A jar of water. Rinse and rinse water through a sieve. until there is no more gunk on the back of the sieve. , gently rinse the sieve under cold running water to remove residual polymer solution. sieve Pat the back of the sieve dry with a paper towel to remove any residue left in the sieve. Count the number of polymer slag. The total number of slag gives the solubility defined above. sand That is, the number of slag per gram of dry polymer or per 100 grams of 1% polymer solution. Ru.

Measurement of intrinsic viscosity is carried out as follows: At a temperature of 25°C, use a viscometer within the applicable range. 4 points in the vague range (0.02 to 0.0 The specific viscosity of the test polymer is determined in the range of 8% by weight). Reduced viscosity, or specific viscosity When the ratio of polymer concentration to polymer concentration is plotted against concentration, a straight line appears in the low concentration range. give. The intercept of this straight line on the Y axis, that is, the reduced viscosity at infinite dilution, is the intrinsic viscosity. degree, expressed in units a/g.

The present invention has the advantage that when the retention agent is a water-soluble polymer with a very high molecular weight, Applying shear to very large flocs that are generated in a This is based on the discovery that good yields can be obtained.

The molecular weight (expressed in intrinsic viscosity) and the degree of shear required to optimize performance are interrelated. For moderately high molecular weights, the required shear is also moderate; for ultra-high molecular weights, Very large shear is also required. The molecular weight is low considering the degree of shearing. (or the degree of shear is too high considering the degree of molecular weight), for example. Even if the grain formation is satisfactory, the yield cut) will be defective. If the molecular weight is too high for the degree of shearing (or If the degree of shear is too low for the degree of volume), the formation is in a satisfactory condition. However, the yield is poor. Thus, between these parameters, the It is possible to optimize the molecular weight by considering the degree of cleavage, and vice versa. It is also possible to optimize the degree of shear.

This discovery contradicts all conventional thinking regarding paper and board yield and formation. It is. In the prior art, molecular weights are moderate (e.g., most often have an intrinsic viscosity of 9 or 10cLi! /g or less), whereas in the present invention, the Must be of high molecular weight. Also, do not apply shear (bentonite and ToV! In contrast to the current conventional method of adding In this case, it is necessary to apply shear.

The present invention is characterized by the ultra-high speed running of the colander onto which the suspension is added. This is particularly effective when some or all of the shear is applied. Therefore another table As currently defined, the present invention preferably provides a unique The use of polymeric retention aids with viscosity and the suspension containing them It can be said that this method is applied to a draining screen that moves at high speed.

Therefore, the present invention provides a screen speed of approximately 80,077 L or more per minute, usually 850 m or more. How to achieve good yields and good formation in modern high-speed paper making beaches where wheels run It provides a solution to the problem of whether This speed is generally 900m per minute. In addition to the above, the distance is usually 925 m or more. A satisfactory result in the present invention is that If the clean speed exceeds 950 m or 975 m per minute, an additional 1. 000m or more, such as 1,050m and 1,100m or more It can be obtained at more than For these speeds, the intrinsic viscosity of the polymer is Preferably those in the range 12-17, often 13-16 mix/g, with intrinsic viscosity Best results are obtained with degree (IV) 14 or 15 coagulation/9. however , for higher speed screens, even higher molecular weights, e.g. intrinsic viscosity 20c. li! /g or more may be used.

The polymer can be added to the headbox with gentle agitation, but In case of formation of thin paper stock (thin 5tock) due to high polymer molecule 9 Polymers can also be added under the same mixing conditions. Especially in the head box or eliminate traditional injections that allow the suspension to be sheared in front of the headbox. There's no need to do that anymore.

Alternatively, the polymer may be placed in suspension under shear - e.g. It can also be added to a fan pump and then drained with a relatively slow screen. I do.

An essential feature of the invention is that the retention aid must be water soluble. too However, if the retention agent is not water-soluble, it will have a poor effect on retention and will Otherwise, the problem arises that insoluble polymer remains on or in the board set. This insolubilization The trend is that as the molecular weight of the retention aid increases (which traditionally This is another reason to use low molecular weight retention aids. However, this is due to accidental crosslinking, for example due to the amount of crosslinker impurities.

Therefore, the monomers and polymerization conditions used must be low enough to achieve crosslinking. the polymer is essentially linear and the separator is It must be ensured that the lulose is present in the form of a true aqueous solution before mixing with the aqueous suspension. It must be Due to insolubility issues, certain monomer charges There is a limit to the molecular weight that can be obtained in a satisfactorily usable state. However, suitable We use monomers with the highest purity and have an intrinsic viscosity of, for example, 20dj! cation with /9 It is possible to obtain a retention aid without excessive withdrawal; anionic or nonionic step having an intrinsic viscosity of up to 30 or 40/9. It is also possible to obtain retention improvers without undue difficulty. these Even those with even higher intrinsic viscosity, if ultra-high I! l! If you use degree monomer, you can get (and can be used in the present invention).

One way to define the linearity of a polymer is the definition of European Special Notice No. 0202780. Refer to ion regain as in . Smell of the present invention and this ion regain is less than 10%, preferably less than 5%, most preferably 0. It is in the range of ~2%.

Polymer retention agents can be prepared by reverse phase emulsification or suspension polymerization; In non-aqueous liquids, aqueous (or is provided as a dispersion of polymer particles (dehydrate). Such dispersions are generally is converted into a polymer solution by mixing with water in the presence of a water-in-oil emulsifier by a known method. can be done. However, oil contamination is undesirable, so polymers are The present invention is fundamentally useful if it is supplied as a solid. This solid is the opposite Phase-grain polymerization (then lizards).

azeotroping the beads from a non-aqueous liquid (111) or Kel polymerization followed by drying and It can be produced by the conventional method of pulverization.

To conduct the polymerization to minimize the presence of insoluble particles, It is important to carefully optimize the formation of reversed-phase dispersions, especially in the polymerization mixture. , to avoid local overheating or local fluctuations in reaction conditions. Game Very good dissolution at the same time as high intrinsic viscosity, prepared by phase polymerization or reverse phase polymerization This cationic polymer is a new material.This polymer has cationic properties. monomers alone or blended with nonionic monomers; can also be prepared using anionic monomers if ampholyte polymers are required. Manufactured. When cationic and nonionic monomers are used, the nonionic The proportion of ionic units is low, for example 5 to 50% by weight, but also cationic Polymers containing 10 to 50% by weight of units and 90 to 50@J% of nonionic units. Often, mer are also prepared.

Suitable cationic monomers include dialkylaminoalkyl (meth)acrylates and and dialkylaminoalkyl (meth)acrylamide. cationic mono The mer is usually used in the form of an acid addition salt or preferably a quaternary ammonium salt. Ru.

Uses any of the nonionic monomers conventionally incorporated into high molecular weight water-soluble polymers However, acrylamide is particularly preferred.

Anionic monomers include ethylenically unsaturated carboxylic acids, such as methacrylate. acid or preferably acrylic acid, or ethylenically unsaturated sulfonic acid, e.g. 2-acrylamidomethylpropanesulfonic acid can be mentioned. Anion The monomer is usually an ammonium or alkali metal (generally sodium) salt. used in the form

Preferably, the retention agent is a copolymer of acrylamide and a cationic monomer. and most preferably 10-95 (preferably 50-90) 111% rylamide and 90 to 5 (preferably 50 to 10)% by weight of a cationic monomer, Most preferably dialkylaminoethyl acrylate quaternary ammonium salt (also is the corresponding methacrylate compound) [The alkyl group in 44 is usually methyl or ethyl It is a copolymer with Chiru].

Particularly preferred copolymers are from about 50 to 80%, often from 70 to about 8% fil1%. of acrylamide and the remaining amount of diethylaminoethyl acrylate or methacrylate. Quaternary ammonium salt of rylate. Other preferred copolymers are: The fourth (Quaternar V) monomer is 50 to 100% by weight of the monomer. If acrylamide or acrylamide quaternizes a polymer, any of the usual quaternization methods can be applied. However, generally methyl sulfate or methyl chloride can be used.

The intrinsic viscosity of the polymer is preferably about 14 or 15 J/9 or more. The polymer is preferably prepared as a powder and dissolved in water to dissolve as described above. give degree.

- Polymer matrix soluble bomber is the last used as a papermaking additive. No. 17353 or subsequent European Patent No. 17353 or the subsequent European Patent The suspension may be substantially unfilled, for example, about 15% or less inorganic filler. and--even if the crotch contains less than about 10% or e.g. more than 15% inorganic filler. may be filled with inorganic fillers (!4 based on the dry weight of the suspension). stomach. If the suspension has high cationic requirements, it is first treated with bentonite It is particularly preferred to then apply a substantially nonionic polymeric retention agent. , these L and L are performed, for example, as described in European Patent No. 17353.

So.

The yield direction and the amount of L agent introduced into the suspension are determined by the conventional amount → For example, the dry weight of the suspension is 100-1000 g dry polymer per tonne, often in the range 200-5009 However, higher contents may be used if desired.

Adding low or medium molecular weight polymers before adding high molecular weight polymers Improved results are obtained, especially for formation. Appropriate feet are 50-10 The range is 0.009/ton. In general, low or medium molecular weight polymers are Cationic, other polymers may be slightly anionic or nonionic , preferably cationic.

Suitable cationic low to medium molecular weight polymers include the cationic monomers listed above. mer (often in the form of a copolymer with acrylamide), diallyldimethylammo prepared from nium chloride (often copolymerized with acrylamide).

Alternatively, this polymer may also be polyethyleneimine or amine-halohydrin. Alternatively, it may be an amine-haloalkane polymer.

Molecular weight typically ranges from 10,000 to 100,000, e.g. intrinsic viscosity from 0.1 to The range is 1 and /9 or 2''7g.

! -tJ Kaiyu It has a molecular weight of about 75% acrylamide and diethylamine ethyl acrylate. A cationic retention improver was prepared. After drying according to the usual method, produce The material typically had a solubility of less than 10 dregs per 100 g. Same preparation monomer When used under reaction conditions known to favor high molecular weights, the intrinsic viscosity It is possible to obtain, for example, 14, but the solubility? ylo.

There is a tendency for the number of slags to be 30 or more per gram. However, cationic monomers and and acrylamide by conventional purification methods to remove virtually all cross-linked components, including all traces. If it is made with 'M' so that it can be removed without removing it, the intrinsic viscosity is about 14 and the solubility is about 100 g. Polymers that give less than 10 slags can be readily obtained.

Solubility formula 'lOO! These cationic polymers giving less than 10 pieces per 7 When comparing two different paper making machines, their performance depends on the operating conditions of the machine. do. While gently stirring the polymer into the headbox as a retention aid. at a screen speed of about 850 meters per minute, a polymer with an intrinsic viscosity of 7 has a good Polymers with an intrinsic viscosity of 14 can give good yields and good formation, but polymers with an intrinsic viscosity of 14 There is a tendency for poor alignment. Increased screen speed to approximately 1,000m per minute Then, a polymer with an intrinsic viscosity of 14 has good yield and good formation (screen speed at 850 m/min (substantially the same as for a polymer with an intrinsic viscosity of 7). In contrast, polymers with an intrinsic viscosity of 7 tend to have poor formation.

Example 2 75% acrylamide and 25% quaternary salt of diethylamine ethyl acrylate Two cationic retention aids, A and B, were prepared by conventional gel polymerization with % Prepared. A has an intrinsic viscosity of 8 cltl/9, and B has an intrinsic viscosity of 13 cltl/! ? have did. The solubility of both polymers was less than 10 pieces per gram of polymer.

Using bleached kraft valve furnish to produce paper grades, industrial paper making 1 il ( Performance was compared using paper machine). 3 of each retention aid to the paper machine It was applied for 0 days, and the following comparative results were obtained as an average of 30 days.

△ 8.0 440 75.6 8osB 1 3.0 350 75.7 859 This result shows that there is a small yield The results showed that the yield was the same with the dosage of top agent, and the speed of the paper machine was also improved. ing. Even when high molecular weight retention agents are used, there is no apparent adverse effect on sheet formation. It wasn't noticed.

Example 3 In order to demonstrate the effect of shear on compositions of different molecular weights (intrinsic viscosity), laboratory The following tests were conducted. 75% acrylamide and 25% diethyla Range of 4 to 171/9 by gel polymerization with quaternary salt of minoethyl acrylate Polymers with different intrinsic viscosities were prepared. Solubility factors for all polymers The number of slags was less than 10 pieces per gram of polymer). Dilute stock (dilute!; tr Stock solutions of these polymers for addition to ick>:ll! Made by l. height For shearing, put this solution in a Brit jar mixer and heat it for a specified time in the range of 15 to 45 seconds. Shear was applied by operating at 1500 rpm.

Dry paper stock (i.e. fibers and (total of fillers) was stored at a polymer dosage of 400 g of dry polymer per ton. The desired amount of stock solution was added. After addition, invert the solution 5 times to ensure complete mixing. Next, preconditioned and weighed fast 3J paper (Whatman NO, 54i Pour into a Hartley funnel (diameter 9.5 CI11) equipped with 1. hartley funnel The device used connects the conical flask to the vacuum source, and the vacuum line is connected to the The vacuum gauge and stopcock are connected. Add stock solution to the Hartley funnel with the stopcock in the open position. Well, I created a vacuum. Start the stopwatch immediately after filling the funnel. Closed the stopcock.

Read the highest value (Pl) on the vacuum gauge and the pad corresponds to excess water being removed. The time required to achieve a uniform matte appearance was measured. Set the draining time to this point. It was recorded.

Air was drawn through the pad and continued to filter until the vacuum gauge reading settled at a constant value. . Set this vacuum pressure to (P2), then immediately release it, remove the pad and the 11th paper, and weigh it. I weighed it. The pressure drop (ΔP) is Pl-P2. Each measurement was carried out 5 times and should be satisfied. The result was a meaningful cohesion. The poorer the formation of the formed pad, the more As air is drawn through the pad, the pressure drop is large, resulting in the pad becoming stiffer. It is. It is preferable to know the draining time. The results are shown below: table This result shows that drain time also increases with increasing shear for all polymers. However, polymers with high intrinsic viscosity, especially those with an intrinsic viscosity exceeding 15, are expensive. It was found that even shearing gives the best draining time, which is unexpected. It was.

These improvements in drain rR come at the cost of poor formation as indicated by pressure drop values. It wasn't something that was done along with it. Intrinsic viscosity compared to conventional low-intrinsic viscosity polymers Unexpectedly, there was no significant difference in pressure horn drop using a polymer with a higher We found that the conditions were favorable.

international search report International study report G2ε900433 S6 2ε35t

Claims (6)

[Claims] (1). Formed from water-soluble ethylenically unsaturated monomers or monomer blends cellulose aqueous suspension containing a water-soluble cationic polymer retention agent In the process of producing paper and paperboard by draining through a screen, The remer retention agent has an intrinsic viscosity as defined herein of at least 12 dl/g. The substance of the yield is determined by applying shear to the suspension before or during draining. improving the formation of paper or paperboard without deterioration; and reverse-phase suspensions. or the polymer in the form of a solution prepared by dissolving the polymer in powder form in water. is introduced into the suspension and its solubility is A method for producing paper and paperboard, characterized in that the ritsu is less than 25 oka. (2). Claim 1, characterized in that the solubility is less than 5 dregs per 1 g. Method. (3). Claim 1, characterized in that the intrinsic viscosity is 13 to 17 dl/g. the method of. (4). While the screen travels at a speed of over 800 meters per minute, Claim 1, wherein the shear is applied by contacting the suspension with the Method described. (5). Claim 4 characterized in that the speed of the screen exceeds 900 m between screens. The method described in. (6). If the polymer is in the form of an acid addition salt or a quaternary ammonium salt, % acrylamide and 100-5% dialkylaminoalkyl (meth) Claim characterized in that it is a polymer with acrylate or monoacrylamide. The method described in 1.