JPH05140897A - Preparation of inner surface-sized paper - Google Patents

Abstract

PURPOSE: To produce an internally sized paper superior in a sizing effect, an yield and a fiber dispersibility by adding a cationic retention aid to a cellulosic suspension, treating it under specified conditions to obtain a suspension of coagulates, draining it to form a sheet and drying it. CONSTITUTION: Preferably 0.01-0.3% (based on a dry weight of cellulose) of a water soluble, cationic retention aid such as cationic starch is added to a cellulosic suspension to form flocs. They are broken without substantial resuspension of fibers down to cationically charged microflocs. A nonionic or anionic size emulsion is added to the suspension after flocculation, and a soln. or dispersion of an anionic compd. selected from org. polymer substances, bentonite and colloidal silicates is added, to obtain a suspension of coagulates contg. the size. Further, the suspension of coagulates is drained to form a sheet, which is dried, to obtain the objective internally sized paper.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to the manufacture of sized cellulosic sheet material. This sheet material will hereinafter be referred to as "paper", but its weight can vary, so that the sheet material is not only a sheet material having a normal paper weight, but also "paperboard". Also included are sheet materials that may be referred to as.

[0002]

Paper is produced by preparing a cellulosic suspension, draining the suspension to form a sheet, and drying the resulting sheet. The paper size can be implemented by surface size or internal size. Surface sizing is usually done by applying sizing to the sheet after partial or complete drying, thus the sizing process is energy-consuming and tends to concentrate the sizing on the surface. The inner surface size is determined by adding a sizing agent to the suspension before draining.

A variety of hydrophobic materials are known for use in internal size, all of which are commonly prepared and used in the form of aqueous emulsions prior to addition to cellulosic suspensions. Suitable sizing agents are rosin sizing agents, including fortified rosin sizing agents, and reactive sizing agents such as ketene dimer sizing agents and anhydride sizing agents.

Of course, sizing agents usually tend to be nonionic or anionic. The usual idea is that the sizing agent should be given the greatest opportunity to be absorbed by any particles that may be contained in the paper sheet,
Therefore, in the conventional method, the addition of the sizing emulsion is carried out at an early stage of the paper making process so that the sizing agent is absorbed by the particles (that is, the cellulosic fibers and any filler particles) before draining the suspension. Bring enough time.
Thus, typically, the sizing is significantly agitated by passing it through a sized suspension prior to draining the liquor, for example by passing it through a centrifugal screen, fan pump or other device that imparts shear stress. Alternatively, it is added at an early stage so that shearing can be performed.

The solid constituents of cellulosic suspensions are, of course, also often anionic, so that the sizing agent is deposited on the fiber or in some other way its direct adherence to the fiber.
It is known that it is desirable to add various substances that enhance the For example, rosin sizing and strengthening rosin sizing, commonly supplied as anionic emulsions, are applied at the same time as alum, which deposits emulsion particles on cellulosic fibers.

When a reactive sizing agent is added, it is usually a cationic emulsion, that is, an emulsion of a nonionic or anionic sizing agent containing a sufficient amount of a cationic substance to render the emulsion particles cationic. Form. For example, commercially available ketene dimer sizes are commonly supplied in the form of cationic emulsions.

Various cationic additives are known to be contained in an emulsion together with a reactive sizing agent to make the emulsion cationic. Cationic additives can have small or very small molecular weights.
For example, a group of cationic additives known to be used with ketene dimer sizing agents consists of dicyandiamide polymers. This material is a formaldehyde condensate that has a low molecular weight (usually well below 1,000) and is added in the water-soluble state. The added formaldehyde condensate makes the ketene dimer particles directly adherent to the cellulosic fibers and then acts as a curing accelerator for the ketene dimer to accelerate the curing of the ketene dimer on paper, and in this step It polymerizes in the meantime to increase its molecular weight and at the same time becomes water-insoluble.

Instead of adding a cationic additive to the sizing agent, it is also known to add the cationic additive to the cellulosic suspension before adding the sizing agent. For example, European Patent Application Publication No. 174911 and No. 1
No. 75647, No. 176479 and No. 22760
No. 0 describes the possibility of adding the cationic substance and the sizing agent in any order, and JP-A-54-09
Nos. 6104 and 54-068405 disclose adding a cationic polymer to a cellulosic suspension prior to adding an anionic sizing agent. Methods such as these involve pre-adding the cationic polymer and subjecting the suspension, which has also been added with a sizing agent, to significant agitation and shear (as in other conventional methods) prior to draining the solution. Conceivable.

Cationic polymers which can be used include water-soluble cationic starches, and are especially water-soluble and of medium solubility.
Alternatively, a synthetic cationic polymer having a high molecular weight is included. Typically, the molecular weight of synthetic cationic polymers is above 500,000, often much above 500,000. Although these substances are also used as retention aids in the paper industry, it is generally believed that for this purpose these substances should be added shortly after draining the suspension after the end of high shear stress application. .. This is because it is well known in the literature that the yield will be adversely affected if shear stress is applied to the suspension after addition of the polymeric retention aid by stirring or the like before draining the liquid. Therefore, when the cationic retention aid is used to enhance the direct adhesion of the sizing agent to the solid components of the suspension in otherwise conventional papermaking processes, the addition of retention aid is Little or no impact on improvement. As a result, in practice, additional retention aids must be added at the end of the papermaking process to achieve the appropriate retention values.

Thus, in the conventional method, prior to carrying out the sizing, applying the shear stress, and adding the usual cationic retention aid just before draining the resulting suspension, the cationic polymer is added at an early process stage. Other retention aids must be used. The yield value may be insufficient even after the addition of a yield improver to be used later, and particularly a large amount of cellulosic fibers and, if present, filler particles tend to be washed out from the sheet into white water. That is, the expected advantage of adding the sizing agent early enough, thereby allowing the sizing agent to be absorbed by all solid particles, is that in fact retention of fine solid particles is insufficient. This leads to the disadvantage that a considerable amount of sizing agent is lost. In this connection, very serious problems arise when the suspension contains a considerable amount of filler. Many of the fillers for cellulosic suspensions are hydrophobic, so there is little or no need to coat the filler with a size. However, since the pretreatment with the cationic substance tends to make the filler particles (and the fibers of the paper) cationic, the adhesion of the sizing agent to the filler particles is promoted by performing the pretreatment. The surface area of the filler particles can be very large, so large amounts of sizing can be unnecessarily absorbed by the filler. As a result of this, the sizing that is brought into the sheet by the filler is often unnecessary, and the sizing that is lost due to insufficient filler retention is wasted.

There are also associated problems when, as is usually the case, the filler content of suspensions changes during long papermaking processes. The above content change can be induced by deliberately changing the amount of the filler. However, changes in filler content often occur arbitrarily. Because the suspension is partly or wholly made from waste paper, it is inevitable that the waste paper will have varying filler content. That is, the amount of filler tends to fluctuate drastically during the paper manufacturing process,
Therefore, the amount of sizing agent unnecessarily absorbed by the filler also tends to vary. As a result, it is difficult, and often even impossible, to obtain a sheet with uniform sizing characteristics, because the amount of sizing agent present on the sheet is excessive depending on the amount wasted and absorbed by the filler particles. It is because or becomes insufficient.

While the ketene dimer sizing composition has the advantage that it can be supplied to the factory as a relatively stable, cationic aqueous emulsion that is easy to use, it also has two major drawbacks. One is that the emulsions are relatively stable but hydrolyze somewhat during storage, which can lead to property degradation if the emulsions are stored for too long, i.e. for weeks. Is. Another drawback is that ketene dimers tend to take a long time to cure, which may require the use of a curing accelerator as described above.

Although anhydrous sizing has the advantage of curing relatively quickly, it also has some drawbacks, primarily due to its high reactivity. Emulsions usually have to be manufactured in the factory because the anhydrous size reacts rapidly with water. However, even if the emulsion is manufactured in the field of use, hydrolysis is likely to occur to a degree sufficient to generate anionic carboxyl groups. Hydrolysis can destabilize the emulsion. A significant problem caused by hydrolysis is that the carboxyl groups can react with the cationic polymer present in the emulsion to form a sticky complex, which is a well-known problem with anhydride sizing agents. One of the problems is that it may cause a problem of peeling of paper during printing and a problem of runnability on a machine. It is well known that runnability problems can also occur with other anionic sizing agents, or potentially anionic sizing agents, but this problem is especially acute when using anhydrous sizing agents. .. The tendency of the anhydride sizing to react with the cationic polymer to form a sticky complex is believed to be greater than similar trends with other anionic sizing agents.

Therefore, the conventional sizing method consumes a fairly large amount of sizing agent and, depending on the sizing agent selected, does not cure sufficiently (without the addition of a curing accelerator),
Or, the problem of running property on the machine occurs. In particular, a commercially preferred size (anhydrous size) for many reasons
Tend to cause runnability problems, which severely limits the applicability of the size. Another problem is that it is difficult to maintain sizing efficiency because the required amount of sizing agent may change due to changes in the filler.

As described above, in order to improve the yield effect in the paper manufacturing method, the yield improver is usually added after the final point of time when the large shear stress is applied. However, a cationic retention aid is added to the suspension to cause flocculation in the suspension, with subsequent flocculation of the flocs, or substantially simultaneously, without substantial resuspension of the fibers. To give cationically charged microflocs, which are flocculated by the addition of a substance such as bentonite or colloidal silicic acid, and agglomerated with an agglomerated suspension.
There are several known methods for forming a sheet by drying the suspension. These methods are described, for example, in U.S. Pat. Nos. 4,388,150 and 4,753,710.
And European Patent No. 235893.

It is also known to apply the method as described above to the manufacture of size paper, in particular EP 2358.
Some examples described in No. 93 add size to a cellulosic suspension in the usual manner, followed by a cationic polymer retention aid, followed by shear stress and then bentonite. Is added. It is also stated that the sizing agent and the cationic polymer retention aid can be present in a single anhydrous composition so that the sizing agent and retention aid can be added to the suspension simultaneously. Addition as a component of a single composition limits the process flexibility. The method as disclosed in EP 235893 is also practiced by adding a conventional cationic sizing emulsion substantially immediately after addition of the retention aid. This again has the disadvantage that, for example, the sizing agent must be compounded with the cationic additive. In particular, there is no suggestion of any means for solving the well-known runnability problem that occurs when ASA sizing agents are used.

[0017]

The ability to improve the efficiency of sizing while avoiding the sticking and runnability problems traditionally associated with anhydrous sizing, and providing excellent retention, moisture removal and fiber dispersion properties. It would be desirable to be able to produce size paper in the process.

[0018]

SUMMARY OF THE INVENTION In one aspect of the invention, the addition of a cationic retention aid causes flocculation in a suspension of cellulosic fibers, the resulting flocs being substantially regenerated of the fibers. Disruption without suspension into cationically charged microflocs, nonionic or anionic anhydrous sizing agents in suspensions that have undergone flocculation and usually also have formed microflocs. Adding an emulsion, aggregating microflocs by adding a solution or suspension of an anionic compound to produce an agglomerate suspension containing a sizing agent, draining the agglomerate suspension to form a sheet. The inner sized paper can be produced by a method that includes forming and drying the sheet.

The sizing agent must be added after the flocculation has occurred in the suspension, preferably the sizing agent breaks the flocs substantially without resuspension of the fibers and is thus microflocculated. And then add. That is, unlike in the case of normal sizing, the sizing agent is attached to the flocculation mass rather than to the individual fibers and filler particles (if present). As a result, the tendency of the sizing agent to be wasted by being absorbed by the filler particles that do not stay in the sheet is less than in the normal sizing process, and the sizing process is modified due to changes in the amount or type of filler. It is also reduced compared to normal size processing.

The present invention, when compared to other methods in which the cationic polymer is added to the suspension prior to the sizing agent,
It has the important advantage that much of the filler is trapped in microflocs, which significantly reduces the surface area of the filler that is exposed to the sizing agent and also significantly improves the retention, thereby further reducing the size requirement. For example, the filler surface area exposed to sizing in the present invention is typically exposed to sizing when the fibers and fillers have not been pre-flocculated to form microflocs, or relatively large flocs. It can be, for example, only 1/10 of the surface area used, that is to say that the invention makes it possible to achieve excellent sizing effects with smaller amounts of sizing agent than previously required.

The present invention is partly because the emulsion does not need to contain a cationic substance, and partly because the size-filled filler and fiber particles are reduced in recycling into white water. It also has the advantage that the problems of sticky complex formation and runnability are trivial.

While the advantages described above are particularly pronounced when the sizing is performed with an anhydrous sizing agent, in another aspect of the invention, the sizing agent can be used with a sizing agent other than the anhydrous sizing agent. Is. The sizing agent other than the anhydride sizing agent may be a sizing agent such as rosin, but is preferably a reactive sizing agent such as the above-mentioned ketene dimer sizing agent and the like.

The addition of a sizing agent is often performed in all aspects of the invention after the final point of application of high shear stress (eg, by a fan pump or centrifugal screen) to break the flocs into microflocks and to remove anionic compounds. Addition is also usually done after the final point of application of large shear stress. It is also possible to add the sizing agent after microflocculation, provided that there is sufficient mixing to distribute the sizing agent throughout the agglomerate structure, and such mixing will usually result in agglomerate structure before draining the suspension. Including breaking into smaller agglomerates. This method is acceptable.
However, it is usually preferred to add the sizing agent during or prior to aggregation. When the sizing agent is added during the aggregation, the sizing agent and the anionic compound can be added as a single composition, but the prolonged contact between the sizing agent and the anionic compound (for example, the anionic compound Could be inconvenient if it could interact with the agent)
In such cases, it is desirable to mix both components immediately prior to addition to the suspension, or to add both components separately, but not too closely.

The cationic retention aid may consist of or contain cationic starch, although
Preferably, it comprises a water-soluble synthetic cationic polymer having a molecular weight of more than 500,000. This synthetic material can be used as the sole retention aid, or can be used in combination with the cationic starch and other materials. Suspensions may have improved dry strength properties or added for other purposes, such as those described in US Pat. No. 4,913,775, the entire disclosure of which is incorporated herein by reference. It may contain resins and / or relatively low molecular weight cationic materials.

The cationic retention aid can have a relatively high molecular weight (eg, an intrinsic viscosity IV greater than 4 dl / g), in which case the suspension is usually added to the suspension immediately prior to sizing. It may be advantageous to also add a water-soluble synthetic cationic polymer having a relatively small molecular weight, for example an IV of 3 dl / g or less, typically 50,000 to 2 million. For example, polydimethyldiallylammonium chloride (or a copolymer with acrylamide) or other low molecular weight cationic material may be added.

Intrinsic viscosity measurements referred to herein are Suspended Level Viscomet.
er in a buffered 1N sodium chloride solution at 25 ° C.

The cationic retention aid is preferably
European Patent No. 235893, US Patent No. 4,91
Nos. 3,775 and 4,753,710, which are one of the substances disclosed in the above documents, and the above-mentioned documents are referred to for the detailed description of the appropriate substances.

Flocculation is induced by the addition of the yield improving agent, and the flocculated suspension is sufficiently stirred to destroy the flocs to form microflocs. If the yield-enhancing agent is large enough, the microflocs become cationically charged, destroying them and essentially resuspending the fibers (and filler, if present) in the suspension as microflocs. It doesn't matter. The amount of cationic retention aid needed to form such stable microflocs depends on the properties of the polymer, the properties of the suspension, and whether any other cationic polymer is added to the suspension. ..
That is, if other cationic substances are present in the suspension, such as, for example, cationic starch, or a relatively low molecular weight synthetic cationic polymer that functions as a dry strength improving resin, the desired cationic yield The amount of enhancer can be less than that required when the suspension is substantially free of other cationic substances. For example, if the other cationic material present in the suspension is a material such as a low molecular weight polymer, the amount of cationic retention aid is 0.005%, or more commonly 0.01% ( It can be as low as 100% of dry polymer per ton of dry weight of paper. But usually
The amount of the cationic retention aid is 0.03% or more, often around 0.1% and even around 0.3%. This amount is generally found in, for example, US Pat. No. 4,753,
The conventional method as disclosed in U.S. Pat. No. 710, namely that the fibers and fillers, if present, are sufficiently cationic to allow direct attachment of the sizing agent, even with the addition of retention aids. The amount of retention aid added is greater than that required in the headbox method to ensure that the flocs are also subjected to shear stress.

The agitation necessary to break the flocs into stable micro-flocs is simply due to turbulent flow along the pipeline of the papermaking machine, or alternatively to a predetermined shearing step such as a fan pump or centrifugal screen. Can be realized by applying

The cationic polymer retention aid is preferably a polymer as described in EP 235893, US Pat. No. 4,753,710 or US Pat. No. 4,913,775, the molecular weight of which is Usually greater than 1 million, often over 5 million, eg 1
~ 30 million or more. When expressed as an intrinsic viscosity number, the value is usually larger than 4 dl / g, often more than 7 dl / g and 10 to 12 dl / g, but it is also possible to use a polymer having a larger value. If the molecular weight of the cationic retention aid is relatively small (eg, below one million or two million and less than 4 dl / g for IV), it may limit the amount of shear applied to the system after the retention aid is added. May be needed. This is because excessive shear increases the tendency for insufficient yield to be achieved without the addition of other steps. However, if the retention aid has a very high molecular weight and is completely water soluble, that is, for example
Linear synthetic cationic polymers having an intrinsic viscosity of greater than dl / g and often greater than 12 dl / g can give good results in shear applications.

If a cationic starch is to be used as the retention aid, a suitable material is US Pat. No. 4,38.
No. 8,150.

The microflocs are subsequently flocculated by the addition of an anionic compound capable of flocculating the microflocs. The compound may be a water soluble anionic polymer and thus, for example, an anionic polymer retention aid having a molecular weight of greater than one million. The synthetic anionic retention aids added last include acrylamide and (meth) acrylic acid or other compounds with an intrinsic viscosity of generally greater than 10 dl / g, often more than 15 dl / g and often more than 20 dl / g. Anionic acrylic polymers such as anionic copolymers with ethylenically unsaturated carboxylic acids are included.

However, preferably the anionic compound is an inorganic substance, in particular colloidal silicic acid as described in US Pat. No. 4,388,150 or WO 86/05826. Is preferred,
Most preferred is bentonite. Bentonite is any suitable anionic swollen clay, ie for example EP 235893 or US Pat.
It may be a smectite as described in 3,710, ie Wyoming bentonite or Ful.
It can be any swollen clay with significant smectite or montmorillonite structure, such as lers Earth, hectorite, sepiolite, attapulgite.

The amount of anionic compound is selected so that the desired aggregation is achieved, but depends in particular on the amount of cationic polymer used above. Appropriate amounts can be readily found by routine experimentation and are usually 0.01-0.
5%. Especially when bentonite is added, its amount is usually at least 0.01% and often 0.03% or more, and as described in U.S. Pat. No. 4,753,710, for example, 0. It can reach 5%. Usually, the amount of bentonite added is about 0.05 to 0.3%.

Highly branched or swellable anionic polymers, ie, for example, crosslinked acrylic acid, before, during or after the addition of the sizing agent, instead of or in addition to the bentonite or water-soluble anionic polymer. It is also possible to add reverse phase emulsifying polymers of acrylamide copolymers.

The method of the present invention makes it unnecessary or undesirable to add the cationic retention aid after the sizing agent, and still has good retention, drainage,
It is advantageous in that fiber dispersion and drying can be realized.

The cellulosic suspension may be any suspension suitable for making size paper. This suspension may include recycled paper. The suspension may or may not contain a filler, and the filler to be contained may be any conventional filler. The invention provides that the suspension is 10% or more and, for example, 50%.
It is particularly effective when the following (dry weight) inorganic filler is contained.

The details of the method of making the suspension and the method of making the paper (including the step of removing water and the step of drying) may be conventional except for those parts described herein. The paper can be any size paper, including paperboard.

The size may be a non-reactive size such as a rosin size or a reinforcing rosin size. Non-reactive sizing agents can be added in combination with alum, but can also be added without alum, in which case the deposition of rosin on the fiber will replace alum and the cationic polymer in suspension. Realize by relying on.

However, preferably the sizing agent is a reactive sizing agent such as any of the previously mentioned reactive sizing agents. Preferably, a nonionic or anionic emulsion of ketene dimer size or anhydride size (eg alkenyl succinic anhydride size) is used. Emulsions may be prepared in the usual way with nonionic or anionic water-in-oil emulsifiers and water, with the exception that the cationic substances which are usually included beforehand are omitted. For example, if the size contains pre-existing cationic starch, the size may instead contain oxidized starch in the present invention.
Anionic emulsifiers or dispersants such as sodium polyacrylates having a molecular weight below 10,000 and naphthalene formaldehyde sulfonate condensates can be used. However, low molecular weight anionic or nonionic emulsifiers or mixtures thereof are usually used.

The preferred composition for the present invention is substantially nonionic and comprises a nonionic emulsifier.

If the size is a ketene dimer size, a hardening accelerator may be included in the suspension during or after addition of the size, if desired.

The present invention has the tendency that the sizing agent is anionic, or potentially anionic, that is, it tends to hydrolyse to become anionic during emulsification or during use of the sizing agent. This is particularly effective when the substance is a substance that tends to cause problems due to its stickiness and difficulty in traveling in the usual method. The present invention is also particularly effective when the size is an anhydride size, especially an alkenyl succinic anhydride (ASA) size because the present invention overcomes the runnability problems associated with anhydride size. This is because a method for realizing a quick sizing process and a good yield without any additional step therefor is provided.

A preferred example of the method of the present invention comprises using a cationic starch as a part or all of the yield improving agent and using colloidal silicic acid as the anionic compound, but usually one of the yield improving agents is used. Preferred is a method comprising using a synthetic cationic polymer as part or all and using bentonite as an anionic compound. The preferred size is ASA size when used as a nonionic or anionic emulsion.

Cationic retention aids may be included in the thick stock and / or in the reclaimed white water, but the retention aids are often added to the thin stock, eg in a fan pump. The anionic sizing agent is usually added at a relatively later stage, usually at the end of the centrifugal screen or at the subsequent stage. For example, the anionic sizing agent can be added with bentonite and other anionic compounds.

Since the sizing agent does not have to be pre-mixed with the cationic retention aid, the sizing agent can be mixed with an aqueous diluent in the presence of a suitable nonionic or anionic emulsifying agent so that the sizing agent can be bentonite or other anionic emulsifier. It will be possible to disperse it directly in the suspension of the compound or in any other aqueous stream used to add the sizing agent to the cellulosic furnish.

One particularly preferred method, such as that disclosed in US Pat. No. 4,753,710 and commercially available as "Hydrocol" .TM., Involves the synthesis of a water-soluble synthetic cationic polymer of high molecular weight (optionally). Is added to the suspension after addition of a low molecular weight cationic polymer such as polyethyleneimine or a dry strength improving resin),
The suspension is then passed through one or more shear pumps and / or centrifugal screens and then fed to the headbox. The bentonite dispersion is fed to the headbox or to any other location behind the final point of high shear stress application, and anhydrous sizing (or other sizing)
The anionic or nonionic emulsion of is either injected into the bentonite dispersion which flows to the point of addition to the cellulosic suspension or directly into the cellulosic suspension at the same time as the addition of bentonite.

The sizing agent may be added in a usual amount, but since the sizing agent is used more effectively in the present invention, it is possible to add a smaller amount than usual. For example, the size is typically 1-20 kg / t, preferably 2-6 kg
/ T.

The method of the present invention significantly reduces the amount of sizing required, especially when the cellulosic suspension contains an inorganic filler, and especially when the cellulosic suspension contains regenerant materials of various qualities. And achieves a very uniform size process. The retention aid functions as a filler and fiber flocculating agent, and the sizing agent is added to the post-flocculation suspension (eg as disclosed in US Pat. No. 4,753,710). Even if the flocs are destroyed by the application of shear stress and become micro-flocs, they can be used much more effectively. Therefore, it is highly desirable to add the sizing agent to the suspension in which flocculation or microflocculation has occurred, rather than to the cellulosic suspension in the initial state in which flocculation has not occurred.

[0050]

EXAMPLES Some examples will be shown below.

Example 1 A papermaking stock consisting of 50% bleached softwood chemical pulp, 40% bleached hardwood chemical pulp and 10% calcium carbonate filler was beaten to 45 ° SR at a concentration of 2%. The thick stock prepared was diluted to a concentration of 0.5% before treatment. A 0.05% aqueous solution of cationic polyacrylamide was added to this fiber suspension in an amount of 0.5 kg per ton of dry paper.
Was added as a dry polymer. Polymer is 7
6 wt% acrylamide and 24 wt% IV 10d
a copolymer with dimethylaminoethyl acrylate quaternized with methyl chloride having 1 / g, IV
It had 10 dl / g. This addition caused flocculation. The suspension was thoroughly mixed by turbulence, breaking the flocs into microflocs.

The non-ionically emulsified alkenyl succinic anhydride size was added as a 5% aqueous emulsion at various dose levels. The sizing emulsion comprises a mixture of 95% by weight conventional alkenyl succinic anhydride and 5% by weight nonionic oil-in-water emulsifier.
Lverson) mixture and added to water. The mixture was vigorously stirred for 1 minute to prepare a 5% active alkenyl succinic anhydride emulsion.

A 0.5% aqueous slurry of pre-hydrated bentonite was prepared and then added at a dose level of 2 kg dry bentonite per ton dry paper.

Handmade paper was produced from the pulp treated as described above in a laboratory paper making machine. The paper was pressed, dried by standard methods, and the extent of sizing was measured by a 1 minute Cobb test (Cobb method water supply test).

Instead of bleached softwood, it consists of 75% newspaper, 18% manila paper and 9% cardboard at 45 ° SR.
The same process was repeated using the finished waste paper material beaten up to. The results are shown below.

Dose level (kg / t) Chemical pulp (Cobb gm.m ^-2 ) Waste paper material (Cobb gm.m ^-2 ) 1 86.7 58.4 2 23.6 17.9 3 18.2 14. 4 4 19.3 15.4 6 16.5 11.1 Excellent yields were obtained in each test. Also,
The low Cobb values obtained at relatively small size doses indicate that sizing is effective.

Example 2 A polymer consisting of a copolymer containing 58: 42% by weight of the same monomers as in Example 1 and having an IV of 7 dl / g was used, the polymer was added at a dose of 1 kg / t and the cellulosic suspension was used. Is a high-grade finished paper material, and the same process as in Example 1 was repeated except that the emulsion was premixed with the bentonite slurry. The following results were obtained.

Dose Level (kg / t) Cobb gm.m ^-2 Value 2 19.6 4 20.0 10 19.8 Similarly, good yields were observed.

Example 3 (Comparative) 50% bleached softwood chemical pulp, 40% bleached hardwood chemical pulp and 10% calcium carbonate filler were beaten at a consistency of 2% to 45 ° SR.

A range of anionic sizing agents was evaluated for sizing performance on stock with no other chemicals added. Standard handsheets were prepared as described in Example 1. The sizing agents used are as follows: i. Alkenyl succinic anhydride (95% w / w) premixed with anionic phosphate ester (5% w / w) emulsifier,
Sizing dose: 0.15-0.175% active ASA.

Ii. Anionic liquid dispersion polymer (26.
Alkenylsuccinic anhydride (66% w / w) premixed with 5% w / w) and anionic phosphate ester (7.5% w / w), sizing dose: same as above.
The anionic liquid dispersion polymer used was a copolymer of 70 mol% acrylamide and 30 mol% sodium polyacrylate.

Iii. Commercially available rosin emulsifier (Beoid
Super 40), Dose: 2.0-2.5% in as-received form.

Iv. Naphthalene sulfonic acid (AKD.
Distearyl alkyl ketene dimer emulsion prepared using 3% dry / dry) in. The final emulsion contains 5% active A.D. K. D. Was applied in its neat form at a dose of 1.5-3.0%.

In all cases, the Cobb test showed that the paper was "sizeless paper", ie, substantially unsized.

Example 4 The procedure of Example 3 was repeated except that the intrinsic viscosity was about 8d.
A copolymer of dimethylaminoethyl acrylate quaternized with about 20 mol% methyl chloride and about 80 mol% acrylamide with 1 / g as a 0.5% active aqueous solution at 1 kg / t (dry / dry). The suspension was added and then the suspension was stirred before the sizing was added. After the size was added, pre-hydrated bentonite was added as a 0.5% aqueous slurry at a dose of 2 kg / t (dry / dry). The results are shown below.

Cationic Sizing Agent Sizing Agent Bentonite Cobb Value Copolymer Dose Dose (gm · m ⁻² ) Dose 1 kg / t (i) 0.15% 2 kg / t 46.9 1 kg / t 0.175% 2 kg / t 27 .4 1 kg / t (ii) 0.15% 2 kg / t 26.9 1 kg / t 0.175% 2 kg / t 25.3 1 kg / t (iii) 2.0% 2 kg / t unsized paper 1 kg / t 2.5% 2kg / t 105.5 1kg / t (iii) * 2.0% 2kg / t 26.2 1kg / t 2.5% 2kg / t 22.4 1kg / t (iv) 1.5% 2 kg / t 21.2 1 kg / t 3.0% 2 kg / t 17.4 * with aluminum sulphate In the above table the doses are explained in Example 3.

The above results again show that satisfactory sizing can be achieved in the present invention. High yield values and rapid dehydration were achieved in all processes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jiyoung Oliver Scottwell UK, West Yorkshire, River Sedge, Hightown, Kotswald Drive 2

Claims (13)

[Claims] 1. A nonionic or anionic sizing emulsion is added to a cellulosic suspension in the presence of a cationic polymer which renders the sizing directly adherent to the solids in the suspension. Drain to form a sheet,
And a method for producing an inner size paper by drying the formed sheet, wherein flocculation is caused in a cellulosic suspension by adding a water-soluble cationic retention aid. , Destroy the resulting flocs into cationically charged microflocs with virtually no fiber resuspension, and add nonionic or anionic sizing emulsion to the suspension after flocculation. A method for producing an inner sized paper, comprising adding a solution or dispersion of an anionic compound to obtain an aggregate suspension containing a sizing agent, and further draining the aggregate suspension to form a sheet. Method. 2. A suspension of cellulosic fibers is caused to undergo flocculation by the addition of a cationic retention aid, and the resulting flocs are destroyed substantially without resuspension of the fibers to become cationic. Charged micro-flocs, the micro-flocs are aggregated by adding a solution or dispersion of an anionic compound, the resulting aggregate suspension is drained to form a sheet, and the formed sheet is dried, A method of making an inner sizing paper comprising the presence of a sizing agent in an aggregate suspension, the method comprising the step of causing flocculation of the suspension by the addition of a cationic retention aid, followed by a nonion or A method for producing inner sized paper, characterized in that a sizing agent in the form of an anionic aqueous emulsion is added to the suspension. 3. The method according to claim 1, wherein the sizing agent is an anhydrous sizing agent. 4. The method according to claim 1, wherein the sizing agent is an alkenyl succinic anhydride sizing agent. 5. The anionic compound is an organic polymer material,
Method according to any one of claims 1 to 4, characterized in that it is selected from bentonite and colloidal silicic acid. 6. The cationic retention aid comprises a material selected from cationic starch and synthetic cationic polymers having a molecular weight greater than 500,000, and the anionic compound is selected from bentonite and colloidal silicic acid. The method according to claim 1, wherein the method is performed. 7. The cationic retention aid is added in an amount of 0.01 to 0.3% dry weight to dry weight, 50.
A synthetic cationic polymer having a molecular weight of more than 10,000, wherein the anionic compound comprises bentonite added in an amount of 0.01 to 0.5% dry weight to dry weight. 6. The method according to any one of 6 above. 8. The cationic retention aid is 4 dl / g.
8. The method of claim 7, comprising a cationic polyacrylamide having an intrinsic viscosity of greater than. 9. The method according to claim 1, wherein the suspension is a filler-containing suspension containing at least 10% by weight of inorganic filler. 10. The method according to claim 1, wherein all the cationic retention aids used are present in the suspension before the sizing is added. 11. The method according to any one of claims 1 to 10, wherein the sizing agent is added to the flocs by stirring to break the flocs into microflocs. 12. The method according to claim 1, characterized in that both the anionic compound and the sizing agent are added after the end of the end point of high shear stress. 13. The method according to claim 12, characterized in that the sizing agent and the anionic compound are added together or separately, but not too far apart.