JP2003301398A - Method of making paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of making a filler-containing paper by which paper strength and the yield from a raw material are improved and the production is stably carried out, and to provide a papermaking method by which the density of the filler-containing paper is reduced. <P>SOLUTION: The paper is made by adding a Hofmann degradation product of an acrylamide-based polymer having a branched cross-linked structure to a pulp slurry containing a filler. As a result, the effect for extremely reducing a production cost is exhibited by enabling the paper strength and the yield from the raw material to be improved even if the concentration of organic impurities in the pulp slurry is high. The concomitant use of an ionic polyacrylamide with a high molecular weight extremely exhibits effects on the reduction of the density of the paper. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a papermaking method. More specifically, it relates to a method for making a paper containing a filler, which is generally called a paper.

[0002]

2. Description of the Related Art In recent years, there has been a social demand for an increase in the used rate of used paper from the viewpoint of resource protection and resource reuse, and a reduction in the amount of factory wastewater discharged to the environment from the aspect of environmental protection, that is, an improvement in the closed rate of water. Various efforts are being made. On the other hand, from the perspective of papermaking technology, various contaminants generated in the waste paper pulp manufacturing process flow into the papermaking system, and the accumulation of these contaminants in the papermaking system progresses due to the improvement of the closed water ratio. The effect of the drug is obstructed and is decreasing.

Particularly, in a papermaking system containing a filler, the yield of not only pulp but also the filler on paper is reduced due to the influence of such contaminants, and the raw material unit is deteriorated, the paper quality is deteriorated, and fine suspended substances in wastewater are generated. The problem of increasing the concentration has become apparent, and useful resources have been re-introduced to solve the problem, resulting in an increase in production costs. On the other hand, there is a demand from the consumer side for price reduction, and it is a major issue to solve the above cost increase factors.

[0004] Usually, as a method for improving the filling yield in the papermaking process, it is general to use some yield improving agent. As the yield improver, a low to high molecular weight polymer having ionicity is used alone or in combination. Among the polymers to which ionicity is imparted, cationic polymers are widely used in view of fixing performance and the like, and among them, cationic polyacrylamide using acrylamide as a raw material is well known.

However, as described above, the concentration of various impurities in the papermaking process has recently increased, and the coexistence of ionic contaminants in particular has impaired the action of the ionic polymer, resulting in insufficient yield effects. To solve this problem, for example, a low molecular weight cationic polymer called a coagulant is added to the papermaking process in advance to block the ionic contaminants, and then a high molecular weight acrylamide polymer is added to improve the retention effect. A way to raise it is proposed. Other than that, various attempts have been made to reduce the influence of impurities and enhance the yield effect.

However, the concentration of contaminants in the actual papermaking process is constantly changing, and the multicomponent control based on the above ionic interaction cannot sufficiently cope with the variation of the concentration of contaminants, resulting in a sufficient yield effect. Has not been obtained.

On the other hand, due to the improvement of the ratio of used paper pulp,
Deterioration of paper quality In particular, deterioration of strength of paper is a problem. In the past, a sufficient effect was obtained with cationized starch, but the effect decreased with the increase in the concentration of the above contaminants, and in order to supplement it, attempts have been made to use a polyacrylamide paper strength enhancer together. However, it has not been fully effective.

[0008] Further, from the viewpoint of environmental protection and resource protection, attempts have been made to make the paper bulky and lightweight. However, by simply making the paper lighter, that is, reducing the basis weight, the opacity of the paper and the printing Optical properties such as strike-through and printability deteriorate.
These characteristics are closely related to the thickness of the paper, and various methods for improving the bulkiness of the paper have hitherto been tried. For example, cross-linked pulp is used (Japanese Patent Laid-Open No. 4-185792), or a filler such as an inorganic substance is filled between pulp fibers (Japanese Laid-Open Patent Publication No. HEI 3).
No. 124895), resulting in voids (JP-A-5-23).
0798) and the like.

However, the use of crosslinked pulp or the like makes recycling of the pulp difficult, and simply filling the filler causes a significant decrease in paper strength. As the bulking agent, a fatty acid polyamide type is commercially available, but in this case as well, the paper strength decreases. In addition, although there are reports of improvements in mechanical aspects, satisfactory performance has not yet been obtained.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a papermaking method for a filler-containing paper which can enhance the paper strength and the raw material yield, and can perform stable production, and a papermaking method which can reduce the paper density. It is in.

[0011]

In view of the above-mentioned problems, the present inventor has added high paper quality by adding a Huffman decomposition reaction product of an acrylamide polymer having a branched and crosslinked structure to a pulp suspension containing filler. In addition, the present inventors have developed a paper making method capable of achieving a raw material yield, and a paper making method capable of reducing the paper density by using a high molecular weight ionic polyacrylamide in combination.

The Hoffman decomposition reaction product of an acrylamide polymer having a branched crosslinked structure, that is, the present invention provides the following (1) to (13). (1) A method for paper making, which comprises adding a Huffman decomposition reaction product of an acrylamide polymer having a branched cross-linking structure to a pulp suspension containing a filling amount for paper making. (2) The method for making paper according to (1), wherein the acrylamide polymer having a branched crosslinked structure has a molecular weight of 1,000,000 to 10,000,000. (3) The paper making method according to (1) or (2), wherein the Hoffman decomposition reaction product is decomposed in a temperature range of 50 to 110 ° C. (4) The method for making paper according to any one of (1) to (3), wherein the pulp concentration of the pulp suspension is 0.1 to 5.0% by weight. (5) The method for making paper according to any one of (1) to (4), wherein the Hoffman decomposition reaction product has a primary amino group content of 25 to 70 mol%. (6) Starch is added to pulp suspension for papermaking (1)
A method for making paper according to any one of to (5). (7) The method for producing paper according to any one of (1) to (6), wherein the starch is a cationic or amphoteric starch. (8) Papermaking is performed by adding ionic polyacrylamide having a molecular weight of 1 to 20 million to the pulp suspension (1).
The method for making paper according to any one of to (7). (9) The ionic polyacrylamide is an anionic and / or cationic polyacrylamide (1) to
The method for papermaking according to any one of (8). (10) The paper-making method according to any one of (1) to (9), wherein starch and ionic polyacrylamide are added to the pulp suspension to make a paper. (11) Hoffman decomposition reaction product of acrylamide polymer having branched and crosslinked structure and molecular weight of 1 to 2000
A paper-making method for paper, which comprises reducing the density of paper by adding ionic polyacrylamide to a pulp suspension containing filler. (12) Hoffman decomposition reaction product of acrylamide polymer having branched and crosslinked structure and molecular weight of 1 to 2000
Bulky paper made by adding a lot of ionic polyacrylamide to a pulp suspension containing filler. (13) Starch is added to the pulp suspension for papermaking (1
1) The method for making paper according to the description.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. As the filler used in the present invention, various known fillers used in the conventional papermaking process can be used, for example, heavy or light calcium carbonate, talc, kaolin, white carbon, titanium dioxide, clay. , Calcined clay, synthetic silica and urea formamide resin loading. These fillers may be mixed from the waste paper pulp into the papermaking process, but if necessary, they are added in an amount of 0 to 40% by weight based on the pulp.

Next, the acrylamide polymer having a branched cross-linking structure is a polymer obtained by polymerizing in a water solvent by using together several kinds of polymerizable monomers containing acrylamide as a main component and specific monomers capable of imparting a branched cross-linking structure. Or a method of dispersing a polymer polymerized in an organic solvent in an aqueous solvent, and an O / W emulsion state, that is, a method of dispersing an aqueous monomer solution in an organic solvent and polymerizing the same. . Among these, the method of polymerizing in a water solvent to prepare a polymer is preferable from the viewpoint of stability in the aqueous polymer solution or dispersion state.

As the polymerizable monomer containing acrylamide as a main component, any one can be used as long as it is copolymerizable with a specific monomer capable of imparting a branched cross-linking structure, and an amide represented by acrylamide. In addition to the monomer having a group, as other monomer, for example,
Examples thereof include ionic monomers, hydrophobic monomers, hydrophilic monomers and the like. These may be used alone or in combination of two or more.

(Amido Group-Containing Monomer) As the amide group-containing monomer, acrylamide may be mentioned specifically from the viewpoint of economy and polymerizability, but methacrylamide may also be used.

(Ionic monomer) Among the ionic monomers, examples of the anionic monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and salts thereof, and vinyl sulfonic acid, Examples thereof include sulfonic acids such as styrenesulfonic acid and acrylamidomethylpropanesulfonic acid, and salts thereof.

Examples of the cationic monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate and N, N. Examples include amines such as dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide and salts thereof, and quaternized products thereof.

(Hydrophobic monomer) Examples of the hydrophobic monomer include acrylonitrile, N, N-di-n-propyl (meth) acrylamide, Nn-butyl (meth) acrylamide and Nn-hexyl (meth) acrylamide. , N-n-octyl (meth) acrylamide, N-te
N-alkyl (meth) acrylamide derivatives such as rt-octyl (meth) acrylamide, N-dodecylacrylamide, Nn-dodecylmethacrylamide, N, N-
Diglycidyl (meth) acrylamide, N- (4-glycidoxybutyl) (meth) acrylamide, N- (5-
N- (ω-glycidoxyalkyl) (meth) acrylamide derivatives such as glycidoxypentyl) acrylamide, N- (6-glycidoxyhexyl) acrylamide,
Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth)
(Meth) acrylate derivatives such as acrylate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, methacrylonitrile, vinyl acetate, vinyl chloride, vinylidene chloride, olefins such as ethylene, propylene and butene, styrene, α- Methylstyrene, butadiene, isoprene, etc. can be mentioned.

(Hydrophilic Monomer) Specific examples of the hydrophilic monomer include, in addition to (meth) acrylamide, diacetone acrylamide, N, N-dimethyl (meth) acrylamide, N-ethyl (meth) acrylamide, N. , N-diethyl (meth) acrylamide, N-propylacrylamide, N-acryloylpyrrolidine,
N-acryloylpiperidine, N-acryloylmorpholine, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, various methoxypolyethylene glycol (meth) acrylates, N-vinylformamide, N-vinylacetamide, N-vinyl-2- Examples thereof include pyrrolidone.

(Specific monomer capable of imparting branched cross-linking) As the monomer capable of imparting a branched structure, a specific N-substituted acrylamide derivative such as N, N-dimethylacrylamide, (meth) allylsulfonic acid and salts thereof, etc. Can be mentioned. Among these, it is preferable to use methallyl sulfonate.

The monomer capable of imparting a crosslinked structure is
For example, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, hexamethylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, divinylbenzene, Bifunctional cross-linkable monomers such as diallyl acrylamide, or 1,3,5-
Examples thereof include polyfunctional crosslinking monomers such as triacryloylhexahydro-S-triazine, triallyl isocyanurate, pentaerythritol triacrylate, trimethylolpropane acrylate, triacrylic formal, and diacryloylimide.

(Polymerization Initiator) The polymerization initiator used in the polymerization is not particularly limited, but a water-soluble one is preferable. Examples of the polymerization initiator include persulfate-based and peroxide-based initiators such as ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide, and tert-butyl peroxide. In this case, it is preferably used alone, but it can also be used as a redox polymerization initiator in combination with a reducing agent. Examples of the reducing agent include sulfites, bisulfites, salts of low ionic valence such as iron, copper and cobalt, organic amines such as N, N, N ′, N′-tetramethylethylenediamine, aldose and ketose. And reducing sugars.

An azo compound is also an initiator which can be used in the present invention, and specific examples thereof include 2,2'-azobis-2-methylpropionamidine hydrochloride and 2,2'-azobis-2-methylpropionamidine hydrochloride.
2'-azobis-2,4-dimethylvaleronitrile,
2,2'-azobis-N, N'-dimethyleneisobutylamidine hydrochloride, 2,2'-azobis-2-methyl-N
-(2-hydroxyethyl) -propionamide, 2,
2'-azobis-2- (2-imidazolin-2-yl)
-Propane and its salts, 4,4'-azobis-4-cyanovaleric acid and its salts, etc. can be used. Furthermore,
It is also possible to use two or more of the above-mentioned polymerization initiators in combination.

(Polymerization method) As a polymerization method using these monomers, radical polymerization is preferable, and a batch (batch) polymerization method in which all monomers are charged in a batch in a reaction vessel and polymerized,
A semi-batch (semi-batch) polymerization method in which a part or all of the monomer is dropped into the reaction vessel to perform polymerization, or a continuous method in which a monomer or the like is continuously supplied and the obtained polymer is continuously extracted may be used. The polymerization initiator may be added to the polymerization vessel in advance or all at once during the polymerization, or may be continuously or intermittently supplied during the polymerization. When supplying at the time of polymerization, the addition rate can be changed as necessary.

The polymerization temperature of the polymer in the present invention is generally 30 to 100 ° C. in the case of a single polymerization initiator,
In the case of redox type polymerization initiator, it is lower, generally 5 to
90 ° C. The polymerization temperature may be kept constant or changed during the polymerization, and cooling and heating can be carried out as necessary.

The atmosphere in the polymerization vessel is not particularly limited,
In order to carry out the polymerization rapidly, it is preferable to replace with an inert gas such as nitrogen gas.

In the production of the polymer, the polymerization pH is not particularly limited, and it can be adjusted to a predetermined pH for the polymerization, and the pH can be changed during the polymerization if necessary. Examples of pH adjusters that can be used in that case include alkalizing agents such as sodium hydroxide, potassium hydroxide and ammonia, mineral acids such as phosphoric acid, sulfuric acid and hydrochloric acid, and organic acids such as formic acid and acetic acid. (Branched cross-linking structure) The weight average molecular weight of the above polymer is preferably 100,000 to 10,000,000, and the weight average molecular weight is 500,000 to 10,
More preferably, it is, 000,000. More preferably, the weight average molecular weight is 1,000,000 to 10,
It is, 000,000.

The polymer of the present invention has a branched crosslinked structure,
The structure can be constructed by combining a monomer capable of imparting a branched structure and a monomer capable of imparting a crosslinked structure and polymerizing the above-mentioned monomer having acrylamide as a main component. Specifically, a batch polymerization method using those monomer mixed liquids,
A branched crosslinked structure can be formed by a semi-batch polymerization method or a continuous polymerization method. Further, in controlling the molecular weight, a polymerization initiator or a known chain transfer agent may be appropriately used, or may be appropriately adjusted depending on the polymerization conditions such as polymerization temperature and polymerization time.

The characteristic values of the branched and crosslinked structure include the molecular weight, the radius of gyration and the molecular chain density derived from them (the value obtained by dividing the molecular weight by the cube of the radius of gyration). The higher the molecular chain density, the denser the molecular structure, and vice versa. Further, the value itself is interlocked with the radius of gyration, and as the radius of gyration increases, the molecular chain density decreases. Although the radius of gyration increases as the molecular weight increases, the increase in the radius gyration can be suppressed by increasing the molecular chain density. Since the radius of gyration roughly correlates with the solution viscosity, the advantage of the branched crosslinked structure is that the increase in solution viscosity can be suppressed and the molecular weight can be increased. That is, in the conventional linear structure, the molecular weight and the radius of gyration (solution viscosity) are uniquely determined, but in the branched crosslinked structure, the relationship between the molecular weight and the radius of gyration (solution viscosity) is determined using the molecular chain density as a parameter.

In the filler-containing paper, since the filler is present in the paper layer, the inter-pulp distance tends to increase, and a structure having a large molecular weight and a large radius of gyration is preferable. That is, the relationship between the radius of gyration and the molecular chain density in the above-mentioned molecular weight range is as follows. In the radius of inertia of 30 nm, the molecular chain density is 15 to 5
3.5 to 15 at 0 and 60 nm, 1.0 at 100 nm
.About.8.0, preferably a molecular chain density of 15 to 30 at an inertia radius of 30 nm, 3.5 to 10.0 at 100 nm, 100 n
In m, it is 1.0 to 6.0. The above-mentioned molecular weight (weight average) and radius of gyration are GPC (gel permeation chromatograph).
It can be measured by a MALS (multi-angle light scattering molecular weight measuring device) device.

(Hoffman Decomposition Reaction) The Hoffman decomposition reaction of an acrylamide polymer will be described. When the acrylamide polymer is produced in an aqueous solution, the acrylamide polymer can be used as it is, or can be diluted as necessary and subjected to the Hoffman decomposition reaction. When the polymerization is carried out with another solvent, solvent replacement is carried out. In this case, the previous solvent may remain as long as it does not affect the performance or workability of the product obtained by the Hoffman decomposition. Further, when the acrylamide polymer is in the form of powder, it is dissolved in water and used as an aqueous solution for the Hoffmann decomposition reaction. The concentration at that time is 1-10%
However, it can be used after further dilution if necessary.

The Hoffmann decomposition reaction is carried out by causing hypohalous acid to act on the amide group of the polymer in the presence of an alkaline substance. Examples of the hypohalogenous acid include hypochlorous acid, hypobromite, Examples include hypoiodic acid.

Examples of the hypochlorite include alkali metal or alkaline earth metal of hypochlorous acid. Specifically, sodium hypochlorite, potassium hypochlorite, lithium hypochlorite, Examples thereof include calcium hypochlorite, magnesium hypochlorite, barium hypochlorite and the like.

Similarly, hypobromite and hypoiodite alkali metal or alkaline earth metal can be mentioned. Alternatively, a halogen gas may be blown into the alkaline solution to generate a hypohalite. On the other hand, examples of the alkaline substance include alkali metal hydroxides, alkaline earth metal hydroxides, and alkali metal carbonates. Among them, alkali metal hydroxides are preferable, sodium hydroxide, potassium hydroxide, and water. Examples thereof include lithium oxide.
The amount of the above-mentioned substances added to the polymer is 0.05 to 2 mol, preferably 0.1 to 1.5 mol, with respect to the amide group in the hypohalite, and the addition amount with respect to the amide group in the alkaline substance. It is 0.05 to 4 mol, preferably 0.1 to 3.0 mol. The Hoffmann decomposition reaction is carried out in the alkaline region, that is, in the pH range of 11-14. The polymer concentration at that time is about 0.1 to 17.
Although it is 5 wt%, it is usually preferable to be 0.1 to 10 wt%, since stirring becomes difficult and gelation easily occurs when the reaction concentration becomes high. Further, when the Hoffman decomposition reaction is carried out at a high temperature for a short time, the reaction rate may be slow when the reaction concentration is less than 1 wt%, so that it is more preferably 1 to 10 wt%.

The reaction temperature of the Hoffman decomposition reaction is 0 to 11
You can select from the range of 0 ℃, but from the low temperature side 50
It is preferable that the temperature is in a high temperature range of up to 110 ° C because the effect as a paper strength enhancer is higher.

The reaction time cannot be generally stated because it depends on the reaction temperature and the polymer concentration in the reaction solution. For example, when the polymer concentration is 1 wt%, it is 30-4 at 0 ° C.
Within 0 hours, within 3 to 4 hours at 20 ° C, within several tens of minutes at 50 ° C, within several minutes at 65 ° C, and within tens of seconds at 80 ° C. The higher the polymer concentration, the shorter the reaction time.

In such a Hofmann-decomposed polymer, the amount of primary amino groups introduced can be controlled by adjusting the amounts of hypohalite and alkali metal hydroxide added to the amide groups. The content of primary amino group is 10-9
It is 0 mol%, preferably 20 to 80 mol%, more preferably 25 to 75 mol%.

Next, after carrying out the Hoffman decomposition reaction under the above-mentioned conditions, it is desirable to stop the reaction in order to suppress the progress of side reactions. However, in the case of using immediately after the reaction, it may not be necessary to stop the reaction.

As a method for stopping the reaction, methods such as (A) adding a reducing agent, (B) cooling, and (C) lowering the pH of the solution by adding an acid can be used alone or in combination. .

(A) is a method of deactivating the remaining hypohalite by reacting with a reducing agent. Specific examples of the reducing agent used include sodium sulfite, sodium thiosulfate, ethyl malonate, thioglycerol, triethylamine and the like. The amount of the reducing agent to be used is 0.00 with respect to the hypohalite usually used in the reaction.
It is 5 to 0.15 times mol, preferably 0.01 to 0.10 times mol.

(B) is a method of suppressing the reaction progress by cooling, and examples of the method include a method of cooling using a heat exchanger or a method of diluting with cold water. The temperature at that time is usually 50 ° C. or lower, preferably 45 ° C. or lower, and more preferably 40 ° C. or lower.

(C) is a method of stopping the Hofmann decomposition reaction by using an acid to lower the pH of a reaction-terminated liquid that normally has a pH of 12 to 13 and at the same time suppresses the progress of hydrolysis. The pH at that time may be neutral or lower, and is preferably in the range of pH 4 to 6. pH
Examples of the acid used for the adjustment include mineral acids such as hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, and organic acids such as formic acid, acetic acid and citric acid.

Next, the reaction liquid stopped by the above reaction can be used as it is, and the aqueous solution is put into a solvent which does not dissolve the polymer such as methanol to precipitate the polymer, and then dried to obtain a powder. You can also Further, the Hofmann-decomposed polymer can be stored in a tank and used as required. The storage temperature at that time is
The temperature may be low enough not to freeze the aqueous solution, preferably 0 to 15 ° C.

The Hoffman decomposition reaction product of the acrylamide polymer produced by the above method can be used in the same manner as a usual paper strength agent. That is, although it can be used alone, it can also be used in combination with an anionic resin such as an anionic acrylamide polymer.

The addition ratio of the Hofmann-decomposed polymer and the anionic resin can be arbitrarily selected, and is preferably in the range of 100: 0 to 10:90 in terms of solid content weight ratio.
The amount of solid content added to the pulp suspension at that time is 0.01 to 5% by weight, preferably 0.05 to 2% by weight, based on the weight of dry solid content of pulp.

The Hofmann-decomposed polymer is used in the process of making paper, and its addition can improve the paper strength and the raw material yield of pulp and filling amount.

When the amount of Hofmann-degraded polymer added is increased, a high filler yield can be achieved and the density of the paper can be reduced even if the amount of the filler added is increased, whereby a bulky paper can be produced.

(Starch) When starch is used in combination with Hoffmann-decomposed PAM, it is more effective in improving the yield of the sizing agent and the filling amount or the paper strength. The starch is preferably cationic starch or amphoteric starch. The cationic starch referred to here is, for example, corn, wheat,
It is a starch in which raw starch such as potato and tapioca contains at least one basic nitrogen selected from primary, secondary, and tertiary amino groups and quaternary ammonium salt.
The amphoteric starch is, for example, the same raw starch as described above using at least one selected from a tertiary amino group and a quaternary ammonium salt, and at least one selected from phosphoric acid, sulfonic acid, etc. And a starch containing anionic properties. The amount of starch added to the pulp suspension was 0.
It is 1 to 5% by weight, preferably 0.2 to 2% by weight.

(High molecular weight ionic polyacrylamide) By using a high molecular weight ionic polyacrylamide together with Hofmann-decomposed PAM, the yield of fine pulp, filler and sizing agent can be further improved. Further, by using them together, bulky paper can be produced even if the amount of Hoffman-decomposed PAM added is reduced. The amount of the Hoffman-decomposed PAM added at that time varies depending on the pulp raw material and the papermaking conditions and cannot be determined unconditionally, but is generally 0.
It is 5% by weight or less. The addition amount of the ionic polyacrylamide used together is 0.005% by weight or more based on the weight of the dry solid content.

The weight average molecular weight is 500,000 to 200.
It is 0,000, preferably 1 to 20,000,000. The ionicity may be anionic, cationic or amphoteric.
Anionic polyacrylamide can be produced by copolymerization with anionic monomer or hydrolysis of polyacrylamide. The above-mentioned monomers can be used as the anionic monomer. Cationic polyacrylamide can be produced by copolymerization with a cationic monomer. The above-mentioned monomers can be used as the cationic monomer. Examples of the production method include a batch polymerization method, a dispersion polymerization method in which a polymer is dispersed in an inorganic salt-dissolved aqueous solution, and a reverse layer suspension polymerization method in which a polymer aqueous solution is suspended in oil. The solid content of the pulp suspension is 0.0 based on the dry solid weight of the pulp.
It is from 01 to 0.5% by weight, preferably from 0.005 to 0.1% by weight. Two types of cationic and anionic polyacrylamides can be added together, or each can be added alone.

(Pulp Suspension) Pulp as referred to in the present invention is separated from a material containing a cellulose component such as wood and straw, and is mainly wood pulp. As pulp produced from wood, there are chemical pulp obtained by chemically removing lignin, semi-chemical pulp, and mechanically physically divided mechanical pulp.

Also, waste paper pulp obtained by disintegrating the recovered waste paper is included, and the ratio of pulp to pulp is increasing year by year.
The actual pulp suspension contains various contaminants in addition to the above-mentioned pulp. There are many types of contents, including those that are entrained and mixed in during the pulp manufacturing process, those that occur during the disintegration process of used paper, and those that the chemicals added during the papermaking process remain in the suspension without being fixed to the pulp. is there. Furthermore,
Concentration of these contaminants will be accumulated and increased by recycling water.

The pulp concentration in the pulp suspension is 0.1 to
It is 5.0% by weight, and will change depending on each step of the papermaking process. On the other hand, although foreign substances have been attracting attention as inorganic substances, organic foreign substances have a stronger binding force with organic chemicals and exert a great influence. The concentration can be measured separately for the ionic contaminant concentration and the total organic contaminant concentration. The ionic contaminant concentration can be measured by colloid titration of the filtrate after filtering the pulp suspension. Similarly, the total organic contaminant concentration can be measured by COD (chemical oxygen demand) or TOC (total organic carbon) after filtering the pulp suspension. These general measured values vary depending on various factors such as paper type and operating conditions and cannot be described unconditionally, but the concentration of ionic impurities is generally 10 to 1000 μeq / l (per liter of filtrate), total organic Contaminant concentration is 50-500 in TOC conversion
It is 0 ppm. In recent years, the concentration of contaminants has increased due to the increase in the utilization rate of waste paper pulp and the improvement of the circulation rate of water, especially white water. The concentration of ionic contaminants is 50 μeq / l or more, and the concentration of all organic contaminants is 100 ppm or more in TOC conversion. And the effect of adding chemicals is reduced.

(Papermaking) Paper as used in the present invention means wood,
Pulp containing cellulose component such as straw and / or waste paper pulp as the main raw material, and containing all the filling amount as an essential component, refers to all produced by water, specifically, various printing / information paper, Examples include coated base paper and newsprint.

Various chemicals are added to the above pulp raw material to make paper. At that time, the chemicals may be added at any place in the papermaking process before the wet sheet is formed, and the chemicals may be added in any order. However, even after the wet sheet is formed, it may be added by spray coating, size press coating, or roll coater coating.

The concentration of the Hoffman decomposition reaction product of the acrylamide polymer added to the pulp suspension is about 0.
It is 1 to 10% by weight, preferably 0.5 to 5% by weight.

The concentration when the filler is added to the pulp suspension may be the product concentration as it is, or may be added after dilution to improve the dispersion in the pulp suspension.

The concentration when starch is added to the pulp suspension cannot be generally stated because it varies depending on the type of starch, the place of addition, the design of the paper machine, etc., but it is generally 0.1-1.
It is 0% by weight.

When adding an ionic polyacrylamide pulp having a molecular weight of 1 to 20 million into a suspension,
Since the molecular weight is large and it takes time to uniformly dilute it, it is preferable to provide an intermediate tank, dilute it to 0.1 to 1% and store it, and then send the required amount from there. Also,
A mixer may be provided in the liquid feeding line to dilute online and continuously add.

The pulp suspension pH at the time of papermaking is not particularly limited, but may be limited depending on the kind of the filler. For example, when using calcium carbonate, the pH is 6.5.
The above is preferable. Further, in order to fully exert the effect of the Hoffman decomposition reaction product of the acrylamide polymer having a branched and crosslinked structure of the present invention, the pH is 5.5 or more, preferably p.
It is H 6.0 or more.

In addition, other chemicals such as sulfuric acid band,
Papermaking can be performed by adding polyaluminum chloride, a sizing agent, a defoaming agent, a fluorescent agent, a dye, etc., as needed to improve the paper quality characteristics.

[0063]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, what is shown by% means% by weight unless otherwise specified.

(Production Example-1 of polyacrylamide) 328.4 g of pure water was put in a five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas introducing pipe, and a dropping port. Was charged and the internal temperature was adjusted to 80 ° C. while blowing nitrogen gas. On the other hand, 50% Acrialamide 3
73.9 g, sodium methallyl sulfonate 2.5 g,
62.5 g of pure water are mixed and dissolved, and the pH is brought to 4.2 with 35% HCl.
Adjusted to. Also, 84% pure 4,4′-azobis-4
-A solution of 0.48 g of cyanovaleric acid dissolved in 64.0 g of pure water was prepared and uniformly dropped into each reaction container over 3 hours. During this time, the internal temperature was kept at 80 ° C. After the dropping is completed,
Further, polymerization was carried out at 80 ° C. for 2 hours. Then 50
% Acrylamide 19.2 g, methylene bis acrylamide 0.4 g, pure water 37.5 g mixed and dissolved to give 35% HC
The pH was adjusted to 4.2 with 1. Also, with a net content of 84% 4,
0.11 g of 4'-azobis-4-cyanovaleric acid was added to pure water 6
A solution dissolved in 4.0 g was prepared and uniformly dropped into each reaction container over 1 hour. During this time, the internal temperature was kept at 80 ° C. After the dropwise addition was completed, the polymerization was further continued at 80 ° C. for 2 hours to obtain a polymer having a nonvolatile content of 20% and a Brookfield viscosity at 25 ° C. of 5,800 mPa · s. GPC
-By the MALLS method, the weight average molecular weight is 1,20.
50,000, the radius of gyration was 44.5 nm, and the molecular chain density calculated from them was 13.7.

(Production Example-2 of polyacrylamide) 376.2 g of pure water was put in a five-necked flask (hereinafter referred to as a reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas introducing pipe, and a dropping port. Was charged and the internal temperature was adjusted to 80 ° C. while blowing nitrogen gas. On the other hand, 50% Acrialamide 2
80.0 g, sodium methallyl sulfonate 1.3 g,
Methylenebisacrylamide 0.1 g, pure water 237.8
g was mixed and dissolved, and the pH was adjusted to 4.2 with 35% HCl.
Further, a solution prepared by dissolving 0.46 g of ammonium persulfate in 48.0 g of pure water was prepared and uniformly dropped into each reaction vessel over 3 hours. During this time, the internal temperature was kept at 80 ° C. After the dropping was completed, the polymerization was further continued at 80 ° C. for 2 hours to obtain a polymer having a nonvolatile content of 15% and a Brookfield viscosity at 25 ° C. of 7,800 mPa · s. GPC-MAL
The weight average molecular weight is 2,510,00 as measured by the LS method.
0, the radius of gyration was 80.1 nm, and the molecular chain density calculated from them was 4.9.

(Production Example-3 of polyacrylamide) 63 parts of pure water was placed in a heat-retaining container equipped with a stirrer, a reflux condenser and a thermometer.
8.6 g, 50% Acrialamide 239.2, and 1.6 g of acrylic acid were mixed and dissolved, and the pH was adjusted to 4. with 25% NaOH.
Adjusted to 5. After raising the temperature of the mixed solution to 45 ° C., a solution of 0.25 g of ammonium persulfate dissolved in 100.0 g of pure water was dropped into the mixed solution. A few minutes later, a solution of 0.05 g of sodium sulfite dissolved in 100.0 g of pure water was added dropwise to the reaction vessel. After the dropping was completed, the polymerization was carried out for 2.5 hours. After completion of polymerization, non-volatile content 12.5%, 25 ℃
Brookfield viscosity at 25,000 mPa
A polymer of s was obtained. By GPC-MALLS method measurement,
Weight average molecular weight is 680,000, radius of gyration is 63.3
nm, and the molecular chain density calculated from them was 2.6. (Production of Hoffman-degraded polyacrylamide)

Next, a method for Hoffmann decomposition of the polymers obtained in Production Examples-1, -2, -3 will be described. 2.0 g of the solid content of the polymer was taken, and this was diluted with pure water to a total of 40.0 g and dissolved. The solution is heated to 70 ° C. and stirred 1
11.20 g of a mixed solution of 2.5% sodium hypochlorite and 20% sodium hydroxide (molar ratio 1: 2) was added 3
Hold for 0 seconds. Then, pre-cooled pure water 15
2.60 g was added, and this was further cooled in ice water to obtain a Hoffman decomposition reaction product. Then, colloid titration was performed with 1/400 N-potassium polyvinylsulfonate aqueous solution using toluidine blue as an indicator. The obtained cation valencies are as shown in the following table and are designated as sample A, sample B and sample C, respectively.

(Papermaking evaluation-1) L which is 400 ml CSF
BKP / NBKP / DIP (waste paper deinked pulp) ratio is 6 /
While stirring 1/3 of the pulp suspension having a concentration of 1.0% (ionic contaminant concentration: 59 μeq / l, TOC: 250 ppm), cationized starch → AKD → band → Sample A
(Alternatively, sample B and sample C) → chemicals were added in the order of light calcium carbonate to prepare a papermaking sample.
The chemicals were added at 1-minute intervals. Table 1 [Table 1]
Shows the added chemicals and their addition amounts. The anionic and cationic retention agents in the table had the following characteristics.

Anionic retention agent: acrylamide-acrylic acid copolymer concentration 5.0%, acrylic acid content 15 mol%, weight average molecular weight 10 million Cationic retention agent: acrylamide-methacryloyloxyethyltrimethylammonium chloride copolymer Polymer concentration 5.0%, methacryloyloxyethyltrimethylammonium chloride content 20 mol%, weight average molecular weight 8 million Take 1 part of the pulp suspension, and measure CSF according to JIS P8121, and also measure DDJ (dynamic, The DDJ yield was measured by the Drainage, Jar) method. The wire mesh used was 40 mesh, the stirring speed was 1000 rpm, and the filtration time was 20 seconds. The rest was paper-made with a TAPPI square sheet machine. The wet sheet made from paper is dried in a drum dryer at 110 ° C for about 3 minutes,
A handmade paper having a basis weight of 80 g was obtained. The obtained dry paper at 23 ° C,
After conditioning the humidity in a constant temperature and humidity room at RH 50% for 24 hours or more,
Basis weight (JIS P8124), Tightness (JIS P811
8), breaking length (JIS P8113), Z-axis strength (internal bond tester, manufactured by Kumagai Riki Kogyo Co., Ltd.),
The ash content (JIS P8128) was measured. The results are shown in Table 2 [Table 2]. The breaking length and Z-axis strength in the table are ash 1
It is an estimated value when it is set to 6.0%.

[0070]

[Table 1]

[0071]

[Table 2]

(Papermaking evaluation-2) TMP (thermo-mechanical pulp)
/ Newspaper DIP (new waste paper deinking pulp) ratio of 6/4 pulp suspension (pulp concentration 3.0%, ionic contaminant concentration:
460 μeq / l, TOC: 1050 ppm and actual white water (suspended substance concentration: 0.54%, ionic contaminant concentration:
A papermaking experiment was conducted using 370 μeq / l, TOC: 850 ppm). While stirring the pulp suspension, add chemicals in the order of neutral rosin sizing agent → band → sample A (or sample B, sample C), and then add actual white water so that the pulp concentration becomes 1%. Then, the chemicals were added in the order of light calcium carbonate and retention agent to prepare a papermaking sample. The chemicals were added at 1-minute intervals. Table 3 [Table 3] shows the added chemicals and their addition amounts.

A part of the pulp suspension was taken, and JIS P8
The CSF was measured according to 121, and the DDJ yield was measured by the DDJ (dynamic, drainage, jar) method. The wire mesh used for the measurement was 40 mesh, the stirring speed was 1000 rpm, and the filtration time was 20 seconds. The rest was paper-made with a TAPPI square sheet machine. The wet sheet made from paper was dried with a drum dryer at 110 ° C. for about 3 minutes to obtain a handmade paper having a basis weight of 50 g. The obtained dry paper was conditioned in a thermo-hygrostat at 23 ° C. and RH 50% for 24 hours or more, and then the basis weight (JIS P8124), the tenacity (JIS P8118), and the breaking length (JIS P811).
3), Z-axis strength (internal bond tester, manufactured by Kumagai Riki Kogyo Co., Ltd.), and ash content (JIS P8128) were measured. The results are shown in Table 4 [Table 4]. The breaking length and Z-axis strength in the table are estimated values when the ash content is 8.0%.

[0074]

[Table 3]

[0075]

[Table 4]

[0076]

EFFECTS OF THE INVENTION According to the present invention, even if the concentration of organic contaminants in the pulp suspension is high, it is possible to improve the paper quality, especially the strength of the paper and the yield of raw materials, which is very effective in reducing the production cost. In addition, the combined use of high molecular weight ionic polyacrylamide is very effective in reducing the density of paper.

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Claims (13)

[Claims] 1. A method for paper making, which comprises adding a Huffman decomposition reaction product of an acrylamide polymer having a branched cross-linking structure to a pulp suspension containing a filling amount to improve paper strength and yield. . 2. The molecular weight of the acrylamide polymer having a branched and crosslinked structure is 1 to 10,000,000.
The method for making paper according to [4]. 3. The Hoffman decomposition reaction product is a decomposition reaction product in the temperature range of 50 to 110 ° C.
The method for making paper according to [4]. 4. The pulp concentration of the pulp suspension is 0.1 to 10.
The paper making method according to any one of claims 1 to 3, which is 5.0% by weight. 5. The method for making paper according to claim 1, wherein the Hoffman decomposition reaction product has a primary amino group content of 25 to 70 mol%. 6. The method for making paper according to claim 1, wherein starch is added to the pulp suspension to make a paper. 7. The method for producing paper according to claim 1, wherein the starch is a cationic or amphoteric starch. 8. A pulp suspension having a molecular weight of 1 to 200,000.
The paper-making method according to any one of claims 1 to 7, wherein the paper-making is performed by adding 0,000 ionic polyacrylamide. 9. The paper-making method according to claim 1, wherein the ionic polyacrylamide is an anionic and / or cationic polyacrylamide. 10. The paper-making method according to claim 1, wherein starch and ionic polyacrylamide are added to the pulp suspension to make a paper. 11. A Huffman decomposition reaction product of an acrylamide polymer having a branched cross-linking structure and a molecular weight of 1 to 2 million.
A method for paper making, which comprises adding 10 million ionic polyacrylamide to a pulp suspension containing filler to reduce the density of the paper. 12. A Huffman decomposition reaction product of an acrylamide polymer having a branched and crosslinked structure and a molecular weight of 1 to 2 million.
Bulky paper made by adding 10 million ionic polyacrylamide to a pulp suspension containing filler. 13. The paper-making method according to claim 11, wherein starch is added to the pulp suspension for paper-making.