JP3494260B2 - How to make paper or paperboard - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing paper or paperboard. Specifically, it relates to a method for producing paper or paperboard having excellent paper strength even in a papermaking system in which a large amount of calcium ions are present.

[0002]

2. Description of the Related Art In recent years, the supply situation of raw wood, which is a raw material for paper, has been getting worse, and an increase in the ratio of used paper has become an important issue. In addition, as part of environmental measures, it is inevitable that the paper or paperboard manufacturing process will be closed, and papermaking conditions such as water quality drop and water temperature rise are getting worse. In particular, as the amount of used magazines and the like increases, and as the neutralization of papermaking systems progresses, the concentration of calcium carbonate in the papermaking system increases, and a large amount of calcium ions are present in the papermaking system.

Further, conventionally, anionic, cationic, or amphoteric acrylamide polymers have been widely used as a paper-strengthening agent in the papermaking process for such paper or paperboard. However, as a result of the large amount of foreign substances (calcium ions, etc.) existing in the papermaking system due to the increase in the ratio of used paper and the closing of drainage, the fixability of the paper-strengthening agent to pulp is reduced, and As a result, it is no longer possible to achieve the full effect. That is, the acrylamide polymer strength enhancer is fixed to the anionic pulp by electrostatic attraction, but the presence of a large amount of electrolyte ions such as divalent calcium ions inhibits the strength of the strength enhancer. It In particular, the presence of divalent calcium ions greatly reduces the ability of the cationic groups in the paper strength additive to fix to the pulp.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing paper or paperboard which has a good fixing ratio to pulp and excellent paper strength even in a papermaking system containing a large amount of calcium ions. The purpose is to

[0005]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems of the prior art, and as a result, as a paper strength enhancer, a specific N-substituted (meth) acrylamide was used as a constituent component. If an ionic (meth) acrylamide water-dispersible polymer is used, since the water-dispersible polymer forms a polymer complex and becomes cloudy, even in a papermaking system in which a large amount of calcium ions are present, The inventors have found that it is possible to produce paper or paperboard having excellent paper strength, and have completed the present invention.

That is, according to the present invention, a pulp slurry containing calcium ions in an amount of 50 ppm to 5000 ppm does not contain, as a paper-strengthening agent, an atomic group in which the N substituent exhibits ionicity, and the N substituent contains 4 to 4 carbon atoms. A paper characterized by being made after adding an ionic (meth) acrylamide water-dispersible polymer having 0.1 to 10 mol% of N-substituted (meth) acrylamide having 20 carbon atoms as a constituent component. Or, it relates to a method for manufacturing paperboard.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The ionic (meth) acrylamide-based water-dispersible polymer of the present invention comprises (meth) acrylamide, an ionic monomer and the aforementioned specific N-substituted (meth).
It is obtained by copolymerizing acrylamide, and further, if necessary, it is obtained by copolymerizing a crosslinkable monomer and other monomers within a range that does not adversely affect the performance.

In the present invention, (meth) acrylamide means acrylamide or methacrylamide (hereinafter the same meaning as (meth)), and these can be used alone or in combination, but from the economical point of view. It is recommended to use acrylamide alone.

Examples of the ionic monomer include anionic monomer and cationic monomer. Examples of the anionic monomer include monocarboxylic acids such as (meth) acrylic acid and crotonic acid; maleic acid, fumaric acid,
Dicarboxylic acids such as itaconic acid, muconic acid, citraconic acid; organic sulfonic acids such as vinyl sulfonic acid, styrene sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid; or sodium salts of these various organic acids. , Potassium salts and the like. Examples of the cationic monomer include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth).
A vinyl monomer having a tertiary amino group such as acrylamide or a salt thereof of an inorganic acid or an organic acid such as hydrochloric acid, sulfuric acid or acetic acid, or a vinyl monomer having a tertiary amino group and methyl chloride or benzyl chloride,
Examples thereof include vinyl monomers containing a quaternary ammonium salt obtained by reaction with a quaternizing agent such as dimethylsulfate and epichlorohydrin. These ionic monomers may be used alone or in combination of two or more and impart anionic, cationic or amphoteric ionicity to the (meth) acrylamide water-dispersible polymer.

The N-substituted (meth) acrylamide of the present invention means that it is bonded to the nitrogen atom of (meth) acrylamide.
Or 4 to 20 carbon atoms instead of 2 hydrogen atoms
A N-substituent having a N-substituent ,
The substituent does not include an atomic group showing ionicity. The atomic group exhibiting ionicity refers to a functional group exhibiting anionic or cationic properties in an acidic or alkaline pH range, such as an anionic functional group such as a carboxyl group or a sulfonyl group, , Amino functional groups such as amino groups. Therefore, those having a functional group exhibiting such ionicity are excluded from the N substituent. And an N substituent composed of 4 to 20 carbon atoms
Is, N substituents, as such as an alkyl group, refers to those composed of only carbon atoms. Further, the carbon number in the N substituent is 4 to 20 because the paper-strengthening agent forms a polymer complex due to the hydrophobicity of the N substituent.
This is to improve the fixability to pulp even in a papermaking system in which a large amount of calcium ions are present. When the carbon number in the N substituent is 3 or less, the fixability cannot be improved. The number of carbon atoms in the N substituent is particularly preferably 6 to 12.

Examples of such an N substituent include, for example, a butyl group, an octyl group, a dodecyl group, a hexadecyl group, an octadecyl group, a 1-methylundecyl group, a 1-methylnonyl group, 1,1,3,3- alkyl group linear or branched, such tetramethylbutyl group.

Further, in the present invention, a crosslinkable monomer may be used in addition to the above monomers. For example, ethylene glycol di (meth) acrylate, diallylamine, bifunctional monomers such as N-methylol acrylamide, triallyl isocyanurate, trifunctional monomers such as N, N-diallyl acrylamide, and tetrafunctional such as tetraallyloxyethane. Monomer or allyl (meta)
Examples thereof include vinyl monomers having a chain transfer substituent such as acrylate, diethylene glycol mono (meth) acrylate, and dimethylacrylamide.

Further, as other monomers, for example, esters of anionic monomers such as (meth) acrylic acid and maleic acid with alcohols, styrene and α-
Methyl styrene, vinyl toluene, acrylonitrile,
Methyl vinyl ether, isopropyl acrylamide,
Examples thereof include vinyl acetate and α-olefin.

The proportions of the (meth) acrylamide, the ionic monomer and the N-substituted (meth) acrylamide used are such that the paper strength containing the ionic (meth) acrylamide water-dispersible polymer obtained by copolymerizing them. The decision should be made with due consideration of the intended use of the enhancer.

That is, the amount of (meth) acrylamide used is usually 80 to 99.8 with respect to the total molar amount of the monomers.
When the amphoteric (meth) acrylamide-based water-dispersible polymer is obtained, it is about 80 to 99.7 mol%. It is preferably about 80 to 99.4 mol%. When it is less than 80 mol%, it is difficult to have a sufficient paper strength effect.

The amount of the ionic monomer used is usually 0.1 to 10 with respect to the total molar amount of the monomers when the anionic (meth) acrylamide water-dispersible polymer is obtained. Mol%, preferably 0.2
When 8 to 8 mol% is used to obtain a cationic (meth) acrylamide water-dispersible polymer, the cationic monomer is used in an amount of 0.1 to 10 mol% based on the total molar amount of the monomers.
About 0.2 to 8 mol% is used. Further, in the case of obtaining an amphoteric (meth) acrylamide-based water-dispersible polymer, the cationic monomer is used in an amount of about 0.1 to 10 mol%, preferably 0.2 to 8 mol% based on the total molar amount of the monomers.
Mol%, anionic monomer, about 0.1 to 10 mol%, preferably 0.2 to 8 with respect to the total molar sum of the monomers.
Use mol%. When the ratio of the ionic monomer is less than the above range, the fixing property of the pulp is deteriorated because the ratio of the ionic component is small, and when the ratio exceeds the above range, the ratio of (meth) acrylamide is small, so that a sufficient paper content is obtained. It is difficult to obtain paper having strength. In addition, in neutral papermaking or weakly acidic papermaking, it is better to use more cationic monomers than anionic monomers. On the other hand, when used in acidic papermaking, it is better to use a large amount of anionic monomer.

The amount of N-substituted (meth) acrylamide used is about 0.1 to 10 mol%, preferably 0.5 to 7 mol%. If the amount is less than 0.1 mol%, the resulting dispersion of the ionic (meth) acrylamide-based water-dispersible polymer does not cloud sufficiently and the fixing rate to pulp is insufficient.
On the other hand, if it exceeds 10 mol%, the fixing rate is improved, but the proportion of (meth) acrylamide is reduced, and as a result, the portion where the ionic (meth) acrylamide water-dispersible polymer is hydrogen-bonded to the pulp is reduced, It is difficult to obtain paper having sufficient paper strength. Further, if it exceeds 10 mol%, the ionic (meth) acrylamide-based water-dispersible polymer tends to separate and settle, and it is difficult to obtain a uniform dispersion liquid. When, for example, styrene or the like is used as the hydrophobic monomer in place of the N-substituted acrylamide in the above-mentioned range of use, a cloudy dispersion having the same appearance as the above is obtained. The strength cannot be obtained.
The reason is that the N-substituted (meth) acrylamide of the present invention is
Due to its excellent copolymerizability with ( meth) acrylamide, a copolymer of uniform composition forms a polymer complex and becomes cloudy, resulting in good fixing of the ionic (meth) acrylamide water-dispersible polymer itself. In contrast to N-substituted (meth) acrylamide, styrene and the like have poor copolymerizability with (meth) acrylamide, resulting in formation of a homopolymer close to styrene and the like, resulting in cloudiness.
This is because the fixability of the acrylamide polymer is not sufficient even if the dispersion liquid shows good fixability.

When a crosslinkable monomer is used, its amount is usually about 5 mol% or less, preferably 2 mol% or less, based on the total molar amount of the monomers. If it exceeds 5 mol%, the copolymer obtained will be gelled, which is not preferable.

When a monomer other than the above is used, the amount used is about 10 mol% or less, preferably 8 mol% or less, based on the total molar sum of the monomers. When it exceeds 10 mol%, the ratio of (meth) acrylamide becomes small, and it is difficult to obtain a paper having a sufficient paper strength effect.

As a method of copolymerizing the above-mentioned monomers to obtain an ionic (meth) acrylamide water-dispersible polymer, various conventionally known methods can be adopted. For example, by charging each of the monomers and water into a predetermined reaction vessel, a persulfate such as potassium persulfate or ammonium persulfate, or a redox-based polymerization initiator in the form of a combination of these with a reducing agent such as sodium bisulfite. An ionic (meth) acrylamide-based water-dispersible polymer can be obtained by adding an ordinary radical polymerization initiator and heating with stirring.

The weight average molecular weight of the obtained ionic (meth) acrylamide water-dispersible polymer is usually about 100,000 to 10,000,000, and the viscosity is 10% by weight of solid content.
It is usually about 30,000 cps (25 ° C) or less,
The property is preferably about 20000 cps (25 ° C.) or less.

The obtained ionic (meth) acrylamide-based water-dispersible polymer dispersion is preferably cloudy to some extent, and exhibits a turbidity of 30 degrees or more at a concentration of 10% by weight. In addition, a material that can maintain a uniformly dispersed state (a material that does not separate and settle) is preferable. Turbidity 30
If it is less than the above range, it cannot be said that the ionic (meth) acrylamide water-dispersible polymer sufficiently forms a polymer complex, and the fixability is not sufficient. Further, if it cannot maintain a uniformly dispersed state, that is, if it is separated and settled, it becomes unsuitable for use as a paper strengthening agent.
The turbidity is a value obtained by measuring scattered light of 180 degrees using infrared light of 900 nm using an ANALITE turbidimeter 152 (manufactured by Central Science Co., Ltd.). Is a standard substance (formazine standard solution 40
0 degree, relative evaluation value with respect to Wako Pure Chemical Industries, Ltd.

In the method for producing paper or paperboard of the present invention, the ionic (meth) acrylamide water-dispersible polymer is added as a paper-strengthening agent to a pulp slurry containing calcium ions in an amount of 50 ppm to 5000 ppm, and then the paper is made. In general, except that the pulp slurry contains a large amount of calcium ions and the specific ionic (meth) acrylamide-based water-dispersible polymer is used as a paper strengthening agent. However, the same conditions as in the method for producing paper or paperboard can be adopted.

That is, the paper-strengthening agent may be added usually in a proportion of about 0.1 to 1% by weight (solid content) based on the pulp solid content. Further, the timing of addition of the paper strengthening agent can be set appropriately, and the pH of the papermaking system can be applied over a wide range from the acidic range to the alkaline range. Further, the type of pulp and the type of papermaking white water may be appropriately determined according to the papermaking conditions, and a sizing agent, a fixing agent, a filler and the like can be appropriately compounded and added.

The calcium ion concentration in the pulp slurry is measured by LASA's pocket water quality meter (Cuvette).
It is a value measured by Test LCK327).

[0026]

According to the present invention, even in a papermaking system mosquito Le Shiumuion is abundant, specific burst strength, breaking length,
It is possible to provide paper or paperboard having paper strength such as surface strength.

[0027]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples. All parts and% are based on weight.

Production Example 1 A flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube was charged with 159 parts of acrylamide and 8 parts of ion-exchanged water.
30 parts, dimethylaminopropyl acrylamide 15.
6 parts, 80% acrylic acid 9 parts, and t-octyl acrylamide 11.4 parts were charged, the pH was adjusted to 4 to 5 using sulfuric acid, and then oxygen in all reaction systems was removed through nitrogen gas. With stirring, the mixture was heated to 60 ° C., 0.21 part of ammonium persulfate and 0.09 part of sodium hydrogen sulfite were added as a polymerization initiator, polymerization was carried out at 85 ° C. for 120 minutes, and then ion-exchanged water was added to give a solid content of 10 An aqueous dispersion of an amphoteric acrylamide polymer having a viscosity of 6% and a turbidity of 170 degrees was obtained.

Production Examples 2 to 18 Same as Production Example 1 except that at least one of the types of monomer components or the amount used (composition ratio: mol%) was changed as shown in Table 1. Was performed to obtain an aqueous dispersion of an ionic acrylamide polymer. Table 2 shows the property values of the obtained aqueous dispersions.

[0030]

[Table 1]

In Table 1, AM: acrylamide, AA: acrylic acid, IA: itaconic acid, DMAPAA: dimethylaminopropyl acrylamide, DM: dimethylaminoethyl methacrylate, tOcAM: Nt-octyl acrylamide, BzAM: N. -Benzylacrylamide, IPAM: N-isopropylacrylamide, DM
AA: dimethylacrylamide, AN: acrylonitrile, St: styrene.

[0032]

[Table 2]

Reference Example BKP was beaten with a Niagara beater, and Canadian standard freeness (CSF) 550 m.
After adding sodium carbonate as a pH adjuster to the pulp adjusted to l, a sulfuric acid band was further added to the pulp 0.5%.
Then, 0.5% of pulp was added to the aqueous dispersion of each ionic acrylamide polymer obtained in each production example shown in Table 3 as a paper strength enhancer, and the mixture was stirred and uniformly mixed.
The resulting pulp slurry (pH 6.5) is diluted to 0.5% and the basis weight is 100 g / cm with a tapping sheet machine.
^The paper was made to have a weight of ² and press dehydrated at 5 kg / m ² for 2 minutes. Then, it was dried in a rotary dryer at 100 ° C. for 4 minutes and dried at 20 ° C. and 65% R.C. H. It was conditioned for 24 hours.

Examples 1 and 2 and Comparative Examples 1 and 2 BKP was beaten with a Niagara type beater to obtain Canadian Standard Freeness (C.S.F.) 550 m.
After adding sodium carbonate as a pH adjuster to the pulp adjusted to l, the amount of calcium ions was adjusted to the predetermined concentration shown in Table 4 or Table 5 with respect to the pulp slurry,
Calcium chloride was added, and a sulfuric acid band was added to the pulp in an amount of 0.5%. Then, an aqueous dispersion of each ionic acrylamide polymer obtained in each of the above production examples shown in Table 4 or Table 5 was added to the paper strength. 0.5% of pulp was added as an agent, and the mixture was stirred and uniformly mixed. Obtained pulp slurry (pH
6.5) is diluted to 0.5% and paper is made with a tapping sheet machine so that the basis weight is 100 g / cm ^2, and 5 kg /
Press dehydration was carried out for 2 minutes at m ² . Then, using a rotary dryer,
Dry for 4 minutes at 0 ° C., 20 ° C., 65% R.C. H. It was conditioned for 24 hours.

Reference Examples, Examples 1-2 and Comparative Examples 1-2
The fixing ratio (%) and the T-type peel strength (g / cm) of the paper obtained in 1. were measured. The results are shown in Tables 3-5.

(Fixing Rate) The nitrogen content of the obtained paper was measured, and the fixing rate to pulp was calculated. Fixing rate (%) = (B
-C) / Ax100. A: Nitrogen measurement value of coated acrylamide water-dispersible polymer, B: Nitrogen measurement value of paper made by adding acrylamide water-dispersible polymer, C: B
Measured nitrogen content of paper made with the same pulp as above, but without addition of acrylamide water-dispersible polymer.

(T-shaped peel strength) J. Tappi No.
It measured according to 19-m.

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

Example 3 Except that in Example 1, sodium carbonate was not added as a pH adjuster, and 20% of calcium carbonate was added instead of calcium chloride to the pulp (calcium ion concentration in the pulp slurry was 100 ppm). Paper was made in the same manner as in Example 1.

The fixing ratio (%) and the breaking length (km) of the papers obtained in Example 3 and Comparative Example 3 were measured.
The results are shown in Table 6.

Breaking length: A test method for tensile strength of paper and paperboard based on JIS P8113.

[0044]

[Table 6]

Example 4 and Comparative Example 4 Corrugated cardboard waste paper and magazine waste paper were mixed at a weight ratio of 1: 1,
Beat it with a Niagara beater, Canadian
After adding 2% of a sulfuric acid band to pulp adjusted to 420 ml of standard freeness (C.S.F.), water of each ionic acrylamide polymer obtained in each of the above production examples shown in Table 7 was obtained. Dispersion as a paper strengthening agent to pulp 0.5
%, Added and stirred, and mixed uniformly. The obtained pulp slurry (pH 5.6, calcium ion concentration 280 pp
m) is diluted to 0.5% and paper is made with a tapping sheet machine so that the basis weight is 160 g / cm ² and 5 kg / m ²
It was dehydrated by press for 2 minutes. Then 110 ° C with a rotary dryer
Dried for 4 minutes at 20 ° C., 65% R.C. H. At 24
Humidified for time.

The fixing ratio (%) and the specific burst strength (kPa) of the papers obtained in Example 4 and Comparative Example 4 were measured. The results are shown in Table 7.

Specific burst strength: A method for testing the burst strength of paper and paperboard based on JIS P8112 using a Mullen low-pressure tester.

[0048]

Example 5 and Comparative Example 5 BKP and Coat Broke were mixed in a weight ratio of 7: 3,
Beat it with a Niagara beater, Canadian
After adding 1.5% of a sulfuric acid band to pulp adjusted to 450 ml of standard freeness (C.S.F.), each ionic acrylamide polymer obtained in each of the above production examples shown in Table 8 was obtained. 0.5% of pulp as a paper strengthening agent was added to the above aqueous dispersion, and the mixture was stirred and uniformly mixed. The resulting pulp slurry (pH 6.6, calcium ion concentration 24
(0 ppm) is diluted to 0.5% and paper is made with a tapping sheet machine so that the basis weight is 100 g / cm ² and 5 kg.
Press dehydration was carried out for 2 minutes at / m ² . Then, it was dried in a rotary dryer at 100 ° C. for 4 minutes and dried at 20 ° C. and 65% R.A. H.
It was conditioned for 24 hours.

The fixing ratio (%) and surface strength (A) of the papers obtained in Example 5 and Comparative Example 5 were measured.
The results are shown in Table 8.

Surface Strength: A method for testing the surface strength of paper and paperboard based on JIS P8129. By a method using a wax pick.

[0052]

[Table 8]

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-234893 (JP, A) JP-A-3-227489 (JP, A) JP-A-7-189176 (JP, A) JP-A-4- 57993 (JP, A) JP-B-46-30964 (JP, B1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (5)

(57) [Claims] 1. A calcium ion content of 50 ppm to 500
The pulp slurry containing 0 ppm contains N as a paper strength enhancer.
Alkyl whose substituent is composed of 4 to 20 carbon atoms
Production of paper or board, characterized in that the paper after the addition of ionic (meth) acrylamide type water-dispersible polymer to the N-substituted (meth) acrylamide from 0.1 to 10 mol% of component a group Method. 2. The method for producing paper or paperboard according to claim 1, wherein the ionicity of the (meth) acrylamide water-dispersible polymer is anionic. 3. The method for producing paper or paper board according to claim 1, wherein the ionicity of the (meth) acrylamide-based water-dispersible polymer is cationic. 4. The method for producing paper or paperboard according to claim 1, wherein the (meth) acrylamide-based water-dispersible polymer is amphoteric. 5. The (meth) acrylamide-based water-dispersible polymer exhibits a turbidity of 30 degrees or more at a concentration of 10% by weight and can maintain a uniformly dispersed state.
5. The method for producing paper or paperboard according to any one of 4 to 4.