JPH02221495A - Paper strength enhancer for z-axis and interlayer paper strength, method for enhancing, freeness improver and paper making - Google Patents

Abstract

PURPOSE:To obtain the subject enhancer, capable of improving Z-axis paper strength, interlayer paper strength and freeness, containing a cationic polyacrylamide produced by reacting a specific acrylamide-based copolymer with a hypohalite within an alkaline region as an active component. CONSTITUTION:The objective paper strength enhancer containing a cationic polyacrylamide produced by reacting an acrylamide-based copolymer containing (A) 97-60mol%, preferably 95-70mol% carbamoyl groups and (B) 3-40mol%, preferably 5-30mol% N,N-dimethyl(meth)acrylamide groups with a hypohalite (e.g. sodium hypochlorite) within an alkaline region as an active component.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a paper strength agent, more specifically, a cationic paper strength agent produced by reacting an acrylamide copolymer with a hypohalite molten salt in an alkaline region. The present invention relates to a paper strength enhancer and method for increasing Z-axis paper strength and living room paper strength, a drainage improver, and paper making, which contain polyacrylamide as an active ingredient.

[Prior art and its problems] Currently, the recycling of paper is progressing, and the amount of used paper as a raw material for manufacturing is on the rise. It has reached 49%,
It is at the highest level in the world. The type of used paper with the highest recovery rate is newspaper, followed by cardboard. Under such circumstances, paper strength tends to decrease due to factors such as the progress of finer AM due to the increase in the use of waste paper as a raw material, and furthermore, the incorporation of fillers, sizing agents, etc. Therefore, in order to suppress the decline in paper strength and maintain paper quality, it is necessary to rely on the use of paper strength enhancers (paper strength agents).Especially for cardboard and newspapers, which have a high recovery rate of used paper, raw materials are a problem. Although this is a serious issue, it is not only an excellent paper strength agent, but also from the following points.
In particular, a paper strength agent with excellent Z-axis paper strength and interlaminar paper strength is desired. For example, in the case of corrugated board, the bonding method used during the molding process has changed from the conventional method using staples or other fasteners to hot melt adhesive. However, problems such as surface peeling are becoming more likely to occur. In order to prevent this problem, an excellent internal paper strength agent that improves Z-axis strength and living room paper strength is essential.

On the other hand, in the multi-layer paper making method, especially as the speed of the paper machine increases, the two-car strength and the living paper strength tend to decrease, and problems such as peeling in the living room tend to occur, so the living paper strength is required.

Furthermore, in order to support offset printing in newspapers, it is desired to develop an excellent paper strength agent that increases Z-axis paper strength.

Acrylamide or methacrylamide based polymers are reacted with hypohalites under alkaline conditions. By carrying out the so-called Hofmann rearrangement reaction, primary amino groups can be introduced into an acrylamide polymer at a relatively low cost. This Hofmann rearrangement reaction product of acrylamide-based polymer is used as a paper strength enhancer, and this product is superior in improving Z-axis paper strength and freeness compared to other materials such as Mannich-modified polyacrylamide. Therefore, by using the Hofmann rearrangement reaction product of an acrylamide polymer, it is possible to make paper with improved Z-axis paper strength. However, one of the drawbacks of the Hofmann rearrangement reaction is that it generates a large amount of inorganic salts during the reaction, especially when used as a paper strength agent, which is used in large quantities.
A problem arises in that the concentration of inorganic salts in white water increases.

Therefore, as white water is becoming more and more closed, the amount of the Hofmann rearrangement reactant used needs to be reduced as much as possible. In other words, although Hofmann rearrangement reaction products of acrylamide-based polymers exhibit excellent Z-axis paper strength, they have problems such as containing a large amount of inorganic salts, and it is necessary to further improve the performance in order to reduce the amount used. be. however.

There are many points that are unclear about the correlation between Z-axis paper strength or interlaminar paper strength and paper strength enhancers, and no guidelines for improving it have been known.

[Means to solve the problem] The present inventor aimed to solve these problems.

It was discovered that by using polyacrylamide copolymerized with N,N-dimethyl(meth)acrylamide and subjected to Hoffmann rearrangement reaction, Z-axis paper strength, living room paper strength, and drainage properties were significantly improved. Completed the invention.

That is, the present invention provides (a) a group 97 containing a carbamoyl group.
60 mol%, (b) an acrylamide copolymer containing 3 to 40 mol% of N,N-dimethyl(meth)acrylamide groups was reacted with hypogenite in an alkaline region. , provides an enhancer for Z-axis paper strength and interlaminar paper strength, which contains an on-type polyacrylamide copolymer as an active ingredient.

The acrylamide copolymer used in the present invention is N,
A Hofmann rearrangement reaction product obtained by reacting an acrylamide copolymer containing 3 to 40 mol%, preferably 5 to 30 mol%, of N-dimethyl (meth)acrylamide groups with a hypohalite in an alkaline region. It is. N, N
- If the amount of dimethyl (meth)acrylamide groups is less than 3 mol%, the effect of N,N-dimethyl (meth)acrylamide copolymerization will be insufficient, that is, the C, S, and F values will not be sufficiently large, and the Z-axis The paper strength is completely insufficient, and on the other hand, if it exceeds 40 mol%, the solubility in water is impaired, and there are also disadvantages such as further deterioration of the C, S, F values and Z-axis paper strength. .

It is also possible to copolymerize the following seven polymers.

Copolymerizable monomers include woody monomers, ionic monomers, and more! l! Examples include oily monomers, and one or more of these monomers can be applied.

Specifically, examples of wood-philic monomers include methacrylamide, diacetone acrylamide, toethyl methacrylamide, and N-ethylacrylamide.

N, N = Nidiethylacrylamide N-propylacrylamide, N-acryloylpyrrolidine, N-acryloylpiperidine, doacryloylmorpholine.

Hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, various methoxypolyethylene glycol (meth)acrylates, tovinyl-2-
Examples include pyrrolidone.

Examples of ionic monomers include acrylic acid.

methacrylic acid, and nyl sulfonic acid, allyl sulfonic acid,
Acids such as methacrylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid and their salts, N,N-dimethylaminoethyl methacrylate), N , N-diethylaminoethyl methacrylate, N, dimethylaminoethyl acrylate, N,
N-dimethylaminopropylacrylamide, N,N-
Examples include amines such as dimethylaminopropylacrylamide and their salts.

Examples of the lipophilic monomer include N,N-di-1-propylacrylamide, N-n-butylacrylamide,
N-n-hexyl acrylamide, N-hexyl methacrylamide, N-n-octylacrylamide,
N-tert-octyl methacrylamide, N-tert-octylacrylamide, tododecyl acrylamide,
Toalkyl (meth)acrylamide derivatives such as N-n-dodecylmethacrylamide, N,N-diglycidyl acrylamide, N,todiglycidyl methacrylamide,
(4-glycidoxybutyl)acrylamide, N-
(4-glycidoxybutyl)methacrylamide, N-
(5-glycidoxybentyl)acrylamide, t(6
-N-(ω
-glycidoxyalkyl) (meth)acrylamide derivatives, methyl (meth)acrylate, ethyl (meth)acrylate.

(Meth)acrylate derivatives such as butyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, glycidyl (meth)acrylate, tolyl methacrylate, vinyl acetate, vinyl chloride, vinylidene chloride.

Examples include olefins such as ethylene, propylene, and butene, styrene, divinylbenzene, α-methylstyrene, butadiene, and isoprene. The amount of the unsaturated monomer used in the copolymerization varies depending on the type of unsaturated monomers and the combination thereof, and cannot be determined unconditionally, but is generally 0 to J.

It is in the range of 11M%.

Next, the above-mentioned monomers are polymerized to produce polyacrylamide. Radical polymerization is preferable as the polymerization method, and polar solvents such as water, alcohol, and dimethylformamide can be used as the pentapolymerization solvent. , since the Hofmann decomposition reaction is carried out in an aqueous solution, aqueous solution polymerization is preferred, at which time the monomer concentration is 2 to 30% by weight, preferably 5
~30% by weight. The fE polymerization initiator is not particularly limited as long as it is water-soluble, and it is usually used after being dissolved in an aqueous monomer solution. Specifically, peroxides include, for example, ammonium persulfate, potassium persulfate, hydrogen peroxide, tert
-butyl peroxide, etc. In this case, it can be used alone, but it can also be used as a redox polymerization agent in combination with a reducing agent. Examples of reducing agents include salts of low ionization such as sulfites, hydrogen sulfites, iron, m, and cobalt.

Examples include organic amines such as N, N, N', N'-tetramethylethylenediamine, and reducing sugars such as aldose and ketose.

In addition, as an azo compound, 2.2'-azobis-2
-amidinopropane hydrochloride, 2.2'-azobis-°
2,4-dimethylvaleronitrile, 4,4'-azobis-4-cyatubaleic 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. What is the amount of initiator added?

0.1 to 10% by weight based on monomer, preferably 0.2
~8% by weight. In addition, in the case of a redox system, the amount of reducing agent added to the initiator is 0.1 to 10 on a molar basis.
．． 0%, preferably 0.2-8.0%.

The redox initiator used in the present invention is not limited as long as it has the ability to initiate radical polymerization.
Examples include inorganic peroxides, organic peroxides, combinations of these peroxides and reducing agents, cerium (IV) ammonium nitrate, and azo compounds. Specifically, ammonium persulfate, potassium persulfate, hydrogen peroxide, tert-
Butyl peroxide, benzoyl peroxide, cumene hydroxy peroxide* Lerj-butyl peroxy-2-ethylhexanoate, butyl perbenzoate, etc., and reducing agents used in combination with these include sulfite,
Examples include salts with low ionic valences such as bisulfite, iron, copper, and cobalt, organic amines such as aniline, and reducing sugars such as aldose and ketose. Examples of azo compounds include azobisisobutyronitrile, 2.2"-azobis-2-amidinopropane hydrochloride, 2.2°-azobis-2,4-dimethylvaleronitrile, 4,4°-azobis-4- Ciatsuvaleic acid and the like can be used.

It is also possible to use two or more of the above polymerization initiators in combination.

The range in which the initiator turbidity is used is usually 0.1 to 5.0% by weight based on the monomer mixture.

In the case of a single polymerization initiator, the polymerization temperature is lower, approximately 3
The temperature is 0 to 90°C, and in the case of a redox polymerization initiator, it is lower, approximately 5 to 5Q"C. Also, it is not necessary to maintain the same temperature during polymerization, and it may be changed as appropriate as the polymerization progresses. Generally, the temperature rises due to the polymerization heat generated as the polymerization progresses.The atmosphere inside the polymerization vessel at this time is not particularly limited, but in order to speed up the polymerization, it is better to replace the atmosphere with an inert gas such as nitrogen gas. 0 There is no particular limitation on the polymerization time, but
It takes approximately 1 to 20 hours.

The acrylamide copolymer thus obtained is a water-soluble polymer containing 97 to 60 mol% of acrylamide groups and 3 to 40 mol% of N,N-dimethyl(meth)acrylamide groups. The Brookfield value of a 10% aqueous solution of this copolymer at 20°C is 100 to 100
,000cps, but usually 100~80.000c
preferably in the range of ps, i.e. 100 cp
s or more is preferable from the point of view of obtaining sufficient performance, while 80,000 cps or less is preferable from the point of view of preventing deterioration in operability and easy occurrence of gelation.

The Hofmann decomposition reaction is carried out by allowing hypohalite to act on the amide group of polyacrylamide in the coexistence of an alkaline substance.
Examples of hypochlorites include metal or alkaline earth metal salts of primary hypochlorous acid, including sodium hypochlorite and hypochlorite. Potassium hypochlorite, lithium hypochlorite, calcium hypochlorite, magnesium hypochlorite, barium hypochlorite, etc. Similarly, hypobromite and hypoiodide salt also contain hypobromite. and alkali metal or alkaline earth metal salts of hypoiodites. It is also possible to generate hypohalite by blowing halogen gas into an alkaline solution. On the other hand, examples of alkaline substances include alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, etc. Among them, alkali metal hydroxides are preferred, and sodium hydroxide, potassium hydroxide, hydroxide Examples include lithium. The amount of the above-mentioned substance added to polyacrylamide is 0.05 to 2.0 mol, preferably 0.1 to 1.5 mol, based on the amide group for hypohalous acid, and 0.1 to 1.5 mol for the amide group for the alkaline substance. from 0.05 to 4.0-f, preferably from 0.1 to 1. There is OT = Lute. The pH at that time is generally in the range of 11-14. The turbidity of the polyacrylamide at this time is approximately 0.1 to 17.5% by weight, but as the reaction concentration increases, stirring becomes difficult and gelation tends to occur, so it is usually 0.1 to 17.5% by weight. It is preferably in the range of 10% by weight, and if the concentration of one reaction is less than 1%, there are problems such as slow reaction rate, so 1 to 10% by weight.
It is more preferable that

On the other hand, the reaction temperature is in the range of 0 to 110°C, and the 0 reaction time to carry out the Hofmann decomposition reaction within this temperature range is the reaction temperature,
It depends on the polymer concentration in the reaction solution, so it cannot be generalized, but6 For example, when the polymer concentration is 1% by weight,
Within 30 to 40 hours at 0℃, within 3 to 4 hours at 20℃, within several tens of minutes at 50℃, within a few minutes at 65℃, ao
'c is sufficient within several tens of seconds. Furthermore, the higher the polymer concentration, the shorter the reaction time.Furthermore, if one reaction temperature is set at 50°C to 110°C and one reaction is completed in a single time, Hofmann-decomposed polyacrylamide produced by a low-temperature reaction can be produced. It is possible to produce cationic polyacrylamide with properties equivalent to or better than that of 50% polyacrylamide, and it also enables on-site production by shortening the reaction time, avoiding the problem of deterioration over time of Hoffmann-decomposed polyacrylamide. It is preferable to carry out the reaction in a temperature range of ℃ to 110℃. In that case, the relationship between reaction time and reaction temperature should be approximately within the range between the following two relational expressions, and the reaction can be carried out within that range. If you do this, you will get good results.

T: Reaction temperature ("C) 50≦T≦110 The cationic polyacrylamide produced under the above conditions has a cation equivalent measured by colloid titration at pH 2 in the range of approximately 0 to 10.0 eq/g. The cation equivalent can be controlled by the amount of hypohalite added.Also, since one reaction is carried out in an alkaline region, the amide group is hydrolyzed and a carboxyl group is produced as a by-product.The amount of the by-product is at pH 10. It is expressed as an anion equivalent measured by colloid titration, and is approximately in the range of 0 to 10.0 ■eq/g.The amount of the by-product can be controlled by the amount of the alkaline substance added.

Next, after carrying out the reaction under the above conditions, it is preferable to stop the reaction in order to suppress the progress of side reactions, however,
When used immediately after the reaction, it may not be necessary to stop the reaction.

Methods for stopping the reaction include (1) adding a reducing agent, (
Methods such as 2) cooling, and (3) lowering the pH of the solution by adding acid can be used alone or in combination. (1) is a method in which remaining hypohalite and the like are deactivated by reaction with a reducing agent. Examples of the reducing agent used include sodium sulfite, sodium thiosulfate, ethyl malonate, thioglycerol, and triethylamine. The amount of the reducing agent used is usually o, oos to 0.15 times the mole, preferably 0.01 to 0.10 times the amount of hypohalous acid used in the reaction. Generally, when the Hofmann decomposition reaction is completed, unreacted compounds containing active chlorine such as hypohalogen salts remain. If such a reaction solution is used as a paper strength agent, it may cause rust in the paper machine, so a reducing agent is usually used to deactivate the active chlorine. However, the primary halite reacts in a molar amount equal to or less than the number of moles of acrylamide units in the polymer.

In addition, when the reaction is carried out at a high temperature, almost no unreacted hypohalite remains at the end of the reaction.

Therefore, it is also possible to use active chlorine as a paper strength agent without deactivating it using a reducing agent.

(2) is a method of suppressing the reaction progress by cooling, which involves cooling using a heat exchanger.

There is a way to dilute it with cold water. The temperature at that time is usually 5
0°C or lower, preferably 45°C or lower, more preferably 40°C or lower
below ℃. In (3), the pH of the solution at the end of the reaction, which usually has an alkaline pH of 12 to 13, is lowered using an acid to stop the Hofmann decomposition reaction and at the same time suppress the progress of the hydrolysis reaction. The pH at that time should just be neutral or lower, preferably in the range of pH 4 to 6. p
Acids used for H adjustment include mineral acids such as sulfuric acid, sulfuric acid, phosphoric acid, and nitric acid, and organic acids such as formic acid, acetic acid, and citric acid.Reaction termination methods include (1) to (3). The method can be selected as appropriate depending on the reaction conditions, and these methods may be combined.

Next, the reaction solution stopped by the above method can be used as it is as an aqueous solution of cationic polyacrylamide, or the aqueous solution is poured into a solvent that does not dissolve cationic polyacrylamide, such as methanol, to precipitate the polymer and then dry it. It can also be made into a powder. Moreover, the cationic polyacrylamide aqueous solution can be stored in a tank and used as needed. The temperature at which the aqueous solution is stored may be as low as not freezing, preferably 10 to 15°C. However, if it is to be used within a relatively short period of time, it can be stored at room temperature.
It is possible to store it for about a month.

In the present invention, the Hofmann rearrangement reaction product of this acrylamide polymer is used as a paper strength enhancer for biaxial paper strength.

Or use it as a drainage improver. The Hofmann rearrangement reaction product of an acrylamide polymer can be used for the above purpose according to a conventionally known method, and if necessary, it can be used in combination with sulfuric acid, anionic resin, etc. for paper making, and the place where it is added can be used. They may be added at any point before the wet sheet is formed, and they may be added in any order or at the same time. Alternatively, it can be added after mixing the cationic polyacrylamide and the anionic resin at a concentration of 9119 or higher. The addition ratio of cationic polyacrylamide and 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 added is 0.01 to 5% by weight, preferably 0.05% by weight, based on the dry solid weight of the pulp.
The second addition site, ˜2% by weight, is added before the wet sheet is formed. However, even after the wet sheet has been formed, it is also possible to add it by spray coating or roll coating, especially when producing laminated paper. In addition, in the present invention, when cationic polyacrylamide is produced by subjecting polyacrylamide to a Hofmann decomposition reaction at high temperature for a long time, it is superior to cationic polyacrylamide obtained by carrying out the same reaction at low temperature for a long time. Although the reason for this is not necessarily clear, it is considered to be a 1-reaction intermediate, as the effect was remarkable when added to pulp slurry, etc., without performing a reaction-stopping operation. It is thought that N-chloro groups and other functional groups generated due to high temperatures directly or indirectly contribute to the development of paper strength. Therefore, it is more desirable to add without performing a reaction termination operation, but
If the reaction is not stopped, it will deteriorate over time, so it must be added immediately after the reaction. Immediately here refers to taking out the aqueous solution after the reaction from inside the pipe, transporting it within the same pipe without transferring it to the outside, and adding it to the pulp slurry.More specifically, the aqueous solution after the reaction is taken out from the pipe. It may be added directly to the pulp slurry through the pipe, or it may be added by adjusting the amount after temporarily retaining it in a stock tank in between.The residence time of the reaction liquid in the pipe is 1. It is acceptable as long as the aqueous solution after the reaction does not deteriorate; however, if it is too long, the device for retaining the liquid will become large and the features of the present invention will not be utilized.

Therefore, in order to suitably carry out the present invention, it is preferable to add the reaction vk within 5 hours, more preferably within 1 hour, and even more preferably within 10 minutes. In addition, depending on the concentration of cationic polyacrylamide after the reaction, the type of pulp, which may be diluted with water and added,
The concentration of cationic polyacrylamide when added is approximately 0.1-10% by weight, preferably 0.5% by weight, although it varies depending on the speed of papermaking and other factors.
-5% by weight, more preferably 0.8-2% by weight.

Paper manufactured using the method described above has a paper strength of 1.

Specifically, it is excellent in burst strength, Z-axis strength, compressive strength, etc. Therefore, if the method of the present invention is applied to materials such as cardboard and newspapers, which have a high proportion of waste paper as a raw material, it will be very effective, and it will be possible to manufacture paper with high paper strength. . Furthermore, by applying the present invention not only to corrugated paper and newspapers but also to papers that require 1 strength, fI
It becomes possible to produce paper with superior paper strength.

[Example] The present invention will be described below with reference to Examples. In addition, in the following, %
means weight % unless otherwise specified.

Examples 1-2 100 parts by weight of a 5% aqueous solution of acrylamide-N,N-dimethylacrylamide copolymer containing 10 IIOfL% of N,N-dimethylacrylamide groups (Brookfield viscosity of a 10% aqueous solution at 20°C: 7800 cps) A mixture of 21.24 parts by weight of a 12.5% aqueous sodium hypochlorite solution and 3.83 parts by weight of a 30% aqueous sodium hydroxide solution (equivalent to twice the mole of sodium hypochlorite) was kept at 20°C. The mixture was added dropwise over 20 minutes, and then the reaction was carried out at the same temperature for 3 hours. Using toluidine blue as an indicator to measure the degree of cationization at this point, l
/40ON-As measured by colloid titration method using potassium polyvinylsulfonate aqueous solution, 2.62 seq,
/g. In addition, the degree of anionization was determined by adding a predetermined amount of 1/20ON-methyl glycol chitosan and using toluidine blue as an indicator at pHlO.
- 1.14 eq as measured by back titration using an aqueous solution of potassium polyvinylsulfonate.

/g. After adding 0.141 i part of sodium sulfite dissolved in a small amount of water to deactivate unreacted sodium hypochlorite, the pH was adjusted to 4.5 using concentrated hydrochloric acid. This solution was poured into about 10 times the volume of methanol for reprecipitation treatment, filtered, dried, and stored. This product had a 1% aqueous solution viscosity of 4.7 cps at 20°C. 1% N with the same composition but different viscosity,
A similar reaction was carried out on an N,N-dimethylacrylamide-acrylamide copolymer containing an N-dimethylacrylamide group to obtain a white powdery Hofmann rearrangement reaction product. These are referred to as Examples 1 and 2, and the results are shown in Table 1.
It was listed on.

Example 3 A 5-layer o1% acrylamide-N,N-dimethylacrylamide copolymer containing N,N-dimethylacrylamide groups (Brookfield viscosity of a 10% aqueous solution at 20°C; 19,0OO cps) was used. was carried out in the same manner as in Example 1 to obtain a white powder of a Hofmann rearrangement reaction product.

Example 4 Performed except that an acrylamide-N,N-dimethylacrylamide copolymer containing 20 sojL% N,N-dimethylacrylamide groups (Brookfield viscosity of a 10% aqueous solution at 20°C; 9,000 cps) was used. The procedure was carried out in the same manner as in Example 1 to obtain a Hofmann rearrangement reaction product as a white powder.

Example 5 A 5% aqueous solution of acrylamide-N,N-dimethylacrylamide copolymer containing 10 on% N,N-dimethylacrylamide groups (Brookfield viscosity of a 10% aqueous solution at 20°C; 7,800 cps) While keeping 100 parts by weight at 80°C, add 21.24 parts by weight of 12.5% aqueous sodium hypochlorite solution and 3.83 parts by weight of 30% aqueous sodium hydroxide solution (equivalent to twice the mole of sodium hypochlorite). ) was added all at once. After reacting at 80°C for 10 seconds, a predetermined amount of cold water was added to adjust the polymer solids concentration to 1%. The degree of cationization and degree of anionization at this time were determined in the same manner as in Examples 1 to 3, and were 2.56 seq, /g, and 1.34 s, respectively.
eq,/g. This product was used for papermaking experiments within 5 minutes after production.

Example 6 Acrylamide-N,N-dimethylmethacrylamide copolymer containing 10 layers on% N,N-dimethylmethacrylamide (Brookfield viscosity of a 10% aqueous solution at 20°C; 7,800 cps) was used. The procedure was carried out in the same manner as in Example 1 to obtain a white powder of a Hofmann rearrangement reaction product.

Comparative example 1 50-〇! Example 1, except that an acrylamide-N,N-dimethylacrylamide copolymer containing L% N,N-dimethylacrylamide groups (Brookfield viscosity of a 10% aqueous solution at 20°C; 3,800 cps) was used. In the same manner, a white powder of the Hofmann rearrangement reaction product was obtained.

Comparative Example 2 Except for using an acrylamide-N,N-dimethylacrylamide copolymer containing 65 on% N,N-dimethylacrylamide groups (Brookfield viscosity of a 10% aqueous solution at 20°C; 3,500 cps) was carried out in the same manner as in Example 1 to obtain a white powder of a Hofmann rearrangement reaction product.

Comparative Example 3 Performed except that an acrylamide-N,N-dimethylacrylamide copolymer containing 80 moJL% of N,N-dimethylacrylamide groups (Brookfield viscosity of a 10% aqueous solution at 20°C; 2,100 cps) was used. The procedure was carried out in the same manner as in Example 1 to obtain a Hofmann rearrangement reaction product as a white powder.

Comparative Examples 4 to 7 The 1G% aqueous solution viscosity at 20°C is 355.2 and 0, respectively.
00.3.400.51.The same procedure as in Example 1 was carried out except that an 800 cps acrylamide homopolymer was used, and a white powder of the Hofmann rearrangement product was obtained.The production results of 0 or more are summarized in Table 1. .

Examples 7 to 12 To a 1% slurry of corrugated waste paper pulp with a freeness of 450 ml csf, 0.5% (based on dry weight) of sulfuric acid was added to the pulp and stirred for 1 minute, and then commercially available anionic polyacrylamide (15% Product, Hobron'11508
(manufactured by Mitsui Toatsu Chemical Co., Ltd.) 1.0% aqueous solution to pulp.
24% (on a dry weight basis) was added and stirring was continued for an additional minute. Then 1% of the Hofmann rearrangement reactants of Examples 1 to 5 were added.
After adding 0.16% (dry weight basis) of the aqueous solution to the pulp, it was further stirred for 1 minute, and a portion of the solution was added according to JIS P8121.
Measure C, S, and F according to .

The remaining paper was made using a TAPPI square sheet machine and then dried for 2 hours in a blow dryer at 110°C until the weight per tsubo was 125.
Regarding the evaluation of handmade paper obtained with ±3 g/m'', [specific bursting strength] according to JIS P8112.
The [biaxial strength] was measured using an internal bond tester manufactured by Kumagai Riki.

Comparative Examples 8 to 14 The same procedure as in Actual Examples 7 to 12 was carried out except that the Hofmann rearrangement reaction products of Comparative Examples 1 to 7 were used, and the basis weight was 125 ± 3 g/rrf.
I obtained handmade paper. [Specific splitting strength] and [Z-axis strength] were measured in the same manner as in Examples 7 to 12, and the results of 0 or more are summarized in Table 2.

Table Example 13 Using the Hoffmann rearrangement reaction product of Example 1, Examples 7 to 1
A wet paper before drying was produced in the same manner as in Example 2. Two sheets of handmade paper were stacked together in a wet state, rolled over several times with stainless steel rolls, and then pressed for 2 minutes at 3.5 kg/cm''. Dry 1
Regarding the evaluation of the 0 handmade paper obtained with a basis weight of 250±6 g/m'', the [living room paper strength] was measured using an internal bond tester manufactured by Kumagai Riki.

Comparative Example 15 Regarding the evaluation of 0 handmade paper obtained by the same method as in Example 13 except that the Hoffman rearrangement reaction product of Comparative Example 6 was used, the paper with a basis weight of 250 ± 6 g/rn' was obtained. Example 13
Measurements were carried out in the same manner as above.

Comparative Example 16 A handmade paper with a basis weight of 250±6 g/rn' was obtained by the same method as in Example 13 except that no paper strength agent was used. Table 3 summarizes the results of 0 or more measured by the same method as No. 13.

Table 3 [Effects of the Invention] According to the present invention, significant improvements in Z-axis paper strength, living room paper strength, and freeness, which could not be achieved with the prior art, were achieved. The reason is not necessarily clear, but N, N
- It was not previously known that the presence of dimethyl (meth)acrylamide group produced such an effect.
It has become possible to produce paper with excellent Z-axis paper strength and interlaminar paper strength.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd. Representative Patent Attorney Nobuaki Sakaguchi

Claims (1)

[Claims] 1. (a) 97 to 60 mol% of groups containing a carbamoyl group;
(b) N,N-dimethyl(meth)acrylamide group 3
Z-axis paper strength and interlaminar paper strength with cationic polyacrylamide as an active ingredient produced by reacting an acrylamide-based copolymer containing ~40 mol% with hypohalite in an alkaline region Enhancer. 2. A drainage improver comprising the cationic polyacrylamide according to claim 1 as a main component. 3. The acrylamide copolymer according to claim 1 is reacted with a hypohalite salt in an alkaline region at a temperature of 50°C to 110°C for a short time, and then immediately added to the pulp slurry. Characteristic paper strength enhancement method. 4. Paper made using the cationic polyacrylamide according to claim 1.