JP2938150B2 - Paper manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing paper having excellent printability and surface strength of paper. More specifically, the present invention relates to a method for producing polyacrylamide at a high temperature and a short time. The present invention relates to a method for producing paper, characterized in that a cationic acrylamide-based polymer obtained by performing a Hoffman decomposition reaction over a long period of time is used as a resin for surface coating.

[Conventional technology and its problems]

Conventionally, for the purpose of increasing the surface strength of paper and improving printability, starch derivatives such as starch, oxidized starch, and cationized starch, cellulose derivatives such as carboxymethyl cellulose, etc. And derivatives thereof, polyacrylamide and modified products thereof, and urea resins, styrene-maleic acid copolymers, polyvinyl acetate, vinyl acetate-maleic acid copolymers, latex-based, emulsion-based surface strength improvers, etc. Is used.

Among these surface strength improvers, polyacrylamide-based resins are known to be rich in the ability to increase the surface strength of paper and improve printability. Hoffman degradation product of polyacrylamide (Hoffman degradation PAM) has a structure in which primary amine groups are directly bonded to the polymer main chain,
It is known that excellent hydrogen strength is exhibited by its hydrogen bonding ability. However, Hoffman-decomposed PAM has a problem that primary amino groups disappear with time when stored in an aqueous solution. The Hoffman decomposition reaction is carried out at a low temperature to suppress side reactions as much as possible, a method of introducing a stabilizer, and a method of using at a low temperature, etc., but each method has advantages and disadvantages, and in general, Not yet used.

[Means for solving the problem]

In view of the above, the present inventors, by performing a Hoffman decomposition reaction of polyacrylamide at a high temperature and in a short time, have excellent performance as compared with the Huffman decomposition PAM manufactured under conventional conditions. Was revealed. In addition, since Hoffman-decomposed PAM can be manufactured in a short time, on-site operation, such as installing a manufacturing apparatus near a place (plant) to be used, has become possible. This point is a major feature of the present invention, and it is possible to avoid deterioration over time, which was a fatal problem of Huffman decomposition PAM, and by using this for surface coating, excellent surface strength can be achieved. It is now possible to produce waste paper.

That is, at least under an alkaline region of pH 11 or more, an acrylamide polymer and a hypohalite,
It is characterized in that a cationic acrylamide polymer obtained by performing a reaction in a temperature (T) range of 60 to 100 ° C. and within a time (t) specified below is coated at 0.01 to 7.00 g / m ^2. Is a method for producing paper.

e ^{15,150 / (273 + T)} × 2.5 × 10 ⁻²⁰ ≦ t (sec) ≦ e ^{15,150 / (273 + T)} × 10 ⁻¹⁸ +30 Hereinafter, the present invention will be described in detail.

The acrylamide-based polymer used in the present invention is a homopolymer of acrylamide (or methacrylamide), or a copolymer of one or more unsaturated monomers copolymerizable with acrylamide (or methacrylamide), The term refers to a graft copolymer onto a water-soluble polymer such as starch.

Examples of the copolymerizable monomer include a hydrophilic monomer, an ionic monomer, and a lipophilic monomer, and one or more of these monomers can be used. Specifically, as a hydrophilic monomer, for example, diacetone acrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide,
N-ethylmethacrylamide, N-ethylacrylamide, N, N-diethylacrylamide, N-propylacrylamide, N-acryloylpyrrolidine, N-acryloylpiperidine, N-acryloylmorpholine, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, Examples thereof include hydroxypropyl acrylate, various methoxypolyethylene glycol (meth) acrylates, and N-vinyl-2-pyrrolidone.

Examples of the ionic monomer include acrylic acid, methacrylic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic acid, and 2-acrylamido-2-methyl. Acids such as propanesulfonic acid and salts thereof, N, N-dimethylaminoethyl methacrylate, N, N
Amines such as -diethylaminoethyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropyl methacrylamide, N, N-dimethylaminopropylacrylamide, and salts thereof.

Examples of the lipophilic monomer include N, N-di-n-propylacrylamide, Nn-butylacrylamide,
-N-hexylacrylamide, Nn-hexylmethacrylamide, Nn-octylacrylamide, N-
n-octyl methacrylamide, N-tert-octylacrylamide, N-dodecylacrylamide, Nn-
N-alkyl (meth) acrylamide derivatives such as dodecyl methacrylamide, N, N-diglycidyl acrylamide, N, N-diglycidyl methacrylamide, N- (4-
N- (ω-) such as glycidoxybutyl) acrylamide, N- (4-glycidoxybutyl) methacrylamide, N- (5-glycidoxypentyl) acrylamide, and N- (6-glycidoxyhexyl) acrylamide Glycidoxyalkyl) (meth) acrylamide derivatives, methyl (meth) acrylate, ethyl (meth) acrylate,
Butyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylate derivatives such as 2-ethylhexyl (meth) acrylate and glycidyl (meth) acrylate, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, vinylidene chloride, ethylene, Examples include olefins such as propylene and butene, styrene, divinylbenzene, α-methylstyrene, butadiene, isoprene and the like. The amount of the unsaturated monomer used for the copolymerization varies depending on the type of the unsaturated monomer and the combination thereof, and cannot be determined unconditionally, but is generally in the range of 0 to 50% by weight.

As the water-soluble polymer for graft-copolymerizing the above-mentioned monomers, any of a natural polymer and a synthetic polymer can be used. Starch and oxidized starch of various origins as a natural system, carboxyl starch, dialdehyde starch, modified products such as cationized starch, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, cellulose derivatives such as hydroxyethyl cellulose, alginic acid, agar, pectin, carrageenan, dextran, Pullulan, konjac, gum arabic, casein, gelatin and the like can be mentioned. Examples of the synthetic system include polyvinyl alcohol, polyvinyl ether, polyvinylpyrrolidone, polyethyleneimine, polyethyleneimine, polyethylene glycol, polypropylene glycol, polymaleic acid copolymer, polyacrylic acid, and polyacrylamide. The amount of the monomer added to the water-soluble polymer is in the range of 0.1 to 10.0 times based on the water-soluble polymer.

Next, the above monomers are polymerized to produce polyacrylamide.Radical polymerization is preferable as the polymerization method, and water, alcohol, and a polar solvent such as dimethylformamide can be used as the polymerization solvent. Since the Hoffman decomposition reaction is carried out in an aqueous solution, aqueous polymerization is preferred. At that time, the monomer concentration is 2 to 30% by weight, preferably 5 to
30% by weight. The polymerization initiator is not particularly limited as long as it is water-soluble, and is usually used after being dissolved in an aqueous monomer solution. Specifically, in the peroxide system, for example, ammonium persulfate, potassium persulfate, hydrogen peroxide, tert-butyl peroxide and the like can be mentioned. In this case, it can be used alone, but can also be used as a redox polymerizer in combination with a reducing agent. As the reducing agent, for example, sulfites, bisulfites, iron, copper, lower ionization salts such as cobalt, N,
Organic amines such as N, N ', N'-tetramethylethylenediamine, and reducing sugars such as aldose and ketose can be mentioned.

As the azo compound, 2,2'-azobis-2-
Amidinopropane hydrochloride, 2,2'-azobis-2,4-dimethylvaleronitrile, 4,4'-azobis-4-cyanovaleic acid and salts thereof can be used. Furthermore,
Two or more of the above-mentioned polymerization initiators can be used in combination. In addition, when graft-polymerizing a water-soluble polymer, in addition to the above-described polymerization initiator as a polymerization initiator, it is also possible to use a transition metal ion such as ceric ion, ferric ion, and the like. You may use together with a polymerization initiator. The amount of the initiator added is 0.01 to 10% by weight, preferably 0.02 to 8% by weight, based on the monomer. In the case of a redox system, the amount of the reducing agent added is 0.1 to 100%, preferably 0.2 to 80%, based on the mole of the initiator.

In the case of a single polymerization initiator, the polymerization temperature is generally 30 to 90 ° C.
In the case of a redox-based polymerization initiator, the temperature is lower and is generally -5 to 50 ° C. Further, it is not necessary to keep the same temperature during the polymerization, and the temperature may be changed as appropriate with the progress of the polymerization. Generally, the temperature is raised by polymerization heat generated as the polymerization proceeds. The atmosphere in the polymerization vessel at that time is not particularly limited, but it is preferable to replace the atmosphere with an inert gas such as a nitrogen gas in order to promptly carry out the polymerization. Although the polymerization time is not particularly limited, it is generally 1 to 20 hours.

Next, a Hoffman decomposition reaction of the polyacrylamide produced by the above method is performed. At that time, when the production of polyacrylamide as a raw material is carried out with an aqueous solution, the polyacrylamide can be used for the reaction as it is or after dilution as necessary. In the case of a graft copolymer, ungrafted polyacrylamide is also by-produced, but it is usually subjected to the reaction without separation.

The Hoffman decomposition reaction is carried out by allowing a hypohalite to act on an amide group of polyacrylamide in the presence of an alkaline substance. Examples of hypohalous acid include hypochlorous acid, hypobromite, and hypoiodite. Is raised. Examples of hypochlorite include metal hypochlorite or alkaline earth metal salts, and specifically, sodium hypochlorite, potassium hypochlorite, lithium hypochlorite, and hypochlorous acid. There are calcium, magnesium hypochlorite, barium hypochlorite and the like. Similarly, hypobromite and hypoiodite include alkali metal or alkaline earth metal salts of hypobromite and hypoiodite. It is also possible to generate a hypohalite by blowing a halogen gas into an alkaline solution. On the other hand, examples of the alkaline substance include an alkali metal hydroxide, an alkaline earth metal hydroxide, and an alkali metal carbonate. Among them, an alkali metal hydroxide is preferable, and sodium hydroxide,
Potassium hydroxide, lithium hydroxide and the like can be mentioned. 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 in hypohalous acid, and 0.05 to 4.0 mol, preferably, 0.1 to 1.5 mol in the alkaline substance. 0.1 to 3.0 mol. The pH at that time is generally in the range of 11-14. The concentration of polyacrylamide at that time is generally 0.1 to 17.5% by weight, but it is usually in the range of 0.1 to 10% by weight, because if the reaction concentration becomes high, stirring becomes difficult and gelation easily occurs. Is preferred. In addition, when the reaction concentration is less than 1%, there is a problem that the reaction rate is slowed down.
More preferably, it is% by weight.

 On the other hand, the reaction temperature ranges from 60 to 100 ° C.

Next, the Hoffman decomposition reaction is performed in a short time within the above-mentioned temperature range.However, the reaction time depends on the reaction temperature and the polymer concentration in the reaction solution, but cannot be said unconditionally.
For example, when the polymer concentration is 1% by weight, it is enough within 65 minutes at 65 ° C. and within several tens seconds at 80 ° C. Further, the higher the polymer concentration, the shorter the reaction time. The relationship between the reaction time and the reaction temperature may be approximately within the range between the following two relational expressions, and a favorable result can be obtained by performing the reaction within that range.

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 meq / g, and the cation equivalent is controlled by the amount of hypohalite added. can do. In addition, since the reaction is carried out in an alkaline region, the amide group is hydrolyzed and the carboxyl group becomes by-product. The by-product amount is indicated by an anion equivalent measured by colloid titration at pH 10 and is in the range of 0 to 10.0 meq / g. The amount of the by-product can be controlled by the amount of the added alkaline substance.

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

The reaction can be stopped by (1) adding a reducing agent,
Methods such as (2) cooling and (3) lowering the pH of the solution by adding an acid can be used alone or in combination. (1) is a method of inactivating remaining hypohalite and the like by reaction with a reducing agent. Generally, at the end of the Hoffman decomposition reaction, a compound having active chlorine such as unreacted hypohalite remains. If such a reaction solution is used as a paper strengthening agent, it may cause rust in a paper machine. Therefore, a reducing agent is usually used to inactivate active chlorine. However, the hypohalite reacts at an equimolar or less relative to the acrylamide unit mole number of the polymer, and when the reaction is performed at a high temperature, almost no unreacted hypohalite remains at the end of the reaction. . Therefore, it can be used as a paper strength agent without deactivating active chlorine by using a reducing agent. (2) is a method of suppressing the progress of the reaction by cooling.
There are methods of cooling using a heat exchanger and diluting with cold water. The temperature at that time is usually 50 ° C or lower, preferably 45 ° C or lower, more preferably 40 ° C or lower. (3) is usually pH
The Huffman decomposition reaction is stopped by lowering the pH of the solution showing the alkalinity of 12 to 13 with an acid using an acid, and at the same time, the progress of the hydrolysis reaction is suppressed. PH at that time
May be neutral or lower, and preferably in the range of pH 4 to 6. The reaction termination method can be appropriately selected from (1) to (3) depending on the reaction conditions, and these methods may be combined.

The present invention resides in that the above Huffman-decomposed PAM is applied to paper as a surface strength improver immediately after production. As a method of applying the Huffman-decomposed PAM to a base paper produced by a paper machine, a conventionally known method can be used. Specifically, it is applied by a roll coater, a bar coater, an air knife coater, a knife coater, or the like, and may be any of on-machine coating and off-machine coating. Among them, it is preferable to use a gate roll coater, a size press, and a calender.
The Hoffman-decomposed PAM may be applied to the base paper by a single-layer coating or a multilayer coating, and may be applied on either one side or both sides.

The Huffman-decomposed PAM can improve the surface strength of paper even when used alone, but naturally derived starch such as starch, oxidized starch, and cationized starch, and cellulose derivatives such as carboxymethyl cellulose. Surface strength improver, polyvinyl alcohol and its derivatives,
Other polyacrylamide and its modified products, further urea resin, styrene-maleic acid copolymer, polyvinyl acetate,
It may be used in combination with a synthetic surface strength improver such as a vinyl acetate-maleic acid copolymer, a latex or an emulsion.

The coating amount of the Hoffman decomposition PAM used in the present invention can vary depending on the coating model and the type of base paper, but is 0.01 to 7.00.
g / m ² . Specifically, if the coating amount of each coating machine is increased, a size press, or when applying using a gate roll, 0.05 to 7.00 g / m ² , preferably 0.10 to 5.00 g / m ²
m ² , more preferably in the range of 0.50 to 3.00 g / m ² .
When applying using a calender, 0.01 to
3.00 g / m ^2, preferably 0.05~1.50g / m ^2, more preferably in the range of 0.10~0.30g / m ^2.

The viscosity at the time of applying the Huffman-decomposed PAM used in the present invention is sufficient as long as it does not hinder the coating treatment, and it cannot be said that it depends on the coating model, but when using a size press, Has a Brookfield viscosity of 5 to 300 cps, preferably 15 to 100 cps, and a Brookfield viscosity of 50 when using a gate roll coater.
0 to 6000 cps, preferably 1000 to 3000 cps, and the range of 5 to 50 cps should be double the calender. In that case, the concentration of Hoffman decomposition PAM is 0.5 to 8 wt
%, Preferably 1 to 6% by weight, 5 to 15% by weight, preferably 8 to 12% by weight for a gate roll coater, 0.05 to 6.0% by weight, preferably 0.1 to 3.0% by weight for a calender. If it is, it can be suitably applied.

The present invention uses a cationic polyacrylamide obtained by subjecting polyacrylamide to a Hoffman decomposition reaction at a high temperature and in a short time as a surface coating agent, and is characterized in that it is used immediately after the reaction. Immediately here means to take out the aqueous solution after the reaction from the inside of the pipe, transport it in the same pipe without transferring it to the outside, and apply it to the base paper. More specifically, the aqueous solution after the reaction may be directly applied to the base paper through the pipe, or a stock tank may be provided during the temporary storage there, and then the coating may be performed by adjusting the coating amount. Good. The residence time of the reaction solution in the pipe may be within a range where the aqueous solution after the reaction does not deteriorate. However, if the length is too long, the device for retaining the liquid becomes large, and the features of the present invention cannot be utilized. Therefore, in order to suitably carry out the present invention, it is preferable to apply the coating within 5 hours after the reaction, more preferably within 1 hour, and even more preferably 10 hours or less.
Within minutes.

Paper coated by the method according to the present invention has particularly excellent surface strength and excellent printing characteristics.

[Examples] Next, the present invention will be described with reference to examples, but the present invention is not necessarily limited to the following examples. %
Certain items are by weight unless otherwise specified.

Production Example 1 A 12.5 wt% aqueous solution of polyacrylamide (Brookfield viscosity at 25 ° C .: 13,400 cp) 120.0 was placed in a 500 ml beaker, diluted with 80.0 g of distilled water, and the solution was heated to 80 ° C. with stirring to form A mixed solution of sodium chlorate and NaOH (sodium hypochlorite concentration: 1.0 mol / kg, NaOH concentration: 2.0mo
After 10 seconds, 89.4 g of cold water at 5 ° C. was added to stop the reaction, and a 5 wt% acrylamide polymer was obtained (Hoffman PAM (A)). A part of the reaction product is taken in an aqueous solution of pH 2 and toluidine blue is used as an indicator.
Colloid titration with a 1 / 400N-potassium polyvinylsulfonate aqueous solution yielded a cation value of 0.58 meq./g. Hoffman PAM (A) was used for coating tests within 10 minutes after production.

Production Example 2 120.0 g of a 12.5 wt% aqueous solution of polyacrylamide (Brookfield viscosity at 25 ° C .: 13,400 cp) was placed in a 500 ml beaker, diluted with 80.0 g of distilled water, and heated to 80 ° C. with stirring. A mixed solution of sodium chlorite and NaOH (sodium hypochlorite concentration: 1.0 mol / kg, NaOH concentration: 2.0mo
After 10 seconds, 78.9 g of cold water at 5 ° C. was added to stop the reaction, and a 5 wt% acrylamide polymer was obtained (Hoffman PAM (B)). The cation value was measured in the same manner as in Production Example 1 to be 1.15 meq./g. Hoffman PAM (B) was used for coating tests within 10 minutes after production.

Production Example 3 A 12.5 wt% aqueous solution of polyacrylamide (Brookfield viscosity at 25 ° C .: 13,400 cp) 120.0 was placed in a 500 ml beaker, diluted with 80.0 g of distilled water, and the solution was heated to 80 ° C. with stirring to give A mixed solution of sodium chlorate and NaOH (sodium hypochlorite concentration: 10 mol / kg, NaOH concentration: 2.0 mol
10 kg later, 57.8 g of cold water at 5 ° C. was added to stop the reaction, and a 5 wt% acrylamide polymer was obtained (Hoffman PAM (C)). The cation value was measured by the same method as in Production Example 1, and it was 2.45 meq./g. Hoffman PAM (B) was used for coating tests within 10 minutes after production.

Production Examples 4 to 6 The Hoffman decomposition reaction was performed at 20 ° C. and the reaction time was 2 hours.
The reaction was carried out in the same manner as in Production Examples 1 to 3, except that cold water at 5 ° C was a 0.01% aqueous sodium sulfite solution,
5% by weight of acrylamide polymer was obtained (Hoffman PAM
(D) (E) (F)).

Example 1 A Hoffman PAM (A) produced in Production Example 1 using a No. 4 coating roll bar on a cardboard exterior kraft liner (hereinafter referred to as a liner) (basis weight 200 g / m ² ) obtained from a certain company. Is applied once, the liquid adhesion amount is weighed, and then 110 ° C.
It was dried with a drum dryer for 50 seconds. 20 ° C, 65% RH
In the constant temperature and humidity room for 24 hours. The surface strength was measured by a wax pick test according to JIS-P-8129. Table 1 shows the results of the coating amount and the paper surface strength.

Examples 2 and 3 Hoffman PAM (B) and Hoffman PAM (C)
A coating test and a surface strength measurement were performed in the same manner as in Example 1 except that PAM (A) was used instead. The results are shown in Table 1.

Comparative Example 1 A coating test and a surface strength measurement were performed in the same manner as in Example 1 except that Hoffman PAM (D) was used instead of Hoffman PAM (A). The results are shown in Table 1.

Comparative Examples 2 and 3 Hoffman PAM (E) and Hoffman PAM (F)
A coating test and a surface strength measurement were performed in the same manner as in Example 1 except that PAM (A) was used instead. The results are shown in Table 1.

[Effect of the Invention] As shown in Table 1, the Hoffman decomposition reaction is carried out at 60 to 100 ° C.
The paper coated shortly after the production of the cationic polyacrylamide, which was performed in a short time in the temperature range of, is superior in surface strength to the paper coated with the cationic polyacrylamide, which was subjected to the Hoffman decomposition reaction at a low temperature for a long time. showed that. Although the mechanism of action is not well understood, it is clear that the paper strength effect can be enhanced by applying a cationic polyacrylamide that has undergone a Hoffman decomposition reaction at a high temperature for a short time.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-200103 (JP, A) JP-A-60-69104 (JP, A) JP-A-60-252800 (JP, A) 112595 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) D21H 19/20 C08F 8/44

Claims (1)

(57) [Claims] 1. An acrylamide polymer and a hypohalite, at least in an alkaline region of pH 11 or more,
It is characterized in that a cationic acrylamide polymer obtained by performing a reaction in a temperature (T) range of 60 to 100 ° C. and within a time (t) specified below is coated at 0.01 to 7.00 g / m ^2. Paper manufacturing method. e ^{15,150 / (273 + T)} × 2.5 × 10 ^-20 ≦ t (sec) ≦ e ^{15,150 / (273 + T)} × 10 ^-18 +30