JPH08337984A - Deinking method - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a deinking method capable of obtaining a high quality deinking pulp having high whiteness and a small number of residual inks. An alkylene oxide adduct of a mixture of oil and fat and a monohydric or polyhydric alcohol in a deinking method comprising at least a step of peeling ink from raw waste paper and a step of removing the peeled ink from a flotation system. A nonionic surfactant such as an alkylene oxide adduct of a fatty acid or an alkylene oxide adduct of a higher alcohol as a deinking agent, and a flotation step of a cationic compound such as a quaternary ammonium salt or a pyridinium salt. PH is in the range of 4-9 in the presence.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to newspapers, leaflets,
The present invention relates to a deinking method for deinking and reusing used paper such as magazines. More specifically, the present invention relates to a deinking method which is excellent in operability and which can obtain an excellent deinking pulp having a higher whiteness and a smaller number of residual inks in a high yield.

[0002]

BACKGROUND ART Waste paper is recycled by removing ink from the waste paper by deinking treatment to obtain recycled pulp and manufacturing recycled paper from the recycled pulp. A conventional deinking method generally includes a step of peeling ink from waste paper and a step of discharging the peeled ink. More specifically, the main steps of the deinking method are (1) a pulping (disaggregation) step of used paper, (2) aging, that is, a step of leaving the disintegrated paper as it is, (3) flotation Process, and (4) washing process. That is, in the deinking process, the ink bound to the used paper fibers is physically or chemically (or biochemically) separated to separate the ink from the fibers. In this way, recycled pulp is obtained.

In performing deinking treatment, generally, an interface of polyoxyethylene alkyl ether or fatty acid is used for the purpose of peeling ink from waste paper or for generating bubbles for adhering the peeled ink. A deinking agent consisting of an activator is used in any of the above steps.

In recent years, the characteristics of waste paper used as a raw material have been diversified due to the increasing demand for beautiful and stable printing and the progress of printing technology. In addition, the degree of binding of ink to paper is wide ranging from mild to strong. Under such circumstances, it is required to improve the quality and yield (that is, productivity) of deinked pulp. In order to achieve this object, various proposals have been made in various fields including a deinking process, a deinking agent, and a device used for deinking.

In the conventional deinking method, the pulping step and the flotation step are generally carried out at an alkaline pH above pH 9, and in extremely few cases,
It is performed at a pH of 9 or less. The deinking method in which the pulping step and the flotation step are performed at pH 9 or lower is described in JP-A-54-23705 and JP-A-59-53532.
And U.S. Pat. No. 4,043,903. Specifically, JP-A-54-23705 discloses that after adding aluminum salt or white water to a suspension of waste paper for flotation, the pH of the suspension is adjusted to pH 4 to 7, A method of adding a polymer flocculant and performing flotation is disclosed. Japanese Patent Laid-Open No. 59-53532 discloses that amine is used at basic pH and 4 at acidic pH.
It is disclosed that a specific alkylamine polyether that behaves as a primary ammonium contributes to the development of the foam characteristics required in each of the pulping step, the washing deinking step and the flotation step. U.S. Pat. No. 4,04
No. 3,903 uses an amine ethylene oxide adduct to strip ink from pulp, disintegrating waste paper and stripping ink from it at high pH, thereby incorporating the ink into micelles and then the system. The method of lowering the pH of the ink to break the micelles, thereby separating (precipitating) the ink from the pulp, and removing the ink from the system by flotation is disclosed.

[0006]

However, in the method described in JP-A-54-23705, the foaming property is remarkably high, so that the pulp yield is lowered and the pulp is rejected (discharged) in the flotation step. An increase in the amount of foam occurs. Such excessive generation of bubbles is not preferable for flotation, resulting in deterioration of productivity and quality. The alkylamine polyether disclosed in JP-A-59-53532 has poorer ink peeling performance than conventional polyoxyethylene alkyl ether type deinking agents, and therefore provides pulp with high whiteness. do not do. Also, the ink peeled from the pulp using such an alkylamine polyether is in the form of very fine droplets and does not have the optimum size suitable for adsorbing to the bubbles during flotation. That is, the ink cannot be sufficiently removed during flotation. U.S. Pat. No. 4,0
The method disclosed in No. 43,903 does not achieve sufficient deinking. The reason is not always clear, but when the ethylene oxide adduct of amine is used as a deinking agent in the disintegration step in which the ink is peeled from the pulp, the ink is not sufficiently peeled from it and during flotation. It is considered that the ink dispersed in the system or dissolved in the micelles adheres to the pulp again when the pH of the system decreases.

[0007]

In view of the above situation, the inventors of the present invention have earnestly studied from the viewpoint of the deinking method. As a result of the research, the present inventors have used a nonionic surfactant as a deinking agent to sufficiently remove the ink from the waste paper, and
It was found that by performing the flotation step at pH 4 to 9 in the presence of a cationic compound, a deinked pulp having a high whiteness and a small number of remaining inks can be obtained. The present invention has been completed based on this finding.

That is, the present invention is a deinking method comprising at least a step of peeling ink from raw waste paper and a step of removing the peeled ink from the flotation system. Provided is a method of using at least one nonionic surfactant and performing at least part of the flotation step in the presence of at least one cationic compound at a pH within the range of 4 to 9.

In other words, the present invention is a deinking method comprising a step of peeling ink from raw waste paper and a step of removing the peeled ink from the flotation system. At least one nonionic surfactant is added, and the p of the system is added before or during the step of removing the peeled ink from the flotation system.
It relates to adjusting H to 4-9 and a method of adding at least one cationic compound before or during the step of removing the peeled ink from the flotation system.

In the present invention, the nonionic surfactant is
It is preferably selected from the group consisting of the following nonionic surfactants (A) to (D). Nonionic surfactant (A): Reaction product obtained by adding alkylene oxide to a mixture of oil and fat Nonionic surfactant (B): Formula: RCOO (AO) _m R ′
(Wherein R represents an alkyl or alkenyl group having 7 to 23 carbon atoms, and R'is a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, or Represents an acyl group having 2 to 22 carbon atoms, AO is
An oxyalkylene group having 2 to 4 carbon atoms is shown, and m is an integer of 1 or more. ) Nonionic surfactant (C): compound represented by the formula: RO (AO) _n H (wherein R represents an alkyl or alkenyl group having 8 to 24 carbon atoms, and AO is 2 to 2 carbon atoms). 4 represents an oxyalkylene group, and n is an integer of 1 or more.) Nonionic surfactant (D): reaction product obtained by adding alkylene oxide to polyvalent carboxylic acid or its acid anhydride, Alternatively, a reaction product obtained by adding an alkylene oxide to a mixture of a polycarboxylic acid or an acid anhydride thereof and an alcohol, in the alkylene oxide adduct in the nonionic surfactant, the addition form of the alkylene oxide is , Block, random, or a mixture thereof.

The at least one cationic compound is preferably added to the flotation system after adjusting the pH of the system to a value within the range of pH 4 to pH 9. In this case, the at least one cationic compound is preferably used in such an amount that the pH of the system for flotation is hardly changed by the addition of such at least one.

The cationic compound is represented by the following formula (a):
A compound represented by (e) and the following formulas (f) to (j), wherein the cationic nitrogen content is 0.01 to 35% by weight,
Further, it is preferably selected from the group consisting of cationic polymers having a weight average molecular weight of 2,000 to 3,000,000.

[0013]

[Chemical 4]

In the formulas (a) to (e), R ₁ and R ₂
Are the same or different from each other and have 10 to 2 carbon atoms, respectively.
4 is an alkyl, alkenyl or β-hydroxyalkyl group, and R ₃ , R ₄ and R ₅ are the same or different from each other and are each an alkyl or hydroxyalkyl group having 1 to 8 carbon atoms, a benzyl group or a formula :-( AO) _n-
Z (here, AO is an oxyalkylene group having 2 to 4 carbon atoms, Z is a hydrogen atom or an acyl group, and n is 1 to 1).
Is an integer of 50), R ₆ is an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms, X ⁻ is a counterion, and Y is 8 carbon atoms. ~ 36 alkyl, alkenyl or β-hydroxyalkyl group, a group represented by the formula: R ₆ COOCH _2- (wherein R ₆ is as defined above), the formula: R ₆ CONH
A group represented by CH ₂ — (wherein R ₆ is as defined above) or a group represented by the formula: R ₆ OCH ₂ — (wherein R ₆ is defined as above) is there.

[0015]

Embedded image

In equations (f) to (j), R ₁ ,
_{R 2, R 3, R 6} , R 7, R 8 and R ₉ are the same or different from each other, respectively, an alkyl group or an alkenyl group having a carbon number of 2 to 24 1 to 24 carbon atoms, R ₄ And R ₅ are the same or different from each other, respectively, a hydrogen atom or a methyl group, X ⁻ and W ⁻ are the same or different from each other, respectively, a counterion, and Y and Z
Are the same or different from each other, respectively, O or NH
And AO is an oxyalkylene group having 2 to 4 carbon atoms, p and q are the same or different from each other, and each is an integer of 1 to 10, and r is an integer of 0 to 10. , L, m and n are positive numbers such that the weight average molecular weight of the polymer is a value within the range of 2,000 to 3,000,000.

The present invention is a deinking method comprising at least a step of peeling ink from used raw paper and a step of removing the ink peeled from it by flotation, wherein the nonionic surfactant (A) is used. Using one or more deinking agents selected from (D) to (D), the pH of the system is adjusted to 4 to 9 during the flotation, and the cationic compound is added to the system during the flotation. Includes those characterized by being present. In this case, the cationic compound is preferably one or more compounds selected from the group consisting of those represented by the formulas (a) to (e).

As described above, according to the method disclosed in JP-A-54-23705, an increase in foaming property is observed during flotation during deinking treatment. As a result of research conducted by the present inventors, the above phenomenon is caused by polyacrylamide (PAM)
It was confirmed that such a nonionic or anionic polymer flocculant was used in flotation under conditions where the aluminum ion concentration of the system was high. In contrast, the deinking method of the present invention in which a nonionic surfactant is used as a deinking agent and the flotation is carried out at pH 4 to 9 in the presence of a cationic compound can produce a high quality deinked pulp with a good yield. There is a remarkable effect of being able to. By using a nonionic surfactant, the ink is sufficiently peeled from the waste paper fiber, and the peeled ink is
Since it is efficiently removed and collected by flotation at pH 4 to 9 in the presence of a cationic compound, it is considered that the present invention can achieve the above effects.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The deinking method of the present invention comprises at least a step of peeling ink from waste paper and a step of removing the peeled ink from a flotation system. First, the nonionic surfactant used as a deinking agent in the present invention will be described.

<Nonionic Surfactant (A): Reaction Product Obtained by Adding Alkylene Oxide to Mixture of Fats and Oils>Alcohol> Nonionic surfactant (A) is a mixture of fats and oils and monovalent or polyvalent. It is an alkylene oxide adduct of a mixture with alcohol. The alkylene oxide is added to the above mixture in an average of 5 to 300 per mol of the mixture.
It is added in an amount of mol, preferably 20 to 150 mol.
Examples of alkylene oxide include ethylene oxide, propylene oxide and butylene oxide, which may be used alone or in the form of a mixture of two or more thereof.

The mixing ratio of fats and oils to alcohol is 1
/0.1 to 1/6 is preferable, and 1 / 0.3 to 1/3 is particularly preferable. When the ratio is within the above range, the ink is sufficiently peeled off, and a regenerated pulp having a good appearance is obtained.

Examples of fats and oils as raw materials for the nonionic surfactant (A) include palm oil, palm oil, olive oil, soybean oil, rapeseed oil, vegetable oil such as linseed oil, animal oils such as lard, beef tallow and bone oil. , Fish oils, hydrogenated and semi-hardened oils thereof, and recovered oils obtained in the refining process of these fats and oils.

Examples of the monohydric alcohol as a raw material for the nonionic surfactant (A) include those having an alkyl or alkenyl moiety having 8 to 24 carbon atoms, and the alkyl moiety having 6 to 14 carbon atoms. Those having an alkylphenyl moiety can be mentioned. Specific examples thereof include 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tridecanol, 1-tetradecanol, 1-pentadecanol, 1
-Hexadecanol, 1-heptadecanol, 1-octadecanol, 1-nonadecanol, 1-eicosanol, 1-heneicosanol, 1-docosanol, 1-
Tricosanol, 1-tetracosanol, 2-octanol, 2-nonanol, 2-decanol, 2-undecanol, 2-dodecanol, 2-tridecanol, 2-
Tetradecanol, 2-pentadecanol, 2-hexadecanol, 2-heptadecanol, 2-octadecanol, 2-nonadecanol, 2-eicosanol, 2-
Octene-1-ol, 2-dodecene-1-ol, 2
-Undecen-1-ol, 2-tetradecen-1-ol, 2-pentadecen-1-ol, 2-hexadecen-1-ol, 2-octadecen-1-ol, 8-
Nonen-1-ol, 10-Undecen-1-ol,
11-dodecen-1-ol, 12-tridecene-1-
All, 15-hexadecen-1-ol, oleyl alcohol, elaidyl alcohol, linoleyl alcohol, linolenyl alcohol, eleostearyl alcohol, ricinoyl alcohol, cyclononanol, cyclodecanol, cycloundecanol, cyclododeca. Nole, cyclotridecanol, cyclotetradecanol,
Mention may be made of cyclopentadecanol, cyclohexadecanol, cycloheptadecanol, cyclooctadecanol, cyclononadecanol, cyclocosanol, octylphenol and nonylphenol.

Examples of the polyhydric alcohol as a raw material of the nonionic surfactant (A) include ethylene glycol, propylene glycol, trimethylene glycol, butylene glycol, 1,6-hexane glycol, 2-ethylbutane-1,2. , 3-triol, glycerin, trimethylolpropane, trimethylolethane, 1,2,
4-butanetriol, 1,2,6-hexanetriol, 1,1,1-trimethylolhexane, tetramethylolcyclohexanol, diglycerin, mannitane, pentaerythritol, erythritol, arabite,
Sorbit, D-glycero-D-galactoheptose,
D-glycero-D-glucoheptose, D-glycero-
D-mannoheptose, D-glycero-L-mannoheptose, D-altroheptulose, D-mannoheptulose, D-altro-3-heptulose, D-glycero-D-galaheptitol, D-erythro-D-galaocty. Tall, D-glycero-D-mannococtulose,
D-erythro-L-glononulose, cellobiose, maltose, lactose, gentianose, cellotriose and stachyose are mentioned.

<Nonionic surfactant (B): Formula: RCO
Compound Represented by O (AO) _m R ′> In the above formula, R represents an alkyl or alkenyl group having 7 to 23 carbon atoms, and R ′
Represents a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms or an acyl group having 2 to 22 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, and m Is an integer of 1 or more. When the number of carbon atoms of the alkyl or alkenyl group in the definition of R is 7 to 23, the nonionic surfactant (B) exhibits excellent ink collecting ability and excellent ink peeling performance, and thereby high It provides recycled pulp that has good whiteness and looks good.

When the alkyl, alkenyl or acyl group in the definition of R'has a carbon number of 22 or less, the nonionic surfactant (B) exhibits excellent ink peeling performance from cellulose, thereby giving a good appearance. It provides a good recycled pulp and exhibits appropriate foamability, thereby achieving excellent productivity.

The nonionic surfactant (B) is produced by adding an alkylene oxide to a fatty acid by a conventional method and optionally esterifying or acylating. Alkylene oxide is a fatty acid, per mol of fatty acid,
It is added in an amount of 5 to 300 mol on average, preferably 10 to 150 mol. That is, the nonionic surfactant (B) is
Usually, each is a reaction product mixture consisting of a compound represented by the above formula: RCOO (AO) _m R ′. Examples of alkylene oxides include those mentioned in the above description relating to the nonionic surfactant (A). In the production of the nonionic surfactant (B), it is preferable to use ethylene oxide and propylene oxide at a molar ratio of ethylene oxide to propylene oxide of 1/5 to 5/1.

Examples of the fatty acid used for producing the nonionic surfactant (B) include those having 7 to 23 carbon atoms in the alkyl or alkenyl moiety corresponding to R, and specific examples thereof. , Caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid,
Margaric acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, stearolic acid, ricinoleic acid, ricinoelaidic acid, nonadecanoic acid, arachidic acid, heneicosanoic acid, behenic acid, brassic acid,
Examples thereof include erucic acid, tricosanoic acid, tetracosanoic acid, coconut oil fatty acid, beef tallow fatty acid, palm oil fatty acid, tall oil fatty acid, rapeseed oil fatty acid and fish oil fatty acid. Among the nonionic surfactants (B), those having an alkyl or alkenyl group represented by R having 11 to 23 carbon atoms are preferable.

<Nonionic surfactant (C): Formula: RO
Compound Represented by (AO) _n H> In the above formula, R represents an alkyl or alkenyl group having 8 to 24 carbon atoms, and AO is
An oxyalkylene group having 2 to 4 carbon atoms is shown, and n is an integer of 1 or more. When the number of carbon atoms of the alkyl or alkenyl group in the definition of R is 8 to 24, the nonionic surfactant (C) exhibits excellent ink peeling ability from cellulose, and therefore has high whiteness and good appearance. Provide good recycled pulp.

The nonionic surfactant (C) is produced by adding an alkylene oxide to a monohydric alcohol by a conventional method. The alkylene oxide is 5 to 300 on average per 1 mol of the monohydric alcohol in the monohydric alcohol.
It is added in an amount of mol, preferably 7 to 150 mol. That is, the nonionic surfactant (C) is usually a reaction product mixture composed of compounds each represented by the above formula: RO (AO) _m H. Examples of alkylene oxides include those mentioned in the above description relating to the nonionic surfactant (A). In the production of the nonionic surfactant (C), it is preferable to use ethylene oxide and propylene oxide at a molar ratio of ethylene oxide to propylene oxide of 1/5 to 5/1.

Examples of the monohydric alcohol used for producing the nonionic surfactant (C) have 8 to 8 carbon atoms.
Examples thereof include those having 24 alkyl or alkenyl moieties and those having an alkylphenyl moiety in which the alkyl moiety has 6 to 14 carbon atoms. Specific examples thereof include those described in the above description relating to the nonionic surfactant (A). Among the nonionic surfactants (C), those in which the alkyl or alkenyl group represented by R has 14 to 24 carbon atoms are preferable.

<Nonionic surfactant (D): reaction product obtained by adding alkylene oxide to polyvalent carboxylic acid or acid anhydride thereof, or polyvalent carboxylic acid or acid anhydride thereof and alcohol The reaction product obtained by adding alkylene oxide to the mixture with the above> Polyvalent (or polybasic) carboxylic acid as a raw material of the nonionic surfactant (D) and its acid anhydride are as follows: Oxalic acid, malonic acid, succinic acid, methylsuccinic acid, maleic acid, glutaric acid, adipic acid, phthalic acid, fumaric acid, itaconic acid, malic acid, tartaric acid, maleated oleic acid,
Citric acid, percitric acid, trimellitic acid, butanetetracarboxylic acid, pyromellitic acid, tetradecanehexacarboxylic acid, maleic anhydride, succinic anhydride, oxalic anhydride, itaconic anhydride, glutaric anhydride, phthalic anhydride,
Examples include trimellitic anhydride, pyromellitic dianhydride, and stearyl succinic anhydride.

Further, dimer acid and polymer acid of higher fatty acid having 14 to 22 carbon atoms are also included in the category of polyvalent carboxylic acid. The dimer acid and the polymer acid referred to here are, for example, monoolefin carboxylic acid or diolefin carboxylic acid such as unsaturated fatty acid monomer such as oleic acid, linoleic acid and linoleic acid, which are subjected to thermal polymerization such as Diels-Alder reaction or other methods. Can be synthesized. The polymer acid referred to here is a polycarboxylic acid having three or more carboxyl groups in one molecule and does not include dimer acid. The dimer acid or polymer acid used here may be a mixture of it and an unreacted monomer acid. That is, unreacted monomer acid may be present as long as the effect of the present invention is not impaired.

Examples of the alcohol as a raw material of the nonionic surfactant (D) include monohydric alcohols and polyhydric alcohols, and specific examples thereof include the above-mentioned nonionic surfactant (A). Mention may be made of those mentioned in the description.

In the production of the nonionic surfactant (D) using the polyvalent carboxylic acid or its acid anhydride (I) and the alcohol (II), the compounds (I) and (II) are compared with (II) The molar ratio of I) is 1 / 0.02-5, especially 1 /
It is preferably used at 0.1 to 3. When the molar ratio is within this range, the nonionic surfactant (D) is
Fine ink droplets can be collected efficiently, and
The collected ink droplets are efficiently removed from the system in flotation.

The nonionic surfactant may be added at any step of the deinking method. However, addition in the pulping step is usually preferred. The amount added is not particularly limited. A sufficient deinking effect cannot be achieved only by the deinking agent other than these nonionic surfactants of the present invention. Known deinking agents other than the above-mentioned nonionic surfactants (A) to (D) can be used in combination therewith.

In the flotation method as one of the deinking methods, the pulp / water slurry is foamed by an appropriate means such as a physical means or a chemical means, and ink droplets are attached to the floating bubbles and discharged. This is characterized by separating the ink from the pulp. In the deinking method of the present invention,
At least part of the flotation step may be carried out at a pH within the range of 4-9, preferably 6-8. Therefore, the pH of the pulp / water slurry may be adjusted within the range of 4-9 in any step before flotation.

The steps before flotation are generally carried out at basic pH. Therefore, in the present invention, a suitable acid or an aqueous solution of an acid is added to the pulp / water slurry before or during the flotation to bring the pH of the slurry to a value within the above range. The method of adding acid is
There is no particular limitation, and an acid or an aqueous solution of an acid may be added to water injected into the slurry before or during the flotation. Examples of the acid used to adjust the pH of the slurry include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, salts thereof, and organic acids such as acetic acid, formic acid and citric acid. The method of adjusting the pH of the slurry is not limited to using an acid. When the pH of the slurry is within the above range in at least a part of the flotation step, the whiteness of the recycled pulp is increased, the number of residual inks in the recycled paper is decreased, and the yield is increased. Furthermore, the equipment and pulp fibers themselves are not adversely affected by the nature of the slurry.

The deinking method of the present invention is also characterized in that a cationic compound is present in the system during flotation. The cationic compound here is one that is cationic or has a cationic group at pH 4 to 9 in flotation. Examples of the cationic compound, mono long-chain alkyl type quaternary ammonium salt, di long-chain alkyl type quaternary ammonium salt,
Examples include pyridinium salts having a substituent on the nitrogen atom, and cationic polymers. In particular, the above formulas (a) to (e)
And a compound represented by the formula (f) to (j),
The cationic nitrogen content is 0.01 to 35% by weight, and
Cationic polymers having a weight average molecular weight of 2,000 to 3,000,000 are preferred.

In each of the formulas (a) to (e), R ₁
Examples of the group in the definition of R ₂ and R ₂ include a lauryl group, a myristyl group, a cetyl group, a stearyl group, a behenyl group, an oleyl group and a linoleyl group. R ₁ and R ₂
May be the same or different from each other. Examples of the alkyl group having 1 to 8 carbon atoms in the definitions of R ₃ , R ₄ and R ₅ include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, an isopropyl group and an isobutyl group. Can be mentioned. R ₃ , R ₄ and R ₅ may be the same or different from each other. Examples of the acyl group in the definition of Z include carbon atoms such as formyl group, acetyl group, propionyl group, butyryl group, lauroyl group, myristoyl group, palmitoyl group, stearoyl group, isobutyryl group, oleoyl group and methacryl group. The thing derived from the fatty acid of several 2-24 is mentioned. Examples of the group in the definition of R ₆ include octyl group, lauryl group, myristyl group, cetyl group, stearyl group, behenyl group, hexacosyl group, hexatriacontyl group, oleyl group and linolenyl group. X ⁻ is a counter ion, and examples thereof include a hydroxyl ion, a halide ion, a monoalkyl sulfate ester ion having an alkyl moiety having 1 to 3 carbon atoms, and an anion derived from an inorganic or organic acid. Specifically, X ⁻ is a halide ion such as chloride ion, bromide ion and fluoride ion, a monoalkyl sulfate ester ion such as methyl sulfate ester ion and ethyl sulfate ester ion, sulfuric acid, nitric acid, carbonic acid, phosphoric acid and the like. 3 shows a counter ion derived from the inorganic acid of the above, or another counter ion derived from a monovalent or polyvalent organic acid such as acetic acid and citric acid.

The cationic polymers represented by the above formulas (f) to (j) each have a weight average molecular weight of 2,000 to 3,000.
0,000, preferably 10,000 to 1,000,000, and
It contains 0.01 to 35% by weight, preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight of cationic nitrogen atom. The cationic nitrogen content is, for example, the nitrogen content (%) of the polymer obtained by the Kjeldahl method, and the obtained nitrogen content (%) is the ratio of the cationic nitrogen to the total nitrogen calculated from the molecular formula of the polymer. It is decided by multiplying.

Examples of the above cationic polymers include acrylamide polymers modified with a group having a quaternary ammonium group, acrylamide / acrylic acid ester copolymer modified with a group having a quaternary ammonium group, and the like. Polymer composed of acrylamide and modified with a group having a quaternary ammonium group; acrylic acid ester polymer modified with a group having a quaternary ammonium group, acrylic modified with a group having a quaternary ammonium group Polymers comprising acrylic acid esters such as acid ester / acrylic acid ester copolymers and modified with a group having a quaternary ammonium group; styrene polymers modified with a group having a quaternary ammonium group; Diallylamine polymers modified with groups having a quaternary ammonium group; cationized cellulose; and catio It includes chitosan.

In each of the expressions (f) to (j),
Examples of the groups in the meaning of R ₁ , R ₂ , R ₃ , R ₆ , R ₇ , R ₈ and R ₉ include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group and a lauryl group. , A myristyl group, a cetyl group, a stearyl group, a behenyl group, an oleyl group, a linoleyl group, an isopropyl group and an isobutyl group. X ⁻ and W in the above formulas (f) to (j)
^- are each counterion. As the embodiments, X in formula (a) ~ (e) ^- include those described in the above description taken in conjunction with the. Further, the above formula (f)-
AO in (j) refers to an oxyalkylene group having 2 to 4 carbon atoms, and examples thereof include an oxyethylene group, an oxypropylene group, and an oxybutylene group.

The cationic compound is, in flotation, 0.001 to 5.0% by weight, preferably 0.01 to 1.0% by weight, based on the weight of the waste paper (that is, the absolute dry weight of the waste paper).
Used in an amount of. If at least one selected above is present in the system, that is, the slurry in the above amount at the time of flotation, the ink can be efficiently removed from the system.

In the present invention, the pulp / water slurry must contain a cationic compound in at least one step of flotation. Therefore, the cationic compound may be added at any step of the deinking process, unless the step is performed after flotation. It may be added in one step before flotation, eg in a disaggregation or bleaching step, or just before or during flotation (eg at the beginning of the flotation step). Preferably, the cationic compound is added to the slurry immediately before or during the flotation, after adjusting the pH of the slurry to a value within the range of 4 to 9. In this case, the cationic compound is preferably used in an amount such that the pH of the system for flotation hardly changes by its addition. The phrase "the pH of the system for flotation hardly changes" means that the pH change of the system is not observed or is observed only at the second decimal place in the pH measurement. By the addition thereof, the amount of the cationic compound "the pH of the system for flotation hardly changes" refers to, for example, 0.01-1.% Based on the weight of waste paper (that is, absolute dry weight of waste paper). It is 0% by weight.

For example, when the flotation system is circulated, the flotation step may consist of two or more steps. In such cases, the pH of the system must be adjusted to a value in the range 4-9 in at least one flotation step. The pH of the system is preferably adjusted as described above during the multiple steps of flotation, just prior to the washing step. Also cationic compounds,
In at least one step of flotation, pH 4 to
It must be present in the 9 system.

In the deinking method of the present invention, the calcium ion concentration of the system at the time of flotation, that is, the slurry is
It is not particularly limited. However, in order to obtain higher quality recycled pulp, the calcium ion concentration of the system at the time of flotation is 10 to 400 ppm, particularly 100 to 25 ppm.
It is preferable to adjust the value within the range of 0 ppm. When the calcium ion concentration is within the above range, the fine ink droplets can be selectively aggregated with each other, and an ink droplet having an optimum size for flotation rejection can be obtained. Therefore,
The ink is easily removed by flotation, and a regenerated pulp with higher whiteness and less residual ink is obtained.

Inorganic calcium salts such as calcium chloride and calcium carbonate, and minerals such as lime can be used for controlling the calcium ion concentration of the system. Furthermore, animal bones, shells and the like may be used as the calcium ion source. In that case, animal bones are reacted with acid,
Ionized. The calcium ion concentration of the system in flotation is preferably adjusted to a value within the above range, but the calcium ion concentration of the system in any step other than the flotation step is not particularly limited. Therefore, the calcium ion concentration of the system may be adjusted in any step (pulping step or the like) before the flotation step as long as it does not affect the ink peeling.

In the deinking method of the present invention, the aluminum ion concentration in the flotation system is preferably 40.
It is adjusted to below ppm, especially below 25 ppm. In order to adjust the aluminum ion concentration of the system, it is preferable to consider the type and amount of water used in flotation. For example, white water and / or tap water generated during papermaking is used in an appropriate amount. When the aluminum ion concentration of the system in flotation is adjusted as described above, both improvement of whiteness of recycled pulp and reduction of residual ink number of recycled paper are achieved, and pulp yield is increased. The aluminum ion concentration of the system in flotation is preferably adjusted to a value within the above range,
The aluminum ion concentration of the system in any step other than the flotation step is not particularly limited. Therefore, the aluminum ion concentration of the system may be adjusted in any step (such as a pulping step) before the flotation step as long as it does not affect the ink peeling.

In the above-described deinking method of the present invention, at least one of the nonionic surfactants (A) to (D) is used, and at least part of the flotation step is performed in the presence of a cationic compound. The method is performed at a pH within the range of 4 to 9, and includes at least a step of peeling the ink from the waste paper and a step of removing the ink peeled from the flotation system. Other steps can be performed according to the conventional deinking method. That is, the deinking method may include a disaggregation (or pulping) step, an aging step, a kneading step if necessary, a flotation step, and a washing step as its main steps. The deinking method may further include other steps, if necessary. Each step may be performed twice or more.

According to the present invention, deinked pulp having a higher whiteness and a smaller number of residual inks can be obtained from the used waste paper. Therefore, bleaching chemicals such as caustic soda, sodium silicate, hydrogen peroxide, and chelating agents are required only in a small amount, and the pulp yield is improved, so that the production cost of deinked pulp can be reduced. .

The mechanism by which the deinking method of the present invention exhibits such an excellent deinking effect is not necessarily clear, but is considered as follows. That is, by using a nonionic surfactant as the deinking agent, the ink is sufficiently peeled from the pulp, and further, the decrease in the pH of the system before or during the flotation depends on the condition of the interface between the pulp and the ink. And causes the preferential adsorption of existing cationic compounds to the ink, causing the ink to aggregate due to the binding of the cationic compounds to each other at their hydrophobic portion. In this case, the presence of nonionic surfactants in the system prevents re-adsorption of the ink on the pulp. In the absence of a nonionic surfactant in the system, the cationic compound adsorbs to both the ink and pulp, which causes the ink to re-adsorb to the pulp. Anyway, in the deinking method of the present invention, (1) a nonionic surfactant is used as a deinking agent, and (2) in the presence of the nonionic surfactant, the pH of the system is set to a low value. It is essential to adjust and (3) to aggregate the ink in the presence of a cationic compound.

[0053]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

<Cationic Compound> Examples 1 to 10 below
The cationic compounds used in 1. are shown in Tables 1 to 5 below.
In Tables 1 to 5, each numerical value in the columns of R _{1 to} R ₆ , R _6a and R _6b means the carbon number of a straight chain alkyl group as a substituent, and is “18 F1”, “18 Hyd” and "12 Hyd" is,
An oleyl group, a β-hydroxystearyl group and a β-hydroxylauryl group are shown. Furthermore, in the following examples,
"EO" and "PO" represent an oxyethylene group and an oxypropylene group, respectively, and the subscript number represents the average number of moles of ethylene oxide or propylene oxide added.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4]

[0059]

[Table 5]

Example 1 Waste paper (newspaper / flyer = 75/25) collected in the city was shredded (2 × 5 cm). A certain amount was put in the table disintegrator. Then, in it, warm water, 1% by weight (vs. raw material)
Caustic soda, 3% by weight (vs. raw material) sodium silicate, 3% by weight (vs. raw material) 30% by weight hydrogen peroxide solution, and 0.2
A mixture was prepared by adding EO ₁₀ / PO ₁₀ block adduct of stearyl alcohol as a deinking agent in wt% (relative to raw material). The waste paper in the mixture was disintegrated at 40 ° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight.
The obtained pulp slurry is kept at 40 ° C. for 60 minutes,
Hot water was then added to the pulp slurry. Thus, a pulp slurry having a pulp concentration of 1% by weight was prepared. Hydrochloric acid is added to the pulp slurry and the pH is adjusted to
The values shown in Table 6 were used. Cationic compounds shown in Table 1 or 2 and Table 6 were further added to the pulp slurry in the amounts shown in Table 6. The pH of the obtained pulp slurry remained almost unchanged by the addition of the cationic compound. After sampling from the obtained pulp slurry (before flotation), the pulp slurry was subjected to a flotation treatment at 40 ° C. for 10 minutes to prepare a pulp slurry (after flotation).

The whiteness of pulp sheets prepared from pulp slurry (before flotation) and pulp slurry (after flotation) was measured. The residual ink area ratio of the pulp sheet obtained from the pulp slurry (after flotation) was also measured. Specifically, aluminum sulfate is added to each of the pulp slurry (before flotation) and the pulp slurry (after flotation) to adjust the pH to 5, and the obtained pulp slurries are respectively subjected to tappi standard sheets. Machine processed into pulp sheets.
The pulp sheet thus obtained was ventilated and dried. The whiteness of the obtained pulp sheet was measured with a colorimetric color difference meter, and the residual ink area ratio of the pulp sheet obtained from the pulp slurry (after flotation) was measured with an image analyzer (magnification: × 100). Was measured using. A 1% improvement in the whiteness of the pulp sheet and a 0.1% decrease in the residual ink area ratio can be visually recognized as a sufficiently improved quality of the pulp sheet.

The pulp yield at the time of flotation is determined by the absolute dry weight of the pulp contained in the pulp slurry before flotation and the absolute dry weight of the pulp contained in the flotation reject [that is, [(before flotation Of the pulp contained in the pulp slurry of the above)-(the absolute dry weight of the pulp contained in the flotation reject)] × 100 / (the absolute dry weight of the pulp contained in the pulp slurry before the flotation) Weight)]. Table 6 shows the results.

[0063]

[Table 6]

Note) The amount of the cationic compound is shown in% by weight based on the weight of waste paper (ie, absolute dry weight of waste paper). The same applies to Examples 2-10 below.

In the above test, Test No. 1 is performed by the same method as the conventional industrial deinking method. According to the method of Test Nos. 8 to 25 (method of the present invention) in which flotation is performed at a specific pH in the presence of a cationic compound,
Compared with the test numbers 1 to 7 (comparative method), selective removal of ink in flotation improves whiteness of recycled paper, reduces the number of residual inks in recycled paper, and increases pulp yield. Can be expected.

Example 2 Using the cationic compounds shown in Tables 1 and 7, a deinking test was conducted according to the method described in Example 1.
The results are shown in Table 7.

[0067]

[Table 7]

Test Nos. 28 to 3 in which flotation is carried out in the presence of the cationic compounds shown in Table 1 at a specific pH.
According to the method of 5 (the method of the present invention), the whiteness of the recycled paper is improved and the whiteness of the recycled paper is improved by selectively removing the ink in the flotation, as compared with the methods of the test numbers 26 and 27 (comparative method). Achieving a reduction in the number of residual inks and an increase in pulp yield can be expected.

Example 3 Using the cationic compounds shown in Tables 2 and 8, a deinking test was conducted according to the method described in Example 1.
Table 8 shows the results.

[0070]

[Table 8]

Test Nos. 38 to 5 in which flotation is carried out at a specific pH in the presence of the cationic compounds shown in Table 2
According to the method 1 (the method of the present invention), the whiteness of the recycled paper is improved and the whiteness of the recycled paper is improved by the selective removal of the ink in the flotation, as compared with the methods of the test numbers 36 and 37 (comparative method). Achieving a reduction in the number of residual inks and an increase in pulp yield can be expected.

Example 4 Using the cationic compounds shown in Tables 3 and 9, a deinking test was conducted according to the method described in Example 1.
In this example, an EO ₂₀ adduct of stearic acid was used as the deinking agent. The results are shown in Table 9.

[0073]

[Table 9]

Test Nos. 54 to 5 in which flotation is carried out at a specific pH in the presence of the cationic compounds shown in Table 3
According to the method of 7 (the method of the present invention), the whiteness of the recycled paper is improved and the whiteness of the recycled paper is improved by selectively removing the ink in the flotation, as compared with the methods of the test numbers 52 and 53 (comparative method). Achieving a reduction in the number of residual inks and an increase in pulp yield can be expected.

Example 5 Using the cationic compounds shown in Tables 4 and 10, a deinking test was carried out according to the method described in Example 1. In this example, the EO ₆₀ adduct of beef tallow / glycerin (1: 1 by mole) mixture was used as the deinking agent. The results are shown in Table 10.

[0076]

[Table 10]

Test Nos. 60 to 6 in which flotation is performed in the presence of the cationic compounds shown in Table 4 at a specific pH.
According to the method 2 (the method of the present invention), the whiteness of the recycled paper is improved and the whiteness of the recycled paper is improved by selectively removing the ink in the flotation, as compared with the methods of the test numbers 58 and 59 (comparative method). Achieving a reduction in the number of residual inks and an increase in pulp yield can be expected.

Example 6 Using the cationic compounds shown in Tables 1, 2 and 5 and Table 11, a deinking test was conducted according to the method described in Example 1. The results are shown in Table 11.

[0079]

[Table 11]

The method of Test Nos. 65 to 69 (method of the present invention) in which flotation is carried out at a specific pH in the presence of the cationic compounds shown in Table 5 optionally together with the cationic compounds shown in Table 1 or 2. According to test numbers 63 and 64
Compared with the method (comparative method), the whiteness of recycled paper is improved by the selective removal of ink in flotation.
It can be expected to reduce the number of residual inks in recycled paper and increase the pulp yield.

Example 7 Waste paper (newspaper / flyer = 75/25) collected in the city was shredded (2 × 5 cm). The fixed amount was put into the high-concentration disintegrator. Then, in it, hot water, 1% by weight (for raw material) caustic soda, 3% by weight (for raw material) sodium silicate, 3
A mixture was prepared by adding 30% by weight of hydrogen peroxide aqueous solution (% by weight) to the deinking agent of Table 12 in the amounts shown in Table 13. The waste paper in the mixture was disintegrated at 40 ° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 15% by weight. Warm water was added to the pulp slurry to give a pulp concentration of 4% by weight.
A pulp slurry of was prepared. The obtained pulp slurry was kept at 40 ° C. for 60 minutes, and then warm water was added to the pulp slurry. In this way, the pulp concentration is 1
A weight percent pulp slurry was prepared. Sulfuric acid was added to the pulp slurry and its pH was set to the value shown in Table 13.
The cationic compounds shown in Table 1, 2 or 3 and Table 13 were further added to the pulp slurry in the amounts shown in Table 13. The pH of the obtained pulp slurry remained almost unchanged by the addition of the cationic compound. After sampling from the obtained pulp slurry (before flotation), the pulp slurry was subjected to a flotation treatment at 40 ° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurry was subjected to papermaking in the same manner as in Example 1. The performance of the pulp sheet thus obtained was evaluated by the same method as in Example 1. The results are shown in Table 13.

[0082]

[Table 12]

[0083]

[Table 13]

Various deinking agents were used respectively, and the flotation was carried out in the presence of a cationic compound at a specific p
Test Nos. 73 to 75 performed in H (method of the present invention)
According to the method, it can be expected that the whiteness of the recycled paper is improved, the number of residual inks in the recycled paper is reduced, and the pulp yield is increased, as compared with the methods of Test Nos. 70 to 72 (comparative method).

Example 8 Waste paper (newspaper / flyer = 75/25) collected in the city was shredded (2 × 5 cm). A certain amount was put in the table disintegrator. Then, in it, warm water, 1% by weight (vs. raw material)
Caustic soda, 3% by weight (vs. raw material) sodium silicate, 3% by weight (vs. raw material) 30% by weight hydrogen peroxide solution, and 0.2
A mixture was prepared by adding EO ₁₀ / PO ₁₀ block adduct of stearyl alcohol as a deinking agent in wt% (relative to raw material). The waste paper in the mixture was disintegrated at 40 ° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight.
The obtained pulp slurry is kept at 40 ° C. for 60 minutes,
Next, warm water was added to the pulp slurry to prepare a pulp slurry having a Ca ²⁺ ion concentration shown in Table 14 with a pulp concentration of 1% by weight. Ca ²⁺ ion concentration in warm water is CaC
Adjust with l _2, Ca ²⁺ of the obtained pulp slurry
The ion concentration was as shown in Table 14. Hydrochloric acid was then added to the resulting pulp slurry and its pH was adjusted to
It was set to the value shown in. To the obtained pulp slurry, the cationic compounds shown in Table 1 or 2 and Table 14 were further added in the amounts shown in Table 14. The pH of the obtained pulp slurry remained almost unchanged by the addition of the cationic compound.
After sampling from the obtained pulp slurry (before flotation), the pulp slurry was subjected to a flotation treatment at 40 ° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurry was subjected to papermaking in the same manner as in Example 1. The performance of the pulp sheet thus obtained was evaluated by the same method as in Example 1. The results are shown in Table 14.

[0086]

[Table 14]

Note) The Ca ²⁺ ion concentration in the above table was measured at the time of flotation. According to the method of Test Nos. 82 to 93 (the method of the present invention), the flotation is performed in the presence of a cationic compound at a specific pH and a specific Ca ²⁺ ion concentration. Method (comparative method)
In comparison with the above, selective removal of ink in flotation can be expected to improve whiteness of recycled paper, reduce the number of residual inks in recycled paper, and increase pulp yield.

Example 9 Waste paper (newspaper / flyer = 75/25) collected in the city was shredded (2 × 5 cm). A certain amount was put in the table disintegrator. Then, in it, warm water, 1% by weight (vs. raw material)
Caustic soda, 3% by weight (vs. raw material) sodium silicate, 3% by weight (vs. raw material) 30% by weight hydrogen peroxide solution, and 0.2
A mixture was prepared by adding EO ₁₀ / PO ₁₀ block adduct of stearyl alcohol as a deinking agent in wt% (relative to raw material). The waste paper in the mixture was disintegrated at 40 ° C. for 10 minutes to prepare a pulp slurry having a pulp concentration of 5% by weight.
The obtained pulp slurry is kept at 40 ° C. for 60 minutes,
Next, warm water was added to the pulp slurry to prepare a pulp slurry having a pulp concentration of 1% by weight, an Al ³⁺ ion concentration shown in Table 15, and a Ca ²⁺ ion concentration shown in Table 15. The Al ³⁺ ion concentration of warm water was adjusted using white water generated during papermaking (test numbers 97, 101, and 105 are white water and aluminum sulfate), and the Al ³⁺ ion concentration of the obtained pulp slurry was measured as shown in Table 15. As shown in. Ca ²⁺ ion concentration of the hot water is controlled using the CaCl _2, the Ca ²⁺ ion concentration of the resulting pulp slurry was as shown in Table 15. Next, hydrochloric acid or sodium hydroxide was added to the obtained pulp slurry, and the pH was adjusted to the values shown in Table 15. The obtained pulp slurry is shown in Table 1.
Or 2 and the cationic compounds shown in Table 15 were further added in the amounts shown in Table 15. The pH of the obtained pulp slurry remained almost unchanged by the addition of the cationic compound. After sampling from the obtained pulp slurry (before flotation), the pulp slurry was subjected to a flotation treatment at 40 ° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurry was subjected to papermaking in the same manner as in Example 1. The performance of the pulp sheet thus obtained was evaluated by the same method as in Example 1. The results are shown in Table 15.

[0089]

[Table 15]

Note) Al in the above table³⁺Ion concentration and Ca
²⁺The ion concentration was measured at the time of flotation. Flotte
Solution to a specific pH in the presence of cationic compounds.
And specific Ca ²⁺Test No. 98-1 performed with ion concentration
According to the method of No. 05 (the method of the present invention), test number 94-
Compared to method 97 (comparative method), the whiteness of recycled paper
In addition, it reduces the number of residual ink on recycled paper and increases the pulp yield.
Can be achieved. Furthermore, slurry during flotation
Al³⁺If the ion concentration is 40 ppm or less, the
It can be expected to obtain the desired quality.

Example 10 Used paper collected in the city (newspaper / flyer = 75/25)
Was treated by the following deinking method, and the performance of the pulp sheet thus obtained was evaluated by the same method as in Example 1. The results are shown in Table 16. In this example, the Ca ²⁺ ion concentration of warm water was adjusted using CaCl ₂ , while its Al ³⁺ ion concentration was adjusted using white water generated during papermaking.

(1) Test Nos. 106 and 107 On a predetermined amount of waste paper, 1% by weight of caustic soda (vs. raw material), 3
% By weight (vs. raw material) sodium silicate, 3% by weight (vs. raw material) 30% by weight hydrogen peroxide solution, and 0.3% by weight (vs. raw material) represented by the following formula (1) as a deinking agent A mixture was prepared by adding the EO ₁₀ / PO ₁₀ adduct of the amine and hot water as described above. The _{(C 4 H 9) 3 C} -NH- (EO) 10 (PO) 10 H (1) paper in the mixture, construed away 10 minutes at 40 ° C., to prepare a pulp concentration of 5% by weight of the pulp slurry. The resulting pulp slurry is held at 40 ° C. for 60 minutes, then
Warm water in which the Al ³⁺ ion concentration and the Ca ²⁺ ion concentration are appropriately adjusted is added to the pulp slurry, and the pulp concentration is 1% by weight, and the Al ³⁺ ion concentration shown in Table 16, and
Pulp slurries having Ca ²⁺ ion concentrations shown in Table 16 were prepared. Hydrochloric acid is added to the pulp slurry and the pH is adjusted to
The values shown in Table 16 were used. After sampling from the obtained pulp slurry (before flotation), the pulp slurry was subjected to a flotation treatment at 40 ° C. for 10 minutes to prepare a pulp slurry (after flotation).
The pulp slurry was subjected to papermaking in the same manner as in Example 1.

(2) Test Nos. 108 and 109 1% by weight of caustic soda (vs. raw material), 3
% By weight of sodium silicate (vs. raw material), 3% by weight (vs. raw material) of 30% hydrogen peroxide, and 0.2% by weight (vs. raw material) of stearyl alcohol as deinking agent EO ₁₀ /
A mixture was prepared by adding the PO ₁₀ block adduct and warm water. Disintegrate the waste paper in the mixture at 40 ° C. for 10 minutes,
A pulp slurry having a pulp concentration of 5% by weight was prepared. The obtained pulp slurry is kept at 40 ° C. for 60 minutes, and then warm water whose Al ³⁺ ion concentration and Ca ²⁺ ion concentration are appropriately adjusted is added to the pulp slurry so that the pulp concentration is 1% by weight. A pulp slurry having an Al ³⁺ ion concentration shown in Table 16 and a Ca ²⁺ ion concentration shown in Table 16 was prepared. Next, hydrochloric acid was added to the obtained pulp slurry, and the pH was adjusted to the values shown in Table 16. Furthermore, 0.
A nonionic polyacrylamide (NP 800, manufactured by Diafloc Co., Ltd.) of 05% by weight (based on the raw material) was added to the slurry. The pH of the resulting pulp slurry changed little with the addition of nonionic polyacrylamide. After sampling from the obtained pulp slurry (before flotation), the pulp slurry was subjected to 1 at 40 ° C.
It was subjected to a flotation treatment for 0 minutes to prepare a pulp slurry (after flotation). Pulp pulp,
Paper was made in the same manner as in Example 1. In Test No. 108, aluminum sulfate was also added to the pulp slurry, and the Al ³⁺ ion concentration of the slurry was set to the value shown in Table 16.

(3) Test Nos. 110 to 112 On a predetermined amount of waste paper, 1% by weight of caustic soda (vs. raw material), 3
% By weight of sodium silicate (vs. raw material), 3% by weight (vs. raw material) of 30% hydrogen peroxide, and 0.2% by weight (vs. raw material) of stearyl alcohol as deinking agent EO ₁₀ /
A mixture was prepared by adding the PO ₁₀ block adduct and warm water. Disintegrate the waste paper in the mixture at 40 ° C. for 10 minutes,
A pulp slurry having a pulp concentration of 5% by weight was prepared. The obtained pulp slurry is kept at 40 ° C. for 60 minutes, and then warm water whose Al ³⁺ ion concentration and Ca ²⁺ ion concentration are appropriately adjusted is added to the pulp slurry so that the pulp concentration is 1% by weight. A pulp slurry having the Al ³⁺ ion concentration shown in Table 16 and the Ca ²⁺ ion concentration shown in Table 16 was prepared. Hydrochloric acid was added to the obtained pulp slurry and its pH was set to the value shown in Table 16. Furthermore, 0.06% by weight
The cationic compounds shown in Tables 1 and 2 (to the raw material) and Table 16 were added to the slurry. The pH of the obtained pulp slurry was hardly changed by the addition of the cationic compound. After sampling from the obtained pulp slurry (before flotation), the pulp slurry was mixed with 40
It was subjected to a flotation treatment at 10 ° C. for 10 minutes to prepare a pulp slurry (after flotation). The pulp slurry was subjected to papermaking in the same manner as in Example 1.

[0095]

[Table 16]

Note) Al ³⁺ ion concentration and Ca in the above table
^{The 2+} ion concentration was measured during flotation. In Test Nos. 106 and 107 (Comparative Example), since a deinking agent having a weak ink peeling force was used in the disintegration step of waste paper, it was confirmed that a large amount of unpeeled ink that was not removed from the pulp by flotation was present in the recycled paper. To be That is,
Regenerated pulp is of poor quality. Test numbers 108 and 109
In (Comparative Example), the addition of polyacrylamide and optional aluminum sulfate causes redeposition of the ink on the cellulose fibers, thus deteriorating the quality of the recycled pulp. Also,
It is recognized that the foaming during flotation is greatly enhanced and the pulp yield is reduced. On the other hand, test Nos. 110 to 112 in which flotation is performed in the presence of a cationic compound at a specific pH, a specific Ca ²⁺ ion concentration, and a specific Al ³⁺ ion concentration
According to the method (the method of the present invention), the whiteness of the recycled paper is improved, the number of residual inks in the recycled paper is decreased, and the pulp yield is increased.

Example 11 A deinking test was conducted in accordance with the method described in Example 1 using the cationic compound i-1 represented by the formula below. The results are shown in Table 17.

[0098]

[Chemical 6]

[0099]

[Table 17]

Note) * The cationic nitrogen content (%) is calculated by multiplying the nitrogen content (%) measured by the Kjeldahl method by the ratio of the cationic nitrogen to the total nitrogen determined from the molecular formula of the polymer. did.

In the above test, the test number 113 is
It is carried out by the same method as the conventional industrial deinking method. Flotation in the presence of a cationic compound at a specific pH
According to the method of Test Nos. 120 to 125 (method of the present invention) carried out in No. 1, compared with the method of Test Nos. 113 to 119 (comparative method), the white color of the recycled paper is increased by the selective removal of the ink in the flotation. It can be expected that the degree of improvement, the reduction of the number of residual inks of recycled paper and the improvement of pulp yield are achieved.

[0102]

According to the present invention, deinked pulp with improved whiteness and reduced residual ink can be obtained from raw waste paper, and bleaching chemicals (caustic soda, sodium silicate, hydrogen peroxide,
It is possible to save the production cost by saving the chelating agent) and increasing the pulp yield.

Claims (8)

[Claims] 1. A deinking method comprising at least a step of peeling ink from raw waste paper and a step of removing the peeled ink from a flotation system, wherein at least one non-inking method is used for peeling ink from waste paper. An ionic surfactant is used, and at least part of the flotation step is carried out in the presence of at least one cationic compound.
Method performed at a pH in the range of -9. 2. The deinking method according to claim 1, wherein the nonionic surfactant is selected from the group consisting of the following nonionic surfactants (A) to (D). Nonionic surfactant (A): Reaction product obtained by adding alkylene oxide to a mixture of oil and fat Nonionic surfactant (B): Formula: RCOO (AO) _m R ′
(Wherein R represents an alkyl or alkenyl group having 7 to 23 carbon atoms, and R'is a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, or Represents an acyl group having 2 to 22 carbon atoms, AO is
An oxyalkylene group having 2 to 4 carbon atoms is shown, and m is an integer of 1 or more. ) Nonionic surfactant (C): compound represented by the formula: RO (AO) _n H (wherein R represents an alkyl or alkenyl group having 8 to 24 carbon atoms, and AO is 2 to 2 carbon atoms). 4 represents an oxyalkylene group, and n is an integer of 1 or more.) Nonionic surfactant (D): reaction product obtained by adding alkylene oxide to polyvalent carboxylic acid or its acid anhydride, Alternatively, a reaction product obtained by adding an alkylene oxide to a mixture of a polyvalent carboxylic acid or its acid anhydride and an alcohol. 3. The deinking method according to claim 1, wherein the flotation type calcium ion concentration is maintained at a concentration of 10 to 400 ppm. 4. The deinking method according to claim 1, wherein the flotation type aluminum ion concentration is maintained at a concentration of 0 to 40 ppm. 5. At least one cationic compound,
5. The deinking method according to claim 1, wherein the flotation system is added after adjusting the pH of the system to a value within the range of pH 4 to pH 9. 6. At least one cationic compound,
The deinking method according to any one of claims 1 to 5, wherein the amount is 0.01 to 1.0% by weight based on the weight of the waste paper. 7. The cationic compound is represented by the following formula (a):
A compound represented by (e) and the following formulas (f) to (j), wherein the cationic nitrogen content is 0.01 to 35% by weight,
The deinking method according to any one of claims 1 to 6, which is selected from the group consisting of cationic polymers having a weight average molecular weight of 2,000 to 3,000,000. Embedded image [In the formulas (a) to (e), R ₁ and R ₂ are the same or different from each other, and each represent an alkyl, alkenyl or β-hydroxyalkyl group having 10 to 24 carbon atoms, R ₃ and R ₄ And R ₅ are the same or different from each other, and are each an alkyl or hydroxyalkyl group having 1 to 8 carbon atoms, a benzyl group, or a formula: — (AO) _n —Z
(Here, AO is a C2-C4 oxyalkylene group, Z is a hydrogen atom or an acyl group, and n is 1-5.
Is an integer of 0), R ₆ is an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms, X ⁻ is a counter ion, and Y is 8 carbon atoms. To 36 alkyl, alkenyl or β-hydroxyalkyl group, a group represented by the formula: R ₆ COOCH ₂ — (wherein R ₆ is as defined above), the formula: R ₆ CONHC
A group represented by H ₂ — (wherein R ₆ is as defined above) or a group represented by the formula: R ₆ OCH ₂ — (wherein R ₆ is as defined above) is there. ] [Chemical 2] [In Formulas (f) to (j), R ₁ , R ₂ , R ₃ , R
₆ , R ₇ , R ₈ and R ₉ are the same or different from each other,
Respectively, an alkyl group having 1 to 24 carbon atoms or 2 to 2 carbon atoms
24 alkenyl groups, R ₄ and R ₅ are the same or different from each other, respectively, a hydrogen atom or a methyl group, and X ⁻ and W ⁻ are the same or different from each other, respectively, a counter ion. Y and Z are the same or different from each other and are O or NH, respectively, AO is an oxyalkylene group having 2 to 4 carbon atoms, and p and q are
They are the same or different from each other, and each is an integer of 1 to 10, r is an integer of 0 to 10, and l, m, and n.
Respectively, the weight average molecular weight of the polymer is 2,000 to 3,
A positive number with a value in the range of, 000,000. ] 8. At least part of the flotation step is performed in the presence of at least one selected from the group consisting of cationic compounds represented by the following formulas (a) to (e):
The deinking method according to claim 1, wherein the deinking method is performed at a pH within the range of -9. Embedded image [In the formulas (a) to (e), R ₁ and R ₂ are the same or different from each other, and each represent an alkyl, alkenyl or β-hydroxyalkyl group having 10 to 24 carbon atoms, R ₃ and R ₄ And R ₅ are the same or different from each other, and are each an alkyl or hydroxyalkyl group having 1 to 8 carbon atoms, a benzyl group, or a formula: — (AO) _n —Z
(Here, AO is a C2-C4 oxyalkylene group, Z is a hydrogen atom or an acyl group, and n is 1-5.
Is an integer of 0), R ₆ is an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms, X ⁻ is a counter ion, and Y is 8 carbon atoms. To 36 alkyl, alkenyl or β-hydroxyalkyl group, a group represented by the formula: R ₆ COOCH ₂ — (wherein R ₆ is as defined above), the formula: R ₆ CONHC
A group represented by H ₂ — (wherein R ₆ is as defined above) or a group represented by the formula: R ₆ OCH ₂ — (wherein R ₆ is as defined above) is there. ]