JPH11256490A - Removal of pitch in pulp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing pitch in stock pulp through addition of a specific water-soluble anionic copolymer in the alkali extraction step in the bleaching process during pulp manufacture to markedly obviate pitch troubles such as pitch adherence to the relevant apparatuses or paper contamination. SOLUTION: This method comprises removing pitch by adding 0.005-2 (pref. 0.01-1) wt.%, on a dry pulp basis, of a copolymer to a pulp slurry flowing into an alkali extraction column after bleaching treatment in pulp manufacturing process. In this case, the copolymer is a water-soluble anionic copolymer composed of at least one kind of unsaturated carboxylic acid compound selected from the group consisting of (meth)acrylic acid, maleic acid, itaconic acid and anhydrides, sodium salts, potassium salts and ammonium salts thereof and at least one kind of 4-18C vinyl compound selected from the group consisting of α-olefins, (meth)acrylic esters, maleic esters, itaconic esters, styrene, α- methylstyrene and styrenesulfonic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing pitch from pulp in a pulp production process, and more particularly, to a method for removing pitch in pulp derived from raw wood in an alkali extraction stage in a bleaching process of pulp production. How to do it.

[0002]

2. Description of the Related Art Pitch in the pulp and paper manufacturing process refers to a hydrophobic sticky substance. Wood, the raw material for paper, contains fats and oils, fatty acids, terpenes, steroids,
It contains natural resins and gum-like substances, which remain in the pulp obtained in the pulping step. In the pulp process and papermaking process, these sticky substances are released and become colloidal and dispersed, but this colloidal state is destroyed by large shear force, sudden pH change, addition of sulfuric acid band, etc. It becomes huge, so-called pitch. In addition, if the cohesion or the size of the cohesion increases, it sticks to manufacturing equipment such as fan pumps, flow pipes, chests, wires, felts, rolls, etc. due to its adhesiveness, and not only causes contamination of the equipment, but also increases the size of the attached matter. After peeling and re-adhering to pulp or paper, it causes quality deterioration due to paper stains and defects and paper breakage, and causes obstacles such as productivity and workability. In recent years, the water environment has become severe and the use of closed water has increased, and the wood resource environment has also become harsh. Grades that used to have a high resin content and are not suitable for pulp production have also been used. Was. For this reason, the pitch disturbance increases and the pitch is complicated. Conventionally, as a method of reducing the pitch derived from wood, seasoning of wood and chips, and strengthening of pulp washing after cooking have been performed. However, seasoning has limitations such as a long period of six months to one year, a large site requirement, and an inability to cope with an increase in production. Further, a method of enhancing the washing of pulp obtained by digesting wood chips requires a large amount of water, but no significant improvement can be expected under the current situation where water is being closed. Therefore, a method has been proposed in which a nonionic surfactant is added to a digester (digester) or a washer after digestion and washed and removed (Japanese Patent Laid-Open No. 57-149592). Has not been obtained.

[0003] Pulp is generally bleached with chlorine, hypochlorite, chlorine dioxide, oxygen, ozone, etc. to improve whiteness before it is sent to the papermaking process. After the bleaching treatment, the dirt containing the decomposed products generated during the bleaching is washed and removed using an alkaline extraction tower. At the same time, pitch-causing substances such as oils and fats, fatty acids, natural resin components, and rubbery substances released from the pulp are washed and removed.

However, in many cases, the treatment in the alkali extraction tower alone has not been enough to solve the pitch hindrance in the preparation process and the papermaking process. For this reason, a method of dispersing pitch with a water-soluble anionic copolymer in a preparation step or a papermaking step to prevent aggregation and agglomeration of pitch (Japanese Patent Publication No. Sho 5
No. 9-28676), a porous inorganic substance such as talc (for example, trade name “Mistrone Vapor”) or clay, a nonionic surfactant, a water-soluble cationic polymer or an amphoteric polymer, and the adhesiveness of pitch・ Method of lowering adhesiveness, method of adsorbing pitch to pulp in a small state and out of system, dissolving / dispersing and removing pitch by adding pitch-soluble organic solvent such as perchlorethane, trichloroethane, kerosene Various methods such as a method have been proposed (JP-A-57-149591, JP-A-57-14951).
149592, JP-A-60-94687,
JP-A-63-264993, JP-A-2-2-1829
No. 95, Japanese Patent Publication No. 61-48975, Japanese Patent Publication No. Sho 6
2-6039, JP-B-63-23320). However, the method of dispersing the pitch with a water-soluble anionic copolymer and preventing the aggregation and agglomeration of the pitch has a limitation in the amount of the sizing agent and filler used in the papermaking process because it prevents fixing of the filler and the filler. . In addition, porous inorganic substances such as talc and clay disperse in white water, causing sludge.Besides, the purpose is achieved by fixing to paper and removing the pitch out of the system. The use of pitch control agents in the preparation and papermaking processes, such as the need for a cationic polymer, reduces the effect of other chemicals such as sizing agents, retention agents, and paper strength agents. This will result in an increase in volume.

[0005]

However, even with such a method, pitch obstacles in the paper making process have not been solved, and a better method has been demanded. The present invention relates to such a pitch hindrance in the pulp and paper manufacturing process.In the pulp bleaching process, by increasing the pulp washing efficiency in the alkali extraction tower after the bleaching process, the pitch cause is increased at this stage. The purpose is to eliminate pitch obstacles in the papermaking process by removing them.

[0006]

Means for Solving the Problems The inventors of the present invention have systematically conducted extensive research on pitch measures in the papermaking process, and as a result,
It has been found that pitch derived from raw wood can be efficiently removed by adding a specific water-soluble anionic copolymer to the pulp slurry of the alkali extraction tower after bleaching of pulp. The invention has been completed. That is, claim 1 of the present invention is characterized in that, in the pulp production step, (a) acrylic acid, methacrylic acid, maleic acid,
At least one unsaturated carboxylic acid compound selected from itaconic acid and anhydrides, sodium salts, potassium salts, and ammonium salts thereof; and (b) α-olefin, acrylic ester, methacrylic ester, maleic ester, After bleaching a water-soluble anionic copolymer containing at least one vinyl compound having 4 to 18 carbon atoms selected from the group consisting of itaconic acid ester, styrene, α-methylstyrene and styrenesulfonic acid, A method for removing pitch from pulp by adding the pulp slurry to a pulp slurry before flowing into an extraction column. Claim 2 of the present invention provides a method for removing unsaturated carboxylic acid compounds, wherein the unsaturated carboxylic acid compound is maleic acid, and anhydrides, sodium salts, and potassium salts thereof. At least one selected from salts and ammonium salts, and has 4 to 18 carbon atoms. Vinyl compound is isobutylene, diisobutylene, styrene, alpha-methylstyrene and pitch removal methods in the pulp of claim 1 wherein the styrene sulfonate is at least one or more selected from acid.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in more detail. The water-soluble anionic copolymer used in the method of the present invention contains (a) an unsaturated carboxylic acid compound and (b) a vinyl compound having 4 to 18 carbon atoms as constituent components.

The unsaturated carboxylic acid compound used in the method of the present invention is at least one unsaturated carboxylic acid selected from acrylic acid, methacrylic acid, maleic acid, itaconic acid and their anhydrides, sodium salts, potassium salts and ammonium salts. A saturated carboxylic acid compound, preferably maleic acid,
And at least one selected from anhydrides, sodium salts, potassium salts, and ammonium salts thereof.

The vinyl compound used in the method of the present invention is a vinyl compound having 4 to 18 carbon atoms, preferably 6 to 12 carbon atoms, and is composed of α-olefin, acrylic ester, methacrylic ester, maleic ester, itaconic ester. , Styrene, α-methylstyrene and styrenesulfonic acid. Among them, examples of the α-olefin include isobutylene, 1-butene, 1-pentene, 1-hexene, cyclohexene, 1-octene, diisobutylene, 1-decene, 1-dodecene, 1-octadecene, and isooctadecene. Examples of ester groups in acrylates, methacrylates and itaconic esters include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,
Hexyl, octyl, nonyl, decyl, dodecyl, cetyl, octadecyl, hydroxyethyl, hydroxypropyl, hydroxybutyl and the like. Among them, particularly preferred vinyl compounds include isobutylene, diisobutylene, styrene, α-methylstyrene and styrenesulfonic acid. When the vinyl compound has 3 or less carbon atoms, the pitch is not sufficiently dispersed in the alkali extraction tower, and the pitch is not sufficiently removed.
Above, the water solubility of the produced copolymer is not sufficient, which is not preferable.

The water-soluble anionic copolymer in the method of the present invention must be dissolved in an aqueous alkali solution of an alkali extraction tower in the pulp bleaching step to be applied, and must have a large pitch dispersing power in the aqueous alkali solution in the step. It is. The solubility of the water-soluble anionic copolymer in water may be such that it is soluble in the aqueous alkali solution in the alkali extraction stage of the pulp bleaching step to be applied. Good. As long as this requirement is satisfied, the preferred polymerization molar ratio of the unsaturated carboxylic acid compound to the vinyl compound having 4 to 18 carbon atoms is 80:20 to 25: 7.
5, more preferably 60:40 to 40:60. The molecular weight of the resulting water-soluble anionic copolymer is preferably from 5,000 to 200,000, and more preferably from 10,000 to 150,000. This molecular weight is closely related to the ability to disperse the pitch, those having a low molecular weight have insufficient pitch dispersibility, and those having too high a molecular weight are not preferred because the cohesiveness of the pitch is increased and the copolymer is not preferable. Manufacture is often not easy or disadvantageous.

The polymerization method for obtaining water solubility of the water-soluble anionic copolymer in the method of the present invention is not particularly limited, and is carried out according to a general radical polymerization method. Polymerization may be carried out under no solvent or under the use of a solvent, and furthermore, the unsaturated carboxylic acid and the vinyl compound having 4 to 18 carbon atoms are put together in a reaction vessel, or
It is arbitrarily selected, for example, by charging at a fixed ratio and reacting.
Examples of the polymerization initiator include azobis compounds such as azobisisobutyronitrile and azobis-2,4-dimethylvaleronitrile, hydrogen peroxide, cumene peroxide, di-te
Peroxides such as rt-butyl hydroperoxide and lauroyl peroxide are generally used. Further, the molecular weight of the copolymer is determined by a chain transfer agent such as thioglycolic acid and its esters, β-mercaptopropionic acid and its esters, alkylmercaptans, (meth) allylsulfonic acid, (meth) allyl alcohol,
It can be controlled by adding hypophosphite, biphosphite and the like.

The water-soluble anionic copolymer in the method of the present invention is usually added to a step intended as an aqueous solution of a sodium, potassium or ammonium salt at a concentration of 1 to 40% by weight, preferably 5 to 10% by weight. Is done. The amount of addition varies greatly depending on the type of pulp, process conditions, pitch generation in the papermaking process, etc., and is not determined uniformly. 0.005-2 polymer
% By weight, preferably 0.01 to 1% by weight.

In the method of the present invention, the water-soluble anionic copolymer is added before the pulp slurry after the bleaching treatment enters the next alkali extraction column. Specifically, it is a suction port of a mixer and a high concentration pump for mixing caustic soda, heating steam and pulp slurry, or a line immediately before an alkali extraction tower.

The method of bleaching pulp to which the method of the present invention is applied is not particularly limited, and generally used chlorine bleaching, hypochlorite bleaching, chlorine dioxide bleaching, oxygen bleaching, hydrogen peroxide There are bleaching, ozone bleaching, hydrosulfite bleaching and the like. Usually, in the pulp production process, some of these bleaching stages and alkali extraction stages are combined,
For example, [chlorine bleaching]-[alkali extraction]-[hypochlorite bleaching]-[alkali extraction]-[chlorine bleaching],
It is performed in a sequence such as [chlorine bleaching]-[alkali extraction]-[hypochlorite bleaching]-[chlorine dioxide bleaching]. The present invention is not limited to these bleaching methods and bleaching sequences. In addition, the bleaching equipment is not particularly limited, and generally used bleaching equipment,
For example, an upflow bleaching tower, a downflow bleaching tower, a displacement bleaching tower, etc. may be used.

The process of the present invention is carried out in an alkali extraction stage after the bleaching treatment. The alkali extraction stage of the present invention is also not particularly limited, and includes generally used equipment, such as caustic soda, a mixer for mixing pulp slurry with steam for heating, a high-concentration pump, and an alkali extraction column. . The alkali extraction column in the present invention is not particularly limited, and there are generally used facilities, for example, a downflow extraction column, a displacement extraction column, and the like, and the operating conditions thereof are not particularly limited. For example, caustic soda 2-5% by weight (based on pulp), pulp concentration 6-1
The reaction is performed at 2% by weight, at a temperature of 40 to 70 ° C, at a pH of 10 to 11, and for a treatment time of 40 to 80 minutes.

The bleaching process increases the whiteness of the pulp, and in the white water, oils and fats, fatty acids, natural resin components, rubbery substances, etc., which cause pitch released from the pulp, increase.
The particles are dispersed as colloidal or fine particle pitch particles. The water-soluble anionic copolymer of the method of the present invention,
The pitch particles dispersed in the white water by the bleaching process in the form of colloids or fine particles are stably dispersed in an alkaline aqueous solution to prevent adhesion to pulp fibers, piping during the process and equipment, and to perform alkali extraction. It is intended to increase the removal and discharge in the tower and to reduce the amount of pitch-causing substances that remain in the pulp and are sent to the papermaking process. The mechanism of action is that the dispersion of pitch particles and pitch causes in the pulp slurry is
The water-soluble anionic copolymer of the present invention enhances anionicity, enhances electrostatic repulsion, is stably dispersed in an alkaline aqueous solution, and is easily removed together with the alkaline aqueous solution in a washing device of an alkali extraction stage. . As a result, the pitch in the pulp sent to the subsequent paper-making process and the cause of pitch can be significantly reduced, and the pitch obstacle in the paper-making process is largely improved.

The water-soluble anionic copolymer used in the method of the present invention is used in the alkali extraction stage, and most of the water-soluble anionic copolymer is removed together with the alkali solution in a washing device after the alkali extraction column. Even if the water-soluble anionic copolymer used in the method of the present invention remains in the pulp, since there is usually a bleaching stage thereafter, it is almost oxidatively decomposed in the bleaching stage. Therefore, the effects of various additives such as pitch control agents, sizing agents, retention agents, paper strength agents, defoamers, and slime control agents used in the papermaking process are not substantially affected.

In particular, the water-soluble anionic copolymer of the present invention may be used in the papermaking process to control the pitch control agent of a porous inorganic substance conventionally used such as mythrone vapor or other talc, or other nonionic interface. It does not hinder the use of a pitch control agent such as an activator at all. Rather, in some cases, more preferable pitch control can be achieved by combining with these pitch control methods.

According to the pitch removing method of the present invention, pulp and paper, as well as fan pumps, pipes, chests, wires,
Pitch adherence to manufacturing equipment such as felt and rolls, and furthermore, this adhered substance is peeled off, and pitch obstacles such as paper stains / defects due to re-adhesion to pulp and paper, and occurrence of paper breakage are greatly improved. , Product quality, productivity and workability are improved.

[0020]

EXAMPLES The present invention will be described in detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

[Chemicals Used for Testing] (Water-soluble anionic copolymer of the present invention) A-1: maleic anhydride-styrene (1: 1 molar ratio)
The sodium salt of the copolymer (molecular weight 5,000) was used. A-2: Maleic anhydride-styrene (1: 1 molar ratio)
The sodium salt of the copolymer (molecular weight 100,000) was used. A-3: maleic anhydride-styrene (1: 3 molar ratio)
The sodium salt of the copolymer (molecular weight 10,000) was used. A-4: maleic anhydride-styrene (4: 1 molar ratio)
The sodium salt of the copolymer (molecular weight 10,000) was used. A-5: The sodium salt of maleic anhydride-isobutylene (1: 1 molar ratio) copolymer (molecular weight 170,000) was used. A-6: The sodium salt of maleic anhydride-diisobutylene (1: 1 molar ratio) copolymer (molecular weight 10,000) was used. A-7: A sodium salt of acrylic acid-hydroxypropyl acrylate (3: 1 molar ratio) copolymer (molecular weight: 6,000) was used. A-8: A sodium salt of acrylic acid-α-methylstyrene (1: 1 molar ratio) copolymer (molecular weight 13,000) was used. A-9: Maleic anhydride-α-olefin mixture having 16 to 18 carbon atoms (1: 1 molar ratio) copolymer (molecular weight: 1)
6,000) sodium salt was used. A-10: A sodium salt of styrene sulfonic acid (2: 1 molar ratio) copolymer (molecular weight 30,000) was used. A-11: Acrylic acid-dimethyl itaconate copolymer (1: 1 molar ratio) (molecular weight: 20,000): a stirrer equipped with a Teflon resin stirring blade, a reflux condenser, a dropping funnel,
In a 1-liter four-necked flask equipped with a thermometer, add water 33
3 g, 23 g of acrylic acid and 23 g of dimethyl itaconate were added, and heated to 55 ° C. while flowing nitrogen gas.
-A solution of 2.3 g of mercaptopropionic acid and 5 g of sodium persulfate dissolved in 15 g of water was quickly added, and the mixture was maintained at 55 ° C while removing heat of reaction. After the generation of heat of reaction is reduced, the temperature is maintained for another 30 minutes.
The reaction was completed by heating at 0 ° C. for 2 hours. The mixture was neutralized with a 50% sodium hydroxide solution to obtain about 10% of a sodium salt of acrylic acid-dimethyl itaconate copolymer.

(Chemicals used for comparison) B-1: The sodium salt of polymaleic acid (molecular weight: 1,000) was used. B-2: polyacrylic acid (molecular weight 2,000,000
The sodium salt of 0) was used. B-3: maleic anhydride-styrene (1: 1 molar ratio)
The sodium salt of the copolymer (molecular weight 1,000) was used. B-4: maleic anhydride-styrene (1: 4 molar ratio)
The sodium salt of the copolymer (molecular weight 10,000) was used. A 10% by weight aqueous solution of this compound was in a cloudy state and was not completely dissolved. B-5: A sodium salt of a maleic acid-methyl acrylate-vinyl acetate (1: 1: 1 molar ratio) copolymer (molecular weight 1,300) was used. B-6: Talc was used.

[Test] In a paper mill producing 300 tons of medium quality paper per day from hardwood (LKP), pitch disturbances were constantly occurring in the preparation process and the papermaking process. In the adjusting step, pitches adhered to the outlet of the fan pump, the mixing chest wall, the machine chest wall, and the pipes, and occasionally peeled off and carried into the paper machine, causing a defective portion. Further, the number of defects of paper spots is always measured, and the apparatus is caustic cleaned once every two weeks to one month so that the number of defects becomes a certain level or less. The pulp bleaching process of the mill is a sequence of [chlorine bleaching] (C)-[alkali extraction] (E)-[hypochlorite bleaching] (H)-[chlorine dioxide bleaching] (D) (Figure 1). ), Chlorine bleaching, chlorine added amount 3% (to pulp), pulp concentration 4
%, Temperature 25-30 ° C, treatment time 60 minutes, pH = 1.
Bleaching was performed under the conditions of 5. The alkali extraction (Fig. 2) was carried out by adding 2.5% of caustic soda (based on pulp), pulp concentration of 12%, temperature of 65 ° C, and treatment time of 60%.
The extraction was performed under the conditions of pH = 11. After chlorine bleaching, a 10% by weight aqueous solution of the water-soluble anionic copolymer of the present invention was added to a mixer for mixing caustic soda and heating steam in front of the alkali extraction tower. The addition amount is 300 ppm (based on pulp) as a water-soluble ionic copolymer.
And added continuously using an injection pump. The effect of the chemical was determined by the following two methods. A pipe having a diameter of 5 cm, a immersed portion of 100 cm length and a length of 2 m was fixed to a completed chest for temporarily storing the pulp from the bleaching step, and the amount of sticking substances adhering to the surface of the pipe for 5 days was measured. The number of paper spots per 100 m ² of paper for 5 days was measured. The results are shown in Table 1. As can be seen from the results, by adding the water-soluble anionic copolymer of the present invention before the alkali extraction tower, the sticky substances in the pulp are reduced, and the number of spots on the paper obtained from the pulp is reduced. It was found that pitch disturbance in the papermaking process could be significantly improved.

[0024]

[Table 1]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Fumihiko Hirai 1 Yoshida, Toyoshima-cho, Anan-shi, Tokushima Oji Paper Co., Ltd. Tomioka Mill (72) Inventor Hiroyoshi Nagamura 1st Yoshida, Toyosu-cho, Anan-shi, Tokushima (72) Inventor Kazuyuki Tezuka 1 Yoshida, Toyoshima-cho, Anan-shi, Tokushima Prefecture Oji Paper Co., Ltd.

Claims (2)

[Claims] In the pulp production process, (a) at least one unsaturated carboxylic acid selected from acrylic acid, methacrylic acid, maleic acid, itaconic acid and their anhydrides, sodium salts, potassium salts, and ammonium salts A compound, (b) an α-olefin, an acrylate ester,
Water-soluble anionic copolymer containing as a constituent at least one vinyl compound having 4 to 18 carbon atoms selected from methacrylic acid esters, maleic acid esters, itaconic acid esters, styrene, α-methylstyrene and styrenesulfonic acid Is added to the pulp slurry after the bleaching treatment and before flowing into the alkaline extraction tower. 2. The unsaturated carboxylic acid compound is at least one selected from maleic acid and anhydrides, sodium salts, potassium salts and ammonium salts thereof, and the vinyl compound having 4 to 18 carbon atoms is The method for removing pitch in pulp according to claim 1, wherein the method is at least one selected from the group consisting of isobutylene, diisobutylene, styrene, α-methylstyrene and styrenesulfonic acid.