WO2018168620A1

WO2018168620A1 - Modified pulp production method

Info

Publication number: WO2018168620A1
Application number: PCT/JP2018/008896
Authority: WO
Inventors: 裕亮多田
Original assignee: 日本製紙株式会社
Priority date: 2017-03-17
Filing date: 2018-03-08
Publication date: 2018-09-20
Also published as: JP2018154740A

Abstract

A modified pulp production method includes a dewatering/washing step for performing a dewatering/washing treatment on the modified pulp, wherein: a plurality of rounds of the dewatering/washing treatment of the modified pulp are performed in the dewatering/washing step; and when the modified pulp, having been collected in a solution-sending source tank, is being dewatered by a dewatering machine in the plurality of rounds of the dewatering/washing treatment, filtrate from the dewatering machine is collected and returned to the solution-sending source tank for a predetermined length of time from a start of supply of solution to the dewatering machine that has been established for each of the rounds.

Description

Method for producing modified pulp

The present invention relates to a method for producing modified pulp such as oxidized pulp and metal-supported pulp.

Cellulose nanofibers are fibers having a nano-level fiber diameter of 1000 nm or less, and can be obtained by defibrating oxidized pulp (modified pulp) with mechanical shearing force (see, for example, Patent Document 1).

Further, by using a metal-supported pulp (modified pulp) in which metal particles are supported on oxidized pulp as a raw material, the manufactured product can have functions such as antibacterial and deodorant (for example, see Patent Document 2).

JP 2008-1728 A Japanese Patent Laying-Open No. 2015-84870

By the way, in the production of oxidized pulp used for the production of the above-mentioned cellulose nanofiber, etc., dehydration and washing are performed several times in order to remove impurities ions etc. remaining in the oxidized pulp obtained by oxidizing the pulp raw material. There is a need to do. In the production of metal-supported pulp, it is necessary to perform dehydration and washing a plurality of times in order to remove metal ions remaining in the moisture of the metal-supported pulp.

However, every time dehydration / washing is performed, the oxidized pulp and the metal-supported pulp flow out into the effluent, so that the amount of modified pulp that can be produced is reduced and the modified pulp cannot be produced efficiently.

An object of the present invention is to provide a method for producing a modified pulp that efficiently produces a modified pulp.

The present invention provides the following (1) to (6).
(1) In the modified pulp manufacturing method including the dehydration / washing step of performing dehydration / washing treatment of the modified pulp, in the dehydration / washing step, the modified pulp is dehydrated / washed multiple times, In the dehydration / washing process, when the denatured pulp stored in the liquid supply source tank is dehydrated by the dehydrator, a predetermined time from the start of the liquid supply to the dehydrator determined each time is determined by the dehydrator. A method for producing a modified pulp, which collects the filtrate and returns it to the liquid supply source tank.

(2) The said predetermined time is the manufacturing method of the modified pulp as described in (1) prescribed | regulated for every kind of the said modified pulp.

(3) The dehydration and washing step includes a reaction solution dehydration for dehydrating the modified pulp dispersion obtained in the previous step, a primary dehydration for dehydrating the modified pulp dispersion after the reaction solution dehydration, The method for producing modified pulp according to (1) or (2), comprising secondary dehydration for dehydrating the dispersion of the modified pulp after the primary dehydration.

(4) The modified pulp production method according to (3), wherein the predetermined time is defined for each of the reaction solution dehydration, the primary dehydration, and the secondary dehydration.

(5) The modified pulp according to (3) or (4), wherein the modified pulp is oxidized pulp, and the predetermined time of the reaction liquid dehydration, the primary dehydration, and the secondary dehydration is 1 to 3 minutes. Manufacturing method.

(6) The modified pulp is a metal-supported pulp, the predetermined time for the reaction liquid dehydration is 1 to 3 minutes, and the predetermined time for the primary dehydration and the secondary dehydration is 3 to 5 minutes. The method for producing a modified pulp according to (3) or (4).

According to the present invention, it is possible to provide a method for producing a modified pulp for efficiently producing a modified pulp.

1 is a configuration diagram of a dehydration / cleaning apparatus according to an embodiment.

Hereinafter, a method for producing modified pulp (oxidized pulp, metal-carrying pulp) according to the embodiment will be described.

1. First, a method for producing oxidized pulp will be described. In the present invention, the pulp raw material means bleached or unbleached wood pulp, bleached or unbleached non-wood pulp, refined linter, pulp derived from herbs such as jute, manila hemp, kenaf, etc. Examples include fine cellulose obtained by depolymerizing cellulose by performing mechanical treatment such as decomposition, enzymatic decomposition, blasting treatment, and vibration ball mill.

(Oxidation process)
Carboxyl groups are introduced into the pulp by oxidizing the above pulp raw material in water using an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds and bromides, iodides or mixtures thereof. Oxidized pulp can be obtained.

The N-oxyl compound is a compound capable of generating a nitroxy radical. As the N-oxyl compound used in the present invention, any compound can be used as long as it promotes the target oxidation reaction.

The amount of the N-oxyl compound used is not particularly limited as long as it is a catalyst amount capable of turning pulp into nanofibers. For example, 0.01 to 10 mmol is preferable, 0.01 to 1 mmol is more preferable, and 0.01 to 0.5 mmol is even more preferable with respect to 1 g of pulp dry.

Bromide is a compound containing bromine, and examples thereof include alkali metal bromide that can be dissociated and ionized in water. Further, an iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol with respect to 1 g of an absolutely dry pulp raw material.

As the oxidizing agent, known ones can be used, and for example, halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide and the like can be used. Among these, from the viewpoint of cost, sodium hypochlorite, which is the most widely used in industrial processes and has a low environmental load, is particularly preferable. The appropriate amount of the oxidizing agent used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and most preferably 3 to 10 mmol with respect to 1 g of the absolutely dry pulp material. preferable.

(Dehydration and washing process)
Impurity ions and the like remain in the oxidized pulp obtained by oxidizing the pulp raw material. Therefore, it is necessary to perform dehydration and washing in order to remove the impurities. The dehydration / washing process is a process of washing the dispersion of oxidized pulp with water after the dehydration process. In the present invention, the dehydration / washing process is performed three times in the dehydration / washing process. By performing this step, an oxidized pulp containing no impurities can be produced.

Here, the dehydration treatment in the dehydration / washing process can use a centrifugal dehydration type, vacuum dehydration type, or pressure dehydration type dehydrator. Specifically, centrifugal dehydration type (Tanabe Wiltech centrifuge, Kokusan centrifuge, etc.), vacuum dehydration type (drum type vacuum dehydrator, Tsukishima Kikai horizontal belt filter, etc.), pressure dehydration type (filter) Press, tube press, screw press, belt press, horizontal belt filter, polydisc filter, vibrating screen, etc.) can be used.

In the present invention, in each dehydration process (reaction liquid dehydration, primary dehydration, secondary dehydration) of the three dehydration / washing processes, the dispersion of oxidized pulp stored in the liquid source tank is sent to the dehydrator for dehydration. In this case, the filtrate from the dehydrator is collected for a predetermined time (for example, 1 to 3 minutes) from the start of the liquid supply to the dehydrator and returned to the liquid source tank.

That is, in the first reaction liquid dehydration, when the oxidized pulp dispersion stored in the liquid supply source tank is sent to the dehydrator and dehydrated, for example, 1 to 3 minutes from the start of the liquid supply to the dehydrator, Collect the filtrate from the dehydrator and return it to the feed tank.

Further, in the first dehydration performed for the second time, the dispersion of the oxidized pulp stored in the liquid supply source tank is sent to the dehydrator, and when dehydrating, for example, 1-3 minutes from the start of the liquid supply to the dehydrator Collect the filtrate from the machine and return it to the feed tank. Further, in the second dehydration performed at the third time, when the oxidized pulp dispersion liquid stored in the liquid source tank is sent to the dehydrator and dehydrated, the dehydration is performed, for example, for 1 to 3 minutes from the start of the liquid supply to the dehydrator. Collect the filtrate from the machine and return it to the feed tank.

The predetermined time is defined for each type of modified pulp, and for a predetermined time, a cake of modified pulp having a predetermined thickness is formed inside the dewatering tank of the dehydrator and the like. What is necessary is just to set suitably the time when the outflow amount decreases. Therefore, different times may be used for reaction liquid dehydration, primary dehydration, and secondary dehydration.

According to the present invention, since the filtrate by the dehydrator is returned to the liquid supply source tank for a predetermined time after the start of the liquid supply to the dehydrator, the amount of oxidized pulp flowing out to the waste water can be reduced. Therefore, the yield of oxidized pulp can be improved and oxidized pulp can be produced efficiently while minimizing the extension of operation time.

2. Method for producing metal-supported pulp (metal support process)
The metal-supported pulp is one in which one or more metal particles selected from the group consisting of Ag, Au, Pt, Pd, Cu and Zn are supported on the oxidized pulp having a carboxyl group. It can be obtained by bringing the metal compound aqueous solution into contact with the oxidized pulp introduced with carboxyl groups into the pulp obtained in the step and bonding the carboxyl groups of the oxidized pulp with the metal compounds.

The metal compound aqueous solution is an aqueous solution of a metal salt or an organometallic compound. Examples of metal salts include complexes (complex ions), halides, nitrates, sulfates, and acetates. The metal salt is preferably water-soluble. Regarding the method of contacting a metal compound, a dispersion of oxidized pulp prepared in advance and an aqueous solution of metal compound may be mixed, and a dispersion containing oxidized pulp is applied onto a substrate to form a film, and the metal compound is applied to the film. An aqueous solution may be dropped and impregnated. At this time, the film may remain fixed on the substrate or may be peeled from the substrate.

The concentration of the aqueous metal compound solution is not particularly limited. You may adjust suitably the time which a metal compound is made to contact. The temperature at the time of contact is not particularly limited, but 20 to 40 ° C. is preferable. The pH of the liquid at the time of contact is preferably 2.5 to 13.

Next, metal particles are formed by reducing the metal compound bound to the oxidized pulp obtained as described above. The reduction reaction may be performed by a known method, but it is preferable to perform the reduction reaction so as not to cleave the bond between the metal compound and the acid group while reducing the metal compound. Examples of such a reduction method include a gas phase reduction method using hydrogen and a liquid phase reduction method using a reducing agent such as an aqueous sodium borohydride solution.

(Dehydration and washing process)
Since metal ions and the like remain in the metal-supported pulp in which the metal is supported on the oxidized pulp, it is necessary to perform dehydration and washing in order to remove the metal ions and the like. The dehydration / washing process is a process of washing the metal-supported pulp dispersion with water after the dehydration process. In the present invention, the dehydration / washing process is performed three times in the dehydration / washing process. By carrying out this step, a metal-supported pulp containing no metal ions or the like can be produced.

Here, in the dehydration treatment in the dehydration / washing step, the same dehydrator as used in the production of oxidized pulp can be used.

In the present invention, in each dehydration process (reaction liquid dehydration, primary dehydration, secondary dehydration) of the three dehydration / washing processes, the metal-supported pulp dispersion liquid stored in the liquid supply source tank is sent to the dehydrator. At the time of dehydration, the filtrate from the dehydrator is collected for a predetermined time (for example, 1 to 5 minutes) from the start of liquid supply to the dehydrator and returned to the liquid source tank.

That is, in the present invention, in the first reaction liquid dehydration, when the metal-supported pulp dispersion stored in the liquid supply source tank is sent to the dehydrator and dehydrated, for example, 1 starts from the start of the liquid supply to the dehydrator. Collect the filtrate from the dehydrator for ~ 3 minutes and return it to the liquid source tank.

In the second primary dehydration, the metal-supported pulp dispersion stored in the liquid source tank is sent to the dehydrator, and when dehydrating, for example, 3 to 5 minutes from the start of the liquid supply to the dehydrator. Collect the filtrate from the machine and return it to the feed tank. Further, in the second dehydration performed for the third time, when the metal-supported pulp dispersion stored in the liquid supply source tank is sent to the dehydrator and dehydrated, the dehydration is performed, for example, for 3 to 5 minutes from the start of the liquid supply to the dehydrator. Collect the filtrate from the machine and return it to the feed tank.

According to the present invention, since the filtrate by the dehydrator is returned to the liquid supply source tank for a predetermined time after the start of the liquid supply to the dehydrator, the amount of the metal-supported pulp flowing out to the waste water can be reduced. Accordingly, the yield of the metal-supported pulp can be improved and the metal-supported pulp can be efficiently manufactured while minimizing the extension of the operation time.

(Experiment)
Using the dehydration / washing apparatus shown in FIG. 1, a measurement experiment was performed on the amount of suspended solids in the filtrate due to changes over time in the dehydrated wastewater from oxidized pulp. The liquid supply source tank 2 in which the oxidized pulp dispersion liquid is stored is connected to a centrifugal dehydrator 6 via a liquid supply pipe 4. Here, the centrifugal dehydrator 6 is used in a state where a filter cloth is wound around the inside of the dewatering tank. A filter cloth having an air permeability of 20 cm ³ / cm ² · sec is used. The liquid feeding pipe 4 is provided with a pump 8 for feeding the oxidized pulp dispersion liquid to the centrifugal dehydrator 6. The centrifugal dehydrator 6 is connected to the liquid supply source tank 2 via a return pipe 10 that returns the filtrate to the liquid supply source tank 2, and is connected to a drainage pit 14 via a drainage pipe 12 that drains the filtrate. Has been. Switching of the flow path from the centrifugal dehydrator 6 to the liquid supply source tank 2 or the drain pit 14 is performed by opening and closing the first valve 16 and the second valve 18.

The dehydration / washing apparatus shown in FIG. 1 is provided with dedicated devices for reaction liquid dehydration, primary dehydration, and secondary dehydration, and suspended substances (oxidation) recovered by reaction liquid dehydration are provided. Pulp) is subjected to primary dehydration, and secondary dehydration is performed using a suspension of suspended matter (oxidized pulp) recovered by the primary dehydration.

In each of the reaction liquid dehydration, primary dehydration, and secondary dehydration, the amount of suspended solids in the filtrate immediately after feeding (after 25 seconds), 1 minute after feeding, 3 minutes after feeding, and 5 minutes after feeding ( g / L) was measured. The measurement results are shown in Table 1.

Next, using the apparatus shown in FIG. 1, a measurement experiment was performed on the amount of suspended solids in the filtrate due to the aging of the metal-supported pulp dewatered waste water. In each of the reaction liquid dehydration, primary dehydration, and secondary dehydration, the amount of suspended matter in the filtrate (g / L) after 1 minute of liquid supply, 2 minutes after liquid supply, 3 minutes after liquid supply, and 4 minutes after liquid supply ) Was measured. The measurement results are shown in Table 2.

(result)
As shown in Table 1, it can be seen that the oxidized pulp is reduced in the amount of suspended solids in the filtrate if the filtrate is collected for 1 minute after the supply of the reaction liquid dehydration, primary dehydration, and secondary dehydration. It was.

As shown in Table 2, the metal-supported pulp is 1 minute after feeding the reaction liquid dehydration, and the primary dehydration and the secondary dehydration are 3 minutes after feeding. If the filtrate is collected, then the suspended matter in the filtrate The amount was found to decrease.

Claims

In the method for producing a modified pulp including a dehydration / washing process for performing dehydration / washing treatment of the modified pulp,
In the dehydration / washing step, the denatured pulp is dehydrated / washed multiple times, and in the dehydration / washing process multiple times, the denatured pulp stored in the liquid source tank is dehydrated by a dehydrator. In addition, a method for producing a modified pulp, wherein the filtrate is collected by the dehydrator and returned to the liquid supply source tank for a predetermined time from the start of the liquid supply to the dehydrator determined for each time.
The method for producing modified pulp according to claim 1, wherein the predetermined time is defined for each type of the modified pulp.
The dehydration / washing process includes
Reaction liquid dehydration to dehydrate the dispersion of the modified pulp obtained in the previous step;
Primary dehydration for dehydrating the dispersion of the modified pulp after dehydration of the reaction solution;
Secondary dehydration for dehydrating the dispersion of the modified pulp after the primary dehydration;
The manufacturing method of the modified pulp of Claim 1 or 2 containing this.
The method for producing a modified pulp according to claim 3, wherein the predetermined time is defined for each of the reaction liquid dehydration, the primary dehydration, and the secondary dehydration.
The modified pulp is oxidized pulp,
The method for producing a modified pulp according to claim 3, wherein the predetermined time of the reaction liquid dehydration, the primary dehydration, and the secondary dehydration is 1 to 3 minutes.
The modified pulp is a metal-supported pulp,
The predetermined time of the reaction liquid dehydration is 1 to 3 minutes;
The method for producing a modified pulp according to claim 3 or 4, wherein the predetermined time of the primary dehydration and the secondary dehydration is 3 to 5 minutes.