JP5025348B2 - Oxidation method of molded body - Google Patents

Description

  The present invention relates to a method for oxidizing a molded body containing natural fibers.

  Patent Document 1 and Non-Patent Document 1 each have a technique for oxidizing and utilizing cellulose. In any of these techniques, a method of bringing a pulp suspension (pulp slurry) into contact with an oxidizing agent is applied.

  In this method, when producing an oxidized molded body, it is necessary to first defibrate the pulp that has not been oxidized as a pretreatment, and bend the pulp fiber as necessary. After contacting the turbid solution with the oxidizing agent, the process of filtration, washing, dehydration, drying, etc., the oxidized pulp fiber is again made into a pulp suspension, and the process of papermaking and drying is required. Is complicated and man-hours increase.

  On the other hand, Patent Document 2 discloses a method for producing an oxidized polysaccharide material in which the surface of the polysaccharide material is oxidized while maintaining the shape of the material.

In this method, the polysaccharide material is only immersed in the oxidation catalyst solution, and only the surface portion of the material is subjected to oxidation modification, and the application range of the obtained oxidized material is limited. It was.
JP 2001-115389 A JP 2003-183302 A Bio MACROMOLECULES Volume7, Number6, June 2006, Published by the American Chemical Society

  This invention makes it a subject to provide the oxidation method of a molded object which can oxidize the surface and the inside containing the natural fiber which can simplify a process and can reduce a man-hour.

  The invention of claim 1 includes, as a solution, a step of bringing a molded body containing natural fibers into contact with an oxidation catalyst solution containing an N-oxyl compound by a mechanical operation, and in the step, the surface of the molded body and Provided is a method for oxidizing a molded body containing natural fibers, wherein the inside is oxidized to bring the carboxyl group content of cellulose constituting the natural fibers into a range of 0.1 to 2 mmol / g.

The invention of claim 4 is a solution to the step of sending a molded body containing natural fibers into an oxidation reaction tank into which an oxidation catalyst solution containing an N-oxyl compound has been injected, and transferring the molded body in the oxidation reaction tank. However, the molded body and an oxidation catalyst solution containing an N-oxyl compound are brought into contact with each other by mechanical operation, and the surface and the inside of the molded body are oxidized to reduce the carboxyl group content of cellulose constituting the natural fiber to 0. A step of making it in the range of 1-2 mmol / g,
A step of washing the molded body after the oxidation treatment with water,
A method of oxidizing a molded body containing natural fibers having
Provided is a method for oxidizing a molded body containing natural fibers, wherein the mechanical operation is to transfer the molded body in an oxidation reaction tank.

The invention of claim 5 is a step of immersing a molded article containing natural fibers in an oxidation reaction tank in which an oxidation catalyst solution containing an N-oxyl compound is injected and a suction means is installed,
The molded product and an oxidation catalyst solution containing an N-oxyl compound are brought into contact with each other by a mechanical operation, and the surface and the inside of the molded product are oxidized to reduce the carboxyl group content of cellulose constituting the natural fiber to 0.1. In the range of ~ 2 mmol / g,
A method of oxidizing a molded body containing natural fibers having
Provided is a method for oxidizing a molded body containing natural fibers, wherein the mechanical operation is to suck the oxidation catalyst solution in the oxidation reaction tank by the suction means.

  According to the oxidation method of a molded article containing natural fibers of the present invention, the processing operation is easy and the number of man-hours can be reduced. Moreover, the molded object by which the surface and the inside were oxidized can be obtained.

<Oxidation method-1 of molded body>
Examples of the molded body containing natural fibers include a sheet containing wood pulp, non-wood pulp, regenerated cellulose, bacterial cellulose, cotton, silk, wool, chitin, chitosan, alginic acid, collagen and the like.

  The size and shape of the molded body are not particularly limited, but the thickness is preferably 0.01 to 10 mm, more preferably 0.03 to 3 mm, and still more preferably 0.05 to 1 mm. A sheet-like molded body is preferable.

  As the oxidation catalyst solution containing an N-oxyl compound, a solution or suspension containing an N-oxyl compound, another oxidizing agent, and a halide is used.

  As the N-oxyl compound, 2,2,6,6, -tetramethyl-1-piperidine-N-oxyl (TEMPO) can be used. The amount of TEMPO used is preferably in the range of about 0.1 to 30% by mass with respect to the molded body (absolute dry basis). Moreover, it is preferable that it is the range used as 0.001-30 mass% as a density | concentration of a catalyst liquid.

  Examples of other oxidizing agents include halogens, hypohalous acids, halous acids, perhalogen acids or their salts, halogen oxides, nitrogen oxides, peroxides, etc. preferable. The usage-amount of an oxidizing agent is the range used as about 1-50 mass% with respect to a molded object (absolute dry reference | standard).

  As the halide, bromide or iodide is preferable, and examples thereof include alkali metal bromide and alkali metal iodide, and sodium bromide is preferable. The amount of halide used is preferably in the range of about 1 to 30% by mass relative to the molded product (absolute dry basis). The concentration of the catalyst solution is preferably in the range of 0.01 to 30% by mass.

  As the solvent, water is used, but from the viewpoint of reducing the surface tension of the oxidation catalyst solution and facilitating the penetration into the molded product, alcohols such as methanol and ethanol, and various surfactants can be contained. The alcohol is preferably a secondary or higher alcohol from the viewpoint of reactivity. This is because when the primary alcohol is used, the oxidation catalyst solution and the primary alcohol itself may react.

  When a mixture of water and an organic solvent such as ethanol is used as the solvent for the oxidation catalyst solution, the content of the organic solvent is preferably 5 to 80% by mass, more preferably 10 to 60% by mass, and further 20 to 50% by mass. preferable.

  The pH of the oxidation catalyst solution is preferably in the range of 9 to 12 from the viewpoint of allowing the oxidation reaction to proceed efficiently.

  In the oxidation treatment, the compact and the oxidation catalyst liquid are brought into contact with each other by mechanical operation. The mechanical operation as used in this application means giving a mechanical motion to a molded object or an oxidation catalyst liquid, for example, there exists the following method.

(I) A method of immersing a molded body in an oxidation catalyst liquid filled in a container, stirring the oxidation catalyst liquid (mechanical operation), and diffusing and / or passing the oxidation catalyst liquid into the molded body,
(II) A method in which an oxidation catalyst liquid is applied or sprayed (mechanical operation) on the molded body to diffuse and / or pass the oxidation catalyst liquid into the molded body,
(III) The molded body is sent into the oxidation reaction tank into which the oxidation catalyst liquid is injected, and the molded body in the oxidation reaction tank is transferred (mechanical operation) to diffuse and / or pass the oxidation catalyst liquid into the molded body. Method,
(IV) a method of diffusing and / or passing the oxidation catalyst liquid into the molded body by gravity through the oxidation catalyst liquid,
(V) A method in which the oxidation catalyst solution is sucked (mechanical operation) to diffuse and / or pass the oxidation catalyst solution into the molded body,
Etc. can be applied.

  In the method (I), as the stirring method, a method of stirring the oxidation catalyst liquid in the container with a stirring device or the molded body itself, a method of vibrating the container itself, a method of ultrasonically vibrating the oxidation catalyst liquid in the container, A method of circulating the oxidation catalyst solution in the container can be applied. In addition, from the viewpoint that the oxidation catalyst solution only needs to move, a method of stirring the solution while filling the oxidation catalyst solution into the container, molding while the oxidation catalyst solution in the container is moving immediately after stirring. The method of putting the body is also applicable. Furthermore, a method of stirring in a state where the molded body is floated on the oxidation catalyst solution can also be applied. In addition, the inside of the oxidation reaction tank mentioned later is also contained in a container.

  In the method (II), when the oxidation catalyst liquid is applied or sprayed on a part of the molded body, for example, a method of applying or spraying the oxidation catalyst liquid on a certain surface or the entire surface of the molded body can be applied. The spray also includes the meaning of injection. For example, in a suitable container, the molded body is fixed in a suspended state, and one side of the molded body (one side in the case of a strip-shaped or sheet-shaped molded body) or the entire surface (in the case of a strip-shaped or sheet-shaped molded body) For example, a method of injecting an oxidation catalyst solution onto both sides) can be applied.

  In the method (III), the reason why the surface and the inside of the molded body can be oxidized by transferring the molded body in the oxidation reaction tank is considered as follows. When the molded body is transferred, disturbance (vortex etc.) of the oxidation catalyst liquid occurs around the molded body, and this disturbance becomes a driving force for diffusing and / or passing the oxidation catalyst liquid into the molded body. Conceivable.

  In the method (IV), when the oxidation catalyst liquid is diffused and / or passed through the molded body by gravity, for example, the molded body is placed in the opening of a container having one side opened, and the oxidation catalyst liquid is placed from above. And a method of allowing the oxidation catalyst solution to diffuse and / or pass through the molded body by gravity can be applied.

  In the method of (V), the oxidation catalyst solution is sucked and the oxidation catalyst solution is diffused and / or passed through the molded body. For example, the molded body is placed in the opening of a container opened on one side, For example, a method may be used in which an oxidation catalyst solution is caused to flow from the surface, suction means such as a suction pump is brought into contact with the lower surface of the molded body, and the oxidation catalyst solution is diffused and / or passed through the molded body with a suction force.

  When the molded body and the oxidation catalyst liquid are brought into contact as described above, it is desirable to hold at 0 to 80 ° C. (preferably 1 to 50 ° C.) for 0.1 to 360 minutes (preferably 1 to 120 minutes).

By such oxidation treatment, the C6 position of the structural unit of cellulose constituting the molded body (natural fiber) is selectively oxidized to a carboxyl group with respect to the surface and the inside of the molded body (—CH ₂ OH → —COONa). ), The carboxyl group content of cellulose constituting the molded body (natural fiber) can be in the range of 0.1 to 2 mmol / g. The carboxyl group content is preferably 0.4 to 2 mmol / g, more preferably 0.6 to 1.8 mmol / g. Carboxyl group content is calculated | required by the measuring method as described in an Example.

  After the oxidation treatment, treatments such as dehydration, washing, and drying can be performed, but any treatment is easier than in the case of a pulp suspension.

  The molded body obtained by the oxidation method of the present invention is suitable as a raw material for producing gas barrier membranes such as oxygen and water vapor, and as a raw material for producing ion exchange membranes, dialysis membranes, desalting membranes and the like.

<Oxidation Method-2 of Molded Body; Continuous Oxidation Method>
The continuous oxidation method will be described with reference to FIG. This is a method utilizing the oxidation method (III). FIG. 1 is a conceptual diagram showing a continuous oxidation method. Hereinafter, it demonstrates for every process. In addition, a molded object, an oxidation catalyst liquid, oxidation treatment conditions, etc. are the same as said oxidation method-1 of a molded object.

  In the first step, a strip-shaped formed body 2 a containing natural fibers is continuously fed out from the raw fabric roll 1.

Next, in the second step, the strip-shaped formed body 2a is introduced into the oxidation reaction tank 3 and brought into contact with the oxidation catalyst solution 4 filled in the oxidation reaction tank 3 by a mechanical operation. The mechanical operation in this case is to transfer the strip-shaped formed body in the oxidation reaction tank as described above. By such an oxidation treatment, the C6 position of the structural unit of cellulose constituting the molded body (natural fiber) 2a is selectively oxidized to a carboxyl group with respect to the surface and the inside of the band-shaped molded body (-CH ₂ OH). → -COONa), the carboxyl group content of the cellulose constituting the strip-shaped molded body (natural fiber) is 0.1 to 2 mmol / g (preferably 0.4 to 2 mmol / g, more preferably 0.6 to 1). .8 mmol / g).

  Next, in the third step, the band-shaped formed body 2b after the oxidation treatment is introduced into a water tank (water washing tank) 5 filled with ion-exchanged water (or distilled water) 6 and continuously washed with water. The conditions for washing with water are such that the strip-shaped molded body 2b stays in the water tank 5 for a total of 10 to 600 seconds.

  Next, in the fourth step, the band-shaped molded body 2c after washing with water is wound up on a roll. If necessary before winding, the band-shaped molded body 2c may be dried by an appropriate method. Drying may be natural drying or blow drying. In the first to fourth steps, the belt-shaped formed body is fed by rotating the feed roll 1 and the take-up roll which can be rotated by the driving means. Support the body.

  According to the continuous oxidation method of the present invention, since oxidation, water washing and drying can be performed continuously, production efficiency can be increased.

  The strip-shaped molded body obtained by the continuous oxidation method of the present invention is suitable as a raw material for producing gas barrier membranes such as oxygen and water vapor, and as a raw material for producing ion exchange membranes, dialysis membranes, desalting membranes and the like.

<Oxidation Method of Molded Body-3; Cyclic Oxidation Method>
The cyclic oxidation method will be described with reference to FIG. This is a method using the oxidation method (V). FIG. 2 is a conceptual diagram showing a cyclic oxidation method. In addition, a molded object, an oxidation catalyst liquid, oxidation treatment conditions, etc. are the same as said oxidation method-1 of a molded object.

  The oxidation reaction tank 11 is filled with an oxidation catalyst liquid 12. Further, a flat plate-like suction means 13 which is detachably fixed by a fixing means (not shown) is immersed in the central portion in the oxidation reaction tank 11, and the flat plate-like suction means 13 is shown in between. The sheet-like molded bodies 14 and 15 including two natural fibers that are detachably fixed by a fixing means that is not attached are immersed. The plate-like suction means 13 and the two sheet-like molded bodies 14 and 15 face each other, and the distance between them is the same.

  The plate-like suction means 13 has a structure in which both sides can be passed, and two return pipes connected to a suction pump (not shown) are connected to the upper end of the oxidation catalyst liquid 12 from the liquid surface. 14a and 15a are connected.

  When a suction pump (not shown) is driven, the oxidation catalyst liquid 12 is sucked from both sides of the plate-like suction means 13, and the sucked oxidation catalyst liquid 12 passes through two return pipes 14a and 15a to be oxidized. It is returned to the reaction tank 11.

In this process, the oxidation catalyst solution 12 diffuses and / or passes through the two sheet-like molded bodies 14 and 15 facing the flat plate suction means 13 at equal intervals, and the natural fibers ( Cellulose) is oxidized. By such oxidation treatment, the C6 position of the structural unit of cellulose constituting the sheet-like molded bodies (natural fibers) 14 and 15 is selectively oxidized to a carboxyl group (—CH ₂ OH → —COONa), and the sheet form The carboxyl group content of cellulose constituting the molded bodies (natural fibers) 14 and 15 is 0.1 to 2 mmol / g (preferably 0.4 to 2 mmol / g, more preferably 0.6 to 1.8 mmol / g). Can be in the range.

  After completion of the oxidation reaction, the two sheet-like molded bodies 14 and 15 are pulled up from the oxidation reaction tank 11 and subjected to treatment such as water washing and drying.

  The sheet-like molded body obtained by the cyclic oxidation method of the present invention is suitable as a raw material for producing gas barrier membranes such as oxygen and water vapor, and as a raw material for producing ion exchange membranes, dialysis membranes, desalting membranes and the like.

  The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention.

  In the above-mentioned <Oxidation method of molded body-2; continuous oxidation method>, a strip-shaped molded body containing natural fibers was continuously fed out from the raw fabric roll 1 and led into the oxidation reaction tank. Instead of the molded body, a sheet-shaped molded body is used for each leaf, and a transfer device with a gripper or the like (for example, a gripper for gripping the sheet-shaped molded body is installed on an annularly connected chain or belt, and a motor It is also possible to transfer the inside of the oxidation reaction tank with a device that moves the chain etc.

  In the production method of the present invention, in order to prevent the strength of the molded body from being lowered by contact with the oxidation catalyst solution, and to prevent the molded body from being broken or from falling off fibers, a certain surface of the molded body is supported by a net that supports the molded body. (One side in the case of a strip-shaped or sheet-like molded body) or the entire surface (both sides in the case of a strip-shaped or sheet-like molded body) can be supported. In addition, the molded body itself can be reinforced by including non-oxidizing long fibers in the molded body. In this case, it is preferable that the net or long fiber to be used does not affect the oxidation reaction and can be easily separated from the natural fiber. For example, it is desirable to use synthetic resin or metal fiber.

  In addition, in order to prevent the strength of the molded body from decreasing due to contact with the oxidation catalyst solution, for example, a wet paper strength agent (for example, polyamide / epichlorohydrin resin) or the like may be appropriately added to the molded body. it can.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following.

(1) Method for measuring carboxyl group content (mmol / g) About 0.5 g of absolutely dry pulp is put in a 100 ml beaker, and ion exchange water is added to make a total of 55 ml, and then 5 ml of 0.01M sodium chloride aqueous solution is added thereto. The suspension was 0.83% by mass and stirred with a stirrer until the pulp was sufficiently dispersed. Then, 0.1M hydrochloric acid is added to adjust the pH to 2.5 to 3.0, and then using an automatic titrator (AUT-501, manufactured by Toa DKK Co., Ltd.), a 0.05M sodium hydroxide aqueous solution is waited for 60 seconds. The electrical conductivity and the pH value of the pulp suspension every minute were measured, and the measurement was continued until the pH reached about 11. And the sodium hydroxide titration amount was calculated | required from the obtained electrical conductivity curve, and carboxyl group content was computed.

(2) The oxidation catalyst and pulp sheet used in the following examples and comparative examples are as follows:
Oxidation catalyst aqueous solution: TEMPO 1.25% by mass, NaClO 12.5% by mass, NaBr 14.2% by mass, ion-exchanged water 9.900% by mass (all of which are based on the absolute dry mass of the pulp sheet used)
Pulp sheet: Trade name Conifer bleached kraft pulp (Manufacturer: Fletcher Challenge Canada, trade name “Machenzie” dimensions (length 50 mm, width 50 mm, thickness 1.5 mm), mass 3 g
Example 1
A pulp sheet having a thickness of 1.5 mm was completely immersed in a 300 ml beaker filled with about 300 ml of an oxidation catalyst solution at room temperature (20 ° C.). In this state, the mixture was allowed to stand for 30 minutes while stirring with a stirrer, then pulled up from the beaker, sufficiently washed until the conductivity of water in the washing filtrate was equal to that of water before washing, and then naturally dried. As a result, the carboxyl group content of cellulose was 0.25 mmol / g, and it was confirmed that the pulp sheet was oxidized.

The conceptual diagram which shows one Embodiment of the oxidation method of this invention. The conceptual diagram which shows other embodiment of the oxidation method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Original fabric roll 2a, 2b, 2c Strip-shaped molded object 3 Oxidation reaction tank 5 Flushing tank 11 Oxidation reaction tank 14, 15 Sheet-shaped molded object

Claims (5)

Sending the molded body containing natural fibers into an oxidation reaction tank into which an oxidation catalyst solution containing an N-oxyl compound is injected,
While the molded body in the oxidation reaction tank is being transferred, the molded body and an oxidation catalyst solution containing an N-oxyl compound are brought into contact with each other by a mechanical operation, and the surface and the inside of the molded body are subjected to an oxidation treatment, whereby the natural fiber The step of bringing the carboxyl group content of cellulose constituting the range of 0.1 to 2 mmol / g,
A step of washing the molded body after the oxidation treatment with water,
A method of oxidizing a molded body containing natural fibers having
A method for oxidizing a molded body including natural fibers, wherein the mechanical operation is to transfer the molded body in an oxidation reaction tank. A step of immersing a molded article containing natural fibers in an oxidation reaction tank in which an oxidation catalyst solution containing an N-oxyl compound is injected and a suction means is installed;
The molded product and an oxidation catalyst solution containing an N-oxyl compound are brought into contact with each other by a mechanical operation, and the surface and the inside of the molded product are oxidized to reduce the carboxyl group content of cellulose constituting the natural fiber to 0.1. In the range of ~ 2 mmol / g,
A method of oxidizing a molded body containing natural fibers having
The method for oxidizing a molded body including natural fibers, wherein the mechanical operation is suction of an oxidation catalyst solution in the oxidation reaction tank by the suction means. 3. The method for oxidizing a molded body containing natural fibers according to claim 1, wherein when the molded body is brought into contact with an oxidation catalyst solution containing an N-oxyl compound by a mechanical operation, one surface or the entire surface of the molded body is supported by a net. . Said shaped body comprising natural fibers is of a thickness of 0.01 to 10 mm, methods oxidation of the molded body containing a natural fiber of any one of claims 1-3. The natural fiber according to any one of claims 1 to 4 , wherein contact between the molded body containing the natural fiber and an oxidation catalyst solution containing an N-oxyl compound is performed at 0 to 80 ° C for 0.1 to 360 minutes. A method for oxidizing a molded body comprising:

Images