JP3036354B2 - Method for producing fine fibrillated cellulose - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of efficiently producing fine fibrillated cellulose which can be added to paper pulp during paper production to increase paper strength or to increase the air permeability of paper. It relates to a method for manufacturing.

[0002]

2. Description of the Related Art When cellulose fibers such as wood pulp are miniaturized, division into fibrils, which are structural units forming a cell membrane, proceeds, so that micronization proceeds while branching while maintaining the fiber morphology. A fine fibrillated cellulose is obtained. It is known that adding such finely fibrillated cellulose to paper pulp to make paper yields paper having a number of interesting properties. For example, the tensile strength and burst strength of paper can be improved by utilizing the binder-like properties of microfibrillated cellulose. In addition, since the fine fibrillated cellulose is fibrous, it forms a dense network and increases the air permeability of the paper.

A technique has been proposed which utilizes such characteristics of microfibrillated cellulose to increase the paper strength of impregnated base paper used for printed wiring boards and the like (Japanese Patent Publication No. 62-033360). Further, utilizing the fact that the aqueous suspension of fine fibrillated cellulose has an appropriate viscosity and good dispersibility, this aqueous suspension is applied to the surface of the paper to increase the strength of the paper. In addition, a technique for improving printability has been proposed (Japanese Patent Laid-Open No. 04-199407).
issue).

It has been well known that fine fibrillated cellulose can be obtained by applying a strong mechanical shear force to cellulose fibers such as pulp for papermaking, and many methods for producing the same have been proposed. For example, in Japanese Patent Publication No. Sho 60-19921, a suspension of fibrous cellulose is passed through a small-diameter orifice, a high velocity is applied to the suspension with a pressure difference of at least 3000 psi, and then the suspension is rapidly impinged. The present invention proposes a method for producing microfibrous cellulose, comprising: a step of performing a cutting action by decelerating; and a step of repeating this step so that the cellulose suspension becomes a substantially stable suspension. ing.

JP-A-4-82907 proposes a method for producing fibrillated natural cellulose by crushing short fibers of natural cellulose fibers in a dry state. Further, JP-A-06-10286 discloses that a suspension of fibrous cellulose is wet-pulverized by a vibration mill pulverizer using beads or balls of a material such as glass, alumina, zirconia, zircon, steel and titania as a pulverizing medium. A method for producing fine fibrous cellulose is disclosed.

[0006]

[Problems to be Solved by the Invention]
The method proposed in 19921 requires that a suspension of fibrous material, such as pulp, be passed at high pressure through a small orifice, and a suspension having a solids concentration greater than 1% by weight is passed through a small orifice. Since the orifice tends to be clogged when it is passed, the solid concentration of the suspension to be treated must be as low as 1% by weight or less, which is problematic in terms of treatment efficiency. Further, in order to concentrate the suspension having a low solid content after the treatment to obtain a high-concentration fine fibrillated cellulose, a large labor is required for the concentration operation. Such inefficiencies in processing efficiency and work efficiency are all reflected in the cost of the microfibrillated cellulose produced, so that the costly microfibrillated cellulose produced by such a method can be produced in a large amount as cheaply as paper. Not available for products produced in the United States.

Further, the fineness method in a dry state as proposed in the above-mentioned Japanese Patent Application Laid-Open No. 4-82907 is different from the wet fineness method in that the fibrillation of cellulose fibers does not occur so much, and the water retention capacity is low. Only small flake-like micronized cellulose is obtained.

Further, in the wet pulverization method using a vibration mill pulverizer proposed in Japanese Patent Application Laid-Open No. 06-10286, very long fibers such as softwood and non-wood fibers are very long. Time treatment is required, and even in the case of short fibers such as hardwoods, the prepared fine fibrillated cellulose has tackiness, so that it is difficult to separate it from beads or balls, which are grinding media, and processing efficiency is increased. There is a problem in the point.

Therefore, the present invention solves the above-mentioned problems in the prior art and can efficiently perform the fine treatment even when the solid content concentration of the pulp slurry to be subjected to the fine treatment is relatively high, and has a high water retention capacity. Moreover, a fine fibrillated cellulose having a uniform fiber length distribution can be obtained,
The purpose of the present invention is to provide a new and improved method for producing finely fibrillated cellulose.

[0010]

That is, the method for producing microfibrillated cellulose according to the present invention has a particle size of 16 to
Using an abrasive plate rubbing device in which a plurality of abrasive plates made of # 120 abrasive particles are rubbed and arranged, the pulp slurry that has been beaten in advance is passed through the rubbing portion of this device to refine the pulp. Thereby, the number average fiber length of the fibers is 0.05 to 0.3 mm, the water retention value is 250% or more, and 95% or more of the total number of fibers relative to the total number of fibers is 0.5 mm or less. Is what you do.

[0011] Even when using an abrasive plate rubbing device as used in the present invention, a pulp slurry of long fibers which has not been subjected to beating treatment in advance was introduced into the abrasive plate rubbing device to perform a finer treatment. In this case, because the water retention of the fibers is poor, dehydration occurs first at the rubbing portion of the abrasive plate, and the fines discharged are much thinner than the concentration of the pulp slurry introduced, and Efficiency gets worse. However, after the beating process is performed on the pulp slurry in advance, by introducing the pulp slurry into the abrasive plate rubbing device and performing the refining process, the refining process is performed while maintaining the solid content concentration of the pulp slurry at a high level. As a result, the desired microfibrillated cellulose having a high water retention value and a uniform fiber length distribution can be efficiently obtained in a relatively short time.

The degree of beating in the preliminary beating treatment can be classified into two types of beating degree depending on the type of pulp used as a raw material. One is a long fiber pulp having a number average fiber length of 0.8 mm or more.
After preliminarily beaten so as to be not more than 00 ml CSF, it is introduced into an abrasive plate rubbing device. Examples of such pulp include domestic spruce, spruce pine, Japanese red pine, larch, etc., and foreign-made softwood such as black spruce, white spruce, Douglas fir, Western hemlock, southern pine, jack pine, etc. Includes fibers extracted by methods or chemical methods. In addition, pulp extracted from non-wood fibers is included. Typical non-wood fibers include cotton pulp, hemp, bagasse, kenaf, esparto, mulberry, mitsumata, ganpi, and the like. Regenerated cellulose such as rayon, tencel, and polynosic fiber is also included in the non-wood fiber.

The other type is a short fiber pulp having a number average fiber length of less than 0.8 mm. In this case, the pulp is pre-beaten so as to have a freeness of 600 ml CSF or less.
Examples of such pulp include domestic radish, linden, sen, poplar, hippo, etc., foreign-made aspen, cottonwood, black willow, yellow poplar, yellow birch, eucalyptus, etc. Includes fibers extracted by chemical methods.
In addition, a part of non-wood fiber, regenerated cellulose having a reduced fiber length by a mechanical method is included.

The pulp that can be used as a raw material in the present invention is not limited in its production method, and pulp obtained by any method can be used. Pulp obtained by a mechanical method includes GP, PGW, RGP, TMP, CTMP,
As a pulp obtained by a chemical method such as SCP or CGP, KP or SP can be used. In addition, pulp obtained by a special pulping method such as anthraquinone pulping, an alkapar method, an explosion method, a biomechanical pulping method, an organosolve pulping method, or a hydrotropic pulping method can be used.

In performing the pre-beating as a pretreatment, a general beater conventionally used for papermaking can be used. For example, any of beaters, Jordan, conical refiners, single disc refiners, double disc refiners and the like can be used. Can be used.

Since the treatment efficiency of the pulp beating machine as described above is very high, it is preferable to minimize the freeness in the preliminary beating treatment using such a beating machine. In this case, it is preferable to set the freeness to 200 ml CSF or less.

FIGS. 1 and 2 schematically show an example of an abrasive plate rubbing apparatus used in the present invention. The illustrated apparatus is configured by arranging an upper fixed abrasive plate 1 and a lower rotating abrasive plate 2 by rubbing, and the opposing inner surfaces of the two abrasive plates are tapered toward the center thereof. The flat surfaces 4a near the outer peripheral edges of the two abrasive plates are in contact with each other to form a rubbing portion 4. A hopper 6 is installed above the central opening 5 of the fixed abrasive plate 1, and the bottom of the hopper 6 communicates with the grinding chamber 3. The central opening of the rotary abrasive plate 2 is closed by a sealing plate 7, and the rotary abrasive plate 2 is rotated by a drive motor 9 via a shaft 8 extending downward from the lower surface thereof. An umbrella-shaped rectifying plate 1 is supported by a support rod 10 extending upward from a sealing plate 7 of the rotary abrasive plate 2.
1 is arranged substantially at the center of the grinding chamber 3.

FIG. 3 is a view of the fixed abrasive plate 1 as viewed from the inner side. A feed groove 12 is formed on the tapered surface forming the grinding chamber 3 in a substantially radial direction from the central opening 5, and the rubbing portion is formed. The feed groove 12 is not formed on the flat surface 4a near the outer peripheral edge. In addition, the form and the number of the feed grooves are not necessarily limited to those illustrated.

The miniaturization processing by this apparatus is performed as follows. When the pulp slurry that has been beaten in advance is supplied to the hopper 6 (arrow A in FIG. 2), the pulp slurry flows down, is dispersed in the radial direction by the rectifying plate 11, and is uniformly supplied into the grinding chamber 3. . The pulp slurry in the grinding chamber 3 is sent to the rubbing portion 4 of the abrasive plates 1 and 2 by the centrifugal force generated by the rotation of the rotary abrasive plate 2 and the action of the feed groove 12 on the inner surface of the grinding chamber 3. The pulp is refined by the rubbing action of the abrasive plate. The slurry of the fine fibrillated cellulose thus generated flows out of the outer peripheral edges of the abrasive plates 1 and 2 by centrifugal force (arrow B in FIG. 2). The slurry of the fine fibrillated cellulose flowing out is recirculated to the hopper 6 and can be subjected to a fine processing until a desired fine fibrillated cellulose is obtained.

The abrasive plate of the abrasive plate rubbing apparatus is formed by solidifying abrasive particles, which are particles of an abrasive, with a binder,
As the material of the abrasive grains, those conventionally used, for example, diamonds, corundum, natural products such as emery,
Artificial products such as synthetic diamond, cubic boron nitride, alumina, silicon carbide, and boron carbide can be used. When using porous ceramics as the material of the abrasive grains, finely divided cellulose enters the pores of the ceramics,
Since there is a possibility that bacteria may be generated, it is desirable to fill the pores of the ceramic with a synthetic resin or the like in advance.

In particular, as the abrasive plate of the abrasive plate rubbing device used in the present invention, it is necessary to use an abrasive having a grain size of No. 16 to 120 which is a grain size specified in JIS R6001. is there. The inventors of the present invention have sequentially examined the abrasive grains having a grain size of No. 5 to No. 240 for the refinement effect of the pulp slurry. However, the desired fineness and uniformity do not progress, while, when the grain size is finer than # 120, clogging is likely to occur at the rubbing portion of the abrasive grain plate, and the refined pulp slurry is discharged. Turned out to be difficult. Therefore, the grain size of the abrasive grains is 16-120,
It is preferably number 24 to number 80.

The reason why the pulp is refined efficiently by rubbing the abrasive grain plates is that the fine abrasive grains constituting the abrasive grain plates form micro-projections on the rubbing surfaces of the abrasive grain plates, so that they are very uneven. It is greatly related to that. The pulp fiber receives a strong shearing force at the protruding portion of such abrasive grains, and the refinement proceeds.However, since the protruding portion exists everywhere on the rubbing surface of the abrasive grain plate, the cell wall of the pulp fiber is damaged. It will be efficiently divided into individual fibrils. Because of such a pulp fiber refining mechanism, any device having an abrasive plate rubbed and arranged can be used, and the device is not necessarily limited to the illustrated device. Further, as a method of supplying the pulp slurry to the abrasive plate rubbing section, various methods using a centrifugal force, gravity, a pressure feed pump, and the like can be adopted other than the structure shown in the drawing. Further, not only two abrasive plates but also an apparatus in which three or more abrasive plates are rubbed together can be used.

In the present invention, the solid content concentration of the pulp slurry supplied to the abrasive plate rubbing device also affects the miniaturization efficiency. If the solid content concentration is too high, the operating load of the abrasive plate rubbing device is excessively applied, making it difficult for the pulp to pass through the abrasive plate rubbing portion, and eventually the pulp is scorched by the heat generated at the rubbing portion. This is not preferable because it also causes a phenomenon in which it occurs. According to the present invention, the pulp slurry to be supplied to the abrasive plate rubbing device has been subjected to beating treatment in advance, so that passage of the pulp slurry through the rubbing portion is not hindered even when the solid content concentration is about 6% by weight. However, a solid concentration of about 4% by weight is optimal. In the miniaturization treatment using a conventional high-pressure homogenizer that allows the small-diameter orifice to pass through, the solid concentration of the pulp slurry that can pass through the small-diameter orifice without clogging was about 1% by weight. The pulp slurry solids concentration in the invention can be said to be quite high, so that
Efficient miniaturization processing becomes possible.

The number average fiber length specified in the present invention is K
A value obtained by integrating the total lengths of the fibers present in a certain pulp suspension and dividing by the number of the fibers, among the data measured by a fiber length measuring machine (model FS-200) manufactured by AJAANI (Finland). The ratio of the integrated number is obtained by measuring with the same fiber length distribution measuring device. LBKP and NBKP, which are ordinary paper raw materials, have a number-average fiber length of about 0.5 mm and 1 mm, respectively, and the number-average fiber length is at least 0.1 even for fibrillated fibers produced by beating. The length is about 35 mm. On the other hand, the number average fiber length of the fine fibrillated cellulose produced in the present invention is 0.05 to 0.3 mm, which is extremely fine.

The water retention value is an index of the degree of swelling of the pulp, and it is possible to distinguish the water taken in and retained in the swollen fibers from the free water existing in the fibers and between the fibers by an appropriate centrifugal force. It is a value measured based on the idea.
The water retention value specified in the present invention is based on the same concept,
APAN TAPPI No. 26 is a value measured by the method indicated in FIG. That is, a mat of a predetermined amount of a sample is previously formed on a prescribed filter, dehydrated with a centrifugal separator at a centrifugal force of 3000 G for 15 minutes, and the amount of retained water is divided by the absolutely dry pulp amount. Shows the value when. Normal unbeaten pulp shows a water retention value of only about 90%, and beaten pulp shows a water retention value of only about 200%.
On the other hand, the water retention value of the finely fibrillated cellulose produced in the present invention is 250% or more, indicating an extremely high water retention value.

The freeness, which defines the degree of beating in the present invention, is a value measured by a Canadian standard freeness tester specified in JIS P8121.

[0027]

The present invention will be specifically described below with reference to examples and comparative examples. % By weight shown in Examples and Comparative Examples
Are based on the absolute dry weight.

EXAMPLE 1 An NBKP pulp slurry (solid content concentration: 4% by weight) obtained by beating beaten unbroken NBKP having a freeness of 720 ml CSF to a freeness of 300 ml CSF using a refiner was used as an abrasive plate as shown in FIGS. Rubbing device (trade name "Super Grindel", Masuko Sangyo Co., Ltd.)
Manufacturing. Abrasive grain size: No. 46. Number of rotation of rotating abrasive plate: 18
00 rpm. (Hopper capacity: 30 liters). The treated pulp slurry discharged from the abrasive plate rubbing section is continuously recirculated to the hopper,
A fine fibrillated cellulose was obtained with a total of 30 minutes for the fine processing time. The obtained finely fibrillated cellulose was added to the unbeaten LBKP in an amount of 5% by weight based on the pulp, to obtain a hand-made sheet of 100 g / m ² by a conventional method.

Example 2 NBKP previously beaten to a freeness of 100 ml CSF
A fine fibrillated cellulose was produced in the same manner as in Example 1 except that the pulp slurry was subjected to a fine treatment, and a handsheet containing the fine fibrillated cellulose was produced.

Comparative Example 1 A pulp slurry (free solids concentration: 4% by weight) made of unbeaten NBKP having a freeness of 720 ml CSF was refined using an abrasive plate rubbing device without preliminary beating. In the same manner as in the above, fine fibrillated cellulose was produced, and a hand-made sheet containing the fine fibrillated cellulose was produced.

Example 3 An LBKP pulp slurry (solid content concentration: 4% by weight) obtained by beating beaten unbroken LBKP having a freeness of 680 ml CSF to a freeness of 500 ml CSF by using a refiner was used as an abrasive plate as shown in FIGS. Rubbing device (trade name "Super Grindel", Masuko Sangyo Co., Ltd.)
Manufacturing. Abrasive grain size: No. 46. Number of rotation of rotating abrasive plate: 18
00 rpm. (Hopper capacity: 30 liters). The treated pulp slurry discharged from the abrasive plate rubbing section is continuously recirculated to the hopper,
A fine fibrillated cellulose was obtained with a total of 30 minutes for the fine processing time. The obtained fine fibrillated cellulose was added to the unbeaten LBKP in an amount of 5% by weight based on the weight of pulp, and a hand-made sheet of 100 g / m ² was obtained by a conventional method.

Example 4 LBKP previously beaten to a freeness of 200 ml CSF
A fine fibrillated cellulose was produced in the same manner as in Example 3 except that the pulp slurry was subjected to a fine treatment, and a hand-made sheet containing the fine fibrillated cellulose was produced.

Comparative Example 2 A pulp slurry (free solids concentration: 4% by weight) composed of unbeaten LBKP having a freeness of 680 ml CSF was subjected to a fine treatment using an abrasive plate rubbing device without preliminary beating. In the same manner as in the above, fine fibrillated cellulose was produced, and a hand-made sheet containing the fine fibrillated cellulose was produced.

Table 1 shows the measurement results of the properties of the fine fibrillated cellulose obtained in the above Examples and Comparative Examples and the hand-made sheet containing the fine fibrillated cellulose.
Shown in In addition, the physical properties of the hand-made sheet are as described in JI below.
It was measured by the method specified in S. Basis weight: JIS P 8124 Thickness and density: JIS P 8118 Column breaking length: JIS P 8113 Specific burst strength: JIS P 8112 Air permeability: JIS P 8117

[0035]

As can be seen from Table 1, when the preliminary beating was performed prior to the refinement treatment by the abrasive plate rubbing device, the fineness was smaller than that without the preliminary beating when compared in the same processing time. Thus, fine fibrillated cellulose having a high water retention value and a uniform fiber length distribution is obtained. In addition, by performing the preliminary beating, the solid content concentration of the fine fibrillated cellulose slurry after the fine treatment can be maintained at a high concentration state which is substantially the same as the solid concentration of the pulp slurry subjected to the fine treatment, so that the efficiency is improved. It can be seen that fine fibrillated cellulose is well obtained.

Further, the characteristics of the sheet containing fine fibrillated cellulose are also obtained without pre-beating the sheet containing fine fibrillated cellulose, which is obtained by pre-beating and then pulverizing. Tensile strength, compared to the sheet containing fine fibrillated cellulose
It can be seen that the burst strength and the air permeability show larger values.

No difference between the pulp raw materials of the N material and the L material was observed, and similar results were obtained in both cases. But,
Since the average fiber length of the unbeaten pulp of the L material is shorter than that of the N material, even if the degree of preliminary beating is not so high as 500 ml CSF (Example 1), the fineness treatment by an abrasive plate rubbing device is possible. Can be performed efficiently.

[0039]

As can be seen from the above description,
According to the present invention, after pre-beating the pulp slurry in advance,
The pulp slurry is refined using an abrasive grain rubbing device consisting of abrasive grains of a specific particle size to obtain very fine fibrillated cellulose having a very fine water retention value and a uniform fiber length distribution. be able to.

Further, since the pulp slurry supplied to the abrasive plate rubbing device is preliminarily beaten, even if the solid content concentration is set to a relatively high concentration of about 6% by weight, an effective refining treatment is performed. Can be. Furthermore, the solid content concentration of the fine fibrillated cellulose slurry after the fine processing is also
Since a concentration as high as the solid content concentration of the pulp slurry supplied to the abrasive plate rubbing device can be maintained, an efficient fine processing can be performed.

Furthermore, the characteristics of the sheet containing fine fibrillated cellulose are also obtained without preliminary beating in the sheet containing fine fibrillated cellulose obtained by subjecting the sheet to fine treatment after preliminary beating. Tensile strength, compared to the sheet containing fine fibrillated cellulose
It can be seen that the burst strength and the air permeability show larger values.

The very fine fibrillated cellulose obtained by the present invention, which has a very high water retention value and a uniform fiber length distribution, can be added, for example, to pulp for papermaking to produce paper.
Since the microscopic network is formed at the holes formed by the pulp network which is held uniformly in the paper and is used as the base, it is possible to increase the paper strength and increase the air permeability.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an abrasive plate rubbing apparatus used in the present invention.

FIG. 2 is a cross-sectional view of the device of FIG.

FIG. 3 is a plan view showing an example of an abrasive plate used in the apparatus shown in FIG. 1;

[Explanation of symbols]

 1: fixed abrasive plate 2: rotating abrasive plate 3: grinding chamber 4: rubbing section 6: hopper 9: drive motor 12: feed groove

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-109699 (JP, A) JP-A-6-10286 (JP, A) JP-A-56-100801 (JP, A) JP-A 57-109 112489 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) D21D 1/20 C08B 15/00 D21D 1/36

Claims (4)

(57) [Claims] An abrasive grain rubbing apparatus in which a plurality of abrasive grains made of abrasive grains having a grain size of 16 to 120 is rubbed and arranged, and a number average fiber length is set in a rubbing portion of the apparatus.
Freeness of long fiber pulp of 0.8 mm or more is 4
The pulp is refined by passing through a pulp slurry that has been beaten in advance so as to be not more than 00 ml CSF, so that the number average fiber length of the fibers is 0.05 to 0.3 mm, the water retention value is 250% or more, and the total number of fibers is calculated. A method for producing fine fibrillated cellulose, characterized in that 95% or more of the number of the fine fibrillated celluloses have a size of 0.5 mm or less. 2. An abrasive plate rubbing device in which a plurality of abrasive plates made of abrasive grains having a grain size of No. 16 to 120 are rubbed and arranged, and a number average fiber length is set in a rubbing portion of the device.
The freeness of short fiber pulp less than 0.8 mm is 6
The pulp is refined by passing through a pulp slurry that has been beaten in advance so as to be not more than 00 ml CSF, so that the number average fiber length of the fibers is 0.05 to 0.3 mm, the water retention value is 250% or more, and the total number of fibers is calculated. A method for producing fine fibrillated cellulose, characterized in that 95% or more of the number of the fine fibrillated celluloses have a size of 0.5 mm or less. 3. A pulp slurry having a solid content concentration of 6% by weight, which is passed through a rubbing portion of the rubbing plate rubbing device.
The method for producing microfibrillated cellulose according to claim 1 or 2, wherein: As claimed in claim 4, wherein said rubbing abrasive plate device, the fixed abrasive plate and the rotary abrasive grain plate and a microfibrillated of claim 1, wherein the use of rubbing up and down position with the device A method for producing cellulose.