JPH06184975A - Production of very fine fibrous cellulose - Google Patents

Abstract

PURPOSE:To efficiently produce fine fibrous cellulose having small fiber width from fibrous or granular cellulose. CONSTITUTION:A cellulose suspension having 0.1-20wt.% concentration, comprising fibrous or granular cellulose is ground in a wet state by using a grinder which is equipped with a cylindrical crushing chamber 2, a main shaft 1 set at the central part of the crushing chamber, plural countershafts 4 arranged symmetrically with respect to the main shaft around the main shaft and a great number of ring-shaped grinding mediums 5 attached to each of the countershafts and the ring-shaped grinding mediums are subjected to centrifugal force and hit to the wall face of the crushing chamber. The ring-shaped grinding mediums 5 are rotated on its axis and revolved around the main shaft on the wall face and the cellulose is ground to produce fine fibrous cellulose.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine fibrous cellulosic fibers which have a high viscosity even in a low-concentration suspension and have a high water retention.

[0002]

2. Description of the Related Art As a method for producing fine cellulose particles, since cellulose is an organic substance and it is difficult to obtain fine cellulose particles only by mechanical pulverization,
A method combining chemical treatment and mechanical grinding is commonly used. As a method combining chemical treatment and mechanical crushing, pulp is slightly acid-hydrolyzed, filtered, washed with water, dried and crushed to produce cellulose fine particles partially containing an amorphous region, or purified pulp is chlorinated with hydrochloric acid. Alternatively, it is known that it is hydrolyzed with sulfuric acid and finely divided, leaving only the crystalline region (Paper and Pulp Technology Times, August 1985, May 5 ~
(See page 11).

As a method for producing fibrous cellulose having a fine fiber width, at least 3 parts of an aqueous suspension of fibrous cellulose is used.
There is known a method of passing a small diameter orifice at a high speed with a pressure difference of 000 psi, that is, a method of treating a fibrous cellulose suspension with a high pressure homogenizer (high pressure homogenizer) (Japanese Patent Publication No. 60-19921 and Japanese Patent Publication No. See 63-44763).

Further, as a method for producing a fine fiberized pulp having a function of strengthening the strength of paper, a method in which an aqueous suspension of pulp is lightly treated with a sand mill is known (Japanese Patent Laid-Open No. Hei 10-1999)
See 4-18186).

[0005]

The problem to be solved by the present invention is that the method using the above-mentioned high-pressure homogenizing apparatus has a low treatment efficiency because it is necessary to apply a high pressure to the fibrous cellulose suspension and pass it through a narrow orifice. In addition, since the sample needs to be sand milled many times even in the sand mill treatment, the treatment efficiency is low, and the present invention provides a method for producing highly productive fine fibrous cellulose with improved treatment efficiency. is there.

[0006]

The method for producing fine fibrous cellulose of the present invention comprises a method of finely pulverizing a cellulosic suspension comprising fibrous cellulose or particulate cellulose by wet pulverization at a concentration of 0.1 to 20% by weight. In the method for producing fibrous cellulose, the cellulose suspension has a cylindrical grinding chamber, a main spindle that is installed in the central portion of the grinding chamber, and is rotatable, and symmetrical about the main spindle with respect to the main spindle. And a plurality of sub-shafts connected to the main shaft by a connecting plate, and a plurality of ring-shaped grinding media attached to each of the sub-shafts. The ring-shaped grinding medium is pressed against the inner wall surface of the grinding chamber by a centrifugal force, and is ground by a grinding device having a mechanism for rotating and revolving on the inner wall surface of the grinding chamber to perform grinding. It is an feature.

The present inventors have paid attention to the action mechanism (defibration action) of micronization of fibrous cellulose by the above-mentioned crushing device, particularly the shearing action, cutting action and friction action, and as a result,
A large number of ring-shaped grinding media attached to each sub-shaft of the crushing device in the present invention are rotated and revolved while being pressed against the inner wall surface of the container by the centrifugal action due to the rotation of the main shaft, and at that time, between the ring-shaped grinding media and the container wall surface. It was found that the sample can be efficiently miniaturized by the compressing action and the shearing action which are applied at.

FIG. 1 shows a cross-sectional explanatory view of the crushing apparatus used in the present invention, and FIG. 2 shows an upper cross-sectional explanatory view. In FIG. 1 and FIG. 2, a rotatable main shaft 1 is provided at the center of the grinding chamber 2.
Is installed, a plurality of counter shafts 4 are installed around the main shaft 1 so as to be symmetrical with respect to the main shaft 1, and are connected to the main shaft 1 by two connecting plates 6 mounted above and below the main shaft 1. .
Further, a large number of ring-shaped grinding media 5 each having a hole larger than the diameter of the sub shaft 4 are passed through each sub shaft 4. When the main shaft 1 rotates, the sub shaft 4 also rotates, and at the same time, a large number of ring-shaped grinding media 5 passing through the sub shaft 4 receive centrifugal force and come into contact with the inner wall 3 of the grinding chamber, and the sub shaft 4
It revolves around the auxiliary shaft 4 while revolving. At this time, the sample is crushed between the ring-shaped crushing medium 5 and the inner wall 3 of the crushing chamber. A trade name: MICROS (manufactured by Nara Machinery Co., Ltd.) is exemplified as a crushing device having such a mechanism, and is advantageously used in the method of the present invention.

As the material of the ring-shaped crushing medium of the crusher used in the present invention, ceramics such as alumina, zirconia, zircon, metal such as stainless steel, and polymer material such as Teflon can be used. As the material of the inner wall of the crushing chamber, ceramics such as alumina, zirconia, zircon or metal such as stainless steel can be used. However, considering the wear and the like, the material of the ring-shaped crushing medium and the inner wall of the crushing chamber are the same. Is preferred.

The concentration of the cellulosic suspension during the pulverization treatment varies depending on the property of the cellulosic sample,
It is preferably adjusted within the range of 20% by weight. Further, the processing conditions such as the processing concentration, the number of revolutions, the number of ring-shaped grinding media, etc. can be appropriately selected depending on the required physical properties of the fine fibrous cellulose. Further, as a treatment method, a batch type may be used, or a continuous type may be used, or several devices may be connected in series to perform rough treatment in the first stage,
It is also possible to perform fine processing in a later stage.

Cellulose samples used in the crushing apparatus used in the present invention include wood pulp such as bleached or unbleached softwood and hardwood chemical pulp, mechanical pulp, dissolving pulp, waste paper pulp, hemp, cotton and the like. Fibrous cellulose such as non-wood pulp, and particulate cellulose can be used.

Water is basically used as a medium for the cellulosic suspension to be treated, but an organic solvent such as lower alcohol, ethylene glycol or glycerin, which is chemically inert and has fluidity in the treatment step, and water are further added. A mixed solvent with an organic solvent can be used.

Next, an example in which a hardwood bleached kraft pulp is used as the fibrous cellulose shows a change in fiber morphology. The untreated pulp and the fine fibrous cellulosic product according to the invention were observed by light and electron microscopy. The untreated pulp has a fiber width of 20 to 30 μm, a length-weighted average fiber length of about 0.7 mm, a smooth and flat cylindrical shape, and is further twisted and bent. It comprises a container according to the invention, a main shaft which rotates therein and a counter shaft which rotates in conjunction with the rotation of the main shaft, and a large number of ring-shaped grinding media are attached to each of the counter shafts. Pulp wet-milled by a crusher that rotates and revolves while being pressed against the inner wall of the container causes fluffing of fine, whisker-like fibers on the surface of the fiber at the beginning of the process, after which the structure of so-called lumen-containing wood fibers is destroyed. As a result, fibers having a fiber width of 2 to 4 μm or fibers and uncrushed portions are bonded to each other by some to several tens or some. Further wet-milling gives fine fibrous cellulose having a fiber width of 1 μm or less, further 0.7 μm or less.

Further, the change in fiber length is such that if the powder is pulverized to some extent, the fiber length is not shortened so much that the water retention capacity is 300.
When the crushing is advanced to about%, the length-weighted average fiber length is 0.5 m.
Although it is in the m-position, regarding the fiber length, since the initial fiber length differs depending on the fibrous cellulose raw material used, if a long fiber length is required depending on the application, a long fiber length raw material may be used, If a fiber having a long fiber length is required, a raw material having a short fiber length may be used.

The fine fibrous cellulose product according to the present invention has properties close to those of pulp that has been beaten if it is in the initial stage of crushing, but the one that has been crushed has properties completely different from ordinary pulp fibers. ing. When wet pulverizing pulp with this pulverizer, the surface area increases as the fibrous cellulose becomes finer, the affinity with water increases, the viscosity increases, and the ability to retain water (water retention) is increased. Get higher

The water-holding power was measured by attaching a G3 glass filter to a cylindrical centrifuge tube having a hole in the lower part, and measuring 300
The sample was dehydrated by centrifugation at 0 G for 15 minutes, and then the treated sample was taken out to measure the weight of the cellulose sample. The sample was then dried at 105 ° C. for at least 5 hours and the dry weight of the sample was measured. Water retention was calculated by subtracting the dry sample weight from the wet sample weight after centrifugation and dividing this by the dry sample weight to give 10
It is a value obtained by multiplying by 0.

However, for the sample to be centrifuged,
Since the water retention of the pulverized product is high, if the water retention is measured as it is, dehydration becomes difficult and the aqueous phase remains on the upper part of the sample. Therefore, as a pretreatment, preliminary dehydration is carried out in advance by filtration etc. and the solid part concentration is 8%. It was made to be -12% and subjected to water retention measurement. The obtained fine fibrous cellulose has an ability to retain water in a considerably large amount, and has a water retention power of 200% or more, and even 300% or more depending on conditions.

Comparing the water-holding powers in the beating of ordinary pulp, hardwood bleached kraft pulp (620 ml of untreated freeness, 105% of water-holding power) was beaten with a refiner at a treatment concentration of 2% to obtain freeness (TAPPI Standard T227m- Measured according to 58) 440 ml,
The water holding powers of the samples treated up to 125 ml and 33 ml were 139%, 174% and 194%, respectively.
In the case of mechanical pulp, the pressure type groundwood pulp had a freeness of 60 ml and a water holding power of 145%.

[0019]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

Example 1 1500% 2% by weight aqueous suspension of hardwood bleached kraft pulp in water
ml was put into a crushing chamber of a crusher (MICROS-2 type, manufactured by Nara Machinery Co., Ltd., effective volume of crushing unit: 1700 ml), and the processing time was changed to 3 minutes, 15 minutes, 30 minutes at a rotation speed of 1400 rpm, and a batch method was used. It was wet-milled. At this time, the ring-shaped grinding medium and the inner wall of the grinding chamber were made of zirconia. Also, cooling the crushing container by discharging water,
The temperature in the grinding chamber was maintained at 30-35 ° C. Table 1 shows the relationship between the treatment time, the length-weighted average fiber length, the water holding power, the viscosity, and the fiber width measured by scanning electron micrograph. In addition,
The length weighted average fiber length was measured with a FS-200 type fiber length measuring device (manufactured by KAJAANI, Finland). Moreover, the viscosity is measured by a DVL-B type viscometer (manufactured by Tokyo Keiki).
Was used under the conditions of a water suspension concentration of 1% by weight, 20 ° C., and a rotor rotation speed of 30 rpm.

It can be seen that as the treatment time is lengthened, the water holding power is increased, but the fiber length is shortened. Regarding the fiber width, the untreated pulp fiber is about 20 μm, but the one having a crushing treatment time of 5 minutes has a fiber width of 2 to 4 because a part of the fiber is destroyed.
Fine fibers of μm came out like a beard from the fiber surface. At this time, the fracture rate of the pulp fiber observed under a microscope (including the one in which the fiber wall was partially opened) was about 40%. When the crushing time is 15 minutes, the cell wall of the fiber is further broken and the fiber width is 2
The number of fibrils of up to 4 μm increased, and the fibers had a shape in which several fibers or fibers having a wide fiber width were bonded to each other with a few fibers to a few dozen fibers. When the pulverization treatment is further advanced, it appears that several tens of fibers having a fiber width of 2 to 4 μm are combined in part by an optical microscope, but when observed by a scanning electron microscope, fibers having a fiber width of 2 to 4 μm are further formed. 05-
It was found that the fiber was a fine fiber of 0.7 μm. Regarding the viscosity, the higher the water retention, the more crushing treatment was performed, and the higher the viscosity was.

[0022]

[Table 1]

Example 2 1500 wt% suspension of bleached softwood kraft pulp in water 1500
ml was put in a crushing chamber of a crusher (MICROS-2 type, Nara Machinery Co., Ltd., effective volume of crushing unit: 1700 ml), and the processing time was changed to 5 minutes, 15 minutes, 30 minutes at 1400 rpm and batch type. It was wet-milled. At this time, the ring-shaped grinding medium and the inner wall of the grinding chamber were made of zirconia. The crushing container was cooled by discharging water to keep the temperature in the crushing chamber at 30 to 35 ° C. Table 2 shows the relationship between treatment time and water retention. The length-weighted average fiber length was the same as in Example 1. As can be seen from Table 2, the water holding power increased as the treatment time became longer, and even the softwood pulp reached 300% or more after the treatment time of 30 minutes.

[0024]

[Table 2]

Example 3 Cellulose particles (trade name: Pulp Flock W-4, manufactured by Sanyo Kokusaku Pulp Co., Ltd.) were prepared with water to a concentration of 15% by weight, and 1500 ml of a cellulose suspension was pulverized (MICRO-2).
Type, manufactured by Nara Machinery Co., Ltd., effective volume of crushing section 1700 ml)
In a crushing chamber of 30 minutes at a rotation speed of 1400 rpm for 6 minutes.
The processing time was changed to 0 minutes and 90 minutes, and wet pulverization processing was performed in a batch system. At this time, the ring-shaped grinding medium and the inner wall of the container were made of zirconia. The crushing container was cooled by discharging water to keep the temperature in the crushing chamber at 30 to 35 ° C. Table 3 shows the relationship between the treatment time and the viscosity, water retention, and average particle diameter of the obtained ground cellulose product. The viscosity is measured using a DVL-B type viscometer (manufactured by Tokyo Keiki),
Water suspension concentration 2% by weight, 20 ° C, rotor speed 30r
It was performed under the condition of pm. The average particle size is SA-CP.
The measurement was performed using a type 3 centrifugal particle sizer (manufactured by Shimadzu Corporation). As is clear from Table 3, the viscosity of 810 cP and the water holding power of 231% were already reached by the crushing treatment for 60 minutes, and the viscosity and the water holding power were further increased as the treatment time became longer. Further, it is considered that the reason why the decrease in average particle diameter is not small even if the treatment time is extended is that the particles are made finer and the spaces between the fine fibers are expanded at the same time as the treatment is advanced.

[0026]

[Table 3]

Comparative Example 1 Using the same hardwood bleached kraft pulp as in Example 1, 150 ml of a 2% by weight aqueous suspension of pulp and 140 ml of glass beads having an average particle diameter of 1 mm were mixed in a 6-cylinder sand mill (made by AIMEX, processing capacity 300 ml). ) In a crushing container, and the temperature is adjusted with circulating water for cooling at a rotation speed of a stirrer of 2000 rpm, and the temperature is 20 ° C. in a batch process for 3 minutes, 1 minute.
The wet pulverization treatment was performed by changing the treatment time to 5 minutes and 30 minutes. Table 4 shows the relationship between treatment time and water retention. As can be seen from Table 4, the production method according to the present invention can improve the water retention force in a shorter treatment time than the sand mill treatment.

[0028]

[Table 4]

[0029]

As described above, according to the method of the present invention in which the cellulose material is wet pulverized by the above-mentioned pulverizing apparatus, it is possible to efficiently produce fine fibrous cellulose having a high water retaining ability in a short time. Became.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a crushing device used in the present invention.

FIG. 2 is an explanatory view of an upper cross section of a crushing device used in the present invention.

[Explanation of symbols] 1 ... Main spindle 2 ... Grinding chamber 3 ... Inner wall of grinding chamber 4 ... Secondary shaft 5 ... Ring-shaped grinding medium 6 ... Main shaft Connecting plate with counter shaft 7 ... Lid of grinding chamber 8 ... Cooling jacket 9 ... Cooling water inlet 10 ... Cooling water outlet

Claims (1)

[Claims] 1. A method for producing fine fibrous cellulose, comprising wet pulverizing a cellulose suspension comprising fibrous cellulose or particulate cellulose at a concentration of 0.1 to 20% by weight, wherein the cellulose suspension is a cylinder. Shape crushing chamber,
A rotatable main shaft that is installed in the central portion of the crushing chamber, and a plurality of auxiliary shafts that are installed around the main shaft so as to be symmetrical with respect to the main shaft and that are connected to the main shaft by a connecting plate. , Consisting of a large number of ring-shaped grinding media attached to each of the sub shafts, and by the rotation of the main shaft,
The ring-shaped crushing medium is subjected to centrifugal force and pressed against the inner wall surface of the crushing chamber, and is crushed by a crushing device having a mechanism for rotating and revolving on the inner wall surface of the crushing chamber to perform crushing. A method for producing fine fibrous cellulose, comprising: