JPH0250937B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to water-soluble cellulose derivatives, such as carboxymethyl cellulose (hereinafter abbreviated as CMC), hydroxyethyl cellulose (hereinafter abbreviated as HEC),
The present invention relates to a method for granulating methylcellulose (hereinafter abbreviated as MC) alone or in a mixture thereof. In general, water-soluble cellulose derivative particles themselves have an extremely fast dissolution rate, so if they are dissolved in water as a powder, a collective adhesion phenomenon (called mamako) between the particles will occur, and water will flow into the inside of mamako. Penetration is severely inhibited and the apparent rate of dissolution becomes very slow. Conventionally, various methods have been proposed to prevent the formation of water-soluble cellulose derivatives and to accelerate their dissolution rate. For example, methods include coating the surface of a water-soluble cellulose derivative with a hydrophobic or non-swelling substance, or adding a foaming agent to facilitate diffusion during dissolution, but these methods have a negative impact on the purity of the product. There are restrictions on its use as it gives . A so-called granulation method, which increases the particle size of powder, is used as a method of preventing mako without such restrictions.
In general, there is a wet granulation method in which a cellulose derivative is mixed and stirred while being sprinkled with water to form granules. However, this method requires drying after granulation, resulting in colored products and complicating the manufacturing process. In addition, when using a fluidized granulation dryer that performs granulation and drying in the same device, the bulk specific gravity of the particles becomes too low, which tends to float on the water surface during dissolution, and the cost of drying is also high. There is a drawback. A method to improve these shortcomings was published in Japanese Patent Application Laid-Open No. 1986-
It is 160460. In other words, when granulating a water-soluble cellulose derivative, the water content is adjusted to 0.5 to 1.0 of the equilibrium water content.
A powdered cellulose derivative adjusted to twice its original size is provided with a hopper as a feeding device and a feed screw inside the hopper, and passed between two rolls rotating with each other with a minute gap (1 to 2 mm) in between to form flakes. Next, it is crushed and classified. However, although this method is useful, if it is operated continuously for a long period of time, the amount of steam used is large, which is not preferable from an energy-saving perspective. Water-soluble cellulose derivatives adhere to equipment such as upper conveyors, and cleaning them requires a considerable amount of time. Furthermore, when the moisture content of the powdered water-soluble cellulose derivative as a raw material is lowered in order to prevent the above-mentioned adhesion, there is a drawback that the disintegration rate and yield of the granular cellulose derivative become extremely poor. Therefore, in order to improve these drawbacks, the present inventors conducted intensive studies and found that the water content of the powdered water-soluble cellulose derivative was adjusted to the equilibrium moisture content (temperature 25°C,
Equilibrium moisture at relative humidity of 70% (same below) is 0.5
Adjust the bulk specific gravity of the powdered water-soluble cellulose derivative to 500 times or less, preferably 0.2 to 0.4 times or less.
A method for producing a granular water-soluble cellulose derivative, which comprises adjusting the amount to ~900 g/, preferably 600 to 800 g/, passing it between two mutually rotating rolls to form flakes, and then crushing and classifying the flakes. They discovered this and completed the present invention. The bulk specific gravity of the powdered water-soluble cellulose derivative is usually adjusted by adding water during the manufacturing process of the water-soluble cellulose derivative, and the bulk specific gravity is adjusted to 500 to 900 g/
In order to make something as high as 100%, it can be achieved by adjusting the amount of water added. In addition, the present invention provides that even if the water content of the powdered water-soluble cellulose derivative is 0.5 times or less than the equilibrium water content, the bulk specific gravity of the powdered water-soluble cellulose derivative is set to 500 to 900 g/2, so that the powdered water-soluble cellulose derivative rotates with respect to each other.
Since the angle of repose during passage between the rolls becomes smaller, the amount of the powdered water-soluble cellulose derivative supplied increases, and the self-adhesion of the powdered water-soluble cellulose derivatives becomes stronger. As a result, it is believed that it is possible to obtain a granular water-soluble cellulose derivative that has an excellent disintegration rate and a good yield when pulverized and classified. In addition, the bulk specific gravity of the powdered water-soluble cellulose derivative
If it is less than 500g/, the disintegration rate and yield will be poor.
If it exceeds 900 g/min, moldability, grinding time, color, and dissolution rate will be poor. An experimental example will be explained below. Experimental example 1

[Table] As is clear from Table 1, the disintegration rate of granular CMC improves as the water content doubles and the bulk specific gravity increases, but when the water content doubles 0.5 or more, the same trend occurs, so it is difficult to save steam. It can be seen that within 0.5 is best. When the water content is multiplied by 0.1, the bulk specific gravity is
The disintegration rate should be 700g/or more, but when it is set to 0.2, it is 570g/or more, and when it is set to 0.5, it shows a good disintegration rate even at 490g/. Experimental example 2

[Table] It is clear from Table 2 that the moisture content times 0.2 to 0.5
Bulk specific gravity 490~920g/(preferably 570~
The yield is the best when the water content is 820g/), and when the water content is 0.1 or less, the yield does not improve even if the bulk specific gravity is increased.
Furthermore, when the bulk specific gravity is increased to 920 or more, the yield of 20 to 60 meshes decreases, but this is because granular CMC of 20 meshes or more increases. Experimental example 3

[Table] From the results in Table 3, when the bulk specific gravity is around 950 for both water content times 0.2 and 0.5, moldability, grinding time, hue, and dissolution rate tend to deteriorate, and the bulk specific gravity is 900 g/or less. It turns out that it is preferable to As is clear from these experimental examples, the moisture content was set to 0.5 or less of the equilibrium moisture content, and the bulk specific gravity was set to 500 to 900 g/
(preferably 600 to 800 g/). In addition, the measurement method of each item in Experimental Examples 1 to 3 is as follows. Γ Formability: Powdered water-soluble cellulose derivative passes through a roll and observes the state of the molded flakes Γ Grinding time: Time required to crush 5 kg of flakes after molding Γ Disintegration rate: Granules (20 to 60 mesh) ) is placed in a container with a porcelain ball and subjected to vibration for 15 hours, then the proportion of particles of 60 mesh or less Γ Hue: Observe the color of the granular cellulose derivative (20 to 60 mesh) with the naked eye Γ Yield: Molding, crushing , Yield of particle size of 20 to 60 mesh when classification is repeated once Γ Dissolution rate: Required for complete dissolution when granular cellulose derivative (20 to 60 mesh) is dissolved in 100 times the amount of water Time Γ Bulk specific gravity (g/): Pour about 200g of powdered cellulose derivative into a 200c.c. measuring cylinder, and place it at a height of 5cm.
Measure the weight and volume when dropped 10 times from a certain point, and calculate the bulk specific gravity. Examples and comparative examples are shown below. Example 1 Powdered CMC (passed through 80 meshes, DS=0.75, moisture content 8%, 0.35 times the equilibrium moisture content, bulk specific gravity 700g/)
2 that rotate each other with a hydraulic pressure of 180Kg/ ^cm2 without humidity adjustment.
The flakes are fed to several rolls to form 1.2 mm thick flakes, which are then crushed and classified into 20 to 60 mesh pieces.
CMC granules were obtained. The moldability of this granule product is good, the crushing time is 1 minute, the yield is 39%, and the disintegration rate is 8%.
The hue is good. The dissolution rate was approximately 4 minutes. Example 2 Powdered HEC (MS = 2.0, water content 4.5%, 0.26 times the equilibrium moisture content, bulk specific gravity 650 g/) was supplied to two mutually rotating rolls with an oil pressure of 180 Kg/cm ² without humidity control. to form flakes with a thickness of 1.5 mm,
Granules of 20 to 60 mesh were obtained through crushing and classification, and the yield was good and the moldability was good and the crushing time was 1 minute.
The disintegration rate was 9%, the color was good, and the dissolution rate was about 4 minutes. Comparative Example 1 Powdered CMC (80 meshes passed, DS = 0.75, 0.3 times the equilibrium moisture content, bulk specific gravity 450g/) was supplied to two mutually rotating rolls with an oil pressure of 180Kg/ ^cm2 without humidity control. , forming flakes with a thickness of 1.5 mm,
CMC granules of 20 to 60 mesh were obtained by crushing and classification, but the yield of these granules was 10% and the disintegration rate was poor, 35%.

Claims (1)

[Claims] 1 Adjust the water content of the powdered water-soluble cellulose derivative to 0.5 times or less of the equilibrium moisture content (temperature 25 ° C., relative humidity 70%), and adjust the bulk specific gravity of the powdered water-soluble cellulose derivative to 500 to 900 g /, Pass it between two mutually rotating rolls to form flakes,
A method for producing a granular water-soluble cellulose derivative, which comprises then pulverizing and classifying the product.