JPH08231730A - Pulverization of cellulose ether - Google Patents

Abstract

PURPOSE: To provide a method for pulverizing a cellulose ether at a low cost with a good efficiency, capable of reducing the degradation of the viscosity of powdery cellulose ether after the pulverization and good in flowability. CONSTITUTION: This method for pulverizing a cellulose ether comprises putting a cellulose ether cooled in advance into an impact crusher 1 attached with a cooling device using a liquefied gas coolant and pulverizing it by an impact crushing while cooling to <=0 deg.C by the cooling device. It is preferable to cool to <=-50 deg.C by the cooling device. The liquefied gas coolant is a liquefied carbon dioxide gas or a liquefied nitrogen. The cellulose ether is at least one kind selected from a methylcellulose, a ethylcellulose, a hydroxyethylcellulose, a hydroxypropylcellulose, a hydroxypropylmethylcellulose, a hydroxyethylmethylcellulose and a carboxymethylcellulose.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pulverizing cellulose ether used as a thickener for various solvents, a water retention agent for building materials, a binder in an extrusion molding method, and the like.

[0002]

2. Description of the Related Art Cellulose ether is an etherified product of the hydroxyl groups of cellulose in order to make it water-soluble. Powdered cellulose ether powdered from cellulose ether is a thickener for various solvents, cement,
It is used in large quantities in many fields such as water retention agents for building materials such as plaster, as well as ceramics and binders in cement-based extrusion molding processes.

The powdered cellulose ether is used by dissolving it in a solvent such as water, and its effect depends on the viscosity of the powdered cellulose ether.

The viscosity of powdered cellulose ether is determined by the degree of polymerization of cellulose molecules, and the higher the degree of polymerization, the higher the viscosity. However, powdered cellulose ether is manufactured using natural wood, cotton, cotton linter, etc. as a raw material, so it is difficult to control the degree of polymerization like other synthetic polymers, and it is not possible to create more than the degree of polymerization of the raw material. Absent.

Cellulose ether is manufactured as follows. After adding sodium hydroxide or potassium hydroxide aqueous solution as a reaction catalyst to purified high-purity cotton linter pulp or wood pulp, methyl chloride is used for methoxy group substitution, and ethyl chloride, hydroxy for ethoxy group substitution. Ethylene oxide when substituting an ethyl group, propylene oxide when substituting a hydroxypropyl group, and monochloroacetic acid when substituting a carboxymethyl group are added, and the reaction is usually carried out at 40 to 120 ° C.

The obtained cellulose ether is purified by removing sodium chloride, potassium chloride, alcohol and glycols produced during the reaction. After that, it is dried to reduce the water content to 10% by weight or less, and then powdered with an impact crusher to give a powdered cellulose ether.

In the process of refining cellulose into a high-purity pulp which is a raw material of cellulose ether, in order to remove lignin and hemicellulose from cellulose, cooking is performed in a high temperature alkaline atmosphere, and bleaching is carried out with peroxide or chlorine. , The degree of polymerization of cellulose will decrease. Furthermore, in the process of making cellulose ether from refined pulp through ether reaction, the degree of polymerization continues to decrease due to the action of reaction catalysts such as sodium hydroxide, potassium hydroxide, and oxygen, and the subsequent polymerization, drying, and crushing processes cause polymerization. And the viscosity of the powdered cellulose ether produced decreases.

Among the manufacturing processes of powdered cellulose ether, the decrease in viscosity is remarkable in the pulverizing process. Even if a highly viscous cellulose ether is produced before pulverization, the viscosity is reduced to one third or less depending on the pulverization method. Since the powdered cellulose ether is intended to increase the viscosity of the solution, it is preferable that the powdered cellulose ether be as fine powder as possible in order to facilitate the dissolution, and the pulverization step cannot be avoided.

As a machine for crushing cellulose ether, a ball mill or a vibration mill for crushing metal balls or rods as a medium by impact and grinding, an impact crusher for impacting and crushing with a high-speed impeller or hammer, high pressure An airflow impact crusher that collides against a fixed impact plate in the airflow and crushes is used.

However, in ball mills and vibration mills, the residence time of cellulose ether during pulverization is comparatively long, and it takes several hours from the start of pulverization to discharge, so that the viscosity is remarkably lowered. Impact crushers and air flow impact crushers such as jet mills have a shorter residence time than ball mills and vibration mills, and are usually discharged within 1 minute, resulting in less deterioration in the degree of polymerization. However, since the cellulose ether is crushed by applying high energy in a short time, the processing amount is limited,
The electric power used was three to four times that of ball mills and vibration mills, and the cost was high.

Further, the fluidity of the powdered cellulose ether after crushing is also important. Since the raw material is cellulose such as wood, cotton, and cotton linter, the fibers of cellulose ether are naturally intricately entangled with each other, the bulk density is very low, and the weight per unit volume is small. When powdered cellulose ether after crushing is compressed by its own weight or external pressure, even if it is a fine powder, it loses fluidity at all, and it may be difficult to discharge it even if it is put in a hopper. . In addition, light fibers can become dusty during handling, which not only worsens the working environment, but can also cause dust explosion.

[0012]

For these reasons,
In the pulverization process of cellulose ether, a powdering method that can efficiently pulverize powdery powder at low cost, has little decrease in viscosity of powdered cellulose ether after pulverization, and has good fluidity has been desired.

The present invention has been made to solve the above problems, and when crushing cellulose ether, it can be efficiently crushed into powder by low cost, and the viscosity of the powdered cellulose ether after crushing is reduced. An object of the present invention is to provide a method for pulverizing cellulose ether having a low content and good fluidity.

[0014]

Means for Solving the Problems The method for pulverizing cellulose ether of the present invention, which has been made to achieve the above object, is a method of pulverizing cellulose ether to pulverize it and liquefying pre-cooled cellulose ether. It is charged into an impact crusher 1 (see FIG. 1) provided with a cooling device using a gas refrigerant, and while being cooled to 0 ° C. or lower by the cooling device,
Impact crush to powder. It is preferable to cool to −50 ° C. or lower with the cooling device. The liquefied gas refrigerant is liquid carbon dioxide gas or liquid nitrogen.

The cellulose ether is preferably at least one selected from methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxyethyl ethyl cellulose, and carboxymethyl cellulose.

[0016]

In the method for pulverizing cellulose ether of the present invention, as shown in FIG. 1, the pre-cooled cellulose ether is impact crushed while being cooled to 0 ° C. or less in the impact crusher 1. When the cellulose ether is cooled, its toughness deteriorates and becomes brittle. Therefore, when the cellulose ether is subjected to impact crushing at a low temperature, the cellulose ether is crushed into columns and easily flows, and no dust explosion occurs.
The lower the cooling temperature of cellulose ether, the better the grinding efficiency.

[0017]

When the cellulose ether is pulverized by the method of the present invention, the cellulose ether can be efficiently pulverized at low cost when pulverized, and the viscosity of the powdered cellulose ether after pulverization is small, and the bulk is large. Good fluidity due to high density.

[0018]

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 1 is a schematic view of a cryogenic crushing apparatus 10 for carrying out the method for pulverizing cellulose ether of the present invention. A tank 3 that stores liquid nitrogen or liquid carbon dioxide for cooling is connected to a freezer 2 for precooling the raw material cellulose ether and an impact crusher 1 via a bifurcated tube. The freezer 2 is connected to a screw feeder 4 that conveys the raw material cellulose ether before crushing to the impact crusher 1, and the impact crusher 1 is connected via a pipe to a cyclone collector 6 that collects the powdered cellulose ether after crushing. Has been done. The cyclone collector 6 has a rotary valve 7 at the product discharge port 9 and is connected to the blower 5 via a pipe. The blower 5 is connected to the raw material supply port 8, the freezer 2, and the impact crusher 1 via a trifurcated tube.

FIG. 2 is a sectional view showing the internal structure of the impact crusher 1. A crushing rotor 12 having a plurality of hammers 11 is rotatably arranged in the center of the impact crushing machine 1, and a liner 13 is fixedly provided at a position facing the hammers 11. Further, a slit opening degree adjusting plate 14 is arranged in a portion through which the powdered cellulose ether after crushing passes, and the slit opening degree adjusting plate 14 can be operated by a handle 15.

As shown in FIG. 1, gaseous nitrogen gas or carbon dioxide gas is discharged from the tank 3 to cool the freezer 2, the screw feeder 4 and the impact crusher 1. The cooling temperatures of the freezer 2 and the impact crusher 1 are adjusted by operating the gas flow rate. The gas that has entered the impact crusher 1 passes through the cyclone collector 6 by the suction wind of the blower 5 and is sent to the raw material supply port 8, the freezer 2 and the impact crusher 1 again, and the excess gas is released to the atmosphere. It

Using the cryogenic crushing apparatus 10 described above, the cellulose ether pulverizing method of the present invention is carried out as follows. The raw material hydroxypropyl methylcellulose before pulverization is put into the freezer 2 through the raw material supply port 8 and precooled, then conveyed by the screw feeder 4 and put into the impact pulverizer 1. The raw material hydroxypropylmethyl cellulose charged into the impact crusher 1 is the hammer 11 of the rotating crushing rotor 12 (see FIG. 2) and the liner 1.
It is crushed by being impacted by 3, and classified by passing through a slit. The classified powdered cellulose ether is collected by the cyclone collector 6 by the suction air of the blower 5, and taken out from the product discharge port 9 via the rotary valve 7.

Example 1 Using high-purity cotton linter pulp, hydroxypropylmethylcellulose was produced as a cellulose ether by a conventional method, and purified with hot water until the residual salt content was about 1% by weight based on hydroxypropylmethylcellulose, Then, it was dried to obtain a raw material hydroxypropylmethylcellulose having a water content of 1.6% by weight.

The obtained raw material hydroxypropylmethylcellulose was made into an aqueous solution having a concentration of 1% by weight, kept at a constant temperature of 20 ° C., and the viscosity was measured by using a Brookfield type rotational viscometer to find that it was 16500 mPa · s. The particle size is the nominal size 1000 specified in JIS Z8801,
710, 500, 355, 250, 180, 150, 1
The average particle size was 5 when measured using a 06 μm sieve.
It was 00 μm.

Liquid nitrogen is used as the liquefied gas refrigerant, and fine Victory Mill FVP is used as the impact crusher 1 (see FIG. 1).
-1 (manufactured by Hosokawa Micron Corp.)
The raw material hydroxypropylmethyl cellulose was pulverized into powder by immersing it in liquid nitrogen in a freezer 2 to precool it, and pulverizing it while maintaining the pulverization temperature at 0 ° C. The particle size was adjusted by adjusting the slit opening.

The powdered hydroxypropylmethyl cellulose obtained after pulverization was made into an aqueous solution having a concentration of 1% by weight, and the viscosity was measured and found to be 12,500 mPa · s. The average particle size was 55 μm, the bulk density was 0.31 g / cc, and the power used for pulverization was 1.6 kwh / kg.

Example 2 The same raw material hydroxypropylmethylcellulose as that used in Example 1 was used, using the same cryogenic pulverizer 10.
Fine Victory Mill FVP-1 was ground and powdered in the same manner as in Example 1 except that the temperature was kept at -50 ° C.

The powdered hydroxypropylmethyl cellulose obtained after pulverization was made into an aqueous solution having a concentration of 1% by weight, and the viscosity was measured and found to be 13750 mPa · s. The average particle size was 74 μm, the bulk density was 0.40 g / cc, and the power used for pulverization was 1.0 kwh / kg.

Comparative Example 1 Using the same raw material hydroxypropylmethylcellulose as that used in Example 1, a shock crusher Victory Mill VP-1 (manufactured by Hosokawa Micron Co., Ltd.) which is not for cooling was used to form a screen having a diameter of 1.0 mm. Attached, crushed and pulverized.

The powdered hydroxypropylmethylcellulose obtained after pulverization was made into an aqueous solution having a concentration of 1% by weight, and the viscosity was measured and found to be 15200 mPa · s. The average particle size was 220 μm, the bulk density was 0.28 g / cc, and the power used for grinding was 0.48 kwh / kg.

Further, 40% of the obtained powdery hydroxypropylmethyl cellulose passed through a 180 μm sieve (hereinafter referred to as “pass product”). When the pass product was made into an aqueous solution with a concentration of 1% by weight and the viscosity was measured, it was 14750 m.
It was Pa · s. The average particle size of the pass product is 75 μm,
The bulk density was 0.26 g / cc, and the power used for pulverization was 2.0 kwh / kg.

Comparative Example 2 The same raw material hydroxypropylmethylcellulose as that used in Example 1 was charged into a batch type vibration mill B-3 type (manufactured by Chuo Kakoki Co., Ltd.) at 300 g per pot and pulverized for 2 hours.

The powdered hydroxypropylmethylcellulose obtained after pulverization was made into an aqueous solution having a concentration of 1% by weight, and the viscosity was measured and found to be 5600 mPa · s. The average particle size was 106 μm, and the bulk density was 0.41 g / cc.

Further, of the obtained powdery hydroxypropylmethyl cellulose, 72% of the pass products passed through a 180 μm sieve. When the pass product was made into an aqueous solution having a concentration of 1% by weight and the viscosity was measured, it was 5500 mPa · s. The average particle size of the pass product is 75 μm and the bulk density is 0.3.
It was 6 g / cc.

Comparative Example 3 The same raw material hydroxypropylmethyl cellulose as that used in Example 1 was pulverized into powder by using the same cryogenic pulverizer 10 without cooling. The grinding temperature was 100 ° C.

The powdered hydroxypropylmethyl cellulose obtained after pulverization was made into an aqueous solution having a concentration of 1% by weight, and the viscosity was measured and found to be 13750 mPa · s. The average particle size was 85 μm, the bulk density was 0.22 g / cc, and the power used for pulverization was 1.4 kwh / kg.

Comparative Example 4 The same raw material hydroxypropylmethylcellulose as that used in Example 1 was used, and the same cryogenic pulverizer 10 was used.
It was immersed in liquid nitrogen in Freezer 2 and pre-cooled, and Fine Victory Mill FVP-1 (manufactured by Hosokawa Micron Co., Ltd.) was ground and powdered without cooling. The grinding temperature was 100 ° C.

The powdered hydroxypropylmethylcellulose obtained after pulverization was made into an aqueous solution having a concentration of 1% by weight, and the viscosity was measured and found to be 14250 mPa · s. The average particle size was 93 μm, the bulk density was 0.24 g / cc, and the power used for pulverization was 1.1 kwh / kg.

[Brief description of drawings]

FIG. 1 is a schematic view of a cryogenic crushing apparatus for carrying out a powdering method of cellulose ether to which the present invention is applied.

FIG. 2 is a cross-sectional view of one part of a cryogenic crushing apparatus for carrying out the method for pulverizing cellulose ether to which the present invention is applied.

[Explanation of symbols]

1 is an impact crusher, 2 is a freezer, 3 is a tank, 4 is a screw feeder, 5 is a blower, 6 is a cyclone collector,
7 is a rotary valve, 8 is a raw material supply port, 9 is a product discharge port, 10 is a deep crushing device, 11 is a hammer, 12 is a crushing rotor, 13 is a liner, 14 is a slit opening adjustment plate,
Reference numeral 15 is a handle.

Claims (4)

[Claims] 1. A method of pulverizing and pulverizing cellulose ether, wherein pre-cooled cellulose ether is
A method for pulverizing cellulose ether, which comprises charging into a shock crusher equipped with a cooling device for a liquefied gas refrigerant, and crushing into powder by impact crushing while cooling to 0 ° C. or lower by the cooling device. 2. The method for pulverizing cellulose ether according to claim 1, wherein the cooling device cools to −50 ° C. or lower. 3. The method of pulverizing cellulose ether according to claim 1, wherein the liquefied gas refrigerant is liquid carbon dioxide gas or liquid nitrogen. 4. The cellulose ether is at least one selected from methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxyethyl ethyl cellulose, and carboxymethyl cellulose. The method for powderizing cellulose ether according to claim 1.