JPH0314607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention enables raw materials such as concrete and mortar in which carbon single fibers are uniformly dispersed to be obtained in a dry state, and can be stored as is for a long period of time. It is intended to be able to be used as is without the need for a conventional method, and to easily form high-performance concrete, mortar, etc.

In recent years, research and development of cement-based composite materials has been actively conducted as a way to improve performance such as bending and tensile strength, impact resistance, and cracking resistance, which are considered to be shortcomings of concrete and mortar.As a result, alkali-resistant glass fiber , attempts have been made to incorporate steel fibers, and this has already been put into practical use in many fields. However, it is a well-established theory that these fibers are thought to have drawbacks in heat resistance, chemical resistance, rust generation, and dispersibility.

Carbon fiber, which is said to be stronger than steel and lighter than aluminum, has appeared in recent years, and although it is a high-performance material that compensates for the drawbacks of the above fibers, it is also expensive, and its uses are limited to sports equipment, heat-resistant materials, etc. It was limited to some. However, recently, the manufacturing and development technology for carbon fiber has progressed rapidly and the possibility of supplying it at a low price has emerged, so it is becoming easier to use it as a cement-based composite material.

In order to use carbon fiber as a cement-based composite material, instead of using long fibers or cross-like fibers as used in other applications, short fibers are used, which are obtained by cutting long fiber bundles into specified dimensions. The practical allowable limit of length is considered to be about 3 to 30 m/m. The diameter of the current single fiber is 8 to 18 microns, and the specific gravity is 1.2 to 1.9.
Due to its light weight and high elasticity, it aggregates into small lumps under pressure during cutting, and in this state, it cannot be mixed with cement, aggregate, etc. in a dry state or in water using a conventional concrete or mortar mixer. Even in a wet state, the fibers form small ball-shaped lumps,
It is extremely difficult to disperse it in the form of single fibers. Currently, the only practical method is to use a special high-performance concrete mixer, and use a wet method in which cement, aggregate, short carbon fibers, dispersants, water-reducing agents, and water are simultaneously added, and special technology to barely disperse the concrete. However, at present, even with this method, it is not possible to disperse fibers with a certain fiber length, which is considered to be the most practical.

The present invention has a plurality of needle-like protrusions on the surface, and rotates a pair of rotating bodies facing each other at different circumferential speeds with a slight gap between them so that the tips of the needle-like protrusions do not come into contact with each other. A small lump of cotton-like short carbon fibers is fed, and while the small lump of carbon short fibers is held down by the needle-like protrusion of the rotating body with a slower circumferential speed, the short carbon fiber is passed through the needle-like protrusion of the rotating body with a faster circumferential speed. Traditionally, small fiber lumps are picked up and dispersed into single fibers, and then each of the dispersed single fibers is dropped into a dry powder such as concrete or mortar that is rotating in a stirring device and mixed uniformly. It is designed to eliminate the drawbacks of

Next, one embodiment of the apparatus of the present invention shown in the accompanying drawings will be described in detail. 1 and 2 are cylindrical bodies with different diameters, on which a belt with metal needle-like protrusions 3 and 4 protruding is wound and fixed, and the gap is as small as possible so that the tips of the needle-like protrusions 3 and 4 do not come into contact with each other. The cylindrical body 1 is rotated in the direction of arrow A at approximately 200 rpm.
The cylindrical body 2 is designed to be able to rotate in the direction of arrow B at approximately 20 rpm. Cleaning rollers 5 and 6 are in contact with the upper and lower parts of the cylinder 2 and are arranged so as to rotate in the directions of arrows C and D. Cleaning rollers 7 and 8 are in contact with both sides of the lower part of the cylinder 1 and are arranged to rotate in the directions of arrows E and F. The cleaning rollers 6 and 7 are arranged so as to be rotatable, and are arranged opposite to each other with a slight gap between them. 9 is a hopper for small lumps 10 of cotton-like short carbon fibers, and 11 is a powder stirring device.

Next, the method of the present invention will be explained. Hopper 9
The flocculent short carbon fiber pellets 10 thrown into the chamber fall between the rotating bodies 1 and 2, and are pulled and sent downward by the needle-like protrusions 3 of the rotating body 1 rotating at a high circumferential speed. At this time, the floc-like short carbon fiber lumps 10 are pushed between the needle-like protrusions 4 of the rotating body 2 rotating upward at a low speed and move upward, but are removed from the needle-like protrusions 4 by the cleaning roller 5 and returned to the hopper. Together with a small lump 10 of short carbon fibers falling from 9, the short carbon fibers are sent between the rotating bodies 1 and 2. Between the rotating bodies 1 and 2, the carbon short fiber pellets are prevented from descending by a needle-like protrusion 4 that moves upward at a low circumferential speed, and are rapidly scraped by the other needle-like protrusion 3 that moves downward at a high speed. Relaxed,
The short carbon fiber powder 12 in the form of single fibers is scattered and falls between the cleaning rollers 6 and 7 below. The short carbon fibers that have entered the needle-like protrusions 3 and 4 of the rotating bodies 1 and 2 and are sent downward are cleaned by cleaning rollers 6 and 7, respectively, and are removed together with the single-filament carbon short fiber powder 12. Complete monofilament short carbon fiber powder 12' falls between the cleaning rollers 6 and 7 and is loosened again by the cleaning roller 7 rotating at a high circumferential speed in the same way as the rotating bodies 1 and 2. It then falls into the stirring device 11 below. Various raw materials such as cement, aggregate powder, or synthetic resin powder are stored in the stirring device 11 and rotated at a predetermined speed, so that the single-filament short carbon fiber powder that falls remains as raw material. dispersed in the mixture.

At this time, the rotational speed of the rotating bodies 1 and 2 may be changed depending on the length of the carbon short fibers, or the rotating body 2 may be changed to the rotating body 1.
It may be rotated in the B′ direction at a lower circumferential speed, or the raw material may be scattered and sprayed to be primarily mixed with the falling short carbon fiber powder. Further, the cleaning roller is not necessarily required, and the position where it is disposed on one side may be changed as appropriate.

According to the method of the present invention, a pair of rotating bodies are provided with a large number of needle-like protrusions on their surfaces and are rotated at different circumferential speeds, with a slight gap between them so that the tips of the needle-like protrusions do not come into contact with each other. A small lump of cotton-like short carbon fibers is fed between them, and while the small lump of carbon short fibers is held down by the needle-like protrusion of the rotating body with a slower circumferential speed, the needle-like protrusion is sent into the rotating body with a faster circumferential speed. The short carbon fiber lumps are picked up and dispersed into single fibers, and then each of the dispersed single fibers is dropped into a dry powder such as concrete or mortar that is rotating in a stirring device so that it is evenly mixed. Because of this, it can be uniformly dispersed into raw materials such as concrete and mortar using ordinary powder stirring equipment in a dry state.
Alternatively, premix mortar can be made and stored as is for a long period of time, and when used, it can be used as usual without the need for a special mixer on site.
It can easily form high-performance concrete, mortar, etc., and is extremely useful in various fields.

The present invention can be directly applied to various powdery and granular raw materials other than concrete and mortar whose performance is enhanced by short carbon fibers.

[Brief explanation of drawings]

The figure is a front view of an embodiment of the device of the present invention. 1, 2...Rotating body, 3, 4...Acicular projection, 9...
... Hopper, 10 ... Cotton-like short carbon fiber mass, 11 ...
...Powder stirring device, 12,12'...Short carbon fiber powder.

Claims (1)

[Claims] 1 A pair of rotating bodies are provided with a large number of needle-like protrusions on the surface, and are rotated at different circumferential speeds with a slight gap between them so that the tips of the needle-like protrusions do not come into contact with each other. A small lump of carbon short fibers is fed, and while the needle-like protrusion of the rotating body with a slower circumferential speed holds down the small lump of carbon short fibers, the small carbon short fiber is transferred to the rotating body with a faster circumferential speed with the needle-like protrusion. Short carbon fibers made by picking up lumps and dispersing them into single fibers, and then dropping each of the dispersed single fibers into dry powder such as concrete or mortar that is rotating in a stirring device so that they are evenly mixed. A method for producing dry powder.