JPH01254233A - Prevention of segregation-separation of powdery material - Google Patents

Abstract

PURPOSE:To prevent segregation-separation phenomena such as density difference, grain size difference, etc., and to obtain a homogeneous powder by dispersing fine diameter fibers in the powder. CONSTITUTION:Fine diameter fibers such as polytetrafluoroethylene fibrin of 100mum or smaller in diameter are dispersed in powder, especially when a mixture of not less than two kinds of powder is to be obtained, whose grain size distributions, densities, etc., are different from one another. This polytetrafluoroethylene fibrin is chemically inactive, water repellent and has properties low in friction factor and high in non-stickiness. It is possible, therefore, to prevent segregation-separations of particles and to obtain a homogeneous powder.

Description

DETAILED DESCRIPTION OF THE INVENTION -1 The present invention relates to a method for preventing segregation and separation phenomena due to differences in specific gravity, differences in particle size, etc. in granular materials.

In operations involving the flow of powder particles, the phenomenon in which the particle size is divided into relatively coarse portions and fine portions is called particle size segregation.

Particle size segregation can also occur when particles are flowed or vibrated in a closed container or thick powder bed, or most significantly when the powder is flowed with open surfaces.

Furthermore, when trying to obtain a mixture of two or more different types of powder and granules, if the properties of the powders and granules are similar, is it possible to obtain a relatively homogeneous mixture? To obtain a mixture of powders and granules with different properties such as density, bulk specific gravity, particle shape, filling characteristics, fluidity, and adhesion, it is possible to obtain a mixture of powders and granules with different properties such as density, bulk specific gravity, particle shape, filling characteristics, fluidity, and adhesion. Segregation from homogeneous conditions is often a serious problem.

In particular, in the case of powders with a large difference in specific gravity or particles with a relatively wide particle size distribution, it is not only difficult to mix them uniformly, but also segregation is likely to occur in the mixture storage tank.

In addition to separation due to particle size segregation, separation due to differences in specific gravity is further promoted in heterogeneous powder mixtures. It is difficult to completely prevent these separation phenomena.

For example, in storage, rather than simply letting the mixture fall from the top of the silo, the mixture may be deposited in a ring shape using a chute, distributor, or cone, or fine compartments may be created within the silo. Or, the diameter of the silo is reduced to make it elongated and cylindrical. In addition, when extracting from the silo, consideration is given to placing a cone in the bottom and using a transport device with a mixing function such as a screw feeder or rotary valve.

However, countermeasures against this problem are difficult when the product is transported by dump truck or the like, or after it has been packed in bags, and especially when a part of the packaged product is taken out and used, the effect of this problem is large for mixtures that have a large separation phenomenon.

I said, ``I'll do it.'' SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and provide a method for obtaining homogeneous granular material by preventing segregation.

The method for preventing segregation and separation of powder and granular material according to the present invention is characterized by dispersing fine diameter fibers in the powder and granular material.

It is preferable to use fine diameter fibers having a diameter of 1100 μm or less.

The finer the diameter, the higher the segregation separation effect can be obtained with a smaller amount.

For example, various chemical fibers such as polypropylene fibers, polyethylene fibers, and vinylon fibers can be used, but it is particularly preferable to use polytetrafluoroethylene fibrils having a very small diameter.

Polytetrafluoroethylene (hereinafter referred to as PTFE) has unique properties such as being chemically inert, water repellent, having a low coefficient of friction, and being highly non-adhesive. Also PTF
E easily forms into fibrils (fibers) under appropriate temperature conditions (50° C. or higher and 320° C. or lower), and the diameter thereof is very fine, on the order of several tens of λ.

As a specific means for dispersing PTFE fibrils in powder, PTFE particles obtained by emulsion polymerization are mixed into a target powder mixture, and this mixture is usually mixed with 50 to 20
When subjected to compression-shear action at a temperature of 0°C, the PTFE particles fibrillate and are dispersed in the powder.

When dispersing fine-diameter fibers that are already in the form of fibers, a simple mixing operation is sufficient.

The present invention is effective not only for powders of one type of substance having a wide particle size distribution, but also for preventing segregation of mixtures of powders and granules of two or more substances having a relatively large difference in specific gravity. Especially effective.

The required amount of fine-diameter fibers to be added is determined by the density of the powder (density difference in the case of a mixture), bulk specific gravity (bulk specific gravity difference in the case of a mixture)
, particle shape 1 Although it varies depending on the particle size distribution etc., it varies greatly depending on the diameter of the fibers to be dispersed. For example, the diameter is lO
In the case of fibers with a diameter of ~looILm, it is preferable to add about 0.2 to 1% by weight to the target powder, but in the case of PTFE fibrils with a diameter of several tens of lambda, the amount is one order of magnitude smaller. That is, 0. At about 1 to 0.2% by weight of O, the same or better effect is exhibited.

Specifically, it may be determined experimentally by taking into consideration the vibrations and shocks given to the powder or granular material until it is finally used.

Since the individual particles of January powder are restrained by the dispersed fine-diameter fibers and have reduced fluidity, it is thought that they will be less likely to cause segregation even if subjected to vibration or impact during transportation. It will be done.

The present invention will be specifically explained below using Examples.

Example 1 Ordinary Portland cement (apparent specific gravity 1.260)8.
perlite based on 5 kg (apparent specific gravity 0.07
4) Added 1.5 kg and further added the above powder to a total of 1110 kg.
16.7 g of PTFE aqueous suspension (PTFE resin solid content: 30% by weight), equivalent to 5 g of PTFE solid content, was added per kg, and mixed for 1 minute with a mixer. This mixture was heated to lOOoC and mixed again for 1 minute using a mixer.

In order to confirm whether or not the cement and pearlite were homogeneously dispersed in this mixture,
kg, put it in a cylindrical container with an inner diameter of 100 mm and a length of 300 mm, lift it 50 mm above the concrete floor, let go of it, apply a drop impact 20 times, divide it into the upper and lower parts of the cylindrical container, and separate them into the upper and lower parts. The apparent specific gravity was measured.

A similar test was also conducted on a sample in which the cement and pearlite were mixed in the same manner as in Example 1 without adding PTFE.

The test results are shown in Table 1.

In normal mixing without dispersing PTFE fibrils, since the pearlite particles are light, if an impact is applied after mixing, particles with different specific gravity easily separate, making it difficult to maintain a uniform composition of the powder mixture.

On the other hand, in the mixture in which PTFE fibrils were dispersed according to the present invention, the apparent specific gravity hardly changed in both the upper layer and the lower layer, and it was observed that the segregation phenomenon was suppressed.

Example 2 Same as Example 1, ordinary Portland cement 5.0k
18.7 g of PTFE aqueous suspension (PTFE resin solid content 30% by weight), equivalent to 5 g of PTFE solid content, was added to a mixture of 5.0 kg of slaked lime (apparent specific gravity 0.562), and heated to 130''C. The PTFE was heated to fibrillate and dispersed in the powder, and the powder was subjected to a segregation test in the same manner as in Example 1.

The degree of mixing was determined by chemically analyzing the mixture and comparing the amount of 5if2. The results are shown in Table 2.

(Margin below) Table 2 Note that 5iOz in the cement was 22.2%, and SiO2 in the slaked lime was 0.3%. Therefore, the average value is 11.
It is 25%.

It is clear that when PTFE fibrils are dispersed in a powder mixture, it is effective in preventing separation of powder and granules due to differences in specific gravity.

Example 3 PTFE aqueous suspension (P
TFE solid content 30%), PTFE solid content 0.0
It was added to a concentration of 5% by weight and mixed for 1 minute using a mixer. This mixture was heated to 100°C and then mixed again with a mixer for 1 minute.

This mixture was placed in a cylindrical container with an inner diameter of 100 mm and a length of 300 mm, lifted 50 mm above the concrete floor, released and subjected to 20 drops, and then the contents of the cylindrical container were poured from the bottom. It was equally divided into 5 blocks (2), (2), (2), and (3), and each block was sieved to measure the particle size distribution.

A similar test was also conducted on a material to which PTFE was not added. The test results are shown in Table 3.

Table 3 When PTFE is added to disperse PTFE fibrils, segregation is suppressed compared to when no addition is made.

Example 4 100g of obsidian pearlite with a diameter of 50mm. Bm, length 3
．． Adding 0.5% by weight of 0mm polypropylene fibers,
Mixed with a mixer for 1 minute.

Put this mixture into a cylindrical container with an inner diameter of 100 mm and a length of 300 mm, lift it 50 mm above the concrete floor, let go of it, apply a drop impact 20 times, and then pour out the contents of the cylindrical container from the bottom ■, ■, It was equally divided into four blocks (1) and (2), and each block was sieved to measure the particle size distribution. The test results are shown in Table 4.

(The following is a blank space) Table 4 Segregation of powder particles is suppressed by requiring a large amount of use or by dispersing polypropylene fibers.

Example 5 Direct 8 instead of polypropylene fiber! lO~100gm,
The same test as in Example 4 was conducted except that 0.5% by weight of polyethylene fibers having a length of 2.2 mm (manufactured by Mitsui Petroleum Chemical Industry Co., Ltd.) were used. The test results are shown in Table 5.

(The following is a blank space) Table 5 Segregation of powder particles is suppressed by requiring a large amount of use or by dispersing polyethylene fibers.

Example 6 Instead of polypropylene fibers, diameter 18 pm and length 3.0
mm vinylon fiber! I (Unitika Kasei ■AA2/4D
) was used in an amount of 0.5% by weight, but the same test as in Example 4 was conducted. The test results are shown in Table 6.

(The following is a blank space) Table 6 Segregation of powder particles is also suppressed by dispersing vinylon fibers.

1. It is possible to effectively prevent segregation and separation phenomena due to differences in specific gravity, particle size, etc. in granular materials or mixtures thereof, and it is possible to obtain homogeneous granular materials.

Claims (1)

[Scope of Claims] 1. A method for preventing segregation and separation of powder and granular material, which comprises dispersing fine diameter fibers in powder and granular material. 2. The method for preventing segregation and separation of powder and granular material according to claim 1, wherein the powder and granular material is a mixture of powder and granular materials of different substances. 3. The method for preventing segregation of powder or granular material according to claim 1 or 2, wherein the fine diameter fibers have a diameter of 100 μm or less. 4. The method for preventing segregation of powder or granular material according to claim 3, wherein the fine diameter fibers are polytetrafluoroethylene fibrils.