JPS62201231A - Preparation of minute foamed body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing microfoams made of thermoplastic resin.

Prior art A method for foaming thermally expandable microspheres in which a volatile liquid foaming agent is encapsulated in a thermoplastic resin shell is described, for example, in U.S. Pat. No. 3,611.
583, Japanese Patent Publication No. 59-53290, Japanese Patent Publication No. 17-25148, etc.

The technology described in US Pat. No. 3,611,583 spreads an aqueous solution (slurry liquid) in which thermally expandable microspheres are dispersed onto a moving horizontal belt, deposits the microspheres, and heats them with air or steam. Along with removing water,
This is a method in which microspheres are heated and foamed.

In this method, the microspheres are heated and foamed in a state where they are in contact with each other or deposited in a layered state on a belt, so that the particles not only coagulate due to fusion and form huge agglomerated particles, but also Since the deposition state of the particles is not uniform, there are drawbacks such as the microspheres are not heated uniformly by the belt 2 and the degree of foaming is non-uniform.

In addition, it is very difficult to disperse the generated aggregated particles, and conventionally they were crushed and dispersed using a high-speed shearing machine such as a Henschel mixer or a dry crusher such as a hammer mill, but the former method However, it is not easy to disperse the aggregated particles, and there are problems such as large variations in particle size and the destruction of the foam particles themselves.The latter method has problems in terms of heat resistance and strength of the foam. be. Furthermore, this method requires a pneumatic transport collection device, resulting in an increase in equipment.

Special Public Showa 5! The technology described in J-53290 is a method in which a slurry of thermally expandable microspheres is sprayed into heated air, the microspheres are dried and foamed, and the foamed microspheres are separated and collected from the air. be.

However, in this method, the heat required for foaming is obtained from heated air, and a collection device must be used to separate the foam from the air, resulting in an increase in equipment.

The technique described in Japanese Patent Publication No. 47-25148 is a method in which thermally expandable microspheres themselves are dropped into an empty tower, and heated air or steam is injected onto the microspheres to foam the particles.

However, in this method, thermally expandable microspheres are heated by falling naturally, so individual microspheres are heated uniformly due to differences in falling speed depending on the size of the microspheres and non-uniformity of air flow within the sky column. Not only will the degree of foaming become uneven, but
There are drawbacks such as the need for huge equipment such as sky towers.

Fishing Hong μ! When foamed microspheres are produced using the conventional method, as shown in the double series of ``Eave Shomo One Side - Shouting Harvest,'' the heat during foaming causes the microspheres to fuse together and coagulate, forming huge aggregated particles. Easy to do. Furthermore, there is no suitable method for uniformly dispersing the aggregated particles, and the particle sizes of the produced aggregated foams vary widely. Furthermore, it is difficult to obtain a product with uniform density because the degree of foaming of individual thermally expandable microspheres is not uniform. Further, there are problems such as the need for huge equipment in implementing the conventional method for manufacturing microfoams.

The present invention solves the second problem, allows thermally expandable microspheres to be uniformly foamed, further minimizes their agglomeration, and makes it possible to easily reduce the generated giant agglomerated particles to a uniform particle size. It is an object of the present invention to provide a method for dispersing and a method that can achieve the following methods with a simple device.

MEANS FOR SOLVING THE PROBLEMS The present invention involves heating a slurry liquid and vapor of heat-expandable microspheres having a thermoplastic resin outer shell containing a volatile liquid blowing agent to a predetermined pressure and temperature in a foaming tube. The first step is to heat and foam the microspheres by continuously mixing them so as to maintain the temperature, and then to rapidly cool the microspheres. The present invention relates to a method for producing microfoams, which includes a second step of dispersing the aggregated foams by passing the foams continuously.

Thermally expandable microspheres that can be used in the present invention are disclosed in US Pat.
It can be easily produced by the method described in Patent No. 11583 and the like.

Thermally expandable microspheres have an outer shell of a thermoplastic resin such as acrylonitrile, methacrylate, styrene, vinyl chloride, vinylidene chloride, acrylate, etc., and a volatile liquid foam such as butane, propane, i-butane, n-pentane, i -Pentane, a hydrocarbon such as neo-pentane, a freon such as trichlorofluoromethane, etc. may be included. As a commercially available product, for example, Microsphere-F-30 or F-50 (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) can be easily prepared manually. Further, the size thereof is not particularly limited, and may be appropriately selected and used with a diameter of 1 to 500 μm.

The thermally expandable microspheres are used as a slurry by dispersing them in water in a range of 2 wt% to 30 wt%. If it is less than 2 wt%, the production efficiency will be poor, and if it is more than 30 wt%, the fluidity of the slurry liquid will be poor and the production efficiency will not be equal to the increased amount.

A feature of the present invention is that while the slurry of thermally expandable microspheres is passed through a foaming tube, heated steam (for example, 120 to 22
0°C) to rapidly raise the temperature of the slurry to above the foaming temperature, and then
sec) After holding, the method is to rapidly cool it by contacting it with cold water, etc. By employing such means, continuous operation becomes possible and the temperature, pressure, residence time, etc. within the foaming tube can be controlled. As a result, the thermally expandable microspheres on each side can be uniformly and easily foamed to any degree. The foaming tube may have any structure as long as it can be supplied with the slurry liquid and steam, mixed and discharged, and preferably has a cylindrical shape.

The size of the foaming tube can be appropriately selected depending on the production capacity. Generally, a diameter of 10 to 50 mm and a length of 150 to 1,000 mm are preferred for practical use.

Specifically, for example, if a cylindrical foam tube with a diameter of 16 concave and a volume of 60 mQ is used, P-50E thermally expandable microspheres 2 to
n can be produced in 28-33 days.

According to the present invention, microfoams are produced by continuously mixing slurry liquid and steam using a compact foaming tube, so that no increase in equipment is required.

The mixed steam has the function of stirring and heating the slurry, and it evenly heats the thermally expandable microspheres dispersed in the water and vaporizes the volatile liquid blowing agent inside the microspheres. Foam.

The temperature inside the foaming tube is adjusted by the amount of slurry liquid flowing into the foaming tube, and the temperature and flow rate of water vapor mixed simultaneously with the slurry liquid.

The temperature in the foaming tube according to the present invention is preferably determined by the temperature measured by a thermocouple installed in the center of the foaming tube, and corresponds to the residence time in the foaming tube and the desired degree of foaming of the thermally expandable microspheres. There are 6 that should be set. For example, if it is desired to increase the degree of foaming and obtain a foam with a lower apparent density, the temperature may be increased and the residence time may be increased. If you want to reduce the degree of foaming and obtain a foam with a low apparent (J density), you can lower the temperature and shorten the residence time.

The temperature inside the foaming tube is 50°C to 200°C, preferably 80°C.
It should be set in the range of 8C to 150C.

If the temperature is set higher than 200° C., foams tend to fuse or aggregate, and it becomes difficult to control the degree of foaming. If the temperature is set lower than 50°C, the microspheres cannot be foamed.

The pressure in the foaming tube depends on the amount of slurry liquid flowing into the foaming tube and the pressure of the steam that is mixed in at the same time,
This is one factor that controls the degree of foaming of microspheres.

The residence time in the foaming tube should be set in accordance with the temperature and pressure in the foaming tube mentioned above and the desired degree of foaming of the thermally expandable microspheres. It is adjusted by the flow rate of steam, the flow rate of slurry liquid flowing out from inside the foaming tube, and the pressure inside the foaming tube.

Next, the heated and foamed microsphere foam-containing slurry liquid flows out of the foaming tube, is mixed with cooling water, and is rapidly cooled. Rapid cooling makes it difficult for foamed microspheres to aggregate. The larger the amount of cooling water, the greater the effect, but the amount of water may be sufficient as long as it can appropriately suppress agglomeration of particles.

Another feature of the present invention is that the foamed microsphere-containing slurry liquid foamed and rapidly cooled as described above is continuously passed between two rotating grindstones arranged with a certain gap between them. Another advantage is that the microsphere agglomerated particles generated during foaming can be efficiently dispersed to a uniform particle size without destroying the particles themselves.

-81 The grindstone used in the present invention may be of a type in which two disc-shaped pieces are placed facing each other and one or both of the grindstones are rotated.

The gap between the grinding wheels may be appropriately selected and set in consideration of the size of the thermally expandable microspheres used as raw materials and the degree of foaming of the microspheres, but it is preferably set to 125 μm or more. If it is smaller than 125 μm, the foamed microspheres themselves are likely to be destroyed. The particle size of the grindstone used may be selected depending on the type of thermoplastic resin that is the outer shell of the thermally expandable microspheres used as the raw material, and a grindstone of 16 to 325 mesh, preferably 60 to 120 mesh, is used. 325
If it is smaller than mesh or larger than 1.6 mesh, it will not be possible to disperse the aggregated particles well.

The rotational speed of the grindstones is set so that the relative rotational speed of one grindstone and the other grindstone is 50 Orpm to 1000 Orpm, preferably 2000 rpm to 5000 rpm. If the speed is lower than 500 rpm, the agglomerated particles cannot be dispersed well, and if the speed is higher than 10,000 rpm, the foamed microspheres themselves will be destroyed.

After passing between the grinding wheels, the foam microspheres are separated from the slurry liquid,
dried.

The microfoam produced as described above can be used in known applications such as, but not limited to, heat insulating agents, soundproofing agents, gungyong agents, and electrical insulating agents.

Yet another feature of the invention is that the apparatus for carrying out the invention can be compactly assembled.

The present invention will be explained in more detail below using examples.

Example 1 FIG. 1 is a flow sheet showing a schematic diagram of a foaming apparatus constructed according to the present invention.

Thermal expandable microspheres Microsphere-F-30 (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.: outer shell resin, vinylidene chloride-acrylonitrile copolymer) (particle size 10-20μff) 50wt
% was introduced into the slurry tank (1) from the water introduction pipe (18) and mixed with the stirrer (5) to prepare a 5 wt % slurry of F-30.

The slurry liquid is pumped through a foaming tube (diameter 16 mm, volume 12 (JmQ
Made of stainless steel (SUS 304 TP) (4)
Furthermore, water vapor (temperature: 47° C., pressure indicated by pressure gauge (9) of 3.0 Kg/am') was supplied from the steam introduction pipe (II) and mixed with the slurry liquid. After mixing, the temperature of the slurry liquid is detected by a thermocouple (6) installed in the center of the foaming tube (4), and a temperature indicator controller (7) is used to detect the temperature of the slurry liquid.
), and the amount of steam mixed in was adjusted by the flow control valve (8) so that the slurry liquid reached the set temperature. In this example, the temperature was set at 120°C.

At that time, the pressure gauge (10) showed 1.8 Kg/cm2.

The slurry liquid flowing out from the foaming tube discharge part (12) is treated with cooling water (water temperature 15°C) supplied from the cooling water introduction pipe (22).
) and the slurry liquid was cooled to 50-60°C and flowed into the upper part of the colloider (14).

At that time, the flow meter (I3) indicated 12 liters/min. Expanded particles 30-70μm that are not agglomerated at this point
60-70% of the particles were agglomerated, and 30-40% of the particles were agglomerated to a size of 100 μm or more.

The inside of the colloider (14) has two disk-shaped grindstones (22) and (23) having a cross section as shown in FIG. Arrows (24) in the figure indicate the flow of slurry liquid passing between the grinding wheels. The grindstones (22) and (23) used had a grindstone grain size of 100 mesh, the clearance between them was 250 μm, and the grindstone (22) was fixed while the grindstone (23) was rotated at 360 rpm. 18 liters of slurry liquid collected at the top of the colloider (14)
The agglomerated particles were dispersed by flowing between the grindstones at a speed of min.

After passing through the colloider (14), the slurry liquid is sent to an intermediate tank (15), where it is mixed and diluted with a large amount of water supplied from the water introduction pipe (21), and then is further transferred to a centrifugal dehydrator (17) by a pump (16). ) will be sent to. Microfoams were separated from the slurry liquid using a centrifugal dehydrator (17). The separated microfoam was dried to form a product.

The obtained microfoam has non-agglomerated foamed particles of 30~
70 μm is 97-99%, and aggregates to 100%.
Several percent of the particles were larger than μm. The apparent density was 0.02 g/ml.

Example 2 Example 1 except that the temperature setting of the foaming tube was varied.
I did the same thing.

The microfoams obtained at each temperature had 97-99% non-agglomerated foam particles with a diameter of 30-70 μm.

The relationship between the temperature of the foaming tube and the appearance of the foam obtained is determined by
Shown in the figure.

As is clear from FIG. 3, if the present invention is used, approximately 0.17
Foams can be obtained with any apparent density in the range from g/cm3 to about 0.02 g/cm3.

Effects of the Invention According to the present invention, microfoams having a predetermined apparent density within a wide range of apparent densities and having a uniform particle size containing almost no aggregated particles can be obtained using a compact device.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a flow sheet of a foaming device, FIG. 2 is a schematic cross-sectional view of a grindstone, and FIG. 3 is a diagram showing the relationship between apparent density and foaming tube temperature. The symbols in the figure are as follows.

Claims (1)

[Claims] 1. A slurry of thermally expandable microspheres having a thermoplastic outer shell containing a volatile liquid blowing agent and steam are continuously mixed in a foaming tube to maintain a predetermined pressure and temperature. The first step is to heat and foam the spheres, and then rapidly cool them.The second step is to continuously pass the obtained foam slurry through the gap between two rotating grindstones to disperse the aggregated foam. A method for producing a microfoam, comprising the steps of 2.