JPS5936658B2 - Ryujiyoufutsusogomu Narabini Sonoseizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a granular fluororubber and a method for producing the same.

Fluororubbers, such as vinylidene fluoride/hexafluoropropene copolymer, vinylidene fluoride/
Tetrafluoroethylene/hexafluoropropene copolymers exhibit outstanding properties such as heat resistance, oil resistance, solvent resistance, and chemical resistance, so they are used in all industrial fields such as chemistry, machinery, electric aircraft, automobiles, and ships. It is widely used as an industrial material.

This fluororubber is generally produced by coagulating and isolating polymer particles from an aqueous dispersion of a fluororubber polymer obtained by polymerization (usually washed with water), using a box dryer, ventilation band dryer, or roll dryer. It is considered to be a product that has been dried using a dryer such as a dryer.

However, in all of the fluororubbers produced in the above-mentioned dryers, the polymer particles fuse together to form a lump or plate shape during drying, making handling such as weighing, transporting, and packaging inconvenient. This poses an obstacle to the automation and continuity of the kneading and molding processes in processing. Further, all of the above-mentioned drying methods have drawbacks such as poor drying efficiency, requiring relatively high temperatures (usually around 130° C.) for drying, and coloring the fluororubber. For example, in the method using a box dryer, centrifugally dehydrated fluororubber particles are placed in a drying tray made of wire mesh and dried at a temperature of about 130°C in the box dryer. Since it fuses under its own weight to form a lump or a plate, the efficiency of contact with heated air is extremely poor, resulting in uneven heating. As a result, much time and heat are required for drying, and the fluororubber may become colored. Furthermore, recently, according to Japanese Patent Application Laid-Open No. 59-84650, a dispersion in which fluororubber powder containing a fluorine-containing plastic component and having a particle size of 10 to 50 μm or less is coagulated from an aqueous dispersion of the fluororubber polymer. It is manufactured by spray drying the liquid through a fluid injection nozzle in air at a temperature of about 121° C. or higher. However, since this fluororubber powder is made by drying the coagulated dispersion as it is, it contains components such as emulsifiers and initiators used in polymerization, which impairs its properties, and the resulting particles are granular. Since it is a fine powder with a diameter of 10 to 50μ or less, it lacks sufficient powder fluidity, tends to generate static electricity, and is also prone to reagglomeration, making it necessary to take appropriate measures to prevent reagglomeration, such as by adding an anti-blocking agent. . The present invention overcomes the above-mentioned drawbacks of the conventional fluorocarbon rubber and its drying method. The total amount of 3+ mesh sieving and 24 mesh sieving amount is 5% by weight or less (particle size is approximately 0.7 to 5.5 mm)
Particulate fluororubber is provided, which is obtained by coagulating polymer particles from an aqueous dispersion containing a fluororubber polymer obtained by polymerization and then monopolizing the polymer particles. It is produced by separating and then fluidized drying in an atmosphere at a relatively low temperature of 50 to 110°C.

Here, the above apparent temperature is measured in accordance with the method for measuring the apparent density of polytetrafluoroethylene molding powder described in JIS K689l, and calculated by the following formula: A: Weight of the receiver (
y) B: Content capacity of the receiver (g) c: Weight of the receiver containing the sample (y) The fluororubber used in the present invention contains vinylidene fluoride and at least one other fluid. Suitable fluorine-containing monomers that are copolymers with elementary monomers include, for example, tetrafluoroethylene, trifluoroethylene, trifluorochloroethylene, hexafluoropropene, pentafluoropropene, trifluoropropene, Examples include perfluoroalkyl perfluorovinyl ethers such as trifluorobutene and perfluoromethyl perfluorovinyl ether.

Furthermore, in the fluororubber of the present invention, at least one of the above monomers is polymerized as a plastic component in the presence of the fluororubber copolymer, so that the plastic component is 2% of the fluororubber copolymer component. This includes so-called improved fluororubber containing up to 20% by weight. This type of fluororubber has particularly good powder fluidity as a granular fluororubber, and is therefore more suitable for the present invention. The fluororubber used as a raw material is generally prepared by coagulating and isolating fluororubber polymer particles obtained by emulsion polymerization of the monomers mentioned above in an aqueous medium in the presence of a polymerization initiator by a conventional method (usually (washed with water) is used,
It is usually in the form of granules containing about 25% or less water by weight (mainly 0.
The particle size is approximately 0.5 to 0.5 and consists of primary particles of 0.01 to 0.5μ.
It is a secondary particle of 5 mm.

) is a fluoro rubber. If the particle size of the fluororubber isolated from the aqueous dispersion is too large, it can be easily ground to the above particle size using a crusher such as a flash mixer.
In the present invention, during coagulation, fillers such as carbon black, talc, calcium carbonate, silica, etc., which do not have a coagulating effect, are added and dispersed in the required amount into the aqueous emulsion of fluororubber. It can also be analyzed. In this case, since the required amount of filler is mixed during coagulation, the particle size of the co-coagulated product is relatively easy to align, and it is more difficult for the fluororubber particles to fuse together during the subsequent drying process, making it more difficult to handle. The advantage of making it easier is recognized. This wet raw material rubber is put into a fluidized drying chamber maintained at a temperature of 50 to 110° C., which is sufficiently lower than the conventional drying temperature, and is fluidized and dried in a floating suspension state by hot air blown up from below.

In drying, temperature conditions are particularly important;
Must be in the range of 110°C. Preferably 60~
A temperature of 100°C should be employed. Drying temperature is 1
If the temperature is 10° C. or higher, the particles of fluororubber will fuse together, making it difficult to obtain the desired type of granular rubber, and the fluororubber may become colored, which is not preferable. Further, if the drying temperature is below 50°C, sufficient drying will not be achieved. As for the other fluidization conditions, an air flow rate that allows the fluororubber to float and be suspended is appropriately selected according to the fluidized bed volume, the particle size of the fluororubber, the amount of the fluororubber added, etc., according to a conventional method. The type of fluidized dryer is not particularly limited, and any type can be used, and either a batch type or a continuous type can be adopted. In this way, the wet raw material fluoro rubber is fluidized and dried. As a result, the individual granular fluororubber particles are hardly fused together, and the dry granular fluororubber which is the object of the present invention can be produced.

The dry fluororubber of the present invention has an apparent density of 0.3 to 1.2.
7/ml, and the total amount of the 3-f mesh sieving amount and the 24 mesh sieving amount of the Tyra standard sieve is 5% by weight or less.

When the apparent density is less than 0.37/ml, it is bulky and difficult to handle, and the powder flowability is poor.
If it is larger, it will be difficult to perform roll kneading during processing and the dispersibility with the compounding agents will also be poor. In addition, when the total amount of the sieved amount and the sieved amount using the Tyra standard sieve is 5% by weight or more, the powder fluidity is poor, it is difficult to handle, and the dispersibility with compounding agents during vulcanization is also poor. . The particle size of dried fluororubber is essentially determined by the particle size of the raw material particles, and in most cases, the particle size of the raw material particles is maintained almost as is. Further, the shape is spherical or a small piece shape close to the spherical shape, and generally, the smaller the particle size, the closer to the spherical shape. The granular fluororubber fluidized and dried in the above manner is obtained with almost no moisture, cooled to room temperature by a conventional method, and recovered as a product.

The granular fluororubber of the present invention can be made easier to handle by adding talc, calcium carbonate, silica, etc. as an anti-blocking agent or separating agent, if necessary. Of course, it is advantageous, as mentioned above, to add these at the time of coagulation. Next, an example of the drying method of the present invention will be explained with reference to the accompanying drawings.

A suitable amount of wet granular fluoro rubber with a particle size of about 0.5 to 5 mm is put into the fluidized drying chamber 1 through the sample input port 3, and the air heated by the heater 6 by the blower 7 is passed through the air filter 15 into the perforated plate 2. The air is blown up from the lower part into the fluidized drying chamber 1, and the granular fluororubber in the fluidized drying chamber 1 is dried while being fluidized.

The fluorine rubber that has been fluidized and dried for a sufficient period of time is taken out from the sample outlet 4 and cooled to room temperature to prevent it from fusing. In addition, in the drawing, A is a cyclone, B is a thermometer,
C represents a temperature controller, and Dl and D2 represent air volume controllers. According to the drying method of the present invention, the desired granular fluororubber can be easily obtained, and since the rubber particles and hot air (lower temperature than conventional methods) come into contact with each other efficiently, drying can be carried out effectively in a short time. .

Another advantage is that the rubber is not colored because it is dried under uniform temperature conditions. The obtained granular fluororubber of the present invention has an apparent density of 0.3 to 1.27/ml.
Since the total amount of the 3-F mesh sieving amount and the 24 mesh sieving amount of the Tyra standard sieve is 5% by weight or less, the powder has a spherical shape or a shape close to it, so it has powder fluidity.
It is advantageous for handling and automation such as weighing, transporting and packaging.

In addition, in terms of processing, the preliminary powder blend allows sufficient mixing with compounding agents such as vulcanizing agents and fillers, thereby improving work efficiency in the next kneading step. Furthermore, it is also suitable for automation and continuous kneading and molding processes such as a continuous extrusion kneading method in which a powder compound is formed and the powder compound is directly fed into an extruder. It also has the advantage of being easy to blend when blended with other synthetic rubbers or synthetic resins, and easily dissolved in solvents when used as a liquid solution type. The granular fluororubber of the present invention is vulcanized in the same manner as conventional fluororubbers under normal vulcanization conditions, and has physical properties comparable to those of vulcanized rubber obtained from conventional types of fluororubber. vulcanized rubber. The present invention will be explained below with reference to Examples.

"Parts" indicate parts by weight. Example 1 Fluororubber (vinylidene fluoride/hexafluoropropene copolymer, molar ratio: 78/22, intrinsic viscosity [η] measured at 35°C in methyl ethyl ketone: 0.78)
The fluororubber particles are coagulated by adding an aqueous solution of magnesium chloride to the aqueous dispersion of the slurry, washed with water, and the slurry is dehydrated using a continuous centrifugal dehydrator at a centrifugal force of 1000 G to reduce the water content to approximately 20% by weight. A viscous fluororubber containing the following was obtained.

The particle size of this granular fluororubber was mostly about 2 to 5 mm. This granular fluororubber 1.2k9 was dried to a diameter of 200mm using a fluidized dryer as shown in the attached drawing. × height 4
00CfL fluidized drying chamber and 7T of 98℃ hot air.
It was fed at a ratio of I1/- and fluidized to dry. Approximately 6 minutes after the start of drying, a portion of the fluoro rubber began to adhere to the walls of the drying chamber, and after 7 minutes, the supply of hot air was stopped and the drying was completed. The dried fluororubber is white and granular, with an apparent density of 0.87/ml, and has a target particle size of granular fluororubber (3-f mesh sieving amount of Tyra 1 standard sieve and 24 mesh sieving amount). The total amount including the sieved amount was 3.4% by weight).
Note that the water content was 0.18% by weight. Example 2 The same granular fluororubber as in Example 1 was fluidized and dried in the same manner as in Example 1, except that 60°C hot air was introduced.

A portion of the fluoro rubber began to adhere to the wall around 26 minutes after the start of drying, and the drying was completed 30 minutes later. The obtained fluororubber had an apparent density of 0.7 t/ml and a target particle size (the total amount of the 3+ mesh sieving amount and the 24 mesh sieving amount of the Tyler standard sieve was 3.8% by weight). The water content was 0.17% by weight. Example 3 The same granular fluororubber as in Example 1 was fluidized and dried in the same manner as in Example 1 except that hot air at 105° C. was introduced.

A portion of the fluoro rubber began to adhere to the wall around 5 minutes after the start of drying, and the supply of hot air was stopped after 6 minutes. When collecting fluorocarbon rubber, adhesion of particles to each other was observed in a small part, but the target particle size (Tyler standard sieve 3 + mesh sieving amount and 2
The total amount including the sieving amount of 4 meshes was 2.7% by weight). The apparent density of this fluoro rubber is 0.8V/m
ι, the water content was 0.18% by weight. Example 4 The same granular fluororubber as in Example 1 was fluidized and dried in the same manner as in Example 1, except that hot air at 50°C was introduced.

Even 60 minutes after the start of drying, no polymer was observed to adhere to the chamber walls, and the supply of hot air was stopped after 70 minutes. The apparent density of the obtained fluorocarbon rubber was 0.6 V/g, and the particle size was within the desired range (the total amount of the 3+ mesh sieving amount and the 24 mesh sifting amount of the Tyler standard sieve was 4.5 V/g). 1% by weight), and the water content was 0.53% by weight. Example 5 Fluororubber (vinylidene fluoride/hexafluoropropene/tetrafluoroethylene copolymer, molar ratio: 69.7/12.8/17.5, intrinsic viscosity measured at 35°C in methyl ethyl ketone [η]: An aqueous solution of magnesium chloride was added to the aqueous dispersion of 0.90), the fluororubber particles were coagulated, and dehydrated in the same manner as in Example 1 to obtain granular fluororubber containing approximately 20% water by weight. I got it.

When the obtained moist granular fluorocarbon rubber was fluidized and dried using the same conditions as in Example 1, the apparent density was 0.8 y/m.
A granular fluororubber was obtained in which the total amount of the 3+ mesh sieve and the 24 mesh sieve of the Tyler standard sieve was 4.1% by weight and the water content was 0.17% by weight.

A photograph of the obtained granular fluororubber is attached here as a reference. Example 6 Pre-emulsion polymerized vinylidene fluoride/hexafluoropropene copolymer (molar ratio: 78/22, intrinsic viscosity [η] measured at 35°C in methyl ethyl ketone:
0.78) (copolymer concentration 19.6% by weight)
), tetrafluoroethylene was emulsion polymerized using an ammonium persulfate polymerization initiator, and the polymer concentration was 21.5.
An aqueous dispersion of % by weight was obtained.

A polymer was coagulated from this dispersion using magnesium chloride, and after washing with water, a continuous centrifugal dehydrator was used in the same manner as in Example 1 to obtain a polymer with a particle size of about 0.5 to 4 mm and a water content of about 20% by weight. Granular fluororubber (fluororubber copolymer/polytetrafluoroethylene (weight ratio): 94/6) was separated. Using this granular fluororubber as a raw material, fluidized drying was performed using the method of Example 1, and the apparent density was 1.0 y/mι, and the total amount of the 3+ mesh sieving amount and the 24 mesh sieving amount of the Tyler standard sieve was 1. Granular fluororubber with a water content of 0.5% by weight and a water content of 0.16% by weight was obtained.

Example 7 According to the polymerization method of Example 6, vinylidene fluoride/hexafluoropropene copolymer (molar ratio:
Example 6 was obtained from the aqueous dispersion obtained by emulsion polymerization of vinylidene fluoride in the presence of 78/22, intrinsic viscosity [η]: 0.78) measured at 35°C in methyl ethyl ketone.
Granular fluororubber (fluororubber copolymer/polyvinylidene fluoride (weight ratio): 88
．． 1/11.9) was used as a raw material, fluidized drying was performed in the same manner as in Example 1, and the apparent density was 0.8 y/g, the total amount of the 3+ mesh sifting amount and the 24 mesh sifting amount of the Tyler standard sieve. Granular fluororubber with a water content of 1.7% by weight and a water content of 0.16% by weight was obtained.

Example 8 According to the polymerization method of Example 6, vinylidene fluoride/
Hexafluoropropene copolymer (molar ratio: 78/22
, the intrinsic viscosity measured at 35°C in methyl ethyl ketone [η
]: 0.78)) was separated from an aqueous dispersion obtained by copolymerizing vinylidene fluoride and tetrafluoroethylene in the same manner as Example 6.
Fluoro rubber copolymer/vinylidene fluoride-tetrafluoroethylene copolymer (molar ratio: approximately 60/40) (
Weight ratio): 87/13) was used as a raw material and fluidized drying was performed in the same manner as in Example 1, and the apparent density was 0.9 V/ml, the amount of 3-F mesh sieving and the amount of 24 mesh sieving of one Tyrer sieve. The total amount is 1.6% by weight, and the water content is 0.16% by weight.
Granular fluororubber was obtained.

It should be noted that the granular fluororubbers of Examples 6 and 7 all had better flowability from the funnel of the apparent density measuring device when their apparent densities were measured in accordance with JIS K689l, as compared to the other examples. , less tendency to form bridges,
It was confirmed that it has excellent fluidity.

Comparative Example 1 The raw material fluoro rubber of Example 1 was placed in a wire mesh drying tray (width 350 cTrL x length 750 cm x height 35 CT) with 50 meshes.
IL) and dry in a box dryer at 130℃ for 6 hours. Dry.

After drying, the fluororubber is plate-shaped and has a water content of 0.15% by weight.
It was hot. This plate-shaped fluororubber could not be made into granules by mechanical crushing. Next, 100 parts of the fluororubber obtained in each Example and Comparative Example were mixed with 20 parts of MT carbon black, 3 parts of magnesium oxide (highly active), 6 parts of calcium hydroxide, and 2 parts of bisphenol AF. O part and 8-benzyl-1,8-diazabicyclo(5.4.O
) Mixed with 0.35 part of undecenoium chloride, breath cured at 170°C for 10 minutes, then 230°C.
Oven vulcanization was carried out for 24 hours in an oven.

Table 1 shows the physical properties of the obtained vulcanized rubber. However, in Examples 6 and 8, bisphenol AF was added to 2
．． 4 parts and 8-benzyl-1,8-diazabicyclo(5.4.0)-J me[undecenonium chloride 0
．． 45 parts were used.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a fluidized fluidized dryer used in the method of the present invention. 1... Fluid drying chamber, 2... Perforated plate, 3...
...Sample input port, 4...Sample removal port, 5
... Air filter 1, 6 ... Heater, 7 ... Blower, A ... Cyclone, B ... Thermometer, C ... ····air conditioner,
Dl, D2... Air volume regulator.

Claims (1)

[Claims] 1. The apparent density is 0.3 to 1.2 g/ml, and the total amount of the 31/2 mesh sieving amount and the 24 mesh sieving amount of the Tyler standard sieve is 5% by weight or less. Granular fluororubber characterized by: 2. Fluororubber is coagulated and isolated from its dispersion, and the obtained granular fluororubber is fluidized and dried in an atmosphere at a temperature of 50 to 110°C, so that the apparent density is 0.3 to 1.2.
Granular fluororubber characterized in that the total amount of the 31/2 mesh sieving amount and the 24 mesh sieving amount of the Tyler standard sieve is 5% by weight or less in terms of g/ml. Production method.