JPH0365375B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coagulating polymer latexes.

In the chemical industry, large quantities of coagulable substances, such as polymer latex and rubber latex, are handled, and some of them are used in liquid form as adhesives and paints, but most of them are treated with coagulants. Currently, it is used after solidifying. Therefore, although the coagulation operation is an important operation in these fields, currently the coagulation methods and coagulation apparatuses are based on old techniques obtained through conventional experience.

By the way, speaking specifically in the resin industry, when producing polymer powder from polymer latex produced by emulsion polymerization, it is generally coagulated by bringing the latex into contact with a coagulant consisting of acids or inorganic polyvalent salts. Usually, the polymer is solidified by a method such as post-heat treatment, and then subjected to operations such as dehydration and drying to form a dry powder of the polymer.
However, according to the commonly used method, the particles of the powder obtained have an irregular shape and a wide particle size distribution, and while they contain coarse particles, a considerable amount of fine powder is also present. Therefore, there is a reduction in yield due to the scattering of the fine powder, or environmental problems, and furthermore, clogging at piping, storage tank outlet, etc. due to the low fluidity of the powder, deterioration of the working environment due to dust generation, and increased risk of dust explosion. It has some undesirable problems. In addition, the bulk specific gravity of the polymer powder is small and dehydration properties in a dehydrator are poor, so transportation and storage costs are high, and moreover, a large amount of thermal energy is consumed in the drying process.

In recent years, in view of the importance of coagulation operations, many studies have been conducted to improve the powder properties of polymer powders. One of these trends in research and development is the slight improvement of conventional coagulation methods or coagulation equipment, and other methods include methods such as spray drying and vapor phase coagulation that utilize gas phase reactions. However, such methods still produce low-grade powders, impose large energy costs and construction costs, and have not yet become a definitive solution.

Under these circumstances, the present inventors have developed an invention in which a high bulk specific gravity powder and granular material substantially free of fine powder and coarse particles can be obtained by discharging emulsified latex into a coagulating liquid from a capillary that satisfies specific conditions. Previously, patent application No. 1983-73115 (Japanese Patent Application No. 187322)
A patent application was filed as

Based on the previous invention, the present inventors conducted further intensive studies and found that a nozzle for coagulating latex, in which a thin tube having a specific gap and a specific length is provided on a substrate, can be used to coagulate polymer latex. The present invention was achieved by discovering that it is possible to produce a polymer powder with extremely excellent physical properties.

In the present invention, when a polymer latex is coagulated in a coagulation liquid to obtain a polymer powder, the gap between the capillary tubes is 1 mm or more on the substrate, and the protrusion length on the substrate is 3 mm.
A latex coagulating nozzle provided with a plurality of thin tubes as described above is used, and the polymer latex is discharged into a coagulating liquid from the thin tubes of the latex coagulating nozzle and coagulated. It is in the coagulation method.

The structure of the latex coagulating nozzle used in the present invention will be explained based on the drawings. Figure 1 shows the case where a thin tube is inserted to the thickness of the substrate.
In addition, a side cross-sectional view 1-1 and a front view 1-2 according to trigonometry in the case of a structure in which the substrate and the holder can be separated, in which 1 is the substrate, 2 is a thin tube, 3 is an adhesive, 4 is a gasket, and 5 is a holder, and 6 is a fastener.
FIG. 2 is a cross-sectional view of the case where the substrate is assembled so that it is located in the center of the thin tube, and the substrate and the holder are integrally formed so that the substrate also serves as a holder. 1' is the substrate; 2 is a tubule.

The structure of the nozzle for latex coagulation in the present invention is not limited to that shown in FIGS. 1 and 2, but the key point is that the gap between the thin tubes is 1 mm or more, and the length of the protrusion on the substrate, that is, A in FIG. Basically, any structure may be used as long as a plurality of thin tubes are provided on the substrate so that the length of B in FIG. 2 is 3 mm or more.

As can be seen from FIGS. 1 and 2, which are representative examples, the external structure of the nozzle for latex coagulation according to the present invention has a characteristic structure similar to that used for fresh flowers, which is composed of a plurality of thin tubes. It has a structure. This Kenzan-like structure improves the contact between the coagulable substance and the coagulating liquid, allowing the coagulable substance discharged from the nozzle to coagulate in a distinctive shape, resulting in a polymer powder with extremely excellent powder properties. This makes it possible to manufacture That is, the polymer latex, which is a coagulable substance, is discharged from inside the nozzle holder through a thin tube into the coagulating liquid. In the present invention, the nozzle is oriented so that the coagulating liquid flows quietly in the same direction as the polymer latex is discharged. and the amount of coagulating liquid is adjusted. On the other hand, the polymer latex discharged from the coagulation nozzle is placed on a laminar coagulation liquid and allowed to coagulate while flowing gently. The gap between the thin tubes of the nozzle should be 1 mm or more.
The protrusion length from the board is 3 mm or more. The coagulating liquid is flowed in the same direction as the discharge direction of the polymer latex, but the flow of the coagulating liquid is obstructed by the nozzle holder or the substrate, and turbulence occurs on the downstream side of these, that is, near the capillary, and a vortex is generated. In order to solidify without being affected by this vortex, it is necessary to make the tip of the thin tube protrude into the laminar region that exists outside the vortex region. The length of the protrusion that reaches the laminar region varies depending on the flow rate of the coagulating liquid, etc., but after careful consideration, we found that the length of the tube is 3 mm or more from the substrate.
Preferably, if it protrudes by 10 mm or more, the tip of the capillary will reach the laminar region that exists outside the vortex region, and the polymer latex discharged from the tip will undergo a coagulation reaction while quietly flowing on the laminar coagulation liquid. It has been found that a polymer powder with a characteristic shape and high bulk specific gravity, which is substantially free of fine powder and coarse particles, can be obtained. In the present invention, the protrusion length of the thin tube from the substrate is not substantially limited, but from the viewpoint of industrial productivity, the upper limit is 200 mm.
It is the rank.

If the gap between the capillary tubes is too narrow, it will be difficult for the coagulating liquid to flow between the capillary groups, making it impossible to achieve good coagulation except in the peripheral areas of the capillary groups. On the other hand, even if the coagulating liquid is forced to flow between the groups of capillary tubes, if the gap between the capillary tubes becomes less than 1 mm, the coagulable material discharged from each capillary will fluctuate due to fluctuations in the jet flow caused by the coagulable material discharged. They coalesce together to form large lumpy particles, making it impossible to produce powder with good properties. Therefore, in the present invention, it is necessary that the gap between the thin tubes be 1 mm or more. Note that the gap between the thin tubes is up to about 20 mm, preferably up to about 10 mm, considering the production rate of the polymer powder.

The materials of the substrate constituting the nozzle for latex coagulation include glasses and inorganic sintered bodies; polymethyl methacrylate, polyvinyl chloride, polyamide, polyester, polycarbonate, polypropylene, polyethylene, ABS resin, polyacetal, AS resin, fluororesin, etc. Synthetic resins; metals such as stainless steel, copper, platinum, gold, and lead are preferred, but any material can be used as long as it is chemically stable against coagulating liquids and coagulable substances. It is. Further, as for the shape of the substrate, any shape such as circular, square, rectangular, oval, etc. can be used.

Furthermore, the thin tube constituting the nozzle for latex coagulation was previously filed in Japanese Patent Application No. 56-73115 (Japanese Unexamined Patent Publication No. 57-731).
187322), and there are no particular restrictions on the tube diameter, but the inner diameter is 3 mm or less,
The outer diameter is preferably 5 mm or less. As for its material, the same material constituting the substrate as described above can be used, and any other material can be used as long as it is chemically stable against coagulating liquids and coagulable substances.

Note that the substrate and the thin tube may be fixed with adhesive as in the case shown in FIG. In this case, any adhesive can be used as long as it is chemically stable to the coagulating liquid and the polymer latex and has the ability to bond the capillary and the substrate, such as epoxy. Type adhesives, rubber adhesives, hot melt adhesives, etc. can be used. Note that this adhesive is not necessarily a necessary member.

On the other hand, other cases in which the base material and the capillary are not fixed with adhesive include cases where the substrate and the capillary are integrated, cases where the substrate and the capillary are directly in close contact with each other, etc. In this case, molding can be done by injection molding using synthetic resin, casting molding using metal, etc. In the latter case, a polymeric material is used to form the substrate in a mold in which the capillary is fixed. A method of fixing the substrate and the thin tube by pouring it into a mold and causing a polymerization reaction, and a method of fixing the substrate and the thin tube by pouring a molten substance forming the substrate into a mold in which the thin tube is fixed, and then cooling and solidifying it. There is.

Furthermore, the shapes of the gasket, holder, and fastener are not particularly limited in the present invention. As the gasket, a rubber plate, a polytetrafluoroethylene plate, an O-ring, etc. can be used. As the material of the holder, the above-mentioned substrate materials such as glasses, inorganic sintered bodies, synthetic resins, metals, etc. can be used. Furthermore, ordinary means such as bolts, vices, and tightening rings can be used as fasteners, and the materials used include glass, which is the material of the substrate, inorganic sintered bodies, synthetic resins, metals, and the like.

As the polymer latex used in the present invention, most polymer latexes that can be obtained by emulsion polymerization and can be recovered can be used. Particularly effective polymer latexes include latexes obtained by emulsion polymerization of ethylenic monomers, rubbery polymer latexes, latexes obtained by graft polymerizing ethylenic monomers onto rubbery polymers, and ethylene. Latexes obtained by graft-polymerizing a rubber-forming monomer onto a polymer of a rubber-forming monomer, and mixed latexes thereof can be mentioned.

Examples of ethylenic monomers include styrene monomers such as styrene, α-methylstyrene, O-ethylstyrene, O-chlorostyrene, P-chlorostyrene, and divinylbenzene, acrylonitrile,
Acrylonitrile monomers such as vinylidene cyanide, acrylic acid esters such as acrylic acid, methyl acrylate, and ethyl acrylate, methacrylic acid esters such as methacrylic acid, methyl methacrylate, and ethyl methacrylate, vinyl esters such as vinyl acetate, Examples include vinylidene such as vinylidene chloride, vinyl halides such as vinyl chloride, vinyl ketone, acrylamide, maleic anhydride, etc. These monomers can be used alone,
or used in combination.

Examples of rubbery polymers include natural or synthetic rubbers such as natural rubber, butadiene rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, isobrene rubber, chloroprene rubber, acrylic rubber, and ethylene-vinyl acetate copolymer. Examples include polymers.

As a coagulant for the polymer latex used in the present invention, all commonly used acids or water-soluble inorganic salts can be used. Examples of acids include mineral acids such as sulfuric acid and hydrochloric acid, and acetic acid, which has a dissociation constant of 10 ^{- 6} mol/or more of organic acids (including benzoic acid, salicylic acid, formic acid, and tartaric acid), salts include sulfates such as magnesium sulfate and sodium sulfate, chlorides, and acetates; mixtures of these can also be used. .

Dispersants, lubricants, thickeners, surfactants, plasticizers, antioxidants, colorants, etc. are added to the polymer latex in advance.
Known additives such as blowing agents can also be added. In particular, the dispersant may greatly affect the particle shape stability of the secondary particles formed by coagulation. As the dispersant, inorganic dispersants and organic dispersants that are commonly used as stabilizers for emulsion polymerization and suspension polymerization can be used. Examples of inorganic dispersants include magnesium carbonate and tribasic calcium phosphate, and among organic dispersants, natural and synthetic polymer dispersants include starch, gelatin, acrylamide, partially saponified polyvinyl alcohol, and partially saponified polymethacrylic acid. Methyl, polyacrylic acid and its salts, cellulose, methylcellulose, polyalkylene oxide, polyvinylpyrrolidone, polyvinylimidazole, sulfonated polystyrene, etc., and as low molecular dispersants, for example, common agents such as alkylbenzene sulfonates, fatty acid salts, etc. Emulsifiers can also be used.

It is also possible to facilitate the formation of secondary particles and control the particle shape by adding starch syrup, paraffin, etc. as a thickener.

To carry out the present invention, the entire latex coagulating nozzle is immersed in a coagulating bath, and the polymer latex is discharged from the inside of the holder through a thin tube into the coagulating bath, so that the polymer latex is substantially free of fine powder and coarse particles. It has excellent effects such as being able to produce polymer powder with a characteristic shape and high bulk specific gravity.

The present invention will be specifically explained below using Examples.
In Examples and Comparative Examples, "parts" and "%" are all "parts by weight" and "% by weight."

Example 1 150 glass tubes with an inner diameter of 1.0 mm, an outer diameter of 2.5 mm, and a length of 50 mm were prepared with a side length of 120 mm and a thickness of 10 mm so that the gap between the tubes was 5 mm and the protrusion length on the substrate was 40 mm.
The thin tube was passed through a polycarbonate square substrate having a diameter of 1 mm, and the thin tube and the substrate were fixed using an epoxy adhesive Araldite (trade name, manufactured by Ciba Geigy). This was joined to a holder made of polycarbonate using a vise with a silicone rubber plate interposed as a gasket.

A latex coagulating nozzle having such a structure is immersed in a coagulating bath in which a coagulating solution containing 1% sulfuric acid flows gently. At this time, the nozzle is installed so that the flow of the coagulating liquid and the flow of the discharged polymer latex are in the same direction. Then butadiene 35
A polymer latex consisting of 20 parts of coagulation, 45 parts of styrene, and 20 parts of acrylonitrile was introduced into the coagulation nozzle and discharged from the thin tube. The discharged polymer latex came into contact with the coagulation liquid and coagulated into threads, so it was transferred to a solidification tank and the temperature of the polymer was raised to 93℃ to solidify the polymer particles. Centrifugal dehydration was performed at a force of 600 G).

The series of operations continued for 24 hours, during which time the latex discharge condition was very stable and no nozzle clogging was observed.

The moisture content of the obtained wet powder was 17% (dry base), the bulk specific gravity of the powder after drying was 0.43, and the average particle size was
0.92mm, 250 mesh standard sieve passing amount to total 0.08
It was %.

Compared to the powder obtained in Comparative Example 1 described later, the powder obtained in this example has extremely good dehydration properties, has a large bulk specific gravity, has a large average particle size, and has an extremely small amount of fine powder. It was a good powder.

Example 2 60 stainless steel thin tubes with an inner diameter of 0.8 mm, an outer diameter of 1.2 mm, and a length of 30 mm were fixed with a jig so that the gap between the tubes was 4 mm, and an amount of methyl methacrylate lap was poured into the jig. After pouring the mixture while adjusting it, it is heated to polymerize the methyl methacrylate, resulting in a thickness of 5.
A structure was obtained in which a disk-shaped substrate with a diameter of 80 mm was used, and the thin tube and the substrate were fixed to each other, and the protruding length of the thin tube on the substrate was 25 mm. Next, this product was joined to a holder made of polymethyl methacrylate having the shape shown in FIG. 1 using a bolt via an O-ring made of neoprene rubber.

The latex coagulating nozzle constructed as described above was immersed and installed in a coagulating bath in which a coagulating solution containing 0.3% sulfuric acid was flowing gently in the same manner as in Example 1. After that, 40 parts of butadiene, 20 parts of methyl methacrylate
A polymer latex consisting of 40 parts and 40 parts of styrene was introduced into the coagulation nozzle and discharged from the thin tube.
The polymer latex coagulated in the form of threads, so it was solidified and centrifugally dehydrated in the same manner as in Example 1, except that the temperature of the polymer was changed to 85°C.

The series of operations continued for 24 hours, during which time the latex discharge condition was very stable and no nozzle clogging was observed.

The moisture content of the obtained wet powder is 15.5% (dry base)
The bulk specific gravity of the powder after drying is 0.46, the average particle size is 0.71 mm, and the total amount passing through a 250-mesh standard sieve is
It was 0.04%.

Example 3 Ninety holes with a diameter of 3.0 mm were made in a bottle-shaped polyvinyl chloride substrate (bottom diameter: 95 mm) having a shape as shown in Fig. 2, with a mutual gap of 2 mm. Inner diameter 1.5mm, outer diameter 3.0mm, length 90mm
After adjusting the protrusion length on the substrate to 10 mm, the tube and the substrate were fixed with epoxy adhesive Araldite (trade name, manufactured by Ciba Geigy), and a latex coagulating nozzle with a cross section as shown in Figure 2 was attached. Created.

Next, use this coagulation nozzle with aluminum sulfate 0.8
% in a coagulation bath in which the coagulation solution flows gently in the same manner as in Example 1. Thereafter, a polymer latex consisting of 50 parts of butyl acrylate, 15 parts of acrylonitrile, and 35 parts of styrene was introduced into the coagulation nozzle and discharged from the thin tube. Since the polymer latex coagulated into threads, it was solidified and centrifugally dehydrated in the same manner as in Example 1 except that the temperature of the polymer was changed to 95°C.

The series of operations continued for 50 hours, during which time the latex discharge condition was very stable and no nozzle clogging was observed.

The moisture content of the obtained wet powder was 21% (dry base), the bulk specific gravity of the powder after drying was 0.45, and the average particle size was
1.54mm, 250 mesh standard sieve passing amount is 0.03 of the total
It was %.

Comparative Example 1 30ml of a 1% aqueous sulfuric acid solution was put into an 80ml container, and while stirring, 20ml of the polymer latex used in Example 1 was added to form a coagulated slurry.

This method is a coagulation method that has been widely used in the past. The slurry was heated to 93° C. to solidify the polymer particles, and then centrifugally dehydrated using a centrifugal dehydrator (centrifugal force: 600 G). The moisture content of the obtained wet powder was 33% (dry basis), the bulk specific gravity of the powder after drying was 0.32, the average particle size was 0.25 mm, and the amount passing through a 250 mesh standard sieve was 203% by weight of the total.

Comparative Example 2 A disk made of polymethyl methacrylate with a thickness of 30 mm has a diameter of 1 so that the distance between the centers of each hole is 3 mm.
Ninety mm pores were drilled. Naturally, the holes pass through the plate and connect the disc to the holder via a neoprene rubber O-ring. This was placed in a coagulation bath in the same manner as in Example 1, and coagulation of the polymer latex was attempted under the same conditions as in Example 1. 13 from the start of the experiment
After a few seconds, coarse lumps of coagulated polymer were observed, and after that, coarse lumps of polymer were continuously generated, and after about 1 minute, most of the pores were blocked. Visual inspection revealed that the cause of the problem was that discharged latex accumulated in the vortex area due to the vortex generated in the downstream area of the coagulation nozzle.

Comparative example 3 Example 2 except that the gap between the thin tubes is 0.5 mm
Coagulation was attempted under the same conditions as in Example 2 using the same nozzle. The discharge state of the latex was unstable, and a coarse lump formed by coalescence of several filamentous coagulums began to form 1 minute and 30 seconds after the start of the experiment. After about 5 minutes, coarse lumps were formed, and it was impossible to produce a powder with excellent powder properties. This is apparently due to the narrow spacing between the tubules.

[Brief explanation of drawings]

1 and 2 are embodiments of the latex solidifying nozzle according to the present invention, and FIG. 1 is a side cross-sectional view 1-1 and a front view 1-1 of the nozzle in which a substrate and a holder are connected by a fastener. -2, and the second
The figure is a sectional view of a nozzle in which the substrate and holder are integrated. 1... Board, 1'... Board that also serves as a holder, 2
... Thin tube, 3 ... Adhesive, 4 ... Gasket, 5
...Holder, 6...Fastener.

Claims (1)

[Scope of Claims] 1. When coagulating a polymer latex in a coagulating liquid to obtain a polymer powder, the substrate is provided with a gap between the capillary tubes of 1 mm or more and a protruding length on the substrate of 3 mm or more. 1. A method for coagulating polymer latex, which comprises using a latex coagulating nozzle provided with a plurality of thin tubes, and discharging polymer latex from the thin tubes of the latex coagulating nozzle into a coagulating liquid and coagulating it. 2. The method for coagulating polymer latex according to claim 1, characterized in that the nozzle is a latex coagulating nozzle with a protruding length on the substrate of 10 mm or more. 3. A method for coagulating polymer latex according to claim 1 or 2, wherein the nozzle is a latex coagulating nozzle in which a substrate and a thin tube are fixed with an adhesive. 4. A method for coagulating polymer latex according to claim 1 or 2, characterized in that the latex coagulating nozzle is a latex coagulating nozzle in which a substrate and a thin tube are fixed by integral molding. 5. The method for coagulating polymer latex according to claim 1 or 2, wherein the nozzle is a latex coagulating nozzle in which a substrate and a thin tube are fixed together by a polymerization reaction. 6. The polymer latex according to claim 1 or 2, which is a latex solidifying nozzle in which the substrate and the thin tube are fixed by cooling and solidifying the molten substance forming the substrate. coagulation method.