JPH032361B2 - - Google Patents

Description

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

In the chemical industry, large amounts 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 used as coagulants. Currently, it is used after being solidified.
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. After that, the polymer is usually solidified by a method such as 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-quality powder,
It is not a decisive improvement measure, as it imposes large energy costs and construction costs.

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. Patent application No. 1987-73115 (Japanese Patent Application No. 187322)
A patent application was filed as

Based on the previous invention, the inventors of the present invention further conducted intensive studies, and found that the nozzle for latex coagulation has a structure that allows the coagulation liquid to be discharged from the center of the substrate.
Moreover, they discovered that by using a substrate with a thin tube having a specific gap and a specific length for coagulating polymer latex, it was possible to obtain a polymer powder with extremely excellent powder properties, resulting in the present invention. did.

The present invention has a structure that allows a latex coagulating nozzle to discharge a coagulating liquid from the center of a substrate when coagulating a polymer latex, and furthermore, the gap between the capillary tubes is 1 mm or more, and the protrusion length on the substrate is 3mm
As described above, this method of coagulating a polymer latex is characterized by using a substrate having a plurality of thin tubes.

The nozzle structure for latex coagulation used in the present invention will be explained based on the drawings. Figure 1 shows a case where the center of the nozzle is hollowed out in a circular shape and the overall shape is a ring donut.
In addition, when the thin tube is inserted to the thickness of the board, the front view of Figure 1-1 and Figure 1-1 is -
1-2 is a side cross-sectional view taken along line 1-2. This structure allows the coagulating liquid to flow from the rear of the nozzle to the periphery and through the center. In addition, Figure 2 shows a case in which a coagulating liquid introduction tube is separately provided in the center of the nozzle, and the thin tube is inserted as far as the thickness of the substrate.It is a front view based on the trigonometry shown in Figures 2-1 and 2-1. FIG. 2-2 is a side cross-sectional view taken along the line 2-2. Such a structure allows the coagulating liquid to flow into the coagulating liquid introducing pipe at an arbitrary flow rate. 1 and 2, a thin tube, 2 a substrate, 3 a holder, and 4
is a gasket, and 5 is a fastener. Further, 6 in FIG. 2 is a coagulation liquid introduction tube. In the nozzles shown in FIGS. 1 and 2, the thin tube 1 and the substrate 2 are fixed directly or with an adhesive or the like. Furthermore, the holder 3 and the substrate 2 are in close contact with each other via the gasket 4, so that coagulable substances such as polymer latex inside the holder will not leak out from the joint between the substrate and the holder.

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 essential point is that the structure allows the coagulation liquid to be discharged from the center of the substrate, and the gap between the thin tubes is 1 mm or more. Basically, any type of thin tube can be used as long as the substrate is provided with a plurality of thin tubes so that the protruding length on the substrate, that is, the length A in Fig. 1 and the length B in Fig. 2 is 3 mm or more. It can also be a structure.

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 is capable of supplying the coagulating liquid to the center of the nozzle, and has a plurality of thin tubes. It has a distinctive structure similar to the tsurugisan used in fresh flowers. This structure improves the contact between the coagulable substance and the coagulating liquid, and allows 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 manufacturing possible.

In this way, supplying the coagulating liquid to the center of the nozzle is essential for stable coagulating operation, but it is important to ensure that the discharge direction of the coagulating substance in the coagulating liquid flow path is in the downstream direction of the coagulating liquid flow. When a nozzle is installed, the flow of the coagulating liquid is obstructed by the nozzle holder or the substrate, causing turbulence on the downstream side of these, ie, near the capillary, and generating a vortex. Therefore, if the capillary protrudes from the substrate by 3 mm or more, preferably by 10 mm or more, the tip of the capillary will reach the laminar region that exists outside the vortex region, and the coagulable substance discharged from the tip will become a laminar coagulating liquid. A polymer powder fluid with a high bulk specific gravity and a characteristic shape substantially free of fine powder and coarse particles is obtained by coagulation reaction while flowing quietly. 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 thereof is about 200 mm.

However, if the gap between the capillary tubes is narrow and less than 1 mm, it will be difficult for the coagulating liquid to flow between the capillary groups, and good coagulation will not be possible except in the periphery of the capillary groups.
On the other hand, even if the coagulating liquid is made to flow between the groups of capillary tubes by forced means, if the gap between the capillary tubes is less than 1 mm, the coagulable material discharged from each capillary will cause fluctuations in the jet flow caused by the coagulable material discharged. The particles coalesce together to form large lumpy particles, making it impossible to produce powder with good properties. Therefore, in the present invention, the gap between the thin tubes must be 1 mm or more, preferably 3 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 material of the substrate constituting the nozzle for latex coagulation is glass; 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 coagulating 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.

Although not shown in the drawings, the thin tube and the substrate must be firmly attached. Examples of the fixing method include a method using an adhesive, a method of directly fixing the thin tube and the substrate, a method of molding the tube as an integral body, and a method of screwing. When using an adhesive, any adhesive can be used as long as it is chemically stable to the coagulating liquid and polymer latex and has the ability to bond the capillary and the substrate, such as epoxy adhesives. , rubber adhesive, hot melt adhesive, etc. can be used. In the method of fixing the thin tube and the substrate in a straight line, the thin tube and the substrate are fixed by pouring a polymerizable substance forming the substrate into a mold in which the thin tube is fixed and causing a polymerization reaction. This can be carried out by a method in which the thin tube and the substrate are fixed by pouring a molten substance forming the substrate and then cooling and solidifying it. In addition, in the method of molding it as an integral part, it can be molded by injection molding using synthetic resin, casting molding using metal, or the like. Furthermore, in the screwing method, the thin tube and the substrate can be fixed by cutting a male thread on the thin tube and a female thread on the substrate and screwing the thin tube into the substrate.

The holder indicated by 3 in the drawing is for distributing the polymer latex supplied from the piping into the thin tubes, and a funnel-shaped holder is usually used, but it is not limited to this. . As the material of the holder, the materials of the substrate described above can be used. Note that, although it is preferable that the substrate and the holder are normally separable for the purpose of easy maintenance, the structure is not necessarily limited to this, and they may be integrally molded. In the case of a structure in which the substrate and holder can be separated as shown in the drawings, they are joined by a fastener through a sealing member such as a gasket. As the gasket, a rubber plate, a polytetrafluoroethylene plate, an O-ring, etc. can be used. Further, ordinary means such as bolts, vices, tightening rings, etc. can be used as the fasteners, and the materials of the above-mentioned substrates can be used as the materials.

Furthermore, the coagulating liquid introduction tube shown by 6 in FIG. 2 is for forcibly supplying an arbitrary amount of coagulating liquid to the vicinity of the nozzle, and the material for the tube may be the same as that of the substrate described above.

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, and the like, and these monomers may be used alone or in combination.

Rubbery polymers include natural or synthetic rubbers such as natural rubber, butadiene rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, isoprene rubber, chloroprene rubber, acrylic rubber, and ethylene-vinyl acetate copolymer. Polymers such as

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 may 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, methyl cellulose, polyalkylene oxide, polyvinylpyrrolidone, polyvinylimidazole, sulfonated polystyrene, etc., and as low molecular weight dispersants, for example, 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.

The nozzle used in the present invention can supply the coagulating liquid from its central part, and as a result, the coagulable substance discharged from the thin tube can come into contact with the coagulating liquid evenly, enabling a good coagulating operation. have certain characteristics.

To carry out the present invention, the entire latex coagulating nozzle is immersed in a coagulating bath, and the polymer latex is introduced into a holder and then discharged from the tip of the capillary tube to come into contact with the coagulating liquid flowing around the nozzle and from the center of the nozzle. As a result, it is possible to obtain a high bulk specific gravity polymer powder which is substantially free of fine powder and coarse particles and has excellent powder characteristics.

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

Example 1 A hole with an inner diameter of 60 mm is bored in the center of the outer diameter.
Glass tubes with an outer diameter of 2.5 mm, an inner diameter of 1.0 mm, and a length of 50 mm are placed on a 200 mm, 5 mm thick polymethyl methacrylate substrate so that the gap between the tubes is 3 mm.
The 600-insertion board and thin tube were fixed with epoxy adhesive Araldite (trade name; manufactured by Ciba Geigy). The protrusion length of the capillary above the substrate is 45 mm. This was joined to a polymethyl methacrylate holder having the shape shown in FIG. 1 via a silicone rubber gasket to produce a coagulation nozzle as shown in FIG.

After a polymer latex introduction pipe is provided in the latex coagulating nozzle having such a structure, the nozzle is immersed in a coagulating bath in which a coagulating solution containing 1% sulfuric acid flows gently. At this time, the position of the nozzle is adjusted so that the flow of the coagulating liquid and the flow of the discharged polymer latex are in the same direction. Then add 35 parts of butadiene, 45 parts of styrene, and 20 parts of acrylonitrile.
A polymer latex consisting of 50% was introduced into the coagulating nozzle and discharged from the thin tube. The discharged polymer latex came into contact with the coagulation liquid flowing in the center of the nozzle and around the nozzle and coagulated into a thread, so it was transferred to a solidification tank and the temperature of the polymer was raised to 93℃ to solidify the polymer particles. Then, it was centrifugally dehydrated using a centrifugal dehydrator (centrifugal force: 600G). The moisture content of the resulting wet powder was 14.7% (dry basis).

The series of operations continued for two hours, during which time the latex discharge condition was extremely stable and no nozzle clogging was observed. In addition, the bulk specific gravity of the powder after drying is 0.46, the average particle size is 0.97mm, 250
The amount passing through the mesh standard sieve was 0.02% of the total.

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 ideal as a powder.

Example 2 A polymethyl methacrylate capillary with an outer diameter of 2 mm, an inner diameter of 0.8 mm, and a length of 50 mm was inserted into a polymethyl methacrylate substrate with an outer diameter of 200 mm and a thickness of 6 mm so that the gap between the capillaries was 4 mm, and then This has an outer diameter of 25
A nozzle as shown in the second diagram was manufactured by attaching a stainless steel coagulation liquid inlet tube with an inner diameter of 20 mm.

Next, after attaching a polymer latex inlet tube to this nozzle, the nozzle is immersed in a coagulation bath in which a coagulating liquid containing 0.4% by weight of sulfuric acid flows gently, so that the flow of the coagulating liquid and the discharge direction of the polymer latex are the same. Adjust the nozzle direction so that the Further, a part of the coagulating liquid is extracted from the coagulating bath and introduced through a pump into a coagulating liquid introduction pipe provided in a nozzle at a flow rate of 7 per minute. Next, a polymer latex consisting of 50 parts of butadiene, 15 parts of methyl methacrylate, and 40 parts of styrene was introduced into the coagulation nozzle and discharged from the thin tube into the coagulation bath. The discharged polymer latex made good contact with the coagulation liquid discharged from the coagulation liquid inlet pipe and the coagulation liquid flowing around the nozzle, and coagulated into a filament, so it was transferred to a solidification tank and the temperature of the polymer was raised to 84°C. After heating to solidify the polymer particles, they were dehydrated using a centrifugal dehydrator (centrifugal force: 600G).

The series of operations continued for 80 hours, during which time the latex discharge condition was extremely stable.
No nozzle blockage was observed.

The moisture content of the obtained wet powder is 16.2% (dry base)
The bulk specific gravity of the powder after drying is 0.46, and the average particle size is
0.86 mm, the amount passing through the standard mesh sieve was less than 0.01% of the total.

Example 3 50 parts of butyl acrylate, 15 parts of acrylonitrile, A polymer latex consisting of 35 parts of styrene was coagulated to obtain a wet polymer powder. The operation continued for 72 consecutive hours,
During this period, the latex discharge condition was extremely stable, and no nozzle clogging was observed. The moisture content of the obtained wet powder was 19.6% (dry base), the bulk specific gravity of the powder after drying was 0.44, and the average particle size was
1.03mm, 250 mesh standard sieve passing amount is 0.10 of the total
It was %.

Example 4 A glass tube with an outer diameter of 2 mm, an inner diameter of 0.5 mm, and a length of 30 mm was inserted into a polycarbonate substrate with an outer diameter of 250 mm and a thickness of 5 mm so that the gap between the tubes was 4 mm, and a stainless steel tube with a diameter of 60 mm was inserted into this. A steel coagulation liquid inlet tube was attached and a nozzle as shown in Fig. 2 was manufactured.

Next, after attaching a polymer latex introduction pipe to this nozzle, the nozzle is immersed in a coagulation bath in which a sulfuric acid solution with a pH of 1.2 is flowing gently as a coagulating liquid, so that the flow of the coagulating liquid and the discharge direction of the polymer latex are the same. Adjust the nozzle direction so that the Further, a part of the coagulating liquid is extracted from the coagulating bath and introduced into a coagulating liquid introducing pipe provided in the nozzle via a pump, and is allowed to flow at a flow rate of 10 per minute. Next, a polymer latex consisting of 50 parts of butadiene, 32 parts of styrene, and 18 parts of acrylonitrile was introduced into the coagulation nozzle and discharged from the thin tube into the coagulation bath. The discharged polymer latex made good contact with the coagulation liquid discharged from the coagulation liquid inlet tube and the coagulation liquid flowing around the nozzle, and coagulated into a thread, so it was transferred to a solidification tank and the temperature of the polymer was raised to 91°C. After heating to solidify the polymer particles, they were dehydrated using a centrifugal dehydrator (centrifugal force: 600G).

The series of operations continued for 50 hours, during which time the latex discharge condition was extremely stable.
No nozzle blockage was observed.

The moisture content of the obtained wet powder is 21.3% (dry base)
The bulk specific gravity of the powder after drying is 0.41, the average particle size is 0.43 mm, and the amount passing through a 250-mesh standard sieve is
It was 0.08%.

Comparative Example 1 30ml of 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 make a coagulation 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 dehydrated using a centrifugal dehydrator (centrifugal force: 600 G).

The moisture content of the obtained wet powder was 33% (dry base), the bulk specific gravity of the powder after drying was 0.32, and the average particle size was
0.25mm, 250 mesh standard sieve passing amount is 2.03 of the total
It was in weight%.

Comparative example 2 The respective diameters are 80mm, 120mm, 160mm and 200mm
Then, holes with a diameter of 2 mm were placed in four circular polymethyl methacrylate substrates with a thickness of 6 mm, with a gap of 3.5 mm between each other.
It was opened so that it was mm. In this case, Examples 1 to 3
Unlike in the previous example, the board was not divided into sections, but 127, 290, 550, and 870 holes were drilled at a point symmetrical diameter on plates with diameters of 80 mm, 120 mm, 160 mm, and 200 mm, respectively.
Next, a glass tube with a diameter of 2 mm, an inner diameter of 0.6 mm, and a length of 50 mm was inserted through each hole so that the protrusion length above the substrate was 40 mm, and the tube and the substrate were fixed using an epoxy adhesive Araldide (trade name, manufactured by Ciba Geigy). did. Furthermore, these were joined to a funnel-shaped glass holder via a silicone gasket to produce a coagulation nozzle.

After this nozzle was provided with a polymer latex introduction tube, the nozzle was immersed and placed in a coagulation bath in which a coagulation solution containing 1% sulfuric acid was flowing gently in the same manner as in Example 1. Thereafter, the same polymer latex as in Example 1 was introduced into the coagulation nozzle and discharged from the thin tube. As a result, a nozzle with 127 thin tubes penetrated through a substrate with a diameter of 80 mm, and a nozzle with 290 tubes penetrated into a substrate with a diameter of 120 mm.
Although the nozzle that penetrated the thin tube was able to perform stable condensation for 8 hours continuously,
For the two nozzles manufactured by passing 550 and 870 thin tubes through the end plates of mm and 200 mm, respectively, coarse lumps of coagulated polymer were continuously generated within 10 minutes after the start of operation. Therefore, stable coagulation operation was impossible.

[Brief explanation of the drawing]

1 and 2 are embodiments of a latex coagulating nozzle according to the present invention, and FIG. 1 is a front view of a ring-doughnut-shaped nozzle with a circularly hollowed-out central portion, taken by the third trigonometric method. FIG. 1 is a side cross-sectional view taken along the - line in FIGS. 1 and 1-1. FIG. 2 is a front view 2-1 of a nozzle in which a coagulating liquid introducing pipe is separately provided in the center of the nozzle, and a side sectional view taken along the line - in FIG. 2-1. 1...Thin tube, 2...Substrate, 3...Holder, 4
... Gasket, 5... Fastener, 6... Coagulation liquid introduction pipe.

Claims (1)

[Scope of Claims] 1. When coagulating polymer latex, the latex coagulating nozzle has a structure capable of discharging coagulating liquid from the center of the substrate, and furthermore, the gap between the capillary tubes is 1 mm or more, and A method for coagulating a polymer latex, characterized in that a substrate is provided with a plurality of thin tubes so that the protruding length of the latex is 3 mm or more. 2. The method for coagulating polymer latex according to claim 1, characterized in that the nozzle is a latex coagulating nozzle having a protruding length on the substrate of 10 mm or more. 3. A method for coagulating polymer latex according to claim 1 or 2, characterized in that 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, wherein the nozzle is a latex coagulating nozzle in which a substrate and a thin tube are fixed together by a polymerization reaction. 5. 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. 6. 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 by integral molding. 7. The method for coagulating polymer latex according to claim 1 or 2, wherein the nozzle is a latex coagulating nozzle in which the substrate and the thin tube are fixed by screwing.