JPH0224295B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pellet shaped moldings directly from emulsified latex.

Emulsion latex obtained by emulsion polymerization is a state in which solid particles with a particle size of 1 μm or less are covered with an emulsifier and dispersed and suspended in water as micelles.Since the particles are too small, it is necessary to separate the solid particles and extract the solid content. It's difficult. Conventionally, it was mainly separated directly as powder using a spray dryer, or
A method is used in which emulsified latex is mixed with salt or acid, coagulated, heated to an elevated temperature to solidify, and then dehydrated and dried to be taken out as powder. The thus obtained powder or granules are used alone or blended with various polymers to produce pellet-shaped products using an extruder, and are then fed to an injection molding machine, a calender, or the like.

However, the former method of using a spray dryer dries the emulsified latex containing a large amount of water as it is, so the amount of water that must be evaporated is large, requiring a large amount of drying energy, and the size and bulk specific gravity of the particles are large. There are many disadvantages such as difficult control and high equipment cost, etc., when the shape of the powder or granule is not considered as a commercial value. The latter method of coagulating and solidifying requires additives such as acids and salts, requires various processes such as dehydration and drying, has large losses during the process, has many breakdowns, and requires a lot of labor. There are many things I don't like. Furthermore, in both methods, it is desirable that the powder be in the form of pellets for feeding into an injection molding machine, a calendar, etc., and a step of pelletizing the granular material using an extruder is required as a pretreatment.

In order to improve these drawbacks, we have tried adding a coagulant to the polymer latex to make it into a paste, solidifying this paste, and mechanically squeezing and dehydrating it in a screw-type water dryer. The remaining water is evacuated and the molten polymer is continuously recovered.The spray drying mechanism is used to disperse droplets of emulsified latex in a coagulating atmosphere to semi-solidify it, and then solidify it in a coagulating liquid. A method of dehydrating and drying the material after that has been proposed.

However, since the method adds a coagulant to form a paste, it becomes highly viscous and requires equipment such as screws and kneaders to handle it, so there is room for improvement from the perspective of energy conservation. This method is superior in that it performs dehydration, plasticization, and drying continuously, but since all three functions are performed simultaneously, operation is unstable and productivity is difficult to increase, and since everything is done using screws, it is difficult to control as a device. There are drawbacks. This method uses the same mechanism as spray drying, so it is easy to obtain spherical powder, but there are limits to the particle size and bulk specific gravity, and because it uses a gas phase to coagulate, the equipment becomes large. It has the disadvantage that it requires many steps such as dehydration, drying, and extrusion, and requires a lot of labor.

The purpose of the present invention is to solve these drawbacks and find a method for producing pellets directly from emulsified latex without using a dehydrator, dryer, extruder, etc. The number (Re) is 200 or less, preferably 100 or less, and discharged in the form of a strand into the coagulation liquid from a capillary that satisfies L/D≧20 (L = length of the capillary, D = equivalent diameter of the capillary). This is a method for producing a pellet-like molded product, which is characterized in that the pellet-like product is obtained by cutting after solidification.

In the present invention, first, a strand of emulsified latex is obtained by gently discharging the emulsified latex from a capillary into a coagulating liquid. This strand-like material can be obtained with good reproducibility by setting the Reynolds number in the capillary used to be 200 or less and by setting the capillary length (L)/equivalent diameter (D)≧20. When the Reynolds number exceeds 200 or when L/D<20, the emulsified latex is partially ejected into the coagulation liquid, making it impossible to obtain a strand-like product. The obtained strand-like material may be cut as is to form a pellet-like product, or if necessary, the temperature may be further increased or the coagulation conditions may be strengthened to solidify the strand, and then the strand may be cut in a partially molten state. It can be made into a pellet-like molded product.

Figure 1 shows an example of the process for manufacturing a pellet-like molded product. In the figure, 1 is a supply pipe for emulsified latex, 2 is a discharge tube for discharging the emulsified latex in a strand shape, and 3 is a coagulation tube. 4 is a coagulation tank, 5 is a guide for the strands, 6 is a solidification tank for further solidifying the coagulated strands, and 7 is a solidified strand that is further heated to a partially molten state. heating machine, 8
is a strand cutter that cuts strand-like materials into pellets. The length and inner diameter of the discharge capillary in step 2 must satisfy the relationship L/D≧20 (Re≦200, preferably Re≦100), and the relationship with the coagulation rate in the coagulation tank must be satisfied. It is necessary to control the length of the tubule. The conditions for the solidification tank and heating machine are as follows:
It is controlled depending on the desired hardness and shape of the pellets, and commonly used heating methods such as direct heating with steam, heat conduction heating, radiant heating, and infrared heating are used. Note that if washing or neutralization is necessary due to the characteristics of the emulsified latex, it is also possible to add a washing step or a neutralizing step.

FIG. 2 is an example of a discharge tube.

The emulsion latex used in the present invention can be applied to almost all recoverable polymer latexes obtained by emulsion polymerization. Particularly effective emulsion latexes include latexes obtained by emulsion polymerization of ethylenic monomers, rubbery polymer latexes, latexes obtained by graft polymerizing ethylenic monomers onto rubbery polymers, and latexes obtained by emulsion polymerization of ethylenic monomers. Examples include mixtures of

Examples of the ethylenic monomer 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, isoprene rubber, chloroprene rubber, acrylic rubber, and ethylene-vinyl acetate copolymer. Examples include polymers.

Add powder, lubricant, thickener, etc. to emulsified latex in advance.
Known additives such as surfactants, plasticizers, antioxidants, colorants, and blowing agents may also be added.
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 low molecular dispersants include, for example, alkylbenzene sulfonates, fatty acid salts, etc. Conventional emulsifiers can also be used.

It is also possible to control the condition of the strands by adding starch syrup, carboxymethyl cellulose, paraffin, etc. as a thickener.

As the coagulant for the emulsified latex used in the present invention, commonly used acids or water-soluble inorganic salts are used. As acids, mineral acids such as sulfuric acid and hydrochloric acid,
Organic acids such as acetic acid with a dissociation constant of 10 ^-6 mol/or higher (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 can also be used.

The concentration of coagulant in the coagulation tank discharged from the capillary tube may be within the concentration range used in normal coagulation processing, but if the coagulant concentration is too low, strands will be difficult to form, and if it is too high, cleaning will be difficult. The concentration of coagulant should be controlled to the most appropriate conditions, since it is difficult to do so and degrades product performance. For example, when coagulating an emulsified latex made by graft copolymerizing styrene and acrylonitrile to polybutadiene with a solid content of 30 to 50% by weight with sulfuric acid, an aqueous solution of 0.01 to 5% by weight, preferably 0.1 to 3.0% by weight, and a coagulant are used. If it is magnesium sulfate, an aqueous solution of 0.1 to 10% by weight, preferably 1 to 5% by weight, should be used as a coagulant. 0.005 to 2% by weight, preferably 0.01 to 0.5 when coagulating with sulfuric acid an emulsified latex made by graft copolymerizing styrene and methyl methacrylate to polybutadiene with a solid content of 30 to 50% by weight.
A % by weight aqueous solution should be used as the coagulant, or if the coagulant is magnesium sulfate, a 0.01-5% by weight aqueous solution, preferably a 0.1-0.5% by weight aqueous solution.

The temperature of the coagulation tank may be within the temperature range that allows coagulation, but generally it is coagulated at 10 to 80℃, and then heated to 30 to 80℃.
A conventional method of pre-solidifying at 98° C. and further solidifying at a temperature range of 5 to 20° C. higher than the heat distortion temperature of the resin is used, and further heating can be performed if necessary.

In the following examples, % is % by weight.

Example 1 Emulsified latex obtained by graft copolymerizing 45% polybutadiene with 39.1% styrene and 15.9% acrylonitrile (solid content 45%, viscosity 0.1 poise,
(density 1 g/cm ³ ) was discharged from a thin tube with an inner diameter of 1 mm and a length of 190 mm into a 1% aqueous sulfuric acid solution at 25° C. at a linear velocity of 25 cm/sec. At this time, the Reynolds number within the tube was 25, fully satisfying the relationship L/D>20.
The strands of emulsified latex discharged in this way are solidified in hot water heated to 90°C, then superheated steam-dried using 5 kg/cm ² of steam, and cut into pellets with a cutter. I got something.

Example 2 Emulsified latex obtained by graft copolymerizing 45% polybutadiene, 39.1% styrene, and 15.9% acrylonitrile (solid content 45%, viscosity 0.1 poise,
(density 1 g/cm ³ ) was discharged from a thin tube with an inner diameter of 0.8 mm and a length of 100 mm into a 1% aqueous sulfuric acid solution at 25° C. at a linear velocity of 100 cm/sec. At this time, the Reynolds number inside the tube is
80, satisfying the relationship of L/D>20. The thus obtained strand-like product was heated to 90°C to solidify and then cut to obtain a pellet-like product.

Reference Example 1 Emulsified latex obtained by graft copolymerizing 45% polybutadiene with 39.1% styrene and 15.9% acrylonitrile (solid content 45%, viscosity 0.1 poise,
(density 1 g/cm ³ ) was discharged from a thin tube with an inner diameter of 1 mm and a length of 15 mm into a 1% aqueous sulfuric acid solution at 25°C at a linear velocity of 180 cm/sec. I couldn't get it. At this time, the Reynolds number inside the capillary is 180, and the capillary length/
The diameter of the capillary tube was 15, and the conditions of the present invention were not met.

Example 3 Styrene and methyl methacrylate were graft copolymerized to a copolymer of styrene and butadiene to produce an emulsified latex (solid content 45%, viscosity 0.1 poise, density 1g/cm ³ ) to the inner diameter
Using a thin tube with a diameter of 0.8 mm and a length of 120 mm, it was discharged into a 0.3% sulfuric acid aqueous solution at a linear velocity of 35 cm/sec, and was coagulated in the form of a strand. At this time, the Reynolds number in the thin tube was 24 and L/D=150, which fully satisfied the conditions of the present invention. The strand-like material thus obtained is heated and solidified in hot water at 80°C, and further heated to a semi-molten state using an infrared heater.
After cooling, pellets were obtained using a cutting machine. The pellets obtained were cylindrical with a diameter of about 1 mm and a length of 5 mm, and the pellets fed into the injection molding machine were very well fed.

Example 4 Styrene and methyl methacrylate were graft copolymerized to a copolymer of styrene and butadiene to produce an emulsified latex (solid content 45%, viscosity 0.1 poise, density 1 g/cm ³ ) was discharged into a 0.3% sulfuric acid aqueous solution at a linear velocity of 180 cm/sec using a thin tube with an inner diameter of 1 mm and a length of 200 mm. At this time, the Reynolds number inside the tube is 180, and L/D
Although the relationship of >20 was satisfied, some fine powder was generated. The obtained strand-like product was solidified in hot water at 80°C and cut to obtain a pellet-like product.

Reference Example 2 Emulsified latex (solid content 45%, viscosity 0.1 poise, density I tried discharging 1g/cm ³ ) into a 0.3% sulfuric acid aqueous solution at a linear velocity of 250cm/sec using a thin tube with an inner diameter of 1mm and a length of 60mm, but the latex diffused greatly in the sulfuric acid aqueous solution and the strands I couldn't get it. At this time, the Reynolds number inside the tube was 250, and the conditions of the present invention were not met.

Example 5 Emulsion latex of vinyl chloride obtained by emulsion polymerization (solid content 35%, viscosity 0.2 poise, density 1 g/
cm ³ , average particle size 0.1μm), inner diameter 1mm, length 200mm
A strand-like product was obtained by discharging it from a thin tube into a 1% aqueous sulfuric acid solution at 30°C at a linear velocity of 20 cm/sec. This strand-like product was solidified by heating in hot water at 90°C, further steam-dried with 5 kg/cm ² of steam, and cut with a cutting machine to obtain a pellet-like product. The pellets obtained were cylindrical with a diameter of about 1 mm and a length of 5 mm. The flow in a capillary has a Reynolds number of 20,
L/D is sufficiently larger than 20 and satisfies the conditions of the present invention.

Example 6 Emulsified latex of polybutadiene with a solid content of 50% and an average particle size of 0.1 μm (viscosity 0.1 poise, density 1 g/
cm ³ ) from a thin tube with an inner diameter of 1.2 mm and a length of 200 mm at a linear velocity of 30
It was discharged into a 10% sulfuric acid aqueous solution at 70°C at a rate of cm/sec to obtain a strand-like product. At this time, the Reynolds number of the flow in the thin tube is 36, and L/D is sufficiently larger than 20, satisfying the conditions of the present invention. The strands thus obtained were heated to 70°C in hot water,
Further, it was solidified and dried in a steam dryer at 80°C, and cut into pellets using a cutter.

[Brief explanation of drawings]

FIG. 1 is a process diagram for directly producing a pellet-shaped molded product from emulsified latex, and FIG. 2 is a discharge tube. 1... Emulsified latex supply pipe, 2... Discharge capillary,
3... Strand-like material, 4... Coagulation tank, 5... Guide,
6...Solidification tank, 7...Heating machine, 8...Strand cutter.

Claims (1)

[Claims] 1. The emulsified latex has a Reynolds number (Re) of 200.
L/D≧20 (L=tubule length, D=
Pellet-like forming characterized by discharging strands into a coagulating liquid from a capillary that satisfies the equivalent diameter of the capillary, heating the obtained strands as necessary, and then cutting to obtain pellets. How things are manufactured. 2. The method for producing a pellet-like molded product according to claim 1, characterized in that the strand-like product is heated and solidified at 30 to 98°C. 3. The strand-like material is heated and solidified at 30 to 98°C, and further heat-treated at a temperature below the melting point of the resin constituting the strand-like material and above the heat distortion temperature. A method for producing a pellet-like molded product.