JP2005248126A - Method for recovering rubber-containing polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover polymer particles having excellent powder characteristics such as blocking resistance from a polymer latex having a high rubber content. <P>SOLUTION: The method for recovering a rubber-containing polymer is carried out as follows. The polymer particles are recovered from the rubber-containing polymer latex and the rubber-containing polymer has ≥50% rubber content therein, ≤0°C glass transition temperature in a rubber part and ≥60% sphericity of the recovered powder. The rubber-containing polymer latex to be recovered is especially preferably brought into contact with a flocculant in a flow through type tubular apparatus in which at least one static type element is mounted and recovered. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for recovering a polymer from a rubber-containing polymer latex obtained by emulsion polymerization or the like. Specifically, the present invention relates to a method for recovering polymer particles having excellent powder characteristics such as blocking resistance.

As a method for recovering a polymer from a rubber-containing polymer latex obtained by emulsion polymerization or the like, a method of obtaining a powdery polymer by adding a coagulant to the polymer latex and coagulating it, and then dehydrating and drying the polymer latex Has been done more. In this conventional method, the polymer latex is coagulated by supplying the polymer latex and the aqueous coagulant solution to a coagulation tank filled with hot water at a temperature suitable for the desired particle size, and stirring in the coagulation tank. It is done by doing.
However, in the conventional method, the recovered polymer particles have a wide particle size distribution and there are many fine powder particles, and the shape of the polymer particles is uneven and distorted. Therefore, (1) there are many fine powder particles, Since the shape is distorted, blocking occurs due to the load caused by loading during storage. (2) Poor dehydration in the dehydration process. (3) Fine particles clogged in the separation / drying process, resulting in decreased productivity. (4) Equipment to prevent dust explosion caused by fine powder particles is required. (5) Fine particles are scattered when fed into the extruder, or powder is bridged in the hopper and fed into the extruder. (6) There is a problem that the bulk density is reduced and a large storage volume is required.
For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 9-59390) discloses a method for controlling the particle size distribution and average sphericity by specifying the coagulation temperature, coagulant concentration, maximum stirring speed, and coagulation time in the coagulation tank. However, when the rubber content in the polymer increases, there is a problem that the bulk specific gravity does not increase. In Patent Document 2 (Japanese Patent Laid-Open No. 2000-86730), a graft copolymer having good powder properties is obtained by a spray drying method. In this method, an emulsifier, a coagulant and the like are removed from a recovered polymer. The cleaning efficiency for removal was low, and impurities remained in the recovered polymer, resulting in the deterioration of the quality of the final product.
JP-A-9-59390 JP 2000-86730 A

An object of the present invention is to recover polymer particles excellent in powder characteristics such as blocking resistance from a rubber-containing polymer latex.

As a result of intensive studies in view of the above problems, the present inventors have found that the rubber content in the rubber-containing polymer is 50% or more, the glass transition temperature of the rubber part is 0 ° C. or less, and the recovered powder It has been found that a rubber-containing polymer having a spheroidizing ratio of 60% or more can solve such a problem, and has reached the present invention.
That is, in the present invention, the rubber content in the rubber-containing polymer produced by emulsion polymerization is 50% or more, the glass transition temperature of the rubber part is 0 ° C. or less, and the spheroidization rate of the recovered powder In order to obtain a rubber-containing polymer having a content of 60% or more, particularly by bringing the rubber-containing polymer latex to be recovered and the flocculant into contact with each other in a flow-through tubular apparatus equipped with at least one stationary element. The polymer can be recovered.

The present invention can recover polymer particles excellent in powder characteristics such as blocking resistance, thereby improving blocking due to loading during storage, and improving dehydration in the dehydration process, thereby separating the particles.・ Prevents clogging of fine particles in the drying process, and prevents scattering of fine particles and bridging of powder in the hopper when it is put into the extruder, increasing the storage density by increasing the bulk density. There is an effect.

  Examples of the rubber-containing polymer latex to which the recovery method of the present invention is applied include a polymer latex produced by emulsion polymerization. For example, acrylonitrile, styrene, α-methylstyrene is added to a rubbery polymer having a glass transition point of 0 ° C. or lower, such as butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), acrylic rubber and the like. A rubber-containing polymer latex obtained by graft polymerization of a copolymerizable monomer such as methyl methacrylate, and the content of the rubber-like polymer is 50% or more.

In addition, the spheroidization rate of the rubber-containing polymer powder recovered in the present invention is required to be 60% or more. When the spheroidization rate is less than 60%, the particle shape becomes indefinite, It is not preferable because the blocking property is deteriorated and problems such as bridging occur in the hopper when being fed into the extruder.
In addition, it is desirable to use a flow-through tubular apparatus as shown below as a method for setting the spheroidization rate of the collected powder to 60% or more.

  Further, as the coagulant used in the recovery method of the present invention, those usually used for coagulation of polymer latex can be used. For example, inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, organic acids such as acetic acid and formic acid, metal salts of these acids (for example, inorganic salts such as calcium chloride, aluminum chloride, aluminum sulfate and magnesium sulfate, calcium acetate , Aluminum acetate, etc.).

  As a flow-through tubular device used in the recovery method of the present invention, it is necessary that at least one stationary element is mounted. As an example, a flow-through tubular device as shown in FIG. Is preferred.

  The internal temperature in the flow-through tubular apparatus can be increased by introducing steam or heating the rubber-containing polymer latex and the coagulant. The set temperature is appropriately selected depending on the rubber-containing polymer latex, and is, for example, 50 ° C. or higher.

In addition, after passing through the flow-through tubular apparatus, by providing a heating tank, it is possible to generate polymer particles having further excellent powder characteristics due to a sintering effect. Moreover, although the preset temperature of a heating tank is suitably selected by rubber-containing polymer latex, it is 70 degreeC or more, for example.

The obtained coagulated slurry is dehydrated by vacuum dehydration, press dehydration, centrifugal dehydration, etc., and then dried using a parallel flow batch dryer, fluid dryer, vacuum dryer, etc., and contains rubber. The polymer can be isolated as a powder.

〔Example〕
In order to describe the present invention more specifically, examples and comparative examples will be described below. However, the present invention is not limited by these. Parts and% are based on weight.

-Preparation of rubber-containing polymer latex-
Rubber-containing polymer latex (a-1-1): 50 parts (solid content) of polybutadiene latex (weight average particle size 0.3 μm, gel content 85%, glass transition temperature −80 ° C.) in a nitrogen-substituted reactor. 140 parts of water, 0.1 part of ethylenediaminetetraacetic acid disodium salt, 0.001 part of ferrous sulfate, 0.4 part of sodium formaldehyde sulfoxylate, heated to 65 ° C, then 15 parts of acrylonitrile and 35 parts of styrene And a mixture consisting of 1.0 part of potassium oleate and 0.2 part of cumene hydroperoxide were continuously added over 3 hours, respectively, and further polymerized at 65 ° C. for 2 hours to obtain a solid content of 41.1%. The rubber-containing polymer latex (a-1-1) was obtained.

Rubber-containing polymer latex (a-1-2): 70 parts (solid content) of polybutadiene latex (weight average particle size 0.2 μm, gel content 90%, glass transition temperature −80 ° C.) in a nitrogen-substituted reactor. Solid content 41. Similar to (a-1-1) except for changing to 8 parts of styrene, 22 parts of methyl methacrylate, 0.2 part of sodium formaldehyde sulfoxylate and 0.1 part of cumene hydroperoxide. A 2% rubber-containing polymer latex (a-1-2) was obtained.

Example 1
The flow-type tubular apparatus shown in FIG. 1 is a rubber-containing polymer latex (a-1-1) 100 using a flow-type tubular apparatus having an inner diameter of 25 mm, a length of 200 mm, and six stationary elements mounted on a scaler type. Part (solid content) and 0.4% sulfuric acid aqueous solution as a coagulant are heated in such a way that 0.7 parts (effective amount of sulfuric acid) per rubber-containing polymer (solid content) are brought into contact with each other at 80 ° C. in a tubular apparatus. The solution was continuously fed. The slurry continuously discharged from the tubular apparatus was sintered in a heating bath heated to 95 ° C., and the resulting slurry was subjected to centrifugal dehydration and fluid drying to obtain a rubber-containing polymer powder (A-1 )

Example 2
The flow-through tubular apparatus shown in FIG. 1 is a rubber-containing polymer latex (a-1-2) 100 using a flow-through tubular apparatus having an inner diameter of 25 mm, a length of 200 mm, and 10 stationary elements mounted on a scaler type. Part (solid content) and 3% magnesium sulfate aqueous solution as a coagulant are continuously heated to 5 parts (magnesium sulfate effective amount) per rubber-containing polymer (solid content) at 85 ° C. in a tubular apparatus. Liquid was sent. The slurry continuously discharged from the tube-type apparatus was sintered in a heating tank heated to 90 ° C., and the resulting slurry was subjected to centrifugal dehydration and fluid drying to obtain a rubber-containing polymer powder (A-2 )

Comparative Example 1
Using a coagulation tank with a stirrer, 100 parts (solid content) of rubber-containing polymer latex (a-1-1) and 0.4 part of a 0.4% sulfuric acid aqueous solution as a coagulant per rubber-containing polymer (solid content) ( (Effective amount of sulfuric acid) was heated in a coagulation tank at 80 ° C. and continuously fed. The slurry continuously discharged from the coagulation tank was sintered in a heating tank heated to 95 ° C., and the resulting slurry was subjected to centrifugal dehydration and fluid drying to obtain a rubber-containing polymer powder (B-1). Got.

Comparative Example 2
Using a coagulation tank with a stirrer, 100 parts of rubber-containing polymer latex (a-1-2) (solid content) and 5 parts of a 3% magnesium sulfate aqueous solution as a coagulant per rubber-containing polymer (solid content) (magnesium sulfate effective) The amount was heated to 85 ° C. in the coagulation tank and continuously fed. The slurry continuously discharged from the coagulation tank was sintered in a heating tank heated to 90 ° C., and the resulting slurry was subjected to centrifugal dehydration and fluid drying to obtain a rubber-containing polymer powder (B-2). Got.

Blocking resistance : 25 g of the obtained rubber-containing polymer was weighed, placed in a cylindrical container with a diameter of 56 mm, and a block was formed by applying a load of 50 g at 70 ° C. for 1 hour, and the powder and the cylindrical container were removed. The maximum diameter of the plane was determined. It shows that blocking resistance is so high that a numerical value is small. (Unit: mm)

Spheroidization rate : The rubber-containing polymer obtained was photographed using a scanning electron microscope (JEOL: JSM-6360LA type), and spherical using an image analyzer (Asahi Kasei: IP-1000C type). The conversion rate was measured.
Spheroidization ratio by graphite area method: 100 × area / area of minimum circumscribed circle (unit:%)

Bulk density : Measured based on JIS-K-6721. (Unit: g / ml)

Fine powder amount : 40 g of powder is screened for 8 minutes with Sonic Shifter L-200P, a sonic vibration sieving machine manufactured by Seishin Co., Ltd., and the ratio of the powder passing through a JIS standard sieve having an opening of 75 microns is measured. (unit:%)

As described above, the rubber-containing polymer particles obtained in the present invention are polymer particles excellent in powder characteristics such as blocking resistance, and do not cause a problem when handling the powder.

It is a figure which shows a flow-through pipe type apparatus.

Explanation of symbols

1: Coagulant aqueous solution inlet 2: Rubber-containing polymer latex inlet 3: Flow-through tube device 4: Stationary element 5: Heating tank 6: Dehydrator 7: Dryer 8: Polymer powder outlet

Claims (2)

A polymer recovery method for recovering polymer particles from a rubber-containing polymer latex, wherein the rubber content in the rubber-containing polymer is 50% or more and the glass transition temperature of the rubber part is 0 ° C or less. And a method for recovering a rubber-containing polymer, wherein the recovered powder is recovered so that the spheroidization rate is 60% or more. 2. The rubber-containing polymer according to claim 1, wherein the rubber-containing polymer latex to be recovered and the flocculant are brought into contact with each other in a flow-through tubular apparatus equipped with at least one stationary element and recovered. Recovery method.

Images