JPH10279640A - Method for recovering rubber-containing polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering a rubber-contg. polymer excellent in powder properties and storage stability. SOLUTION: A copolymer latex obtd. by grafting an emulsion-polymerizable monomer capable of forming a hard polymer onto a rubbery polymer is subjected to two-stage coagulation and solidification. Then, an aggregation preventive in an amt. of 0.1-3.0 pts.wt. (based on 100 pts.wt. polymer in the resultant slurry) is added to the slurry in a heatable tightly sealed stirring vessel, and the slurry is heated to 85-150 deg.C. Thus, the surfaces of polymer particles are uniformly covered with the aggregation preventive. The sum of the amts. of a coagulant (based on 100 pts.wt. polymer solid in a latex to be recovered) added in the first and second steps is 1.0-4.0 pts.wt., and the amt. of that added in the first step is 0.2-2.0 pts.wt. The coagulation temp. in the first step is 80-110 deg.C, and that in the second step, 90-120 deg.C. The solid content at the time of coagulation in the first step is 3-20 wt.%, and that in the second step, 3-20 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering a rubber-containing polymer having excellent storage properties as well as powder properties.

[0002]

2. Description of the Related Art Generally, a polymer produced by an emulsion polymerization method is recovered by adding a coagulant to a latex containing the polymer, coagulating and coagulating. The most common coagulation method is to put a large amount of coagulant into latex, or to put latex into a large amount of coagulant. -59929, a method of vapor-phase coagulation of latex, a powdery latex as shown in JP-A-58-87103, and a continuous coagulation method such as an instantaneous coagulation method using a coagulant. Many have been proposed. However, even when using a method that considers an apparatus and a construction method, as well as a general method, in many cases, the obtained powder has a distorted particle or it is difficult to control the particle diameter. Further, as a result, the particle size distribution tends to be widened, and more fine powder is generated, and this fine powder causes problems such as dust explosion risk and work environment deterioration due to dust, and further decreases in dehydration during dehydration after coagulation. Another problem is productivity. As a measure against such fine powder, improvement of powder characteristics by optimizing coagulation conditions has been proposed as shown in Japanese Patent Application Laid-Open No. 5-77684. However, these proposals basically only prevent the generation of fine powder, and do not discuss at all the storage stability of a polymer by an emulsion polymerization method having a large rubber content. Similarly, as a countermeasure against fine powder, Japanese Patent Application Laid-Open
728 and JP-A-8-48717 have proposed a two-stage solidification method in which gradual solidification is performed in the first stage and completed in the second stage. However, in this method, secondary aggregation is likely to occur in the second stage, and it is easy to generate enlarged particles or a wide particle distribution associated therewith. In addition, especially in the above-mentioned JP-A-3-51728, since there is no distinction in the order of charging the latex and the coagulant, when the latex is charged into the coagulant, spherical particles cannot be obtained and the recovered powder is consolidated. The likelihood increases. Furthermore, Japanese Patent Publication No. 58-
As shown in US Pat. No. 48584, it has been proposed to improve the powder properties by blending a high rubber content polymer and a low rubber content polymer. However, this method is possible if the blended mixture is in the form of a product or almost product, but when the high rubber content polymer is an intermediate material, it is mixed with a specific low rubber content polymer and stored. There are problems such as being unable to do so. Further, a method of adding a lubricant or silicon after solidification has also been proposed, but in these methods, only particles having a distorted shape are generated, and the additive does not work efficiently due to the size of the surface area. When the amount added is increased to enhance the effect, there is a problem that the physical properties of the obtained polymer are reduced.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to recover a wide range of rubber-containing polymers having a small amount of fine powder, an increased bulk specific gravity and excellent storage stability based on the above-mentioned conventional technology. Things.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, when recovering a rubber-containing polymer, two-stage solidification under specific conditions was carried out. Is performed, to generate spherical particles having a narrow particle size distribution, and then, under a specific condition in a heat treatment step in a closed stirring tank, by adding a specific anti-caking agent, polymer particles It has been found that the object can be achieved by efficiently coating the surface of the surface with an anti-caking agent. What is important here is the timing of addition of the anti-caking agent. Even if added before the first stage solidification or before the second stage solidification, the desired particle size, particle shape,
Since the hardness is not obtained, the anti-caking agent does not uniformly coat the particles. Therefore, in order to uniformly coat the anti-caking agent on the particles having the desired particle size, shape, and hardness,
It is to be added after the solidification in the second stage and before the heat treatment.

According to the present invention, a latex of a copolymer obtained by graft-polymerizing a monomer capable of forming a hard polymer, which can be emulsion-polymerized on a rubber-like polymer, is represented by the following (A) to (A).
The two-stage coagulation and solidification are performed under the condition (d),
Further, after the solidification in the second stage, 0.1 to 3.0 parts by weight of an anti-caking agent is added to 100 parts by weight of the solid content in the solidified slurry in a warmable closed stirring tank, and the mixture is heated to 85 to 150 ° C.
A method for recovering a rubber-containing polymer, characterized in that the surface of the polymer particles is uniformly coated with an anti-caking agent by: The total amount of the coagulant in the first and second stages is 1.0 to 4.0 parts by weight with respect to 100 parts by weight per minute, and (b) the amount of the coagulant added in the first stage is 0.1 to 4.0 parts by weight. 2 to 2.0 parts by weight (c) Coagulation temperature is first stage 80 to 100 ° C Second stage 90 to 120 ° C (d) Solid content concentration at the time of solidification is first stage 3 to 20% by weight Second stage 3 -20% by weight.

According to the method of the present invention, desired spherical particles are generated by two-stage solidification, and the particles are uniformly coated with an anti-caking agent, so that powder characteristics are excellent and storage stability is also improved. An excellent rubber-containing polymer can be recovered.

[0007] In the method for recovering a rubber-containing polymer of the present invention, the method of emulsion polymerization used is not particularly limited, and may be an emulsifier, an initiator, or a polymerization auxiliary that is generally used. That is, examples of the emulsifier include sodium oleate, sodium laurate, and sodium lauryl sulfate, and examples of the initiator include hydrogen peroxide and persulfate. Using the above emulsifier, initiator, etc.,
A polymer latex is obtained by graft-polymerizing a monomer that forms a hard polymer onto a rubber-like polymer.

The rubber polymer in the polymer latex used in the present invention includes butadiene polymers such as polybutadiene, styrene-butadiene copolymer, styrene-isoprene copolymer acrylonitrile-butadiene copolymer and the like. And acrylate polymers such as butyl acrylate and octyl acrylate, and silicone rubber. One or more of these rubbery polymers are used.

Examples of the monomer capable of being graft-polymerized to the rubber polymer include aromatic vinyl such as styrene and α-methylstyrene, acrylates such as methyl methacrylate and ethyl methacrylate, and vinyl cyanide such as acrylonitrile and methacrylonitrile. And from these, a single compound or a combination of two or more compounds is also possible.

Examples of the rubber-containing polymer in the method of the present invention include, as generally known, MBS resin,
ABS resin, ABSM resin, AAS resin, AES resin,
Examples include MES resin, but the present invention is not limited to this. Here, it is preferable that the rubber polymer in the graft polymer is 20 to 80 parts by weight and the total of the monomers capable of graft polymerization is 20 to 80 parts by weight.

The method for recovering a polymer of the present invention is based on two-stage coagulation, heat treatment in a closed stirring tank, dehydration and drying. During the two-stage coagulation, the coagulation is performed separately in the first stage and the second stage under the conditions described above. Coagulation in the first stage is a pretreatment step for completing coagulation.Here, by slow coagulation, the basic particles of the enlarged particles are coagulated in the second stage, and in the second stage, The particles produced in the first stage are enlarged to approximately spherical particles by the addition of a further coagulant. In the two-stage solidification process, by controlling under the above-described conditions, particles having an optimal shape can be generated.

After the two-stage coagulation, an anti-caking agent is dropped into a sealed stirring tank under specific conditions, and the mixture is uniformly spread on the surface of the polymer particles.
Preferably, coating is performed in a state where a film is formed. This is because particles having a desired shape, distribution, and porosity (which can be expressed as a dry powder by bulk density, water content, etc.) are coated with an anti-caking agent, and the unnecessary This is for preventing fusion and increasing the desired final particle diameter, the spherical shape as the particle shape, and the hardness of the particles. As a result, since the particles are hard and spherical, the anti-caking agent effectively coats the particles, and even after being made into a dry powder, is stably stored by the effect of the anti-caking agent. .

The bulk specific gravity is preferably at least 0.30, particularly preferably at least 0.35, and the water content is preferably at least 42.
%, Particularly preferably 38% or less, and the particle size distribution (d ₅₀ ) is preferably 200 to 1000 μm, particularly preferably 400 to 1000 μm, and the fine particles are preferably less than 5%, particularly preferably less than 3%. It is. The shear value used as an index of storage stability or substitute property is preferably 50 g / cm ² or less, particularly preferably 40 g / cm 2.
² or less.

As the coagulant used in the present invention, those generally used for coagulating latex can be used. For example, inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, acetic acid, acetic anhydride, formic acid and the like can be used. Organic acids or metal salts thereof. Examples of the metal salt include calcium chloride, magnesium sulfate, aluminum chloride, and aluminum sulfate.

As the anti-caking agent used in the present invention, it is basically sufficient to coat the polymer particles. Therefore, conventional anti-caking agents such as silica, sodium carbonate,
Inorganic substances such as calcium carbonate and titanium oxide can also be mentioned, but they are added later if necessary to the rubber polymer obtained as a powder so as not to affect the physical properties of the rubber polymer. . Commonly available ones such as lubricants, antioxidants, ultraviolet absorbers, release agents and the like are preferred. However, in the heat treatment in a closed stirring tank, the particle surface is uniformly coated to prevent unnecessary fusion between particles, and preferably, in order to form a film, the particle diameter and melting point of the anti-caking agent are specified. There is a need to. When the particle size of the anti-caking agent is 1
An anti-caking agent that can be dispersed to 0 μm or less, preferably 1 μm or less, and has a melting point of 85 to 150 ° C., preferably 95 to 135 ° C. is used. If the melting point of the anti-caking agent is less than 85 ° C., the possibility of adhesion of the powder particles in a storage tank or the like which can be high temperature is extremely high, and if it exceeds 150 ° C., the polymer particles cannot be uniformly coated. . Although many such anti-caking agents can be mentioned, for example, among the above additives, examples of lubricants include fatty acid amides such as stearoamide, oxystearamide, oilrelamide, and ethylenebis-stearamide. . When this lubricant is used, it may be used alone, or two or more kinds may be used in combination.

The solidification conditions in the present invention will be described. The total amount of coagulant was 100 solids in the polymer latex.
It is 1.0 to 4.0 parts by weight, preferably 1.5 to 3.0 parts by weight, based on parts by weight. If the amount of total coagulant is
If the amount is less than 1.0 part, coagulation does not take place, and only the emulsification becomes unstable. If the amount exceeds 4.0 parts by weight, a large amount of coagulant remains and the resulting polymer has poor thermal stability. This leads to deterioration of physical properties.

Regarding the method of distributing the coagulant in two stages,
In the total amount of coagulant, the amount of coagulant in the first stage is 0.2 ~
2.0 parts by weight, preferably 0.5 to 1.5 parts. When the amount of the coagulant added in the first stage is less than 0.2 part, the emulsification is merely in an unstable state,
If it exceeds the portion, rapid solidification occurs in the first stage, and particles having the same distorted shape as usual are generated, and the desired particles cannot be obtained. Regarding the temperature of coagulation, in the first stage 80 to 10
0 ° C., 90 to 120 ° C. in the second stage, preferably 85 to 95 ° C. in the first stage, 90 to 120 ° C. in the second stage.
100. If the temperature in the first stage is lower than 80 ° C., the precipitated particles are very fine, so that during the heat treatment in a closed stirring tank, which is a subsequent step, secondary agglomeration occurs to generate giant particles. On the other hand, when the temperature exceeds 100 ° C., the initial particles become too large, which causes blockage of the production line, which is not preferable in production. When the temperature of the second stage is less than 90 ° C, the particle density does not increase, and when the temperature exceeds 120 ° C, secondary aggregation occurs,
Generates giant particles. Further, the obtained polymer latex is diluted with pure water in order to obtain a desired concentration. However, the ratio of the solid content in the mixture of the latex and the added pure water (hereinafter, referred to in the present invention) The solid content is 3 to 20% in the first stage and 3 to 20% in the second stage.
In the first stage, if it is less than 3%, the initial particles become small,
%, The coagulation tank becomes poorly stirred. The same applies to the second stage.

Further, the temperature in the heat treatment step in a sealed stirring tank is 85 to 150 ° C., preferably 1 to 150 ° C.
00 to 135 ° C. In this case, when the temperature is lower than 85 ° C., there is no change in the particle density, and when the temperature exceeds 150 ° C., the fusion between particles greatly increases. The heat treatment time is 5-6.
0 minutes is good, and preferably 10 to 40 minutes. If the heat treatment time is shorter than 5 minutes, the heat treatment is not sufficient, and if the heat treatment time is longer than 60 minutes, the productivity and the physical properties of the obtained polymer due to the heat history are reduced.

The method of charging the coagulant will be described. The coagulant is added in each coagulation step in the presence of the polymer obtained by emulsion polymerization, that is, after the polymer latex is charged into the coagulation tank. On the contrary, when latex is added in the presence of a coagulant, the particles obtained are not spherical but have a distorted shape, and when the powder after dehydration and drying is stored, the number of contact points between the particles increases and consolidation occurs. Easy to invite.

The method of adding the anti-caking agent will be described.
The anti-caking agent needs to be emulsified in advance using water, an emulsifier, or the like in order to disperse the anti-caking agent small and uniformly in the addition stirring tank. About the time of addition of the anti-caking agent in the emulsified state, before the first-stage coagulation, before the second-stage coagulation, before the heat treatment, it is also possible before and after dehydration drying,
As described above, in order to uniformly and efficiently coat the anti-caking agent on the particles having the desired particle diameter, shape, and hardness, the anti-caking agent must be provided after the solidification in the second stage and before the heat treatment. The means for adding the anti-caking agent adds the anti-caking agent in the presence of the coagulated slurry. On the contrary, when the coagulation slurry is added in the presence of the anti-caking agent, the anti-caking agent is taken into the slurry particles, and a sufficient effect cannot be exhibited. here,
The amount of the anti-caking agent to be added is 0.1 to 3.0 parts by weight, preferably 0.5 to 2.0 parts by weight, based on 100 parts by weight of the polymer solids in the coagulated slurry. If it is less than 0.1 part, the effect of preventing caking is not obtained, and if it exceeds 3 parts, the properties of the obtained polymer are not reduced, and proper interparticle fusion in the closed system stirring layer is not performed.

[0021]

The method of the present invention will be described in more detail with reference to the following examples, which do not limit the scope of the present invention.

Measurement method Bulk specific gravity Measured according to JIS-K-6721.
(Unit: g / ml) Moisture content The moisture content was represented by the amount of water that had disappeared after drying, in the water-containing powder after dehydration.

Shear value Using a powder shear value measuring device (manufactured by Tsutsui Rika Kiki Co., Ltd.), dry powder is put into two-stage box-shaped cylinders that can make surface contact, and the cylinders are pulled in opposite directions, respectively.
The maximum shear value at that time was measured. In other words, it is shown that the larger the value, the easier the consolidation.

Particle Size Distribution Using a sieve specified by ASTM-EH70, the particle size distribution was determined from the sieve distribution.
Its average particle diameter: d ₅₀ is the particle diameter at 50% cumulative value determined from the cumulative distribution curve of the particle size distribution.

Amount of fine particles The amount of powder passing through a 200 mesh wire net was determined from the total amount of powder.

Synthesis Example 1 Polybutadiene was used as a rubbery polymer, and styrene and acrylonitrile were selected as monomers for forming a hard polymer by graft polymerization of the rubber polymer, and 65 parts by weight of polybutadiene were obtained by ordinary graft emulsion polymerization. And a latex having a solid content of 36% by weight, comprising 10 parts by weight of acrylonitrile and 25 parts by weight of styrene.

Example 1 Pure water was added to this latex to adjust the solid content to 7.5% by weight, and the mixture was put into a first-stage coagulation tank. Thereafter, 0.5 part by weight of sulfuric acid as a coagulant was continuously added to 100 parts by weight of the polymer solid content in the latex, and the obtained coagulation slurry was charged into a second-stage coagulation tank. In this second step, 2.0 parts by weight of sulfuric acid was continuously added, and the resulting solidified slurry was charged into a closed stirring tank which was the next step. Here, in a separate stirring tank, ethylene bis stearamide (trade name: Kao, EB-P, melting point: 100 wt.
(146 ± 2.5 ° C.) A mixture comprising 45 parts by weight of pure water, 100 parts by weight of pure water, and 5 parts by weight of an emulsifier was heated to 135 ° C., and was emulsified by sufficient stirring. This emulsified mixture was analyzed using a laser diffraction / scattering particle size analyzer (manufactured by Horiba).
The measured average particle diameter was 3 μm. After 5.0 parts by weight of the emulsified mixed solution containing the anti-caking agent was continuously added to the closed stirring tank, the temperature of the closed stirring tank was heated at 130 ° C. for 30 minutes. Thereafter, the polymer component was separated, washed with water, and dehydrated using a centrifugal separator, and further dried with hot air (at 60 ° C. for 5 hours) to obtain a dried polymer. The powder properties of the obtained polymer were evaluated.

Examples 2 to 12 Using the latex obtained in Synthesis Example 1, as shown in Table 1, the same operations as in Example 1 were carried out except for the changes.

The classification according to the changed points is as follows.

In Examples 2 to 7, various conditions in the solidification step were changed.

In Examples 8 to 12, various conditions in the heat treatment were changed.

In Example 12, OA-2246 (2,2-
Methylene bis (4-methyl 1-6-t-butylphenol) manufactured by Yoshitomi Pharmaceutical Co., Ltd., trade name: Yoshinox 224
6, melting point: 125 ° C.) in the same manner as in Example 1.

Synthesis Example 2 Polybutadiene was used as a rubbery polymer, and styrene and acrylonitrile were selected as monomers for forming a hard polymer by graft polymerization of the rubbery polymer. , 25 parts by weight of acrylonitrile and 55 parts by weight of styrene to obtain a latex having a solid content of 35%.

Example 13 The same operation as in Example 1 was carried out except that the latex obtained in Synthesis Example 2 was used.

Comparative Examples 1 to 12 Using the latex obtained in Synthesis Example 1, as shown in Table 2, the same operations as in Example 1 were carried out except for the changes.

The classification according to the changed points is as follows.

Comparative Example 1 was carried out in the same manner as in Example 1 except that no anti-caking agent was added.

Comparative Examples 2 and 3 were carried out in the same manner as in Example 1 except that the timing of adding the anti-caking agent was changed.

In Comparative Examples 4 to 10, the conditions in the solidification step were changed.

In Comparative Examples 11 to 13, various conditions in the heat treatment process were changed.

In Comparative Example 11, OBP (octadecyl 3, OBP) which is generally used as an antioxidant was used as an anti-caking agent.
5-Di-t-butyl 4-hydroxyhydrocinnamate:
Yoshitomi Pharmaceutical Co., Ltd., melting point: 49-54 ° C.) was used.

Tables 1 and 2 show the results of the powder characteristics in Examples 1 to 13 and Comparative Examples 1 to 13, respectively. In Tables 1 and 2, the amount of the coagulant is based on 100 parts by weight of the polymer solids in the latex to which the coagulant is added, and the amount of the anti-caking agent is based on the polymer solids in the coagulated slurry. It is indicated in parts by weight per 100 parts by weight per minute.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

According to the present invention, two-stage coagulation of the polymer latex is performed under specific conditions to produce desired spherical particles,
By uniformly coating the particles with an anti-caking agent,
A rubber-containing polymer having excellent powder characteristics and excellent storage stability can be recovered.

Claims (4)

[Claims] A latex of a copolymer obtained by graft-polymerizing a monomer capable of forming a hard polymer, which can be emulsion-polymerized on a rubber-like polymer, is obtained under the following conditions (a) to (d). The coagulation and coagulation of the step are performed, and after the coagulation of the second step, the anti-caking agent is added in an amount of 0.1 to 100 parts by weight of the solid content in the coagulated slurry in a heatable sealed stirring tank.
3.0 parts by weight, heat-treated at 85 to 150 ° C., and the polymer particle surface is uniformly coated with an anti-caking agent. The total amount of the coagulant in the first stage and the second stage is 1.0 to 4.0 parts by weight, based on 100 parts by weight of the solids in the latex to be recovered. The amount of the coagulant added in one stage is 0.2 to 2.0 parts by weight. (C) The coagulation temperature is the first stage 80 to 100 ° C The second stage 90 to 120 ° C (d) The solid content concentration at the time of coagulation First stage: 3 to 20% by weight Second stage: 3 to 20% by weight 2. The rubber polymer in the graft polymer is from 20 to 20.
The method for recovering a rubber-containing polymer according to claim 1, wherein the rubber-containing polymer is 80 parts by weight, and a total amount of monomers forming a hard polymer capable of being graft-emulsion polymerized to the rubbery polymer is 20 to 80 parts by weight. 3. The anti-caking agent has a particle size of 10 μm or less, and has a melting point of 85 to 150 ° C.
3. The method for recovering a rubber-containing polymer described in 1. above. 4. The rubber-containing polymer according to claim 1, wherein the anti-caking agent is previously emulsified, and the emulsifying anti-caking agent is added in the presence of spherical particles formed by two-stage solidification. Collection method.