JP3163195B2 - Method for producing powdery granular polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention has a sharp particle size distribution,
The present invention also relates to a method for producing a granular polymer having a high bulk specific gravity.

[0002]

2. Description of the Related Art Hard inelastic polymers such as polyvinyl chloride resins, styrene resins, acrylonitrile styrene resins, methyl methacrylate resins, polycarbonate resins, polyether resins and the like, and acrylonitrile in the presence of a rubbery polymer. A method of improving impact resistance by blending a styrene or a graft copolymer obtained by polymerizing styrene or methyl methacrylate with styrene is generally used. This graft copolymer is obtained as a powdery polymer by coagulating the obtained graft copolymer latex to form a slurry, followed by dehydration and drying.

Hitherto, various methods have been studied for improving the powder properties of the obtained granular polymer when recovering the granular polymer from the graft copolymer latex containing a large amount of the elastic base polymer. For example, JP-A-60-217224
Japanese Patent Application Laid-Open Publication No. Hei 5 (1994) discloses a method of slowly coagulating a polymer latex under a specific coagulant concentration condition.
JP-A-5-90520 discloses a method in which a hard polymer is added to the obtained coagulated slurry or dried powder to modify the bulk specific gravity or blocking resistance of the powder. However, in the method of slow coagulation in the presence of a specific coagulant concentration, a spherical powder having a sharp particle size distribution is obtained, but the moisture content of the wet powder after dehydration is high, and in order to obtain solid particles, When heat treatment is performed at a high temperature during solidification, the fine particles in the coagulated particles are fused without being densely packed, so that coagulated particles having a high particle density cannot be obtained, and as a result, particles having a high bulk specific gravity can be obtained. It has the disadvantage that it cannot be done. In addition, the method of modifying the powder by adding a hard polymer to the obtained coagulated slurry or dried powder is to increase the bulk specific gravity by increasing the packing structure of the coagulated particles to increase the bulk specific gravity. Although the decrease in bulk specific gravity due to agglomeration of particles is improved, the effect of improving the particle density of the coagulated particles themselves cannot be expected, and there is a disadvantage that a sufficiently satisfactory bulk specific gravity cannot be obtained.

[0004]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies with the aim of solving the above-mentioned problems, and as a result, have found that a coagulated slurry or polymer powder obtained from a specific graft copolymer latex contains: A specific amount of a hard inelastic polymer and / or an inorganic compound is added, and the obtained polymer powder is compressed at a specific pressure and crushed to obtain a powder having a sharp particle size distribution and a high bulk specific gravity. The present inventors have found that a polymer can be provided and arrived at the present invention.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a graft obtained by emulsion-polymerizing a rigid polymer-forming monomer with an elastic base polymer, wherein the content of the elastic base polymer is 60% by weight or more. 0.1 to 10 parts by weight of the hard inelastic polymer (B) is added to the coagulated slurry or polymer powder obtained from the latex of the copolymer (A) based on 100 parts by weight of the graft copolymer (A). ) And / or an inorganic compound (C), and the graft copolymer (A) powder is subjected to a surface pressure of 100 to 10
00 [Kg / cm ² ] or a linear pressure of 100 to 1000 [Kg]
/ Cm], followed by crushing after compression under pressure.

Hereinafter, the present invention will be described specifically. The graft copolymer (A) latex used in the present invention is obtained by emulsion-polymerizing a hard polymer-forming monomer with an elastic base polymer. Examples of the elastic base polymer constituting the graft copolymer (A) latex include diene polymers such as butadiene, isoprene, and chloroprene; and acrylate esters having an alkyl group having 4 to 10 carbon atoms such as butyl acrylate and octyl acrylate. Examples thereof include polymers, dimethylsiloxane polymers, and copolymers thereof with monomers copolymerizable therewith. As copolymerizable monomers, styrene, aromatic vinyl compounds such as α-methylstyrene, methyl methacrylate, alkyl methacrylates such as ethyl methacrylate, methyl acrylate, alkyl acrylates such as ethyl acrylate having 1 to 3 carbon atoms. Examples thereof include vinyl cyanide compounds such as alkyl acrylate, acrylonitrile, and methacrylonitrile.

[0007] Monomers forming the hard polymer include aromatic vinyl compounds such as styrene and α-methylstyrene;
Methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate and butyl methacrylate,
Examples thereof include vinyl cyanide compounds such as acrylonitrile and methacrylonitrile, and vinyl halides such as vinyl chloride and vinyl bromide. These monomers are used alone or in combination of two or more.

A graft copolymer (A) obtained by emulsion-polymerizing a hard polymer-forming monomer with the above-mentioned elastic base polymer.
In the latex, the content of the elastic backbone polymer is 60% by weight or more,
More preferably, it is desirably 70% by weight or more.
When the content of the elastic base polymer is less than 60% by weight, if the fusion of the fine particles constituting the coagulated particles is not sufficient, fine powder is liable to be generated in the dehydration and drying steps, which is not preferable. In coagulating the graft copolymer (A) latex of the present invention in two stages, the copolymer latex is added to the copolymer latex.
It is necessary that a total of 0.05 to 0.5 parts by weight of the sulfate-based and / or sulfonic acid-based anionic surfactant is present based on the weight part.

Among the surfactants, the sulfate anionic surfactants include, for example, higher alcohol sulfates and polyoxyethylene alkyl sulfates, and the sulfonic acid anionic surfactants include, for example, alkyl sulfates. Sulfonates, alkylbenzenesulfonates, alkylsulfosuccinates, alkyldiphenylethersulfonates and the like can be mentioned. The surfactant may be added at any time before, during, or after the polymerization.

When the content of the surfactant is less than 0.05 part by weight, the emulsification state maintaining effect of the surfactant becomes too weak against the emulsification state destruction effect of the acid, and the precipitated state of the coagulated particles is stabilized. It is difficult to control and difficult to obtain a powdery polymer having a sharp particle size distribution. On the other hand, when the amount exceeds 0.5 parts by weight, the emulsification state maintaining effect of the surfactant becomes too strong, and coagulation will not occur unless a large amount of acid is used.

The emulsion polymerization method of the copolymer of the present invention may be a commonly used method, and there is no particular limitation on the initiator and other polymerization aids, and any commonly used method may be used. Examples of the first-stage coagulant used in the present invention include inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid, and organic acids such as formic acid and acetic acid.

In the present invention, as the first stage of coagulation, it is necessary to coagulate the polymer in the latex by 40 to 80% by weight. The amount of the polymer coagulated here was determined by using the coagulated slurry of Toyo Filter Paper No. The solution was filtered through 131 (third class of JIS P3801), and the polymer concentration in the filtrate was measured. If the amount of coagulated polymer is less than 40% by weight, a large amount of copolymer latex will coagulate in a state of strong emulsifying state destruction when coagulation is completed, and a powdery polymer having a sharp particle size distribution will be obtained. Becomes difficult, which is not preferable. If it is 80% by weight or more, it is difficult to obtain a powdery polymer having a sharp particle size distribution because the emulsifying state breaking action is too strong.

The acid used in the first stage is p during coagulation.
It is preferable to add H to the latex so that the following conditions are satisfied.

[0014]

(Equation 2)

(Wherein X is the graft copolymer (A) 100
If the pH exceeds the value on the right-hand side, the emulsification state maintaining effect of the surfactant becomes too strong against the emulsification state destruction effect of the acid, and the pH value exceeds the value on the right side. It is not preferable because it does not coagulate or it takes a long time to coagulate.

As the coagulant used in the second stage, the above-mentioned acids used in the first stage, inorganic salts such as aluminum sulfate, magnesium sulfate, sodium chloride, calcium chloride, sodium sulfate and magnesium chloride, acetic acid Organic salts such as sodium and calcium acetate are applicable, and these may be used alone or in combination.

Further, it is preferable that the pH of the slurry after the precipitated particles are completely precipitated is 2.0 or more. If the pH of the coagulation slurry is less than 2.0, the resulting powdery polymer has poor thermal stability, which is not preferred. In that case, it is preferable to adjust the pH to 2 to 4 with an alkali such as sodium hydroxide.

In the present invention, the coagulated graft copolymer (A) powder is added with the hard inelastic polymer (B) and / or the inorganic compound (C) to prevent coagulation. It is essential that the surface of the precipitated particles be surface-modified so as to be slippery. The step of adding the polymer (B) and / or the compound (C) can be performed at any step after coagulation, such as after coagulation, after solidification, after drying, as long as it is before compression under pressure. However, in the case of a polymer that is strongly agglomerated, it is preferable to add it to the coagulated slurry before solidification.

The amount of the polymer (B) and / or the compound (C) is 0.1 to 10 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the graft copolymer (A).
-5 parts by weight. If the amount exceeds 10 parts by weight, the physical properties of the graft copolymer (A) are undesirably impaired. If the amount added is less than 0.1 part by weight (B)
And the effect of the additive (C) cannot be sufficiently exhibited, which is not preferable.

The hard inelastic polymer for powder modification (B) used in the present invention has a Tg higher than 25 ° C., and is preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, styrene and It is produced from a monomer containing at least 80% by weight of one or more monomers selected from the group consisting of α-methylstyrene. The remaining monomer may be any other copolymerizable ethylenically unsaturated monomer, for example, a monomer forming a soft polymer such as an acrylate having 1 to 4 carbon atoms in the alkyl group. can give.

The inorganic compound (C) for modification may be an oxide or chloride of one or more elements selected from the group consisting of Si, Mg, Al, Ca, Ba, Zn and Ti. , Hydroxides, carbonates and sulfates alone or in mixtures thereof. Specific examples thereof include, for example, SiO 2
_{2, MgO, Mg (OH)} 2, MgCO 3, Al 2 O 3, A
l (OH) ₃ , Al ₂ (CO ₃ ) ₃ , CaO, CaCO ₃ ,
Examples include TiO ₂ , talc, clay, diatomaceous earth, calcium metasilicate, and the like. These inorganic compounds are 25 ° C
Is preferably 0.5 g / 100 cc or less.

The coagulated particles obtained in the present invention are subjected to a solidification treatment and then dehydrated and dried. At this time, if solidified at a high temperature, the moisture content of the wet powder after dehydration decreases, and the heat energy in the drying step can be reduced.

A powdery polymer having a high bulk specific gravity can be obtained by compressing and compressing the dried graft copolymer (A) powder under pressure. When the dry powder is compressed under pressure, it forms a block. At this time, voids inside the coagulated particles can be eliminated. Examples of the method of pressurizing and compressing include, but are not limited to, compression granulators such as tabletting and briquetting, and extrusion granulators. In the block-shaped dry powder obtained here, the surface of the coagulated particles is modified with the hard inelastic polymer (B) and / or the inorganic compound (C), so that the block can be easily converted into the original coagulated particles. It can be disintegrated into a state of precipitated particles. At this time,
The coagulated particles are in a state where the inside of the particles is compacted.

The pressure at the time of pressurizing and compressing is from 100 to 100
1000 [Kg / cm ² ] or 100 to 1000 at linear pressure
[Kg / cm], preferably 200 to 700 [K
g / cm ² ] or 100 to 700 [Kg / cm] at a linear pressure.
Is good. If both the surface pressure and the linear pressure are less than the lower limits, the consolidation effect is not sufficient and a satisfactory bulk specific gravity cannot be obtained. Also, when the pressure exceeds the upper limit, or when pressurized and compressed without performing surface modification of the coagulated particles, the block cannot be disintegrated, and cannot be returned to the original state of the coagulated particles,
The bulk specific gravity, which is the object of the present invention, cannot be improved.

As the method of crushing the block, a crusher such as a hammer crusher, a crusher such as a hammer mill and a pin mill, and a fine crusher such as a jet mill are used. These pulverizers are selected according to the hardness of the block and used in combination.

A typical apparatus used to carry out the present invention will be described with reference to FIG. Graft copolymer (A)
Latex is sent from the metering pump (1) and acid is sent from the metering pump (2) to the first tank (5). The acid added to increase the recovery of the polymer is sent from the metering pump (3) to the second tank (6). An alkali as a pH adjuster of the slurry is sent from the metering pump (4) to the third tank (7). After the slurry is heat-treated in the fourth tank (8), it is further washed with water (not shown), dewatered, dried, compressed under pressure and crushed to obtain a powdery polymer.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In addition, the Example was performed using the apparatus shown in FIG.

Example 1 70 parts by weight of a styrene-butadiene elastic base polymer were polymerized with 15 parts by weight of styrene, 13.2 parts by weight of methyl methacrylate, and 1.8 parts by weight of ethyl acrylate to obtain a graft copolymer latex (solid content). 3
6% by weight). The average particle size of the obtained latex is 0.1 μm, the pH is 8.0, and the type and amount of the surfactant present in the latex are as shown in Table 1.

The above latex and the acid of the type shown in Table 1 were supplied so that the pH in the first tank and the amount (%) of coagulated polymer became the values shown in Table 1. Acids of the type shown in Table 1 were supplied to the second tank so that the pH became the value shown in Table 1. Third
An alkali of the type shown in Table 1 was supplied to the tank so that the pH became the value shown in Table 1. In addition, the temperature of each tank was controlled so as to be a value shown in Table 1. After the slurry discharged from the fourth tank is washed with water, dehydrated and dried, hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd., product number: R972, average particle size 0.014 μm)
m) was dry blended by 0.5% by weight to obtain a dry powder.

The obtained dry powder was pressed and compressed at a pressure of 300 [Kg / cm ² ] with a tableting machine having a diameter of 50 mm to form a block. This block was crushed using a screen mill to obtain a powdery granular polymer. The bulk specific gravity of the obtained granular polymer, the uniformity of the particles, and the thermal stability were evaluated by the methods described below. Table 1 shows the results.

Particle Uniformity: The particle uniformity N was represented by the following formula. N = D ₇₅ / D ₂₅ (where D ₇₅ is the particle diameter (μm) at 75% of the cumulative weight distribution curve or D ₂₅ is 25% of the cumulative weight distribution curve of the particle group
Represents the particle diameter (μm). ) Bulk specific gravity: Measured according to JIS K-6721. Thermal stability: The dried powder was placed in a gear oven maintained at a constant 120 ° C., and the change with time in the state of thermal coloring was visually evaluated. The state of coloring was evaluated in the following three stages. ○ Almost no coloring. △ Color yellow. × Burn to brown.

Examples 2 and 3 The same as Example 1 except that the type of surfactant present in the latex, the pH in the first tank, and the amount of coagulated polymer were changed as shown in Table 1. To obtain a powdery polymer. Table 1 shows the evaluation results.

Example 4 The amount of the surfactant present in the latex, the pH of the first tank, the amount of coagulated polymer, and the pH of the second tank were changed as shown in Table 1, and the third tank was changed. A powdery polymer was obtained in the same manner as in Example 1, except that the pH was changed as shown in Table 1 without adding the alkali. Table 1 shows the evaluation results.

Example 5 The type and amount of surfactant present in the latex, the pH of the first tank, the amount of coagulated polymer, and the pH of the second tank were changed as shown in Table 1, A powdery polymer was obtained in the same manner as in Example 1 except that the pH was changed as shown in Table 1 without adding alkali in the tank. Table 1 shows the evaluation results.

[0035]

[Table 1]

Examples 6 and 7 A powdery polymer was obtained in the same manner as in Example 5 except that the heat treatment temperature in the fourth tank was changed as shown in Table 2. Table 2 shows the evaluation results.

Examples 8 and 9 A powdery polymer was obtained in the same manner as in Example 5 except that the compression pressure was changed as shown in Table 2. Table 2 shows the evaluation results.

[0038]

[Table 2]

Example 10 12.5 parts by weight of styrene, 11 parts by weight of methyl methacrylate and 1.5 parts by weight of ethyl acrylate were added to 75 parts by weight of an elastic styrene / butadiene base polymer.
The weight part was polymerized to obtain a graft copolymer latex (solid content: 36% by weight). The average particle diameter of the obtained latex is 0.1 μm, the pH is 8.0, and the type and amount of the surfactant present in the latex are as shown in Table 3.

The above latex and the acid of the type shown in Table 3 were supplied so that the pH in the first tank and the amount (%) of coagulated polymer became the values shown in Table 3. Acids of the type shown in Table 3 were supplied to the second tank so that the pH became the value shown in Table 3. In the third tank, alkalis of the type shown in Table 3 were supplied so that the pH became the value shown in Table 3, and further, methyl methacrylate 85
2 parts by weight of a rigid inelastic polymer latex (solid content: 25% by weight, average particle size: 0.1 μm) obtained by emulsion polymerization of 15 parts by weight of butyl acrylate and 100 parts by weight of the graft copolymer. (In terms of solid content) was added. In addition,
The temperature of each bath was controlled so as to be a value shown in Table 3. 4th
The slurry discharged from the tank was washed with water, dehydrated, and dried to obtain a dry powder.

The obtained dry powder was compressed into a block shape using a roller compactor (roll diameter: 10 inches, roll width: 4 inches). The obtained block-like material was crushed using a Fitzmill manufactured by Hosokawa Micron to obtain a powdery polymer. Table 3 shows the evaluation results.

Example 11 The type and amount of the surfactant present in the latex, the pH of the first tank and the amount of the coagulated polymer, and the pH of the second tank were changed as shown in Table 3, A powdery polymer was obtained in the same manner as in Example 10 except that the pH was changed as shown in Table 3 without adding the alkali in the tank. Table 3 shows the evaluation results.

Examples 12 and 13 Powdered and granular polymers were obtained in the same manner as in Example 11 except that the heat treatment temperature in the fourth tank was changed as shown in Table 3. Table 3 shows the evaluation results.

[0044]

[Table 3]

Comparative Example 1 The same procedure as in Example 4 was carried out except that the pH in the first tank was changed as shown in Table 4, and no acid was supplied to the second tank because coagulation was completed in the first tank. To obtain a powdery polymer. Table 4 shows the evaluation results.

Comparative Example 2 A powdery polymer was obtained in the same manner as in Example 4 except that the pH in the first tank and the amount of the coagulated polymer were changed as shown in Table 4. Table 4 shows the evaluation results.

[Comparative Examples 3 and 4] pH of the second and third tanks
Was changed as shown in Table 4 to obtain a powdery polymer in the same manner as in Example 5. Table 4 shows the evaluation results.

[0048]

[Table 4]

[Comparative Examples 5 and 6] Table 5 shows the compression pressure of the tableting machine.
Except having been changed as shown in the above, a powdery polymer was obtained in the same manner as in Example 4. Table 5 shows the evaluation results. The block-like material obtained in Comparative Example 6 was firm and difficult to disintegrate.

Comparative Examples 7 and 8 Powdered and granular polymers were obtained in the same manner as in Example 11 except that the roll pressure of the roller compactor was changed as shown in Table 5. Table 5 shows the evaluation results. The block obtained in Comparative Example 8 was firm and difficult to disintegrate.

[0051]

[Table 5]

[0052]

According to the method of the present invention, by controlling the amount of the rubber-containing polymer latex containing a specific amount of the surfactant during the first stage of coagulation, the fine powder is reduced and the particle size is reduced. A powdery polymer having a sharp distribution can be easily obtained, and a powder having a high bulk specific gravity can be obtained by compressing and pulverizing a dry powder obtained by surface modification after coagulation.

[Brief description of the drawings]

FIG. 1 is an example of an apparatus used in the present invention.

[Explanation of symbols]

 1, 2, 3, 4 Metering pump 5 First tank 6 Second tank 7 Third tank 8 Fourth tank

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-60-217224 (JP, A) JP-A-55-90520 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 3/12

Claims (3)

(57) [Claims] 1. A latex of a graft copolymer (A) obtained by emulsion-polymerizing a rigid polymer-forming monomer with an elastic base polymer and having an elastic base polymer content of 60% by weight or more. 0.1 to 10 parts by weight of the hard inelastic polymer (B) and / or the inorganic compound (C) are added to the obtained coagulated slurry or polymer powder in 100 parts by weight of the graft copolymer (A). ) And compressing the graft copolymer (A) powder at a surface pressure of 100 to 1000 [Kg / cm ² ] or a linear pressure of 100 to 1000 [Kg / cm], followed by crushing. A method for producing a powdery or granular polymer, comprising: 2. A polymer latex containing a total of 0.05 to 0.5 parts by weight of a sulfate ester type and / or sulfonic acid type anionic surfactant per 100 parts by weight of the graft copolymer (A), Using an acid, a pH of 40
2. The method for producing a powdery granular polymer according to claim 1, wherein the coagulation is completed by coagulation by 80 to 80% by weight and further adding an acid or a salt. (Equation 1) (Where X is the number of parts by weight of the sulfate ester-based and sulfonic acid-based anionic surfactant based on 100 parts by weight of the graft copolymer (A)) 3. An acid is used for coagulation in the second stage, and p
3. The method according to claim 2, wherein the coagulation is completed at H2.0 or more.