JPH10101804A - Production of thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject resin excellent in color tone and appearance, low in water content with reduced rise in cost by a drying caloric value by coagulating a polymer latex by an aqueous solution of magnesium sulfate adjusted to a specific pH. SOLUTION: (A) A thermoplastic polymer latex obtained by polymerizing a monomer by using an emulsifying agent which is a compound containing a group of the formula -PO3 M2 [M is an alkaline (earth) metal] or a group of the formula -PO2 M in the molecule [e. g. a compound of the formula (R<1> is a 4-8C alkyl or alkenyl; R<2> is an ethylene group or a propylene group; (x) is 4-8; (y) is 1 or 2; (z) is 3 y] is brought into contact with (B) an aqueous solution of magnesium sulfate adjusted to pH6.5-8.0 and coagulated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thermoplastic resin by emulsion polymerization, and more particularly to a method for recovering a polymer from a polymer latex of a thermoplastic resin obtained by emulsion polymerization.

[0002]

2. Description of the Related Art A polymer recovered from a polymer latex obtained by emulsion polymerization is added as a modifier to ABS resin, high impact styrene resin, vinyl chloride resin, methacrylic resin, and the like. In some cases. It is a widely known fact that impact resistance, thermal properties and moldability are improved by adding a polymer recovered from a polymer latex by emulsion polymerization to the resin or the like.

[0003] As a method for recovering a polymer from a polymer latex which is an emulsion polymer, generally, a method of adding an inorganic salt such as aluminum chloride or sodium sulfate, aluminum sulfate or sodium nitrate, or an acid such as sulfuric acid is used. There is a method of adding. However, depending on the type of inorganic salt used, the recovered polymer is affected, and various physical properties may be impaired. An example is as follows.

(1) When an inorganic salt having chloride ions is used, the obtained polymer causes metal rust and causes a problem in the production process.

(2) When nitrate ions are added, the recovered polymer is colored. When an inorganic salt having a monovalent cation and a monovalent or divalent anion such as sodium chloride and sodium sulfate is used, it is necessary to add a large amount of the inorganic salt in order to stably recover the polymer. is there.
Further, when the obtained polymer is added to a methacrylic resin or the like, hot water whitening is remarkable.

(3) When sulfuric acid is used, the color of the recovered polymer is good, but AB containing the polymer is good.
S resin has a large amount of deposits on the mold during the molding process, and the gloss of the surface is reduced, so that the appearance of the molded product is inferior. Therefore, it is desirable to stably recover the polymer from the polymer latex without the above-mentioned adverse effects.

On the other hand, when the wet polymer recovered from the latex is to be dried using a compression dehydrator or a hot air drier, the lower the water content, the faster the drying speed and the more efficient. The water content of the wet polymer is affected by differences in hardness and glass transition temperature of the polymer, but is also greatly affected by the combination of an emulsifier and a coagulant. Therefore, when recovering the polymer from the polymer latex, it is desirable to reduce the water content of the polymer as much as possible by the combination of the emulsifier and the coagulant.

The present applicant has described a method for recovering a polymer which has low metal corrosiveness during molding and does not deteriorate the physical properties of a resin composition obtained when added to another resin. ₃ M _2, -PO ₂ M (however, M is an alkali metal or alkaline earth metal) a process for preparing thermoplastic resin comprising contacting the latex obtained with the emulsifier represented by an aqueous solution of magnesium sulfate Patent application (JP-A-63-227606). However, in this method, although the metal corrosiveness during the molding process is small, the water content of the wet polymer recovered from the latex is relatively high, and as a result, a large amount of heat is required for drying and the product cost is increased. I found that there was a problem.

[0009]

Means for Solving the Problems Accordingly, the present inventors have conducted intensive studies in view of such a situation, and as a result, when coagulating a polymer latex with an aqueous solution of magnesium sulfate, the pH of the aqueous solution was adjusted to a salt or an aqueous solution. It has been found that the above problems can be solved by adjusting the pH to 6.5 to 8 using a base, and a polymer having further excellent color tone and appearance can be recovered.

That is, the present invention provides at least one of compounds having a group represented by —PO ₃ M ₂ or —PO ₂ M (where M represents an alkali metal or an alkaline earth metal) in the molecule as an emulsifier. A thermoplastic polymer latex obtained by polymerizing a monomer using one kind is prepared to have a pH of 6.5 to 6.5.
A method for producing a thermoplastic resin, comprising contacting and coagulating with an aqueous solution of magnesium sulfate adjusted to 8.0.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, monomers include alkyl methacrylate, alkyl acrylate, aromatic vinyl compound, acrylonitrile,
At least one of methacrylonitrile and butadiene
Those containing 0% by weight or more are exemplified.

Examples of the alkyl methacrylate include:
Methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, etc .; alkyl acrylates, such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate; and aromatic vinyl compounds, styrene. , Vinyltoluene, α-methylstyrene and the like are used.

The other monomer units constituting not more than 20% by weight of the polymer together with not less than 80% by weight of the above units include:
In addition to methacrylic acid, acrylic acid, hydroxyethyl methacrylate, etc., ethylene glycol dimethacrylate,
Multifunctional monofunctional compounds such as divinylbenzene, 1,4-butylene glycol diacrylate, allyl methacrylate, triallyl cyanurate, allyl cinnamate, allyl sorbate, diallyl maleate, diallyl phthalate, triallyl trimellitate, diallyl fumarate Dimer.

The emulsifier used when emulsion-polymerizing these monomers includes —PO ₃ M ₂ , —PO ₂ M
(However, M is an alkali metal or alkaline earth metal)
Is a compound having a group represented by the formula: Specifically, a phosphoric acid ester salt represented by the following general formula (1) or a mixture thereof, or a phosphoric acid ester salt represented by the following general formula (2) or a mixture thereof is preferable. Mono-n-butylphenylpentaoxyethylene phosphate, di-n-butylphenylpentaoxyethylene phosphate, mono-n-pentylphenylhexaoxyethylene phosphate, di-n-pentylphenylhexaoxyethylene phosphate, mono- n-heptylphenylpentaoxyethylene phosphate, di-n-heptylphenylpentaoxyethylene phosphate, mono-n-pentyloxyheptaoxyethylene phosphate, di-n-pentyloxyheptaoxyethylene phosphate, mono-n- Hexyloxypentaoxyethylene phosphate, di-n-hexyloxypentaoxy Alkali metal salts or alkaline earth metal salts of ethylene phosphoric acid.

[0015]

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[0016]

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The alkali metal is preferably sodium or potassium, and the alkaline earth metal is preferably calcium or barium. These phosphate ester salts can be used alone or as a mixture of a monoester and a diester.

The amount of the phosphoric acid ester salt represented by the above general formulas (1) and (2) is closely related to the type of the monomer to be polymerized, the polymerization conditions, etc. Although not possible, it is in the range of 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts of the monomer.

The method of initiating the polymerization is not particularly limited. Examples of the radical polymerization initiator include benzoyl peroxide, cumene hydroperoxide, peroxides such as hydrogen peroxide, azo compounds such as azobisisobutyronitrile, and the like. Examples thereof include persulfate compounds such as ammonium persulfate and potassium persulfate, perchloric acid compounds, perboric acid compounds, and redox-based initiators comprising a combination of a peroxide and a reducing sulfoxy compound.

The monomers and the polymerization initiator may be added by any known method such as a batch addition method, a split addition method, a continuous addition method, a monomer addition method and an emulsion addition method. In order to promote the reaction smoothly, the reaction system is replaced with nitrogen, the reaction system is heated after completion of the reaction to remove residual monomers, or a special catalyst is added. You may.

Examples of the thermoplastic resin in the present invention include an acrylic multi-layer structure polymer in which the water content of the wet polymer recovered from the latex tends to be high.
As a specific structure, for example, the inner layer is a soft polymer layer, the outer layer is a two-layer polymer having a hard polymer layer, or the innermost layer is a hard polymer layer, the middle layer is a soft polymer layer, and the outermost layer is hard. A three-layer polymer that is a polymer layer, or a four-layer in which the innermost layer is a soft polymer layer, the second layer is a hard polymer layer, the third layer is a soft polymer layer, and the outermost layer is a hard polymer layer. There are structural polymers and the like.

The appropriate polymerization temperature for forming the polymer of each layer is in the range of 30 to 120 ° C., preferably 50 to 100 ° C. for each layer. The ratio of monomer / water is not particularly limited, and is about 1/1 to 1/5, usually 1 / 1.5 to 1.5.
It is performed in the range of 1/3. In addition, in the polymerization, additives usually added at the time of polymerization, such as a continuous transfer agent and an ultraviolet absorber, can be used.

In the operation of recovering the polymer from the polymer latex, the concentration range of the aqueous solution of magnesium sulfate used is 0.1 to 30% by weight, more preferably 1 to 15% by weight.
% By weight. If the amount is less than 0.1% by weight, it may not be possible to recover the polymer stably. If the amount exceeds 30% by weight, the cost increases, and the amount of the polymer remaining in the recovered polymer is undesirably large. Magnesium sulfate is preferably used alone. If necessary, it can be used in combination with other inorganic salts or acids. However, when used in combination with a calcium salt, it is not preferable because it becomes insoluble calcium sulfate.

The pH of the aqueous solution of magnesium sulfate used in the present invention is in the range of 6.5 to 8.0. pH6.
If it is less than 5, the effect of reducing the water content of the obtained wet polymer is relatively small, and if it exceeds pH 8.0, alkali hydrolysis of the polymer occurs when the polymer obtained after coagulation is shaped, and The appearance may be easily impaired.

Compounds used for adjusting the pH of the aqueous magnesium sulfate solution include sodium hydrogen carbonate, sodium carbonate, sodium hydroxide and potassium hydroxide. Dissolve these salts or bases in a small amount of water,
Easy addition to magnesium sulfate aqueous solution
H can be adjusted to 6.5 to 8.0.

The temperature at which the latex is brought into contact with an aqueous solution of magnesium sulfate adjusted to a predetermined pH cannot be unambiguously specified because the fusibility differs depending on the polymer structure, but is preferably in the range of 30 ° C. to 100 ° C. At this time, the polymer thus set is washed with about 1 to 100 times of water and dried using a fluidized drier or a press dehydrator.

[0027]

The present invention will be further described with reference to the following examples.
In the description, “parts” represents “parts by weight”, and “%” represents “% by weight”. Prior to the description, Table 1 shows the emulsifiers used in each of the Examples and Comparative Examples and the amounts (parts) of the emulsifiers.

[0028]

[Table 1]

The various evaluation items used in the table will be described below. Regarding the physical properties of the polymer in the evaluation items, a test piece obtained by injection-molding the polymer using a “V-17-65 screw-type automatic injection molding machine” manufactured by Nippon Steel Works under the following conditions was performed. Injection molding conditions: cylinder temperature 250 ° C., injection pressure 700 kg / cm ² Test piece size: 110 mm × 110 mm × 2 mm (thickness) 70 mm × 12.5 mm × 6.2 mm (thickness)

(1) Izod impact strength (with notch) Measured according to ASTM-D-256.

(2) Appearance of Molding Visual judgment was made according to the following criteria. ◎ Clear and extremely good ○ Good △ Slightly yellowish × Extremely yellowish

(3) Metal Corrosion The polymer is extruded into pellets, and a general mild steel having a mirror-polished surface is added to a large number of pellet particles.
After holding for a minute, the surface of the mild steel was observed. ○ ・ ・ ・ The metallic luster of the surface hardly changed △ ・ ・ ・ The metallic luster of the surface slightly decreased × ・ ・ ・ The metallic luster of the surface was lost

(4) Hot Water Whitening The injection molded plate was immersed in hot water of 95 ° C., kept for 120 minutes, and the surface was observed. No change was observed, slight whitening was observed, and whitening was marked as x.

(5) Mold Adhesion At the time of injection molding, after the mold surface is washed, the light reflectance (α = 60 °) of the third shot molding plate is set to a reference value of 100 and 50
The value of the shot was shown as a relative value.

(6) Moisture content (W _c )% 5 g of the wet polymer was dried with hot air at 180 ° C. for 1 hour, and the dry weight (W _D ) was measured. The formula: W _c = [(5-W _D ) /
It was determined using the W _D] × 100.

(7) Fluid drying characteristics The wet polymer [5 × (100 + W _c )] g weighed so as to have a dry powder amount of 500 g was heated at a hot air temperature of 70 ° C. and an air volume of 7 g.
1 cm ³ / sec, blowing speed of warm air 40 cm / sec
After drying for 60 minutes under the condition of c, the water content at that time was determined.

Example 1 (A) Deionized water 30 was placed in a stainless steel reaction vessel.
0 parts were charged and heated. When the internal temperature reached 80 ° C., a mixture having the following composition ratio was charged. Formaldehyde sodium sulfoxylate dihydrate (hereinafter referred to as Rongalit) 0.48 part Ferrous sulfate 0.4 × 10 ^-6 parts Disodium ethylenediaminetetraacetate 1.2 × 10 ^-6 parts

After holding for 15 minutes after charging, a mixture having the following composition ratio, which had been replaced with nitrogen in advance, was added dropwise over 2 hours, and polymerization was carried out for 1 hour while maintaining at 80 ° C. The polymerization rate of the obtained latex was 99% or more. 1,3-butylene methacrylate 1.1 parts Diallyl maleate 0.14 parts t-butyl hydroperoxide 0.08 parts Emulsifier A 1.20 parts

(B) Subsequently, the mixture (a) having the following composition ratio was charged into the reactor and maintained for 15 minutes.
The mixture was added dropwise over a period of time, and polymerization was further performed for 3 hours. The polymerization rate of the obtained latex is 99% or more, and the particle size is 0.33 μm.
m. (A) Rongalit 0.2 part Deionized water 5 parts (b) Styrene 11.0 parts Butyl acrylate 49.0 parts 1,3-butylene methacrylate 0.2 parts Diallyl maleate 1.0 part Cumene hydroperoxide 0.17 parts Emulsifier A 1.8 parts

(C) Next, a mixture (c) having the following composition ratio was charged into the reactor and maintained for 30 minutes, and then a mixture (d) having the following composition ratio, which had been preliminarily replaced with nitrogen, was taken over 3 hours. The mixture was added dropwise and polymerized for another hour. The polymerization rate of the obtained latex is 99% or more, and the particle size is 0.27 μm.
Met. (The latex obtained here is referred to as Lx-A.) (C) Rongalit 0.2 part Deionized water 5 parts (d) Methyl methacrylate 95 parts Methyl acrylate 5 parts t-butyl hydroperoxide 0.2 Part Normal octyl mercaptan 0.3 part

(D) A 2.6% aqueous magnesium sulfate solution was charged into a stainless steel container as a collecting agent, and a 5% sodium hydrogen carbonate solution was added to adjust the pH of the aqueous magnesium sulfate solution to 6.5. The temperature was raised to 90 ° C. with stirring, and the latex (Lx-A) previously produced was continuously added.
Hold for 0 minutes. After cooling to room temperature, the polymer was filtered with a centrifugal dehydrator while washing with deionized water to obtain a white wet polymer (water content: 75%). Table 2 shows the drying characteristics.
Shown in

Next, a mixture of 2000 g of the powder and 2000 g of a methacrylic resin (Acrypet (registered trademark) VH: manufactured by Mitsubishi Rayon Co., Ltd.) was mixed with a screw-type extruder having an outer diameter of 40 mmφ (manufactured by Nippon Steel Works, Ltd.). , P-40-
26AB-V type, L / D = 26), melt-kneaded at a cylinder temperature of 200 to 260 ° C. and a die temperature of 250 ° C. to form pellets, and the content of the multilayer acrylic elastic body is 25.
% Of an impact-resistant methacrylic resin composition was obtained. Table 2 shows the evaluation results of the resin composition.

[Examples 2 to 9] and [Comparative Examples 1 to 9] Using the latex (Lx-A) obtained in Example 1,
Table 2 shows the pH adjuster and the pH of the aqueous magnesium sulfate solution.
Except for the following changes, a wet polymer was obtained in the same manner as in Example 1. After drying, this powder and a methacrylic resin were blended in the same manner as in Example 1 to obtain an impact-resistant methacrylic resin composition having a multilayer acrylic elastic body content of 25%. Table 2 collectively shows the water content, the drying characteristics, and the evaluation results of the impact-resistant methacrylic resin composition of the wet polymer.

[0044]

[Table 2]

Examples 10 to 18 and Comparative Examples 10 to 3
8] Emulsion polymerization was carried out in the same manner as in Example 1, except that the emulsifier and the amount added were changed as shown in Table 1.

Using each of the obtained latexes,
Table 3 shows the pH adjuster and the pH of the aqueous magnesium sulfate solution.
A wet polymer was obtained in the same manner as in Example 1 except that the polymer was changed as shown in Nos. 4 to 4. After drying, this powder and a methacrylic resin were blended in the same manner as in Example 1 to obtain an impact-resistant methacrylic resin composition having a multilayer acrylic elastic body content of 25%. The water content of the wet polymer of each example, drying characteristics,
The evaluation results of the impact-resistant methacrylic resin composition are collectively shown in Tables 3 and 4.

[0047]

[Table 3]

[0048]

[Table 4]

[0049]

According to the present invention, it is possible to obtain a thermoplastic resin which is excellent in drying efficiency when drying a wet polymer recovered from a polymer latex and which has excellent color tone.

Claims (3)

[Claims] 1. Emulsion polymerization of a monomer using a compound having a group represented by —PO ₃ M ₂ or —PO ₂ M (where M is an alkali metal or an alkaline earth metal) in a molecule as an emulsifier. A process for collecting a polymer from the latex obtained by contacting the latex with an aqueous solution of magnesium sulfate adjusted to pH 6.5 to 8.0 to coagulate the latex. 2. The method of adjusting the pH of the aqueous magnesium sulfate solution,
The method for producing a thermoplastic resin according to claim 1, wherein at least one compound selected from the group consisting of sodium hydrogen carbonate, sodium carbonate, sodium hydroxide, and potassium hydroxide is added. 3. The method for producing a thermoplastic resin according to claim 1, wherein the emulsifier is at least one selected from the following general formulas (1) and (2). Embedded image Embedded image