JPH07173217A - Production of resin powder - Google Patents

Abstract

PURPOSE: To reduce the residual impurities in a resin powder obtained from a polymer latex and to obtain a resin powder having a high heat stability.

CONSTITUTION: When preparing a resin powder from a polymer latex, the polymer latex is mixed with a coagulant to prepare a solid slurry with a pH of lower than 6, which is then heated at from 50 to 125°C to solidity the coagulated particles. Subsequently, by adding a basic substance to the solid slurry or by converting the dehydrated cake, obtained by dehydrating the solid slurry, back into a slurry using a solution containing a basic substance, a solid slurry having a pH of 6 or larger is obtained. Then, by adding an acidic substance to this solid slurry or by converting the dehydrated cake, obtained by dehydrating the solid slurry, back into a slurry using a solution containing an acidic substance, the pH is adjusted to 5.5 or lower.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing resin powder. More specifically, when producing resin powder from polymer latex, the polymer latex is coagulated with inorganic salts, acids, etc., and the coagulated slurry is heated to solidify coagulated particles and then treated with a basic substance. Then p
H is adjusted to 6 or more, preferably 7 or more, more preferably 10 or more to prepare a coagulated slurry, and then pH with an acidic substance
The amount of contaminants such as emulsifiers is remarkably small, and the thermal stability, transparency, and physical properties such as maintaining the taste (taste test) of the resin powder are extremely good. Regarding manufacturing method.

[0002]

2. Description of the Related Art When recovering a resin powder from a polymer latex, it is common to obtain a resin powder by coagulating the polymer latex with a coagulant such as an inorganic salt or an acid.

In this method, first, a polymer latex is brought into contact with an aqueous solution of a coagulant to form a coagulated slurry, which is then heated and heated to solidify the coagulated particles, dehydrated and washed, and then dried to obtain a resin powder. The operation of is taken.

Various processes have been studied so far for this method. For example, by dispersing a polymer latex in the form of droplets in a coagulant atmosphere to coagulate, a very small amount of fine powder having a controlled particle size is obtained. A method for obtaining spherical particles (JP-A-53-30647) or a method for producing substantially spherical coagulated particles by slow coagulation (JP-A-60-217)
Various technologies have been proposed, such as Japanese Patent No. 224).

Typical examples of the resin powders produced by these methods are resin powders for improving the impact resistance of vinyl chloride resins represented by MBS resin powders and resin powders for improving the processability of acrylic vinyl chloride resins. can give.

[0006]

In the case of the coagulation method as described above, due to the nature of the above-mentioned production process, polymerization aids such as emulsifiers and polymerization initiators, unpolymerized monomers, coagulants, etc. It tends to remain in the product, and the influence of residual impurities on the quality is often a problem.

For example, contaminants such as emulsifiers remaining in the resin powder cause deterioration of the external appearance such as heat stability and transparency of the molded product obtained by mixing the resin powder with vinyl chloride resin. . In addition, it may cause deposits at the die outlet during extrusion molding, and may cause problems such as deterioration of the quality of the molded product due to smoke during molding and deterioration of the working environment. Furthermore, vinyl chloride resin compositions containing these modifying resin powders are also widely used for food packaging applications, and for example, regarding the taining, which is an important physical property when used in bottles for drinking water, resin powders are also used. It is known that the residual contaminants inside are the cause of the problem.

As described above, it is desirable to reduce the content of residual contaminants in the resin powder as much as possible, and the technique for producing resin powder that meets this purpose is extremely significant industrially. Until now, various manufacturing methods have been proposed to reduce the residual impurities in the resin powder.

[0009] For example, in Japanese Patent Publication No. 3-24486, when a thermoplastic resin latex made of butadiene, methyl methacrylate and styrene is coagulated to produce a thermoplastic resin powder, coagulation is carried out under a temperature condition within a specific range. Perform the operation to add a basic substance to the solidified slurry under a temperature condition within a specific range to raise the pH of the solidified slurry to 0.1 or more higher than the initial value, and
A manufacturing method has been proposed, which is characterized by adjusting to 6.0 or less and does not require a cleaning step.

However, the resin powder produced by this method is not sufficiently effective because the pH adjustment of the slurry is limited to 6.0 or less and the treatment with an acidic substance is not carried out. Insufficient thermal stability.

In Japanese Patent Publication No. 49-41334, a vinyl chloride resin having excellent thermal stability is obtained by adjusting the pH of a coagulated slurry obtained by coagulating a vinyl chloride resin modifying resin latex to 7 to 13. A method for producing a modifying resin powder has been proposed.

However, in this method, since the coagulated slurry is placed under basic conditions, it is difficult to maintain the coagulated state of the particles that have once coagulated, and the coagulated particles disintegrate, fine particles are generated by re-emulsification, and the filter cloth is used. This will cause problems in the manufacturing process such as clogging. Further, in the case of a resin powder containing a diene monomer, especially butadiene as its monomer component, such as MBS resin powder, the resin powder treated under such a high pH condition will not oxidize the resin powder. This is not preferable from the viewpoint of safety during manufacturing, since it is more likely to occur and the risk of fire accident due to oxidation heat generation in the drying process increases. In other words, a technique for producing a resin powder, which is capable of sufficiently removing residual contaminants such as an emulsifier and at the same time having high safety during production and having no problem in the production process, has not been established so far.

According to the present invention, when a resin powder is produced from a polymer latex, the residual amount of impurities such as an emulsifier in the resin powder is sufficiently reduced, and at the same time, the resin powder which solves the above-mentioned problems in production. It was made to establish the manufacturing technology of.

[0014]

[Means for Solving the Problems] The present inventors have made it possible to control the content of contaminants such as emulsifiers remaining in the resin powder with high safety during the manufacturing of the resin powder, no problems in the manufacturing process. As a result of earnest studies to establish a manufacturing technique for reducing as much as possible, after solidifying the solidified particles by heating the solidified slurry obtained by solidifying the polymer latex by a normal method under specific temperature conditions, When the resin powder is produced by a series of operations in which the solidified particles are treated with a basic substance so as to be under the pH condition of a specific range, and then with an acidic substance so as to be kept under the pH condition of the specific range. Has a specific effect in solving the above problems, that is, the content of contaminants such as residual emulsifier in the resin powder produced by such a production method is significantly reduced, and Physical properties such as thermal stability, transparency, and tainting of molded products made from a composition in which powder is mixed with vinyl chloride resin, for example, are highly safe during manufacturing, and workability in the manufacturing process is improved. They have found that it is possible to manufacture without any loss, and have completed the present invention.

That is, according to the present invention, when a resin powder is produced from a polymer latex, a coagulant is added to the polymer latex to prepare a coagulated slurry having a pH of less than 6 and then 50 to 50%.
The solidified particles are solidified by heat treatment at a temperature of 125 ° C, and then the basic substance is added to the solidified slurry, or the dehydrated cake obtained by dehydrating the solidified slurry is treated with a solution containing a basic substance. The coagulated slurry was adjusted to pH 6 or more, preferably 7 or more, and more preferably 10 or more by returning to the slurry, and then an acidic substance was added to the coagulated slurry or the coagulated slurry was dehydrated. The present invention relates to a method for producing a resin powder, which comprises adjusting the pH to 5.5 or less by returning a dehydrated cake to a slurry with a solution containing an acidic substance.

[0016]

EXAMPLES Examples of the polymer latex that can be the subject of the present invention include the following.

A vinyl group-containing compound comprising at least one selected from aromatic vinyl, vinyl halide, methacrylic acid ester, acrylic acid ester and vinyl cyanide is added to a diene or acrylic acid ester type rubbery polymer. A latex of a graft copolymer obtained by graft polymerization. For example, aromatic vinyl 0-50%
(% By weight, the same shall apply hereinafter), a diene monomer, especially 50 to 100% butadiene, preferably 65 to 100% and a copolymer 20 to 85 consisting of 0 to 10% of a monomer copolymerizable therewith.
0 to 50% acrylic acid ester, 0 to 10% methacrylic acid ester in 40 parts to 75 parts by weight, preferably 40 to 75 parts.
80% to 15 parts of a monomer consisting of 0%, 0 to 90% of aromatic vinyl and 0 to 20% of a monomer copolymerizable therewith, preferably
A latex of a copolymer (MBS resin) obtained by graft-polymerizing 60 to 25 parts (total 100 parts) in one or more stages, preferably in two or more stages.

Methyl methacrylate 50 to 100%, alkyl methacrylate having an alkyl group having 2 to 8 carbon atoms 0
A latex of a copolymer comprising -50%, 0-40% of an acrylate ester, and 0-20% of a monomer copolymerizable therewith.

Copolymer consisting of 80 to 100% of at least one monomer of methyl methacrylate, acrylic acid ester, aromatic vinyl and substituted aromatic vinyl and 0 to 20% of a monomer copolymerizable therewith. Alkyl acrylate having 0 to 70 parts of combined component and alkyl group having 2 to 8 carbon atoms 20 to
100%, aromatic vinyl 0-80%, substituted aromatic vinyl 0
A latex of a copolymer consisting of 100 to 30 parts (total 100 parts) of a copolymer component consisting of 40% and 0 to 20% of a monomer copolymerizable therewith.

Specific examples of the diene-based or acrylic ester-based rubbery polymer in the above-mentioned latex are, for example, polybutadiene, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (N
BR), ethylene-propylene-diene terpolymer rubber (EPDM), butyl polyacrylate, ethyl polyacrylate, 2-ethylhexyl polyacrylate and copolymer rubbers of these acrylates, vinyl group-containing compounds, etc. Specific examples of the aromatic vinyl, vinyl halide, methacrylic acid ester, acrylic acid ester and vinyl cyanide which are are, for example, styrene, α-methylstyrene, etc., vinyl chloride, vinyl bromide, vinyl fluoride, etc. Methyl acid, ethyl methacrylate, n-butyl methacrylate, methacrylic acid t
-Butyl, lauryl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, etc., ethyl acrylate, methyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, cyclohexyl acrylate, acrylonitrile, Examples thereof include methacrylonitrile.

Specific examples of the diene-based monomers described in the above-mentioned specific examples of the latex and the monomers copolymerizable therewith include, for example, butadiene, isoprene, bromoprene, chloroprene and the like, acrylic acid n-
Examples thereof include butyl, 2-ethylhexyl acrylate, styrene and the like.

Specific examples of the above-mentioned latex include, for example, MBS resin latex, ABS resin latex, acrylic weather resistance and impact resistance improving resin latex.

The alkyl methacrylate having an alkyl group having 2 to 8 carbon atoms in the above latex,
Specific examples of the acrylate ester and the monomer copolymerizable therewith include, for example, ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, methyl acrylate, ethyl acrylate, Examples thereof include n-butyl acrylate, 2-ethylhexyl acrylate, styrene, α-methylstyrene, acrylonitrile and the like.

Specific examples of the above-mentioned latex include acrylic processing aid latex.

Further, in the above latex, 0 to
Specific examples of acrylic acid ester, aromatic vinyl, substituted aromatic vinyl and monomers copolymerizable with these which constitute 70 parts of the copolymer component include, for example, methyl acrylate, ethyl acrylate, acrylic acid, respectively. n-butyl, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc., styrene, etc., α-methylstyrene, etc., butyl methacrylate, lauryl methacrylate,
2-hydroxyethyl methacrylate, glycidyl methacrylate, acrylonitrile and the like can be mentioned.

In the above-mentioned latex, 100 to 30 parts of a copolymer component, alkyl acrylate having an alkyl group having 2 to 8 carbon atoms, aromatic vinyl, substituted aromatic vinyl, and a copolymerizable monomer with these are used. Specific examples of the monomer include ethyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc.
Examples thereof include styrene and the like, α-methylstyrene and the like, n-butyl methacrylate, t-butyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, acrylonitrile and the like.

In the present invention, when the resin powder is produced from the polymer latex, the pH of the polymer latex is first adjusted by adding a coagulant to the polymer latex.
Replaced with a solidified slurry of less than 6.

As the coagulant, those commonly used can be used. For example, inorganic salts such as sodium chloride, potassium chloride, calcium chloride, magnesium chloride, magnesium sulfate and aluminum sulfate, sulfuric acid, hydrochloric acid and phosphoric acid. Acids such as acetic acid are used.
These may be used alone or in combination of two or more.

The amount and method of use of the coagulant are not particularly limited, and they may be used according to the usual amount and the usual method.

The obtained solidified slurry is then 50 to 12
Obtained by adding a basic substance after heat treatment at 5 ° C to solidify the solidified particles or by heat treatment at 50 to 125 ° C to solidify the solidified particles and then dehydrating the solidified slurry. By returning the dehydrated cake to a slurry with a solution containing a basic substance, a coagulated slurry having a pH adjusted to 6 or more is obtained.

The preferred temperature for heat-treating the coagulated slurry is slightly different depending on the kind of the polymer latex used. For example, in the case of the above polymer latex, 50 to 95 ° C. is preferable, and the temperature of the polymer latex is In the case of 85 to 125 ° C., in the case of the polymer latex, 50 to 95 ° C. is preferable.

If the heat treatment temperature is lower than the lower limit of the above temperature range, it tends to be difficult to maintain the solidified state of the particles once solidified after the treatment with the basic substance. Are likely to occur, and the solidified particles are likely to be disintegrated, fine particles are generated due to re-emulsification, and the filter cloth is clogged, which causes problems such as difficulty in operation in the manufacturing process. Further, when the heat treatment temperature is higher than the upper limit of the temperature range, respectively, there is a tendency that the solidified particles are completely fused and solidified, and then treated with a basic substance such as an emulsifier. It becomes difficult to expect the effect of reducing residual impurities by washing.

After the heat treatment, the solidified slurry is adjusted to pH.
Specific examples of the basic substance used for adjusting to 6 or more include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, calcium carbonate, sodium phosphate, potassium phosphate, ammonia and the like. To be

The pH of the coagulated slurry is adjusted with a basic substance in the present invention by dehydrating the heat-treated slurry once to obtain a dehydrated cake containing a basic substance in a solution containing, for example, 0.001 to 10% of hydroxylated water. A method of returning to a slurry with a sodium aqueous solution or the like is preferable in terms of the effect of reducing residual impurities such as an emulsifier by washing, but a method of directly adding a basic substance to the slurry after heat treatment may be used. However, in both cases, it is important that the pH of the slurry after addition of the basic substance is 6 or more from the viewpoint of the effect of reducing residual impurities such as emulsifiers by washing, and a further excellent washing effect. The pH is preferably 7 or higher from the standpoint of obtaining a good cleaning effect, and the pH is preferably 10 or higher from the viewpoint of providing a further excellent cleaning effect. When the pH of the slurry after addition of the basic substance is lower than 6, the effect of removing residual contaminants such as emulsifier becomes insufficient, and the resin particles produced by such a method are blended with, for example, vinyl chloride resin. The effect of improving the physical properties of the final product from the composition, such as thermal stability, transparency, and tinting, cannot be fully expected.

In the present invention, the acidic substance is added subsequent to the treatment with the basic substance, and the pH is adjusted to 5.5 or less, further 4 or less.

Specific examples of the acidic substance include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid and carbonic acid.

The above-mentioned acidic substance may be added directly to the slurry after the treatment with the basic substance, or the dehydrated cake obtained by once dehydrating the slurry after the treatment with the basic substance is treated with the acidic substance. A solution containing, for example 0.001-10%
Although it may be returned to the slurry with a hydrochloric acid solution of a certain degree, it is important that the pH of the slurry after addition of the acidic substance is 5.5 or less in any case.

By carrying out such an acid treatment, the thermal stability is remarkably improved as compared with the case where only the treatment using a basic substance is carried out. Further, if this acid treatment is not carried out, the coagulated particles will proceed to a process such as drying while the pH of the coagulated particles remains high. For example, the coagulated particles treated under such a high pH condition will be mentioned as the above-mentioned specific examples. MBS
When it contains a diene monomer, especially butadiene as its monomer component, as in the case of resin powder,
Since it is easy to generate heat due to oxidation, the risk of fire and explosion increases, and it is desirable to perform acid treatment from the viewpoint of safety during manufacturing.

PH of slurry after addition of acidic substances
Is 4 or less, it is more preferable from the viewpoints of safety during production and thermal stability of the final product in the medium and long term.

The resin powder produced from the polymer latex by the production method of the present invention has a significantly reduced residual amount of impurities such as an emulsifier in the resin powder. Physical properties such as heat stability, transparency, and tainting of the product are significantly improved. Further, the acid treatment remarkably improves the thermal stability of the resin powder, as compared with the case where only the base treatment is performed.

The production method of the present invention will be described below based on examples.

Example 1 200 parts of water, 1.5 parts of sodium oleate, 0.002 parts of ferrous sulfate (FeSO ₄ .7H ₂ O), and 0.005 parts of ethylenediaminetetraacetic acid-2Na salt were placed in a pressure-resistant polymerization machine.
Parts, formaldehyde sodium sulfoxylate 0.2 parts,
Tripotassium phosphate 0.2 parts, butadiene 71 parts, styrene 29
Parts, divinylbenzene 1.0 part and diisopropylbenzene hydroperoxide 0.1 part were charged and polymerized by an ordinary method to obtain a latex of a copolymer. 210 parts of this latex (70 parts of solid content), 200 parts of water, 1st of sulfuric acid
Add 0.002 parts of iron, 0.004 parts of ethylenediamine tetraacetic acid 2Na salt, and 0.1 parts of sodium formaldehyde sulfoxylate and add 15 parts of styrene at 70 ° C.
Part, 15 parts of methyl methacrylate and 0.1 part of cumene hydroperoxide were continuously added to obtain a latex of a copolymer obtained by polymerization.

The obtained latex was coagulated with 10% hydrochloric acid to obtain a coagulated slurry. At this time, the temperature of the slurry was 40 ° C. and the pH was 1.2.

Next, the solidified slurry was heated to 60 ° C. to solidify the solidified particles for 5 minutes and then dehydrated to obtain a dehydrated cake. The dehydrated cake obtained was returned to the slurry using 0.005% sodium hydroxide aqueous solution to make a slurry having a pH of 10.1, and then dehydrated, and the obtained dehydrated cake was returned to the slurry using 0.01% hydrochloric acid to obtain a pH of 3.0. Made into a slurry. At this time, the slurry temperature was 40 ° C. After that, the slurry was centrifugally dehydrated, washed with water, and sufficiently dried to obtain a resin powder.

Using the obtained resin powder, the residual impurities were quantified, the safety at the time of production and the physical properties of the molded product from the composition mixed with the vinyl chloride resin were evaluated by the following methods.
The results are shown in Table 1.

The abbreviations in the tables below are as follows.

St: Styrene Bd: Butadiene MMA: Methyl methacrylate EA: Ethyl acrylate BA: n-Butyl acrylate (quantification of residual contaminants) 5 g of the obtained resin powder was added to 50 ml of pure water.
The mixture was boiled at 140 ° C. for 90 minutes to separate the impurities in the resin by steam distillation, and after cooling, the fraction containing the impurities was contacted with dichloromethane to extract the impurities. The above operation was continuously performed using an apparatus manufactured by Chrompack. Contaminants were quantified from the obtained extract by gas chromatography.

Table 1 shows the amount of residual emulsifier as a representative value of the amount of residual contaminants.

(Safety at the time of production) Regarding the decrease in safety at the time of production due to the heat of oxidation of the resin, the exothermic reaction start temperature of the resin by differential thermal analysis (DTA) and the oxygen absorption induction period at 170 ° C. do not cause the heat of oxidation. Since it is known that they serve as an index of ease, these were evaluated and the order of safety was judged relative to A to E as an index of safety during production.

It should be noted that A is not easily oxidized and is extremely safe, B is safe because it does not generate heat due to oxidation under normal operating conditions, and C is exposed to high temperature conditions for a long time, such as the resin adhered in the process. If accumulated, there is a danger of oxidation and heat generation, D is easy to oxidize, and there is a high risk of heat generation and ignition under normal operating conditions, and E is extremely easy to oxidize, always heat generation and ignition under normal operating conditions. Is associated with the danger of.

As a specific measuring method, the heat generation start temperature was obtained by using a Thermal Analyzer DT-30 manufactured by Shimadzu Corporation at a temperature rising rate of 10 ° C. per minute.

In the oxygen absorption induction period, the time until the oxygen absorption of the resin starts at 170 ° C. was measured.

(Physical Properties of Molded Article Made from Vinyl Chloride Resin Composition) 100 parts of vinyl chloride resin (average degree of polymerization 660), epoxidized soybean oil (Adeka Sizer O-130 P manufactured by Asahi Denka Co., Ltd.) 1.5 Parts, zinc stearate 0.14 parts, calcium stearate 0.16 parts, fatty acid polyol ester (Loxiol G-M made by Henkel) 1.2 parts, oxidized polyethylene wax (A-C316 A made by Allied Chemicals)
The following test was conducted using a composition prepared by mixing 0.3 part and 10 parts of the resin powder.

A Transparency and Scatterability After kneading with an 8-inch roll at 170 ° C. for 5 minutes, 170 ° C.
The total light transmittance (%) and the proportion (%) of scattered light were measured using a plate having a thickness of 5 mm prepared by pressing the plate for 15 minutes.

B Thermal Stability A 0.5 mm-thick sheet prepared by kneading at 170 ° C. for 5 minutes using an 8-inch roll was placed in an oven at 175 ° C., and the degree of discoloration of the sheet due to heat was measured with time. (initial,
The thermal stability was determined by visual observation (three times in the middle term and long term).
The order of good thermal stability was A, B, C, D, and E.

The initial period is before putting into the oven, the middle period is after being placed in the oven for one hour, and the long period is after two and a half hours.

Further, A is a state in which there is almost no discoloration, B is a state in which a slight yellow discoloration is recognized, C is a state in which the yellow discoloration progresses and is close to brown, which is apparently a problem in practical use,
D shows a state in which blackening has started to become dark brown, and E shows a state in which it is completely blackened.

Example 2 The pH of the treatment with the aqueous sodium hydroxide solution performed in Example 1 was 7.2, and the pH of the treatment with hydrochloric acid thereafter was 7.2.
Evaluation was performed in the same manner as in Example 1 except that the value was set to 4.0. The results are shown in Table 1.

Example 3 Evaluation was made in the same manner as in Example 1 except that the pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 1 was changed to 6.2. The results are shown in Table 1.

Example 4 The pH of the treatment with the aqueous sodium hydroxide solution performed in Example 1 was 7.2, and the pH of the treatment with hydrochloric acid thereafter was 7.2.
Evaluation was made in the same manner as in Example 1 except that the value was set to 5.5. The results are shown in Table 1.

Example 5 The same as Example 1 except that a 0.005% aqueous potassium hydroxide solution was used in place of the aqueous sodium hydroxide solution used in Example 1 and the pH of the treatment with the aqueous potassium hydroxide solution was 10.2. evaluated. The results are shown in Table 1.

Example 6 The same as Example 1 except that 0.05% potassium phosphate aqueous solution was used in place of the sodium hydroxide aqueous solution used in Example 1, and the pH of the treatment with the potassium phosphate aqueous solution was 9.6. evaluated. The results are shown in Table 1.

COMPARATIVE EXAMPLE 1 Without being treated with the aqueous sodium hydroxide solution used in Example 1, it was solidified with 10% hydrochloric acid (p.
H1.2) was washed with water by a usual method and then dried to obtain a resin powder, which was evaluated in the same manner as in Example 1. The results are shown in Table 1.
Shown in.

Comparative Example 2 Evaluation was carried out in the same manner as in Example 1 except that the pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 1 was changed to 5.6. The results are shown in Table 1.

Comparative Example 3 The pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 1 was adjusted to 6.0, and then the resin powder was obtained without treatment with hydrochloric acid to obtain a resin powder, which was evaluated in the same manner as in Example 1. did. The results are shown in Table 1.

Comparative Example 4 The pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 1 was adjusted to 10.2, and thereafter the resin powder was obtained without treatment with hydrochloric acid to obtain a resin powder, which was evaluated in the same manner as in Example 1. did. The results are shown in Table 1.

Comparative Example 5 The pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 1 was 10.0, and the pH of the treatment with hydrochloric acid thereafter was 10.0.
Evaluation was made in the same manner as in Example 1 except that the value was 6.0. The results are shown in Table 1.

[0068]

[Table 1]

Comparative Example 1 in Table 1 corresponds to the conventional manufacturing method.

It can be seen from Table 1 that the amount of residual emulsifier was remarkably reduced and transparency and thermal stability were further improved in each of the Examples as compared with the conventional production method. Furthermore, it can be said that the manufacturing safety is uniformly excellent.

On the other hand, in Comparative Examples 1 and 2, the amount of residual emulsifier is large, the removal of impurities is insufficient, and the transparency and heat stability are relatively inferior.

Further, in Comparative Examples 3 to 5, the effect of washing with the aqueous sodium hydroxide solution was recognized, and the amount of residual emulsifier was sufficiently reduced, but the subsequent acid treatment was not performed or was insufficient. Inferior mid- and long-term thermal stability
At the same time, it can be seen that the safety during manufacturing is also reduced.

Next, the type of polymer latex used was changed and evaluated.

Example 7 1.5 parts of sodium oleate and 0.1 part of potassium persulfate were added to 20 parts of water.
A monomer mixture consisting of 80 parts of methyl methacrylate and 10 parts of ethyl acrylate was added to 0 parts of the solution and polymerized for 5 hours, and then 10 parts of methyl methacrylate was continuously added. Polymerized. The obtained copolymer latex was coagulated by a usual method using 10% hydrochloric acid to prepare a coagulated slurry. At this time, the slurry temperature is 40 ° C and the pH is 1.
It was 2.

Next, the obtained solidified slurry is heated to 95 ° C. to solidify the solidified particles for 5 minutes and then dehydrated to obtain a dehydrated cake. The dehydrated cake is slurried with a 0.005% sodium hydroxide aqueous solution. Returned to. PH at this time
Was 10.6.

The obtained slurry was dehydrated, and the obtained dehydrated cake was returned to the slurry with 0.01% hydrochloric acid. At this time, the pH was 3.0 and the slurry temperature was 40 ° C.
After that, the slurry was centrifugally dehydrated, washed, and sufficiently dried to obtain a resin powder.

The resin powder thus obtained was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 6 A product obtained by coagulating with 10% hydrochloric acid without performing the treatment with the aqueous sodium hydroxide solution carried out in Example 7 (p.
H1.2) was washed with water by a usual method and then dried to obtain a resin powder, which was evaluated in the same manner as in Example 1. The results are shown in Table 2.
Shown in.

Comparative Example 7 Evaluation was made in the same manner as in Example 1 except that the pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 7 was changed to 5.7. The results are shown in Table 2.

Comparative Example 8 The pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 7 was set to 10.0, and then the resin powder was obtained by drying without treatment with 0.01% hydrochloric acid. Evaluated. The results are shown in Table 2.

[0081]

[Table 2]

Comparative Example 6 in Table 2 almost corresponds to the conventional manufacturing method.

From Table 2, it can be seen that in Example 7, the amount of residual emulsifier was remarkably reduced and the transparency and heat stability were dramatically improved as compared with the conventional production method.

On the other hand, in Comparative Examples 6 and 7, the washing with the aqueous sodium hydroxide solution was not performed or the washing was insufficient, so that the amount of residual emulsifier was large and the transparency and thermal stability were relatively poor. You can see that In addition, Comparative Example 8
Although the amount of residual emulsifier was sufficiently reduced, it was found that since the subsequent acid treatment was not performed, the thermal stability in the middle and long term was inferior.

Example 8 Sodium oleate (1.5 parts) and potassium persulfate (0.1 parts) were added to water (20 parts).
Dissolve it in 0 parts and add 40 parts of styrene and n-acrylic acid.
A monomer mixture consisting of 35 parts of butyl and 10 parts of methyl methacrylate was added and polymerized for 5 hours, and then 15 parts of methyl methacrylate was continuously added and polymerized. The obtained copolymer latex was coagulated with 10% hydrochloric acid by an ordinary method to obtain a coagulated slurry. The slurry temperature at this time is
The temperature was 40 ° C and the pH was 1.2.

Next, the solidified slurry is heated to 75 ° C. to solidify the solidified particles for 5 minutes, then dehydrated to obtain a dehydrated cake, and the dehydrated cake thus obtained is slurried with a 0.005% aqueous sodium hydroxide solution. I brought it back. PH at this time is 10.0
Met.

The obtained slurry was dehydrated, and the obtained dehydrated cake was returned to the slurry with 0.01% hydrochloric acid. At this time, the pH was 3.0 and the slurry temperature was 40 ° C.
After that, the slurry was centrifugally dehydrated, washed, and sufficiently dried to obtain a resin powder.

The resin powder thus obtained was evaluated in the same manner as in Example 1. The results are shown in Table 3.

Comparative Example 9 A product obtained by coagulating with 10% hydrochloric acid without performing the treatment with the aqueous sodium hydroxide solution carried out in Example 8 (p
H1.2) was washed with water by a usual method and then dried to obtain a resin powder, which was evaluated in the same manner as in Example 1. The results are shown in Table 3.
Shown in.

Comparative Example 10 The pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 8 was 5.8, and the pH of the treatment with hydrochloric acid thereafter was 5.8.
Evaluation was made in the same manner as in Example 1 except that the value was 3.6. The results are shown in Table 3.

Comparative Example 11 The pH of the treatment with the aqueous sodium hydroxide solution carried out in Example 8 was adjusted to 10.0, and the resin powder was obtained by drying without subsequent treatment with hydrochloric acid. Evaluation was carried out in the same manner as in Example 1. did. The results are shown in Table 3.

[0092]

[Table 3]

Comparative Example 9 in Table 3 corresponds to the conventional manufacturing method.

From Table 3, it can be seen that in Example 8, the amount of residual emulsifier was remarkably reduced as compared with the conventional production method, and the transparency and thermal stability were dramatically improved. On the other hand, in Comparative Examples 9 and 10, the amount of residual emulsifier was large and the transparency and thermal stability were relatively poor because the aqueous sodium hydroxide solution was not washed or the washing was insufficient. I understand. Further, in Comparative Example 11, the amount of residual emulsifier is sufficiently reduced, but since the subsequent acid treatment is not performed, the medium-term,
It can be seen that the long-term thermal stability is poor.

Next, evaluation was performed by changing the heat treatment temperature before cleaning.

Example 9 Evaluation was carried out in the same manner as in Example 1 except that the heat treatment condition before treating the coagulated hydrochloric acid with the aqueous sodium hydroxide solution was 80 ° C. for 5 minutes.

In place of the safety during production in Example 1, the stability of coagulated particles during dehydration was evaluated as an index of operability during industrial production. In the above evaluation, the stability is excellent and the particles are hardly broken, the good is slightly broken, but the normal dehydration operation is not problematic, the failure is that the particles disintegrate and become fine, and the filter cloth is clogged. Show.
The results are shown in Table 4.

Comparative Example 12 Evaluation was carried out in the same manner as in Example 9 except that the heat treatment temperature before treating the coagulated hydrochloric acid in Example 9 with the aqueous sodium hydroxide solution was 40 ° C. The results are shown in Table 4.

In this case, since the heat treatment temperature was too low at 40 ° C., the coagulated particles were exposed to the basic condition after being left in the soft agglomerated state, so that the coagulated particles collapsed during the washing with the sodium hydroxide aqueous solution. However, industrial production problems such as generation of fine powder due to re-emulsification, clogging of filter cloth in the dewatering process and cloudiness of drainage occurred, and operability was remarkably reduced.

Comparative Example 13 Evaluation was carried out in the same manner as in Example 9 except that the heat treatment temperature before treating the coagulated hydrochloric acid in Example 9 with the aqueous sodium hydroxide solution was 140 ° C. The results are shown in Table 4.

[0101]

[Table 4]

From Table 4, in the case of Example 9, the coagulated particles are solidified by performing the heat treatment at 80 ° C. before washing with the aqueous sodium hydroxide solution, so that the coagulation is stable even under the basic condition thereafter. It can be seen that the state is maintained and the operability during industrial production is excellent.

On the other hand, when the heat treatment temperature is too high as 140 ° C. as in Comparative Example 13, the coagulated particles are completely fused and solidified. Therefore, the subsequent washing with an aqueous sodium hydroxide solution is performed. It can be seen that the above effect cannot be obtained sufficiently, the amount of residual emulsifier is large, and a satisfactory improvement effect cannot be obtained in terms of transparency and heat stability.

As in Comparative Example 12, the heat treatment temperature was 40%.
It can be seen that if the temperature is too low, the problem occurs during industrial production.

[0105]

According to the method of the present invention, the residual amount of contaminants such as an emulsifier is extremely low, and a resin powder having good thermal stability can be obtained by a usual manufacturing process.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Betz Josef Leon Belgium, 2260 Westerloe, Mechelsstraat 83 (72) Inventor Ryuichi Takagi Belgium, 2930 Braskirt, Emi Erei 8 (72) Inventor Riichi Nishimura 2-63, Okihama-cho, Takasago-machi, Takasago-shi, Hyogo Kounyo Dormitory (72) Akira Takagi 1-2-13-202, Kotoku-cho, Nada-ku, Kobe-shi, Hyogo (72) Toshihiko Hasegawa Kitahonjo, Harima-cho, Kako-gun 6 -3-23

Claims (16)

[Claims] 1. When a resin powder is produced from a polymer latex, a pH of 6 is obtained by adding a coagulant to the polymer latex.
After the solidified slurry is less than 50 ° C., the solidified particles are solidified by heat treatment at a temperature of 50 to 125 ° C., and then the basic substance is added to the solidified slurry, or the solidified slurry is dehydrated. A dehydrated cake obtained by returning the cake to a slurry with a solution containing a basic substance to obtain a coagulated slurry having a pH adjusted to 6 or more, and then adding an acidic substance to the coagulated slurry or dehydrating the coagulated slurry. A method for producing a resin powder, characterized in that the pH is adjusted to 5.5 or less by returning to a slurry with a solution containing an acidic substance. 2. The polymer latex is a diene-based or acrylic acid ester-based rubber-like polymer, and at least one selected from aromatic vinyl, vinyl halide, methacrylic acid ester, acrylic acid ester, and vinyl cyanide. It is a graft copolymer latex obtained by graft-polymerizing a vinyl group-containing compound consisting of seeds, the coagulated slurry is heat-treated at a temperature of 50 to 95 ° C, and the coagulated slurry adjusted with a basic substance has a pH of 6 It is above, The manufacturing method of Claim 1. 3. The method according to claim 2, wherein the pH of the coagulated slurry adjusted with a basic substance is 7 or more. 4. The method according to claim 2, wherein the pH of the coagulated slurry adjusted with a basic substance is 10 or more. 5. The polymer latex comprises 50 to 100% by weight of methyl methacrylate, 0 to 50% by weight of alkyl methacrylate having an alkyl group having 2 to 8 carbon atoms, 0 to 40% by weight of acrylate ester, and these. Is a copolymer latex comprising 0 to 20% by weight of a monomer copolymerizable with
The temperature for heat treatment of the solidified slurry is 85 ~ 125 ℃,
The method according to claim 1, wherein the pH of the coagulated slurry adjusted with a basic substance is 6 or more. 6. The method according to claim 5, wherein the pH of the coagulated slurry adjusted with a basic substance is 7 or more. 7. The method according to claim 5, wherein the pH of the coagulated slurry adjusted with a basic substance is 10 or more. 8. The polymer latex comprises 80 to 100% by weight of at least one monomer selected from methyl methacrylate, acrylic acid ester, aromatic vinyl and substituted aromatic vinyl, and a copolymerizable monomer. 0 to 70 parts by weight of a copolymer component composed of 0 to 20% by weight of the polymer, 20 to 100% by weight of alkyl acrylate having an alkyl group having 2 to 8 carbon atoms, 0 to 80% by weight of aromatic vinyl, and substituted A copolymer latex comprising 0 to 40% by weight of aromatic vinyl and 0 to 20% by weight of a copolymerizable monomer with 100 to 30 parts by weight of a copolymer component. The coagulated slurry is heat-treated. Temperature is 50
The method according to claim 1, wherein the pH of the coagulated slurry adjusted with a basic substance is 6 or higher, and the pH is 6 or more. 9. The method according to claim 8, wherein the pH of the coagulated slurry adjusted with a basic substance is 7 or more. 10. The method according to claim 8, wherein the pH of the coagulated slurry adjusted with a basic substance is 10 or more. 11. A copolymer 20 to 20 wherein the polymer latex comprises 0 to 50% by weight of aromatic vinyl, 50 to 100% by weight of a diene monomer, and 0 to 10% by weight of a monomer copolymerizable therewith. In 85 parts by weight, 0 to 50% by weight of acrylic acid ester, 0 to 100% by weight of methacrylic acid ester, 0 to 90% by weight of aromatic vinyl and 0 to 90% by weight of a monomer copolymerizable therewith
15 to 80 parts by weight of a monomer consisting of 20% by weight is added in one stage or 2
It is a copolymer latex obtained by additional graft polymerization in stages or more, the temperature for heat treatment of the coagulated slurry is 50 to 95 ° C, and the coagulated slurry obtained by solidifying the coagulated particles obtained by the heat treatment. The production method according to claim 1, wherein the dehydrated cake obtained by dehydrating the product is adjusted to a slurry with an aqueous solution containing a basic substance. 12. The method according to claim 11, wherein the pH of the coagulated slurry adjusted by returning to the slurry with an aqueous solution containing a basic substance is 7 or more. 13. The method according to claim 11, wherein the pH of the coagulated slurry adjusted by returning to the slurry with an aqueous solution containing a basic substance is 10 or more. 14. The method according to claim 11, wherein the diene-based monomer is butadiene. 15. The method according to claim 14, wherein the pH of the coagulated slurry adjusted by returning to the slurry with an aqueous solution containing a basic substance is 7 or more. 16. The method according to claim 14, wherein the pH of the coagulated slurry adjusted by returning the slurry with an aqueous solution containing a basic substance is 10 or more.