JP2002293845A - Method for growing rubber latex particle and producing its grafted polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain rubber latex particles enabling each of them to have a required particle diameter and to be produced stably also with a good productivity, without forming a coagulated product in a growing stage of the rubber latex particle and to produce a grafted polymer using the same efficiently. SOLUTION: In a method for growing small size rubber latex particles obtained by emulsion polymerization, by using an acid anhydride aqueous dispersion, this method for growing the same is specific in using the acid anhydride aqueous dispersion having above 60% of light transmittance obtained by using a halogen lump light source and according to formula 1 which is expressed as: light transmittance (%)=(A/Ao)×100 (wherein A is quantity of transmitted light trough a cell containing a mixed dispersion; Ao is quantity of transmitted light trough a cell containing water; a cell is made from quarts and thickness of a sample layer is 4 mm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for enlarging a rubber latex particle to a desired particle size in the step of enlarging the rubber latex particle while hardly generating aggregates, and a graft polymer using the enlarged rubber latex particle. A method for producing the same.

[0002]

2. Description of the Related Art ABS resins and ASA resins include vinyl cyanide monomers such as acrylonitrile, aromatic vinyl monomers such as styrene, and unsaturated carboxylate esters such as acrylate. It is a resin composition obtained by graft polymerizing a monomer mixture of a polymer and a rubber-like polymer, and is widely used in various applications because of its characteristics such as high impact resistance, high surface gloss, and good fluidity. . The properties of the ABS resin generally depend on the properties of the rubbery polymer, the diameter and particle size distribution of the dispersed particles in the matrix resin, the amount of the graft copolymerized on the rubbery polymer, the thickness of the graft layer, and the like. It has been known. Therefore, in order to balance properties such as impact resistance, fluidity, and appearance of a resin molded product on a high level, the properties of the rubbery polymer, the amount of the graft copolymerized to the rubbery polymer, and the thickness of the graft layer must be adjusted. In addition, it is extremely important to control the dispersion particle size and particle size distribution of the rubber-like polymer in the matrix resin according to each application.

[0003] The average particle size of the dispersed particles is 150 to
The range of 400 nm is common. However, it takes a very long time to produce a rubber-like polymer latex having an average particle size of 150 to 400 nm by an emulsion polymerization method,
Productivity was low. Therefore, many attempts have been made in advance to produce a rubbery polymer latex having a relatively small particle diameter of less than 150 nm, and to enlarge the average particle diameter of the small particle rubbery polymer latex to 150 to 400 nm by some method. Have been. For example, Japanese Patent Publication No. 32-95
No. 92 and Japanese Patent Publication No. 33-4437 propose a method of enlarging particles by a freezing method. However, this method is not industrially suitable because the equipment required for the enlargement process becomes enormous and the cost becomes too high.

Further, Japanese Patent Publication No. 37-10565, Japanese Patent Publication No. 41-982, and Japanese Patent Publication No. 60-19930 propose a method of enlarging a latex particle by applying a mechanical force such as a shearing force. However, this method has problems that coagulated material is easily generated, and it is difficult to stably obtain rubber latex particles having a uniform particle diameter. Japanese Patent Publication No. 46-35976 proposes a method of enlarging a latex obtained by polymerizing or copolymerizing a monomer having an acid group with a rubbery polymer latex. However, also in this method, a rubbery polymer that does not sufficiently enlarge remains, and it is difficult to obtain a rubbery polymer having a uniform particle size.

Further, Japanese Patent Publication No. 46-32056, Japanese Patent Application Laid-Open No. 7-48455, and Japanese Patent Application Laid-Open No. 11-80208
Japanese Patent Application Laid-Open No. 2000-38454 proposes a method of enlarging an acid by adding an acid substance or an acid anhydride. Since the conditions are not clear and the mixed dispersion state is not quantitative, it is not likely to disperse sufficiently and the concentration becomes locally high, or the acid anhydride is likely to be hydrolyzed due to excessive mixing. There is a problem that a coagulated product is easily generated and a latex having a desired particle diameter cannot be stably obtained. For example, in the method disclosed in Japanese Patent Publication No. 46-32056, it is difficult to stably obtain a certain dispersion state, and it is difficult to control the dispersion state.
There is a problem that a sufficient dispersion state cannot be obtained under the respective conditions when a static mixer is used as disclosed in Japanese Patent Publication No. 4 (JP-A-4). As described above, various proposals have been made for a method for enlarging rubber latex particles, but each method has a problem that should be improved for industrial use.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing latex particles having a desired particle size with little generation of agglomerates in a step of enlarging rubber latex particles.
Another object of the present invention is to develop a method for obtaining a product with good productivity and a method for efficiently producing a graft polymer using the method.

[0007]

That is, the present invention relates to a method for enlarging a small particle rubber latex obtained by emulsion polymerization using an aqueous dispersion of an acid anhydride. The present invention also provides a method for enlarging rubber latex particles, characterized by using a dispersion having a light transmittance of 60% or more by a halogen lamp light source according to the following formula 1, and the present invention provides an enlarged rubber latex An object of the present invention is to provide a method for producing a graft polymer using particles. Light transmittance (%) = (A / A ₀ ) × 100 (Equation 1) A: Amount of light transmitted through a cell containing a mixed dispersion A ₀ : Amount of light transmitted through a cell containing water Cell: quartz The present invention will be described in detail below.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The small particle rubber latex used in the present invention is obtained by emulsion polymerization and has an average particle size of less than 150 nm, usually around 80 nm. This small-particle rubber latex is a substance that exhibits neutral to alkaline (pH> 6) and is unstable in an acidic (pH ≦ 6) region, in which particles are easily aggregated, the particle diameter is enlarged, or a coagulated product is formed. And so on.

The type of emulsifier used in the emulsion polymerization is not particularly limited as long as the above-mentioned object is achieved, and examples thereof include sodium oleate, sodium stearate, sodium laurate, mixed fatty acid sodium and potassium salts thereof. Rosin acid soaps represented by fatty acid soaps and abietic acid salts can be used. Two or more of these may be used in combination.
The amount of the emulsifier to be used is preferably about 0.5 to 5 parts by mass used for ordinary emulsion polymerization with respect to 100 parts by mass of the polymer (rubber).

Polymer (rubber) of small particle rubber latex
The composition is not particularly limited as long as it exhibits rubber-like properties at normal temperature. Examples thereof include polybutadiene rubber, styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and polybutyl acrylate rubber. These may be used alone or in combination. Further, the concentration of the small particle rubber latex greatly affects the particle diameter and the amount of coagulated product. If the concentration is high, the particle size increases, but the amount of undesired coagulates increases. On the other hand, when the concentration decreases, the opposite tendency is observed. Therefore, it is necessary to select an appropriate concentration according to the composition and processing conditions, but if the concentration is too low, a large amount of acid or acid anhydride is required, and if the concentration is too high, a large amount of coagulated product is generated. Therefore, the preferred concentration range is 20 to 50% by mass.

There is no particular limitation on the polymerization initiator used in the emulsion polymerization. "Hot rubber" formula using ordinary potassium persulfate, organic peroxide and reducing agent,
A so-called "cold rubber" formulation using a catalyst (redox formulation) and the like can be used.

In the method of the present invention, the small particle rubber latex obtained by emulsion polymerization is treated with an aqueous dispersion of an acid anhydride to enlarge the particles. The acid anhydride to be used is not particularly limited as long as it is hydrolyzed to an acid in rubber latex, but acetic anhydride, maleic anhydride,
Carboxylic anhydrides such as propionic anhydride, benzoic anhydride, glutaric anhydride, valeric anhydride, isovaleric anhydride, succinic anhydride, citraconic anhydride, and itaconic anhydride are preferred, and the particle diameter is particularly adjusted. Acetic anhydride and maleic anhydride are suitable because of their ease.

The amount of the acid anhydride to be used is adjusted mainly depending on the intended particle size. When the amount of the acid anhydride is increased, a large amount of rubber latex having a large particle diameter is obtained, and when the amount is decreased, a large amount of rubber latex having a small particle diameter is obtained. If the amount of the acid anhydride is too small, the pH is insufficiently reduced and the enlargement itself does not easily proceed, so the amount of the acid anhydride to be used is appropriately adjusted in accordance with the pH of the small particle rubber latex itself. . The amount used depends on the type of the acid anhydride, but is generally preferably 0.1 to 2.0 parts by mass with respect to 100 parts by mass (solid content) of the small particle rubber latex.

In order to uniformly disperse the acid anhydride in the rubber latex, the acid anhydride must be dispersed in water in advance and added as a dispersion having an appropriate dispersion state and dispersion concentration. is necessary. The concentration of the acid anhydride can be enlarged even if used at a high concentration, but a large amount of coagulated material is easily generated.On the other hand, if the concentration is too low, the coagulated product is hardly generated. It is not practical because the enlarged rubber latex particles become thin. Therefore, an appropriate concentration depends on the type of the acid anhydride, but is usually 0.1%.
-20% by mass, and preferably 0.5-10% by mass.

The method of mixing and dispersing an acid anhydride in water can be easily achieved by using a flow-type tubular device.
Although there is no particular limitation on the apparatus, any of an apparatus for dynamically stirring such as an in-line mixer and an apparatus for mixing and stirring by a fluid flow using a stationary element such as a static mixer can be used. From the viewpoints of maintenance cost, energy saving, and space saving, a static mixer is preferable.

The dispersion state of the acid anhydride in water is determined by measuring the light transmittance using a halogen lamp light source, and it is necessary that the light transmittance determined from the above equation 1 is 60% or more. The higher the light transmittance, the better the results are obtained, preferably 80% or more, more preferably 98% or more. When the light transmittance is less than 60%, the acid anhydride is not uniformly dispersed in water and the acid anhydride locally has a high concentration, so that a coagulated product tends to be easily generated. In this dispersion, it is important that the acid anhydride is in the form of particles and is uniformly dispersed in water.If the dispersion is left standing too much, the acid anhydride particles may be re-fused or hydrolyzed to form particles. By disappearing, a coagulated material tends to be easily generated.

As a method of adding the dispersion of the acid anhydride to the small particle rubber latex, it is preferable to directly supply the dispersion to the rubber latex solution. It is also possible to supply the solution by inserting it into the liquid or to supply the solution by using a discharge port provided at the bottom of the stirring tank. In the method of adding the rubber latex to the liquid surface by dropping a droplet, aggregates may be generated by physical assault with the droplet near the liquid surface.

Further, the addition of the acid anhydride must be carried out under appropriate stirring, since it is necessary to uniformly diffuse the acid anhydride in the rubber latex. If the stirring is insufficient, the acid anhydride is not uniformly dispersed, so that the generation of coagulated matter increases. After the acid anhydride is uniformly diffused in the rubber latex, the acid anhydride is gradually hydrolyzed, so that the entire homogeneity is maintained, so that it is not necessary to perform stirring. Further, as a method for uniformly diffusing the acid anhydride into the small particle rubber latex, a method of continuously supplying and mixing an aqueous dispersion of the acid anhydride and the small particle rubber latex into a flow-type tubular device is used. Can be. There is no limitation on the flow-type tubular device at this time, and the same device as that used for mixing the acid anhydride and water can be used.

The rubber latex liquid thus obtained is separately placed in a container and allowed to stand for a predetermined time, whereby the rubber latex particles are enlarged. The acid anhydride added to the small particle rubber latex is gradually hydrolyzed according to the hydrolysis rate to become an acid, and the small particle rubber latex is enlarged. Therefore, an enlarging time corresponding to the hydrolysis rate of the acid anhydride is required, and the time is appropriately adjusted according to the type of the acid anhydride. Usually, more than tens of minutes are required. It should be noted that applying an excessive shearing force in the flow-through tubular apparatus may cause a remarkable increase in the growth rate of the particles and the generation of solidified products.

The rubber latex particles which have been enlarged by standing for a predetermined time are stabilized by adding a basic substance. As the basic substance, basic substances such as sodium hydroxide, potassium hydroxide, ammonium hydroxide (aqueous ammonia), sodium carbonate and potassium carbonate can be used. Potassium oxide is suitable. The concentration of these basic substances is adjusted somewhat depending on the substances and the like, but they are added as an aqueous solution of 1 to 10% by mass. Concentration 1
When the content is more than 0% by mass, a coagulated material is easily generated. When the content is less than 1% by mass, the concentration of the rubber latex particles tends to be too low. The addition method may be the same as the method in which the acid anhydride dispersion was previously added to the rubber latex liquid.

By the treatment with the acid anhydride, the rubber latex particles having an average particle diameter of less than 150 nm, often around 80 nm, are enlarged to particles having an average particle diameter of 150 to 400 nm suitable for the production of a graft polymer. Is done. The average particle size is less than 150 nm or 400 nm
It is not preferable to exceed the value, because the impact resistance of the finally obtained resin is lowered and the practical value is reduced.

The enlarged rubber latex particles thus obtained are subjected to graft polymerization with a vinyl cyanide monomer, an aromatic vinyl monomer, and other copolymerizable vinyl monomers. Provided. As the graft polymerization method, a known method combining emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, or a combination of two or more of these polymerization methods can be used. Examples of the monomer to be graft-polymerized include vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, and vinylidene cyanide; vinyl toluenes such as styrene, α-methylstyrene, and p-methylstyrene; and p-chlorostyrene. Halogenated styrenes, pt-butylstyrene, dimethylstyrene,
Examples thereof include aromatic vinyl monomers such as vinyl naphthalenes.

Further, depending on the purpose, methyl acrylate,
Ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-hexyl acrylate,
Unsaturated carboxylic acid ester monomers such as methyl methacrylate and ethyl methacrylate, unsaturated dicarboxylic anhydrides such as maleic anhydride, itaconic anhydride and citraconic anhydride, maleimide, N-methylmaleimide, N-butylmaleimide , N-phenylmaleimide, one or two or more selected from the group consisting of imide compounds of unsaturated dicarboxylic acids such as N-cyclohexylmaleimide, and glycidyl methacrylate as needed.
Other monomers such as methacrylic acid, acrylic acid, methacrylamide, 2-hydroxyethyl methacrylate, and polyethylene glycol monomethacrylate may be used in combination of 20% by mass or less, preferably 15% by mass or less.

Preferred monomers in the present invention include:
Acrylonitrile can be mentioned as the vinyl cyanide monomer, and styrene or α-methylstyrene can be mentioned as the aromatic vinyl monomer. The usage ratio of the monomer is usually vinyl cyanide monomer / aromatic vinyl monomer / other monomer (mass ratio) = 10 to 50/50 to 90/0 to 4
0, preferably 15-45 / 45-85 / 0-2
0. The reaction ratio between the enlarged rubber latex and the monomer is as follows: enlarged rubber latex (solid content) / monomer mixture (mass ratio) = 5 to 70/30 to 95, preferably 10 to 65/35. ~ 90. The graft polymer obtained by the graft polymerization in this manner is solidified by adding an acid or a salt to a reaction solution, which is a usual polymer recovery method, and then recovered as a powdery solid through an isolation step and a drying step. can do.

[0025]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The percentages and parts in the following examples are based on parts by mass unless otherwise specified. The measurement of the degree of mixing of the acid anhydride and water (light transmittance) and the measurement of the particle size in Examples and Comparative Examples were performed according to the methods described in 1) and 2) below. The small particle rubber latex was produced by the method described in 3) below.

1) Measurement of Degree of Mixing The acid anhydride and water were continuously flowed through a static mixer, and a laser diffraction type measuring device (LA-910, manufactured by Horiba, Ltd.) was connected to the discharge port of the mixer. The light transmittance by a halogen lamp (tungsten filament) light source was measured in real time by a 4 mm quartz cell. 2) Measurement of particle size The particle size of the rubber latex is determined by placing an ultra-dilute rubber latex droplet on a copper mesh for a transmission electron microscope, staining this with osmium tetroxide, evaporating water to dryness, and evaporating the water to dryness. After taking a picture with (magnification 20,000 times), 30
The size of 0 to 500 rubber particles was counted. From these results, the average particle size (mass average) was determined by calculation.

3) Production of small particle rubber latex (A) In a 10-liter stainless steel autoclave equipped with a supply device, a stirrer, and a thermometer, 150 parts of deionized water (hereinafter, simply referred to as water) and 10 parts of styrene. , 1.5 parts of potassium oleate, 1.5 parts of potassium rosinate, 0.1 part of potassium hydroxide, 0.3 parts of sodium sulfate, and 0.3 parts of potassium persulfate. Butadiene 90
Then, the internal temperature was raised to 70 ° C., and polymerization was carried out for 10 hours. After removing the remaining butadiene monomer from the reaction solution by steam distillation, the solution was cooled to give an average particle size of 85 nm,
A small particle rubber latex (A) having a solid content of 40.1% and a pH of 11.0 was obtained.

[0028]

Example 1 A dispersion was prepared by feeding water at 1440 g / min and acetic anhydride at 60 g / min to a static mixer (manufactured by Noritake Co., Ltd., model 1 / 4-N40-172-0). . The light transmittance of this dispersion was 99.8%. This dispersion was placed in a 200 L inner diameter 10 L glass reactor equipped with a stirrer.
100 parts (solid content) of small particle rubber latex (A) having an average particle diameter of 85 nm, which is stirred at rpm, is sent under the liquid level through an insert tube, and 0.56 parts of acetic anhydride is added to 100 parts of rubber latex. When the liquid was sent, each liquid feeding was stopped. Stirring was continued for 1 minute and then allowed to stand for about 30 minutes. Next, 0.45 parts of a 2% aqueous sodium hydroxide solution was added under the liquid level through an insert tube, and after 5 minutes, stirring was resumed to finally adjust the pH to 11.0, and the average particle diameter was 301 n.
m, a solidified rubber latex particle having a solid content of 34.5% was obtained. When the coagulated product obtained by filtering the rubber latex particles with gauze was dried, the amount of the coagulated product was as very small as 0.01% by mass. Next, 45 parts of the enlarged rubber latex particles (solid content) and 142 parts of deionized water (including water in the rubber latex) were charged into a 10 L glass reactor, and 16 parts of acrylonitrile and 39 parts of styrene were added thereto. In addition, graft polymerization was performed by a known emulsion polymerization method to obtain an ABS graft polymer.

[0029]

Example 2 Water was added to a static mixer (manufactured by Noritake Co., Ltd .: Model T3-12R-1PT) at 840.
g / min and acetic anhydride were fed at 35 g / min. The light transmittance of the obtained dispersion was 99.8%. The obtained dispersion and small particle rubber latex (A)
Static mixer (manufactured by Noritake Co., Ltd .: Model 3 at a speed of 75 g / min and 15600 g / min)
/ 4-N60-331-1), mixed, and introduced from the bottom outlet of a 100 L glass reactor having an inner diameter of 550 mm equipped with a stirrer for 5 minutes. Then, it was left still for 100 minutes. Next, 7000 g of a 2% aqueous sodium hydroxide solution was added below the liquid level from the top of the reactor through an insert tube. After 5 minutes, stirring was resumed to finally adjust the pH to 10.8, an average particle diameter of 300 nm and a solid content of 33.5. % Of the expanded rubber latex particles. When the coagulated product obtained by filtering the latex particles through gauze was dried, the amount of the coagulated product was as small as 0.02% by mass.

[0030]

Example 3 In the same static mixer as in Example 1,
Water was sent at 480 g / min, and acetic anhydride was sent at 20 g / min. The light transmittance of this dispersion is 69.0%.
Met. Using this dispersion, enlargement was performed according to the method of Example 1. The final pH was 10.5, and enlarged rubber latex particles having an average particle diameter of 300 nm and a solid content of 35.0% were obtained. When the coagulated product obtained by filtering the rubber latex particles through gauze was dried, the amount of the coagulated product was as small as 0.10% by mass.

[0031]

Comparative Example 1 Water was supplied to the same static mixer as in Example 1 at 120 g / min, and acetic anhydride was supplied at 5 g / min. The light transmittance of this dispersion was 23.5%. Next, this dispersion was used to perform enlargement in the same manner as in Example 1. The pH of the final liquid was 11.0, and rubber latex particles having an average particle diameter of 185 nm and a solid content of 33.5% were obtained. When the coagulated product obtained by filtering the latex particles through a gauze was dried, the amount of the coagulated product was as large as 6.8% by mass.

[0032]

Comparative Example 2 Water was sent to the same static mixer as in Example 1 at 288 g / min, and acetic anhydride was sent at 12 g / min. The light transmittance of this dispersion was 40.0%. Using this dispersion, enlargement was performed in the same manner as in Example 1. The pH of the final solution was 10.5, and rubber latex particles having an average particle diameter of 235 nm and a solid content of 34.5% were obtained. When the coagulated product obtained by filtering the latex particles through gauze was dried, the amount of the coagulated product was as large as 3.2% by mass.

[0033]

Comparative Example 3 In the same manner as described in Example 2, the feed rates were 240 g / min for water and 10 g / mi for acetic anhydride.
n. The light transmittance of this dispersion was 43.5%. Further, the feed rate of the small particle latex is set to 450
The solution was changed to 0 g / min and fed for 10 minutes. Then 11
Let stand for 0 minutes and then add 2% aqueous solution of sodium hydroxide 400
0 g was added, and after 5 minutes, stirring was resumed to finally adjust the pH of the solution.
Was 10.8. The average particle diameter of the obtained rubber latex particles was 214 nm, and the solid content was 33.5%. When the coagulated product obtained by filtering the latex particles through gauze was dried, the amount of the coagulated product was as large as 3.3% by mass, and a large amount of coagulated material adhered in the used static mixer. It was recognized that.

[0034]

As described above in detail, according to the present invention, a desired particle diameter (150 nm to 4 nm) is hardly generated in the step of enlarging rubber latex particles while hardly generating aggregates.
(00 nm) can be stably produced with high productivity. The enlarged rubber latex particles thus obtained are suitable for producing a graft polymer, and their practical value is extremely high.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Nakai 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Otake Works F-term (reference) 4J026 AA17 AA45 AA49 AA68 AC11 AC18 AC32 BA05 BA31 CA08 DA04 EA03 FA04

Claims (3)

[Claims] 1. A method for enlarging a small-particle rubber latex obtained by emulsion polymerization using an aqueous dispersion of an acid anhydride, wherein the aqueous dispersion of an acid anhydride is a light beam from a halogen lamp light source according to the following formula 1. A method for enlarging rubber latex particles, comprising using a dispersion having a transmittance of 60% or more. Light transmittance (%) = (A / A ₀ ) × 100 (Equation 1) A: Amount of light transmitted through a cell containing a mixed dispersion A ₀ : Amount of light transmitted through a cell containing water Cell: quartz , Sample layer thickness 4mm 2. The method for enlarging rubber latex particles according to claim 1, wherein a basic substance is added to the solution containing the expanded rubber latex particles to make the solution neutral or alkaline. 3. A method for producing a graft polymer, wherein graft polymerization is carried out using the rubber latex particles enlarged by the method of claim 1 or 2.