WO2001088021A1

WO2001088021A1 - Process for producing acrylic polymer

Info

Publication number: WO2001088021A1
Application number: PCT/JP2001/004153
Authority: WO
Inventors: Kouji Matsumura; Akihiro Toritani; Masahiro Oosuka; Seiji Takei
Original assignee: Mitsubishi Rayon Co., Ltd.
Priority date: 2000-05-19
Filing date: 2001-05-18
Publication date: 2001-11-22
Also published as: CN1429244A; CN100341924C; JP2001329067A

Abstract

A process for producing a powder which is excellent in powder properties such as handleability, flowability, and antiblocking property, has excellent redispersibility during melt-kneading together with other resin(s), and is reduced in fish-eye generation. The process comprises spraying an emulsion polymerization latex containing an acrylic polymer as the main component in a drying chamber, simultaneously introducing a drying gas thereinto through an inlet of the drying chamber to dry the latex and thereby form a powder of the acrylic polymer, and collecting the powder through an outlet of the drying chamber. In this process, the spraying of the latex is conducted with a spray nozzle, the temperature of the gas around the inlet of the drying chamber is regulated to below 200°C, and the temperature of the gas around the outlet of the drying chamber is regulated to a temperature lower than the temperature higher by 30°C than the minimum film-forming temperature of the emulsion polymerization latex. Thus, a powder having excellent performances is obtained.

Description

Method for producing acryl-based polymer

The present invention relates to a method for producing an acryl-based polymer powder from an emulsion-polymerized latex containing an acryl-based polymer as a main component. The present invention relates to a method for producing an acryl-based polymer capable of obtaining a powder having good redispersibility when melt-kneaded with a resin.

This application is based on a patent application to Japan (Japanese Patent Application No. 2000-149900), and the contents of the Japanese application are incorporated as a part of this specification.

Background art

Acrylic polymers used as modifiers for various plastic products such as vinyl chloride resins are generally produced by emulsion polymerization. The acryl-based polymer after the emulsion polymerization is finally melt-kneaded with other resins and used as a powder from the emulsion-polymerized latex (hereinafter simply referred to as latex) after the emulsion polymerization. You.

As a method for recovering an acrylic polymer (polymer) as a powder from such a latex, there is a spray drying method in which the latex is directly sprayed into hot air and dried. The acrylic polymer powder obtained in this manner (hereinafter sometimes simply referred to as powder) must have the following powder performance in order to be used as a modifier. You.

(1) Excellent handling, fluidity, and blocking resistance when handling powder. (Hereinafter, these characteristics are referred to as powder characteristics.)

(2) Excellent dispersibility when melt-kneaded with other resins such as vinyl chloride resin (hereinafter referred to as redispersibility), and fish-eye-like defects (hereinafter fisheye) caused by undispersed modifier. ) Is low.

The powder characteristics of (1) above are such that the smaller the particle size of the powder and the coarser the structure of the powder, On the contrary, the redispersibility of the above (2) becomes better as the particle size of the powder is smaller and the structure of the powder is coarser.

Therefore, it is necessary to control the operating conditions of the dryer in order to obtain powder that satisfies such conflicting requirements.

For example, in Japanese Patent Application Laid-Open No. 8-169914, in a method of spray-drying latex that has been post-contact reacted with an initiator, the outlet temperature of a dryer is determined by changing the glass transition temperature of a polymer (hereinafter referred to as Tg). The method is described based on

However, in this method, since a rotating disk is used as a method of spraying latex, there is a problem that the obtained powder has a small particle size and is inferior in fluidity. In addition, if powder with a large particle diameter is to be recovered using this rotating disk, fine powder and coarse powder increase, and the particle size distribution tends to become extremely wide, resulting in a decrease in powder performance. .

In addition, since the outlet temperature of the dryer is set based on the Tg of the polymer, accurate control of the powder structure of the powder cannot be performed, and as a result, the powder characteristics and redispersibility cannot be improved. There was a problem. This was also the case when the average T g of the particles (apparent T g) was used.

If the outlet temperature is set on the basis of Tg, the powder structure cannot be controlled accurately because recent acrylic polymer powders require various performances as modifiers. Therefore, it is considered that the structure is often a multilayer structure, and the T g of such a multilayer structure cannot be generally specified.

As described above, it is difficult to obtain a powder excellent in both of the above-mentioned powder characteristics (1) and redispersibility (2). , Not yet reported. Disclosure of the invention

An object of the present invention is to provide a method for producing an acryl polymer which is obtained by spray-drying an emulsion polymerization latex containing an acrylic polymer as a main component to obtain an acrylic polymer powder. Excellent powder properties such as heat resistance, excellent redispersibility during melt-kneading with other resins, low generation of fish eyes, The purpose is to set the operating conditions of the dryer from which powder suitable as a stick resin modifier is obtained.

The present inventors have conducted intensive studies, focusing on the fact that the powder characteristics and redispersibility of an acrylic polymer are greatly affected by the particle size of the powder and the structure of the polymer constituting the powder. As a result, the latex is sprayed into the dryer using a spray nozzle to control the particle size of the droplets to be sprayed, and the temperature inside the dryer, particularly the temperature near the outlet of the dryer, is controlled to the minimum latex composition. By setting the film temperature (hereinafter referred to as MFT) as a reference, it was found that both the powder characteristics and redispersibility of the obtained acrylic polymer were improved, and the present invention was completed.

That is, in the method for producing an acrylic polymer of the present invention, an emulsion polymerization latex containing an acrylic polymer as a main component is sprayed into a drier, and a drying gas is sent from an inlet of the drier to obtain the latex. Drying an acrylic polymer powder to obtain an acrylic polymer powder, and collecting the powder from an outlet of the dryer. The temperature of the drying gas near the dryer inlet was set to less than 200 ° C., and the temperature of the drying gas near the dryer outlet was added to the minimum film forming temperature of the emulsion polymerization latex by 30 ° C. The temperature is lower than the temperature. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

First, the dryer used in the present invention will be described. The dryer includes a spray nozzle for spraying at least a latex obtained by emulsion polymerization into a container, an inlet for introducing a drying gas for drying the sprayed latex, a drying gas and after drying. And an outlet portion serving as an outlet for powder. In addition, the spray nozzle is provided at the upper part of the dryer, the inlet part is provided at the upper part of the dryer so that a drying gas is applied to the sprayed latex, and the outlet part is provided at the lower part of the dryer. It is preferable to use a type in which the working gas flows from the upper part of the dryer to the lower part.

The overall shape of such a dryer is not particularly limited, and its capacity is There is no particular limitation, and any one can be used, from a small-scale one used in a laboratory to a large-scale one used industrially. A pressure nozzle capable of applying a pressure of 0.1 to 20 MPa to the latex and ejecting the latex from the nozzle at a high speed to atomize the latex is preferably used. In particular, a pressurizing swirl nozzle that applies a swirl flow to the latex to be sprayed and ejects it is preferable.

In this spray nozzle, the particle size of the obtained powder can be adjusted by adjusting the spray pressure when atomizing the latex, so that the desired particle performance can be obtained. The latex can be sprayed. As will be described later, the range of the particle diameter at which the desired powder performance can be obtained depends on the structure of the polymer and the like, and is appropriately adjusted according to the structure of the polymer, the MFT of the latex, and the like. According to such a method, a powder having a large particle diameter can be obtained as compared with the spraying method using a rotating disk as in the conventional example.

The temperature of the drying gas near the inlet of the dryer (hereinafter referred to as the inlet temperature) is lower than 200 ° C, preferably lower than 190 ° C. At 200 ° C. or higher, the fusion of the surface portion of the obtained powder proceeds, redispersibility at the time of melt-kneading is reduced, and the amount of generated fish is increased.

The lower limit of the inlet temperature is not particularly limited, but is appropriately set so that the temperature in the vicinity of the outlet of the dryer described later falls within a predetermined temperature range, and is preferably 140 ° C. or more. If the above inlet temperature is lower than 140 ° C., the air volume of the drying gas will increase extremely.

The gas temperature near the outlet of the dryer (hereinafter referred to as the outlet temperature) is lower than the temperature obtained by adding 30 to the MFT of the latex. Preferably, the temperature is lower than the temperature obtained by adding 20 ° C to MFT.

Here, the latex MFT is the lowest temperature at which a transparent continuous film can be formed when a film is formed from latex, and is a value representative of the Tg of the latex particle surface. MFT correlates with the adhesive force of the latex polymer / particle surface layer, which is a determinant of the powder structure, and serves as an index indicating the adhesive force. As described above, by setting the temperature based on the MFT, the polymer structure of the powder can be controlled, that is, characteristics such as fluidity and redispersibility of the powder can be controlled. Further, even when the polymer has a multilayer structure, the powder properties and redispersibility of the powder can be similarly controlled.

Therefore, if the outlet temperature of the dryer is set to a temperature lower than the temperature obtained by adding 30 ° C to the MFT, even when a plurality of latexes having different compositions are dried to obtain a powder, the powder characteristics and redispersibility are good Powder can be obtained.

If the above temperature is equal to or higher than the temperature obtained by adding 30 ° C to the MFT of the latex, Hi-adhesion of the surface of the powder proceeds and the re-dispersibility during melt-kneading of the powder decreases, resulting in fishy generation. Increase.

The lower limit of the gas temperature at the outlet of the dryer is not particularly limited, but is preferably higher than 50 ° C. When the temperature is lower than 50 ° C, drying of the powder may be insufficient. As a method of measuring the MFT of the latex, first, a heating device or a cooling device is provided at both ends of a horizontally installed aluminum plate as necessary, so that the aluminum plate has a temperature gradient. Next, the latex is spread uniformly and thinly on the aluminum plate having the temperature gradient, and dried. Then, the lowest temperature at which the latex forms a transparent continuous film is measured, and this is defined as the MFT.

The preferred particle size of the powder obtained by drying under the conditions described above cannot be determined unconditionally because it depends on the polymer structure of the powder. For example, particles with low Tg (or MFT) generally have essentially poor powder performance, so it is necessary to set the particle size larger than those with high glass transition temperature (or MFT). However, it is preferably between 60 and 300 m, more preferably between 100 and 200 / m. If the particle diameter is less than 60 zm, the handling properties, flowability and blocking resistance of the powder will be reduced due to the increase in fine powder, etc.If it exceeds 300 xm, it will be classified when mixed with resin powder such as vinyl chloride resin. It becomes difficult to mix uniformly.

The emulsion polymerization latex containing an acrylic polymer as a main component used in the above production method is not particularly limited, but preferably has an MFT of 20 ° C or more. More preferably, the MFT is above 50 ° C. If MFT is below 20 ° C, dry The temperature at the dryer outlet is 50 ° C or less, resulting in insufficient drying.

Such latexes include, specifically, methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, aryl acrylate, glycidyl acrylate, methyl methacrylate, Using one or more acrylic monomers such as ethyl methacrylate, butyl methacrylate, propyl methacrylate, 2-ethylhexyl methacrylate, aryl methacrylate, glycidyl methacrylate, acrylamide, acrylonitrile, etc. Is obtained by copolymerization, seed polymerization, or graft polymerization. In addition, as monomers other than the above-mentioned acrylic monomers, it is also possible to use a small amount of monomers such as styrene, para-methylstyrene, 1,3-butadiene, biel acetate, vinylpyridine, etc. which can be used for emulsion polymerization. It is preferable to contain 50% by mass or more of the acryl-based monomer.

In addition, it is also possible to use a cross-linking agent such as divinylbenzene, 1,3-butylenedimethacrylate, arylmethacrylate, and glycidyl methacrylate, and a chain transfer agent such as mercaptans and terpenes.

The polymerization initiator used in the emulsion polymerization of the acryl-based polymer is not particularly limited, but water-soluble persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, diisopropylbenzene hydroperoxide, P- Mentane Hydrate Peroxide, cumine hydroperoxide, redox-based initiators containing organic peroxides as one component, such as t-butyl octyl peroxide, can be used.Used for emulsion polymerization of the above acryl-based polymers. The emulsifier is not particularly limited, but one or more alkali metal salts of higher fatty acids such as disproportionated rosin acid, oleic acid, and stearic acid, and alkali metal salts of sulfonic acids such as dodecylbenzenesulfonic acid are combined. Can be used.

There is no particular limitation on the emulsion polymerization method and emulsion polymerization conditions for the latex used in the above-mentioned production method, and the method can be carried out by conventionally known methods and conditions.

The above latex may be used alone, or may be a mixture of a plurality of latexes. Also, in order to prevent oxidation in the dryer, a suitable antioxidant or additive can be added to the latex to be sprayed and spray dried.

Furthermore, in order to improve the powder performance such as blocking resistance and bulk specific gravity of the obtained acrylic polymer powder, inorganic fillers such as silica, talc, calcium carbonate, etc., polyacrylate, polyvinyl alcohol, polyacrylamide, etc. Can be added and spray dried.

In the method for producing an acrylic polymer according to the present invention, the emulsion polymerization latex is sprayed by the spray nozzle into the dryer whose temperature is adjusted as described above, and this is dried and collected from the outlet. Thereby, an acryl-based polymer powder having desired powder performance can be obtained.

In the present invention, the spray-drying apparatus, method, conditions, etc. are not particularly limited except for the range of the gas temperature at the inlet and outlet of the dryer and the spray method. Air is preferred as the drying gas because of its low cost, but it is also possible to use an inert gas or a mixture of air and an inert gas.

As described above, in the method for producing an acrylic polymer of the present invention, the latex is sprayed using the spray nozzle, and the temperature in the dryer is controlled based on the MFT of the latex. And the structure of the acrylic polymer can be controlled according to the composition of the acrylic polymer (polymer), and a powder with excellent powder performance can be obtained.

That is, according to the present invention, the powder has excellent handling properties in handling powder, fluidity, powder properties such as blocking resistance, and dispersibility when melt-kneaded with another resin such as a vinyl chloride resin. An acrylic polymer powder with less generation of fish eyes can be produced. Example

Hereinafter, the present invention will be described based on examples. In addition, the number of parts in Examples and Comparative Examples represents parts by mass unless otherwise specified.

After synthesizing the acrylic resin composition and measuring the minimum film formation temperature (MFT) of the obtained latex, the powder was collected by spray drying and evaluated for various physical properties. Dryer Table 1 shows the outlet temperature, dryer inlet temperature, and evaluation results.

(Examples 1, 2 and Comparative Examples 1, 2, 3)

(1) Synthesis of acrylic resin composition

85 parts of methyl methyl acrylate, 15 parts of butyl methacrylate, 0.003 parts of tert-dodecylmer sulfide, 1.5 parts of potassium alkenyl succinate, and 190 parts of deionized water were charged into the reactor and purged with nitrogen. After that, the temperature was raised while stirring. Thereafter, when the temperature in the reactor reached 40, a mixture of 2.0 parts of potassium persulfate and 10 parts of deionized water was charged into the reactor, polymerization was started, and after 200 minutes, the obtained mixture was obtained. The latex was taken out of the reactor.

(2) MFT measurement

The MFT of the above latex was measured using a minimum film formation temperature measuring device (manufactured by Takabayashi Rika Co., Ltd.).

The measurement temperature conditions at this time were 20 ° C on the low temperature side and 180 ° C on the high temperature side.

As a result of measurement, the MFT of the latex was 85.

(3) Spray drying

The latex was introduced into a dryer and spray-dried. At this time, the dryer used was one with an inner diameter of 3.5 m for the straight body, a height of 4 m for the straight body, and a height of 2.8 m for the cone. The spraying device was a pressurizing nozzle (spray pressure 2.4 Mpa ) Was used. Air was used as the drying gas.

Table 1 shows the latex supply speed, heated gas air flow, dryer inlet temperature, and outlet temperature.

(4) Evaluation of various physical properties

[Powder average particle size]

Using a particle size distribution evaluation device being defined by the Japanese Industrial Standards (JIS No. 40), was measured median size of the mass (median diameter is denoted usually D _5. A.). (Particle size equivalent to 50% of the cumulative mass distribution curve)

[Powder fluidity]

Put 50 gr of powder into the bulk density meter used in JI SK-6721, The flow state when the damper was removed was visually observed and evaluated in the following five stages. ◎

····· Good

△ ... good

X · · · bad

[Fish eye evaluation]

After melt-kneading a resin having the following composition using an 8-inch roll (150 ° C) for 4 minutes, add 2.0 parts of the acrylic resin powder obtained above, and melt for 5 minutes. After kneading, the plate-like resin was cut out to prepare a fishy evaluation test piece. Thereafter, the number of fish eyes per unit area (Z16 cm ² ) contained in the prepared specimen was evaluated visually by irradiating light from the rear of the resin.

Vinyl chloride resin (n = l 300) L 00 part Trioctyl trimellitate

(Product name: T-80, manufactured by Kao Stone Co., Ltd.) 80 parts Ba-Zn type stabilizer

(Nissan Hueguchi Co., Ltd. Product name: 1 ^ -45) 1.0 咅 15 Epoxidized soybean oil

(Tokyo Fine Co., Ltd. product name NF-3000) 5.0 parts Titanium oxide (Ishihara Sangyo Co., Ltd. product name R-830) 2.0 parts Carbon black 0.1 part

(Example 3.4 Comparative Example 4)

(1) Synthesis of acrylic resin composition

After charging 46 parts of methyl methacrylate, 9 parts of butyl acrylate, 0.01 parts of tert-dodecyl mercaptan, 1.0 parts of potassium alkenyl succinate, and 190 parts of deionized water into the reactor, and after purging with nitrogen, Then, the temperature was increased while stirring, and when the temperature in the reactor reached 40 ° C, a mixture of 2.0 parts of potassium persulfate and 10 parts of deionized water was charged into the reactor and polymerized. Started. After holding for 120 minutes, a mixture of 37 parts of methyl methyl acrylate and 8 parts of butyl acrylate! The mixture was charged into the reactor over a period of 100 minutes, held for 100 minutes, and then taken out of the reactor.

(2) MFT measurement

The procedure was performed in the same manner as in Example 1. As a result of the measurement, the MFT of the latex was 72 ° C.

(3) Spray drying

The procedure was performed in the same manner as in Example 1. Table 1 shows the latex feed rate, heated gas flow rate, dryer inlet temperature, and outlet temperature.

(4) Evaluation of various physical properties

The procedure was performed in the same manner as in Example 1.

(Examples 5, 6 Comparative Example 5)

(1) Synthesis of acrylic resin composition

Into the reactor were charged 1.5 parts of polyoxydylene alkyl ether phosphite, 0.01 parts of potassium hydroxide, and 200 parts of deionized water, and after purging with nitrogen, 25 parts of methyl methacrylate and Cumene Hydro. 0.0003 parts of the peroxide was added to the mixture while stirring, and the temperature was raised. Then, when the temperature in the reactor reached 50 ° C, a mixture of 0.3 parts of sodium formaldehyde sulfoxylate and 10 parts of deionized water was charged into the reactor to start polymerization, Hold for 100 minutes. Thereafter, a mixture of 30 parts of styrene, 25 parts of butyl acrylate, 1.0 part of tert-dodecyl mercaptan, and 0.003 part of cumine hydroperoxide was charged into the reactor over 100 minutes and 120 minutes. Held. Thereafter, a mixture of 20 parts of methyl methacrylate and 0.003 part of cumine hydroperoxide was charged into the reactor over 60 minutes, held for 100 minutes, and then taken out of the reactor.

(2) MFT measurement

The procedure was performed in the same manner as in Example 1. As a result of measurement, the MFT of the latex was 62.

(3) Spray drying

The procedure was performed in the same manner as in Example 1. Table 1 shows the latex feed rate, heated gas flow rate, dryer inlet temperature, and outlet temperature. (4) Evaluation of various physical properties

The procedure was performed in the same manner as in Example 1.

(Comparative Example 6)

Example 3 was carried out in the same manner as in Example 3, except that a dryer of a rotating disk spray system (rotation speed: 15000 rpm) was used.

As a result, it was confirmed that the average particle diameter was 50 m, but the fine powder and coarse powder increased and the fluidity decreased.

(Comparative Example 7)

The same method as in Comparative Example 4 was performed except that the number of revolutions was set to 6500 rpm in order to obtain powder having a particle diameter of about 100 / im by the rotating disk method. As a result, undried droplets adhered to the wall surface, and the entire amount of the sprayed latex could not be recovered as a dry powder.

From these results, it can be seen that in Examples 1 to 6, a powder having high fluidity and high redispersibility can be obtained. In comparison, in Comparative Examples 1 to 5 in which the temperature in the dryer was outside the range specified by the present invention, it was found that the redispersibility of the powder was inferior. Further, in Comparative Example 6 in which spraying was performed using a rotating disk, the fluidity of the powder was poor, and in Comparative Example 7 in which a rotating disk was used and the particle diameter was set to be large, the powder was removed. Could not be recovered. . Industrial Applicability

As described above, according to the present invention, an acrylic polymer having excellent powder properties such as handling properties, fluidity, and blocking resistance, excellent redispersibility at the time of melt-kneading, and having a low fisheye generation amount. Powder can be obtained.

Acrylic polymer powders with such excellent powder properties include impact modifiers such as vinyl chloride resin, polystyrene, polycarbonate, ABS resin, acrylic resin, and other various plastics. It can be suitably used as a processability improver.

The present invention may be embodied in various other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely an example in every respect and should not be construed as limiting. The scope of the present invention is defined by the appended claims, and is not restricted by the specification. Further, all modifications and changes belonging to the equivalent scope of the patent claim are within the scope of the present invention.

Claims

The scope of the claims

1. Spray an emulsion polymerization latex containing an acrylic polymer as a main component into a dryer, and send a drying gas from the inlet of the dryer to dry the latex and dry the acrylic polymer. A method for producing an acrylic polymer, comprising the steps of obtaining a powder and recovering the powder from an outlet of a dryer.

The latex is sprayed by a spray nozzle, the temperature of the drying gas near the dryer inlet is set to less than 200 ° C, and the temperature of the drying gas near the dryer outlet is set to the minimum composition of the emulsion polymerization latex. A method for producing an acryl-based polymer, wherein the temperature is lower than a temperature obtained by adding 30 ° C. to a film temperature.

2. The method for producing an acrylic polymer according to claim 1, wherein the temperature of the drying gas near the entrance of the dryer is 190 or less.

3. The method for producing an acryl-based polymer according to claim 2, wherein the temperature of the drying gas near the entrance of the dryer is 140 to 190.

4. The acrylic system according to claim 1, wherein the temperature of the drying gas near the outlet of the dryer is lower than a temperature obtained by adding 20 ° C to the minimum film forming temperature of the emulsion polymerization latex. A method for producing a polymer. '

5. The method for producing an acryl-based polymer according to claim 1, wherein a minimum film forming temperature of the latex is 20 ° C or more.

6. The method for producing an acryl-based polymer according to claim 5, wherein a minimum film forming temperature of the latex is 50 ° C or more.