CN1429244A - Process for producing acrylic polymer - Google Patents

Abstract

The object of the present invention is to obtain a powder that is excellent in powder properties such as handleability, fluidity, and anti-blocking properties, and also has excellent redispersibility when melt-kneaded with other resins, and has a small amount of fish eyes. While spraying the polymer latex with propylene polymer as the main component into the drier, a drying gas is passed through the inlet of the drier to dry the latex to obtain a propylene polymer powder, which is then passed through the drier The powder is recovered at the outlet of the above-mentioned dryer, which is characterized in that the above-mentioned latex is sprayed with a nozzle, the gas temperature near the inlet of the dryer is set to be lower than 200 ° C, and the temperature near the outlet of the dryer is set to A temperature lower than the minimum film-forming temperature of the above emulsified polymer latex plus 30°C, so a powder with excellent properties can be produced.

Description

Production method of propylene-based polymer

technical field

The present invention relates to a method for producing propylene-based polymer powder from emulsified polymerized latex mainly composed of propylene-based polymer, and specifically relates to a method for obtaining a powder having excellent fluidity and other properties and redispersible when melt-kneaded with other resins. A method for producing a powdery propylene-based polymer with excellent properties.

This application is based on a patent application filed in Japan (Patent Application No. 2000-149069), and the content described in the Japanese application is described as a part of the specification of the present invention.

Background technique

Propylene polymers used as modifiers for various plastic products such as polyvinyl chloride resins are usually produced by emulsion polymerization. Furthermore, the propylene-based polymer after emulsion polymerization is finally used for melt kneading with other resins, and the emulsion polymerized latex (hereinafter referred to simply as "latex") after emulsion polymerization is recovered as powder.

As a method of recovering a propylene-based polymer as a powder from such a latex, there is a spray drying method in which the latex is spray-dried directly in hot air.

Furthermore, the above-mentioned propylene-based polymer powder obtained in this way (hereinafter, may be simply referred to as "powder") is required to have the following powder properties in order to be used as a modifier.

(1) Excellent operability, fluidity and anti-blocking properties during powder operation. (Hereafter, these characteristics are referred to as "powder characteristics")

(2) The dispersibility (hereinafter referred to as "redispersibility") when melt-kneading with other resins such as polyvinyl chloride resin is excellent, and fish-eye-like defects due to undispersed substances of modifiers rarely occur ( Hereinafter, referred to as "fisheye").

The powder characteristic of the above (1) is that the smaller the particle size of the powder is, and the coarser the powder structure is, the worse it is. The thicker the better.

Therefore, in order to obtain a powder satisfying such opposite requirements, it is necessary to control the operating conditions of the dryer.

For example, the method described in JP-A-8-169914 is: In the method of spray-drying the latex after the post-contact reaction with the initiator, the glass transition temperature of the polymer (hereinafter referred to as "Tg") ) as a reference to set the outlet temperature of the dryer.

However, in this method, since the latex spray method uses a rotating disk, there is a problem that the obtained powder has a small particle size and poor fluidity. Furthermore, when using the rotating disc to recover powders with large particle sizes, both the fine powder and the coarse powder tend to increase and the particle size distribution becomes extremely wide, which often leads to a decrease in powder performance.

In addition, since the outlet temperature of the dryer is set based on the Tg of the polymer, the correct powder structure of the powder cannot be controlled, and as a result, powder properties and redispersibility are poor. This is the same even when the average Tg (apparent Tg) of the powder particles is used.

When the outlet temperature is set on the basis of Tg in this way, the reason why the powder structure cannot be accurately controlled is that in the recently produced propylene-based polymer powder, since various properties are required as a modifier, the structure is often multilayer constructions, and the Tg of such multilayer constructions generally cannot be specifically determined.

Thus, it is difficult to obtain a powder excellent in both the powder properties of (1) and the redispersibility of (2), and there is no report on the operating conditions of a dryer for obtaining a powder with such properties.

Contents of the invention

The object of the present invention is: in the production method of the propylene polymer that sprays and dries the emulsified polymer latex that is the main component of the propylene polymer to obtain the propylene polymer powder, the operating conditions of the drier are set so that each The propylene-based polymer powder used as a modifier for plastic resins has the following properties: excellent powder properties such as handling, fluidity, and anti-blocking properties, and excellent redispersibility when melted and kneaded with other resins. few.

The inventors of the present invention have intensively studied the great influence of the particle size of the powder and the structure of the polymer constituting the powder on the powder characteristics and redispersibility of the propylene-based polymer. As a result, it was found that by spraying the latex into the dryer with a nozzle and controlling the particle size of the sprayed droplets, the drying temperature was set based on the minimum film forming temperature (hereinafter referred to as "MFT") of the latex. The temperature in the dryer, especially the temperature near the outlet of the drier, in order to simultaneously improve the powder properties and redispersibility of the obtained propylene-based polymer, thus completing the present invention. That is, the method for producing a propylene-based polymer of the present invention comprises: spraying an emulsified polymer latex mainly composed of a propylene-based polymer into a drier, and passing a drying gas through the inlet of the drier to make the above-mentioned The process of drying the latex to obtain propylene-based polymer powder and recovering the powder from the outlet of the drier is characterized in that the above-mentioned latex is sprayed with a nozzle, and the temperature of the drying gas near the inlet of the drier is set at a low temperature. At 200°C, the drying gas temperature in the vicinity of the outlet of the drier was set at a temperature lower than the minimum film-forming temperature of the emulsion polymerization latex plus 30°C.

Detailed ways

Next, the present invention will be described in detail.

First, the dryer used in the present invention will be described. The dryer has at least: a spray nozzle for introducing the sprayed latex obtained by emulsion polymerization into the container, an inlet for drying the sprayed latex, and an outlet as an outlet for the drying gas and dried powder. department. And, above-mentioned nozzle is arranged on drier top, and above-mentioned inlet part is arranged on drier top so that drying gas contacts with the sprayed latex, and above-mentioned outlet part is arranged on lower part, and the drying gas used preferably appears to be provided by the drying device. The upper part flows while descending to the lower part.

In addition, the overall shape of such a dryer is not particularly limited, nor is its capacity particularly limited, and it can be used from a small scale used in laboratories to a large scale used in industrial production.

As the above-mentioned nozzle, it is preferable to use a pressure nozzle capable of forming fine particles by applying a pressure of 0.1 to 20 MPa to the sprayed latex so that the latex is ejected from the nozzle at a high speed. In particular, it is preferable to use a pressurized rotary nozzle that sprays the sprayed latex into a swirling flow.

The latex can be sprayed with this nozzle, and the particle size of the obtained powder can be adjusted by adjusting the spray pressure when the latex is formed into fine particles, so that it has a particle size that can obtain the required powder properties. The particle size range in which desired powder properties can be obtained also depends on the structure of the polymer as will be described later, so it can be appropriately adjusted according to the structure of the polymer, the MFT of the latex, and the like.

By adopting such a method, a powder with a larger particle size can be obtained compared with the rotating disc spraying method of the prior art example.

The drying gas temperature in the vicinity of the inlet of the dryer (hereinafter referred to as "inlet temperature") is lower than 200°C, preferably lower than 190°C. When the temperature is higher than 200°C, the surface of the obtained powder is partially thermally blocked, the redispersibility during melt-kneading is lowered, and the amount of fish eyes generated increases.

Although the lower limit of the inlet temperature is not particularly limited, it can be set within a certain temperature range by appropriately setting the temperature near the outlet of the drier described later, preferably 140° C. or higher. When the above-mentioned inlet temperature is lower than 140° C., the air volume of the drying gas increases extremely.

The gas temperature in the vicinity of the outlet of the dryer (hereinafter, referred to as "outlet temperature") is a temperature lower than the MFT of the above-mentioned latex plus 30°C.

Here, the MFT of the latex is the lowest temperature at which a transparent continuous film can be formed when the latex is used to form a film, and is a value representing the Tg of the latex particle surface. In addition, MFT is related to the adhesive force of the latex polymer particle surface layer which is a factor determining the powder structure, and is also used as an index showing the above-mentioned adhesive force.

In this way, the polymer structure of the powder can be controlled by setting the temperature based on the MFT, that is, the properties of the powder such as fluidity and redispersibility can be controlled. Furthermore, the powder properties and redispersibility of the powder can also be controlled even if the polymer is multi-layered.

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

When the above temperature is above the MFT of the latex plus 30°C, due to the adhesion of the surface part of the powder, the redispersibility of the powder during melting and kneading is reduced, resulting in an increase in the amount of fish eyes produced.

In addition, the lower limit of the gas temperature at the outlet of the drier is not particularly limited, but is preferably higher than 50°C. When it is lower than 50°C, the drying of the powder may be insufficient.

As a method of measuring the MFT of the above-mentioned latex, first, a heating device and a cooling device are provided as necessary at both ends of a horizontally installed aluminum plate, so that the temperature of the aluminum plate has a temperature gradient. Secondly, spread the latex in a thin layer on the above-mentioned aluminum plate with temperature gradient to dry it. The lowest temperature at which the latex forms a transparent continuous film is then determined and taken as the MFT.

The preferred particle size of the powder obtained by drying under the above-mentioned conditions cannot be generalized since it also depends on the polymer structure of the powder and the like. For example, generally, those with a low Tg (or MFT) have actually poor powder properties, and therefore need to set the particle diameter larger than those with a high glass transition temperature (or MFT). However, when it is preferably 60-300 μm, it is more preferably 100-200 μm. When the particle size is less than 60 μm, due to the increase of fine powder, etc., the operability, fluidity and anti-blocking property of the powder will be reduced; Does not mix evenly.

The emulsified polymer latex mainly composed of the propylene-based polymer used in the above production method is not particularly limited, but preferably has an MFT of 20°C or higher, and more preferably has an MFT of 50°C or higher. When the MFT is lower than 20°C, drying is insufficient because the outlet temperature of the drier is 50°C or lower.

For such latex, specifically, one or more than two kinds of propylene monomers described below can be used to copolymerize, seed polymerize or graft polymerize the compound. These propylene monomers are: methyl acrylate, ethyl acrylate , butyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, allyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid Propyl ester, 2-ethylhexyl methacrylate, allyl methacrylate, glycidyl methacrylate, acrylamide, acrylonitrile, etc. In addition, as monomers other than the above-mentioned propylene-based monomers, a small amount of monomers that can be used in emulsion polymers such as styrene, 2-methylstyrene, 1,3-butadiene, vinyl acetate, and vinylpyridine can also be used in combination. monomers, preferably 50% by mass or more of propylene-based monomers.

In addition, crosslinking agents such as divinylbenzene, 1,3-dibutylene dimethacrylate, allyl methacrylate, and glycidyl methacrylate, mercaptans, and ruecenes can also be used together. such as chain transfer agents.

The polymerization initiator used for the emulsion polymerization of the above-mentioned propylene-based polymer is not particularly limited, but a redox-based initiator in which potassium persulfate, sodium persulfate, ammonium persulfate, etc. are dissolved in water can be used. Redox initiators such as persulfate, dicumyl hydroperoxide, terpane hydroperoxide, cumene hydroperoxide, tert-butyl hydroperoxide and other organic peroxides as one of the ingredients.

The emulsifier used in the emulsion polymerization of the above-mentioned propylene-based polymer is not particularly limited, and one or more of the following substances can be used in combination, that is, bases of higher fatty acids such as disproportionated rosin, oleic acid, and stearic acid Metal salts, alkali metal salts of sulfonic acid such as dodecylbenzenesulfonic acid.

The emulsification polymerization method and emulsification polymerization conditions of the latex used in the above-mentioned production method are not particularly limited, and can be carried out according to conventionally known methods and conditions.

In addition, the above-mentioned latex may be single or a mixture of plural kinds of latex.

In addition, in order to prevent oxidation in the dryer, it is also possible to spray dry by adding appropriate antioxidants and additives to the sprayed latex.

Furthermore, in order to improve the powder properties such as anti-blocking property and loose specific gravity of the obtained propylene polymer powder, inorganic fillers such as silica, talc, calcium carbonate, and polyacrylate, polyvinyl alcohol, polyvinyl alcohol, etc. can also be added. Acrylamide, etc. are spray-dried.

In the production method of the propylene-based polymer of the present invention, by spraying the above-mentioned emulsified polymer latex into the drier whose temperature is adjusted as described above through the above-mentioned nozzle, drying it and then recovering it from the outlet part, it is possible to obtain Propylene polymer powder with the required powder properties.

In addition, in the present invention, there are no particular limitations on the spray drying apparatus, method, conditions, etc., except that the spraying method and the gas temperature range at the inlet and outlet of the drier are specified. In addition, low-cost air is preferable as the drying gas, but an inert gas or a mixture of air and inert gas can also be used.

In this way, in the method for producing a propylene-based polymer of the present invention, while using a nozzle to spray the latex, the MFT of the latex is used as a reference to control the temperature in the drier, so that the particle size of the powder can be appropriately controlled, and the powder particle size can be controlled appropriately. The architecture of the propylene-based polymer can be controlled according to the composition of the polymer to produce a powder with excellent powder properties.

That is to say, according to the present invention, powder properties such as operability, fluidity, and anti-blocking properties during powder production, and redispersibility during melt-kneading with other resins such as polyvinyl chloride resin are excellent, and there are few fish eyes. Propylene polymer powder.

Example

Next, the present invention will be described based on examples. "Parts" in Examples and Comparative Examples mean "parts by mass" unless otherwise specified.

The propylene-based resin composition was synthesized, and after the minimum film forming temperature (MFT) of the obtained latex was measured, it was spray-dried, the powder was recovered, and various physical properties were evaluated. Table 1 summarizes the dryer outlet temperature, dryer inlet temperature, and evaluation results.

Embodiment 1, 2 and comparative example 1, 2, 3

(1) Synthesis of Propylene Resin Composition

Add 85 parts of methyl methacrylate, 15 parts of butyl methacrylate, 0.003 parts of tert-dodecyl mercaptan, 1.5 parts of potassium alkenyl succinate, and 190 parts of deionized water into the reactor, and use nitrogen After the replacement, temperature rise was started while stirring. Thereafter, when the temperature in the reactor reached 40° C., a mixture of 2 parts of potassium persulfate and 10 parts of deionized water was added to the reactor to start polymerization, and after keeping for 200 minutes, the resulting mixture was taken out from the reactor. latex.

(2) Determination of MFT

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

The measurement temperature conditions at the time of measurement were set to 20° C. at the low temperature end and 180° C. at the high temperature end. As a result of the measurement, the MFT of the latex was 85°C.

(3) spray drying

The above-mentioned latex is introduced into a drier for spray drying. As the drier at this time, the inner diameter of the straight barrel was 3.5 meters, the height of the straight barrel was 4 meters, and the height of the cone was 2.8 meters. As the spraying device, a pressurized nozzle (spray pressure of 2.4 MPa) was used.

In addition, air is used as the drying gas.

Table 1 shows the feed rate of the latex, the blowing volume of the heating gas, the dryer inlet temperature, and the outlet temperature at this time.

(4) Evaluation of various physical properties

A. Powder average particle size

Using a particle size distribution evaluation device specified in Japanese Industrial Standards (JIS No. 40), the mass-based median diameter (medium diameter, usually expressed as "D50") was measured. (Particle size equivalent to 50% of the integral mass distribution curve)

B. Powder fluidity

Add 50 grams of powder to the bulk specific gravity measuring instrument used in JIS-K-6721 standard, observe the flow state when the baffle plate is removed by visual inspection, and evaluate by dividing into the following four levels.

◎………Excellent

○………quite good

△…………OK

×…………not good

C. Evaluation of fisheye

After melting and kneading the resin composed of the following ingredients using an 8-inch roll (at 150°C) for 4 minutes, add 2 parts of the acrylic resin powder obtained above, and then melt and knead for 5 minutes, cut out the plate-shaped resin, and prepare the evaluation fish Eye test strips. Thereafter, light was irradiated from the back of the resin, and the amount of fisheyes produced per unit area contained in the produced test piece was evaluated visually (pieces/16 cm 2 ).

The ingredients are:

Polyvinyl chloride resin (n=1300) 100 parts

trioctyl trimellitate

(manufactured by Kao Shiji Co., Ltd., trade name T-80) 80 servings

Ba-Zn type stabilizer

(manufactured by Nissan Ferro Co., Ltd., trade name LTL-55) 1.0 parts

Epoxidized soybean oil

(manufactured by Tokyo Fine Co., Ltd., product name NF-3000) 5.0 parts

Titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., trade name R-830) 2.0 parts

Carbon black 0.1 parts

Embodiment 3, 4, comparative example 4

(1) Synthesis of Propylene Resin Composition

Add 46 parts of methyl methacrylate, 9 parts of butyl acrylate, 0.01 part of tert-dodecyl mercaptan, 1 part of potassium alkenyl succinate, and 190 parts of deionized water into the reactor, and after nitrogen replacement , began to heat up while stirring. When the temperature in the reactor reached 40°C, a mixture of 2 parts of potassium persulfate and 10 parts of deionized water was added to the reactor to start polymerization, and after that, after keeping for 120 minutes, 37 A mixture of 1 part methyl methacrylate and 8 parts butyl acrylate was added into the reactor, kept for 100 minutes and then taken out from the reactor.

(2) Determination of MFT

Measured with the same method as in Example 1. As a result of the measurement, the MFT of the latex was 72°C.

(3) spray drying

Carry out with the method identical with embodiment 1. Table 1 shows the supply rate of the latex, the blowing volume of the heating gas, the dryer inlet temperature, and the outlet temperature.

(4) Evaluation of various physical properties

Carry out with the method identical with embodiment 1.

Embodiment 5,6, comparative example 5

(1) Synthesis of Propylene Resin Composition

Add 1.5 parts of polyoxyethylene alkyl ether phosphides, 0.01 parts of potassium hydroxide, and 200 parts of deionized water into the reactor, and after nitrogen replacement, add 25 parts of methyl methacrylate, 0.03 parts of iso Propylene peroxide, began to heat up. Thereafter, 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 added into the reactor to start polymerization, and kept for 100 minutes. Thereafter, a mixture of 30 parts of styrene, 25 parts of butyl acrylate, 1 part of t-dodecyl mercaptan, and 0.003 parts of cumene hydroperoxide was added to the reactor over another 100 minutes and maintained for 120 minutes. Thereafter, a mixture of 20 parts of methyl methacrylate and 0.003 parts of cumene hydroperoxide was added to the reactor over 60 minutes, kept for 100 minutes, and then taken out from the reactor.

(2) Determination of MFT

Measured with the same method as in Example 1. As a result of the measurement, the MFT of the latex was 62°C.

(3) spray drying

Carry out with the method identical with embodiment 1. Table 1 shows the supply rate of the latex, the blowing volume of the heating gas, the dryer inlet temperature, and the outlet temperature.

(4) Evaluation of various physical properties

Carry out with the method identical with embodiment 1.

Comparative Example 6

Except using the drier of rotating disc spray mode (rotation number is 15000rpm), all the others are carried out with the same method as embodiment 3.

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

Comparative Example 7

In order to obtain a powder with a particle size of about 100 μm by means of rotating disk spraying, the method was the same as that of Comparative Example 4 except that the rotation speed was 6500 rpm. As a result, undried liquid droplets adhered to the wall surface, and all the sprayed latex could not be recovered as dry powder.

From these results, it can be seen that in Examples 1-6, powders having high fluidity and redispersibility were obtained. In contrast, it can also be seen that in Comparative Examples 1 to 5 in which the temperature in the drier was set outside the temperature range specified in the present invention, the redispersibility of the powder was all poor. In addition, in Comparative Example 6 in which the rotary disk was used for spraying, the fluidity of the powder was also poor, and in the same manner using the rotary disk spraying method, in Comparative Example 7 in which the particle size was set to be large, the powder could not be recovered. .

According to the present invention as described above, it is possible to obtain a propylene-based polymer powder having excellent powder properties such as handleability, fluidity, and anti-blocking property, excellent redispersibility during melt-kneading, and less generation of fish eyes.

Such propylene-based polymer powder with excellent powder properties is suitable for processing such as impact modifiers and lubricants for polyvinyl chloride resin, polystyrene, polycarbonate, ABS resin, acrylic resin, and other various engineering plastics. sex enhancer.

The present invention can be implemented in various other forms without departing from its spirit or main characteristics. Therefore, the above-mentioned embodiment is only an illustration in every respect, and should not be interpreted as a limitative. The protection scope of the present invention is determined by the scope described in the claims, and is not subject to any restriction by the text of the description. Furthermore, modifications or changes of equivalents falling within the protection scope of the claims are within the scope of the present invention. Example comparative example 1 2 3 4 5 6 1 2 3 4 5 6 7 Minimum film forming temperature (°C) 85 85 72 72 62 62 85 85 85 72 62 72 62 Latex supply speed (kg/hr) 45 45 50 50 55 55 45 45 31 50 55 50 55 Heating gas supply volume (N·m ³ /hr) 850 800 800 850 900 900 1200 1100 850 1000 1000 810 1000 Dryer inlet temperature (℃) 160 185 160 185 160 185 195 205 195 205 205 160 205 Dryer outlet temperature (°C) 70 80 60 80 60 80 120 120 120 103 100 60 100 Average particle size D50(μm) 95 102 85 91 110 106 96 98 101 88 118 50 (100) fluidity ○ ○ ○ ○ ◎ ◎ ○ ○ ○ ○ ◎ x - Number of fish eyes (pcs/16cm ² ) 65 90 5 18 2 10 1051 1210 1120 285 120 25 -

Claims (6)

1. A method for producing a propylene-based polymer, comprising the steps of: spraying an emulsified polymer latex having a propylene-based polymer as a main component into a drier, and passing a drying gas through the inlet of the drier , drying the above-mentioned latex to obtain a propylene-based polymer powder, and then recovering the powder from the outlet of the drier, is characterized in that: the above-mentioned latex is sprayed with a nozzle, and the temperature of the drying gas near the inlet of the above-mentioned drier is set to It is set to be lower than 200°C, and the drying gas temperature in the vicinity of the outlet of the drier is set to a temperature lower than the minimum film-forming temperature of the emulsion polymerization latex plus 30°C. 2. The method for producing a propylene-based polymer according to claim 1, wherein the temperature of the drying gas in the vicinity of the inlet of the drier is lower than 190°C. 3. The method for producing a propylene-based copolymer according to claim 2, wherein the temperature of the drying gas near the inlet of the drier is 140°C to 190°C. 4. The method for producing a propylene-based copolymer according to claim 1, wherein the temperature near the outlet of the drier is lower than the minimum film-forming temperature of the emulsion polymerized latex plus 20°C. 5. The method for producing a propylene-based polymer according to claim 1, wherein the minimum film-forming temperature of the latex is 20°C or higher. 6. The method for producing a propylene-based polymer according to claim 5, wherein the minimum film-forming temperature of the latex is 50°C or higher.