JPS6031213B2 - Method for producing aromatic polyester spherical powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for powdering a crystalline saturated polyester having an aromatic ring in its structural unit, such as poly(alkylene terephthalate).

More specifically, the present invention relates to a method for producing crystalline aromatic saturated polyester powder whose particle shape is close to spherical. Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and ethylene glycol, 1
・3-pro/gundiol, 1,4-butanediol,
Crystalline aromatic saturated polyesters, which have structural units obtained by condensation with alkylene glycols such as neobentyl glycol, have excellent mechanical, chemical, and thermal properties, so they can be used in fibers, films, and molding. It is widely used as a material and is extremely useful industrially.

However, despite the above-mentioned superiority of crystalline aromatic saturated polyester, at present it is hardly used as a powder material.

One of the important reasons for this is thought to be that crystalline aromatic saturated polyesters have excellent physical and chemical properties and are therefore difficult to powder. The present inventor believed that if crystalline aromatic saturated polyester could be powdered, its excellent properties could be utilized in many more fields, and as a result of extensive research, the present invention was achieved. It is something.

That is, the present invention provides a method for preparing a crystalline aromatic saturated polyester having an aromatic ring in a structural unit in one or more aromatic solvents having a boiling point of 23,000 or more or a mixed solvent containing the aromatic solvent as one component. The invention relates to the production of polyester powder whose particle shape is close to spherical by heating and dissolving the powder and then cooling it.

It is of great industrial importance that the present invention can provide a new polyester powder material that can be applied to powder coatings, fillers, molding raw materials, adsorbents, and various other fields of application. Conventionally, many polymer powders such as polystyrene, polyethylene, polyvinyl chloride, and polyamide have been known as polymer powder materials, and are actually used for various purposes.

Methods for obtaining a polymer in powder form include a method in which a polymer suspended in fine particles is obtained by suspension polymerization and then dried to obtain a powder; [B) a method in which the polymer is mechanically pulverized; ,'○ A reprecipitation method in which a polymer is dissolved in a solvent and then a poor solvent is added to precipitate it.A dish polymer is dissolved in a high-temperature solvent, and then a precipitate is formed.
A cooling precipitation method is known in which the temperature is lowered by cooling and a precipitate is precipitated by utilizing the difference in solubility depending on the temperature. First, the worst method is often used for polymers obtained by radical polymerization, and the particles tend to become spherical, so it is suitable for obtaining granular materials, but it is difficult to apply to condensation polymers. .

Next, method [B} is applicable to all polymers in principle, and examples of its application to aromatic saturated polyesters are also known. However, although mechanical pulverization is suitable for coarse pulverization, there is a limit to its ability to form fine particles, and it is an extremely inefficient method, especially in the case of crystalline thermoplastic polymers with high toughness such as the above-mentioned polyester. becomes. Furthermore, powder particles obtained by mechanical pulverization tend to have irregular shapes with many corners and irregularities, or have whisker-like protrusions, and are often unsuitable as powder materials. The reprecipitation method (C) is a widely known method for purifying polymers, but in most cases, the precipitate is obtained in the form of fibrils or fibers, and only very rarely is it in the form of powder. There is. For example, only when the molecular weight of the polymer is so low that it has no ability to form fibers, or when the concentration of the polymer is extremely low. Further, even if a powdery precipitate is obtained, the grains thereof are small, approximately equal to or less than the number r, and therefore, this method is generally not preferred as a method for obtaining a powdery material as the object of the present invention. Furthermore, the cooling precipitation method of 'D' has been applied to polyamide, etc., and it seems that powder materials with relatively good sphericity can be obtained, but this method is useful for polyamide-based polymers. It is not necessarily useful for In particular, crystalline aromatic saturated polyesters, mainly consisting of poly(ethylene terephthalate) or poly(tetraethylene terephthalate), are crystalline polymers with high melting points, so they have poor solubility and can only be dissolved in extremely limited solvents. Therefore, powderization by cooling precipitation method has hardly been attempted. Furthermore, even if the particles are dissolved, they tend to become fipril-like at the stage of precipitation, so there is a problem that the particles do not have a desirable shape as a powder material. Therefore, the present inventor conducted various studies on the solvent and particle precipitation conditions for obtaining spherical powder particles of crystalline aromatic saturated polyester by the cooling precipitation method. The inventors have discovered that a method of precipitating a precipitate is optimal, and have arrived at the present invention.

Examples of the crystalline aromatic saturated polyester used in the present invention include poly(ethylene terephthalate), poly(tetraethylene terephthalate), poly(hexamethylene terephthalate), poly(cyclohexanedimethanol terephthalate), and poly(P-hydroxybenzoic acid). ), but it is not limited to these homocondensates, and copolymers can be used as long as the crystallinity is not lost.

For example, the brewing ingredients include 30 mol% or more of terephthalic acid and 70 mol% of one or more dibasic acids or oxycarboxylic acids such as isophthalic acid, phthalic acid, adipic acid, sebacic acid, and -hydroxycaproic acid. A mixture consisting of the following may also be used. The glycol component includes 30 mol% or more of ethylene glycol or tetramethylene glycol, and other polyhydric alcohols such as trimethylene glycol, propylene glycol, hexamethylene glycol, cyclohexanedimethanol (1.4), 2
・2,4,4-tetramethylcyclobutanediol (1
-3) It may be a mixture consisting of 70 mol% or less of one or more diol compounds such as hydroquinone. Furthermore, it may contain a small proportion of trifunctional or higher-functional carboxylic acid, alcohol, or oxycarunic acid. Furthermore, two or more types of polyesters having different compositions or molecular weights may be mixed and used. The aromatic saturated polyester used in the present invention needs to be "crystalline".

The word "crystalline" here does not mean "gives crystalline reflection in X-rays," but it means "capable of forming a spherulite structure in optical microscopy." That is, those having such crystallinity that the formation of precipitates can occur accompanied by the growth of spherulites can be used in the present invention. Therefore, although the above-mentioned copolymerized polyesters include some that are not recognized as crystalline by X-ray, optically they are recognized as crystalline because they can have a spherulite structure, and can be used in the present invention. be.
Examples of the aromatic solvent having a boiling point of 230° or higher used in the present invention include Q-methylnaphthalene, Q-ethylnaphthalene,
Examples include alkylnaphthalenes such as 8-methylnaphthalene and dimethylnaphthalene, alkylbenzenes such as dodecylbenzene, n-decylbenzene, octylbenzene, and hexamethylbenzene, biphenyl, diphenyl ether, and benzyl ether.

The solvent used for dissolving the polyester may be one or a mixed solvent of two or more of the above-mentioned aromatic solvents, or a combination of the aromatic solvent and another high-boiling point solvent, such as p-terphenyl, tetradecane, octadecane, fluid The solvent may be a hydrocarbon solvent such as paraffin, or a mixed solvent with one or more alcohols such as octadecanol, cetyl alcohol, tetramethylene glycol, triethylene glycol, and ethylene glycol monobenzyl ether.

Furthermore, many other solvents that have heat resistance and boiling points that do not cause operational problems during heating and melting, and are compatible with aromatic solvents can be used. The type and proportion of the aromatic solvent in the mixed solvent should be selected appropriately depending on the type of polyester to be powdered and the target particle size, but approximately 5% by volume or more, preferably 7% by volume. The above is appropriate.

If the proportion of the aromatic solvent is less than 5% by volume, the shape of the precipitated particles generally becomes non-spherical or the solubility becomes insufficient, which is not preferable. Any method can be used to dissolve the polyester in a solvent. The melting temperature depends on the type of polyester,
Although it is necessary to select the solvent appropriately depending on the solvent composition, it is generally preferable that the dissolution temperature is 180 to 2300C. If the melting temperature is higher than 230 qo, the degree of polymerization of the polyester will drop significantly, which is not preferable. However, polyethylene terephthalate homopolymers or polyethylene terephthalate copolymers containing 90 mol% or more of ethylene terephthalate polymer units may be difficult to dissolve in aromatic solvents at temperatures below 230 qo.
It is desirable to melt at the above temperature in as short a time as possible. Care should be taken to ensure that the solvent and polymer do not contain water to prevent hydrolysis during dissolution. Additionally, it is effective to add a small amount of antioxidant to prevent thermal scaling. The weight (weight) of the polyester to be dissolved in 100 parts of the solvent is suitably 1 to 30 parts, preferably 5 to 20 parts.

If the concentration of polyester is too high, the viscosity of the system becomes extremely high when the precipitate particles are precipitated, making it impossible to flow, which is not preferable. Furthermore, if the polyester concentration is too low, the amount of powder obtained in one charge will be small, which is industrially disadvantageous. Note that additives other than polyester, such as pigments, dyes, surfactants, other polymers, antioxidants, deterioration inhibitors, and other additives, may be present during dissolution. In the method of the present invention, the most important point for obtaining spherical polyester powder is that the crystalline saturated polyester dissolved in an aromatic solvent at high temperature is precipitated as spherulites by means of "cooling." The cooling method is extremely important, and it is necessary to satisfy conditions such that spherulite formation is always dominant.

However, when using the aromatic solvent of the present invention, the formation of spherical particles becomes dominant over a wide range that satisfies the condition that the entire system is cooled while maintaining a substantially uniform temperature distribution. method can be adopted. The simplest method is to simply stop heating and allow it to cool. Other methods include forcing the container to cool by blowing air, pouring cold soot into the jacket, and bringing it into contact with a cold liquid that is immiscible with the solvent. Air cooling or water cooling is usually sufficient for cooling, but if necessary, it may be cooled to below room temperature using appropriate cold soot.

Since the cooling rate affects the size and shape of the polyester powder particles produced, it is necessary to select the cooling rate appropriately depending on the application. It is not difficult for a person of ordinary skill in the art to know what cooling conditions to choose to achieve the desired particle size. Generally, as the cooling rate increases, the grain fleas become smaller and the shape of the grains becomes non-spherical. While cooling the system during cooling is effective in making the temperature distribution within the system uniform, excessive cooling should be avoided as it will hinder the spheroidization of the particles. In the method of the present invention, the average particle size of the polyester spherical powder can be freely adjusted within the range of 10 to 1,004 by selecting the concentration and cooling rate.

The thus obtained slurry containing spherical polyester particles is centrifugally dehydrated or filtered to separate the particles from the solvent, and then washed with a low-boiling inert solvent and re-washed as necessary. It is dried by centrifugal deliquification or filtration to obtain powdered polyester.

At this stage, the polyester powder has a certain degree of agglomeration, especially when the particle size is small.
It is desirable to grind to break the light bonds between the particles. The crushing energy required at this time is much smaller than when crushing polyester chips, and the purpose can be achieved, so extreme crushing should be avoided. Since the aromatic saturated polyester spherical powder obtained by the method of the present invention is a new material obtained for the first time by the method of the present invention, its uses are limitless, but the following are the fields of use that are considered to be immediately applicable at the present time. It is as follows.

First, it can be used as a resin powder for powder coating.
When forming coatings using various powder coating techniques such as fluidized bed immersion, electrostatic spray coating, or flame spray coating, the shape of individual particles is an important factor in handling the powder and in the coating formation process. It is recognized that That is, the closer the particle shape is to a spherical shape, the better the fluidity of the powder is, the more dense the filling is possible in the first step of coating formation, and the easier it is to form a better coating. For such purposes, polyester spherical powder produced by the method of the present invention is suitable. Furthermore, the excellent physical properties of polyester make it more than suitable for use as a powder coating. In addition, in the method of the present invention, by adding colored pigments to the cooling precipitation solvent, direct coloring,
Another advantage is that polyester spherical powder can be obtained. Next, it can be used as a filler when added to other polymers to improve their physical properties.

For example, by adding a large amount to polyethylene, the rigidity and heat resistance can be significantly improved. Moreover, the polyester spherical powder obtained by the method of the present invention can be suspended in a non-melting, low-boiling medium and can be applied in the form of a paste or suspension for many purposes. For example, a transparent polyethylene terephthalate film is immersed in a solution made by suspending polyester spherical powder in a mixed solvent of butanol and acetone, and then dried at a temperature near the softening point of the powder to make the film opaque. Surface drawing properties can be imparted. In addition, by applying the paste to the surface of the article and drying and curing it,
A transparent or colored film can also be formed on the surface of the article. Next, since the polyester spherical powder obtained by the method of the present invention has excellent sphericity, it has an interesting property of having a high theoretical plate number and being excellent in separation chambers as a packing material for gas chromatography or liquid chromatography. have.

Other uses include resin powder for press molding.

By subjecting the polyester spherical powder obtained by the method of the present invention to solid phase polymerization under high-temperature vacuum, it is possible to obtain a powder with an extremely high degree of polymerization, thereby making it possible to obtain a molded product with excellent strength. By physically or chemically treating, modifying, or adding polyester spherical powder, it can be applied to even more uses.

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way.

Example 1 Poly(ethylene terephthalate) waste yarn (intrinsic viscosity number measured in a 3000°C temperature bath using an Ubbelohde viscometer using an equal weight mixture of phenol and tetrachloroethane as the solvent) = Add 0.63 d'/200 g of boiling diphenyl ether (temperature 258 qC) to 800 g of boiling diphenyl ether (containing 0.50% by weight of titanium oxide),
After stirring for a minute to completely dissolve the mixture, the container (separable round bottom flask) was wrapped in a futon made of glass wool and allowed to cool.

The liquid temperature in the container decreased to 128 oo after 3 hours.
Continue to cool as it is, take out the container that has cooled to room temperature after one hour, filter the precipitated polyester powder,
After washing with methanol five times, drying under normal pressure at 100 qo for 3 hours, and drying under reduced pressure at 80 qo, polyester powder was obtained. This powder is a smooth powder with a tap bulk specific gravity of 0.78 ta'c, and from the results of photographic observation using a scanning electron microscope, it is found that the particles are close to perfect spheres with an average particle size of about 35 mm. Understood.

Although a lamellar structure was observed on the surface from the enlarged photograph, it was estimated from the measurement of pore distribution using a mercury porometer that there were almost no pores inside the particles and that the inside had a delicate structure. Example 2 10 muscle volume parts of liquid paraffin, 1 part of Q-methylnaphthalene
Two parts of a mixed solvent consisting of 0 parts by volume were placed in a round bottom flask with a volume of 3, and immersed in 190 CO oil. When the temperature became constant, poly(tetramethylene glycol) (
Add 100 chips of [ri]=0.87d[/event],
After completely melting the chips in 15 minutes while worshiping, turn off the oil heater, and when it reaches 13,000 after 2 hours, set the oil temperature to 130oo, and leave it in that state for one more hour. A precipitate was separated out.

Then, the flask was taken out of the oil rack and allowed to cool, and after several hours the temperature was set to 5,000. During this time, the inside of the flask was cleaned using a Teflon strainer. p. It continued to make losses at a loss speed of m. The deposited precipitate was filtered, thoroughly washed with acetone, air-dried overnight, and then dried at 13,000 for 5 hours to obtain a white powdery polyester. Since the powder was slightly agglomerated, it was ground in a household mixer about 3 times. The tap bulk specific gravity of the polyester powder obtained in this way is 0.65 /
According to microscopy, they were spherical particles with an average particle size of 70 mounds.

Comparative example 1N-N-dimethylformamide 100 desktop,
Poly(ethylene terephthalate) was placed in a hard glass sealed tube, and after being melted, it was immersed to an oil rating of 19,000, taken out from time to time, and stirred to completely dissolve in 10 minutes, and allowed to cool to 8,000 after 6 hours. The mixture was then taken out into the air and allowed to cool to precipitate.

A portion of the precipitate was taken out, washed with methanol, and dried.
When observed with a scanning electron microscope, it was an aggregate of fibril-like objects several hundred amps wide and several thousand squares to several feet long. Comparative Example 2 Example 1 was added to 800% of a mixed solvent consisting of 10 parts by volume of phenol and 30 parts by volume of N.N-dimethylformamide.
In the same manner as above, 50 pieces of poly(ethylene terephthalate) waste yarn were dissolved at 180°C, and then allowed to cool while being kept warm with glass wool.

The resulting precipitate was filtered, washed, dispersed in benzene, and freeze-dried to obtain a powder with extremely low cage specific gravity, and as a result of observation using an electron microscope, the particle shape was found to be fibrous. It was fibrillar. Comparative Example 3 Poly(ethylene terephthalate) waste yarn 50 mm was added to 800 mm of cresol in the same manner as in Example 1.
The solution was dissolved at 0 and slowly cooled to precipitate.

The shape of Shen Yi was fibrillar. Example 3 Acid components are terephthalic acid 60 mol%, isophthalic acid 4
Tetralin 100% copolymerized polyester 10% containing 0 mol% and whose glycol component is ethylene glycol
The solution was dissolved in a mixed solvent of 100 parts by volume and 5 parts by volume of dodecylbenzene at 19,000 ml, and allowed to cool to room temperature to precipitate.

The obtained particles were spherical and had a particle diameter of about 20 mm, and although almost no reflection was observed in the X-ray examination due to the fact that they were not based on crystals, a cross shape was observed in the fat field image obtained using a polarizing microscope.

This indicated that the optical axis of the particles was oriented in the radial direction of the spherical powder, and it was recognized that the particles had a spherulite structure. Example 4 A copolymerized polyester whose dibasic acid components are 60 mol% of terephthalic acid, 20 mol% of adipic acid, and 20 mol% of isophthalic acid and whose glycol component is ethylene glycol was mixed with 10 volumes of Q-methylnaphthalene. The solution was dissolved in a mixed solvent 400 consisting of 5 parts by volume of biphenyl, 10 parts by volume of mineral oil at a temperature of 22,000, and cooled in air to below 5,000 in about 4 hours to precipitate.

Thereafter, the precipitate was filtered, washed with methanol, and dried to obtain a powder. As a result of microscopic observation, the obtained powder particles were found to be approximately spherical particles with a particle diameter of several to 30 mm.

Comparative Example 4 50 g of the same poly(ethylene terephthalate) waste thread as in Example 1 was mixed with 800 g of boiling diphenyl ether.
After stirring for 15 minutes to dissolve,
The liquid temperature was lowered to 150q0, and mixed xylene 1 was added as a precipitant.
was added dropwise over 3 minutes to precipitate.

Furthermore, after cooling to around room temperature, precipitated particles were filtered out, washed with excess xylene and methanol, and dried. As a result of microscopic observation, the obtained powder particles had a particle size of 0.
．． It had an amorphous or fibrillar shape with one to several slender edges and many corners, and aggregated into lumps during drying.

Additionally, clogging occurred during filtration. Furthermore, since it solidified into a hard plate shape during drying, it was pulverized for a long time using a pulverizer to form a powder. As described above, in the reprecipitation method in which precipitated particles are precipitated by adding a precipitant, the particle shape becomes non-spherical and particles with a large particle size cannot be obtained. Example 5 Poly(p-hydroxybenzoic acid) (intrinsic viscosity measured at 30 CO in 0-chlorophenol) = 0.55 d
'/evening) 10 evenings boiling diphenyl ether (
It was melted in the ground at a temperature of 25 to 0)500, and the container (separable round bottom flask) was wrapped in futon cotton made of glass wool and left to cool.

The temperature of the liquid in the container decreased to about 10,000 ℃ after 3 hours. The container was left to cool as it was, and after 2 hours, the container cooled to room temperature was taken out, the precipitated polyester powder was filtered, thoroughly washed with methanol and n-hexane, and dried to obtain polyester powder. This powder has a tap bulk specific gravity of 0.
It was a smooth powder with a grain size of 66 to 60 mm, and microscopic observation revealed that it was a spherical particle with a size of about 30 to 60 mm.

Claims (1)

[Claims] 1 A crystalline saturated polyester having an aromatic ring in its structural unit is treated with one or two aromatic solvents having a boiling point of 230°C or higher.
1. A method for producing polyester spherical powder, which comprises heating and dissolving in a mixed solvent containing at least 50% by volume of the aromatic solvent and then cooling.