JPS59219333A - Production of microspherical cellulose acetate powder - Google Patents

Abstract

PURPOSE:To obtain microspherical cellulose acetate powder in good efficiency, by mixing an organic solvent solution of cellulose acetate with an aqueous medium containing a dispersant, a surfactant and an antifoaming agent by agitation and evaporating the solvent by heating. CONSTITUTION:An organic solvent solution of cellulose acetate is mixed by agitation with an aqueous medium containing a dispersant, a surfactant, and an antifoaming agent under a condition such that the peripheral speed of the tips of impellers is 450m/min or above and the agitator speed is 2,000rpm for 10sec or longer, and the aqueous medium containing the formed suspended particles is heated to vaporize the organic solvent. In this way, microspherical cellulose acetate powder of an average particle diameter of 2-37mu can be obtained. The degree of substitution of the cellulose acetate used is preferably 1.2-3.0. Cellulose acetate of a degree of substitution of 1.2 or below requires a long saponification time, which is disadvantageous from the economical viewpoint. The degree of polymerization is suitably 80-360.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing spherical and finely powdered cellulose acetate.

In recent years, fine powders of various polymer resins have been used as cosmetic additives, colorants, and lubricants instead of inorganic fine powders.

It has been widely used as an anti-blocking agent.

Spherical fine powder of cellulose acetate, for example, has appropriate oil absorption, hygroscopicity, and water retention properties as a cosmetic additive, and not only has a high affinity for the skin and provides a favorable feeling of use, but also has good dispersibility regarding the uniformity of cosmetics. It is thought that it has good mixability, and is also excellent in moldability, fillability, and safety.

However, no cosmetic additive has yet been obtained that satisfies the following conditions: spherical shape and average particle size of 2 to 37 microns.

As a method for producing spherical fine particles of cellulose acetate known so far, for example, according to JP-A-53-7759, cellulose triacetate is dissolved in methine chloride/or chloroform or a mixed solvent mainly containing these. There is a method of obtaining spherical particles of cellulose triacetate by dropping the solution into an aqueous medium (while stirring) and heating the aqueous medium containing the generated suspended particles to evaporate the organic solvent.

In Jin's method, in which a cellulose triacetate solution is dropped into an aqueous medium, the average particle size is 2-. In order to obtain relatively small spherical fine particles such as 57μ, it is necessary to lower the solution viscosity of the cellulose triacetate solution. There must be. However, lowering the concentration is economically disadvantageous as more organic solvent must be evaporated, and lowering the degree of polymerization of cellulose triacetate also reduces the physical strength of the resulting cellulose triacetate spherical microparticles. There are problems such as the impact on

Furthermore, when the aqueous medium is a liquid in which only a dispersing agent such as gelatin or polyvinyl alcohol is dissolved, when heating the aqueous medium containing suspended particles of cellulose triacetate to evaporate the organic solvent, it is necessary to In order to avoid severe foaming, the temperature must be maintained at 2 to 6° C. lower than the boiling point of the organic solvent for a certain period of time to evaporate the organic solvent of Ml, which is disadvantageous in terms of time and energy.

Furthermore, JP-A-55-28763 discloses a method of obtaining spherical microparticles by spray-drying a solution in which cellulose fatty acid ester is dissolved in a mixed solvent of three or more solvents having a boiling point difference of 60° C. or more. Disclosed. In order to obtain relatively small spherical fine particles with an average particle size of 2 to 37 μm using this method, it is necessary to reduce the size of the droplets after ejection using an atomizer, and this method is different from the method described in JP-A-53-7759. Similarly, there are economic disadvantages such as the need to lower the viscosity of the cellulose fatty acid disester solution.

The present invention relates to a method for efficiently producing spherical microparticles of cellulose acetate having an average particle size of 2 to 57 microns.

That is, in the present invention, a solution of cellulose acetate in an organic solvent is mixed with an aqueous medium containing a dispersant such as geladine or carboxymethylcellulose, a surfactant, and an antifoaming agent using a homogenizer or the like at a circumferential speed of 450 m/min or more in the rotating field. 2+0 [
]Orpm or higher stirring speed to form an aqueous medium containing suspended particles mainly composed of cellulose acetate solution, and heat the mixture as it is to evaporate the organic solvent to obtain an average particle size of 2.
This is a method for efficiently producing fine spherical cellulose acetate powder of ~37μ.

The cellulose acetate used in the present invention is obtained by acetylating valve linters, etc. with acetic acid, acetic anhydride, or sulfuric acid in a conventional manner. Those produced by the method described on page 60 of ``Publication'' may be used.

A suitable degree of substitution for cellulose acetate is 1.2 to 3.
．． 0, but preferably 1.4 to 2.9. 1.
If it is less than 2, the longer the saponification time, the more economically disadvantageous it becomes. Further, the degree of polymerization and l- are suitably 80 to 360, but preferably t is 120 to 320.

It is also possible to mix and use two or more types of cellulose acetate having different degrees of substitution and degree of polymerization in any proportion. Furthermore, cellulose acetate butyrate, cellulose acetate propionate, etc. may be mixed.

The solvent for dissolving cellulose acetate needs to be appropriately selected depending on the degree of substitution, and methylene chloride, chloroform, ethane, methyl ethyl ketone, etc. may be used alone, or a mixture of two or more of these may be used. It is also possible to mix methanol, ethanol, acetone, nitromethane, water, etc. with these solvents as the main component.

In order to obtain fine powder with an average particle size of 2 to 37 microns in good yield, the appropriate concentration of the cellulose acetate solution is 1 to 15% by weight, preferably 5 to 12% by weight. If it is less than one electric current, the manufacturing efficiency will be poor and it will be economically disadvantageous.

In addition, the average particle size of the obtained spherical particles was 67% by weight.
It is difficult to keep it below /1.

However, the average particle size depends not only on the concentration of cellulose acetate solution but also on the degree of polymerization of cellulose acetate.

Since it is also related to the type of solvent system used, the average particle size 2
It is necessary to comprehensively determine an appropriate value within the range of ~37μ.

Depending on the purpose, plasticizers, dyes, etc. may be added to the cellulose acetate solution.
Pigments, antistatic agents, ultraviolet absorbers.

A fragrance or the like may also be added.

The aqueous medium used in the present invention includes gelatin and carboxymethyl cellulose as dispersants.

polyvinyl alcohol, hydroxyethylcellulose,
Hydroxypropyl cellulose, albumin, gum arabic, etc. 0.05 to 4.5% by weight, preferably 0.3 to 4.5% by weight
1.5 weight [, anionic or nonionic surfactant or a mixture thereof as a surfactant, 0.02 to 1.
5% by weight, preferably 0.1 to 1.0% by weight, as an antifoaming agent/recon resin, modified silicone resin, nonionic polyether type, polyalkylene glycol type antifoaming agent, etc. from 0.02 to 102% by weight 10% by weight or 0.1-0
．． 5. Water that engages the holder is used.

Examples of anionic surfactants include higher alcohol sulfate ester sodium salts, alkyl phosphate salts, dialkyl sulfosuccinates, polyoxyethylene sulfate salts, etc., and nonionic surfactants include polyoxyethylene alkyl ethers, sorbitan fatty acid esters, and polyoxyethylene sulfate salts. Oxyethylene sorbitan fatty acid ester, polyoxyethylene acyl ester, etc. are removed.

The above-mentioned dispersants and surfactants are necessary to create a stable suspension by mixing and stirring, and generally there is no dispersant.
．． If the surfactant is less than 0.05% by weight or the surfactant is less than 0.02% by weight, the particles may fuse together to form T2 lumps when the solvent in the suspension solution is evaporated, making it difficult to stably produce microspherical powder. Have difficulty.

On the other hand, although it is acceptable to exceed the above amounts, it is economically disadvantageous. Furthermore, antifoaming agents are extremely effective in suppressing foaming when mixing and stirring a cellulose acetate solution and an aqueous medium and when evaporating the solvent in a suspended solution. When foaming is significant during mixing and stirring, when the foam collapses, particle fusion occurs and becomes dust-like, so suppressing foaming is advantageous in terms of yield.

Furthermore, when the solvent in the suspended solution is evaporated, if bubbles are generated violently, the suspended solution will also be distilled off at the same time as the solvent evaporates, making it difficult to separate the solvent.

Generally, if the amount of antifoaming agent added is less than 0.022% by weight, the foam suppressing effect will be small, and if the amount is more than 10% by weight, it is economically disadvantageous.

The mixing ratio of the organic solvent solution and the aqueous medium obtained as described above is not particularly limited, but it can generally be carried out within the range of 100 parts of the former to 50 parts of the latter at a ratio of 1 to 5,000.

Stirring methods used in the present invention include methods using a homogenizer, Pomo mixer, colloid mill, and the like.

The peripheral speed of the tip of the rotor during stirring is 450 to 3+500 m.
/min, preferably 900 to 1,800m/min,
The rotation speed of the rotary blade is 2.000 to 15,000 rpm, preferably 4.00 rpm. oOo ~ 8,000 rpm. The stirring time is 10 seconds to 30 minutes, preferably 30 seconds to 10 minutes.

A method of evaporating an organic solvent in a suspended solution by heating and [
7. The usual method is oil bath.

Examples include heating the liquid in a water bath or the like, blowing hot air into the suspended solution, blowing steam into the suspension, and the like. After the organic solvent in the suspension solution has been evaporated, the aqueous dispersion containing spherical particles of cellulose acetate is subjected to solid-liquid separation by centrifugation, filtration, etc., and then dried to obtain the desired powder particles. It will be done.

The shape of the spherical microparticles of cellulose acetate in the present invention was confirmed by observation using a microscope or the like. The average spherical diameter was measured using a Coulter Counter manufactured by Coulter Electronics. It is extremely useful as a lubricant, an antiblocking agent, a colorant, etc., and as a material for producing sintered bodies.

Examples are shown below to explain the present invention in more detail. However, the present invention is not limited to these examples. Commercial capital indicates parts by weight.

Example 1 100 parts of cellulose acetate (degree of substitution 2.9, average degree of polymerization 280, raw material cellulose: pulp) was mixed in a mixed solvent of methylene chloride and methanol (mixing ratio).

Methylene chloride/methanol-91/9 supernatant ratio) 1,9
00 parts of welt liquid (A), 6.6 parts of gelatin, 2.2 parts of higher alcohol sulfate ester soda m, and 8.0 parts of a modified silicone resin antifoaming agent were dissolved in 2,000 parts of water.
2.000 parts of the aqueous medium solution (B) was put into a homogenizer container, the liquid temperature was 20°C, the tip peripheral speed of the rotor blade was 1.39 m/min, and the rotation speed of the rotor blade was 6. 000rp
The mixture was stirred for 5 minutes at m, to form a suspension solution containing microparticles of cellulose acetate solution. Transfer this suspension solution into a flask [7
While stirring at a rotation speed of 100 rpm, the liquid temperature was raised by external heating using a water bath, and methylene chloride and methanol were evaporated and removed from the system. The time required to evaporate a total of 1.67Of of methylene chloride and methanol (including some water) from the start of heating the suspension solution was approximately 10
It was 0 minutes.

The obtained aqueous dispersion in which fine particles of cellulose acetate were dispersed was separated into solid and liquid using a centrifuge (7,000 rpm), and the fine particles were dried to obtain a fine powder of cellulose acetate.

When the obtained fine powder was observed under a microscope, it was found to be almost perfectly spherical. The average sphere diameter measured with a Coulter Counter (Coulter Electronics) was 4.2 .mu.m.

Comparative Example 1 The solution (A) used in Example 1 and 6.6 parts of gelatin were mixed with 2 parts of water.
．． 000 parts of the aqueous medium (0) was stirred in the same manner as in Example 1 to form a suspension solution, but the suspension solution clearly had collapsed bubbles and fused particles to become dust-like. There were things floating on the surface. Furthermore, this suspension solution was transferred to a flask and the temperature of the solution was raised in the same manner as in Example 1, but the suspended microparticles of the cellulose acetate solution fused and formed into large lumps, and no fine powder was obtained. Ta.

Comparative Example 2 The solution (A) used in Example 1, 6.6 parts of gelatin, and 2.2 parts of higher alcohol sulfate ester soda salt were mixed with 2.0 parts of water.
00 parts of the aqueous medium solution (D) was stirred in the same manner as in Example 1, the resulting suspension was transferred to a flask, and the liquid temperature was raised in the same manner as in Example 1, but the solvent Simultaneously with the distillation of , the suspended solution was also distilled off. Only the solvent could not be evaporated or removed from the system.

Example 2 Cellulose acetate (degree of substitution 2.1. Average degree of polymerization i20. Raw material cellulose: pulp) 10 parts of a mixed solvent of methylene chloride and methanol (mixing ratio: methylene chloride/methanol = 91/9 weight ratio)1. Solution dissolved in 900 parts (
m) and the solution (B) used in Example 1 were treated in the same manner as in Example 1 to obtain a fine powder of cellulose acetate.

The obtained fine powder was spherical and had an average particle size of 5.4μ.

Example 5 100 parts of the cellulose acetate used in Example 2 was dissolved in 1,900 parts of methyl ethyl ketone.
was treated in the same manner as in Example 1 to obtain a fine powder of cellulose acetate.

The obtained fine powder was spherical and had an average particle size of 16.8μ.

Example 4 150 parts of the cellulose acetate used in Example 1 was mixed with a mixed solvent of methylene chloride and methanol (mixing ratio).

Methylene chloride/methanol-91/9 ratio) 1.85
0 parts of solution (G) and solution (B) were treated in the same manner as in Example 1 to obtain fine powder of cellulose acetate.

The obtained fine powder was spherical and had an average spherical diameter of 10.6μ.

Comparative Example 3 Salary liquid (A) used in Example 1! It was dropped into i (B) being stirred at +0 [] rpm through a nozzle with a nozzle diameter of 1 mm to form a suspension solution, and then the solvent was evaporated, solid-liquid separated, and dried in the same manner as in Example 1. , a fine powder of cellulose acetate was obtained.

The obtained fine powder was spherical and had an average particle size of 46 μm.

Comparative Example 4 The cellulose acetate solution used in Example 4←) was used in Comparative Example 5.
It was dropped into the liquid (B) which was being stirred at 300 rpm from the nozzle used in .

However, the particles did not become spherical, but instead became thread-like.

Example 5 After stirring the solution (1) obtained by mixing 30 parts of diethyl phthalate with the solution (A) used in Example 1 and 2,000 parts of the aqueous medium solution (B) in the same manner as in Example 1, the organic solvent was added. The mixture was evaporated, solid-liquid separated, and dried to obtain a fine powder of cellulose acetate containing diethyl phthalate.

The obtained fine powder was spherical and had an average spherical diameter of 4.511. Example 6 100 parts of cellulose acetate (degree of substitution 2.9, average degree of polymerization 280, raw material cellulose: linter) was mixed with methylene chloride and methanol. mixed solvent (methylene chloride/methanol = 91
/9 weight ratio) were treated in the same manner as in Example 1 to obtain a fine powder of cellulose acetate.

The fine powder was spherical and had an average spherical diameter of 4.0μ.

Claims (1)

[Claims] A solution of cellulose acetate in an organic solvent and an aqueous medium containing a dispersant, a surfactant, and an antifoaming agent are stirred for at least 10 seconds at a rotational blade tip circumferential speed of at least 450 m1 minute or more and at a stirring speed of 2,000 rpm or more. A method for producing a spherical micropowder of cellulose acetate, which comprises stirring and mixing the above, and heating an aqueous medium containing the generated suspended particles to evaporate the organic solvent.