JPH05247226A - Readily soluble power of acrylonitrile polymer - Google Patents

Abstract

PURPOSE:To prevent lump formation to thereby obtain a more homogeneous solution by homogeneously dispersing an acrylonitrile polymer into a solvent and dissolving the polymer in slurry form. CONSTITUTION:The title powder is composed of particles of an acrylonitrile polymer having an acrylonitrile unit content of 85wt.% or higher. The particles have diameters of 20-80mum and a void content of 20% or higher, with closed cells accounting for up to 10% of the voids.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylonitrile-based polymer powder used as a raw material for fibers and the like, and particularly to an acrylonitrile-based polymer powder excellent in solution shapeability.

[0002]

2. Description of the Related Art It is well known that acrylonitrile polymers are widely used as fibers, films and molded products. Among them, a polymer having an acrylonitrile content of 85% is not only widely used as a fiber for clothing because of its excellent weather resistance and heat resistance, but also becomes more important as a precursor of carbon fiber. There is. In order to industrially make these polymers into fibers, a wet spinning method, a dry-wet spinning method, and a dry spinning method are performed using a solution obtained by dissolving the polymer in a solvent as a spinning stock solution. Examples of the solvent include dimethylformamide, dimethylacetamide, dimethylsulfoxide, γ-butyrolactone, nitric acid aqueous solution and sodium thiosulfate aqueous solution.

The solubility of such polymers in these solvents has a great influence not only on the performance of the products produced but also on the stability of the production process. Therefore,
Conventionally, various studies have been made to improve such revision, and it is generally well known to make the particles of polymer powder fine. For example, Japanese Patent Fairness 3-6
No. 7100 describes that it is preferable to reduce the weight per powder particle.

[0004]

When dissolving an acrylonitrile-based polymer, a method of uniformly dispersing the polymer in a solvent once and making it into a slurry and then dissolving can suppress the occurrence of so-called "mamako". It is possible to obtain a more uniform solution.

According to the research conducted by the present inventors, it was found that the homogeneity of dispersion at this time governs the homogeneity of the subsequent solution, and for that reason, it is important to reduce the powder particle diameter. However, as a result of further detailed study, it became clear that how quickly and uniformly the solvent can be distributed in the powder particles is important, and the present invention has been completed.

[0006]

The gist of the present invention is to provide an acrylonitrile-based polymer powder having an acrylonitrile unit content of 85% by weight or more, having a particle diameter of 2
The powder is characterized by having 0 to 80 microns, a porosity of 20% or more, and closed cells of 10% or less.

In a polymer containing 85% by weight or less of acrylonitrile, the length of the acrylonitrile repeating unit in the molecular chain is stochastically shortened, so that the solubility is sufficiently high. In contrast, acrylonitrile is 85
If the content is more than wt%, consideration must be taken to ensure the solubility. The present invention has 8 acrylonitrile units.
It relates to an acrylonitrile-based polymer of 5% by weight or more.

In order to increase the surface area in the melting step, the smaller the particle diameter of the powder, the better. However, if it is too small, dissolution progresses in a slurry state, resulting in "Mamako".
Are easily generated, and it becomes difficult to handle the powder. Therefore, the average diameter of the particles is preferably 20 to 80 μm. This particle diameter is measured by a Coulter counter.

The higher the porosity of the powder, the larger the surface area and the better the solubility. Specifically, it is preferably 20% or more. This porosity is measured by a mercury porosimeter.

The most important point of the polymer of the present invention is that this hole is a penetration term. That is, when the holes are classified into those having two or more openings and those having only one opening or no openings at all, the former is more likely to invade the solvent in the slurrying stage. While, the latter is convenient for dissolving the particles, the latter is less likely to contribute to the dissolution because the solvent penetration is hindered. In particular, those without any openings are useless for melting. In the present invention, closed cells refer to such holes.
It is advantageous for the closed cells to be 10% or less for efficient dissolution.

The polymer powder can be obtained by optimizing the polymerization method. For example, if the solution polymerization is carried out in dimethyl sulfoxide and the solution is directly dried, the empty efficiency becomes too low, and in the aqueous suspension polymerization, the closed cells become 20% or more. By adding a water-soluble metal salt such as or the like or ethylene glycol, the independent bubbles generated after the polymerization are connected to each other, and it becomes possible to provide an opening on the powder surface. This closed cell can be obtained from the particle diameter and the powder density measured by the density gradient tube method.

The solubility of the polymer powder is determined by adding 15 times the weight of dimethylacetamide cooled to 0 ° C. to a diameter of 3 cm.
Put the stirring blade into the glass tube of the
It can be evaluated by adding the polymer powder while stirring by rotation and continuing stirring for 1 minute, and then putting it in a thermostat at 80 ° C. and measuring the heating time required for complete dissolution.

The present invention will be described below with reference to examples.

【Example】

Example 1 A composition obtained by adding 20 parts of ethylene glycol to 100 parts of a monomer mixture of AN / vinyl acetate = 95/5 (w / w) was dissolved at 50 ml / min and 0.24% by weight of sodium persulfate was dissolved. 125 ml of the prepared aqueous solution per minute
Then, an aqueous solution in which 0.28% by weight of sodium bisulfite was dissolved was 125 ml / min, and the temperature was kept at 50 ° C for 500 m.
A polymer was obtained by a continuous polymerization method in which the polymerized polymer was taken out while dropping it in 1 l of water. Such polymers are listed in Table 1.
It had the following properties.

[Table 1]

(Example 2) AN / vinyl acetate = 95/5
A composition obtained by adding 20 parts of ethylene glycol to 100 parts of the (w / w) monomer mixture was added at 40 ml / min, and at the same time, a solution of azobisisobutyronitrile at 0.05% by weight in dimethylacetamide was dissolved at 167 ml / min. Further, a polymer was obtained by a continuous polymerization method in which 33 ml of water per minute was dropped into 500 ml of a water / dimethylacetamide (1/5 (w / w)) mixture solution kept at 55 ° C. to take out the polymerized polymer. . The polymer had the properties shown in Table 1.

(Comparative Example 1) AN / vinyl acetate = 95/5
A composition in which 20 parts of ethylene glycol was added to 100 parts of a (w / w) monomer mixture was 40 ml / min, an aqueous solution in which 0.24% by weight of sodium persulfate was dissolved was 125 ml / min, and sodium bisulfite was added in an amount of 0. A polymer was obtained by a continuous polymerization method in which 125 ml / min of an aqueous solution in which 28% by weight was dissolved was added dropwise to 500 ml of water kept at 50 ° C. to take out the polymerized polymer. The polymer had the properties shown in Table 1.

(Comparative Example 2) AN / vinyl acetate = 95/5
A composition in which 20 parts of ethylene glycol was added to 100 parts of a (w / w) monomer mixture was 40 ml / min, an aqueous solution in which 0.16% by weight of sodium persulfate was dissolved was 200 ml / min, and sodium bisulfite of 0. A polymer was obtained by a continuous polymerization method in which an aqueous solution in which 18% by weight was dissolved was added dropwise to 200 ml / min of water to 800 ml of water kept at 50 ° C. to take out the polymerized polymer. The polymer had the properties shown in Table 1.

(Comparative Example 3) AN / vinyl acetate = 95/5
A composition obtained by adding 20 parts of ethylene glycol to 100 parts of a (w / w) monomer mixture is 40 ml per minute, and an aqueous solution in which 0.6% by weight of sodium persulfate is dissolved is 4 minutes per minute.
An aqueous solution in which 0.7% by weight of sodium bisulfite was dissolved was 0 ml, and the solution was kept at 50 ° C. at 40 ml / min.
A polymer was obtained by a continuous polymerization method in which the polymerized polymer was taken out while dropping it in ml of water. The polymer had the properties shown in Table 1.

[0018]

INDUSTRIAL APPLICABILITY The acrylonitrile-based polymer powder of the present invention efficiently dissolves in the solution shaping industry such as spinning, thereby streamlining the process, improving efficiency, stabilizing, and further improving product performance.

Claims (1)

[Claims] 1. An acrylonitrile-based polymer powder having an acrylonitrile unit content of 85% by weight or more, having a particle diameter of 20 to 80 μm, a porosity of 20% or more, and closed cells of 10% or less. Easy-to-dissolve acrylonitrile-based polymer powder.