JPH03130410A - Fibrillated fiber and its production - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having high reinforcing effect by mixing a polymer component containing a specific amount of acrylonitrile with a polymer solution containing a specific amount of methyl methacrylate, spinning and drawing the mixture, cutting the obtained fiber to a specific aspect ratio and beating the cut fibers. CONSTITUTION:The objective fiber composed of plural fibrils having a diameter of <=2mu and an aspect ratio of >=1,000 and having a root stem part with a diameter larger than 10 times the diameter of the fibril can be produced by mixing (A) 1 pt.wt. of a solution having a viscosity of 100-2,000 poise at 50 deg.C and produced by dissolving a polymer containing >=85% of acrylonitrile in a solvent and (B) 1-100 pts.wt. of a solution having a viscosity of 100-2,000 poise at 50 deg.C and produced by dissolving a polymer containing >=90% of methyl methacrylate in a solvent, spinning and drawing the obtained mixed solution containing the component A dispersed in the component B in the form of fine particles having a diameter of 1-100mu, cutting the drawn fiber to an aspect ratio of 1,000-100,000 and beating the cut fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to fibrillated fibers suitable for reinforcing polymer molded articles mainly composed of methyl methacrylate, and a method for producing the same.

[Conventional technology]

Due to its excellent transparency, methyl methacrylate polymers are widely used in the fields of optical materials, lighting equipment, ornaments, building materials, etc., and their shapes vary widely, including three-dimensional shapes, plate shapes, and sheet shapes. However, despite these features, the use of this polymer is sometimes limited due to its low strength, particularly impact strength.

For this reason, methods of reinforcing fibers using fibers made of acrylonitrile polymers have been considered to be particularly promising, especially for the purpose of improving impact strength. The reason for this is that the refractive index of polymethyl methacrylate and polyacrylonitrile is very close, 1.49 for the former and 1.506 for the latter. In reality, it is transparent and does not impair the features of the polymer.

However, in reality, when trying to disperse a-fibers from acrylonitrile-based polymers into a polymer mainly composed of methyl methacrylate, it is actually very difficult to avoid the phenomenon of fibers becoming entangled with each other and the formation of fiber balls. This is hindering the practical application of this technology.

[Problem to be solved by the invention]

In view of this situation, the inventors of wood have conducted research on fibers that can be easily dispersed uniformly in polymers mainly composed of methyl methacrylate and have a high reinforcing effect. Developed fibers and completed the present invention.

[Means to solve the problem]

That is, the gist of the present invention is that the polymer is made of a polymer having an acrylonitrile content of 85 mm or more, and has a diameter of 2 microns or less, preferably 1 micron.
Or less than 1 micron, even better! (15 microns or less, more preferably 11 microns or less, and the length is 1000 times or more the diameter, preferably 10000 times or more,
More preferably, the root dry parts of a plurality of fibrils have a diameter that is 100,000 times or more, preferably 50 or more times the diameter of the fibrils, and share fibers made of methyl methacrylate polymer. It is fibrillation, which is characterized by the fact that it becomes fibrillated.

The fiber of the present invention is made of an acrylonitrile-based polymer, and has a structure in which extremely thin fibril aggregates of 2 microns or less and cL 1 micron or less share a trunk fiber made of a methyl methacrylate polymer that is 10 times or more thicker than the fibril aggregate. Since the thin fibrils have a large specific surface area and a large aspect ratio (fiber length/fiber diameter), they have a high reinforcing effect. Also, since the trunk is very thick, it is easy to disperse uniformly, making it difficult to make fiber poles. Furthermore, since the trunk is made of polymethyl methacrylate, it firmly adheres to the polymer mainly composed of methyl methacrylate to be reinforced.

The fibrillated fiber of the present invention is prepared by dissolving a polymer containing acrylonitrile of 85 or more in a solvent capable of dissolving the polymer, and 1 part by weight of a solution A having a viscosity of 100 to 2000 voids at 50°C and methyl A 100/1 to 10000/1 polymer mixture of a polymer containing methacrylate of 90 or more and, if necessary, a binary copolymer consisting of acrylonitrile and methyl methacrylate or a ternary copolymer consisting of acrylonitrile, methyl methacrylate, and another third monomer. A solution B1-10 having a viscosity of 100 to 2000 voids at 50° C. obtained by dissolving the polymer mixture in a solvent capable of dissolving the polymer mixture.
0 parts by weight are mixed to form a state in which solution A is dispersed in the form of fine particles with a diameter of 1 to 100 microns in a continuous phase consisting of solution B, and the mixed solution is calculated from the diameter of a circle with an equivalent pore cross-sectional area. A composite coagulated yarn obtained by dry-wet or wet spinning from a spinneret having a discharge hole with an effective diameter of 100 microns or less, preferably 50 microns or less, and most preferably 30 microns or less, The drawn yarn obtained by stretching the yarn by 2 times or more, preferably 4 times or more, more preferably 6 times or more according to a conventional method, has an aspect ratio of 1000 to 10.
It is produced by cutting it into pieces with a size of 0,000 and beating it by a conventional method.

In the present invention, the larger the molecular weight of the acrylonitrile-based polymer, the longer the diameter of the fiber obtained, which is much longer than estimated from the size of the dispersed particles in the solution state. For example, if the size of the dispersed particles of a solution containing a 10% acrylonitrile polymer is 5 microns, and the diameter of the fiber obtained by spinning this is 0.6 microns, one fiber will form from one dispersed particle. If it is assumed that F is formed, its length will be at most (12 m).However, according to the method of the present invention, the length of the fiber obtained is
It was found that there were more than il saw and even several pieces.

This was something that was completely unknown in the first place.
Although the detailed mechanism is unknown, it is presumed that the long chain length of acrylonitrile-based bo-117- causes a change in the dispersion state of the solution during spinning.

Furthermore, it is desirable that the molecular weight of the polymer be as high as possible for the following reasons! Yes. In order to obtain thin fibers, it is desirable that the polymer concentration in solution A be as low as possible for spinning, and in order to ensure the necessary viscosity for spinning at a low concentration, the molecular weight of the polymer should be high. . If the molecular weight is lower than, for example, 150,000, the resulting ultrafine fibers will lack so-called flexibility and, in extreme cases, will exhibit brittleness.

This is because if the concentration of the solution is too low, voids are likely to occur during the coagulation process, so the polymer concentration is preferably 54 or more and 304 or less! It is best to set the coefficient between 10 and 25, and in order to maintain an appropriate viscosity within this range from 100 poise to 2000 poise, as described later, the molecular weight should be 10 to 25.
It needs to be between 50,000 and 1,500,000, preferably between 300,000 and 1,000,000.

It is necessary that the polymer +- contains 854 or more acrylonitrile in order to maintain the refractive index of the fiber at a level close to that of polymethyl methacrylate.

The solvents of the solution and B may be different or the same. The solvent for solution A is an organic solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, gamma-butyrolactone, or an aqueous solution of thiocyanate, an inorganic acid such as nitric acid, or the like.

The solution of solution B [is, in addition to those exemplified above, acetone,
These include chloroform, dichloromethane, and tetrahydrofuran.

The content of methyl methacrylate may be 8041 or more from the viewpoint of adhesion to the reinforcing polymer mainly composed of methyl methacrylate.

Furthermore, the molecular weight is not particularly limited, but if the molecular weight is too low or too high, the spinnability will be insufficient, and the button width will vary from 20,000 to 10,000 yen.
Around 00,000 is appropriate.

Solution A is dispersed in solution B, which is a continuous phase, as fine particles with a diameter of 1 to 100 microns, but depending on the composition, viscosity, and other conditions, the dispersion state may easily collapse, so it may be necessary to disperse the solution A as soon as the dispersion state is created. It is preferable to take a method such as spinning or use a dispersion stabilizer.

The dispersion stabilizer is suitably a binary copolymer consisting of acrylonitrile and methyl methacrylate or a ternary copolymer consisting of acrylonitrile, methyl methacrylate and another third monomer, particularly a copolymer consisting of acrylonitrile polymer portions 10 to 504, methyl methacrylate and vinyl acetate. A block copolymer consisting of copolymer portions 50-904 is very effective.

The viscosity of solution M or B is important to ensure stringiness, but for example, if the viscosity at 50°C is 100 to 200
If the poise is 0, a method for producing a 0 poise dispersion may be achieved by using an apparatus capable of applying high IAV air.

Next, the liquid is forced out through a nozzle with a hole diameter as large as possible.

For example, the material is spun in a dry or wet manner from a spinneret having an effective diameter calculated from the diameter of an equivalent circle with a pore cross-sectional area of 100 microns or less, preferably 50 microns or less, and more preferably 30 microns or less.

The discharged liquid may be brought into contact with a coagulating liquid that can coagulate the polymer at the same time.

Examples of the coagulating liquid include water, methanol, ethanol, isopropanol, glycerine, etc.
, B may be mixed with the solvent.

The obtained coagulated filament has a density of at least 2 times, preferably 4 times, according to a conventional method.
A composite drawn yarn is obtained by stretching the yarn by a factor of at least 6 times, more preferably by a factor of 6 times or more. For stretching, cold stretching, full water stretching, and hot stretching may be appropriately combined.

The obtained drawn yarn has an aspect ratio of 1000 to 1000.
The fibrillated #&fiber of the present invention can be obtained by cutting the fiber into a shape of 0.00 and beating it by a conventional method.

At this time, the drawn yarn needs to be cut to match the above aspect ratio in order to exhibit its reinforcing effect.

As the beating method, a method using a high-speed rotating blade, a mill, etc. can be used.

The characteristics of the fibers thus obtained can be easily determined, such as fiber diameter and length, using a scanning electron microscope or the like.

〔Example〕

The present invention will be specifically explained below using Examples.

The "molecular weight" of /17 mer is expressed as the weight average molecular weight measured by the dilute solution viscosity method. ``憾'' means heavy ginseng.

Examples 1 to 5 A rust solution prepared by dissolving 1 wl of polyacrylonitrile with a molecular weight of 80,000 and 1.5 million in dimethylacetamide. At this time, the solution viscosity divided by the polymer concentration #i at 50° C. was adjusted to approximately 500 poise.

On the other hand, a ternary block copolymer (hereinafter abbreviated as compatibilizer a) consisting of a polymethyl methacrylate homopolymer having a molecular weight of 300,000 and an acrylonitrile polymer portion 304 and a copolymer portion 70e6 of methyl methacrylate and vinyl acetate. /1 mixture was dissolved in dimethylacetamide to make a solution with a concentration of 124 (solution B) 6 When solutions A and solution B were mixed, a solution mass with a diameter of 1 to 100 microns was formed in the continuous phase consisting of solution B. It was confirmed by observation using an optical microscope that a finely dispersed state was created. The mixed solution is discharged from a spinneret having a discharge hole with an rIL diameter of 50 microns into a coagulating liquid consisting of a mixed solution of water/dimethylacetamide ('1/1),
Stretched 2 to 15 times in warm water at 60°C, and finally stretched to 150
A drawn yarn was obtained by continuous drying with a roller at ℃. The drawn yarn was cut into lengths of 30 mm and dry beaten using a blade rotating at a speed of 1700 times per minute.

When these ultrafine fibers were observed using a scanning electron microscope, the results were as shown in Table 1.

Table Examples 6 to 8 The same procedure as Example 3 was carried out except that in Example 5 Kb C, the compatibilizing agent was changed to 1150 to 1/200 DO relative to polymethyl methacrylate.

When these ultrafine fibers were observed using a scanning electron microscope, the results were as shown in Table 2.

table 2

Claims (1)

[Claims] 1. Made of a polymer containing 85% or more of acrylonitrile, having a diameter of 2 microns or less and an aspect ratio of 1000.
A fibrillated fiber characterized in that the root dry parts of a plurality of fibrils as described above share fibers made of a methyl methacrylate polymer having a diameter 10 times or more the diameter of the fibrils. 2. 1 part by weight of a solution A having a viscosity of 100 to 2000 poise at 50°C obtained by dissolving a polymer containing 85% or more acrylonitrile in a solvent, a polymer containing 90% or more methyl methacrylate, and acrylonitrile as necessary. and methyl methacrylate or a tertiary copolymer consisting of acrylonitrile, methyl methacrylate, and another third monomer at 50°C.
Solution B having a viscosity of 100 to 2000 poise at
1 to 100 parts by weight are mixed to form a state in which solution A is dispersed in the form of fine particles with a diameter of 1 to 100 microns in a continuous phase consisting of solution B, and then the mixed solution is passed through a spinneret using a dry-wet method or a wet method. The fibrillation according to claim 1, which is obtained by stretching the composite coagulated yarn by twice or more times, cutting the drawn yarn to have an aspect ratio of 1,000 to 100,000, and beating it by a conventional method. Fiber manufacturing method. 3, the ternary copolymer has an acrylonitrile polymer portion of 10
3. The method according to claim 2, wherein the block copolymer is a block copolymer consisting of 50% to 90% copolymer portion of methyl methacrylate and vinyl acetate.