JPS61163151A - Acrylonitrilic chopped fiber and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to acrylonitrile-based chopped fibers, and particularly to acrylonitrile-based chopped fibers that are excellent as fibers for reinforcing cement.

[Prior art]

Traditionally, asbestos has been primarily used to reinforce cement. However, since its carcinogenicity has been pointed out, its use has been restricted.

As a substitute for such asbestos, acrylic fibers, which have good alkali resistance in cement slurry or during its curing, have attracted attention and have been studied. However, since conventional acrylic fibers have low mechanical strength, they have not yet been put into practical use for reinforcing cement.

The present inventors first conducted 1. We have proposed an acrylonitrile fiber with high mechanical strength that can meet these demands. However, when acrylonitrile fiber yarn with high mechanical strength, especially acrylonitrile fiber yarn with a smooth surface obtained by dry/wet spinning, is cut into chopped fibers using a cutter, the cut ends melt. This causes phenomena such as swelling in layers, mutual fusion, or fibrillation.

Chopped fibers with swollen cut ends, mutual fusion, or fibrillation are difficult to uniformly disperse in cement slurry, and the high mechanical strength of the acrylonitrile fibers mentioned above is difficult to achieve. It has the disadvantage that it cannot be fully utilized for reinforcing cement, especially for reinforcing slate, and there are still problems in putting it into practical use.

[Object of the Invention] The object of the present invention is to have sufficient mechanical strength to be applicable to matrix reinforcement such as cement, and to have high uniform dispersibility in the matrix, thereby exhibiting a high matrix reinforcing effect. The purpose of the present invention is to provide a chopped acrylonitrile fiber that can be used.

[Structure of the invention]

The acrylonitrile chopped fiber of the present invention that achieves the above object is made of an acrylonitrile polymer mainly composed of acrylonitrile with an intrinsic viscosity of 2.5 or more, a tensile strength of 10 g/d or more, and a fiber length of 10 mm. The following short fibers are characterized in that the fiber diameter at the cut end of the short fibers is substantially the same as the fiber diameter at the intermediate portion in the longitudinal direction.

In addition, as a method for manufacturing the above chopped fiber,
An acrylonitrile polymer mainly composed of acrylonitrile with an intrinsic viscosity of 2.5 or more is dry-spun and the resulting coagulated fiber thread is drawn to a total draw ratio of 10 times or more, and then the cutting edge is cooled with a cutter. However, it is characterized in that it can be cut into chopped fibers of 10 mm or less.

The acrylonitrile polymer constituting the chopped acrylonitrile fiber of the present invention contains 90 mol% or more of acrylonitrile, preferably 97 to 100 mol%.
and an acrylonitrile polymer or copolymer comprising 10 mol % or less, preferably 0 to 3 mol %, of a vinyl compound having copolymerizability with respect to acrylonitrile. It is desirable to set the copolymerization ratio of the vinyl compound to 0 to 3 mol % in order to prevent the formation of a fused layer between single filaments in dry/wet spinning described later.

The vinyl compound is not particularly limited as long as it is copolymerizable with acrylonitrile, but
For example, acrylic acid, methacrylic acid, itaconic acid, and their lower alkyl esters, vinyl acetate, sodium allylsulfonate, sodium methacrylsulfonate, p-
Examples include sodium styrene sulfonate.

In the present invention, the intrinsic viscosity is a value measured by the following measuring method.

That is, about 75 mg of dry polymer sample was
Pour into a ml flask and add 0. Add dimethylformamide containing IN sodium thiocyanate to completely dissolve.

The specific viscosity of the obtained solution was measured at 20° C. using an Ostwald viscometer, and the intrinsic viscosity was calculated from the specific viscosity according to the following formula.

Intrinsic viscosity=<,/T-〒, 32 xasa*1)/
0,1 In the present invention, the above-mentioned intrinsic viscosity of 2.5 or more means that the tensile strength of the fiber is 10 g/d or more, which is necessary for reinforcing a matrix such as cement, and that the fiber has a chopping strength with less fusion between single filaments. This is important in obtaining fiber optics. If the tensile strength is less than 10 g/d, sufficient reinforcing effect cannot be obtained, and it is unsuitable for reinforcing corrugated plate, which is a typical example of fiber-reinforced cement. More preferably, the tensile strength is 12 g/d.

Further, as shown in FIG. 1, the fiber length of the shortened chopped fiber 9 must be 10 mm or less, preferably 3 to 6 mm. When the fiber length is greater than 10 mm, entanglement increases, reducing uniform dispersibility in the matrix, especially cement slurry, and reducing the reinforcing effect of the matrix. Furthermore, in order to improve such uniform dispersibility, it is necessary to make the fiber diameter D at the cut end of the chopped fiber 9 substantially the same as the fiber diameter at the longitudinally intermediate portion. be.

That is, the cut end of the chopped fiber does not have a uniform diameter as described above, and as shown in FIGS. 2A and 2B.

As in the chopped fiber 10 shown in FIG.
If there are any fibrillar particles 5 (Fig. B) or fibrillar looseness 5 (Fig. 2 C), the uniform dispersibility in a matrix such as cement will be reduced. For example, the influence of adhesion between single yarns of chopped fibers on paper formability and slate performance (bending strength) during slate production is extremely large.

The method for manufacturing the chopped fiber mentioned above is as follows:
The above-mentioned acrylonitrile polymer solution having an intrinsic viscosity of at least 2.5 is dry/wet spun from a spinneret having a large number of discharge holes, and the resulting undrawn fiber yarn is at least 10 times or more, preferably 12 times or more. Stretch. Afterwards,
This drawn fiber thread is cut into one piece by a so-called press-cut cuffer
Use chopped fiber of 0 mm or less.

As a spinning dope containing an acrylonitrile polymer, dimethyl sulfoxide (DMSO),
The acrylonitrile polymer can be obtained by dissolving the acrylonitrile polymer in a concentrated aqueous solution of an organic solvent such as dimethylformamide (DMF) or dimethylacetamide (DMAC) or a water-soluble inorganic compound such as zinc chloride, calcium chloride, rhodan soda, or nitric acid. It will be done. The solvent is preferably an organic solvent, particularly a spinning dope using DMSO.

The concentration of acrylonitrile polymer in the spinning dope is as follows:
Depending on the intrinsic viscosity of the polymer and the type of solvent, it is usually 5 to 2.
It is preferably in the range of 10 to 18% by weight.

If it is less than 5% by weight, the denseness of the fibers obtained by the above-mentioned dry/wet spinning tends to be insufficient, making it difficult to obtain high-strength fibers. Moreover, if it exceeds 20% by weight, the viscosity of the spinning dope becomes too high, which tends to cause drips and yarn breakage during spinning.

The solution viscosity of the spinning dope is at least 15 at 45°C.
It is preferable to adjust the viscosity so that it has a viscosity of 0.00 voids, preferably 3,000 to 10,000 voids. That is, if the solution viscosity is lower than 1500 poise, it becomes difficult to form coagulated fiber threads that have excellent drawability and form a dense fiber structure. Moreover, if the solution viscosity becomes too high, spinnability will be lost.

The spinning dope having the acrylonitrile polymer concentration and solution viscosity as described above is maintained at 30 to 100°C and subjected to dry/wet spinning. In this case, the distance between the spinneret and the coagulation bath liquid level is approximately 1-20mm, preferably 2-10m
It is better to set it to m. If the above distance is shorter than In+n+,
The spinneret surface tends to come into contact with the liquid surface, making dry and wet spinning difficult. Moreover, if it exceeds 20 m+, thread breakage of the discharged fiber threads and fusion between single threads are likely to occur.

Further, as the coagulation bath, an aqueous solvent solution of the acrylonitrile polymer is used. The solvent concentration of this aqueous solvent solution is 30 to 75% by weight, preferably 40 to 65%, and the aqueous solution maintained at a temperature range of 0 to 40°C is used.

The undrawn coagulated fiber yarn coagulated in the coagulation bath is washed with water,
After drying and other treatments, it is preferably dried under dry heat for 1
In heated air at a temperature range of 60 to 220°C, under the development of a drawing tension of at least 1.0 g/d, preferably 165 to 2.0 g/d, the total drawing ratio is at least per original length of the coagulated fiber yarn. It is stretched 10 times, preferably 12 times or more. - The drawn fiber yarn obtained as described above is cooled at the cutting edge by a cutter, preferably a so-called push-cut cutter (commonly called an EC cutter) as shown in Fig. 3.4. However, the fibers are cut to have a fiber length of 10 mm or less. As a cooling method, for example, blowing cold air onto the blade surface may be used. Further, during this cutting, it is preferable to cut the drawn fiber yarn at a tow moisture content of 2 to 40%, preferably 5 to 30%. With such a tow moisture content, it is possible to prevent tow from scattering during cutting.

In the push-cut cutter shown in FIGS. 3 and 4, 1 is a drum 1 that is rotationally driven by a rotating shaft 3, and a large number of knives 2 are arranged around this drum 1 with their cutting edges facing outward.
They are arranged and fixed in a circumferential manner with a pitch of 10 mm or less. Further, a presser roller 6 is rotatably provided on the outside of the knives 2 arranged in a circumferential manner in close proximity to the cutting edge thereof. Reference numeral 5 denotes a guide that guides the fiber thread 4 toward the drum 1.

In the cutter described above, the fiber thread 4 supplied via the guide 5 is wound around the cutting edges of a large number of knives 2 arranged in a circumferential manner, and the winding diameter thereof gradually increases.

During this winding process, the fiber thread 4 having a winding diameter exceeding the pressure roller 6 is pushed toward the cutting edge of the knife 2, and as shown in the figure, the short fibers 4a, 4b, 4c, 4d
The fiber is cut into a chopped fiber.

As mentioned above, this push-cut cutter is made by bringing the side surface of the fiber thread 4 into contact with the blade of the knife 2, and pushing the fiber thread 4 toward the knife 2 side. , cut into short fibers. By cutting with such a push cutter, and by cutting the cutting edge while cooling it by blowing cold air, even if the fiber yarn has a large tensile strength of Log/d or more, the fiber diameter D of the cut end can be reduced. As shown in FIG.
% or more. Note that it is necessary to immediately replace the knife of the cutter that performs the above-mentioned cutting when its sharpness deteriorates, and to maintain it so that it always exhibits good sharpness.

The above-mentioned cutting may be performed by a so-called guillotine-type cutter in which a knife blade is pushed toward the fiber thread side, as long as the cutting edge is cooled before cutting. However, compared to the case of the above-mentioned push-cut type cutter, the cut end has layered bulges 11, mutual fusion 12, or fibrillar looseness 13 as shown in FIGS. 2A, B, and C.
This tends to occur, and productivity suffers.

〔Effect of the invention〕

As mentioned above, the chopped fiber of the present invention is made of an acrylonitrile polymer mainly composed of acrylonitrile with an intrinsic viscosity of 2.5 or more, and a tensile strength of 10 g/
d or more, and the fiber length is 10 mm or less, and the fiber diameter at the cut end of the short fiber is made substantially the same as the fiber diameter at the intermediate portion in the longitudinal direction, so that dispersion in the matrix is achieved. can improve sexual performance. Therefore, Lo
Acrylonitrile fibers having a high tensile strength of g/d or more can be used as reinforcing fibers.

〔Example〕

Example 1 An acrylonitrile-based polymer consisting of 99.5 mol% of acrylonitrile with an intrinsic viscosity of 3.0 and 0.5 mol% of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) was prepared at a polymer concentration of 14%. (% by weight) as a solvent in dimethyl sulfoxide (DMSO) to obtain a yarn protection stock solution.

This yarn-protecting stock solution was once discharged into the air through the pores, and then coagulated in a 30% DMS0 aqueous solution at a temperature of 20°C.

This coagulated filament was washed with water, stretched five times in hot water, and then dried. The dried yarn was stretched 2.6 times using a hot plate with a surface temperature of 200°C, and then subjected to tension heat treatment using two rollers with a surface temperature of 220°C.

The fiber properties of the obtained acrylic synthetic fiber were determined according to JISL10.
13, the denier is 1.5 denier, the tensile strength is 12.3 g/d, the elongation is 7°8%, and the initial elastic modulus is 21.
It was 5g/d. This tow was immersed in a 0.1 weight aqueous solution of a polymer flocculant, and then squeezed to a moisture content of 15%.The acrylic synthetic fiber tow to which the polymer flocculant was attached was then cut under three different cutting conditions. Various chopped fibers were obtained. When the cut end of this chopped fiber was observed with an optical microscope, as shown in the optical micrographs (40x magnification) in Figure 5 A, B, and C, the cut end of the fiber varied depending on the type of cutter and cutting conditions. You can see that it changes.

Using the obtained chopped fibers, 2 parts by weight of chopped fibers, 2 parts by weight of cellulose pulp, 10 parts by weight of silica powder (average particle size 0.6 microns), and 86 parts by weight of Portland cement were mixed at a solid concentration of 2 parts by weight. A cement laminate was obtained by wet papermaking using a slurry obtained by mixing with water to a concentration of 5% by weight. This laminate is pressure molded to a thickness of 6
A flat plate of u was prepared, and then subjected to wet curing for 28 days and then dry curing to obtain a test piece.

The bending strength and impact strength of this test piece were determined according to JIS K-691.
1, and the results are shown in Table 1.

(Margins below this page) Table 1 From Table 1, fibers obtained from fibers in which the fiber diameter at the cut end of the fiber is substantially the same as the fiber diameter in the middle part have excellent paper formability and good mechanical properties. I understand that there is something.

Example 2 Using the tow obtained in Example 1, samples were prepared in which the cut length was changed while cooling the canter blade and the tow. Using the obtained chopped fiber, a slate was made in the same manner as in Example 1.

At the same time, as reference examples, 15 parts by weight of Kritstile asbestos, 2 parts by weight of cellulose pulp, and 8 parts by weight of Portland cement.
3 parts by weight were mixed with water to give a solids concentration of 15% by weight, and test pieces were prepared according to the wet papermaking method.The bending strength and impact strength of the test pieces are also listed in Table 2.

(Blank below this page) From Table 2, it can be seen that the mechanical properties of the present invention are higher than those of the reference example. When the fiber length is 1 mm, the paper formability is good, but the mechanical properties are low. On the other hand, it can be seen that when the fiber length exceeds 10 mm, paper formability deteriorates.

[Brief explanation of the drawing]

FIG. 1 is an enlarged side view showing a chopped fiber according to an embodiment of the present invention, and FIGS. 2A and 2B are views. C is a side view of a chopped fiber not according to the present invention, FIG. 4 is a sectional view taken along the It/-IV arrow in FIG. 3, and FIG. 5A. B and C are optical micrographs (40x magnification) showing the cut ends of the chopped fibers obtained in Example 1, respectively. 9...Chopped fiber. Figure 1 Figure 3 IV Figure 5A Figure 5B 5zr Procedural Amendment Act May 1985 228 1. Indication of the Case 1985 Patent Application No. 3249
No. 2, Name of the invention Acrylonitrile chopped fiber and its manufacturing method 3, Relationship with the case of the person making the amendment Patent amount, @Person, Address (Residence) Name (Name) (315) Toshi Co., Ltd. 4 , Agent Address: 5, Pelican Building, 3-3-3 Nishi-Shimbashi, Minato-ku, Tokyo 105, Date of amendment order: April 30, 1985 Sent: Remedial amendment order 6, Amendment (7) HtlL specification "Brief explanation of drawings" column (1) Specification page 20, No. 1
Lines 3 to 16 “Figure 5 A is...”
is corrected to "FIG. 5A. B and C are optical micrographs (40x magnification) showing the cut end (fiber shape) of the chopped fiber obtained in Example 1."

Claims (5)

[Claims] (1) Short fibers made of an acrylonitrile polymer mainly composed of acrylonitrile with an intrinsic viscosity of 2.5 or more, a tensile strength of 10 g/d or more, and a fiber length of 10 mm or less, and cut ends of the short fibers. An acrylonitrile chopped fiber characterized in that the fiber diameter of the fiber is substantially the same as the fiber diameter of the longitudinally intermediate portion. (2) The acrylonitrile chopped fiber according to claim 1, wherein the content of acrylonitrile in the acrylonitrile polymer is 97 mol% or more. (3) The acrylonitrile chopped fiber according to claim 1, which has a tensile strength of 12 g/d or more. (4) The acrylonitrile chopped fiber according to claim 1, wherein the fiber length is 3 to 6 mm. (5) Dry/wet spinning an acrylonitrile-based polymer whose main component is acrylonitrile with an intrinsic viscosity of 2.5 or more,
A method for producing an acrylonitrile-based chopped fiber, which comprises stretching the obtained coagulated fiber thread to a total stretching ratio of 10 times or more, and then cutting it into chopped fibers of 10 mm or less with a cutter while cooling the cutting edge.