JPS6233328B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing acrylonitrile synthetic fibers. More specifically, the purpose is to produce acrylonitrile synthetic fibers with excellent pill resistance by spinning an acrylonitrile polymer solution and stretching it under specific conditions. Pills generated when clothing is worn significantly impair its beauty and texture. Synthetic fibers generally generate a large amount of pill, so their modification has become an important issue. In particular, since acrylonitrile (referred to as AN) fibers are mainly used in the spannitting field, pilling is likely to occur, and anti-pilling is strongly required. The basic idea of imparting anti-pilling properties to AN-based fibers, especially at the raw cotton stage, is to (a) select conditions that do not produce fuzz, which is the main cause of pill formation, and (b) to ensure that even if fuzz does occur, it will not occur. There are two ways to make the pill fall off before it is formed.The first method generally limits the composition and use of the product, and its effects are also poor in permanence, while the second method allows for freedom in commercialization. The effect is also expected to be relatively large.
As a specific means in this case, many attempts have been made to reduce the strength and elongation properties of single fibers, particularly to reduce the loop strength and elongation or knot strength and elongation. Nodule strength and elongation have a close relationship with pill resistance,
Not limited to AN-based synthetic fibers, conventional materials with good pill resistance are characterized by knot strength (DKS) and knot elongation (DKE).
The product DKS x DKE is small, and when measured according to JIS-L1074, it is approximately 25 or less. In the present invention, this product is defined as toughness. It can be seen that such fibers with low toughness have developed so-called defective parts in terms of molecular structure or more macroscopically, and in other words, they act as brittle points in the fracture behavior. On the other hand, for AN-based synthetic fibers, sufficient anti-pilling properties have not always been achieved using conventional methods. The reason for this is that AN-based synthetic fibers generally have a large amount of plastic deformation, and as a result, the above-mentioned toughness is extremely large. Therefore, in order to reduce this toughness, it is necessary to introduce extreme brittle points into the fiber.
As a result, macroscopic damage occurs, reducing the operability of spinning and processing. As a result of various studies on the method of introducing brittle points and anti-pilling, the present inventors found a new technique and arrived at the present invention. The gist of the present invention is that after spinning an AN-based polymer solution, it is introduced into water at 40 to 60°C and stretched at an effective stretching ratio defined by formula () in the range of 0.3 to 0.8, and then washed. It is characterized in that it is then subjected to a relaxing heat treatment.
Concerning the manufacturing method of AN-based synthetic fibers. Effective stretching ratio = Adopted stretching ratio / Maximum stretching ratio……(
) (However, in the formula, the maximum draw ratio refers to the maximum draw ratio at which the fibers break due to stretching.) The technical idea of the present invention is as follows. That is, the spun so-called undrawn yarn has an incomplete fiber structure and extremely low strength. Generally, this is stretched to increase the degree of orientation and improve strength. As a result, DKS also tends to increase at the same time. Among the stretching conditions adopted at this time, the basic temperature is selected in a temperature range where molecular mobility is large, that is, at least a temperature higher than the glass transition point (Tg) of the AN polymer. Stretching at a sufficient magnification is adopted by taking advantage of the properties of the film. In general, in the production of AN-based polymer fibers, the temperature range is approximately 100% in a dry heat atmosphere, although it varies slightly depending on the polymer composition.
℃ or higher, the preferred stretching temperature is 140 to 180℃
However, in hot water or other humid heat conditions, the temperature is about 80°C or above, and the preferred condition is 95 to 100°C in hot water.
Even if some stretching is applied at conditions lower than this temperature, the conventional method is to subsequently perform main stretching at a temperature higher than Tg to determine the fiber structure. In contrast, the present invention focuses on the stretching properties in a temperature range lower than Tg. That is, in the temperature range below Tg, the molecular mobility of the undrawn yarn is in a semi-frozen state or a frozen state. When this frozen undrawn yarn is drawn, the drawing points tend to concentrate in the easily stretchable structural parts, and in some cases exhibit a drawing behavior similar to typical netting drawing, while maintaining the undrawn yarn structure. It was found that a structural element with a relatively stretch orientation was formed, and the physical properties of the resulting fiber showed fracture behavior including the brittle point described above. In particular, elongation and toughness decrease. The draw ratio that can be adopted at such low temperatures is considerably smaller than that for stretching above Tg, but in that range, DS and DKS moderately improve as the draw ratio increases, while DKE increases. It was found that this significantly reduced the toughness of the nodule and contributed to the target reduction of nodule toughness. The present invention will be explained below based on its implementation. The present invention uses an AN-based polymer as a starting material. As such a polymer, both an AN homopolymer and a copolymer of a monomer copolymerizable with AN can be used. The content of AN in the copolymer is at least 40 ~
The content is 50wt% or more, and in the case of clothing fibers which are the object of the present invention, it is generally 85wt% or more. The AN content has a slight effect on the above-mentioned Tg, so care must be taken, but when the AN content is 40 wt% or more, the effects of the present invention are fully achieved. Moreover, the method for producing the polymer is not particularly limited. This polymer can be used for spinning by dissolving it in conventional solvents such as organic solvents such as dimethylformamide (DMF), dimethylacetamide (DMAC), and dimethyl sulfoxide, as well as concentrated aqueous solutions of inorganic substances such as nitric acid, rhodan salt, and zinc chloride. After preparing the dope, it is spun using a dry method, a semi-dry-semi-wet method, or a wet method to produce an undrawn yarn. The obtained undrawn yarn is washed to substantially remove the solvent, and then subjected to low elongation drawing according to the present invention to determine the fiber structure. The undrawn yarn usually contains 5 to 50 wt% of solvent based on the weight of the fiber, although this varies depending on the spinning method. This residual solvent affects the subsequent drawability, and the drawability is slightly higher than that of fibers from which the residual solvent has been substantially removed, that is, undrawn yarns with residual solvent of 2wt% or less, and the molecular structure from the viewpoint of this drawability. It was found that the freezing temperature, or Tg, was lower by about 10°C compared to the latter. This situation is shown in Figure 1. 1 in Figure 1 is AN/methyl acrylate/sodium methacrylsulfonate =
This graph shows the relationship between the drawing temperature and the stretch ratio at break when a 6-denier undrawn yarn containing a solvent was drawn in water by dry spinning an AN-based polymer of 93.5/6/0.5 (wt%). , 2 shows the relationship between the underwater stretching temperature and the breaking stretch ratio of the undrawn yarn of 1 after desolvation under a fixed length in hot water, and 3 shows the relationship between the underwater drawing ratio and the breaking stretch ratio of dry spinning of polyacrylonitrile. This is what is shown. From the results shown in FIG. 1, it can be seen that the freezing temperature of the yarn in the presence of a solvent is approximately 60°C or lower, and that of the yarn substantially free of solvent is approximately 70°C or lower. This indicates that this temperature is not significantly affected by the composition of the polymer. From an analysis of such phenomena, it has been found that it is best to apply a stretching temperature of about 60 DEG C. or lower in obtaining the target fiber of the present invention or in the combination of stretching and washing steps. On the other hand, if this stretching temperature is too low, the possible stretching ratio will be extremely small, so it is usually about
The temperature is preferably 40°C or higher. On the other hand, regarding the draw ratio to be adopted, it is important to adopt a draw ratio higher than a certain level even at such low temperatures to balance the performance.This will introduce brittle points into the fiber and improve its strength properties. Can be maintained. The effective stretching ratio of the stretching ratio is preferably in the range of 0.3 to 0.8. If the effective stretching ratio is less than 0.3, the physical properties of the final fiber obtained will be extremely low and will not be of practical use. On the other hand, if it exceeds 0.8, it may cause various problems such as the generation of fluff during stretching. Preferably 0.4~
Adopt a range of 0.65. Note that the effective stretch ratio is
Even in the range of 0.3 or more, there may be cases where the employed stretch ratio is smaller than 1.0, but in this case, the employed stretch ratio of 1.0 or more is applied. The drawn yarn thus obtained is further washed to remove residual solvent. Then, it is either dried once or subjected to a relaxing heat treatment. This heat treatment alleviates stretching strain, imparts shape stability, and improves dyeability. For this reason, it is usually desirable to allow the fibers to shrink by about 10% or more in this step, and for this reason, the heat treatment is generally carried out at a temperature of 100 to 140° C. under stress-free moist heat or steam heat. At this time, the nodule toughness tends to increase, but even on this premise, the anti-pilling properties of the present invention are sufficiently maintained. The above are the basic process conditions of the present invention, but if necessary, the fibers dried after stretching or the fibers subjected to relaxation heat treatment are further heated at a temperature higher than the low-temperature stretching temperature, in other words, the Tg Some stretching can also be applied at higher temperatures. In this case, the low-temperature stretched structure can be almost fixed by heat treatment, and the contribution of brittle points is basically not eliminated, and the orientation effect can improve the yarn quality, especially the strength of the raw cotton. As described above, the present invention is characterized by specifying the drawing step in the process of producing fibers from AN polymers, and is a useful basic technology regardless of the spinning method. The effects of the present invention are particularly remarkable in fibers produced by dry spinning. In other words, fibers made by dry spinning are generally dense in structure and have high knot toughness, and although it has traditionally been considered extremely difficult to achieve pill resistance, the method of the present invention has made it relatively easy to achieve pill resistance. It became possible to modify it. The invention also applies to the production of conventional composite fibers. The present invention will be described in more detail below with reference to Examples. Example 1 The composition was AN/methyl acrylate/sodium methallyl sulfonate = 93.5/6/0.5 (wt%), and its specific viscosity (0.1 g of polymer was dissolved in 100 ml of DME containing 0.1 N of Rodan soda, 25 (measured in °C) is 0.15
The AN-based polymer was dissolved in DMF in a conventional manner to a concentration of 30 wt%, and the mixture was degassed and degassed to obtain a spinning dope. This dope was discharged at 185°C at a discharge temperature of 135°C.
The filament was dry-spun in hot air from a yarn-proof nozzle with a hole diameter of 0.15 mmφ and 500 holes, a small amount of water was added to the formed filament, and the filament was wound at a speed of 300 cm/min to obtain an undrawn yarn with a single fiber fineness of 6 denier. Ta. The amount of residual solvent in the obtained undrawn yarn was 17.5 wt%. Using this undrawn yarn, a drawing experiment was conducted as described below. As shown in Table 1 below, the stretching temperature was varied in cascade water, and the effective stretching ratio was
0.6 stretch, then further washed to a fixed length in hot water at 80°C, treated with oil, mechanically crimped, then dried and dried in humid air with a dew point of 90°C and a processing air temperature of 140°C. A relaxation treatment was performed to obtain the final fiber. Table 1 shows the stretching conditions and the physical properties of the obtained fibers. The yarn quality was measured in accordance with JIS L-1074 using a Tensilon type tensile tester at a yarn length of 2 cm and a tensile speed of 2 cm/min. The value is based on the average value of 20 measurements.

[Table] Example 2 An experiment was conducted in which the effective stretching ratio was changed using the method of Experiment No. 3 (60° C. underwater stretching) in Table 1 of Example 1. Table 2 shows the stretching conditions and the physical properties of the resulting fibers. Note that the treatment after stretching was the same as in Example 1, but the respective relaxation shrinkage rates are as shown in Table 2.

[Table] As is clear from Table 2, from the viewpoint of anti-pilling properties,
Although it is effective over a wide range of effective stretching ratios, when the effective stretching ratio is less than about 0.3, the physical properties are extremely poor and practicality cannot be obtained. Example 3 An undrawn yarn obtained by dry spinning in the same manner as in Example 1 was introduced at a speed of 50 m/min and thoroughly washed in hot water at 98°C to a fixed length to remove any remaining solvent in the yarn. was set to 1wt% or less. Subsequently, it was stretched 1.8 times (effective stretching ratio 0.6) in hot water at 60°C, and then an oil agent was applied and drying and heat treatment were performed in the same manner as in Example 1. On the other hand, for comparison, instead of the above-mentioned hot water stretching at 60°C, a method of stretching in boiling water (98°C), which is usually carried out industrially, was applied, and the results shown in Table 3 were obtained.

[Table] As shown in the above table, when stretched at 98°C, the knot toughness is extremely large regardless of the stretching ratio, and pill resistance cannot be achieved either. Example 4 An AN polymer with a composition of AN/methyl acrylate/sodium methallylsulfonate = 91.5/8/0.5 (wt%) and a specific viscosity of 0.160 was dissolved in DMAC to form a spinning dope with a polymer concentration of 24 wt%. Prepared. Hole diameter 0.075mm
Wet-spun the yarn into a DMAC 50wt% aqueous solution kept at 40℃ from a spinning nozzle with φ and 200 holes, and
After being drawn at a speed of 10 minutes, it was continuously stretched 2.8 times in hot water at 50°C (effective stretching ratio 0.6), then washed in boiling water at a constant length, and then an oil agent was applied and the surface temperature was 120°C. The material was passed through a drying roll for drying and densification. Then, it was subjected to relaxation treatment in pressurized steam at 130°C to give it 30% shrinkage to produce a single fiber with a fineness of 3 denier (Experiment No. 15). On the other hand, in Experiment No. 15, the fiber after drying and densification was further stretched between a pair of heated rolls with a surface temperature of 170°C.
A fiber was obtained by dry heat stretching 1.5 times and relaxation treatment (Experiment No. 16). Also, for reference, we have summarized the physical properties of each fiber, including a similar fiber (experiment No. 17) when stretching 5.2 times in boiling water (effective stretching ratio 0.6) instead of stretching in hot water at 50°C. and as shown in Table 4.

[Table] As is clear from Table 4, the anti-pilling properties of the low-temperature drawn fibers of Experiment Nos. 15 and 16 are good. Also experiment No.15
The strength level of the fibers is slightly low, but the addition of secondary stretching (Experiment No. 16) is intended to improve this, and depending on the balance with anti-pilling properties, it may be significant in terms of improving processability. be.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the yarn drawing temperature in water and the breaking drawing ratio.

Claims (1)

[Claims] 1. After spinning an acrylonitrile polymer solution, it is introduced into water at 40 to 60°C and stretched at an effective stretching ratio defined by formula () in the range of 0.3 to 0.8, then washed, and then A method for producing acrylonitrile-based synthetic fibers, characterized by performing post-relaxation heat treatment. Effective stretching ratio = Adopted stretching ratio / Maximum stretching ratio……(
) (However, in the formula, the maximum draw ratio refers to the maximum draw ratio at which the fiber breaks due to stretching.) 2. A method for producing acrylonitrile synthetic fiber according to claim 1, in which spinning is performed by a dry spinning method. .