JPH0135925B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a foamed fiber made of a polyacrylonitrile polymer (hereinafter referred to as a PAN polymer) and a method for producing the same, and in particular to a foamed fiber useful as a fiber for woven or knitted fabrics such as a fiber for handicrafts and a fiber for interior decoration. The purpose is to provide a manufacturing method thereof. Regarding foamed fibers made of PAN-based polymers,
Although it has been known in patents and literature, it has not yet been widely used as a practical fiber.
So far known PAN foamed fibers include one consisting of honeycomb-shaped cells as shown in Example XI of U.S. Pat. A typical example is one with a grass-like foam structure. The foamed fibers disclosed in the former U.S. patent are
It has a honeycomb-like foam structure consisting of closed cells surrounded by a polygonal thin film. Although such foamed fibers are excellent in terms of uniformity of cell size and degree of foaming, when used as fibers for textiles and knitting, for example, even when dyed, only the outer layer is dyed, and dyeing with high fastness is difficult. In addition, it has drawbacks such as low strength and low elongation, and poor handling in weaving and knitting processes. On the other hand, the latter foamed fiber disclosed in JP-A No. 54-11172 seems to have a texture and structure similar to natural straw, but it lacks flexibility and is easily fibrillated due to abrasion. However, it is difficult to use it as a general-purpose woven or knitted fiber. In addition, foamed fibers (hereinafter referred to as
The manufacturing method for PAN-based foamed fibers is as follows:
Since water can be used both as a plasticizer and a foaming agent, a method of melt extrusion using water as a plasticizer (US
P.2585444, JP-A-48-49839, JP-A-54-
93122) has been proposed. However, in this method, if the amount of water is increased to increase the degree of foaming, there will be many cuts due to the blowing of steam, and if the amount of water is decreased, the viscosity of the melt will become high, making it difficult to mold, and at the same time, the degree of foaming will be low and it will not work. It is difficult to match the adjustment of the degree of foaming and the adjustment of the viscosity of the melt to achieve uniform foaming, and it is extremely difficult to produce PAN-based foamed fibers with any uniform degree of foaming. The present inventors have conducted extensive research to solve these various problems, and as a result, have arrived at the present invention. That is, the gist of the present invention is as follows. A thermoplastic elastomer (hereinafter referred to as thermoplastic elastomer) consisting of a conjugated diolefin and a monovinyl-substituted aromatic compound is added to 100 parts by weight of a polyacrylonitrile polymer containing at least 40% by weight of acrylonitrile.
~40 parts by weight, and at least one inorganic particle
Polyacrylonitrile foam fiber containing 0.1 to 50 parts by weight. A thermoplastic elastomer (hereinafter referred to as thermoplastic elastomer) consisting of 100 parts by weight of a polyacrylonitrile polymer containing at least 40% by weight of acrylonitrile, 5 to 40 parts by weight of water, a conjugated diolefin and a monovinyl-substituted aromatic compound (hereinafter referred to as thermoplastic elastomer) 1 to 40 parts by weight After heating and melting a polymer composition consisting of 20 parts by weight or less of a polyacrylonitrile polymer solvent and 0.1 to 50 parts by weight of at least one inorganic particle under autogenous pressure or higher pressure, A method for producing polyacrylonitrile foam fiber, which comprises foaming and extruding from a spinning orifice. The present invention will be explained in more detail below. The acrylic polymer as used in the present invention refers to a polymer containing acrylonitrile alone or at least 40% by weight, more preferably 60% by weight or more of acrylonitrile, with the remainder consisting of at least one ethylenically unsaturated compound. Here, ethylenically unsaturated compounds include vinyl chloride, vinyl bromide,
Vinyl halides and vinylidene halides such as vinyl fluoride and vinylidene chloride; acrylic acid,
Unsaturated carboxylic acids such as methacrylic acid, maleic acid, itaconic acid and their salts; methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, ethoxyethyl acrylate,
Acrylic esters such as phenyl acrylate and cyclohexyl acrylate; Methacrylic esters such as butyl methacrylate, octyl methacrylate, methoxyethyl methacrylate, phenyl methacrylate, and cyclohexyl methacrylate; Methyl vinyl ketones; Vinyl formate, acetic acid vinyl,
Vinyl esters such as vinyl propionate, vinyl butyrate, and vinyl benzoate; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; Acrylamide and its alkyl substituted products;
Unsaturated sulfonic acids and their salts such as vinyl sulfonic acid and p-styrene sulfonic acid; Styrene and its alkyl or halogen substituted products such as styrene, d-methylstyrene and chlorostyrene; Allyl alcohol and its esters or ethers; Vinyl Basic vinyl compounds such as pyridine, vinylimidazole, dimethylaminoethyl methacrylate; vinyl compounds such as acrolein, methacrolein, vinylidene cyanide, glycidyl methacrylate, methacrylonitrile, etc., and also include mixtures thereof. It is important that the expanded PAN fiber of the present invention contains a thermoplastic elastomer in addition to the PAN polymer. The effect of containing this thermoplastic elastomer is that in addition to imparting a smooth texture and flexibility to the foamed fibers, it also imparts toughness and, although the reason is not clear, has good dyeability even at a high degree of foaming. The reason is that not only the epidermal layer but also the inner layer is easily dyed. The thermoplastic elastomer used in the present invention is a block copolymer composed of a conjugated diolefin and a monovinyl-substituted aromatic compound, and is represented by the following general formula. A-B-A (A-B) _o B-(A-B) _o (A-B) _o -A (A-B) _o X (wherein A is substantially a monovinyl-substituted aromatic compound/block , B is a conjugated diolefin polymer block, X is carbon or hydrocarbon, carbonyl group,
Phosphorus, silicon, alkyl silicon, or n is 2 to 10
The block copolymers represented by these general formulas are:
Generally, it can be obtained as follows. That is,
It is obtained by using a lithium hydrocarbon as a polymerization initiator in a hydrocarbon solvent, and by alternately introducing a conjugated diolefin and a monovinyl-substituted aromatic to form blocks of each polymer.
A block copolymer of a desired shape can be obtained by changing the order and number of additions or by using a coupling agent. Any polymerization method in which a conjugated diolefin and a monovinyl-substituted aromatic compound are added alternately and polymerized, and the next compound is added and polymerized when the polymerization of the previously added compound is completed or almost completed. Good too. Further, these thermoplastic elastomers may be used alone or in a mixture of two or more. The conjugated diolefin referred to here is:
1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, etc., or a mixture of two or more thereof can be selected, and as monovinyl aromatic compounds, styrene, vinyltoluene, vinyl Xylene, ethylstyrene, α-methylstyrene, ethylstyrene, isopropylstyrene, ethylvinyltoluene, t-butylstyrene, vinylnaphthalene, etc., or a mixture of two or more thereof can be selected. Further, as the coupling agent, for example, a halogenated hydrocarbon having two or more halogen groups, phosgene, phosphorus trichloride, silicon tetrachloride, 1,2 bis(methylchlorosilyl)ethane, etc. are used. In addition, in the present invention, the molecular weight of the block copolymer is
5,000 to 500,000, and the content of the monovinyl-substituted aromatic compound is preferably 10 to 70% by weight. The content of the thermoplastic elastomer is 1 to 40 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the PAN polymer. If the content is 40 parts by weight or more, the physical properties of the molded product will change drastically, and the characteristics of the PAN polymer, such as weather resistance, heat resistance, and chemical resistance, will be impaired. Moreover, if the content is less than 1 part by weight, the effect will hardly be exhibited and the object of the present invention cannot be achieved. The foamed fibers of the present invention contain 0.1 to 50 parts by weight of at least one inorganic particle. The inorganic particles referred to in the present invention are inorganic particles that are not substantially dissolved in the solvent of the PAN polymer and have an average particle diameter of 40 μm or less. Specifically, calcium carbonate, magnesium carbonate, barium carbonate, kaolin, alumina, talc, titanium oxide, and mixtures thereof can be used. If the amount of such inorganic particles exceeds 50 parts by weight, the foamed fibers will become brittle and the physical properties will significantly deteriorate, which is not preferable. Another object of the present invention is to provide a method for easily producing such PAN-based foamed fibers. In the method of the present invention, a PAN polymer, water,
Thermoplastic elastomer, PAN polymer solvent,
The blending ratio of inorganic particles is important. When obtaining foamed fibers from a composition containing only a PAN polymer and water as in the conventional technology, it is difficult to adjust the foaming degree and the viscosity of the melt in a consistent manner. It has been extremely difficult to stably produce foamed fibers. The manufacturing method of the present invention can solve this problem, and the respective compounding ratios will be described below. The amount of water is 5 to 100 parts by weight of the PAN polymer.
It is 40 parts by weight. Preferably it is 10 to 30 parts by weight. If the water exceeds 40 parts by weight, when extruding with a normal extruder, water vapor will blow out from the molding orifice, or the water will separate, causing a backflow toward the raw material supply hopper and eating into the raw material polymer. Problems such as defects occur frequently. If the amount of water is less than 5 parts by weight, the melt viscosity increases, making molding difficult and at the same time causing poor foaming.
In addition, increasing the molding temperature in order to lower the viscosity is not preferable because decomposition and coloration will become significant. The blending effect of the thermoplastic elastomer is as described above, but in melt molding, it also has the effect of improving the fluidity of the melt during molding and making stable molding possible. Also, the amount to be added is as described above. Although the object of the present invention can be achieved by blending water and a thermoplastic elastomer with a PAN polymer as described above, it is desirable to blend a solvent for the PAN polymer in order to further improve moldability. be. The solvent for the PAN polymer in the present invention is generally known, such as dimethylformamide,
Dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, ethylene carbonate,
Sulfolane etc. can be used. The blending amount of the solvent is 20 parts by weight or less per 100 parts by weight of the PAN polymer. At 20 parts by weight or more,
Even if the amount is increased further, the viscosity reduction effect will be small.
This is not preferred because the amount of solvent remaining in the foamed fibers increases and the disadvantage of degrading the physical properties of the foamed fibers becomes noticeable. Furthermore, in order to improve uniform foamability and moldability, it is more desirable to incorporate inorganic particles. The effect of blending inorganic particles is that, although the reason is not clear, the melt viscosity of the composition is further reduced and a uniform and fine foamed structure is more easily obtained. The inorganic particles referred to in the present invention include water and
These are inorganic particles that do not substantially dissolve in PAN polymer solvents and have an average particle size of 40μ or less. Specifically, calcium carbonate, magnesium carbonate, barium carbonate, kaolin, alumina, talc, titanium oxide, and mixtures thereof can be used. In particular, when calcium carbonate, kaolin, and talc are used, the above-mentioned effects of the present invention can be achieved. These are particularly desirable inorganic particles because of their remarkable effects. The optimal range of the amount of these inorganic particles to be blended varies depending on the type of inorganic particles used, but
0.1 to 50 parts by weight, more specifically 0.1 to 20 parts by weight for calcium carbonate, preferably 0.2
~15 parts by weight, 5 to 50 parts for kaolin and talc
Parts by weight are preferably 5 to 40 parts by weight. If the amount exceeds the upper limit, the foamed fibers will become brittle and the physical properties will significantly deteriorate. If the amount is below the lower limit, the above-mentioned effects of the present invention cannot be achieved, and only non-uniform foamed fibers with coarse cells can be obtained. Such a blended composition is heated and melted under autogenous pressure or higher pressure, and then foamed and extruded from a spinning orifice to obtain foamed fibers. Various methods can be used for heating and melting and extruding. That is, (a) the specific ratio
PAN polymer, water, thermoplastic elastomer,
The solvent of the PAN polymer and the inorganic particles are uniformly mixed in a suitable mixer such as a ball mill to prepare a powdery composition, and this composition is placed in a sealable container such as an autoclave through a valve. A method of melting the powder by heating in a container having an outlet connected to a spinning orifice in a closed or pressurized atmosphere, opening a valve after melting, and extruding from the orifice, (b) the powder composition of (a) above. A method in which the powder and granular composition of (a) is supplied to the hopper of a screw extruder for molding. (2) When using a screw extruder, the PAN polymer, thermoplastic elastomer, and inorganic particles are supplied from a hopper, and water and as necessary Depending on the situation, a method is adopted in which the solvent for the PAN polymer is injected as an aqueous solution or aqueous dispersion through an injection hole at an appropriate location in the middle of the extruder, and then heated and melted while being transferred through a heating zone and extruded. I can do it. Although the object of the present invention can be achieved by any of the above methods, it is convenient to use a conventional single-screw or twin-screw extruder. The heating temperature is 120℃ or higher and 200℃ or lower, preferably
The temperature is 150℃ or higher and 190℃ or lower. At temperatures below 120°C, it becomes difficult to melt and mold, and at temperatures above 200°C, the polymer decomposes and becomes discolored, making it impractical. In addition, when extruding from the spinning orifice, a measuring device such as a gear pump can be used as necessary. Any type of spinning orifice can be used, including one with a single hole, one with multiple holes, one with a circular cross section, and one with a non-circular (so-called irregularly shaped) cross section. The extrusion atmosphere is preferably air at normal pressure. The foam extruded in this manner is subjected to a stretching operation, if necessary. The stretching ratio in this case is appropriately selected depending on the physical properties, thickness, etc. of the foamed fibers to be obtained. Continuously or once rolled up 90
Ordinary stretching and heat treatment can be carried out in a high temperature atmosphere of .degree. C. or higher, if necessary. The foamed fibers of the present invention can be obtained by appropriately selecting these conditions, but in order to achieve the purpose of the present invention, the bulk density and closed cell volume fraction of the foamed fibers to be obtained, as defined later, must be adjusted. It is desirable to adjust it to an appropriate range. If the bulk density becomes too low, the strength and elongation of the foamed fibers tends to decrease, and if the bulk density becomes too high, the foam fibers tend to lose flexibility. In the foamed fiber of the present invention, a practically preferable range is 0.1 to 0.3 g/cm ³ . On the other hand, foamed fibers with a high closed cell percentage and most of them are unfavorable because only the outermost layer is dyed under normal dyeing conditions, as mentioned earlier. . Further, in the case of a foamed fiber having a low closed cell volume fraction and most of the cells being open cells, it is not possible to maintain the firm elasticity characteristic of the foamed fiber. In the foamed fiber of the present invention, a range of 5 to 60% is practically preferable. In addition, the above-mentioned bulk density and volume fraction of closed cells can be adjusted as appropriate by selecting the manufacturing conditions described above. The acrylic foamed fiber thus obtained has superior strength, elongation, and flexibility compared to conventionally known acrylic foamed fibers, and is flexible, and can fully demonstrate the good dyeability that is characteristic of acrylic fibers. be. Therefore, in addition to the above-mentioned properties, the foamed fiber of the present invention has features such as a lightweight feel, excellent heat retention, and excellent water absorption properties due to the uniform fine foam structure, and also has a smooth feel. It has a rich, unique texture and luster, and is useful in a wide range of applications, including handicraft fibers, interior fibers such as wallpaper and rugs, water-absorbent fibers for clothing, and agricultural materials. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is not limited in any way by the description of these Examples. In addition, the bulk density and the volume fraction of closed cells in Examples were measured by the following method. (1) Take an appropriate amount of sample (40 to 50 cm in length) and measure its weight. Let it be W(g). (2) Measure the volume of the sample using an air comparison hydrometer (manufactured by Petskuman). Let it be V ₁ (cm ³ ). (3) Thoroughly immerse the above sample in melted paraffin, take it out, quickly place it in the basket (10 cm in diameter) of a Centor dehydrator kept at 100-110℃, leave it for 1 minute, and then rotate it at 1800 rpm. Dehydrate at high speed to obtain a paraffin coated sample. (4) The volume of the above paraffin coated sample is (2)
Measure in the same way. V ₂ (cm ³ ). (5) Calculate using the following formula. Bulk density = W/V ₂ (g/cm ³ ) Closed cell volume fraction = [(V ₁ −W/1.17)/
(V ₂ −W/1.17)]×100 (%) Note that 1.17 is the specific gravity of the polymer. The flexibility was evaluated as follows. The bending rigidity at a curvature of 1.0 was measured using a pure bending tester (KES-F ₂ ; manufactured by Kato Iron Works Co., Ltd.), and each value was divided by the smallest value among the obtained values to evaluate as a comparative value. . Furthermore, the condition of the dyed product is ME RED3 as a dye.
(manufactured by Sumitomo Chemical) at 100° C. for 1 hour, and after drying, the yarn was evaluated by observing the cross section and observing the state of the yarn surface when Sellotape was attached to the surface and peeled off. Also, the melt viscosity was measured using a Koka type flow tester.
This is the apparent viscosity measured at 180° C. under an extrusion load of 30 kg/cm ² using an orifice having a pore of 1 mm in diameter and L/D=1. Example 1 90% by weight acrylonitrile, methyl acrylate
PAN polymer consisting of 10% by weight and styrene 40
Thermoplastic elastomer consisting of 3 blocks of (styrene)-(butadiene)-(styrene) containing % by weight, thermoplastic elastomer consisting of 4 blocks of (butadiene)-(styrene)-(butadiene)-(styrene) Using an elastomer, a block copolymer called {(styrene)-(butadiene)} _4Si containing 30% by weight of styrene, a powder composition was prepared by uniformly mixing using a ball mill at the blending ratio shown in Table 1. Then, the melt viscosity was measured using a Koka type flow tester. In addition, to melt the sample, keep the sample at the specified temperature (180℃).
After filling the cylinder, the orifice was plugged and held for 2 minutes. Thereafter, the orifice was quickly uncorked and extrusion was started. Table 1 shows the measurement results and the condition of the obtained extrudate. In Table 1, the composition of the composition is in parts by weight, type of thermoplastic elastomer A: (styrene)-(butadiene)-(styrene), B: (butadiene)-(styrene)-(butadiene)-(styrene). ), C; {(styrene)-(butadiene)} ₄ Si, solvent EC; ethylene carbonate, α-BL; α-butyrolactone.

[Table] Example 2 Acrylonitrile 92% by weight, methyl acrylate
For 100 parts by weight of a PAN polymer consisting of 7.5% by weight and 0.5% by weight of sodium methallylsulfonate,
13 parts by weight of water, 15 parts by weight of a thermoplastic elastomer consisting of four blocks of (butadiene)-(styrene)-(butadiene)-(styrene) containing 40% by weight of styrene, 5 parts by weight of ethylene carbonate,
A composition containing 5 parts by weight of calcium carbonate was supplied through the hopper of a single screw extruder having three heating zones, and foaming extrusion was performed. 120℃ in the first heating zone counting from the hopper side.
The second heating zone was set at 150°C, and the third heating zone and spinning orifice were set at 190°C. A spinning orifice having one pore with a diameter of 1 mm was used, and extrusion was carried out at an extrusion pressure of 70 kg/cm ² . The extruded foamed extrudate was rolled up at 120 m/min to obtain foamed fibers.
The physical properties and spinning state of the obtained expanded fibers are shown in Table 2 along with other examples. Example 3 In the composition of Example 2, a composition was prepared in which the amount of thermoplastic elastomer was changed to 30 parts by weight, and foaming extrusion was performed using the same equipment and conditions as in Example 2. The results are shown in Table 2. Comparative Example 1 A composition was prepared by blending 30 parts by weight of water with 100 parts by weight of the same PAN polymer as in Example 2, and extruded using the same equipment and conditions as in Example 2. The results are shown in Table 2. Comparative Example 2 Ethylene carbonate 5 was added to the composition of Comparative Example 2.
A composition containing 10 parts by weight and 10 parts by weight of talc was prepared and extruded using the same equipment and conditions as in Example 2. The results are shown in Table 2.

[Table] * (Note) Tensile, strength, and elongation values are after shrinkage treatment in boiling water.

Claims (1)

[Scope of Claims] 1. A thermoplastic elastomer comprising a conjugated diolefin and a monovinyl-substituted aromatic compound based on 100 parts by weight of a polyacrylonitrile polymer containing at least 40% by weight of acrylonitrile.
~40 parts by weight, and at least one inorganic particle
Polyacrylonitrile foam fiber containing 0.1 to 50 parts by weight. 2. The expanded fiber according to claim 1, wherein the thermoplastic elastomer is a block copolymer of a conjugated diolefin and a monovinyl-substituted aromatic compound containing 10 to 70% by weight of the monovinyl-substituted aromatic compound. 3. The foamed fiber according to claim 1, wherein the inorganic particles are selected from calcium carbonate, kaolin, and talc. 4 100 parts by weight of a polyacrylonitrile polymer containing at least 40% by weight of acrylonitrile bound, 5 to 40 parts by weight of water, 1 to 40 parts by weight of a thermoplastic elastomer consisting of a conjugated diolefin and a monovinyl-substituted aromatic compound, a polyacrylonitrile polymer A polymer composition comprising 20 parts by weight or less of a coalescing solvent and 0.1 to 50 parts by weight of at least one type of inorganic particle is heated and melted under autogenous pressure or higher pressure, and then foamed and extruded from a spinning orifice. A method for producing polyacrylonitrile foam fiber, characterized by: 5. The method for producing expanded fibers according to claim 4, wherein the thermoplastic elastomer is a block copolymer of a conjugated diolefin and a monovinyl-substituted aromatic compound containing 10 to 70% by weight of the monovinyl-substituted aromatic compound. 6. The method for producing expanded fibers according to claim 4, wherein the inorganic particles are selected from calcium carbonate, kaolin, and talc.