JP6552242B2 - Super alkali resistant aramid fiber composite - Google Patents

Description

  The present invention relates to super-alkali resistant aramid fiber composites, and more particularly to super-alkali resistant aramid fiber composites that can be used in applications used for decades such as concrete.

  Poly (p-phenylene terephthalamide) fibers are synthetic fibers having high strength and heat resistance, and are used in various industrial material applications because they are lightweight and flexible as compared to metals. However, since polyparaphenylene terephthalamide fiber is inferior in chemical resistance to polyolefin fiber, it is not suitable as it is for applications requiring high alkali resistance such as concrete reinforcement.

  As a method of imparting alkali resistance to an aramid fiber, a method of coating an ethylene-methacrylic acid copolymer resin and / or a polysulfide-modified epoxy resin on a para-aramid fiber yarn using a cord processing machine has been proposed ( Patent Document 1). The fiber coated with the resin by the above-described method has a strength retention of 90 to 96% after being immersed in acid or alkali at 50 ° C. for 1,000 hours. The strength retention of the non-resin-coated untreated fibers is considerably improved compared to 24 to 77%.

  As with Patent Document 1, using a cord processing machine, para-aramid fibers are coated with a polyolefin resin, and a knitted fabric (mesh sheet) made of a core-sheath yarn using the coated yarn as a core yarn is impregnated with synthetic rubber and dried. -It has also been proposed to heat-treat into a civil engineering material sheet (see Patent Document 2). Also in this case, the strength retention after immersion at 50 ° C. × 1,000 hr of the obtained sheet for civil engineering materials remains at 95% even in an alkaline aqueous solution with a low concentration of 0.1%.

  According to the above conventional method, in the aramid fiber coated with the ethylene-methacrylic acid copolymer resin, a result with relatively good alkali resistance is obtained, but even in that case, the strength retention rate is slightly reduced Yes. Considering the service life of concrete reinforcement applications, it is most desirable to maintain the fiber tenacity retention near 100% so that it can withstand several decades in alkaline environments.

JP 2004-115958 A JP 2004-150003 A

  The present invention has been made in view of the problems of the prior art, and the strength retention after alkali immersion is maintained at around 100%, and can be used for applications such as concrete used for several decades. It is an object of the present invention to provide an ultra-alkali resistant aramid fiber composite.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors coated the outer peripheral surface of the aramid multifilament yarn almost uniformly and in a thin film with a thermoplastic resin having good hydrolysis resistance. As a result, the inventors have found that the chemical resistance of the aramid fiber is dramatically improved as compared with that before coating, and that the object can be achieved, and the present invention has been achieved.

  That is, the present invention is as follows.

(1) A linear low density polyethylene resin having a thickness of 0.03 to 0.1 mm on the outer peripheral surface of one untwisted aramid multifilament yarn (but not impregnated with a thermosetting resin) A super-alkali resistant aramid fiber composite characterized by being coated with a layer.
(2) The super low resistance described in the above (1), wherein a part of the linear low density polyethylene resin is interposed between the filaments of the aramid multifilament yarn so as to adhere to each other. Alkaline aramid fiber composite.
( 3 ) The super alkali-resistant aramid fiber composite as described in (1) or (2) above, wherein the tenacity retention rate after being immersed in a 10 wt% aqueous sodium hydroxide solution at 90 ° C for 7 days is 100% .
( 4 ) One untwisted aramid multifilament yarn (not impregnated with a thermosetting resin) is passed through the melthead crosshead die of a melt extruder, and melted with linear low density polyethylene resin The method for producing a super-alkaline-resistant aramid fiber composite according to any one of the above (1) to (3), which comprises coating.

  The super alkali-resistant aramid fiber composite of the present invention maintains the initial strength retention even in a high concentration (10 wt%) aqueous alkali solution. Flexible and excellent workability. Thus, it is possible to provide a material that can be widely used in various applications, including concrete reinforcement applications.

Sectional photograph of the aramid fiber composite of the present invention example.

  In the present invention, an aramid fiber is a fiber having at least one divalent aromatic group which may be usually substituted in repeating units of a polymer forming the fiber, and a fiber having at least one amide bond. There is no particular limitation, and it may be a wholly aromatic polyamide fiber or a known one referred to as an aramid fiber. In the above, “an optionally substituted divalent aromatic group” means a divalent aromatic group which may have one or more substituents which are the same or different.

  The aramid fibers include para-aramid fibers and meta-aramid fibers. The present invention is particularly effective and preferable for para-aramid fibers having excellent tensile strength. Examples of the para-aramid fiber include polyparaphenylene terephthalamide fiber (manufactured by DuPont, Inc., Toray DuPont, trade name “Kevlar” (registered trademark)), copolyparaphenylene-3,4′-oxydi. Examples thereof include phenylene terephthalamide fiber (manufactured by Teijin Limited, trade name “Technola” (registered trademark)). Examples of meta-aramid fibers include polymetaphenylene terephthalamide fibers (manufactured by DuPont, USA, trade name “NOMEX” (registered trademark)). Among these aramid fibers, polyparaphenylene terephthalamide fibers are desirable.

  The aramid multifilament yarn is one in which filaments (single yarns) are gathered to form a bundle of yarn. The number of filaments constituting the bundle is preferably 100 to 50,000 filaments, more preferably 500 to 5,000 filaments. If the number of filaments is too small, it may not be preferable because sufficient breaking strength of the composite can not be obtained. On the other hand, when the number of filaments is too large, the processability becomes poor, which may be undesirable. The single yarn fineness of one filament constituting the multifilament yarn is not particularly limited, but is preferably in the range of 0.5 to 10 dtex, particularly preferably 1 to 5 dtex.

As the thermoplastic resin, a resin having good hydrolysis resistance is preferable. The hydrolysis resistance of the resin can be evaluated by JIS K 7114: 2001 “Plastics—Test method for determining the effect of immersion in liquid chemicals”. Specifically, the thermoplastic resin having good hydrolysis resistance is preferably a resin having no —COO— or —CONH— bond in the main chain of the polymer, and —OH, —NH ₂ , — The resin which does not contain a water-absorbent functional group such as HSO ₃ , -COOH, -O-, -COO- or -CONH- is preferable.
Specific examples include polyolefin resins such as polyethylene, polypropylene, polybutylene and copolymers of these materials; polystyrene resins such as polystyrene and ABS; polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, polysulfone, polyethersulfone And the like.

Among the above-mentioned thermoplastic resins, polyolefin resins are preferable from the viewpoint of having no —O— bond in the main chain of the polymer, and containing no functional group in the molecular structure and being hydrophobic. Among the polyolefin resins, polyethylene is preferable in view of its low melting point and excellent economy and processability . In particular, linear low density polyethylene (LLDPE) is suitable.

The aramid fiber composite of the present invention can be produced by coating aramid multifilament yarn with a thermoplastic resin. The thermoplastic resin coating needs to completely cover the outer peripheral surface of the aramid multifilament yarn. However, the aramid filaments (single yarns) do not have to be covered with the thermoplastic resin. Further, in the aramid fiber composite of the present invention, as described in the examples below, the thermoplastic resin intrudes into the gaps between filaments close to the outer peripheral surface of the aramid multifilament yarn, and the thermoplastic resin serves as an anchor. It forms an anchor structure that plays a role. Therefore, the resin coating layer is extremely effective in preventing the penetration of the alkali into the aramid filament.
Incidentally, the aramid fiber composite of the present invention is extremely excellent in super-alkaline resistance since the tensile strength retention after immersion in a 10% by weight aqueous solution of sodium hydroxide at 90 ° C. for 7 days is 100%. .

  As the aramid multifilament yarn, one impregnated with a thermosetting resin in advance can also be used. The thermosetting resin is not particularly limited, and examples thereof include phenol resin, epoxy resin, unsaturated polyester resin, vinyl ester resin (epoxy acrylate resin), urethane acrylate resin and the like. A known curing catalyst may be added to these thermosetting resins. Among these, vinyl ester resins are preferable in terms of heat resistance and the like.

In the present invention, the coating amount of the thermoplastic resin on the aramid multifilament yarn is preferably such that the thickness of the coating layer on the multifilament yarn is in the range of 0.03 to 0.1 mm. Is 0.03 to 0.08 mm. When the thickness of the coating layer is 0.03 mm or more, the superalkali resistance of the aramid fiber composite is exhibited. The thickness of the covering layer is 0 . Even if it exceeds 1 mm, the super alkali resistance effect obtained by the coating is saturated and uneconomical. In addition, depending on the type of resin to be coated, the aramid fiber composite may be hard and the processability may be deteriorated.
The thickness of the thermoplastic resin coating layer can be determined by measuring the length based on the cross section obtained by cutting the aramid fiber composite of the present invention at right angles to the longitudinal direction.

  The cross-sectional shape of the super-alkaline-resistant aramid fiber composite may be circular, rectangular, flat, rectangular, or other different cross-sectional shape, and in terms of handling, it is preferably circular or nearly circular.

  The super-alkaline-resistant aramid fiber composite of the present invention can be produced by a method of impregnating a single aramid multifilament yarn in a hot melt obtained by heat-melting a thermoplastic resin. For example, the method by a pultrusion method can be mentioned. A tension is applied to one aramid multifilament yarn, and it is passed through a crosshead die of a melt extruder in a non-twisted state and coated with a molten thermoplastic resin. By this, it becomes possible to coat the thermoplastic resin uniformly on the outer peripheral surface of the aramid multifilament yarn.

  To the thermoplastic resin, known heat stabilizers, antiaging agents, weathering stabilizers, lubricants, flame retardants, antistatic agents, fillers and the like can be added within the range not impairing the object of the present invention.

  The super alkali-resistant aramid fiber composite of the present invention is processed into a woven or knitted fabric, braided string, linear body, etc., and is suitable as a building material such as a ground reinforcement net, road pavement material, concrete reinforcement material, anti-peeling material, and building member. Can be used. In addition, it can be used for members such as gas turbines, burners and nozzles, members of automobiles, freight cars, ships, etc., members of home appliances, and the like.

  EXAMPLES The present invention will be more specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples and the like, “% by weight” is abbreviated as “%” and “parts by weight” is abbreviated as “parts” unless otherwise specified.

Example 1
Poly-p-phenylene terephthalamide multifilament (made by Toray Dupont: Kevlar (R) 29, single yarn diameter 12 μm, 1,000 filaments, total fineness 1,670 dtex) using one multifilament and melt extruding this Machine through a crosshead die (200 ° C) and coated with LLDPE (Sumika Chemical's Sumikasen (R) -L) to which 1 part of carbon black was added, and immediately lead to a cooling water layer to cool the coating portion It solidified.
The resulting polyparaphenylene terephthalamide fiber composite has a cross section as shown in FIG. 1, and a polyethylene resin coating thickness of about 0 on the outer periphery of the polyparaphenylene terephthalamide multifilament yarn having an outer diameter of about 0.5 mm. .05 mm and was coated in an annular shape.
Further, from FIG. 1, the polyparaphenylene terephthalamide fiber composite was interposed such that a part of the polyethylene resin whose cross section was coated in an annular shape was adhered between the filaments.

  The poly (p-phenylene terephthalamide) fiber complex was immersed in a 10% aqueous sodium hydroxide solution at 90 ° C. for 7 days. The tensile strength before and after alkali treatment of the composite was measured to determine the strength retention. The tensile strength was measured in accordance with JIS L1013.

(Example 2)
Using one Kevlar (R) 29 multifilament as in Example 1, 100 parts of vinyl ester resin (R3130, manufactured by Showa Polymer Co., Ltd.) and a trade name “Akazo Akzo” as a thermosetting catalyst An uncured thermosetting resin containing 4 parts of CADOX BCH 50 and 1 part of Kayabutyl B, and 1 part of calcium carbonate (NS # 200, average particle diameter about 2.0 μm) manufactured by Nitto Powder Co., Ltd. It was introduced into the resin impregnation tank, and the filament bundle was impregnated with the thermosetting resin. Subsequently, the filament bundle impregnated with the uncured resin was drawn by drawing it to a drawing nozzle having an inner diameter that was reduced stepwise to obtain a thin filament having an outer diameter of 0.50 mm.
After coating this with LLDPE in the same manner as in Example 1, it was guided to a pressurized steam curing tank having a length of 36 m provided with pressure seal portions at the inlet and outlet at a speed of 50 m / min and 150 ° C. (0.4 MPa). The polyparaphenylene terephthalamide fiber composite having an outer diameter of 0.60 mm was obtained by continuously feeding to a diameter adjusting device equipped with a diameter adjusting die having a final inner diameter of 0.605 mm.
This was immersed in a 10% by weight aqueous solution of sodium hydroxide at 90 ° C. for 7 days in the same manner as in Example 1, and the strength retention was determined.

(Comparative example 1)
Kevlar (R) 29 used in Example 1 was not impregnated with the resin, but was immersed in a 10 wt% sodium hydroxide aqueous solution at 90 ° C for 7 days as it was to obtain the strength retention.

  The evaluation results of Examples and Comparative Examples are shown together in Table 1.

The polyparaphenylene terephthalamide fiber composite obtained in Example 1 maintained the initial breaking strength even after 7 days of alkali treatment, and was super alkali resistant. On the other hand, the poly (p-phenylene terephthalamide) fiber of Comparative Example 1 deteriorated to such an extent that the breaking strength after the alkali treatment could not be measured.

  The processability of the poly (p-phenylene terephthalamide) fiber composite obtained in Example 1 was evaluated by the minimum bending diameter. The minimum bend radius was obtained by bending the polyparaphenylene terephthalamide fiber composite into an arc shape, decreasing the diameter, and determining the inner diameter immediately before the breakage occurred. As a result, the minimum bending radius was 3 mm. From this, it was confirmed that the polyparaphenylene terephthalamide fiber composite is excellent in processability and can be processed into a braid or woven fabric.

  The super-alkali resistant aramid fiber composite of the present invention is suitably used for applications in contact with concrete.

Claims (4)

The outer peripheral surface of one untwisted aramid multifilament yarn (but not impregnated with thermosetting resin) is covered with a linear low density polyethylene resin layer having a thickness of 0.03 to 0.1 mm. A super alkali-resistant aramid fiber composite, characterized in that   2. The super alkali-resistant aramid fiber composite according to claim 1, wherein a part of the linear low density polyethylene resin is interposed between the filaments of the aramid multifilament yarn so as to adhere to each other. body. The super-alkaline-resistant aramid fiber composite according to claim 1 or 2, wherein the tenacity retention after immersion in a 10 wt% aqueous sodium hydroxide solution at 90 ° C for 7 days is 100%. Passing a single untwisted aramid multifilament yarn (not impregnated with a thermosetting resin) through a melt extruder crosshead die and coating with molten linear low density polyethylene resin The manufacturing method of the super-alkali-resistant aramid fiber composites in any one of the Claims 1-3 characterized by these.