JP2004168643A - Polypropylene fiber for cement reinforcement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyolefin resin fiber for cement reinforcement to which hydrophilicity can be imparted, and which has excellent adhesive properties with a cement matrix, can reinforce a cement molding, and can improve the bending strength and impact strength of the cement molding. <P>SOLUTION: A polypropylene fiber is subjected to surface oxidation treatment, and the wetting index of the surface is controlled to ≥38 dyn/cm, so that the polyolefin resin fiber for cement reinforcement is obtained to which excellent affinity can be imparted to the interface between the polypropylene fiber and cement, and which has excellent adhesive properties with the cement matrix, can reinforce a cement molding, and can improve the bending strength and impact strength of the cement molding. <P>COPYRIGHT: (C)2004,JPO

Description

  TECHNICAL FIELD The present invention relates to a polypropylene fiber for cement reinforcement having an excellent reinforcing effect for concrete and mortar.

Instead of asbestos, which has been used for many years as a reinforcing material for cement molded products, for example, polyvinyl alcohol resin, polyolefin resin, polyacrylonitrile resin, polyamide resin and the like are used as synthetic resin fibers.
However, in recent years, the curing of cement molded products has been increasing in autoclaves for the purpose of improving dimensional stability, shortening the curing time, etc. When such autoclave curing is performed, fibers other than polyolefin fibers are resistant to heat and alkali. However, it could not be used as a reinforcing fiber because it was deteriorated due to the shortage.
From these facts, polyolefin resin fibers are often used because of their heat-resistant alkali resistance, but polyolefin resins have few hydrophilic groups or functional groups effective for adhesion to cement in their molecular structure, Adhesion to the cement matrix is extremely poor, and when the cement molded body reinforced with polyolefin resin fibers is broken, the fibers are easily pulled out, and even if the impact strength and bending fracture energy due to the fiber pull-out resistance are increased, There is a disadvantage that the bending strength cannot be greatly improved.

In order to improve the affinity of the polyolefin resin fiber with the cement, a surfactant, for example, a surfactant comprising an alkali metal salt of a normal alkyl phosphate, or a polyoxyalkylene alkylphenyl ether phosphate and a polyoxyalkylene fatty acid A method of applying a surfactant or the like made of an ester has been proposed (for example, Patent Documents 1 and 2).
However, since the surfactants proposed above do not have an adhesive property with polyolefin resin fibers, even if the cement matrix and the surfactant are adhered, there is a disadvantage that sufficient adhesive strength cannot be obtained between the fibers and the matrix. .

JP-A-5-170497 (1 page) JP-A-10-236855 (page 1)

The present invention has been made in order to solve the above-described problems of the prior art,
Polyolefin resin fibers for cement reinforcement, which can impart hydrophilicity to polyolefin resin fibers, have excellent adhesion to the cement matrix, can strengthen cement molded products, and improve the bending strength and impact strength of cement molded products. The purpose is to provide.

The present invention has been found to achieve the above object by technically solving the above-mentioned problems by subjecting a polyolefin resin fiber to a surface oxidation treatment and setting the surface wetting index to a specific value or more. Was completed.
That is, the gist of the present invention resides in a polypropylene fiber for cement reinforcement, characterized in that the surface of a polypropylene fiber is subjected to a surface oxidation treatment so that the surface has a wettability index of 38 dyn / cm or more.

  The polypropylene fiber for cement reinforcement of the present invention is capable of imparting excellent affinity at the interface between the polypropylene fiber and the cement by subjecting the polypropylene fiber to a surface oxidation treatment and setting the surface wetting index to a specific value or more. It is possible to obtain a polypropylene fiber which has excellent adhesiveness to a cement matrix, can strengthen a cement molded product, and can produce a cement molded product excellent in bending strength and impact strength of the cement molded product.

The polypropylene used in the present invention may be a propylene homopolymer, a known polypropylene copolymer such as an ethylene-propylene block copolymer or a random copolymer, or a mixture thereof. For cement reinforcement requiring high strength and heat resistance, propylene homopolymer is desirable, and it is particularly desirable to select one having an isotactic pentad ratio of 0.95 or more.
Here, the isotactic pentad fraction is defined as the isotactic pentad fraction in a pentad unit in a polypropylene molecule measured using 13C-NMR, which is disclosed in Macromolecules 6 925 (1973) by A. Zambelli et al. Means rate.
The polypropylene may have a melt flow rate (hereinafter abbreviated as MFR) of 0.1 to 50 g / 10 min, preferably 1 to 40 g / 10 min, and more preferably 5 to 30 g / 10 min.

As a method for producing the polypropylene fiber, a known melt-spinning method can be employed, but a polypropylene fiber which is spun using a continuous yarn-shaped die capable of a high-magnification drawing treatment is more preferable. In this method, polypropylene is melt-extruded from a continuous-thread-shaped die, and then subjected to a drawing treatment with the extruded continuous-thread-shaped tape to form fibers.
The continuous thread-shaped die has a shape in which at least two nozzles are connected in series, but usually has a shape in which 5 to 20, preferably 10 to 15 nozzles are connected.

The drawing process of the polypropylene fiber is performed at a temperature equal to or lower than the melting point of the polypropylene and equal to or higher than the softening point. As a heating method, any method such as a hot roll method, a hot plate method, an infrared method, and a hot air method can be adopted. In this case, a hot plate type in which heating is performed on a convex hot plate heated from the inside by electroheating is preferred in terms of high-speed productivity and stability.
The heated polypropylene fiber is drawn by a peripheral speed difference between the front and rear rolls. The stretching ratio is usually in the range of 3 to 20 times, preferably 5 to 15 times, more preferably 8 to 12 times.
The drawn fiber has a tensile strength of 5 g / dt or more, preferably 7 g / dt or more. If the tensile strength is less than 5 g / dt, the reinforcing effect becomes insufficient.

  The single fiber fineness of the formed polypropylene fiber is generally less than 5 to 200 dtex (abbreviated as dt), preferably in the range of 5 to 100 dt, and more preferably in the range of 10 to 60 dt. If the single yarn fineness is less than 5 dt, the fibers are too fine and the dispersion becomes non-uniform. If too large, the contact area with cement is reduced and the reinforcing effect is poor.

  The present invention is characterized in that the surface of the polypropylene fiber is subjected to a surface oxidation treatment, and the surface has a wetting index of 38 dyn / cm or more, preferably 40 to 70 dyn / cm. When the surface wetting index is less than 38 dyn / cm, the hydrophilicity cannot be sufficiently imparted to the polyolefin resin fiber, and the bending strength and impact strength of the cement molded product cannot be improved. The surface oxidation treatment is at least one treatment method selected from a corona discharge treatment, a plasma treatment, a flame plasma treatment, an electron beam irradiation treatment, and an ultraviolet irradiation treatment, and is preferably a corona discharge treatment or a plasma treatment.

The corona discharge treatment is carried out under commonly used treatment conditions, for example, at a distance of 0.2 to 5 mm between the electrode tip and the base cloth to be treated. The treatment amount is 5 w · min or more per 1 m ^{2 of} polypropylene fiber, Preferably it is in the range of 5 to 200 W · min / m ² , more preferably in the range of 10 to 180 W · min. If it is less than 5 W · min / m ² , the effect of the corona discharge treatment is insufficient, and the wetting index of the fiber surface cannot be within the above range, and the bending strength and impact strength of the cement molded product can be improved. Can not.

  The plasma treatment step is a simple gas such as argon, helium, krypton, neon, xenon, hydrogen, nitrogen, oxygen, ozone, carbon monoxide, carbon dioxide, sulfur dioxide or a mixed gas thereof, for example, having an oxygen concentration of 5 to 15 volumes. % Of a mixed gas of oxygen and nitrogen containing hydrogen, by applying a voltage between the opposed electrodes under a pressure near the atmospheric pressure to generate a plasma discharge, thereby electronically exciting the mixed particles with a plasma jet. The removal can be carried out by spraying the removed and electrically neutralized excited gas mixture onto the surface of the plastic substrate. As the plasma processing conditions, for example, the distance between the electrodes through which the plastic substrate to be processed passes is appropriately determined according to the thickness of the substrate, the magnitude of the applied voltage, the flow rate of the mixed gas, and the like. 50 mm, preferably in the range of 2 to 30 mm, and the voltage applied between the electrodes is preferably applied so that the electric field strength when applied is 1 to 40 kv / cm. , 1 to 100 kHz.

  The flame plasma treatment step can be performed by spraying ionized plasma in a flame generated when natural gas or propane is burned onto the surface of the plastic substrate.

  The electron beam irradiation step is performed by irradiating the surface of the plastic substrate with an electron beam generated by an electron beam accelerator. As the electron beam irradiation apparatus, for example, an apparatus “electro curtain” (trade name) that can irradiate a uniform electron beam in a curtain shape from a linear filament can be used.

  The ultraviolet irradiation step is performed, for example, by irradiating the surface of the plastic substrate with ultraviolet light having a wavelength of 200 to 400 mμ.

  The polypropylene fiber obtained above is cut to a predetermined length. The fiber length to be cut is in the range of 3 to 30 mm, preferably in the range of 5 to 15 mm. If the fiber length is less than 3 mm, it will fall out of the cement, and if it exceeds 30 mm, the dispersibility will be poor.

  In the polypropylene fiber, additives such as an antioxidant, a lubricant, an ultraviolet absorber, an antistatic agent, an inorganic filler, an organic filler, a crosslinking agent, a foaming agent, a nucleating agent, etc., within a range not departing from the gist of the present invention. May be blended.

Examples of the cement to which the polypropylene fiber of the present invention can be mixed include cements such as hydraulic cements such as Portland cement, white Portland cement and alumina cement, and air-hardening cements such as gypsum and lime.
The blending amount of the polypropylene fiber is 0.1 to 10% by weight, preferably 0.5 to 5% by weight based on the cement. If the amount is less than 0.1% by weight, the reinforcing effect is inferior. If the amount is more than 10% by weight, uniform dispersion is difficult, and the bending strength is undesirably reduced.

  As a method of mixing the polypropylene fiber of the present invention with cement, a method of dispersing polypropylene fiber in cement powder, a premix method of dispersing polypropylene fiber in cement slurry, a spray-up method of simultaneously spraying cement, polypropylene fiber and water A known method such as the above can be used. The cement slurry obtained by these methods is molded according to a known molding method such as a paper forming method, an extrusion molding method, an injection molding method, or the like according to the application, and is left in the air or water at room temperature for several tens days, or a natural curing method. After curing at a daily temperature of 2 to 3 and curing at a temperature of 100 to 200 ° C., the composition is cured by an autoclave curing method to obtain a cement molded product.

  The use of the cement molded article manufactured by using the polypropylene fiber of the present invention includes all kinds of cement products.For example, a building wall material, a floor concrete, a finishing mortar, a waterproof concrete, a slate roof material, etc. Or, as civil engineering related members, roads, pavement such as runways, road signs, road members such as gutters, pipes such as sewer pipes, cable ducts, fishing reefs, seawalls, tetrapots, etc. It can be used for flower pots and the like.

Hereinafter, an example will be described in more detail.
Example 1
Polypropylene (MFR = 1.0 g / 10 min) is fed to an extruder, extruded at a resin temperature of 230 ° C. from a continuous yarn nozzle having a diameter of 2 mm × 10 holes, drawn at a hot plate contact drawing method at a drawing temperature of 130 ° C., and at an annealing temperature. The film was stretched at 135 ° C. and a stretching ratio of 12 times. The single yarn fineness of the obtained drawn yarn was 50 dt.
The surface of the drawn yarn was subjected to a corona discharge treatment as a surface oxidation treatment at a rate of 20 w · min / m ^{2 of the} drawn polypropylene yarn surface. The obtained polypropylene drawn yarn had a wetting index of 42 dyn / cm on the surface.
The drawn polypropylene yarn was cut to a length of 10 mm to obtain short fibers.
The molding of the cement molded product was performed according to JISR5201. That is, 100 parts by weight of Portland cement and 200 parts by weight of standard sand are sufficiently mixed, 5 parts by weight of the above composition is added, and 65 parts by weight of water are added and kneaded so that the whole becomes uniform, and then 40 mm × 40 mm × The mixture was poured into a 160 mm formwork, left in the air at room temperature for 48 hours, and then cured in an autoclave at 165 ° C. for 20 hours.
The obtained molded product had a bending strength of 26.0 MPa, a Charpy impact strength of 9.5 KJ / m ² , and a good dispersibility.

(Test method)
(1) MFR: Conforms to JIS K692-1 (2) Flexural strength: Conforms to JIS A1408 (3) Charpy impact strength: Conforms to JIS B7722 (4) Dispersibility evaluation: A polypropylene fiber and cement are kneaded to prepare a cement slurry. It was evaluated visually.

Example 2:
The same procedure as in Example 1 was carried out except that the corona discharge treatment was performed at a rate of 30 w · min per 1 m ^{2 of the} drawn polypropylene yarn surface, and the wetness index of the obtained drawn polypropylene yarn surface was 45 dyn / cm.
The bending strength of the obtained molded product was 26.5 MPa, the Charpy impact strength was 9.8 KJ / m ² , and the dispersibility was good.

Comparative Example 1
As the surface treating agent, an aqueous solution of the surface treating agent was prepared by mixing 50% by weight of polyoxyethylene nonylphenyl ether phosphate (HLB = 8.0) and 50% by weight of polyoxyethylene oleate (HLB = 9.0). Then, the same procedure as in Example 1 was carried out except that the immersion treatment was followed by drying and application of 1% by weight of a surface treatment agent.
The bending strength of the obtained molded product was 19.0 MPa, the Charpy impact strength was 6.5 KJ / m ² , and the fiber dispersibility was good.

Comparative Example 2
As a surface treatment agent, 70% by weight of polyoxyethylene nonylphenyl ether phosphate (HLB = 8.0) and 30% by weight of polyoxyethylene oleate (HLB = 9.0) were mixed to form an aqueous solution of the surface treatment agent. A cement molded product was formed in the same manner as in Example 1 except that it was prepared, dipped, dried and coated with 1% by weight of a surface treating agent.
The obtained molded product had a bending strength of 16.5 MPa, a Charpy impact strength of 3.5 KJ / m ² , and poor fiber dispersibility.

Comparative Example 3
As a surface treatment agent, 30% by weight of polyoxyethylene nonylphenyl ether phosphate (HLB = 8.0) and 70% by weight of polyoxyethylene oleate (HLB = 9.0) were mixed to form an aqueous solution of the surface treatment agent. A cement molded product was formed in the same manner as in Example 1 except that it was prepared, dipped, dried and coated with 1% by weight of a surface treating agent.
The bending strength of the obtained molded product was 17.5 MPa, the Charpy impact strength was 2.8 KJ / m ² , and the dispersibility of the fiber was slightly poor.

Claims (2)

  A polypropylene fiber for cement reinforcement, characterized in that the surface of the polypropylene fiber is subjected to a surface oxidation treatment so that the surface has a wetting index of 38 dyn / cm or more. The polypropylene fiber for cement reinforcement according to claim 1, wherein the surface oxidation treatment is a corona discharge treatment or a plasma treatment, and the wettability index of the surface of the polypropylene fiber after the treatment is in a range of 40 to 70 dyn / cm.