JP2005289707A - Cement-reinforcing fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement-reinforcing fiber being a hydrophilized polypropylene fiber, exhibiting good dispersibility in cement and good physical bonding to cement, and giving a cement molding improved in flexural strength and flexural toughness. <P>SOLUTION: The cement-reinforcing fiber is a monofilament fiber which is obtained by spinning a composition containing 100 pts.wt. polypropylene and 1 to 10 pts.wt. composite-structure graft copolymer composed of 50 to 90 wt.% ethylene/vinyl acetate segments and 50 to 10 wt.% vinyl polymer segments, drawing the yarn, and embossing the drawn yarn, has an average flatness i.e., a thickness/width ratio in a cross section of the fiber, in the range of 1/1.5 to 1/7 and a monofilament fineness of 200 dt or higher, and is in the form of a wave having an amplitude of 1 to 4 mm, a wavelength of 2 to 20 mm, and an amplitude/wavelength ratio of 1/2 to 1/5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cement reinforcing fiber excellent in reinforcing effect of concrete or mortar.

  Conventionally, cement molded products using mortar and concrete, or outer walls of buildings, inner walls of tunnels, slope slopes, etc. have been constructed, but these are relatively brittle as molded bodies, tensile strength, bending If physical properties such as proof stress, bending toughness, and impact resistance are not sufficient, there is a risk of water leakage due to cracks on the wall surface or an accidental peeling off of the outer wall. And mixing of steel fiber and polyvinyl alcohol fiber is widely performed for the purpose of reinforcement of concrete.

  However, concrete mixed with steel fibers has been pointed out to be disadvantageous in that it is difficult to transport and mix materials because the specific gravity of steel fibers is as high as 7.8, and that steel fibers rust. In addition, concrete mixed with polyvinyl alcohol fibers has the disadvantage that the fibers themselves have water absorption properties, and that the fibers are hydrolyzed when they are alkali and high temperature.

In order to solve such a problem, in recent years, there has been an attempt to use polyolefin fibers instead of steel fibers or polyvinyl alcohol fibers for reasons such as good moldability, light weight, and low cost (for example, Patent Document 2). ).
As the polyolefin-based fiber, generally, a single yarn, a bundled yarn, or a split yarn short fiber having a fineness of 100 dt or less and a fiber length of 5 mm or less is often used. From this fiber shape, the properties of the fiber with low fineness and short length are disadvantageous in that fiber balls called fiber balls are formed and bulky and difficult to uniformly disperse in the cement. If the thickness is made thicker, the adhesiveness with the cement is inferior, and when a bending stress is applied, there is a tendency that a sufficient reinforcing effect cannot be obtained, for example, fibers are pulled out.

In order to improve the hydrophilicity of the polyolefin resin fiber with cement, a short fiber obtained by cutting a monofilament of polypropylene having a specific wave shape has a wave amplitude of 1 to 4 mm, a wavelength of 2 to 20 mm, and an amplitude. There has been proposed a method in which a surfactant composed of a polyoxyalkylene alkylphenyl ether phosphate ester and a polyoxyalkylene fatty acid ester is applied to one having a wavelength ratio in the range of 1/2 to 1/5 (for example, Patent Document 3).
However, since the above-mentioned surfactants do not have sufficient adhesion to polyolefin resin fibers, even if they are bonded to the cement matrix, sufficient adhesion cannot be obtained between the polyolefin resin fibers and the cement matrix, and cement molding The bending toughness of the object could not be improved.

Japanese Patent Publication No. 1-40786 (1 page) JP-A-9-86984 (page 2) JP-A-11-116297 (page 2)

  The present invention was made to solve the problems of the prior art as described above, can impart hydrophilicity to polypropylene fibers, has good dispersibility with cement and physical bonding with cement, An object of the present invention is to provide a cement reinforcing fiber that improves the bending toughness of a cement molded product.

In order to technically solve the above-mentioned problems, the present invention has found that the above object can be achieved by blending a specific surfactant with polypropylene to form a fiber, and has completed the present invention. .
That is, the gist of the present invention is a composite structure composed of 50 to 90% by weight of an ethylene-vinyl acetate copolymer segment and 50 to 10% by weight of a vinyl polymer segment with respect to 100 parts by weight of polypropylene. The composition comprising 1 to 10 parts by weight of the graft copolymer was spun, stretched, and embossed to obtain an average flatness ratio, which is the ratio of the thickness and width of the fiber cross section. In the range of 1.5 to 1/7, the single yarn fineness has a wave shape of 200 dt or more, the amplitude of the wave is 1 to 4 mm, the wavelength is 2 to 20 mm, and the ratio of the amplitude to the wavelength is 1/2. A cement reinforcing fiber, which is a monofilament fiber of ˜1 / 5.

  The cement-reinforced fiber of the present invention is a monofilament fiber having a specific corrugated shape obtained by spinning and stretching a blend of a specific composite structure graft copolymer with polypropylene and then embossing it. This makes it possible to provide excellent affinity at the interface between polypropylene fibers and cement, and to produce cement moldings with excellent adhesion to the cement matrix and excellent bending strength and bending toughness. It becomes.

  In the present invention, the polypropylene resin used as the fiber raw material may be a polypropylene copolymer such as a propylene homopolymer, an ethylene-propylene block copolymer or a random copolymer, or a mixture thereof. Among these, a propylene homopolymer is desirable for cement reinforcement requiring high strength and heat resistance, and it is particularly desirable to select one having an isotactic pentad ratio of 0.95 or more. The melt flow rate (hereinafter abbreviated as MFR) of this polypropylene resin is selected from the range of 0.1 to 30 g / 10 min, more preferably from 1 to 10 g / 10 min in terms of continuous stable productivity. It is good to do.

  If necessary, other polyolefins may be added to the polypropylene resin in the spinning process. Other polyolefins here include polyethylene resins such as high density polyethylene, linear low density polyethylene, low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-alkyl acrylate copolymer, polybutene-1, etc. It is.

Next, the composite structure graft copolymer will be described.
This graft copolymer is composed of 50 to 90% by weight of an ethylene-vinyl acetate copolymer segment (hereinafter abbreviated as A segment) and 50 to 10% of a vinyl polymer segment (hereinafter abbreviated as B segment). It is composed of wt%. The A segment is usually the main chain of the graft copolymer, and the B segment is the side chain of the graft copolymer.

  The ethylene-vinyl acetate copolymer constituting the A segment has a vinyl acetate content of 10% by weight or more, preferably 10 to 80% by weight, and more preferably 20 to 50% by weight. If the vinyl acetate content is less than 10% by weight, the hydrophilicity is insufficient, which is undesirable. The ethylene-vinyl acetate copolymer has a weight average molecular weight of 1,000 to 1,000,000, preferably 5,000 to 600,000. When the weight average molecular weight is less than 1000, the heat resistance is not lowered. On the other hand, if the weight average molecular weight exceeds 1,000,000, molding processability is lowered, which is not desirable.

Next, the vinyl polymer forming the B segment of the graft copolymer is obtained by polymerizing one or more of unsaturated carboxylic acids or these unsaturated carboxylic acid esters.
Examples of the unsaturated carboxylic acids include α, β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, maleic anhydride, and metal salts thereof.
Examples of unsaturated carboxylic acid esters include α, β-unsaturated carboxylic acid esters such as methyl acrylate, n-butyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate. .
Of these, the combination of methacrylic acid and its methyl methacrylate is preferred.
The weight average molecular weight of the vinyl polymer is 1,000 to 1,000,000, preferably 5,000 to 500,000. When the weight average molecular weight is less than 1,000, the compatibility with the resin to be modified is lowered, which is not desirable. Moreover, when exceeding 1 million, it is not desirable for the same reason.

  The proportion of the A segment in the composite structure graft copolymer is 50 to 90% by weight, preferably 60 to 80% by weight. Therefore, the proportion of the B segment in the composite structure graft copolymer is 50 to 10% by weight, preferably 40 to 20% by weight. When the proportion of the A segment is less than 50% by weight, the improvement effect of the ethylene-vinyl acetate copolymer becomes insufficient, which is not preferable. On the other hand, if the A segment exceeds 90% by weight, the adhesion to the cement matrix is lowered, and the impact strength and bending strength of the cement molded product cannot be improved.

  The particle diameter of the dispersed polymer is 0.001 to 10 μm, preferably 0.01 to 5 μm. When the dispersed particle diameter is less than 0.001 μm or exceeds 10 μm, the dispersibility is low, for example, the appearance of the obtained molded product is deteriorated or the mechanical properties are decreased.

  The grafting method for producing the composite structure graft copolymer may be any of the generally known chain transfer method, ionizing radiation irradiation method, etc., but the method shown below is preferred. That is, it is because the grafting efficiency is high and secondary aggregation due to heat does not occur, so that the performance is more effective and the production method is simple.

  Next, the manufacturing method of a composite phase structure graft copolymer is demonstrated concretely. First, 100 parts by weight of an ethylene-vinyl acetate copolymer is suspended in water, and 1 to 400 parts by weight of at least one vinyl monomer is added to one or two kinds of radical polymerizable organic peroxides. A polymerization initiator having a decomposition temperature of 40 to 90 ° C. for obtaining a mixture of 0.1 to 20 parts by weight with respect to 100 parts by weight of the vinyl monomer and a half-life of 10 hours is used. A mixed solution in which 0.01 to 5 parts by weight is dissolved with respect to 100 parts by weight of the total of the monomer and the radical polymerizable organic peroxide is added.

  Next, heating is carried out under conditions in which decomposition of the polymerization initiator does not substantially occur, and the ethylene-vinyl acetate copolymer is impregnated with a vinyl monomer, a radical polymerizable organic peroxide and a polymerization initiator. Increase the temperature of the aqueous suspension. Then, a vinyl monomer and a radical polymerizable organic peroxide are copolymerized in an ethylene-vinyl acetate copolymer to obtain a grafted precursor.

  A composite structure graft copolymer can be obtained by kneading the grafted precursor under melting. At this time, even if an ethylene-vinyl acetate copolymer is mixed in the grafting precursor and kneaded under melting, a composite structure graft copolymer can be obtained.

  Examples of the radical polymerizable organic peroxide include t-butylperoxyacryloyloxyethyl carbonate, t-amylperoxyacryloyloxyethyl carbonate, and t-hexylperoxyacryloyloxyethyl carbonate. -Bonate, 1,1,3,3-tetramethylbutylperoxyacryloyloxyethyl carbonate, cumylperoxyacryloyloxyethyl carbonate, p-isopropylcumylperoxyacryloyloxyethyl Carbonate, t-butylperoxymethacryloyloxyethyl carbonate, t-amylperoxymethacryloyloxyethyl carbonate, t-hexylperoxymethacryloyloxyethyl carbonate, t- Butyl peroxyallyl carbonate, t-butyl peroxymethallyl carbonate A bonnet or the like is preferably used.

  The MFR (190 ° C., 2160 g load, JIS K6922-1) of the composite structure graft copolymer is in the range of 0.1 to 20 g / 10 minutes, preferably in the range of 0.5 to 10 g / 10 minutes. is there.

  The polypropylene fiber for reinforcing cement of the present invention is in the range of 1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of polypropylene. If the blending ratio of the composite structure graft copolymer is less than 1 part by weight, the effect of imparting hydrophilicity to the polyolefin resin fiber is lowered, and the effect of improving the adhesion to the cement matrix is lowered, which is not preferable. On the other hand, when the amount exceeds 10 parts by weight, the mechanical strength against the polyolefin resin fiber is lowered, which is not desirable.

  The polypropylene composition includes an antioxidant, a lubricant, an ultraviolet absorber, an antistatic agent, an inorganic filler, an organic filler, a crosslinking agent, a foaming agent, a core, and the like within a range that does not depart from the gist of the present invention. You may mix | blend additives, such as an agent.

  The polypropylene fiber spun in the present invention is a short fiber obtained by cutting a relatively thick monofilament, and its production method is not particularly limited, and is circular, elliptical, atypical, In addition, a manufacturing technique for extruding a filament from a continuous yarn-shaped die can be employed.

  In addition to the basic monolayer filament, a composite monofilament having a polypropylene high melting point component as a core layer and a polypropylene low melting point component as a sheath layer can also be used as the monofilament structure. In this manufacturing method, polypropylene of each layer is melt-kneaded with an extruder, a core layer made of a high melting point component is supplied from a central discharge hole of a die in which two discharge holes are provided on a substantially concentric circle, A sheath layer composed of a melting point component is extruded and coated to obtain a composite monofilament. In this case, since the substantial strength depends on the physical properties of the core layer, it is preferable to use a propylene homopolymer, isotactic polypropylene or the like as the high melting point component, while the propylene-ethylene block copolymer is used as the low melting point component. Polymers, random copolymers, syndiotactic polypropylene and the like are preferable. By using the composite monofilament thus obtained, it is possible to suppress thermal degradation of the polypropylene fiber during heat curing during concrete molding.

  Next, the monofilament is subjected to heat drawing and heat relaxation treatment, and the rigidity of the filament is increased by this heat treatment to obtain a polypropylene monofilament suitable for cement reinforcement having a small elongation. This hot stretching is carried out at a temperature below the melting point of polypropylene and above the softening point. Usually, the stretching temperature is 90 to 150 ° C., and the stretching ratio is usually 5 to 12 times, preferably 7 to 9 times. As the hot stretching method, a hot roll method, a hot plate method, an infrared irradiation method, a hot air oven method, a hot water method, or the like can be adopted.

  The monofilament fineness of the formed polypropylene monofilament is 200 dt or more, preferably in the range of 200 to 10,000 dt, more preferably in the range of 2,000 to 6,500 dt. If the single yarn fineness is less than 200 dt, the fibers are too thin and the dispersion in the concrete mixture is non-uniform and easily becomes fiber balls, which is problematic in terms of workability and reinforcement. On the other hand, if the single yarn fineness exceeds 10,000 dt, the contact area of the fiber with the concrete admixture decreases, and it becomes easy to pull out against bending stress, so that the reinforcing effect is inferior.

  The tensile strength of the polypropylene filament is 5 g / dt or more, preferably 6 g / dt or more. Further, the tensile elongation is 20% or less, preferably 15% or less. If the tensile strength and tensile elongation are out of these ranges, the strength as a cement reinforcing polypropylene fiber is insufficient, which is not preferable.

  Polypropylene monofilaments need to have irregularities on the surface as the next step of spinning and hot drawing. As a result, the contact area between the fiber and the concrete can be increased, and the reinforcement effect can be enhanced by suppressing the pull-out of the fiber after the concrete is hardened. An example of a method for forming irregularities on the surface is a method of embossing a monofilament. Embossing is performed by passing an embossing roll before or after stretching the monofilament, and irregularities are continuously formed in the longitudinal direction of the monofilament.

  Here, by passing the embossing roll, as shown in FIGS. 1 and 2, the average flatness ratio of 1 / 1.5 to 1/7, which is the ratio of the thickness Y and the width X of the fiber cross section 1 by crushing, is obtained. It is required to be in the range, preferably 1 / 1.8 to 1/7. When the fiber cross-section 1 is flattened, wave-shaped shaping becomes easy. The average flatness is a numerical value showing an average ratio of width and height in the cross-sections of various shaped shapes, and the average flatness is less than 1 / 1.5 with respect to the fiber surface. Since there are few uneven shapes, there is no difference between the smooth surface fiber and the reinforcing effect. On the other hand, if the average flatness ratio exceeds 1/7, the strength deterioration due to shaping is significant. Dispersibility tends to deteriorate, which is a problem.

  The shape of the wave-shaped monofilament 2 such as the amplitude H and the wavelength L can take various numerical values. The amplitude H is 1 to 4 mm, the wavelength L is 2 to 20 mm, and the ratio of the amplitude H to the wavelength L. Is important to be 1/2 to 1/5. When the amplitude H is less than 1 mm, the wavelength L is less than 2 mm, and the ratio of the amplitude H to the wavelength L is greater than 1/2, the reinforcing effect is not recognized, the amplitude H exceeds 4 mm, the wavelength L exceeds 20 mm, and the amplitude If the ratio of H to wavelength L is less than 1/5, the dispersibility in concrete deteriorates, such being undesirable.

  Such a polypropylene monofilament is cut into a predetermined length to become a short fiber for cement reinforcement. The apparent length of the short fiber is 5 to 70 mm, preferably 20 to 50 mm. If the apparent length is less than 5 mm, the cement will come off, and if it exceeds 70 mm, the dispersibility becomes poor.

  The cement reinforcing fiber of the present invention is used as a reinforcing fiber material by mixing it with cement, fine aggregate, coarse aggregate, water and an appropriate amount of concrete admixture. Here, examples of the cement include hydraulic cement such as Portland cement, blast furnace cement, silica cement, fly ash cement, white Portland cement, and alumina cement, or cement such as plaster and air-hardening cement such as lime. Examples of materials include river sand, sea sand, mountain sand, quartz sand, glass sand, iron sand, ash sand, and other artificial sands. Examples of coarse aggregates include reki, gravel, crushed stone, slag, and various artificial lightweight aggregates. Is a typical example.

  The blending amount of the fiber in the cement is preferably 0.1 to 10% by volume based on the cement solid content. Also, as a method of mixing polypropylene fiber with cement, known methods such as a method of dispersing fibers in cement powder, a premix method of dispersing fibers in cement slurry, and a spray-up method of spraying cement, fibers and water simultaneously, etc. The method can be used.

  The fiber-reinforced cement molded body covers a wide range of cement products. For example, building wall materials, flooring concrete, finished mortar, waterproof concrete, slate roofing materials, etc. Pavements such as roads, runways, tunnels and sloped shotcrete, road signs, road members such as gutters, pipes such as sewer pipes, cable ducts, fishing reefs, revetment blocks, tetrapots, and other various structures such as sleepers, Can be used for benches, flower pots, etc.

Example 1:
As a composite structure graft copolymer, a graft copolymer of ethylene-vinyl acetate copolymer and methacrylic acid ester-methacrylic acid (ethylene-vinyl acetate copolymer / methacrylic acid ester / methacrylic acid = 80/10/10 composition ratio) ) And MFR (190 ° C., 21.18N load, JIS K6922-1) of 2.0 g / 10 min was used. However, the vinyl acetate content in the ethylene-vinyl acetate copolymer was 28% by weight.
To 100 parts by weight of polypropylene (isotactic pentad fraction = 0.96, MFR = 5.0 g / 10 min), 4 parts by weight of the above composite structure graft copolymer was added to an extruder. After spinning from a circular nozzle and cooling, it is heated with a heater by a hot plate contact-type stretching method, and is subjected to longitudinal uniaxial stretching at a stretching temperature of 130 ° C., an annealing temperature of 135 ° C. and a draw ratio of 12 times, and a monofilament having a single yarn fineness of 6400d Molded.
This monofilament is embossed through a multi-stage embossing roll, the thickness Y of the fiber cross section 1 is 0.75 mm, the width X is 1.2 mm, the wave amplitude A is 2.3 mm, and the wavelength L is 6.8 mm. After obtaining the corrugated monofilament 2, the fiber length was cut to 50 mm to obtain polypropylene short fibers. .

Next, 0.4 v% of short fibers were blended in a mixture having a water cement ratio of 65% and a fine aggregate ratio of 52%, and the mixture was kneaded with a closed concrete mixer so as to be uniform. The fiber floating ratio of the cement mixture was 0%, and the dispersibility was good. Next, after obtaining a 10 mm × 10 mm × 40 mm specimen, standard curing was performed for 28 days, and an evaluation test was performed by the following method. The evaluation results are as follows: the compressive strength is 25.6 N / mm ² , the tensile strength is 2.46 N / mm ² , the bending strength is 4.51 N / mm ² , the bending toughness is 20.7 N / mm, and the bending toughness coefficient is 2 The bending property was excellent at .44 N / mm ² .

In the examples, an evaluation test was performed by the following method (1) The compressive strength was determined in accordance with JIS A1108.
(2) Tensile strength was determined in accordance with JIS A1113.
(3) Bending strength and bending toughness were performed according to JSCE-G552 by a bending strength and bending toughness test method of steel fiber reinforced concrete.
(4) For dispersibility evaluation, cement reinforcing fiber and cement were kneaded and the surface condition was evaluated visually.

Comparative Example 1:
Polypropylene (isotactic pentad fraction = 0.96, MFR = 5.0 g / 10 min) is charged into an extruder, spun from a circular nozzle, cooled, and then heated with a heater by a hot plate contact stretching method. Then, longitudinal uniaxial stretching was performed at a stretching temperature of 130 ° C., an annealing temperature of 135 ° C., and a draw ratio of 12 times to form a monofilament having a single yarn fineness of 6400d.
This monofilament is embossed through a multi-stage embossing roll, the thickness Y of the fiber cross section 1 is 0.75 mm, the width X is 1.2 mm, the wave amplitude A is 2.3 mm, and the wavelength L is 6.8 mm. A wave-shaped monofilament 2 was obtained.
On the other hand, 50 parts by weight of polyoxyalkylene alkylphenyl ether phosphate ester (HLB = 8.0) and 50 parts by weight of polyoxyalkylene fatty acid ester (HLB = 9.0) were mixed to prepare an aqueous surface treatment agent solution. The corrugated monofilament previously formed was immersed in this aqueous solution of the surface treatment agent and then dried to cut the average fiber length to 50 mm, thereby obtaining short fibers.

Next, 0.4 v% of short fibers were blended into a mixture having a water cement ratio of 65% and a fine aggregate ratio of 52%, and the mixture was kneaded with a closed concrete mixer so that the whole was uniform. The fiber floating ratio of the cement mixture was 0%, and the dispersibility was good. Next, after obtaining a 10 mm × 10 mm × 40 mm specimen, standard curing was performed for 28 days, and an evaluation test was performed.
As a result of the evaluation, the compressive strength is 25.3 N / mm ² , the tensile strength is 2.42 N / mm ² , the bending strength is 4.12 N / mm ^{2, the} bending toughness is 18.2 N / mm, and the bending toughness coefficient is 2 It was .14 N / mm ² and the bending characteristics were insufficient.

Comparative Example 2:
The same procedure as in Comparative Example 1 was performed except that the monofilament was not embossed and a wave shape was not formed.
As a result of the evaluation, the compressive strength is 25.2 N / mm ² , the tensile strength is 2.02 N / mm ² , the bending strength is 3.96 N / mm ² , the bending toughness is 9.8 N / mm, and the bending toughness coefficient is 1 At .64 N / mm ² , the bending properties were significantly insufficient.

It is sectional drawing of the cement reinforcement fiber of this invention. It is explanatory drawing which shows the waveform of the cement reinforcement fiber of this invention.

Explanation of symbols

1 Fiber cross section Y Fiber thickness X Fiber width 2 Wave shape monofilament H Waveform amplitude L Waveform wavelength

Claims (3)

  1 to 10 weight percent of a composite graft copolymer composed of 50 to 90 weight percent of an ethylene-vinyl acetate copolymer segment and 50 to 10 weight percent of a vinyl polymer segment with respect to 100 weight parts of polypropylene. The average flatness, which is the ratio of the thickness and width of the cross section of the fiber, obtained by spinning, stretching and embossing the composition containing the part is 1 / 1.5 to 1/7 A monofilament fiber having a wave shape with a single yarn fineness of 200 dt or more, an amplitude of the wave of 1 to 4 mm, a wavelength of 2 to 20 mm, and a ratio of the amplitude to the wavelength of 1/2 to 1/5. Cement reinforced fiber characterized by being.   The cement-reinforced fiber according to claim 1, wherein the vinyl polymer is a polymer obtained by polymerizing one or more of unsaturated carboxylic acids or unsaturated carboxylic acid esters thereof.   The cement-reinforced fiber according to claim 1, wherein the vinyl polymer is a polymer obtained by polymerizing methacrylic acid and methyl methacrylate thereof.

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