Deformed fiber

Deformed fiber which is either a long fiber prepared by such a manner that plural parallel yarns are unified by formation of connecting parts at appropriate intervals on the longitudinal direction of yarn or particularly a short fiber prepared by cutting the above wherein the plural parallel yarns of filaments are spun from a thermoplastic resin for obtaining the deformed fiber which is effective as pile yarn or gas permeating woven fabric having a specific shape or as fiber for reinforcement of cement for improving tensile strength, bending strength, shock resistance, crack resistance, etc. of molded cement product by improving the working ability and reinforcing property as a result of compounding the short fiber prepared by cutting the deformed fiber with hydraulic substance such as concrete or mortar as a material for public works or buildings.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a deformed fiber which is a fiber spun
 from thermoplastic resin and is characterized in its specific shape where
 the filaments arranged in parallel are basic elements. More particularly,
 it relates to a deformed fiber which improves the applying and reinforcing
 properties of molded cement product by compounding with a hydraulic
 substance such as concrete and mortar as materials for public works and
 buildings whereby fiber for reinforcement of cement improving tensile
 strength, bending strength, shock resistance, cracking resistance, etc.
 can be prepared.
 2. Prior Art
 Synthetic fiber having modified cross section and uneven surface has been
 used in many fields for each of their purposes.
 For example, pile yarn having modified cross section has been developed for
 artificial grass. However, monofilament and flat yarn having smooth
 surface have significant difference from natural grass due to their poor
 recovery from pressing bend and strong surface gloss and have
 disadvantages that they are not suitable as artificial grass. Pile yarn
 having modified cross section has been developed for solving such a
 disadvantage.
 In various basic material sheets consisting of laminated sheet of textile
 and film, they are woven from a drawn yarn of modified shape having
 groove-like uneven surface so that laminated resin is invaded into spaces
 of the groove-like uneven surface to give a strong thermal fusion.
 Besides the above, adhesive sheets where multifilament with many surface
 undulations and split yarn with naps are used as basic material whereby
 adhesion is improved and tufted products where lined latex is used
 together for strong unification have been available. As such, there have
 been many attempts in which modified cross section or surface undulation
 of synthetic fiber are utilized.
 In addition, when deformed fiber which is cut in a short size is
 accumulated followed by bonding to give felt or nonwoven fabric, both
 flexibility and thermal fusion are improved and suppression of detachment
 of fiber can be expected and, therefore, deformed fiber is used as short
 fiber. Among various uses of deformed short fiber, the use as a fiber for
 reinforcement of cement by compounding with hydraulic substance such as
 concrete and mortar has been receiving public attention. Its background
 will be explained as hereunder.
 Molded cement products using conventional concrete or mortar and cement
 constructions such as outer wall of buildings, inner wall of tunnels,
 inclined surface, etc. are relatively fragile as molded products.
 Especially, their physical properties such as tensile strength, bending
 resistance, bending toughness, etc. are insufficient and there are risks
 that the molded product shows cracks and is broken or that leakage of
 water or exfoliation takes place whereby many problems in terms of safety
 control have been pointed out.
 In order to solve such problems, many molded cement products are reinforced
 by iron rods. However, there is a problem that transportation and
 assembling of iron rods increase cost for materials and for labor.
 Therefore, reinforcing means where less expensive fiber materials such as
 steel fiber, glass fiber, aramid fiber, carbon fiber and synthetic fiber
 are compounded with concrete instead of iron rods have been conducted.
 Steel fiber is strong, has a high Young's modulus and is easily compatible
 with cement. In addition, there has been a proposal (U.S. Pat. No.
 5,451,471) where V-shaped notches and grooves are formed on the steel
 fiber or the fiber is deformed near both ends so as to improve the
 adhesion to cement. However, since specific gravity of steel fiber is as
 high as 7.8, transportation and mixing work of the material are difficult.
 Further, there is a possibility that workers have their feet pricked by
 the steel fiber scattered around there upon application causing an injury.
 There is another problem that generation of rust lowers the reinforcing
 effect or deteriorates the beautiful appearance.
 Although glass fiber uses an alkali-resistant glass, there is still a
 problem in durability and there is a disadvantage that the fiber is apt to
 be broken upon kneading with cement. In addition, fibers are apt to be
 tangled each other and a special kneader is necessary so as to form no
 fiber ball. Disadvantage of aramid fiber and carbon fiber is that they are
 expensive.
 Unlike the glass fiber, synthetic fiber represented by resin of a polyvinyl
 alcohol type and a polypropylene type is less expensive, light in weight
 and strong and has a good handling property. However, it has a poor
 compatibility with cement and there is a problem that severe spots are apt
 to be generated on the molded cement product. In addition, short fiber in
 a simple shape has a disadvantage that it is apt to be dropped out from
 the molded cement product by bending stress and its reinforcing effect is
 not sufficient.
 Therefore, many methods have been proposed where the short fiber shape of
 synthetic fiber for reinforcement of cement is improved to reduce the
 dropping out from molded cement product achieving a sufficient reinforcing
 effect. For example, short fiber consisting of elongated polyolefin tape
 where undulation is formed on the surface by an embossing treatment
 (Japanese Patent Laid-Open No. 116297/1999), short fiber prepared by
 elongation together with giving undulation thereto upon spinning, short
 fiber where nearly spiral projections are formed on the fiber surface and
 short fiber consisting of cleaved fiber of polypropylene film are
 available.
 However, any of the above-mentioned disclosed art is insufficient. For
 example, in the deformed fiber where surface and cross section of the
 fiber are irregularly changed, it is difficult to keep a stable quality
 upon a continuous production. In addition, many disadvantages in the
 manufacture such as that productivity is poor because of difficulty in
 uniform spinning and winding, that conditions for production such as
 temperature setting upon extrusion and elongation are severe and that
 devices for the production are specific have been pointed out.
 Further, modified polyolefin has been proposed for improving the adhesion
 of polyolefin short fiber to cement. For example, modification using a
 reactive silicon (Si(IV) moiety) is proposed in U.S. Pat. Nos. 4,710,540
 and 4,952,631. However, it is inevitable that the chemical modification of
 polyolefin results in a high cost as compared with multipurpose
 polyolefin.
 SUMMARY OF THE INVENTION
 In order to solve the problems in the conventional deformed fiber and
 deformed short fiber as mentioned above, an object of the present
 invention is to offer deformed long fiber and deformed short fiber in a
 low cost which is composed of thermoplastic resin of a common commercial
 base and is capable of ensuring the stable quality in a continuous
 production.
 The first feature of the present invention is a deformed fiber consisting
 of long fiber where parallel yarns consisting of plural filaments spun
 from a thermoplastic resin are unified by means of connecting parts formed
 with appropriate intervals to the longitudinal direction of the yarn.
 The second feature of the present invention is a deformed fiber where short
 fiber is prepared from the parallel yarns in which most of them have
 plural connecting parts.
 The third feature of the present invention is a deformed fiber where the
 above deformed short fiber is advantageously used as a fiber for
 reinforcement of cement.
 To be more specific, the present invention relates to a deformed fiber
 where parallel yarns consisting of 2-5 filaments of a single yarn fineness
 of 500-5,000 deniers spun from a thermoplastic resin are unified by means
 of connecting parts formed with intervals of 1-30 mm on a longitudinal
 direction of the yarn to give a fiber of total fineness of 2,000-12,000
 deniers and the resulting fiber wherein most of the parallel yarns still
 have plural connecting parts is made into a short fiber within a fiber
 length range of 5-100 mm. The thermoplastic resin which is advantageously
 used here is a polypropylene resin having an isotactic pentad rate of not
 less than 0.95 and melt flow rate of 0.1-50 g/10 minutes.

DETAILED DESCRIPTION OF THE INVENTION
 There is no limitation for the thermoplastic resin giving the deformed
 fiber of the present invention so far as it is a resin which can be spun.
 Its examples are polyolefin resins such as linear low-density
 polyethylene, medium-density polyethylene, high-density polyethylene,
 polypropylene, polybutene-1, poly-4-methylpentene-1, ethylene-vinyl
 acetate copolymer, ethylene-ethyl acrylate copolymer, polyolefin modified
 with maleic acid anhydride and ethylene-propylene copolymer, polyvinyl
 chloride, polystyrene, polyester, polyamide and polyvinyl alcohol. Each of
 the above-mentioned thermoplastic resins may be compounded with various
 additives such as antioxidant, lubricant, ultraviolet absorber, antistatic
 agent, inorganic filler, organic filler, cross-linking agent, foaming
 agent and nucleic agent depending upon the object of use of the fiber.
 The deformed fiber of the present invention has a characteristic in its
 shape. As one of the examples, the deformed fiber 1 of the most basic two
 parallel yarns is shown in FIG. 1. The first characteristic feature of
 this deformed fiber 1 is that plural filaments 2 are in a parallel state.
 The second characteristic feature is that a unified fiber is formed by a
 partial connection at connecting parts 3 of the adjacent filaments 2.
 Connection of the filaments 2 with appropriate intervals by means of the
 connecting parts 3 expands the surface area as the deformed fiber and
 forms undulation on the fiber surface. Due to such characteristic
 features, deformed fiber which can be used in various uses is prepared.
 For example, when this deformed fiber is used as pile yarns for artificial
 grass, light is irregularly diffused on the fiber surface to suppress the
 gloss of the surface whereby an appearance similar to natural grass is
 achieved. In addition, woven cloth consisting of the deformed fiber has a
 good compatibility with coated/adhered laminated resin or latex whereby a
 strong adhesion is achieved. Further, as shown in FIG. 1, the unified
 filaments 2 have gaps 4 in addition to the connected parts 3. Therefore,
 the woven cloth in which this deformed fiber is incorporated has a high
 strength and the gaps 4 become aeration pores. As a result, it can be used
 for filters, agricultural coating materials, etc. where an appropriate gas
 permeability is requested.
 As hereunder, method for the manufacture of the deformed fiber of the
 present invention will be illustrated. However, the gist of the present
 invention is in a specific shape of the deformed fiber and, therefore, the
 present invention is not limited to the following manufacturing method.
 Firstly, the above-mentioned thermoplastic resin which is poured into an
 extruder together with additives if necessary is extruded from plural
 nozzles in a heated and melted state, cooled, subjected to a longitudinal
 uniaxial elongation to an extent of about 3- to 15-fold by a heating
 elongating machine such as a hot roll type, a hot plate type and a hot-air
 oven type and then subjected to a relaxation treatment to spin into
 parallel yarns having high rigidity, high strength and low elongation.
 The parallel yarns may be in such a state that plural filaments 2 are
 aligned and it is not necessary to be completely separated or spaced. The
 term parallel yarns also cover connected yarns where a part of the
 adjacent filaments having more undulations than the yarns in a simple
 shape are adhered. Therefore, the nozzle hole of each nozzle may be
 separated each other and arranged in parallel or a part of the adjacent
 nozzle holes may be connected. Even if the adjacent filaments are adhered
 to give connected yarns at the stage before elongation, that is an
 adhesion at the part where the thickness is thin and the thermal
 elongation takes place highly to the longitudinal direction whereby an
 orientation is given and the product is apt to be cracked to the
 longitudinal direction. In addition, the filaments in a connected yarn can
 be separated by breaking into a single yarn filament by a step where outer
 force such as formation of connecting part which will be mentioned later.
 Unless the plural nozzles in parallel are made in a specific positional
 relation or shape, it is easy to make the filaments in a connected yarn
 into a single yarn. Shape of the nozzle may be not only in circle or
 ellipse but also in polygon such as triangle and tetragon and other
 irregular shape such as Y-shape or star-shape.
 After that, partial connecting parts 3 are formed in the parallel yarns and
 plural filaments are made into one single fiber. The connecting parts 3
 may be formed by a method where other materials such as adhesive and
 binder are applied to the filament followed by drying. However, in such a
 method, treating steps are complicated and production speed is not high
 whereby that is less practical. Appropriate methods are that where bar,
 plate, roll, etc. in which the surface is made uneven by means of
 engraving are pushed with heating or the filament is sandwiched by them
 and that where the filament is crushed and the spread area is subjected to
 a thermal adhesion to form a connecting part 3. The above methods are the
 applicable art and that is because the filament 2 is a thermoplastic
 resin. The use of emboss roll is particularly effective because the
 connecting parts 3 can be formed quickly and in a stable manner. The
 connecting parts 3 suppress the isolation of the parallel yarns and, at
 the same time, form the undulations on the fiber surface. Thus, the
 parallel yarns themselves result in undulations to the direction of width
 of the fiber while the connecting parts 3 result in undulations to the
 direction of length of the fiber.
 The deformed fiber 1 consisting of such a fiber can be used as fiber for
 weaving/knitting and as pile fiber in a normal state or in a crimped or
 twisted state. Further, it can be cut by a roller cutter or a straw cutter
 to cut the fiber length into a short size and the resulting one can be
 used as a short fiber. This deformed short fiber can be used as a material
 for felt or nonwoven fabric as a fiber web. It is particularly effective
 as a fiber for reinforcement of cement. The deformed short fiber of the
 present invention used as a fiber for reinforcement of cement will be
 explained as hereunder.
 The deformed short fiber of the present invention which is used as a fiber
 for reinforcement of cement may use the above-mentioned resin or the like
 which can be fusion molded to thermoplastic resin. Polypropylene resin
 having high crystallinity, high rigidity and easy molding property is
 particularly preferred.
 The polypropylene resin used here means a homopolymer of propylene, known
 polypropylene copolymers such as ethylene-propylene block copolymer and
 random copolymer and a mixture thereof. Among them, a homopolymer of
 propylene is preferred for reinforcement of cement which is requested to
 exhibit high strength and thermal resistance. That which has an isotactic
 pentad rate of not less than 0.95 is particularly preferred. The isotactic
 pentad rate is a value measured by means of .sup.13 C-NMR reported by A.
 Zambelli, et al. in Macromolecules, 6, 925 (1973) and is an isotactic
 ratio in terms of a pentad unit in polypropylene molecule. The higher this
 value, the higher the crystallinity and, as a result, rigidity and thermal
 resistance of the molded product are improved. With regard to the melt
 flow characteristics of the resin, the melt flow rate (MFR) is selected
 from the range of 0.1-50 g/10 minutes, preferably 1-40 g/10 minutes or,
 more preferably, 5-30 g/10 minutes.
 In the deformed short fiber used as a fiber for reinforcement of cement, it
 is preferred that each of the filaments which constitute the parallel
 yarns has a fineness of 500-5,000 deniers. As a reinforcing effect of the
 fiber for reinforcement of cement, it is generally expected that the
 initial elastic modulus of the fiber is 150-700 kg/mm.sup.2. Fineness is
 settled from this viewpoint by taking the shape of fiber and the spinning
 property and the dispersing property in cement of the filament into
 consideration.
 Appropriate intervals between the connecting parts are within a range of
 1-30 mm. Thus, when the interval is less than 1 mm, the fiber is in a form
 of tape and the effect as parallel yarns is poor whereby the homogeneous
 dispersion in concrete is difficult while, when the interval is more than
 30 mm, an adhesive force of the short fiber is low, isolation of filament
 is apt to take place and the effect of reinforcing the cement,
 particularly the effect against pulling out of fiber, is poor.
 In the deformed short fiber, the filaments are in parallel and the fiber
 consists of at least two filaments although the upper limit of the numbers
 of the parallel yarns are about five. This upper limit is closely related
 to the fineness of the filament of the above-mentioned single yarn. In the
 deformed short fiber where many filaments of low fineness are aligned in
 parallel, the initial elasticity is low and enlargement of the undulations
 on the surface cannot be expected. On the other hand, filament of high
 fineness has a poor productivity and there is a problem in handling such
 as worsening of dispersibility upon compounding with cement. Therefore,
 the total fineness of the parallel yarns is preferably 2,000-12,000
 deniers. Thus, when the total fineness is less than 2,000 deniers,
 handling as a fiber for reinforcement of cement is poor while, when it is
 more than 12,000 deniers, fiber blocks are formed upon compounding with
 cement resulting in bad dispersion whereby the reinforcing effect for
 molded cement product is not well achieved. However, in the use other than
 for the fiber for reinforcement of cement, the fiber is not limited to the
 above-mentioned conditions.
 Fiber length of the deformed short fiber is to be 5-100 mm or, more
 preferably, 15-80 mm. Thus, when the fiber length is shorter than 5 mm,
 detachment from the compounded cement is apt to take place while, when it
 is longer than 100 mm, dispersibility is poor and that is not preferred.
 When the fiber length is within the above-mentioned range, most of the
 short fiber is present in a state of parallel yarn having plural
 connections and that is suitable as a fiber for reinforcement of cement.
 The deformed fiber of the present invention can be applied with various
 treatments before and after cutting the molded fiber. For example,
 surface-active agent, dispersing agent, coupling agent, etc. may be
 applied on the fiber surface or corona discharge, irradiation with
 ultraviolet rays, irradiation with electron beam, etc. may be conducted to
 activate or cross-link the surface. The deformed short fiber is compounded
 with a hydraulic substance such as Portland cement, white Portland cement,
 alumina cement, gypsum and lime and is used as a material for public works
 and for constructions.
 EXAMPLES 1-7
 Polypropylene resin (isotactic pentad rate: 0.96: MFR=5.0 g/10 minutes;
 Tm=163.degree. C.) (100 parts by weight) was compounded with 1 part by
 weight of pigment of a gray type and 2 parts by weight of ultraviolet
 absorber. The mixture was poured into an extruder and extruded from dice
 having a lip where two nozzle pores were placed in parallel. The extruded
 material was cooled, subjected to a uniaxial longitudinal elongation by a
 hot-air oven elongating machine to an extent of 9.2-fold and subjected to
 a releasing treatment to give parallel yarns of total fineness of 6,400
 deniers consisting of two flat monofilaments having a single yarn fineness
 of 3,200 deniers.
 The parallel yarns were sent by in-line to a striped metal roll and made
 into a predetermined shape by means of an embossing process with
 compression and heating. As a result, the parts where width is expanded
 were heat-fused to give connecting parts. After that, parallel yarns were
 dipped in an aqueous surfactant solution in which 50 parts by weight of
 polyoxyalkylene alkyl phenyl ether phosphate (HLB=9) and 50 parts by
 weight of polyoxyalkylene fatty acid ester (HLB=12) were mixed. The dried
 parallel yarns were cut in a fiber size of 30 mm using a rotary cutter to
 manufacture a deformed short fiber of Example 1. Microscopic pictures of
 the fiber of Example 1 are shown in FIG. 2 (.times.10), FIG. 3 (.times.50)
 and FIG. 4 (.times.100). In the parallel monofilaments, formation of gaps
 of width of about 0.35 mm and length of about 2 mm was confirmed except at
 the connecting parts.
 In Examples 2-7, the same materials and manufacturing method as in Example
 1 were applied although fineness and numbers of monofilaments and fiber
 length were changed. In Comparative Examples, polypropylene fiber, Vinylon
 fiber and steel fiber in a common monofilament shape were selected and
 evaluated. Data for each of them are given in Table 1.
 TABLE 1
 Total Fineness
 (Single Yarn Specific Fiber
 Items Material Shape Fineness) Gravity Length
 Example 1 PP 2 in parallel 6,400 (3,200) 0.91 30 mm
 deniers
 Example 2 PP 2 in parallel 6,400 (3,200) 0.91 15 mm
 deniers
 Example 3 PP 2 in parallel 6,400 (3,200) 0.91 80 mm
 deniers
 Example 4 PP 2 in parallel 3,200 (1,600) 0.91 30 mm
 deniers
 Example 5 PP 3 in parallel 2,400 (800) 0.91 30 mm
 deniers
 Example 6 PP 3 in parallel 9,600 (3,200) 0.91 30 mm
 deniers
 Example 7 PP 5 in parallel 8,000 (1,600) 0.91 30 mm
 deniers
 Comp. PP single yarn 6,400 deniers 0.91 30 mm
 Ex. 1
 Comp. Steel single yarn 0.6 mm diameter 7.8 30 mm
 Ex. 2
 Comp. PVA single yarn 6,200 deniers 1.3 30 mm
 Ex. 3
 Examples and Comparative Examples were evaluated as follows as fibers for
 reinforcement of cement. Each sample was prepared as follows. Thus, 100
 parts of high-early-strength Portland cement, 220 parts of sand of
 standard roughness, 110 parts of broken stone and 60 parts of tap water
 were kneaded in a rotary drum mixer for about two minutes, 1% (by volume)
 of a deformed short fiber was added under stirring the mixer and the
 mixture was kneaded for one minute more and hardened by pouring into a
 mold to prepare a sample. The sample was evaluated in accordance with
 "Test Method for Compressive Strength and Compressive Toughness of
 Concrete Reinforced by Steel Fiber" regulated by the Japanese Society of
 Civil Engineering (JSCE G551-1983), "Test Method for Bending Strength and
 Bending Toughness of Concrete Reinforced by Steel Fiber" regulated by the
 Japanese Society of Civil Engineering (JSCE G552-1983), JIS-A1132 and
 JIS-A1106 and the result is given in Tables 2 and 3. Table 2 shows the
 relative comparison of reinforcing effect for concrete due to changes in
 diameter and length of fiber based upon the data for the short fiber
 prepared in Example 1. Table 3 shows the influence of fineness, fiber
 length, numbers of parallel yarns, etc. on physical property of cement in
 Examples 2-7 which are within the coverage of the present invention.
 TABLE 2
 Compressing Tensile Bending Bending
 Evaluating Strength Strength Strength Toughness
 Items (N/mm.sup.2) (N/mm.sup.2) (N/mm.sup.2) (N .multidot. mm)
 Example 1 41.8 4.03 5.10 27.4
 Comp. Ex. 1 35.6 3.07 3.75 17.6
 Comp. Ex. 2 43.6 4.00 5.23 30.7
 Comp. Ex. 3 38.1 3.12 3.77 16.2
 TABLE 3
 Compressing Tensile Bending Bending
 Evaluating Strength Strength Strength Toughness
 Items (N/mm.sup.2) (N/mm.sup.2) (N/mm.sup.2) (N .multidot. mm)
 Example 2 35.8 3.84 4.98 25.4
 Example 3 42.9 4.22 5.23 28.6
 Example 4 35.0 3.88 5.00 25.4
 Example 5 33.6 3.80 4.87 24.7
 Example 6 45.4 4.45 5.22 28.1
 Example 7 43.3 4.11 5.14 26.3
 From the result of Table 2, far better reinforcing effect to cement was
 noted in Example 1 than the synthetic resin fiber in a conventional shape
 as shown in Comparative Examples 1 and 3. The effect is in such an extent
 that the effectiveness resulted by the deformed short fiber in a specific
 shape can be confirmed and is in such a high level as the steel fiber of
 Comparative Example 2 has. From the result of Table 3, there is a tendency
 that, in the case of a short fiber, the longer the fiber length or the
 more the total fineness, the better the reinforcing effect. In actual use,
 an appropriate selection is necessary depending upon the object and use of
 the molded cement product and applying method taking the homogeneous
 dispersibility with cement and the inconveniences such as resistance
 during the transportation by pipe into consideration. From the measured
 values in the Examples, it has been confirmed that, in various
 specifications, the short fiber of the present invention greatly improves
 the physical property of the molded cement product.
 EXAMPLE 8
 High-density polyethylene was poured into an extruder as a material and
 extruded from dice having a lip where three nozzle holes are placed in
 parallel. The extruded material was cooled, subjected to a uniaxial
 longitudinal elongation by a hot-air oven elongating machine to an extent
 of 7.5-fold and subjected to a releasing treatment to give parallel yarns
 of total fineness of 2,400 deniers consisting of three flat monofilaments
 having a single yarn fineness of 800 deniers.
 The parallel yarns were sent by in-line to a striped metal roll and made
 into a predetermined shape by means of an emboss process with compression
 and heating. As a result, the parts where width is expanded were
 heat-fused to give a deformed fiber having connecting parts with 10 mm
 intervals. This deformed fiber was used as warps and woofs in a count of
 (15.times.15)/inch and woven into a plainly woven tissue and the resulting
 product was used as a net for prevention of sprinkling of the paint upon
 application. Undulation of the surface of the deformed fiber expanded the
 surface area of the fiber and improved the adhesion of mist. As a result,
 the product showed additional 20% or more mist-collecting effect as
 compared with the net where common monofilament was used.
 EXAMPLE 9
 The same operation as in Example 8 was conducted except that 2 parts by
 weight of a green pigment was compounded with 100 parts by weight of Nylon
 6 resin to manufacture a deformed fiber consisting of three parallel
 yarns. Then this deformed fiber was planted on a tufted cloth as a cut
 pile to prepare an artificial grass where the back surface was processed
 with latex. The resulting artificial grass showed so good compatibility
 between the latex with the roots of piled yarns at the back surface of the
 tufted cloth that they were strongly adhered and unified. In addition, the
 artificial grass which was placed outdoor showed a good recovery after
 stepped-on pressure and the artificial grass was found to have a good
 appearance where artificial gloss was suppressed.
 As illustrated hereinabove, the deformed fiber of the present invention has
 a specific shape where parallel yarns consisting of plural filaments are
 connected at the connecting parts having a predetermined intervals to a
 longitudinal direction of the fiber. Therefore, in terms of manufacture,
 parallel yarns spun from thermoplastic resin are the basic constitution
 and its manufacture is easy whereby the product can be manufactured in a
 low cost together with keeping the quality in the continuous production.
 In terms of use, undulations formed on the surface and spaces among the
 filaments make the surface area of the fiber bigger whereby compatibility
 with laminated resin or latex is good and a strong adhesion is now
 possible. Further, the use where the spaces in the deformed fiber function
 as aeration pores is possible and, therefore, the deformed fiber of the
 present invention can be used in various product forms.
 Especially, the deformed short fiber prepared by cutting the above deformed
 fiber and used as a fiber for reinforcement of cement shows easy handling
 such as transportation and pouring due to its small specific gravity as
 compared with the frequently used steel fiber and is economical where the
 weight of the fiber compounded with cement in the same ratio by volume is
 small. In addition, in terms of reinforcement of cement, there are more
 undulations on the surface than the fiber in a simple shape and,
 accordingly, the uneven surface significantly improves a physical binding
 to concrete, etc. to prevent the separation of the material and to
 suppress the pulling-out of the fiber after hardening whereby the
 reinforcing effect in the same degree as in the case of steel fiber can be
 expected. Further, unlike the steel fiber, the possibility of punctured
 injury on the sole caused by the fallen fiber due to a rebound is little
 and beautiful appearance of concrete is not deteriorated due to no
 generation of rust. Thus, as a whole, the present invention is quite
 effective as a fiber for reinforcement of cement.