JP2829762B2 - Manufacturing method of reticulated molded body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a net-like molded product, and particularly to a structure used in the field of civil engineering and construction, particularly as a plate-like structure such as a roof, a wall, a floor, and a pit. The present invention relates to a fiber-reinforced inorganic plate and a method of producing a reticulated molded body capable of effectively exhibiting properties such as tensile strength and elastic modulus of a reinforcing fiber in an FRP.

[Conventional technology]

Conventionally, various proposals have been made for a fiber-reinforced inorganic plate, and a fiber-reinforced inorganic plate in which short fibers as a reinforcing material are randomly oriented, and a fiber-reinforced inorganic plate in which continuous fibers are oriented and laminated in one or two directions. (Kashima Institute of Construction Technology Annual Report No. 29, pp. 81-88, and No. 30,
57-68: JP-A-59-138647).

A fiber-reinforced inorganic plate cannot provide a reinforcing effect commensurate with the strength of the reinforcing material unless the bonding strength between the fiber as the reinforcing material and the inorganic material as the binder is sufficient. This problem is particularly important when high strength reinforcements or fiber bundles are used. That is, when used in a carbon fiber of 80 kgf / mm ² as low strength short fiber monofilament, for the surface area of the fibers is larger than the cross-sectional area of the fibers, the fibers when the tensile stress is added It exerts a reinforcing effect until it breaks. However, when a high-strength fiber or fiber bundle is used, the fiber comes off and a reinforcing effect corresponding to the original strength of the reinforcing fiber cannot be obtained.

In order to improve this, there has been proposed a method in which continuous high-strength fibers are formed into a entangled woven fabric having a strong intersection-binding force, a resin is impregnated and cured to form a net-like molded body, and then arranged in a cement mortar. JP-A-63-111045 and JP-A-63-22636). However, at present, the original tensile properties of the fibers of the woven fabric, that is, tensile strength, elastic modulus, etc., have not yet been fully utilized.

[Problems to be solved by the invention]

The present invention eliminates the drawbacks of the conventional entangled fabric molding,
It is an object of the present invention to provide a method for producing a reticulated body in which the intrinsic tensile properties of a woven fiber are exhibited more.

[Means for solving the problem]

The present invention relates to a method for producing a net-shaped molded article in which an entangled fabric is fixed with a resin, after impregnating the entangled fabric with a resin, solidifying the resin in a state where tension is applied in a weft direction of the woven fabric,
And the tension is the preparation of reticulated molded body characterized by weft tortuosity C _f of the net shaped body defined by the following formula is such strength less than 0.03 L _f : average distance between adjacent warps D _f : average distance between one vertex of the center line waveform of the weft and a line connecting two adjacent vertices in the cross-section along the weft direction of the reticulated body It is.

Hereinafter, before describing the present invention, a conventional entangled fabric will be described first.

In the weave structure of the entangled fabric, as shown in FIG.
A set of warps 1, 1 'is entangled with each other and bent. Further, as shown in FIG. 1 (b), the weft 3 is subjected to a force in the length direction by the warp yarns 1 and 1 ', and therefore is also bent. A reticulated formed body using a woven fabric conventionally used for cement mortar is obtained by fixing such an entangled woven fabric with a resin. When a load is applied to this molded body, the fibers are not straightened because the fibers are fixed with resin, and when the load increases, local strain and stress concentration are likely to occur in the bent portion, and the original fiber strength is 100% The inventor of the present invention has found that breakage occurs at the bent portion before being exerted.

Particularly, conventionally, in the case of continuously manufacturing a net-shaped molded article from an entangled fabric, the entangled fabric is impregnated with a resin liquid by using a prepreg manufacturing apparatus, and then dried and cured. At this time, since tension is applied in the warp direction of the woven fabric, the weft receives the force of the warp and the bend of the weft increases, and the weft is fixed as it is with the resin. It has been found that this causes a reduction in the strength of the reticulated body, particularly in the weft direction.

According to the present invention, when tension is applied in the weft direction when the entangled fabric is fixed with the resin, and the degree of bending described below is made smaller than a specific value, the inherent tensile properties of the fiber are utilized.

Tortuosity C _f of the weft as defined above in the present invention are those representing the degree of bending of the weft. This will be described with reference to FIG. In the drawings, the bending of the yarn is exaggerated for easy understanding.

FIG. 2 is assumed to be an enlarged photograph of a net-like molded product (fixed with a resin) cut along the weft direction, the cut surface placed vertically on top, and taken from directly above. Draw the center line 11 of the weft 3 and measure the distance D _f between one vertex 12 of the center curve 11 and a straight line 15 connecting the vertices 13 and 14 adjacent thereto.
By dividing the distance L _f between the warp yarns, the tortuosity of the weft (C _f).
In the present invention, C _f is an average value of values from at least 10 randomly selected points.

In the present invention, curvature of C _f weft <0.03, preferably <0.
02. In conventional entangling fabric by the inventors examined, it is generally C _f is 0.08 degree or more.

The tensile properties of the mesh shaped body fixed in a small state of bending, as defined by C _f in the present invention will be described below.
For this purpose, a concept called fiber utilization factor (F) is used. Tensile speed of reticulated body sample (width 25mm, length 15mm)
The breaking strength A per unit cross section of the fiber is determined from the breaking strength obtained by pulling at 0 mm / min. A is divided by the strength B per unit cross section of the fiber of the raw material for forming the reticulated body.

F (%) = A × 100 / B In a tensile test of a reticulated molded body solidified with resin, the bending (if any) of the yarn in the tensile direction is elongated and it is possible that the yarn is straightened without any local stress concentration. No break at break. It is considered that the resin itself contributes very little to the tensile strength. Therefore, if F is 100%, it means that the original strength of the used fiber is completely utilized. The larger the value of F, the smaller the amount of reinforcing material required to obtain a predetermined tensile property in a composite material using the same.

The strength utilization rate F of the reticulated molded body is determined by the type of fiber, the weaving method,
And are the resin amount is, in the present invention's prior art leno fabric molded body was studied when C _f is 0.08 as in the prior art F is about 40%. According to the present invention, when C _f is 0.03, F is about 60
% And C _f are 0.01, F becomes 70-80%.

As described above, in order to make the degree of bending of the weft less than the above-described value, tension may be applied in the weft direction when fixing with a resin.
The magnitude of the required tension varies from case to case and can easily be determined by experiment.

Preferably, the warp has a special structure, so that the bending in the weft direction can be reduced and the bending in the warp direction can be reduced at the same time. That is, the warp is composed of two or more yarns having different stiffness, and at least one yarn having the highest stiffness is substantially on one side of the weave structure. FIGS. 3 (a) and 3 (b) show a case where the warp is composed of two kinds of yarns. One set of warp yarns 1 and 2 is a highly rigid yarn 1
The high-rigidity yarn 1 is substantially not entangled, and the low-rigidity yarn 2 is tangled with 1 in order to avoid bending of the high-rigidity fiber and maintain linearity. Therefore, the high-rigidity yarn 1 is
It is almost straight and lies on substantially one side of the woven tissue.
On the other hand, as shown in FIG. 3 (b), since the weft 3 hardly receives the bending force of the warps 1 and 2, it is also substantially straight. When such a yarn is used, even if tension is applied in the weft direction, almost no force is required to bend the high-rigidity yarn 1, so that the strength in the weft direction can be improved without sacrificing the strength in the warp direction. In addition, although the case where two kinds of yarns are used as the warp and one kind of yarn is used as the weft is described above, the present invention is not limited to this. For example, two or more yarns can be used as the low-rigidity yarn and entangled. Two or more high-rigidity warps may be used, each of which may be entangled with a low-rigidity yarn. Two or more wefts can be used. The high-rigidity yarn needs to have high strength, and examples thereof include carbon fiber, aramid fiber, high-strength vinylon fiber, and glass fiber. The low rigidity yarn combined with the high rigidity yarn is expected to have only the intersectional binding force of the woven fabric. It can be selected from a wide range such as acrylic fiber, polyamide fiber and polyester fiber. The high-rigidity yarn and the low-rigidity yarn may have the same material but different cross-sectional areas (for example, different numbers of filaments and different fiber diameters) as long as there is a difference in the rigidity as a yarn.

The warp (not low rigidity) and the weft of the reticulated molded article of the present invention can be selected from carbon fibers having high strength, aramid fibers, high-strength vinylon fibers, glass fibers, and the like. When a cement component is used as the inorganic material matrix reinforced by the reticulated formed body of the present invention, it is preferable that the yarn has alkali resistance. Thus, it is easy to select an appropriate fiber according to the mixing conditions of the inorganic material matrix.

The weave density of entangled fabrics is generally coarse. For example, in the case of using aggregate-containing cement as the inorganic material matrix, it is desirable to set the openings at intervals of about 3 to 50 mm in consideration of the fact that the particle size of the aggregate (2 to 25 mm) can pass through the reticulated molded body. .

The resin for fixing the entangled fabric is impregnated into the woven fabric by a suitable means such as dipping or spraying. As the resin, any of a thermoplastic resin and a thermosetting resin can be used. In the present invention, it is preferable to use a thermosetting resin, and specific examples thereof include an epoxy resin, a urethane resin, a phenol resin, a polyimide resin, a vinyl ester resin, and an unsaturated polyester resin.
As the thermoplastic resin, a polyamide resin, a polyester resin, a polyphenylene sulfide (PPS) resin, a vinyl chloride resin, a polystyrene resin, or the like can be used. When a cement is present as a component of the inorganic material used as the matrix, it is desirable to have long-term durability against alkalinity, and if possible, even if subjected to autoclave curing at about 180 ° C. for about 5 hours. Those having a small decrease in strength are preferred.

After impregnating the resin, the resin is fixed while tension is applied to the entangled fabric in the weft direction. First, a case where a thermosetting resin is used will be described. With ordinary thermosetting resin,
What is necessary is just to harden the resin under tension. Thereby, the entangled fabric is fixed with the resin. Means for applying tension include curved rubber rollers, rotary sliding rollers,
A scroll, a tenter, or the like can be used, but a tenter in which the fabric does not entirely contact is most suitable. The resin before curing is in the A stage or the B stage. Since the curing of the resin is performed in order to maintain the form of the woven fabric, it is necessary that at least the resin does not flow. Complete curing is not necessarily required, and the B stage may be in a state close to the C stage. But,
From the viewpoint of product stability, it is preferable that the curing proceeds as much as possible. The means for curing is not particularly limited, and a known method can be used.

The respective curing stages used here will be briefly described. The A stage, the B stage, and the C stage are qualitative divisions and are not strictly defined. A stage refers to a state in which a crosslinking reaction has hardly occurred yet, and individual molecules are freely moving without being restrained.
The B stage refers to a state in which cross-linking is partially observed, but the degree of freedom of each molecule is large and fluidity is observed when heated. The C stage is a state in which crosslinking has progressed considerably and fluidity due to heating can no longer be seen.
In the present invention, as the definition of the C stage, the resin has a spinning property even when heated on a hot plate at any temperature, as shown in the curing time test method of a thermosetting resin (JIS C 6487). There was no state.

When using a curable resin with low fluidity before curing, among the curable resins, apply tension in the weft direction after softening the resin impregnated in the entangled fabric (or while softening). Alternatively, a method of curing the resin as it is can be used. Even under tension to the fabric without softening the resin, the weft does not become straight, the value of C _f of interest is not achieved, is softened by heating the resin once.
The heating temperature is equal to or higher than the softening point of the resin and is set to a temperature high enough not to denature the resin.

When using a curable resin which is easily deformed by heating even after curing, the resin is impregnated into the entangled fabric, cured, and then heated to a temperature higher than the softening point of the resin (or while being heated). A method can be used in which tension is applied to the resin, and then the resin is cooled to below the softening point of the resin and then the tension is released. In this method, the curing of the resin can be performed in a series of drying steps following the impregnation. Curing is performed until the resin is in the so-called C stage. Note that, in order to facilitate softening, it is preferable to set a state where hardening has not progressed much in the C-stage state, that is, a state where the softening point is low. The means for applying tension can use the same method as described above. In this case, in consideration of the ease with which the resin is deformed, it is preferable to heat the softening point by 50 ° C. or more. At this time, if the tension is released before cooling below the softening point, the resin has a three-dimensional crosslinked structure, so that a force acts to return to the state before the tension was applied. Therefore, the weft bending degree
It is extremely difficult to make the value of C _f less than 0.03. In addition, curing proceeds during heating to a temperature higher than the softening point, and the softening point of the resin may be further increased. Therefore, the cooling at the time of releasing the tension may be set below the softening point at this time.

When using a thermoplastic resin, after heating (or heating) the prepreg of the impregnated resin above the softening point of the resin, a tension is applied in the weft direction of the fabric to eliminate the bending of the weft, and then Allow to cool and solidify. As the means for applying tension, the method described above for the thermosetting resin can also be used.

Here, the softening point of the resin in the present invention is a temperature at which resin constituent molecules rapidly increase the degree of freedom of movement, and is qualitatively synonymous with a so-called glass transition point. Specific measurement methods include measuring the inflection point with a differential scanning calorimeter (DSC), measuring the inflection point of the elastic modulus with a viscoelasticity measuring device,
There are methods such as measurement of the coefficient of thermal expansion at the inflection point using a thermomechanical analyzer (TMA) and measurement of the softening point using the TMA, and they all show almost similar values. Adopted. That is, the softening point was measured as follows: First, a small piece (one resin-solidified thread) of a net-like molded body was cut out and placed in a TMA to measure the displacement in the thickness direction. The load is 20g and the temperature rise rate is 5 ℃ /
Minutes and the displacement due to temperature rise was recorded. In this temperature-displacement curve, a sharp decrease in thickness is observed at a certain temperature. The temperature at the intersection of the extension of the straight line before and after the inflection point was defined as the softening point.

In the present invention, it is essential to apply tension in the weft direction of the entangled fabric, but this does not exclude applying an appropriate tension in the warp direction.

As the inorganic hardened material as a matrix reinforced by the reticulated molded body of the present invention, Portland cement, alumina cement, ordinary cements such as blast furnace cement,
Various binders such as pulverized calcium silicate compound composed of calcareous and siliceous materials, gypsum (semihydrate gypsum, anhydrous gypsum, etc.), blast furnace slag, and granulated slag hydraulic material such as a mixture of granulated slag and gypsum Examples thereof include those obtained by kneading natural or artificial aggregates, admixtures, and admixtures with water and water as needed. Conventional plastics can also be used in FRP.The reticulated molded body obtained as described above is arranged at the position where the tensile stress of the structure is applied, the matrix material is poured, and the fiber is cured to obtain a fiber reinforced structure. . The strength, elastic modulus, number of filaments, and the like of the high-rigidity fiber to be used may be determined according to the target strength of the product, and the type of the fiber may be selected. As the structure using the reticulated molded article of the present invention, a plate-like article in which the reticulated molded article is embedded in the vicinity of the surface is particularly preferable. By using the reticulated molded article of the present invention, the strength and rigidity of the fiber-reinforced structure can be improved, or the amount of fibers of the reticulated molded article used as a reinforcing material can be reduced.

〔Example〕

Comparative Example 1 A carbon fiber bundle having a tensile strength of 460 kgf / mm ² (3,00
(A filament, single yarn diameter 7 micron), the same carbon fiber bundle (6,000 filaments) was used as the weft, and the weaving density was 3.3 / 25 mm for both the warp and the weft. A woven fabric having the structure shown in FIG. 1 and FIG. 1 (b) was produced.

 A resin solution for impregnation having the following formulation was prepared.

Bisphenol A type epoxy resin 100 parts (GY-260, manufactured by Ciba Geigy) Dicyandiamide 10 parts Imidazole type accelerator 2 parts (Curesol 2P4MHZ, Shikoku Kasei Co., Ltd.) Solvent (methyl cellosolve) 120 parts Using prepreg machine, apply resin to fabric. It was impregnated (41% by weight based on the molded body) and dried and cured at 150 ° C. for 15 minutes.

Comparative Example 2 A resin was impregnated in the same manner as in Comparative Example 1, dried, wound up as a B-stage prepreg, and then tensioned in the weft direction with a clip tenter.
Cured at 8 ° C. for 8 minutes. However, since the tension was reduced, C _f
Was 0.04.

It is similar to Example 1 Comparative Example 2, except 0 and C _f and strong tension.
01. The results are shown in the table below.

Here, F _f is the weft direction, the F _w represents the intensity utilization warp direction.

Example 2 A set of warps has a tensile strength of 46 as a highly rigid fiber.
0kgf / mm ² carbon fiber bundle (6,000 filaments, single yarn diameter 7
Micron) as an aramid fiber Kevlar
29 (400 denier) was used. The same carbon fiber bundle (6 k, fil) as above was used as the weft.

Weaving density is 3.3 / 25mm for both warp and weft yarns.
A woven fabric having the structure shown in FIG. 3A and FIG. 3B was produced.

Impregnated with resin in the same manner as in Example 1 to make a prepreg,
Next, it was cured by applying tension in the weft direction. The results were as follows.

Use the C _{f F f F w} 0.005 using the same tangled fabric and 79% 78% Comparative Example 3 Comparative Example 1, the impregnating resin solution similar formulation except that the 1 part of imidazole accelerators and Comparative Example 1 Was. The woven fabric was impregnated with a resin using a prepreg machine (41% by weight based on the molded body), and dried and cured at 150 ° C. for 5 minutes.

Example 3 In the same manner as in Comparative Example 3, the entangled fabric was impregnated with a resin.
It was dried and cured at 0 ° C. for 5 minutes. At this time, the softening point of the resin was 53 ° C. The entangled fabric was fixed to a frame-shaped simple tenter capable of applying tension in two directions. This was placed in an oven at 180 ° C. for 1 minute, and when sufficiently softened, tension was applied in the weft direction of the woven fabric. Immediately after removing from the oven and cooling to room temperature, the reticulated molded body was removed from the simple type tenter. C _f of this reticulated body is 0.02
Met.

Example 4 Example 3 was repeated for the same entangled fabric as in Example 2. C _f of the resulting net shaped body was 0.01.

Comparative Example 4 Same as Example 4, but immediately after taking out the fabric from the oven, the tension was released and then cooled to room temperature. The obtained reticular molded body, in order to release the tension higher than the softening point temperature, then recovery bending of original yarn, C _f became 0.07.

The results in Examples 3 and 4 and Comparative Examples 3 and 4 are shown in the following table.

Comparative Example 5 The same entangled fabric as in Comparative Example 1 was used. Further, a resin solution for impregnation having the following formulation was prepared.

Cresol novolak type epoxy resin 100 parts (ECN 1280, manufactured by Ciba Geigy) Dicyandiamide 10 parts Solvent (methyl cellosolve) 120 parts Impregnated resin into woven fabric using a prepreg machine (41% by weight based on molded product), Dried for minutes. The resin was B-stage, but was in a solid state at room temperature. After winding this as a prepreg, tension was applied in the weft direction by a clip tenter, and the clip was pulled so that it slipped. Then, the clip was fixed and cured at 160 ° C. for 15 minutes. Although the tension was increased as much as possible, the prepreg at the time of applying the tension was kept at room temperature and the resin was in a solid state.

Example 5 A prepreg was produced in the same manner as in Comparative Example 5. This was tensioned in the weft direction by a clip tenter. At this time, hot air at 150 ° C. was applied to the prepreg for 1 minute to sufficiently soften the resin, and then tension was applied. Thereafter, the clip was fixed and cured at 160 ° C. for 15 minutes. The degree of bending of the weft of the obtained net-like molded product was extremely small.

Example 6 Using the same woven fabric as in Example 2, resin impregnation, drying, heat softening, and curing were performed under exactly the same conditions as in Example 5.

The results of Comparative Example 5 and Examples 5 to 6 are shown in the following table.

(Effects of the Invention) By the method of the present invention, while taking advantage of the entangled fabric, which is effective in imparting toughness to the matrix, the binding force between the yarns at the intersections, the tensile strength of the reinforcing fibers particularly in the weft direction, As a result, a reticulated body was obtained, which exhibited an elastic modulus effectively and could reduce the amount of reinforcing fibers added.

[Brief description of the drawings]

1 (a) and 1 (b) are a plan view and a cross-sectional view of an entangled fabric. 1, 1 '... warp yarn, 3 ... weft yarn Fig. 2 is an explanatory diagram of a method for measuring the degree of bending of a weft yarn. 1,2 ... warp yarn, 3 ... weft yarn 11 ... center line of weft yarn 12 ... vertex of center line waveform 13,14 ... ... adjacent vertex of center line waveform 15 ... 13 and 14 are connected Straight Line FIGS. 3 (a) and 3 (b) are a plan view and a cross-sectional view of an example of the specially entangled woven fabric molded article according to the present invention. 1 ... high rigidity warp yarn 2 ... low rigidity warp yarn 3 ... weft yarn

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hironori Naganuma 5-15-39 Kitaurawa, Urawa-shi, Saitama 819 (72) Inventor Yoshio Nakazawa 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Shin-Nippon Steel Corporation (1) Inside the Technical Research Institute (72) Inventor Ryusuke Hayashi 1618 Ida, Nakahara-ku, Kawasaki City, Kanagawa Prefecture New Nippon Steel Corporation 1st Research Laboratory (72) Inventor Kanji Yamada 1618 Ida, Nakahara-ku, Kawasaki City, Kanagawa Prefecture New Made in Japan (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 70/00-70/24 D06M 15/00-15/70

Claims (2)

(57) [Claims] 1. A method for producing a net-like molded product in which an entangled fabric is fixed with a resin, wherein after impregnating the entangled fabric with the resin, the resin is solidified in a state where tension is applied in a weft direction of the woven fabric; the tension methods for producing net shaped body, wherein the weft tortuosity C _f of the net shaped body defined by the following formula is such strength less than 0.03 L _f : average distance between adjacent warps D _f : average distance between one vertex of the center line waveform of the weft and a line connecting two adjacent vertices in the cross-section along the weft direction of the reticulated body . 2. The warp of the entangled fabric is composed of two or more kinds of yarns having different stiffness, and at least one kind of the yarn having the highest stiffness has a bend so as to exist on substantially one side of the woven structure. 2. The method according to claim 1, wherein the amount is small.