JPH07107102B2 - Fiber reinforced resin molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention provides a polyvinyl alcohol-based synthetic fiber (hereinafter abbreviated as PVA-based fiber) having a flat cross section and a large crystal length-width ratio. The present invention relates to a fiber-reinforced resin molded product (hereinafter abbreviated as FRP) used as a reinforcing material.

<Prior Art> Conventionally, glass fiber is the most popular as a reinforcing material for FRP and is used in a wide range of fields. However, in recent years, diversification of demand fields and high functionality have been demanded, and in particular, organic fibers have been attracting attention as a reinforcing material satisfying impact resistance and light weight.

PVA fibers have the highest strength and elasticity among general-purpose organic fibers and are used in many industrial material applications by taking advantage of their performance, but they are suitable for reinforcing physical properties and reinforcement as reinforcing materials for FRP. No one having a fiber morphology has been obtained.

The performance required of the reinforcing fiber is said to be firstly high strength and high elasticity. When the fibers do not have sufficient strength and elasticity, the obtained fiber-reinforced molded product naturally does not have toughness.

Secondly, the performance required is that the reinforcing fiber has excellent adhesiveness with the FRP resin. When the adhesion between the reinforcing fiber and the FRP resin is insufficient, the fiber-reinforced molded product will not be cracked or broken while the strength and elasticity of the reinforcing fiber are not fully utilized against external stress and the reinforcing effect cannot be obtained. Will occur. It is effective to increase the surface area of the fiber in order to improve the adhesiveness between the fiber and the FRP resin, and specifically, there are methods such as flattening, deforming, and fine denier of the cross section of the fiber.

The most typical method of producing PVA-based fibers is a method in which a PVA aqueous solution is wet-spun during coagulation / melting at room temperature containing salts having a dehydrating ability, stretched, heat-treated, and optionally acetalized. is there. Although the PVA-based fiber obtained by this method has a relatively large surface area with a cocoon-shaped cross section having a two-layer structure of a skin core as well known,
Since it can be drawn only at a total draw ratio of about 8 times and the strength is only about 7 g / d, it is unsatisfactory as a reinforcing fiber from the viewpoint of strength.

Also, as a method for obtaining higher strength PVA-based fibers,
There are methods proposed in the publications such as 8-32623, JP-B-53-1368, JP-A-60-126312 and JP-A-61-108712. However, although the fibers obtained by these methods have greatly improved strength and elasticity, they are extremely homogeneous and have a cross section close to a circle. As the reinforcing fibers have a small surface area, they have an adhesive force with FRP resin. It is low, and even with such fibers, the FRP obtained is not satisfactory in terms of mechanical properties.

On the other hand, as a means for intentionally increasing the surface area, there is a method in which a modified nozzle is used for spinning and the cross section is modified. However, in this method, in the case of PVA type fibers, it is necessary to increase the spinning draft, and accordingly, not only the drawability is greatly reduced and the strength is lowered as compared with the case of using a normal circular nozzle,
It is not preferable because the spinnability is deteriorated and the productivity is reduced.
Another method is to increase the surface area of the fiber per unit amount by decreasing the denier of the fiber, but the direction of fine denier causes a decrease in spinnability and productivity and is further obtained. This is not preferable because the dispersibility of the fiber in the matrix is deteriorated.

As described above, the PVA-based fibers that have been known so far have high strength and
There is nothing that has both high elasticity and adhesiveness with FRP resin, so no PVA-based fiber reinforced resin molded product with high strength, high elasticity and excellent impact resistance has been obtained. .

<Problems to be Solved by the Invention> In view of the above points, the present invention has an object to provide an FRP that has high strength and high elasticity and is excellent in impact resistance.

<Means for Solving Problems> As a result of examining the reinforcing effect of various PVA-based fibers in order to develop an FRP having excellent mechanical properties, the reinforcing effect was found to be the strength of the reinforcing fiber.・ The ratio of the length (L) to the width (W) of the fiber crystal (hereinafter abbreviated as L / W) is more closely related than the elastic modulus, but a sufficient reinforcing effect is obtained. It is essential that the L / W is 2.1 or more and the cross-section solidity is 65% or less, and preferably, the L / W is 2.3 or more and the cross-section solidity is 60% or less. Invented. The crystal length L of the fiber has little correlation with the mechanical properties and reinforcing effect of the fiber, and L /
The strong correlation appears for the first time as W.

An effective method for producing a PVA-based resin used in the present invention is a spinning stock solution of a PVA aqueous solution containing boric acid or a borate salt,
This is a method of wet spinning into an alkaline coagulation solution at 55 to 95 ° C. containing a salt having a dehydrating ability, and stretching the resulting spun raw yarn at a draw ratio of 17 times or more. Such a method is conventionally 20 ~ 50 ℃
This is performed at a solidification melting temperature of
It is characterized in that the temperature is raised to ℃. The obtained fiber has a flat cross section, and since the drawability is greatly improved, the L / W of the fiber is increased and the mechanical properties of the fiber are also significantly improved. I'm not sure why, but
It is considered that the solidification mechanism is completely different from that of the conventional spinning method.

Hereinafter, one example of the method for producing the PVA fiber used in the present invention will be described in detail.

The degree of polymerization of PVA used is 1500 or more, preferably 2000 or more,
More preferably, it is 3000 or more.

The spinning solution is an aqueous solution having a concentration of 5 to 30% by weight of the PVA,
The content of boric acid or borate is 0.5 to 5% by weight based on the PVA, and the concentration of PVA is preferably 6 to 25% by weight, more preferably 7 to 18% by weight, depending on the degree of polymerization of PVA. It is preferable to adjust it appropriately.

The spinning dope temperature is 85 to 125 ° C., preferably 95 to 120 ° C. If it is too low, the drawability is hindered, and if it is too high, the stock solution boils. In order to stabilize the spinning condition, an appropriate amount of organic acid such as acetic acid or inorganic acid such as nitric acid may be added to the stock solution for spinning.

The temperature for solidification and dissolution is 55 to 95 ° C, preferably 60 to 80 ° C.
When the temperature is 55 ° C or lower, the cross section of the fiber is not so flat, and the drawability is low, so that the L / W does not increase. On the other hand, if the temperature is 95 ° C or higher, it is not preferable because boiling of the coagulating bath and sticking between the single fibers occur.

A caustic alkali such as sodium hydroxide or potassium hydroxide is used as the alkali component of the coagulation bath, and the concentration thereof is 2
~ 200 g / l, preferably 5-50 g / l. Further, as the salt component of the coagulation bath, a salt having a dehydrating ability such as sodium sulfate and sodium carbonate is used, and the concentration is 100 g / l to a saturated concentration, and it is preferable that the concentration is close to saturation.

As the spinning nozzle, an ordinary circular nozzle or a nozzle having a shape close to it is used. For the fiber after spinning, alkali neutralization, wet heat drawing, washing with water, drying, drawing and heat treatment may be carried out in accordance with a usual method, but at least 17 It is necessary to perform stretching at least twice, preferably at least 20 times. The larger the draw ratio, the larger the L / W.
If it is less than 7 times, the L / W will not reach 2.1.

Regarding the thickness of the PVA-based fiber, a fiber having a thickness used in ordinary FRP, for example, 0.1 to 100 denier is used.

The resin used in the present invention is not particularly limited, and is a thermosetting resin such as unsaturated polyester resin, phenol resin, epoxy resin, melamine resin, polyester resin, polyamide resin, polyethylene resin, polypropylene. Either resin or thermoplastic resin such as polyvinyl chloride resin may be used.

In the present invention, such a PVA fiber may be used as a short fiber or a chopped strand, or may be used in a roving, woven or non-woven state depending on the application.

The ratio of the PVA fiber in the resin molded product of the present invention is 1 to 5
0% by weight is preferred. In the resin molded product of the present invention, P
In addition to the VA fiber and the resin, other fibers, fillers, curing agents, thickeners, coloring agents and the like may be added.

As a method for producing a molded product, a method of mixing the PVA-based fiber and the thermosetting resin with a kneader and subjecting the bulk molding compound to compression molding or injection molding, or a method of molding the thermosetting resin and the PVA-based fiber A method for forming a sheet molding compound by covering the opposite sides with polyethylene film or the like and forming a sheet molding compound, or a method for forming by a conventional handlay-up method, and the like are used. In any case, the PVA-based fiber can be formed into a molded body by the usual FRP manufacturing method, like the general-purpose glass fiber.

<Effects of the Invention> The FRP obtained according to the present invention has the following features.

1) Compared to conventional PVA fiber, the fiber used in the present invention is L / W
Is large, has excellent mechanical performance, and has a
Since the cross section is flat such as 65% or less and the surface area is large, the obtained FRP has high strength and high elastic modulus and high impact resistance.

2) The mechanical properties of FRP are far superior to those of general-purpose glass fiber, and the surface smoothness is improved, and the weight can be reduced.

By utilizing the above excellent performance, the fiber-reinforced resin composition of the present invention can be applied to a wide range of applications such as building materials, housing equipment, industrial parts, transportation equipment, automobiles, boats and the like.

Hereinafter, the present invention will be described more specifically with reference to Examples. Note that the cross-sectional solidity defined in the present invention (the degree of flatness of the cross-section,
The smaller the number is, the flatter it is), the length-width ratio (L / W) and the mechanical properties of the crystal are measured by the following methods.

○ Cross-section perfection A cross-sectional photograph of the fiber is enlarged to about 100 mm ² and the cross-sectional area F is obtained.

Next, the widest width B in the cross section was obtained and calculated by the following formula.

In addition, this value is obtained for 20 single fibers arbitrarily taken out from one multifilament yarn, and the average value thereof is defined as the cross-sectional solidity of the fibers constituting the multifilament yarn.

○ Ratio of crystal length and width It was measured under the following conditions by a known wide-angle X-ray diffraction method.

Wide-angle X-ray (1) Rigaku Denki Co., Ltd. rotating anticathode type X-ray diffractometer (Type RAD-rA) with 40kV, 100mA CuKα (Graphite Monochromator) scintillation counter (2) Goniometer slit system: DS1 / 2 °, SS1 / 2 °, RS0.15mm Scanning speed: 2θ = 1/2 ° / min (3) Sample (125 mg of fibers arranged in parallel with 2.5 cm in length and 1.5 cm in width) on the fiber sample stand Then, the diffraction curves of surface indices (020) and (100) were measured by the transmission method, and the half width B (hkl) of each curve was obtained.

Ratio of crystal size (L / w) Calculate each crystal size from Scherrer's formula from the value of half-value width B (hkl) of peaks of plane index (020) and (100) obtained by the above transmission method. did.

D (hkl) = Kλ / Bo (hkl) COSθ (hkl) where K = 0.9 λ = 1.5418 (Å) The spread of the diffraction curve after correction of the slit by the method of Bo: Jones (radian) θ (hkl): Bragg angle (Deg.) L / W = D (020) / D (100).

○ Dry rupture strength / elongation, initial elastic modulus (1) Sample …… Multifilament yarn (2) Dry rupture strength / elongation, initial elastic modulus …… Complies with JIS-1017 in an atmosphere of temperature 20 ℃ and relative humidity 65% Then, it was measured with an Instron tester at a test length of 20 cm and a pulling speed of 10 cm / min, and the initial elastic modulus was obtained from its elongation-load curve.

(3) Number of measurements: 10 measurements were performed and the average value was calculated.

Examples 1 to 3, Comparative Examples 1 and 3 Fully saponified PVA having a degree of polymerization of 3500 was dissolved in water to a concentration of 9% by weight, and boric acid was added to the PVA at 3.5% by weight to prepare a spinning dope. The spinning dope is then heated to 105 ° C and contains 6 g of sodium hydroxide and 350 g / l of sodium sulphate.
Through a die having a 1000-hole circular nozzle in a coagulating bath made of an aqueous solution at each temperature of 0 ° C. (Example 1), 70 ° C. (Example 2), 90 ° C. (Example 3) and 30 ° C. (Comparative Example 1). It was spun and allowed to leave the bath at a speed of 6 m / min. Subsequently, roller stretching, neutralization, wet heat stretching, washing with water and drying are carried out according to a conventional method.
Dry-stretching was performed at 230 ° C. to produce a reinforcing fiber having a single fiber fineness of 2 dr. The total draw ratio was 22.5 (Example 1), 26.8 (Example 2), 25.4 (Example 3) and 14.6 (Comparative Example 1).

Next, unsaturated polyester resin (manufactured by Takeda Yakuhin; Polymer
6709) 150 parts, MgO (Kyowa Chemical Co., Ltd .; Kyowamag 40F) 2
Parts, release agent (manufactured by NOF CORPORATION; zinc stearate) 8 parts,
Hardener (Nippon Petroleum; Perbutyl Z) 0.5 part and CaCO ₃
(Nitto Koka Kogyo; S Light # 1200) 275 parts were put in a kneader and mixed uniformly for 15 minutes. Then, 100 parts of the PVA fiber or commercially available glass fiber (comparative example 3) cut into 3 mm was added and further fixed for 5 minutes. After rapid stirring, BMC (bulk molding compound) was obtained. Put the obtained BMC in a mold and 160
FRP having a thickness of 5 mm was prepared by compression molding at 100 kg / cm ^{2 for} 10 minutes at ℃. The above results are shown in Table 1.

Comparative Example 2 A fully saponified PVA having a degree of polymerization of 3500 was dissolved in dimethylsulfoxide at a concentration of 10% by weight to prepare a spinning stock solution, which was dry-wet spun through a 50-hole nozzle into a methanol coagulation bath at 10 ° C. The obtained spun raw yarn was subjected to 6 times wet drawing while being desolvated and dried. Next, dry heat drawing was carried out at 240 ° C., and the total draw ratio was 24 times. The cross-sectional solidity of the obtained fiber was extremely high at 92% and was almost circular. L / W is 2.6
The strength was 21.0 g / d and the elastic modulus was 530 g / d. Using this fiber, an FRP was prepared in the same manner as in the above-mentioned example. The results are shown in Table 1.

From Table 1, L / W is 2.1 or more, and the cross-sectional solidity is 65%.
It is clear that the following FRP using PVA fiber is excellent in bending strength and impact resistance.

Bending strength performance evaluation method: According to JIS K 6911.

Falling ball impact test evaluation method; conforms to JIS K 7211.

Examples 4 and 5 Comparative Example 4.5 PV with cross-sectional solidity and L / W monofilament fineness 2dr shown in Table 2
Styrene-soluble vinyl acetate on A fiber (Dainippon Ink)
1% / fiber attached and cut into 1 inch to make a stranded strand mat. 100 parts of unsaturated polyester resin, 2 parts of MgO, 8 parts of release agent, 3 parts of curing agent (perbutyl Z) and A sheet molding compound (SMC) was manufactured by impregnating 300 parts of CaCO ₃ into a homogeneous mixture. Put this SMC in a mold, 160 ℃, 10 minutes, 100kg /
A FRP having a thickness of 5 mm was obtained by compression molding at cm ² . As is clear from Table 2, the FRP manufactured from the SMC reinforced with the PVA fiber of the present invention has excellent bending strength and impact resistance. Further, the same tendency as in Table 1 was observed even when PVA fibers having different cross-section perfection and L / W were used.

Front page continued (72) Inventor Shoichi Nishiyama 1-2-1 Kaigan-dori, Okayama-shi, Okayama Kuraray Co., Ltd. (72) Hideki Hojo 1-2-1 Kaigan-dori, Okayama-shi, Okayama Stock Company Within Kuraray (56) Reference JP-A-49-62550 (JP, A) Actually-opened 61-202443 (JP, U)

Claims (1)

[Claims] 1. A fiber-reinforced resin molded article comprising a polyvinyl alcohol-based synthetic fiber as a reinforcing material, which has a cross-sectional solidity of 65% or less and a crystal length / width ratio of 2.1 or more.