JP3314826B2 - Thermoplastic composite sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic composite sheet in which a reinforcing matrix fiber is uniformly impregnated with a thermoplastic matrix resin.

[0002]

2. Description of the Related Art Conventionally, as a product in this field, there has been a sheet-shaped prepreg obtained by impregnating a continuous reinforcing fiber with a thermosetting resin or a thermoplastic resin. However, there is a problem that a molded product obtained by laminating these molding materials into a certain structure has an extremely low delamination strength as compared with the reinforcing direction of the reinforcing fibers. For this reason, when a molded product is used for a long period of time, peeling between layers occurs, causing problems such as a decrease in strength and a decrease in reliability, and the characteristics of a fiber-reinforced composite material having excellent mechanical properties are not sufficiently utilized. In the current situation.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has as its object to provide a thermoplastic composite having improved interlayer and / or intralamellar peel strength of a molded product obtained by molding. To provide a sheet for use.

As a result of intensive studies to solve the above problems, the present invention has been completed.

[0005]

That is, the present invention comprises a composite yarn satisfying the following requirements (I) to (III) and has a critical strain energy release rate of 1.0K.
J / m ² or more, comprising: (I) a discontinuous reinforcing fiber, a discontinuous thermoplastic matrix fiber, and a continuous thermoplastic matrix fiber; and (II) the two discontinuous fibers are: Both are substantially non-twisted and are blended at a blending degree of 20% or more (II
I) The mixed fiber is wound and coated with the continuous thermoplastic matrix fiber in a weight ratio of 1% or more and 10% or less with respect to the composite yarn, and the above-mentioned (I) to (III) After textile processing a composite yarn satisfying the requirements, pressurizing at a temperature higher than the melting point of the discontinuous and continuous thermoplastic matrix fibers, impregnating the discontinuous and continuous thermoplastic matrix fibers into reinforcing fibers. To provide a method for producing the thermoplastic composite sheet.

Here, the degree of blending is defined by Equation 1.

(Equation 1) However, in the above formula, N is the total number of discontinuous reinforcing fibers,
NcX indicates the number of discontinuous reinforcing fibers when the group is divided into several groups, and X indicates the number of filaments in one specific group. Also, 100 (NX) / (N-
1) means a mixed fiber state, and the smaller X is, the better the mixed fiber state is, and NcX / (N / X) indicates how important the filament is to the visual effect in the whole mixed fiber. Or mean.

The discontinuous reinforcing fibers (hereinafter referred to as fiber A) used in the present invention include carbon fibers, aramid fibers, glass fibers and the like. However, the reinforcing fibers used in the present invention are not limited to the above fibers.

[0008] Discontinuous and continuous thermoplastic matrix fibers used in the present invention (hereinafter referred to as fiber B and fiber C, respectively)
Polyolefin fibers including polyethylene, polypropylene and copolymers and modified products thereof, nylon 6,
Examples include polyamide fibers such as nylon 66 and nylon 12, polyester fibers such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate fibers, polyetherimide fibers, polyphenylene sulfide fibers, and polyether ketone fibers. However, the thermoplastic matrix fibers used in the present invention are not limited to the above fibers.

The weight ratio of the fiber A used in the present invention is not particularly limited, but is preferably in the range of 30 to 80% with respect to the thermoplastic composite yarn.

The fibers A and B used in the present invention need to be substantially non-twisted fibers. This is because, when a composite sheet is prepared by forming the composite sheet after the textile processing, the fibers A are displaced at the time of molding, and both ends of the fiber are oriented in a three-dimensional direction, thereby improving the mechanical properties of the composite sheet.

The average fiber length of the fibers A and B used in the present invention is not particularly limited, but it is preferable that both of them are 50 mm or more.

The fibers A and B used in the present invention must be blended at a blending degree of 20% or more. This is because if the degree of mixing is 20% or more, impregnation of the fiber A into the fiber A is performed in a short time at the time of melting, but if the degree of mixing is less than 20%, the impregnation takes time and is uneconomical. This is because the mechanical properties of the molded product are reduced due to insufficient molding.

[0013] As a means for mixing, a continuous reinforcing fiber and a thermoplastic matrix fiber are separately cut out to obtain a sliver, and then the slivers are mixed and cut out to obtain a mixed sliver, or a continuous sliver is obtained. Any of the methods such as a method of drawing a reinforced fiber, mixing a discontinuous sliver of a thermoplastic matrix fiber obtained by a card process or the like with a continuous process or a roving process after obtaining a sliver, and obtaining a mixed sliver or a mixed roving yarn Means may be used.

The mixed fiber used in the present invention is wound and covered with the fiber C. The fiber C must have a weight ratio of 1% to 10% with respect to the thermoplastic composite yarn. By doing so, it is possible to achieve both textile processing properties and composite physical properties. This will be described in detail below.

Incidentally, the weight ratio referred to here is defined by equation (2). Weight ratio = {c / (a + b + c)} × 100 (%) (Equation 2) a: Amount of fiber A (g / m) b: Amount of fiber B (g / m) c: Amount of fiber C (g / m) m)

In the actual process, the thermoplastic composite yarn is subjected to heat and pressure so that the fiber B
And C are melted and impregnated into the fiber A, and after a cooling process, become a thermoplastic composite sheet. Therefore, as a factor that governs the physical properties and appearance of the thermoplastic composite sheet, the molten state of the above two types of fibers (fibers B and C) is raised. The main role of the continuous thermoplastic matrix fibers is in textile processability.
That is, the fibers A can be obtained without damaging the fibers during the textile processing, and it is satisfactory that the fibers A are cut into a predetermined shape as a material to be subjected to molding and preformed. It is important that once the pre-shaping has been performed, it melts as smoothly as possible and leaves no trace of the wound coating. If traces of the fiber C remain, a resin-rich portion exists and not only impairs the surface appearance of the molded product, but also deteriorates the mechanical properties of the molded product. In addition, the binding force of the fibers C acts during molding, so that the dispersion between the fibers A becomes insufficient, and the physical properties between the fiber bundles also decrease. In order to avoid these drawbacks, the weight ratio of the fiber C needs to be 10% or less, and on the other hand, in order to satisfy the above-mentioned textile workability, the weight ratio needs to be 1% or more.

Further, in order to improve the textile workability, it is preferable that the fiber C is wound and coated while being substantially uniformly dispersed in the yarn axis direction of the mixed fiber. As a method of substantially uniformly dispersing the fibers, the fibers C can be spread by an electric fiber spreader and then superimposed on the mixed fiber and supplied to an oscillating apron roller. However, the method is not limited to this method. Absent.

Further, as a means for improving the surface appearance of the thermoplastic composite sheet, it is effective to lower the melting point and the melt viscosity of the fiber C than that of the fiber B to improve the fluidity of the fiber C during molding.

As a surface treating agent for the thermoplastic matrix fiber, a so-called spinning oil is generally used in order to maintain the fiber production process and the post-process passability. However, since this type of treating agent inhibits the adhesive force between the reinforcing fiber of the composite and the matrix interface, it is preferable not to use it as much as possible in the present invention.

The composite yarn thus obtained is processed into a braid, a woven fabric, a knitted fabric or the like without damaging the reinforcing fibers during textile processing.
The reinforcing fibers can be arranged in the direction to be reinforced.

In the present invention, the composite yarn is subjected to a textile processing and then subjected to a molding step. At this time, the fibers B and C are heated to a temperature equal to or higher than the melting point of the fibers, and the fibers A are impregnated by applying pressure in a molten state to form a thermoplastic composite sheet. Here, the textile processing refers to fabricating a blade or the like from the composite yarn of the present invention, arranging and / or laminating the composite yarn of the present invention to a desired thickness, or combining these. It means things.

The critical strain energy release rate (G1c) of the thermoplastic composite sheet of the present invention is 1.0 kJ.
/ M ² or more. This is G1c 1.
If it is less than 0 kJ / m ² , when the obtained molded article is used for a long period of time, peeling off between layers occurs, and problems such as a decrease in strength and a decrease in reliability occur. Therefore, in the present invention, a non-twisted discontinuous fiber is used as the reinforcing fiber in order to improve G1c. This is because if the reinforcing fibers are non-twisted discontinuous fibers, the process of melting, pressing and impregnating the thermoplastic matrix fibers, compared with the case of continuous reinforcing fibers,
This is because the reinforcing fibers can easily move in the circumferential direction of the composite yarn, and both ends thereof are oriented in the three-dimensional direction, thereby improving the mechanical properties of the thermoplastic composite sheet, that is, G1c.

The G1c value is obtained as follows. First, the thermoplastic composite yarns are aligned in one direction and laminated, and a temperature of 250 ° C. and a pressure of 10 kg / c are set in a mold.
Pressurization is performed under the conditions of m ² and a holding time of 10 minutes, then cooled and taken out of the mold to form a flat plate having a thickness of 3 mm. In addition, in order to form a delamination part, when the mold is put into a mold, the thickness is 20 mm.
A μm aluminum foil is inserted into the center of the stack. The formed flat plate is cut into a width of 25 mm and a length of 150 mm to prepare a double cantilever beam (hereinafter, DCB) test piece, and a stress-strain curve is obtained using the DCB test piece by a tensile tester. The load speed is 1 mm / min. The G1c value is calculated by Expressions 3 and 4. G1c = (3P1 ² λ1 ^1/3 ) / (4A1BH) (Equation 3) (a / 2H) = A1λ1 ^1/3 + A0 (Equation 4) However, it is as follows. P1: Initial limit load (N) λ1: Compliance of initial elastic part in stress-strain curve (mm / N) H: Half of plate thickness (mm) A1: Slope of straight line in equation 4 ((N / mm) ^{1 / 3} ) A0: Straight intercept in equation 4 (dimensionless) B: Specimen width (mm) a: Crack length (mm)

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

[0025]

Example 1 Carbon fiber was used as fiber A and nylon 6 fiber was used as fiber B. Both fibers were untwisted and the average fiber length was 70 mm. These mixed yarns were wound and coated with nylon 6 filaments of 40 denier / 24 filaments as the fiber C in the S direction and the Z direction to prepare a composite yarn. Details of the creation method are as follows.
First, traction slivers of fibers A and B were obtained, mixed with a drawing machine and drafted to obtain 236 gel /
The mixed yarn was 6 yards. Next, after drafting the mixed sliver, a nylon 6 filament was wound and coated in a S direction and a Z direction by a hollow spindle under a condition of 260 t / m to obtain a composite yarn of Nm 1.7. The weight ratio of the fiber A in the yarn was 58%, the weight ratio of the fiber C was 2%, and the degree of mixing of the mixed fiber was 65%. The above-described composite yarns are aligned in one direction and laminated, and in a mold, the temperature is 250 ° C., the pressure is 10 kg / cm ² , and the holding time is 10 minutes.
Min., And then cooled and taken out of the mold to form a flat plate having a thickness of 3 mm. In addition, in order to form an interlayer peeling part, an aluminum foil having a thickness of 20 μm was inserted into the center of the lamination at the time of charging into a mold. The formed flat plate was cut into a width of 25 mm and a length of 150 mm to prepare a DCB test piece, and G1C was determined using a tensile tester. G1C value is 1.8k
J / m ² .

[0026]

Comparative Example 1 Continuous carbon fiber of 12K instead of fiber A,
A mixed fiber was prepared using continuous nylon 6 fiber of 6000 denier / 580 filament instead of fiber B. The carbon fiber and the nylon 6 fiber were aligned and supplied to an air nozzle and entangled at an air pressure of 0.7 kg / cm ² to obtain a mixed fiber of 11200 denier. The weight ratio of the carbon fibers was 56%, and the degree of fiber mixture was 30%. A DCB test piece was prepared from the obtained mixed fiber in the same manner as in Example 1, and G1c was determined using a tensile tester. The value of G1c was 0.8 kJ / m ² .

[0027]

Comparative Example 2 A prepreg was prepared using 12K carbon fiber in place of fiber A and a thermosetting bisphenol-based epoxy resin in place of fiber B. The weight ratio of the reinforcing fibers in the prepreg was 60%. A DCB test piece was prepared from the obtained prepreg in the same manner as in Example 1, and G1c was determined using a tensile tester. The value of G1c is 0.2k
J / m ² .

[0028]

According to the present invention, as is apparent from the above constitution, the peel strength between layers and / or between layers of a molded product obtained by molding is obtained by uniformly impregnating the reinforcing fiber with the thermoplastic matrix resin. And a method for producing the same. Specifically, the thermoplastic composite sheet of the present invention,
The present invention is applicable to a racket frame or bat for tennis or badminton, a golf club head, or the like. As described above, the thermoplastic composite sheet of the present invention can be applied to a wide range of uses, and the effect is great.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29B 11/16 B29B 15/08-15/14 C08J 5/04-5/10 C08J 5/24

Claims (2)

(57) [Claims] 1. A thermoplastic composite sheet comprising a composite yarn satisfying the following requirements (I) to (III) and having a critical strain energy release rate of 1.0 kJ / m ² or more. . (I) Consisting of discontinuous reinforcing fibers, discontinuous thermoplastic matrix fibers and continuous thermoplastic matrix fibers, (II)
Both of the discontinuous fibers are substantially non-twisted and are mixed with a degree of blending of 20% or more. (III) The blended fiber is mixed in a weight ratio of 1 to the composite yarn. % To 10% of the continuous thermoplastic matrix fiber. 2. After textile processing a composite yarn satisfying the following requirements (I) to (III), the composite yarn is pressurized at a temperature higher than the melting point of the discontinuous and continuous thermoplastic matrix fibers. The method for producing a sheet for thermoplastic composite according to claim 1, wherein the continuous thermoplastic matrix fiber is impregnated into the reinforcing fiber. (I) Consisting of discontinuous reinforcing fibers, discontinuous thermoplastic matrix fibers and continuous thermoplastic matrix fibers, (II)
Both of the discontinuous fibers are substantially non-twisted and are mixed with a degree of blending of 20% or more. (III) The blended fiber is mixed in a weight ratio of 1 to the composite yarn. % To 10% of the continuous thermoplastic matrix fiber.