JPH02130138A - Molding thermoplastic composite sheet and molded body thereof - Google Patents

Abstract

PURPOSE:To enhance dynamical strength by forming a multi-axial laminated sheet by blended fiber yarns of reinforcing fibers and a thermoplastic resin. CONSTITUTION:Reinforcing fibers and thermoplastic resin fibers are drawn and aligned to be opened electrostatically and the monofilaments of both of them are mutually entangled in an opened state to form blended fiber yarns. A multi-axis laminated sheet is formed from the blended fiber yarns thus obtained. A plurality of these sheets or one or more of this sheet and other kind of a sheet are laminated and heated to the melting and flowing temp. of the thermoplastic resin fibers to be subjected to press molding. The multi-axis laminated sheet and other kinds of sheets to be laminated are laminated, for example, for the purpose of enhancing the surface smoothness of a molded body, imparting coloring and decorative effect and enhancing weatherability and subjected to press molding to be integrated. Since this multi-axis laminated sheet is composed of yarns arranged straightly, reinforcing effect is effectively developed as compared with a conventional plain fabric.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a moldable thermoplastic composite sheet formed from a mixed yarn of reinforcing fibers and thermoplastic resin fibers, and a molded article thereof.

[Conventional technology] Long fiber reinforced plastic composites include so-called advanced composites mainly for aerospace applications, and general-purpose FRPs used for ships, bathtub units, automobiles, etc.
It is broadly divided into. In both cases, a thermosetting resin is usually used as the matrix resin, and the former uses an epoxy resin or resin, and the latter uses an unsaturated polyester resin.

As described above, when a thermosetting resin is used as the matrix resin, there are drawbacks that a curing treatment is required to harden the matrix resin after molding and that the composite lacks toughness.

It is known that the above drawbacks can be improved by using a thermoplastic resin as the matrix resin.

However, since the melting temperature of thermoplastic resin is high, it is technically difficult to impregnate continuous reinforcing fibers with molten resin. Since long fiber mats that are relatively loosely assembled and randomly arranged are easily impregnated with molten resin, a method of impregnating such long fiber mats has been used. The disadvantage is that the mechanical properties of the composite cannot be sufficiently enhanced due to the inability to increase the content of reinforcing fibers and the low degree of orientation of the reinforcing fibers in the sheet surface direction.

Therefore, in order to solve this problem, reinforcing fibers and thermoplastic resin fibers are mixed to form a mixed yarn, which is made into a sheet shape and heated to a temperature where the thermoplastic resin fibers melt and flow. Attempts have been made to press mold the material. In such thermoplastic composites, the content of reinforcing fibers can be significantly increased compared to those impregnated with molten resin.

[Problems to be solved by the invention] However, even such conventional thermoplastic composites may have insufficient mechanical strength, and there is a desire for thermoplastic composites with higher mechanical properties than conventional ones. Ta.

Therefore, an object of the invention according to this application is to provide a thermoplastic composite sheet for molding and a molded product thereof that can exhibit higher mechanical strength than conventional sheets.

[Means and effects for solving the problem] The present inventors conducted extensive research to improve the mechanical strength of thermoplastic composites compared to conventional ones, and as a result, the present inventors developed a blended yarn of reinforcing fibers and thermoplastic resin fibers. It has been discovered that by forming a multiaxially laminated sheet, the mechanical strength can be significantly improved compared to the conventional one, and the invention according to this application has been completed.

That is, the invention of claim 1 is a thermoplastic composite sheet for molding, which is made of a multiaxially laminated sheet formed from a mixed yarn of reinforcing fibers and thermoplastic resin fibers.

The invention of claim 2 is a molded body of a thermoplastic composite sheet according to the invention of claim 1, in which a multiaxially laminated sheet formed from a mixed yarn of reinforcing fibers and thermoplastic resin fibers is It is a thermoplastic composite formed by heating to a temperature at which it melts and then press-molding it.

Examples of thermoplastic resin fibers used in the invention of this application include polyethylene terephthalate, polybutylene terephthalate, nylon 66, polypropylene, fully aromatic liquid crystal polyester, polyphenylene sulfide, polyetherimide, and polyether ether ketone. Examples include those made in the form of

The degree of orientation of the fibers is not particularly limited, and may be any drawn yarn with highly molecular orientation, semi-drawn yarn with moderate molecular orientation, or undrawn yarn with low molecular orientation. However, it is necessary to have mechanical properties that can withstand the next fiber mixing process. As an example of a particularly preferable thermoplastic resin fiber, a polyethylene terephthalate fiber having a degree of molecular orientation and an intensity ratio Ixy/Iyy measured with a polarized Raman spectrometer of 3.0 or more is preferable. A typical example is a partially oriented yarn of so-called polyethylene terephthalate (Partially 0
oriented yarn). Intensity ratio determined by polarization Raman spectrometer ■X Y / I y y
is a value measured as follows.

That is, first, a polyethylene terephthalate fiber is fixed in a stretched state in the fiber direction, and a beam focused to 1 μm is irradiated to the center of the fiber. The polarization of the incident light is in the fiber axis direction (Y
). Using an analyzer, the peak intensity IYY of the polarized light in the direction of the fiber axis of the scattered light and the peak intensity IXY of the polarized light in the direction perpendicular to the fiber axis are measured. The value of IY Y + IX Y measured at 630 cm-' band is 128
The value of IXY/IYY is determined by comparing in the 0 cm-' band.

The reason why it is preferable to use a material with a strength ratio 1xy/Ivy of 3.0 or more is because the crystallization rate during molding can be accelerated and a molded product with good mechanical properties can be obtained.

In addition, the reinforcing fibers used in the invention of this application are not particularly limited, but for example, carbon fibers,
Continuous yarns such as glass fibers and aramid fibers are exemplified.

Methods for obtaining mixed fiber yarns include a method in which reinforcing fibers and thermoplastic resin fibers are aligned and opened electrostatically, and the single fibers of the two are entangled with each other, or the reinforcing fibers and thermoplastic resin fibers are aligned and separated in a turbulent flow of air jets. Examples include a method of opening and entangling the fibers by passing through the fibers.

In the invention according to this application, a multiaxially laminated sheet is formed from the thus obtained mixed fiber yarn.

A multiaxially laminated sheet is a sheet in which multiple layers of threads uniaxially oriented and aligned at different angles are laminated and integrated. Such multi-axis laminated sheets include, for example, those made by laminating layers of yarn perpendicular to two axes, or those made by laminating layers of yarn perpendicular to two axes,
An example is one in which four layers of threads oriented at /90°/-45°/ are laminated.

The sheet is formed by laminating one or more sheets, or by laminating these sheets with sheets of other types, heating the sheet to a temperature at which the thermoplastic resin fibers melt and flow, and press-molding the sheet. Other types of sheets that are laminated with the multiaxially laminated sheet are laminated and press-formed to be integrated, for example, for the purpose of improving the surface smoothness of the molded product, coloring it, giving it a decorative effect, improving its weather resistance, etc. It is something. For example, for the purpose of imparting weather resistance, a resin film of the same type as the thermoplastic resin fiber mixed with an effective amount of an ultraviolet absorber can be laminated. Further, for the purpose of imparting electromagnetic shielding properties, a sheet having an electromagnetic shielding effect can be inserted into the surface or an intermediate layer and laminated. Furthermore, for the purpose of imparting conductivity, conductive fibers may be used as some of the reinforcing fibers to form a mixed yarn, which may be made into a sheet. For the purpose of improving surface smoothness, for example, a film containing a crystal nucleating agent, inorganic particles, etc. can be laminated.

In the invention of claim 2, the heating and press forming method includes a method in which the multiaxially laminated sheet is heated in advance to a temperature higher than the melting temperature of the thermoplastic resin fibers and then press forming while cooling, and a method in which press forming and heating are performed. An example of this method is to perform both at the same time. The former is practically preferable in terms of simplicity of the press device and productivity of the press device. However, in the former case, heating shrinkage of the thermoplastic resin fibers may cause dimensional changes or loss of flatness of the multiaxially laminated sheet, so it is necessary to heat the multiaxially laminated sheet while applying tension with a pin tenter before feeding it to the press. is preferred. Furthermore, when press molding is performed while cooling, it is necessary to consider the time so that the thermoplastic resin fibers melt and move around the reinforcing fibers while maintaining fluidity and become uniform.

[Effects of the Invention] In the invention according to this application, a multiaxially laminated sheet is used as the composite sheet. Since the threads of the multiaxially laminated sheet are linearly arranged, it exhibits a more effective reinforcing effect than conventional plain woven fabrics.

In addition, when multi-axis laminated sheets are stacked and processed to form three-dimensional shapes, it is possible to easily change the angle of the yarn axis between the layers, and there is also a degree of freedom in expanding the yarn spacing within the layers. Therefore, it has the advantage that three-dimensional shaping processing can be easily performed. In addition, in this case, the stitch thread used to integrate the sheets is a thermoplastic resin that melts during melt pressing.
In particular, it is preferable that the resin is the same type as the thermoplastic resin fiber.

In addition, since the invention according to this application uses a multiaxially laminated sheet, the distribution of reinforcing fibers is uniform and highly controlled compared to conventional SMC, injection molded products, and stampable sheets. obtain.

Therefore, it can be designed to suit the purpose. For example, in the case of an elongated shape such as a pamper beam, the sheets can be arranged and press-formed so that the proportion of reinforcing fibers arranged in the elongated direction is generally increased. Further, a desired composite molded body can be obtained by press molding using a mated die mold, for example.

In addition, when highly oriented polyethylene terephthalate fibers with an intensity ratio IxY/IYY measured by a polarized Raman spectrometer of 3.0 or more are used as thermoplastic resin fibers, this can be used as a mixed yarn and multiaxially laminated. Since the sheet is heated and press-molded, the reinforcing effect of the reinforcing fibers is fully exhibited, and the orientation of the polyethylene terephthalate fibers can also be reflected in the composite after press-molding. Therefore, even better mechanical strength can be exhibited.

[Example] Example 1 As a polyethylene terephthalate fiber, the diameter of a single yarn was 18 μm, and the intensity ratio I
Y/I Y One continuous yarn of 4550 denier with a Y of 3.5 was used as a reinforcing fiber, and the diameter of the single yarn was 12μ.
A mixed fiber yarn was produced using a continuous yarn of 1050 denier and E glass fiber of m. A surface treatment agent made by emulsifying a vinyl silane coupling agent and a polyester adhesive with an anionic activator was applied to the surface of the glass fiber in advance in an amount of 0.4% based on the glass fiber.

The fibers were mixed using the Taslan processing method. The blending conditions were as follows: polyethylene terephthalate fibers were supplied with an overfeed of 0.63% relative to glass fibers, the blending processing speed was 100 m/min, and the fluid pressure was 5.0 m/min.
．． The fibers were mixed so that the weight was 0 kg/cm2.

The obtained mixed fiber yarn is oriented at 0° in the yarn axis direction (machine direction): 8
．． 7 threads/cm, yarn axis direction 45°: 2.3 threads/cm, thread axis direction 90° (width direction): 5.8 threads/cm1 thread axis direction -45°: 2.3 threads/cm, and thread Axial direction 0°:
8.7 filaments/cm of each layer and these five layers were made of polyethylene terephthalate continuous filament (
75D/36 filament) to obtain a 0.5 m wide multiaxial laminated sheet with a basis weight of 4.8 kg/m2.

A multiaxially laminated sheet was cut out so that the length of the sheet in the machine direction was 40 cm and the length of one sheet in the width direction was 20 cm.
Fix the ends of this multiaxial laminated sheet with pins and heat it to 160°C.
It was dried with heated air for 30 minutes.

After that, continue to fix it with a pin and heat it with an infrared heater.
Raised the temperature to 80℃ and immediately pressed it to a thickness of 2.5m.
A fiber reinforced polyethylene terephthalate of m was obtained. When the mechanical properties of the obtained sheet were measured, the bending strength in the machine direction of the sheet was 88 kgf/mm2,
The bending elastic modulus is 3610 kgf/mm2, the isot impact value is 142 kgf*cm/cm, the bending strength is 49 kgf/mm2 in the sheet width direction, and the bending elastic modulus is 2270 kgf/cm.
The value was mm2. This is the value of a commercially available stampable sheet made of a glass mat impregnated with polypropylene, that is, the bending strength is 16.5 kgf/mm2, and the bending elastic modulus is 55.
2kg f/mm2, Izotsu impact value 89kgf-c
This value was overwhelmingly higher than m/cm, and it was found that the sheet was extremely tough.

The obtained sheet was heated to 280° C. and then press-molded using a 50+ press machine using a matte die method. Diameter 5c
It was possible to obtain a molded article with a smooth surface and hemispherical protrusions of 2.5 cm and a height of 2.5 cm.

In the above example, the edges of the multiaxially laminated sheet are fixed and heated, but after drying with heated air at 160°C for 30 minutes in a free state without fixing the edges of the multiaxially laminated sheet. Then, I tried raising the temperature to 280°C using an infrared heater. As a result, mechanical strength similar to that of the above example was obtained. However, the sheet shrank significantly, became taut, and wrinkled the sheet surface.

Further, a multiaxially laminated sheet was prepared using 200D Kevlar fiber as the stitch thread, and hot press molded under the same conditions as in the above example to obtain a thermoplastic composite sheet. When we tried press-molding this using a mated die, we were able to obtain something with higher mechanical strength than before, but the hemispherical protrusions that were formed were somewhat inferior in terms of symmetry.

Comparative Example 1 Using the same blended yarn as in the above example, the basis weight was 960g.
/ m2 of plain fabric was made and cut into 40cm x 20cm.
This plain woven fabric was stacked in five layers so that the length and width were aligned, the ends were fixed with pins, and hot press molding was performed in the same manner as in Example 1 above to obtain a fiber-reinforced polyethylene terephthalate sheet with a thickness of 0.52 mm. Ta. When this sheet was used to mold a hemispherical protrusion molded body in the same manner as in Example 1, the sheet was torn and the molded body could not be obtained.

Claims (2)

[Claims] (1) A thermoplastic composite sheet for molding, characterized in that it consists of a multiaxially laminated sheet formed from a blend of reinforcing fibers and thermoplastic resin fibers. (2) Thermoplastic, characterized in that a multiaxially laminated sheet formed from a mixed yarn of reinforcing fibers and thermoplastic resin fibers is press-molded by heating to a temperature at which the thermoplastic resin fibers melt and flow. Composite molded body.