JP2720489B2 - Precursors for thermoplastic composites - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a precursor for molding a thermoplastic composite, which comprises a filament obtained by mixing continuous reinforcing fibers and continuous thermoplastic organic fibers. It is about.

[Problems to be Solved by the Prior Art and the Invention] A thermoplastic composite precursor obtained by mixing a continuous reinforcing fiber and a thermoplastic organic continuous fiber is disclosed in JP-A-60-209034 and JP-A-61-130345. As disclosed in, for example, Japanese Unexamined Patent Application Publication No. H10-157, a so-called drawn yarn is usually used as a thermoplastic organic continuous fiber, and these conventional precursors have a sufficient yarn strength and an appropriate elongation. .

However, when molding is performed using these conventional precursors, defects such as unevenness of the matrix amount in the longitudinal direction, insufficient impregnation and impregnation are caused, and there is a problem that the obtained molded body lacks toughness. In addition, there is a problem that a molded body having an excellent surface state cannot be obtained.

An object of the present invention is to provide a thermoplastic composite precursor useful for molding a thermoplastic composite that is lightweight, tough, and excellent in surface smoothness.

[Means for Solving the Problems] The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, the above-mentioned problems are caused by the heat shrinkage behavior between the reinforcing continuous fibers and the thermoplastic organic continuous fibers during molding. The inventors have found that a difference is caused, and have accomplished the present invention.

That is, the present invention relates to a method in which a continuous fiber for reinforcement and a continuous thermoplastic organic fiber are blended, and the degree of blending defined by the following formula is set to 10% or more, and the dry heat shrinkage B method of JIS-L-1013 It is characterized by comprising a filament having a maximum temperature rising thermal shrinkage of 15% or less as measured by the following method.

N: Total number of continuous reinforcing fibers NcX: Number of groups when reinforcing continuous fibers are divided into groups (groups) X: Number of filaments in one specific group in group [Effects of the Invention] A thermoplastic composite precursor in which continuous reinforcing fibers and thermoplastic organic continuous fibers are mixed can be subjected to heat press molding or the like to produce a molded article having a complicated curved surface. it can. It is also used in a pultrusion method, a filament winding method and the like.

In any of the production steps, it is necessary to heat the thermoplastic composite precursor to melt the thermoplastic organic continuous fibers and sufficiently impregnate the reinforcing continuous fibers. At that time, when there is a difference in the thermal behavior of the continuous fiber for reinforcement and the thermoplastic organic continuous fiber, especially when there is a difference in heat shrinkage behavior, immediately before or at the time of melting,
Both fibers are separated or cut (fused), and good impregnation cannot be obtained.

According to the present invention, since the yarn is constituted by a filament having a maximum temperature rising thermal shrinkage of 15% or less, it is possible to melt the continuous fiber for reinforcement and the thermoplastic organic continuous fiber without disturbing the state. The continuous fiber for use can be impregnated with a resin in a favorable state. Further, it is desirable that the difference between the maximum heat shrinkage of the continuous reinforcing fiber itself and the maximum heat shrinkage of the thermoplastic organic continuous fiber itself is small. In the case of using a fiber with a low maximum temperature rise of heat shrinkage, such as glass fiber or carbon fiber, as the continuous fiber for reinforcement, it is necessary to set the maximum heat rise of the thermoplastic organic continuous fiber to 15% or less. become.

In this specification, the maximum temperature-rising heat shrinkage is defined as JIS-L-101.
This is a value measured by the dry heat shrinkage B method of 3. That is, the temperature at which the sample is heated is changed, the dry heat shrinkage rate is plotted against the heating temperature, and the highest value is taken as the temperature-rise maximum heat shrinkage rate. Dry heat shrinkage rate B specified in JIS-L-1013
The method is as follows. The heating temperature is ± 1
Control within ° C.

Apply an initial load to the sample, measure 500 mm correctly, hit two points, take the initial load, suspend it in a dryer at a predetermined heating temperature, leave it for 30 minutes, remove it, cool it to room temperature, A load is applied, the length between the two points is measured, and calculated by the following equation. The number of tests is five, and the average value is shown.

Here, 1 indicates the length (mm) between two points.

Generally, in the case of a thermoplastic organic continuous fiber having a crystallinity of 15% or less, for example, a polyethylene terephthalate fiber, the temperature rise maximum heat shrinkage rate is often around 100 ° C. in many cases. On the other hand, when the degree of crystallinity exceeds 15%, the fiber often has a maximum temperature-rise heat shrinkage near the melting point of the fiber.

If the maximum temperature rise heat shrinkage exceeds 15%, during heating and melting, slack will occur between the reinforcing continuous fiber and the thermoplastic organic continuous fiber, and the mixing state of both fibers will deteriorate, resulting in low impregnation. However, only molded articles having impregnation spots can be obtained.

As a means for blending the continuous fiber for reinforcement and the thermoplastic organic continuous fiber, any method such as a method of blowing gas, an electric fiber opening method, and a lapping method may be used.
It is preferably at least 10%. The degree of fineness referred to in this specification is defined by the following equation.

Here, N indicates the total number of reinforcing continuous fibers, NcX indicates the number of groups when the reinforcing continuous fibers are divided into several groups, and X indicates a specific number in the group. The number of filaments in one group is shown.
In the above equation, 100 × (N−X) / (N−1) is
The mixed state means that the smaller X is, the better the mixed state is. NcX / N / X is a weight.

When the degree of fiber mixture is 10% or more, impregnation into the continuous reinforcing fibers during melting is performed in a short time. On the other hand, when the degree of fiber mixture is less than 10%, the impregnation takes time and is uneconomical, and the impregnation becomes insufficient.

The precursor for the thermoplastic composite of the present invention may be a filament itself, or a belt-shaped filament,
It may be in the form of a knit, a woven fabric, a laminate, or the like. Particularly preferably, it is a cloth-like precursor that is multiaxially laminated and integrated. Multiaxially laminating means laminating and unifying a plurality of layers of yarn that are uniaxially oriented and aligned at different angles from each other, for example, laminating yarn layers orthogonal to two axes. And a stack of four oriented yarn layers of 0 ° / 45 ° / 90 ° / −45 °. The use of a fabric-like precursor that is multiaxially laminated and integrated facilitates deformation even when molding molded products having various curved surfaces.

In this specification, a thread means a yarn composed of a large number of continuous single yarns. Examples of the multiaxially laminated fabric include a knitted fabric and a knitted fabric laminated and integrated so that the uniaxially oriented thread-like layer forms a multiaxial structure. Since the fabric-like precursor has the yarns arranged linearly, the reinforcing effect can be more effectively exhibited as compared with a plain fabric or the like. Further, when deep drawing is performed on the precursor, there is an advantage that shaping is easy because the yarn axis between the layers is easily deflected or the interval between the yarns in the layer is increased.

Typical examples of continuous reinforcing fibers used in the present invention include carbon fibers, glass fibers, and aramid fibers.

The thermoplastic organic continuous fibers used in the present invention include polyolefin fibers such as polyethylene and polypropylene, polyester fibers such as polyethylene terephthalate and polybutylene terephthalate, polyamide fibers such as nylon 6 and nylon 66, polyphenylene sulfide fibers, and polyether ether. Ketone fibers, polyetherketone fibers, polyetherketoneketone fibers, and the like are included. However, the thermoplastic organic continuous fibers used in the present invention are not limited to the above fibers.

In the present invention, the blending ratio of the continuous reinforcing fiber and the thermoplastic organic continuous fiber is not particularly limited, but the volume fraction (Vf) of the continuous reinforcing fiber is in the range of 20% to 80%. preferable.

Further, as a thermoplastic organic continuous fiber, the degree of crystallinity is 10
% Or less is desirable. Here, the degree of crystallinity can be calculated from the known crystal part density and amorphous part density by measuring the density by, for example, a floating and sedimentation method. In the case of polyethylene terephthalate fiber, CCl ₄ -C ₆ H ₄ (CH ₂ ) ₂
Measure the density by floatation method using
/ cm ³ and the density of the amorphous part is 1.335 g / cm ³ , and the volume fraction is calculated and used. Crystallinity of thermoplastic organic continuous fiber
If it exceeds 10%, the melting energy during melting increases,
It becomes uneconomical because a large amount of heat needs to be given.

EXAMPLES Example 1 One 5250-denier continuous yarn of E glass fiber having a surface treatment of a single yarn having a diameter of 12 μm and a single yarn having a diameter of 18 μm
And a continuous yarn of 2270 denier of polyethylene terephthalate fiber was mixed by the Taslan method to obtain a mixed fiber. The volume fraction (Vf) of the E glass fiber was 60%. As for the fiber mixing conditions, polyethylene terephthalate fiber was supplied with 0.3% overfeed to the glass fiber, the fluid pressure was 5 kg / cm ² , and the fiber mixing speed was 100 m / min. The obtained mixed fiber yarns are aligned and put into a bundling mold, heated to 265 ° C., and pressurized at 265 ° C. and 55 kg / cm ² for 2 minutes.
After a minute, the mixture was rapidly cooled to 40 ° C. The obtained molded body is
It was a unidirectionally reinforced flat plate having a width of 15 mm, a length of 120 mm, and a thickness of 3 mm. The bending properties, delamination strength, Izod impact strength and melting energy of the obtained flat plate were measured,
The results are shown in Table 1. Bending characteristics, Izod impact strength and delamination strength are JIS-K-7555 and JIS-K-7110, respectively.
And JIS-K-7057. Melting energy was measured using a differential scanning calorimeter (DSC-10A manufactured by Rigaku Denki).
The value of ΔH (cal / g) measured under a stream of argon at a temperature rising rate of 20 ° C./min and a sample amount of 10 mg was used.

Example 2 A one-way reinforced flat plate was prepared in the same manner as in Example 1 except that the maximum temperature-rise heat shrinkage of the polyethylene terephthalate fiber was 15%, and the characteristics were measured. The results are shown in Table 1.

Comparative Example 1 A one-way reinforced flat plate was prepared in the same manner as in Example 1 except that the polyethylene terephthalate fiber had a maximum temperature-rise heat shrinkage of 25%, and the properties were measured. The results are shown in Table 1.

Comparative Example 2 One-way reinforced flat plates were prepared in the same manner as in Example 1 except that the degree of fiber mixture of the precursor was 5%, and the characteristics were measured. The results are shown in Table 1.

Example 3 Except that the degree of crystallinity of the polyethylene terephthalate fiber was 15%, a unidirectionally reinforced flat plate was produced in the same manner as in Example 1, and the characteristics were measured. The results are shown in Table 1.

Example 4 The mixed fiber obtained in the same manner as in Example 1 was aligned in one layer and pressed at 250 ° C. and 30 kg / cm ² for 2 minutes to produce a unidirectional prepreg. This one-way prepreg is 0 ゜, 90
In ° direction by laminating 26 sheets alternately, cut to a size of 100 mm × 100 mm (basis weight 6g / m ^2), 265 ℃ in mold 100 mm × 100 mm
And pressurize at 55kg / cm ² for 2 minutes, and after 5 minutes
Rapidly cooled to 40 ° C, width 100mm, length 100mm, thickness 3m
m was prepared. The properties of this laminate were measured and are shown in Table 1. In Examples 4 to 6, the bending characteristics were measured in the 0 ° direction.

Example 5 The unidirectional prepreg obtained in Example 4 was subjected to 0 ° / 45 ° / 90
A four-axis reinforced laminated board was formed by alternately laminating 26 sheets on four axes of {/ -45}. The properties of the four-axis reinforced laminate were measured and are shown in Table 1.

Example 6 The mixed fiber obtained in the same manner as in Example 1 was made into a plain woven fabric (basis weight: 230.8 g / m ² ), and the woven fabric was laminated in 26 layers to obtain a reinforced slab in the same manner as in Example 4. Was. The properties of the obtained flat plate were measured and are shown in Table 1.

As is clear from Table 1, Examples 1 and 2 according to the present invention exhibited superior mechanical strength and superior toughness as compared with Comparative Examples 1 and 2. In addition, in terms of the smoothness of the surface of the molded product,
Examples 1 and 2 were superior to Comparative Examples 1 and 2.

In Example 3 using a thermoplastic organic continuous fiber having a high crystallinity of 15%, it was confirmed that the melting energy was higher than in Examples 1 and 2.

For Examples 4 to 6, the sheet was preheated at 270 ° C. for 5 minutes, and heated in a spherical mold having a radius of 3 cm at 265 ° C. and 55 kg / cm ^2.
And pressurized to 40 ° C. after 5 minutes in a pressurized state to attempt molding. As a result, in Examples 4 and 5, a spherical surface having a radius of 3 cm was formed more clearly than in Example 6. From this, it was confirmed that the use of the precursor in the form of a fabric laminated and integrated multiaxially was superior to the precursor of the plain fabric in the formability of a complicated shape.

Claims (1)

(57) [Claims] Claims: 1. A continuous fiber for reinforcement and a continuous organic thermoplastic fiber are blended, and the degree of blending defined by the following formula is 10% or more; N: Total number of continuous reinforcing fibers NcX: Number of groups when reinforcing continuous fibers are divided into groups (groups) X: Number of filaments in one specific group in group A thermoplastic composite precursor characterized by comprising a filament having a maximum temperature-rise heat shrinkage of 15% or less as measured by a dry heat shrinkage B method of JIS-L-1013.