JPH08309748A - Molding material - Google Patents

Abstract

PURPOSE: To provide a molding material which can be used for the manufacture of a molding containing fibers as a reinforcing material in high density but highly dispersible in the case of injection molding, and besides, with significantly improved mechanical strength, especially impact strength, and almost free from fiber breakage. CONSTITUTION: This molding material A consists of a fibrous reinforcing material comprising a single fiber C and a thermoplastic resin B, with which an area between the single fibers C as the constituent unit of the fibrous reinforcing material, is impregnated, by application of the resin B to the periphery of the single fiber C. The molding material A is of the angular or columnar shape, and the fibrous reinforcing material packed in the molding material is equivalent to at least, 50wt.% and 90wt.% or lower. In addition, the fibrous reinforcing material is continuously arranged almost in parallel with an axial direction over the entire length of the molding material A. Further, the surface equivalent to 90% or higher of the single fiber C as the constituent unit of the fibrous reinforcing material is covered by the thermoplastic resin B, and every piece of the single fiber C is ideally dispersed in the thermoplastic resin B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding material, and more particularly, it has good dispersibility at the time of molding despite containing a fiber as a reinforcing material in a high concentration, and further has a breakage of the fiber. The present invention relates to a molding material that is convenient for use in injection molding and that can provide a molded product having a significantly improved mechanical strength, particularly, an impact strength.

[0002]

2. Description of the Related Art Conventionally, most fiber-reinforced thermoplastic resin compositions are those obtained by dry-blending a thermoplastic resin with glass fibers having a length of, for example, about 3 mm, kneading it with an extruder and pelletizing it.

However, when such a dry blend is kneaded with an extruder, the glass fibers tend to be bridging and matting, the dispersion of the fibers becomes insufficient, and the fibers break, resulting in a length of about 0.3 mm. There is a problem that the reinforcing effect is reduced by irregularly arranging in a normally distributed length having a central portion.

Further, due to the above-mentioned problem of dispersion, the glass fiber filling rate is usually 30% by weight at the upper limit, and if an attempt is made to obtain a molding material having a higher filling rate than this, it will be difficult to disperse the fibers during kneading, and the filling rate will increase. The effect was not obtained.

On the other hand, in order to solve the above problems, a method of coating glass fiber or the like with a thermoplastic resin has been proposed.
For example, Japanese Examined Patent Publication No. 49-41105 and Shokai No. 60-62
In No. 912, a continuous body of glass fiber or the like is passed through a die perforation, while a thermoplastic resin melted by an extruder is introduced into the die perforation to coat the fiber bundle, and after cooling, cut into a certain length to form a circle. It is intended to obtain a columnar injection molding material.

However, in this method, the reinforcing fibers tend to aggregate in the center of the molding material, and the surface of the single fibers (filaments) existing in the inner layer of the fiber bundle is not covered with the resin, so that the fibers at the time of injection molding are Is not well dispersed, the fibers are broken and the fiber length before injection molding cannot be maintained, so that the reinforcing effect is not yet satisfactory.

Further, according to the above method, when the glass fiber comes into contact with the molten resin in the die punching, a large shearing force is applied to the surface of the glass fiber, and this shearing force increases with the occupancy rate of the fiber in the die punching. Increase and eventually break as the fiber passes through the die perforations. For this reason, the upper limit of the fiber filling rate in the molding material is usually 50.
It is said to be% by weight, and there is a problem that a molding material having a fiber filling rate higher than this cannot be obtained.

Further, due to the above-mentioned problem of dispersibility of the fiber, the filling rate of the reinforcing fiber is limited, and when it exceeds 50% by weight, injection molding becomes practically difficult, so that a satisfactory injection molding material can be obtained. Has not been done.

[0009]

Therefore, the present invention has good dispersibility at the time of injection molding in spite of containing a fiber as a reinforcing material in a high concentration, and has little breakage of the fiber and mechanical strength. In particular, it is an object to provide a molding material capable of providing a molded product having a significantly improved impact strength.

[0010]

Means for Solving the Problems The inventors of the present invention have achieved the present invention as a result of extensive studies to achieve the above object, and the molding material according to the present invention is a thermoplastic resin. In a molding material comprising a fibrous reinforcing material, a filling rate of the fibrous reinforcing material is 50% by weight or more and 90% by weight or less, and the fibrous reinforcing material is substantially axially formed over the entire length of the molding material. The fibers are arranged continuously in parallel, and 90% or more of the surfaces of the single fibers (filaments) that are the constituent units of the fiber reinforcement are covered with the thermoplastic resin.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
First, a typical structure of this molding material will be described with reference to FIGS. 1 and 2. 1 and 2 are partially enlarged perspective views showing the structure of the molding material of the present invention. FIG. 1 shows one having a square shape (rectangular shape), and FIG. 2 shows one having a cylindrical shape. Show.

In the figure, A is a molding material, B is a thermoplastic resin, and C is a single fiber. L is the length of the molding material, that is, the fiber length, and is preferably 1.0 to 10 mm. 1.0
If it is less than 10 mm, the fiber length is short and a sufficient reinforcing effect cannot be expected. On the contrary, if it exceeds 10 mm, molding becomes difficult due to problems such as bridging in the hopper, which is not preferable.

On the other hand, W, H, and D are width, height, and diameter, respectively. Although not specified, W = 1 to 10 mm, H = 0.1 to 5 mm, D from the viewpoint of biting into the screw. =
0.5-5 mmφ is preferable.

The types of fibrous reinforcing material used in the present invention include glass fibers such as E-glass and S-glass, carbon fibers such as polyacrylonitrile-based, pitch-based and rayon-based fibers.
Examples thereof include aromatic polyamide fibers represented by Kevlar manufactured by DuPont, silicon carbide fibers such as Nicalon manufactured by Nippon Carbon Co., Ltd., and metallic fibers. These fibrous reinforcing materials may be used alone or in combination.

Although the fiber diameter varies depending on the type of the fiber, for example, in the case of glass fiber, it is usually 5 to 25 μm, but it is preferable that it is thin from the viewpoint of mechanical characteristics. The surface treatment of the fibrous reinforcing material is preferable from the viewpoint of adhesiveness to a thermoplastic resin. In the case of glass fiber, for example, it is particularly preferable to treat the fibrous reinforcing material with a silane-based or titanate-based coupling agent.

The thermoplastic resin used in the present invention is not particularly limited and may be selected according to the application. For example,
Polypropylene, styrene acrylonitrile copolymer,
Polystyrene, acrylonitrile / butadiene / styrene copolymer (methyl methacrylate / butadiene / styrene, methyl methacrylate / acrylonitrile / butadiene / styrene, acrylonitrile / butadiene / α
-Including methylstyrene / styrene copolymer), polyphenylene ether (including modified PPO), polyethylene, polyoxymethylene, polycarbonate, polyamide, polymethylmethacrylate, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, poly Examples thereof include sulfone, polyether sulfone, polyether ether ketone, polyether ketone, polyimide and polyether imide.

The filling factor of the fibrous reinforcing material in the molding material is
It is 50% by weight or more and 90% by weight or less. If it is less than 50% by weight, the feature of high filling of fibers, which is the effect of the present invention, cannot be exhibited, and if it is used as a masterbatch described later, it is not preferable from the viewpoint of economy.

On the other hand, if it exceeds 90% by weight, the surface of the single fiber cannot be sufficiently covered with the thermoplastic resin, and therefore the fiber is broken during the injection molding, and the reinforcing effect is deteriorated, which is not preferable.

90% of the monofilament which is the constituent unit of the fiber
The above surface is coated with the thermoplastic resin,
The single fibers are well dispersed in the resin, so that the molding material has a porosity of 10% or less, that is, a coverage of 90% or more, and the fibers are well impregnated with the resin.

The molding material of the present invention can be obtained by cutting a continuous fiber / thermoplastic resin composite in which the surface of a single fiber is coated with a thermoplastic resin, to a predetermined length.

As a method of impregnating continuous fibers with a thermoplastic resin and coating the surface of a single fiber (filament) which is a constituent unit of the fiber with the thermoplastic resin, all usual methods can be used.

For example, a melt impregnation method in which a fibrous reinforcing material is impregnated with a thermoplastic resin in a molten state, or a powdery thermoplastic resin is suspended in air or suspended in a liquid such as water for impregnation. The fluidized bed method can be mentioned.

A melt impregnation method is disclosed in Japanese Patent Laid-Open No. 61-22.
No. 9534, No. 61-229535, No. 61-229.
As typified by Japanese Patent Application No. 536 and Japanese Patent Application No. 61-216253, there may be mentioned a method in which a fibrous reinforcing material is brought into contact with a heating roll or a heating belt having a molten resin on the surface to impregnate it.

That is, in this method, unidirectional long fibers drawn from a plurality of bobbins, for example, a fiber sheet in which tows are aligned or multidirectional continuous fibers are applied with a constant tension in a pulling direction by a tension adjusting roll. On the other hand, the thermoplastic resin is heated and melted by an extruder, and is applied to a lower belt on a heating roll surface heated to a predetermined temperature from a die. Then, the above-mentioned fiber sheet or multidirectional continuous fibers are sandwiched between a pair of upper and lower belts and passed through one or a plurality of heating roll groups to impregnate them.

The sufficiently impregnated continuous fiber / thermoplastic resin composite thus obtained is laminated as it is, or if necessary, after laminating and heat-pressing a required number of sheets so as to have a desired thickness, it is parallel to the fibers in a desired width. After slitting, a rectangular (square) molding material can be obtained by cutting into a desired length in the direction perpendicular to the fibers.

As the method of laminating and hot pressing, for example, the surface of the composite is heated to a temperature above the softening point of the thermoplastic resin and then laminated, or after laminating, it is heated above the softening point of the resin in a heating furnace. To do.

Then, the composite is passed through a cold nip roll having a semicircular groove to form a columnar shape in a state where tension is applied to the fibrous reinforcing material and cooled to a temperature not higher than the solidification temperature of the resin. Reached by.

As a method of obtaining a cylindrical molding material, the continuous fiber / thermoplastic resin composite after impregnation is drawn out from a die having a cylindrical shape heated above the softening point of the thermoplastic resin. Examples of the method include shaping, then cooling to below the solidification temperature of the resin, and then cutting to a desired length.

The molding material thus obtained is used for injection molding as it is or as a so-called masterbatch which is dry-blended with a fiber-unreinforced thermoplastic resin so as to have a desired fiber filling rate.

[0030]

The present invention will be described below in more detail with reference to examples and comparative examples. Example 1 A molding material was obtained from polypropylene and glass fibers as follows. FIG. 3 shows an outline of the apparatus used.

2. 100 rovings of glass fiber (fiber diameter 13 μm, number of converging fibers 1600) drawn out from 100 bobbins 1 are aligned in one direction by an aligner 3, and then tension adjusting rolls 4, 5, 150 mm through 6
The width of the fiber sheet 7 was used.

On the other hand, polypropylene melted and heated to 210 ° C. by an extruder (not shown) is passed through the die 8 and the lower belt 10 is heated to 220 ° C. by the lower belt roll 9 (here, three rolls). It was applied on the surface to a thickness of 105 μm. Next, the sheet is rolled into a lower belt 11 and an upper belt roll 11
Upper belt 12 heated to 220 ° C (3 here)
The diameter is 240mm, which is heated to 220 ℃ while sandwiched between them.
150 kg between the impregnating rolls 13 (here, 3 rolls)
Was applied at a speed of 50 cm / min.
The glass fiber / polypropylene composite 14 thus obtained was cooled to 100 ° C., and then the take-up rolls 15, 1
After being taken up by 6, the slitter 17 slitted it at intervals of 5 mm and then cut by a cutter 18 into a length of 3 mm to obtain a molding material having a thickness of 0.25 mm and a glass fiber filling rate of 80% by weight.

As a result of observing the dispersion state of the filaments (filaments) on the cut surface of the obtained molding material with a scanning electron microscope, the filaments were well dispersed in the resin, and 90% by weight or more of them were dispersed. It was confirmed that the resin was well covered.

Next, 62.5 parts by weight of the molding material and 37.5 parts by weight of fiber-unreinforced polypropylene resin were dry-blended, and a test piece having a glass fiber filling rate of 50% by weight was prepared using an injection molding machine. When the cross section of the test piece was observed with a scanning electron microscope, the dispersion of the fiber was good and no phenomenon such as blocking was observed.

The Izod impact strength and the fiber length were measured using the test piece. The results are shown in Table 1. As shown in Table 1, the central part of the fiber length distribution was about 1.5 mm, which showed less breakage of the fibers during injection molding and about twice the Izod impact strength as compared with the prior art product.

Comparative Example 1 Polypropylene melted was fed by an extruder in a crosshead die having a hole having a diameter of 3 mm and a length of 300 mm.
On the other hand, the 12 glass fibers used in Example 1 were passed through the perforations, passed through a crosshead heated to 220 ° C. and brought into contact with molten polypropylene, and then taken out to obtain a glass fiber filling rate of 60% by weight. An attempt was made to obtain a molding material, but the fibers were cut inside the perforations of the crosshead, and could not be smoothly collected. Therefore, after reducing the number of glass fibers to 9 and performing the above operation to coat the fibers with a resin, the fibers are cooled to 100 ° C. or lower and taken out, and then cut into a length of 3 mm to have a diameter of 3 mm and a glass fiber filling rate of 48. A molding material having a cylindrical shape of wt% was obtained. The cross section of the obtained molding material was observed with a scanning electron microscope to examine the dispersed state of the single fibers.Most of the fibers were present in a bundle at the center of the molding material, and The coated single fiber was only the surface layer of the fiber bundle, and the single fiber group of the inner layer was not coated with resin at all.

Then, the obtained molding material was used as it was by the injection molding machine used in Example 1 to obtain a glass fiber filling rate of 48.
A weight% test piece was prepared. When the cross section of the test piece was observed with a scanning electron microscope, the dispersion of the fibers was insufficient and the phenomenon of blocking was observed.

The Izod impact strength and the fiber length were measured using the test piece. The results are shown in Table 1. As shown in Table 1, the central portion of the fiber length distribution was about 0.5 mm, and fiber breakage during injection molding was more severe than in Example 1, and as a result, the Izod impact strength was significantly reduced.

Comparative Example 2 After using the apparatus of Example 1 to obtain a glass fiber / polypropylene composite having a fiber filling rate of 92%, the width was 5 mm and the length was 3 m.
m injection molding material was obtained. As a result of observing the dispersion state of the single fibers on the cut surface of the obtained molding material with a scanning electron microscope, the fibers were partially blocked, and most of the single fibers were not coated with the resin at all.

Next, 54 parts by weight of the molding material and 46 parts by weight of fiber-unreinforced polypropylene resin were dry blended and injection-molded to obtain a test piece having a glass fiber filling rate of 50% by weight. When the cross section of the test piece was observed with a scanning electron microscope, the fiber was considerably blocked and the dispersion was poor.

Further, the Izod impact strength and the fiber length were measured using the test piece. The results are shown in Table 1. As shown in Table 1, the central portion of the fiber length distribution was about 0.4 mm, and the breakage during molding was severe, and the Izod impact strength was also reduced.

Examples 2 to 4 By using the fibers and resins shown in Table 1 and using the apparatus of Example 1, composites were obtained.

Next, after slitting to a width of 5 mm, it was cut into the length shown in Table 1 to obtain a molding material. Then, after dry blending with the fiber-unreinforced resin in the proportions shown in Table 1, a test piece was obtained by injection molding, and the fiber length and Izod impact strength were measured.

The results are shown in Table 1.

[0045]

[Table 1]

[0046]

According to the present invention, it is possible to provide a molding material which can sufficiently exert the reinforcing effect of fibers, can be highly filled, and has good moldability.

[Brief description of drawings]

1 and 2 are partially enlarged perspective views showing the structure of the molding material of the present invention, and FIG. 3 is a schematic diagram showing an example of an apparatus for producing the molding material according to the present invention. A: Molding material B: Thermoplastic resin C: Single fiber

Claims (3)

[Claims] 1. A fibrous reinforcing material composed of a monofilament (filament) and a monofilament (filament) applied around a monofilament (filament) which is a constituent unit of the fibrous reinforcing material.
In a molding material comprising a thermoplastic resin impregnated between the molding material, the molding material has a rectangular shape or a cylindrical shape, and the filling rate of the fibrous reinforcing material in the molding material is 50% by weight or more.
0% by weight or less, the fibrous reinforcing material is continuously arranged substantially parallel to the axial direction over the entire length of the molding material, and further, a single fiber (filament) which is a constituent unit of the fiber reinforcing material. 90% or more of the surface is covered with the thermoplastic resin, and the single fibers (filaments) are well dispersed in the thermoplastic resin. 2. The molding material according to claim 1, which is used as an injection molding material. 3. The molding material according to claim 1 or 2, wherein the molding material is obtained by a melt impregnation method or a fluidized bed method.