JPH0144144B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to a method for continuously producing a long fiber-reinforced thermoplastic resin.

(Prior art) Fiber-reinforced thermoplastic resin (hereinafter referred to as
FRTP) is used in a variety of ways as a material that combines the excellent mechanical properties derived from reinforcing fibers with the excellent moldability, heat fusion properties, recyclability, and ease of repair derived from thermoplastic resins. It is attracting attention in various fields. In particular, long FRTP that uses long, continuous reinforcing fibers has superior mechanical properties compared to those that use short reinforcing fibers, and can also be cut into molding materials such as chips. Due to its advantages, it has been particularly expected in recent years. However, in manufacturing such long FRTP, it may not be possible to use a method of combining reinforcing fibers and thermoplastic resin through a mixing operation, etc., as in the case of manufacturing using short reinforcing fibers. It's hot and quite difficult.

That is, long FRTP is manufactured by passing a reinforcing fiber bundle through a crosshead extruder to impregnate it with a thermoplastic resin, and then drawing it through a die (U.S. Patent No.
3993726), reinforcing fiber bundles are immersed in a molten thermoplastic resin, run to get wet, and then pulled out through a die (Japanese Patent Application Laid-open No. 181852/1983), but the former The bending strength, which is one of the mechanical properties, is said to be considerably lower than the expected value with the method of
This method is said to be effective only for thermoplastic resins with relatively low melt viscosity, and cannot be said to be a versatile method.

On the other hand, for thermoplastic resins with a high melt viscosity of more than 300 poise, a method has been proposed in which the thermoplastic resin is diluted with a solvent. This method is generally called a wet impregnation method or a solution impregnation method, but there are problems in that the solvent removal step is complicated and the working environment becomes poor.

(Problems to be Solved by the Invention) The purpose of this invention is to solve the above-mentioned problems of the conventional method and efficiently produce long FRTP with excellent properties that are very close to the expected mechanical properties. This is to provide a way to do so.

(Means for Solving the Problems) In order to achieve the above object, the present invention brings a reinforcing fiber bundle into contact with a molten thermoplastic resin while continuously traveling, so that the thermoplastic resin adheres to the reinforcing fiber bundle. The reinforcing fiber bundle to which the thermoplastic resin is attached is placed under tension in a heating region maintained at a temperature where the thermoplastic resin has a melt viscosity in the range of 200 to 20,000 poise, and a temperature below the softening point temperature. The reinforcing fiber bundle to which the thermoplastic resin is attached is heated between a pair of endless belts having a cooling region maintained at A process of impregnating a reinforcing fiber bundle with a thermoplastic resin by compressing it so that the thickness or thickness is in the range of 20 to 80%, and passing it through a cooling region to solidify the thermoplastic resin. Provides a manufacturing method.

To explain this invention in more detail, in the present invention, first, a reinforcing fiber bundle is brought into contact with a molten thermoplastic resin while continuously traveling, and the thermoplastic resin is adhered to the reinforcing fiber bundle.

The reinforcing fiber bundle is a so-called strand made of high-strength, high-modulus reinforcing fiber such as carbon fiber, glass fiber, or aromatic polyamide fiber. The number of single threads is
It depends on the type of reinforcing fiber, but usually 1000~
Approximately 30,000 pieces. These reinforcing fibers can also be used in combination. Moreover, in order to improve the wettability with respect to the molten thermoplastic resin, various known surface treatments can be applied.

It is preferable that the reinforcing fiber bundle has no twists, or even if it has twists, it has very few twists. In other words, although twisting improves handling, single yarns can become intertwined with each other, so when FRTP is made, the intertwined points are likely to become points of failure, reducing the strength, elasticity, etc. of FRTP. Mechanical properties may be reduced. In addition, if the number of twists is large, the impregnation with the thermoplastic resin in the subsequent process may not be sufficiently carried out, and the mechanical properties may also deteriorate. moreover,
When there is twist, the degree of expression of the characteristics of the reinforcing fiber is lower than when there is no twist.

The reinforcing fiber bundles may be brought into contact with the molten thermoplastic resin with just one reinforcing fiber bundle, or may be brought into contact with the reinforcing fiber bundles in parallel to each other and aligned in the form of a tape or sheet. Alternatively, after contacting with the molten thermoplastic resin, they may be drawn parallel to each other and aligned in the form of a tape or sheet. Furthermore, when drawing them together, they may be drawn apart from each other or may be drawn so that they are in contact with each other. If they are drawn apart from each other, a linear FRTP can be obtained, and if they are drawn in contact with each other, a tape or sheet-like FRTP can be obtained.

On the other hand, thermoplastic resins include nylon 6, nylon
Nylon such as 66, nylon 11, nylon 12, nylon 610, nylon 612, copolymerized nylon of these nylons, polyethylene terephthalate,
Polyesters such as polybutylene terephthalate, copolyesters of these polyesters, polycarbonates such as polybisphenol A carbonate, polyamideimide, polyetheramide, polyetherimide, polyphenylene sulfide, polyphenylene Oxide, polysulfone, polyethersulfone,
It is like polyetheretherketone.

The above-mentioned thermoplastic resin may contain various additives depending on the use of FRTP, such as heat resistant agents, weather resistant agents, ultraviolet deterioration inhibitors, antistatic agents, lubricants, mold release agents, dyes, pigments, and flame retardants. , a crystallization accelerator may be added.

In order to cause the reinforcing fiber bundle to come into contact with the molten thermoplastic resin while running continuously and to adhere the thermoplastic resin, for example, the reinforcing fiber bundle can be immersed in the molten thermoplastic resin and passed through it, or the reinforcing fiber bundle can be passed through a coating die. This can be done by passing the fiber bundle through, or by extruding molten thermoplastic resin around the reinforcing fiber bundle using a die. When the reinforcing fiber bundle comes into contact with the molten thermoplastic resin, the thermoplastic resin adheres around it.
Some of it penetrates inside and sticks. The amount of thermoplastic resin to be deposited depends on the application, etc., but is usually set so that the reinforcing fiber content in the obtained FRTP is in the range of 10 to 70% by volume.

In this invention, next, the reinforcing fiber bundle to which the thermoplastic resin is attached, obtained in the above-mentioned process, is placed under tension so that the thermoplastic resin has a melt viscosity of 200 to
A heating region maintained at a temperature in the range of 20,000 poise and a cooling region maintained at a temperature below the softening point temperature are guided between a pair of endless belts in this order. Using the pressing force of
The reinforcing fiber bundle is compressed to a range of 80% and impregnated with thermoplastic resin, and then passed through a cooling region to solidify the thermoplastic resin.

The tension applied to the reinforcing fiber bundle is low so as not to impede the impregnating properties of the thermoplastic resin, but sufficient tension is applied to keep each single yarn aligned in one direction. It is.

An endless belt is made by stretching a flat belt made of metal such as stainless steel between a plurality of rolls, for example, between two rolls. Place and use. It is preferable to apply a mold release agent such as a fluorine-based mold release agent to the flat belt.

The pair of endless belts has a heating region on the side to which the reinforcing fiber bundle to which the thermoplastic resin is attached is guided, and a cooling region on the opposite side. The heating zone is then maintained at a temperature such that the thermoplastic resin attached to the reinforcing fiber bundle has a melt viscosity in the range of 200 to 20,000 poise, preferably 350 to 15,000 poise. The upper limit is, of course, the temperature at which the thermoplastic resin does not decompose.

The temperature in the heating region is such that the thermoplastic resin has a melt viscosity of less than 200 poise;
When the reinforcing fiber bundle is impregnated with thermoplastic resin, the air bubbles are not completely removed, and many fine voids are generated in FRTP, which becomes the starting point of fracture, resulting in poor mechanical properties of FRTP. It will be significantly lower. On the other hand, at temperatures exceeding 20,000 poise, the impregnation of the reinforcing fiber bundle with the thermoplastic resin is greatly reduced, making it impossible to obtain FRTP with excellent mechanical properties. Here, the melt viscosity is
Measured under relatively low shear rates. Approximately, using a capillary viscometer using a die with a diameter of 0.5 mm and a length of 1 mm, assuming Newtonian viscosity, the shear rate may be determined in the range of 50 to 500 sec ^-1 .

Meanwhile, the cooling zone is maintained at a temperature below the softening point temperature of the thermoplastic resin. Here, the softening point temperature is the melting temperature of crystals for crystalline thermoplastic resins, and the glass transition temperature for amorphous thermoplastic resins.

In such heating and cooling regions, for example, the roll on the side on which the flat belt is stretched and the reinforcing fiber bundle to which the thermoplastic resin is attached is guided is a hot roll whose temperature can be controlled, and the roll on the opposite side is a hot roll. It can be easily formed by using a water-cooled roll.

Now, in the heating region, as mentioned above, by using the pressing force between the pair of endless belts, the reinforcing fiber bundle to which the thermoplastic resin is attached is heated to a thickness in the range of 20 to 80%. The reinforcing fiber bundle is compressed and impregnated with thermoplastic resin. In other words, in this heating region, the thermoplastic resin has a melt viscosity of
Since the temperature is maintained in the range of 200 to 20,000 poise, when the reinforcing fiber bundle with the thermoplastic resin attached passes through this heated region, the thermoplastic resin softens or melts and flows, forming a pair of endless poises. The reinforcing fiber bundle penetrates into the inside of the reinforcing fiber bundle by the pressing force applied by the belt. That is, it is impregnated. In this process, if the compression of the reinforcing fiber bundle to which the thermoplastic resin is attached is less than 80%, the thermoplastic resin will not be sufficiently impregnated, and there will be parts in the reinforcing fiber bundle where no thermoplastic resin exists. Therefore, the resulting FRTP has very poor mechanical properties. Furthermore, if the compression is greater than 20%, the direction of the single fibers that make up the reinforcing fiber bundle will be disturbed, or so-called single fiber breakage will occur, making it impossible to obtain FRTP with excellent mechanical properties. .

On the other hand, since the cooling region is maintained at a temperature lower than the softening point temperature of the thermoplastic resin, the thermoplastic resin that has softened or melted and flowed in the heating region is solidified.

Thus, FRTP is obtained. Obtained FRTP
is pulled out from the endless belt using a take-up roll or the like. The drawn-out FRTP can be transported as is to the molding process, or it can be rolled up into a paper tube or plastic tube and stored. It can also be cut into appropriate lengths to make chips for use in injection molding and the like.

Although the steps described above can be performed as separate, completely separate steps, they are usually performed consecutively. Depending on various conditions such as the method of attaching the thermoplastic resin to the reinforcing fiber bundle and the length of the endless belt, the speed is about 0.1 to 10 m/min.
FRTP can be manufactured.

(Example) Example 1 Carbon fiber bundle "Torayca" T300 manufactured by Toray Industries (average single fiber diameter: 7 μm, number of single fibers: 3000) and polyphenylene sulfide manufactured by Phillips Petroleum (melting at 310°C) A linear FRTP with a viscosity of 1500 poise was manufactured.

That is, as shown in the drawing, a plurality of carbon fiber bundles 1 arranged in parallel at intervals are continuously fed into a resin to which molten polyphenyl sulfide (temperature: 310°C) is supplied from an extruder 2. After being passed through a bath 3 into contact with the molten polyphenyl sulfide, it is drawn through a die (diameter: 1 mm) 4;
A carbon fiber bundle 5 having a thickness of about 0.7 mm and around which polyphenylene sulfide was attached was obtained.

Next, the carbon fiber bundle 5 to which polyphenylene sulfide is attached is transported along the transport direction.
It was continuously guided between a pair of upper and lower endless belts 6 and 7, each having a heating area maintained at 310±5°C and a heating area maintained at 220±5°C. Endless belt 6
, a stainless steel flat belt 6c is stretched between a hot roll 6a and a water-cooled roll 6b. Similarly, the endless belt 7 also has a hot roll 7.
A stainless steel flat belt 7c is stretched between the roll 7a and the water-cooled roll 7b. In both endless belts, the distance between the axes of the hot roll and the water-cooled roll is 2000 mm, and the endless belts 6 and 7 are arranged so that the distance between the flat belts 6c and 7c is 0.3 mm.

When the carbon fiber bundle 5 to which polyphenylene sulfide is attached is guided between the endless belts 6 and 7, the polyphenylene sulfide is melted as it passes through the heating area, and at the same time, the carbon fiber bundle 5 is guided between the endless belts 6 and 7. The thickness is 0.3 due to the pressing force of flat belts 6c and 7c.
The polyphenylene sulfide was impregnated into the carbon fiber bundle by being compressed to a diameter of 1 mm, and the polyphenylene sulfide was further solidified in a cooling region.
In this way, a linear FRTP8 made of carbon fiber and polyphenylene sulfide was obtained. The obtained FRTP 8 is rolled into a pair of rubber rolls 9a, 9.
It was taken up by a take-up roll 10 consisting of b.

The obtained FRTP had a carbon fiber content of about 50% by volume. Further, when the cross section was observed with an optical microscope, the carbon fiber and polyphenylene sulfide were completely integrated, and no voids were observed. Furthermore, when a bending test was performed, the bending strength was 160 Kg/mm ² and the bending modulus was 10.5 ton/mm ² . The expected bending strength and flexural modulus are given by the product of the carbon fiber's tensile strength and tensile modulus and its volume content.
Both the bending strength and bending modulus reached approximately 90%, indicating that the FRTP produced by this method has properties that are extremely close to the expected mechanical properties.

Example 2 Example 1 except that polybutylene terephthalate manufactured by Toray Industries (melt viscosity at 275°C: 1000 poise) was used instead of polyphenylene sulfide.
A linear FRTP was obtained in the same manner. However, the temperature of the molten polybutylene terephthalate in the resin bath 3 was 260°C, and the temperature in the heating region of the endless belts 6 and 7 was 275°C.

The obtained FRTP had a carbon fiber content of about 60% by volume. Further, when the cross section was observed with an optical microscope, it was found that the carbon fibers and polybutylene terephthalate were completely integrated, and no voids were observed. Furthermore, when a bending test was conducted in the same manner as in Example 1, the bending elastic modulus was 13 tons/mm ² , which was about 93% of the expected value.

Example 3 Instead of polyphenylene sulfide,
A linear FRTP was obtained in the same manner as in Example 1, except that polyether sulfone manufactured by ICI (melt viscosity at 420° C.: 2000 poise) was used. However, the temperature of the molten polyether sulfone in resin bath 3 is
The temperature was set at 400°C, and the temperature in the heating region of the endless belts 6 and 7 was set at 420°C.

The obtained FRTP had a carbon fiber content of approximately 45% by volume. Further, when the cross section was observed using an optical microscope, it was found that the carbon fiber and polyether sulfone were completely integrated, and no voids were observed. Furthermore, when a bending test was conducted in the same manner as in Example 1, the bending elastic modulus was 9 ton/ ^mm2 ,
It was about 85% of the expected value.

Example 4 Instead of polyphenylene sulfide,
A linear FRTP was obtained in the same manner as in Example 1, except that polyetheretherketone manufactured by ICI (melt viscosity at 420°C: 5000 poise) was used. however,
The temperature of the molten polyetheretherketone in the resin bath 3 was 400°C, and the temperature in the heating region of the endless belts 6 and 7 was 420°C.

The obtained FRTP had a carbon fiber content of about 40% by volume. Further, when the cross section was observed using an optical microscope, it was found that the carbon fiber and polyetheretherketone were completely integrated, and no voids were observed. Furthermore, when a bending test was conducted in the same manner as in Example 1, the bending elastic modulus was 8.1 ton/mm ² , which was about 86% of the expected value.

Example 5 Carbon fiber bundles to which polyphenylene sulfide was obtained, obtained in the same manner as in Example 1, were arranged so as to be in contact with each other and guided to an endless belt. below,
Similar to Example 1, the thickness is 0.2 mm and the width is 40 mm.
A tape-like FRTP was obtained.

The obtained FRTP had a carbon fiber content of about 50% by volume. Further, when the cross section was observed with an optical microscope, it was found that the carbon fibers and polyphenylene sulfide were completely integrated, no voids were observed, and the arrangement of the carbon fibers was not disordered.

Example 6 In Example 5, instead of the carbon fiber bundle, a glass fiber bundle “Glaslon” manufactured by Asahi Fiberglass Co., Ltd.
ECG150 1/8 (single thread diameter 9μm, number of single threads: 1600)
In addition, nylon manufactured by Toray Industries (melt viscosity at 250°C: 700 poise) was used in place of polyphenylene sulfide. however,
The temperature of the molten nylon 6 in the resin bath 3 is 250°C,
The temperature in the heating area of endless belts 6 and 7 is 255
℃.

The obtained tape-shaped FRTP with a thickness of 0.2 mm is
The glass fiber content was approximately 53% by volume. Also,
When the cross section was observed using an optical microscope, it was found that the glass fiber and nylon 6 were completely integrated, and no voids were observed. Furthermore, when a bending test was conducted in the same manner as in Example 1, the bending strength was
The weight was 90Kg/mm ² and the flexural modulus was 3.4ton/mm ² , both of which were about 90% of the expected values.

(Effects of the Invention) This invention comprises a process of causing a reinforcing fiber bundle to come into contact with a molten thermoplastic resin while running continuously, and adhering the thermoplastic resin to the reinforcing fiber bundle; The fiber bundle is placed under tension.
The thermoplastic resin is guided between a pair of endless belts having a heating region maintained at a temperature where the melt viscosity is in the range of 200 to 20,000 poise and a cooling region maintained at a temperature below the softening point temperature, and in the heating region , using the pressing force of a pair of endless belts,
The reinforcing fiber bundle with the thermoplastic resin attached is compressed so that its thickness or thickness is in the range of 20 to 80%, the reinforcing fiber bundle is impregnated with the thermoplastic resin, and the reinforcing fiber bundle is passed through a cooling area to cool the thermoplastic resin. Since it individualizes the resin, as shown in the examples, it is possible to efficiently produce long FRTP with excellent properties that are very close to the expected mechanical properties. In addition, unlike the conventional wet impregnation method and solution impregnation method described above, this invention does not use a solvent, so there is no need for a solvent removal process, and the work environment is degraded by the solvent. Nor.

[Brief explanation of drawings]

The drawing is a schematic perspective view showing how the invention is implemented. 1: carbon fiber bundle (reinforced fiber bundle), 2: extruder,
3: Resin bath, 4: Die, 5: Carbon fiber bundle to which polyphenylene sulfide (thermoplastic resin) is attached, 6: Endless belt, 6a: Hot roll, 6
b: water-cooled roll, 6c: flat belt, 7: endless belt, 7a: hot roll, 7b: water-cooled roll, 7
c: flat belt, 8: FRTP (fiber reinforced thermoplastic resin), 9a: roll, 9b: roll, 10: take-up roll.

Claims (1)

[Claims] 1. A step of bringing the reinforcing fiber bundle into contact with a molten thermoplastic resin while continuously traveling and adhering the thermoplastic resin to the reinforcing fiber bundle, and placing the reinforcing fiber bundle to which the thermoplastic resin is attached under tension. The thermoplastic resin is guided between a pair of endless belts having a heating region maintained at a temperature where the melt viscosity is in the range of 200 to 20,000 poise and a cooling region maintained at a temperature below the softening point temperature. In this step, the reinforcing fiber bundle to which the thermoplastic resin is attached is compressed using the pressing force of the pair of endless belts so that the thickness or thickness thereof is in the range of 20 to 80%, thereby forming a reinforcing fiber bundle. A method for producing a fiber-reinforced thermoplastic resin, comprising the steps of: impregnating a thermoplastic resin with a thermoplastic resin, and passing the thermoplastic resin through a cooling region as it is to solidify the thermoplastic resin.