JP3237716B2 - Method for producing thermoplastic composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic composite material, and more particularly, to a method of continuously impregnating a continuous reinforcing fiber with a thermoplastic resin to obtain a wire, rod, pellet or the like of the thermoplastic composite material. And a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a thermosetting resin has been often used for a matrix of a composite material. However, there are problems such as storage stability, toughness, and work environment, and in recent years, thermoplastic resins have attracted attention and are being actively developed. However, thermoplastic resins generally have a high melt viscosity, and it is difficult to continuously impregnate reinforcing fibers. Therefore, various methods have been developed. For example, dissolving a thermoplastic resin in a solvent, reducing the viscosity, a method of impregnating the reinforcing fibers, or adding a plasticizer to the thermoplastic resin to reduce the melt viscosity,
There is a method of impregnating reinforcing fibers. In addition, there is a method of impregnating a reinforcing fiber with a monomer of a thermoplastic resin and then polymerizing the same to obtain a high molecular weight to obtain a composite material. Further, there are a method of squeezing the reinforcing fibers in the molten thermoplastic resin and forcibly impregnating the reinforcing fibers, and a method of impregnating the reinforcing fibers in a high-pressure die filled with the thermoplastic resin.

[0003]

The above-mentioned method using a solvent is basically limited in application to a thermoplastic resin soluble in a solvent, and at the same time, it is necessary to remove and recover the solvent after impregnation. It is inefficient and it is very difficult to remove all the solvent in the resin, and the residual solvent may adversely affect the physical properties of the obtained composite material. further,
The use of a solvent deteriorates the working environment. On the other hand, in the method using a plasticizer, it is necessary to remove the plasticizer similarly after impregnation, which is inefficient, and it is very difficult to completely remove the plasticizer in the resin. There may be adverse effects on physical properties. In the method using a monomer, a low viscosity state can be obtained without using a solvent or the like,
The resins that can be polymerized after impregnation are quite limited. In addition, it is often difficult to control the degree of polymerization during polymerization, and it is difficult to obtain a composite material of a constant quality.

Further, in the method of forcibly impregnating reinforcing fibers in a molten thermoplastic resin, the type of the thermoplastic resin is not limited and there is no problem with a solvent or the like. The tension is high and it is difficult to increase the production speed. Further, if the speed is forcibly increased, fluffing of the reinforcing fibers occurs, and eventually, the reinforcing fibers are cut, which has a serious adverse effect on productivity.
Similarly, the method of impregnating reinforcing fibers in a high-pressure die filled with a thermoplastic resin requires that the pressure be increased in proportion to the speed in order to increase the production speed, and the speed is naturally limited . As described above, it has been difficult to realize a high production rate without using a solvent or the like in the related art.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, as a result of intensive studies, they have reached the present invention. That is, the present invention
In a method of impregnating a continuous reinforcing fiber with a thermoplastic resin,
The first die having the S-shaped curved surface is passed through, and the S-shaped die has a groove through which the reinforcing fibers can pass while maintaining an open state according to the S-shape. While passing , the midpoint of each of the two arcs forming the S-shape is
And connect the vertex to the center of the radius of curvature of each arc.
The angle of the line is defined as the angle reference, and the counterclockwise direction is defined as positive.
In this case, the molten thermoplastic resin is discharged from two resin discharge ports, which are provided within ± 60 ° from each vertex of the arc forming the S-shape of the groove and are equal to or smaller than the groove width, After partially impregnating the one side and the other side of the opened reinforcing fiber with a molten thermoplastic resin, the fiber is passed through a second linear die continuous with the first die. This is a method for producing a plastic composite material. In the present invention, any thermoplastic resin that can be melted without using a solvent or the like can be used, and since it has excellent impregnation properties, a high production rate can be realized. Hereinafter, the present invention will be described in detail.

The continuous reinforcing fiber used in the present invention is not particularly limited as long as it has a melting point higher than the melting point of the thermoplastic resin used for the matrix, and is preferably, but not particularly limited to, carbon fiber, glass fiber, aramid fiber, SiC fiber, or the like. Metal fibers and the like are preferable. The continuous reinforcing fiber is preferably a multifilament, and the number of filaments is 50 to 20,000.
The number is preferably about 200, more preferably 200 to 10000, but is not limited thereto. Further, it is desirable that these fibers be substantially untwisted. Substantially no twist means a twist of 1 turn / m or less. Further, these fibers are preferably subjected to a treatment for improving the adhesiveness with the thermoplastic resin used. These fibers may be used in combination of different types of fibers, or a plurality of fibers of the same type may be used at the same time, and may be selected according to the properties required for the finally desired composite material. .

On the other hand, the thermoplastic resin serving as the matrix is not particularly limited as long as it is a meltable resin, and may be selected according to the required characteristics of the composite material. For example, polyolefins such as polyethylene, polypropylene, and copolymers and modified products thereof, nylon 6, 66, 4
Polyamides such as 5, 12 and the like, polyethylene terephthalate, polyethylene naphthalate, polyesters such as polybutylene terephthalate, thermoplastic elastomers such as thermoplastic polyurethane, polyacetal, liquid crystal polymer, polyphenylene sulfide, polyetherimide, polyether ketone, Polyether ether ketone and the like are not limited thereto. The melt viscosity of such a resin may be selected according to the required characteristics of the composite material, but is preferably as low as possible. Preferably, the melt viscosity at zero shear rate at a melting point + 20 ° C. is 200 to 10,000 poise, more preferably 500 to 10,000 poise.
It is 4000 poise, but is not limited to this. If the melt viscosity is less than 200 poise, the physical properties of the resulting composite material tend to be poor, while
If the poise is exceeded, impregnation tends to be difficult.

The impregnating die used in the present invention has two shapes. The first die has an S-shaped or similar curved surface as shown in FIG. The curved surface is necessary for maintaining the open state of the continuous reinforcing fiber, and applies the molten thermoplastic resin under the open state. The curvature of the surface must be determined after careful consideration. If the radius of curvature is too small, the reinforcing fibers are liable to be fluffed, which may cause yarn breakage and also increase the take-up tension, making high-speed production difficult. On the other hand, if the radius of curvature is too large, the force of the reinforcing fiber pressed against the curved surface becomes small, and impregnation becomes difficult. In particular, when a highly rigid reinforcing fiber is used, if it is forced to follow a curved surface, the possibility of breakage or damage is extremely high. Therefore, it is necessary to make the reinforcing fibers to be used along curved surfaces having actually different curvatures so as to be hardly damaged.

A reinforcing fiber is maintained on the curved surface in an open state,
There is a groove of a width that can pass (FIG. 2). The width of the groove varies depending on the number of bundles of reinforcing fibers used and the state of opening, but is preferably equal to or smaller than the width opened by bending and opening. The surface of the groove must be finished smoothly, and it is preferable that the material and processing are selected so as to have a low coefficient of friction. Further, although the shape of the bottom of the groove is preferably flat, it may be curved in the width direction so as to further facilitate the opening of the reinforcing fiber. (FIG. 3).

The groove has a discharge port for molten thermoplastic resin. Each of the discharge ports has two arcs forming an S-shape.
Is the vertex, and the vertex and the radius of curvature of each arc
Using the line connecting the centers of
Are defined within ± 60 ° from the apex of each of the arcs forming the S-shape of the groove,
Preferably, they are provided one by one at an angle of 0 to 30 ° from the apex, and the shape may be arbitrary, but a slit shape is preferable, and the width must be equal to or slightly smaller than the width of the groove. . The resin discharge port as described above discharges the resin from the center side of the curvature of the curved surface, applies the resin to one side of the reinforcing fiber at the first discharge port, and then the other discharge port to the other side of the reinforcing fiber. To a resin.

The reinforcing fiber supplied to the groove is given an appropriate tension and is supplied to the curved surface, whereby the fiber is opened along the curved surface and maintains the state. The fiber opening here is
It means that the multifilaments of the supplied continuous reinforcing fibers are widened in the lateral direction and their distribution is not uneven.
Preferably, especially in the case of reinforcing fibers that are bundled with a sizing agent or the like, the fibers are spread by a known spread means, separated into single fiber levels, and given a tension capable of maintaining a spread state on a curved surface. Supplied. The higher the tension, the more advantageous for impregnation, but the higher the pulling tension, which is not preferable. On the other hand, if it is too low, the spread state is not maintained on the curved surface, and the impregnation state becomes worse. Therefore, the supply tension must be carefully considered. Although it depends on the type of reinforcing fiber used and the melt viscosity of the thermoplastic resin, it is preferably about 0.1 to 5 g / denier. As described above, by pressing the reinforcing fiber against the curved surface while squeezing by the supply tension, the resin is applied while maintaining the spread state, so that the impregnation between the single yarns is performed more quickly. In addition, it is desirable that the reinforcing fibers be heated to a temperature near the melting temperature of the resin to be used, just before being supplied to the curved surface. As a heating method, a contact heater, an infrared heater, or the like can be used.

The amount of resin discharged from the two resin discharge ports on the curved surface is 30% of the final desired resin weight of the composite material.
９０90%, preferably 40-70%. When the resin discharge amount is less than 30% by weight, the resin impregnated state of the finally obtained composite material deteriorates. On the other hand, when the resin discharge amount exceeds 90% by weight, the take-up tension increases, and at the same time, the resin stays in the groove. This causes deterioration of the resin. The discharge amount of such a resin can be controlled using, for example, a gear pump or the like.

[0013] In this way, impregnation is performed on the curved surface. The degree of impregnation varies depending on the conditions, but is about 30 to 70%, which is not perfect. Further, it is preferable to adjust the supply tension and the like so as to obtain such a degree of impregnation. Here, the degree of impregnation means the ratio of the number of single yarns of the reinforcing fiber that is wetted by 50% or more with the resin to the number of single yarns of all the reinforcing fibers. More than half is wet with resin (resin is in close contact)
Means that. As a method of measuring the degree of impregnation, a cross-sectional photograph of the obtained composite material is taken at an appropriate magnification, a transparent film is attached on the photograph, and a dot is formed on a reinforcing fiber which is wetted by 50% or more with a resin. The number of points of this film was counted using an image processing apparatus, and the film was calculated according to the above definition. That is, when this impregnation degree is represented by an equation,

(Equation 1) Becomes

[0014] The partially impregnated reinforcing fibers are thus supplied to a second linear die which is installed continuously with the first die. The straight die is used to further improve the impregnation. Therefore, it is preferable that the linear die is filled with resin and is under pressure. The shorter the length of the linear die, the higher the take-up tension is preferable, but it may be determined by the melt viscosity of the resin or the production rate. Although the higher the pressure in the die, the more advantageous for impregnation, in the case of the present invention, the pressure in the linear die may be low because the impregnation is partially performed in the first die. Preferably, it is 0.1 to 25 kg / cm ² , more preferably 5 to 15 kg / cm ² , but it may be determined according to the melt viscosity of the resin. The cross-sectional dimension of the linear die is preferably sufficiently large with respect to the cross-sectional area of the reinforcing fiber.

Further, between the first die and the second die,
The width may be the same as that of the first die, but may have an aperture portion that is lower only in height (FIG. 4). By such a narrowed portion, the impregnation is promoted while the opened state of the reinforcing fiber is maintained. However, the height must be high enough to allow the reinforcing fibers partially impregnated with the resin to pass through. If the height is too low, the take-up tension will be excessive, or the attached resin will be scraped off and the first die Or stay in
This is because the reinforcing fibers can be caught and cause thread breakage. Also, the length of the constricted portion must not be too long. This is because the tension is increased by the narrowed portion, and if the length is too long, the production speed cannot be improved and the thread may be broken. Also, the resin filled in the second die flows back into the first die at the narrowed portion, and the first die is filled with the resin.
It also serves as a weir to prevent the die from filling with resin.

The shape of the outlet of the second die may be the same as the final shape of the reinforcing fibers impregnated with the resin, or may be a flat shape in order to maintain an open state in the die. However, in the latter case, it is necessary to perform post-shaping to obtain a desired final shape. For such post-shaping, a shaping die can be used after the second die, or a shaping compression roller can be used. Moreover, they are also useful for further improving impregnation, and in particular, compression rollers are useful for achieving higher productivity speeds. Also, the cross-sectional area at the outlet of the second die must be determined after careful consideration to achieve the desired fiber content. The thermoplastic composite material thus obtained has a degree of impregnation of 45% or more, preferably 60% or more. If the impregnation degree is lower than 45%, it is difficult to obtain the desired tensile strength, bending strength and impact strength as a composite material.

[0017]

As described above, the continuous reinforcing fiber is supplied to the first S-shaped curved die while applying tension to the first S-shaped curved die, and the continuous reinforcing fiber is fed along the curved surface so that the continuous reinforcing fiber is filled to the full groove width of the curved die. The fiber can be spread and passed while maintaining the spread state. In this open state, when the molten thermoplastic resin is applied from the resin discharge port, the tension of the reinforcing fiber and the discharge pressure of the resin, and furthermore, the reinforcing fiber follows the curved surface, so that the resin is quickly interposed between the single yarns of the reinforcing fiber. Impregnate. At the stage of the first S-shaped curved die, the amount of resin discharged is less than the amount ultimately desired as a composite material. Therefore, the impregnation is partial. However, if the amount of the discharged resin is increased to exceed 90% of the finally desired resin weight of the composite material, the reinforcing fibers do not carry all the resin and the resin fills the first die. This causes an increase in tension due to the viscous resistance of the resin and deterioration of the resin. On the other hand, if the amount of the discharged resin is less than 30%, only a composite material having a poor impregnation state can be finally obtained.

Further, since the resin outlet is located near the apex of the curved surface, the distance between the resin and the curved surface is reduced, and the resin is applied to each side so that the resin and the curved surface are similarly formed. The distance which becomes the resistance of the wire is shortened, and the increase of the pulling tension is prevented. As described above, since the impregnation is performed without filling the first die with the resin, the take-up tension can be suppressed low. However, because the impregnation is only partial with this first die, a second linear die is used to further improve the impregnation. In the second die, the impregnation is improved by the discharge pressure of the resin. However, since the impregnation is partially performed by the first die, a high pressure and a long time are not required. Therefore, the length of the die can be shortened, and it is possible to prevent an increase in the drawing tension due to the viscous resistance. In this manner, by suppressing the take-up tension to be low, a thermoplastic composite material having a good impregnation degree can be obtained at a high production rate. Further, if production at a higher speed is required, a compression roller or a shaping die may be used after the second die as an auxiliary impregnation means for further improving the impregnation.

[0019]

According to the present invention, a thermoplastic composite material having a high degree of impregnation can be produced at a higher speed than conventional methods, and the thermoplastic composite material can be developed in various fields.

[0020]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A reinforcing fiber was impregnated in the process shown in FIG. 5 using an impregnation die as shown in FIG. The first S-shaped die is
The radius of curvature is 25 mm, and the width of the groove is 4 mm. The resin discharge ports are located at the vertices of the curved surface, and have a width of 4.
mm and a 1 mm thick slit. A second linear die having a width of 15 mm, a height of 6 mm and a length of 150 mm was used in succession. The second die is provided with two upper and lower resin discharge ports near the connection with the first die. Also the second
There is a pressure sensor at the center of the die to detect the pressure inside the die. The resin was supplied to the die in a fixed amount using a gear pump after the extruder.

Glass fibers were used as continuous reinforcing fibers. This glass fiber is a direct roving having a single yarn diameter of 13.3 μm, a number of filaments of 1600, and 575 tex. This glass fiber is provided with an aminosilane and an acrylic surface treatment agent. Further, the glass fiber was taken out horizontally, actively unwound, and supplied to a die in a substantially untwisted state. On the other hand, nylon 6 was used as the thermoplastic resin. The melt viscosity of this nylon 6 at a zero shear rate at a melting point + 20 ° C. was 2560 poise.

The exit of the second die has a width of 3 mm and a height of 0.2
It was 5 mm in length and 3 mm in length. When the above glass fiber and nylon 6 resin were used, the fiber content was set to be 50% by weight. The glass fibers were opened while squeezing with five rods having a diameter of 10 mm, and supplied to a die with a tension of about 400 g.
The amount of resin discharged from the first die is 50% of the desired amount of resin,
One-to-one distribution was made to each discharge port. In the second die, the remaining 50% was set to be provided. At this time, the pressure in the second die was adjusted to about 10 kg / cm ² . Table 1 shows the relationship among the take-up speed, the take-up tension, and the impregnation degree.

[0024]

[Table 1]

Example 2 In Example 1, the ratio of the discharge amount of the first die was changed, and the resin discharge amount of the second die was changed accordingly.
The take-off speed was 25 m / min. Table 2 shows the results. From this result, the ratio of the ejection amount in the first die is 30
It can be seen that ~ 90% gives good results for impregnation. (Here, Nos. 1, 2, and 7 in Table 2 are comparative examples.)

[0026]

[Table 2] In Table 2, the ejection amount is the resin in the first die.
This is the discharge amount.

Example 3 In Example 1, as shown in FIG. 4, a drawn portion having a width of 4 mm, a height of 0.3 mm and a length of 5 mm was provided between the first die and the second die. 50% discharge rate at first die, take-off speed 2
The test was performed at 5 m / min. The take-up tension was 6.7 kg and the degree of impregnation was 87%. The take-up tension has increased slightly,
The degree of impregnation has improved.

[0028]

Comparative Example 2 In Example 2, the resin was not discharged from the first die, and the impregnation was performed only with the second die. At this time, the pressure in the die was about 10 kg / cm2. The results are shown in Table 2 No. 1. Although the pulling tension is low,
The impregnation degree was poor.

Comparative Example 3 In Example 2, 100% of the resin was discharged from the first die.
And the resin was not discharged from the second die. In this case, the take-up tension gradually increases, and eventually becomes 1
0.2 kg, and the impregnation degree was as low as 41%.
The results are shown in No. 7 of Table 2.

Comparative Example 4 A thermoplastic composite material was obtained in the same manner as in Example 2 except that the resin discharge from the first die was set to 20%. At this time, the pressure in the die was about 10 kg / cm ² . The results are shown in No. 2 of Table 2.
Although the take-up tension was low, the impregnation degree was poor.

Comparative Example 5 Using the reinforcing fiber of Example 1, resin impregnation was attempted using only the second die. At a pressure in the die of 35 kg / cm ² and a take-up speed of 3 m / min, the degree of impregnation was 33%, but the take-up tension was as high as 15 kg. Further, the pressure in the die was changed to 55 kg / cm ² , but the impregnation degree did not improve so much to 35%. When the speed was further increased to 7 m / min, the glass fibers were cut.

Comparative Example 6 Three fixed iron bars having a diameter of 3 mm were provided in the second die without using the first die.
The impregnation was attempted at 0 kg / cm2. The reinforcing fibers used were the same as in Example 1. The impregnation degree was 72% at 3 m / min, but the take-up tension was as high as 23 kg, and the glass fiber was cut 3 minutes after the start of operation. This is because a large number of glass fiber single yarns were broken by the ironing rod.

Example 4 Six pairs of glass rollers of Example 1 were arranged in parallel, fed into a die as shown in FIG. 6, impregnated, and formed into a round cross-sectional shape ( It was impregnated and shaped through Fig. 7). The take-up speed is 30m / min,
The degree of impregnation was 73%. The reinforcing fiber content was 50% by weight. The rod-shaped body having a round cross section thus obtained was cut into a length of 12 mm to obtain a pellet, which was subjected to injection molding. The notched Izod impact strength of the obtained injection molded article was as high as 40 kgcm / cm.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a configuration of a die according to an embodiment of the present invention.

FIG. 2 is an example of a groove of a first S-shaped die.

FIG. 3 is an example of a groove in another form of the first S-shaped die.

FIG. 4 is a schematic diagram illustrating another form of the die of one embodiment according to the present invention.

FIG. 5 is a schematic diagram of each device of one embodiment of an embodiment according to the present invention.

FIG. 6 is a schematic diagram of each device of one embodiment of another aspect according to the present invention.

FIG. 7 is an enlarged view of an example of a compression roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st S-shaped die 2 2nd linear die 3 Die exit 4 Resin discharge port 5 Groove 6 Restriction part 7 Creel 8 Reinforcement fiber 9 Opening bar 10 Water tank 11 Pulling machine 12 Winding machine 13 Gear pump 14 Extrusion Machine 15 Compression roller concave 16 Compression roller convex 17 Impregnated thermoplastic composite material 18 Pelletizer 19 Pellets

Continuation of the front page (72) Inventor Masaru Nakagawa 2-1-1 Katata, Otsu-shi, Shiga Examiner, Hiroki Amano, Research Institute, Toyobo Co., Ltd. (56) References JP-A-60-9961 (JP, A) JP-A-62-158728 (JP, A) JP-A-5-162130 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29B 15/08-15/14 B29B 11/16 B29C 70/06

Claims (5)

(57) [Claims] In a method of impregnating a continuous reinforcing fiber with a thermoplastic resin, the continuous reinforcing fiber is passed through a first die having an S-shaped curved surface,
The S-shaped die has a groove through which the reinforcing fiber can pass while maintaining an open state according to the S-shape , and while allowing the reinforcing fiber to pass through the groove under tension, the two arcs forming the S-shape are formed. Respectively
Is the vertex, and the vertex and the radius of curvature of each arc
Using the line connecting the centers of
When defined as a groove, the molten thermoplastic resin is discharged from two resin discharge ports, which are provided within ± 60 ° from each apex of the arc forming the S-shape of the groove and are equal to or smaller than the groove width. After discharging, the impregnated reinforcing fiber is impregnated partially on one side and subsequently on the other side with a molten thermoplastic resin, and then passed through a second linear die continuous with the first die. A method for producing a thermoplastic composite material. 2. The method for producing a thermoplastic composite material according to claim 1, wherein the thermoplastic composite material has an impregnation degree of 45% or more as defined in the text. 3. The method for producing a thermoplastic composite material according to claim 1, further comprising a drawn portion between the first S-shaped die and the second linear die. 4. The discharge amount of the molten thermoplastic resin from the two resin discharge ports of the first S-shaped die is 30 to 90% of the resin weight of the final desired thermoplastic composite material. A method for producing a thermoplastic composite material. 5. The method according to claim 1, further comprising means for improving the impregnation after the second linear die.