JPH1177677A - Production of fiber reinforced thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fiber reinforced thermoplastic resin sheet having reduced warpage and good plate properties. SOLUTION: In a method for producing a fiber reinforced thermoplastic resin sheet in which a thermoplastic resin is heated at a temperature of at least the softening point of the resin, made to be penetrated in continuous reinforcing fibers, held between cooling rolls 5, 6 of a pair, pressed, cooled below the softening point, and led to a guide roll 8, the cooling roll 6 of the pair on the side where the sheet is warped along the surface of the guide roll 8, in a place where in the inter-axial distance of the rolls 5, 6, is installed to be shifted by 1-20 mm in the reverse direction to the traveling direction of the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a fiber-reinforced thermoplastic resin sheet. More specifically, the present invention relates to a method for producing a fiber-reinforced thermoplastic resin sheet in which continuous reinforcing fibers are impregnated with a thermoplastic resin, and to a method for producing a fiber-reinforced thermoplastic resin sheet having a low warpage ratio.

[0002]

2. Description of the Related Art As a method for producing a fiber-reinforced thermoplastic resin sheet by impregnating a continuous fiber with a thermoplastic resin, for example, Japanese Patent Application Laid-Open No. 61-229534 discloses a method in which a fiber sheet is coated with a thermoplastic resin. A method is disclosed in which a thermoplastic resin is transferred to a fiber sheet after being guided to an application roll, and then brought into contact with a heating roll to impregnate the resin. According to this method, the thermoplastic resin easily adheres to the heating roll, and when staying for a long time, is thermally degraded, which impregnates the fiber sheet, and causes the quality of the obtained fiber-reinforced thermoplastic resin sheet to deteriorate. Becomes

[0003] Also, JP-A-2-48907 discloses that
The thermoplastic resin is applied to at least one of a pair of belts heated to a temperature equal to or higher than the softening point of the thermoplastic resin, and the coating film is introduced between a pair of opposed belts, and a fiber sheet is interposed between the pair of belts. A method for producing a fiber-reinforced sheet-like prepreg by impregnating a fiber with a thermoplastic resin by passing through a prepreg is disclosed. This method is an excellent method that enables stable continuous production and obtains a high-performance fiber-reinforced thermoplastic resin sheet with little deterioration of the impregnated resin. However, the resulting sheet may be warped, which is not always a satisfactory method for producing a fiber-reinforced thermoplastic resin sheet having excellent flatness.

[0004] In principle, if a uniform molten resin sheet is generally kept flat and both the front and back surfaces are cooled at the same speed, the resulting sheet will not be warped. However, usually, when manufacturing various sheets, films, etc., cooling rolls for cooling, transporting, taking up, winding, etc. the resin sheet,
A large number of rolls such as guide rolls are used to apply a stress that causes the resin sheet to bend. Therefore, even when a plurality of pairs of cooling rolls are used, it is extremely difficult to produce a warped resin sheet at a high speed. Also,
There is known a method in which a molten resin sheet is pressed into contact with a pair of cooling belt conveyors to cool and form the sheet. However, this method requires a large installation space, increases the installation cost, and is industrially practical. poor.

[0005] The fiber-reinforced thermoplastic resin sheet is generally used by laminating it with paper, nonwoven fabric, other resin sheets or films. Therefore, it is desirable that the fiber-reinforced thermoplastic resin sheet has less warpage. But,
Since a composite material composed of a resin and a reinforcing fiber has a different shrinkage rate due to heating and cooling as compared with a homogeneous material, it is difficult to produce a sheet having no more warpage than the homogeneous material.
Further, it is difficult to control the distribution of fibers in the thickness direction of the fiber-reinforced thermoplastic resin sheet. That is, since the amount of resin present on the front and back surfaces of the sheet is difficult to be uniform,
The degree of warpage is not constant, and flexibility is required for the warp improvement method.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a fiber-reinforced thermoplastic resin sheet which has less warpage and good flatness in view of the above problems.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a thermoplastic resin is heated to a temperature above the softening point to impregnate continuous reinforcing fibers, and then a pair of cooling rolls is used. During cooling by pinching and pressing, the cooling roll installed on the side where the fiber-reinforced thermoplastic resin sheet is curved and bent by the guide roll is specified in the negative direction in the running direction of the sheet. It has been found that the above-mentioned problems can be solved by cooling using a pair of cooling rolls which are set at a distance shifted from each other by the distance described above.

That is, according to the present invention, a thermoplastic resin is heated to a temperature equal to or higher than the softening point, impregnated with continuous reinforcing fibers, and then sandwiched between a pair of cooling rolls 5 and 6.
A method for producing a fiber-reinforced thermoplastic resin sheet that is pressed and cooled to a temperature lower than the softening point, and then guided to a guide roll, wherein a fiber-reinforced thermoplastic resin sheet along a surface of the guide roll among a pair of cooling rolls. The cooling roll 6 on the side where the curve is curved has a distance of 1 to 20 in the direction opposite to the running direction of the fiber-reinforced thermoplastic resin sheet at an axial distance from the other cooling rolls 5.
A method for producing a fiber-reinforced thermoplastic resin sheet, wherein the method is provided so as to be shifted by a distance of mm.

A feature of the present invention is that when cooling a fiber-reinforced thermoplastic resin sheet heated to a temperature equal to or higher than the softening point of the thermoplastic resin, the fiber-reinforced thermoplastic resin sheet is guided by a guide roll among a pair of cooling rolls. The cooling and shaping is performed by using a pair of cooling rolls, which are provided on a side where the sheet is curved and bent, and are shifted by a specific distance in the negative direction in the sheet traveling direction. By employing such a configuration, a fiber-reinforced thermoplastic resin sheet having less warpage and good flatness can be manufactured.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The outline of the present invention is that, in a hot-melt impregnation step, reinforcing fibers aligned in parallel are impregnated with a thermoplastic resin heated to a temperature equal to or higher than the softening point, and then sandwiched and pressed using a pair of cooling rolls. Then, cooled to a temperature below the softening point of the resin, then guided to a guide roll and transported to the next step,
This is a method for producing a fiber-reinforced thermoplastic resin sheet. In the present invention, the method for impregnating the reinforcing fibers with the thermoplastic resin in the hot melt impregnation step is not particularly limited, and a known method may be used. For example, a method disclosed in JP-A-2-48907 is preferably applied.

The unidirectionally continuous reinforcing fibers used in the present invention are known as rovings, yarns and tows, which are aggregates of filaments constituting the fibers. These are used plurally. It is preferred that the filaments be long enough and have sufficient strength to pull against the molten thermoplastic coating under the conditions used. Cloth materials can also be used. Preferred materials include glass fibers, carbon fibers, boron fibers, metal fibers such as stainless steel, and synthetic resin fibers. Of these, glass fibers are more preferable in consideration of price, versatility, and the like. The synthetic resin fibers are preferably surface-treated to have an adhesive property with the thermoplastic resin to be impregnated. Further, it is necessary that the properties such as strength do not change with the melting temperature of the thermoplastic resin used. Examples of the synthetic resin fiber include an aramid resin (registered trademark “Kepler” or the like).

The glass fiber or the carbon fiber is coated with a surface treatment agent such as a silane-based or titanium-based coupling agent on the fiber surface in order to improve the adhesiveness with the resin according to the thermoplastic resin used. Is preferred. In addition, a sizing agent can be used so that roving or tow is not loosened during handling within a range that does not hinder the impregnation of the thermoplastic resin.

A plurality of the continuous reinforcing fibers are arranged in parallel in, for example, one direction in the machine direction, are controlled so as not to cross each other, are spread in the width direction, are adjusted to an appropriate thickness, and are adjusted to an appropriate thickness. It is formed in a sheet shape like a warp.
Specifically, continuous fibers are wound on multiple bobbins,
It is desirable that the fibers are unwound from each bobbin while applying an appropriate tension, and are arranged in a sheet through an aligner having a sieve-like shape in a line with an appropriate width in the machine direction.

Although the thickness of the fiber-reinforced thermoplastic resin sheet also depends on the thickness of the fibers used (roving and tow),
It can be controlled by the arrangement and density of rovings and tows in the width direction. Since the thickness accuracy affects the variation of the impregnation state,
It is preferably within ± 10% of the target thickness of 50 to 500 μm.

The thermoplastic resin used in the present invention includes polystyrene, polyvinyl chloride, polyethylene, polypropylene, nylon, polycarbonate, polypropylene terephthalate, polyethylene terephthalate and the like. Considering price, versatility, heat resistance, mechanical properties, etc., polypropylene is preferred.

When the fiber-reinforced thermoplastic resin sheet (prepreg) obtained according to the present invention is used for applications requiring structural strength, it is preferable that the resin has a high elastic modulus and a high tensile strength. Examples include engineering resins such as polyethersulfone, polysulfone, polyphenylsulfide, polyimide, polyetherimide (trade name “ULTEM”), polyetheretherketone, and the like.

When using these resins, it is preferable to dry them in advance, and it is more preferable to add a coupling agent such as a titanium-based resin to the resins for the purpose of improving the adhesion to the reinforcing fibers. The viscosity of the resin when the thermoplastic resin is impregnated into the reinforcing fibers is preferably from 500 to 50,000 poise, more preferably from 1,000 to 5,000 poise. The temperature at which the resin viscosity is obtained varies depending on the type of the thermoplastic resin, but is usually about 180 to 420 ° C.

In the present invention, the softening point is defined by JIS K-7210 using a melt index measuring device (manufactured by Toyo Seiki Co., Ltd., type: melt indexer S-111) under a load of 5 kg. 5 g of the sample is measured based on the method described above, and is set to the lowest temperature at which the molten thermoplastic resin is extruded from the cylinder die.

In the above-mentioned hot-melt impregnation step of impregnating the continuous reinforcing fibers arranged in parallel with the thermoplastic resin, a coating film of the thermoplastic resin heated to a softening point or higher is provided, and An apparatus characterized by passing continuous reinforcing fibers between a pair of pressed belts can be used.

For example, the thermoplastic resin is melted inside the extruder, extruded from a die provided at the tip of the extruder, and applied to the surface of the lower belt which has been heated in advance. The resin temperature inside the extruder is determined according to each resin characteristic so that a uniform resin coating is formed. Normally, the resin temperature is [(Tg) +
1] to [(Tg) +200] ° C. The width of the resin coating may be equal to or greater than the width of the continuous reinforcing fibers aligned in parallel, and the thickness of the resin coating on the lower belt is adjusted to an appropriate thickness corresponding to the thickness of the continuous fibers. This thickness is a value experimentally determined by a set target value (20 to 80% by weight) of the resin content in the finally obtained fiber-reinforced thermoplastic resin sheet. The thickness of the resin coating is 10-100
0 μm is preferred, and more preferably 20 to 200 μm. The thickness accuracy of the resin coating is ± 1
It is preferably 0%, more preferably within ± 5%.

Thus, the continuous fiber sheet is pressed against a roll via a hot-melt impregnated portion, for example, a belt, provided with a resin coating, and the continuous fiber is impregnated with the resin. Fiber sheet
It is sandwiched between a pair of cooling rolls at a temperature of [(Tg) -1] to [(Tg) -150] ° C, pressed and cooled to a temperature lower than the softening point. Conventionally, as the running speed of the fiber-reinforced thermoplastic resin sheet becomes higher, the cooling of the sheet is also performed by a guide roll in a later process, so the uneven cooling of the front surface or the back surface of the sheet proceeds, and the warpage is reduced. It is easy to occur. Furthermore, the state of the glass fiber and resin in the sheet,
Speaking of the cross-sectional shape of the sheet, glass fibers gather in the center and resin increases in the surface layer. Generally, when the linear expansion coefficients of the glass fiber and the resin are significantly different, warpage is likely to occur. Also, as the central layer with a large amount of glass fibers becomes thinner than the surface layer with a large amount of resin, the warpage increases. The present invention solves this phenomenon even at a high line speed of 0.5 to 100 m / min by the method described below.

The method of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a plane orthogonal to a roll axis, showing an example of an arrangement relationship between a hot-melt impregnation section, a pair of cooling rolls, and a guide roll. The thermoplastic resin 1 and the reinforcing fibers 2 are supplied to the hot-melt impregnating section 3 to form a fiber sheet 4 impregnated with the molten thermoplastic resin. The fiber sheet 4 has a cooling roll 5
A pair of cooling rolls composed of a pair of cooling rolls 6 and 6 are cooled and shaped by being pressed and pressed into a fiber-reinforced thermoplastic resin sheet 7, curved along the surface of the guide roll 8 and bent in the direction in which the cooling roll 6 is installed. And transported to the next step.

The present invention is characterized by a method of installing a pair of cooling rolls. In the example shown in FIG. 1, the cooling roll 6 in which the fiber-reinforced thermoplastic resin sheet 7 is installed on the side where the fiber-reinforced thermoplastic resin sheet 7 is curved and bent along the surface of the guide roll 8 is a fiber-reinforced reinforcing roll. The sheet is shifted in the direction opposite to the running direction of the thermoplastic resin sheet 7, that is, in the direction in which the distance between the cooling roll 6 and the hot-melt impregnated section 3 is shortened. When the direction in which the fiber-reinforced thermoplastic resin sheet 7 is curved and bent along the surface of the guide roll 8 is opposite to the direction of the example shown in FIG. 1, the cooling roll 5 runs on the fiber-reinforced thermoplastic resin sheet 7. The cooling roller 5 and the hot-melt impregnated section 3 are disposed so as to be shifted in the opposite direction, that is, the direction in which the distance between the cooling roll 5 and the hot-melt impregnated section 3 becomes shorter.

According to the present invention, depending on the direction in which the fiber-reinforced thermoplastic resin sheet 7 is curved and bent along the surface of the guide roll 8 as described above,
It is characterized in that one of them is installed at a specific distance in a direction opposite to the running direction of the fiber-reinforced thermoplastic resin sheet 7.

The present invention employing such a configuration utilizes the fact that the resin is most likely to keep its shape formed at a temperature near its softening point while the cooling of the molten resin proceeds. In the hot-melt impregnation step, the resin in the sheet heated and melted above the softening point is then cooled by the cooling roll 5 or the cooling roll 6 which is first touched, until one of the upper and lower cooling rolls is pressed to the press contact point. The roll is cooled to a temperature equal to or higher than the softening point, and then wound around a cooling roll 5 or a cooling roll 6 from a pressure contact point with both rolls, and cooled to a temperature lower than the softening point of the resin. The sheet can easily maintain a warped shape when wound on the cooling roll 5 or the cooling roll 6 from the pressure contact point between the two cooling rolls.

First, when the sheet is cooled to a temperature below the softening point between the cooling rolls 5 and 6 by the cooling roll 5 or the cooling roll 6 which first comes into contact with the cooling rolls, the molten resin flows between the fibers. Does not spread sufficiently, and the surface formability of the sheet deteriorates when pressed by the cooling rolls 5 and 6. Thus, by shifting the axes of the cooling rolls 5 and 6 in the direction opposite to the running direction of the sheet by the specific distance as described above, the sheet is formed so as to cancel the warp given by the guide roll 8 following the cooling roll portion. It is possible to adjust the warpage rate of the final product to almost 0% by giving a warp in the opposite direction. This shift distance is preferably in the range of 1 to 20 mm.

Shifting the installation positions of the pair of cooling rolls by the distance in the above range can be easily performed even with existing equipment, so that it can be applied to a wide range of equipment. Therefore, the present invention is extremely useful as a method for producing a fiber-reinforced thermoplastic resin sheet having no warpage and good flatness.

[0028]

The present invention will be described in more detail with reference to the following examples. The warp rate of the fiber-reinforced thermoplastic resin sheet shown in the examples is a value measured by the following method. (1) Warpage rate (%) Measured according to the method specified in JIS K-6911. As the sample, a square test piece having a side length of 650 mm is used. The sign attached to the data is (+) when the edge of the sheet fed from the cooling unit jumps up from the center when viewed from above. (2) Resin content in product (% by weight) Measured according to the method specified in JIS K-7052. The sample piece is 10 g, and the average value of three measurements is defined as the amount of resin in the product.

Example 1 The specifications of each part of the apparatus shown in FIG. 1 were such that the width of the cooling rolls 5 and 6 was 800 mm and the diameter was 200 mmφ, and the width of the succeeding guide roll 8 was 800 mm and the diameter was 200 mmφ. Polypropylene (manufactured by Mitsui Toatsu Chemicals, Inc., trade name: Noblen, viscosity at 250 ° C .: about 1,000 poise) is used as the thermoplastic resin, and glass fiber is used as the continuous reinforcing fiber (trade name, manufactured by Nitto Boseki Co., Ltd.) : Roving RS] was used. The continuous glass fibers drawn out from the 100 rovings were aligned to form a fiber sheet having a width of 500 mm, which was then impregnated with 175 ° C. molten polypropylene discharged in a sheet form from a die of an extruder in a hot-melt impregnating section. The 220 ° C. glass fiber reinforced polypropylene sheet unwound from the hot melt impregnation section was cooled to 110 ° C. by passing between a pair of cooling rolls 5 and 6 kept at 70 ° C. At that time, the displacement width of the cooling rolls 5 and 6 is +3 mm
(The cooling roll 6 was shifted by 3 mm in the direction of the hot-melt impregnated portion from the cooling roll 5). Shift width here (+)
Means the cooling roll 6 (upper roll) and the cooling roll 6
(Lower roll) Shows how much the axis is displaced in the direction opposite to the running direction of the glass fiber reinforced polypropylene sheet. Indicates Then, it passed through the guide roll 8 and was wound at a speed of 30 m / min.
The obtained glass fiber reinforced polypropylene sheet has a resin amount of 32% by weight and a thickness of 0.13 mm.
The warpage rate based on -6911 was 0%. The main production conditions and the obtained results are shown in [Table 1].

Examples 2 to 10 and Comparative Examples 1 to 4 The main production conditions such as the thermoplastic resin and reinforcing fibers used, the temperature of the cooling roll, the width of the displacement of the cooling roll, etc. were changed as shown in Table 1. A fiber-reinforced thermoplastic resin sheet was manufactured in the same manner as in Example 1. The main production conditions and the obtained results are shown in [Table 1]. In addition, PP described in [Table 1]
Is polypropylene [manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name: Noblen, viscosity at 250 ° C .: about 1,000 poise], PA is polyamide [manufactured by Toyobo Co., Ltd., trade name: Toyobo Nylon], and LDPE is low density. Polyethylene [manufactured by Mitsui Petrochemical Industry Co., Ltd., trade name: Mirason], PS is polystyrene [manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name: Toporex], PI is polyimide [manufactured by Mitsui Toatsu Chemical Co., Ltd.]
(Trade name: Aurum), PC is polycarbonate (Idemitsu Petrochemical Co., Ltd., trade name: Taflight), PEEK is polyetheretherketone (Victrex, trade name: Victrex PEEK), GF is glass fiber [Nittobo Co., Ltd., trade name: Roving RS], CF denotes carbon fiber [Toray Co., Ltd., trade name: Trading Card].

[0031]

[Table 1]

[0032]

According to the method of the present invention, when a fiber-reinforced thermoplastic resin sheet heated to a temperature equal to or higher than the softening point of a thermoplastic resin is cooled, the fiber-reinforced thermoplastic resin is guided by a guide roll of a pair of cooling rolls. By using a pair of cooling rolls that are installed by being shifted by a specific distance in the negative direction in the running direction of the sheet, the cooling rolls installed on the side where the resin sheet is bent are cooled and shaped, so that there is no warpage.
A fiber-reinforced thermoplastic resin sheet having good flatness can be continuously obtained at high speed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a plane orthogonal to a roll axis, showing an example of an arrangement relationship between a hot-melt impregnation section, a pair of cooling rolls, and a guide roll.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermoplastic resin 2 Continuous reinforcing fiber 3 Hot melt impregnated part 4 Fiber sheet impregnated with molten plastic resin 5 Cooling roll 6 Cooling roll 7 Fiber reinforced thermoplastic resin sheet 8 Guide roll

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Michiyo Tsukamoto 2-1-1 Tango-dori, Minami-ku, Nagoya-shi, Aichi Mitsui Toatsu Chemicals Co., Ltd.

Claims (2)

[Claims] 1. A thermoplastic resin is heated to a temperature equal to or higher than the softening point, impregnated with reinforcing fibers continuous in one direction, and then sandwiched and pressed by a pair of cooling rolls 5 and 6 to have a temperature lower than the softening point. A method for producing a fiber-reinforced thermoplastic resin sheet which is guided to a guide roll after cooling to a temperature, wherein a cooling roll on a side where the fiber-reinforced thermoplastic resin sheet is curved along a surface of the guide roll among a pair of cooling rolls. Wherein the fiber-reinforced thermoplastic resin sheet 6 is displaced by a distance of 1 to 20 mm in the direction opposite to the running direction of the fiber-reinforced thermoplastic resin sheet at an axial distance from the other cooling rolls 5. Sheet manufacturing method. 2. The method for producing a fiber-reinforced thermoplastic resin sheet according to claim 1, wherein the line speed is 0.5 to 100 m / min.