JP2626345B2 - Method for producing fiber reinforced thermoplastic resin sheet - 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 fiber-reinforced thermoplastic resin sheet.

[0002]

2. Description of the Related Art A method for producing a sheet-like material having substantially no air bubbles by integrating a reinforcing fiber mat and a thermoplastic resin is disclosed in, for example, JP-B-63-15135.
By the way, although the form of the fiber mat to be used greatly affects the impregnation speed of the resin (sheet productivity), the strength of the impregnated sheet, the performance such as moldability, and the pressing force required at the time of impregnation, it is almost always specified. It has not been. With a few exceptions, Japanese Patent Publication No. 1-53896 and Japanese Patent Publication No. 5
There is a report in JP-A-2-25864. In the former, the space volume of the fiber mat is specified to be 40% by volume or less, and in the latter, when producing a fiber-reinforced thermoplastic foam, the fiber mat is determined by the compression force and the bulk density at that time. Is defined.

[0003]

[Problems to be Solved by the Invention]
In Japanese Patent Publication No. 6, the definition that the space volume of the fiber mat is 40% by volume or less is that the space ratio e of the fiber mat is 0.6 in the expression of the present invention.
This corresponds to the above. However, the porosity of the fiber mat (the ratio of the void volume in the mat) varies greatly depending on the pressure to be measured. That is, the higher the pressure, the smaller the value of e. FIG. 2 shows an example of the measurement of the relationship between the pressing force and the void ratio of the glass fiber mat. As shown in the figure, the porosity of the fiber mat changes greatly depending on the pressing force of the mat,
It is meaningless if the measurement pressure is not limited to the pressure applied to the material in the impregnation step. If the description of the above patent is interpreted as expressing the form of the fiber mat at zero pressing force, this case also has no substantial meaning. For example, even if the fiber mat has exactly the same porosity as measured under a pressing force of 0.5 kg / cm ² , the apparent porosity e at zero pressing force with and without a needle punch is extremely large. Can be three times different.

[0004] Next, in the case of specifying the form of the fiber mat by the compressive force and the bulk density at that time in Japanese Patent Publication No. 52-25864, the bulk density is defined in the present invention if the fiber density is limited. It can have the same meaning as the porosity of the fiber mat. However, there is no mention of the composition ratio of the matrix and the fiber mat, that is, the relationship between the weight ratio or volume ratio and the form of the proper mat.

An object of the present invention is to provide a method for producing a fiber-reinforced thermoplastic sheet having an excellent reinforcing effect by solving the above-mentioned problems, with a high material yield and at low cost.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above-mentioned object, and variously changed the composition ratio (volume ratio) of the matrix and the fiber, and changed the form (space ratio) of the fiber mat. As a result of various changes, we found that there was an appropriate combination of material composition and mat form,
The present invention has been made.

That is, in the present invention, the impregnation pressure for impregnating the fiber mat with the matrix is 2 kgf / cm ² or less, and the ratio of the volume (A) of the matrix before impregnation to the volume (B) of the fibers of the fiber mat (A / B, where A + B = 1),
And a porosity of the fiber mat under the impregnation pressure is determined in advance, and a fiber mat having a porosity in which the porosity is in the range of A to (AB) is used. The matrix is supplied, heated until the matrix is in a state of softening and flowing, and the matrix is impregnated into the fiber mat at the impregnation pressure, and then the matrix is cooled and solidified while applying pressure so that the mat does not expand in the sheet thickness direction. The present invention relates to a method for producing a fiber-reinforced thermoplastic resin sheet.

[0008] The matrix and the fiber, which are constituents of the fiber reinforced thermoplastic resin sheet, are selected according to the use of the sheet, required characteristics, and the like. As the thermoplastic resin used as the matrix, , Polyethylene resin, polypropylene resin, ethylene-propylene copolymer resin, ethylene-vinyl acetate copolymer resin,
Ethylene-acrylate copolymer resin, nylon resin, polyethylene terephthalate resin, polystyrene resin, polyvinyl chloride resin, polyvinylidene chloride resin,
Examples thereof include a polycarbonate resin, a polyamide resin, a polyacetal resin, a methacrylic resin, and a blend resin containing these.

The fibers can be selected from those used for fiber-reinforced thermoplastic resin sheets. Examples of the fibers include glass fibers, carbon fibers, metal fibers, and aramid fibers. The exemplified high modulus fibers are generally rigid and have poor entanglement of the fibers required to form the nonwoven fabric, so that synthetic fibers such as polypropylene and polyester may be added as necessary. The fiber length is suitably about 6 to 100 mm, especially about 13 to 50 mm, and the aspect ratio is preferably 1000 or more.

The volume ratio of the matrix (A) / fiber (B) is determined from the strength of the fiber-reinforced thermoplastic resin sheet and the like.
About 0.95 / 0.05 to 0.60 / 0.40, preferably 0.9 / 0.1 to 0.
It is set within the range of about 7 / 0.3.

In the fiber mat, the space ratio of the mat under the pressure applied to the fiber mat in the matrix impregnation step is A to (in the matrix / fiber volume ratio (A / B, where A + B = 1)). Those which fall within the range of AB) are used. FIG. 1 shows the result of determining the relationship between the porosity and the matrix remaining outside the fiber mat without being impregnated. In the figure, □ indicates the case where the volume ratio of the fiber is 5% (accordingly, the volume ratio of the matrix is 95%), ◆ indicates the case where the volume ratio of the fiber is 10%, ○ indicates 20%, Δ indicates 30%, and ■ indicates the case of 40%. In the present invention, a fiber mat having a porosity in which the volume ratio of the matrix remaining outside the mat in FIG. 1 is 0 to 50% is used. This is shown in the table below. The preferred porosity is such that the volume fraction of the matrix remaining outside the mat is 0 to 46%, particularly 5 to 30%.

[0012]

[Table 1]

Since the actual fiber mat is not always completely homogeneous, even if the average value of e is the same as the upper limit value, there may be a portion locally exceeding this value. In such a case, there is about 5
About 90% by volume (e = 0.895 in the case of 90/10) may remain. If the fiber mat is homogeneous, e may be equal to the upper limit.

The porosity e of the nonwoven fabric when pressure is applied during the above-mentioned melt impregnation of the matrix can be determined as follows. First, total weight W [g], area S
A fiber non-woven fabric having an arbitrary thickness measured in [cm ² ] is set in a pressing device having a vertical plate and a predetermined pressure is uniformly applied to the non-woven fabric until the thickness of the non-woven fabric no longer changes (usually (Approximately 5 minutes) Continue applying the same pressure. Next, the thickness t [cm] and the area S '[cm ² ] (usually the same as the initial area S) of the compressed nonwoven fabric are measured. As a result, the space ratio e is obtained by the following equation.

[0015]

Embedded image v ₁ : true volume of fiber [cm ³ ] = W / σ σ: specific gravity of fiber v ₂ : apparent volume of non-woven fabric at compression [cm ³ ] = t × S ′

When the porosity e of the fiber mat hardly changes with temperature, the measurement may be performed at room temperature. However, when the fiber mat before impregnation contains a material other than reinforcing fibers, for example, a fibrous matrix, a powdery matrix, and an emulsion matrix, those excluding these components, that is, function as a reinforcing fiber mat during the impregnation step. Only components should be used for porosity measurements. If the porosity of the fiber mat changes significantly with temperature, measure the porosity at a temperature equal to the temperature of the impregnation step.

Fiber mats having different porosity can be manufactured as follows. A discontinuous fiber bundle (chopped strand) of commercially available fiber, for example, glass fiber, is opened by applying a relatively weak shear force to the fiber bundle using an apparatus such as a Henschel mixer. At this time, the degree of fiber bundle opening can be changed by changing the stirring time in the mixer. That is, when the stirring is performed for a long time, the fiber opening proceeds more, and the aggregate of the produced fibers has a low bulk density. In this way, fiber aggregates having different bulk densities are dispersed in a mat shape using a fiber feeder or a condenser used in the nonwoven fabric industry, and fiber mats having different bulk densities, that is, different void ratios can be manufactured.

Other methods for opening the fiber bundle include a method using a cylinder opener with a spike, a method for removing the fiber sizing agent with a solvent or the like, and a method for blowing high-speed air.

As a method of easily adjusting the porosity of the fiber mat, a large amount of a high porosity mat and a low porosity mat having a known porosity are prepared in advance, and both are laminated or mixed. By doing so, an arbitrary space ratio mat can be manufactured.

The fiber mats may be joined by a needle punch or may be joined by a binder. Further, some or all of the fibers may be oriented in one direction. Further, the structure may be non-uniform in the thickness direction, that is, a structure in which layers having different porosity may be laminated, and as disclosed in Japanese Patent Application Laid-Open No. 3-47740, the porosity is continuously increased in the thickness direction. A structure that changes may be used. In the case of a mat that is not uniform in the thickness direction, the entire porosity e can be used as a representative value. However, it is desirable from the viewpoint of the reinforcing effect that all the layers have a porosity of not less than the lower limit of the present invention. A fiber mat in which 30-95% of the fibers are oriented in one direction and 70-5% in a random direction can be manufactured as follows.

The fibers used as raw materials are inexpensive discontinuous fiber bundles (chopped strands) in which tens to thousands of single fibers are bundled, or continuous fibers are cut into arbitrary lengths before use. The discontinuous fiber bundle may be used without being spread, but it is preferable to partially open the fiber bundle. The degree of spreading is preferably such that a part of the fiber is spread to a monofilament. 50% by weight or more, preferably 50% by weight of unopened
About 90% by weight is appropriate.

A rotating drum-shaped cylinder having spikes on its surface in a state where the discontinuous fiber bundle cut to a length of 6 to 100 mm is left as it is, or in a state where the fiber is opened to any extent within a range where the fiber is not significantly damaged. Quantitatively.

The most typical method for opening a discontinuous fiber bundle is to use an apparatus called a spreader, a beater or a blender which is widely used as one of dry nonwoven fabric manufacturing apparatuses. As another method, a so-called Henschel mixer may be used. Further, it is possible to open the fiber bundle to some extent only by air-feeding the fiber bundle with air through a cotton feeder having rotating blades or the like.

The method for quantitatively supplying the discontinuous fiber bundle to the drum-shaped cylinder having spikes on the surface can be directly applied to a dry nonwoven fabric manufacturing technique.

As a drum having a spike on its surface (spike drum), a drum mounted on a card machine which is widely used in the nonwoven fabric industry can be used as it is. In card machines, the fed fibers are generally brought into contact with a rotating drum cylinder having spikes on the surface. Spikes arrange the fibers into a nonwoven fabric just like a comb squeezes hair. The fibers arranged on the rotating cylinder are ultimately transferred to a drum having other adjacent spikes, called a doffer, and transferred to the next step. The shape of the spike is generally a so-called metallic wire (saw blade shape) or a garment (needle shape).

The length protruding from the drum surface is several mm to 1
cm. The number of spikes planted is generally the number of points +
~ Several hundred pieces / inch ² . In the card machine, a rotating drum such as a takein, a walker, a stripper or the like can be provided in addition to the cylinder and the doffer in accordance with a target nonwoven fabric.

A nonwoven fabric in which a part of the constituent fibers is oriented in one direction can be formed by changing the rotation speed of a plurality of drums having spikes on the surface rotating adjacent to each other. The proportion of fibers oriented in one direction (the direction of rotation of the drum) depends on the type of fiber used, that is, the material mixture, fiber length, fiber diameter, etc.
The shape, number and rotation speed of the spikes on the drum used,
It changes depending on the fiber feed speed and the like. In other words,
If the fibers to be used and the apparatus are determined, the rate of the fibers oriented in one direction can be controlled by controlling the feed speed of the fibers and the rotation speed of each drum.
Therefore, the feed rate and the number of rotations of each drum are changed in advance for the fiber and the device to be used, and the ratio of the fiber oriented in one direction in the nonwoven fabric formed for each condition is obtained. You only need to drive. The minimum number of spike drums is two, and usually about 2 to 10, usually 2 to 5 spike drums.
Generally, the higher the rotation speed of the latter spike drum is, the higher the proportion of fibers oriented in one direction is, and the greater the number of spike drums connected in series is, the more the state is increased. You. Even if the number of rotations of the latter spike drum is not faster than that of the former spike drum, some of the fibers are oriented in the rotation direction. The method of measuring the percentage of fibers blended in one direction is generally measured directly by visual observation, but the other method is to quantify an enlarged photograph of the nonwoven fabric by computer image processing. Can also.

The porosity of the formed nonwoven fabric is influenced not only by the type and orientation of the fibers but also by the degree of fiber opening. In addition, the fiber opening progresses during the formation of the nonwoven fabric by passing through a spike drum or the like. However, if the fiber to be used and the device are determined, the porosity of the nonwoven fabric formed according to the feed speed of the fiber and the rotation speed of each drum becomes substantially constant. Then, it is sufficient to drive the vehicle based on this data.

The nonwoven fabric which can be produced by using a card machine is usually made of glass fiber and has a basis weight of several g / m ² to several + g / m ² , at most 100 g / m ² . Therefore, in order to produce a nonwoven fabric having an arbitrary basis weight, a method of arranging a plurality of card machines, stacking the nonwoven fabrics discharged from each card machine in multiple stages, and winding the nonwoven fabric produced by one card machine in a roll shape. After preparing a plurality of rolls, a method of laminating the nonwoven fabric while feeding out each roll, a combination of the above methods, and the like are considered. The laminate of the nonwoven fabric thus formed can be joined by mechanical means such as a needle punch to improve the strength of the nonwoven fabric. However, in these processes, the void ratio e of the processed nonwoven fabric is out of the range of the present invention. It is necessary to take care not to become Further, the nonwoven fabric laminate can be joined by a binder.

On the other hand, in the present invention, an oriented nonwoven fabric having an arbitrary basis weight can be obtained by a simplified process. The long nonwoven fabric taken out of one card machine is folded on a conveyor moving in parallel with the long direction, and the weight is set to an arbitrary weight so that the fiber orientation is not disturbed.
The folding may be performed by providing a device for reciprocating the conveyor in a preceding stage in the traveling direction on the conveyor, and feeding out the long nonwoven fabric therefrom. What has a web feeding function, such as a conveyor and a reel, may be used for this apparatus. The folded laminated nonwoven fabric is made into a nonwoven fabric joined by processing such as needle punching. As a result, a nonwoven fabric having an arbitrary basis weight can be obtained without disturbing the fiber orientation in a single card machine with a minimum process and space.

The matrix may be in any form of a film, a molten resin, a powder, a granule, a fiber, and an emulsion. Further, known additives may be added.

After supplying the matrix, the mat is impregnated with the matrix by applying heat and pressure until the matrix is at least softened and fluidized. The heating temperature is a temperature that can at least soften the matrix,
This depends on the type of matrix.

The impregnation pressure used in the present invention is 2 kgf / cm ² or less. In the case of continuously producing a sheet, a method of impregnating and cooling between two endless belts is known (Japanese Patent Publication No. 63-15135). The low pressure may make the impregnating device inexpensive, and may increase the material yield without using a sealing material. However, since there is a possibility that the reduction in the sheet thickness may gradually progress with time, it is better to perform clearance control (lower limit control) on the pressed surface.

According to the method of the present invention, a fiber-reinforced thermoplastic resin foam can also be produced. In this case, after impregnation without bubbles, the pressure applied to the sheet is made lower than the pressure in the impregnation step, and the sheet is expanded in the thickness direction by the repulsive force of the fiber mat while heating to a temperature at which the resin can flow.

After impregnating the fiber mat with the matrix, the matrix may be cooled and solidified while applying pressure so that the mat does not expand in the sheet thickness direction.

[0036]

In the method of the present invention, the porosity under the pressure applied during the impregnation of the fiber mat is such that when the matrix is impregnated, 50% by volume of the sheet is changed from the state where the matrix just fills the space of the fiber mat. A material that is not impregnated into the mat but falls within the range of the remaining state is adopted. The present inventors have found that when the porosity is equal to or less than the lower limit, the reinforcing effect of the fiber is significantly reduced. When the porosity is less than the above lower limit, when pressure and temperature are applied to the material in the impregnation step, the remaining 50% by volume or more of the matrix that does not impregnate the fiber mat is removed before the impregnation is completed. Leaked to This phenomenon is high pressure,
This is more noticeable as the viscosity of the matrix is lower and the time for pressurization is longer. As a result, in the impregnated sheet, the material (especially the matrix) decreases in the material yield due to the outflow in the width direction, the fiber content increases due to the outflow of the matrix, the thickness of the impregnated sheet decreases, and the like, resulting in an increase in material cost and Quality becomes unstable. In order to prevent this phenomenon, it is necessary to attach a sealing material having a predetermined thickness around the material in the impregnation step and the cooling step, but when using a fiber mat having a porosity adopted in the present invention, In this case, the outflow of the matrix is small even without this sealing material.

[0037]

【Example】

Example 1 Fuji Fiberglass Glass Chopped Strand F
ES-13-1250 (13mm fiber length, 17μm fiber diameter, 13 bundles)
5) into a Henschel mixer FM75J manufactured by Mitsui Miike Kakoki Co., Ltd.
Then, the ZoSo blades were stirred at a rotation speed of about 40 m in peripheral speed. The stirring time was changed to 10, 30, 60, and 120 seconds. Observation of the glass fiber aggregate obtained after each stirring time revealed that fiber bundle opening progressed with an increase in the stirring time and gradually became bulky and flocculent. The fibers after each stirring time were continuously fed by air to a cotton collecting device called a condenser manufactured by Chuo Cotton Machine Works, and four types of fiber mats having a width of 750 mm and a length of 1500 mm were obtained. The approximate mat of the fibers was fed to a device called a so-called random weber, and the fibers were dispersed and accumulated on a moving conveyor to obtain a target fiber mat. The basis weight of each fiber mat was adjusted to about 994 g / m ² by adjusting the conveyor speed of the random weber.
Next, the porosity e of each fiber mat was measured under the conditions of a pressure of 1 kgf / cm ² .

Thus, the basis weight is 994 g / m ² , the porosity e at a pressure of 1 kgf / cm ² is 0.60, 0.67, 0.75, 0.80, respectively, and the thickness for this pressure is 1.0, 1.2, 1.6,
A 2.0 mm glass fiber mat (without needle punch) was obtained. For the glass fiber mats with each space ratio of 30cm x 30cm, two of them and the polypropylene film 4 also having a size of 30cm x 30cm, a film thickness of 0.78mm and MI of 60g / 10min.
The sheets were laminated in the order of polypropylene film / glass fiber mat / polypropylene film / polypropylene film / glass fiber mat / polypropylene film.
The laminate had a matrix / fiber volume ratio of 0.80 / 0.
It becomes 20. This laminate is sandwiched between two 1 mm-thick stainless steel plates, and pressed at 200 ° C. with a hot press of 1 kgf / cm ^2.
For 4 minutes. Then, it was immediately moved to a cooling press at 25 ° C. together with the stainless steel plate, and was cooled and pressed at a pressure of 1 kgf / cm ² for 1 minute. No spacers or seals were used. As shown in FIG. 3, the cross section of the obtained sheet had a matrix 3 spread over almost the entire mat of the fibers 2 in the thickness direction except for e = 0.60. Table 1 shows the evaluation results.

Comparative Example 1 The void ratio e at 1 kgf / cm ² of the glass fiber mat was 0.56 and
A sheet was produced in exactly the same manner as in Example 1 except that the value was 0.85. In this sheet, the one with e = 0.56 has a greater outflow to the periphery of the matrix, so that the fiber content is higher than the set value of 20% by volume and the sheet thickness is higher than the set value of 3.8 to 4.0 mm. It has become thin. Further, as shown in FIG. 4, the cross section of the sheet 1 had a clearly laminated structure of the matrix 3 and the fiber 2, and the reinforcing effect and the bending strength were low. In the case of e = 0.85, as shown in FIG. 6, the matrix could not fill the inside of the mat, and there were impregnation defective portions 4 (FIG. 4). Table 2 shows the evaluation results.

[0040]

[Table 2]

Example 2 The impregnation step and the cooling step were performed continuously between two endless belts. The clearance between the belts was 3.8 mm. The belt temperature is 200 ° C in the impregnation process and 30 ° C in the cooling process
I tried to be. No sealing material was used. The glass fiber mat uses the mat of Example 1 having a space factor e = 0.75 at 1 kgf / cm ² and the matrix uses the polypropylene film of Example 1, and the composition ratio is matrix / fiber = 80/20% by volume. And The belt pressure was set at 1 kgf / cm ² .

Example 3 A fiber mat having an inclined structure in which the porosity continuously changes in the thickness direction (Japanese Patent Laid-Open No. 3-47740) and a total porosity e of 0.75 measured at 1 kgf / cm ^2. Example 2 is the same as Example 2 except that the following was used.

Example 4 A chopped strand glass fiber (“FES-50-1250”, manufactured by Fuji Fiber Glass Co., Ltd.) having a fiber length of 50 mm, a fiber diameter of 11 μm, and a bundle number of 135 was opened with a fiber opening machine (“Super Blender NDWG-20”). And Ikegami Kikai Co., Ltd.) to pre-spread the fiber bundle. This pre-opened glass fiber 5 is transferred to a card machine ("Card machine 60-M32",
(Manufactured by Co., Ltd.). This card machine has a diameter of 806m
It has three spike rolls: a cylinder roll 6 of mφ, a doffer roll 7 of 522 mmφ, and a takein roll 8 of 229 mmφ. Further, five walker rolls each having a diameter of 127 mmφ and five stripper rolls each having a diameter of 78 mmφ (all are shown in the drawing) Not included).

The supply rate of the glass fiber is about 30 kg / hr, and the speed of taking out the nonwoven fabric from the doffer roll 7 is about 15 mp.
m, a nonwoven fabric 9 having a basis weight of 22 g / m ² was obtained. After laminating 23 pieces of this glass fiber nonwoven fabric with the same fiber orientation direction, needle punching was performed at a pitch of 5 pieces / cm ² from the top and bottom.

This glass fiber nonwoven fabric has a basis weight of about 500 g / m ^2.
In about 60% of fibers are oriented in one direction, 1.0kgf / c
The porosity e at a pressure of m ² was 0.75. Four nonwoven fabrics have a thickness of 150μ with a MI of 10g / 10min.
1.0kg with a press heated to 200 ° C with a predetermined number of m-thick films (“F-150H”, manufactured by Nippon Petrochemical Co., Ltd.)
5 minutes at a pressure of f / cm ² and then 1.0 kgf / cm ²
To obtain a fiber-reinforced thermoplastic resin sheet having a thickness of 4 mm and a glass fiber content of 19% by volume. Table 3 shows the orientation direction of the sheet and the mechanical strength in the direction perpendicular to the orientation.

FIG. 8 shows a schematic diagram of a cross section of this sheet. The thermoplastic resin 3 sufficiently impregnated the nonwoven fabric of the glass fiber 2, and no air bubbles remained in the sheet.

Example 5 The same 80 parts by weight of glass fiber and 20 parts by weight of polypropylene fiber as those used in Example 4 were treated with the same opening machine as in Example 4 and preliminarily opened, while simultaneously mixing both fibers. did.
This mixture is supplied to the company's automatic hopper feeder (Ikegami Kikai Co., Ltd.)
) Was quantitatively supplied to the same card machine as in Example 4 at a rate of 30 kg / hr. The take-out speed from the doffer roll 8 was 25 mpm to obtain a nonwoven fabric 9 having a basis weight of 13 g / m ² .

As shown in FIG. 9, Ikegami Kikai
The web layer 1KH-30 (manufactured by Co., Ltd.) 10 was fed while being folded on a conveyor 11 moving parallel to the fiber orientation direction. The web cloth layer has a head 12 that moves back and forth in a direction parallel to the fiber orientation. The speed of the conveyor 11 was adjusted to fold the nonwoven fabric in the thickness direction of the nonwoven fabric so that 29 nonwoven fabrics were stacked, and the folded body 13 was needle-punched from above and below at a pitch of 5 / cm ² each. The obtained nonwoven fabric has a basis weight of 375 g / cm ² (of which 300 g / cm ² is glass fiber), about 80% of oriented fibers, and a nonwoven fabric space ratio e of 0.75 at a pressure of 1.0 kgf / cm ^2. there were.

A fiber reinforced thermoplastic resin sheet having a thickness of 4 mm and a glass fiber content of 19% by volume was obtained in the same manner as in Example 4, and the mechanical strength was examined. Table 3 shows the results.

The glass fiber mat laminated Comparative Example 2 roving 300 g / m ² was drawn aligned in one direction and random chopped strand mat 300 g / m ² ( "Ramimatto LM303KA-104", product of Nitto Boseki Co.
Co., Ltd.) and a 150 μm thick polypropylene film (“F
-150H "(manufactured by Nippon Petrochemical Co., Ltd.) were alternately laminated with the same number of rovings in the same direction and laminated in the same manner as in Example 4 to a thickness of 4 mm and a glass fiber content of 40% by weight.
Sheet was obtained. The space factor e of the glass fiber mat is 1.0kgf
The pressure was 0.45 for a pressure of / cm ² , and the fiber orientation component was about 50%.

Table 3 shows the mechanical strength of the obtained sheet. FIG. 10 shows a schematic diagram of a cross section of this sheet. The thermoplastic resin 3 was not sufficiently impregnated in the glass fiber mat 13, and the resin and fiber layers were separated without being integrated.

As is evident from Table 3, the fiber-reinforced thermoplastic sheet according to the present invention achieves sufficient impregnation of the resin, and particularly has high flexural strength and flexural modulus at which the influence of the impregnation appears remarkably. In addition, the orientation and the strength in the vertical direction are at a high level even without a random fiber mat as in the comparative example.

[0053]

[Table 3]

[0054] performs a 1 cm ² per 20 times of needle punching to Example 5 fiber mat, 2 kgf / mat voidage in cm ² glass fiber mat 0.78 (fiber length 50 mm, fiber diameter 11 [mu] m) was obtained. Using this mat, a sheet once impregnated was produced in the same manner as in Example 1 (the pressure during impregnation was 2 kgf / cm ² ). Next, heating was continued at 200 ° C. in a state where the pressure was released without moving to the cooling step, and the sheet was expanded in the thickness direction by the repulsive force of the fiber mat. The foamed sheet obtained by cooling this was a high-strength foam with a matrix attached to almost the entire surface of the fiber.

[0055]

According to the present invention, a fiber reinforced thermoplastic sheet having excellent reinforcing effect, low outflow of the matrix during impregnation, high material yield, and low pressure can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the fiber mat porosity under impregnation pressure and the volume% of matrix remaining outside the mat after impregnation for each matrix / fiber volume ratio.

FIG. 2 is a graph showing a relationship between a pressing force and a void ratio of a fiber mat.

FIG. 3 is a cross-sectional view schematically showing an impregnated sheet obtained in an example.

FIG. 4 is a cross-sectional view schematically showing an impregnated sheet obtained in a comparative example.

FIG. 5 is a cross-sectional view schematically showing an impregnated sheet obtained in an example.

FIG. 6 is a cross-sectional view schematically showing an impregnated sheet obtained in a comparative example.

FIG. 7 is a side view schematically showing a fibrous nonwoven fabric manufacturing apparatus used in one embodiment of the present invention.

FIG. 8 is a schematic sectional view of an example of a fiber-reinforced thermoplastic sheet according to one embodiment of the present invention.

FIG. 9 is a side view schematically showing an apparatus for laminating a fibrous nonwoven fabric used in one embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view of a comparative example of a fiber-reinforced thermoplastic sheet.

Claims (1)

(57) [Claims] An impregnating pressure for impregnating a fiber mat with a matrix is 2 kgf / cm ² or less, and the volume of the matrix before impregnation (A) and the volume of fibers of the fiber mat (B)
(A / B, where A + B = 1) and the porosity of the fiber mat under the impregnation pressure are determined in advance, and a fiber mat having a porosity in which the porosity is in the range of A to (AB) is obtained. The fiber mat is supplied with an amount of the matrix that satisfies the above range, heated until the matrix is in a state of softening and flowing, and the matrix is impregnated with the fiber mat at the impregnation pressure. A method for producing a fiber-reinforced thermoplastic resin sheet, comprising cooling and solidifying a matrix while applying pressure so as not to swell.