JP7619218B2 - Fiber-reinforced resin molded body and its manufacturing method, composite pellets, and chopped strands - Google Patents

Description

The present invention relates to a fiber-reinforced resin molding containing resin and glass filaments.

Conventionally, glass fiber reinforced molded bodies are known that are formed by blending glass fibers with thermoplastic or thermosetting resins. Glass fiber reinforced molded bodies are widely used as materials for various structures due to their excellent mechanical properties.

In recent years, various studies have been conducted with the aim of further improving the performance of structures. For example, Patent Document 1 discloses a resin composition consisting of 40 to 99 parts by weight of a thermoplastic resin made of an aromatic polycarbonate resin and 1 to 60 parts by weight of a reinforcing filler. The reinforcing filler is composed of (1) flat cross-section glass fibers having an average cross-sectional major axis of 10 to 50 μm and an average ratio of the major axis to the minor axis of 1.5 to 8, and (2) circular cross-section short glass fibers having an average fiber length to average fiber diameter ratio (aspect ratio) of 10 or less, and the weight ratio of the flat cross-section glass fibers to the circular cross-section short glass fibers is 5/95 to 95/5.

Patent Document 2 also discloses a glass fiber-reinforced polyamide resin composition containing a polyamide resin and glass fibers. Some or all of the glass fibers contained in the glass fiber-reinforced polyamide resin composition are flat cross-section glass fibers, and the flat cross-section glass fibers are composed of flat cross-section glass fibers having a minor axis/major axis ratio of 0.3 to 0.5 and flat cross-section glass fibers having a minor axis/major axis ratio of 0.2 to 0.3. The mass ratio of the flat cross-section glass fibers to the flat cross-section glass fibers is 0:100 to 100:0.

JP 2007-186571 A International Publication No. WO2019/074038

When a structure made of a glass fiber reinforced molding is thinned (the thickness of the structure becomes thinner), the structure becomes more susceptible to warping after resin molding, and the mechanical properties of the structure tend to decrease. In response to increasing demands for the performance of structures, there is a demand for further improvements in the warping resistance (warping suppression properties) and mechanical properties of the structures.

One aspect of the present invention aims to provide a fiber-reinforced resin molding that combines warpage suppression properties and mechanical properties.

In order to solve the above problem, a fiber-reinforced resin molding in one embodiment of the present invention is a fiber-reinforced resin molding containing a resin and a plurality of glass filaments, the plurality of glass filaments having a flat cross-sectional shape with an aspect ratio (major axis/minor axis) in a range of more than 1.0 and not more than 7.0, (i) the blending ratio of the glass filaments having an aspect ratio classified in a first aspect ratio category of more than 2.8 and not more than 4.6 is 50 to 100% relative to a specific total number of the plurality of glass filaments, and (ii) the blending ratio of the glass filaments having an aspect ratio classified in a second aspect ratio category of more than 4.6 and not more than 7.0 is 0 to 50%, and a first histogram showing the distribution of the aspect ratio for the specific total number of glass filaments, with the horizontal axis being the aspect ratio, the vertical axis being the blending ratio, and a class width of 0.2, has at least two peaks.

In one embodiment of the present invention, the composite pellets include a resin and a plurality of glass filaments, and the glass filaments have a flat cross-sectional shape with an aspect ratio (longer diameter/minor diameter) in a cross section in the range of more than 1.0 and not more than 7.0. The glass filaments (i) have an aspect ratio classified in a first aspect ratio range of more than 2.8 and not more than 4.6, and the glass filaments (ii) have an aspect ratio classified in a second aspect ratio range of more than 4.6 and not more than 7.0, in relation to a specific total number of the glass filaments, and the first histogram showing the distribution of the aspect ratios for the specific total number of glass filaments, with the horizontal axis representing the aspect ratio, the vertical axis representing the blending ratio, and a class width of 0.2, has at least two peaks.

In one embodiment of the present invention, the chopped strand is a chopped strand including a plurality of glass filaments, the glass filaments having a flat cross-sectional shape with a flatness ratio (longer diameter/minor diameter) in a range of more than 1.0 and not more than 7.0, (i) the blending ratio of the glass filaments having a flatness ratio classified in a first flatness ratio range of more than 2.8 and not more than 4.6 is 50 to 100% relative to a specific total number of the plurality of glass filaments, and (ii) the blending ratio of the glass filaments having a flatness ratio classified in a second flatness ratio range of more than 4.6 and not more than 7.0 is 0 to 50%, and a first histogram showing the distribution of the flatness ratio for the specific total number of glass filaments, with the horizontal axis representing the flatness ratio, the vertical axis representing the blending ratio, and a class width of 0.2, has at least two peaks.

In addition, the manufacturing method of a fiber-reinforced resin molding in one aspect of the present invention includes a preparation step of preparing the chopped strands, a pellet formation step of kneading the chopped strands with a thermoplastic resin to form composite pellets, and an injection molding step of performing injection molding using the composite pellets.

According to one aspect of the present invention, it is possible to provide a fiber-reinforced resin molding that combines warpage suppression properties and mechanical properties.

1 is a schematic diagram showing a configuration of a fiber-reinforced resin molded body in one embodiment of the present invention. FIG. FIG. 2 is a cross-sectional view of a glass filament cut along a plane (transverse section) perpendicular to the longitudinal direction. 4 is a histogram showing the distribution of the aspect ratio of glass filaments contained in a fiber-reinforced resin molding according to one embodiment of the present invention. 3 is a histogram showing the distribution of circle-equivalent diameters of glass filaments contained in a fiber-reinforced resin molding according to one embodiment of the present invention.

One embodiment of the present invention will be described below. Note that the following description is intended to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

In one embodiment of the present invention, first, molten glass is drawn out of a bushing and cooled to form flat fibers with an elliptical cross section and a circle-equivalent diameter of several μm to several tens of μm. Next, a treatment agent is applied to the flat fibers and they are bundled together to form strands (glass strands). The strands are then cut to a predetermined length to obtain chopped strands.

Glass fiber is a general term for aggregates of glass filaments (for example, a bundle of 100 or more filaments) and individual single fibers dispersed from glass fibers (resulting from the opening of glass fibers). The single fibers that make up glass fiber are called glass filaments, an aggregate of multiple glass filaments is called a glass strand, and glass strands cut to a specified length are called chopped strands.

In this specification, the term "flatness ratio" refers to the ratio of the major axis to the minor axis in the shape of the surface to be calculated. The term "flatness ratio in the cross section" of a glass filament is used in the following sense. That is, when measuring the flatness ratio in the cross section of a glass filament contained in a resin molding, the end face of the glass filament is usually observed. In this case, the end face is not necessarily flat, but the shape formed by the outer edge of the end face when the end face is viewed from a line of sight parallel to the longitudinal direction of the glass filament (e.g., an ellipse or a rounded rectangle) is regarded as the shape of the "cross section" of the glass filament to calculate the flatness ratio.

The distribution of the aspect ratio means the frequency distribution, and can be understood, for example, by a histogram with the horizontal axis representing the aspect ratio and the vertical axis representing the frequency (number) or relative frequency (mixture ratio). The distribution of the aspect ratio indicates the bias and variation in the aspect ratio in a collection of a specific total number of measurement objects (for example, glass filaments).

(Brief Description of the Findings of the Invention)
Prior to describing the fiber-reinforced resin molding according to one embodiment of the present invention, the findings of the present inventors will be outlined below.

The fiber-reinforced resin molding may contain resin, glass filaments constituting the glass fibers, and glass filaments dispersed from the glass fibers. Unless otherwise specified in this specification, the characteristics of the glass filaments described below are characteristics that appear when both the glass filaments constituting the glass fibers and the glass filaments dispersed from the glass fibers are mixed together. For example, the characteristics of the glass filaments contained in the fiber-reinforced resin molding described in this specification refer to the overall characteristics of the multiple glass filaments contained in the fiber-reinforced resin molding, which appear in combination without distinguishing the specific aspects of the individual glass filaments. Also, in a fiber-reinforced resin molding formed using chopped strands, the overall characteristics of the glass filaments contained in the fiber-reinforced resin molding are approximately the same as the overall characteristics of the glass filaments contained in the chopped strands.

A resin molded body formed to include glass filaments having a cross-sectional shape with an aspect ratio of about 4 can have improved mechanical properties. Generally, resin molded bodies undergo thermal shrinkage during the manufacturing process. The effect of thermal shrinkage of the resin is small in resin molded bodies having a relatively large thickness. However, warping is likely to occur in resin molded bodies having a relatively small thickness. It is believed that glass filaments having a cross-sectional shape with an aspect ratio of about 4 do not sufficiently suppress warping of resin molded bodies.

In contrast, glass filaments with a cross-sectional shape having an aspect ratio of greater than 4 have relatively good fluidity (dispersibility) in molten resin and are relatively effective in suppressing warping of resin molded bodies. However, resin molded bodies formed to include glass filaments with a cross-sectional shape having an aspect ratio of greater than 4 have a problem in that they have mechanical strength lower than the required performance when the thickness of the resin molded body is reduced.

In this situation, the inventors have conducted extensive research and have discovered the following findings. That is, the aspect ratio distribution of the glass filaments contained in the resin molding is appropriately adjusted (details will be described later). This allows the resin molding to contain both glass filaments with an aspect ratio shape that is likely to improve the property of suppressing warping and glass filaments with an aspect ratio shape that is likely to improve mechanical properties. Specifically, chopped strands are manufactured so that the aspect ratio distribution of the glass filaments shows a histogram containing multiple peaks, and the chopped strands can be used to obtain a fiber-reinforced resin molding according to one embodiment of the present invention.

The glass filaments contained in the chopped strands may have various distributions of flatness ratios due to differences in the manufacturing process. For example, the flatness ratio distribution of the glass filaments contained in the strands can be changed by adjusting the hole shape (hole arrangement) of the bushing that draws out the molten glass and various manufacturing temperatures and other conditions. On the other hand, when two or more types of chopped strands having different medians in the flatness ratio distribution of the glass filaments are simply mixed, the proportion of glass filaments having flatness ratios between the respective medians of the two or more types of chopped strands increases. As a result, chopped strands showing a histogram that does not include a peak (for example, a half-width of 2.0 or more, or no half-width exists) can be obtained. In other words, the fiber-reinforced resin molding in one embodiment of the present invention has improved performance compared to a resin molding manufactured by simply mixing two or more types of chopped strands.

(Fiber reinforced resin molded body)
Fig. 1 is a schematic diagram showing the configuration of a fiber reinforced resin molded body 1 in this embodiment. In Fig. 1, for simplification, the fiber reinforced resin molded body 1 is illustrated as a rectangular parallelepiped. The shape of the fiber reinforced resin molded body 1 can be appropriately changed depending on the purpose of use, and the specific shape is not particularly limited.

As shown in FIG. 1, the fiber-reinforced resin molding 1 includes resin 10, glass fibers 20, and glass filaments 21 dispersed from the glass fibers 20, with a large number of glass fibers 20 and glass filaments 21 dispersed in the resin 10.

The fiber-reinforced resin molding 1 may have a total content of resin 10, glass fiber 20, and glass filament 21 of 90% by mass or more, and may have a total content of 95% by mass or more. In addition to resin 10 and glass filament 21, fiber-reinforced resin molding 1 may also have other additive components.

(resin)
The resin 10 may be a thermosetting resin or a thermoplastic resin. Examples of the thermoplastic resin include polyamide resin and polycarbonate resin. By using a thermoplastic resin as the resin 10, injection molding becomes possible as described below, and it becomes easier to mold various structures. The resin 10 may be a mixture of two or more types of resin.

(Glass fiber/glass filament)
The glass fiber 20 is formed by bundling a plurality of glass filaments 21 and has an elongated shape. In the fiber reinforced resin molding 1, the content of the glass filaments 21 may be 10% by mass or more and 70% by mass or less, or 20% by mass or more and 50% by mass or less. If the content of the glass filaments 21 is less than 10% by mass, it is difficult to obtain a glass fiber reinforced resin molding having sufficient mechanical properties. If the content of the glass filaments 21 is more than 70% by mass, the moldability of the fiber reinforced resin molding 1 is poor.

Figure 2 is a cross-sectional view of glass filament 21 cut in a plane (cross section) perpendicular to the longitudinal direction. The long diameter of the cross-sectional shape of glass filament 21 is designated as long diameter L1, and the short diameter is designated as short diameter L2. In this specification, the longest length in the cross section of glass filament 21 is defined as "long diameter of glass filament 21", and the longest length in the cross section of glass filament 21 perpendicular to the long diameter is defined as "short diameter of glass filament 21".

The glass filaments 21 have a flattened cross-sectional shape, with the flatness ratio in the cross section, i.e., the ratio of the long diameter L1 to the short diameter L2 (long diameter L1/short diameter L2) (average value) being greater than 1.0 and less than or equal to 7.0.

The cross-sectional shape of the glass filaments 21 is not limited to an ellipse, and may be any shape as long as the flattening ratio (average value) represented by major axis L1/minor axis L2 is greater than 1.0 and less than or equal to 7.0. The glass filaments 21 have a flat shape with an irregular cross section, and may have a flat shape such as an oval, an ellipse, or a rounded rectangle. It is preferable that the glass filaments 21 have an oval flat shape. If the flattening ratio of the glass filaments 21 is greater than 7.0, it is difficult to obtain a fiber-reinforced resin molding 1 that satisfies the required characteristics.

The composition of the glass filaments 21 may be, for example, E glass, ECR glass, A glass, AR glass, C glass, D glass, S glass, T glass, NE glass, H glass, etc. The composition of the glass filaments 21 is not particularly limited as long as it is possible to produce a fiber-reinforced resin molding 1 that has both warp suppression properties and mechanical properties. In addition, the fiber-reinforced resin molding 1 may be a mixture of two or more types of glass filaments 21.

The glass filament 21 may have a minor axis L2 in cross section of 4 to 20 μm, or 6 to 15 μm. The glass filament 21 may have a major axis L1 in cross section of 10 to 50 μm, or 20 to 35 μm.

(Flatness ratio distribution)
The aspect ratio distribution of the glass filaments 21 contained in the fiber reinforced resin molding 1 in this embodiment will be described below. The aspect ratio distribution of the glass filaments 21 contained in the fiber reinforced resin molding 1 is approximately the same as the aspect ratio distribution of the glass filaments 21 contained in the chopped strands used in the manufacturing process of the fiber reinforced resin molding 1. Therefore, the chopped strands used in the manufacturing process of the fiber reinforced resin molding 1 may be used for the various measurements described below.

First, the measurement of the aspect ratio distribution is described as follows. That is, the aspect ratio distribution is measured for a specific total number of glass filaments. This "specific total number" may be the total number of glass filaments 21 whose aspect ratios have been measured, and may be, for example, 1000 or more. Hereinafter, the specific total number may be expressed as N. In order to observe the cross section of the glass filaments 21, the glass filaments 21 are embedded vertically in room temperature curing resin Technovit (manufactured by Kulzer), and polished after the resin has hardened. Next, the cross-sectional shape of the glass filaments 21 is observed with an electron microscope, and the lengths of the major axis L1 and minor axis L2 of the observed glass filaments 21 are measured to calculate the aspect ratio. Then, the specific total number of glass filaments 21 whose aspect ratios have been calculated are classified into a plurality of aspect ratio ranges, and the blending ratio in each aspect ratio range is quantified.

In the fiber-reinforced resin molding 1, the distribution of the flatness ratio of the glass filaments 21 measured as described above is as shown below. That is, with respect to a specific total number of the glass filaments 21, (i) the blending ratio of the glass filaments 21 having an aspect ratio classified in the flatness ratio category of greater than 2.8 and less than or equal to 4.6 (hereinafter referred to as the first flatness ratio category A1) is 50 to 100%, and (ii) the blending ratio of the glass filaments 21 having an aspect ratio classified in the flatness ratio category of greater than 4.6 and less than or equal to 7.0 (hereinafter referred to as the second flatness ratio category A2) is 0 to 50%. If the blending ratio of the first flatness ratio category A1 is less than 50%, it is difficult to obtain a fiber-reinforced resin molding 1 having both sufficient mechanical properties and warp suppression properties.

Furthermore, in the fiber-reinforced resin molding 1, the aspect ratio distribution of the glass filaments 21 shows a multi-peaked histogram (a histogram having multiple peaks). This will be explained below with reference to Figure 3. Figure 3 is a histogram showing the distribution of the aspect ratio of the glass filaments 21 contained in the fiber-reinforced resin molding 1 of this embodiment.

The histogram shown in Figure 3 is a histogram (first histogram) showing the flattening ratio distribution, created with the horizontal axis representing the flattening ratio of the glass filaments 21, the vertical axis representing the glass filament 21 blending ratio, and a class width of 0.2. Figure 3 also shows the cumulative blending ratio (the cumulative relative frequency in the histogram) in each of the above-mentioned first to third flattening ratio categories. The value of the cumulative blending ratio is shown on the right axis.

In this embodiment, the fiber-reinforced resin molding 1 has at least two peaks in the first histogram. When the fiber-reinforced resin molding 1 has two peaks in the first histogram, both peaks have peak positions in an aspect ratio range greater than 2.8.

Furthermore, in the first histogram, the fiber-reinforced resin molding 1 may include a class that indicates at least one peak value of a peak in both the first aspect ratio division A1 and the second aspect ratio division A2.

In the example shown in FIG. 3, the first histogram has a first peak centered (peak position) on the aspect ratio class of greater than 3.8 and equal to or less than 4.0, and a second peak centered (peak position) on the aspect ratio class of greater than 5.0 and equal to or less than 5.2. The fiber reinforced resin molding 1 includes a plurality of glass filaments 21 that form the first peak in the aspect ratio distribution, thereby effectively improving the mechanical properties. The fiber reinforced resin molding 1 includes a plurality of glass filaments 21 that form the second peak in the aspect ratio distribution, thereby improving the warpage suppression properties. As a result, the fiber reinforced resin molding 1 has both good mechanical properties and warpage suppression properties.

Furthermore, the fiber reinforced resin molding 1 may have a blending ratio of glass filaments 21 having an aspect ratio classified into an aspect ratio category greater than 1.0 and not greater than 2.8 (hereinafter referred to as the third aspect ratio category A3) of 0 to 15% relative to a specific total number (N) of the glass filaments 21. If the blending ratio of the third aspect ratio category A3 exceeds 15%, it is difficult to obtain a fiber reinforced resin molding 1 having both sufficient mechanical properties and warp suppression properties.

In one embodiment of the present invention, the fiber-reinforced resin molding 1 may have a glass filament 21 having an aspect ratio classified in the third aspect ratio division of 0 to 10%, a glass filament 21 having an aspect ratio classified in the first aspect ratio division of 60 to 80%, and a glass filament 21 having an aspect ratio classified in the second aspect ratio division of 20 to 40%. In addition, the fiber-reinforced resin molding 1 may have a glass filament 21 having an aspect ratio classified in the third aspect ratio division of 0 to 5%, a glass filament 21 having an aspect ratio classified in the first aspect ratio division of 65 to 75%, and a glass filament 21 having an aspect ratio classified in the second aspect ratio division of 25 to 35%. This can further improve the mechanical properties and warp suppression properties.

Furthermore, in one embodiment of the fiber-reinforced resin molding 1 of the present disclosure, in the first histogram, (i) the difference between the maximum and minimum values of the blending ratio in each class included in the first aspect ratio division is 5% or more, (ii) the difference between the maximum and minimum values of the blending ratio in each class included in the second aspect ratio division is 5% or more, and (iii) at least either the first aspect ratio division or the second aspect ratio division may include a class showing a peak value of one peak.

Furthermore, the fiber-reinforced resin molding 1 may have a peak value of the blending ratio of each of at least two peaks in the first histogram of 5% or more. In one embodiment of the fiber-reinforced resin molding 1 of the present disclosure, the half-width of each of at least two peaks in the first histogram may be 0.5 to 1.6.

In one embodiment of the fiber-reinforced resin molding 1 of the present disclosure, the difference between the class values of different classes that indicate the peak values of at least two peaks in the first histogram may be 0.4 or more. In the example shown in FIG. 3, the difference between the class values of different classes that indicate the peak values of two peaks is 1.2.

(Circle equivalent diameter distribution)
The circle equivalent diameter distribution of the glass filaments 21 contained in the fiber-reinforced resin molding 1 in this embodiment will be described below. Similar to the above-mentioned method used in measuring the aspect ratio distribution, the circle equivalent diameter distribution can be measured for a specific total number of multiple glass filaments.

In the fiber-reinforced resin molding 1 of this embodiment, it is preferable that the equivalent circle diameter of the glass filaments 21 in the cross section is in the range of 6 to 27 μm. If the equivalent circle diameter of the glass filaments 21 is less than 6 μm, it is difficult to manufacture the fiber-reinforced resin molding 1 while maintaining a flat cross-sectional shape, and if the equivalent circle diameter of the glass filaments 21 is more than 27 μm, it is difficult to obtain sufficient mechanical properties and warp suppression properties.

Furthermore, it is preferable that the fiber reinforced resin molding 1 has a composition ratio of glass filaments 21 having a circle equivalent diameter classified into a circle equivalent diameter category of 6 μm or more and less than 13 μm (hereinafter referred to as the first circle equivalent diameter category B1) of 15 to 25%, (ii) a composition ratio of glass filaments 21 having a circle equivalent diameter classified into a circle equivalent diameter category of 13 μm or more and less than 15 μm (hereinafter referred to as the second circle equivalent diameter category B2) of 55 to 65%, and (iii) a composition ratio of glass filaments 21 having a circle equivalent diameter classified into a circle equivalent diameter category of 15 μm or more and less than 27 μm (hereinafter referred to as the third circle equivalent diameter category B3) of 15 to 25% with respect to a specific total number of the glass filaments 21. According to the above configuration, a fiber reinforced resin molding having both warp suppression properties and mechanical properties can be easily obtained.

Furthermore, in the fiber reinforced resin molding 1, the distribution of the equivalent circle diameters of the glass filaments 21 shows a unimodal histogram. This will be explained below with reference to FIG. 4. FIG. 4 is a histogram showing the distribution of the equivalent circle diameters of the glass filaments 21 contained in the fiber reinforced resin molding 1 of this embodiment. In addition, FIG. 4 also shows the cumulative blending ratio (the cumulative relative frequency in the histogram) in each of the first to third equivalent circle diameter categories mentioned above. The value of the cumulative blending ratio is shown on the right axis.

The histogram shown in Figure 4 is a histogram (second histogram) showing the distribution of equivalent circle diameters, created with the horizontal axis representing the equivalent circle diameter of the glass filaments 21, the vertical axis representing the glass filament 21 blending ratio, and a class interval of 0.25.

In the fiber-reinforced resin molded body 1 according to one embodiment of the present disclosure, the second histogram has a unimodal distribution. In other words, in the fiber-reinforced resin molded body 1 according to one embodiment of the present disclosure, the second histogram has only one peak. The second histogram shown in FIG. 4 has only one peak centered (peak position) on the class in which the aspect ratio is greater than 13.0 μm and equal to or less than 13.25 μm. By having the above configuration, a fiber-reinforced resin molded body having both warp suppression properties and mechanical properties can be easily obtained.

(Fiber length)
The multiple glass filaments 21 contained in the fiber-reinforced resin molding 1 may have an average fiber length of 1 μm or more and 9000 μm or less, 10 μm or more and 900 μm or less, 100 μm or more and 500 μm or less, or 300 μm or more and 400 μm or less.

In the fiber reinforced resin molding 1 of this embodiment, the average fiber length of the glass filaments 21 can be calculated as follows. First, the fiber reinforced resin molding 1 is heated in an incinerator at 650°C to decompose the organic matter in the fiber reinforced resin molding 1, thereby obtaining the glass filaments 21 contained in the fiber reinforced resin molding 1. The obtained glass filaments 21 are transferred to a glass petri dish, and the glass filaments 21 are dispersed in the glass dish using a solvent such as acetone. Next, the fiber length of the glass filaments 21 in the glass petri dish is measured using an electron microscope. The fiber lengths of 1,000 or more glass filaments 21 were measured, and the average value was taken as the average fiber length.

(Other ingredients)
The fiber reinforced resin molded body 1 in this embodiment may contain a colorant, a flame retardant, etc., as necessary. By containing these components, for example, the fiber reinforced resin molded body 1 can be colored to a desired color. In addition, the fire resistance of the fiber reinforced resin molded body 1 can be improved.

[4. Manufacturing method of fiber reinforced resin molded body]
A method for producing the fiber reinforced resin molded body 1 in this embodiment will be described. The method for producing the fiber reinforced resin molded body 1 in this embodiment includes a preparation step of preparing chopped strands, a pellet formation step, and an injection molding step.

In the above preparation process, it is sufficient to prepare a chopped strand containing a plurality of glass filaments 21 having the desired flatness ratio distribution as described above, and the specific method is not particularly limited. For example, the chopped strand may be manufactured by forming a bundle (strand) of flat fibers having the desired flatness ratio distribution and continuously cutting the strand to an appropriate length. For example, the flatness ratio distribution of the strand can be changed by adjusting the hole shape (hole arrangement) of the bushing that draws out the molten glass and various manufacturing conditions.

The chopped strand in one embodiment of the present invention includes a plurality of glass filaments 21, and the glass filaments 21 have a flat cross-sectional shape with a flatness ratio (long diameter/short diameter) in a range of more than 1.0 and not more than 7.0. In the chopped strand in this embodiment, the blending ratio of the glass filaments 21 having an aspect ratio classified in the first aspect ratio section A1 of more than 2.8 and not more than 4.6 is 50 to 100% relative to a specific total number (N pieces) of the plurality of glass filaments 21, and the blending ratio of the glass filaments 21 having an aspect ratio classified in the second aspect ratio section of more than 4.6 and not more than 7.0 is 0 to 50%. In the chopped strand in this embodiment, the first histogram showing the distribution of the flatness ratio for the specific total number (N pieces) of glass filaments 21, with the horizontal axis representing the flatness ratio, the vertical axis representing the blending ratio, and the class width of 0.2, has at least two peaks.

Next, in the pellet forming process, the chopped strands and a thermoplastic resin are kneaded to form composite pellets. As the thermoplastic resin, polyamide resin, polycarbonate resin, etc. can be used. The composite pellets formed in the pellet forming process are also included in the scope of the present invention. In one embodiment of the present invention, the composite pellets include resin 10, a plurality of glass fibers 20, and glass filaments 21 dispersed from the glass fibers 20. The glass fibers 20 include a plurality of bundled glass filaments 21 having a flat cross-sectional shape. The glass filaments 21 have an aspect ratio (major axis/minor axis) in the cross section in the range of more than 1.0 and not more than 7.0. In the composite pellet of this embodiment, the blending ratio of the glass filaments 21 having an aspect ratio classified in the first aspect ratio range of greater than 2.8 and less than or equal to 4.6 is 50 to 100% relative to a specific total number (N) of the glass filaments 21, and the blending ratio of the glass filaments 21 having an aspect ratio classified in the second aspect ratio range of greater than 4.6 and less than or equal to 7.0 is 0 to 50%. In the composite pellet of this embodiment, the first histogram showing the distribution of the aspect ratio for the specific total number (N) of glass filaments 21, with the horizontal axis representing the aspect ratio, the vertical axis representing the blending ratio, and the class width of 0.2, has at least two peaks.

The injection molding process is a process in which injection molding is performed using the composite pellets formed in the pellet formation process. The fiber-reinforced resin molded body 1 is produced by the injection molding process.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the above description are also included in the technical scope of the present invention.

Below, we will explain examples of fiber-reinforced resin moldings according to one aspect of the present invention, but the present invention is not limited to these examples.

Chopped strands containing glass fibers of E-glass composition with adjusted flatness distribution, etc., were mixed with polyamide resin PA66 (Zytel 1011, manufactured by DuPont) using a twin-screw kneading extruder. In this way, composite pellets of glass fibers and resin were produced.

Then, the obtained composite pellets were used for injection molding using an injection molding machine to prepare test pieces conforming to ASTM D638 (Type-1), ASTM D790, and ASTM D6110 for tensile strength tests, bending strength tests, and Charpy impact strength tests. In addition, a 150 x 150 x 2.5 mm flat plate was prepared using an injection molding machine as a test piece for measuring the warpage height.

The tensile strength, flexural strength, Charpy impact strength, and warp height were measured using the methods described below.

<Tensile strength>
A test was performed on a test piece conforming to ASTM D638 (Type-1) using a precision universal testing machine (Autograph AG-X plus 50 kN, manufactured by Shimadzu Corporation) under conditions conforming to ASTM D638 (Type-1) to measure the tensile strength.

<Flexural strength>
Test pieces conforming to ASTM D790 were subjected to a precision universal testing machine (Autograph AG-X plus 10 kN, manufactured by Shimadzu Corporation) under conditions conforming to ASTM D790 to measure bending strength.

<Charpy impact strength>
Test pieces conforming to ASTM D6110 were subjected to an impact test under conditions conforming to ASTM D6110 using an impact tester (UF impact tester manufactured by Ueshima Seisakusho Co., Ltd.) to measure the tensile strength.

<Warp height>
A flat plate of 150 mm x 150 mm x 2.5 mm was used as a test piece for warpage height, and one end of the test piece was placed on a flat surface, and the maximum deformation distance from the flat surface was measured with a vernier caliper to determine the warpage height.

(evaluation)
The mechanical properties of the obtained fiber-reinforced resin molding were evaluated as high when the tensile strength was 175 MPa or more, the flexural strength was 240 MPa or more, and the Charpy impact strength was 10 kJ/m ² or more. The warp suppression property was evaluated as high when the warp height was 12 mm or less.

(Test Results)
Fiber-reinforced resin molded bodies were obtained in Examples 1 to 4 and Comparative Examples 1 to 6. The test results for each fiber-reinforced resin molded body are shown in Table 1. In Table 1, "Number of peaks (peak positions)" indicates the number and peak positions of peaks in the first histogram showing the aspect ratio distribution.

As shown in Table 1, the fiber-reinforced resin moldings of Examples 1 to 4 had an average glass filament flatness ratio in the range of more than 1.0 and not more than 7.0, a first flatness ratio range of 50 to 100%, and a second flatness ratio range of 0 to 50%. The third flatness ratio range of 0 to 15%. The flatness ratio distribution had two peaks. It can be seen that Examples 1 to 4 have both mechanical properties and warpage suppression properties.

On the other hand, the fiber-reinforced resin moldings of Comparative Examples 1 to 6 did not satisfy the conditions of the present invention, and at least one of the mechanical properties and warpage suppression properties was insufficient.

1 Fiber-reinforced resin molded body 10 Resin 20 Glass fiber 21 Glass filament

Claims (16)

A fiber-reinforced resin molding comprising a resin and a plurality of glass filaments,
The plurality of glass filaments have a flat cross-sectional shape with a flatness ratio (major axis/minor axis) in a transverse cross section in a range of more than 1.0 and not more than 7.0,
(i) a blending ratio of the glass filaments having an aspect ratio classified into a first aspect ratio section greater than 2.8 and equal to or less than 4.6 is 50 to 100%, and (ii) a blending ratio of the glass filaments having an aspect ratio classified into a second aspect ratio section greater than 4.6 and equal to or less than 7.0 is 0 to 50%, relative to a specific total number of the plurality of glass filaments;
A fiber-reinforced resin molding, in which a first histogram showing a distribution of the aspect ratio for the specific total number of glass filaments, the horizontal axis being the aspect ratio, the vertical axis being the blending ratio, and the class interval being 0.2, has at least two peaks. The fiber-reinforced resin molding according to claim 1, wherein both of the two peaks in the first histogram have peak positions in a range of flatness ratios greater than 2.8. The fiber-reinforced resin molding according to claim 1 or 2, wherein the blending ratio of the glass filaments having an aspect ratio classified into a third aspect ratio category of greater than 1.0 and less than or equal to 2.8 is 0 to 15% relative to the specific total number of the glass filaments. The fiber-reinforced resin molding according to claim 3, wherein the blending ratio of the glass filaments having an aspect ratio classified in the third aspect ratio category is 0 to 10%, the blending ratio of the glass filaments having an aspect ratio classified in the first aspect ratio category is 60 to 80%, and the blending ratio of the glass filaments having an aspect ratio classified in the second aspect ratio category is 20 to 40%. The fiber-reinforced resin molding according to claim 3 or 4, wherein the blending ratio of the glass filaments having an aspect ratio classified in the third aspect ratio category is 0 to 5%, the blending ratio of the glass filaments having an aspect ratio classified in the first aspect ratio category is 65 to 75%, and the blending ratio of the glass filaments having an aspect ratio classified in the second aspect ratio category is 25 to 35%. The glass filaments have a cross-sectional equivalent circle diameter in the range of 6 to 27 μm,
(i) the blending ratio of the glass filaments having a circle equivalent diameter classified into a first circle equivalent diameter division of 6 μm or more and less than 13 μm is 15 to 25%, (ii) the blending ratio of the glass filaments having a circle equivalent diameter classified into a second circle equivalent diameter division of 13 μm or more and less than 15 μm is 55 to 65%, and (iii) the blending ratio of the glass filaments having a circle equivalent diameter classified into a third circle equivalent diameter division of 15 μm or more and 27 μm or less is 15 to 25%, relative to the specific total number of the plurality of glass filaments. The fiber-reinforced resin molding according to any one of claims 1 to 5. The fiber-reinforced resin molding according to claim 6, wherein a second histogram showing the distribution of the equivalent circle diameters for the specific total number of glass filaments, with the horizontal axis representing the equivalent circle diameter, the vertical axis representing the blending ratio, and a class interval of 0.25 μm, is a unimodal distribution. In the first histogram,
the difference between the maximum and minimum values of the blending ratio in each class included in the first aspect ratio division is 5% or more;
the difference between the maximum and minimum values of the blending ratio in each class included in the second aspect ratio division is 5% or more;
The fiber-reinforced resin molding according to any one of claims 1 to 7, wherein at least one of the first flattening ratio division or the second flattening ratio division includes a class indicating a peak value of one peak. The fiber-reinforced resin molding according to any one of claims 1 to 8, wherein the peak value of the blending ratio of each of the at least two peaks in the first histogram is 5% or more. The fiber-reinforced resin molding according to any one of claims 1 to 9, wherein the half-width of each of the at least two peaks in the first histogram is 0.5 to 1.6. The fiber-reinforced resin molding according to any one of claims 1 to 10, wherein the difference between the class values of the different classes showing the peak values of the at least two peaks in the first histogram is 0.4 or more. The fiber-reinforced resin molding according to any one of claims 1 to 11, wherein in the first histogram, both the first aspect ratio division and the second aspect ratio division include a class showing at least one peak value of a peak. The fiber-reinforced resin molding according to any one of claims 1 to 12, wherein the resin is an injection-moldable thermoplastic resin. A composite pellet comprising a resin and a plurality of glass filaments,
The glass filaments have a flat cross-sectional shape with a flatness ratio (major axis/minor axis) in a cross section in the range of more than 1.0 and not more than 7.0,
(i) a blending ratio of the glass filaments having an aspect ratio classified into a first aspect ratio section greater than 2.8 and equal to or less than 4.6 is 50 to 100%, and (ii) a blending ratio of the glass filaments having an aspect ratio classified into a second aspect ratio section greater than 4.6 and equal to or less than 7.0 is 0 to 50%, relative to a specific total number of the plurality of glass filaments;
A composite pellet, wherein a first histogram showing a distribution of the aspect ratio with the horizontal axis representing the aspect ratio, the vertical axis representing the blending ratio, and a class interval of 0.2 for the specific total number of glass filaments has at least two peaks. A chopped strand including a plurality of glass filaments,
The glass filaments have a flat cross-sectional shape with a flatness ratio (major axis/minor axis) in a cross section in the range of more than 1.0 and not more than 7.0,
(i) a blending ratio of the glass filaments having an aspect ratio classified into a first aspect ratio section greater than 2.8 and equal to or less than 4.6 is 50 to 100%, and (ii) a blending ratio of the glass filaments having an aspect ratio classified into a second aspect ratio section greater than 4.6 and equal to or less than 7.0 is 0 to 50%, relative to a specific total number of the plurality of glass filaments;
A chopped strand, wherein a first histogram showing a distribution of the aspect ratio with the horizontal axis representing the aspect ratio, the vertical axis representing the blending ratio, and a class interval of 0.2 for the specific total number of glass filaments has at least two peaks. A preparation step of preparing chopped strands according to claim 15;
a pellet forming step of kneading the chopped strands with a thermoplastic resin to form composite pellets;
and an injection molding step of performing injection molding using the composite pellets.

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