JP7643267B2 - Glass nonwoven fabric, glass fiber reinforced plastic molded body, glass chopped strand, and method for manufacturing glass nonwoven fabric - Google Patents

Description

The present invention relates to glass nonwoven fabrics containing glass filaments.

In recent years, various studies have been conducted with the aim of further miniaturization or improving the mechanical properties of electrical insulating boards, printed wiring boards, etc. For example, glass nonwoven fabric is used as a reinforcing material for substrates.

Glass nonwoven fabric containing flat glass fibers has better mechanical properties than glass nonwoven fabric containing round glass fibers. Therefore, it has relatively high strength even when made thin.

Patent Document 1 describes a glass nonwoven fabric that contains flat glass fibers and is densified without increasing the binder content. Patent Document 2 describes a glass nonwoven fabric that contains flat glass fibers and a binder, with the binder content being 3 to 8% by weight.

Japanese Patent Application Publication No. 6-257042 JP 2004-100142 A

In response to the growing demand for lighter and more compact electronic components, there is a need to further improve the strength and productivity of glass nonwoven fabrics.

One aspect of the present invention aims to realize a glass nonwoven fabric that has high strength and is practically manufacturable.

In order to solve the above problems, the glass nonwoven fabric according to one embodiment of the present invention contains glass filaments that have a flattened cross section and satisfy the following conditions (1), (2), and (3): (1) the average flatness ratio (major axis/minor axis) of the cross section is 1.5 or more and 8.0 or less; (2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less; (3) the standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less.

In one embodiment of the present invention, the glass chopped strand has a flattened cross section and contains glass filaments that satisfy the following conditions (1), (2), and (3): (1) the average flatness ratio (major axis/minor axis) of the cross section is 1.5 or more and 8.0 or less; (2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less; (3) the standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less.

In one embodiment of the present invention, the method for producing a glass nonwoven fabric includes a preparation step of preparing glass chopped strands containing glass filaments that have a flat cross section and satisfy the following conditions (1), (2), and (3): (1) an average flatness ratio (major axis/minor axis) of the cross section is 1.5 to 8.0; (2) an average equivalent circle diameter of the cross section is 5 μm to 20 μm; (3) a standard deviation in the distribution of the equivalent circle diameters is 0.5 to 4.0; an opening step of immersing the glass chopped strands in white water and stirring the strands; and a papermaking step of using the white water to produce a glass nonwoven fabric.

According to one aspect of the present invention, it is possible to realize a glass nonwoven fabric that has high strength and is practically manufacturable.

1 is a partially enlarged optical microscope photograph of a glass nonwoven fabric according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of a glass filament cut along a plane (transverse section) perpendicular to the longitudinal direction. 1 is a histogram showing the distribution of the aspect ratio of glass filaments contained in a glass nonwoven fabric according to one embodiment of the present invention. 1 is a schematic diagram showing a configuration of a glass fiber reinforced plastic molded body in 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 having a circle equivalent diameter of several μm to several tens of μm. Next, a treatment agent is applied to the flat fibers and the fibers are bundled to form strands. The strands are then cut to a predetermined length to obtain chopped strands.

Glass fiber is a general term for an aggregate of glass filaments (for example, a bundle of 100 or more fibers) 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 filament fibers is called a glass strand, and a glass strand cut to a specified length is called a chopped strand (glass chopped strand).

In this specification, the term "flatness ratio" refers to the ratio of the major axis length to the minor axis length in the shape of the surface to be calculated. The term "flatness ratio of the cross section" of a glass filament is used in the following sense. That is, when measuring the flatness ratio of the cross section of a glass filament, the end face of the glass filament is usually observed without cutting the glass filament to form a cross section. 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 the distribution of the aspect ratios of multiple glass filaments 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 (e.g. glass filaments).

(Brief Description of the Findings of the Invention)
Prior to describing the glass nonwoven fabric according to one embodiment of the present invention, the findings of the present inventors will be outlined below.

Glass nonwoven fabrics are generally manufactured by dispersing multiple glass fibers (chopped strands) in white water, then making paper and drying. The glass fibers are dispersed (opened) into aggregates of glass filaments in the white water. The glass filaments may then aggregate in the white water over time. If paper is made with the glass filaments in an aggregated state, the resulting glass nonwoven fabric will have an appearance that is unsuitable for use as a product. Therefore, the worse the dispersibility of the glass fibers in the white water (in other words, the resistance to aggregation), the lower the productivity of the glass nonwoven fabric may be.

The inventors have conducted detailed studies on the relationship between the shapes (flattening ratio and equivalent circle diameter) of the chopped strands used in the production of glass nonwoven fabric and the glass filaments contained in the glass nonwoven fabric, the aggregation resistance of the chopped strands (multiple glass fibers) in white water, and the strength of the resulting glass nonwoven fabric. As a result, they have found that by using glass filaments having a flat cross-sectional shape and by setting the flattening ratio and equivalent circle diameter of the glass filaments within a predetermined range, a glass nonwoven fabric with improved performance can be realized.

By setting the average flatness ratio of the glass filaments contained in the glass nonwoven fabric and chopped strands within an appropriate range, the glass filaments are less likely to aggregate in white water and the strength of the glass nonwoven fabric can be increased. Glass filaments with a circular cross section are relatively prone to aggregation in white water. In addition, glass nonwoven fabric is formed by interweaving multiple glass filaments, and the larger the bonding area between multiple glass filaments, the higher the bonding strength. Glass nonwoven fabric containing glass filaments with a flat cross section has a relatively high tensile strength because the bonding area between the glass filaments can be increased.

In addition, by setting the average value of the circle-equivalent diameter of the glass filaments contained in the glass nonwoven fabric and the chopped strands within an appropriate range, the glass filaments are less likely to aggregate in the white water and the strength of the glass nonwoven fabric can be increased. For example, if the weight of chopped strands (i.e., the weight of the glass filaments) added to a certain amount of white water is constant, the following can be said. That is, when the circle-equivalent diameter of the glass filaments is small, the number of glass filaments contained in the white water is greater than when glass filaments with a large circle-equivalent diameter are added to the white water. As a result, the glass filaments become relatively more likely to entangle in the white water, and the aggregation start time is shortened. On the other hand, when the number of glass filaments contained in the white water is large, the number of adhesion points between the glass filaments in the glass nonwoven fabric increases, and the tensile strength of the glass nonwoven fabric becomes relatively high.

Furthermore, it was found that it is also important to keep the standard deviation in the distribution of the equivalent circular diameters of the glass filaments contained in the glass nonwoven fabric and chopped strands within an appropriate range. When the distribution of the equivalent circular diameters of the glass filaments contained in the glass nonwoven fabric and chopped strands is wide (the standard deviation in the distribution is large), relatively thin glass filaments and relatively thick glass filaments are mixed, which tends to shorten the time to start coagulation in white water and tends to reduce the tensile strength of the glass nonwoven fabric. This is because relatively thin glass filaments tend to become entangled in white water, and when the glass nonwoven fabric contains relatively thick glass filaments, the number of adhesion points between the glass filaments decreases, which tends to reduce the tensile strength of the glass nonwoven fabric.

The glass nonwoven fabric in one aspect of the present invention was conceived based on the above findings, and can be manufactured while ensuring resistance to aggregation in white water, while also having high strength.

(Glass nonwoven fabric)
Fig. 1 is an optical microscope photograph of a part of a glass nonwoven fabric 1 according to the present embodiment, which is magnified and captured. As shown in Fig. 1, the glass nonwoven fabric 1 is formed by intertwining a plurality of glass filaments 10. The majority of the glass nonwoven fabric 1 according to the present embodiment is formed by the glass filaments 10. In Fig. 1, since it is difficult to capture an image of a substance (such as a secondary binder described below) that is translucent to the observation light, images of the glass filaments 10 are mainly shown.

The glass nonwoven fabric 1 may have a secondary binder in addition to the glass filaments 10, and may also have other additive components. The secondary binder may have an ignition loss of 5% by mass or more and 30% by mass or less, or 10% by mass or more and 20% by mass or less. For example, an acrylic resin or an epoxy resin may be used as the secondary binder. The ignition loss can be measured in accordance with JIS R 3420 (2013). The content of other additive components in the glass nonwoven fabric 1 may be 3% by mass or less, or 2% by mass or less. Examples of other additive components include a treatment agent (primary binder) contained in the glass fibers. The treatment agent is dissolved in white water during the manufacturing process, but may be mixed into the glass nonwoven fabric 1 to a certain extent.

(glass filament)
In the glass nonwoven fabric 1, the content of the glass filaments 10 is not particularly limited, but may be, for example, 70% by mass or more and 95% by mass or less, or 80% by mass or more and 90% by mass or less.

Figure 2 is a cross-sectional view of the glass filament 10 cut in a plane (cross section) perpendicular to the longitudinal direction. The long diameter of the cross-sectional shape of the glass filament 10 is designated as long diameter L1, and the short diameter is designated as short diameter L2. In this specification, the length of the longest line segment connecting two points on the outer edge in the cross section of the glass filament 10 is defined as the "long diameter of the glass filament 10," and the length of the longest line segment in the direction perpendicular to the long diameter in the cross section of the glass filament 10 is defined as the "short diameter of the glass filament 10."

The cross-sectional shape of the glass filament 10 is not limited to an ellipse. The glass filament 10 may have a flat shape with a non-circular cross section, for example, an oval, an ellipse, or a flat shape such as a rounded rectangle. It is preferable that the glass filament 10 has an oval flat shape.

The glass filaments 10 contained in the glass nonwoven fabric 1 in this embodiment satisfy all of the following conditions (1) to (3).

(1) The average cross-sectional flatness ratio (long diameter L1/short diameter L2) is 1.5 or more and 8.0 or less;
(2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less;
(3) The standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less.

Regarding (1) above, if the average cross-sectional aspect ratio of the glass filaments 10 contained in the glass nonwoven fabric 1 is less than 1.5, the bonding area between the glass filaments 10 tends to be small, making it difficult to achieve high tensile strength. On the other hand, if the average cross-sectional aspect ratio of the glass filaments 10 is greater than 8.0, the glass filaments 10 tend to break easily, making it difficult to obtain sufficient tensile strength for the glass nonwoven fabric 1.

Regarding (2) above, if the average value of the equivalent circle diameter of the cross section of the glass filaments 10 contained in the glass nonwoven fabric 1 is less than 5 μm, the glass filaments 10 may break during the papermaking process. On the other hand, if the average value of the equivalent circle diameter of the cross section of the glass filaments 10 contained in the glass nonwoven fabric 1 exceeds 20 μm, the porosity of the glass nonwoven fabric 1 increases and the number of bonding points between the glass filaments 10 decreases. As a result, the tensile strength of the glass nonwoven fabric 1 decreases.

Regarding (3) above, when the standard deviation in the distribution of the equivalent circle diameters of the cross sections of the glass filaments 10 contained in the glass nonwoven fabric 1 is less than 0.5, hundreds to thousands of glass filaments 10 having a more uniform cross-sectional shape are bundled together, making it difficult for the glass fibers to open up in the white water. On the other hand, when the standard deviation in the distribution of the equivalent circle diameters is greater than 4.0, the number of relatively thin glass filaments 10 that tend to aggregate and the number of relatively thick glass filaments 10 that lead to a decrease in strength are too large, resulting in a shorter aggregation start time and a decrease in the tensile strength of the glass nonwoven fabric 1.

The glass nonwoven fabric 1 in this embodiment has high strength because the glass filaments 10 contained therein satisfy the above (1) to (3), and the glass filaments are less likely to aggregate during the papermaking process in the manufacturing process (the aggregation start time can be extended), resulting in practical productivity.

The composition of the glass filaments 10 may be any composition that can produce a glass nonwoven fabric 1 having high strength and practical productivity, and the composition of the glass filaments 10 contained in the glass nonwoven fabric 1 in this embodiment is not particularly limited. The composition of the glass filaments 10 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 glass filament 10 may have a minor axis L2 in cross section of 3 to 15 μm, or 5 to 12 μm. The glass filament 10 may have a major axis L1 in cross section of 10 to 50 μm, or 15 to 30 μm.

(Flatness ratio distribution)
The aspect ratio distribution of the glass filaments 10 contained in the glass nonwoven fabric 1 in this embodiment will be described below. The aspect ratio distribution of the glass filaments 10 contained in the glass nonwoven fabric 1 is approximately the same as the aspect ratio distribution of the glass filaments 10 contained in the chopped strands used in the manufacturing process of the glass nonwoven fabric 1. Therefore, the chopped strands used in the manufacturing process of the glass nonwoven fabric 1 may be used to measure the aspect ratio distribution described below.

First, the measurement of the flattening ratio distribution will be described. That is, the flattening ratio distribution is measured for a specific total number of glass filaments. This "specific total number" may be the total number of glass filaments 10 whose flattening 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 10, the glass filaments 10 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 10 is observed with an electron microscope, and the lengths of the major axis L1 and minor axis L2 of the observed glass filaments 10 are measured to calculate the flattening ratio. Then, the specific total number of glass filaments 10 whose flattening ratios have been calculated are classified into a plurality of flattening ratio ranges, and the blending ratio in each flattening ratio range is quantified.

The glass nonwoven fabric 1 may have the following distribution of the flatness ratio of the glass filaments 10 measured as described above. That is, the ratio of the number of glass filaments classified into a certain flatness ratio category to a specific total number of the glass filaments 10 is defined as the blending ratio, (i) the total blending ratio of glass filaments 10 having flatness ratios classified into a flatness ratio category of 1.5 or more and less than 3.0 (hereinafter referred to as the first flatness ratio category A1) is 0 to 20%, (ii) the total blending ratio of glass filaments 10 having flatness ratios classified into a flatness ratio category of 3.0 or more and less than 5.0 (hereinafter referred to as the second flatness ratio category A2) is 30 to 70%, and (iii) the total blending ratio of the glass filaments having flatness ratios classified into a flatness ratio category of 5.0 or more and 8.0 or less (hereinafter referred to as the third flatness ratio category A3) is 30 to 60%. By setting the distribution of the aspect ratio of the glass filaments 10 as described above, the aggregation resistance of the glass filaments 10 in the white water during the papermaking process can be improved, and the strength of the glass nonwoven fabric 1 can be increased.

Furthermore, it is preferable that the glass nonwoven fabric 1 shows a histogram in which the aspect ratio distribution of the glass filaments 10 includes 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 10 contained in the glass nonwoven fabric 1 of this embodiment.

The histogram shown in FIG. 3 is a histogram showing the flattening ratio distribution, created with the horizontal axis representing the flattening ratio of the glass filaments 10, the vertical axis representing the glass filament 10 blending ratio, and a class width of 0.25. FIG. 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. As shown in FIG. 3, the glass nonwoven fabric 1 in this embodiment has at least two peaks in the histogram showing the flattening ratio distribution.

Here, the glass filaments 10 with a relatively small aspect ratio tend to have a cross section close to a circular shape and a relatively small equivalent circle diameter, and such glass filaments 10 tend to aggregate in white water as described above. Also, the glass filaments 10 with a relatively large aspect ratio tend to have a relatively large equivalent circle diameter, and such glass filaments 10 can reduce the strength of the glass nonwoven fabric 1 as described above. In one embodiment of the present invention, the glass nonwoven fabric 1 contains glass filaments 10 that satisfy the above-mentioned conditions (1) to (3), and further, the standard deviation in the distribution of the aspect ratio of the cross section of the glass filaments 10 contained in the glass nonwoven fabric 1 may be 0.5 to 1.5. According to the above configuration, the proportion (number) of glass filaments 10 with an aspect ratio smaller than the average aspect ratio of the glass filaments 10 and glass filaments 10 with an aspect ratio larger than the average aspect ratio contained in the glass nonwoven fabric 1 can be reduced. Therefore, when the glass filaments 10 are dispersed in white water during the papermaking process, the glass filaments 10 have appropriate dispersibility and good resistance to aggregation, and the strength of the glass nonwoven fabric 1 can be increased.

The many glass filaments 10 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 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 glass nonwoven fabric 1 in one embodiment of the present invention has improved performance compared to the case where two or more types of chopped strands are simply mixed and dispersed in white water to be made into paper.

(Circle equivalent diameter distribution)
Regarding the circle-equivalent diameter distribution of the glass filaments 10 contained in the glass nonwoven fabric 1 in this embodiment, the circle-equivalent diameter distribution can be measured for a specific total number of a plurality of glass filaments in the same manner as in the above-mentioned method used for measuring the aspect ratio distribution.

Although not shown in the figure, the standard deviation in the distribution of the equivalent circle diameters of the glass nonwoven fabric 1 may be 0.5 or more and 4.0 or less, and the distribution may show a unimodal histogram.

Here, the distribution of the flattening ratio and the distribution of the equivalent circle diameter of the glass filaments 10 contained in the glass nonwoven fabric 1 are related to each other. In the manufacturing process of the strands used in the manufacture of the glass nonwoven fabric 1, there is usually a relationship in which the wider the distribution of the flattening ratio of the glass filaments 10 contained in the chopped strands, the wider the distribution of the equivalent circle diameter of the glass filaments 10. Therefore, if the glass filaments 10 contained in the glass nonwoven fabric 1 show the above-mentioned distribution of flattening ratios (histogram having at least two peaks), it is easy to make the standard deviation in the distribution of the equivalent circle diameter of the glass filaments 10 contained in the glass nonwoven fabric 1 0.5 to 4.0.

(Method of manufacturing glass nonwoven fabric)
A method for producing the glass nonwoven fabric 1 in this embodiment will be described. The method for producing the glass nonwoven fabric 1 in this embodiment includes a preparation step, a fiber-opening step, and a paper-making step.

The preparation process is a process for preparing chopped strands containing glass filaments that satisfy the above-mentioned conditions (1) to (3). In the preparation process, first, the raw materials are weighed to obtain the desired glass composition, and the weighed glass raw materials are melted in a melting furnace. Next, the obtained molten glass is drawn out as flat fibers from a platinum bushing. Next, a treatment agent (glass fiber bundling agent) is applied as a primary binder to the drawn out hundreds to thousands of flat fibers with a circle equivalent diameter of 5 to 20 μm by a roll coater method. After that, the flat fibers are bundled and wound up on a paper tube placed on a rotating collet to form a wound body. Next, chopped strands are produced by cutting and drying as necessary. For example, the flatness ratio distribution of the chopped strands 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 strands prepared by the above preparation process also fall within the scope of the present invention.

The glass fibers, which are bundles of glass filaments 10 contained in the chopped strands, may have their surfaces coated with a sizing agent made of an organic material containing components such as aminosilane, urethane resin, acrylic resin, epoxy resin, olefin resin, lubricant, and antistatic agent. The blending ratio of the components of the sizing agent is determined according to the purpose of use. The mass ratio of the sizing agent to the total mass of the glass filaments 10 and the sizing agent is preferably 0.01 to 0.2 mass%.

The fiber-opening process is a process in which the chopped strands are immersed in white water and stirred. The white water may be any conventionally known type that is generally used when making paper from glass fibers, etc., and the specific components of the white water are not particularly limited. The specific components of the white water do not have a significant effect on the tensile strength of the glass nonwoven fabric 1.

The viscosity of the white water can be measured by a known method, for example, in accordance with JIS Z8803 (2011). The viscosity of the white water may be, for example, 1 to 40 cP, or 1 to 20 cP. The stirring speed after immersing the chopped strands in the white water may be 200 rpm to 500 rpm. For example, the amount of chopped strands added per 500 ml of white water may be 1 g to 100 g. The length of the chopped strands may be 3 mm to 30 mm.

In the opening process, the chopped strands added to the white water are opened, dispersing the glass filaments 10 in the white water, causing the white water to become cloudy. Then, over time, the glass filaments 10 aggregate in the white water, producing visible aggregates. These aggregates are, for example, about 3 mm in diameter.

The time from when the chopped strands are added to the white water to when the aggregates are visually observed is determined as the aggregation start time. For example, the aggregation start time (the timing of the formation of aggregates) can be determined based on photographs or videos taken at a specified time interval.

The papermaking process is a process for making glass nonwoven fabric 1 using white water in which glass filaments 10 are dispersed and before agglomerates form. In the papermaking process, a papermaking machine is used to make the white water in which glass filaments 10 are dispersed, and then a secondary binder is applied using a spray device or the like. The glass nonwoven fabric 1 can then be made by drying. A conventional wet papermaking method may be used for the papermaking process.

The secondary binder that covers at least a portion of the surface of the glass nonwoven fabric 1 may have an ignition loss of 5% to 30% by mass, or 10% to 20% by mass. For example, acrylic resin or epoxy resin can be used as the secondary binder. The ignition loss can be measured in accordance with JIS R 3420 (2013).

In the manufacturing method of the glass nonwoven fabric 1 in this embodiment, the time (minutes) at which the chopped strands start to aggregate when immersed in white water with a viscosity of 20 cP and stirred at 200 rpm is defined as A, and the tensile strength (N/100 mm) of the glass nonwoven fabric 1 obtained by papermaking using the white water is defined as B, and it is preferable that A×B≧50,000 be satisfied.

(Glass fiber reinforced plastic molding)
4 is a schematic diagram showing the configuration of a glass fiber reinforced plastic molded body 50 in this embodiment. As shown in FIG. 4, the glass fiber reinforced plastic molded body 50 has a pair of conductor layers 51 facing each other and a plurality of prepregs 52.

The prepreg 52 is a member in which the glass nonwoven fabric 1 is impregnated with resin. The resin may be a thermosetting resin or a thermoplastic resin. Examples of the thermoplastic resin that may be used include polyesters such as polycarbonate, polypropylene, polyamide, polyetherimide, and polyethylene terephthalate (PET). Examples of the thermosetting resin that may be used include epoxy resin, phenol resin, polyimide resin, and unsaturated polyester resin.

The glass fiber reinforced plastic molded body 50 contains one or more layers of glass nonwoven fabric, and can be manufactured, for example, as follows. First, a desired number of prepregs 52 are placed on one conductor layer 51. Next, the other conductor layer 51 is placed on the opposite side of the laminated prepregs 52 from the one conductor layer 51. Next, the pair of conductor layers 51 are pressed in the direction in which the prepregs 52 are placed. This makes it possible to manufacture a glass fiber reinforced plastic molded body 50 in which multiple prepregs 52 (in other words, glass nonwoven fabrics 1) are arranged between the pair of conductor layers 51.

[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 glass nonwoven fabric in one aspect of the present invention, but the present invention is not limited to these examples.

First, chopped strands with a length of 13 mm, containing glass fibers of E-glass composition with the flatness ratio distribution adjusted as shown in Table 1 below, were dispersed in white water, and the glass nonwoven fabrics of Examples 1 to 7 and Comparative Examples 1 to 4 were produced using a papermaking machine.

The tensile strength and aggregation start time of the glass nonwoven fabric were measured using the measurement method described below.

<Tensile strength>
The tensile strength was measured in accordance with JIS R-3420 7 4 using a precision universal testing machine (Autograph AGS-X 10 kN, manufactured by Shimadzu Corporation).

<Aggregation start time>
A beaker with an inner diameter of 110 mm was prepared, containing 1000 mL of an aqueous solution of sodium polyacrylate adjusted to a viscosity of 20 cP at 25° C. Next, a two-blade blade with a rotation diameter of 75 mm, a height of 30 mm, and a thickness of 3 mm was disposed at a position 10 mm from the bottom of the beaker, and the two-blade blade was rotated at 200 rpm, and 3 g of chopped strands cut to a length of 13 mm were put into the aqueous solution of sodium polyacrylate. After the chopped strands were opened, the time required for the glass filaments to aggregate was measured. Incidentally, whether or not the glass filaments aggregated was judged by visual observation.

(evaluation)
In the examples of the glass nonwoven fabric according to one aspect of the present invention, the obtained glass nonwoven fabric was evaluated as having high strength when the tensile strength was 196 N/100 mm or more, and as having good agglomeration resistance, i.e., having practical productivity, when the agglomeration start time was 150 minutes or more.

(Test Results)
For the glass nonwoven fabrics of Examples 1 to 7 and Comparative Examples 1 to 4, data on the glass filaments contained in the glass nonwoven fabrics and the test results of the above tests are shown in Table 1. In Table 1, the "number of peaks in the aspect ratio distribution" indicates the number of peaks in a histogram showing the aspect ratio distribution.

As shown in Table 1, the glass nonwoven fabrics of Examples 1 to 7, which met all of the conditions (1) to (3) of the present invention, had high strength and were practically manufacturable.

On the other hand, the glass nonwoven fabrics of Comparative Examples 1 to 4 did not satisfy any of the conditions (1) to (3) of the present invention, and at least either the tensile strength or the cohesion resistance was insufficient.

1 Glass nonwoven fabric 10 Glass filament

Claims (6)

The cross section is flattened and contains glass filaments that satisfy the following conditions (1), (2), and (3):
The ratio of the number of glass filaments classified into a certain aspect ratio range to the specific total number of the plurality of glass filaments is defined as a blending ratio,
(i) the total blending rate of the glass filaments having an aspect ratio classified in a first aspect ratio range of 1.5 or more and less than 3.0 is 0 to 20%, (ii) the total blending rate of the glass filaments having an aspect ratio classified in a second aspect ratio range of 3.0 or more and less than 5.0 is 30 to 70%, and (iii) the total blending rate of the glass filaments having an aspect ratio classified in a third aspect ratio range of 5.0 or more and 8.0 or less is 30 to 60%,
A glass nonwoven fabric , in which a histogram showing the distribution of the flatness ratio of the plurality of glass filaments, with the horizontal axis being the flatness ratio and the vertical axis being the blending ratio, and with a class interval of 0.25, has at least two peaks :
(1) The average cross-sectional flatness ratio (major axis/minor axis) is 1.5 or more and 8.0 or less;
(2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less;
(3) The standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less. Further comprising a secondary binder covering at least a portion of the surface of the glass nonwoven fabric;
The glass nonwoven fabric according to claim 1 , wherein the secondary binder has an ignition loss of 5 to 30% by mass. The glass nonwoven fabric according to claim 1 or 2 , wherein the standard deviation in the distribution of the aspect ratio is 0.5 or more and 1.5 or less. A glass fiber reinforced plastic molding comprising at least one layer of the glass nonwoven fabric according to any one of claims 1 to 3 . The cross section is flattened and contains glass filaments that satisfy the following conditions (1), (2), and (3):
The ratio of the number of glass filaments classified into a certain aspect ratio range to the specific total number of the plurality of glass filaments is defined as a blending ratio,
(i) the total blending rate of the glass filaments having an aspect ratio classified in a first aspect ratio range of 1.5 or more and less than 3.0 is 0 to 20%, (ii) the total blending rate of the glass filaments having an aspect ratio classified in a second aspect ratio range of 3.0 or more and less than 5.0 is 30 to 70%, and (iii) the total blending rate of the glass filaments having an aspect ratio classified in a third aspect ratio range of 5.0 or more and 8.0 or less is 30 to 60%,
A glass chopped strand , in which a histogram showing the distribution of the flatness ratio of the plurality of glass filaments, with the horizontal axis being the flatness ratio and the vertical axis being the blending ratio, and with a class interval of 0.25, has at least two peaks :
(1) The average cross-sectional flatness ratio (major axis/minor axis) is 1.5 or more and 8.0 or less;
(2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less;
(3) The standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less. A preparation step of preparing a glass chopped strand containing glass filaments having a flat cross section and satisfying the following conditions (1), (2), and (3);
(1) The average cross-sectional flatness ratio (major axis/minor axis) is 1.5 or more and 8.0 or less;
(2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less;
(3) the standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less;
a fiber-opening step of immersing the glass chopped strands in white water and stirring the strands;
A papermaking process of making a glass nonwoven fabric using the white water ,
The glass chopped strands are
The ratio of the number of glass filaments classified into a certain aspect ratio range to the specific total number of the plurality of glass filaments is defined as a blending ratio,
(i) the total blending rate of the glass filaments having an aspect ratio classified in a first aspect ratio range of 1.5 or more and less than 3.0 is 0 to 20%, (ii) the total blending rate of the glass filaments having an aspect ratio classified in a second aspect ratio range of 3.0 or more and less than 5.0 is 30 to 70%, and (iii) the total blending rate of the glass filaments having an aspect ratio classified in a third aspect ratio range of 5.0 or more and 8.0 or less is 30 to 60%,
A method for producing a glass nonwoven fabric, wherein a histogram showing a distribution of the aspect ratios of the plurality of glass filaments, with the horizontal axis being the aspect ratio and the vertical axis being the blending ratio, and with a class interval of 0.25, has at least two peaks .

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