JPH038857A - Inorganic fiber nonwoven fabric - Google Patents

Abstract

PURPOSE:To obtain the subject nonwoven fabric, composed of a specifically arranged filament inorganic fiber layer and short inorganic fiber layer, excellent in heat resistance, mechanical strength, etc., and used for producing FRP reinforcing materials improved in dimensional stability, etc. CONSTITUTION:The objective nonwoven fabric obtained by arranging at least one layer of fiber group obtained by opening a fiber assembly composed of plural filament inorganic fibers (e.g. glass fiber) oriented parallel in the longitudinal direction according to a chemical method, etc., and short inorganic fibers prepared by cutting the aforementioned filaments to 20-30mm length so as to provide at least one layer of the short inorganic fibers in the direction nearly perpendicular to the above-mentioned filaments (at preferably <=0.7 ratio of the longitudinal to the transverse directions when the filaments are arranged in the longitudinal direction and the short fibers are arranged in the transverse direction) and preferably bonding the arranged layers with a silane compound composition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inorganic fiber nonwoven fabric used as a reinforcing material during molding of fiber reinforced plastics (hereinafter referred to as FRP).

[Prior Art] Conventionally, inorganic fibers have been widely used because they have excellent properties such as heat resistance, mechanical strength, chemical stability, and electrical insulation. Among them, glass fiber nonwoven fabrics have been used mainly for electrical insulation boards, printed materials, etc. It is used as a reinforcing material for various FRPs such as wiring boards (hereinafter referred to as PCBs). Particularly recently, inexpensive PCBs with excellent punching workability and drilling workability have been increasingly used as reinforcing fiber base materials. The characteristics required of glass fiber nonwoven fabric for reinforcing PCBs include having hot strength that will not break during the manufacturing process of PCBs, and
In addition to being able to provide excellent dimensional stability and heat resistance when using B, it can also contribute to the production of PCBs with strong bending strength as PCBs have recently become thinner.

Conventionally, as an inorganic fiber nonwoven fabric for reinforcing FRP, one in which cut inorganic fibers are randomly piled up and simply adhesively fixed with a binder is known. It is also known to be manufactured by a wet method in which cut glass fibers are stirred and dispersed in water and then made into paper using a paper machine, and the latter type of nonwoven fabric is mainly used as glass fiber nonwoven fabric for PCB reinforcement. ing.

In the case of the wet method, the fiber length is limited to short in order to uniformly disperse the glass fibers, and a water-soluble dispersant is further added. Furthermore, the orientation of the fibers can hardly be controlled, and glass fibers do not have the property of intertwining with each other, making it difficult to heat-seal them, so a binder is used to develop the strength of the glass fiber nonwoven fabric.

(Problem to be Solved by the Invention) When processing FRP using prepreg, pultrusion molding, etc., the tensile strength of the reinforcing fiber base material has a large effect on its processability, and as mentioned above, it mainly affects the binder to develop strength. The conventionally known inorganic fiber nonwoven fabrics that rely on them suffer from a significant drop in tensile strength due to heat and solvents, which limits production efficiency during FRP processing.Therefore, regarding the binder used to develop the strength of inorganic fiber nonwoven fabrics, Although various improvements have been made, there are limits to these improvements.Furthermore, in order to increase the tensile strength of the reinforcing fiber base material during FRP processing, for example, the running direction (
Attempts have also been made to attach filamentous glass fibers, continuous glass rovings, glass strands, etc.
563) However, in this case, although the tensile strength of the reinforcing fiber base material during FRP processing is improved, the resin impregnation of the glass fiber nonwoven fabric is deteriorated due to the use of focused rovings and strands. In addition to inviting
The glass fiber distribution in the glass fiber nonwoven fabric becomes uneven,
This has the disadvantage of impairing the dimensional stability of FRP.

In addition, especially for PCBs, dimensional stability of the substrate is an essential condition, and good dimensional stability cannot be obtained due to uneven distribution of glass fibers and disordered arrangement of glass fibers, which is one of the major drawbacks. . Furthermore, regarding the bending strength of PCBs, glass fiber nonwoven fabrics made using conventional wet methods have a small reinforcing effect due to short fiber lengths and disordered arrangement, and the fiber packing density does not increase. It placed restrictions on the use of. In addition, PC by adding water-soluble dispersant, which is essential for wet nonwoven fabric manufacturing method.
The decrease in heat resistance of B is one of the major drawbacks of wet-laid nonwoven fabrics.

The present invention aims to produce FRP that has such high nonwoven strength that there is no need to impose any restrictions on the manufacturing conditions of FRP, has excellent dimensional stability and heat resistance, and has excellent bending strength especially in thin sheets. The purpose is to provide an inorganic fiber nonwoven fabric that can contribute to

[Means for Solving the Problems] The object of the present invention is to have at least one fiber group consisting of a plurality of long fiber inorganic fibers arranged substantially in parallel, and a layer of liquid long fiber inorganic fibers arranged at right angles to each other. This is achieved by an inorganic fiber nonwoven fabric comprising at least one layer of fibers consisting of a plurality of short inorganic fibers arranged in a manner similar to that of the present invention.

As used herein, a plurality of long fiber inorganic fibers arranged substantially in parallel means that a plurality of long fiber inorganic fibers are preferably distributed in individual monofilament units and arranged substantially in parallel; Arranging perpendicularly means that the short fibers are arranged orthogonally to the arrangement direction of the long inorganic fibers, that is, the short fibers are arranged with variation within a certain angle range centered on the perpendicular direction, but the short fibers as a whole means that they are arranged at right angles.

When the short fibers are arranged perpendicularly to the long fiber inorganic fibers, a microwave orientation meter (manufactured by Kanzaki Paper Corporation) is used.
It can be measured by In other words, when the alignment direction of the short fibers is measured using microwaves with the alignment direction of the long inorganic fibers being the vertical direction, if the length/width strength ratio is less than 1, the short fibers are arranged orthogonally. I reckon. Preferably, the vertical/horizontal strength ratio is 0.7 or less.

Preferably, the layer of long inorganic fibers and the layer of inorganic short fibers disposed orthogonally to this layer are integrally bonded to each other. For this integral bonding, the binder used for bonding conventional inorganic fiber nonwoven fabrics may be used as is, but it is preferable to use a functional group that is reactive with the resin used when molding FRP. It is desirable that the silane compound composition has the following properties. It is also possible to fly the short fibers in a defibrated state into a fluid, and at the same time, continuously supply thermoplastic resin powder such as PEE, mix it with the flying short fibers, and use it as a binder. be.

Preferably, layers of long fiber inorganic fibers are arranged on both surfaces of the layer of short fiber inorganic fibers, and a high-speed fluid,
For example, by applying a water jet to entangle short fibers (horizontal direction) and long fibers (vertical direction), the integration can be made more pronounced.

The term "short fiber" as used in the present invention refers to fibers obtained by cutting long fibers or fibers made in advance as short fibers.

Any short fiber length can be used, but 20 m is recommended for reinforcing the bending strength of FRP.
It is preferable to use short fibers with a fiber length of m to 30 mm.

The inorganic fibers used in the present invention are not particularly limited, and include ceramic fibers such as glass fibers and alumina fibers,
Any mineral fiber etc. may be used, and it is selected as appropriate depending on the purpose.
Additionally, aramid fiber, carbon fiber, PEEK can be used as required.
It is used in combination with heat-resistant engineering plastic fibers such as PPS. The diameters of the long fibers and short fibers used are usually in the range of 2 to 15 feet, but depending on the purpose, fibers of several diameters may be mixed and used.

When producing the inorganic fiber nonwoven fabric of the present invention, it is first necessary to prepare a fiber group consisting of long fiber inorganic fibers. For this purpose, a large number of strands consisting of a plurality of long fibers, ie, filaments, are arranged in parallel and supplied, and the filaments in the individual strands are dispersed. For the above-mentioned dispersion, for example, there are chemical methods such as dissolving and dispersing a binder used to bundle filaments of inorganic fibers in a solvent, methods of physically spreading the fibers by mechanical means, and static electricity. A method of reversing filaments to each other can be used alone or in combination. In order to facilitate the dispersion of the filaments in the strand, it is desirable that the strand be substantially untwisted and that the filaments in the strand be not crimped or the like. Furthermore, in order to obtain a uniform inorganic fiber nonwoven fabric, it is preferable to arrange the individual strands at uniform intervals even when the strands are arranged in parallel.

Next, in order to arrange a fiber group consisting of a plurality of short fiber inorganic fibers almost perpendicularly on the fiber group consisting of long fiber inorganic fibers, a step of preparing and dispersing short inorganic fibers, and a step of dispersing On top of the fiber group consisting of long-fiber inorganic fibers are the short fibers that have been made! 'The process of orthogonally arranging is required.

As the step of preparing and dispersing the short fibers, it is preferable to use a step of cutting the strands of long inorganic fibers into predetermined lengths and defibrating and separating them using a fiber splitting flying device. The separating flying device may be any device that can separate and discharge the short fibers obtained by cutting, such as a known device that rotates around a horizontal axis. A fiber roller or the like can be used. Note that instead of using strands of long fiber inorganic fibers, a mat made of short fibers may be fed to a fiber splitting flying device to be split. Further, it may be configured such that the fiber splitting flying device itself can split the long fibers without cutting them. In order to split and disperse the short fibers, it is preferable to use strands of inorganic fibers to be supplied that are not provided with a fiber sizing agent and are not twisted or crimped. .

A water stream may be used to arrange the dispersed and discharged short fibers perpendicularly on the fiber group consisting of long fiber inorganic fibers. For this purpose, a conveyor is run below the fiber separation flying device, and a group of fibers made of the above-mentioned long fiber inorganic fibers is placed on this conveyor in advance. In this case, the long inorganic fibers are arranged parallel to the running direction (vertical direction) of the conveyor. The water stream is supplied onto the conveyor using a nozzle having an opening that widens in a direction (horizontal direction) perpendicular to the running direction (vertical direction) of the conveyor, and the dispersed short fibers ride on this water stream and deposited on the conveyor. At this time, the directions of the fiber axes of the short fibers are aligned in the horizontal direction, and as a result, the short fibers are placed perpendicularly on top of the fiber group consisting of long fiber inorganic fibers arranged parallel to the vertical direction and running on the conveyor. It will be placed. Note that if a suction device is provided below the conveyor, the short fiber accumulation area can be defined within a predetermined range.

If necessary, a small amount of binder is applied to a fiber group consisting of at least two layers of long fibers in the vertical direction and short fibers in the horizontal direction, compression molding is performed, and drying and winding are performed to form a roll. An inorganic fiber nonwoven fabric is obtained.

If a plurality of the above-mentioned fiber splitting flying devices, for example 2 to 5 pieces, are arranged in the running direction of the conveyor and the short fibers are deposited several times, it is useful to make the distribution of the short fibers more uniform.

Using a water stream to arrange the short fibers into the long fibers as described above helps increase the density of the short fibers, and also reduces the scattering of the short fibers into the air compared to when using an air stream for this process. This can be prevented and helps improve the working environment.

In addition, instead of the method of separating short fibers in a dry manner using the above-mentioned fiber separation flying device, the short fibers are dispersed in a liquid as in the conventional paper making method, and then the dispersion is spread in the horizontal direction as described above. It is also possible to use a method in which the short fibers are fed to a nozzle having an opening such that the short fibers are placed on the long fibers on a conveyor.

Next, the method for manufacturing the inorganic fiber nonwoven fabric of the present invention will be specifically described with reference to FIG. 1, which shows an example of an apparatus for manufacturing the inorganic fiber nonwoven fabric of the present invention. A fiber aggregate 3 in which long fiber inorganic fibers are arranged in the longitudinal direction wound around a roll 1 is immersed in an aqueous solution 5 contained in a tank 2, and is chemically defibrated. The fiber assembly 6 is physically further defibrated by a curved surface body 4 that vibrates in the horizontal direction and is provided in the fiber assembly 4, thereby obtaining an aligned fiber aggregate 6, which is sent onto a stacking conveyor 15. Next, the long fiber inorganic fibers 7 to be used in the horizontal direction are supplied to a cutting device 8, cut into an arbitrary cutting length, and then supplied to the introduction port 9 of the fiber splitting device 12.

The supplied plurality of short fibers are guided by a guide roll 10 to a contact point with a flying splitting roll 11 rotating at high speed, and split into single fibers by the flying splitting roll 11. The short fibers separated into single fibers are continuously passed through the nozzle 1.
3, it is caused to fly by riding on the water flow 14 that is supplied and spread in the horizontal direction (perpendicular to the plane of the drawing). The short fibers carried by the water stream are deposited on a fiber aggregate 6 made of long fiber inorganic fibers aligned in the vertical direction while keeping the fiber axes in the horizontal direction. Accumulation of short fibers is controlled within a predetermined range by an air intake device 10 that uniformly draws air.

By repeating this deposition two or more times as shown in FIG. 1, the distribution of the short inorganic fibers can be made more uniform. Furthermore, as shown in FIG. 1, if another fiber aggregate 6 is placed on top of the layer of short inorganic fibers, the integrity is further improved. The superimposed inorganic fiber aggregate 17 obtained in this way is immersed in a binder solution 19 contained in a tank 18, and after applying a small amount of binder, it is compressed with a squeeze roll 20 to be integrally bonded, and then dried. It is dried in a device 21 to obtain an inorganic fiber nonwoven fabric 22 of the present invention.

The inorganic fiber nonwoven fabric according to the present invention is of an unprecedented type, and its characteristics are: (1) the fibers making up the inorganic fiber nonwoven fabric are arranged almost orthogonally in two directions, vertical and vertical; and (2) the vertical direction. The fiber aggregate is composed of fibrillated long fibers.

In other words, the fibers constituting the inorganic fiber nonwoven fabric are
By having anisotropy in the two horizontal directions and arranging them almost perpendicularly, it is possible to increase the fiber packing density of the inorganic fiber nonwoven fabric and to increase the reinforcing effect in both the vertical and horizontal directions. Become.

As a result, the dimensional stability and bending strength of FRP using the inorganic fiber nonwoven fabric, especially the bending strength of a thin plate, can be improved compared to FRP using an inorganic fiber nonwoven fabric in which fibers are randomly arranged and have the same basis weight as the inorganic fiber nonwoven fabric. became possible.

Furthermore, by adopting a dry method for dispersing fibers when supplying short fibers in the horizontal direction, water-soluble dispersants, which are indispensable for dispersing fibers in the wet method of making paper using conventional paper machines, can be used. It is no longer necessary to add it, and it has become possible to significantly improve the heat resistance and electrical insulation properties after moisture absorption of FRP using the inorganic fiber nonwoven fabric.

In addition, by composing the fiber aggregate in the vertical direction with fibrillated long fibers, it is possible to prevent the impregnation of the inorganic fiber nonwoven fabric with resin and impair the dimensional stability of FRP. It has become possible to provide nonwoven fabric strength that does not need to be limited by conditions.The inorganic fiber nonwoven fabric according to the present invention has extremely high dimensional stability, especially among FRPO.
P that requires heat resistance, electrical insulation, and bending strength in thin plates
Its performance is particularly effectively exhibited in reinforcing materials for CB.

Note that the resins used in manufacturing FRP using the inorganic fiber nonwoven fabric of the present invention include, for example, epoxy resins, polyimide resins, phenol resins, polyester resins, silicone resins, polyurethane resins, and mixtures thereof, which are conventionally used in the manufacture of PCBs. Thermosetting resins that can be cured by heat can be used, but it goes without saying that thermoplastic resins produced by thermoforming can also be used. In addition, although the absolute values of various characteristic values of FRP using the inorganic fiber nonwoven fabric of the present invention vary depending on the type of resin used, the degree of the difference in displacement is relative to that when using the conventional inorganic fiber nonwoven fabric. The characteristics achieved by the present invention are not impaired depending on the type of resin used.

[Examples] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

In addition, in evaluating the FRP using the inorganic fiber nonwoven fabric of the present invention in comparison with a comparative example, the inorganic fiber woven fabric was used for each of the upper and lower layers of the outer layer of the reinforcing fiber base material, and the inorganic fiber woven fabric was used for the inner layer. Sandwich-structured FRP, so-called composite boards, were created using the inorganic fiber nonwoven fabrics of Examples and Comparative Examples.
Physical properties were evaluated.

A glass fiber nonwoven fabric in which layers of long inorganic fibers were arranged on both sides of a layer of short inorganic fibers was produced using a manufacturing apparatus having the configuration illustrated in FIG.

A roll in which untwisted strands of ECG-75110 were aligned and wound at an interval of 4 strands/inch was prepared as a long fiber for the vertical direction. In addition, 10 untwisted strands of ECG-75110 were used as short fibers for the horizontal direction and cut to have an average fiber length of 25 pieces.

Furthermore, an epoxy binder was used as a binder to obtain the inorganic fiber nonwoven fabric of the present invention.

When observing the arrangement of the longitudinally long inorganic fibers of the obtained inorganic fiber nonwoven fabric, it was found that most of the glass fiber monofilaments were individually dispersed and arranged, and the side surfaces of two or more monofilaments were continuous. There was little contact.

On the other hand, when the arrangement of the short fibers was measured using a microwave orientation meter, the vertical/horizontal strength ratio was 0.5, proving that the short fibers were arranged perpendicularly to the long fibers.

Table 1 shows the properties of the obtained glass fiber nonwoven fabric.

Glass fibers having an average yarn length of 1511111 and an average diameter of 9p were uniformly dispersed in water, paper was made, and the epoxy binder used in Example 1 was used as a binder to produce a glass fiber nonwoven fabric by a wet method.

The vertical/horizontal strength ratio of the glass fiber nonwoven fabric of Comparative Example 1 measured by a microwave orientation meter was 3.2, and from this value, Comparative Example 1
It was found that the constituent short fibers in the glass fiber nonwoven fabric were arranged more in the longitudinal direction.

Table 1 shows the properties of the obtained glass fiber nonwoven fabric.

, L Comparison
Glass fibers of G-751101 and OZ were bonded together using an epoxy binder to create a combined glass fiber nonwoven fabric.

Table 1 shows the properties of the obtained glass fiber nonwoven fabric.

1.1 Prepreg A was obtained by impregnating and coating the glass fiber nonwoven fabric prepared in Example 1 with an epoxy resin face of the following formulation example and drying at 125'C. Next, two sheets of this prepreg A are laminated, and an epoxy resin face of the following composition that does not contain an inorganic filler is applied on the top and bottom surfaces of the glass woven fabric (Cross Style 7628 surface finish treatment AS-450 manufactured by Asahi Schniebel) by impregnation. One sheet each of prepreg B obtained by drying at 125°C was layered, and one sheet each of copper foil with a thickness of 35 cm was layered on the top and bottom surfaces of prepreg B, and heated at 175°C.
Compression molding was performed at 30 kg/cffl to obtain a copper-clad laminate with a thickness of 1.0 u.

After the copper foil of this copper-clad laminate was removed by etching, the characteristics of the laminate were tested.

Table 2 shows the characteristics of the obtained FRP.

Epoxy resin face composition AEII-711 100 parts (Renkasei epoxy resin) Dicyandiamide 2.5 parts Benzyldimethylamine 0.2 parts Dimethylformamide 12 parts Methyl cellosolve
12 parts methyl ethyl ketone
25 parts aluminum hydroxide
Example 2 using the glass fiber nonwoven fabric prepared in Comparative Example 1
A laminate was obtained in the same manner as above.

Table 2 shows the characteristics of the obtained FRP.

Example 2 using the glass fiber nonwoven fabric prepared in Comparative Example 2
A laminate was obtained in the same manner as above.

Table 2 shows the characteristics of the obtained FRP.

As is clear from Tables 1 and 2, the inorganic fiber nonwoven fabric of the present invention has a nonwoven fabric strength that does not require any restrictions on the FRP manufacturing conditions, and has improved dimensional stability, heat resistance, and electrical insulation. This makes it possible to manufacture FRP with excellent bending strength, especially in thin sheets.

Table 1 Table 2 Hot strength = Solvent resistance strength r measured in a 120°C atmosphere Bending strength measured at room temperature after immersed in MEK for 10 minutes: Heat resistance measured according to JIS-6911: 120°C pressure After absorbing water for 1 hour using Kunkar, it was floated on molten solder at 260°C and the time until blistering was measured.Electrical insulation resistance after absorbing water After absorbing water for 4 hours in boiling water,
Dimensional change rate measured according to JIS-C-6481: Dimensional change rate - (Initial dimension - Dimension after heating) / Initial dimension X 10
0 Dimensional change after heating at 170°C for 130 minutes [Effect of the invention] Since the inorganic fiber nonwoven fabric of the present invention is configured as described above, it has excellent strength as an inorganic fiber nonwoven fabric, and as a result, the inorganic fiber nonwoven fabric of the present invention It helps improve the dimensional stability, heat resistance, and bending strength of FRP made using nonwoven fabric.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing an example of an apparatus used for manufacturing the inorganic fiber nonwoven fabric of the present invention. 3... Long fiber inorganic fiber aggregate for vertical direction, 7... Long fiber inorganic fiber for horizontal direction, 8... Cutting device, 12... Fiber separation device, 13... Nozzle, 14 ...water flow, 1
5... Deposition conveyor, 16... Intake device, 2
2...Inorganic fiber nonwoven fabric.

Claims (1)

[Claims] at least one layer of fibers consisting of a plurality of long fiber inorganic fibers arranged substantially in parallel; and at least one layer of fibers consisting of a plurality of short fiber inorganic fibers arranged substantially orthogonally on the long fiber inorganic fibers. An inorganic fiber nonwoven fabric containing a group of fibers.