JP2986561B2 - Composite molded article and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite molded article having a porous core as an inner layer and a fiber-reinforced resin composite material as a surface layer (outer shell) (hereinafter sometimes abbreviated as a sandwich material as required) and It relates to a method for producing it efficiently.

[0002]

2. Description of the Related Art A fiber-reinforced resin composite material (hereinafter sometimes abbreviated as FRP) is used as an outer shell and a porous resin molded product (generally, a foamed resin molded product is sometimes abbreviated as a porous core hereinafter). The molded product as the inner layer is used as a lightweight material together with a honeycomb core and the like for various structural materials and the like, from aircraft, space equipment, etc. to housing construction. In such a molded product, the porous core layer is usually homogeneous, and the outer shell is molded (for example, by internal pressure molding), and then foamed, or the porous core of the core is preliminarily molded and used as a reinforcing material. After being wrapped in, it was inserted into the mold again, and the liquid resin was injected and molded. Recently, the inner layer is molded with a hard foamed resin and this is used as a foam core, reinforcing fibers are placed outside the foam core, put into a mold, and the resin is put between the hard foam (foam core) and the mold and heated to form a hard foam. A thermally expandable transfer molding method has been proposed in which a resin is foamed into a reinforcing fiber layer and a resin is molded at a stretch (JP-A-63-162207).

[0003] All of them substantially separately form a porous core layer and a fiber reinforced resin composite (FRP) layer.
That interface exists. In these methods, even if the resin forming the porous core and the resin forming the composite material layer are the same, an interface occurs, and this interface becomes a defect in the mechanical properties and other aspects of the molded product. It is easy. For example, the method described in JP-A-63-162207 produces a good composite sandwich core molded product, that is, a composite molded product having a porous core obtained by foaming and molding the inner layer of a fiber reinforced resin composite material (FRP). According to the method, a heterogeneous layer is bonded between the fiber reinforced resin composite material (FRP) of the outer shell and the foamed porous core of the inner layer, and a clear interface exists. For this reason, depending on the shape of the molded product, there are cases where the foam core is easily broken due to low strength or the like.
In addition, this method requires that a thermoelastic rigid foam core conforming to the shape and size of the final molded product be prepared in advance, so that the actual process is complicated.

On the other hand, various simple molding methods have been studied. For example, there is a method in which a preform or prepreg of a reinforcing fiber is molded and put into a mold, and an expandable resin is injected. The present inventors have first made the expandable (expandable) particles into a separation layer together with the liquid resin. We proposed a method of wrapping in a material, foaming it in a mold, and simultaneously molding the core, which is the foamed core, and the surface layer made of the fiber-reinforced resin composite material (Japanese Patent Application Nos. 179830 and 2-95069). . However, even with this method, it is not always easy to efficiently form a molded product in the form of a sandwich material having excellent shapes.

[0005]

The problems of the sandwich material molded article are that the physical properties of the molded article are inferior due to the strength of the foam core and the like, and the interface between the porous core layer and the fiber reinforced resin composite material is peeled off. There is a problem to do. These are already known, and for solving them, for example,
No. 44, Japanese Patent Application Laid-Open No. 2-282913 and the like have been proposed. An object of the present invention is to effectively solve the problems of the strength of the foam core and the separation of the interface. That is, the present invention provides a novel composite molded article in which the interface between the porous core layer and the fiber-reinforced resin composite material is eliminated, and a method for easily producing a composite molded article with such an improvement. It is something to offer.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a molded product obtained by wrapping a foam core with a syntactic foam and covering it with FRP which is integral with the syntactic foam is obtained. It was found that the above-mentioned problem could be solved. Also, as a method for efficiently producing this molded product, consider using a material in which foamable resin particles are wrapped with a separation layer material together with a foam core,
The present invention has been reached.

That is, in the composite molded article of the present invention, the core is a foam core, the outside of which is covered with a syntactic foam, and the outside of which is covered with a fiber-reinforced resin layer which is integrated with the syntactic foam. It is a novel composite molded article characterized by the above.

[0008] In the present invention, in order to always maintain the physical properties of the molded product at a certain level or more, a separation layer for partitioning the outermost FRP layer and the next (syntactic foam) layer between the outermost FRP layer and the next layer Is preferably present.

According to the present invention, in producing this composite molded product, (a) a separating layer which does not substantially pass the expandable resin particles but does allow the liquid resin to pass is provided in a molding die; ) A liquid resin present inside and / or outside the separation layer,
(c) Both the foam core and the foamable resin particles, which have been foam-molded in advance, are present in the portion to be the porous core after molding (that is, inside the separation layer), and (d) a predetermined region of the mold is heated to a sufficiently high temperature. And / or the heat of reaction of the curable resin heats the expandable resin particles in the mold to cause volume expansion, thereby expanding and expanding the separation layer and / or inside the separation layer.
Alternatively, the resin on the outside is pressed against the inner surface of the mold, and the resin is penetrated into the separation layer, and at least a part of the resin is allowed to pass through the separation layer to reach the inner region, and the resin is formed into at least the foam core. A method is employed in which pressure is applied to the surface to cure or solidify the liquid curable resin, and the obtained composite molded product is removed from the mold.

[0010] Outer shell (skin) in the composite molded article of the present invention
The fiber reinforced resin composite material (FRP) used as the reinforcing fiber material is a variety of woven fabrics, knitted fabrics, nonwoven fabrics, and the like, and the nonwoven fabrics include a papermaking product, a spray-up prepreg, and the like. The material of the reinforcing fiber material is glass fiber, carbon fiber, alumina fiber, polyamide fiber, aramid fiber,
Polyester fibers, polyarylate fibers, polyolefin fibers and the like are used, and glass fibers are particularly preferable. Carbon fibers and the like are used for high-end products. It is not necessarily required to be a long fiber, and it is used for a woven fabric, a knitted fabric, a nonwoven fabric, a web or the like. These can be used as a separation layer, but it is preferable to separately arrange them outside the separation layer.

The resin to be impregnated into the reinforcing fiber material is a usual thermosetting resin, such as epoxy resin, polyester resin, vinyl ester resin, polyurethane resin, polyamide resin, phenol resin, cyclopentadiene resin and the like. Is used. These resins may be precursors, raw materials (monomers), and the like, and in the present invention, these are collectively referred to as thermosetting resins. These resins are selected from those whose curing is completed at or above the foaming start temperature of the foamable resin particles.

The syntactic foam is formed from expandable resin particles and a curable resin. As expandable resin particles, those which partially decompose during heating polymerization to generate gas, and raw materials which generate gas are blended. And a gas-containing material, a gas-dissolved material, and the like. In addition to those that generate gas, those that self-expand can be mentioned. In particular, those having an average particle diameter of about 1 μm to 1 mm, which are called expanded balloons and expandable particles, are preferable. Product names include, for example, "Microsphere" from Dow Chemical and Matsumoto Yushi, "Expancel" from Expancel,
"Eslen beads" of Sekisui Plastics Co., Ltd. and the like.
Resin components constituting these particles include polyvinylidene chloride, polyacrylonitrile, polyolefin, polyphenylene, polyurethane, polyester, polyamide, epoxy and the like. On the other hand, the curable resin is preferably the same as or has affinity with the resin forming the FRP layer.

In addition, non-expandable hollow fine particles or light-weight fine particles, for example, inorganic light-weight fine particles such as glass balloons, silica balloons, and shirasu balloons;
An organic hollow body or lightweight fine particles such as "E" may be added.
By the addition of the non-expandable hollow fine particles, the amount of foaming can be adjusted and the amount of the raw material supplied to the molding die can be adjusted. This is an important factor in handling the actual mold. Also,
It is also useful for improving the syntactic foam layer, and may improve the strength, elastic modulus and the like of the molded product.

The non-expandable hollow fine particles or lightweight fine particles are preferably blended in an amount of 10 to 200% by weight based on the expandable resin particles.

In the present invention, it is preferable that a separation layer exists between the FRP layer of the outer shell (skin) and the syntactic foam layer. The separation layer used here is a woven fabric, a knitted fabric, or a nonwoven fabric such as a reinforcing fiber having a small opening that allows the resin to pass through but does not allow the expandable resin particles to pass therethrough, and may be a porous thin sheet. After wrapping the expandable resin particles, it is preferable that they are not broken until the molding is almost completed, and the material is selected according to the purpose, but glass fiber, carbon fiber, polyamide fiber, aramid fiber, polyester fiber, polyarylate fiber,
Fabrics, knits, and non-woven fabrics such as polyolefin fibers and polyvinylidene chloride fibers are exemplified. Natural fibers, for example, cotton woven fabric, knitted fabric, nonwoven fabric, paper and the like are also used.

As the foam core constituting the central part of the composite molded product, ordinary polyurethane foam is preferable, but not limited thereto. The foam core is preferably a rigid foam, but may be a flexible foam depending on the application. The cells of the foam may be either closed cells or open cells, but preferably have at least a density lower than that of the syntactic foam layer.

The thickness and size of the foam core can be appropriately selected according to the size and shape of the molded product to be produced. Appropriate additives and reinforcements may be included in the foam core.

The composite molded article of the present invention has the above-mentioned constitution. In general, in the case of a sandwich material, a syntactic foam generally tends to improve physical properties such as strength in a molded article more than a foam core. In addition, the physical property of the sandwich material largely involves the problem of separation between the skin layer and the core material. The intention of the present invention is that the epidermal FRP
The layer is formed integrally with a durable syntactic foam to improve the physical properties of the molded product, and furthermore, to increase the fruit by making the central portion a foam core that is easily reduced in weight. On the other hand, in the method of simultaneously forming the skin FRP and the core material core, for example, the method of Japanese Patent Application No. 1-179830 described above, if the syntactic foam core layer becomes thick, it becomes difficult to make this layer uniform.

Next, a method for efficiently producing the composite molded article of the present invention will be described in detail.

As one embodiment of the method of the present invention, a foam core and foamable resin particles previously foam-molded with a separation layer material are wrapped in a mold for molding (hereinafter referred to as a mold), and the mold is substantially cooled. After closing the mold, a liquid resin is injected into the mold from a nozzle provided in the mold, and then the mold is heated to expand the foamable resin particles inside, and the liquid resin is used by utilizing the force. Is taken into a region inside the separation layer and molded.
In such a case, unless a non-expandable resin is present between the foamable resin particles in advance, the foamed particles and the like are directly adhered to each other at the time of molding, and the partition walls between the porous cells become thinner. In some cases, it is difficult to obtain physical properties. Therefore, it is also preferable to form a non-expandable resin in the presence of a non-expandable resin between the expandable resin particles. In such a case, it is preferable to use a material in which the non-expandable resin is added to the inside of the separation layer in advance. This resin is particularly preferably a solid resin that dissolves in the liquid resin to be additionally injected and becomes integral after molding.

The resin put into the separation layer together with the expandable resin particles may be thermoplastic or thermosetting as long as it has fluidity during molding. Those which are easily dissolved by the resin inside the separation layer or outside the separation layer are preferable, and those having at least compatibility are preferable. As such a resin, polyvinyl chloride, polyolefin, polyurethane, rubber, or the like, or an epoxy resin that is solid at room temperature is used, and the latter is particularly preferable.

In such an embodiment, the expandable resin particles (and hollow particles, etc.) are arranged outside the foam core, covered with a separation layer which can also serve as a reinforcing material, and housed in a mold. , The liquid resin can move easily in this part,
Therefore, the resin can be easily injected, which is extremely advantageous, for example, as compared with the above-mentioned thermal expansion transfer molding method (see JP-A-63-162207) and the ordinary foam RTM method.

Also, as a preferred embodiment of the method for producing a molded article of the present invention, foamable resin particles which can easily be replaced with a foam core having a rough shape instead of a rigid foam core very similar to the molded article Using a packaged product in a bag made of a separation layer, while forming a porous molded product corresponding to the shape of the outer shell and corresponding to the FRP of the outer shell, and / or forming the outermost shell While pressing the reinforcing fiber material and the resin impregnated therein / or the resin impregnating them into the inner surface of the mold, a molded product having an outermost shell of FRP and an inner layer of a porous core can be given. That is, this method uses a foam core molded into an appropriate shape in advance and a foam material inside the separation layer and a resin outside the separation layer together with a foam core molded into an appropriate shape when making a porous molded product of the core portion, and syntactic foam between the two. A layer is formed.

Therefore, in the composite molded article according to the method of the present invention, the fiber reinforced composite material constituting the outermost shell (skin) and the porous core of the next layer have the same resin, and the molding is performed simultaneously. Therefore, there is one characteristic that an interface cannot be substantially formed. Further, the resin of the syntactic foam on the outer side of the foam core in the center part can be infiltrated by the inflation pressure to be firmly bonded. Further, the density and other properties of the foam core and the skin FRP at the center and the syntactic core layer between the two can be easily adjusted separately.

When such a molding is performed, the presence of the resin together with the foamed resin particles inside the separation layer in advance is useful for adjusting the porous core (core material) layer to be molded. In particular, it is useful for giving a slight difference in resin properties between the density and the skin FRP layer.

In carrying out the method of the present invention, the foam core and the expandable resin particles are covered with a separating layer impregnated with a resin, and the outside thereof is covered with a reinforcing fiber material. When taken into the region inside the separation layer through the separation layer and molded, the reinforcing fiber material may be impregnated with a resin in advance and put into a mold. Alternatively, a resin may be applied. In this case, foamable resin particles and a foam core wrapped with a separation layer material are put between them. In addition, the foamed resin particles and the foam core wrapped with the separation layer material are covered with a reinforcing fiber woven fabric or nonwoven fabric, a web or the like, placed in a mold, and the mold is closed. You may put in a layer, such as a web. In this case, it may be preferable to pre-evacuate the inside of the mold when the mold is closed. At this time, in selecting the expandable resin particles, those which do not expand at the time of applying a vacuum should be selected.

However, in the method of the present invention, this vacuum operation is usually unnecessary, which is also one of the advantages of the method of the present invention. In other words, due to the exhaustion due to the foaming expansion and the dissolution of the gas under pressure into the resin layer, molding can be performed without outstanding bubbles. In addition, the resin to be injected at this time can be made to exist only on the surface by adding, for example, calcium carbide or mica as a modifier for the surface layer.

The foam core and the expandable resin particles covered with the resin-impregnated separation layer and the reinforcing fiber material are placed in a mold and heated. At this time, it may be preferable to provide a nozzle on the upper part of the mold in advance and discharge a part of the resin and gas. However, during molding, an internal pressure is always generated, and the resin inside and outside the separation layer is applied to the area inside the separation layer (that is, the area that becomes the syntactic foam layer).
Take in. The porous core layer foamed by this resin is fixed. At this time, if the nozzle is loosened until molding is completed, a relatively light one can be obtained, and a relatively heavy one can be obtained by closing the nozzle. This can also be one means for determining the amount of the porous core layer depending on the target molded product.

Next, an example of a specific method will be described. The foam core and the expandable resin particles (balloon), for example, “Expancel” are put in a non-woven fabric bag serving as a separation layer. The bag entrance is fused to close the bag. Separately, a woven fabric of the reinforcing fibers is prepared and has a predetermined shape. A bag containing a foam core and a balloon is sandwiched (wrapped) with the woven fabric in a mold prepared in advance. At this time, for example, the reinforcing fiber woven fabric is fixed by being sandwiched between molds. Nozzles are provided on the upper and lower sides of the mold, respectively, and they are attached so as to communicate with the inside through a fiber layer sandwiched between the molds. The interior of the mold is evacuated by evacuating from the upper nozzle, and after closing the nozzle, a liquid curable resin is injected from the lower nozzle. If necessary, a calcium carbide powder or the like is added to the resin to increase the hardness of the surface of the molded product. At first, the resin is sucked in, and then press-fit. At this time, the bag containing the balloon is crushed. When the resin has completely entered into every corner, the lower nozzle is closed, and the upper nozzle is slightly opened to heat and foam. Open / close and adjust the opening of the nozzle as necessary. When the curing is completed, the molded product is taken out after cooling. The resulting molded product has a surface of F
RP, a syntactic foam immediately below the FRP and an integrated part thereof, and a connection part at least in the interior formed of a foam core impregnated with a resin of the syntactic foam.

[0030]

The novel composite molded article according to the present invention is a composite molded article in which the foam core is covered with a syntactic foam and further covered with an FRP which is integral with the syntactic foam. It is a molded product having excellent specific strength and specific rigidity, which is a syntactic foam having high physical properties and a seamless form between the FRP layer and a lightweight foam core whose core is well bonded to the syntactic foam layer.

According to the method of the present invention, a lightweight, durable and relatively inexpensive FRP is used as the outermost shell, a syntactic foam in which this is integrated with the resin layer is used as the next layer, and the foam core is used as the innermost layer. Thus, it is possible to efficiently produce a molded product excellent in specific strength and the like in which the intermediate portion is connected by a syntactic foam.

The thus obtained composite molded product is used for building,
It is useful in the field of structural materials (for example, backing materials) and parts for aircraft and vehicles, and in the field of sports equipment.

[0033]

EXAMPLES Next, examples of the present invention and comparative examples will be described in detail, but the present invention is not limited thereto. still,
“Parts” in each example are parts by weight unless otherwise specified.

[0034]

Example 1 A urethane foam slab was purchased and made 2 mm thick. From this slab material, a slightly smaller sample was cut out according to the mold described below.

An epoxy resin and a curing agent made of an oiled shell,
"Epicoat 828" 100 parts, "Epomate YLH006" 3
3 parts were mixed. This is designated as resin A. On the other hand, Matsumoto Yushi Pharmaceutical's foam balloon “Matsumoto Microsphere F-
30D "44 parts" and crushed epoxy resin "Epicoat 10
20 "(solid at room temperature). This mixture is referred to as a foamable mixture B.

A long-fiber non-woven fabric with a small aperture, known as "UNI-CELL", made of a non-woven fabric of polyethylene terephthalate and polypropylene fibers, was prepared. This is a custom product. Using this, a slightly smaller bag was made according to the inner dimensions of the mold described below. This bag was filled with a cut sample of the urethane foam slab material and the foamable mixture B.

A mold having a Teflon frame sandwiched between two aluminum plates was formed, and nozzles were provided at upper and lower ends. Two glass cloths each of which were filled with a metal mold, and ten glass glass cloths each having a length matching the metal mold and a width covering the nozzle were prepared, and all of them were sufficiently impregnated with the resin A. Using a large glass cloth, the resin-impregnated glass cloth / bagging of the foamable mixture B / the resin-impregnated glass cloth were placed in a mold in this order. Small glass cloth was overlapped to fill the position covering the nozzle, that is, the upper and lower ends. The mold was closed as it was while evacuating the air inside the mold with some resin using the upper nozzle, and the nozzle was closed.

The mold was placed in a warm bath at 80 ° C., and when the internal pressure became positive, the upper nozzle was slightly opened. The resin was cured while removing excess resin from the nozzle.

After one hour, the mold was taken out of the warm bath, and after cooling, the mold was opened to take out the molded product. Thus, a lightweight and good sandwich material having a glass fiber reinforced epoxy resin on the surface and an epoxy resin foam and polyurethane foam on the inner layer was obtained. This sandwich material has a specific gravity of 0.48, and as a result of a bending test, a strength of 7.6 kg / m
m ² and an elastic modulus of 780 kg / mm ² .

[0040]

Example 2 A mold for making a bar of 40 mm × 60 mm square was prepared. It was made of aluminum and provided with nozzles with valves on the top and bottom.

On the other hand, a commercially available urethane foam slab material (hard urethane foam manufactured by Toyo Tire & Rubber Co., Ltd.) was purchased and purchased.
A 5 mm x 45 mm square bar was made. Also, 100 parts of "Epicoat 807", an epoxy resin and a curing agent made of oily shell,
31 parts of "Epomate YLH006" were mixed. This is resin A
And

A non-woven fabric was made from polyethylene terephthalate and polypropylene fibers. It is a custom-made long-fiber nonwoven fabric with a small opening known under the trademark "Unicell". This made a cylinder with a circumference of 200 mm and closed one side.

Further, a unidirectionally arranged carbon fiber sheet (Anchor
Reinforcements, Inc. Ancaref C250) and one carbon fiber strand T400D-3000-40D with 96 braids with a braid angle of 40 ° were prepared.

The urethane foam slab material was placed in the above-mentioned tubular bag of nonwoven fabric, and the above carbon fiber sheet was covered thereon. Eight layers were successively covered, and the outermost layer was covered with one layer of the above-mentioned blade. This was placed in a mold and the same “Matsumoto Microsphere F-30D” as in Example 1 was placed between the nonwoven fabric and the urethane slab material. Then, the end of the bag was closed, the end of the carbon fiber blade was processed and placed in a mold, and the mold lid was closed.

Next, the upper nozzle of the mold was opened, the resin A was injected from the lower nozzle, and the injection was stopped when the resin began to overflow from the upper nozzle. After standing, the mold was placed in a dryer at 80 ° C. with the upper nozzle facing upward. The resin discharged from the upper nozzle was recovered.

After one hour, the product was taken out of the dryer, cooled, and the molded product was taken out of the mold. Thus, a rod having an epoxy resin on the surface, a carbon fiber reinforced epoxy resin on the inside, a syntactic foam of the epoxy resin in the next layer, and a urethane foam in the center was obtained. As a result of the bending test of this rod, the bending fracture moment was 9.4 × 10 ⁵ kgf-mm and the bending rigidity was 1.7 × 10 ⁹ kgf-mm ² .

[0047]

[Comparative Example 1] A square rod having the same size as that of Example 2 was formed by using urethane foam having remaining expansion force, eight carbon fiber sheets used in Example 2, one blade layer, and one Unicell layer. Molding was carried out using the same mold as in Example 2 by the method described in JP-A-63-162207. As a result of a bending test, the obtained molded product (bar) was found to have a bending fracture moment of 7.3 × 10 ⁵ kgf-m.
m, and the flexural rigidity was 1.4 × 10 ⁹ kgf-mm ² .

Claims (9)

(57) [Claims] 1. A composite molded article characterized in that the core is a foam core, the outside of which is covered with a syntactic foam, and the outside of which is covered with a fiber-reinforced resin layer integrated with the syntactic foam. . 2. The composite molded article according to claim 1, wherein the density of the foam core is lower than the density of the syntactic foam. 3. The composite molded article according to claim 1, wherein a separation layer is provided between the syntactic foam and the fiber-reinforced resin layer, the separation layer not allowing the foamed particles of the syntactic foam to pass through. (1) A separating layer which does not substantially pass the expandable resin particles but does allow the liquid resin to pass therethrough in a molding die, and (2) the inside and / or the outside of the separating layer. (3) Pre-foamed foam core and foamable resin particles should be present in the portion that will become the porous core after molding, (4) Heat a predetermined area of the mold to a sufficiently high temperature And / or the heat of reaction of the resin causes the foamable resin particles in the mold to be heated to cause volume expansion, thereby expanding the separation layer and displacing the liquid resin inside and / or outside the separation layer with gold. While pressing against the inner surface of the mold,
Infiltrating the liquid resin into the separation layer, and passing at least a part of the liquid resin through the separation layer to reach the inner region, and pressurizing and infiltrating the resin to at least the surface of the foam core; (5) curing the liquid resin Or solidifying, and
(6) A method for producing a composite molded product, comprising taking out the obtained composite molded product from a mold. 5. The foam core is covered with a separating layer together with foamable resin particles, and if necessary, further covered with a reinforcing fiber material, placed in a mold, and a liquid resin is injected into the mold. The manufacturing method according to claim 4, wherein 6. The method according to claim 4, wherein the expandable resin particles are hollow thermally expandable resin particles. 7. The method according to claim 4, wherein the expandable resin particles are non-hollow resin particles containing a foaming component. 8. The method according to claim 4, wherein the separation layer also serves as a reinforcing material for the surface layer. 9. The method according to claim 4, wherein light-weight fine particles which do not expand substantially are present together with the expandable resin particles in a portion which becomes a porous core after molding inside the separation layer.