JPH04310726A - Manufacture of light composite molded material - Google Patents

Abstract

PURPOSE:To provide the rationalized method for molding a new, light composite molded material of good mechanical physical properties compared with its weight. CONSTITUTION:A web-like fiber aggregate containing particles foam-expansible by heating is manufactured by the dry process, and the aggregate is impregnated with resin, heated and molded while the particles are foam-expanded to manufacture a light composite molded material. A sandwiching material having the light composite molded material as a core material and an FRP skin can be manufactured by laminating the web and a fiber-reinforced fabric or the like and molding toegther with the resin.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing lightweight composite molded articles containing a porous core, which has been widely used in recent years.

0002

[Prior Art] Molded products mainly consisting of porous cores can be used as lightweight materials as they are or in combination with other materials.
For example, it is widely used as a sandwich material in fields such as aerospace materials and sporting goods.

[0003] Such porous molded products are usually a type of resin molded products in industrial terms. Conventionally, this has been industrially molded using foamable resin (that is, foam molding). This method can be roughly divided into (1) a method in which a resin or its raw material that foams when heated or reduced pressure is placed in a mold, and (2)
) There is a method in which specific resins are foam-molded into particles (primary foam), which are then placed in a mold and further expanded (secondary foam).

[0004] As a method of making this into a lightweight structure such as a side switch material, the foam molding can be used as a skin material, such as a pre-formed fiber-reinforced resin molding (hereinafter referred to as FRP if necessary).
It is common practice to bond a foamed material (abbreviated as ), to cover a foam molded product with prepreg or the like, or to inject a foamable resin into a pre-formed hollow outer shell and perform foam molding.

[0005] In recent years, as improvements to these methods, methods have been proposed such as internal pressure molding using foam expansion and methods using a thermally expandable molded product as a porous material material (for example, Japanese Patent Application Laid-Open No. 1-255530, (No. 162207, 1983).

As a molding method that further improves these methods, the present inventors have proposed a method for molding a sandwich material using expandable particles that are first foamed by heating and a liquid curable resin, and an intermediate material thereof. (Patent application 1998-1798)
No. 30, Japanese Patent Application No. 1-255305, Japanese Patent Application No. 1-229
No. 425, Japanese Patent Application No. 2-095069, Japanese Patent Application No. 2-23
No. 5796).

[0007] The method of using expandable particles has many advantages and is an industrially preferable method.
There remains a problem that it is difficult to say that it is suitable in all cases. In addition, in methods using expandable particles, non-expandable lightweight particles, hollow particles, etc. are often used in combination, but in such cases, these lightweight particles, hollow particles, etc. also float, making the problem even more problematic. big. In addition, for molded products using foam cores and syntactic cores, the strength and adhesion of the core affect the physical properties of the molded product, and depending on the shape of the molded product, problems may arise.
Measures such as reinforcement are being taken (for example, Japanese Patent Application Laid-Open No. 1-11
No. 0943, Japanese Unexamined Patent Publication No. 1-110944, Japanese Unexamined Utility Model No. 2-1
No. 04226, etc.).

[0008]

OBJECTS OF THE INVENTION The present invention solves the above-mentioned problems observed in the production of conventional molded products having porous cores, and also inexpensively and easily produces lightweight composite molded products. It is intended to provide a method. This is a simple method that uses an intermediate material, and has the advantage of avoiding unnecessary uneven distribution of particles that foam and expand when heated. More specifically, when molding a sandwich material using particles that can be expanded and expanded by heating, the present invention provides a method for manufacturing a novel composite molded product that can suppress the foaming of the particles and at the same time provide a reinforcing effect on the core part. This is what we are trying to provide.

[0009]

[Means for Solving the Problems] As a result of intensive research in order to achieve the above-mentioned object, the present inventor has achieved the above-mentioned goal by using a dry fiber web containing particles that can be foamed and expanded by heating (expandable particles). The inventors have discovered that the object can be achieved and have arrived at the present invention.

That is, the present invention is a method of forming a fibrous web by a dry method using expandable particles and fibers or fibrils, and producing a lightweight composite molded article from this expandable particle-containing fibrous web and resin. Impregnating a dry fiber web containing expandable particles with a resin or placing the web alone or with a reinforcing fiber material on the outside of the web in a mold,
This method of manufacturing a lightweight composite molded article is characterized in that the particles are foamed and molded by heating in the presence of a resin.

[0011] In particular, as a molding method, molding is performed using a thermally expandable web impregnated with resin, and if a mold is used, it can be positioned as internal pressure molding.

A method of forming a syntactic core using particles that can be expanded by heating (expandable particles) is well known. However, particles that have become lighter due to foaming and expansion tend to float, often resulting in uneven distribution or failure to settle in the intended position. This problem becomes more serious when non-expandable lightweight particles such as hollow particles are used together with expandable particles. The present invention seeks to solve this problem by locating expandable particles and lightweight particles in a dry fibrous web. At the same time, the syntactic core is effectively reinforced by the fibers that make up the web. Therefore, even if there is some leakage, the dry fiber web used in the present invention is a web that does not substantially allow these particles to pass through when foamable and expandable particles are used together with lightweight particles such as hollow particles. be.

[0013] Such a dry fiber web can be produced by various methods, and fibrils, short fibers,
It can be made using any long fiber. A typical example of dry web formation of short fibers is web formation using a card or land web.For the purpose of the present invention, a card web or the like may be used as it is, but a needle punched web is more preferable. The expandable particles can be added at or during the application of the card or web, or they can be added during needle punching.

[0014] Examples of long fiber webs include the spunbond method and the opening method. In either case, after forming the first layer, it is convenient to form the second layer by dispersing non-expandable lightweight particles such as particles that can be foamed and expanded by heating, hollow particles, etc. For bonding the two layers and fixing the particles, it is convenient to use a low-temperature adhesive, a needle punching method, etc. that can bond at a temperature below the temperature at which the expandable particles expand and foam.

[0015] A web using fibrils or the like is produced by, for example, forming a web using a spray method. That is, the method involves mixing a small amount of adhesive with fibrils and spray-molding the fibrils, which can also be carried out by mixing particles that can be expanded. After forming the first layer,
The second layer can also be formed by spraying expandable particles or the like.

[0016] All of these are illustrative of embodiments of the method of the present invention, and are not limited thereto. For example, it is also possible to adhere foamable and expandable particles by a method using a long fiber web. Therefore, in the present invention, the web through which foamable and expandable particles do not substantially pass through does not simply mean the size of the opening.

[0017] The fibers or fibrils to be made into the web are:
Examples include polyester, polyamide, especially aramid, polyacrylonitrile, polyolefin, natural fibers, etc.
Examples of so-called polymerized fibrils (fibrils obtained during polymerization) include polyolefins, particularly polyethylene, and aramids, particularly polyparaphenylene terephthalamide. Of course, a mixture of these may also be used. Although inorganic fibers such as carbon fibers and glass fibers can also be used, organic fibers are preferred from the viewpoint of ensuring the expandability of the web during expansion.

The short fibers used in the present invention are ordinary short fibers and have a length and thickness suitable for forming into a web. However, in general, the diameter is preferably about 1 to 50 μm, particularly about 2 to 20 μm, and the length is preferably about 1 to 50 mm, especially 5 to 20 mm.

The fibrils used in the present invention include branched short fibers, beaten and finely divided fibers, and the like. These are, for example, Special Publication No. 61-42004 and Special Publication No. 60-5
Although methods such as No. 6801 are preferred, other fibrils that can be made into dry webs, such as natural fibrils, may also be used. Generally, the freeness is 30°S.
R (Shopper Rigler method standard) or less is used. Preferably, the SR is 20°SR or less, and those having such a degree of beating are easy to use.

[0020] The expandable particles that can be expanded by heating include particles of polyvinylidene chloride, polyacrylate, polyphenylene oxide, or a thermoplastic polymer mainly composed of these, containing a cell-forming material such as a hydrocarbon or a halogen compound. Examples include "Microspheres" by Matsumoto Yushi Pharmaceutical Co., Ltd., "Expancel" by Expancel, and "Eslen Beads" by Sekisui Plastics Co., Ltd., which are made of polystyrene and a blowing agent. A pulverized resin containing a blowing agent, such as ABS resin with a blowing agent added thereto, can also be used by skillfully selecting the softening temperature and foaming temperature of the resin. In the present invention, it is essential to use these expandable particles because the use of such particles provides advantages such as internal pressure molding in mold molding.

[0021] The properties of the expandable particles depend on the shape and structure of the intended molded product, but since they are used to include expansion molding, they should substantially expand in volume by at least 5% during molding. Preferably. Especially 1
It is preferable that the volume expands by 0% or more.

In the present invention, in addition to the expandable particles described above, non-expandable lightweight particles can be used in combination. Such particles include organic or inorganic hollow particles, in particular:
Inorganic hollow fine particles called glass balloons, glass balloons, etc. are preferably used.

The ratio of fibers or fibrils to expandable particles used varies depending on the main purpose of carrying out the method of the invention, but generally the ratio of fibers (or fibrils) to expandable particles is 5/1 by weight. It is preferably about 1/5 to 1/5. However, the main purpose of using short fibers and fibrils is to reinforce the foam core layer or to prevent the foam expansion particles from floating.
The preferred range differs depending on whether to prevent coalescence of bubbles or to form a preform containing fibers, and when fibrils are used, their properties also differ. For example, it is possible to mold a web, which is a preform containing short fibers, with the main purpose of reinforcing the molded product and preventing "sink marks," but in such a case, the expandable particles are In some cases, it may be about 0.05 times as large as 0.05 times. Therefore, the above amounts are presented as preferred examples and are not intended to limit the present invention numerically. Generally, the amount of expandable particles added increases when weight reduction or internal pressure molding is aimed at, and the amount added changes depending on the degree of entanglement of fibrils.

[0024] When forming these into a web, various materials can be added in addition to the expandable particles depending on the purpose. For example, inorganic powders, particles, etc. can also be mixed.

[0025] Reinforcing fibers that may be used together with the above-mentioned fiber web during molding include synthetic fibers such as polyester, especially polyarylate fiber, holamide, especially aramid fiber, polyacrylonitrile fiber, polyolefin, especially fiber called high polymerization degree polyethylene, etc., and cotton. , natural fibers such as linen,
Examples include woven fabrics, knitted fabrics, webs, nonwoven fabrics, etc. of inorganic fibers such as glass fibers, carbon fibers, alumina fibers, and silicon carbide fibers, and mixtures thereof. As a matter of course, it is preferable that the reinforcing fiber has particularly excellent elastic modulus and strength.

[0026] The resin can be either thermosetting or thermoplastic, and in most cases, an uncured thermosetting resin is preferred. Examples of such resins include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenol resins, and cycloolefin resins. However, thermoplastic resins such as polyamides and phenoxy resins can also be used.

These resins can also be used in the form of their precursors, monomers, etc. In either case, it is necessary that the material exhibits fluidity at least at the expansion temperature of the expandable particles during molding, and that it hardens (solidifies) during or immediately after molding.

The above-mentioned web can be used as it is or impregnated with a resin, and used alone or laminated with the above-mentioned reinforcing fibers or resins, that is, prepreg or a reinforcing material impregnated with a resin, FR.
It is convenient to stack it with P etc. and put it in a mold and mold it. The mold is preferably a closed mold, but a non-closed mold may also be used. A fiber web containing expandable particles is impregnated with resin to form an intermediate material, and a reinforcing fiber sheet, etc. is attached to this and placed in a mold, and the resin in the intermediate material permeates into the reinforcing fiber sheet while being heated and foamed. It is also possible to adopt a method of However, the reinforcing fiber sheet can be impregnated with the resin, or both can be impregnated with the resin.

For example, a glass cloth impregnated with a resin, particularly a soft thermosetting resin (such as an uncured unsaturated polyester resin), is pasted on the inner surface of a mold, and the intermediate material is laminated thereon, and then the glass cloth impregnated with a resin is laminated. The cloth is pasted one on top of the other, and this is repeated in some cases.The mold is then closed and heated to form and harden.

Alternatively, the web, that is, the intermediate material and the reinforcing fibers may be laminated, placed in a mold, for example, and then heated and molded by injecting a resin. In the present invention, any means may be used as long as the web is impregnated with resin during molding.

[0031] During molding, a woven fabric, non-woven fabric, etc. with small openings may be laminated on the surface of the above-mentioned fibrous web. In this way, it is easy to obtain a molded product with a clean surface.

[0032] Due to the heating during molding, the particles within the fiber web expand and expand to form a porous and lightweight core portion, and the resin hardens (solidifies) to form a molded product of a predetermined shape.

[0033]

[Effects of the Invention] According to the present invention as described above, a lightweight structural material reinforced with short fibers or fibrils or a lightweight structural material having a syntactic core reinforced with short fibers or fibrils as a core can be produced relatively easily and at low cost. You can. In particular, when molding is performed, a type of internal pressure molding can be performed, and when molding is performed with reinforcing fibers as an intermediate material, the resin impregnated in the intermediate material can be infiltrated into the reinforcing fibers and molded all at once. There is.

[0034]

[Examples] Next, the present invention will be explained in detail with reference to Examples. These are illustrative of the present invention and are not intended to limit the invention. In the following examples, "part"
Parts are by weight unless otherwise specified.

[0035]

[Examples 1-2] Two aluminum plates and "Teflon"
I made a mold. A Teflon spacer is sandwiched between two aluminum plates. The size is approximately 1
The size is 80 mm x 200 mm, and the thickness is 3 mm (depending on the spacer thickness). A nozzle was provided on one side of the mold.

[0036] Polymetaphenylene isophthalamide fiber ("Conex" manufactured by Teijin) was cut into a fiber length of 20 mm to obtain a carded web of 70 g/m2. Matsumoto Yushi Pharmaceutical Co., Ltd. (
Expandable particles "Microsphere F-30D" manufactured by Co., Ltd. were uniformly dispersed, and the above carded web was layered and needle punched. This will be used as an intermediate material. Next, two pieces of this intermediate material were cut out to be slightly smaller than the above mold. Next, the intermediate material was immersed in the following mixed resin to fully impregnate it with the mixed resin.

Glass cloth (MS manufactured by Asahi Fiberglass)
253-1040-2NT-10FS) was obtained. Similar to the intermediate material, two pieces of this glass cloth were cut out to be slightly smaller than the mold described above. Glass cloth was similarly immersed in the following mixed resin to fully impregnate it with the mixed resin.

100 parts of epoxy resin "Epicote 807" manufactured by Yuka Shell Co., Ltd. and 31 parts of "Epomate YLH006" were mixed. This is called mixed resin. This is the resin impregnated into the web and glass cloth mentioned above.

Two resin-impregnated intermediate materials were sandwiched between two resin-impregnated glass cloths and laminated together, and then placed in a mold.

After closing the mold, the mold was placed in an oil bath at 85° C. and removed from the oil bath after about 1 hour. At this time, excess resin was discharged from the nozzle. However, the nozzle closed halfway.

After cooling, the mold was opened and the molded product was taken out. The obtained molded product was a sandwich material in which the surface layer was a glass fiber-reinforced resin layer and the core layer was a short fiber-containing porous resin layer, and had a good appearance and a suitable strength. The specific gravity of this molded product is 0.87, and the bending strength is 9.2 kg/mm2.
, the elastic modulus was 560 kg/mm2.

Similarly, without using glass cloth, only the intermediate material impregnated with resin was placed in the mold, and 8
It was placed in an oil bath at 5°C and removed from the oil bath after about 1 hour. At this time, the excess resin was discharged from the nozzle and the nozzle was closed halfway.

After cooling, the molded product was taken out. The obtained molded product has a specific gravity of approximately 0.65 and a bending strength of 4.2 kg/mm.
2, the elastic modulus was 319 kg/mm2.

[0044]

[Example 3] Terephthalic acid and paraphenylenediamine/
Ultra-stretched fibers of a copolymer of 3,4' diaminodiphenyl ether ("Technora" manufactured by Teijin) were cut into fiber lengths of 2 mm and processed according to the method described in Japanese Patent Publication No. 61-42004.
-Melmethyl 2-pyrrolidone was beaten in an aqueous solution to form fibrils, which were then dried. The freeness was 14.1°SR by the Schopper-Rigler method.

[0045] For 100 parts of this fibril, 50 parts of "Microsphere F-30D" manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.
A small amount of acrylic acid adhesive was added and sprayed up to obtain a dry web. This web had a specific gravity of about 0.2 and a thickness of about 3 mm. This is called an intermediate material web.

As in Examples 1 and 2, 100 parts of epoxy resin "Epicote 807" manufactured by Yuka Shell Co., Ltd. and 31 parts of "Epomate YLH006" were mixed. This is called mixed resin.

On the other hand, glass cloth (MS253-1040-2NT-10FS manufactured by Asahi Fiberglass) was obtained. In addition, a thin, long-fiber polyester nonwoven fabric with small openings was prepared. Unicel Co., Ltd.'s nonwoven fabric "Unicell B"
T0404”.

Next, a mold was made from two aluminum plates and Teflon. It is similar to Example 1, and 2
A Teflon spacer is sandwiched between two aluminum plates. The size is approximately 180mm x 200m
m, and the thickness is 3 mm (depending on the spacer thickness). Nozzles were provided above and below one of the molds.

[0049] The intermediate material web was cut out to be slightly smaller than this mold. Additionally, two pieces each of glass cloth and nonwoven fabric were cut out to fit the mold.

[0050] A nonwoven fabric "Unicell BT0404" manufactured by Unicell Co., Ltd. was layered on both sides of this web, and glass cloth was laminated on the outside thereof, and this was placed in the above mold.

[0051] The mold was closed while compressing the web, etc., and the above mixed resin was injected into the mold. The mold was evacuated using one nozzle to create a vacuum inside the mold, and the resin was injected while continuing to evacuate. It was confirmed that the resin had filled up and reached the exhaust nozzle.

The mold was closed with one nozzle closed and the other open, and the mold was placed in an oil bath at 85° C., and removed from the oil bath after about 1 hour. At this time, excess resin was discharged from the nozzle. However, the nozzle was closed halfway.

After cooling, the mold was opened and the molded product was taken out. The molded product obtained had a good appearance and appropriate strength. Its specific gravity is approximately 0.923, and as a result of a bending test, its strength is 10.8 kg/mm2 and its elastic modulus is 627 kg.
/mm2, tensile test result: strength 5.1kg/m2
m2, and the elastic modulus was 136 kg/mm2.

[0054]

Example 4 The mold and glass cloth used in Example 3 were prepared. The mixed resin is “Epicoat 10” manufactured by Yuka Shell Co., Ltd.
01" and 30 parts of "Epicoat 837" were mixed at 80° C., and 30 parts of phthalic anhydride and 1.5 parts of 2-methylpyrrolidone were added and mixed. In addition, as particles that can be foamed and expanded by heating, “
"Microsphere F-80D" was prepared.

Similar to Example 1, a fiber mainly made of polymetaphenylene isophthalamide ("Conex" manufactured by Teijin) was used.
) was cut into fiber lengths of 20 mm to obtain a 70 g/m2 carded web.

[0056] On top of this card web, "Microsphere F-
80D" was evenly spread thereon, and the above carded web was further layered and needle punched. This needle-punch web was immersed in a melt of the mixed resin described above to sufficiently impregnate the web with the mixed resin, and then pulled out and allowed to cool and solidify.

Glass cloth (MS made by Asahi Fiberglass)
253-1040-2NT-10FS) and two sheets of web impregnated with the mixed resin were cut out to fit the respective molds. Two webs were stacked, glass cloth was placed on both sides, and placed in a mold, and the inside of the mold was evacuated.

[0058] The mold was closed and placed in an oil bath at 140°C, and removed from the oil bath after about 1 hour. At this time, the nozzle was opened halfway and excess resin was discharged from the nozzle. However, the nozzle closed halfway.

After cooling, the mold was opened and the molded product was taken out. The molded product obtained had a good appearance and appropriate strength. Specific gravity is approximately 0.87, bending strength is 9.2kg/mm
2, the elastic modulus was 502 kg/mm2.

[0060]

Example 5 A tow of undrawn polyester yarn was crimped using a crimper and then opened. This and a sheet made of burst-spun polystyrene (burst fiber) were laminated to form a web, and the weight was approximately 70 g/m2.

[0061] Unicel Co., Ltd.'s nonwoven fabric "Unicel BT0
908'', thermally expandable particles ``Expancel DU461'' manufactured by Expancel, and inorganic hollow particles ``Silica Balloon Q-Cell'' manufactured by Asahi Glass Co., Ltd. were prepared.

The above-mentioned web and the above-mentioned non-woven fabric were arranged so that the outside of the 5-layer web was covered with the above-mentioned non-woven fabric "Unicell", and the particles DU461 and Q-Cell were sandwiched between the webs. The ratio of DU461 and Q-Cell was 3/1 by weight. The total amount was about 1000g/m2. Needle punch this to a thickness of about 4 mm.
It was made into a laminated web of mm. This will be used as an intermediate material.

[0063] In the same manner as in Example 3, the same glass cloth and the above intermediate material were cut to fit the mold (spacer thickness: 5 mm). Two pieces of glass cloth and one piece of intermediate material were used.

[0064] The glass cloth and the intermediate material were soaked in the same mixed resin as in Example 3, and were sufficiently impregnated. Glass cloth was attached to both sides of the intermediate material and laminated.

[0065] This was put into a mold, and the mold was closed while being compressed. The nozzle of the mold was left open to allow excess mixed resin to flow out, and after confirming that almost all of the resin had flowed out, the nozzle was closed.

[0066] Next, the mold was placed in an oil bath at 105°C and heated to about 1
It was removed from the oil bath after an hour. At this time, one nozzle was opened and excess resin was discharged. However, the nozzle closed halfway. After cooling, the mold was opened and the molded product was taken out.

The molded product obtained had a good appearance and appropriate strength. The specific gravity of the molded product is approximately 0.88, the bending strength is 9.4 kg/mm2, and the elastic modulus is 449 kg/mm2.
Met.

Claims (10)

[Claims] [Claim 1] A fibrous web containing at least particles that can be foamed and expanded when heated and substantially impermeable to the particles is produced by a dry method, impregnated with a resin, and heated to foam and expand the particles. A method for manufacturing a lightweight composite molded article, which is characterized by molding. 2. The method for producing a lightweight composite molded article according to claim 1, wherein the fibrous web produced by the dry process is a web mainly composed of long fibers. 3. The method for producing a lightweight composite molded article according to claim 1, wherein the fibrous web produced by the dry process is a web mainly composed of short fibers. 4. The method for producing a lightweight composite molded article according to claim 1, wherein the fibrous web produced by the dry process is a web mainly composed of fibrils. 5. A fibrous web produced by a dry method contains non-expandable lightweight particles as well as particles that can be foamed and expanded when heated, and substantially does not allow the passage of both particles. 4. The method for producing a lightweight composite molded article according to any one of 4. 6. The method for producing a lightweight composite molded article according to claim 5, wherein the non-expandable lightweight particles are hollow particles. 7. A dry-processed fiber web containing particles that can be foamed and expanded at least when heated is placed in a mold, the web is impregnated with a resin and heated, and the particles are foamed and expanded to perform internal pressure molding. The method for producing a lightweight composite molded article according to any one of claims 1 to 6. 8. The lightweight composite according to any one of claims 1 to 7, characterized in that a sheet-like fiber reinforcing material is laminated together with a dry-processed fiber web containing at least particles that can be foamed and expanded when heated. Method of manufacturing molded products. 9. Any one of claims 1 to 6 and 8, characterized in that a dry-processed fiber web containing particles that can be foamed and expanded at least when heated is impregnated with a resin to form an intermediate material, which is then subjected to molding. A method for producing a lightweight composite molded article according to claim 1. 10. A sheet-like reinforcing fiber material and a dry-processed fiber web containing at least particles that can be expanded and expanded when heated are laminated, placed in a mold, impregnated with resin, and heated,
10. The method for producing a lightweight composite molded article according to claim 1, wherein the particles are foamed and expanded and subjected to internal pressure molding.