JPH09278903A - Production of fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject material, free from the danger of explosion, etc., having high storage stability and capable of polymerizing with sole application of heat by compounding a specific biimidazole compound with a hydrogen- donating compound. SOLUTION: A composition containing (A) a polymerizable unsaturated compound, (B) a hexaarylbiimidazole compound expressed by the formula [L1 to L3 are each a (substituted) aryl], (C) a hydrogen-donating compound and (D) a reinforcing fiber material. The composition is cured by heating. Further, the component D is preferably a carbon fiber, and the component C is preferably a 1,3-dicarbonyl compound, especially a 1,3-diketone compound, or a mercapto compound having a heterocycle, especially one kind selected from mercaptobenzothiazole, mercaptobenzimidazole and mercaptobenzoxazol.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a fiber-reinforced composite material. More specifically, a polymerizable unsaturated compound, a biimidazole compound as a polymerization initiator, and 1,3
A fiber composite material by impregnating a fiber reinforcing material with a polymerizable composition comprising a combination of a hydrogen donating compound such as a dicarbonyl compound or a mercapto compound having a heterocycle, and heating the resin to cure the polymerizable composition. It relates to a method of manufacturing.

[0002]

2. Description of the Related Art A radical polymerization initiator is a thermal polymerization initiator that decomposes by heat to generate radicals, that is, an organic diazo compound, an organic peroxide, an organic peracid and its ester, or a molecule upon irradiation with light such as ultraviolet rays. Known are photopolymerization initiators that cleave to generate radicals to initiate polymerization, that is, acetophenones, thioxanthones, benzophenones, and the like.

Since the thermal polymerization initiator is characterized by being decomposed by heat, the thermal stability of the compound itself is poor and it needs to be stored at low temperature. There is also a problem in safety during manufacturing and storage, and there is always a risk of explosion.

On the other hand, as a photopolymerization initiator, an ultraviolet photopolymerization initiator is generally known, and it does not have the above-mentioned problems like a thermal polymerization initiator, and it also has problems of global environment, energy saving, and labor cost increase. From the viewpoint of labor saving and the like, the development has been conducted with attention being paid to the characteristics of photopolymerization, such as the fact that the polymerization can be carried out at room temperature, the quick-drying property, and the possibility of solvent-free property.

In recent years, it has been used in various fields such as curing, drying and printing of coating films, resin convex printing, printed circuit board preparation, resist or photomask, black and white or color transfer coloring sheet or coloring sheet preparation. ing.

However, the curing by ultraviolet light is 20
A polymerizable unsaturated compound is polymerized and cured by irradiation with ultraviolet light of 0 to 400 nm, and a composition or FRP containing an additive having a high concealment ratio such as a dye, a pigment, a fiber reinforcement, and a filler. In the case of a material having a large thickness such as a molded body, it has a low transparency to ultraviolet light and is difficult to be used because the curing is insufficiently completed. Further, although curing by electron beam solves the problem of transparency of ultraviolet light, there is an essential problem that enormous capital investment and safety equipment are required.

On the other hand, a photopolymerization reaction has been studied using near infrared light, which has a longer wavelength than ultraviolet light and is superior in transparency and which can be irradiated by an inexpensive device. At present, it has not been widely used because of the fact that it is difficult to obtain the functional material at low cost.

By the way, composite materials produced by adding a fiber reinforcement to a polymerizable unsaturated compound, polymerizing and curing it have been widely used in recent years because of various physical properties such as moldability, economic efficiency and strength. It is used. In particular, carbon fiber reinforced composite materials are more than double the strength of iron and weigh 1/5 the weight, so they have attracted attention in various fields of application including reinforcement of structural materials and building materials. There is.

However, the production of these composite materials is generally carried out by thermosetting reaction using the above-mentioned thermal polymerization initiator, and the stability of the polymerizable composition, the risk of explosion of the polymerization initiator, etc. There is a problem in terms. In order to avoid these problems, it is unavoidable to reduce the addition amount of the polymerization initiator or use a thermal polymerization initiator having a high decomposition temperature. for that reason,
As a condition necessary for the thermal polymerization reaction, a high temperature and a long time were often required.

As a method for improving such problems of the thermal polymerization initiator, a method utilizing radiation curing of electron beam, ultraviolet ray, etc. has been proposed. However, as described above, since ultraviolet light has low light transmittance, it is practically difficult to cure a thick material such as a composition containing various additives such as a reinforcing material or FRP. is there. Especially when applied to the production of carbon fiber composite materials with low light transmission,
There has been known a proposal to improve chemical resistance and the like by ultraviolet curing only the surface of the material (for example, JP-A-58-96543). Also, the method of applying an electron beam (for example, Japanese Patent Laid-Open No. 61-152433) is not practical considering the economical efficiency of equipment.

[0011]

DISCLOSURE OF THE INVENTION The present invention avoids the need for low-temperature storage of a thermal polymerization initiator and the risk of explosion in the conventional production method by thermosetting reaction, and is difficult to cure by light irradiation. It is an object of the present invention to provide a method for producing a fiber-reinforced composite material, which is capable of efficiently causing polymerization and curing a composition containing a conventional fiber reinforcement.

[0012]

In order to solve this problem, the present inventors have heretofore known a photopolymerization initiator, which is a compound stable in a polymerizable composition during storage at room temperature, ie, biimidazole. The inventors have diligently studied a polymerization initiation reaction in which a compound and a hydrogen donating compound are combined. as a result,
Surprisingly, they have found that a polymerization initiator in which a biimidazole compound and a hydrogen donating compound are combined can cause a polymerization reaction only by heating to produce a fiber-reinforced composite material, and completed the present invention.

According to the present invention, a polymerizable unsaturated compound and a hexaarylbiimidazole compound represented by the general formula (1) are represented by the general formula (1);

Embedded image (In the formula, L ₁ , L ₂ and L ₃ each independently represent an aryl group or a substituted aryl group), a hydrogen donating compound and a fiber reinforcing material are combined to form a composition, which is then heated to reinforce the fiber. Composite materials can be manufactured.

It has been conventionally known that a combination of a biimidazole compound and various compounds is used as a photopolymerization initiator. For example, a method of combining with a tertiary amine and a leuco dye (Japanese Patent Publication No. 45-37377), a method of combining with a chain transfer agent and a visible light absorbing compound, and polymerizing with visible light (JP-A-47-2528, 57-21401,
59-56403), a method of combining a 2-polycyclic arylbiimidazole compound and a hydrogen donor and polymerizing with ultraviolet light (JP-A-57-161742, 58-4521).
0) etc. are disclosed.

However, in the past, the purpose was to cure thin films such as paints, inks, image forming materials, etc., and it was applied to a material having a large thickness or a composition to which a fiber reinforcing material or a filler was added. No examples were known.
Further, the polymerization initiator was only used as a photopolymerization initiator.

The present inventors apply a combination of a biimidazole compound and a hydrogen donor to a polymerization-curing reaction of a material having a large thickness and a composition containing various additives such as a fiber reinforcing material or a filler. As a result of repeated studies on the method, it was surprisingly found that the above object was achieved by applying heat energy, and the present invention was completed.

That is, a polymerizable unsaturated compound, a biimidazole compound, a hydrogen donating compound, a fiber reinforcing material and, if necessary, various fillers are mixed to form a composition, which is heated by various methods. It has been found that a polymerization-curing reaction occurs and a composite material can be manufactured. The combination of a biimidazole compound and a hydrogen donating compound has been known as a photopolymerization initiator as described above, but according to the present invention, thermal energy causes hydrogen transfer from the hydrogen donating compound to the biimidazole compound. ,
It is presumed that it functioned as a thermal polymerization initiator. There is no finding that the polymerization initiator acts as a thermal polymerization initiator. Moreover, compared to other conventional thermal polymerization initiators,
Its chemical stability is extremely high.

The biimidazole compound referred to in the present invention is
A compound having the structure of the general formula (1), specifically, bis (2,4,5-triphenyl) imidazole, bis (2-o-chlorophenyl-4,5-diphenyl) imidazole, bis (2- o, p-dichlorophenyl-4,
Examples thereof include 5-diphenyl) imidazole and bis (2-o-bromophenyl-4,5-diphenyl) imidazole.

The hydrogen-donating compound referred to in the present invention is a compound that donates hydrogen to the biimidazole compound to function as a radical and functions as a polymerization initiator, and has a tertiary amine compound, a mercapto compound, and an active methylene group. Examples of the compound include a 1,3-dicarbonyl compound and a mercapto compound having a heterocycle. More preferred are 1,3-diketone compounds such as dimedone and 1,3-dioxocyclohexane, mercaptobenzothiazole, mercaptobenzoxazole, and mercaptobenzimidazole.

The amounts of the hexaarylbiimidazole compound and the hydrogen donating compound which are the polymerization initiators contained in the composition used in the present invention depend on the kind and amount of the polymerizable compound, the kind and amount of the fiber reinforcing material, the thickness and the like. Although the optimum value is different, generally 0.01 to 10% by weight of the polymerizable compound is added. If it is too small, the polymerization and curing reaction may not proceed sufficiently, and if it is too large, it is economically disadvantageous and the physical properties of the produced composite material are deteriorated. The ratio of the biimidazole compound to the hydrogen donating compound is arbitrary, but is generally 1
It is in the range of / 10 to 10/1 (weight ratio).

As the polymerizable unsaturated compound, there is disclosed in JP-A-4-
Examples include 362935 and those described in JP-A-6-75374, and examples thereof include (meth) acrylic acid, esterified products of (meth) acrylic acid and various alcohols, (meth) acrylonitrile, (meth). (Meth) acrylic compounds such as acrylamide and methylenebisacrylamide; vinylbenzenes such as styrene, vinyltoluene and chlorostyrene; vinyl ethers such as vinyl isobutyl ether and 2-ethylhexyl vinyl ether; vinyl acetate, vinyl propionate, vinyl benzoate. And vinyl compounds such as vinyl esters, and monomers containing an allyl group such as allyl alcohol, allyl acetate and diallyl phthalate. Further, as the monomer, a hydroxyl group-containing monomer such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate, a phosphorus-containing polymerizable unsaturated monomer,
Addition products of isocyanate compounds such as butyl isocyanate and phenyl isocyanate with the above hydroxyl group-containing monomers; Addition products of phosphoric acid and the above hydroxyl group containing monomers; N
Nitrogen-containing unsaturated monomers such as -vinylpyrrolidone, N-vinylcarbazole, N-vinylacetamide, and vinylpyridines can also be used. Further, the monomer includes a compound having a plurality of polymerizable unsaturated groups such as diethylene glycol diacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, and pentaerythritol tetraacrylate.

A product obtained by reacting an adduct of a polyhydric alcohol with ethylene oxide with acrylic acid and / or methacrylic acid; a reaction product of the above-mentioned adduct of a polyhydric alcohol with propylene oxide with acrylic acid and / or methacrylic acid. Oligomers such as products obtained by reacting acrylic acid and / or methacrylic acid with the above-mentioned adduct of polyhydric alcohol and ε-caprolactone, and specific examples of the polymerizable unsaturated polymer Is a polyester (meth) acrylic acid condensed resin, an ethylenically unsaturated group-containing polyurethane resin, an ethylenically unsaturated group-containing epoxy resin, an ethylenically unsaturated group-containing phosphorus epoxy resin, an ethylenically unsaturated group-containing acrylic resin Resin, ethylenically unsaturated group-containing silicone resin, ethylenically unsaturated group-containing Such as Ramin resin and the like.

The fiber reinforcing material contained in the composition used in the present invention may be any known fiber material such as glass fiber, aramid fiber, carbon fiber and vinylon fiber. Considering the physical properties, the effectiveness of the polymerization and curing reaction by heat conduction, and the like, carbon fiber is particularly preferable.

As the carbon fiber, any carbon fiber manufactured by various manufacturing methods can be used, for example, pitch-based, PAN (polyacrylonitrile) -based, vapor-phase growth method-based carbon fiber, etc. can be used. More preferably, the tensile strength is 2 GPa or more,
It is a high-strength and high-modulus carbon fiber having an elastic modulus of 100 GPa or more. The carbon fiber is generally formed by combining about 2000 to 20000 filaments having a diameter of about 10 μm.

The ratio of the polymerizable unsaturated compound to the fiber reinforcement is arbitrary, but it is generally 1/10 to 10/1 (weight ratio). If the ratio is too small, the adhesion between fibers, the surface shape, etc. deteriorate. If the ratio is too large, the contact area between the fibers becomes small and various physical properties such as strength deteriorate, and the heat conduction during curing decreases, which may cause problems such as delay of the polymerization and curing reaction.

If desired, various fillers can be added to the composition used in the present invention. Examples of the organic filler include finely pulverized various polymers, and microballoons such as polyvinylidene chloride and polyacrylonitrile. Microballoons are expected to have a function of suppressing curing shrinkage of the composition.

As the inorganic filler, silica, silica-alumina, alumina, aluminum hydroxide, quartz, glass, calcium carbonate, kaolin, clay, talc, mica, aluminum sulfate, barium sulfate, calcium sulfate, titanium oxide. , Calcium phosphate and the like, and those obtained by coating the surface of the powder with a polyfunctional (meth) acrylate-based monomer or a silane coupling agent.

Further, as the inorganic / organic composite filler,
Examples thereof include those obtained by mixing the above-mentioned inorganic filler with an ethylenically unsaturated compound, polymerizing and curing it, and then finely pulverizing it.
These fillers may be added separately or after mixing two or more fillers of the same type or different types.

The filler may be added in any amount, but it is generally added in an amount of 0 to 500% by weight, preferably 0 to 300% by weight, based on the polymerizable unsaturated compound. If it is too small, the effects of hiding, strength, stress relaxation, etc. will decrease,
If the amount is too large, the workability and operability are deteriorated, the bubbles are difficult to escape, or the light transmission is poor, and the polymerization curing reaction is adversely affected. There is a risk.

The heating method in the production method of the present invention can be appropriately selected in consideration of the shape and composition of the composite material to be cured, the temperature and time required for curing, and the like. Specific examples include conventional methods, such as heating in a heating furnace, heating with hot air, and radiation with a heater. The heating method is not limited as long as the temperature of the fiber reinforcement impregnated with the curable composition reaches the temperature required for curing.

Since the curable composition needs to be stable when stored at room temperature, it is heated to a higher temperature during curing, that is, generally to about 70 ° C to 250 ° C. Although the reaction rate becomes faster when heated to a high temperature, a lower temperature is preferable from the viewpoint of problems of internal stress and strain during curing, energy efficiency and the like. Considering them, 1
Curing at 00 ° C to 150 ° C is desirable.

The heating time varies depending on the heating temperature, but is generally in the range of 1 minute to 60 minutes. When applying the production method of the present invention to continuous production, it is preferable that the time is short,
Cure at relatively high temperature in a short time (eg 200 ° C / 1
Minutes). Further, when it is necessary to heat a material including a material having a problem with heat resistance, it is possible to perform the curing reaction at a low temperature for a relatively long time (for example, 70 ° C. /
2 hours).

[0033]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 Unsaturated polyester resin Rigolac G-200GMA (manufactured by Showa High Polymer Co., Ltd.) 100 g,
Bis (2-o-chlorophenyl-4,5-diphenyl)
A curable composition was prepared by mixing 2 g of imidazole (hereinafter abbreviated as HABI) and 2 g of mercaptobenzothiazole. Twenty carbon fiber sheets (manufactured by Toho Rayon Co., Ltd.) cut into 10 cm × 6 cm were laminated, and the above composition was sufficiently impregnated at room temperature. After that, pressure was applied so that the weight ratio of the curable composition of the laminate to the carbon fiber was adjusted to 1: 1. The thickness of the laminate before curing at this time was 4.0 mm. The laminate was put in a drier at 120 ° C., and after 10 minutes, taken out, and the strength was measured. Both the front surface and the back surface had a Barcol hardness (hardness) of 48 and were sufficiently hardened.

Comparative Example 1 A production test for a fiber-reinforced composite material was carried out in the same manner as in Example 1 except that HABI was not added. A curing reaction was carried out at 120 ° C. for 10 minutes, but the Barcol hardness was 15 as measured by a soft hardness meter, and there was surface tack, and the fibers were peeled off, which was in an insufficiently cured state.

Example 2 The curable composition of Example 1 was
In the same manner as in Example 1, glass fiber was used as a # 30 surface mat / # 450 chopped strand mat 3 pl.
It was impregnated into a laminate of a y / # 30 surface mat having a thickness of 3 mm. The curing reaction was performed in a dryer at 120 ° C. as in Example 1. When the hardness of the cured product was measured, both the front and back surfaces had Barcol hardness (for hardness) 4
It was 6 and was sufficiently cured.

Example 3 As in Example 1, carbon fiber was impregnated with a curable composition. Irradiation with an infrared radiator (manufactured by Heraeus, trade name TWIN TUBE) was performed for 10 minutes. The internal temperature of the carbon fiber reached 150 ° C.
According to the hardness measurement of the cured product, both the front surface and the back surface had a Barcol hardness (for hardness) of 49, which was sufficiently cured.

Comparative Example 2 As in Example 3, carbon fiber was impregnated with the curable composition. Wavelength range 200-400
Ultraviolet light was irradiated for 10 minutes by a high pressure mercury lamp having a spectral distribution in the range of nm. Although only the front surface was cured by photoreaction, no temperature rise was seen on the inner and back surfaces,
The curing reaction did not proceed.

(Example 4) A polymerizable composition prepared by diluting epoxy acrylate resin Lipoxy SP-1509 (manufactured by Showa Polymer Co., Ltd.) with styrene by 30% in place of the unsaturated polyester resin RIGOLAC G-200GMA of Example 1 was used. A production test of the fiber-reinforced composite material was carried out in exactly the same manner as in Example 1 except that it was used. According to the strength measurement, both front and back
It had a Barcol hardness (for hard) of 40 and was sufficiently cured.

(Example 5) Instead of the mercaptobenzothiazole of Example 1, dimedone (5,5-dimethyl-
The production test of the fiber-reinforced composite material was carried out in the same manner as in Example 1 except that 2 g of 1,3-cyclohexadione) was used. According to the strength measurement, both the front surface and the back surface had a Barcol hardness (for hard) of 49, indicating that the surface was sufficiently hardened.

Comparative Example 3 A production test of a fiber-reinforced composite material was carried out in the same manner as in Example 1 except that HABI was not added. A curing reaction was carried out at 120 ° C. for 10 minutes, and the Barcol hardness was 10 as measured by a soft hardness meter, and there was surface tack, and the fibers were peeled off, which was in an insufficiently cured state.

(Example 6: Storage stability test of composition) The curable composition of Example 1 was subjected to a storage test in a thermostat at 40 ° C. The composition was tested for shape and curing after 3 weeks and was the same as the result before the storage test.

(Comparative Example 4) 100 g of unsaturated polyester resin Rigolac G-200GMA (manufactured by Showa High Polymer Co., Ltd.)
And 4 of lauroyl peroxide, which is a thermal polymerization initiator,
g was added, and a storage stability test was conducted in the same manner as in Example 6. Four
After 1 week at 0 ° C, gelation occurred and sufficient storage stability could not be obtained.

Comparative Example 5 3,3'-4,4'-tetrakis (t-butyldioxycarbonyl) benzophenone 4 was used in place of the lauroyl peroxide of Comparative Example 4.
A storage stability test was conducted in the same manner as in Comparative Example 4 except that g was added. After 1 week at 40 ° C, gelation occurred and sufficient storage stability could not be obtained.

[0045]

EFFECTS OF THE INVENTION The present invention provides a method for producing a fiber-reinforced composite material using a polymerization initiator having no risk of explosion and a curable composition having high storage stability.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hirotoshi Kamada 1-1-1, Onodai, Midori-ku, Chiba-shi, Chiba Showa Denko K.K. (72) Inventor Kazuhiko Oga 1-chome, Onodai, Chiba-shi, Chiba No. 1-1 Showa Denko Co., Ltd. Research Institute (72) Inventor Tomio Yamamoto 13 Shikata, Honjo City, Saitama Prefecture (72) Inventor Kazuo Otani 673-8 Kuboshima, Kumagaya City Saitama Prefecture (72) Inventor Hideki Chiyo Kawasaki, Kanagawa Prefecture 618-1, Mizonokuchi, Takatsu-ku, Yokohama

Claims (5)

[Claims] 1. A composition containing a polymerizable unsaturated compound, a hexaarylbiimidazole compound represented by the general formula (1), a hydrogen donating compound, and a fiber reinforcement is cured by heating. A method for producing a fiber-reinforced composite material, which is characterized. General formula (1); (In the formula, L ₁ , L ₂ and L ₃ each independently represent an aryl group or a substituted aryl group.) 2. The fiber reinforcement is carbon fiber.
A method for producing the fiber-reinforced composite material described. 3. The method for producing a fiber-reinforced composite material according to claim 1, wherein the hydrogen-donating compound is a 1,3-dicarbonyl compound or a mercapto compound having a heterocycle. 4. The 1,3-dicarbonyl compound is 1,3
-The method for producing a fiber-reinforced composite material according to claim 3, which is a diketone compound. 5. The method for producing a fiber-reinforced composite material according to claim 3, wherein the mercapto compound having a heterocycle is at least one selected from mercaptobenzothiazole, mercaptobenzimidazole, and mercaptobenzoxazole.