JPH057410B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a thermosetting resin with high heat resistance. death,
The present invention relates to a method for producing a thermosetting resin having high strength and high heat resistance, which is obtained by increasing the molecular weight and developing a crosslinked structure.

[Conventional technology]

Polycarbodiimide, which is a known polymer compound, and aromatic polycarbodiimide in particular, is generally known as a compound with fairly high heat resistance, but among polycarbodiimides, those with high molecular weight are only slightly resistant to heat at temperatures around 200°C. Although it softens, most of it is infusible and insoluble in solvents, and therefore cannot be practically processed as a polymer compound.

Further, attempts have already been made to overcome the above-mentioned drawbacks of polycarbodiimide as a thermosetting resin, namely, L.M. Alberino et al. (J. Appl.
Polym.Sci., 21 , 1999 [1977], when producing polycarbodiimide from organic diisocyanate, the molecular weight of the resulting polymer is controlled by coexisting an organic monoisocyanate, and polycarbodiimide is made fluid under pressure and heating. It is true that the polycarbodiimide obtained by this method becomes a cured resin by heating to a temperature of around 200℃, but it takes an extremely long time to cure, for example, at around 200℃. Polycarbodiimide remains in a softened state for several tens of minutes at a temperature of I couldn't say it.

In addition, organic diisocyanate, for example, 4,4'-
It is self-evident that when diphenylmethane diisocyanate is heated in the presence of a catalyst that promotes carbodiimidation, it undergoes decarboxylation condensation and gradually increases in molecular weight.However, if the reaction is stopped midway through, a relatively large amount of unreacted isocyanate will be produced. A low molecular weight compound is obtained, and this relatively low molecular weight compound is
It is also known that when pressurized at °C, it melts, flows, and gradually hardens, but because the isocyanate remains in the compound, it foams under pressure and heat, making it difficult to obtain a dense cured resin. Not suitable for
In addition, the curing reaction is extremely slow, and in this respect, not only is it of little practical value, but the resulting cured resin is
It suffers from thermal decomposition at around 200 to 250°C, and has the fatal drawback of not having sufficient heat resistance.

As mentioned above, when the polycarbodiimidation reaction is advanced to the extent that there are virtually no unreacted isocyanate groups, the molecular weight increases and the resulting polymeric polycarbodiimide hardly exhibits fluidity under pressure and heat. That's exactly what I did.

[Problem to be solved by the invention]

The inventors of the present invention have found that the above-mentioned drawbacks of polycarbodiimide as a thermosetting resin are based on the following properties of polycarbodiimide.

That is, polycarbodiimide is a compound that has extremely highly active carbodiimide bonds in a regular manner. Therefore, when trying to obtain a high molecular weight polycarbodiimide, the carbodiimide bonds tend to partially polymerize and crosslink. Therefore, high molecular weight polycarbodiimide loses its processability. On the other hand, end-capped polycarbodiimide has a relatively low molecular weight, so even if a slight crosslinking reaction occurs, its fluidity is completely lost. Although it is not lost, in order to cure it, it is necessary to allow sufficient polymerization of carbodiimide bonds to proceed, and therefore, to obtain a cured resin, heating at a high temperature and a long time are required.

[Means to solve the problem]

The present invention solves the above-mentioned trade-offs, namely that polycarbodiimides with relatively high molecular weights have poor processability, and polycarbodiimides with relatively low molecular weights take a long time to cure, by effectively acting on carbodiimide bonds and trimerizing them. This problem was solved by using a compound that can promote the trimerization reaction of carbodiimide, and its structure is to coexist polycarbodiimide with a compound that can accelerate the trimerization reaction of carbodiimide, and to heat it to an appropriate temperature. This is a characteristic feature.

That is, the inventors of the present invention analyzed highly heat-resistant thermosetting resins by various means, and found that
We obtained knowledge that suggests that these resins contain iminotriazine structures that have heat resistance, and based on this, we continued intensive research from the perspective of deriving the iminotriazine structures from carbodiimide bonds, and as a result, we have developed the present invention. This has been completed, and the detailed explanation is as follows.

The polycarbodiimide used in the present invention is a polymer compound having a large number of carbodiimide bonds in the molecule, and among them, it is a linear polymer compound obtained by polycondensing one or more organic diisocyanates having two or more isocyanate groups at the terminals by decarboxylation. It has excellent moldability, and its number average molecular weight is regulated to 400 to 5000, preferably 1000 to 3000, by stopping polycondensation using one or more organic monoisocyanates. is excellent in terms of heat meltability.

The above polycarbodiimide having two or more carbodiimide bonds in the molecule can usually be produced from an organic polyisocyanate in the presence of a catalyst that promotes carbodiimidation of the isocyanate. , 4-tolylene diisocyanate, 2,6
-tolylene diisocyanate, 2,4- and 2,6
- mixture of tolylene diisocyanates, crude tolylene diisocyanate, crude methylene diphenyl diisocyanate, 4,4',4''-triphenylmethylene triisocyanate, 4,4',-dimethyldiphenylmethane-2,2'-5, 5'-Tetraisocyanate, xylene diisocyanate, hexamethylene-1,6-diisocyanate, lysine diisocyanate methyl ester, hydrogenated methylene diphenyl isocyanate, m-phenylene diisocyanate, naphthylene-1,5-diisocyanate, 1-methoxyphenyl- 2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl-4, 4'-biphenyl diisocyanate, 3,3-dimethyldiphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, and these organic polyisocyanates are used in stoichiometric excess with respect to the polyfunctional active hydrogen compound. The so-called terminal isocyanate prepolymer obtained can be exemplified,
Further, as the organic monoisocyanate for controlling the molecular weight by blocking the terminal of the polycarbodiimide described above, phenyl isocyanate, (ortho, meta, para)-tolyl isocyanate, dimethyl phenyl isocyanate, cyclohexyl isocyanate, methyl Examples include isocyanate, chlorophenyl isocyanate, trifluoromethylphenyl isocyanate, naphthylisocyanate, and the like.

Further, as a compound capable of promoting the trimerization of carbodiimide, as a result of research according to the present invention, it has been found that all trimerization catalysts for organic isocyanates known to those skilled in the art in polyurethane chemistry can be used. In particular, compounds having at least one tertiary nitrogen atom in the molecule, such as diazabicycloundecene, p-dimethylaminophenol, tris(dialkylaminoalkyl)hexahydro-s-triazine, or their organic Acids or inorganic acid salts, organic metal salts such as sodium acetate, potassium acetate, and sodium benzoate, or mixed systems of tertiary amines and alkylene oxides work well.

In the present invention, one or more of these carbodiimide trimerization promoting compounds are obtained by handling polycarbodiimide, but in order to obtain a thermosetting resin in a shorter time, it is necessary to process the polycarbodiimide at a temperature of, for example, 100°C or higher and 300°C or lower. Just heat it.

In addition, polycarbodiimide can be prepared using a suitable solvent such as
Since it can be made into a solution of trichlene, THF, xylene, DMF, DMSO, etc., it is also possible to mix the above-mentioned trimerization promoting compound with this solution and use it as a varnish. Of course, it is possible to form

In addition, a fibrous reinforcing material, powder, or crystalline filler can also be blended with the polycarbodiimide in which the trimerization promoting compound is coexisted, and after the filler is blended with the polycarbodiimide, the trimerization promoting compound is allowed to coexist with the polycarbodiimide. It's okay.

[Operation and effect of the invention]

The thermosetting resin according to the present invention is obtained by treating polycarbodiimide with a compound that can promote trimerization of carbodiimide, and in this case, the polycarbodiimide is once softened and hardened in a short time. In other words, in the present invention, it is possible to dramatically shorten the curing time without impairing the fluidity, that is, the processability, of polycarbodiimide. It is something.

Furthermore, since the reaction that occurs during curing is trimerization of carbodiimide without producing volatile components as by-products, the molded product obtained is of course very dense and has high strength.

As mentioned above, polycarbodiimide is a known polymer compound, and aromatic polycarbodiimide in particular is known to have fairly high heat resistance, but the thermosetting resin of the present invention has poor heat resistance. It does not introduce functional groups or use compounds with groups that inherently have poor heat resistance, and does not impair the originally high heat resistance of polycarbodiimide; in fact, it has a high heat resistance. It can also be said that it has a heat resistance superior to that of polycarbodiimide due to the introduction of an imino-s-triazine structure, which is considered to be a group.

〔Example〕

Examples of the present invention will be described below.

Thoroughly mix 30 g of end-capped polycarbodiimide (number average molecular weight approximately 1000) and 0.3 g of diazabicycloundecene in a mortar, and mix the resulting mixture.
After press molding at 150°C for 5 minutes, press molding was further performed at 200°C for 10 minutes to obtain a yellow resin molded product.

The physical properties of this product were as follows.

Density 1.22 g/cm ³ Bending strength 322 Kg/cm ² 10 g of end-capped polycarbodiimide (number average molecular weight approximately 2000) is completely dissolved in 100 ml of n-methyl-2-pyrrolidone with stirring. Add 2.0 g of p-dimethylaminophenol to this solution and continue stirring for an additional 5 minutes. The obtained solution was evenly applied on a glass plate and left at room temperature for 5 minutes.
Next, a tough transparent film was obtained by drying at 50°C for 3 minutes and then at 100°C for 2 hours.

The infrared absorption spectrum of this film is 1630cm
An absorption considered to be caused by the trimerized structure of polycarbodiimide was observed near ^-1 .

Add 100 g of end-capped polycarbodiimide (number average molecular weight approximately 2500) to tetrahydrofuran.
Trichlorethylene (2:1) mixed solvent 1000ml
Stir vigorously until completely dissolved. After stirring for 30 minutes at room temperature, 0.5 g of N,N',N''-tris(diethylaminopropyl)hexahydro-s-triazine is added and stirred, and the solution is then gently heated until the system temperature reaches 50 When the temperature reaches ℃, the solution rapidly thickens and becomes a transparent gel-like substance. When this gel-like substance is crushed and dried, a white powder is obtained.

A yellow resin molded product was obtained by pressure molding 30 g of the white powder in a mold at 200° C. for 25 minutes.

The physical properties of this resin molded product were as follows.

Density 1.30g/cm ³ Bending strength 354Kg/cm ² 500g of polycarbodiimide (number average molecular weight approx. 4000) with sealed ends and 150g of potassium titanate,
Grind and mix 1 g of potassium acetate in a ball mill for one week.

100 g of the white powder thus obtained was pressure molded in a mold at 210° C. for 45 minutes to obtain a yellow resin molded product.

The physical properties of this product were as follows.

Density 1.68g/cm ³ Bending strength 602Kg/cm ² Thoroughly mix 100g of end-blocked polycarbodiimide (number average molecular weight approximately 2200) and 1g of diazabicycloundecene in a mortar. The resulting mixture was impregnated into 35g of long glass fiber strand mat kept at 190℃, cooled to room temperature to obtain a glass fiber reinforced resin, and this glass fiber reinforced resin was pressure molded at 230℃ for 5 minutes to strengthen it. A molded product was obtained.

The physical properties of this product were as follows.

Density 1.71g/cm ³ Bending strength 4200Kg/cm ² Thoroughly mix 100g of end-capped polycarbodiimide (number average molecular weight approximately 2500), 1g of diazabicyclooctane, and 1.5g of phenyl glycidyl ether in a mortar. A glass cloth was impregnated with the obtained mixture and pressure molded at 200° C. for 5 minutes to obtain a reinforced molded product.

The physical properties of this product were as follows.

Density 1.37g/cm ³ Bending strength 3800Kg/cm ²

Claims (1)

[Scope of Claims] 1. A method for producing a thermosetting resin with high heat resistance, which comprises coexisting polycarbodiimide with a compound capable of promoting trimerization reaction of carbodiimide and heating the mixture to an appropriate temperature. 2. The method according to claim 1, characterized in that polycarbodiimide is allowed to coexist with a compound capable of promoting trimerization reaction of carbodiimide, and heated at a temperature of 100°C or more and 300°C or less. 3 Polycarbodiimide is a substantially linear polymer compound obtained from organic diisocyanate by decarboxylation reaction, and has a number average molecular weight of
4. A method according to claim 1, characterized in that it is between 400 and 5000. 4. The method according to claim 3, wherein the polycarbodiimide is obtained by sealing its ends with an organic monoisocyanate. 5. The method according to any one of claims 1 to 4, wherein the compound capable of promoting the trimerization reaction of carbodiimide is of the same type as the trimerization catalyst of organic isocyanate. 6 A compound capable of promoting the trimerization reaction of carbodiimide has at least one tertiary compound in the molecule.
6. The method according to claim 5, wherein the method is characterized in that the method is characterized in that the method has a nitrogen atom. 7 Compounds that can promote the trimerization reaction of carbodiimide include diazabicycloundecene,
Claim 5, characterized in that the compound is one or more compounds selected from p-dimethylaminophenol, tris(dialkylaminoalkyl)hexahydro-s-triazine, or an organic acid or inorganic acid salt thereof. Method described. 8. The method according to claim 5, wherein the compound capable of promoting the trimerization reaction of carbodiimide is an organic acid metal salt such as sodium acetate, potassium acetate, or sodium benzoate. 9. The method according to claim 5, wherein the compound capable of promoting the trimerization reaction of carbodiimide is a mixed system of a tertiary amine and an alkylene oxide.