JPS6261209B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a melamine group-containing thermosetting resin that has thermosetting properties due to polymerization of ethylenically unsaturated bonds. Melamine resin has high hardness, high flame retardancy and heat resistance, and also has excellent electrical properties such as arc resistance and tracking resistance, so it has a wide range of uses such as decorative boards, electrical parts, tableware, etc. . Melamine resins, like phenolic resins and urea resins, are produced by a condensation reaction between melamine and formaldehyde. However, this production method has disadvantages in terms of environment and energy consumption, such as the smell of formalin gas during the reaction and the need for high temperature and pressure for the reaction. Attempts are known to provide thermoset properties and to provide heat curing by addition polymerization of ethylenically unsaturated bonds instead of relying on methylolation and methylenation with formaldehyde. For example, an alkyl ether derivative of a methylolated melamine compound is transetherified with a hydroxyalkyl (meth)acrylate to introduce an ethylenically unsaturated bond (see US Pat. No. 3,020,255). Although it is not necessarily clear what kind of compound is obtained in this case, it is likely that hydroxyalkyl (meth)acrylate is bonded to the methylol group of methylolated melamine through an ether bond because of transetherification. Presumed. In addition, there are products in which ethylenically unsaturated bonds are introduced by reacting methylolated melamine compounds (including their alkyl ether derivatives) with hydroxyalkyl (meth)acrylates (UK patent No.
628150). Although it is not necessarily clear what kind of compound is obtained in this case, it is presumed that the hydroxyalkyl (meth)acrylate is bound to the methylol group of the methylolated melamine compound through an ether bond. . However, according to the knowledge of the present inventors, cured products obtained by thermally polymerizing these materials tend to easily swell in hot water and turn white. In addition, heat resistance and rigidity are low. The present invention aims to provide a solution to the above-mentioned problems, and attempts to achieve this objective by reacting a methylolated melamine compound with an acrylamide compound in order to impart thermosetting properties through ethylenically unsaturated bonds. It is something to do. Therefore, the method for producing a thermosetting resin according to the present invention involves reacting a methylolated melamine compound represented by the following formula (A) with an acrylamide-based compound selected from the group consisting of acrylamide and α-lower alkyl-substituted acrylamide. It is characterized by: [In the formula, R is a methyl group, a phenyl group,

[Formula] or a group represented by the following formula R ₁ to _{R 10} each represent hydrogen or a CH ₂ OH group, at least one of which is a CH ₂ OH group; Y is hydrogen or a CH ₂ OH group]. In the present invention, the methylolated melamine compound represented by the general formula (A) has already been industrially produced in large quantities and is widely used mainly in the paint field as a crosslinking agent for various alkyds, acrylic polymers, etc. Therefore, it is easy to obtain. Some specific examples of this methylolated melamine compound are as follows. Hexamethylolmelamine, pentamethylolmelamine, trimethylolmelamine, dimethylolmelamine, tetramethylolacetoguanamine, trimethylolacetoguanamine, dimethylolacetoguanamine, tetramethylolbenzoguanamine, trimethylolbenzoguanamine,
Dimethylolbenzoguanamine, and mixtures thereof. Particularly suitable for the purpose of the present invention is the formula
In (A), R ₁ to R ₁₀ are -CH ₂ OH groups, and R is -N
(CH ₂ OH) ₂ or phenyl group or methyl group. These compounds have already been industrially produced in large quantities and are stable compounds. In addition, examples of acrylamide and α-lower alkyl-substituted acrylamide include acrylamide,
Methacrylamide, α-propylacrylamide, α-butylacrylamide, and mixtures thereof are generally suitable. As the α-lower alkyl group, those having 1 to 4 carbon atoms are generally suitable. Mixtures of these can also be used. Less than 50 mol% of this acrylamide compound may be replaced with an acrylic ester (the number of carbon atoms in the ester moiety is 1 to 6). In the practice of the present invention, the reaction between methylolated melamine and acrylamide-based compound is
in the presence of a catalyst, preferably at a temperature of 30 to 70 °C,
The reaction is carried out at a pH of 2 to 4. The reaction time varies depending on the rate of distillation of water generated as the reaction progresses, but is usually about 2 to 10 hours. This reaction can and usually is carried out without the use of a solvent, but it can also be carried out in the presence of a suitable solvent or dispersion medium if desired. Examples of the solvent or dispersion medium in this case include those inert with respect to the reaction, such as dioxane, tetrahydrofuran, and cyclohexanone. The molar ratio of the acrylamide compound to the methylolated melamine compound (A) is usually about 1/1 to 11/1, preferably about 2/1 to 7/1. The specific molar ratio is determined by the number of moles of the acrylamide compound bound to the compound (A). As a catalyst, various inorganic acids such as sulfuric acid,
Hydrochloric acid, boron trifluoride, etc. can be used, but concentrated sulfuric acid, which has a dehydrating effect, is most suitable. The amount of catalyst used is
For example, in the case of concentrated sulfuric acid, the amount is usually about 0.05 to 2% by weight, preferably about 0.5 to 1% by weight, based on the total amount of compound (A) and acrylamide compound. Since an acrylamide compound is present in the reaction system according to the invention as a reactant and in the product, it is generally necessary to prevent its polymerization. Various compounds are known for preventing the polymerization of ethylenically unsaturated bonds such as acrylamide, and any suitable compound can be used in the present invention. Specific examples include phenolic compounds, amine compounds, and air. Blowing air into the reaction system is preferable because air can not only inhibit polymerization but also promote the distillation of produced water. Note that since air alone may not have sufficient polymerization inhibitory effect, it is preferable to use a polymerization inhibitor other than air in combination. This reaction can be carried out according to various operating modes. Specifically, for example, compound (A), an acrylamide compound, a catalyst (and optionally a solvent or dispersion medium) are charged into a reactor equipped with a stirring device, a cooler, and an air blowing device, and
The temperature is gradually raised while blowing a small amount (150 to 600 c.c./min) of air into the reaction system (liquid phase). Once the predetermined temperature is reached, stirring is continued to allow reaction for a predetermined time. The thermosetting resin produced as described above according to the present invention is generally a pale yellow isomer or a transparent viscous liquid, and this compound is a melamine group-containing (meth)acrylamide-based compound represented by the following formula []. It is. [In the formula, R is a methyl group, a phenyl group,

[Formula] or an organic group represented by the following formula. Y each represents hydrogen or Z ¹¹ . ^Z1 to ^Z11 each represent _{-CH2NHCOCR1 =} ^CH2 or _-CH2OH . At least one of Z ¹ to Z ¹¹ is −
_CH2NHCOCR1 ^{= CH2} . R is -H or -
CH ₃ ]. The thermosetting resin represented by the general formula [] obtained by carrying out the present invention is generally a white to pale yellow transparent viscous liquid or solid. Since this thermosetting resin has at least one ethylenically unsaturated bond derived from an acrylamide compound, it is polymerized and cured by radical polymerization (or ionic polymerization in some cases). When the bound acrylamide compound is 1 mole, the cured product obtained by polymerization is usually soluble, but when the bound acrylamide compound is 2 moles or more, the cured product is It is usually insoluble and infusible. The means for curing the product of the invention, ie, the thermosetting resin, may be any suitable means for radical polymerization (or ionic polymerization) of ethylenically unsaturated bonds. Specifically, examples include heating, irradiation with high-energy radiation, irradiation with ultraviolet to visible light, decomposition of compounded radical polymerization or ionic polymerization initiators, and others. One of the preferred means is
It consists of blending a radical polymerization initiator, such as an organic peroxide, with a redox catalyst, if necessary, and heating, if necessary. Furthermore, the thermosetting resin produced according to the present invention can be cured into an appropriate shape in a form dissolved in an ethylenically unsaturated monomer and, if necessary, together with an appropriate filler or reinforcing agent. Can be done. The polymerization initiator varies depending on the curing mode to be employed. For example, in the case of ultraviolet curing, examples include benzophenone, benzoin ethers, anthraquinones, etc., and in the case of heat curing, examples include azo compounds, organic peroxides, etc. Some specific examples of these polymerization initiators are as follows. Benzoyl peroxide, methyl ethyl ketone peroxide, acetyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, cumene hydroperoxide, dicumyl peroxide, t-butyl perbenzoate, parachlorobenzoyl peroxide, cyclohexanone Peroxide, t-butyl acetate, etc. The amount of the polymerization initiator used is usually about 0.01 to 5% by weight based on the thermosetting resin of formula [] or the sum of this resin and the ethylenically unsaturated monomer. In addition, as the ethylenically unsaturated monomer, styrene, which can be copolymerized with the resin represented by the formula [],
These include vinyltoluene, chlorostyrene, vinylstyrene, methyl methacrylate, acrylic acid, 2-hydroxyethyl acrylate, tetrahydrofuryl methacrylate, 2-ethylhexyl methacrylate, trimethylolpropane triacrylate, diallyl phthalate, and mixtures thereof. The amount of such monomer used is arbitrary, but to give an example, 40 to 250% by weight of the resin of formula [],
Preferably it is about 60 to 140% by weight. In addition to polymerization initiators and ethylenically unsaturated monomers,
Furthermore, other auxiliary components can be added to the thermosetting resin depending on the purpose. Specific examples of such auxiliary components include solvents such as acetone, methyl ethyl ketone, dimethyl formamide, ethyl acetate and others, thermal polymerization inhibitors such as hydroquinone and others, ultraviolet absorbers such as 2,4-dihydroxybenzophenone,
2-hydroxy-4-methoxybenzophenone,
2-Hydroxy-4-n-octoxybenzophenone, "Tinuvin P" (manufactured by Ciba), other antioxidants, colorants, fillers or reinforcing agents such as glass fiber or its woven fabric, clay, carbon fiber, There are others. The thermosetting resin produced according to the present invention can be made into, for example, a film, sheet, etc. using the above-mentioned curing method.
It can be formed into various molded products by board, casting, injection molding, transfer molding, etc., and the molded products obtained in this way have high hardness and excellent heat resistance and electrical properties. Therefore, it can be used in a wide range of industrial fields. In addition, the thermosetting resin represented by the general formula [] obtained by carrying out the present invention does not rely on methylolization and methyleneation with formaldehyde for imparting thermosetting properties and thermosetting. Since the polymerization of the ethylenically unsaturated bonds introduced therein can be prevented to the necessary extent, the various problems observed in the conventional melamine resins described above are solved. Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that all parts in the examples are based on weight. Example 1 In a 2-liter separable flask equipped with a stirrer, a distillation condenser, and a glass tube for blowing air,
Hexamethylolmelamine 31 parts, acrylamide
71 parts, 2 parts of sulfuric acid, 100 parts of cyclohexanone, and 1 part of hydroquinone methyl ether,
Gradually heat to 60℃ while blowing air at a rate of cc/min.
The reaction was carried out by keeping the temperature at the same temperature for 3 hours.
After the reaction, add about 200 ml of cold water, mix, separate the aqueous phase and organic phase, and incubate the organic phase at 30-60℃ for 30 minutes.
Treat under reduced pressure of ~50 mmHg to remove a white precipitate of approx.
I got it. An infrared absorption spectrum and a nuclear magnetic resonance spectrum are shown in FIG. 1 and FIG. 2, respectively. The melting point of this product is approximately 145-155°C, and it is presumed that the main component of this product is a compound represented by the following general formula. Example 2 31 parts of tetramethylolbenzoguanamine, 42 parts of acrylamide, 2 parts of sulfuric acid, 100 parts of methyl isobutyl ketone and 1 part of hydroquinone methyl ether were placed in the same apparatus as in Example-1, and air was introduced at a rate of 300 c.c./min. Raise the temperature to 60℃ while blowing
React at the same temperature for 3 hours and perform the same treatment for 60
A portion of a white product was obtained. The melting point of this product is about 110-120°C, and the structure of the main component of this product is shown by the following formula. Example 3 54 parts of trimethylolmelamine, 53 parts of acrylamide, 2 parts of sulfuric acid, 50 parts of dioxane, and 1 part of hydroquinone methyl ether were placed in the same apparatus as in Example 1, and air was introduced at a rate of 300 c.c./min. Raise the temperature to 55℃ while blowing, and react at the same temperature for 3 hours.
Approximately 20 parts of solid material was obtained by the same treatment. This solid is a mixture, and if this mixture is represented by one compound, about 2.5 of the methylol groups in trimethylolmelamine are _-CH2 .
It corresponds to a compound substituted with NH・CO・CH=CH ₂ group. Production Example of Cured Product Example 1 20 parts of styrene monomer, 30 parts of asbestos, and 2 parts of benzoyl peroxide were mixed with 100 parts of the white solid resin obtained in Example-1. This mixture
It was compression molded for 5 minutes at 170° C. and 100 kg/cm ² to harden. The typical physical properties of this cured product were as follows. Heat deformation temperature *1 210℃ Bending strength *2 9.0Kg/mm ² Flexural modulus *2 350Kg/mm ² Barcol hardness *3 50 Boiling resistance in hot water *4 Appearance remains unchanged even after 30 days
No change in hue was observed. Example 2 Add 40 parts of asbestos fiber and 1 part of benzoyl peroxide to 100 parts of the white solid resin obtained in Example-2.
The mixture was mixed uniformly and then pressure molded at 130° C. for 5 minutes to obtain a molded plate having the following physical properties. Heat distortion temperature *1 Bending strength over 250℃ *2 10Kg/mm ² Arc resistance *5 150 seconds/25℃ Measurement method *1: ASTM-D648 *2: JIS K-6911 *3: ASTM-D2583 *4: Hardening Place objects in boiling water and examine appearance, change in hue, and presence or absence of swelling *5: JIS K-6911

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are an infrared absorption spectrum and a nuclear magnetic resonance spectrum, respectively, of the product obtained in Example-1.

Claims (1)

[Claims] 1. A method for producing a thermosetting resin by reacting a methylolated melamine compound represented by the following formula (A) with an amide compound selected from the group consisting of acrylamide and α-lower alkyl-substituted acrylamide. . [In the formula, R is a methyl group, a phenyl group,
[Formula] or a group represented by the following formula R ₁ to _{R 10} each represent hydrogen or a CH ₂ OH group, at least one of which is a CH ₂ OH group; Y is hydrogen or a CH ₂ OH group]. 2. The method according to claim 1, wherein the reaction is carried out while blowing air into the reaction system in the presence of a polymerization inhibitor. 3. The method according to claim 1, characterized in that the reaction is carried out in the presence of sulfuric acid.