CH625255A5 - Process for the preparation of esterified methylolaminotriazines - Google Patents

Description

The present invention relates to a process for the preparation of thermosetting etherified methylolaminotriazines, to the aminoplast resins obtained and to their use for the production of compacts.

It is known to produce moldings by pressing combinations of heat-curing aminoplast resins, carrier materials and, if appropriate, further additives, such as pigments, flow aids and lubricants or release agents, at elevated temperature. Carrier materials that are suitable for this purpose are in principle all absorbent inorganic or organic structures. The carrier materials can be impregnated with the aminoplast resins in a known manner, for example by application with brushes or with rollers, spraying on or dipping, and dried to a certain residual moisture content. The generally sheet-like combinations obtained in this way can be placed on top of one another in several layers and pressed into moldings at elevated temperature.

Flat combinations of carrier material with aminoplast resins are also suitable for the surface coating of other materials, such as wood or chipboard. For example, they can be used in the furniture industry, for example to coat chipboard, hardboard or plywood or other wood-based materials. Here, the carrier materials impregnated with aminoplast resin are pressed onto the wood materials, for example using a gluing agent under the action of heat and pressure. Filled urea resins, melamine resins and / or blends thereof as well as so-called cold glues based on polyvinyl acetate dispersion are used as gluing agents.

A further known possibility of producing molded articles by pressing consists, for example, in combining aminoplast resins with powdered fillers and, if appropriate, further known additives, such as pigments, flow aids and, if appropriate, lubricants or release agents, and pressing these products in molds at elevated temperature.

The properties of the compacts produced by one of the above-mentioned processes depend to a large extent on the type of aminoplast resin used. The previously known aminoplast resins have disadvantages, some of which significantly limit their usability for the purposes stated above. For example, the films that can be produced by impregnating paper or fabric webs with the previously known melamine resins were not sufficiently elastic for some purposes. It was known that the elasticity and thus the bending radius can be improved if modifying agents such as glycols are added to the aminoplast resin. However, the resulting improvement in elasticity was associated with a deterioration in the water resistance, so that the films could not be used for some applications, for example for sheathing profile strips. The laminates or molded wood parts produced by pressing paper or fabric webs or veneers with known aminoplast resins by impregnation do not show sufficient elasticity, especially when it comes to using the obtained molded parts where they are exposed to alternating thermal loads .

Also in electrical engineering, the molded articles produced with previously known aminoplast resins do not show the desired properties, such as high electrical resistance and high tracking resistance, owing to their electrolyte content.

Previously known etherified methylolaminotriazines were prepared by methylolation and simultaneous or subsequent etherification of the methylolaminotriazines in the presence of acidic catalysts (cf. Houben-Weyl, vol. 14/2, pages 359-368 Ulimann Enzyklopadie der techn. Chemie vol. 3, pages 487-489 ). The degree of methylolation, for example in the case of melamine, is generally 3-6. After the reaction had ended, it was necessary to neutralize the acid catalyst used and to remove the salt formed by filtration. However, this was generally only incomplete, so that undesirable turbidities occurred during storage of the products thus produced, which can be attributed to further salt dropping and, moreover, the non-removable salt residues to an extraordinarily strong reduction in the electrical resistance and the tracking resistance of those produced with such aminoplast resins Moldings led.

Previously known methylolaminotriazines etherified with long-chain alcohols were mainly caused by

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tion of the corresponding methyl ether obtained under acidic catalysis.

Surprisingly, it has now been found that thermosetting etherified methylolaminotriazines which are free of electrolytes and contain on average 1.3 to 2n methylol groups per mole of aminotriazine, where n is the number of amino groups of the aminotriazine, which is at least 33% with a glycol derivative of the formula

R- (OCH2CH2) mOH (I)

wherein R is an alkyl group with 1 to 4 carbon atoms and m is an integer from 1 to 4, are etherified, do not show the disadvantages of the previously known thermosetting aminoplast resins and are therefore particularly advantageous for the production of laminates and molded wooden parts with high elasticity and high water resistance as well as of electrical laminates and molded parts with high electrical resistance and high tracking resistance.

According to the invention, such etherified methylolaminotriazines are prepared by an aminotriazine with 1.3 to 2n moles of formaldehyde per mole of aminotriazine, where n is the number of amino groups of the aminotriazine, and is at least 2 and with an excess of a glycol derivative of the formula

R- (OCH2CH2) mOH (I)

wherein R is an alkyl group with 1-4 carbon atoms and m is an integer from 1-4, in the absence of acids and alkalis, condensation is continued until the degree of etherification is at least 33%.

Glycol derivatives of the formula I which can be used in the process according to the invention are, for example, methyl and ethyl glycol, di-, tri- and tetraglycol monomethyl-monoethyl and monopropyl ether, tri- and tetraglycol monobutyl ether.

Aminotriazines which can be used in the process according to the invention are, for example, melamine, benzoamine and acetoguanamine.

Heat-hardened, etherified methylolaminotriazines prepared by the process according to the invention and suitable for use as aminoplast resins are electrolyte-free and contain on average 1.3 to 2n methylol groups per mole of aminotriazine, which are at least 33% etherified with a compound of the formula I, where n is the number of amino groups of the aminotriazine.

Etherified methylolaminotriazines are preferred which contain on average 1.8 to 2n, in particular 1.8 to 1, 2n, methylol groups per mole of aminotriazine. Etherified methylolaminotriazines in which at least 50% of the methylol groups are etherified are also preferred.

Of the glycol derivatives of the formula I used in the etherification process according to the invention, preference is given to those in which R denotes a methyl group and also those in which m represents the number 1 or 2. Those in which R in formula I denotes a methyl group and m represents the number 1 or 2 are particularly preferred.

Another group of preferred etherified methylolaminotriazines obtainable according to the invention are those which are derived from melamine.

It was surprising that the use of glycol derivatives of the formula I for the etherification of the methylolaminotriazines makes the use of acidic catalysts superfluous and that the molar ratio of aminotriazine to formaldehyde can be varied within much broader limits than was previously known for normal etherified melamine formaldehyde condensates .

Because of the absence of acidic catalysts, there is none

Neutralization of the reaction mixture is required so that completely electrolyte-free products are obtained.

The absence of electrolytes is decisive for the excellent electrical properties of compacts produced from aminoplasts obtainable according to the invention and the wide range of the degree of methylolation allows the properties of such compacts, in particular with regard to the elasticity, the water resistance and the temperature and temperature change resistance, also to extreme requirements to adapt to practice.

In the process according to the invention, the condensation takes place at a temperature of, for example, 50-180 ° C., preferably 80-140 ° C. The glycol excess to be used can be 1.2 to 20 times the theoretical amount. After the desired degree of condensation has been reached, the remaining excess of glycol is expediently distilled off, preferably in vacuo. The water of reaction formed during the condensation is preferably distilled off continuously. Distilling off the water of reaction is also conveniently carried out in vacuo.

If the water of reaction is continuously distilled off during the reaction, the degree of etherification of the reaction product achieved can be determined from the amount thereof.

The formaldehyde is preferably used in the form of paraform aldehyde. However, aqueous solutions of formaldehyde can also be used, or solutions of formaldehyde in the glycol derivatives of the formula I used according to the invention for etherification.

The production of compacts using the etherified methylolaminotriazines prepared according to the invention is carried out by combining the etherified methylol aminotriazine with a carrier or filler and pressing the combinations under pressure at elevated temperature to give moldings.

The combinations can be obtained by, for example, impregnating sheet-like absorbent materials, such as fabric webs, random-fiber nonwovens or also wood veneers, with the aminoplast resin produced according to the invention. The impregnation can be carried out in a manner known per se. Powdery filling materials can be mixed with the aminoplast resin produced according to the invention, likewise in a manner known per se.

Particularly suitable sheet-like materials are, for example, fabric webs made of natural or synthetic fibers, in particular cellulose fibers, or random fiber nonwovens, in particular paper. Wood veneer can also be used as the carrier material for the resin. The carrier materials mentioned can be impregnated with the aminoplast resin in a known manner, for example by application with brushes or rollers, spraying on or dipping, the procedure generally being such that the impregnated materials contain 25-75% by weight of the aminoplast resin. After impregnation, the materials are expediently dried to a residual moisture content of 1-11% by weight. The sheet-like combinations obtained in this way can be placed on top of one another in several layers and pressed into pressed bodies at a temperature of 110-170 ° C. and a pressure of 2.0-800 kp / cm.

The use of absorbent papers as sheet-like carrier material is particularly preferred.

It is possible, for example, to decoratively print the web-shaped carrier materials before impregnation with pigment dyes or, if the sheet-like carrier materials contain cellulose fiber or textile fibers, to dye or print them with textile dyes.

The preferred raw material for random fiber nonwovens and fabric webs is cellulose. However, other known ones can also be used

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Fiber materials on which the sheet-like carrier materials are based.

The pressing time for the production of laminates is generally 10-60 min.

Surface coatings using the combinations described are generally produced in such a way that, as in the production of laminates, a sheet-like carrier material is first impregnated with the resin. The impregnation can be carried out as described above. The resin content of the combination can be 25-45% by weight, preferably 30-40% by weight, based on the weight of the entire combination. As described, the impregnated carrier materials are expediently dried to a residual moisture content of 3-10% by weight. The sheet-like resin / carrier combinations thus obtained can be applied to the surface to be coated using an adhesion promoter under a pressure of 2-12 kp / cm, preferably 4-6 kp / cm, at a temperature of 110-170 ° C., preferably 140-150 ° C. The pressing time is generally 30 s to 4 min, preferably 1-2 min. In this way it is also possible to produce decorative surface coatings by using a correspondingly printed or colored decorative paper as the sheet-like carrier material.

Other known auxiliaries and modifiers according to the prior art can also be added to the combinations.

For the production of molded articles, for example, several layers of sheet-like carrier materials impregnated with the aminoplast resin are pressed at a temperature of 110-170 ° C. under a pressure of 50-120 kp / cm2 to form laminate materials.

The kneading of powdered filling material with the aminoplast resin produced according to the invention can be carried out at a temperature of 70-140 ° C. Kneading at an elevated temperature brings significant advantages in terms of the energy required for kneading and the achievable homogeneity of the combination. After mixing, the resulting combination can be cooled to room temperature, generally becoming solid. The solid product can be granulated and then pressed. The pressing is generally carried out at a temperature of 120-180 ° C. under a pressure of 200-800 kp / cm, the pressing time generally being 30 s to 5 min.

Cellulose powder is primarily used as the powdery filler. Further suggestions relate to the use of cellulose, wood flour, cotton flakes or cellulose ester powders. Flour, starch but also peat or other waste from the wood industry are also used.

Known lubricants that can be contained in the combinations to be pressed are, for example, zinc, magnesium or calcium stearate.

With the combination described, curved surfaces, such as profile strips, can also be coated perfectly because of their extraordinarily high elasticity. It is also possible to coat chipboard all around, for example, by pulling the described sheet-like combination around the edges. This was not possible with previously known coating materials based on aminoplast. Here the individual flat surfaces had to be coated separately.

The laminates obtainable using the aminoplast resins produced according to the invention are notable for excellent elasticity and, at the same time, very good water resistance. Because of their extraordinarily high electrical resistance values and high tracking resistance, they are ideal for the manufacture of components for the electrical industry. The same valuable properties also have compacts which can be obtained using the aminoplast resins produced in accordance with the invention in combination with powdery fillers. Other advantages of the pressed bodies and surface coatings available as described are their resistance to high and low temperatures and temperature changes, the excellent dimensional stability according to Martens, high impact strength and flexural strength and low post-shrinkage.

The following percentages of concentration and parts are by weight.

example 1

5200 ml of methyl glycol, 1372 g of melamine and 650 g of p-form aldehyde are stirred at 120 ° C. A clear solution has occurred after 90 min. About 1.5 l of methyl glycol are distilled off. A melamine resin solution with a condensate content of 66% (determined by the weight loss on a sample by heating for 1 hour at 120 ° C), an unlimited water dilutability and a limited dilutability with n-butanol, i.e. 1 part of the present resin can be diluted with 1 part n-butanol at 20 ° C without becoming cloudy. The analysis of the product shows that 15.4% is present as bound formaldehyde and 21.3% as bound methylglycol. The solvent content is 33.8% determined as methylglycol.

Example 2

1260 g of melamine, 450 g of p-formaldehyde and 61 methylglycol are stirred at a bath temperature of 140 ° C. for 90 minutes. A solution occurs. Now 1.51 methyl glycol are distilled off. A resin is obtained which has a water dilutability of 1: 2.0 (i.e. 1 ml of resin takes up 2 ml of water at 20 ° C. without becoming cloudy) and a dilutability with n-butanol of 1: 0.8. The resin can be thinned indefinitely with methyl glycol. The content is 53% (1 h 55 ° C / 20 mm Hg), the viscosity measured in a DIN cup with a 4 mm nozzle for 18.5 s.

Example 3

126 g of melamine, 40 g of p-formaldehyde and 500 ml of methyl glycol are stirred at a bath temperature of 140 ° C. for 2 hours, a clear solution occurs. About 200 ml of methyl glycol are then distilled off. A 62% resin (content determination as above) is obtained, which contains 11.2% formaldehyde and 18% methylglycol in bound form.

Example 4

126 g of melamine, 90 g of p-formaldehyde and 1.21 of ethylene glycol colmonobutyl ether are stirred at 140 ° C. with a descending condenser until no more water is distilled off.

After distilling off 600 ml of alkylene glycol monobutyl ether i. Vac. a 60% resin that can be thinned indefinitely with n-butanol.

Example 5

187 g of benzoguanamine, 120 g of p-formaldehyde and 11 methylglycol are heated to 120 ° C. for 20 minutes, a clear solution occurs. Now 600 ml of methyl glycol and water are distilled off. 540 g of a 62% resin are obtained, which are infinitely miscible with n-butanol, can be diluted with 4 parts of xylene and can be diluted 1: 2 with water. The viscosity is 17 s (4 mm DIN cup).

Example 6

126 g of melamine, 180 g of p-formaldehyde and 1.21 of methyl glycol are boiled under reflux for 1 h, then 680 g of methyl glycol and water are slowly distilled off.

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730 g of an 80% resin are obtained, which can be diluted indefinitely with water and n-butanol.

Example 7

1008 g of melamine, 800 g of p-formaldehyde and 8 l of methyl glycol are boiled under reflux for 8 hours, then about 6 l of methyl glycol and water are distilled off.

This gives 3 kg of a 91% resin which is miscible with water in all proportions.

Example 8

71 diglycol monomethyl ether, 630 g melamine and 480 g p-formaldehyde, molar ratio 1: 3, are heated to 120-130 ° C. with stirring under a vacuum of 400-500 torr.

600 ml of water of reaction are distilled off.

Now the excess diglycol monomethyl ether (approx. 41) is distilled off at a bath temperature of 100 ° C. under a vacuum of 10 torr. This recovered diglycol monomethyl ether can be used again in further batches.

This gives 2.1 kg of a 75% resin (content determined by the content of free - not etherified methyldiglycol, since, due to the high boiling point of this alcohol, determination of solids by the usual method does not provide reproducible values), which can be mixed with water as desired. The dilutability with the following solvents is:

Toluene: 1:10

n-butanol: 1: 3 methanol: 1:00

If instead of methyldiglycol, methyltriglycol or ethyltriglycol and the procedure otherwise described in Example 8 is used, the results are essentially similar. With these very high-boiling glycol derivatives, it is advisable to concentrate using a thin-film evaporator at 1 Torr.

The following examples illustrate some of the possible uses of the aminoplast resins produced according to the invention.

Example 9

10 sheets of 80 g / m heavy electrolyte-free paper are impregnated in the aminoplast resin prepared according to Example 1. The resin content after drying, which is carried out at 130 ° C, is about 60%, the residual moisture content (determined by drying a sample for 5 minutes at 160 ° C) is about 6%. The stacked papers are pressed in a multi-day press between high-gloss chrome-plated nickel sheets at a temperature of 1400 C and a pressure of 80 kp / cm2 for 15 min.

After cooling the laminate under pressure to about 70 ° C, a 1.1 mm thick laminate is obtained. The following data are measured on this laminate:

Hardening level Kiton test: 2-3 Electrical surface resistance DIN 53482: 5.5 • 1012Q tracking resistance DIN 53480: level KA 3b

Example 10

An 80 g / m heavy printed wood sample paper is impregnated in a solution of the aminoplast resin prepared according to Example 7, diluted with water to 40% by weight of solid resin. The resin content of the impregnated paper is approx. 38%, the residual moisture content approx. 2%.

The impregnated paper is cold glued onto a chipboard using a commercially available polyvinyl acetate glue. Depending on the thickness of the board, the film is left over the edges of the chipboard and wrapped in a second step by bending the film around the edge using white glue. The film is so elastic that there are no breakages when wrapping it. The coated chipboard can then be coated with an acid-curing paint.

Example 11

70 parts of the resin prepared according to Example 6, 30 parts of microcellulose, 4 parts of titanium dioxide, 1 part of zinc stearate are rolled out on a roller mill at 110 ° C. to a rolled skin. After granulating the rolled skin, a shaped body is produced in a standard rod shape at 150-155 ° C 250 kp / cm and 10 minutes pressing time (or 8 minutes for testing for post-shrinkage), which has the following properties:

Bending strength according to DIN 52362: 840 kp / cm2 tracking resistance according to DIN 53480: KA3c heat resistance according to Marten (DIN 53462): 121 ° C post-shrinkage according to DIN 53464: 1%

Impact resistance according to DIN 53453: 7 kpcm / cm.

Example 12

The product obtained according to Example 8 is diluted with isopropyl alcohol to a concentration of approximately 45%. 2% p-toluenesulfonic acid (based on solid resin) is added to accelerate the curing process.

In this solution, an approx. 250 g / m cellulose carrier web is impregnated to a resin content of approx. 25%, based on the final paper weight, and dried at 130 ° C. to a residual moisture content of 1%. During the drying process, the resin in the film hardens. The melamine resin film is then given a varnish

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an acid-curing commercially available lacquer, approx. 30 g / m, and is glued onto a chipboard edge as a highly elastic edge band using a commercially available hot melt adhesive based on ethylene / vinyl acetate copolymers.

Example 13

In a solution of the resin obtained according to Example 8, diluted to 50% with water, 0.8 mm thick veneers are impregnated to a resin content of approximately 28-32% and dried to a solid moisture content of 7-8% in a circulating air cabinet. 10 layers of these veneers are pressed at 140 ° C and a pressure of 110 kp / cm for 18 minutes between high-gloss chrome-plated nickel sheets to a plate. The following values are measured on the plate:

Bending strength according to DIN 52362: 2237 kp / cm2 Impact resistance according to DIN 53453: 21.2 kpcm / cm Water absorption after storage 96 60 ° C: 11.7%

After the plate has been tempered 3 x 20 h at 80 ° C and cooled to 20 ° C three times, no cracks are obtained.

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Claims (10)

625255 1. A process for the preparation of thermosetting etherified methylolaminotriazines, characterized in that an aminotriazine with 1.3 to 2 n mol of formaldehyde per mole of aminotriazine, where n is the number of amino groups of the aminotriazine, and is at least 2 and with one Excess of a glycol derivative of the formula R- (OCH2CH2) mOH (I) wherein R is an alkyl group with 1-4 carbon atoms and m is an integer from 1-4, in the absence of acids and alkalis, condensation is continued until the degree of etherification is at least 33%. 2. Aminoplast resins prepared by the process according to claim 1, characterized in that they are free of electrolytes and contain, on average, 1.3 to 2n methylol groups per mole of aminotriazine, which are at least 33% etherified with a compound of formula I, wherein n is the number of amino groups of the aminotriazine. 2nd PATENT CLAIMS 3. Use of the aminoplast resins according to claim 2 for the production of compacts by pressing a heat-curing combination of the electrolyte-free, etherified methylolaminotriazine with a carrier or filler material under pressure and at elevated temperature. 4. The method according to claim 1, characterized in that 1.8 to 2 n mol, preferably 1.8 to 1.2 n mol, of formaldehyde are used per mole of the aminotriazine. 5. The method according to claim 1, characterized in that condensation is continued until the degree of etherification is at least 50%. 6. The method according to claim 1, characterized in that a glycol derivative of formula I, wherein R is a methyl group, is used. 7. The method according to claim 1 or 6, characterized in that a glycol derivative of the formula I, in which m represents the number 1 or 2, is used. 8. The method according to claim 1, characterized in that melamine is used as aminotriazine. 9. Use according to claim 3 for the production of a surface coating by pressing the thermosetting combination, optionally using a glue, onto the surface to be coated. 10. Use according to claim 3 or 9, characterized in that the combination also contains pigments, flow aids, lubricants or release agents or a mixture thereof.