DE1669716C3 - Melamine-formaldehyde condensate molding compounds - Google Patents

Description

(CH ₄

RN

C = O

where R is hydrogen or an alkyl radical having 1 to 4 carbon atoms and η is an integer from 3 to 11, have been prepared.

The invention relates to molding compounds based on curable melamine-formaldehyde condensates. she relates in particular to molding compounds of this type, which are characterized by good flow properties during processing to mark pressed pieces.

The processing of a melamine-formaldehyde-I condensate molding compound as well as the properties of the finished molding are known to be strong determined by the fluidity of the molding compound. A well-flowing molding compound enables the manufacture! development of high-walled pressed pieces. However, good fluidity is also a guarantee of perfect fluidity and closed surface of the pressed pieces.

To improve the flowability of melamine-formaldehyde condensate molding compounds numerous chemical compounds have already been proposed as additives. Of these substances that in more or less large amounts depending on the intended efficiency of the melamine-formaldehyde mixture Are added during the condensation, the substituted guanamines, such as the benzoguanamine or Acetonguanamine, the best-known additives. The Gehall of the molding compounds on these materials is to Achievement of the desired effect but relatively high and is generally up to 40 percent by weight, based on the proportion of melamine. This high proportion of higher quality substances means a commercial degradation of melaniin molding compound, which has a prohibitive effect on the entrance of this qualitatively valuable molding compound in many areas. To the For others, these additives also reduce the good properties of the pure melamine resin. Often they also have a detrimental effect on the curing time of the molding compounds.

It was an object of the present invention to provide free-flowing melamine-formaldehyde condensate molding compounds to develop that can easily be processed by pressing technology to high quality pressed pieces, a The lowest possible proportion of other types of additives and, at the same time, the shortest possible curing time exhibit.

It has now been found that molding compounds based on melamine-formaldehyde condensates are common Fillers and optionally customary additives the desired advantageous properties if they contain melamine-formaldehyde condensates caused by the condensation of melamine and formaldehyde in an aqueous medium in the presence of 2 to 15 percent by weight, based on the Surrune the amounts of melamine and formaldehyde, added to lactams of the formula

(CHj) _n

RN-

C = O

where R is hydrogen or an alkyl radical having 1 to 4 carbon atoms and η is an integer from 3 to 11, have been prepared.

The melamine-formaldehyde condensates of the molding compounds according to the invention are said to be produced by condensation of melamine and formaldehyde in an aqueous medium, preferably in an alkaline medium, in the presence of 2 to 15 and in particular 5 to 10 ge

ao weight percent, based on the amount of melamine and formaldehyde used, of lactams of the specified Kind of made. The condensation reaction can be carried out in a manner which is customary per se be, where appropriate melamine - and

S5 possibly together with minor amounts of other common aminoplast-forming substances, such as urea derivatives or arylsulfonamides
is condensed with formaldehyde in such a quantitative ratio that 1.8 to 4 and in particular 2 to 3.5 moles of formaldehyde come to 1 mole of melamine. It is advisable to condense until the condensate becomes cloudy when diluted with the same amount of water at 20 ° C.

Particularly suitable lactams of the type mentioned are pyrrolidone, caprolactam, capryllactam, lauryllactam and N-methylpyrrolidone, of which caprolactam is preferred.

The proportion of melamine-formaldehyde condensates to the fillers is the usual one. Very suitable proportions are 40 to 80 and in particular 50 to 70 parts by weight of melamine-formaldehyde condensate to 60 to 20 and in particular 50 to 30 parts by weight of fillers.
Examples of suitable customary fillers are: cellulose, comminuted cotton and other textile fabrics, wood flour, rock flour, asbestos fibers or glass fibers.

The usual additives which can be contained in the molding compounds in the usual quantities include:

Lubricants, e.g. B. zinc stearate, waxes, dyes and curing accelerators, e.g. B. phthalic acid.

The melamine-formaldehyde condensates can with the fillers and optionally the additives in the usual way - ■ preferably in a kneader - mixed, pre-hardened and ground.

The molding compounds can be processed in the customary manner at customary temperatures and temperatures Printing can be done. As a result of the good flow behavior of the molding compounds according to the invention, they can also produce larger pressed pieces with a relatively short hardening time.

The resulting moldings are of high quality and have an excellent surface quality with very little susceptibility to cracking. They are resistant to heat, hot water and organic Solvent, hard and scratch-resistant. The molding compounds according to the invention are particularly suitable for Manufacture of technical parts for electrical

Industry, such as housings or switches, containers or household items.

The parts and percentages given in the following examples are weight units. The specified The flow paths and times of the molding compounds were determined with the aid of the company's flow tester Zwick & Co., Einsingen over Ulm, determined.

example 1

A suspension containing 700 parts of melamine, 811 parts containing 37% formaldehyde solution, 70 parts of water and caprolactam in the indicated amounts in Table 1, is adjusted heated to 90 ⁰ C and aqueous sodium hydroxide solution by adding to a pH value of 8.7 . The pH value is kept constant by continuously adding aqueous sodium hydroxide solution. The reaction mixture is kept at the specified temperature until a sample becomes cloudy ^{when diluted with the same amount of water at 20 ° C.}

The 65% strength aqueous solution thus obtained is mixed with bleached cellulose in a ratio of 70 parts Condensate (100%) mixed with 30 parts of pulp and the usual additives in a kneader, then added 70 ° C to a water content of 4 to 5%, dried in a vacuum drying cabinet, pre-hardened and compacted after grinding to form a molding compound.

The flow path-flow time behavior of the so produced Table 1 shows molding compounds.

Comparative experiment 1

The procedure is as indicated in Example 1, however worked without the addition of caprolactam. The flow path / flow time behavior of the molding compounds produced in this way shows table 1.

Comparative experiment 2

The procedure is as indicated in Example 1, but instead of caprolactam benzoguanamine in the amounts given in Table 1 were added. The flow path / flow time behavior of the molding compounds produced in this way Table 1 shows.

Comparative experiment 3

The procedure is as indicated in Example 1, but instead of caprolactam 10%, based on the Amount of melamine and formaldehyde used. Acrylamide added. The flow path-flow time behavior Table 1 shows the molding compounds produced in this way.

Comparative experiment 4

The procedure is as indicated in Example 1, but instead of caprolactam 10%, based on the Amount of melamine and formaldehyde used, added to polyacrylic acid. The flow path-flow time behavior Table 1 shows the molding compounds produced in this way.

Example 2

The procedure is as indicated in Example 1, but 10% capryllactam instead of caprolactam added, the amount relating to the amount of melamine and formaldehyde used. the Properties of the molding compounds and the moldings produced with them correspond to those according to Bei-ϊο game 1 produced with the addition of 10% caprolactam.

Example 3

630 parts melamine, 811 parts formaldehyde (37%),

»5 46.5 parts of caprolactam and 365 parts of water will be at pH 8.7 at 90 ° C condenses up to a water tolerance of 1 to 1.5. Then 63 parts of melamine are added and dissolved, and a further 29.3 parts are added while the batch is being cooled p-Toluenesulfonamide added.

The resulting 55% resin solution is, as in

Example 1 given, processed into a molding compound.

The molding compound has very good flow and the compacts have excellent surface properties.

Example 4

630 parts of melamine, 762 parts of formaldehyde (37%), 38 parts of N-methylpyrrolidone and 372 parts of water are, as indicated in Example 3, condensed to a water compatibility of 1 to 1.5 and then with a further 63 parts of melamine and the 19 parts of p-toluenesulfonamide are added to the cooling.
The 57% strength resin solution obtained is, as in

M Example 1 given, processed into a molding compound. The compacts obtained are distinguished by a good closed surface.

Table 1
Flow path-flow time behavior of modified melamine-formaldehyde-condensate molding compounds.

PreO mass of Lot·) additive Art Flow time Flow path 1% Caprolactam Seconds mm example 1 5% Caprolactam 3.84 36.3 example 1 10% Caprolactam 7.6 50.0 example 1 0 - 10.5 63.0 Comparative experiment 1 15% Benzoguanamine 2.66 29.0 Comparative experiment 2 35% Benzoguanamine 1.83 25.5 Comparative experiment 2 10% Acrylamide 6.78 52.0 Comparative experiment 3 10% Polyacrylic acid 4.15 45.3 Comparative experiment 4 1.56 36.4

*) Based on the total amount of melamine and formaldehyde used.

Claims (1)

Patent right: Molding compounds based on melamine-formaldehyde condensates, customary fillers and optionally customary additives, thereby characterized in that they contain melamine-formaldehyde condensates contain, by condensation of melamine undjformaldehyde in aqueous Medium in the presence of 2 to 15 percent by weight, based on the sum of the amounts of melamine and formaldehyde, on lactams of the formula