NO140343B - PROCEDURE FOR REFINING MELTED GLASS AND DEVICE FOR CARRYING OUT THE PROCEDURE - Google Patents

Abstract

Process for refining molten glass and device for carrying out the process.

Description

Curable mixtures of unsaturated polyesters and thus copolymerizable, monomeric ethylene compounds.

It is known that with the help of radical organic peroxides triggerable polymerization reactions can be accelerated by adding small amounts of a catalytically active cobalt compound. When using organic hydroperoxides such as cyclohexanone peroxide, methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide and cumene hydroperoxide as a radical-forming substance, the acceleration is particularly pronounced, so that the polymerization can be carried out with only a minor increase in temperature, often even without heat input. These hydroperoxide-accelerator combinations are particularly important for the cross-linking mixture polymerization-based curing of mixtures of unsaturated polyesters containing α-|3 unsaturated ethylene carboxylic acid esters and copolymerizable, monomeric ethylene compounds such as vinyl, acrylic, methacryl - or allyl compounds, which mixtures are often termed "unsaturated polyester resins".

In the technique, it is only such cobalt compounds which, regardless of their composition, are easily soluble in the unsaturated polyester resins, which have stood the test, as they must be able to be mixed quickly and evenly. Furthermore, the cobalt-containing mixtures must also not show signs of deterioration during long-term storage, and finally, the cobalt compound must not lead to tarnishing in the curing product.

The cobalt compounds which satisfy these requirements, such as the preferably used cobalt salts of higher, soap-forming carboxylic acids, e.g. octoate, naphthenate, resinate and linoleate, furthermore the cobalt salts of dicarboxylic acid half-esters as well as the already known compounds with chelated cobalt of the type cobalt acetate diester and cobalt acetylacetonate, however, have the disadvantage that the resulting hardening products when using these accelerators are often green-colored. The green coloring is promoted by low curing temperatures. Less reactive polyester resins increase the tendency to discolouration, but even when using reactive types, whereby the unobtrusive and far less intense pink color tone in starting mixtures with added cobalt accelerator is usually retained also in the curing product, there is some satisfactory certainty that this greening will not occur. The green coloring is particularly pronounced when the curing takes place at room temperature and there is a large surface in relation to the volume, when the heat produced during curing can easily be dissipated, which e.g. is the case when using unsaturated polyester resins as varnishes.

It is assumed that the color change from faint pink to deep green which occurs when curing unsaturated polyester resins with hydroperoxides and soluble cobalt accelerators must be attributed to divalent cobalt being oxidised to trivalent by the hydroperoxide.

As is well known, this green coloring can be avoided by adding compounds of trivalent phosphorus, namely phosphoric acid and esters of this acid. However, there is then an extension of the "gelation time", i.e. of the time which, after the addition of the peroxide, is used for the gelation of the polyester resin. The time extension can be particularly noticeable when an unsaturated polyester-resin mixture to which cobalt accelerator and phosphoric acid or its esters have been added in advance has been stored for a longer time before further processing, i.e. before triggering the hardening by mixing in a peroxide.

It is also known that, particularly in the presence of cobalt accelerators, the gelation time can be shortened if, possibly without the cobalt accelerator, you also add other catalysts, so-called "promoters", and preferably amines. The most effective promoters are tertiary aromatic amines. Secondary and primary aromatic, as well as tertiary, secondary and primary aliphatic amines have a somewhat lesser effect. Polyamines can also have a promoter effect. The presence of several hydroxyl groups in hydroxy-amines has the consequence, as established, that the activating effect of the amine decreases and that the polymerization is often even made impossible. While thus e.g. diethylethanolamine is a good activator, an extension of the gelation time is found when triethanolamine is used. The shortening of the gelation time by means of amines in the presence of cobalt accelerators again has the disadvantage that the curing products are consistently even more intensely colored than those obtained without the addition of amines. Thus, numerous amines, such as dipropylamine, diethylethanolamine, tripropylamine, tributylamine and dodecylamine, enhance green coloration. Others, such as dimethylaniline, diethylaniline and dimethyl-p-toluidine lead to strongly yellow to brown colored curing products, while polyamines such as diethylenetriamine, hexamethylenediamine and tetraethylenpentamine can induce strong red and violet coloration which is significantly more intense than the light pink tint in the polyester resin containing only the cobalt accelerator.

It was now surprisingly found that by combined use of phosphoric acids, or compounds which can form such acids in the polyester, and amines which shorten the gelation time, the green coloring is avoided without the gelation time being extended. Even if the polyester solution, with phosphorus compounds and cobalt accelerator added, has been stored for a longer time, the gelation time is not extended or at most only insignificantly, provided that the curing takes place in the presence of an amine that shortens the gelation time. It is also irrelevant at what point the amine is mixed with the polyester resin. Examples of suitable phosphorus compounds can be mentioned: phosphoric acid, pyrophosphoric acids, phosphoric acid, phosphonic acids, phosphinic acids, phosphonic acids (phosphonic acids), amides or partial esters of these acids, phosphorus pentoxide, phosphorus trioxide, phosphorus pentachloride, phosphorus trichloride, phosphorus oxybromide and ester halides of phosphorus further acidifies the corresponding thiophosphoric compounds, such as phosphorus thiochloride, thiophosphoric acid amides and thiophosphoric acid ester halides.

Suitable amine accelerators are, for example: Propylamine, butylamine, amylamine, dodecylamine, stearylamine, dipropylamine, dibutylamine, triethylamine, diethylethanolamine, tripropylamine, tributylamine, triamylamine, trihexylamine, tetrahydroquinoline, morpholine, N,N'-tetramethylethylenediamine, 1-amiino- 3-m'ethyl-aminopropane, dimethylaniline, diethylaniline, dimethyl-p-toluidine and N-p-hydroxyethylaniline.

The amines are suitably added to the unsaturated polyester resins or to the cobalt accelerators. The mentioned phosphorus compounds can be stirred into the molten polyester at an elevated temperature. But they can also, if there are no difficulties with the solution, be added to the polyester resin, i.e. the solution of the unsaturated polyesters in a copolymerizable monomer, or to the cobalt accelerator.

As a rule, the phosphorus-containing compounds are fully active immediately after they have been added. Many connections, e.g. phosphorus thiochloride and ester halides of thiophosphoric acids, however, only achieve their full effect several days after they have been added.

The cobalt content, which usually amounts to between 0.01 and approx. 0.05 percent calculated on the unsaturated polyester resin is decisive for the most favorable addition of the phosphorus compounds. Furthermore, the reactivity of the polyester plays a role insofar as the highly reactive types need a smaller addition than the less reactive ones. In each case, it is easy to find the required quantity by simple experiments. In general, it is sufficient when one gram atom of cobalt corresponds to approx. 0.1 to approx. 3.0 grams of phosphorus.

The concentration of the amines that are used in combination with the phosphorus compounds is largely dependent on the nature of the amine as well as on the concentration of the phosphorus-containing compounds. Here, too, the most favorable concentration can be determined by simple experiments. It is usually sufficient to add approx. 0.001 to approx. 0.5% amine calculated on the unsaturated polyester resin. Further addition can be harmful, because the discolourations so typical of the amines can then appear again.

Even after a week's storage, no adverse effects whatsoever, such as fading or darkening, could be observed, either before or after curing, as a result of the addition of phosphorus compounds and amines in appropriate concentrations.

In the following examples, all quantities are parts by weight. To determine the gelation time and to assess the color of the curing products, 10 g samples are used in test tubes, which, in order to dissipate the heat of reaction, are allowed to stay in a thermostatically controlled water bath at 20° C until curing has taken place.

Example 1.

A polyester produced by condensation of 235 parts of maleic anhydride and 828 parts of phthalic anhydride with 738 parts of butanediol-1,3 while adding 0.5 parts of hydroclinone is dissolved in an equal amount of styrene. The gelation times of the polyester solution thus obtained, as well as the color of its curing products when catalyzed with different cobalt compounds and different hydroperoxides, are listed in table 1. Furthermore, the table contains the corresponding data for polyester solutions which have also been modified by the addition of different phosphorus compounds and according to the invention by phosphorus -compounds and various amines. The addition of the hydroperoxide always takes place at the end and - unless otherwise specified - without intermediate storage after the addition of the other substances.

Example 2.

The experiments compiled in Tables 2 and 3, for which the unsaturated polyester solution described in Example 1 is the basis, show that with the combined use of phosphorus compounds and amines according to the invention, the gelation time is to a considerable extent independent of the storage time. In these experiments, the unsaturated polyester solution described in example 1 is adjusted to a cobalt content of 0.016 percent by adding cobalt naphthenate. According to tables 2 and 3, it also contains phosphorus compounds and possibly amines. After the polyester solutions containing the aforementioned additives have been stored for various long periods of time, curing is triggered by mixing in 2.0 percent cyclohexanone peroxide.

Example 3.

An unsaturated polyester produced by condensation of 297 parts of maleic anhydride and 833 parts of phthalic anhydride and 674 parts of propylene glycol-1.2 with the addition of 0.45 parts of hydroquinone is dissolved in an equal amount of styrene. After catalysis with 0.016% cobalt added as a naphthenate solution in toluene and further with 2.0% cyclohexanone peroxide, the polyester solution gels at 20° after 22 minutes to form a green-colored curing product.

However, before the solution in styrene, 0.017% phosphorus pentoxide is stirred into the unsaturated polyester at 140° and the thus obtained unsaturated polyester solution is catalysed, to which is also added 0.16% n-propylamine mixed with the cobalt naphthenate solution used, as stated above, then, after the same gelling time, a colorless hardening product is obtained.

Using a spray gun, both catalyzed polyester solutions, to which 1.4 per cent of a 10 per cent paraffin solution in tdluol has also been added in order to achieve surface drying in the usual way, are transferred onto bleached maple wood , then both polyester resin varnishes form after 2 to 3 hours at room temperature dry varnish films, of which the one from the unmodified polyester solution is greenish-coloured, while the varnish to which phosphorus pentoxide and propylamine have been added is, on the other hand, colourless.

Also after sanding and polishing the varnishes, which due to secreted paraffin has become dull, the color difference remains, so that the light natural color of the wood becomes visible only through the varnish according to the invention.

Example 4.

A 50 per cent styrene solution of an unsaturated polyester obtained by condensation of 882 parts maleic anhydride 1332 parts phthalic anhydride, 1098 parts glycol and 963 parts trimethylolpropane diallyl ether with the addition of 0.43 parts hydroquinone is mixed with 0.016 per cent cobalt, added in the form of a 20 per cent .solution of cobalt naphthenate in toluene, and 2.0 percent cyclohexanone peroxide, after which it is cured at 20° after a gelation time of 10 minutes, forming a green colored product.

Adding 0.038% N,N'-tetramethyl-ethylene-diamine to the polyester solution

and 0.062 percent of a mixture of mono-iso-cetyl-phosphoric acid and di-iso-cetyl-phosphoric acid, as obtained by reacting 1 mol of phosphorus pentoxide and 4 mol-2-ethyl-hexanol-1, then recovered by the same catalysis and with unchanged gelation time an almost colorless curing product.

Claims (2)

1. Curable mixtures of unsaturated polyesters and thus copolymerizable, monomeric ethylene compounds with a content of organic peroxides, preferably hydroperoxides, as radical-forming substances, soluble cobalt accelerators and phosphorus compounds, characterized by an addition of phosphorus acids or phosphorus compounds which forms such acids, as well as of amines which accelerate the polymerization. 2. Curable mixtures according to claim 1, characterized in that 0.01 to 3.0 gram atoms of phosphorus are used in the mixtures per gram-atom cobalt, and in that the addition of amines amounts to 0.001 to 0.5 weight percent calculated on the curable mixture.