HU202565B - Process for thermosetting furane-resines - Google Patents

Abstract

Furane and phenolic resins are crosslinked by liquid aromatic acid chlorides, pref. benzene- and/or toluene-sulpho-chlorides mixed with at least one of the following cpds.: -aromatic acids, pref. sulphonic acids, silanes, pref. di:methyl-di: diloro-silane -maleic-acid-anhydride -titanium-tetra;chloride. - Instead of, or as well as above cpds. phosphoric acid or acid-phosphates may also be added to the resins.

Description

The present invention relates to a process for the crosslinking of furan resins.

Furan resins as used herein include furfuryl alcohol resins on the one hand and furfuryl alcohol formaldehyde resins on the other. One problem with the application technology of these resins is their crosslinking and manageability. It is precisely because of these difficulties that many solutions have already been found.

The bonding problems are similar for other aromatic resins containing oxymethyl groups, especially phenolic (resole) resins.

The most important cross-linking solutions, mainly for furans resins, but also partially for phenolic resins include:

the. ) For this purpose, it is customary to use a mixture of mineral acids with water, and possibly with ethyl alcohol (e.g., U.S. Patent Nos. 123,763, U.S. Patent Nos. 1,665,235 and 1,665,237);

b. A18126; GDR patent proposes Lewis acids, SnCU and AlCl2;

c. ) A151.536. the use of maleic anhydride as a crosslinking agent known in the Hungarian patent;

d. ) Solid sulfonic acid derivatives have already been proposed, e.g. p-toluene sulfochloride and / or. use of ammonium salts of various aromatic sulfonic acids, e.g. No. 2,471,600. U.S. Pat.

e. ) Proposes a different solution in 3.033.804. U.S. Pat. No. 3,800,198, namely triphenyl phosphite in the presence of an acid catalyst;

f. ) No. 2,653,118. U.S. Pat. finally

g. ) 159,650. Soviet patent favors the use of benzenesulfonic acid.

Although the proposed solutions are suitable for the crosslinking of furans resins, it is quite difficult to find the amount of acid and acidity corresponding to the given temperature, mixed resin mass and air humidity, which leads to the whole curing process, when using solutions of strong mineral acids and strong organic acids. however, it provides a resin composition that can be applied without sudden heating or thickening. Suddenly thickening, heating resin composition results in a lack of fluid tight bedding e.g. furan resin mortar coatings. Insufficient crosslinking of furan resin due to underdosing or thinner crosslinking agent, eg. when used as a binder for chemical-resistant coatings, it has unsatisfactory hardness, is chemically resistant, and is thus damaged when used. While this could be assisted by a permanent heat treatment of 80-100 ° C, it is often impracticable when finished. Too hard a hardening process usually results in a finished product of uneven quality.

When a solid aromatic acid chloride or other sulfonic acid derivative is used, it is customary to associate it with a mineral filler. so e.g. conventional use of p-toluene sulfochloride in association with graphite. However, even when carefully dispersed, solid crosslinking agents leave unreacted crosslinking particles in the finished hard resin, which, for example, has the properties of the finished product. it degrades chemical resistance.

However, when ammonium salts are used as the sulfonic acid derivative, its nitrogen content reduces the chemical resistance. In addition, the bonded acid in the form of the ammonium salt does not sufficiently catalyze the bonding reaction, which results in a significant post-heat treatment requirement.

The present invention seeks to overcome the above disadvantages by using a curing agent which safely cures furan resins and does not degrade their quality and does not require substantial post-heat treatment.

The present invention is based on the recognition that liquid aromatic sulfochlorides should be used at room temperature in place of solid acid chlorides, preferably with reactive additives.

It has also been found that the liquid curing agent does not thicken the mixture to be applied, but rather dilutes it, thus making it possible to obtain an acid-insulating mortar with a more favorable filling degree.

Finally, we have discovered that cross-linking agents not only promote cross-linking itself, but are also incorporated into furan resins and improve their quality.

Accordingly, the present invention provides a process for crosslinking furan resins in an acidic medium by crosslinking an aromatic acid chloride to form a homogeneous solution of anhydrous aromatic acid chloride crosslinker and additives at room temperature, thereby dissolving and crosslinking the resin in this homogeneous phase.

The aromatic acid chloride is preferably benzene sulfochloride and the additive is at least one of the strong mineral acids and / or compounds which hydrolyze them to form a homogeneous solution of the acid chloride, preferably dimethyldichlorosilane and / or titanium tetrachloride.

Since the crosslinking agent does not introduce water into the system, as opposed to the mineral acid crosslinking slides diluted with water, the main reaction, the polycondensation process that results in the cleavage of water, is not inhibited by mass law. However, the low concentration but continuous formation of hydrochloric acid resulting from the reaction with the excess alcoholic hydroxyl groups and the water content of the furan resin undergoes the bonding reaction.

Much less by-product water does not form a substantial cohesive inclusion, e.g. graphite grains and thus does not impair the compactness of the finished product with the labyrinth system formed at the site of the inclusions, since the acid chloride, which causes the crosslinking, is partially affected by chemical uptake of water.

Since the reactivity of liquid aromatic acid chlorides in pure state is lower than that of solid acid chlorides, it is advisable to add various additives, in particular to facilitate the start of the crosslinking process. so e.g. organic chlorine compounds which emit hydrochloric acid and are well miscible with the liquid aromatic sulfochlorides at high hydrolysis rates, preferably ldorosilanes, may be added to the fo-2HU 202565Β liquid crosslinking agent, preferably dimethyl dichlorosilane in an amount of from be. The silane is also chemically incorporated into the furan resin network, enhancing its "phobia", that is, the repulsive nature of the solvent, water, which manifests itself in a reduction in its liquid uptake. It also improves its chemical resistance by blocking excess oxymethyl groups that are not involved in the crosslinking of the furan resin.

However, other additives may be used in place of or in addition to the silane additive. so e.g. in addition to the aromatic acid chloride, the aromatic acid may also be present in an amount such that the weight ratio of acid chloride to acid is 100: 1 to 5. so e.g. adding water to the benzene sulfochloride and partially hydrolyzing it with stirring and heating to remove the phase boundary results in a mixture having a benzene sulfonic acid content of about 1-3%. However, 1-2 parts by weight of finely powdered benzenesulphonic acid may be added to 100 parts by weight of benzene sulphochloride to dissolve the desired mixtures.

Titanium tetrachloride may also be used as an additive, either in addition to or in place of silane. Preferably the weight ratio of aromatic acid chloride to titanium tetrachloride is 100: 1-5. Titanium tetrachloride is also incorporated in the furan resin network and is also soluble in aromatic acid chloride.

The process of the present invention, by making safer crosslinking of furan resins, also enables the preparation of higher quality, more dense than average, furan resins. In this way, it is possible to produce self-supporting furan resin moldings and coatings which are resistant to complex technical media, mixtures of acidic chlorinated solvents. For this purpose, they are more suitable than the previously used polyester and epoxy resins, moreover known as "teflon" it is prone to cold flow and difficult to combine.

The furan resins produced by the process of the invention are particularly suitable for e.g. for bonding of chemical resistant ceramic coatings, for making rolled and hand-applied glass fiber reinforcing self-supporting plastic structures, for making coatings.

To support the above, the results of the comparative experiment below should be used.

The results are shown in Figure 1, which shows the result of soaking the crosslinked furan resins in dimethylformamide. In the figure, time is plotted on the horizontal axis (in hours) and on the vertical axis is the% change in mass of furan resin. The hours on the horizontal axis are plotted linearly for 4 hours, but then compressed.

In each case, 25 g of furan resin and 30 g of graphite filler were used. The curve 1 represents the mass change of the furan resin prepared according to the invention (solid line). The curve 2 (dashed line) and curve 3 (circular vo4) represent furan resin prepared by cross-linking according to known procedures.

For curve 1, 1 g of a crosslinker containing benzene sulfochloride containing 7 wt% dimethyldichlorosilane was used for the indicated amount of furan resin and ground filler.

After curing the furan resin, a gentle heat treatment at 60 ° C for 2 hours was performed and the furan resin was exposed to dimethylformamide.

In the case of curve 2, 1.5 g of benzene sulfonic acid was used as the crosslinker for the indicated amount of furan resin for the ground graphite filler. This furan resin hardened only after 2 days (16 hours a day) of heat treatment. When mixed, it became very warm and thickened. After stirring was stopped, the bonding reaction was greatly slowed down.

The furan resin prepared above was exposed to dimethylformamide, resulting in dark brown dissolution due to uneven bonding.

In the case of curve 3, 1.5 g of para-toluene sulfochloride crosslinker was used for the indicated amount of furan resin and ground graphite filler. When the material was stirred, it became very warm, thickened, and remained slightly soft the next day, so it received a heat treatment of 60 'C for 2 hours.

The furan resin prepared as described above was then exposed to dimethylformamide, which resulted in a strong dark brown dissolution, followed by a very short burst of material.

Thus, the result obtained shows that while the (cross-linked) furan resin of the present invention is practically non-volatile when immersed in dimethylformamide, the curve 2 material exhibits a mass change of 10% within 1/2 hour. which increases to 30% in 12 hours. The curve 3 material undergoes a mass change of about 15% after about 1 hour and about 60% within about 1.5 hours, i.e., disintegrates within a short time.

This experiment proves that it has not been possible to obtain stable furan resins by the previous processes (crosslinking), but only by the process according to the invention.

The invention is illustrated in more detail by the following examples, which are not limited thereto.

Example 1 Benzene sulfochloride (g) was stirred at room temperature with 2 g of molten benzenesulfonic acid. A calcium chloride tube was installed for waterproofing. The resulting homogeneous crosslinking solution was added at room temperature, also under stirring, to 300 g of furfuryl alcohol formaldehyde resin (viscosity 50 MPa, free formaldehyde content 61%). The crosslinking reaction was accompanied by blackening of the dark brown reaction mixture and slight heat generation. Gelation occurred within 4 hours. The product also withstood the soaking stress of hardened dimethylformamide over 24 hours.

-3HU 202565Β

Example 2

All were carried out as in Example 1, except that 150 g of furan resin were cured with the crosslinker. The gelation occurred within 2 hours.

Example 3

All were carried out as in Example 1, but 600 g of furan resin were cured at 60 ° C.

Example 4

As described in Example 1, a crosslinking agent was prepared from 10g of benzene sulphochloride and 0.7g of dimethyldichlorosilane at room temperature to crosslink 250g of furfuryl alcohol formaldehyde resin (viscosity 500 MP, free formaldehyde 2.51%) at room temperature for 3 hours. The solidified product was suitably chemical resistant.

Example 5

The procedure described in Example 1 was followed except that a crosslinking agent obtained by absorbing 0.2 g of dry hydrochloric acid gas in 10 g of benzene sulfide was used.

Example 6

The procedure described in Example 1 was followed, but using a homogeneous solution of benzene sulfochloride (10 g) and titanium tetrachloride (2 g) at room temperature. 250 g furfuryl alcohol-formaldehyde resin (viscosity 200 MP, free formaldehyde gelled at 51% / 2 hours).

Example 7

The procedure was as described in Example 4, but using a solution of 10 g of benzene sulphochloride and 0.2 g of 961% sulfuric acid as crosslinker.

Example 8

A homogeneous solution of 10 g of benzene sulfochloride, 0.4 g of molten benzenesulfonic acid, 0.5 g of titanium tetrachloride and 0.3 g of dimethyldichlorosilane was prepared as described in Example 1. This was added as a crosslinking agent to 300 g of furfuryl alcohol resin (viscosity 30 MP, formaldehyde 01%). Gelation occurred within 5 hours, and the binding reaction was completed after 24 hours at 100 ° C for 2 hours.

Example 9

All were prepared as in Example 8, but using the same amount of ortho-toluene sulfochloride instead of benzene sulfochloride.

Claims (3)

PATENT CLAIMS CLAIMS 1. A process for cross-linking furan resins in an acidic medium with an aromatic sulfonic acid chloride crosslinker, comprising forming a homogeneous solution of anhydrous aromatic sulfonic acid chloride crosslinker and additives at room temperature to dissolve and crosslink the resin. 2. The process of claim 1 wherein the aromatic sulfonic acid chloride is benzene sulfochloride. Process according to claim 1 or 2, characterized in that at least one of the following is used as an additive: strong mineral acids and / or compounds which hydrolyze them to form a homogeneous solution in acid chloride, preferably dimethyldichlorosilane and / or titanium tetrachloride.