Use of polymerization inhibitor compositions

Abstract

The present invention relates to the use of at least two phenol derivatives jointly with at least one ancillary polymerization inhibitor which is different from these two phenol derivatives and particularly is selected from phenol derivatives, amine derivatives, thiazine derivatives, nitroso compounds, N-oxyl derivatives, metal salts, quinone derivatives, and mixtures thereof, to inhibit the polymerization of ethylenically unsaturated monomers comprising at least one heteroatom, it being also possible for a dispersant to be incorporated. The present invention also relates to a corresponding polymerization-inhibiting composition and to the corresponding process for preparing ethylenically unsaturated monomers comprising at least one heteroatom, and particularly acrylic monomers.

Claims

1. A method for inhibiting polymerization of ethylenically unsaturated monomers that comprise at least one heteroatom, comprising manufacturing, purifying, storing, and/or transporting such monomers in the presence of at least two phenol derivatives and at least one ancillary polymerization inhibitor which is different from the two phenol derivatives, wherein the two phenol derivatives are para-methoxyphenol and pyrocatechol and the at least one ancillary polymerization inhibitor comprises hydroquinone and phenothiazine as a mixture.

2. The method according to claim 1 wherein the method limits and/or prevents fouling of industrial equipment used in the preparation of the ethylenically unsaturated monomers.

3. The method according to claim 2, wherein the method limits and/or prevents fouling of industrial equipment used during distillation of the ethylenically unsaturated monomers.

4. The method according to claim 1, wherein the amount of the two phenol derivatives is effective to enhance the polymerization-inhibiting effectiveness of the at least one ancillary polymerization inhibitor.

5. The method according to claim 1, wherein the monomers are manufactured, purified, stored, and/or transported in the presence of the at least two phenol derivatives, the at least one ancillary polymerization inhibitor, and, optionally, para-dimethoxybenzene.

6. The method according to claim 1, wherein the two phenol derivatives are para-methoxyphenol and pyrocatechol, and the weight ratio of para-methoxyphenol to pyrocatechol is from 1 to 99.

7. The method according to claim 1, wherein the two phenol derivatives and the at least one ancillary polymerization inhibitor are present in a total amount of from 20 ppm to 1%, relative to the total weight of the monomers, the two phenol derivatives, and the at least one polymerization inhibitor.

8. The method according to claim 1, wherein the monomers are manufactured, purified, stored, and/or transported in the presence of the at least two phenol derivatives, the at least one ancillary polymerization inhibitor, and at least one dispersant.

9. The method according to claim 8, wherein the dispersant is selected from sulfonates, esters, succinimides, tristyrylphenols, acrylates, amides, amines, imidazoline, phenates, phosphates, and mixtures thereof.

10. The method according to claim 1, wherein the ethylenically unsaturated monomers comprising at least one heteroatom are selected from the group consisting of halogenated unsaturated monomers, acrylic monomers, unsaturated acrylic resins, unsaturated amides, unsaturated ethers, and vinylpyridines.

Description

EXAMPLES 1 TO 6

(1) The effectiveness of inhibitor and/or stabilizer systems, in accordance with the invention or control systems, was validated in a reflux distillation test simulating a step of distillative purification of methyl methacrylate.

(2) The apparatus used comprises a 100 ml round-bottom flask in glass, surmounted by a double-wall refrigerating column with spikes, with a height of 33 cm.

(3) The inhibitors considered are as follows: Hydroquinone sold by Solvay, referred to as HQ, phenothiazine sold by Sigma-Aldrich, referred to as PTZ, para-methoxyphenol sold by Solvay, referred to as PMP, and pyrocatecol sold by Solvay, referred to as PC.

(4) The dispersant used is as follows: polyalkylnaphthalenesulfonate sold by Solvay under the name Supragil MNS/90.

(5) For each of the tests, 50 ml of methyl methacrylate are introduced into the flask with the inhibitor system tested, when present. Table 1 below shows the nature of the compounds forming each system tested, and their respective weight proportions.

(6) Distillation is carried out at 100 C. under atmospheric pressure for 48 hours.

(7) The phenomenon of polymerization, where it occurs, is recorded by visual examination of the walls of the flask and of the refrigerating column. These observations are likewise reported in table 1 below.

(8) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 (comparative) (comparative) (comparative) (comparative) (Invention) (Invention) Inhibitor WITHOUT 100 ppm HQ 150 ppm HQ + 100 ppm PMP + 100 ppm HQ + 100 ppm HQ + 100 ppm and/or and 100 ppm 150 ppm 100 ppm PC 100 ppm PTZ + PTZ + 50 ppm stabilizer PTZ PTZ 100 ppm (PMP + (PMP + PC) + 50 ppm system PC) Supragil Tested MNS/90 Observation Polymer Polymer Polymer Polymer No polymer No polymer deposit after 48 h deposits in the deposits deposits deposits in the deposit is is observed either in flask and within the within the flask and observed either the flask or within column column column column in the flask or the column within the column

(9) The results given above show that only the distillation of methyl methacrylate carried out in the presence of a polymerization stabilizer and/or inhibitor system in accordance with the invention completely removes the phenomenon of polymerization both in the flask and in the column. Contrary to all expectation, the PMP+PC inhibitor system allows a significant boost in the effectiveness of the traditional inhibitor system comprising HQ and PTZ. Similarly, the PMP+PC+dispersant stabilizer system jointly with the traditional HQ+PTZ inhibitor system prevents the unwanted polymer deposition.