UNIFORM CROSSLINKING OF AZIRIDINE POLYMERS WITH DIMER ACIDS

By Renato Rindone/President & Director of Research

Volume I, Issue October, 2009

 

Polyaziridines, such as Xama-2 and Xama-7 are used in a number of applications such as:

 One of the problems with the use of aziridines is their vulnerability to homo-polymerization initiated by protonation of the aziridine ring.

This problem can interfere with systems where cross linking of an aziridine with a poly functional carboxylic acid (or carboxylic acid anhydride) is the desired end product.

 

As a result, formulations that involve the cross linking reaction of poly acids with polyaziridines must be carefully controlled to eliminate homopolymerization of the aziridine.  The use of Hycat™ catalysts eliminates the problem of homopolymerization and improves the application for these systems.  Examples of this benefit are experimentally shown below.

 

REACTION OF PENTAERYTHRITOL-TRIS-3-(1-AZIRIDINYL)-PROPIONATE (XAMA-7; CAS NUMBER: 57116-45-7) WITH A DIMER ACID

Into a mixing cup were weighed 15.5 grams (100.3 meq) of Xama-7, 27.7 grams (101.6 meq) of Empol 1016 dimer acid and 4.28 grams of Hycat™ 2000/2000S.  The mixture was mixed for two minutes with a spatula, and then placed into a Garner wire-stirred gel timer (Model GT-S) at 32 OC.  After one minute of stirring the contents of the cup were completely solidified into a uniform, hard rubbery mass.  Considerable heat was liberated during this period.

As a control, the reaction was also performed without the use of the Hycat™ catalyst.  Into an aluminum pan (60 mm diameter) were weighed1.6 grams (10.36 meq) of Xama-7 and 2.7 grams (9.90 meq) of Empol 1016 dimer acid and mixed for 2 minutes with a spatula then allowed to stand at 32 OC overnight.  After 15 minutes the composition was tacky which solidified into a semi-tacky mass on standing overnight.

 

REACTION OF PENTAERYTHRITOL PENTAERYTHRITOL-TRIS-3-(1-AZIRIDINYL)-PROPIONATE (XAMA-7) WITH METHYLHEXAHYDRO-PHTHALIC ANHYDRIDE (MHHPA)

MHHPA, 4.3 grams (51.1 meq) and Xama-7, 2.5 grams (17.6 meq) were weighed into a 30 ml beaker and thoroughly mixed.  A small sample, 0.6 gram, was transferred into a 15 ml beaker for a control. To the larger portion (6.2 grams) was added 0.4 gram of Hycat™ 3000/3000S catalyst. The contents of both flasks were allowed to react at room temperature (22° C).  After a 10 minute reaction period the Hycat™ catalyzed material was no longer mobile when the beaker was tipped on its side.  The material in the control beaker was still mobile. After a 25 minute reaction period the control reaction was not mobile. Although the Hycat™ catalyzed reaction was complete at least twice as fast as the control reaction, both the control and chromium catalyzed reaction products showed an equal amount of hardness when prodded with a pointed spatula. Both reaction products were insoluble in acetone.

 

REACTION OF PENTAERYTHRITOL-TRIS-3-(1-AZIRIDINYL)-PROPIONATE (XAMA-7) WITH BICYCLO (2.2.2) OCT-7-ENE-2,3,5,6-TETRACARBOXYLIC DIANHYDRIDE (BTA)

Into an aluminum weighing pan was put 6.6 grams (53.2 meq) of BTA, 7.7 grams (54.1 meq) of Xama-7 and 0.4 grams of Hycat™ 3000/3000S.  After 45 minutes at 41° C. the contents of the pan cured to a hard, brittle olive green solid.

 

ATTEMPTED HOMOPOLYMERIZATION OF XAMA-7 WITH HYCAT™ CATALYST

To show that Xama-7 does not homopolymerize in the presence of Hycat™ catalysts even at elevated temperature, 6.8 grams of Xama-7 and 0.4 grams of Hycat™ 2000/2000S were placed into an aluminum pan, thoroughly mixed with a spatula then heated to 41 OC for 3.25 hours.  The contents of the pan were still quite fluid.  After 9 days storage at about 20 OC the contents of the pan remained fluid.

Hycat™ Catalysts are more than just Epoxy Reaction Accelerators

By Renato Rindone/President & Director of Research

Volume I, Issue September, 2009

If Hycat™ catalysts accelerates the reaction of oxiranes with carboxylic acids, anhydrides and imides, then why can’t the reaction of other small ring compounds be accelerated as well? The use of activated Chromium (III) carboxylates (ACC’s) for the acceleration of reactions of epoxides with carboxylic acids, anhydrides and imides is well known and literature references are documented in the Dimension Technology Chemical Systems, Inc., (DTCS) website. ACC’s can be prepared by a number of synthetic routes. DTCS has developed a cost effective, proprietary process to manufacture ACC’s in commercial quantities. DTCS offers these activated catalysts to chemical industry under the “Hycat™” trade name. As the technology of the use of the Hycat™ catalysts for epoxide ring opening reactions became more understood, one relevant question needed answering. In a recent patent to DTCS [US 6,359,147; Reactions Catalyzed by Chromium (III) Carboxylates; March 19, 2002] that question was answered. Activated Chromium (III) carboxylates (Hycat™) are very effective catalysts to accelerate the reaction of: Aziridines with Carboxylic acids, anhydrides and carbonate esters Alcohols, Diols and Polyols with anhydrides, lactones and carbonate esters Oxetanes with anhydrides, carboxylic acids and imides Epoxides with lactones and carbonate esters Thiiranes with anhydrides and carboxylic acids These reactions will be discussed in more detail in future DTCS-News Letters. Contact DTCS for a copy of the patent or talk to the inventor directly at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .