POLYMERIZABLE COMPOSITIONS FOR PREPARING POLYISOCYANURATE-BASED PLASTICS HAVING EXTENDED WORKLIFE

Abstract

The invention relates to polymerizable compositions that are suitable for preparing polyisocyanurate-based plastics and have an extended worklife as compared to the compositions conventionally used for this purpose.

Claims

1. A polymerizable composition having a molar ratio of isocyanate groups to isocyanate-reactive groups of at least 1.5:1.0 comprising: a) a polyisocyanate composition A comprising at least 1% by weight of NCO, wherein polyisocyanates present in the polyisocyanate composition A consist of oligomeric polyisocyanates to an extent of at least 80% by weight; b) at least one trimerization catalyst B which is a carboxylate; and c) at least 150 ppm of CO.sub.2 based on a total amount of liquid constituents of the polymerizable composition.

2. The polymerizable composition as claimed in claim 1, wherein the carboxylate comprises a phosphonium, ammonium, or metal ion as a counterion.

3. The polymerizable composition as claimed in claim 1, wherein the carboxylate has a pKa value of at least 3.5 and at most 5.0.

4. The polymerizable composition as claimed in claim 1, wherein the polyisocyanates consist of oligomeric polyisocyanates comprising biuret groups to an extent of not more than 20% by weight.

5. The polymerizable composition as claimed in claim 1, wherein a proportion of mono- and polyisocyanates having aromatically bonded isocyanate groups in the polyisocyanate component A is not more than 50% by weight.

6. The polymerizable composition as claimed in claim 1, wherein at 23° C. and a CO.sub.2 concentration of not more than 90 ppm a combination of polyisocyanate composition A and trimerization catalyst B reaches a gel point within 1 to 22 hours.

7. (canceled)

8. (canceled)

9. (canceled)

10. A process for producing a polymerizable composition having an elevated pot life, comprising combining a polyisocyanate composition A, a catalyst composition comprising a trimerization catalyst B which is a carboxylate, and CO.sub.2, wherein the polyisocyanates present in the polyisocyanate composition A comprise oligomeric polyisocyanates to an extent of at least 80% by weight, wherein a) the CO.sub.2 concentration achieved in the polymerizable composition is at least 150 ppm based on a total amount of liquid constituents of the polymerizable composition; and b) isocyanate-reactive compounds are employed only in an amount such that in the polymerizable composition a molar ratio of isocyanate groups to isocyanate-reactive groups of at least 1.5:1.0 is achieved.

11. The process as claimed in claim 10, wherein upon reaching the CO.sub.2 concentration at least 150 ppm the pot life of the polymerizable composition is at least twice as long as for a CO.sub.2 concentration of not more than 90 ppm.

12. The process as claimed in claim 10, wherein the CO.sub.2 concentration of the polymerizable composition is reached by using a polyisocyanate composition A having a suitable CO.sub.2 content.

13. The process as claimed in claim 10, wherein the CO.sub.2 concentration of the polymerizable composition is established by addition of CO.sub.2 to the polymerizable composition after addition of the polyisocyanate composition A and the catalyst composition to one another.

14. The process as claimed in claim 10, further comprising producing a composite material, a potting compound, a coating, an adhesive, or a three-dimensional printed component, at least in part, from the polymerizable composition.

15. A process for producing a polymer comprising: a) providing a reaction mixture comprising (i) a polyisocyanate composition A containing at least 1% by weight of isocyanate groups, (ii) at least one trimerization catalyst B which is a carboxylate and (iii) at least 150 ppm of CO.sub.2 based on a total amount of liquid constituents in the polymerizable composition; and b) curing the reaction mixture at a temperature between 80° C. and 300° C.

Description

EXAMPLES

General Information:

[0087] Unless otherwise stated all reported percentage values are in percent by weight (% by weight).

[0088] The ambient temperature of 23° C. at the time of performing the experiment is referred to as RT (room temperature).

[0089] The methods specified hereinbelow for determining the corresponding parameters were used for performing and evaluating the examples and are also the methods for determining the parameters relevant according to the invention in general.

Determination of Phase Transitions by DSC

[0090] The phase transitions were determined by means of DSC (differential scanning calorimetry) with a Mettler DSC 12E (Mettler Toledo GmbH, Giessen, Germany) in accordance with DIN EN 61006. Calibration was effected via the melt onset temperature of indium and lead. 10 mg of substance were weighed out in standard capsules. The measurement was effected by three heating runs from −50° C. to +200° C. at a heating rate of 20 K/min with subsequent cooling at a cooling rate of 320 K/min. Cooling was effected by means of liquid nitrogen. The purge gas used was nitrogen. The reported values are in each case based on evaluation of the 1st heating curve since in the investigated reactive systems, changes in the sample are possible in the measuring process at high temperatures as a result of the thermal stress in the DSC. The glass transition temperature T.sub.g was obtained from the temperature at half the height of a glass transition step.

Determination of Infrared Spectra

[0091] The infrared spectra were measured on a Bruker FT-IR spectrometer equipped with an ATR unit.

Acid Number Determination

[0092] Acid number was determined using method according to DIN ISO 2114.

Gel Time Determination

[0093] Gel time was determined using the instrument Geltimer GT-SP 100.50 from Gelnorm with measurement pins made of steel and a length of L=150 mm.

Determination of Carbon Dioxide Content

[0094] To determine the CO.sub.2 content of a sample this was examined according to DIN EN ISO/IEC 17025. The specified samples were analyzed under identical conditions by gas chromatography. A sample stored for 4 weeks in an air atmosphere having a measured CO.sub.2 content of 410 ppm was used as a reference sample.

[0095] All other samples were related to the comparative sample using mass-selective evaluation.

Starting Compounds

[0096] Polyisocyanate A1: HDI trimer (NCO functionality >3) having an NCO content of 23.0% by weight from Covestro AG. It has a viscosity of about 1200 mPa-s at 23° C. (DIN EN ISO 3219/A.3).
Polyisocyanate A2: HDI/IPDI polyisocyanate having an NCO content of 21.0% by weight from Covestro AG. It has a viscosity of about 22 500 mPa-s at 23° C. (DIN EN ISO 3219/A.3).
Potassium acetate was obtained in a purity of >99% by weight from ACROS.
Polyethylene glycol (PEG) 400 was obtained in a purity of >99% by weight from ACROS.
Zinc stearate having a zinc proportion of 10-12% was obtained from Sigma-Aldrich.
The release agent INT-1940 RTM was obtained from AXEL PLASTICS.
Catalyst K1 is a mixture of 10-30% potassium 2-ethylhexanoate in ethylene glycol and diethylene glycol from Evonik Industries AG.
Glass fiber mat: A P-D INTERGLAS TECHNOLOGIES GmbH 90070 (US Type 1610) plain weave glass fiber mat having a weight of 82 g/m.sup.2 was used.
All raw materials except for the catalyst were degassed under reduced pressure prior to use, and the polyethylene glycol was additionally dried.

Production of Catalyst K2:

[0097] Potassium acetate (5.0 g) was stirred in the PEG 400 (95.0 g) at RT until all of it had dissolved. This afforded a 5% by weight solution of potassium acetate in PEG 400 which was used as catalyst without further treatment.

Production of the Reaction Mixture

[0098] Unless otherwise stated the polyisocyanurate composites were produced by first producing the isocyanate composition by mixing the appropriate isocyanate components (A1 or A2) with an appropriate amount of catalyst (K1-K2) and additives at 23° C. in a Speedmixer DAC 150.1 FVZ from Hauschild at 1500 rpm for 120 seconds.

[0099] A portion of the mixture was then transferred into a mold (metal lid, about 6 cm in diameter and about 1 cm in height) and cured in an oven.

[0100] The remainder of the mixture was investigated for gel time using a gel timer.

Working Example 1

[0101] A resin mixture composed of degassed polyisocyanate A1 (85.0 g), catalyst K2 (3.64 g), zinc stearate (0.23 g), INT-1940RTM (2.04 g) and dry ice (9.09 g) was produced as described hereinabove (acid number: 27.4 mg KOH/g). Curing in the oven afforded a solid material having a T.sub.g of 98° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of open storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 2

[0102] A resin mixture composed of degassed polyisocyanate A1 (44.52 g), catalyst K2 (3.81 g), zinc stearate (0.24 g), INT-1940RTM (2.14 g) and a previously produced mixture of degassed polyisocyanate A1 (44.52 g) and dry ice (4.77 g) was produced as described hereinabove. Curing in the oven afforded a solid material having a T.sub.g of 88° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 3

[0103] A resin mixture composed of degassed polyisocyanate A1 (29.22 g), catalyst K2 (3.75 g), zinc stearate (0.23 g), INT-1940RTM (2.11 g) and a previously produced mixture of degassed polyisocyanate A1 (58.44 g) and dry ice (6.25 g) was produced as described hereinabove. Curing in the oven afforded a solid material having a T.sub.g of 93° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was more than 22 h. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 4

[0104] A resin mixture composed of degassed polyisocyanate A1 (60.32 g), catalyst K2 (3.87 g), zinc stearate (0.24 g), INT-1940RTM (2.18 g) and a previously produced mixture of degassed polyisocyanate A1 (30.16 g) and dry ice (3.23 g) was produced as described hereinabove. Curing in the oven afforded a solid material having a T.sub.g of 86° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 5

[0105] A resin mixture composed of freshly opened polyisocyanate A1 (93.5 g) (CO.sub.2 content: 88 ppm), catalyst K2 (4.0 g), zinc stearate (0.25 g), INT-1940RTM (2.25 g) and dry ice (0.5 g) was produced as described hereinabove (CO.sub.2 content of mixture: 426 ppm). The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 6

[0106] A resin mixture composed of freshly opened polyisocyanate A1 (93.5 g), catalyst K2 (4.0 g), zinc stearate (0.25 g), INT-1940RTM (2.25 g) and dry ice (1.0 g) was produced as described hereinabove. The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 7

[0107] Freshly opened polyisocyanate was left open for 24 hours at room temperature. A resin mixture composed of the polyisocyanate A1 stored open at room temperature for 24 h (93.5 g), catalyst K2 (4.0 g), zinc stearate (0.25 g) and INT-1940RTM (2.25 g) was produced as described hereinabove. (CO.sub.2 content: 410 ppm, acid number: 25.7 mg KOH/g). The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 8

[0108] A resin mixture composed of degassed polyisocyanate A2 (93.5 g), catalyst K2 (4.0 g), zinc stearate (0.25 g), INT-1940RTM (2.25 g) and dry ice (0.5 g) was produced as described hereinabove. Curing in the oven afforded a solid material having a T.sub.g of 148° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 9

[0109] A resin mixture composed of degassed polyisocyanate A1 (95.0 g), catalyst K1 (1.0 g), zinc stearate (0.25 g), INT-1940RTM (2.25 g) and dry ice (0.5 g) was produced as described hereinabove. Curing in the oven afforded a solid material having a T.sub.g of 98° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 10

[0110] A resin mixture composed of freshly opened polyisocyanate A1 (93.5 g), zinc stearate (0.25 g) and INT-1940RTM (2.25 g) was produced as described hereinabove. The mixture was then stirred uncovered at 1500 rpm for 10 min with a dissolver. The catalyst K2 (4.0 g) was then added and the mixture stirred again uncovered at 1500 rpm for 10 min with a dissolver. The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a gelled film on its surface was obtained.

Working Example 11

[0111] A resin mixture composed of freshly opened polyisocyanate A1 (93.5 g) (CO.sub.2 content: 88 ppm, acid number: 24.5 mg KOH/g), catalyst K2 (4.0 g), zinc stearate (0.25 g), INT-1940RTM (2.25 g) and dry ice (0.1 g) was produced as described hereinabove (CO.sub.2 content of mixture: 388 ppm). The gel time of the resin mixture at room temperature was more than 22 hours. After 24 h of storage at room temperature a liquid material having a slightly elevated viscosity was obtained.

Comparative Example 12

[0112] A resin mixture composed of degassed polyisocyanate A1 (93.5 g), catalyst K2 (4.0 g), zinc stearate (0.25 g) and INT-1940RTM (2.25 g) was produced as described hereinabove. Curing in the oven afforded a solid material having a T.sub.g of 93° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was less than 22 hours. After 24 hours of storage at room temperature a fully gelled material was obtained.

Comparative Example 13

[0113] A resin mixture composed of freshly opened polyisocyanate A1 (93.5 g) (CO.sub.2 content: 88 ppm, acid number: 24.5 mg KOH/g), catalyst K2 (4.0 g), zinc stearate (0.25 g) and INT-1940RTM (2.25 g) was produced as described hereinabove. Curing in the oven afforded a solid material having a T.sub.g of 93° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was 4 hours 40 min. After 24 h of storage at room temperature a fully gelled material was obtained.

Comparative Example 14

[0114] A resin mixture composed of degassed polyisocyanate A2 (93.5 g), catalyst K2 (4.0 g), zinc stearate (0.25 g) and INT-1940RTM (2.25 g) was produced as described hereinabove. Curing in the oven afforded a solid material having a T.sub.g of 149° C. Thermal curing reduced the height of the characteristic NCO band between 2300 to 2250 cm.sup.−1 by at least 80%. The gel time of the resin mixture at room temperature was less than 22 hours. After 24 hours of storage at room temperature a fully gelled material was obtained.