AROMATIC POLYISOCYANATES WITH A HIGH SOLIDS CONTENT

Abstract

The invention relates to an aromatic allophanate polyisocyanate based on aromatic diisocyanates, containing a) 15 mol-% of allophanate groups, based on the sum of urethane, allophanate and isocyanurate groups, b) 50 mol-% of isocyanurate groups, based on the sum of urethane, allophanate and isocyanurate groups and c) 1.5% by weight of monomeric diisocyanates, based on the total weight of the aromatic allophanate polyisocyanate. Furthermore, the invention relates to a process for producing aromatic allophanate polyisocyanates and their use in polyisocyanate compositions or two-component systems.

Claims

1: An aromatic allophanate polyisocyanate based on aromatic diisocyanates, containing a) 15 mol-% of allophanate groups, based on the sum of urethane, allophanate and isocyanurate groups, b) 50 mol-% of isocyanurate groups, based on the sum of urethane, allophanate and isocyanurate groups and c) 1.5% by weight of monomeric diisocyanates, based on the total weight of the aromatic allophanate polyisocyanate.

2: The aromatic allophanate polyisocyanate according to claim 1, containing 20 mol-% of allophanate groups, based on the sum of urethane, allophanate and isocyanurate groups.

3: The aromatic allophanate polyisocyanate according to claim 1, containing 40 mol-% of isocyanurate groups, based on the sum of urethane, allophanate and isocyanurate groups.

4: The aromatic allophanate polyisocyanate according to claim 1, containing 1.0% by weight of monomeric diisocyanates, based on the total weight of the aromatic allophanate polyisocyanate.

5: The aromatic allophanate polyisocyanate according to claim 1, wherein the aromatic diisocyanate is selected from the group consisting of toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, and a mixture of toluene 2,4- and 2,6-diisocyanate.

6: The aromatic allophanate polyisocyanate according to claim 1, wherein the aromatic diisocyanate is a mixture of toluene 2,4- and 2,6-diisocyanate in a weight ratio of from 3:2 to 10:0.

7: The aromatic allophanate polyisocyanate according to claim 1, having an isocyanate functionality of 2.5 to 8.0.

8: A process for preparing an aromatic allophanate polyisocyanate according to claim 1, comprising the steps of (i) reacting at least one aromatic diisocyanate with at least one hydroxyl group containing compound to form a urethane groups containing polyisocyanate, (ii) reacting the urethane group containing polyisocyanate with an excess of at least one aromatic diisocyanate in the presence of at least one catalyst to form allophanate groups, (iii) stopping the reaction by deactivation of the at least one catalyst, and (iv) removing the unreacted monomeric diisocyanate.

9: The process according to claim 8, wherein the hydroxyl group containing compound has an average molecular weight of 62 to 5000.

10: The process according to claim 8, wherein the catalyst is a compound containing one or more selected from the group consisting of lead, zinc, tin, zirconium, bismuth, calcium, magnesium and lithium.

11: The process according to claim 8, wherein the catalyst is selected from the group consisting of a zinc carboxylate, a zinc halide, a zirconyl halide, a tetraalkoxyzirconium, zirconium carboxylate and a zirconyl carboxylate.

12: The process according to claim 8, wherein deactivation of the catalyst in step (iii) is conducted by addition of at least one catalyst stopper, wherein the amount of catalyst stopper is 50 equivalent-%, based on the molar amount of active metal in the catalyst used.

13: The process according to claim 8, wherein deactivation of the catalyst in step (iii) is conducted by addition of at least one catalyst stopper, wherein the catalyst stopper is selected from the group of consisting of sulfonic acid, monoalkyl phosphate, dialkyl phosphate, and mixtures thereof.

14: In a method for prohibiting aromatic allophanate group cleavage, the improvement comprising including a catalyst stopper selected from the group consisting of inorganic acids, acyl chlorides, sulfonic acids, sulfonic esters, mono- and dialkyl phosphates and silylated acids, and mixtures thereof.

15: A polyisocyanate composition comprising at least one aromatic allophanate polyisocyanate according to claim 1 and at least one solvent which is inert towards isocyanate groups, wherein the polyisocyanate composition has a non-volatile content of 40% by weight.

16: The polyisocyanate composition according to claim 15, having a viscosity of 50 to 20000 mPas, measured at 23 C. in accordance with DIN EN ISO 3219:1994-10.

17: In a process of crosslinking an adhesive or a coating composition, the improvement comprising including an aromatic allophanate polyisocyanate according to claim 1 as a crosslinker.

18: A two-component system comprising an isocyanate component A), containing at least one aromatic allophanate polyisocyanate according to claim 1, and a NCO-reactive component B), containing at least one compound which is reactive towards isocyanate groups.

19: A process for producing a composite system or a coated substrate, the process comprising applying a two-component system according to claim 18 to at least one substrate and at least one further step in which the two-component system is cured, optionally, under the action of heat.

20: The composite system or coated substrate, obtained by the process according to claim 19.

Description

EXAMPLES

[0107] All percentages are, unless indicated otherwise, by weight.

[0108] The determination of the NCO contents was carried out titrimetrically in accordance with DIN EN ISO 11909:2007-05.

[0109] The residual monomer contents were determined gas-chromatographically using an internal standard in accordance with DIN EN ISO 10283:2007-11.

[0110] The molar contents of allophanate, urethane and isocyanurate groups were determined by .sup.13C-NMR spectroscopy using CDCl.sub.3 as solvent in accordance with DIN EN ISO 10283:2007-11.

[0111] Allophanate mol-%=Integration of peak @154.0-156.0 ppm/(integration of peaks @154.0-156.0 ppm+integration of peaks @151.7-153.7 ppm+integration of peaks @146.7-148.7 ppm/3).

[0112] Urethane mol-%=Integration of peak @151.7-153.7 ppm/(integration of peaks @154.0-156.0 ppm+integration of peaks @151.7-153.7 ppm+integration of peaks @146.7-148.7 ppm/3).

[0113] Isocyanurate mol-%=(Integration of peak @146.7-148.7 ppm/3)/(integration of peaks @154.0-156.0 ppm+integration of peaks @151.7-153.7 ppm+integration of peaks @146.7-148.7 ppm/3).

[0114] The viscosity of synthesized polyisocyanates was measured at 23 C. by use of viscometer (HAAKE Viscotester VT550) with a standard rotator of MV-DIN in accordance with DIN EN ISO 3219:1994-10.

[0115] The distribution of the oligomers was determined by gel permeation chromatography in accordance with DIN 55672-1:2016-03 using polystyrene as standard and tetrahydrofuran as eluent.

[0116] The non-volatile content (NVC) was determined in accordance with DIN EN ISO 3251:2008-06 using a drying temperature and time of 2 hours at 120 C. and a test dish diameter of 75 mm and a weighed-in quantity of 2.00 g +/0.02.

[0117] The average isocyanate group functionality F of the allophanate polyisocyanate present in the polyisocyanate composition is determined in accordance with the following formula:

F(GPC)=Mn(GPC)% NCO(Titr.)/42/% NVC

wherein the NCO content is given in % by weight and is determined titrimetrically in accordance with DIN EN ISO 11909:2007-05, the average number molecular weight (Mn) is determined by gel permeation chromatography (GPC) in accordance with DIN 55672-1:2016-03 using polystyrene as standard and tetrahydrofuran as eluent, and the non-volatile content (NVC) is given in % by weight by testing method in accordance with DIN EN ISO 3251:2008-06 using a drying temperature and time of 2 hours at 120 C. and a test dish diameter of 75 mm and a weighed-in quantity of 2.00 g +/0.02.

[0118] The thinnability of polyisocyanates was evaluated by diluting tested products with ethyl acetate to an applied cup viscosity (16-18 by Chinese Tu 4-cup at 23 C.) according to Chinese standard GB/T 1723:1993, and then the non-volatile contents were measured according to the NVC determination method as described above. The drying properties of the coating systems were determined in accordance with DIN 53 150:2002-09.

[0119] Chemical substance used in the examples:

[0120] Polyether LP 112propylene glycol based polyether polyol with an OH value of 112 mg/g KOH, Mw 1000, functionality is 2; manufactured by Covestro AG

[0121] Desmophen 3170high functional polyether polyol with an OH value of 100 mg/g KOH, Mw 3350, functionality is 6; manufactured by Covestro AG

[0122] Polyether L 300bifunctional polyether polyol with an OH value of 190 mg/g KOH, Mw 590; manufactured by Covestro AG

[0123] Polyether L 800bifunctional polyether polyol with an OH value of 515 mg/g KOH, Mw 220; manufactured by Covestro AG

[0124] Desmophen 3600 Zbifunctional polyether polyol with an OH value of 56 mg/g KOH, Mw 2000; manufactured by Covestro AG

[0125] PolyTHF 1000bifunctional polytetrahydrofuran glycol with an OH value of 116 mg/g KOH, Mw 1000, manufactured by BASF SE

[0126] Arcol Polyol 1071trifunctional polyether polyol with an OH value of 235 mg/g KOH, Mw 716; manufactured by Covestro AG

[0127] Desmophen 1300 X, manufactured by Covestro AG, a fatty acid modified polyester polyol with an OH content of 3.2% by weight, and a non-volatile content of approx. 75%.

[0128] Desmodur L75urethane adduct, NCO % is 13.3%, viscosity at 23 C. is 1600 mPas, NVC % is 75.0%, manufactured by Covestro AG.

[0129] Desmodur IL 1351 EATDI isocyanurate, NCO % is 8.0%, viscosity at 23 C. is 350 mPas, NVC % is 51.0%, manufactured by Covestro AG.

[0130] Octa-Soligen Zinc 23manufactured by OMG Borchers GmbH.

[0131] Octa-Soligen Zinc 12manufactured by OMG Borchers GmbH.

[0132] Octa-Soligen Zirconium 18manufactured by OMG Borchers GmbH.

[0133] Borchi Kat 22manufactured by OMG Borchers GmbH.

[0134] Dodecylbenzenesulfonic acidNACURE 5076, manufactured by King Industries.

[0135] Dibutyl phosphatesupplied by Sigma-Aldrich (Shanghai) Trading Co., Ltd.

Example 1 (Inventive)

[0136] 1700 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 95 C., and 125 parts of diethylene glycol were added. After reaching an isocyanate (NCO) content of 39.6%, 0.05 parts of Octa-Soligen Zinc 23 were added into the reaction mixture to form allophanate, until the NCO content decreased to 36.7%. Then 0.08 parts of dibutylphosphate (DBP) were added to fully stop the reaction. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P1 with the following characteristics:

Isocyanate group content: 14.4%
Non-volatile content: 73.8%
Viscosity: 921 mPas

Free TDI %: 0.45%

[0137] Allophanate %: 61.0 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=4.1

Example 2 (Comparative)

[0138] 1700 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 95 C., and 125 parts of diethylene glycol was added. After reaching an isocyanate (NCO) content of 39.6%, 0.018 parts of Octa-Soligen Zinc 23 were added into the reaction mixture to react till NCO content decreased to 36.4%. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P2 with the following characteristics:

Isocyanate group content: 14.0%
Non-volatile content: 73.1%
Viscosity: 1343 mPas

Free TDI %: 1.68%

[0139] Allophanate %: 61.7 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=4.2

[0140]

TABLE-US-00001 TABLE 1 Storage stability at 50 C., increase of free TDI over time Polyisocyanate TDI %/ TDI %/ TDI %/ composition Stopper 0 days 15 days 22 days P1 DBP 0.45 0.53 0.53 P2 no deactivation 1.68 1.89 2.39

Example 3 (Comparative)

[0141] 4000 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 41 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 271 parts of diethylene glycol was added. After reaching an isocyanate (NCO) content of 40.13%, 4.12 parts of Octa-Soligen Zinc 12 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and heated up to 95 C. to react until NCO content decreased to 35.8%. Next, 0.12 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P3 with the following characteristics:

Isocyanate group content: 12.6%
Non-volatile content: 74.5%
Viscosity: 21770 mPas

Free TDI %: 4.11%

[0142] Allophanate %: 76.6 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=4.3

Example 4 (Inventive)

[0143] 1000 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 73.5 parts of diethylene glycol was added. After reaching an isocyanate (NCO) content of 39.4%, 0.53 parts of Octa-Soligen Zinc 12 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and heated up to 95 C. to react till NCO content decreased to 37.9%. 0.15 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P4 with the following characteristics:

Isocyanate group content: 13.9%
Non-volatile content: 74.9%
Viscosity: 450 mPas

Free TDI %: 0.19%

[0144] Allophanate %: 32.2 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=3.0

Example 5 (Inventive)

[0145] 1700 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 103.5 parts of diethylene glycol were added. After reaching an isocyanate (NCO) content of 40.6%, 0.0782 parts of Octa-Soligen Zinc 12 were added into the reaction mixture and heated up to 95 C. to react until NCO content decreased to 36.8%. 0.2 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P5 with the following characteristics:

Isocyanate group content: 14.4%
Non-volatile content: 73.7%
Viscosity: 1181 mPas

Free TDI %: 0.32%

[0146] Allophanate %: 87.7 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=4.7

Example 6 (Inventive)

[0147] 1700 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 125 parts of diethylene glycol were added. After reaching an isocyanate (NCO) content of 39.6%, the reaction temperature was increased to 95 C., and 0.041 parts of Octa-Soligen Zinc 12 were added into the resulted reaction mixture and reacted till NCO contend decreased to 37.5%. 0.125 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P6 with the following characteristics:

Isocyanate group content: 14.0%
Non-volatile content: 73.7%
Viscosity: 367 mPas

Free TDI %: 0.27%

[0148] Allophanate %: 39.2 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=3.5

Example 7 (Inventive)

[0149] 1600 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 2 L flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 108 parts of diethylene glycol was added. After reaching an isocyanate (NCO) content of 40.1%, 0.0.31 parts of Octa-Soligen Zirconium 18 were added into the resulted reaction mixture and heated up to 100 C. to react till NCO content decreased to 35.2%. 0.34 parts of dibutyl phosphate (DBP) were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P7 with the following characteristics:

Isocyanate group content: 14.5%
Non-volatile content: 74.0%
Viscosity: 1483 mPas

Free TDI %: 0.45%

[0150] Allophanate %: 55.9 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 10.6 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=3.8

Example 8 (Inventive)

[0151] 1700 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and a mixture of 120 parts of diethylene glycol and 50 parts of Arcol Polyol 1071 were added. After reaching an isocyanate (NCO) content of 37.8%, 1.82 parts of Borchi Kat 22 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and heated up to 100 C. to react till NCO content decreased to 32.4%. 0.48 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P8 with the following characteristics:

Isocyanate group content: 12.8%
Non-volatile content: 71.2%
Viscosity: 1966 mPas

Free TDJ %: 0.38%

[0152] Allophanate %: 56.8 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=4.2

Example 9 (Inventive)

[0153] 800 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 11 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 200 parts of Polyether L800 were added. After reaching an isocyanate (NCO) content of 30.2%, 0.69 parts of Octa-Soligen Zinc 12 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and heated up to 95 C. to react till NCO content decreased to 26.6%. 0.29 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P9 with the following characteristics:

Isocyanate group content: 11.3%
Non-volatile content: 74.7%
Viscosity: 536 mPas

Free TDI %: 0.23%

[0154] Allophanate %: 47.6 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=3.7

Example 10 (Inventive)

[0155] 1411 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture were heated to 85 C., a mixture of 91.5 parts of trimethylolpropane (TMP) and 46.5 parts of diethylene glycol (DEG) were added. After reaching an isocyanate (NCO) content of 35.5%, 0.26 parts of Borchi Kat 22 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and heated up to 98 C. to react till NCO content decreased to 34.5%. 0.17 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P10 with the following characteristics:

Isocyanate group content: 15.7%
Non-volatile content: 71.9%
Viscosity: 988 mPas

Free TDI %: 0.32%

[0156] Allophanate %: 15.0 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=3.9

Example 11 (Inventive)

[0157] 900 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 575 parts of Polyether LP 112 were added. After reaching an isocyanate (NCO) content of 25.8%, the reaction temperature was increased to 95 C., and 1.33 parts of Borchi Kat 22 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and reacted till NCO contend decreased to 22.7%. 0.75 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P11 with the following characteristics:

Isocyanate group content: 7.2%
Non-volatile content: 76.1%
Viscosity: 223 mPas

Free TDI %: 0.14%

[0158] Allophanate %: 77.0 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=4.9

Example 12 (Inventive)

[0159] 820 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 11 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 150 parts of Desmophen 3170 were added. After reaching an isocyanate (NCO) content of 39.6%, the reaction temperature was increased to 95 C., and 1.4 parts of Octa-Soligen Zinc 12 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and reacted till NCO content decreased to 38.8%. 0.39 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P12 with the following characteristics:

Isocyanate group content: 5.8%
Non-volatile content: 66.4%
Viscosity: 225 mPas

Free TDI %: 0.49%

[0160] Allophanate %: 63.7 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=5.9

Example 13 (Inventive)

[0161] 560 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 1 L flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 380 parts of Polyether L 300 was added. After reaching an isocyanate (NCO) content of 22.7%, the reaction temperature was increased to 95 C., and 2.4 parts of Octa-Soligen Zinc 12 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and reacted till NCO content decreased to 18.5%. 0.60 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P13 with the following characteristics:

Isocyanate group content: 8.2%
Non-volatile content: 73.8%
Viscosity: 228 mPas

Free TDI %: 0.13%

[0162] Allophanate %: 53.7 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=3.6

Example 14 (Inventive)

[0163] 599 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 21 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 767 parts of Desmophen 3600 Z were added. After reaching an isocyanate (NCO) content of 18.4%, the reaction temperature was increased to 95 C., and 3.31 parts of Borchi Kat 22 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and reacted till NCO content decreased to 16.5%. 1.70 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P14 with the following characteristics:

Isocyanate group content: 4.3%
Non-volatile content: 74.5%
Viscosity: 135 mPas

Free TDI %: 0.06%

[0164] Allophanate %: 62.5 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=4.2

Example 15 (Inventive)

[0165] 600 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 11 flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C., and 383 parts of PolyTHF 1000 were added. After reaching an isocyanate (NCO) content of 25.7%, the reaction temperature was increased to 98 C., and 2.70 parts of Borchi Kat 22 (10% solution in 2-ethylhexane-1,3-diol) were added into the reaction mixture and reacted till NCO contend decreased to 21.8%. 1.83 parts of dodecylbenzenesulfonic acid were added to deactivate the catalyst. The excess monomeric isocyanate was then removed under reduced pressure. The obtained resin was dissolved in ethyl acetate to get a polyisocyanate composition P15 with the following characteristics:

Isocyanate group content: 5.5%
Non-volatile content: 74.9%
Viscosity: 1133 mPas

Free TDJ %: 0.43%

[0166] Allophanate %: 58.3 mol-% (=molar share of allophanate/(allophanate+urethane+isocyanurate groups))
Isocyanurate %: 0 mol-% (=molar share of isocyanurate/(allophanate+urethane+isocyanurate groups))

F(GPC)=6.4

Thinnability Evaluation:

[0167] As the key component of a two-component polyurethane coating or adhesive formulation, the thinnability of a polyisocyanate crosslinker is a very important requirement for low VOC coating development. In order to evaluate the thinnability of the synthesized allophanate polyisocyanates, ethyl acetate was added to dilute the obtained products to a given viscosity (16-18, T4-cup at 23 C.) according to ASTM D 1200-2010. Then the non-volatile content was measured according to DIN EN ISO 3251:2008-06. Resulting non-volatile contents (NVC) are summarized in Table 2.

TABLE-US-00002 TABLE 2 Thinnability comparison of different polyisocyanate compositions Desmodur L75/ Desmodur Desmodur IL 1351 Polyisocyanate L75 (70:30 by weight) composition (comparative) P4 P6 P7 P9 P10 (comparative) Viscosity after 1689 1607 1734 1609 1790 1755 1706 dilution NVC % 56 60 58 55 60 57 47

[0168] It is clearly shown that by introducing allophanate groups into the product the thinnability could be kept or even improved, while compared to that of the market standard Desmodur L75 (Covestro AG).

Application Testing:

[0169] For polyisocyanate compositions P4-P10, Desmodur L75 and the mixture Desmodur L75/Desmodur IL 1351 (70:30 by weight), drying performance was tested by blending with Desmophen 1300 X (manufactured by Covestro AG, fatty acid modified polyester polyol with OH content of 3.2% by weight and a non-volatile content of approx. 75%) as NCO-reactive component B). The molar ratio of isocyanate groups to hydroxyl groups was 1:1 and the solid content of the final formulation was 40% by weight, after further diluting with butyl acetate. After being mixed together homogenously, the mixture was immediately applied onto transparent glass panels using a film applicator at a thickness of wet film of 120 m) and was allowed to dry at 23.5 C. and a humidity of 50%. The drying speed was measured according to DIN 53 150:2002-09 and the obtained results were summarized in Table 3.

TABLE-US-00003 TABLE 3 Drying speed of different two-component systems Polyisocyanate Desmodur L75/ composition Desmodur IL 1351 used in two- Desmodur L75 (70:30 by weight) component system (comparative) P4 P5 P6 P7 P8 P9 P10 (comparative) Polyisocyanate 6.0 6.0 6.0 6.0 8.0 5.0 8.0 8.0 67.1 Desmophen 12.9 10.5 10.9 13.3 15.7 8.1 11.4 15.3 100 1300 X Butyl acetate 16.5 14.5 14.6 16.7 21.5 11.0 17.0 20.3 85.0 Drying speed T1 (min) 10 13 11 9 13 11 11 12 11 T3 (min) 239 183 65 240 58 106 182 150 107 T4 (min) 333 227 100 305 130 183 244 269 145

[0170] The experimental results in table 3 show that the use of the inventive allophanate polyisocyanates in two-component systems leads to the surprising effect of a fast drying speed while keeping beneficial thinnability as well as a high solids content.