Hydroxyaldimine and curable polyurethane composition with a low monomeric isocyanate content

Abstract

Hydroxyaldimines of formula (I), their reaction products, in particular products of their reaction with polyisocyanates, and compositions including isocyanate groups and containing such reaction products. The hydroxyaldimine permits compositions which have good storage stability, a long open time, low odour, rapid, bubble-free curing and good mechanical properties, and which are not susceptible to plasticizer migration and have a particularly low content of monomeric diisocyanates. In particular, it permits reactive hot-melt adhesives with a particularly good workability.

Claims

1. A hydroxyaldimine of the formula (I) ##STR00011## wherein A is a divalent aliphatic or cycloaliphatic or arylaliphatic hydrocarbyl radical optionally containing ether oxygen and having a molecular weight in a range of from 28 to 500 g/mol, and Z is a radical of the formula (II): ##STR00012## where R is a radical of the formula ##STR00013## R.sup.1 and R.sup.2 are each an alkyl radical and together have 9 to 13 carbon atoms.

2. The hydroxyaldimine as claimed in claim 1, wherein A is selected from the group consisting of 1,2-ethylene, 1,2-propylene, 1,3-propylene, 1,5-pentylene, 1,6-hexylene, (1,5,5-trimethylcyclohexan-l-yl)methane-1,3 , and 3-oxa-1,5-pentylene.

3. A reaction product containing at least one of the hydroxyaldimine as claimed in claim 1, obtained from a reaction of at least one amine of the formula (III) with at least one aldehyde of the formula (IV) in a condensation reaction with release of water, wherein the at least one aldehyde was present stoichiometrically or in a stoichiometric excess in relation to the primary amino groups, and the formulae (III) and (IV) are: ##STR00014##

4. A mixture including two or more of the hydroxyaldimines as claimed in claim 1, wherein R is selected from the group consisting of branched decyl, undecyl, dodecyl, tridecyl, and tetradecyl radicals.

5. A reaction product having aldimino groups of the formula (V) ##STR00015## obtained from a reaction of at least one of the hydroxyaldimine as claimed in claim 1 with at least one polyisocyanate.

6. The reaction product as claimed in claim 5, further comprising isocyanate groups , and an OH/NCO ratio in the reaction is in a range of from 0.05/1 to 0.5/1.

7. The reaction product as claimed in claim 5, wherein the reaction product is free of isocyanate groups and an OH/NCO ratio in the reaction is in a range of from 1/1 to 1.5/1.

8. A composition containing isocyanate groups, comprising at least one of the reaction product as claimed in claim 5.

9. The composition as claimed in claim 8, further comprising at least one ingredient selected from the group consisting of catalysts, fillers, plasticizers, and solvents.

10. The composition as claimed in claim 8, wherein the composition is an adhesive or a sealant or a coating.

11. The composition as claimed in claim 10, wherein the composition is a reactive hotmelt adhesive.

12. A method of reducing content of monomeric diisocyanates in a polyurethane polymer containing isocyanate groups by reacting it in a substoichiometric OH/NCO ratio with at least one of the hydroxyaldimine as claimed in claim 1, with exclusion of moisture.

13. The hydroxyaldimine as claimed in claim 1, wherein A is 3-oxa-1,5-pentylene or (1,5,5-trimethylcyclohexan-l-yl)methane-1,3.

14. The hydroxyaldimine as claimed in claim 1, wherein A is (1,5,5-trimethylcyclohexan-l-yl)methane-1,3.

15. The mixture as claimed in claim 4, wherein A is 3-oxa-1,5-pentylene or (1,5,5-trimethylcyclohexan-l-yl)methane-1,3.

16. The mixture as claimed in claim 4, wherein A is (1,5,5-trimethylcyclohexan-l-yl)methane-1,3.

Description

EXAMPLES

(1) Adduced hereinafter are working examples which are intended to elucidate the invention described in detail. It will be appreciated that the invention is not restricted to these described working examples.

(2) Aldehydes Used: Aldehyde-1: Fractionated reaction mixture obtained from formylation, catalyzed by means of HF—BF.sub.3, of C.sub.10-14-alkylbenzene, containing mainly branched 4-(C.sub.10-14-alkyl)benzaldehydes. (mean aldehyde equivalent weight 290 g/eq) 2,2-Dimethyl-3-lauroyloxypropanal Aldehyde-1 is a mixture of aldehydes of the formula (IV). 2,2-Dimethyl-3-lauroyloxypropanal serves as a comparison.

(3) Preparation of Hydroxyaldimines:

(4) The amine value (including aldimino groups) was determined by means of titration (with 0.1 N HClO.sub.4 in acetic acid versus crystal violet).

(5) The viscosity was measured with a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 50 mm, cone angle 1°, cone tip-plate distance 0.05 mm, shear rate 10 s.sup.−1).

(6) Hydroxyaldimine A1:

(7) 25.00 g of aldehyde-1 were initially charged in a round-bottom flask under a nitrogen atmosphere. While stirring, 8.60 g of 2-(2-aminoethoxy)ethanol were added and then the volatile constituents were removed at 80° C. and a reduced pressure at 10 mbar. A pale yellow, odorless and pH-neutral liquid having a viscosity at 20° C. of 0.4 Pa.Math.s and an amine value of 142.9 mg KOH/g was obtained.

(8) Hydroxyaldimine A2:

(9) 25.00 g of aldehyde-1 were initially charged in a round-bottom flask under a nitrogen atmosphere. While stirring, 14.02 g of 3-aminomethyl-3,5,5-trimethylcyclohexanol were added and then the volatile constituents were removed at 80° C. and a reduced pressure at 10 mbar. A pale yellow, odorless and pH-neutral liquid having a viscosity at 20° C. of 34.3 Pa.Math.s and an amine value of 122.3 mg KOH/g was obtained.

(10) Hydroxyaldimine R1:

(11) 24.46 g of 2,2-dimethyl-3-lauroyloxypropanal were initially charged in a round-bottom flask under a nitrogen atmosphere. While stirring, 8.60 g of 2-(2-aminoethoxy)ethanol were added and then the volatile constituents were removed at 80° C. and a reduced pressure at 10 mbar. An almost colorless, odorless liquid having an amine value of 144.3 mg KOH/g was obtained.

(12) Hydroxyaldimine R2:

(13) 24.46 g of 2,2-dimethyl-3-lauroyloxypropanal were initially charged in a round-bottom flask under a nitrogen atmosphere. While stirring, 14.02 g of 3-aminomethyl-3,5,5-trimethylcyclohexanol were added and then the volatile constituents were removed at 80° C. and a reduced pressure at 10 mbar. A pale yellow, odorless liquid having an amine value of 124.2 mg KOH/g was obtained.

(14) The hydroxyaldimines A1 and A2 are hydroxyaldimines of the formula (I) and are inventive examples. The hydroxyaldimines R1 and R2 are comparative examples.

(15) Preparation of Polymers Containing Isocyanate Groups

(16) Polymer P1:

(17) 4000 g of polyoxypropylenediol (Acclaim® 4200, from Covestro; OH number 28.5 mg KOH/g) and 520 g of diphenylmethane 4,4′-diisocyanate (Desmodur® 44 MC L, from Covestro) were reacted by a known method at 80° C. to give an NCO-terminated polyurethane polymer which is liquid at room temperature and has a content of free isocyanate groups of 1.85% by weight.

(18) Polymer P2:

(19) 300.0 g of polyoxypropylenepolyoxyethylenediol (Desmophen® L300, from Covestro; OH number 190.0 mg KOH/g) and 228.8 g of isophorone diisocyanate (Vestanat® IPDI, Degussa) were reacted by a known method at 60° C. to give an NCO-terminated polyurethane polymer which is liquid at room temperature and has a content of free isocyanate groups of 8.35% by weight.

(20) Preparation of Reaction Products of the Hydroxyaldimines:

(21) Reaction Product U1:

(22) 227.30 g (about 100 mmol NCO) of polymer P1, 9.41 g (about 24 mmol) of hydroxyaldimine A1 and 0.13 g of Coscat® 83 (Bi(III) neodecanoate, from Vertellus) were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(23) Reaction Product U2:

(24) 227.30 g (about 100 mmol NCO) of polymer P1, 11.02 g (about 24 mmol) of hydroxyaldimine A2 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(25) Reaction Product U3:

(26) 227.30 g (about 100 mmol NCO) of polymer P1, 18.82 g (about 48 mmol) of hydroxyaldimine A1 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(27) Reaction Product U4:

(28) 227.30 g (about 100 mmol NCO) of polymer P1, 22.05 g (about 48 mmol) of hydroxyaldimine A2 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(29) Reaction Product U5:

(30) 227.30 g (about 100 mmol NCO) of polymer P1, 39.61 g (about 101 mmol) of hydroxyaldimine A1 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino groups and was free of isocyanate groups was obtained.

(31) Reaction Product U6:

(32) 227.30 g (about 100 mmol NCO) of polymer P1, 46.42 g (about 101 mmol) of hydroxyaldimine A2 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino groups and was free of isocyanate groups was obtained.

(33) Reaction Product U7:

(34) 60.00 g (about 115 mmol NCO) of polymer P3, 15.82 g (about 40.4 mmol) of hydroxyaldimine A1 and 0.05 g of Coscat® 83 were mixed in a honey jar under argon and then left to react in an air circulation oven at 60° C. for 16 hours. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(35) Reaction Product U8:

(36) 60.00 g (about 115 mmol NCO) of polymer P3, 18.51 g (about 40.4 mmol) of hydroxyaldimine A2 and 0.05 g of Coscat® 83 were mixed in a honey jar under argon and then left to react in an air circulation oven at 60° C. for 16 hours. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(37) Reaction Product Q1:

(38) 227.30 g (about 100 mmol NCO) of polymer P1, 9.33 g (about 24 mmol) of hydroxyaldimine R1 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(39) Reaction product Q2:

(40) 227.30 g (about 100 mmol NCO) of polymer P1, 10.84 g (about 24 mmol) of hydroxyaldimine R2 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(41) Reaction Product Q3:

(42) 227.30 g (about 100 mmol NCO) of polymer P1, 18.66 g (about 48 mmol) of hydroxyaldimine R1 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(43) Reaction Product Q4:

(44) 227.30 g (about 100 mmol NCO) of polymer P1, 21.68 g (about 48 mmol) of hydroxyaldimine R2 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(45) Reaction Product Q5:

(46) 227.30 g (about 100 mmol NCO) of polymer P1, 39.26 g (about 101 mmol) of hydroxyaldimine R1 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino groups and was free of isocyanate groups was obtained.

(47) Reaction Product Q6:

(48) 227.30 g (about 100 mmol NCO) of polymer P1, 45.62 g (about 101 mmol) of hydroxyaldimine R2 and 0.13 g of Coscat® 83 were stirred in a planetary mixer under reduced pressure at 70° C. for 90 minutes. A clear reaction product which is liquid at room temperature and has aldimino groups and was free of isocyanate groups was obtained.

(49) Reaction Product Q7:

(50) 60.00 g (about 115 mmol NCO) of polymer P3, 15.69 g (about 40.4 mmol) of hydroxyaldimine R1 and 0.05 g of Coscat® 83 were mixed in a honey jar under argon and then left to react in an air circulation oven at 60° C. for 16 hours. A clear reaction product which is liquid at room temperature and has aldimino and isocyanate groups was obtained.

(51) The reaction products U1 to U8 are reaction products having aldimino groups of the formula (V) and are inventive examples. The reaction products Q1 to Q7 are comparative examples.

(52) Content of Monomeric Diisocyanates

(53) 14 days after production, the content of monomeric 4,4′-MDI in polymer P1 and in some reaction products thereof was determined by means of HPLC (detection via photodiode array; 0.04 M sodium acetate/acetonitrile as mobile phase). The results are reported in table 1.

(54) TABLE-US-00001 TABLE 1 4,4′-MDI content Polymer P1 2.52% by weight Reaction product U1 0.99% by weight Reaction product U3 0.35% by weight Reaction product Q1 1.88% by weight Reaction product Q3 0.20% by weight

(55) One-Component Compositions

(56) Compositions Z1 to Z3 and Ref1 to Ref3

(57) For each composition, the ingredients specified in table 2 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute and stored with exclusion of moisture. Each composition was tested as follows:

(58) As a measure of storage stability, the Viscosity (1d RT) was determined the day after production, and the Viscosity (7d 60° C.) after storage in a closed container in an air circulation oven at 60° C. for 7 days. The viscosity was measured, at a temperature of 20° C. in each case, with a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 50 mm, cone angle 1°, cone tip-plate distance 0.05 mm, shear rate 10 s.sup.−1).

(59) As a measure of the open time, the Tack-free time was determined. For this purpose, a few grams of the composition were applied to cardboard in a layer thickness of about 2 mm and, under standard climatic conditions, the time until, when the surface of the composition was gently tapped by means of an LDPE pipette, there were for the first time no residues remaining any longer on the pipette was determined.

(60) To determine the mechanical properties, each composition was poured onto a PTFE-coated film to give a film of thickness 2 mm and stored under standard climatic conditions for 7 days, and a few dumbbells having a length of 75 mm with a bar length of 30 mm and a bar width of 4 mm were punched out of the film and these were tested in accordance with DIN EN 53504 at a strain rate of 200 mm/minute for Tensile strength (breaking force), Elongation at break, Modulus of elasticity 5% (at 0.5-5% elongation) and Modulus of elasticity 50% (at 0.5-50% elongation).

(61) Appearance was assessed visually on the films produced. “Nice” was used to describe a clear film with a nontacky surface without blisters.

(62) Odor was assessed by smelling by nose at a distance of 2 cm from the freshly produced films. “No” means that no odor was perceptible.

(63) The results are reported in table 2.

(64) Compositions Z1 to Z3 are inventive examples. Compositions Ref1 to Ref3 are comparative examples.

(65) TABLE-US-00002 TABLE 2 Composition (in parts by weight) and properties of Z1 to Z3 and Ref1 to Ref3. Composition Z1 Ref1 Z2 Ref2 Z3 Ref3 Reaction product U1 Q1 U2 Q2 U4 Q4 80.00 80.00 80.00 80.00 80.00 80.00 Salicylic acid 1.50 0.50 1.50 0.50 1.50 0.50 solution.sup.1 Viscosity (1 d RT) 201 77 73 82 121 137 [Pa .Math. s] (7 d 60° C.) 371 94 98 104 148 180 Tack-free time 195′ 400′ 165′ 195′ 45′ 45′ Tensile strength 3.41 5.51 1.16 0.60 0.57 0.69 [MPa] Elongation at break 946 >1200 >1200 494 >1200 >1200 [%] Modulus of elasticity 1.33 1.32 0.85 0.91 0.76 0.58 5% [MPa] Modulus of elasticity 0.70 0.67 0.48 0.53 0.39 0.28 50% Appearance nice nice nice nice nice nice Odor no no no no no no .sup.15% in dioctyl adipate

(66) Compositions Z4 and Z5 and Ref4

(67) For each composition, the ingredients specified in table 3 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute and stored with exclusion of moisture. Each composition was tested as follows:

(68) As a measure of plasticizer migration, each composition was applied to a cardboard underlayer such that it had a round base area of diameter 12 mm and a height of 20 mm, and was stored under standard climatic conditions for 7 days. Around each composition, thereafter, a dark oval speck had formed on the cardboard. The dimensions thereof (height and width) were measured and reported in table 3 as Migration.

(69) Compositions Z4 and Z5 are inventive examples. Composition Ref4 is a comparative example.

(70) TABLE-US-00003 TABLE 3 Composition (in parts by weight) and properties of Z4 and Z5 and Ref4. Composition Z4 Z5 Ref4 Reaction product U7 U8 Q7 25.0 25.0 25.0 Chalk.sup.1 25.0 25.0 25.0 Silica.sup.2 1.9 1.9 1.9 Dibutyltin dilaurate.sup.3 2.5 2.5 2.5 Salicylic acid.sup.4 5.0 5.0 5.0 Migration Height 1 1 8 [mm] Width 1 1 6 .sup.1ground calcium carbonate coated with fatty acid .sup.2hydrophobically modified fumed silica .sup.35% in diisodecyl phthalate .sup.45% in dioctyl adipate

(71) Two-Component Compositions

(72) Compositions Z6 and Z7 and Ref5 and Ref6

(73) For each composition, the ingredients specified in table 4 were mixed in the specified amounts (in parts by weight) of the first component K1 by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) and stored with exclusion of moisture.

(74) As the second component K2, Desmodur® N 3300 (HDI trimer having an NCO content of 21.8% by weight, from Covestro) was used in the amount specified in table 4 (in parts by weight).

(75) Subsequently, the two components of each composition were processed by means of centrifugal mixer to give a homogeneous liquid and this was tested immediately as described for the composition Z1.

(76) The results are reported in table 4.

(77) Compositions Z6 and Z7 are inventive examples. Compositions Ref5 and Ref6 are comparative examples.

(78) TABLE-US-00004 TABLE 4 Composition (in parts by weight) and properties of Z6 and Z7 and Ref5 and Ref6. Composition Z6 Ref5 Z7 Ref6 Component K1: Reaction product U5 Q5 U6 Q6 75.00 75.00 75.00 75.00 Salicylic acid solution.sup.1 1.50 0.50 1.50 0.50 Component K2: Desmodur ® N 3300 6.83 6.79 6.67 6.74 Tack-free time 55′ 45′ 70′ 70′ Tensile strength [MPa] 1.60 1.80 1.66 1.88 Elongation at break [%] 127 150 161 202 Modulus of elasticity 5% 2.29 2.32 1.15 0.72 [MPa] Modulus of elasticity 50% 1.53 1.51 0.85 0.54 [MPa] Appearance nice nice nice nice Odor no no no no .sup.15% in dioctyl adipate

(79) Reactive Hotmelt Adhesives

(80) Adhesives H1 and HR1 and HR2:

(81) A mixture of 30.6 g of polyoxypropylenediol (OH number 56.0 mg KOH/g), 7.2 g of polyoxypropylenediol (OH number 112.5.0 mg KOH/g) and 23.4 g of room temperature-solid acrylate polymer (copolymer of methyl methacrylate and n-butyl methacrylate) was heated up to 140° C. under reduced pressure with stirring until the acrylate polymer had completely dissolved. Then 18.0 g of room temperature-crystalline, linear polyester diol (formed from hexanediol and adipic acid; OH number 28.0 mg KOH/g) were added and the mixture was stirred at 140° C. under reduced pressure for 1 h. Subsequently, 13.6 g of diphenylmethane 4,4′-diisocyanate (Desmodur® 44 MC L, from Covestro) were added and the mixture was stirred at 140° C. under reduced pressure for 30 minutes. Then either 7.2 g of hydroxyaldimine A1 (adhesive H1) or 7.2 g of hydroxyaldimine R1 (adhesive HR1) or neither (adhesive HR2) were added and the mixture was stirred at 140° C. under reduced pressure for a further 30 minutes, before being cooled and stored with exclusion of moisture.

(82) Each adhesive was tested as follows:

(83) 4,4′-MDI content was determined by means of HPLC (detection via photodiode array; 0.04 M sodium acetate/acetonitrile as mobile phase).

(84) Viscosity was determined the day after production by Brookfield Thermosel at 5 rpm with spindle 27 at the specified temperature and referred to as “Viscosity (fresh)”.

(85) In the determination of the early strength and mechanical properties, the respective hotmelt adhesive was applied at 150° C. to silicone paper and left to cool, so as to form a film of thickness 500 μm. Test specimens of 20×100 mm were cut out of this and stored under standard climatic conditions. After 30 min, Tensile strength (measure of early strength) was determined for a first time, then again the tensile strength and Elongation at break after 14 days, each in accordance with DIN EN 53504 at a strain rate of 10 mm/min.

(86) To determine Thermal stability in the molten state with ambient humidity, the adhesive was left to rotate under standard climatic conditions on an open roll at a temperature of 140° C. Viscosity was measured at regular intervals (Brookfield Thermosel, 5 rpm, spindle 27).

(87) The results are reported in table 5.

(88) Adhesive H1 is an inventive example. Adhesives HR1 and HR2 are comparative examples.

(89) TABLE-US-00005 TABLE 5 Properties of adhesives H1, HR1 and HR2. Adhesive H1 HR1 HR2 Hydroxyaldimine added A1 R1 — 4,4′-MDI content 0.28% by weight 0.12% by weight 1.90% by weight Viscosity (fresh) at 140° C. 0.3 Pa .Math. s 3.5 Pa .Math. s 0.5 Pa .Math. s Tensile strength (after 30′) 0.35 MPa 0.61 MPa <0.3 MPa Tensile strength (after 14 d) 6.9 MPa 6.0 MPa n.d.* Elongation at break (after 14 d) 590% 530% n.d.* Viscosity (140° C.) after  0.5 h 0.3 Pa .Math. s 3.7 Pa .Math. s 0.5 Pa .Math. s  1.0 h 0.3 Pa .Math. s 4.4 Pa .Math. s n.d.  1.5 h 0.3 Pa .Math. s 6.8 Pa .Math. s n.d.  2.0 h 0.3 Pa .Math. s 7.1 Pa .Math. s n.d.  2.5 h 0.3 Pa .Math. s 7.6 Pa .Math. s n.d.  3.0 h 0.3 Pa .Math. s 8.0 Pa .Math. s n.d.  3.5 h 0.3 Pa .Math. s 12.4 Pa .Math. s n.d.  4.0 h 0.3 Pa .Math. s 16.6 Pa .Math. s n.d.  4.5 h 0.3 Pa .Math. s 24.7 Pa .Math. s 0.6 Pa .Math. s  5.0 h 0.3 Pa .Math. s n.m. n.d.  8.0 h 0.3 Pa .Math. s n.m. n.d.  9.0 h 0.3 Pa .Math. s n.m. n.d. 10.0 h 2.0 Pa .Math. s n.m. n.d. 12.0 h 4.7 Pa .Math. s n.m. n.d. 14.0 h 5.4 Pa .Math. s n.m. n.d. 16.0 h 4.8 Pa .Math. s n.m. 2.2 Pa .Math. s “n.m.” means “not measurable” (viscosity too high/gelated). “n.d.” means “not measured”. *blisters in the film