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Description of key information

The registration substance is a UVCB substance containing many constituents, the constituents of the substance are methoxy-, ethoxy- or mixed methoxy/ethoxy silanes and methanol/ethanol.

Since the registration substance is a UVCB substance, two aspects need to be considered in relation to physicochemical properties:

1) In the context of raw material handling and safe use, it is important to understand the properties of the product/substance as a whole as discussed below:

The substance is a liquid at room temperature and pressure, with a measured melting point of <-180°C at 1013 hPa and a measured boiling point of 101°C at 1013 hPa. It has a measured relative density of 0.998 at 22.1°C and a measured kinematic viscosity value of 1.77 mm2/s at 25°C. A calculated vapour pressure of 1200 Pa at 25°C is used for assessment purposes; this value determined for the whole substance based on predicted vapour pressures for individual constituents and the mole fraction of each constituent in the substance.

 

The substance is classified for flammability (Flammable Liquid Category 2) according to Regulation (EC) No. 1272/2008, on the basis of a measured flash point of 8°C at 1013 hPa and boiling point of 101°C at 1013 hPa. It has a measured auto-ignition temperature of 270°C at 1023.3-1035 hPa, and is not explosive and not oxidising on the basis of examination of the structure. Also, none of the constituents of the substance are expected to be surface active.

2) For the purposes of assessing environmental fate and behaviour, in the environment, individual constituents may behave independently of each other. It is therefore essential to consider the properties of individual constituents and a whole property data may have no real scientific meaning or significance.

The properties of the constituents have been measured or estimated using appropriate methods. In solution, the amine groups present in some of the constituents will protonate; therefore, the estimated log Kow values for the unionised form of the constituents were corrected for ionisation using the equation CORR = 1/1 +10A(pH-pKa) [where A = 1 for acids, -1 for bases; pH = pH-value of the environment; pKa = acid/base dissociation constant].

Where there is more than one constituent within a constituent Block, the weighted average of the constituents in the Block was calculated and the calculated weighted average used for the Chemical Safety Assessment (CSA).

The pKa values for the alkylamine groups are estimated as approximately 10, therefore, the ionised (protonated) form predominates at environmentally relevant pH values.

The key physicochemical data for each constituent and the weighted average for each constituent Block where relevant are reported in the table below.

 

Table: Key physicochemical properties of parent constituents of the substance

Constituent

SMILES

Molecular weight (g/mol)

Vapour pressure (parent) - Pa

Water solubility (parent) mg/L

log Kow (parent)- corrected for amine ionisation

Hydrolysis half-lives

Constituent A1 (trimethoxy)

CO[Si](OC)(OC)C

136.22

2100

9.1E+04

0.7*

<0.033 h at pH 4, 2.2 h at pH 7 and 0.11 h at pH 9 and 25°C (OECD 111)

Constituent A2 (ethoxy)

CCO[Si](OC)(OC)C

150.25

850

2.9E+04

1.2*

0.1 h at pH 4, 1.6 h at pH 7, and 0.03 h at pH 9 and 20-25°C (QSAR)

Constituent A3 (diethoxy)

CCO[Si](OCC)(OC)C

164.28

295

9.2E+03

1.7*

0.2 h at pH 4, 3.1 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent A4 (triethoxy)

CCO[Si](OCC)(OCC)C

178.31

103

2.9E+3

2.2*

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Weighted average for Constituents A

 

 

1400

5.9E+4

1.0

0.1 h at pH 4, 2.0 h at pH 7, and 0.1 h at pH 9 and 20-25°C

Constituent B1 (methoxy)

NCCC[Si](OC)(OC)OC

179.29

18.5

5.7E+5

1.7**

pH 2 = -4, pH 4 = -4, pH 7 = -1.3, pH 9 = 0.7

0.2 h at pH 4, 2.6 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent B2 (ethoxy)

NCCC[Si](OCC)(OC)OC

193.32

6.7

1.8E+5

-0.2**

pH 2 = -4, pH 4 = -4, pH 7 = -2.8, pH 9 = -0.8

0.3 h at pH 4, 5.5 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent B3 (diethoxy)

 

NCCC[Si](OCC)(OCC)OC

207.34

2.5

5.5E+4

0.7**

pH 2 = -4, pH 4 = -4, pH 7 = -2.3, pH 9 = -0.3

0.8 h at pH 5, 8.5 h at pH 7, and 0.15 h at pH 9 and 24.7°C (Read-across from Constituent B4)

Constituent B4

NCCC[Si](OCC)(OCC)OCC

221.37

0.94

1.7E+4

1.2**

pH 2 = -4, pH 4 = -4, pH 7 = -1.8, pH 9 = 0.2

0.8 h at pH 5, 8.5 h at pH 7, and 0.15 h at pH 9 and 24.7°C (OECD 111)

Weighted average for Constituents B

 

 

11.0

3.2E+5

-2.4 at pH 7

0.3 h at pH 4, 4.8 h at pH 7, and 0.1 h at pH 9 and 20-25°C

Constituent C1

 

CO[Si](CCCOCC1CNCCC[Si](O1)(OC)OC)(OC)OC

383.59

5.9E-4

2.3E+5

-0.3**

pH 2 = -4, pH 4 = -4, pH 7 = -3.3, pH 9 = -1.3

0.4 h at pH 4, 7.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent C2 (ethoxy)

CCO[Si]1(OC)CCCNCC(O1)COCCC[Si](OC)(OC)OC

397.62

4.8E-4

6.9E+4

0.2**

pH 2 = -4, pH 4 = -4, pH 7 = -2.8, pH 9 = -0.8

0.4 h at pH 4, 8.5 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent C3 (diethoxy)

 

CCO[Si]1(CCCNCC(O1)COCCC[Si](OC)(OC)OC)OCC

411.65

2.4E-4

2.1E+4

0.7**

pH 2 = -4, pH 4 = -4, pH 7 = -2.3, pH 9 = -0.3

0.4 h at pH 4, 9.2 h at pH 7, and 0.2 h at pH 9 and 20-25°C (QSAR)

Constituent C4 (triethoxy)

 

CCO[Si](CCCOCC1CNCCC[Si](O1)(OCC)OCC)(OC)OC

425.67

1.2E-4

6.1E+3

1.2**

pH 2 = -4, pH 4 = -4, pH 7 = -1.8, pH 9 = 0.2

0.5 h at pH 4, 18.0 h at pH 7, and 0.3 h at pH 9 and 20-25°C (QSAR)

Constituent C5 (tetraethoxy)

CCO[Si](OCC)(CCCOCC1CNCCC[Si](O1)(OCC)OCC)OC

439.70

6.3E-5

1.9E+3

1.7**

pH 2 = -4, pH 4 = -4, pH 7 = -1.3, pH 9 = 0.6

0.8 h at pH 4, 35.0 h at pH 7, and 0.5 h at pH 9 and 20-25°C (QSAR)

Weighted average for Constituents C

 

 

3.7E-4

6.4E+4

-2.5 at pH 7

0.4 h at pH 4, 10.8 h at pH 7, and 0.2 h at pH 9 and 20-25°C

Constituent D1 (methoxy)

CO[Si](OC(COCCC[Si](OC)(OC)OC)CNCCC[Si](OC)(OC)OC)(OC)C

519.82

2.4E-5

1.7E+4

-1.2**

pH 2 = -4, pH 4 = -4, pH 7 = -4, pH 9 = -2.2

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent D2 (ethoxy)

 

CCO[Si](CCCNCC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)(OC)OC

533.84

1.2E-5

5.2E+3

-0.7**

pH 2 = -4, pH 4 = -4, pH 7 = -3.7, pH 9 = -1.7

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent D3 (diethoxy)

 

CCO[Si](OCC)(CCCNCC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)OC

547.87

5.9E-6

1.5E+3

-0.2**

pH 2 = -4, pH 4 = -4, pH 7 = -3.2, pH 9 = -1.2

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent D4 (triethoxy)

 

CCO[Si](OCC)(OCC)CCCNCC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC

561.90

2.9E-6

4.6E+2

0.3**

pH 2 = -4, pH 4 = -4, pH 7 = -2.7, pH 9 = -0.7

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent D5 (tetraethoxy)

 

CCO[Si](CCCOCC(O[Si](OC)(OC)C)CNCCC[Si](OCC)(OCC)OCC)(OC)OC

575.93

1.4E-6

1.4E+2

0.8**

pH 2 = -4, pH 4 = -4, pH 7 = -2.2, pH 9 = -0.3

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent D6 (pentaethoxy)

 

CCO[Si](OCC)(CCCOCC(O[Si](OC)(OC)C)CNCCC[Si](OCC)(OCC)OCC)OC

589.95

7.1E-7

4.1E+1

1.3**

pH 2 = -4, pH 4 = -4, pH 7 = -1.7, pH 9 = 0.24

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Weighted average for Constituents D

 

 

1.0E-5

5.2E+3

-3.3 at pH 7

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C

Constituent E1 (ethoxy)

CCO[Si](CCCN(CC1COCCC[Si](O1)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)(OC)OC

738.14

 

3.1E-9

 

6.1E+2

 

-1.5**

pH 2 = -4, pH 4 = -4, pH 7 = -4, pH 9 = -2.5

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent E2 (diethoxy)

CCO[Si](OCC)(CCCN(CC1COCCC[Si](O1)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)OC

 

752.17

 

1.5E-9

 

1.8E+2

 

-1.0**

pH 2 = -4, pH 4 = -4, pH 7 = -4, pH 9 = -2.0

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent E3 (triethoxy)

 

CCO[Si](OCC)(OCC)CCCN(CC1COCCC[Si](O1)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC

 

766.20

 

7.5E-10

 

5.4E+1

 

-0.5**

pH 2 = -4, pH 4 = -4, pH 7 = -3.5, pH 9 = -1.5

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent E4 (tetraethoxy

CCO[Si](OCC)(OCC)CCCN(CC1COCCC[Si](O1)(OC)OCC)CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC

780.23

 

3.6E-10

1.6E+1

0.02**

pH 2 = -4, pH 4 = -4, pH 7 = -3.0, pH 9 = -1.0

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Weighted average for Constituents E

 

 

1.8E-9

3.0E+2

-3.7 at pH 7

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C

Constituent F1 (methoxy)

 

CO[Si](CCCN(CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)(OC)OC

 

860.34

 

4.6E-10

 

1.4E+2

 

-2.8**

pH 2 = -4, pH 4 = -4, pH 7 = -4, pH 9 = -3.9

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent F2 (ethoxy)

 

CCO[Si](CCCN(CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)(OC)OC

 

874.37

 

2.3E-10

 

4.1E+1

 

 

-2.4**

pH 2 = -4, pH 4 = -4, pH 7 = -4, pH 9 = -3.4

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent F3 (diethoxy)

 

CCO[Si](OCC)(CCCN(CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)OC

 

888.40

 

1.1E-10

 

3.5

 

-1.9**

pH 2 = -4, pH 4 = -4, pH 7 = -4, pH 9 = -2.9

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent F4 (triethoxy)

 

CCO[Si](OCC)(OCC)CCCN(CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC

 

902.42

 

5.3E-11

 

3.5

-1.4**

pH 2 = -4, pH 4 = -4, pH 7 = -4, pH 9 = -2.4

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent F5 (tetraethoxy)

 

CCO[Si](OCC)(OCC)CCCN(CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OCC)(OC)OC

 

916.45

 

2.5E-11

 

1.1

-0.9**

pH 2 = -4, pH 4 = -4, pH 7 = -3.9, pH 9 = -1.9

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Constituent F6 (pentaethoxy)

CCO[Si](OCC)(OCC)CCCN(CC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)CC(O[Si](OC)(OC)C)COCCC[Si](OCC)(OCC)OC

940.47

1.2E-11

3.1E-1

-0.4**

pH 2 = -4, pH 4 = -4, pH 7 = -3.4, pH 9 = -1.4

 

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)

Weighted average for Constituents F

 

 

1.4E-10

2.9E+1

-3.9 at pH 7

0.3 h at pH 4, 5.9 h at pH 7, and 0.1 h at pH 9 and 20-25°C

Constituent G1 (methoxy) [18186-97-5; 242-072-8]

 

CO[Si](O[Si](OC)(OC)C)(OC)C

 

226.38

 

4.9E+1

 

2.9E+4

 

1.6*

0.4 h at pH 4, 11.6 h at pH 7, and 0.2 h at pH 9 and 20-25°C (QSAR)

Constituent G2 (ethoxy/methoxy)

CCO[Si](O[Si](OC)(OC)C)(OC)C

240.41

1.7E+1

8.8E+3

2.1*

0.4 h at pH 4, 11.6 h at pH 7, and 0.2 h at pH 9 and 20-25°C (QSAR)

Weighted average for Constituents G

 

 

3.7E+1

2.1E+4

1.8

0.4 h at pH 4, 11.6 h at pH 7, and 0.2 h at pH 9 and 20-25°C

*ionisation not applicable

**calculated log Kow for the unionised form

In contact with water, all of the constituents of the registration substance undergo moderate to rapid hydrolysis to produce their corresponding silanol hydrolysis products and methanol/ethanol. The constituents of the substance are methoxy-, ethoxy- or mixed methoxy/ethoxy silanes. The alkoxysilane groups are susceptible to hydrolysis, producing silanols and ethanol and/or methanol.

The hydrolysis products for each constituent blocks are reported below:

Constituents A: methylsilanetriol (1 mole, Silanol HP-X) and methanol/ethanol (3 moles)

Constituents B: (3-aminopropyl)silanetriol (1 mole, Silanol HP-Z) and methanol/ethanol (3 moles)

Constituents C: disilyl(alkylamine)-heptol (1 mole, Silanol HP-Y) and methanol/ethanol (5 moles)

Constituents D: disilyl(alkylamine)-heptol (1 mole, Silanol HP-Y), methylsilanetriol (1 mole, Silanol HP-X) and methanol/ethanol (8 moles)

Constituents E: trisilyl(alkylamine)-undecol (1 mole, Silanol HP-W), methylsilanetriol (1 mole, Silanol HP-X) and methanol/ethanol (10 moles)

Constituents F: trisilyl(alkylamine)-undecol (1 mole, Silanol HP-W), methylsilanetriol (2 moles, Silanol HP-X) and methanol/ethanol (13 moles)

Constituents G: methylsilanetriol (2 moles, Silanol HP-X) and methanol/ethanol (4 moles)

Therefore, due to the moderate to rapid hydrolysis of the constituents of the substance, the properties of the silanol hydrolysis products are also assessed and are reported in the table below.

 

Table: Key physicochemical properties of silanol hydrolysis products

Hydrolysis product No

Hydrolysis product

SMILES

Molecular Weight (g/mol)

Vapour Pressure (Pa)

log Kow

Water solubility (mg/L) at 20°C

Silanol HP-X

Methylsilanetriol

C[Si](O)(O)O

94.14

0.053 at 25°C

-2.4 at 20°C

1.0E+06 but condensation possible at around 100 mg/L or below

Silanol HP-Z

(3-Aminopropyl)silanetriol

NCCC[Si](O)(O)O

137.21

2.5E-04 at 25°C

-2.9 at 20°C (unionised)

-4 at pH 2, -4 at pH 4, -4 at pH 7, -3.5 at pH 9 (ionised values)

1.0E+06 but condensation possible at aaround 100 mg/L or below

Silanol HP-Y

Disilyl(alkylamine) heptol

OC(COCCC[Si](O)(O)O)CNCCC[Si](O)(O)O

331.47

4.0E-13 at 25°C

-4 at 20°C (unionised)

-4 at pH 2, -4 at pH 4, -4 at pH 7, -4 at pH 9 (ionised values)

1.0E+06 but condensation possible at around 100 mg/L or below

Silanol HP-W

Trisilyl(alkylamine) undecol

OC(CN(CC(COCCC[Si](O)(O)O)O)CCC[Si](O)(O)O)COCCC[Si](O)(O)O

525.73

4.6E-42 Pa at 25°C

-4 at 20°C (unionised)

-4 at pH 2, -4 at pH 4, -4 at pH 7, -4 at pH 9 (ionised values)

1.0E+06 but condensation possible at around 100 mg/L or below

 

 

The saturation concentrations in water of the silanol hydrolysis products are limited by condensation reactions that can occur over time at loadings at or below 100 mg/L. However, the silanol hydrolysis products are very hydrophilic; predicted key physicochemical results for the silanol hydrolysis products are reported in the table above.

The silanol hydrolysis products are not expected to be surface active.

Methanol is miscible with water, has low log Kow (-0.82 to -0.64) and high vapour pressure (12790 Pa at 20°C) (OECD 2004a).

Similarly, ethanol is miscible with water, has low log Kow (-0.3) and high vapour pressure (7910 Pa at 25°C).

 

Reference:

OECD (2004a). SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18 - 20 October 2004, Methanol, CAS 67-56-1).

Additional information