Amino functional alkoxysilanes

Endpoint summary

Description of key information

The registration substance is a UVCB substance containing many constituents as follows:

Constituent A: Trimethoxy(methyl)silane (CAS 1185-55-3; EC No. 214-685-0)

Constituent B: 3-(Trimethoxysilyl)-1-propanamine (CAS 13822-56-5; EC No. 237-511-5)

Constituent C: Disilyl(cycloalkylamine), pentamethoxy

Constituent D: Trisilyl(alkylamine), octamethoxy-methyl

Constituent E: Tetrasilyl(alkylamine), decamethoxy-methyl

Constituent F: Pentasilyl(alkylamine), tridecamethoxy-methyl

Constituent G: Methyl(methoxy) functional disiloxanes

Constituent H: Methanol (CAS 67-56-1; EC No. 200-659-6)

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 standard temperature and pressure, no melting point was obtained using a differential scanning calorimetry, but a glass transition temperature at about -137°C at 1013 hPa was observed. The substance has a measured boiling point of 96.2°C at 1013 hPa. It has a measured density of 1.0078 g/cm³ at 20°C and a measured vapour pressure of 2220 Pa at 20°C and 2995 Pa at 25°C.

The registration substance is classified for flammability according to Regulation (EC) No. 1272/2008 on the basis of a measured flash point of 13°C at 1013 hPa and a measured boiling point of 96.2°C at 1013 hPa. It has a measured auto-ignition temperature of 276°C at 1013 hPa and is not explosive and not oxidising on the basis of chemical structure.

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 K_ow values for the unionised form of the constituents were corrected for ionisation using the equation CORR = 1/1 +10^A(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 1.4.2 Key physicochemical properties of constituents and blocks of the substance

Constituent No	Constituent	SMILES	Molecular Weight (g/mol)	Vapour Pressure (Pa)	Log Kow	Water solubility (mg/L) at 20°C	Hydrolysis half-lives
Constituent A	Trimethoxy(methyl)silane	CO[Si](OC)(OC)C	136.22	2990 Pa at 20°C   14710 Pa at 50°C	0.7 at 20°C	9.1E+04	<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 B	3-Aminopropyl(trimethoxy)silane	NCCC[Si](OC)(OC)OC	179.29	21 at 25°C	0.2 at 20°C (unionised) -4 at pH 2, -4 at pH 4, -2.8 at pH 7, -0.8 at pH 9 (ionised values)	5.7E+05	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 C1	Disilyl(cycloalkylamine), penta(methoxy)-	CO[Si](CCCOCC1CNCCC[Si](O1)(OC)OC)(OC)OC	383.59	5.9E-04 at 25°C	-0.3 at 20°C (unionised) -4 at pH 2, -4 at pH 4, -3.3 at pH 7 and -1.3 at pH 9 (ionised values)	2.3E+05	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	Disilyl(cycloalkylamine)-disiloxane, hexa(methoxy)-	CO[Si](O[Si](OC)(OC)C)(CCCOCC1CNCCC[Si](O1)(OC)OC)OC	473.75	4.3E-5 Pa at 25°C	0.6 at 20°C (unionised) -4 at pH 2, -4 at pH 4, -2.4 at pH 7 and -0.42 at pH 9	4.6E+4	0.5 h at pH 4, 16 h at pH 7, and 0.2 h at pH 9 and 20-25°C (QSAR)
Constituent C Weighted average			385.86	5.8E-4 Pa at 25°C	-3.3 at pH 7	2.2E+5	0.4 h at pH 4, 8.1 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)
Constituent D1	Trisilyl(alkylamine), octamethoxy-methyl-	CO[Si](OC(COCCC[Si](OC)(OC)OC)CNCCC[Si](OC)(OC)OC)(OC)C	519.82	2.4E-5 Pa at 25°C	-1.2 at 20°C (unionised) -4 at pH 2, -4 at pH 4, -4 at pH 7 and -2.2 at pH 9 (ionised values)	1.7E+04	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	Trisilyl(alkylamine)-disiloxane, nonamethoxy-dimethyl-	CO[Si](O[Si](OC)(OC)C)(OC(COCCC[Si](OC)(OC)OC)CNCCC[Si](OC)(OC)OC)C	609.97	2.7E-6 Pa at 25°C	-0.3 at 20°C (unionised) -4 at pH 2, -4 at pH 4, -3.2 at pH 7 and -1.3 at pH 9 (ionised values)	3.9E+3	0.4 h at pH 4, 12 h at pH 7, and 0.2 h at pH 9 and 20-25°C (QSAR)
Constituent D Weighted average			524.44	2.3E-5 Pa at 25°C	-4.0 at pH 7	1.7E+4	0.3 h at pH 4, 6.2 h at pH 7, and 0.1 h at pH 9 and 20-25°C (QSAR)
Constituent E	Tetrasilyl(alkylamine), decamethoxy-methyl-	CO[Si](OC(CN(CC1COCCC[Si](O1)(OC)OC)CCC[Si](OC)(OC)OC)COCCC[Si](OC)(OC)OC)(OC)C	724.12	6.4E-9 Pa at 25°C	-1.9 at 20°C (unionised) -4 at pH 2, -4 at pH 4, -4 at pH 7 and -3 at pH 9	2.1E+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 F	Pentasilyl(alkylamine), tridecamethoxy-methyl-	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 Pa at 25°C	-2.8 at 20°C (unionised) -4 at pH 2, -4 at pH 4, -4 at pH 7 and -3.9	1.4E+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 G1	Methyl(methoxy) functional disiloxane	CO[Si](O[Si](OC)(OC)C)(OC)C	226.38	49 Pa at 25°C	1.6 at 20°C	2.9E+4	0.4 h at pH 4, 12 h at pH 7, and 0.2 h at pH 9 and 20-25°C (QSAR)
Constituent G2	Alkylamino(methoxy)-methyl-functional disiloxane	NCCC[Si](O[Si](OC)(OC)C)(OC)OC	269.45	0.48 Pa at 25°C	-1.1 at 20°C (unionised) -4 at pH 2, -4 at pH 4, -1.9 at pH 7 and 0.09 at pH 9	1.6E+5	0.5 h at pH 4, 16 h at pH 7, and 0.2 h at pH 9 and 20-25°C (QSAR)
Constituent G Weighted average			234.99	39 Pa at 25°C	0.9	5.5E+4	0.4 h at pH 4, 12.8 h at pH 7, and 0.2 h at pH 9 and 20-25°C (QSAR)
Constituent H	Methanol	CO	32.04	12790 Pa at 20°C	-0.82 to -0.64	Miscible with water

 

In contact with water, all of the constituents of the registration substance undergo rapid to moderate hydrolysis to produce the corresponding silanol hydrolysis products and methanol. Further details on the hydrolysis reactions are attached in Section 13. The half-lives of the constituents and the resulting weighted average for the blocks are reported in the table above.

The hydrolysis products for each constituent are reported below:

Constituent A: methylsilanetriol (Silanol HP-X) and methanol

Constituent B: (3-aminopropyl)silanetriol (Silanol HP-Z) and methanol

Constituent C1: disilyl(alkylamine)-heptol (Silanol HP-Y) and methanol

Constituent C2: disilyl(alkylamine)-heptol (Silanol HP-Y), methylsilanetriol (Silanol HP-X) and methanol

Constituent D1: disilyl(alkylamine)-heptol (Silanol HP-Y), methylsilanetriol (Silanol HP-X) and methanol

Constituent D2: disilyl(alkylamine)-heptol (Silanol HP-Y), methylsilanetriol (Silanol HP-X) and methanol

Constituent E: trisilyl(alkylamine)-undecol (Silanol HP-W), methylsilanetriol (Silanol HP-X) and methanol

Constituent F: trisilyl(alkylamine)-undecol (Silanol HP-W), methylsilanetriol (Silanol HP-X) and methanol

Constituent G1: methylsilanetriol (Silanol HP-X) and methanol

Constituent G2: (3-aminopropyl)silanetriol (Silanol HP-Z), methylsilanetriol (Silanol HP-X) and methanol

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

 

Table1.4.3 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 around 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 K_ow (-0.82 to -0.64) and high vapour pressure (12790 Pa at 20°C) (OECD 2004a).

 

Reference:

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