Process for producing compositions crosslinkable to elastomers
Neutral moisture curable organopolysiloxane compositions are prepared from silanol-stopped organopolysiloxanes, alkoxysilanes, aminosilanes, and ketoximino silanes, and contain less than 1 weight percent oximes upon storage.
1. A process for producing moisture curable compositions crosslinkable to elastomers, comprising:
in a first step, providing a mixture comprising
(1) at least one organopolysiloxane having at least two hydroxyl groups,
(2) at least one alkoxysilane of the formula
RSi(OR 1 ) 3 (I),
and/or partial hydrolysates thereof,
where R is a monovalent hydrocarbyl radical having 1 to 18 carbon atoms, and
R 1 is identical or different and is a monovalent hydrocarbyl radical having 1 to 8 carbon atoms, and
(3) organosilicon compounds having at least one radical containing basic nitrogen and bonded via carbon to silicon,
in a second step, adding to the mixture of the first step
(4) at least one ketoximosilane of the formula
R 2 Si(ON═CR 3 2 ) 3 (II)
and/or their partial hydrolysates,
where R 2 is a monovalent hydrocarbyl radical having 1 to 18 carbon atoms, and
R 3 is identical or different and is a monovalent hydrocarbyl radical having 1 to 5 carbon atoms, in amounts of at most 1 wt %, based on the total weight of the composition,
and optionally adding further alkoxysilanes (2) and/or their partial hydrolysates and optionally further organosilicon compounds (3) in the second step or optionally in a third step subsequent to the second step, and adding and mixing
(5) condensation catalysts,
optionally
(6) fillers,
optionally
(7) adhesion promoters,
optionally
(8) plasticizers,
optionally
(9) stabilizers, and
optionally
(10) additives different from components (1)-(9), wherein in the third step, further alkoxysilanes (2) of the formula (I) and/or their partial hydrolysates and further organosilicon compounds (3) are added to the reaction mixture from the second step.
2. The process of claim 1 , wherein in the first step, organopolysiloxanes (1), alkoxysilanes (2) of the formula (I) and/or their partial hydrolysates, organosilicon compounds (3), and optionally plasticizers (8) are mixed with one another.
3. The process of claim 1 , wherein alkoxysilanes (2) and/or their partial hydrolysates are used in a total amounts of 1 to 25 parts by weight, based on 100 parts by weight of organopolysiloxane (1).
4. The process of claim 1 , wherein alkoxysilanes (2) and/or their partial hydrolysates are used in a total amounts of 2 to 15 parts by weight, based on 100 parts by weight of organopolysiloxane (1).
5. The process of claim 1 , wherein alkoxysilanes (2) and/or their partial hydrolysates are used in the first step in an amount of 1 to 5 parts by weight, based on 100 parts by weight of organopolysiloxans (1).
6. The process of claim 1 , wherein at least one organopolysiloxane (1) has the formula
HO—[R 4 2 SiO] n —H (III),
where
R 4 is identical or different and is an optionally substituted hydrocarbyl radical having 1 to 18 carbon atoms and
n is an integer from 500 to 2000.
7. The process of claim 1 , wherein at least one organosilicon compound (3) has at least one radical containing basic nitrogen and is bonded via carbon to silicon, and comprises an aminosilane of the formula
ASi(OR 5 ) 3 (IV),
where
A is a radical of the formula —R 6 —(NR 7 —R 8 —) x NR 7 2 ,
R 5 is identical or different and is a monovalent hydrocarbyl radical having 1 to 8 carbon atoms,
R 6 is a divalent hydrocarbyl radical having 1 to 8 carbon atoms,
R 7 is identical or different and is a hydrogen atom or a monovalent hydrocarbyl radical having 1 to 8 carbon atoms,
R 8 is a divalent hydrocarbyl radical having 1 to 18 carbon atoms, and x is 0, 1, 2 or 3.
8. The process of claim 1 , wherein organosilicon compounds (3) are used in a total amount of 0.25 to 10 parts by weight, based on 100 parts by weight of the organopolysiloxanes (1).
9. The process of claim 1 , wherein organosilicon compounds (3) are used in a total amount of 1 to 7.5 parts by weight, based on 100 parts by weight of the organopolysiloxanes (1).
10. The process of claim 1 , wherein organosilicon compounds (3) are used in the first step in amounts of 0.1 to 1 part by weight, based on 100 parts by weight of organopolysiloxanes (1).
11. The process of claim 1 , wherein at least one condensation catalyst (5) is a tin catalyst.
12. The process of claim 1 , wherein additives (10) comprise at least one pigments, dyes, odorants, fungicides, oxidation inhibitors, agents for influencing the electrical properties, flame retardants, light stabilizers, heat stabilizers, thixotropic agents, and/or organic solvents.
13. The process of claim 1 , wherein fillers (6) are added to the reaction mixture from the second or optionally from the third step and then tin catalysts (5), optional adhesion promoters (7), optional stabilizers (9), and optional additives (10), when present, are subsequently added and mixed with one another.
14. The process of claim 1 , wherein adhesion promoters (7), and thereafter fillers (6) are added to the reaction mixture from the second or optionally from the third step and then tin catalysts (5), optional stabilizers (9), and optional additives (10), when present, are subsequently added and mixed with one another.