DE1720523C3 - Process for increasing the molecular weight of organosilicon compounds - Google Patents

Description

The use of diorganotin salts as polymerization catalysts for organosilicon compounds has long been known. These are for example often as crosslinking catalysts for organopolysitoxanes which cure to elastomers at room temperature used.

The tin compounds used so far correspond to the general form!

R ₂ Sn (OAc) ₂

where R is alkyl radicals and Ac is acyl radicals of fatty acids.

Despite their proven usefulness, these types of tin compounds have some serious ones Disadvantage. This includes the relative instability of these compounds, which results in a loss of their effectiveness when left standing, especially in damp conditions.

This phenomenon occurs all the more when the catalyst is in the form of an aqueous emulsion. On the other hand, however, it is necessary for organopolysiloxane coatings in emulsion form, aqueous Use emulsions of the catalysts. For example, there are numerous organosilicon release coatings used for paper in emulsion form and then hardened.

Under these conditions it is necessary for the catalyst emulsion to be stable on storage. Further kt it is necessary for the coating bath that it remains stable during the coating process, when a mixture of the catalyst emulsion and the organopolysiloxane emulsion by different mechanical means is applied to the paper. This can be done by pumping up the emulsion and spreading it on the same on the paper surface by means of application rollers or knife coating or by The emulsion is sprayed onto the paper using spray nozzles. Through this mechanical movement and stress, there is a risk that the emulsion will break and, in particular, its effectiveness of the catalyst is reduced.

These problems, which arise with the tin catalysts used to date, can be avoided by the catalyst used according to the invention can be avoided or largely mitigated.

Another problem that arises with the organotin compounds used hitherto lies on the Field of food release agents. In this application, solutions of resinous phenylmethylsiloxanes are used Applied to the surfaces of roasting and baking equipment and then hardened. This Types of resins are particularly suitable for use in frying pans, baking trays, and others Devices that are used to heat food. The purpose of this measure is to to allow easy removal of all types of food, and thus the use of Feu entirely avoid or reduce to a minimum and also cleaning the baking and roasting equipment facilitate. It was found that when using the catalysts which can be used according to the invention Separability of the siloxane film is increased considerably.

The present invention therefore relates to a process for increasing the molecular weight of organosilicon compounds that are at least contain a Si-bonded hydroxyl group and an average of 0.9 to 3 organic radicals, which with linked to the Si atom by a Si — C bond are characterized by contact with organotin compounds as catalysts is that you di-n-octyltin-di-iso-octyl mercapioacetate used as a catalyst.

The catalyst used in the present invention is a valuable polymerization catalyst through which the molecular weight of the organosilicon compound is increased and in particular a curing catalyst, which makes a polyfunctional organosilicon compound insoluble and infusible.

The catalyst used according to the invention stands out as compared to the crosslinking factors for organopolysiloxanes which cure at room temperature, diorganotin salts known by its better stability in humid conditions. which especially appears when the Catalyst is in the form of an aqueous emulsion. The catalyst which can be used according to the invention is therefore usable as a storage-stable catalyst emulsion, which can also be used with subsequent mechanical The stress on the treatment bath remains stable. as is clear from the example of paper coating proven.

In addition, the inventively used Catalyst also used for solutions of organopolysiloxanes in organic solvents find how using the example of the production of release coatings for cooking and baking equipment according to Example 1 is shown. Here, too, the better storage stability of what can be used according to the invention Catalyst clearly visible, which even after months of storage of the coating solution before Use enables a good separating effect after application to the devices, as from the determination of the separability miliels eggs can be seen.

From the German patent specification 935 455 there are already organic sulfur compounds in which an H atom bonded directly to S is replaced by metal. as a hardening accelerator for silicone resins known. These are curing catalysts for heat-hardenable silicone resin lacquers, which are usually must be cured at temperatures of at least 250 C, for which long times are required Child. At lower temperatures there are However, hardening accelerators are not useful, as demonstrated by the example of paper coating would.

The effectiveness of the catalyst used according to the invention extends to those mentioned above Organosilicon compounds. which contain at least one Sigebundenc hydroxyl group.

720

In addition, the Qrganosilikjumverbindungen and other types of silicon functional groups (SiX) contain that with water, with the formation of Si - OH groups or react with Si — OH groups directly to form Si — O — Si bonds F. Elimination of HX respond.

This means that it was used according to the invention Catalyst can also be mixed with organosilicon compounds that. only contain SiX groups and the mixture is then exposed to moisture. This will be the radicals X are hydrolyzed to OH groups, which then condense under the action of the catalyst.

As is known, such radicals X include hydrogen atoms: alkoxy groups such as methoxy, ethoxy and - OCH ₂ CH ₂ OCH ₃ ; Acyloxy groups such as acetoxy, propionyloxy and benzoyloxy; Ketoxime such as groups such as -ON = C (CHj) ₂ ; Carbamate groups, such as

Il

- OCN (C ₂ H ₅ ) ₂

V-CsN

and hydrocarbon radicals substituted with amino, amido and sulfide groups. Most preferred are alkyl, vinyl, phenyl and R _f CH ₂ CH _r radicals, in which Rf denotes a perfluoroalkyl radical.

In terms of structure, the organosilicon compounds to be polymerized can be built up from any combination of units of the formulas R ¹ SiO ₃ , ₂ , RVSi O, Rj'SiO, 2 and limited amounts of SiO _4/2 units. They can also contain Si atoms which, directly or through divalent hydrocarbon radicals, such as methylene, dimethylene, hexamethylene and phenylene radicals or hydrocarbon ether radicals,

C ₆ H ₄ OC ₆ H ₄ .

Silazane bonds. how

as well as groups of the formula OW ₂ . wherein Y is a hydrocarbon radical, such as methyl. Ethyl or phenyl; Halogen atoms such as Cl. Br and F; and any other hydiolysable. residues linked to the Si atom.

The organosilicon compounds to be polymerized with the aid of the catalyst used according to the invention contain by definition 0.9 to 3 organic radicals R ″, which go through with the Si atom Si - C bonds linked "ind. The nature of this Substituent is not critical. These can, for example, be any, optionally substituted. Be hydrocarbon residues. Hydrocarbon radicals, especially aliphatic hydrocarbon radicals, such as Methyl, ethyl, octadecyl, myricyl, vinyl, allyl. Hexenyl and isopropyl radicals: cycloaliphatic hydrocarbon radicals, such as cyclohexyl-, cyclopentyl-. Methylcyclohexyl, cyclohexenyl and methylcyclohexenyl radicals: aromatic hydrocarbon residues such as phenyl, toiyl, xenyl, xylene and naphthyl residues: and Aralk) l residues. such as benzyl, / f-phenylethyl and , -i-phenylpropyl radicals, however, are preferred.

Preferred radicals are also halogenated hydrocarbon radicals, such as chloromethyl, -, - chloropropyl ·. Bromocf.tadecyl-, chlorophenyl-, bromxenyi-, fluorocyclohv-xyl-, chlorobutenyl-, «,«, n-trifluorotolyl-. 3.3. 3-Trifluoropropyl and C ₇ F ₁₅ CH ₂ CH ₂ radicals Further examples of substituted hydrocarbon radicals are hydrocarbon ether radicals. how

- (CH ₂ ), CKCH, CH ₂ O) _n CH ₃

- (CH ₂ ), OC ₂ H ₅
Estcrrcste. how

- (CH ₂ ) JOOCCH = CH ₂

- (CH ₂ ) ₆ OOCCHj
and

-CH ₂ CH ₂ COOC ₂ H ₅

Niltrile remains. how

-CH ₂ CH ₂ CN

- (CH ₂ ) jC = N

60

f'5 SiNSi

CH ₃

j
- SiNSi-

and sulfide bonds, such as SiSSi, with other Si atoms are linked.

The organosilicon compounds in kö ^r; n in any polymerization catalyst used according to the invention into contact be brought. For example, silanols or diols can be combined with the tin compounds or precondensed siloxanols for final curing of the molding compounds.

The di-n-octyltin-di-iso-octyl mercaptoacetate used here is a commercially available product. Such compounds can be obtained by reacting Tin oxides of the general formula

[R ₂ SnO] ₁

with mercaptides of the formula

jl

HSCH ₂ COR '

getting produced. The tin oxides can be obtained in a simple manner by hydrolysis of R ₂ SnCl ₂ . ; which in turn can be obtained by reacting RMgCl with SnCl ₄ .

Examples of radicals R in the formula given above are methyl. Ethyl-. Butyl-, Octyk Octadecyl-. Myricylic. Phenyl-. ToIyI-. Vinyl-. Allyl-. Acyl or Xe: nyl residues: Examples of residues R 'are methyl-. Ethyl, butyl, octyl. Octadecyl and myricyl residues. Preferably R and R 'are alkyl radicals with at least 4 carbon atoms.

The amount of catalyst is not decisive for the implementation of the polymerization. It is general advantageous, as is usually the case with catalysts, to use the smallest amount, the corresponding Polymerization causes.

The temperature during the polymerization is also not critical. It can vary widely

depending on the nature of the oryano silicon compound. With some compounds, the polymerization begins at room temperature or below, others require elevated temperatures. The temperature is also dependent on the f. The time available to carry out the polymerization depends on the time available. For example elevated temperatures may be required to cure a coating in a few seconds 24 hours are required for this curing at room temperature

The catalyst which can be used according to the invention can be used in the production of laminates, moldings!) and for curing films and coatings with resinous liquids or elastomers Compositions are used.

example 1

This example shows the superior effect of a commercially available baking and roasting product release agent based on organopolysiloxane, according to the invention with di-n-octyltin-di-iso-octyl mercaptoacetate (1) was catalyzed compared to the release effect. that achieved with other organotin catalysts would. The following compositions were used for the individual tests:

3.10 percent by weight of a resinous methylphenylpolysiloxane containing 4 percent by weight of SIG-bonded OH groups, with a ratio of phenyl groups to Si atoms of 0.53 and a ratio of methyl-phenyl groups to Si atoms of 1.35.
0.01 percent by weight of dipropylene glycol ^{mono- - 1-} methyl ether.

0.20 percent by weight of a hydroxylated one. liquid dimethylpolysiloxane containing 4.2 percent by weight of Si-bonded OH groups.
1.79 percent by weight methyltriacetoxysilane and 94.90 percent by weight 1,1,1-trichloroethane.

The various premixes of these compositions were each made with the following catalysts in an amount of 1 percent by weight tin per 100 parts by weight of total solids mixed with organosilicon compounds:

1. Di - η - octyltin - di - iso - octyl mercaptoacel; it (according to the invention),

2. Di-octyltin di-octoate (for comparison).

3. Di-ociyltin-dilaurate (for comparison).

4. Di-butyltin di-laurate (for comparison).

Each of the mixtures was kept in a sealed container at the times and at the temperatures which are given in the following tables. Then each composition was placed on an aluminum pan applied and air dried. Then eggs were placed in the coated pan Fried without added fat at 135 ° C and recorded. fv> how often a satisfactory separation of the same was possible.

There have been four different approaches to the phenylmethyl resin used, which are identified in Tables I, II and III.

In each trial, the individual Ingredients mixed, tested immediately and then aged at 21 ° C for the specified time periods.

catalyst

Aging time in months

Approach I. 4th 5 71 66 63 - 23 - 25th 29

83

Seed / III

5! 6th

62 j 78 31 8 53 73

65

1 1

·) The experiment was terminated after 5 <1 separations.

In the following runs, each sample in the container was at the specified temperature aged and then checked for their ability to separate over eggs.

Table II

20;

Alierizeii in months

• vatalv pera- saior door ι Ci 1 38 4th 3 pp 1 49 4th 49 1 66 4th 66

77
59
75
62
90
0

Anr-ul / I

94 j 54

lOOi 80

70j 90

60 66

35 34

55 j 52

Approach H

Approach II

73! 73 73 83: 54 6S

lOSI 67 10Γ 72 53 (114 70.49

109! 791 78 ^ 52 52i 7ό! 77-77

50

s The measure of the ability of the eggs to separate is not a very precise determination, so it was necessary. to test a fairly large number of individual samples in order to determine with certainty the really best product. The superiority of the catalyst (1) is confirmed by the fact that it showed a superior separating effect with respect to all catalysts in 26 cases, with respect to at least one catalyst in 29 cases and was only worse in 10 cases. In addition, the catalyst 11) was better in 9 out of 10 cases with regard to aging at 21 ^° C., which corresponds to the normal storage conditions for a commercially available product.

Example 2

This example shows the stability of the invention to be used catalyst in aqueous emulsion and under mechanical stress. the Catalyst emulsion was prepared by mixing the following ingredients:

1,875 percent by weight polyvinyl alcohol. 0.500 percent by weight dodecylbenzene nairium

sulfonate, 14,875'Vo water,

then became a mixture of

20.00 percent by weight di - η - octyltin - di - iso-

mercaploacetate.

6.00 percent by weight tetrachlorethylene. 24.00 percent by weight toluene,

and a mixture of

30.75% water.
2.00 percent by weight glycerine added.

This emulsion contained 20 percent by weight of the analyzer.

The siloxane emulsion contained the following components:

38.800 percent by weight of liquid dimethylpolysiloxane with OH groups in the terminal units,
1,200 percent by weight methylhydrogenpolysil · ·

oxane,

4,500 percent by weight of toluene,
5,500 percent by weight perchlorethylene,
47.077% water.

1.875 weight percent polyvinyl alcohol and
1.048 percent by weight octylphenylpolyethoxyethanol.

25 parts by weight of the siloxane emulsion were with 2.5 parts by weight of the catalyst emulsion and 72.5 parts by weight of water mixed. The thus obtained Emulsion was applied to parchment paper with a glass rod and 2 minutes at 12TC hardened. Excellent curing of the siloxane was achieved, thanks to the good release values is displayed, which remain practically constant as the bath ages.

Example 3

When mixing the following organosilicon compounds The catalyst from Example 1 was used to polymerize at the temperatures indicated achieved:

temperature

(C)

10

Table III Subsequent
liability All of the
Coating
emulsion
in hours Cut-off value
in grams 160 0 5 145 2 5 142 4th 5 140 c; 6th 140 6th 6th 268

35

40

The release value was determined by applying a strip of adhesive plaster to the cured siloxane and measuring determined the force that was required to pull the strip off the surface at an angle of 180 ° to be deducted. The strip so removed was then applied to a steel plate and the force applied determined that was required. to pull it off again. The values listed above show that the strip separated easily from the coated paper and that no appreciable amount of siloxane remained attached to it, as evidenced by the excellent adhesion to steel.

The excellent stability of the emulsion under mechanical stress is demonstrated by the fact confirms that the emulsion was produced within 6 hours when processed with applicator rollers at one speed of 0.914 m / min, no gel or oil parted. That means a flexing stability of more than 6 hours.

30th

150 150

30th

150

Organosilicon compound

Mixture of

HO

CH ₂ CH ₂ CF ₃ Si-O

Ι CH ₃

and ethyl polysilicate

Mixture of

HO-

- Si - O - f - H

CH ₃

and

Mixture of

CH = CH, HO - SJ —O -

I CH ₃ and

CH ₂ = CHSi [ON = qCH ₃ ) ₂ ] ₃

a mixed polymer containing SiOH groups

20 mole percent of CH ₃ SiO _3/2 10 mole percent of C ₁₈ H ₃₇ SiO ₃₁₂ 20 mole percent C ₆ H ₅ SiO ₃ Z ₂ CH ₃

45 mole percent C ₆ H ₅ SiO 5 mole percent (C ₆ H ₅ ) ₂ SiO

409 612/1

Claims (1)

Claim: Process for increasing the molecular weight ve · »Organosilicon compounds, the contain at least one Si-bonded hydroxyl group and an average of 0.9 to 3 organic Residues that are linked to the Si atom by a Si - C bond through contact with organotin compounds as catalysts, characterized in that the catalyst used is di-n-octyltin-di-iso-octylinercaptoacetate used.