DD234683A1 - METHOD FOR PRODUCING POLYMER LONG-TERM STABILIZERS WITH HALS GROUPS - Google Patents

Abstract

The aim and object of the invention is to produce long-term protected polymers against exposure to light and oxygen. According to the invention, the object has been achieved by initially preparing silanol-group-containing polymers by anionic copolymerization of olefins with cyclic siloxanes and stopping the polymerization with acetic acid. To stabilize these polymers are reacted with alkoxysilane or alkoxysiloxane containing HALS compounds. The HALS residues are covalently bound in this way and stable to hydrolysis in the polysiloxane block of the polymer. They are not volatile under the conditions of plastic processing and are preferably in the surface layer of the polymer. With minimal use of HALS connection, maximum protection against light and oxygen is guaranteed.

Description

R ³ O (SiO) _n SiOE ³ η = 0-20

R ¹ R ¹ where R ¹ = -CHOHCHO

MeA λ, Me

f E '

R '= He, H

1 2

R may be partially replaced by R R ² = alkyl, aryl

(mono-trifunctional terminators are also possible) mean, implemented.

Field of application of the invention

The invention relates to a process for the preparation of light and oxygen long-term protected polymers of the general formulas:

L '(BA) _n η = 1-3

A (BL ¹ J ₂

(L'BAB) _n

where A = polyolefin block

B = polysiloxane block

L '= silanyl or siloxanyl with HALS (hindered amine light stabilizer) residues, e.g. B. sterically hindered piperidine radicals, the general formula:

R ^{2 }} n R ² t I (SiO SiO r τ ~ 'it Xl.

..ie '' -ie R '

R '= He, H

R can partially through

R replaced his

H ² = alkyl, aryl η = 0-20

(analogous compounds with mono- or trifunctional silane units are also possible). Characteristic of the known technical solutions

In the art, the stabilization of polymers with HALS compounds is usually carried out by physical admixing of the stabilizers. Due to the high volatility, however, the applied substances tend to significantly diffuse out during thermal processing. Therefore, attempts have been made to develop less volatile, higher molecular weight compounds. A technical solution has been used in the synthesis of higher molecular weight compounds such . B.

R ₁ Si 4-n

Me Me

'M-O-

Me Me

η = 1-4

(SU 406 833, 407 908, 468 942, 553 262, 610 843, 696 022, 732 324, DT 2 204 659)

R Si

2Ϊ-Ε '

Me ifte

R '=

η = 1-4

(SU 521 268; DT 2621 842.2621856). Since the SiOC bonds of the substances are not resistant to hydrolysis, long-term storage by atmospheric moisture low molecular weight fragments are formed, which in turn have a high volatility.

There are also higher molecular weight, Si-free compounds such. B.

Me Me Me Me

Lie Me

U-H

TIImUYIH 770 (DT 2 258 752)

described. In another solution variant, suitable compounds were polymerized to high molecular weight products, e.g.

Polymerization with KOH (JA 57 168 916)

The disadvantage of these higher molecular weight HALS compounds is that they only a small part of the

Surface of the polymer where they have their main activity, i.e., that a large part of the HALS product contained in the polymer remains ineffective.

In connection with the solution according to the invention can be demonstrated from the literature that the outer layer of a

Poiystyrene-polydimethylsiloxane copolymer consists of pure polydimethylsiloxane. (Clark, DT, Dilks, A., Peeling, J .;

Thomas, H.R .; Faraday Discuss. Chem. Soc. 60 (1976) 183-95).

It has already been found (DD-PS 147247) that can be terminated by anionic polymerization prepared mono- or dianions with antioxidants containing halogen or Acyloxysüanen.

It was further found (DD-PS 208471) that one can anchor UV absorber firmly in the siloxane content of copolymers,

by breaking off the mono- or dianions produced by anionic copolymerization of olefins with cyclic siloxanes with reactive halogen-containing silicon compounds and then by polymer-analogous nucleophilic substitution of the halogen atoms of the halopropyl groups hydroxyl-containing UV stabilizers such. B. 2,4-

Dihydroxybenzophenone. Both installation options are unsuitable for the HALS connections and do not lead to the desired products.

Object of the invention

The aim of the invention is to produce polymers which are protected against time of exposure by HALS groups against the action of light and oxygen. The HALS groups should preferably be located on the surface of the polymer and even after prolonged storage or thermal treatment of the polymers, such as. B. shaping, do not volatilize. It should be achieved with a relatively low proportion of HALS compound maximum light and oxidation protection of the polymers.

Explanation of the essence of the invention

The object of the invention is to synthesize polymers having HALS radicals in which the HALS radical is bonded stable to hydrolysis, does not volatilize during processing and is preferably located in the surface layer. The process according to the invention for the preparation of such polymers consists in an anionic block copolymerization of olefins with cyclic siloxanes and the termination of the polymerization with acetic acid. In this way, block copolymers with SiOH end groups are formed. By subsequent reaction of the SiOH end-group copolymers with alkoxysilane- or alkoxysiloxane-containing HALS compounds, the HALS residues are covalently linked to the polymer with ROH cleavage and formation of SiOSi bonds. The anionic polymerization is preferably carried out in aprotic (eg hexane) or aprotic dipolar solvents (eg tetrahydrofuran), the polymerization temperature is -8O ⁰ C to + 5O ⁰ C. As initiators are organometallic compounds of the 1st to 3rd main group of the Periodic Table (eg, Li-alkyls) or alkali metal aromatics (eg, Na or K naphthalene).

In the copolymerization of olefins with cyclic siloxanes, such as. B. hexamethylcyclotrisiloxane (D ₃ ) or Oktamethylcyclotetrasiloxan (D ₄ ), depending on the initiator used polymer anions of the type AB ~ or ~ BAB ~ (A = polyolefin, B = polysiloxane) with Silanolatendgruppen. These polymer mono- or dianions are quenched with acetic acid at room temperature. Subsequently, the silanol groups are reacted with alkoxysilane or alkoxysiloxane-containing HALS compounds under the catalytic action of a Sn-organic compound. This results in products of the general formulas: L '(BA) _n η = 1-3 A (BL') ₂ (L'BAB) where A = polyolefin block

B = polysiloxane block

L '= silanyl or siloxanyl with HALS radicals, eg. B. sterically hindered piperidine radicals, the general formula:

H ² R ² R ¹ = -GH ₀ CH ₀ GH ₉ O

ft ddd

(SiO) _n SiO 1 ¹

1 -Hi «

R '= Me, EL R can be partially R ² = alkyl, aryl! ^d urch be replaced η R ² = 0-20 j

(analogous compounds with mono-trifunctional silane units are also possible)

mean. For the inventive method, the HALS compounds z. B. be prepared so that initially by known methods 2,2,6,6-tetramethyl or 1,2,2,6,6-pentamethylpiperidin-4-ol won and converted with allyl chloride in the corresponding allyl ether. By addition of alkoxysilanes of the formula:

HSi (OR ³ )

3-n

the allyiethers give rise to products of the following formula:

CH ₂ Si (OR ³⁾ _n H _'a ire, H

^H ? -N * ² = ^A1

T? -> _T, r _Λ

Lie Q = 1-3

R '

The corresponding di- and trifunctional alkoxysilanes with HALS residues may eventually be converted to alkoxysiloxanes by partial hydrolysis. For example, a difunctional alkoxysilane reacts according to the following equation:

OGH ₂ GH ₂ GH ₂ SiC OR ³ ) ₂ R ²

me

+ Η _Λ 0

R '= Me, H

Advantages of the method according to the invention are the non-inflexibility of the HALS compound, its hydrolysis-stable linkage with the siloxane-containing polymer and, since according to the invention the HALS compounds are in the polysiloxane block, a high concentration of the stabilizer groups in the surface layer. The advantages mentioned represent a technical advance of the previously known solutions.

Embodiments.

Example 1: Preparation of polystyrene-polydimethylsiloxane copolymers of the type L'BA

15.6 g (0.15 mol) of styrene are mit0,04g (6.3 x 10 ~ ⁴ mol) of n-butyl-lithium (dissolved in 5 ml of hexane) as an initiator in tetrahydrofuran at -78 ° C under inert conditions anionic. Subsequently, 15.6 g (0,07MoI) of hexamethylcyclotrisiloxane (D _3), dissolved in 40 ml of tetrahydrofuran, is added at room temperature and the mixture heated to 30-50 ⁰ C. After completion of the copolymerization is quenched with 1 ml of acetic acid and then added to 1 g of sodium bicarbonate solution

Dibutyl tin dilaurate added propylsilane and a few drops and one for Stabilisierung'wird the polymer solution with 0.48 g (1.26 x 10 ~ ³ months!) Ethoxymethylphenyl (yloxy i ^^ öjS-pentamethylpiperid - - ^ ') Hour heated to 100 ⁰ C.

 For workup, the stabilized polymer solution is precipitated from methanol and reprecipitated. After aspiration, the polymer is dried for one week in a vacuum oven at 60 ° C.

Example 2: Preparation of polybutadiene-polydimethylsiloxane copolymers of the type L'BA

37.4 g (0.69 mol) of butadiene with 1.19 g (1.86 x 10 ^"2 mole) of n-butyl lithium (dissolved in 17,8ml hexane) as an initiator in hexane at 5O ⁰ C under inert conditions anionic. Subsequently, 17.5 g (0.079 mol) of hexamethylcyclotrisiloxane

(D ₃ ) dissolved in 50 ml of tetrahydrofuran. Stabilization and workup see example 1

Examples 3 to 6: Preparation of Polystyrene or Polybutadiene-Polydimethylsüoxan Copolymersn the Types L '(BA) ₂ and

L '(BA) ₃

The procedure was as described in Example 1 or 2. Diethoxymethyl (1,2,2,6,6-pentamethylpiperid-4-yloxy) propylsilane and triethoxy (1,2,2,6,6-pentamethylpiperid-4-yloxy) propylsilane were used as the aikoxysians.

Claims (1)

Invention claim: Process for the preparation of long-term protected against light and oxygen exposure, produced by anionic polymerization polymers, characterized in that the resulting in the anionic copolymerization of olefins with cyclic siloxanes polymer chains are terminated with Silanolatendgruppen with acetic acid. The silanol-containing polymers thus obtained are described below with alkoxysilane or alkoxysiloxane-containing HALS compounds of the formula: