DD234682A1 - METHOD FOR PRODUCING LONG-TERM STABILIZED POLYMERS WITH HALS GROUPS - Google Patents

Abstract

The aim and object of the invention is to produce long-term protected polymers against light and oxygen by admixing high molecular weight siloxane-containing HALS compounds. The polymeric HALS compounds should be stable to hydrolysis, preferably located on the surface of the polymers to be protected, be largely compatible with them and not be covert in a thermal treatment of the protected polymers. According to the invention, the object is achieved by initially preparing polymeric HALS compounds by anionic copolymerization of olefins with cyclic siloxanes, terminating the polymerization with acetic acid and reacting the silanol-containing copolymers with alkoxysilane- or alkoxysiloxane-containing HALS compounds. The high molecular weight HALS compounds thus obtained are blended with other polymers.

Description

Field of application of the invention

The invention relates to a process for the preparation of polymeric siloxane-containing long-term stabilizers with HALS groups.

The HALS products mentioned have the following general formulas:

L '(BA) _n η = 1-3 A (BL') ₂

(L'BAB) _n

where A = polyolefin block B = polysiloxane block

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

R ¹ = -

(SiO) _n SiO ~ ρ ¹ τ? ¹

ΈΓ = alky!, Aryl η = 0-20

R '= Me, H

R ¹ may be partially replaced by

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

The stabilizers mentioned can be added to polymers and show a very good compatibility with the products to be stabilized.

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 exude to a considerable degree 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.

Me Me VL-.

R "Si 4-n

MJ-O

η = 1-4

i.ie

η η

(SU 406833, 407908, 468942, 553262, 610843, 696022, 732324, DT 2204659)

or.

R Si 4-n

me

Vl

0- /

i \ i-R

Me isle

R'is ilkvl ^TJ η = 1-4

(SU 521268; DT 2621842, 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.

0 0

►-0-C- (GH ₂ ) gC-0-

Hey Me Me '

IIHU7IIT 770 (DT 2 258 752)

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

Polymerization with KOH (JA 57 168 916)

The disadvantage of these higher molecular weight HALS compounds is that they are only to a small extent on the surface of the polymer where they have their main activity, d. h., That a large part of the HALS product contained in the polymer remains ineffective.

It is known that polyolefin-polysiloxane copolymers in polyolefins preferentially migrate into the surface layers, so that the outer layer of a polystyrene containing polystyrene-polysiloxane copolymers consists of pure polysiloxane. (Clark, D.T., Dilks, A., Peeling, J .; Thomas, H.R., Faraday Discuss, Chem. Soc. 60 [1976] 183-95).

Object of the invention

The aim of the invention is to obtain nichtfiüchtige, hydrolysis-stable, polymeric HALS compounds which are well compatible with the polymer to be protected and ensure that the HALS residues are preferably concentrated in the surface layers. In this way, a maximum light protection of the polymers should be achieved with a relatively low proportion of HALS compound.

Explanation of the essence of the invention

The object of the invention is to produce high molecular weight HALS compounds which are as far as possible compatible with the polymer to be protected, stable to hydrolysis and non-volatile and are preferably located in the surface layers.

According to the invention the object is achieved in that polyolefin-polysiloxane copolymers which contain attached to the siloxane block HALS residues are prepared. The process according to the invention for the preparation of the other polymers of high molecular weight HALS compounds which can be mixed is an anionic copolymerization of olefins with cyclic siloxanes and the termination of the polymerization with acetic acid. This results in copolymers with SiOH eride groups. By subsequent reaction of the SiOH end-group copolymers with aoxysilane 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 at -80 ° C to +50 ⁰ C. Suitable initiators are organometallic compounds of the 1st to 3rd main group of the periodic table (for. Example, Li-alkyls) or Alkalimetallaromaten, (z. B.

Na or K naphthaien).

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 aoxysilane- 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

(L'BAB) _n

where A = polyolefin block

B = polysiloxane block

L '= silanyl or siloxanyl with HALS residues / z. B.

sterically hindered piperidine radicals, of the general formula:

R ² R ² R = -GH CH GH 0 J ι d d 2. (SiO) SiO * - R ¹ HeJ

me

R '= Me, H ι R can partially through

R replaces its R ² = ialkyl, aryl η = 0-20

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

mean. For the inventive method, the HALS compounds z. Example, 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 )

» _O η

the allyl ether gives rise to products of the following formula:

R '= Me, H

R ³ = Me, Bt ^E η = 1-3

OCH I 2 ^CH 2 ^CH ; r MeI J ^ Me , Si (OR ³ )

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

i (OR ³ )

E ³ O (SiO)

me

Advantages of the process according to the invention are the non-volatility of the added HALS compound, its hydrolytic stability and compatibility with the polymer to be protected and the enrichment of the stabilizer on the surface of the polymer to be stabilized

 The advantages mentioned represent a technical advance of the previously known solutions.

embodiments

Example 1! Polystyrenhaltigen stabilizing polymer with the polystyrene-polysiloxane HALS compound of the type BA L'For the preparation of the stabilizer to be 15.6 g (0.15 mol) of styrene with 0.04 g (6.3 x 10 ^"4 mole) n-Butyl lithium (dissolved in 5 ml of hexane) as an initiator in tetrahydrofuran is anionically polymerized under inert conditions at -78 ° C. Subsequently, 15.6 g (0.07 mol) of hexamethylcyclotrisiloxane (D3) dissolved in 40 ml of tetrahydrofuran are added at room temperature and the mixture is heated to 30-50 ° C. After the copolymerization has ended, the mixture is quenched with 1 ml of acetic acid and then 1 g of a sodium bicarbonate solution is added.

The polymer solution is then mixed with 0.48 g (1.26 × 10 ^-3 mol) of ethoxymethylphenyl (1,2,2,6,6-pentamethylpiperid-4-yloxy) propylsilane and a few drops of di-butyi-Sn dilaurate and heated to 100 ⁰ C for one hour.

For workup, the polymer solution is precipitated from methanol and reprecipitated. After filtration with suction, the polymer is dried for one week in a vacuum oven at 6O ⁰ C.

To stabilize polystyrene, the appropriate amount of high molecular weight HALS compound is mixed together with dsm polymer to be stabilized in a M.v. Ardenne vibrator. For larger quantities, all known mixing methods are suitable.

Example 2 Stabilization of polybutadiene-containing polymers with the polybutadiene-polysiloxane-HALS compound of the type L'BA

For the preparation of the stabilizer 37.4 g (0.69 mol) of butadiene with 1.19 g (1.8 x 10 ~ ² MoIj n-butyl lithium (dissolved in 17,8m! Hexane) as an initiator of hexane at 50 ° C under inert conditions Then, 17.5 g (0.079 mol) of hexamethyicyclotrisiloxane (D ₃ ) dissolved in 50 ml of tetrahydrofuran are added, followed by the procedure described in Example 1.

Claims (1)

Invention claim: Process for the preparation of polymeric long-term stabilizers with HALS groups, characterized in that non-volatile, compatible with the polymers to be stabilized and surface-enriching HALS group-containing polymers by anionic block copolymerization of olefins and cyclic siloxanes, termination of the polymerization with acetic acid and subsequent linkage be obtained with alkoxysilane or alkoxysiloxane containing HALS compounds to form a SiOSi bond.