CS233433B1 - Stabilized polyethylene - Google Patents

Abstract

Stabilized polyethylene containing 97 to 99% of polyethylene with a content of 0.1 to 0.2% by weight of antioxidants such as 2,6-ditertbutyl-4-methylphenol or phenylethyl-phenylphosphite and 1 to 3% by weight of grafted polyethylene containing a bound UV stabilizer from the group of substances comprising secondary alicyclic amines and a sterically hindered nitrogen atom such as 1,7-bis-(3,3,5,5-tetramethyl-4-azacyclohexyl)-2-oxo-1,7-diazaheptane or* dispiro(5,1,5,3)-7,15-diazahexadecane in an amount of 0.20 to 0.36% by weight based on the total weight of the material. Stabilized polyethylene can find application in agriculture, healthcare, food processing and wherever it is necessary to facilitate the extraction of chemicals from polymers.

Description

233433 2

The invention relates to a process for stabilizing polyethylene.

In the prior art polyethylene stabilization methods are used! preferably low molecular weight or polymeric substances containing a stabilizer in the macromolecule. Low-molecular substances are often provided to reduce volatility by bulky moieties, or multiple molecules merge together. Prepare polymer stabilizers! by polymerization, copolymerization, polycondensation, polyaddition or polymerized conversion to the finished polymer. Low molecular weight substances have! the disadvantage is that the polymer can escape, on the one hand, during its processing, on the other hand, in its use (by migration it reaches the surface from which it can be washed or otherwise extracted), although the polymeric stabilizers are not lost from the polymer, however, due to the reduced mobility in the polymer, their activity is significantly reduced. Most of the time, it is also the fact that such materials are! often insufficient to tolerate the polymer into which it is stirred.

These disadvantages can be avoided by the stabilized polyethylene of the present invention in that it contains 97 to 99 wt. % of polyethylene containing 0.1 to 0.2% by weight of antioxidants such as 2,6-di-tert-butyl-4-methylphenol or phenylethyl-phenyl-phosphite; grafted polyethylene containing bound UV stabilizer from the group of other secondary alicyclic amines with a sterically hindered nitrogen atom such as 1,7-bis- (3,3,5,5-tetramethyl-4-aza-cyclohexyl) -2- oxo-1,7-diazaheptane or dispiro (5,1,5,3) -7,15-diazahexadecane in an amount of 0.20 to 0.36% by weight. related to the cell! material weight.

The polymeric material as a fixed stabilizer concentrate is prepared by bonding molecular weight stabilizers to epoxy-containing grafted polyethylene, prpp. e-fluorine groups (see AO 218 602 and AO 222 090). Through them, polymers can be bonded with a moving hydrogen atom as you are! amines or acids. The HALS species mentioned herein have been crawled either through the nitrogen in the alicyclic ring (piperazine type) or the non-ring nitrogen (4-amino-piperidine type). The reaction takes place in heterogeneous conditions at temperatures of 95-120 ° C, with 1 train being used for fixation of more than 90% of the reactive groups of the polyethylene carrier.

Most particularly important is the powdered polymeric material with a fixed stabilizer, it can be added as a concentrate of the fabric to the polymer before processing. When mixing the concentrate into polyethylene, it is necessary to work in optimum conditions to avoid mechanical destruction of the polymer, especially inoculated into polyethylene. I recommend! temperature and shorter mixing times. The bound stabilizer is not removed from the polymer at temperatures higher than that for polyethylene. The stabilizer cannot be washed from the polymer in water with an emulsifier even at pH = 11 at 90 ° C for 50 hours.

The method of stabilizing polyethylene according to the invention is set forth in the following examples, but is not limited to these examples. Example 1 In a Brabender plastograph, a mixture of 0.49 wt. d. a polyethylene copolymer containing 0.07 wt. d. bound dispiro (5,1,5,3) -7,15-diazahexa-decane, 0.04 wt. d. 2,6-diterebutyl-4-methylphenol and 36.47 wt. d. polyethylene. Prepared in Salsh at 180 ° C for 0.15 mm thick foil. The foil strips were placed in Xenotest.1200 and subjected to IR analysis at certain time intervals. From the graphical record, the induction period in hours was evaluated, during which the absorbance of the carbonyl groups of the polyethylene was 0.2. At the same time, 3 parallel samples were measured and the arithmetic center of the induction period was determined. Under the same conditions, reference samples containing no UV stabilizer were also tested in the Xeno-test. Examples of UV stabilization of polyethylene are summarized in Table 1, maintaining the procedure of Example 1. 233433 I a b u I k a 1 Examples of UV stabilization of polyethylene by fixed substances according to the invention Example No. fixed stabilizer 8 1 Substance ermostabilizer of mass. % Induction Period 'h Substance Mat. % 1 Dispiro 0,20 2,6-diterc-0,1 900 (5,1,5,3) -7,15-diaza-butyl-4-methyl-hexadecane phenol (AO-4) 2 1,7 -bie (3,3,5,5-tetra-0,36 0,1 1,000 methyl-4-aza-cyclohexyl) -2-oxo-1,7-diazaheptane 3 0,36 Phenyl-ethyl-phenyl- 0.2 1000-phosphite (AO-6) and the stabilizing agent were fixed to polyethylene containing 1.2 wt. % of epoxy oxygen through epoxide groups. Such a stabilizer concentrate was mixed into the polyethylene in the amount required to form a given concentration of polyethylene.

The induction period was evaluated during the stay of the test samples in Xenoteste 1200, by analysis to change the concentration of the carbonyl groups of the polyethylene. It is given as the time at which the absorbance of the sample changed by 0.2. The sample without UV stabilizer had an induction period of 500 hours.

As shown in the data tab. The obtained inductive periods in the presence of the fixed stabilizers used on the polyethylene are little affected by both the type of substance used and the composition of the most stabilization system. The reasons for this are not known by the very mechanism of the function of the investigators even in low molecular weight form. Tab. 1, only those examples where a longer induction period than in the presence of 0.2 wt. % of a commercial low-molecular stabilizer 2-hydroxy-4-n-octoxybenzophenone (Cyasorb UV 531). In his presence, she had a value of 800 hours and served to assess the stabilization level.

Another factor that is important for the function of the fixed substance is its good miscibility with polyethylene, which is to allow its good dispersion. It is important that the fixed substance does not have sufficient migration and forms a concentrate locally in the polymer. It can be assumed that if the substance is bonded to a copolymer of which one part is polyethylene, as in the invention described herein, its incorporation into polyethylene will be ultra-light.

By mixing the fixed stabilizer into the polymer in the amount necessary for its lifetime from the point of view of light stability, a valuable polymer is prepared, which in turn extends from the ecological site. The stabilizer does not leak from it either during processing or during use. Polymers of this kind are suitable for use in health, agriculture, food, and where they are increasingly restricted by extraccylchemicals from polymers. Therefore, the tendency to solve all the ingredients of the polymers in the fixed 4 form is at most topical. The complex solution would be aided by the synthesis of substances with a combined special effect whose activity would not fall below a certain threshold even in a fixed form.

By the process of stabilizing polyethylene according to the invention, the induction period of the formation of the carbonyl groups of the polyethylene in the Xenoteste is increased from 1200 to 500 hours per 1000 hours.

Claims (1)

With the introduction of the invention, costly investment is involved in the manufacturing sector and no substantial change in the manufacturing modes used in the production of comonomer polymers is required. BACKGROUND OF THE INVENTION Stabilized polyethylene comprising 97 to 99 wt. polyethylene containing 0.1 to 0.2 wt. antioxidants such as 2,6-di-tert-butyl-4-ethylphenol or phenyl-ethyl-phenyl-phosphite; grafted polyethylene containing an unquenched UV stabilizer of the group consisting of secondary alicyclic amines with sterically hindered nitrogen such as 1,7-bis (3,3,5,5-tetramethyl-4-aza-cyclohexyl) -2-oxo-1; 7-diazaheptane or dispiro (5,1,5,3) -7,15-diazahexadecane in an amount of 0.20 to 0.36% by weight; based on the total weight of the material. Severografia, n. P., MOST Price 2,40 Kcs