CS233433B1 - Stabilized polyethylene - Google Patents

Abstract

Stabilized polyethylene containing 97. \ T up to 99% haot. polyethylene containing 0.1 and 0,2 0.2 wt. antioxidants such as 2,6-di-tert-butyl-4-methylphenol or phenyl-ethyl- % fanyl foafite and 1 to 3 wt. vaccinated polyethylene containing bound UV stabilizer from the group of substances including secondary alicyclic amines and sterically with a hindered nitrogen atom such as 1,7-bis- (3,3,5,5-tetramethyl-4-aza-cyklohezyl) -2- -oxo-1,7-diazaheptane or dispiro (5,1,5,3) - -7,15-diazahexadecane at 0.20 to 0.36 wt. by weight material. The stabilized polyethylene can be found application in agriculture, health, food and wherever it is needed to refine the extraction of chemicals from polymers.

Description

The invention relates to a method of stabilizing polyethylene.

In the prior art methods of stabilizing polyethylene, mostly low molecular weight substances or polymeric substances containing a stabilizer incorporated in the macromolecule are used. Low molecular weight substances are often provided to reduce the volatility of bulky groups in a molecule, or combine multiple molecules into a single unit. Polymeric stabilizers aa are prepared by polymerization, copolymerization, polycondensation, polyaddition or polymer-analogue conversion to the finished polymer. Low-molecular-weight substances have the disadvantage that they can escape from the polymer both during its processing and during its use (by migrating it to the surface from where it can be washed or otherwise extracted). Although the macromolecular stabilizers do not disappear from the polymer, they are greatly reduced due to the reduced mobility in the polymer and their activity. This is also due to the fact that such materials are often insufficiently compatible with the polymer to which they are mixed.

These disadvantages can be overcome by the stabilized polyethylene according to the invention, which comprises 97 to 99 wt. % polyethylene with a content of 0.1 to 0.2 wt. % of antioxidants such as 2,6-di-tert-butyl-4-methylphenol or phenyl-ethyl-phenyl-phosphite; vaccinated polyethylene containing a bound UV stabilizer selected from the group consisting of 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 0.20-0.36 wt. based on the total weight of the material.

The polymeric material as a fixed stabilizer concentrate is prepared by wetting low-molecular-weight stabilizers onto grafted polyethylene containing epoxide or epoxy-containing polymers. chlorohydrin groups (see AO 218 602 and AO 222 090). They can be used to bind substances with a movable hydrogen atom, such as amines or acids, to the polymer. The HALS-type compounds disclosed herein were bonded either through nitrogen in the alicyclic ring (piperazine type) or out-of-ring nitrogen (4-amino-piperidine type). The reaction is carried out under heterogeneous conditions at temperatures of 95 to 120 ° C, whereby more than 90% of the reactive groups of the polyethylene carrier can be used for fixing.

Especially the powdered polymeric material with a fixed stabilizer is most important; It can be added to the polymer as a concentrate of the fabric to be treated prior to processing. When mixing the concentrate into polyethylene, it is necessary to work under optimum conditions to avoid mechanical destruction of the polymer, in particular grafted on polyethylene. Higher working temperatures and shorter mixing times are recommended. The bound stabilizer does not detach from the polymer even at temperatures higher than those processed for polyethylene. The stabilizer cannot be washed from the polymer in emulsifier water even at pH = 11 at 90 ° C for 50 hours.

The method of stabilizing the polyethylene of the present invention is described in more detail in the following examples, without being limited thereto.

EXAMPLE

In a Brabender plastograph, a mixture of 0.49 wt. d. a copolymer of polyethylene containing 0.07 wt. d. bound dispiro (5,1,5,3) -7,15-diazahexadecane, 0.04 wt. d. 2,6-diterobutyl-4-methylphenol and 36.47 wt. d. polyethylene. The prepared mixture was further pressed at 180 ° C to 0.15 mm thick sheets. The foil strips were placed in Xenotest 1200 and subjected to IR analysis at certain time intervals. The graphical record was used to evaluate the induction period in hours during which the absorbance of polyethylene carbonyl groups increased by 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, samples containing no UV stabilizer were subjected to Test 1 in Xenotest.

Examples of UV stabilization of polyethylene are summarized in Table 1, following the procedure of Example 1.

I and 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 ermostabilizátor wt. % induction period " h substance wt. % 1 dispiro 0.20 2,6-di-tert-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-diazaheptán 3 0.36 Phenyl-ethyl-phenyl-0,2 1 000 -phosphite (AO-6)

^and The stabilizing agent was fixed to polyethylene containing 1.2 wt. % of epoxy oxygen, through epoxy groups. Such a stabilizer concentrate was mixed into the polyethylene in an amount necessary to produce the given concentration in the polyethylene.

The induction period was evaluated during the residence of the test specimens in Xenotest 1200 by IR analysis to change the concentration of polyethylene carbonyl groups. It is given as the time for which the absorbance of the sample changed by 0.2. The sample without UV stabilizer had an induction period of 500 hours.

As is clear from the data tab. The induction periods obtained in the presence of the fixed polyethylene stabilizers used are little affected by both the type of substance used and the composition of the thermostabilization system. The causes for this are not known; the mechanism of function of the test substances, even in low molecular weight form, is not simple. In tab. 1, only those examples where a longer induction period than in the presence of 0.2 wt. % commercial low molecular weight stabilizer 2-hydroxy-4-n-octoxybenzophenone (Cyasorb UV 531). In its presence it was 800 hours and served to assess the stabilization level.

Another factor which is important for the function of the fixed substance is its good miscibility with polyethylene, which is to allow it to disperse well. This is important because the fixed substance does not have the possibility of sufficient migration and creates local concentrations in the polymer. It can be assumed that if the substance is bound to a copolymer of which one part is polyethylene, as described herein, its mixing into polyethylene will be facilitated.

By mixing the fixed stabilizer into the polymer in an amount necessary for its expected lifetime from the point of view of light stability, a valuable polymer is prepared which complies in particular from the ecological point of view. The stabilizer does not escape from it during its processing or use. Polymers of this kind are suitable for. i. even in medical, agricultural, food and wherever the extraction of chemicals from polymers needs to be more and more restricted. Therefore, the tendency to address all polymer ingredients in a fixed form is at most topical. The synthesis of drugs with combined special effects, whose activity would not fall below a certain level even in fixed form, would help to achieve a comprehensive solution.

The method of stabilizing the polyethylene of the present invention will prolong the induction periods of formation of the polyethylene carbonyl groups in the Xenotest 1200 from 500 to 1,000 hours.

The introduction of the invention does not entail costly investment in the manufacturing sector and does not require any substantial change in the manufacturing regimes used in the production of commercial polymers.

Claims (1)

OBJECT OF THE INVENTION Stabilized polyethylene, characterized in that it contains 97 to 99 K wt. % polyethylene containing 0.1 to 0.2 wt. % antioxidants such as 2,6-di-tert-butyl-4-ethylphenol or phenyl-ethyl-phenyl-phosphite; vaccinated polyethylene containing an unsupported UV stabilizer selected from the group consisting of secondary allcyclic amines with an age-defended nitrogen atom such as 1,7-bis (3,3,5,5-tetramethyl-4-aza-cyclohexyl) -2-oxo-1,7-diazaheptene or dispiro (5,1,5,3) -7,15-diazahexedecane in an amount of 0.20 to 0.36 wt. based on the total weight of the material.