CS261169B1 - A method for stabilizing linear polyethylene β ethylene copolymers with higher 1-olefins - Google Patents

Abstract

Ethylene polymers and copolymers with a flow index of 0.01 to 0.70 g/10 minutes, intended for the production of high-strength blown articles, are stabilized against UV radiation using a powder concentrate prepared by sorption of 1 to 18% by weight of stabilizers of the benzophenone or piperidine type, which have acyl or alkoxyl groups with at least 6 carbon atoms per powder polymer of the given type. In this way, low-molecular-weight fractions are not introduced into the polymer, as is the case with the use of previously known stabilizing concentrates, which reduce the strength of the products.

Description

The present invention relates to a process for stabilizing linear polyethylene and copolymers of higher ethylene

1-olefins with stabilizing concentrates.

Products made of polyolefinic polymers such as polyethylene, polypropylene and their copolymers exhibit very low oxidation stability. Therefore, they need to be protected when processed into granules, processed into finished products, as well as for their future application. For this purpose the following substances are used:

a) which react with free radicals formed on polymer chains. This class of stabilizers includes, for example, differently substituted phenols and amines.

b) which react with hydroperoxides in the polymer system. They are, for example, substituted phosphites, thiodipropionic acid esters.

c) which reduce the rate of initiation of photooxidation reactions by means of radiation filtration.

They are, for example, UV absorbers of variously substituted benzophenones, benzotriazoles or salicylic acid esters.

d) which extinguishes excited states of molecules (characteristic compounds used in polymer systems are nickel compounds).

(e) which inhibit photooxidation reactions by the mechanism of (a), (b), include HALS-type compounds.

Addition with these compounds is carried out:

1) at the polymer manufacturer by homogenizing the powdered polymer or copolymer with the appropriate powder stabilizing agents by means of a premix (in the case of a liquid additive this is metered directly into the main powder stream) and the mixture is granulated.

2) In the final processor, the granulate is mixed with the granular special stabilizing concentrate to produce the final product.

The production of the special stabilizing concentrates is generally carried out by mixing the linear or branched polyethylene or polypropylene in an amount of up to 30% by weight with the respective stabilizing additive. and granulated. For this purpose, polymeric carriers with a high flow index are generally used which guarantee very good dispersibility of the stabilizing additive in the final product.

However, some stabilizing ingredients may be prepared to give a granular stabilizing concentrate having an active ingredient content of the order of only a few percent by weight. This is due to the fact that the stabilizer additive blooms on the surface of the stabilizer concentrate granules at higher concentrations and consequently becomes a sticky granulate, resulting in additional agglomeration of the granules produced, which makes them difficult to dispense.

However, decreasing the concentration of the active ingredient in the granular concentrate results in the need to meter several times the amount of stabilizing concentrate during production of the final product, thereby introducing a large amount of low molecular weight polymers into the polymer system, especially when processing high molecular types.

However, the use of high molecular weight polymer matrices for the production of stabilizing concentrates is not a solution because the granular concentrate prepared on the high molecular weight carrier is poorly dispersed.

The need for high molecular weight polyethylene and solar stabilized copolymers is relatively low. It is therefore almost a rule that the manufacturer of the basic granulate produces only the type that contains stabilizing additives against the effects of thermo-oxidative degradation and the final processor who needs increased photooxidation stability for its products provides it through stabilizing concentrates of additives intended to protect against photodegradation.

It has been shown that this route is the most advantageous from a technical and economic point of view, since the stabilizing concentrate can be fed continuously into the feedstock stream, thereby guaranteeing homogeneity of the stabilizer dispersion in the final product.

SUMMARY OF THE INVENTION The present invention provides a process for stabilizing linear polyethylene and copolymers of ethylene with 1-olefins and mixtures thereof with other polyolefinic polymers by means of stabilizing concentrates containing stabilizers of the benzophenone and piperidine type. % of the piperidine core, adsorbed at a concentration of 1 to 18 wt. to the surface of the linear polyethylene powder or ethylene-1-olefin copolymers having a flow index of 0.01 to 0.70 g / 10 minutes, prepared on supported catalysts, and the concentrate thus prepared is stabilized at a concentration of 0.5 to 15 wt. powdered or granulated polymer or copolymer of ethylene with a flow index of 0.01 to 0.70 g / 10 minutes, or mixtures thereof with other polyolefinic polymers, modifiers, organic, inorganic dyes and other processing aids, the concentration of the stabilizing additive in the final product being 0.04 to 0.5 wt.

Production of final products according to our new workflow can be organized by several alternative workflows:

1. Production of final product from powder raw material and powder concentrate

1.1. Polyethylene or polyethylene copolymers with higher 1-olefins in powder form, to which the anti-oxidative degradation additives are mixed, are prepared by the polymer manufacturer in fluidized bed supported catalysts. This powder mixture is transported to the final processor.

1.2 Part of this powder mixture is added to the mixer (planetary, fluid, etc.) and the appropriate stabilizer is added, if necessary, the mixture is heated and homogenized.

1.3. To the main part of the powder mixture referred to in paragraph 1.1 containing thermo-oxidative degradation stabilizers, add the powder stabilizer concentrate referred to in paragraph 1.2, optionally add granulated or powdered colorants, modifiers and other processing aids, and mix on the processing line hollow objects.

2. Production of final product from granulated raw material and powder concentrate

2.1. The powder mixture referred to in 1.1 containing linear polyethylene or ethylene copolymers with higher 1-olefins and stabilizers against thermo-oxidative degradation shall be granulated and transported to the final processor.

2.2. Linear polyethylene or copolymers of ethylene with 1-olefins in powder form are introduced into the mixer, the appropriate stabilizing additive is added, if necessary, the mixture is heated and homogenized.

2.3. To the main granular mixture referred to in paragraph 2.1 containing stabilizers against thermo-oxidative degradation, add the powdered stabilizing concentrate, whose production is mentioned in paragraph 2.2, or add granular or powdered colorants, modifiers and other processing additives, and mix on the processing line hollow objects.

3. Production of the final product from a mixture of granulated raw materials and powder stabilizer concentrate

3.1. Granular mixtures of linear polyethylene or copolymers of ethylene with higher 1-olefins, which are mixed with granular other polyolefinic polymers and, where appropriate, other modifiers, organic and inorganic colorants and other processing aids, are used as the raw materials.

3.2. Powder stabilization concentrate is prepared as described in 1.2 or 2.2.

3.3. The mixture of granulated raw materials referred to in paragraph 3.1 shall be mixed with the powder stabilizer concentrate referred to in paragraph 3.2 by means of a metering device, and hollow articles shall be blown on the processing line.

4. Production of the final product from a mixture of powdered linear polyethylene or powdered copolymers of ethylene with higher 1-olefins and granulated other raw materials

4.1 Mixtures of powdered linear polyethylene or copolymers of ethylene with higher 1-olefins with granulated other components such as low density polyethylene, dyes, modifiers and other processing additives can be used as the basic raw materials.

4.2. Powder stabilization concentrate is prepared by the method described in paragraphs 1.2 or 2.2 or 3.2.

4.3. The mixture of powdered and granulated raw materials referred to in paragraphs 4 and 1 shall be mixed by means of a metering device with the powder stabilizer concentrate referred to in paragraph 4.2 and the hollow articles shall be blown out of the mixture.

The procedures described in the preceding chapters can be successfully implemented using benzophenone derivatives or piperidine which contain a substituent with at least 4 linearly-arranged -CH 3 - groups, for benzophenone derivatives in the alkoxy substituent, for piperidine derivatives in the acyl group. These compounds are liquid at normal temperature or exhibit relatively low melting points, which, together with partially or fully linear -CH ₂ - groups, explains their good sorption properties on the surface of powdered polyethylenes.

Benzophenone and piperidine derivatives having a melting point of not more than 120 ° C can be sorbed on the surface of some high molecular weight types of powdered polymers or copolymers of ethylene with propylene or butene produced on supported catalysts.

The powder concentrates thus prepared have certain advantages over granular concentrates, which can be specified as follows:

a) Concentrates prepared by sorption on high molecular weight polyethylene powder or its copolyraers can be applied in high molecular weight linear and branched polyethylenes, copolymers and mixtures with other polymers at any concentration because the polymer matrix of the powder concentrate does not adversely affect the mechanical properties of the final product different from the basic material being processed.

b) The polymer matrix of the concentrate is not thermally stressed twice (in the case of a granular concentrate, first in its manufacture, then in its application).

c) Of particular interest is the combination of the processed high molecular weight powder types of high density ethylene copolymers of very low flow indexes of the order of hundredths of g / 10 min, with additional UV stabilization powder stabilizer concentrate produced using a high molecular weight polymer carrier and benzophenone or piperidine derivatives. We get high strength material. This technology then makes it possible, for example, to substantially reduce the wall thickness of blown hollow articles, which leads to significant material savings.

d) The preparation of the concentrate by sorption on a powdered polymeric support is less expensive than the preparation of the granular concentrate by extrusion of the mixture.

e) They can be applied to both powdered and granulated polymers of ethylene and its copolymers.

f) Homogeneous distribution of the stabilizing additive in the final processor throughout the granulate to be processed, for example in a fluidized bed mixer, is technologically disadvantageous and low economic.

(g) The homogeneous distribution of the stabilizing additive in the final processor to the entire processed volume of the powdered or ethylene copolymers in the fluidic mixer may be very perfect, but economically unbearable. While the bulk density q

The granules of linear polyethylene and its copolymers range from 0.50 to 0.60 g / cm @ 2 for powder materials and are reduced to 0.37 to 0.52 g / cm @ 2. This homogenization technology would increase the homogenisation capacity of processors disproportionately. '

The following examples illustrate the invention. The polymers and copolymers used in the examples are polymers and copolymers of ethylene produced in a fluidized bed on supported catalysts, with the exception of polymer X. The examples given in the examples are by weight.

Used stabilizing additives

1-2 hydroxy-4-isooctyloxybenzophenone (Lankromark LE 230)

- 2,2,6,6 tetramethylpiperidinol stearyl ester

3- 2-hydroxy-4-octyloxybenzophenone (Chimasorb 81)

4- 2,4 dihydroxy benzophenone

Used polymers and copolymers

Polymer A: Powdered linear polyethylene prepared on supported catalysts with a flow index of 0.02 g / 10 min

Polymer B: Powdered linear polyethylene prepared on supported catalysts with a flow index of 0.62 g / 10 min

Polymer C: Granular linear polyethylene prepared on supported catalysts with a flow index of 0.01 g / 10 min

Polymer D: Granular linear polyethylene prepared on carrier catalysts with a flow index of 0.57 g / 10 min

Copolymer E: Powdered linear copolymer of ethylene with butene, containing 0,001 mol% of butene component with a flow index of 0,02 g / 10 min

Copolymer F: Powdered linear copolymer of ethylene with butene, containing 4,1 t molar butene components with a flow index of 0,61 g / 10 min

Copolymer G: Granular linear copolymer of ethylene with propylene containing 0.01 mol molar propylene components with a flow index of 0.01 g / 10 min

Copolymer H: Granular ethylene-propylene linear copolymer containing 3.95 mole% propylene component with a flow index of 0.57 g / 10 min

Polymer I: Branched polyethylene with a flow index of 0.30 g / 10 min, density 921 kg / m (Brálen RB 03-23)

Polymer J: Powdered linear polyethylene prepared on supported catalysts with a flow index of 6 g / 10 min

For blowing 501 liter drums, a Voith-Fischer polymer A was used on the line, which was stabilized with 3% powder stabilizer concentrate prepared in a fluidic mixer using polymer A as the polymer carrier and 5% stabilizer additive 1. The drums passed the drop test. A portion of the barrel produced was stamped on a 1 mm thick plate and exposed in Xenotest 450 until bursting. Reagent plate life of 2,980 hours.

Example 2

For blowing 501 liter drums, a Voith-Fischer polymer, B was used on the line, which was stabilized with 1% powder stabilizer concentrate prepared in a mixer using polymer B as the polymer carrier and 7% molten stabilizer additive 2. The drums complied. A portion of the barrel produced was stamped on a 1 mm thick plate and exposed in Xenotest 450 until bursting. The plate life was 3 020 hours.

Example3

After blowing the 10 liter canisters, a polymer blend containing 49% Type C, 49% Type I was used, stabilized with 2% powder stabilizer concentrate prepared in a fluidic mixer using polymer B as the polymer carrier and 10% molten stabilizer additive. was stamped on a 1 mm thick plate and exposed in Xenotest 450 until bending rupture. Plate life was 3,100 hotin.

Example 4

A blend of polymers containing 49% type was used to blow the open 8 liter vessel

D and 49% Type I and 1% dye concentrate. The mixture was stabilized with a 1X powder stabilizer concentrate prepared in a mixer using Polymer B as the polymeric carrier and 15% molten stabilizer additive 3. Part of the container was molded onto a 1 mm thick plate and exposed in Xenotest 450 until bursting. The lifetime of the board was

990 hours.

Example 5

For blowing 501 liter drums, a Voith - Fischer line copolymer E was used on the line, which was stabilized with a 5% powder stabilizer concentrate prepared in a mixer using copolymers E as polymer carrier and 3% stabilizer additive 1. Despite the barrel wall thickness was 20% lower than the thickness of conventional technology, the drop test complied with the barrels. A portion of the barrel produced was stamped on a 1 mm thick plate and exposed in Xenotest 450 until bursting. Plate life was 3,090 hours.

Example6

For blowing 501 liter drums, a Voith-Fischer copolymer F was used on the Voith-Fischer line, which was automatically stabilized by a 5% powder stabilizer concentrate dispenser prepared in a fluidic mixer using copolymers F as carrier and 2% molten stabilizer.

2. During the drop test the barrels complied. A portion of the barrel produced was stamped on a 1 mm thick plate and exposed in Xenotest 450 until bursting. Plate life was 2115 hours.

Example 7

For blowing 10 liter canisters, a blend containing 35% Type G and 50% Type X was used, which was automatically stabilized with 15% powder stabilizer concentrate prepared in a fluidic mixer using copolymers F as carrier and 1% molten stabilizer.

The third part of the produced canister was pressed into a 1 mm thick plate and exposed in the Xenotest 450 until bursting. Plate life was 2,965 hours.

Example. 8

A blend containing 47% type H, 39% type I and 10 S EPDM rubber and 1% dye concentrate was used to blow the open 8 liter vessel. The mixture was automatically stabilized with a 3% stabilizer concentrate dispenser prepared using copolymers F as a carrier and 5% stabilizer additive 1. A portion of the container was made into a 1 mm thick plate and exposed in a Xenotest 450 to bursting. The plate life was 3,515 hours.

Example?

For blowing 501 liter drums, a copolymer H was used, which was automatically stabilized with a 5% powder stabilizer concentrate dispenser prepared in a fluidic mixer using polymer J as carrier and 3% stabilizer additive 1. The drums failed in the drop test. A portion of the barrel produced was stamped on a 1 mm thick plate and exposed to bend rupture in the Xenotest 450. The life of the plate varied greatly depending on the degree of dispersion-stabilizer used.

Example 10

For blowing 501 liter drums, copolymer H was used, which was automatically stabilized by a 3% powder stabilizer concentrate dispenser prepared in a fluidic mixer using copolymers F as carrier and 5% stabilizer additive 4. The sorption of the stabilizer on the powder carrier surface was imperfect. the polymer carrier was separated from the stabilizing additive 4. The test had to be stopped prematurely.

Example 11

For blowing 501 liter drums, a Voith - Fischer copolymer G was used on the Voith - Fischer line, which was fully stabilized in a fluidized bed mixer with 0.15% stabilizing additive 3. Parts of the produced drum were molded into foils and stabilizer concentrations measured by UV spectroscopy. The times required for perfect mixing of the stabilizer in such organized production have been shown to be economically inefficient.

Example 12

A blend of open 801 liter containers was used to blow a mixture of polymers containing both 49 i type F and 49% type I, 1% dye concentrate and 1% powder stabilizer concentrate prepared using copolymers F as carrier and 5% additive 3. Part of the container was molded 1 mm thick and exposed in Xenotest 450 to bend rupture. Plate life was 3,110 hours.

Claims (1)

SUBJECT OF THE INVENTION Process for stabilizing linear polyethylene and copolymers of ethylene with higher 1-olefins and mixtures thereof with other polyolefinic polymers by means of stabilizing concentrates containing stabilizers of the benzophenone and piperidine type, characterized in that stabilizing additives having acyl or alkoxy groups with at least 6 carbon atoms on the benzophenone or piperidine the cores are adsorbed at a concentration of 1 to 18% by weight. to the surface of the linear polyethylene powder or ethylene-1-olefin copolymers having a flow index of 0.01 to 0.70 g / 10 minutes, prepared on supported catalysts and the concentrate thus prepared is stabilized at a concentration of 0.5 to 15 wt. powdered or granulated polymer or copolymer of ethylene with a flow index of 0.01 to 0.70 g / 10 minutes, or mixtures thereof with other polyolefinic polymers, modifiers, organic, inorganic colorants and other processing additives, the concentration of stabilizing additive in the final product being 0.04 to 0.5 wt.