RU2798936C2 - Stablizied polypropylene composition for production of film threads - Google Patents

Abstract

FIELD: organic chemistry.

SUBSTANCE: stabilized polypropylene composition for producing pigmented film threads. Composition includes a polymer and a stabilizing mixture containing an oligomeric polyphosphite of the following general formula:

where R₁ = alkyl C₁ - C₄; n = 8-12, with an average molecular weight M_n 2500-4000; as well as a hindered secondary aromatic amine N-phenyl-2-naphthylamine or N-isopropyl-N'-phenyl-1,4-phenylenediamine; and rutile titanium dioxide. The stabilizing mixture is introduced into the polymer at a ratio of 1-10 mass parts per 100 mass parts of the polymer in form of a powder previously obtained by grinding the components together to a particle size of 0.5-10 mcm. The stabilizing mixture contains a mixture of phosphite, aromatic amine and titanium dioxide at a mass ratio of components 1:0.75-1.5:5-50, respectively.

EFFECT: increased resistance to long-term thermal and photo-oxidative degradation.

2 cl, 2 tbl, 2 ex

Description

The present invention relates to stabilized polymer compositions based on polypropylene, intended for obtaining film threads for the manufacture of soft containers and containers.

To ensure the stability of materials and products obtained from polyolefins, in particular film threads and actually soft containers and containers, to thermal-oxidative and photo-oxidative degradation (thermal and light aging), a certain set of stabilizing additives is introduced into their composition.

The main components of the stabilized composition for polypropylene film filaments claimed in the present invention, organic phosphites and hindered aromatic amines, are already known as stabilizing additives for polymeric materials and compositions.

Organic phosphites (esters of phosphorous acid) are known as secondary antioxidants used in polyolefin, polyvinyl chloride and elastomeric compositions and materials. In most cases, low molecular weight organic phosphites are used in polymer compositions. Examples of such known phosphites are described in the literature [N. Zweifel (Ed) Plastics Additives Handbook, 5th edition, Hanser Publishers, Munich 2000].

In addition to organic phosphites, other stabilizing additives can be used in polyolefin compositions: phenolic antioxidants, amine stabilizers, epoxy compounds, etc., as well as various pigments, dyes, fillers.

Known polymer composition [RF Patent No. 2150535] for the production of pigmented thermoplastic polymer (including polyolefin) fibers, including an organic dye or an inorganic pigment and an effective amount of a stabilizing mixture consisting of a UV absorber, which is used as phenol derivatives, such as o -hydroxy-phenylbenzotriazole, o-hydroxy-phenyl-8-triazine or 2-hydroxy-4-octyl-oxy-benzophenone, and a hindered secondary amine, which is used, in particular, 2,2',6,6 '-tetramethyl-piperidines.

The disadvantages of the polymer composition are the difficulty of obtaining the claimed stabilizing additives, their high cost and the inaccessibility of the starting reagents used for the synthesis of these compounds.

Known polymer composition [RF Patent No. 2126065] to obtain a stabilized polypropylene fiber with high light and heat resistance and high resistance to discoloration gases, containing 0.05 to 5.0 wt. % of a stabilizing mixture consisting of a hindered amine of a certain structure, low molecular weight phosphite or phosphonite and hydroxylamine, with a mass ratio of components from 1:1:1 to 100:2:1.

The disadvantages of this polymer composition containing low molecular weight phosphite is the lack of thermal stability of the composition, the high volatility of low molecular weight phosphites and their decomposition products during processing of the polymer composition at elevated temperatures. In addition, this composition is not intended to obtain pigmented fibers.

More effective stabilizing additives for polyolefins compared to low molecular weight phosphites are organic oligomeric polyphosphites, the advantages of which are good compatibility with the polymer, high efficiency of the stabilizing action, higher thermal stability, no emission of volatile products during processing at elevated temperatures [Organophosphate antioxidants and polymer color stabilizers. Monograph / N.A. Mukmeneva, S.V. Bukharov, E.N. Cherezov, G.N. Nugumanova; Kazan, Mrs. tech nol. un-t. Kazan, 2010].

Known polymer composition [RF Patent No. 2132852], containing an organic polymer, which can be used as polypropylene, and a stabilizer, and as a stabilizer it contains in the amount of 0.01-10 wt. % at least one oligomeric compound selected from oligomeric aliphatic phosphites or phosphonites containing structural elements of sterically hindered amino light stabilizers of general formula (I):

where: L is a group containing structural elements of sterically hindered amino-light stabilizers, in particular piperidine derivatives of various compositions; R is C ₁ -C ₈ - alkyl, C ₅ -C ₈ - cycloalkyl, tetrahydroabietyle; m=1-2; n=2-10.

This stabilized polymer composition can be used, among other things, for the production of films, fibers, tapes. However, the composition is not intended for the production of pigmented polyolefin film threads (there are no pigmenting additives or fillers in its composition).

The disadvantages of the known polymer compositions are low resistance to long-term thermal and photo-oxidative degradation, as well as the difficulty of obtaining the claimed phosphites of a complex structure, the high cost and inaccessibility of the starting reagents used for the synthesis of these compounds.

Closest to the claimed invention is a stabilized polypropylene composition [AS. USSR No. 378394], intended for the production of polypropylene monofilament and films, including polyolefin and a stabilizing mixture consisting of oligomeric polyphosphite - polydiphenylolpropanephenylphosphonate of the following formula:

where: R-phenyl.

with molecular weight up to 1800 amu and bis-(2-methyl-5-tert-butyl-4-hydroxyphenyl)monosulfide. The stabilizing mixture contains oligomeric phosphite and monosulfide in the ratio 3-1÷1-3.

The disadvantage of this composition is its insufficient thermal and light stability during prolonged exposure, which manifests itself in a decrease in mechanical properties in the process of light-thermal aging and a very low synergistic effect of stabilizing polyolefins. In addition, this composition is not intended for the production of pigmented film filaments.

The purpose of the present invention is to obtain a stabilized polymer composition based on polypropylene, intended for the production of pigmented film threads, with increased resistance to long-term thermal and photo-oxidative degradation during processing and subsequent operation.

This goal is achieved by using a stabilizing mixture in the composition of the stabilized polypropylene composition, including oligomeric polyphosphite (III) - polydiphenylol propane alkyl phosphite, a secondary aromatic amine and titanium dioxide, in an amount of 1-10 mass parts of the stabilizing mixture per 100 mass parts of polypropylene. The stabilizing mixture contains an oligomeric polyphosphite (III) of the general formula:

where R ₁ =alkyl C ₁ -C ₄ ; n=8-12 with an average molecular weight M _n 2500-4000.

Also, the stabilizing mixture contains sterically hindered N-phenyl-2-naphthylamine or N-isopropyl-N'-phenyl-1,4-phenylenediamine as a secondary aromatic amine, and rutile titanium dioxide as titanium dioxide. The stabilizing mixture contains an oligomeric polyphosphite, a secondary aromatic amine and titanium dioxide at a mass ratio of components of 1:0.75-1.5:5-50, while it is introduced into polypropylene in the form of a powder, previously obtained by joint grinding of the components to a particle size of 0 .5-10 microns.

The organic oligomeric polyphosphite(III) claimed in the composition differs from the oligomeric phosphite(II) specified in the prototype: it contains an ether group, and as a substituent R ₁ -alkyl fragments, and not a phenyl residue, as in the prototype:

where R ₁ = alkyl C ₁ - C ₄ ; n=8-12

In addition, the claimed polyphosphite has a significantly higher average molecular weight M _n =2500-4000, which helps to achieve a higher stabilizing effect.

Another difference between the claimed composition and the prototype is that, in addition to the oligomeric polyphosphite, other components are used in the stabilizing group than in the prototype, namely, secondary aromatic amine and titanium dioxide, and the claimed components of the stabilizing mixture - polyphosphite, secondary aromatic amine and titanium dioxide are taken in a strictly defined mass ratio equal to 1:0.75-1.5:5-50, at which a synergistic increase in the stabilizing effect is observed - a significant mutual enhancement of the stabilizing effect of the additives.

As the secondary aromatic amine, known compounds used as antioxidants and light stabilizers, such as N-phenyl-2-naphthylamine and N-isopropyl-N'-phenyl-1,4-phenylenediamine, which are commercially available, are used. However, there is no information on the use of these compounds in combination with the claimed polyphosphite of the above composition and molecular weight, in a strictly defined ratio, at which a synergistic stabilizing effect is achieved.

In addition, as part of the claimed composition, titanium dioxide TiO ₂ is used - an industrial product that simultaneously acts as a light stabilizer and a pigmenting additive, and titanium dioxide of a strictly defined structure and composition is used - crystalline rutile titanium dioxide. There is no information on the joint use of crystalline rutile titanium dioxide in combination with the claimed polyphosphite of the above composition and molecular weight, and secondary aromatic amines, in a strictly defined ratio, to achieve a synergistic stabilizing effect.

It is this joint use of the claimed polyphosphite, the above composition and molecular weight, in combination with secondary aromatic amines and titanium dioxide, the specified structure, taken in a strictly defined ratio, not previously described, ensures the achievement of a synergistic stabilizing effect when used as part of polypropylene.

The content of the stabilizing composition in polypropylene, at which a stable stabilizing effect is achieved, is from 1 to 10 mass parts per 100 mass parts of the polymer.

An additional advantage of the claimed polymer composition is the production of pigmented threads due to the presence of titanium dioxide in its composition.

EFFECT: obtaining a stabilized polypropylene composition with increased resistance to long-term thermal and photo-oxidative degradation for the manufacture of durable materials and products, in particular, pigmented film threads used in the production of soft weather-resistant containers.

The inventive oligomeric polyphosphites obtained by polycondensation of diphenylolpropane [2,2'-bis(4-hydroxyphenyl)propane] and alkyldichloro-phosphites AlkO-P-Cl ₂ [Organophosphorus antioxidants and polymer color stabilizers. Monograph / N.A. Mukmeneva, S.V. Bukharov, E.N. Cherezov, G.N. Nugumanova; Kazan, Mrs. technol. un-t. Kazan, 2010].

The synthesis of oligomeric polyphosphite was carried out as follows: a toluene solution of alkyldichlorophosphite R ₁ OP-Cl ₂ (R ₁ - alkyl C ₁ -C ₄ ) at a molar ratio of reagents 1:1. The reaction is carried out in the presence of a base at a temperature of 110-115°C for 10-12 hours. The reaction mass is filtered, the filtrate is evaporated using a vacuum rotary evaporator. After drying under high vacuum, an oligomeric polyphosphite(III) is obtained in a practical yield of 92-95%. The average molecular weight M _n of the resulting polyphosphite varies from 2500 to 4000.

For the synthesis of polyphosphites, the available feedstock is diphenylolpropane (GOST 12138-86), which is an industrial product, and alkyl dichlorophosphites RiO-P-Cl ₂ , which were obtained by a well-known method, by the interaction of phosphorus trichloride with alcohols [General organic chemistry / Ed. D. Barton and W.D. Ollis. T 4. Carboxylic acids and their derivatives. Phosphorus compounds. M: Chemistry. 1982].

The composition of the resulting polyphosphites is determined by elemental analysis. The average molecular weight of polyphosphites is found by gel chromatography (GPC-2000 System, Waters).

Oligomeric polyphosphite, unlike low molecular weight organic phosphites, does not sublimate and is not consumed during the processing of a polyolefin compound. As a consequence, this provides a longer thermal-oxidative stability of the polymer base.

In addition, the claimed diphenylolpropane-containing polyphosphite is more effective as a stabilizer of thermo-oxidative degradation than any other low molecular weight organic phosphites. Moreover, polyphosphite-diphenylolpropane, which is formed during the inevitable hydrolysis under the action of moisture, exhibits a synergistic effect with the secondary aromatic amine present in the composition, and also prevents the accumulation of colored amine oxidation products in the polymer system and thereby suppresses the change in color of the initial polymer material.

The specified molecular weight of the proposed polyphosphite (M _n = 2500-4000) is optimal in terms of its properties. A decrease in the molecular weight of polyphosphite below 2500 leads to a deterioration in its stabilizing effect (see Table 2). Obtaining polyphosphite with a molecular weight M _n more than 4000 causes significant technological difficulties due to the crosslinking of oligomeric macromolecules at the stage of synthesis with the formation of an insoluble product. The cross-linked polyphosphite is poorly compatible with the polymer and therefore does not have a stabilizing effect.

Obtaining the claimed stabilized polymer composition based on polyphosphite(III) includes the following steps:

• obtaining a composition of stabilizers by mixing the components in the required ratio and subsequent grinding of the resulting mixture in a ball mill;

• combining the composition of stabilizers with polypropylene in a mixer, followed by extrusion of the stabilized polymer composition.

Film threads were obtained from a stabilized polypropylene composition on a laboratory molding machine.

The following reagents were used to prepare the stabilizer composition:

• N-phenyl-2-naphthylamine (neozone-D), GOST 39-66;

• N-isopropyl-N'-phenyl-1,4-phenylenediamine (diaphen FP), TU 2492-002-0576-1637-99;

• rutile pigment titanium dioxide grade R-1, GOST 9808-84.

The components of the stabilizing composition - oligomeric polyphosphite, secondary aromatic amine and titanium dioxide, were pre-mixed under the conditions of example 1 at a mass ratio of components 1:0.75-1.5:5-50, respectively.

It was found that the subsequent joint grinding of the components of the stabilizing mixture - in the above ratio in a ball mill to a particle size of 0.5-10 microns, when introduced into the polymer, leads to excellent results in terms of the color stability of the polymer and polymer threads and increases the effectiveness of the stabilizing action. For comparison in table. 2 shows an example of a stabilized polymer composition (13a) containing a stabilizing mixture (11) obtained by mixing the components without their joint grinding in a mill.

To confirm the claimed ratio of components under the conditions of example 1, compositions of stabilizers (1-6) corresponding to the indicated ratios and compositions (7-10) containing components in amounts beyond the claimed ratios were obtained. The compositions of the compositions of the stabilizers are given in table. 1.

In the preparation of stabilized polymer compositions, polypropylene brand "Balen" 01030, TU 2211-074-05766563-2005 was used. For the preparation of polymer compositions, a mixture of stabilizers previously obtained under the conditions of example 1 (table. 1), in an amount of 1-10 wt. including mixed with 100 wt. hours of granulated polypropylene before feeding into the extruder.

Obtaining stabilized polypropylene compositions was carried out in an extruder in accordance with the conditions of example 2. The compositions of the obtained stabilized polymer compositions are given in table. 2.

Film threads were obtained similarly to the conditions of the prototype on a laboratory molding plant at a temperature of 265-270°C, the resulting thread was pulled 5-6 times at 135°C.

To assess the stability of the claimed stabilized polypropylene compositions and film threads obtained on their basis to photo- and thermal-oxidative degradation, parameters and techniques similar to those given in the prototype were used.

The resistance of the obtained polypropylene compositions to thermal oxidative degradation was evaluated by the induction period of polymer oxidation.

The oxidation induction period was determined on a manometric setup at 200°C and a pressure of 250 mm Hg. according to the well-known technique [K.P. Piotrovsky, Z.N. Tarasova Aging and stabilization of synthetic rubbers and vulcanizates. Moscow: Chemistry, 1980]. The induction period of polymer oxidation characterizes the effectiveness of the stabilizing action of antioxidants: the longer the duration of the induction period, the higher the stabilizing effect of the antioxidants used, the greater the inhibition of the chain process of polymer oxidation.

The resistance of threads to heat aging was evaluated by the decrease in the strength of the thread after heating in air at 150°C for 8 and 16 hours.

The resistance of the threads to light aging was evaluated by the decrease in the strength of the thread after irradiation on a device with a mercury-quartz lamp DRT-400 for 10 and 20 days.

The strength of the threads (breaking load) - initial and after heating or after irradiation for a specified time was determined according to GOST 6611.2-73 on a tensile testing machine IR 5061-0.05 at a temperature of 20°C.

The change in the strength of the polypropylene thread is a consequence of the processes of thermal and photo-oxidative degradation and characterizes the effectiveness of the stabilizing additives.

As follows from Table. 2, the claimed stabilized polypropylene compositions (1a-8a) are characterized in comparison with the prototype by a significantly higher resistance to thermal-oxidative degradation in terms of the oxidation induction period. So in the prototype, the value of the induction period is from 50 to 400 minutes, while for the claimed polymer compositions, the induction period is not less than 500 minutes (from 500 to 600 minutes), i.e. ~1.5-10 times more.

The high stability of the film threads obtained on the basis of the claimed stabilized compositions (1a-8a) to prolonged thermal exposure is confirmed by the results of determining the residual strength of the threads after thermal (150°C) exposure: the strength of the thread does not change after heating for 8 hours. Moreover, it was found that, unlike the prototype, the strength of the thread does not change even after a 2-fold increase in the duration of heating - up to 16 hours (Table 2).

The higher resistance of the film threads obtained on the basis of the claimed stabilized compositions (1a-8a) to prolonged light exposure is confirmed by the results of determining the residual strength of the threads after UV irradiation: the strength of the threads does not change after exposure for 10 days, while in the prototype it decreases by 10%. Moreover, it was found that after a 2-fold increase in the duration of UV exposure (up to 20 days), the strength of the threads either does not change or decreases slightly by 3–5% (Table 2).

Going beyond the claimed ratios of the components of the stabilizing mixture and the specified content of stabilizers in the polypropylene composition (compositions 7-10, Table 1) leads to a decrease in the stabilizing synergistic effect, and as a result, to a decrease in the stability of the polymer composition to thermal-oxidative degradation and deterioration in the light and heat resistance of the resulting film threads (compositions 9a-12a, Table 2).

The absence of preliminary grinding of the mixture of stabilizers in the mill to a particle size of 0.5–10 μm (composition 11, Table 1) leads to a decrease in the effectiveness of its stabilizing action in the composition of polypropylene (composition 13a, Table 2).

The use of polyphosphite(III) stabilizers in the composition with a molecular weight lower than the declared one (composition 12, Table 1) leads to a decrease in the effectiveness of its stabilizing action (composition 14a, Table 2) in the polypropylene compound.

It has been established that a change in the nature of the alkyl residue R ₁ (from C ₁ to C ₄ ) in the composition of the proposed polyphosphite(III) does not lead to a noticeable change in its stabilizing effect (Table 2).

Thus, the claimed stabilized polypropylene composition for producing film threads is characterized in comparison with the prototype by a higher resistance to thermal-oxidative degradation, and the film threads obtained on its basis have higher light and heat resistance. It is important that the resulting film threads retain their operational properties under prolonged exposure - with the duration of thermal and light exposure twice as long as specified in the prototype.

Example 1. Preparation of a stabilizing mixture.

The components of the stabilizing mixture: oligomeric polyphosphite(III), N-phenyl-2-naphthylamine and rutile titanium dioxide, taken in a mass ratio of 1:1:10, are mixed in a high-speed mixer at room temperature for 10 minutes. Next, the mixture is loaded into a ball mill and ground at room temperature for 30 min to a particle size of 0.5-10 μm. Get a mixture of stabilizers (1) (table. 1).

Similarly, stabilizing mixtures (2-12) are obtained, the composition of which is given in table. 1.

Example 2 Preparation of a stabilized polypropylene composition.

For the preparation of a stabilized polypropylene composition 100 wt. including polypropylene mixed with 1 wt. including stabilizing mixture (1) (table. 1), obtained under the conditions of example 1, in a high-speed mixer at room temperature for 10 minutes. Next, the mixture is extruded on a single screw extruder with a screw length to diameter ratio of 20:1 at 200-210°C to obtain a stabilized polypropylene composition (1a) in the form of granules.

Similarly, stabilized polypropylene compositions (2a-14a) are obtained, the composition of which is given in table. 2.

In experiments No. 7-10, examples of the composition of the stabilizing mixtures that go beyond the declared ratios of the components are given.

When preparing the mixture according to experiment No. 11, the mixture of components was not ground in a mill.

When preparing a mixture according to experiment No. 12, an oligomeric polyphosphite (III) with a lower than the declared molecular weight M _n was used.

When preparing the composition (13a), the mixture of stabilizers was not ground in a mill.

In the preparation of composition (14a) as part of the stabilizing mixture, polyphosphite(III) with a lower than the declared molecular weight M _n was used.

Claims (4)

1. A polypropylene composition stabilized against photo- and thermal-oxidative degradation for producing film filaments, including a polymer and a stabilizing mixture containing phosphite, a hindered secondary aromatic amine and titanium dioxide in an amount of 1-10 mass parts per 100 mass parts of the polymer, characterized in that that the stabilizing synergistic mixture contains polyphosphite, a secondary aromatic amine and crystalline rutile titanium dioxide at a mass ratio of components of 1:0.75-1.5:5-50, the stabilizing mixture is obtained by joint grinding of the components to a particle size of 0.5-10 μm, as a phosphite, it contains an organic oligomeric polyphosphite of the general formula:

where R ₁ = alkyl C ₁ - C ₄ ; n = 8-12, with an average molecular weight M _n 2500-4000. 2. Stabilized polypropylene composition according to claim 1, characterized in that it contains hindered N-phenyl-2-naphthylamine or N-isopropyl-N'-phenyl-1,4-phenylenediamine as a secondary aromatic amine.