Dialkyl peroxide composition for modifying the rheology of polypropylene in molten state

Abstract

The present invention relates to a liquid composition comprising at least one dialkyl peroxide, in liquid form at ambient temperature, at a content comprised within a range of from 75 to 77% by weight relative to the total weight of the composition, and at least one mineral oil with viscosity greater than 15 mPa.Math.s, measured at a temperature of 10° C. and at a shear rate of 1000 s.sup.−1. Furthermore, the invention relates to the use of said composition to modify the melt rheology of the polypropylene.

Claims

1. A liquid composition comprising at least one dialkyl peroxide, in liquid form at ambient temperature, with a content greater than 72% by weight and strictly less than 80% by weight, relative to the total weight of the composition, and at least one mineral oil with viscosity greater than 15 mPa.Math.s, measured at a temperature of 10° C. and a shear rate of 1000 s.sup.−1.

2. The composition according to claim 1, wherein the dialkyl peroxide is selected from the group consisting of 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexyne-3, ditert-butylperoxide, ditert-amyl peroxide, 2,5-dimethyl-2,5(di(tert-butylperoxy)hexane, and mixtures thereof.

3. The composition according to claim 1, wherein the dialkyl peroxide comprises 2,5-dimethyl-2,5(di(tert-butylperoxy)hexane.

4. The composition according to claim 1, wherein the content of the dialkyl peroxide is comprised within a range of from 73 to 79% by weight, relative to the total weight of the composition.

5. The composition according to claim 1, wherein the mineral oil has a viscosity of from 15 to 1000 mPa.Math.s, measured at a temperature of 10° C. and at a shear rate of 1000 s−1.

6. The composition as claimed in claim 1, wherein the mineral oil is chosen among the paraffin oils.

7. The composition as claimed in claim 1, wherein the composition shows a low or no effect when heated under confinement.

8. A method for modifying a melt rheology of a polypropylene comprising extruding the polypropylene at a temperature of between 140 and 300° C., for a few seconds to a maximum of a few minutes in the presence of the composition of claim 1.

9. The method according to claim 8, of visbreaking the polypropylene.

10. The method according to claim 8, wherein the melt flow index of the polypropylene is increased.

11. The method according to claim 8, wherein the polypropylene comprises a propylene homopolymer or propylene copolymer comprising at least one comonomer selected from the group consisting of ethylene, 1-butene, 1-hexene and 1-octene.

12. A method of decreasing the explosion intensity of a composition comprising at least one dialkyl peroxide in a content strictly greater than 70% by weight, relative to the total weight of the composition, comprising introducing at least one mineral oil with viscosity greater than 15 mPa.Math.s, measured at a temperature of 10° C. and at a shear rate of 1000 s.sup.−1.

Description

EXAMPLES

(1) The composition according to the invention (A) and two comparative compositions (B) and (C) were prepared using the following raw materials:

(2) A. Raw Material Used

(3) The dialkyl peroxide used is 94.4% pure 2,5-dimethyl-2,5(di(tert-butylperoxy)hexane sold by ARKEMA under the brand name Luperox® 101.

(4) B. Method used to Prepare the Compositions

(5) Firstly, the 2,5-dimethyl-2,5(di(tert-butylperoxy)hexane was diluted in a white mineral oil with a viscosity of 321 mPa.Math.s at 10° C., 1000 s.sup.−1, to obtain: a composition comprising 77% by weight of dialkyl peroxide relative to the total weight of the composition (composition A according to the invention); and a composition comprising 71% by weight of dialkyl peroxide relative to the total weight of the composition (comparative composition B).

(6) Then, the 2,5-dimethyl-2,5(di(tert-butylperoxy)hexane was diluted in isododecane with a viscosity of 1.7 mPa.Math.s at 10° C., 1000 s.sup.−1, to obtain: a composition comprising 71% by weight of dialkyl peroxide relative to the total weight of the composition (comparative composition C).

(7) Viscosities were measured at a temperature of 10° C. with a Haake VT550 viscotester equipped with an NV rotor and at different shear rates. Viscosity at 1000 s.sup.−1 was interpolated from the results with similar shear rates.

(8) C. Comparative Tests

(9) Comparative tests were conducted in accordance with UN methods E1 and E2 in the sections on organic peroxides of the Manual of Tests and Criteria of the UN Recommendations on the Transport of Dangerous Goods, revised edition of 2015.

(10) The purpose of UN methods E1 and E2 is to determine the sensitivity of compositions (A), (B) and (C) when heated to high temperatures under defined confinement. These methods are defined in section 25, “Test Series E”, of the UN Manual of Tests and Criteria, 6.sup.th revised edition.

(11) The method UN E1 consists in rapidly heating a certain amount of product to be tested in a closed tube with a calibrated aperture in its upper portion. Based on the deformation of the tube, if any, or on the rupture diagram of the tube, the result is classified as “explosion” or “no explosion”, for each test conducted. The tests were conducted at diameters increasing from 1 to 10 nm until 3 “no explosion” results were obtained for a given diameter. The limiting diameter recorded in the results is the largest diameter for which at least one test in three had an “explosion” result. Depending on the limiting diameter and on the deformation diagram of the tube, the effect is classified as “violent”, “moderate”, “low” or “null”.

(12) The method UN E2 consists in rapidly heating a certain amount of product to be tested in a closed tube with a calibrated aperture in its upper portion and a rupture disk with a burst pressure of 6 bars. The degree of sensitivity of a substance to heating under confinement in accordance with test UN E2 is expressed in limiting diameter.

(13) The is the largest diameter, in mm, of the calibrated aperture for which the rupture disk burst in at least one test in three.

(14) D. Results

(15) The results are complied in the following tables:

(16) 1. Results according to method UN E1

(17) TABLE-US-00001 Concentration Solvent Results Compo- in organic viscosity for a diameter of sition peroxide Solvent (mPa .Math. s) 1 mm 1.5 mm C 71% Isododecane 1.7 Explosion No explosion A 77% White 321 Explosion No mineral oil explosion *Measured at 10° C., 1000 s.sup.−1

(18) 2. Results According to Method E2

(19) TABLE-US-00002 Concentration Limiting in organic Viscosity diameter Composition peroxide Solvent (mPa .Math. s) in mm C 71% Isododecane 1.7 s.sup.−1 2 B 71% White 321 1 mineral oil A 77% White 321 2 mineral oil

(20) The tests conducted on heating under confinement resulted in a “low” intensity of the decomposition of the dialykyl peroxide, for the three products tested in accordance with the UN recommendations.

(21) These results, as a supplement to other tests, led to the classification by the BAM (“Bundesanstalt für Materialforschung und -prüfung”) classification of the three products tested as type F for transport and storage pursuant to the UN classification.

(22) Moreover, the use of a solvent having a high-viscosity enables to reduce the violence of decomposition, for an identical concentration, or, for the same degree of violence of decomposition in the test of heating under constraint, to substantially increase the concentration in active material.

(23) Dialkyl peroxide composition for modifying the rheology of polypropylene in molten state.

(24) The present invention relates to a liquid composition comprising at least one dialkyl peroxide, in liquid form at ambient temperature, at a content comprised within a range of from 75 to 77% by weight relative to the total weight of the composition, and at least one mineral oil with viscosity greater than 15 mPa.Math.s, measured at a temperature of 10° C. and at a shear rate of 1000 s.sup.−1.

(25) Furthermore, the invention relates to the use of said composition to modify the melt rheology of the polypropylene.