Powder mixture comprising organic peroxide

Abstract

Powder mixture comprising: 20-90 wt % of one or more powdered organic peroxides and 10-80 wt % of one or more powdered filler materials, at least 60 wt % thereof being barium sulphate.

Claims

1. Powder mixture comprising: 20-90 wt % of one or more powdered organic peroxides and 10-80 wt % of one or more powdered filler materials, at least 60 wt % thereof being barium sulphate.

2. Powder mixture according to claim 1 wherein the powder mixture comprises 1-30 wt % of water.

3. Powder mixture according to claim 1 wherein the organic peroxide is selected from the group consisting of dibenzoyl peroxide, substituted dibenzoyl peroxides, di (tert-butylperoxyisopropyl)benzene, dicumyl peroxide, di(dichlorobenzoyl)peroxides, diisopropyl peroxydicarbonate, di(t-butylcyclohexyl)peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, and didecanoyl peroxide.

4. Powder mixture according to claim 3 wherein the organic peroxide is selected from the group consisting of dibenzoyl peroxide and substituted dibenzoyl peroxides.

5. Powder mixture according to claim 4 wherein the organic peroxide is di(4-methylbenzoyl) peroxide.

6. Powder mixture according to claim 1 wherein barium sulphate contains primary particles with an average particle size (d50) in the range 0.5-3 microns.

7. Process for the preparation of a powder mixture according to claim 1 wherein 20-90 wt % of one or more powdered organic peroxides and 10-80 wt % of one or more powdered filler materials, at least 60 wt % thereof being barium sulphate, are homogenized and de-agglomerated until an average particle diameter (d50) below 200 microns is reached.

8. Process according to claim 7 wherein the powdered organic peroxide contains 5-70 wt % of water.

9. Process according to claim 7 wherein the organic peroxide is selected from the group consisting of dibenzoyl peroxide, substituted dibenzoyl peroxides, di(tert-butylperoxyisopropyl)benzene, dicumyl peroxide, di(dichlorobenzoyl)peroxides, diisopropyl peroxydicarbonate, di (t-butylcyclohexyl)peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, and didecanoyl peroxide.

10. Process according to claim 9 wherein the organic peroxide is selected from the group consisting of dibenzoyl peroxide and substituted dibenzoyl peroxides.

11. Process according to claim 10 wherein the organic peroxide is di(4-methylbenzoyl) peroxide.

12. Coating composition comprising the powder mixture according to claim 1.

13. A method of curing a radically curable thermosetting resin comprising the step of curing the radically curable thermosetting resin with the powder mixture of claim 1.

14. A method of curing a coating composition comprising the step of curing the coating composition with the powder mixture of claim 1.

15. A method for radical polymerization comprising the step of initiating the radical polymerization with the powder mixture of claim 1.

Description

EXAMPLES

Example 1

(1) Three different compositions of di(4-methylbenzoyl)peroxide and barium sulphate were prepared by manually mixing barium sulphate with di(4-methylbenzoyl)peroxide. The resulting mixtures were treated with a hammer mill equipped with a 1.5 mm sieve to obtain a homogeneous mixture.

(2) The compositions differed in peroxide content and type of barium sulphate (natural or synthetic).

(3) Composition A: 65 wt % synthetic BaSO.sub.4 (Blanc Fixe micro, ex. Sachtleben Chemie GmbH; d50=0.7 microns) and 35 wt % di(4-methylbenzoyl)peroxide.

(4) Composition B: 60 wt % natural BaSO.sub.4 (CIMBAR EX, ex CIMBAR Performance Minerals; d50=0.8-1.4 microns) and 40 wt % di(4-methylbenzoyl)peroxide containing 25 wt % of water.

(5) Composition C: 60 wt % natural BaSO.sub.4 (CIMBAR UF, ex CIMBAR Performance Minerals; d50=1.6-5.8 microns) and 40 wt % di(4-methylbenzoyl)peroxide containing 25 wt % of water

(6) Each composition was tested for segregation stability by charging it into a stainless steel cylinder (diameter 10-11 cm, length 50 cm) tilted at an angle of 15 and slowly (71 min.sup.1) rotating it around its axis for 200.5 minutes.

(7) From the upper, middle, and lower part of the cylinder, a sample was taken and the active oxygen content of each sample was determined by iodometric titration. These active oxygen contents were compared with the active oxygen content of the composition prior to the segregation test ('the starting sample').

(8) A mixture is considered to segregate if:
(|p.sub.op.sub.u|)/p.sub.o>M or (|p.sub.op.sub.m|)/p.sub.o>M or (|p.sub.op.sub.l|)/p.sub.o>M

(9) wherein: p.sub.o=active oxygen content of the starting sample

(10) p.sub.u=active oxygen content of the upper layer sample

(11) p.sub.m=active oxygen content of the middle layer sample

(12) p.sub.i=active oxygen content of the lower layer sample

(13) M=the accepted relative deviation (10%)

(14) The results for the three compositions were as follows:

(15) TABLE-US-00001 Relative deviation (%) Composition Upper layer Middle layer Lower layer A 2.4 2.4 0.7 B 0.9 3.0 2.9 C 2.2 1.4 0.7

(16) All three samples were therefore considered stable to segregation.

Example 2

(17) Two different compositions of a peroxide and barium sulphate were prepared by manually mixing barium sulphate with the peroxide. The resulting mixtures were treated with a hammer mill equipped with a 1.5 mm sieve to obtain a homogeneous mixture.

(18) Composition D: 70 wt % synthetic BaSO.sub.4 (Blanc Fixe micro, ex. Sachtleben Chemie GmbH; d50=0.7 microns) and 30 wt % di(tert-butylperoxy-isopropyl)benzene.

(19) Composition E: 70 wt % natural BaSO.sub.4 (Blanc Fixe micro, ex. Sachtleben Chemie GmbH; d50=0.7 microns) and 30 wt % dicumylperoxide.

(20) Each composition was tested for segregation stability using the test described in Example 1. The results were as follows:

(21) TABLE-US-00002 Relative deviation (%) Composition Upper layer Lower layer D 2.9 0.6 E 3.3 1.7

(22) Both samples were considered stable to segregation.

Comparative Example

(23) A composition comprising 30 wt % di(4-methylbenzoyl)peroxide and 70 wt % magnesium sulphate heptahydrate (ex-Sigma Aldrich) was prepared by manually mixing the magnesium sulphate with di(4-methylbenzoyl)peroxide. Immediately after this mixing, a very wet mixture was obtained that could not be milled. This was due to the hygroscopy of magnesium sulphate.

(24) A powder mixture could therefore not be obtained.

(25) Using anhydrous magnesium sulphate was not an option. Anhydrous magnesium sulphate is very hydroscopic and reacts exothermically with water or moisture. As a result, contact with water or moisture will increase the temperature of the composition and may lead to decomposition of the di(4-methylbenzoyl)peroxide.