Alpha halo substituted asymmetrical diacyl peroxides in co-initiator systems

Abstract

Organic peroxide polymerization co-initiator compositions and their use in the initiation of the polymerization of certain monomers and comonomers such as vinyl chloride, ethylene and methyl methacrylate. The co-initiator composition contains an alpha halo substituted diacyl peroxide and a coperoxide selected from t-alkyl peresters of t-hydroperoxides, peroxydicarbonates, acyl peroxycarbonic esters, and aliphatic diacyl peroxides. Typical is acetyl 2-chlorooctanoyl peroxide with t-butyl peroxy neodecanoate.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to organic peroxide compositions and their use in the polymerization of monomers and comonomers. More particularly, the invention relates to co-initiator compositions which combine an alpha halo substituted diacyl peroxide with a coperoxide.

2. Brief Description of the Prior Art

Various co-initiator compositions have been employed for initiating polymerization of monomers such as vinyl chloride. U.S. Pat. Nos. 3,687,867 and 3,420,807 disclose co-initiator systems containing peresters and diacyl peroxides.

U.S. Pat. Nos. 3,022,282 and its Re. 25,763 disclose the use of a combination of dialkyl peroxy dicarbonate with lauroyl peroxide.

U.S. Pat. No. 3,781,255 discloses a co-catalyst system of tertiary alkyl peresters with acetyl cyclohexyl sulfonyl peroxide (ACSP).

Alpha halo substituted asymmetrical diacyl peroxides (AHSADP) of the type used in the present co-initiator system are disclosed in U.S. Pat. No. 3,652,681, but not in a coinitiator system.

Acyl peroxy carbonic esters of the type utilized herein as coperoxides with AHSADP are disclosed in U.S. Pat. Nos. 3,585,232, 3,652,524, 3,736,344 and 3,108,093, but not in a co-initiator system.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The novel co-initiator compositions of this invention provide improvements over the prior art in several ways. The polymer end product obtained with the use of the present initiators demonstrates improved heat stability, as well as having a finer particle size distribution. The co-initiators also demonstrate improved efficiencies in polymer yield, particularly under certain polymerization conditions. In accordance with the present invention these improvements are obtained with an organic peroxide polymerization co-initiator composition comprising:

(a) an alpha halo substituted diacyl peroxide of the structure ##STR1## where R = alkyl group of 1-11 carbon atoms AND R' = alkyl group of 2-10 carbon atoms; And (b) a coperoxide selected from (1) t-alkyl peresters of t-hydroperoxides of the structure ##STR2## where R = t-alkyl of 4-20 carbon atoms and R' = t-alkyl of 4-20 carbon atoms (2) peroxydicarbonates of the structure ##STR3## where each R = alkyl or cycloalkyl of 1-18 carbon atoms (3) acyl peroxycarbonic esters of the structure ##STR4## where R = alkyl or aryl of 1-11 carbon atoms and R' = alkyl of 1-18 carbon atoms (4) aliphatic diacyl peroxides of the structure ##STR5## where each R = alkyl of 2-11 carbon atoms

In the case where the coperoxide is a t-alkyl perester of a t-hydroperoxide, the perester preferably has the formula ##STR6## wherein R' has the above definition, R.sub.1 and R.sub.2 are alkyl groups with 1-4 carbon atoms and R.sub.3 is a straight-chain or branched alkyl group with 1-18 carbon atoms.

Examples of such peresters are found in the peresters utilized in the co-catalyst system of U.S. Pat. No. 3,781,255. Within these preferred peresters it is desirable that R' have the formula ##STR7## in which each of R.sub.4, R.sub.5 and R.sub.6 is an alkyl group and where no more than one of R.sub.4, R.sub.5 and R.sub.6 is a methyl group. Preferred peresters of this latter type are utilized in the co-initiator systems of U.S. Pat. No. 3,687,867.

Examples of peroxy dicarbonate coperoxides are secbutyl peroxydicarbonate (SBPC) and diisopropyl peroxydicarbonate (IPP).

Examples of acyl peroxycarbonic ester coperoxides are found in the above cited prior art patents, the disclosures of which are incorporated herein by reference.

Typical aliphatic diacyl peroxides include lauroyl peroxide, decanoyl peroxide and 3,5,5-trimethyl hexanoyl peroxide.

The co-initiators are employed in any weight ratio which provides the desired improved results. Typically, the weight ratio of alpha halo substituted diacyl peroxide to coperoxide is about 3:1 to 1:3, preferably 1:2.

The co-initiator is utilized to initiate the polymerization of various monomers and comonomers. To date the present coinitiators have been found to be beneficial in the polymerization of vinyl chloride monomer to form polyvinyl chloride homopolymer and for copolymerization of vinyl chloride with comonomer such as vinyl acetate. The co-initiators are also useful for the polymerization of ethylene and acrylates such as methyl methacrylate. Generally, the polymerization conditions will be similar to the prior art polymerization of these monomers in terms of concentrations, solvents, temperatures, pressures and the like. For example, the temperature range for polymerization of the above mentioned monomers and comonomers with the exception of ethylene is approximately 30.degree.-80.degree. C. Ethylene is polymerized at elevated temperatures and pressure as is known in the art. In the case of the polymerization of vinyl chloride, in accordance with the present invention best results have thus far been obtained where the polymerization is executed in a aqueous suspension medium at a pH of about 11.

The following examples will illustrate the present invention. For comparison, the present co-initiators were tested against co-initiator systems containing ACSP as disclosed in U.S. Pat. No. 3,781,255. This comparative prior art system was selected because it is presently the preferred commercial system and has approximately the same ten hour half-life temperature as the present alpha halo substituted diacyl peroxides.

Throughout this application the following abbreviations are used:

Tbpn -- t-butyl peroxyneodecanoate Tbpp -- t-butyl peroxypivalate Appc -- acetyl peroxy n-propyl carbonate A2clOP -- acetyl 2-chlorooctanoyl peroxide P2clOP -- propionyl 2-chlorooctanoyl peroxide L2clbp -- lauroyl 2-chlorobutyryl peroxide

A series of suspension polymerizations were executed in pop bottles with the results shown in Tables 1-3. In general, the suspension polymerizations were performed in pop bottles similar to the method described in Pat. application Ser. No. 520,072 filed Nov. 1, 1974.

Both uninhibited vinyl chloride and vinyl acetate were used in this work. The following table lists some general information about the polymerization procedure used:

______________________________________ Amt. SuspensionMixing Speed, H.sub.2 O/Monomer Agent/100 g.RPM Ratio Monomer______________________________________42 2.5 0.35 g. Dow Methocel 90 HG, 100 cps______________________________________ Buffering solutions were prepared as shown in the following table. pH of each suspension solution was determined by use of a pH meter. ______________________________________pH Amount Buffering Agents/100 g. Monomer______________________________________ 4 3.83 g. potassium hydrogen phthalate and 0.0014 g. HCl11 0.23 g. NaOH and 0.54 g. NaHCO.sub.3______________________________________ Table 1__________________________________________________________________________Comparison Between Co-initiator Systems as Initiators of Vinyl Chlorideat 55.degree. C. Total Moles 100 g. VCM % ConversionCo-initiator System % Wt. (.times. 10.sup.-4 moles pH Hrs. 1.5 3.5 5.5__________________________________________________________________________1. TBPN/ACSP 0.0367/0.0183 2.33 7 31.3 63.9 82.4 4 35.6 68.1 81.4 11 16.9 43.4 65.82. TBPN/A2ClOP 0.0367/0.0196 2.33 7 24.2 60.6 79.2 4 27.7 64.3 80.8 11 25.2 55.9 77.63. TBPP/ACSP 0.0367/0.0183 2.94 7 35.6 66.1 81.5 4 27.0 52.1 71.8 11 10.7 27.0 57.34. TBPP/A2ClOP 0.0367/0.0196 2.94 7 15.9 46.9 65.6 4 16.0 47.2 66.1 11 15.3 38.3 57.6__________________________________________________________________________ Table 2__________________________________________________________________________Comparison Between Co-initiator Systems as Initiators of Vinyl Chlorideat 60.degree. C. Total Moles 100 g. VCM % ConversionCo-initiator System % Wt. (.times. 10.sup.-4 moles pH Hrs. 1.5 3.5 5.0__________________________________________________________________________1. TBPN/ACSP 0.034/0.017 2.16 7 34.1 69.0 79.7 4 44.3 73.5 80.8 11 24.1 53.9 70.42. TBPN/A2C10P 0.034/0.0182 2.16 7 33.5 70.4 80.1 4 30.3 68.1 79.5 11 29.2 65.3 78.33. TBPN/P2C10P 0.034/0.0193 2.16 7 35.5 70.4 80.5 4 36.5 73.2 82.2 11 33.2 65.4 78.34. TBPN/L2C1BP 0.034/0.0247 2.16 7 34.3 70.6 80.5 4 33.6 66.9 78.4 11 31.8 67.4 78.35. TBPP/ACSP 0.0367/0.0183 2.94 7 33.6 64.6 80.4 4 32.7 64.1 79.8 11 15.7 44.6 64.66. TBPP/A2C10P 0.0367/0.0196 2.94 7 23.9 58.5 76.4 4 23.5 58.8 77.0 11 23.7 53.7 75.87. SBPC/ACSP 0.0255/0.0085 1.47 7 32.5 65.7 82.2 4 30.9 63.3 80.1 11 37.5 51.1 66.58. SBPC/A2C10P 0.0255/0.0091 1.47 7 28.2 63.6 79.4 4 29.3 62.2 77.4 11 27.1 52.7 70.49. APPC/ACSP 0.0307/0.0153 2.58 7 29.4 56.6 78.2 4 29.4 56.5 76.8 11 3.8 4.5 4.710. APPC/A2C10P 0.0307/0.0164 2.58 7 24.3 56.7 74.9 4 21.5 51.0 72.6 11 11.0 16.8 20.7__________________________________________________________________________ Table 3__________________________________________________________________________Comparison Between Co-initiator Systems as Initiators in CopolymerizationofVinyl Chloride/Vinyl Acetate88%/12% Vinyl Chloride/Vinyl Acetate Total Moles Polym. 100 g. Monomer Temp. % ConversionCo-initiator System % Wt. (.times. 10.sup.-4 moles) pH .degree. C Hrs. 1.5 3.5 5.0 5.5__________________________________________________________________________Set 11. TBPN/ACSP 0.0367/0.0183 2.33 7 55 34.7 66.9 -- 80.82. TBPN/A2C10P 0.0367/0.0196 2.33 7 55 25.0 59.3 -- 78.4Set 23. TBPN/ACSP 0.034/0.017 2.16 7 60 37.3 68.3 76.3 -- 11 60 34.7 61.8 72.1 --4. TBPN/A2C10P 0.034/0.0182 2.16 7 60 26.0 64.0 75.0 -- 11 60 34.8 62.6 71.7 --5. TBPP/ACSP 0.0367/0.0183 2.94 7 60 31.7 61.6 76.9 -- 11 60 28.6 57.5 73.6 --6. TBPP/A2C10P 0.0367/0.0196 2.94 7 60 23.5 55.3 72.3 -- 11 60 24.3 53.5 70.3 --7. APPC/ACSP 0.0307/0.0153 2.58 7 60 27.9 56.8 75.5 --8. APPC/A2C10P 0.0307/0.0164 2.58 7 60 24.0 52.1 72.3 --__________________________________________________________________________ Table 1 at 55.degree. C 13 The coinitiator system of TBPN/A2ClOP has almost equivalent efficiency at pH's 4 and 7 as TBPN/ACSP, and has superior efficiency at pH 11. The coinitiator system of TBPP/A2ClOP is not as efficient at pH's 4 and 7 as TBPP/ACSP, but is as efficient at PH 11. In addition, the drop-off in conversion at pH 11 with TBPP/A2ClOP is not as large as with TBPP/ACSP. Table 2 at 60.degree. C -- All of the coinitiator systems of TBPN/AHSADP performed as efficiently at pH's 4 and 7 compared to TBPN/ACSP as occurred at 55.degree. C. Again, superior performance was obtained at pH 11. With the other three co-initiator pairs, the ones containing A2ClOP have almost equivalent efficiencies at pH's 4 and 7 and superior efficiencies at pH 11 compared to the ones containing ACSP.

In the copolymerization of 88%/12% vinyl chloride/vinyl acetate in Table 3, testing was done at two pH levels: 7 and 11. The co-initiator system of TBPN/A2ClOP is almost as efficient as TBPN/ACSP at both 55.degree. and 60.degree. C. However, with the other two co-initiator pairs, the systems containing A2ClOP are not quite as efficient as those containing ACSP. In addition, the superior performance found at pH 11 in homopolymerization is not evident in copolymerization.

Another way of demonstrating the advantage gained from the present preferred co-initiator systems containing AHSADP is to compare the heat stability of these resins to those made from coinitiator systems containing ACSP. The same weight ratios of initiators were used as shown in Tables 1-3 at pH 7, so that heat stability of the resin pairs obtained at the same total molar initiator levels were compared. Both homopolymer and copolymer resins were collected; each was a composite of five bottles. Outstanding results were obtained with the copolymer resins. Typical formulations were chosen where copolymer resins would normally be used, as for calendered and/or vacuum-formed clear sheets or for phonograph records. The control is a commercial 85/15 vinyl chloride/vinyl acetate copolymer (VYHH, Union Carbide) used in these applications. Tests were run similar to those described in Tables III-V of U.S. Pat. No. 3,558,537. Results are found in Tables 4 and 5. In four out of five resin pair comparisons, the resins made from coinitiator systems containing AHSADP had superior heat stability. All the resins were better than the control in both tests.

Table 4__________________________________________________________________________Heat Stability of Vinyl Chloride/Vinyl Acetate Copolymer Resins Collectedat 60.degree. C at pH 7Tested at 350.degree. F., 60 parts resin milled with 1.8 parts dibutyltin dialkyl maleateCoperoxide (A) TBPP TBPP APPC APPC TBPN ControlACSP or A2C10P (B) ACSP A2C10P ACSP A2C10P A2C10P --Avg. Resin Yield, g. 57.42 54.05 56.39 52.62 55.79 --Standard Deviation 0.20 0.27 0.30 0.30 0.04 --Elapsed Time,Minutes 0 Colorless Colorless Colorless Colorless Colorless Colorless15 Do..sup.1) Do. Do. Do. Do. Do.30 Pale Yellow Do. Pale Yellow Do. Do. Olive Green45 Lt. Yellow Pale Yellow Lt. Green Pale Yellow Pale Yellow Green Brown60 Med. Olive Lt. Green Med. Olive Lt. Yellow Lt. Yellow Lt. Brown Green Green Green Green75 Dark Olive Med. Olive Dark Olive Med. Yellow Med. Yellow Med. Brown Green Green Green Green Green90 Med. Green Dark Olive Dark Green Med. Straw Dark Olive Dark Brown Brown Green Brown Yellow Green105 Dark Brown Lt. Brown Dark Brown Dark Straw Lt. Brown Dark Brown Yellow__________________________________________________________________________ .sup.1) Ditto Table 5__________________________________________________________________________Heat Stability of Vinyl Chloride/Vinyl Acetate Copolymer Resins Collectedat 60.degree. C at pH 7Tested at 300.degree. F., 60 parts resin milled with 0.6 part lead bariumlaurateCoperoxide (A) TBPN TBPN TBPP TBPP APPC APPC ControlACSP or A2C10P (B) ACSP A2C10P ACSP A2C10P ACSP A2C10P --Avg. Resin Yield, g. 57.78 55.79 57.42 54.05 56.39 52.62 --Standard Deviation 0.29 0.04 0.20 0.27 0.30 0.30 --Elapsed Time,Minutes 0 Colorless Colorless Colorless Colorless Colorless Colorless Colorless15 Do. Do. Do. Do. Do. Do. Do.30 Do. Do. Do. Do. Do. Do. Pale Yellow45 Pale Yellow Do. Pale Yellow Pale Yellow Pale Yellow Pale Yellow Black60 Lt. Yellow Pale Yellow Lt. Yellow Lt. Yellow Lt. Yellow Lt. Yellow Do.75 Do. Do. Do. Lt. Olive Lt. Olive Do. -- Green Green90 Olive Green Pale Green Lt. Olive Olive Green Yellow Green Lt. Olive -- Green Green105 Med. Green Lt. Olive Olive Green Med. Green Med. Yellow Med. Yellow -- Green Green Green120 Dark Green Med. Yellow Med. Yellow Dark Yellow Green Do. -- Brown Green Green Green__________________________________________________________________________

Sieve analyses were also run on the resins collected for heat stability testing. Two hundred grams of composite resin were added to the top sieve (20 mesh) in the stack. The stack was covered and placed in a Cenco-Meinzer Sieve Shaker for ten minutes at 5 setting on the control dial (10 maximum). Results of testing resins made from four co-initiator pairs are shown in Table 6. As can be seen, resins made from the preferred co-initiator systems containing AHSADP have a finer particle size distribution in three out of four pairs.

Table 6__________________________________________________________________________Sieve Analysis of Various Resins Collected at 60.degree. C. at pH 7 Avg. Resin Standard Sieve Analysis - % Retained on Tyler Standard SieveCo-initiator System Yield, g. Deviation Sieve No. 20 35 60 80 100 Pan__________________________________________________________________________Set 1 - Homopolymer1. TBPP/ACSP 60.95 0.25 3.3 36.0 39.8 7.5 4.2 9.5TBPP/A2ClOP 59.12 0.09 2.3 25.5 42.6 10.8 5.8 13.02. SBPC/ACSP 61.94 0.23 3.5 36.4 40.1 8.0 4.1 7.9SBPC/A2ClOP 59.43 0.18 3.7 31.0 41.5 9.5 4.8 9.5Set 2 - Copolymer3. TBPN/ACSP 57.78 0.29 2.5 10.7 56.1 13.0 7.2 10.5TBPN/A2ClOP 55.79 0.04 2.6 7.4 50.1 17.2 8.9 13.84. APPC/ACSP 56.39 0.30 3.1 5.9 52.5 17.2 9.1 12.2APPC/A2ClOP 52.62 0.30 6.9 7.2 43.1 19.4 9.5 13.9__________________________________________________________________________

Claims

1. In the polymerization and copolymerization of vinyl chloride, polymerization of ethylene and polymerization of acrylates by subjecting said monomers and comonomers to polymerization conditions in the presence of an initiating amount of an organic peroxide, the improvement wherein said organic peroxide is a coinitiator composition comprising:

(a) an alpha halo substituted diacyl peroxide of the structure ##STR8## where R = alkyl group of 1-11 carbon atoms and R' = alkyl group of 2-10 carbon atoms;

and

(b) a coperoxide selected from

(1) t-alkyl peresters of t-hydroperoxides of the structure ##STR9## where R = t-alkyl of 4-20 carbon atoms and R' = t-alkyl of 4-20 carbon atoms

(2) peroxydicarbonates of the structure ##STR10## where each R -- alkyl or cycloalkyl of 1-18 carbon atoms (3) acyl peroxycarbonic esters of the structure ##STR11## where R = alkyl or aryl of 1-11 carbon atoms and R' = alkyl or 1-18 carbon atoms

(4) aliphatic diacyl peroxides of the structure ##STR12## where each R = alkyl of 2-11 carbon atoms, wherein the weight ratio of alpha halo substituted diacyl peroxide to coperoxide is about 3:1 to 1:3.

2. The improved method in accordance with claim 1, wherein the monomer being polymerized in vinyl chloride and the polymerization is executed in an aqueous medium at a pH of about 11.

3. The improved method in accordance with claim 1, wherein said coperoxide selected from t-alkyl peresters of t-hydroperoxides has the formula: ##STR13## wherein R' has the definition of claim 1, R.sub.1 and R.sub.2 are alkyl groups with 1-4 carbon atoms and R.sub.3 is a straightchain or branched alkyl group with 1-18 carbon atoms.

4. The improved method in accordance with claim 3, wherein R' has the formula: ##STR14## in which each of R.sub.4, R.sub.5 and R.sub.6 is an alkyl group.

5. The improved method in accordance with claim 4, wherein each of R.sub.4, R.sub.5 and R.sub.6 is methyl.

6. The improved method in accordance with claim 4, wherein not more than one of R.sub.4, R.sub.5 and R.sub.6 is a methyl group.

7. The improved method in accordance with claim 4, wherein R.sub.4, R.sub.5 and R.sub.6 collectively contain 8 carbon atoms to form part of a neodecanoate group.

8. The improved method in accordance with claim 1, wherein said coperoxide is the peroxydicarbonate sec-butyl peroxydicarbonate.

9. The improved method in accordance with claim 1, wherein said coperoxide is a t-alkyl perester of a t-hydroperoxide as defined therein.

10. The improved method in accordance with claim 1, wherein said coperoxide is a peroxydicarbonate as defined therein.

11. The improved method in accordance with claim 1, wherein said coperoxide is an acyl peroxycarbonic ester as defined therein.

12. The improved method in accordance with claim 1, wherein said coperoxide is an aliphatic diacyl peroxide as defined therein.

13. The improved method in accordance with claim 1, wherein said coperoxide is the acyl peroxycarbonic ester acetyl peroxy n-propyl carbonate.

14. The improved method in accordance with claim 1, wherein said alpha halo substituted diacyl peroxide is acetyl 2-chlorooctanoyl peroxide.

15. The improved method in accordance with claim 1, wherein said alpha halo substituted diacyl peroxide is propionyl 2-chlorooctanoyl peroxide.

16. The improved method in accordance with claim 1, wherein said alpha halo substituted diacyl peroxide is lauroyl 2-chlorobutyryl peroxide.

17. The improved method in accordance with claim 1, wherein the weight ratio of alpha halo substituted diacyl peroxide to coperoxide is about 1:2.

18. The improved method in accordance with claim 7, wherein the monomer being polymerized is vinyl chloride and the polymerization is executed in an aqueous medium at a pH of about 11.