Process for making an oxymethylene polymer

Abstract

A process for making an oxymethylene polymer comprising polymerizing at least one compound capable of forming —CH.sub.2O— repeat units (monomer) in the presence of at least one ester of the general formula I (ester): R.sup.1—CO—O—R.sup.2 (I) wherein R.sup.1 can be hydrogen, wherein R.sup.1 and R.sup.2 are independently of each other linear or branched C.sub.1 to C.sub.10 alkyl C.sub.5 to C.sub.7 cycloalkyl —[R.sup.3-0-].sub.nR.sup.4 wherein R.sup.3 is a linear or branched C.sub.2 to C.sub.5 alkylen and R.sup.4 is a linear of branched C.sub.1 to C.sub.5 alkyl and n is an integer of from 1 to 5. and in the presence of at least one Lewis acid.

Claims

1. A process for making an oxymethylene polymer comprising polymerizing at least one compound capable of forming —CH.sub.2O— repeat units (monomer) and at least one comonomer which is a cyclic ether or cyclic formal in the presence of at least one ester of the formula I (ester)
R.sup.1—CO—O—R.sup.2   (I) wherein R.sup.1 can be hydrogen, with the proviso that R.sup.2 is C.sub.2 alkyl or linear C.sub.3 to C.sub.4 alkyl, wherein R.sup.1 and R.sup.2 are independently of each other linear or branched C.sub.1 to C.sub.4 alkyl and in the presence of at least one Lewis acid, wherein the Lewis acid is an halogenide of boron, tin, titanium, phosphorus, antimony or arsenic, wherein the at least one Lewis acid is premixed with the at least one ester (premixture) and the weight ratio of the at least one ester to the at least one Lewis acid being of from 10:1 to 300:1.

2. The process according to claim 1, wherein the monomer is at least one cyclic oligomer of formaldehyde.

3. The process according to claim 1, wherein the premixture is added to the at least one monomer, the latter being liquid.

4. The process according to claim 3, wherein the premixture is first added to the at least one comonomer, the latter being liquid.

5. The process according to claim 1, wherein the Lewis acid is a boronhalide.

6. The process according to claim 1, wherein the at least one monomer is 1,3,5-trioxane.

7. The process according to claim 1, wherein the at least one comonomer is 1,3-doxolane or 1,3-dioxepane or a mixture thereof.

8. The process according to claim 1, wherein at least one chain transfer agent is present.

9. The process according to claim 8, wherein the chain transfer agent is methylal or butylal.

Description

EXAMPLES

(1) Molar Mass Determination

(2) The molar masses of the polymers were determined via size-exclusion chromatography in a SEC apparatus. This SEC apparatus was composed of the following combination of separating columns: a preliminary column of length 5 cm and diameter 7.5 mm, a second linear column of length 30 cm and diameter 7.5 mm. The separating material in both columns was PL-HFIP gel from Polymer Laboratories. The detector used comprised a differential refractometer from Agilent G1362 A. A mixture composed of hexafluoro isopropanol with 0.05% of potassium trifluoro acetate was used as eluent. The flow rate was 0.5 ml/min, the column temperature being 40° C. 60 microliters of a solution at a concentration of 1.5 g of specimen per liter of eluent were injected. This specimen solution had been filtered in advance through Millipor Millex GF (pore width 0.2 micrometers). Narrowly distributed PMMA standards from PSS (Mainz, DE) with molar masses M from 505 to 2.740.000 g/mol were used for calibration.

(3) Polydispersity Index

(4) Polydispersity index is defined as the weight average molecular weight divided by the number average molecular weight.

(5) Weight Loss Determination

(6) The thermal stability of the purified polymers was determined by heating a polymer sample under a constant flow of 15 l/h of nitrogen at 222° C. for two hours. The polymer sample was weighed prior to the heat treatment and after a cooling time of 20 minutes.

(7) Process for the Manufacture of Homopolymer:

Examples 1 to 12 and Comparative Examples C1 to C3

(8) A batch-wise, bulk polymerization of 100 g of the monomer 1,3,5-trioxane was carried out in air at 80° C.

(9) The reaction was initiated using 80 ppm a BF3*alkylether coordination compound (Lewis acid) dissolved an ester (premixture) as specified in Table 1. The premixture was dosed to the monomer.

(10) The polymer obtained was ground and extracted using a refluxing methanol/water/sodium carbonate (10 weight % solution in water) (23:44:1) mixture. After cooling the polymer was filtered and rinsed further with a 5 weight % sodium carbonate solution. The weight of the polymeric materials obtained after these two purification steps in relation to the mass of monomer used in the reaction is defined as the Yield given in Table 1.

(11) TABLE-US-00002 TABLE 1 Weight average Example and Ratio molecular Comparative Eter/Lewis weight MW Polydispersity Example Lewis acid Ester acid Yield (kg/mol) index 1 BF3*OMe2 Ethyl acetate  50:1 87 2 BF3*OMe2 Propyl acetate  50:1 86 3 BF3*OMe2 Propyl propionate  50:1 85 C1 BF3*OMe2 Benzene  50:1 51 4 BF3*OMe2 Ethyl acetate 100:1 89 176 9 5 BF3*OMe2 Propyl acetate 100:1 89 194 11 6 BF3*OMe2 Propyl propionate 100:1 90 153 8 C2 BF3*OMe2 Benzene 100:1 79 191 12 7 BF3*OEt2 Ethyl acetate 200:1 92 8 BF3*OEt2 Propyl acetate 200:1 88 9 BF3*OEt2 n-Butyl acetate 200:1 90 10  BF3*OEt2 Methyl propionate 200:1 92 11  BF3*OEt2 Ethyl propionate 200:1 81 12  BF3*OEt2 Propyl propionate 200:1 90 C3 BF3*OEt2 Methyl formate 200:1 80

Examples 13 and 14

(12) The process was carried out as specified above with the exception that instead of 80 ppm of Lewis acid 50 ppm of Lewis acid were used. See Table 2 for the respective summary.

(13) TABLE-US-00003 TABLE 2 Example and Ratio Comparative Ester/Lewis Example Lewis acid Ester acid Yield 13 BF3*OMe2 Ethyl acetate 300:1 93 14 BF3*OMe2 Propyl acetate 300:1 92
Process for the Manufacture of Copolymer:

Examples 15 to 18 and Comparative Examples C4

(14) A batch-wise, bulk polymerization of 96 g of the monomer 1,3,5-trioxane and 4 g of the comonomer 1,3-dioxolane was carried out in air at 80° C. The reaction was initiated using 80 ppm a BF3*OEt2 (Lewis acid).

(15) The Lewis acid was first dissolved an ester as specified in Table 3. This premixture was further mixed with the comonomer and then dosed into the monomer.

(16) The purification was carried out as described above for the homopolymers.

Examples 19 to 21 and Comparative Example C5

(17) The process was carried out as described above with the exception that the premixture was dosed to the mixture of monomer and comonomer.

(18) TABLE-US-00004 TABLE 3 Weight loss Weight average Example and Ratio upon thermal molecular Comparative Ester/Lewis treatment in N2 weight Polydispersity Example Lewis acid Ester acid Yield (wt %) (kg/mol) index 15 BF3*OEt2 Ethyl acetate 50:1 97.5 8.9 100 4.8 16 BF3*OEt2 Propyl acetate 50:1 97.3 12.6 122 6.0 17 BF3*OEt2 n-Butyl acetate 50:1 95.7 13.9 129 7.2 18 BF3*OEt2 Methyl formate 50:1 95.3 7.0 144 7.2 C4 BF3*OEt2 Benzene 50:1 96.7 8.6 151 7.0 19 BF3*OEt2 Ethyl acetate 100:1  97.8 8.6 130 6.6 20 BF3*OEt2 Propyl acetate 100:1  97.5 8.7 117 5.7 21 BF3*OEt2 n-Butyl acetate 100:1  97.6 13.6 116 5.7 C5 BF3*OEt2 Benzene 100:1  97.8 8.3 120 5.2