Polyetherpolyol with Low Content of Cyclic Oligomers

Abstract

The present invention refers to polyetherpolyols which are characterized by a low content of cyclic by-products as well as to a method for producing the polyetherpolyol and an adhesive composition comprising the same.

Claims

1. A polyetherpolyol that is the reaction product by co-polymerization of a compound A containing at least one epoxide moiety and a compound B capable of undergoing a ring opening reaction, wherein compound A and compound B are different from each other and wherein the co-polymerization is carried out in the presence of a Brønsted acid with a weakly coordinating and non-nucleophilic anion.

2. The polyetherpolyol according to claim 1 wherein compound B is selected from five-membered heterocyclic rings and six-membered heterocyclic rings, wherein the five-membered heterocyclic rings and six-membered heterocyclic rings can be optionally substituted.

3. The polyetherpolyol according to claim 1 wherein compound B is selected from five-membered cyclic ethers and six-membered cyclic ethers, wherein the five-membered cyclic ethers and six-membered cyclic ethers can be optionally substituted.

4. The polyetherpolyol according to claim 1 wherein compound A has a molecular weight of 40 to 200 g/mol.

5. The polyetherpolyol according to claim 1 wherein compound A and/or compound B is obtained from renewable sources.

6. The polyetherpolyol according to claim 1 wherein the difference between the number average molecular weight M.sub.n of the inventive polyetherpolyol as determined by GPC and the number average molecular weight M.sub.n of the polyetherpolyol as determined by end group titration is less than 50%, based on the number average molecular weight M.sub.n of the inventive polyetherpolyol as determined by GPC.

7. The polyetherpolyol according to claim 1 wherein the difference between the number average molecular weight M.sub.n of the inventive polyetherpolyol as determined by GPC and the number average molecular weight M.sub.n of the polyetherpolyol as determined by end group titration is less than 20%, based on the number average molecular weight M.sub.n of the inventive polyetherpolyol as determined by GPC.

8. The polyetherpolyol according to claim 1 wherein the Brønsted acid with a weakly coordinating and non-nucleophilic anion is selected from the group consisting of H.sub.3PW.sub.12O.sub.40*×H.sub.2O with 10≤x≤44, H.sub.3PMo.sub.12O.sub.40, HBF.sub.4, CF.sub.3COOH, CF.sub.3SO.sub.3H, triflimidic acid and HSbF.sub.6.

9. The polyetherpolyol according to claim 1 wherein the polyetherpolyol has an average number molecular weight M.sub.n of 500 to 5000 g/mol, determined by GPC.

10. The polyetherpolyol according to claim 1 wherein the polyetherpolyol has a hydroxyl value (OH-value) of 10 to 200 mg KOH/g, determined according to DIN 53240.

11. A method for the production of a polyetherpolyol, comprising: providing a compound A containing at least one epoxide moiety; providing a compound B capable of undergoing a ring opening reaction, wherein compound B is different from compound A; providing a reaction vessel; charging compound B into the reaction vessel; and polymerizing compound A and compound B by adding compound A to the reaction vessel over a period of time to in the presence of a Brønsted acid with a weakly coordinating and non-nucleophilic anion.

12. The method according to claim 11, wherein the polymerization is carried out in the presence of a nucleophilic initiator.

13. The method according to claim 11, wherein the polymerization is carried out in the presence of a nucleophilic initiator and the amount of initiator is 1 to 15 mol-%, with respect to compound A.

14. An adhesive composition comprising a polyetherpolyol according to claim 1.

15. The adhesive composition of claim 14, being a polyurethane adhesive or a silane-based adhesive.

Description

EXAMPLES

Example A (Reference)

[0027] A reaction vessel was charged with 2-methyl THF and BF.sub.3.2H.sub.2O was added. Propylene oxide was introduced dropwise into the reaction mixture and the resulting contents were left to stir. Then, an aqueous solution of sodium hydroxide was added. The resulting aqueous phase was extracted with an organic solvent. The obtained organic phase was washed and dried. After removal of the organic solvent, the polyetherpolyol was obtained.

Example B (According to the Invention)

[0028] A reaction vessel was charged with 2-methyl THF and phosphortungstic acid H.sub.3PW.sub.12O.sub.40* 24 H.sub.2O) was added, followed by the addition of an alcohol. Propylene oxide was introduced dropwise into the reaction mixture and the resulting contents were left to stir. Then, an aqueous solution of sodium carbonate was added. Any excess of 2-methyl THF was evaporated under reduced pressure. The obtained polyetherpolyol was dissolved in an organic solvent and filtered through a pad of silica. After removal of the volatiles in the filtrate, the inventive polyether polyol was obtained.

[0029] The molecular weight of the obtained polyetherpolyols was determined via GPC-APC (GPC) and by way of end-group titration (OHZ). The results are summarized in Table 1.

TABLE-US-00001 TABLE 1 Deviation Mn (OHZ) Molar relative to Polyether MTHF/PO OHZ in mg Mn (GPC) Mn (OHZ) Mn (GPC) polyol ratio KOH/g PDI in g/mol in g/mol in % #1 obtained 52:48 35 2.3 1134 3206 183 by Example A #2 obtained 37:63 64 2.1 1311 1753 34 by Example B #3 obtained 35:65 94 2.0 1012 1194 18 by Example B #4 obtained 37:63 70 1.7 1464 1603 10 by Example B

[0030] GPC analysis of the samples was carried out on an Acquity Advanced Polymer Chromatography System available from Waters Corporation (USA) with an RI and PDA detector. THF with a flow rate of 0.5 ml/minute was used as the eluent and the molecular weights were determined against a polystyrene standard (PSS) of 266 to 1210000 Dalton. Evaluation of the average molecular weight values was carried out using a calibration curve of the 5.sup.th order (“Streifenmethode”).

[0031] End group titration was carried out according to standard procedure as described in DIN 53240 by acetylation of the free hydroxyl groups of the sample with acetic anhydride in pyridine solvent. After completion of the reaction, water was added, and the remaining unreacted acetic anhydride converted to acetic acid and measured by titration with potassium hydroxide.

[0032] The inventive polyetherpolyol was reacted with a diisocyanate (4,4′-methylene diphenyl diisocyanate) at a ratio of 2.2 (NCO/OH) to obtain a polyurethane adhesive. Films were casted (13 cm×5 cm, thickness of 2 mm) and stored for 7 days at 23° C. and 50% relative humidity. The same procedure was applied using PPG 2000 and pTHF as comparable polyetherpolyols, respectively. The obtained films were then characterized by stress-strain tests. The results are summarized in Table 2. It was surprisingly found that the adhesive based on the inventive polyetherpolyol reached a higher tensile strength than the commonly employed PPG (2.18 n/mm.sup.2 compared to 1.54 n/mm.sup.2) at 50% elongation.

TABLE-US-00002 TABLE 2 pTHF1000- Inventive PPG200- reference, polyetherpolyol reference, Elongation tensile strength tensile strength tensile strength [%] [N mm.sup.−2] [N mm.sup.−2] [N mm.sup.−2] 50 5.00 2.18 1.54 100 5.80 2.49 1.87 200 6.00 2.81 2.30 300 8.20 3.00 2.75

[0033] The stress-strain test was conducted using a Z010 test system from Zwick-Roell equipped with a 500 N probe head. Speed of sample elongation was 50 mm/min according to DIN 535049.