Aqueous dispersion of an oxazoline group-containing polymer

Abstract

A process for preparing aqueous dispersions of polymers containing oxazoline groups, by aqueous emulsion polymerization initiated by free radicals. The polymerization are carried out in two stages. In the first polymerization stage, an ,-monoethylenically unsaturated compound having at least one acid group, an monoethylenically unsaturated compound having at least one carboxylic acid amide group, a monoethylenically unsaturated compound having at least one carboxylic acid amide group are copolymerized. In the second polymerization stage, a monoethylenically unsaturated compound having at least one oxazoline group, a monoethylenically unsaturated compound having at least one carboxylic acid amide group and an ethylenically unsaturated compound are copolymerized with the final product from the first polymerization stage.

Claims

1. A process for preparing an aqueous polymer dispersion by aqueous emulsion polymerization initiated by free radicals, the process comprising: in an aqueous polymerization medium, performing first free radical polymerization of: 0.1 and 15 wt. % of at least one ,-monoethylenically unsaturated compound having at least one acid group (monomers A1), 0 and 10 wt. % of at least one monoethylenically unsaturated compound having at least one carboxylic acid amide group (monomers A2), and 75 and 99.9 wt. % of at least one ethylenically unsaturated compound which differs from monomers A1, A2 and B1 (monomers A3), wherein the amounts of monomers A1 to A3 total 100 wt. %, to give a polymer A, and in the presence of polymer A, performing second free radical polymerization of: 0.1 and 2.0 wt. % of at least one monoethylenically unsaturated compound having at least one oxazoline group (monomers B1), 0 and 10 wt. % of at least one monoethylenically unsaturated compound having at least one carboxylic acid amide group (monomers B2), and 70 and 99.9 wt. % of at least one ethylenically unsaturated compound which differs from monomers A1, B1 and B2 (monomers B3), wherein the amounts of monomers B1 to B3 total 100 wt. %, wherein a weight ratio of the sum of the total amounts of monomers A1 to A3 (total monomer amount A) to the sum of the total amounts of monomers B1 to B3 (total monomer amount B) is in the range of 1:9 to 9:1, a pH of the aqueous polymerization medium during the first free radical polymerization is <5 and thereafter, and before starting the second free radical polymerization the pH of the aqueous polymerization medium is increased to >6 by addition of a base, wherein the sum of the total amounts of monomers A2 and monomers B2 is 0.1 and 10 wt. %, based on the sum of total monomer amount A and total monomer amount B (total monomer amount).

2. The process of claim 1, wherein the monomers A1 comprises a carboxylic acid group, a phosphoric acid group, or both of the carboxylic acid group and phosphoric acid group.

3. The process of claim 1, wherein the monomers A1 are at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid; maleic acid, fumaric acid, crotonic acid, vinylacetic acid, vinyllactic acid, vinylphosphonic acid and (meth)acryloxy (poly)alkoxy phosphate.

4. The process of claim 1, wherein the monomers B1 are compounds of formula II: ##STR00004## wherein R is a C.sub.2-20-alkylene radical having an ethylenically unsaturated group; and R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are selected, independently of each other, from the group consisting of hydrogen, halogen, C.sub.1-20-alkyl, C.sub.2-20-alkenyl, C.sub.6-20-aryl, C.sub.7-32-arylalkyl, C.sub.1-20-hydroxyalkyl, C.sub.1-20-aminoalkyl and C.sub.1-20-haloalkyl.

5. The process of claim 1, wherein the monomers B1 are at least one selected from the group consisting of 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl-4,4-dimethyl-2-oxazoline, 2-vinyl-5,5-dimethyl-2-oxazoline, 2-vinyl-4,4,5,5-tetramethyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-4-ethyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-4,4-dimethyl-2-oxazoline, 2-isopropenyl-5,5-dimethyl-2-oxazoline and 2-isopropenyl-4,4,5,5-tetramethyl-2-oxazoline.

6. The process of claim 1, wherein the monomers A2, the monomers B2 or both of the monomers A2 and the monomers B2 are at least one selected from the group consisting of acrylamide and methacrylamide.

7. The process claim 1, wherein the total amount of monomers A1 is 4.0 and 12 wt. %, based on the total monomer amount A.

8. The process claim 1, wherein the total amount of monomers B1 is 0.5 and 5.0 wt. %, based on the total monomer amount B.

9. The process claim 1, wherein the sum of the total amounts of monomers A2 and monomers B2 is 1.0 and 3.0 wt %, based on the total monomer amount.

10. The process of claim 1, wherein the weight ratio of the total monomer amount A to the total monomer amount B is in the range of 1:2 to 2:1.

11. The process of claim 1, wherein the total amount of monomers A1 in the first free radical polymerization and the total amount of monomers B1 in the second free radical polymerization is chosen such that the molar ratio of acid groups to oxazoline groups is 5.

12. The process of claim 1, wherein the base employed for increasing the pH before the second free radical polymerization has a boiling point of 20 C. under a pressure of 1.013 bar (absolute).

13. The process of claim 1, wherein nature and amount of monomers A1 to A3 and/or monomers B1 to B3 are chosen such that a polymer built up solely from these monomers has a glass transition temperature in the range of 15 and 100 C.

14. An aqueous polymer dispersion obtained by the process of claim 1.

15. A binder, comprising: the aqueous polymer dispersion of claim 14.

16. A method for improving a tear strength of a fiber nonwoven under action of heat, the method comprising: contacting the fiber nonwoven with the aqueous polymer dispersion of claim 14.

17. A method for increasing a bursting pressure of a filter paper under wet conditions, the method comprising: contacting the filter paper with the aqueous polymer dispersion of claim 14.

Description

EXAMPLES

(1) Polymer Dispersion 1 (PD1)

(2) 10.3 g of a 33 wt. % strength aqueous polystyrene seed (weight-average particle diameter 30 nm) and 327.4 g of deionized water were introduced into a 2 l reactor with an anchor-type stirrer under a nitrogen atmosphere and heated up. When an internal temperature of 75 C. was reached 13 g of a 7 wt. % strength aqueous sodium peroxodisulfate solution were added within 2 minutes and the mixture was stirred at an increasing temperature for 5 minutes. When the reaction temperature of 85 C. was reached the pH was then determined as 3.8 and 30.3 g of a 7 wt. % strength aqueous sodium peroxodisulfate solution were then metered in over 180 minutes at a flow rate which remained constant. Starting at the same time, a monomer emulsion comprising 55.0 g of deionized water 18.3 g of a 3 wt. % strength aqueous sodium pyrophosphate solution 1.2 g of a 45 wt. % strength aqueous dodecyl diphenyl ether-disulfonic acid sodium salt solution (Dowfax 2A1 from Dow Chemical) 9.8 g of a 28 wt. % strength aqueous sodium lauryl polyethaxysulfate solution (Disponil FES 27 from BASF SE) 34.3 g of a 15 wt. % strength aqueous methacrylamide solution 22.0 g of acrylic acid 147.5 g of styrene and 111.4 g of n-butyl acrylate

(3) was metered in during 90 minutes at a flow rate which remained constant. At the end of the feeding in the feed line was flushed with 33.0 g of deionized water, and 27.5 g of a 25 wt. % strength aqueous ammonia solution were then metered in within 15 minutes, during which a pH of 8.7 was established in the aqueous polymerization mixture. A monomer emulsion comprising 55.0 g of deionized water 18.3 g of a 3 wt. % strength aqueous sodium pyrophosphate solution 1.2 g of a 45 wt % strength aqueous dodecyl diphenyl ether-disulfonic acid sodium salt solution 9.8 g of a 28 wt. % strength aqueous sodium lauryl polyethoxysulfate solution 34.3 g of a 15 wt. % strength aqueous methacrylamide solution 5.2 g of isopropenyl-2-oxazoline 142.3 g of styrene and 111.4 g of n-butyl acrylate

(4) was metered in over 70 minutes at a flow rate which remained constant. At the end of the feeding in the polymerization mixture was subjected to after-polymerization at the reaction temperature for a further 15 minutes and the temperature was then lowered to 80 C. When 80 C. was reached, starting at the same time 5.5 g of a 10 wt. % strength aqueous tert-butyl hydroperoxide solution and 3.7 g of a 13 wt. % strength aqueous acetone bisulfite solution (1:1 addition product of acetone and sodium hydrogen sulfite) were metered in via separate feeds within 60 minutes at a flow rate which remained constant. After cooling to room temperature (20 to 25 C.) and addition of 33.0 g of deionized water, an aqueous polymer dispersion having a solids content of 42 wt. %, a pH of 9.2 was obtained. The glass transition temperature of the dispersion was determined as 34.4 C.

(5) The determination of the pH before, during and after the polymerization reaction was generally carried out by means of a calibrated InPro 325X pH electrode of Mettler Toledo GmbH.

(6) The glass transition temperatures were generally determined in accordance with DIN EN ISO 11357-2 (2013 September) via differential scanning calorimetry (DSC) with a heating up rate of 20 K/min by means of a DSC Q2000 of TA Instruments. The midpoint temperatures were used here for the determination

(7) The solids contents were generally determined by drying a defined amount of the aqueous polymer dispersion (approx. 0.8 g) to constant weight at a temperature of 130 C. with the aid of the HR73 Moisture Analyzer of Mettler Toledo. Two measurements are carried out in each case and the mean of these two measurements is stated.

(8) Polymer Dispersion 2 (PD2)

(9) 9.0 g of a 33 wt. % strength aqueous polystyrene seed (weight-average particle diameter 30 nm) and 361.4 g of deionized water were introduced into a 2 l reactor with an anchor-type stirrer under a nitrogen atmosphere and heated up. When an internal temperature of 75 C. was reached 11.3 g of a 7 wt. % strength aqueous sodium peroxodisulfate solution were added and the mixture was stirred at an increasing temperature for 5 minutes. When the reaction temperature of 95 C. was reached the pH was then determined as 3.9 and 26.4 g of the 7 wt. % strength aqueous sodium peroxodisulfate solution were then metered in over 145 minutes at a flow rate which remained constant. Starting at the same time, a monomer emulsion comprising 55.0 g of deionized water 18.3 g of a 3 wt. % strength aqueous sodium pyrophosphate solution 1.2 g of a 45 wt. % strength aqueous dodecyl diphenyl ether-disulfonic acid sodium salt solution 8.6 g of a 28 wt. % strength aqueous sodium lauryl polyethoxysulfate solution 29.9 g of a 15 wt. % strength aqueous methacrylamide solution 23.5 g of acrylic acid 126.6 g of styrene and 97.2 g of n-butyl acrylate

(10) was metered in during 70 minutes at a flow rate which remained constant. At the end of the feeding in the feed line was flushed with 28.8 g of deionized water, and 28.9 g of a 25 wt. % strength aqueous ammonia solution were then metered in within 15 minutes, during which a pH of 8.1 was established in the aqueous polymerization mixture. A monomer emulsion comprising 96.0 g of deionized water 1.1 g of a 45 wt. % strength aqueous dodecyl diphenyl ether-disulfonic acid sodium salt solution 8.6 g of a 28 wt. % strength aqueous sodium lauryl polyethoxysulfate solution 29.9 g of a 15 wt. % strength aqueous methacrylamide solution 4.5 g of isopropenyl-2-oxazoline 122.0 g of styrene and 97.2 g of n-butyl acrylate

(11) was then metered in over 70 minutes at a flow rate which remained constant. At the end of the feeding in the polymerization mixture was subjected to after-polymerization at the reaction temperature for a further 15 minutes and the temperature was then lowered to 75 C. When 75 C. was reached, starting at the same time 4.8 g of a 10 wt. % strength aqueous tert-butyl hydroperoxide solution and 3.3 g of a 13 wt. % strength aqueous acetone bisulfite solution were metered in via separate feeds within 60 minutes at a flow rate which remained constant. After cooling to room temperature and addition of 28.8 g of deionized water, an aqueous polymer dispersion having a solids content of 40 wt. %, a pH of 8.8 was obtained. The glass transition temperature of the dispersion was determined as 35.5 C.

(12) Polymer Dispersion 3 (PD3)

(13) 9.0 g of a 33 wt. % strength aqueous polystyrene seed (weight-average particle diameter 30 nm) and 361.4 g of deionized water were introduced into a 2 l reactor with an anchor-type stirrer under a nitrogen atmosphere and heated up. When an internal temperature of 75 C. was reached 11.3 g of a 7 wt. % strength aqueous sodium peroxodisulfate solution were added and the mixture was stirred at an increasing temperature for 5 minutes. When the reaction temperature of 95 C. was reached the pH was then determined as 3.7 and 26.4 g of the 7 wt. % strength aqueous sodium peroxodisulfate solution were then metered in over 145 minutes at a flow rate which remained constant. Starting at the same time, a monomer emulsion comprising 96.0 g of deionized water 16.0 g of a 3 wt. % strength aqueous sodium pyrophosphate solution 1.1 g of a 45 wt. % strength aqueous dodecyl diphenyl ether-disulfonic acid sodium salt solution 8.6 g of a 28 wt. % strength aqueous sodium lauryl polyethoxysulfate solution 29.9 g of a 15 wt. % strength aqueous methacrylamide solution 14.4 g of acrylic acid 135.7 g of styrene and 97.2 g of n-butyl acrylate

(14) was metered in during 70 minutes at a flow rate which remained constant. At the end of the feeding in the feed line was flushed with 28.8 g of deionized water, and 12.6 g of a 25 wt. % strength aqueous ammonia solution were then metered in within 15 minutes, during which a pH of 8.0 was established in the aqueous polymerization mixture. A monomer emulsion comprising 96.0 g of deionized water 1.1 g of a 45 wt. % strength aqueous dodecyl diphenyl ether-disulfonic add sodium salt solution 8.6 g of a 28 wt. % strength aqueous sodium lauryl polyethoxysulfate solution 29.9 g of a 15 wt. % strength aqueous methacrylamide solution 2.8 g of isopropenyl-2-oxazoline 123.7 g of styrene and 97.2 g of n-butyl acrylate

(15) was then metered in over 70 minutes at a flow rate which remained constant. At the end of the feeding in the polymerization mixture was subjected to after-polymerization at the reaction temperature for a further 15 minutes and the temperature was then lowered to 75 C. When 75 C. was reached, starting at the same time 4.8 g of a 10 wt. % strength aqueous tert-butyl hydroperoxide solution and 3.3 g of a 13 wt. % strength aqueous acetone bisulfate solution were metered in via separate feeds within 60 minutes at a flow rate which remained constant. After cooling to room temperature and addition of 28.8 g of deionized water, an aqueous polymer dispersion having a solids content of 40 wt. %, a pH of 9.2 was obtained. The glass transition temperature of the dispersion was determined as 35.5 C.

(16) Polymer Comparative Dispersion 1 (PC1)

(17) The preparation of polymer comparative dispersion 1 was carried out analogously to the preparation of polymer dispersion 1 with the difference that only 257.7 g instead of 327.4 g of deionized water were initially introduced in the polymerization vessel and the monomer emulsion of the first polymerization stage had the following composition: 18.3 g of a 3 wt. % strength aqueous sodium pyrophosphate solution 1.2 g of a 45 wt. % strength aqueous dodecyl diphenyl ether-disulfonic acid sodium salt solution 9.8 g of a 28 wt. % strength aqueous sodium lauryl polyethoxysulfate solution 181.0 g of a 15 wt. % strength aqueous methacrylamide solution 147.5 g of styrene and 111.4 g of n-butyl acrylate

(18) An aqueous polymer dispersion having a solids content of 42 wt. %, a pH of 9.2 was obtained. The glass transition temperature of the dispersion was determined as 32.7 C.

(19) Polymer Comparative Dispersion 2 (PC2)

(20) The preparation of polymer comparative dispersion 2 was carried out analogously to the preparation of polymer dispersion 1 with the difference that the monomer emulsion of the first polymerization stage had the following composition: 84.1 g of deionized water 18.3 g of a 3 wt. % strength aqueous sodium pyrophosphate solution 1.2 g of a 45 wt. % strength aqueous dodecyl diphenyl ether-disulfonic acid sodium salt solution 9.8 g of a 28 wt. % strength aqueous sodium lauryl polyethoxysulfate solution 32.3 g of acrylic acid 147.5 g of styrene and 111.4 g of n-butyl acrylate

(21) and the monomers stage of the second polymerization stage had the following composition: 84.2 g of deionized water 18.3 g of a 3 wt. % strength aqueous sodium pyrophosphate solution 1.2 g of a 45 wt. % strength aqueous dodecyl diphenyl ether-disulfonic acid sodium salt solution 9.8 g of a 28 wt. % strength aqueous sodium lauryl polyethoxysulfate solution 34.3 g of a 15 wt. % strength aqueous methacrylamide solution 5.2 g of isopropenyl-2-oxazoline 142.3 g of styrene and 111.4 g of n-butyl acrylate

(22) An aqueous polymer dispersion having a solids content of 42 wt. %, a pH of 9.2 was obtained. The glass transition temperature of the dispersion was determined as 33.7 C.

(23) Use Tests

(24) For the use tests the abovementioned polymer dispersions PD1 to PD3 and the polymer comparative dispersions PC1 and PC2 were diluted to a solids content of 10.0 wt. % by homogeneous mixing with deionized water at room temperature.

(25) For preparation of the impregnated filter papers a cellulose filter paper having a weight per unit area of 103 g/m.sup.2 was used as the untreated paper. For application of the diluted aqueous polymer dispersions (impregnation) the sheets of paper were passed in the longitudinal direction in each case through 10.0 wt. % strength aqueous polymer dispersions over a continuous PES filter belt with a belt running speed of 2.0 m per minute. By subsequent sucking off of the aqueous polymer dispersions the wet application was adjusted to 206 g/m.sup.2 (corresponding to 20.6 g/m.sup.2 of binder calculated as solid). The impregnated filter papers obtained in this way were dried at 90 C. for 5 minutes in a Mathis oven on a net of plastic as a support at the maximum hot air stream and directly thereafter were crosslinked for one minute at 180 C. in a Mathis oven at the maximum hot air stream and then cooled to room temperature.

(26) Determination of Wet Tear Strength

(27) 5 test specimens in dumbbell shape of 115 mm length with a test bar of 6 mm width were cut out of the impregnated sheets of paper in each case longitudinally and transversely to the running direction. The test specimens obtained were then stored in a climatic chamber at 23 C. and 50% relative atmospheric humidity for 24 hours.

(28) For determination of the wet tear strength the test specimens were stored for 2 minutes in a 2 wt. % strength aqueous solution of a sodium alkylsulfonate (Emulgator E 30 of Leuna Tenside GmbH) and thereafter the excess aqueous solution was dabbed off with a woven cotton fabric. The determination of the wet tear strength was carried out on a tensile tester of Zwick Roell, type Z005. In this test the test specimens were introduced vertically into a clamping device such that the free clamped length was 70 mm. The clamped test specimens were then subsequently drawn apart in the opposite direction at a speed of 50 mm per minute until the test specimens tore. The tear strength is stated in N/mm.sup.2. The higher the tear strength measured when the test specimens tear, the better the corresponding tear strength is to be evaluated. In each case 5 measurements were made in the longitudinal and transverse direction. The values stated in Table 1 in each case represent the mean of these measurements.

(29) Determination of the Bursting Pressure, Wet

(30) The determination of the bursting pressure, wet, was likewise carried out n a test machine from Zwick-Roell, type Z005 with the bursting pressure test module.

(31) In this test a membrane having a thickness of 0.86 mm which bulged by 9.0 mm under a pressure of 30 kPa was used; the delivery of the hydraulic system was 95 ml/min (DIN ISO 2758 and DIN ISO 2759, TestXpert software of Zwick).

(32) Test specimens of 175230 mm were cut out of the impregnated papers to be tested. The test specimens were then stored in a climatic chamber at 23 C. and 50% relative atmospheric humidity for 24 hours. The test specimens were then likewise stored in a 2 wt. % strength aqueous solution of Emulgator E 30 for 2 minutes and thereafter the excess aqueous solution was dabbed off pith a woven cotton fabric. The clamp test specimens obtained in this way were then clamped over the elastic, circular membrane such that they were able to bulge with the membrane. The membrane was bulged with a uniform delivery of the hydraulic liquid until the corresponding test specimen burst, the maximum pressure applied for bursting being called the bursting pressure, wet. In each case 5 individual measurements were carried out. The values stated in Table 1 represent the means of these 5 individual measurements. The test results are to be evaluated as better here the higher the corresponding bursting pressure.

(33) Determination of the Electrolyte Stability

(34) The determination of the electrolyte stability was carried out by a procedure in which one drop of the particular (undiluted) polymer dispersion was dropped into a 0.1 wt. % strength aqueous calcium chloride solution at room temperature. The electrolyte stability of the aqueous polymer dispersions was evaluated visually here, coagulation of the polymers being evaluated as negative and a homogeneous distribution of the polymers as positive. The corresponding evaluations obtained are likewise listed in Table 1.

(35) TABLE-US-00001 TABLE 1 Wet tear strengths and bursting pressures of the corresponding test specimens and electrolyte resistance of the corresponding polymer dispersions Polymer dispersions PC1 PC2 PD1 PD2 PD3 Wet tear 0.6 1.6 2.2 3.2 2.7 strength longitudinal (N/mm.sup.2) transverse 0.4 1.3 1.7 2.4 2.0 (N/mm.sup.2) Bursting 51 102 114 158 141 pressure wet (kPa) Electrolyte positive negative positive positive positive stability

(36) It can be clearly seen from the results that the polymer dispersions PD1 to PD3 according to the invention have both improved wet tear strengths and bursting pressures. It also becomes clear from the results that the monomers containing carboxylic acid amide groups have an advantageous effect on the electrolyte stability of the corresponding polymer dispersions.