POLYMODAL POLYMER COMPOSITIONS FOR COATING APPLICATIONS

Abstract

The present invention relates to a polymodal polymer composition having homogeneous as well as heterogeneous particles formed by radical emulsion polymerization of monomers from category A which forms homopolymers with Tg above 15° C. and monomers from category B which forms homopolymers with Tg below −15° C. The polymer composition is composed of at least two different populations of particles, differing in mean particle size value by at least a factor of 2. Thus, the two different populations of polymer particles in the polymer composition differ with respect to size and monomer composition of the particles.

Claims

1. A polymodal polymer composition formed by radical emulsion polymerization of monomers from category A which forms homopolymers with Tg above 15° C. and monomers from category B which forms homopolymers with Tg below −15° C. characterized in that the polymodal polymer composition is composed of at least two different populations of particles, said populations differing in mean particle size value by at least a factor of 2, wherein said two different populations jointly constitute at least 80% by weight of the total polymeric content within said composition and the Tg difference between the two populations being less than 20° C., wherein (a) a population P.sub.2 is constituted by at least 80% by weight of homogeneous particles containing polymer chains built of monomers A.sub.2 and B.sub.2 wherein the total content of said monomers A.sub.2 and B.sub.2 in these polymer chains is at least 80% by weight, and (b) a population Pi, distinctive of P.sub.2 by mean particle size value and monomer composition, of which the particles are constituted of polymer chains predominantly built of monomers A.sub.1, B.sub.1, and A.sub.2, B.sub.2 wherein said population P.sub.1 being constituted by at least 80% by weight of monomers selected from categories A and B wherein category A and category B monomers are not randomly co-polymerized, but in a sequential process whereby monomers A.sub.2 and B.sub.2 are polymerized after the monomers A.sub.1 and B.sub.1, inducing compositional heterogeneity in those polymeric chains constituting the particles of said population, but where at least one of the monomers from the same category (either A or B) forming P.sub.1 and P.sub.2 are different from each other.

2. The polymodal polymer composition of claim 1, wherein the total amount of monomers from categories A and B are at least 80% by weight of the total monomer amount and the ratio of monomers in category A to category B is from 20% to 80% by weight and, correspondingly the ratio of monomers in category B to category A is from 20% to 80% by weight, based on the combined amount A+B.

3. The polymodal polymer composition of claim 1, further comprising up to 15% of other monomers which can also be selected from categories A and B, up to 5% of functional monomers containing carboxylic, sulfonic or phosphoric acid functionality, poly-unsaturated monomers, epoxy, hydroxy, amino, amido, di-carbonyl, and siloxane, and up to 5% of surface-active components including anionic and non-ionic surfactants, water-soluble colloids and polyelectrolytes capable of stabilizing polymer particles in the aqueous medium.

4. The polymer composition of claim 1, wherein monomer A.sub.1 is methyl methacrylate and when A.sub.2 is not the same as A.sub.1 it is styrene, and vice versa.

5. The polymer composition of claim 1, wherein monomer B.sub.1 is butyl acrylate and when B.sub.2 is not the same as B.sub.1 it is ethyl acrylate or 2-ethylhexyl acrylate, and vice versa.

6. The polymer composition of claim 1, wherein monomers B (B.sub.1 and B.sub.2) are alkyl acrylates and when they are different they differ by at least 2 C atoms.

7. The polymer composition of any of claim 1 wherein B.sub.1 and B.sub.2 are the same monomers but A.sub.1 and A.sub.2 are different.

8. The polymer composition of any of claim 1 wherein A.sub.1 and A.sub.2 are the same monomers but B.sub.1 and B.sub.2 are different.

9. The polymer composition of claim 1, wherein the sum of populations P.sub.1 and P.sub.2 constitutes over 90% by weight of the polymer.

10. The polymer composition of claim 1, wherein the sum of populations P.sub.1 and P.sub.2 represents the entire population of particles present in the polymer composition.

11. Use of tho The polymer composition of claim 1 for use as a coating, a binder in coatings such as paints, binders for nonwovens and textiles, saturants, ink formulations, leather and paper coating formulations, paper impregnations and adhesives.

12. A process for producing the polymer composition of claim 1, comprising the steps of: separately providing a seed polymer having an average particle size of 20 nm to 200 nm, providing a first monomer emulsion comprising monomers A.sub.1 and B.sub.1, and providing a second monomer emulsion comprising monomers A.sub.2 and B.sub.2, respectively, polymerizing the first monomer emulsion by radical emulsion polymerization in an aqueous polymerization medium containing a first seed polymer; adding a second seed polymer and the second monomer emulsion to the polymerization medium; and polymerizing the second monomer emulsion, so as to produce particles of populations P.sub.1 and P.sub.2.

13. The process of claim 12, wherein monomers A.sub.1 and B.sub.1are polymerized by at least 90% before monomers A.sub.2 and B.sub.2 are added to the polymerization medium.

14. The process of any of claim 12, further comprising a redox post polymerization treatment to reduce the level of residual monomer below 1%.

Description

EXAMPLES

[0087] The different exemplary embodiments are summarized and explained in detail below. Examples 5 is in accordance with the present invention.

Comparative Example 1

[0088] Seed addition (for bimodal particle size distribution) method has been used but the monomer composition only includes the below given Emulsion 5.1 structure.

Comparative Example 2

[0089] Seed addition method to obtain a bimodal particle size distribution has been used but only one monomer composition is prepared in a single emulsion vessel comprising all the monomers of Emulsion 5.1 and Emulsion 5.2 with the same amounts in total.

Comparative Example 3

[0090] Seed addition method has not been used, monomodal structure with same monomer composition as in Reference Example 5.

Comparative Example 4

[0091] Seed addition (bimodal particle size distribution) method has been used but the monomer composition only includes the below given Emulsion 5.2 structure.

Example 5

[0092] Inventive embodiment for a bimodal polymer composition having heterogeneous particles.

Comparative Example 1

[0093] Preparation of Monomer Emulsions

[0094] For the preparation of Emulsion 1.1, 21.4 g of surfactant A* and 12 g of surfactant B** were dissolved in 162 g deionized water and added to an emulsion vessel equipped with a stirrer. 400 g 2-ethyl hexyl acrylate, 360 g methyl methacrylate and 12.4 g of acrylic acid monomers were added into the same vessel, respectively. [0095] *Surfactant A is fatty alcohol ether sulphate, sodium salt degree of ethoxylation about 30. [0096] **Surfactant B is disodium ethoxylated alcohol (C10-12) half ester of sulfosuccinic acid.

[0097] The water-surfactant mixture was placed under high shear agitation at 200 rpm in the vessel. The monomers were slowly added into the water-surfactant mixture under sufficient stirring to make a monomer pre-emulsion. The required mixing time was 10 minutes for all the trials. The resulting monomer emulsions were homogenous, viscous and milky in appearance.

[0098] Preparation of Starting and Delayed Initiator

[0099] The starting initiator was prepared by adding 2.1 g of ammonium persulfate into 21 g of deionized water and stirred by using a magnetic bar. For the delayed initiator, 1.6 g of ammonium persulfate was dissolved in 64 g of deionized water and added into the reactor by 3 hours of feeding.

[0100] Polymerization Procedure

[0101] Delayed radical emulsion polymerizations and seeded polymerization were used for the initiation and the mere role of the surfactant in this system is simply to avoid coagulation by maintaining the stability of the polymer particles. All polymerizations were carried out using deionized water (Dl). The seed had a particle size around 50 nm and has been used in the initiation step of the polymerization in order to control the particle size distribution. For the polymerization procedure 11 g of 50 nm seed dispersion with a 33% of solid (seed polymer) content, the starting initiator, and water were initially charged into the reactor. The monomer emulsion (Emulsion 1.1) and the delayed initiator were fed parallel in two streams both having the same feeding time of 3 hours, using a peristaltic pump via silicone tubing. The feed rate was monitored volumetrically. The reactions were performed in a 1 liter, round-bottomed reactor glass flask with a mechanical agitator and stirred at 180 rpm. The reactor flask was equipped with a reflux condenser, thermocouple and metallic stirrer. Polymerization temperature was maintained at 84-86° C., and agitation rate was increased when necessary. After 50% of the emulsion feeding, 34,5 g of 50 nm seed dispersion with a 33% of solid (seed polymer) content was added into the reactor for the formation of small particles. After the end of the feed, the monomer mix beaker was flushed with water and post-heated for 30 min. The reaction mixture was then cooled down to 55° C. and post redox reaction was done. A redox post polymerization process provides lower residual monomer levels and/or lower volatile organic compound levels for emulsion systems. As the redox couple t-butyl hydroperoxide and sodium salt of an organic sulfonic acid derivative were selected. In a neutralization step, ammonia solution (28%) was used to adjust the pH to approximately 7.0±0.5. Then, the polymer was filtered into a suitable container.

Comparative Example 2

[0102] Preparation of Monomer Emulsions

[0103] For the preparation of Emulsion 2.1, 21.4 g surfactant A* and 12 g surfactant B** were dissolved in 162 g deionized water and added to an emulsion vessel equipped with a stirrer. 230 g of butyl acrylate and 12.4 g of acrylic acid, 200 g of 2-ethylhexyl acrylate, 150 g of styrene, 180 g methyl methacrylate were added into the same vessel, respectively.

[0104] The water-surfactant mixture was placed under high shear agitation at 200 rpm in the vessel. The monomers were slowly added into the water-surfactant mixture under sufficient stirring to make a monomer pre-emulsion. The required mixing time was 10 minutes for all the trials. The resulting monomer emulsions were homogenous, viscous and milky in appearance.

[0105] *Surfactant A is fatty alcohol ether sulphate, sodium salt degree of ethoxylation about 30.

[0106] **Surfactant B is disodium ethoxylated alcohol (C10-12) half ester of sulfosuccinic acid.

[0107] Preparation of Starting and Delayed Initiator

[0108] The initiator was prepared by adding 2.1 g of ammonium persulfate into 21 g of deionized water and stirred by using a magnetic bar. For the delayed initiator, 1.6 g of ammonium persulfate was dissolved in 64 g of deionized water and added into the reactor by 3 hours of feeding.

[0109] Polymerization Procedure

[0110] Delayed radical emulsion polymerizations and seeded polymerization were used for the initiation and the mere role of the surfactant in this system is simply to avoid coagulation by maintaining the stability of the polymer particles. All polymerizations were carried out using deionized water (DI). The seed polymer had particle size of around 50 nm and had been used in the initiation step of the polymerization in order to control the particle size distribution. For the polymerization procedure 11 g of 50 nm seed dispersion with a 33% of solid (seed polymer) content, the starting initiator and water were initially charged into the reactor. The monomer emulsion (Emulsion 2.1) and the delayed initiator were fed parallel in two streams both having the same feeding time of 3 hours, using a peristaltic pump via silicone tubing. The feed rate was monitored volumetrically. The reactions were performed in a 1 liter, glass made and round-bottomed reactor flask with a mechanical agitator and stirred at 180 rpm. The reactor flask was equipped with reflux condenser, thermocouple and metallic stirrer.

[0111] Polymerization temperature was maintained at 84-86° C., and agitation rate was increased if necessary. After 50% of the emulsion feeding, 34.5 g of about 50 nm seed dispersion with a 33% of solid (seed polymer) content was added into the reactor for the formation of small particles. After the end of the feed, the monomer mix beaker was flushed with water and was post-heated for 30 min. The reaction mixture was then cooled down to 55° C. and post redox reaction was applied. A redox post polymerization process provides lower residual monomer levels and/or lower volatile organic compound levels for emulsion systems. As the redox couple t-butyl hydroperoxide/sodium salt of an organic sulfonic acid derivative were selected. In a neutralization step, ammonia solution (28%) was used to adjust the pH to approximately 7.0±0.5. Then, the polymer was filtered into a suitable container.

Comparative Example 3

[0112] Emulsion 3.1:10.7 g surfactant A* and 6 g surfactant B** were dissolved in 81 g deionized water and added in a vessel equipped with a stirrer. 200 g 2-ethylhexyl acrylate, 180 g methyl methacrylate and 6.2 g of acrylic acid were added into the same vessel, respectively.

[0113] Emulsion 3.2:10.7 g surfactant A* and 6 g surfactant B** were dissolved in 75.6 g deionized water and added in a vessel equipped with a stirrer. 230 g 2butyl acrylate, 6.2 g of acrylic acid, 150g styrene were added into the same vessel, respectively. The only difference in this example was making the polymerization reaction without a seed polymer addition in the first or in any other stage of the polymerization process. The resulting polymer had a monomodal particle size distribution, although the same monomer composition as in Reference Example 5 had been used. [0114] *Surfactant A is fatty alcohol ether sulphate, sodium salt degree of ethoxylation about 30. [0115] **Surfactant B is disodium ethoxylated alcohol (C10-12) half ester of sulfosuccinic acid.

Comparative Example 4

[0116] Same as in Comparative Example 1 but the monomer composition of Emulsion 4.1 is 1.0 different than Emulsion 1.1.

[0117] Emulsion 4.1:21.4 g surfactant A* and 12 g surfactant B** were dissolved in 81 g deionized water and added in a vessel equipped with a stirrer. 300 g styrene, 12.4 g of acrylic acid, and 400 g butyl acrylate were added into the same vessel, respectively. [0118] *Surfactant A is fatty alcohol ether sulphate, sodium salt degree of ethoxylation about 30. [0119] **Surfactant B is disodium ethoxylated alcohol (C10-12) half ester of sulfosuccinic acid.

Example 5

[0120] Preparation of Monomer Emulsions

[0121] Emulsion 5.1:10.7 g surfactant A* and 6 g surfactant B** were dissolved in 81 g deionized water and added in a vessel equipped with a stirrer. 200 g 2-ethylhexyl acrylate , 180 g methyl methacrylate and 6.2 g of acrylic acid were added into the same vessel, respectively.

[0122] Emulsion 5.2:10.7 g surfactant A* and 6 g surfactant B** were dissolved in 75.6 g deionized water and added in a vessel equipped with a stirrer. 230 g butyl acrylate, 6.2 g of acrylic acid, 150 g styrene were added into the same vessel, respectively.

[0123] The water-surfactant mixture was placed under high shear agitation at 200 rpm. The monomer mixtures were slowly added into the water/surfactant mixture under sufficient stirring to make a monomer pre-emulsion. The required mixing time was 10 minutes for all the trials. The resulting monomer emulsions were homogenous, viscous and milky in appearance. [0124] *Surfactant A is fatty alcohol ether sulphate, sodium salt degree of ethoxylation about 30. [0125] **Surfactant B is disodium ethoxylated alcohol (C10-12) half ester of sulfosuccinic acid.

[0126] Preparation of Starting and Delayed Initiator

[0127] The initial initiator was prepared by adding 2.1 g of ammonium persulfate into 21 g of deionized water and stirred by using a magnetic bar. For the delayed initiator, 1.6 g of ammonium persulfate was dissolved in 64 g of deionized water and added into the reactor by 3 hours of feeding.

[0128] Polymerization Procedure

[0129] Delayed radical emulsion polymerizations and seeded polymerization were used for the initiation and the mere role of the surfactant in this system is simply to avoid coagulation by maintaining the stability of the polymer particles. All polymerizations were carried out using deionized water (Dl). The seed polymer had an average particle size of around 50 nm and had been used in the initiation step of the polymerization in order to control the particle size distribution. For the polymerization procedure, 11 g of 50 nm seed dispersion with a 33% of solid (seed polymer) content, starting initiator, and water were initially charged into the reactor. The monomer emulsion 5.1 (Emulsion 1) and half of the delayed initiator were fed parallel in two streams both having the same feeding time of 1.5 hours, using a peristaltic pump via silicone tubing. The feed rate was monitored volumetrically. The reactions were performed in a 1 liter, glass made and round-bottomed reactor flask with a mechanical agitator and stirred at 180 rpm. The reactor flask was equipped with reflux condenser, thermocouple and metallic stirrer. Polymerization temperature was maintained at 84-86° C., and agitation rate was increased if necessary. After the first feed, 34.5 g of about 50 nm seed dispersion with a 33% of solid (seed polymer) content was added into the reactor for the formation of small particles and the monomer emulsion 5.2 (Emulsion 2) and rest of the delayed initiator were fed for another 1.5 hour. After the whole feed, the monomer mix beaker was flushed with water, and was post-heated for 30 min. The reaction mixture was then cooled to 55° C. and post redox reaction was applied. A redox post polymerization process provides lower residual monomer levels and/or lower volatile organic compound levels for emulsion systems. As the redox couple t-butyl hydroperoxide/sodium salt of an organic sulfonic acid derivative were selected. In a neutralization step, ammonia solution (28%) was used to adjust the pH to approximately 7.0±0.5. Then, the polymer was filtered into a suitable container.

[0130] Characterization, Analysis and Testing

[0131] The thermal properties of the polymers were measured by differential scanning calorimeters (Mettler Toledo, DSC 821e) in a flowing air atmosphere from −80° C. at a scanning rate of 10° C./min. Solid content was measured by drying the polymer films at 150° C. for 20 minutes after filtered from 60 micron filter. Weight of polymer (w1) and dried latex (w2) has been calculated by the following equation. Solid %=w2/w1×100

[0132] Coagulum content of polymer latex was measured after filterable solids of any runs were dried at room temperature for 24 hours. Then, coagulum content was measured by the weight of filterable solid in 1 liter of polymer dispersion. (ISO 4576) Free monomer measurements were performed by HS-GC (Perkin Elmer, HS 40 XL, Auto System XL) with FID detector and N2 was used as carrier gas.

[0133] Viscosity was measured by Brookfield viscosimeter under room conditions by LVT 3/60 (ISO 3219).

[0134] pH of polymers was determined under room temperature according to ISO 976 by calibrated pH meter.

[0135] Surface tension of polymer dispersions has been measured by Du Nouy ring method according to ISO 1409.

[0136] Wet scrub resistance is measured according to EN ISO 11998:2006.

[0137] Hardness of the coating film has been measured using the Persoz or Konig Pendulum. Evaluation of the hardness of paints and related coatings is made in accordance with EN ISO 1522:2006. The procedure as per König is based on the measurement of the damping of a pendulum oscillating on the paint film.

[0138] Thickening response of a polymer emulsion is the thickening response achieved with the addition of same amount of thickeners to paints (coatings) formulations in which different type of polymers are added.

[0139] Blocking performance determines the ability of a paint to withstand sticking to itself after a given amount of time to dry.

[0140] Water resistance of an emulsion polymer is measured by applying the liquid polymer emulsion 200 micron on glass panel. After 7 days curing at RT, glass panels are dipped into the water. The water whitening of the polymer films are compared with standard.

[0141] The water resistance (in paper impregnation application) was measured by Cobb test.

[0142] Cellulosic paper specimen was cut in the dimensions of 13.2 cm and 14 cm and dipped in a tank filled with polymer and waited for 10 seconds of penetration.The excess of polymer on paper was squeezed through double rollers and the coating weight was adjusted by calculating the difference in weight of neat and coated paper. The coated paper was dried in an electric oven with air circulating system at 140° C. for 2 minutes. 20 g/m2 dry coating was obtained. The coated test specimen was placed in the apparatus which is used for Cobb test, 100 ml of deionized water was poured into the ring, which has 100 cm2 testing area, as rapidly as possible and waited for 45 seconds. Then the water was quickly poured from the ring and test specimen was carefully placed on a sheet with its wetted side up. The surplus water was immediately removed by moving the hand roller once back and once forward and reweighed to calculate the COBB results.

[0143] The results are summarized in the following Tables:

TABLE-US-00001 TABLE 1 Water whitening results Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 Water Whitening 4 2 1 5 1 Performance after 1 hour in water* Water Whitening 5 3 2 5 2 Performance after 5 hours in water* *5 worst (white); 3 moderate (no whitening but blurish); 1 best (no whitening)

[0144] Water whitening results of example 5 is best according to “after 1 hour” results and between moderate and best according to “after 5 hours” results.

TABLE-US-00002 TABLE 2 Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 Tensile strength 4.86 2.00 6.95 1.85 3.43 (Mpa) Elongation (%) 621.91 997.45 879.13 1283.51 659.34 Elastic modulus 1.88 1.00 1.56 0.89 1.74 (MPa)

TABLE-US-00003 TABLE 3 % 35 PVC Satin paint formulation Component Weight (g) Water 60.1 Natrosol HR 250 0.4 NaOH 1.0 Calgon N 0.6 Dispersant K 850 8.0 BYK 093 2.0 Kronos 2310 200.0 Turkcarb 75x 75.0 Water 23.5 OW 2000 80.0 Water 85.5 Binder 460.0 Tafigel PUR 44 3.0 BYK 093 1.0 Total 1000

TABLE-US-00004 TABLE 4 Thickening response Ex1 Ex2 Ex3 Ex4 Ex5 Thickener amount 0.45% 0.3% 0.45% 0.3% 0.3% Initial Brookfield 5300/3100/1980 8950/5360/3480 5350/2980/1910 7800/4440/2980 11800/7080/4700 Viscosity (sp 4/20-50-100 rpm) Overnight 6900/3940/2500 15100/9200/5750 8250/4080/2440 12400/7720/5000 13700/7960/5000 Brookfield Viscosity (sp 4/20-50-100 rpm) Storage stability 12800/7760/4800 18600/11100/7100 19500/12300/7750 16700/10700/6750 17100/10400/6450 (50° C., 1 week) Brookfield viscosity (mPa .Math. s)

[0145] Initial measurement of thickening response is the best with patent trial Example 5. Overnight and storage stability results are also one of the best with example 5 among the other trials. The combination of all measurements for thickening response shows that this property has been improved with the present invention.

TABLE-US-00005 TABLE 5 Application performance Ex1 Ex2 Ex3 Ex4 Ex5 Opacity (23° C. 97.40% 97.88% 97.49% 97.36% 98.33% cured) Gloss(20°/60°/ 6.1/18.6/71.5 9.0/35.9/82.0 4.8/9.7/60.8 7.5/30.2/72.6 8.8/33.7/79.6 85°) Scrub resistance 6.11 2.89 5.98 1.90 2.99 ISO micron loss Scrub resistance 8.97 5.30 8.33 3.53 4.83 ISO g/m{circumflex over ( )}2 loss Blocking at 23° C., 7-7 6-7 7-7 6-6 7-7 3,5 hours, 2 kg Blocking at 50° C., 4-4 3-3 7-7 3-3 5-5 3.5 hours, 2 kg (10:en iyi, 1:en kötü) L-a-b (blue 63.28/−15.02/−36.53 63.17/−15.58/−37.45 63.78/−15.29/−36.69 61.27/−15.10/−37.06 62.26/−15.52/−36.75 pigmented) 1st day Koenig 17 c, 10 c, 15 c, 11 c, 14 c, Hardness (counts/ 23 s 14 s 21 s 14 s 19 s seconds) 3rd day Koenig 19c, 11c, 17c, 11c, 15c, Hardness (counts/ 26 s 15 s 23 s 15 s 21 s seconds)

[0146] The combination of measurements for opacity, gloss, blocking resistance in Table 5 shows that the dry film performance in terms of opacity, gloss, blocking resistance are best in Ex 5. These results clearly show that the dry film performance in terms of opacity, gloss and blocking resistance are improved with the present invention.

[0147] Additionally, according to the visual comparison stain resistance is good in Ex 5, especially for tea, coffee, red wine and water stains.

[0148] Moreover, dry film of example 5 and 1 are less tacky while Example 2, 3, 4 are tacky.

[0149] The resulting polymers of Example 1 to 5 are also applied in paper impregnation. Good water resistance has been obtained with example 5 when compared with the other comparative examples.