SUSPENSIONS IN AQUEOUS MEDIA

Abstract

Provided is a method of suspension polymerization comprising (i) providing a suspension of liquid droplets in an aqueous medium, wherein said droplets comprise (a) one or more water-insoluble vinyl monomers, and (b) a polyelectrolyte (PED) having a polarity, (c) one or more initiators, and wherein said aqueous medium comprises a polyelectrolyte (PEW) having a polarity that is opposite to the polarity of said polyelectrolyte (PED), (ii) polymerizing said vinyl monomer or allowing said vinyl monomer to polymerize.

Claims

1. A method of suspension polymerization comprising (i) providing a suspension of liquid droplets in an aqueous medium, wherein said droplets comprise (a) one or more water-insoluble vinyl monomers, and (b) a polyelectrolyte (PED) having a polarity, (c) one or more initiators, and wherein said aqueous medium comprises a polyelectrolyte (PEW) having a polarity that is opposite to the polarity of said polyelectrolyte (PED), (ii) polymerizing said vinyl monomer or allowing said vinyl monomer to polymerize.

2. The method of claim 1, wherein the suspension has a pH of 5 to 10.

3. The method of claim 1, wherein said polyelectrolyte (PED) has negative polarity and said polyelectrolyte (PEW) has positive polarity.

4. The method of claim 1, wherein said polyelectrolyte (PED) comprises polymerized units of ionic monomer in an amount of 3 mole % to 12 mole %.

5. The method of claim 1, wherein said polyelectrolyte (PEW) comprises polymerized units of ionic monomer in an amount of 40 mole % to 100 mole %.

6. The method of claim 1, wherein said polyelectrolyte (PED) is a vinyl polyelectrolyte.

Description

EXAMPLE 1: PREPARATION OF SUSPENSION

[0106] The aqueous solution of Preparation 2 was placed into a 90 mL reactor. Then the non-aqueous solution of Preparation 3 was placed into the same reactor. The mixture was stirred at 500 rpm with a pitched-blade impeller for 30 minutes. A suspension was produced that contained droplets containing styrene, DVB, and BPO, distributed through an aqueous medium.

EXAMPLE 2: PREPARATION OF POLYMER

[0107] The mixture suspension from Example 1 was heated to 80° C. at 1° C. per minute and then held at 80° C. for 5 hours. The mixture was then heated to 92° C. over 45 minutes and then held at 92° C. for 60 minutes. Polymer beads were produced by suspension polymerization of the droplets.

EXAMPLE 3: INTERFACIAL COMPRESSION TESTING

[0108] Three samples were tested in the interfacial compression test. The results were as follows:

TABLE-US-00001 Wrinkles Example Aqueous Solution Non-Aqueous Solution observed? 3-1C 0.5 pbw p(DAD) 54 pbw styrene no 99.5 pbw DIW 06 pbw DVB 40 pbw MIBC 0.005 pbw stearic acid 3-2 0.05 pbw p(DAD) 54 pbw styrene yes 99.95 pbw DIW 06 pbw DVB 40 pbw MIBC 0.05 pbw PSS 3-3C 0.4 pbw P(DAD) 54 pbw styrene yes 0.2 pbw gelatin 06 pbw DVB 0.2 pbw boric acid 40 pbw MIBC 0.27 pbw NaOH 0.037 pbw NaNO.sub.2 98.983 pbw DIW
Comparative Example 3-1C shows that use of stearic acid, a monomeric surfactant, does not lead to wrinkling; the lack of wrinkling indicates that use of stearic acid does not lead to a mechanically strong surface of the drop. Example 3-2 and Comparative Example 3-3C both show wrinkling, which indicates a mechanically strong surface of the drop. Comparative Example 3-3C uses gelatin, which is undesirable, and Comparative Example 3-3C did not add polyelectrolyte to the non-aqueous solution.

EXAMPLE 4: SHAKE TESTING

[0109] Results of shake tests were as follows. Each aqueous solution was PE2 (poly(AM-co-DADMAC)) in the amount shown, dissolved in tris buffer solution of pH=7.5, as describe in Preparation 1 above. Each non-aqueous solution was PE3 (poly(2-EHA-co-AA)) in the amount shown, dissolved in solvent, where the solvent was a mixture of 90% styrene and 10% DVB, by weight based on the weight of the solvent.

TABLE-US-00002 PE2 in PE1 in Example Aqueous Solution.sup.(1) Non-Aqueous Solution.sup.(2) Shake Test 4-1 0 0 fail 4-2 0 0.5% fail 4-3 0   1% fail 4-4 0.1% 0 Fail 4-5 0.1% 0.5% Pass 4-6 0.1%   1% Pass 4-7 0.3% 0 Fail 4-8 0.3% 0.5% Pass 4-9 0.3%   1% Pass .sup.(1)amount of PE2, by weight based on the weight of the aqueous solution .sup.(2)amount of PE1, by weight based on the weight of the non-aqueous solution
Example 4-1 formed two clear layers that did not mix or form droplets at all. Examples 4-2 and 4-3 formed a turbid layer at the top of the vial instead of the desired opaque white layer, and so they are said to fail. The fact that Examples 4-2 and 4-3 formed some turbidity shows that the PE1 reduced the interfacial tension somewhat between the non-aqueous solution and the aqueous solution.
Results of additional shake tests were as follows:

TABLE-US-00003 PE2 in PE1 in Example Aqueous Solution.sup.(1) Non -Aqueous Solution.sup.(2) Shake Test 4-10 0.5% 0 Fail 4-11 0.5% 0.5% Pass 4-12 0.5%   1% Pass 4-13 1.0% 0 Fail 4-14 1.0% 0.5% Pass 4-15 1.0%   1% Pass .sup.(1)amount of PE2, by weight based on the weight of the aqueous solution .sup.(2)amount of PE1, by weight based on the weight of the non-aqueous solution
The above table demonstrates that when PE1 and PE2 are both used, the mixture passes the shake test, which indicates that a suspension is formed that would be suitable for use in suspension polymerization.

EXAMPLE 5: ADDITIONAL SUSPENSION POLYMERIZATION

[0110] Each reactor vessel was loaded with 30 grams of aqueous solution and 20 grams of non-aqueous solution and stirred with a pitch-blade impeller at 700 rpm. The mixture was heated at 1° C. per minute to 80° C. and held at 80° C. for 5 hours. The mixture was then heated gradually over 45 minutes to 92° C. and held at 92° C. for 60 minutes. The products were cooled to 25° C. and analyzed.

[0111] Each aqueous solution was PE2 (poly(AM-co-DADMAC)) at 1 wt % based on the weight of the aqueous solution, dissolved in tris buffer at either pH=7.5 or tris buffer at pH=8.5. Each non-aqueous solution was initiator and PE1 (poly(2-EHA-co-AA)) dissolved in a solvent of 90% styrene and 10% DVB by weight based on the weight of the solvent. The initiator was either t-BP (at 0.4 wt % of the t-BP stock solution, based on the weight of the non-aqueous solution) or BPO (at 0.3 wt % based on the weight of the non-aqueous solution). The amount of PE2 was 1 wt % based on the weight of the non-aqueous solution. The size of the resulting polymer beads was measured by light scattering using a Beckman-Coulter particle size analyzer and reported as the median diameter on a volume basis. Results were as follows:

TABLE-US-00004 Example initiator pH Bead diameter (μm) 5-1 t-BP 7.5 none.sup.(3) 5-2 t-BP 8.5 352 5-3 BPO 7.5 429 5-4 BPO 8.5 460 .sup.(3)polymerization failed to produce beads

EXAMPLES 6 AND 7: SHAKE TESTS INVOLVING MIBC

[0112] First, the following mixtures were made, using 0.2 grams polyelectrolyte (PED) and 18.8 grams of solvent in a vial. Each solvent had the amount of MIBC shown, and the remainder of the solvent was styrene and DVB in a weight ratio of styrene to DVB of 9:1. In some cases, some sedimentation was observed at the bottom of the vial, showing that the polyelectrolyte (PED) did not dissolve completely. In all cases, a clear solution formed at the top portion of the vial.

[0113] A sample of 6 grams of solution was removed from the top of each vial and mixed with 9 grams of aqueous solution in a shake test performed as above. The aqueous solution was tris buffer at pH=7.5, mixed with 1% by weight (based on the weight of the aqueous solution) of PEEI.

TABLE-US-00005 Example MIBC.sup.(4) (PED) Shake Test Result 6-1 0 PTBEAM fail 6-2 1 PTBEAM fail 6-3 1.7 PTBEAM fail 6-4 2.8 PTBEAM fail 6-5 4.6 PTBEAM fail 6-6 7.77 PTBEAM pass 6-7 12.9 PTBEAM pass 6-8 21.5 PTBEAM pass 6-9 35.9 PTBEAM fail 6-10 59.9 PTBEAM fail .sup.(4)weight % based on the weight of the solvent
When the specific polyelectrolyte (PED) is PTBEAM, then the correct amount of MIBC to make PTBEAM soluble in the droplets is 7 to 30% by weight.

TABLE-US-00006 Example MIBC.sup.(4) (PED) Shake Test Result 7-1 0 PSM fail 7-2 1 PSM fail 7-3 1.7 PSM fail 7-4 2.8 PSM fail 7-5 4.6 PSM fail 7-6 7.77 PSM pass 7-7 12.9 PSM pass 7-8 21.5 PSM pass 7-9 35.9 PSM pass 7-10 59.9 PSM pass .sup.(4)weight % based on the weight of the solvent
When the specific polyelectrolyte (PED) is PSM, then the correct amount of MIBC to make PTBEAM soluble in the droplets is 7 or more by weight.

EXAMPLE 8: HEAT-AGED SAMPLES FROM SHAKE TEST

[0114] Samples were subjected to the shake test as described above and then were heated at 50° C. for 5 hours. After heating, the samples were judged as “pass” or “fail” according to the same criteria as in the shake test. The results were as follows:

TABLE-US-00007 Example PE2.sup.(1) PE1.sup.(2) Result 8-1 1 0.5 fail 8-2 0.3 0.5 fail 8-3 0.1 1 pass 8-4 0.3 1 pass 8-5 0.5 0.5 pass 8-6 0.5 1 pass 8-7 1 1 pass .sup.(1)amount of PE2, by weight based on the weight of the aqueous solution .sup.(2)amount of PE1, by weight based on the weight of the non-aqueous solution
Many of the inventive examples also have the additional desirable property of heat stability.