DROPLETS DISTRIBUTED IN AN AQUEOUS MEDIUM

Abstract

Provided is a composition comprising droplets distributed in an aqueous medium, wherein the droplets comprise one or more boronic acids, and wherein the aqueous medium comprises polyvinyl alcohol.

Claims

1. A composition comprising droplets distributed in an aqueous medium, wherein the droplets comprise one or more boronic acids, and wherein the aqueous medium comprises polyvinyl alcohol.

2. The composition of claim 1, wherein the one or more boronic acids are present in an amount of 0.0015% to 0.03% by weight based on the weight of the droplets.

3. The composition of claim 1, wherein the polyvinyl alcohol is present in an amount of 0.01% to 0.5% by weight based on the weight of the aqueous medium.

4. The composition of claim 1, wherein the droplets additionally comprise one or more monomers and one or more initiators.

5. The composition of claim 1, wherein the droplets additionally comprise one or more monomers and one or more initiators, and wherein the one or more monomers are present in an amount of 95% to 99.99% by weight based on the weight of the droplets.

6. The composition of claim 1, wherein the droplets additionally comprises one or more porogens, and wherein the one or more porogens are present in an amount of 10% to 60% by weight based on the weight of the droplets.

Description

PREPARATIVE EXAMPLE 1: ORGANIC SOLUTIONS

[0097] Organic solutions were prepared by combining the following ingredients:

TABLE-US-00001 Organic Solution Ingredients: Ingredient amount.sup.(1) Styrene balance.sup.(2) DVB 9.6% BPO 0.3% sulfur 0.0052 boronic acid variable Note: .sup.(1)% by weight based on the total weight of droplet ingredients. Note: .sup.(2)to make up 100% by weight

PREPARATIVE EXAMPLE 2: AQUEOUS SOLUTIONS

[0098] Aqueous solutions were prepared by combining the following ingredients:

TABLE-US-00002 Aqueous Solution Ingredients ingredient amount.sup.(3) DI water balance.sup.(5) CMMC variable PVOH.sup.(4) 0.06% NaNO.sub.2 0.016% Note: .sup.(3)% by weight based on the total weight of aqueous phase ingredients Note: .sup.(4)either PVOH1 or PVOH2 Note: .sup.(5)to make up 100% by weight

EXAMPLE 3: INTERFACIAL TENSION TESTING

[0099] The interface between a layer of organic solution and a layer of aqueous solution was tested using the IFT procedure described above. It is contemplated that a strong interface in this test would indicate that the same combination of aqueous solution and organic solution would form a good suspension of droplets of organic solution in aqueous solution. Approx. means approximately. The results were as follows:

TABLE-US-00003 Example % VPBA IFT (d/cm) Observations 3-2 0.0001 approx. 12 normal 3-3 0.001 approx. 12 normal 3-4 0.003 7.2 skin formed 3-5 0.005 6.7 membrane and skin; air IFT 46.8 d/cm 3-6 0.0075 4.8 membrane and skin; air IFT 41.9 d/cm 3-7 0.01 4.9 membrane and skin; air IFT approx. 48 d/cm
Further IFT test results were as follows:

TABLE-US-00004 Example % VPBA IFT (d/cm) Observations 3-8 0.015 6.5 membrane and skin; air IFT 45.3 d/cm 3-9 0.02 10.5 precipitate; ring did not pull through the monomer layer 3-10 0.025 11.3 precipitate; ring did not pull through the monomer layer 3-11 0.03 11.4 precipitate; ring did not pull through the monomer layer 3-12 0.05 12.2 precipitate 3-13 0.1 10.2 precipitate

[0100] Examples 3-2 and 3-3 showed that with too little amount of boronic acid, the desired strengthening of the interface does not occur. All the other examples showed useful behavior, at least initially. Examples 3-4 through 3-11 showed especially desirable behavior, with the interface between the organic solution and the aqueous solution forming a very strong membrane-like layer.

EXAMPLE 4: PREPARATION OF SUSPENSIONS WITHOUT CMMC

[0101] During the preparation of the suspension, some individual ingredients or partial mixtures were, if necessary, temporarily heated to achieve good mixing, but the suspension was provided at approximately 25 C.

[0102] Using the organic and aqueous solutions described in Examples 1 and 2, suspensions of droplets of organic solution suspended in a medium of aqueous solution were made using the jetting procedure described in U.S. Pat. No. 4,444,960 and U.S. Pat. No. 4,623,706. This procedure consistently produces droplets with volume-average diameter of 480 m and uniformity coefficient less than 1.1. In the resulting suspension, the volume fraction of droplets of organic solution was 0.4.

[0103] A thin layer of each suspension was placed on a glass slide and examined by optical microscopy to produce a photomicrograph. The photomicrographs were manually examined. The droplets of diameter of approximately 400 m to 600 m (normal droplets) were counted, as were the droplets having diameter less than approximately 250 m (small droplets). The number of small droplets per 100 normal droplets is reported herein as the small count. No CMMC was used. PVOH type was PVOH1. Ex. means Example. Examples with designation ending in C are comparative. Results were as follows:

TABLE-US-00005 Example % VPBA Diameter.sup.(1) (m) Small Count 4-1C 0 480 118 4-2 0.01 480 3 Note: .sup.(1)volume-average diameter, known from the consistent results of the jetting procedure.
As the small count shows, Example 5-2 has a far more uniform distribution of droplet sizes than Comparative Example 5-1C.

EXAMPLE 5: SUSPENSIONS WITH CMMC

[0104] During the preparation of the suspension, some individual ingredients or partial mixtures were, if necessary, temporarily heated to achieve good mixing, but the suspension was provided at approximately 25 C.

[0105] Using the organic and aqueous solutions described in Examples 1 and 2, suspensions of droplets of organic solution suspended in a medium of aqueous solution were made using the jetting procedure described in U.S. Pat. No. 4,444,960 and U.S. Pat. No. 4,623,706. In the resulting suspension, the volume fraction of droplets of organic solution was 0.4.

[0106] Monomer droplet size was volume-average diameter of 480 m, resulting from the jetting procedure.

[0107] Jetting was performed at approximately 25 C., and the suspension was held with stirring for approximately 20 hours. Then the temperature was raised to 80 C. and held at a temperature between 80 C. and 100 C. for 10 hours, and then the composition was cooled to approximately 25 C. The composition underwent a process of suspension polymerization, converting the monomer droplets to polymer particles.

[0108] Size of the polymer particles was analyzed by performing optical microscopy to form digital images of the particles, then performing image analysis to determine the diameter of each particle, and then calculating the desired statistics from the data base of observed diameters. Results were as follows:

TABLE-US-00006 PVOH Ex % VPBA % CMMC type HMS (m) UC LT355 5-1 0.01 0.15 PVOH2 468 1.06 1.66 5-2 0.01 0.15 PVOH2 466 1.06 3.45 5-3 0.01 0.15 PVOH2 477 1.07 0.41 5-4 0.0025 0.15 PVOH2 469 1.11 4.35 5-5C 0 0.23 PVOH1 443 1.7 15.6 5-6C 0 0.23 PVOH1 407 1.37 12.2
Examples 5-1, 5-2, and 5-3 are replicate samples. Also, Examples 5-5C and 5-6C are duplicate samples. All of the inventive examples 5-1 through 5-4 have much more uniform particle size distributions (i.e., smaller values of UC and lower values of LT355) than the comparative examples 5-5C and 5-6C. The difference in uniformity between the inventive examples and the comparative examples is considered to be extremely significant; at a production scale, this difference could mean that the inventive process was economically viable while the comparative process was prohibitively expensive.