METHOD OF PREPARING MALEIMIDE-BASED COPOLYMER

Abstract

Provided is a method of preparing a maleimide-based copolymer, which comprises adding a monomer mixture including an aromatic vinyl-based monomer and a maleimide-based monomer to an aqueous solution consisting of an aqueous solvent and a first vinyl cyanide-based monomer and performing polymerization.

Claims

1. A method of preparing a maleimide-based copolymer, comprising: adding a monomer mixture including an aromatic vinyl-based monomer and a maleimide-based monomer to an aqueous solution consisting of an aqueous solvent and a first vinyl cyanide-based monomer and performing polymerization.

2. The method of claim 1, wherein the monomer mixture includes a second vinyl cyanide-based monomer.

3. The method of claim 1, wherein the polymerization is performed while continuously adding the monomer mixture to the aqueous solution.

4. The method of claim 1, wherein the aqueous solution includes the first vinyl cyanide-based monomer in a dissolved state.

5. The method of claim 1, wherein the aqueous solution includes 100.0 parts by weight of water and 1.0 to 10.0 parts by weight of the first vinyl cyanide-based monomer.

6. The method of claim 1, wherein the aqueous solution includes 100.0 parts by weight of water and 3.5 to 9.5 parts by weight of the first vinyl cyanide-based monomer.

7. The method of claim 2, wherein the aqueous solution includes the first vinyl cyanide-based monomer in an amount of 30.0 to 90.0 parts by weight with respect to 100.0 parts by weight of the sum of the first vinyl cyanide-based monomer and the second vinyl cyanide-based monomer.

8. The method of claim 2, wherein the aqueous solution includes the first vinyl cyanide-based monomer in an amount of 40.0 to 85.0 parts by weight with respect to 100.0 parts by weight of the sum of the first vinyl cyanide-based monomer and the second vinyl cyanide-based monomer.

9. The method of claim 3, wherein the continuous addition of the monomer mixture is terminated when a polymerization conversion rate reaches 65.0 to 80.0%.

10. The method of claim 1, wherein the polymerization is suspension polymerization.

Description

Examples 1 to 5

[0036] An aqueous solution described in Table 1 below, 0.02 parts by weight of 1-di(t-butylperoxy)cyclohexane, 1.3 parts by weight of tricalcium phosphate, and 0.1 parts by weight of t-dodecyl mercaptan were input into a reactor. The temperature inside the reactor was raised to 110° C. Immediately after the reactor temperature elevation, suspension polymerization was performed while continuously adding a first monomer mixture described in Table 1 below at a constant rate until a polymerization conversion rate reached 70%.

[0037] After the continuous addition of the first monomer mixture was terminated, polymerization and aging were performed for 180 minutes and then terminated. Subsequently, formic acid was input into the reactor so that the pH of a polymerization slurry became 2.5, and washing, dehydration, and drying were performed to prepare a copolymer in the form of bead.

Comparative Example 1

[0038] An aqueous solvent described in Table 2 below, 0.02 parts by weight of 1-di(t-butylperoxy)cyclohexane, 1.3 parts by weight of tricalcium phosphate, and 0.1 parts by weight of t-dodecyl mercaptan were input into a reactor. The temperature inside the reactor was raised to 110° C. Afterward, a second monomer mixture described in Table 2 below was batch-added, and then suspension polymerization was performed for 360 minutes and terminated. Subsequently, formic acid was input into the reactor so that the pH of a polymerization slurry became 2.5, and washing, dehydration, and drying were performed to prepare a copolymer in the form of bead.

Comparative Example 2

[0039] An aqueous solvent described in Table 2 below, 0.02 parts by weight of 1,1-di(t-butylperoxy)cyclohexane, 1.3 parts by weight of tricalcium phosphate, and 0.1 parts by weight of t-dodecyl mercaptan were input into a reactor. The temperature inside the reactor was raised to 110° C. Immediately after the reactor temperature elevation, suspension polymerization was performed while continuously adding a third monomer mixture described in Table 2 below at a constant rate until a polymerization conversion rate reached 70%.

[0040] After the continuous addition of the third monomer mixture was terminated, polymerization and aging were performed for 180 minutes and then terminated.

[0041] Subsequently, formic acid was input into the reactor so that the pH of a polymerization slurry became 2.5, and washing, dehydration, and drying were performed to prepare a copolymer in the form of bead.

Comparative Example 3

[0042] An aqueous solution described in Table 2 below, 0.02 parts by weight of 1,1-di(t-butylperoxy)cyclohexane, 1.3 parts by weight of tricalcium phosphate, and 0.1 parts by weight of t-dodecyl mercaptan were input into a reactor. The temperature inside the reactor was raised to 110° C. Immediately after the reactor temperature elevation, suspension polymerization was performed while continuously adding a third monomer mixture described in Table 2 below at a constant rate until a polymerization conversion rate reached 70%.

[0043] After the continuous addition of the third monomer mixture was terminated, polymerization and aging were performed for 180 minutes and then terminated. Subsequently, formic acid was input into the reactor so that the pH of a polymerization slurry became 2.5, and washing, dehydration, and drying were performed to prepare a copolymer in the form of bead.

Experimental Example 1

[0044] The properties of the maleimide-based copolymers prepared in Examples and Comparative Examples were calculated by methods described below, and results thereof are shown in Tables 1 and 2 below.

[0045] (1) Final polymerization conversion rate (%): 4 g of a maleimide-based copolymer was completely dissolved in tetrahydrofuran, and methanol was then added to obtain a precipitate. The obtained precipitate was dried under vacuum to completely remove a solvent, thereby obtaining a sample. The sample was weighed, and the weight of the sample was substituted into the following equation to calculate a final polymerization conversion rate.

Final polymerization conversion rate (%)=(Weight of sample)/(Total weight of monomers added in preparation of 4 g of maleimide-based copolymer)×100

[0046] (2) Amount of AN unit in maleimide-based copolymer: A maleimide-based copolymer was collected whenever polymerization conversion rates described in Tables 1 and 2 below were reached during the preparation process of the maleimide-based copolymer, and the amount of an acrylonitrile unit in the maleimide-based copolymer was measured by elemental analysis.

[0047] In this case, the polymerization conversion rate was calculated in the same manner as in (1) Final polymerization conversion rate (%).

[0048] (3) Glass transition temperature of maleimide-based copolymer: A maleimide-based copolymer was collected whenever polymerization conversion rates described in Tables 1 and 2 below were reached during the preparation process of the maleimide-based copolymer, and the glass transition temperature of the maleimide-based copolymer was measured by differential scanning calorimetry.

[0049] In this case, the polymerization conversion rate was calculated in the same manner as in (1) Final polymerization conversion rate (%).

TABLE-US-00001 TABLE 1 Examples Classification 1 2 3 4 5 Preparation Aqueous solution Distilled 140.0 140.0 140.0 140.0 140.0 method (parts by weight) water AN 4.2 5.6 7.0 9.8 12.0 First monomer mixture AN 7.8 6.4 5.0 2.2 0 (parts by weight) ST 48.0 48.0 48.0 48.0 48.0 PMI 40.0 40.0 40.0 40.0 40 Maleimide- Final polymerization conversion rate (%) 94.2 94.6 94.5 94.8 94.5 based Amount of Polymerization 15 3.5 4.3 5.6 6.7 6.8 copolymer AN unit conversion 30 3.8 4.5 5.9 7.2 7.1 (wt %) rate 50 4.5 5.2 6.2 7.7 7.7 70 5.9 6.4 7.1 8.6 8.5 90 10.1 10.2 10.2 10.3 10.3 Glass Polymerization 15 204.3 199.4 192.5 183.2 183.0 transition conversion 30 200.8 496.7 190.2 180.0 179.9 Temperature rate 50 198.6 193.8 189.1 178.2 178.3 70 190.1 186.2 182.6 175.2 175.1 90 170.1 170.4 171.2 172.1 172.0 AN: Acrylonitrile ST: Styrene PMI: N-Phenylmaleimide

TABLE-US-00002 TABLE 2 Comparative Examples Classification 1 2 3 Preparation method Aqueous solvent Distilled water 140.0 140.0 0 (parts by weight) Aqueous solution Distilled water 0 0 140.0 (parts by weight) AN 0 0 7.0 ST 0 0 28 Second monomer mixture AN 12.0 0 0 (parts by weight) ST 48.0 0 0 PMI 40.0 0 0 Third monomer mixture AN 0 12.0 5.0 (parts by weight) ST 0 48.0 20.0 PMI 0 40.0 40.0 Maleimide-based Final polymerization conversion rate (%) 94.6 94.3 94.5 copolymer Amount of Polymerization 15 2.3 2.2 2.2 AN unit conversion rate 30 2.7 2.3 2.5 (wt %) 50 3.3 2.9 3.1 70 5.2 4.2 5.0 90 10.2 10.1 10.2 Glass transition Polymerization 15 216.4 215.8 216.0 temperature conversion rate 30 209.8 213.2 212.6 50 205.5 208.1 207.4 70 194.8 199.2 198.8 90 168.3 167.7 168.1 AN: Acrylonitrile ST: Styrene PMI: N-Phenylmaleimide

[0050] Referring to Tables 1 and 2, in the case of Examples 1 to 5 in which suspension polymerization was performed while continuously adding a first monomer mixture to an aqueous solution, it can be confirmed that maleimide-based copolymers having no great difference in the amount of acrylonitrile-based units throughout polymerization were prepared, as compared to Comparative Example 1 in which suspension polymerization was performed after a second monomer mixture was batch-added to an aqueous solvent, Comparative Example 2 in which suspension polymerization was performed while continuously adding a third monomer mixture to an aqueous solvent, and Comparative Example 3 in which suspension polymerization was performed while continuously adding a third monomer mixture to an aqueous solution including styrene and acrylonitrile. Also, it can be confirmed that, since N-phenylmaleimide did not excessively participate in polymerization at the early and middle stages of the polymerization, maleimide-based copolymers having no great difference in glass transition temperature throughout polymerization were prepared. From these results, it can be predicted that, according to the method of preparing a maleimide-based copolymer of the present invention, specific amounts of a vinyl cyanide-based monomer and a maleimide-based monomer can participate in polymerization throughout the polymerization, and thus a maleimide-based polymer with a consistent composition will be prepared.