Acrylic syrup preparation method and acrylic syrup

1. An acrylic syrup preparation method, comprising the steps of:

performing bulk photopolymerization by initiating a UV irradiation of a composition containing a photoinitiator and one or more types of acrylic monomers;

stopping the UV irradiation at the time point when the temperature is increased by about 5° C. to about 40° C. from the time point when the temperature at which the UV irradiation of the composition is initiated; and

purging the composition with an oxygen-containing inert gas after the UV irradiation is stopped,

wherein the composition does not comprise a molecular weight adjusting agent.

2. The acrylic syrup preparation method of claim 1 , wherein the oxygen-containing inert gas contains oxygen in an amount of about 10 vol % to about 30 vol %.

3. The acrylic syrup preparation method of claim 1 , wherein stirring is carried out at least while the composition is purged with the oxygen-containing inert gas.

4. The acrylic syrup preparation method of claim 1 , wherein the composition is purged with the oxygen-containing inert gas until the time point when the temperature of the composition reaches at least about 20° C. to about 50° C.

5. The acrylic syrup preparation method of claim 1 , wherein the acrylic monomers is polymerized at a conversion rate of about 4% to about 20% until the time point when the UV irradiation is stopped.

6. The acrylic syrup preparation method of claim 1 , wherein an acrylic polymer having a weight average molecular weight of about 1,000,000 g/mol to about 20,000,000 g/mol is formed by the bulk photopolymerization until the time point when the UV irradiation is stopped.

7. The acrylic syrup preparation method of claim 1 , wherein a nitrogen purging of the composition is started and carried out from before the UV irradiation is initiated.

8. The acrylic syrup preparation method of claim 7 , wherein stirring is carried out at least while the composition is purged with nitrogen.

9. The acrylic syrup preparation method of claim 1 , wherein the temperature of the composition is set to about −10° C. to about 80° C. when the time point when the UV irradiation is initiated.

10. The acrylic syrup preparation method of claim 1 , further comprising: the step of preparing the composition by mixing the photoinitiator in an amount of about 0.001 part by weight to about 1 part by weight based on about 100 parts by weight of the one or more types of acrylic monomers.

11. The acrylic syrup preparation method of claim 1 , wherein the one or more types of acrylic monomers comprise one selected from the group consisting of a (meth)acrylic acid ester-based monomer which comprises an alkyl group having 1 to 15 carbon atoms; a (meth)acrylic acid ester-based monomer which comprises a hydroxy group, a carboxyl group, and an amine group; and a combination thereof.

12. The acrylic syrup preparation method of claim 1 , wherein the photoinitiator absorbs light with a wavelength of about 100 nm to about 400 nm.

13. An acrylic syrup which does not comprises a molecular weight adjusting agent, and is prepared by means of bulk photopolymerization by the acrylic syrup preparation method according to claim 1 .

14. The acrylic syrup of claim 13 , wherein the acrylic syrup comprises an acrylic polymer having a weight average molecular weight of 1,000,000 g/mol to 20,000,000 g/mol.

15. The acrylic syrup of claim 13 , wherein the acrylic polymer has a polydispersity index of 1.98 to 10.

16. The acrylic syrup of claim 13 , wherein the acrylic syrup has a conversion rate of 4% to 20%.

17. The acrylic syrup of claim 13 , wherein the acrylic syrup has a viscosity of 1,000 cps to 100,000 cps at 20° C.