WO2014092246A1 - Highly branched polycarbonate resin, and method for preparing same - Google Patents

Abstract

The present invention relates to a highly branched polycarbonate resin which has Mark-Houwink constant of approximately 0.50 to approximately 0.60 and branches of approximately 0.5 to approximately 1. The highly branched polycarbonate resin of the present invention is prepared by a specific polymerization mode so as to be eco-friendly, has maximized branches, and is a without a loss of quality caused by an addition reaction such as a formation of networking between resins.

Description

Highly branched polycarbonate resin and its manufacturing method

The present invention relates to a highly branched polycarbonate resin and a method for producing the same. More specifically, the present invention relates to a highly branched polycarbonate resin having a high degree of branching without deterioration of quality due to a post-addition reaction such as networking between resins even when the melt polymerization method by a transesterification reaction is applied, and a manufacturing method thereof. .

Polycarbonate is very excellent in heat resistance, impact resistance, mechanical strength, transparency, etc., and is widely used in the manufacture of compact discs, transparent sheets, packaging materials, automobile bumpers, and sunscreen films, and the demand is rapidly increasing. However, in the case of extrusion molding polycarbonate resin, a product having a non-uniform thickness is made due to the low viscosity coefficient of the molten state, or a satisfactory molded product is not obtained due to the shrinkage of the product.

Therefore, when manufacturing a large-capacity hollow container or a large size panel, a specific polycarbonate resin having a viscosity average molecular weight and a viscosity coefficient different from a general polycarbonate resin is required. Such specific polycarbonates can be obtained by introducing an appropriate amount of branching agent into the polycarbonate resin. Conventionally, this branched polycarbonate production process can be divided into an interfacial polymerization process using phosgene, a melt polymerization process without phosgene, and a solid phase polymerization process.

The interfacial polymerization process is described in US Pat. No. 3,799,953, which includes aromatic hydroxy compounds such as bisphenol A, 1,1,1-tris (4-hydroxyphenyl) ethane, 1- [α-methyl-α- (4 '-Hydroxyphenyl) ethyl] -4- [α', α'-bis (4'-hydroxyphenyl) ethyl] benzene, α, α ', α-tris (4-hydroxyphenyl) -1,3 A process of mixing a solution of a branching agent such as, 5-triisopropylbenzene and a gaseous phosgene in an organic solvent to allow a polymerization reaction to proceed at an interface between the aqueous solution layer and the organic solvent layer. The process is relatively easy to produce a high molecular weight polycarbonate resin in a continuous process, but the use of toxic poisonous gases and pollutant chlorine-based organic solvents are very dangerous, there is a problem that requires a huge equipment cost.

On the other hand, the melt polymerization process is a method of proceeding polymerization in the state of melting the raw material monomer, there is an advantage that there is little risk because no toxic substances are used, but in order to produce a high amount of extrusion polycarbonate to process a high viscosity reactant Not only the high temperature and high vacuum equipment is required, but also the quality may be degraded.

In US Pat. No. 4,888,400, a technique is known for melt polymerizing linear polycarbonates and branching agents having a number average molecular weight of 10,000 to 30,000 while extruding in the presence of a catalyst. In addition, US Pat. No. 5,021,521 discloses a technique for producing branched polycarbonates by melt polymerizing linear polycarbonates and branching agents in the presence of a catalyst. U.S. Patent No. 5,597,887 discloses a technique for producing branched polycarbonates containing high concentrations of branching agents by melt polymerization and then melt polymerizing with linear polycarbonates to finally produce branched polycarbonates.

However, in the process of introducing the branching agent during melt polymerization, which has been spotlighted as an environmentally friendly method, it is difficult to control the reactivity by the amount of branching agent or the type or timing of the branching agent, and an addition reaction such as networking phenomena between resins is produced. There are also changes in the properties of branched polycarbonates.

In particular, when an excessive amount (more than 0.5 mole) of polyfunctional phenolic branching agent for melt polymerization is used per mole of dihydroxy to produce highly branched polycarbonate, gel formation occurs more rapidly. Polycarbonate production can be difficult.

In addition, in the case of the melt polymerization method, the ratio of the terminal hydroxyl group which may adversely affect the heat resistance and color tone of the polycarbonate resin should be minimized. When the polyfunctional phenols are used as the branching agent, there is a problem of increasing the terminal hydroxyl group.

KR 2008-0131363 discloses a technique using a branching agent with modified terminal hydroxy to produce branched polycarbonates with reduced hydroxyl groups. The weight-average molecular weight of the prepared branched polycarbonate is lower than 25,000 and the Mark-Houwink constant α is 0.65 or more, which is similar to that of the linear polycarbonate having almost no branching degree.

In order to manufacture high-branched polycarbonate, there is a problem of degrading the quality of polycarbonate due to gel formation side reaction during melt polymerization by adding branching agent, and excessive amount of branching agent (more than 0.5 mol) is used to increase branching. A large amount of cyan gel is formed. In the case of modifying the branching agent to solve this problem, there is a problem in that it is difficult to manufacture a highly branched polycarbonate due to low reactivity and low molecular weight and degree of branching.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly branched polycarbonate resin and a method for producing the same, wherein the reactivity is adjustable and the degree of branching is maximized while minimizing the resin networking.

Another object of the present invention relates to a highly branched polycarbonate resin and a method for producing the same, without deterioration of quality due to networking-adding reaction between resins even using environmentally friendly melt polymerization.

Still another object of the present invention is to provide a highly branched polycarbonate resin in which the weight average molecular weight of the polycarbonate is significantly increased even with the use of a small amount of branched body, and a method for producing the same.

Still another object of the present invention relates to a highly branched polycarbonate resin having excellent polymerization stability and a method for producing the same.

Another object of the present invention relates to a highly branched polycarbonate resin and a method for producing the same that can be economically produced.

The above and other objects of the present invention can be achieved by the present invention described below.

One aspect of the present invention relates to a highly branched polycarbonate resin.

The high-branched polycarbonate resin has a mark-ink ink constant of about 0.50 to about 0.60, and branches of about 0.5 to about 1.

About 0.1 g of the highly branched polycarbonate resin is added to dichloromethane (1 mL), and there is no insoluble particle of about 0.5 mm or more when stirred at room temperature for about 1 hour.

In embodiments, the weight average molecular weight of the highly branched polycarbonate resin may be about 30,000 to about 50,000 Dalton.

In embodiments, the highly branched polycarbonate resin may have a branch frequency of about 0.1 to about 0.5 Hz.

In embodiments, the highly branched polycarbonate resin has a length of about 290 ° C. spiral injection of about 20 cm or more and a length of about 330 ° C. spiral injection of about 30 cm based on a flow index (Melt Flow Index, 300 ° C./1.2 kg) 8. Can be.

In embodiments, the highly branched polycarbonate resin may have a polydispersity index (PDI) of about 3 to about 5.

In embodiments, the highly branched polycarbonate resin may have a mark-ink ink constant of about 0.50 to about 0.57, and branches of about 0.7 to about 1.

The high branched polycarbonate resin is obtained from a linear polycarbonate, a branching agent and a diaryl carbonate, and the branching agent may be represented by the following Chemical Formula 1:

[Formula 1]

In Formula 1, X, Y and W are each independently a hydrogen atom, a halogen atom, a C ₁ -C ₁₈ alkoxy group, a C ₁ -C ₁₀ alkyl group or a C ₆ -C ₁₈ aryl group, n is 0-4 R is hydrogen, a substituted or unsubstituted C ₁ -C ₁₀ alkyl group, a substituted or unsubstituted C ₆ -C ₁₈ aryl group.

The unit represented by Formula 1 may include about 0.6 to about 0.9 mol%.

The linear polycarbonate may have a weight average molecular weight of about 1,000 or more and less than about 10,000 daltons.

In embodiments, the highly branched polycarbonate resin may have a concentration of terminal hydroxyl groups of about 5 mol% or less of the total terminal groups.

Another aspect of the present invention relates to a method for producing the highly branched polycarbonate resin. The method may include the step of melt polymerization by adding a diaryl carbonate and a branching agent to a linear polycarbonate.

The linear polycarbonate may have a weight average molecular weight of about 1,000 or more and less than about 10,000 daltons.

The diaryl carbonate may be added at about 0.6 to about 0.9 moles based on 100 parts by weight of the linear polycarbonate, and the branching agent may be added at about 0.6 to about 0.9 moles based on 100 parts by weight of the linear polycarbonate.

The diaryl carbonate and the branching agent may be introduced at a molar ratio of about 1: 1 to 1.05.

The present invention is capable of controlling reactivity and maximizing branching while minimizing resin-to- resin networking, and using environmentally friendly melt polymerization, without deterioration in quality due to additive reactions such as resin-to- resin networking, and using a small amount of branching agent. Has an effect of providing a highly branched polycarbonate resin and a method for producing the same, which have a markedly increased weight average molecular weight, excellent polymerization stability, and can be economically produced by adding a branching agent to a low molecular weight linear polycarbonate.

In the present invention, "substituted" means that the hydrogen atom is selected from the group consisting of a halogen group, C1 'to C30 alkyl group, C1' to C30 haloalkyl group, C6 'to C30 aryl group, C1' to C20 alkoxy group and combinations thereof Mean substituted by a substituent.

In the present invention, "branching agent" means a low molecular monomer having three or more functional groups.

The high-branched polycarbonate resin according to the present invention may be prepared by melt polymerization by adding a diaryl carbonate and a branching agent to a linear polycarbonate.

In another embodiment, a linear polycarbonate may be prepared by transesterifying an aromatic dihydroxy compound and a diaryl carbonate, and then, by adding a diaryl carbonate and a branching agent to the linear polycarbonate and melt-polymerized by an in-situ reaction. Can be.

The linear polycarbonate may have a weight average molecular weight of about 1,000 daltons or more and less than about 10,000 daltons, preferably about 4,000 to about 9,000 daltons. In the above range, the molecular weight control and the viscosity control according to the reaction time are advantageous.

The aromatic dihydroxy compound may be represented by the following formula (2):

[Formula 2]

In Formula 2, A is a single bond, substituted or unsubstituted C ₁ to C ₃₀ linear or branched alkylene group, substituted or unsubstituted C ₂ to C ₅ alkenylene group, substituted or unsubstituted C ₂ to C ₅ alkylidene group, substituted or unsubstituted C ₁ to C ₃₀ straight or branched haloalkylene group, substituted or unsubstituted C ₅ to C ₆ cycloalkylene group, substituted or unsubstituted C ₅ to C ₆ cycloalkenylene group, substituted or unsubstituted C ₅ to C ₁₀ cycloalkylidene group, substituted or unsubstituted C ₆ to C ₃₀ arylene group, substituted or unsubstituted C ₁ to C ₂₀ is a linear or branched alkoxylene group, a halogen acid ester group, a carbonate ester group, a linking group selected from the group consisting of CO, S and SO ₂ , R ₁ and R ₂ are each independently substituted or unsubstituted a C ₁ to C ₃₀ alkyl group or a substituted or unsubstituted in the C ₆ ring Not an aryl group of C ₃₀ and, n ₁ and n ₂ are each independently an integer of 0 to 4.

The diaryl carbonate may be represented by the following Chemical Formula # 3 '.

[Formula 3]

(In Formula 3, R ₁ and R ₂ are each independently a substituted or unsubstituted C ₆ -C ₂₀ aryl group.)

In embodiments, the diaryl carbonate may be added at about 0.60 to about 0.90 mol, preferably about 0.65 to about 0.85 mol, based on 100 parts by weight of the linear polycarbonate. Within this range, branches can be highly increased.

The branching agent may be represented by the following Chemical Formula 1.

[Formula 1]

In Formula 1, X, Y and W are each independently a hydrogen atom, a halogen atom, a C ₁ -C ₁₈ alkoxy group, a C ₁ -C ₁₀ alkyl group or a C ₆ -C ₁₈ aryl group, n is 0-4 R is hydrogen, a substituted or unsubstituted C ₁ -C ₁₀ alkyl group, a substituted or unsubstituted C ₆ -C ₁₈ aryl group.

In some embodiments, the branching agent may be added in an amount of about 0.60 to about 0.90 moles, preferably about 0.60 to about 0.80 moles, based on 100 parts by weight of the linear polycarbonate. Within this range, the degree of branching can be highly increased.

Preferably, the branching agent and the diaryl carbonate are added together. By injecting a branching agent and a diaryl carbonate in this manner, it is possible to obtain high branching while suppressing the addition reaction such as networking between resins.

Preferably, the branching agent and the diaryl carbonate may be introduced at a molar ratio of about 1: 1 to 1.05. By controlling the reactivity of the branching agent in the above range it is possible to reduce the networking (networking) formation by the branching agent.

The melt polymerization may be carried out at a temperature range of about 200 to about 300 ℃. Melting is carried out at this temperature to proceed with stirring, and the reaction pressure is reduced to about 1 to 10 Torr for about 30 minutes to about 3 hours. Stirring may be performed for about 3 to about 10 hours at this high temperature and reduced pressure. Preferably about 5 to about 9 hours of stirring is performed. It is easy to control phenol recovery, molecular weight and viscosity in the above range, it is easy to control the oxidation and reactivity of the branching agent.

Phenol generated during the reaction can be recovered by a conventional method.

The mark hulk equation is established between the molecular weight and the intrinsic viscosity of the polymer, and the a value of the above equation is called the mark huw constant. The value of a can easily be measured when using GPC for relative viscosity comparison. In general, linear polymers have MarkHuken constant values of about 0.65- about 0.7, and branched polymers have values of less than about 0.65. The smaller the value of a, the higher the degree of branching.

The highly branched polycarbonate resins of the present invention have a Mark-Hink constant of about 0.50 to about 0.60, in particular about 0.50 to about 0.57.

In addition, the highly branched polycarbonate resin may have a polydispersity index (PDI) of about 3 to about 5, for example about 3.5 to about 5.

The high branched polycarbonate resin is characterized in that the branching (branches) is highly branched from about 0.5 to about 1.0, preferably from about 0.6 to about 0.95, more preferably from about 0.7 to about 0.9.

The high branched polycarbonate resin may have a branch frequency of about 0.1 to about 0.5, preferably about 0.15 to about 0.45.

As described above, the highly branched polycarbonate resin of the present invention has excellent branches and has high viscosity compared to linear polycarbonate at low shear, low viscosity at high shear, and spiral injection molding. The practical fluidity is high due to the shear thinning effect compared to the linear polycarbonate in the same flow.

In embodiments, the highly branched polycarbonate resin has a length of 290 ° C. spiral injection of at least about 20 cm, for example about 21-35 cm, based on a Melt Flow Index (300 ° C./1.2 kg) 8, 330 The spiral injection may be at least about 30 cm in length, for example about 35-45 cm.

In addition, the highly branched polycarbonate resin does not form a gel by minimizing inter-resin networking. In an embodiment, 0.1 g of the highly branched polycarbonate resin is added to dichloromethane (1 mL), and stirred at room temperature for about 1 hour, and no more than about 0.5 mm of insoluble particles are present.

The weight average group molecular weight of the highly branched polycarbonate resin may be about 30,000 to about 50,000 daltons. The weight-average molecular weight is measured by GPC (Gel Permeation Chromatography) by dissolving polycarbonate resin (20 mg) in dichloromethane solvent (4 mL) with VISCOTEC TDA 302 GPC equipment.

In embodiments, the highly branched polycarbonate resin may have a concentration of terminal hydroxyl groups of about 5 mol% or less of the total terminal groups. In the above range, there is a merit of minimizing the thermal stability decrease due to the terminal group phenol.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, the following examples are provided to help the understanding of the present invention, and the scope of the present invention is not limited to the following examples. Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

Example

Example 1

500 ml stirred glass reactor equipped with condenser with weight average molecular weight of 8000 daltons 　 100.0 g of phosphorus bisphenol-A (BPA) low molecular linear polycarbonate and 0.686 g (0.82 mole) of diphenyl carbonate (DPC, manufactured by Cheil Industries) and trihydroxyphenylethane (THPE, Sigma-Aldrich Korea 326844 (Batch # 03901BH) as a branching agent )) 0.934 g (0.78 mol) (branching agent: diphenyl carbonate = 1: 1.05) was added thereto, the temperature was raised to 280 ℃ at normal pressure, and melted for 30 minutes. When melting to start stirring, the reaction pressure was slowly lowered to 1 Torr for 1 hour. The mixture was stirred for 7 hours at the high temperature and reduced pressure. During the reaction, a small amount of reaction by-products and phenol were generated, and the phenol generated was recovered in the condenser. After the reaction, the weight average molecular weight of the branched polycarbonate resin analyzed by GPC was 35,729 daltons. In addition, as a result of analyzing the prepared branched polycarbonate resin through GPC-TDA, it was confirmed that the branch was formed with a Mark-Houwink constant ('a') of 0.557, and the branch was formed with a high branch of 0.754. Could. In particular, 0.5 mole excess of branching agent was used, but there was no addition reaction such as network formation between resins.

Comparative Example 1

The same procedure as in Example 1 was conducted except that a linear polycarbonate having a weight average molecular weight of 20,000 daltons was applied.

Comparative Example 2

The above procedure was carried out except that 0.48 μg (0.57 mmol) of diphenyl carbonate (DPC) and 0.654 μg (0.54 mmol) of trihydroxyphenylethane (THPE) were added as a branching agent (branching agent: diphenyl carbonate = 1: 1.05). It carried out similarly to Example 1.

Comparative Example 3

Without DPC, it was carried out in the same manner as in Example 1 except that only 0.747 g (0.62 mmol) of trihydroxyphenylethane (THPE) was added as a branching agent.

Comparative Example 4

The same procedure as in Example 1 was conducted except that no DPC and a branching agent were used.

Comparative Example 5

The above operation was carried out except that 0.823 μg (0.98 mmol) of diphenyl carbonate (DPC) and 1.121 g (0.94 mmol) of trihydroxyphenylethane (THPE) were added as a branching agent (branching agent: diphenyl carbonate = 1: 1.05). It carried out similarly to Example 1.

The physical properties of the polycarbonate-based resins of Examples 1 and Comparative Examples 1 to 4 were evaluated by the following methods, and the results are shown in Table 1:

Property measurement method

(1) Weight average molecular weight and number average molecular weight: Polycarbonate resin (20 mg) was dissolved in dichloromethane solvent (4 mL) using VISCOTEC TDA 302 GPC and measured by GPC (Gel Permeation Chromatography). PDI was calculated as Mw / Mn.

Mark-Houwink Contant (MH, "a"): Mark-Houwink Contant (MH, "a"): Mark-Houwink Contant (MH) is a slope when the proportional relationship between the weight average molecular weight (Mw) and the intrinsic viscosity ) And measured by the GPC-TDA method. In the case of the linear structure, the M-H constant is measured to be close to 0.7. The higher the degree of branching, the smaller the M-H constant.

(3) Branches: Assuming the molecular weight as the reference molecular weight, the average number of branches was measured by the GPC-TDA method.

(4) branch frequency: The average number of branches attached to one polymer chain was measured by GPC-TDA method.

(5) Networking between resins: Linear and branched polycarbonates in dichloromethane solvents are well dissolved, but the networked resins are not very well dissolved and visually confirmed using solubility differences. In a container with a screw cap (10 mL volume vial), polymerized branched PC (0.1 mg) was placed in dichloromethane (1 mL), and stirred at room temperature for 1 hour, after which insoluble particles of 0.5 mm or more were observed. It was judged that the resin exists and the network was formed.

6, the terminal hydroxyl group concentration of: Bruker 500 MHz 1H magnetic resonance ⁽¹ H Nuclear Magnetic Resonance, NMR) quantitative structural analysis of the polymers and the ratio of hydrogen of the hydrogen and the terminal phenyl of the terminal phenol resin using Calculated as

(7) Spiral test: Sample injection point (1 cm) after injection using a common spiral mold at 290 ° C and 330 ° C, based on 8 g / 10 min of Melt Flow Index (300 ° C / 1.2kg). The number was measured by measuring the length.

Table 1

			Example 1	Comparative Example 1	Comparative Example 2	Comparative Example 3	Comparative Example 4	Comparative Example 5
Reaction Raw Material	Linear PC (parts by weight)	8000g / mol	100	-	100	100	100	100
		20,000g / mol	-	100	-	-	-	-
	Basin (Mall)		0.781	0.781	0.547	0.625	-	0.937
	DPC (Mall)		0.820	0.820	0.574	-	-	0.984
Analysis	Mn		7,258	25,343	9,272	11,689	7,732	11,698
	Mw		35,729	62,422	20,387	31,717	15,232	37,622
	PDI		4.956	2.463	2.112	2.714	1.970	3.216
	MH a		0.557	0.639	0.599	0.595	0.700	0.555
	branches		0.754	0.335	0.333	0.538	-	1.138
	branch frequency		0.274	0.169	0.141	0.479	-	0.743
	Formation of resin network		X	X	X	○	X	○
	Concentration of terminal OH (mol%)		2.4	3.5	7.2	21.5	22.7	3.1
	Spiral Length (cm)	290 ℃	22	13	25	21	17	23
		330 ℃	37	22	39	35	28	36

As shown in Table 1, Comparative Example 3 with the addition of a branching agent was found to have a higher molecular weight rise and higher PDI than Comparative Example 4 without the administration of a branching agent, the branching reaction proceeded. However, in Comparative Example 3 in which only the branching agent was administered, the inter resin networking side reaction occurred. In Comparative Example 2, in which the branching agent and the diphenyl carbonate were used in less than 0.6 mol, the inter-resin networking could not be confirmed, but the branching degree was low. It can be seen that in the case of Comparative Example 1 in which the molecular weight of the linear PC exceeds 10,000 daltons, the branching degree is low. In addition, in the case of Comparative Example 5, in which the branching agent and the diphenyl carbonate were used exceeding 0.9 mol, the inter-resin networking side reaction occurred.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (15)

1. A highly branched polycarbonate resin having a mark-ink ink constant of about 0.50 to about 0.60 and a branching degree of about 0.5 to about 1.
2. The high-branched polycarbonate resin according to claim 1, wherein about 0.1 g of the highly branched polycarbonate resin is added to dichloromethane (1 mL), and then stirred at room temperature for about 1 hour, wherein no insoluble particles are present.
3. The highly branched polycarbonate resin of claim 1, wherein the weight average molecular weight of the highly branched polycarbonate resin is about 30,000 to about 50,000 Daltons.
4. The highly branched polycarbonate resin of claim 1, wherein the branched polycarbonate resin has a branch frequency of about 0.1 to about 0.5 Hz.
5. According to claim 1, wherein the high-branched polycarbonate resin has a flow rate (Melt Flow Index, 300 ℃ / 1.2kg) 8 based on the length of the 290 ℃ spiral injection is about 20 cm or more, the 330 ℃ spiral injection length of about Highly branched polycarbonate resin that is 30 cm or larger.
6. 2. The highly branched polycarbonate resin of claim 1, wherein the highly branched polycarbonate resin has a polydispersity index (PDI) of about 3 to about 5.
7. The high branched polycarbonate resin of claim 1, wherein the high branched polycarbonate resin has a mark-ink ink constant of about 0.50 to about 0.57 and a branching of about 0.7 to about 1.
8. The high-branched polycarbonate resin according to claim 1, wherein the highly branched polycarbonate resin is obtained from a linear polycarbonate, a branching agent, and a diaryl carbonate, and the branching agent is represented by the following Chemical Formula 1:

   [Formula 1]

   

   In Formula 1, X, Y and W are each independently a hydrogen atom, a halogen atom, a C ₁ -C ₁₈ alkoxy group, a C ₁ -C ₁₀ alkyl group or a C ₆ -C ₁₈ aryl group, n is 0-4 R is hydrogen, a substituted or unsubstituted C ₁ -C ₁₀ alkyl group, a substituted or unsubstituted C ₆ -C ₁₈ aryl group.
9. The highly branched polycarbonate resin according to claim 8, wherein the unit represented by Chemical Formula 1 contains about 0.6 to about 0.9 mol%.
10. 9. The highly branched polycarbonate resin according to claim 8, wherein the linear polycarbonate has a weight average molecular weight of 1,000 or more and less than 10,000 daltons.
11. The high-branched polycarbonate resin according to claim 1, wherein the high-branched polycarbonate resin has a concentration of terminal hydroxyl groups of 5 mol% or less of all terminal groups.
12. Method for producing a highly branched polycarbonate resin comprising the step of melt polymerization by adding a diaryl carbonate and a branching agent to a linear polycarbonate.
13. The method of claim 12, wherein the linear polycarbonate has a weight average molecular weight of 1,000 or more and less than 10,000 daltons.
14. The method of claim 12, wherein the diaryl carbonate is added in an amount of about 0.6 to about 0.9 mol based on 100 parts by weight of the linear polycarbonate, and the branching agent is added in an amount of about 0.6 to about 0.9 mol based on 100 parts by weight of the linear polycarbonate. Characterized in that the method.
15. 13. The method of claim 12, wherein the diaryl carbonate and the branching agent are introduced at a molar ratio of 1: 1 to 1.05.