HK1236212B - Method for preparing highly transparent and highly heat-resistant polycarbonate ester - Google Patents

Description

Method for preparing polycarbonate having high transparency and high heat resistance

Technical Field

The present invention relates to a novel method for preparing polycarbonate with excellent transparency and high heat resistance, and more particularly to a method for preparing a bio-based polycarbonate having repeating units derived from the reaction of 1,4:3,6-dianhydrohexitol, carbonate, and 1,4-cyclohexanedicarboxylate.

Background Art

Unlike traditional materials used in the petrochemical industry, 1,4:3,6-dianhydrohexitol is a bio-based material derived from biomass—a renewable resource composed of polysaccharides such as corn, wheat, and potatoes. In particular, bioplastics containing bio-based materials have attracted widespread attention as a material for reducing carbon dioxide production, thereby addressing the global issue of global warming, as the carbon dioxide produced by bioplastics during post-use degradation can be reused in the biomass growth process.

1,4:3,6-dianhydrohexitol has the following three stereoisomers. Due to the different relative configurations of the two hydroxyl groups, these three stereoisomers have different chemical properties: isomannide (as shown in the chemical structure a below, melting point: 81-85°C), isosorbide (as shown in the chemical structure b below, melting point: 61-62°C) and isoidide (as shown in the chemical structure c below, melting point 64°C).

【Chemical formula a】

【Chemical formula b】

【Chemical formula c】

In particular, when 1,4:3,6-dianhydrohexitol is used as a monomer to prepare polycarbonate, a typical engineering plastic, the resulting polycarbonate exhibits excellent thermal and optical properties. This is attributed to the molecular structural characteristics of 1,4:3,6-dianhydrohexitol, namely its chirality and rigid saturated heterocyclic structure, as well as the advantages of bioplastics. Therefore, 1,4:3,6-dianhydrohexitol has been widely used as a typical raw material for the development of bioplastics.

Furthermore, 1,4-dimethylcyclohexanedicarboxylate (DMCD) or its hydrolysis product, 1,4-cyclohexanedicarboxylic acid (CHDA), possesses a cyclohexane ring structure at the center of its molecule. Therefore, incorporating DMCD or CHDA into a polymer chain improves not only the polymer's weather resistance and UV stability, but also its gloss retention, yellowing resistance, hydrolytic stability, corrosion resistance, and chemical resistance, due to the unique combination of flexibility and hardness within the molecular structure.

Poly(1,4-cyclohexylene 1,4-cyclohexanedicarboxylate) (PCCD), a homopolyester of DMCD/cyclohexanedimethanol (CHDM), is an example of a commercially available polymer material made from DMCD. Due to its excellent weather resistance, chemical resistance, fluidity, and low refractive index, DuPont in the United States has used PCCD in the preparation of a polycarbonate/PCCD alloy (trademark name: Xyrex) to improve the transparency of polycarbonate.

Industrial methods for producing polycarbonate can be categorized into solution polymerization and melt polycondensation. Unlike solution polymerization, which uses phosgene as a carbonate source, the melt polycondensation method utilizes diphenyl carbonate (DPC). Therefore, the raw materials used in conventional melt polycondensation typically include DPC and bisphenol A (BPA) as diols. The transesterification reaction between BPA and DPC produces phenol as a byproduct of the melt polycondensation reaction.

The inventors of the present invention have developed a novel method for preparing isosorbide-based polycarbonate, which is prepared from 1,4-diphenyl-cyclohexanedicarboxylate (hereinafter referred to as DPCP) derived from DMCD or CHDA.

The present invention utilizes DPCD as the material for forming the ester bonds in the polymer chain when preparing isosorbide-based polycarbonate (or carbonate). The resulting polycarbonate is a novel bioplastic with excellent light transmittance and high heat resistance. Certain properties and molding processability of this bioplastic can be adjusted by varying the DPCD content. Compared to conventional bioplastics disclosed in U.S. Patent Application Publication No. 2011/0003101 and U.S. Patent No. 8,399,598, the bio-based polycarbonate of the present invention exhibits superior heat resistance, surface hardness, and impact strength.

Summary of the Invention

Technical issues

The present invention provides a novel method for preparing polycarbonate with high heat resistance, high transparency, a high degree of polymerization, and excellent mechanical properties. This polycarbonate comprises rigid polymer repeating units and is free of BPA, which may produce environmental hormones. It is highly useful in a variety of applications, including automotive glass replacements, optical lenses or films, baby bottles, and food containers.

Technical Solution

The present invention provides a method for preparing bio-based polycarbonate, comprising the following steps:

(1) converting the compound represented by Chemical Formula 2 into an intermediate reactant having a functional group that can be easily separated, and causing the intermediate reactant to undergo a nucleophilic reaction with phenol to generate the compound represented by Chemical Formula 3;

(2) subjecting the compound represented by Chemical Formula 3, the compound represented by Chemical Formula 4, and 1,4:3,6-dianhydrohexitol prepared in step (1) to a polycarbonate melt polycondensation reaction, thereby generating a bio-based polycarbonate comprising a repeating unit represented by Chemical Formula 1;

【Chemical Formula 1】

【Chemical Formula 2】

【Chemical Formula 3】

【Chemical Formula 4】

in:

R is methyl or hydrogen;

_R1 and _R2 are independently a substituted or unsubstituted _C1 - _C18 aliphatic group or _{a substituted or unsubstituted C1-C18 aromatic} group; and

x is a real number satisfying 0<x<1.

Beneficial effects of the present invention

Compared to traditional production methods, the method for preparing bio-based polycarbonate described herein utilizes a nucleophilic reaction between an intermediate reactant with easily separable functional groups and phenol to produce high-purity, high-whiteness DPCD in high yield, thereby reducing production costs. The bio-based polycarbonate produced by this method exhibits high transparency and heat resistance, and can be effectively used in a variety of applications, including automotive glass replacements, optical lenses or films, baby bottles, and food containers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is the nuclear magnetic resonance hydrogen spectrum ( ¹ HNMR) of DPCD;

FIG2 is a schematic diagram showing the change of the glass transition temperature (Tg) of a polymer with the DPC content;

FIG3 is a ¹ H NMR spectrum of the bio-based polycarbonate prepared in Example 1;

FIG4 is an infrared spectrum of the bio-based polycarbonate prepared in Example 1.

DETAILED DESCRIPTION

Hereinafter, the present invention will be described in detail.

The present invention provides a method for preparing bio-based polycarbonate, comprising the following steps:

(1) converting the compound represented by Chemical Formula 2 into an intermediate reactant having a functional group that can be easily separated, and causing the intermediate reactant to undergo a nucleophilic reaction with phenol to generate the compound represented by Chemical Formula 3; and

(2) subjecting the compound represented by Chemical Formula 3, the compound represented by Chemical Formula 4, and 1,4:3,6-dianhydrohexitol prepared in step (1) to a polycarbonate melt polycondensation reaction, thereby generating a bio-based polycarbonate including a repeating unit represented by Chemical Formula 1;

【Chemical Formula 1】

【Chemical Formula 2】

【Chemical Formula 3】

【Chemical Formula 4】

in,

R is methyl or hydrogen;

_R1 and _R2 are independently a substituted or unsubstituted _C1 - _C18 aliphatic group or _{a substituted or unsubstituted C1-C18 aromatic} group;

x is a real number satisfying 0<x<1.

In step (1), the compound represented by Chemical Formula 2 is converted into an intermediate reactant having a functional group that can be easily separated. The intermediate reactant undergoes a nucleophilic reaction with phenol to form a compound represented by Chemical Formula 3, namely 1,4-diphenyl-cyclohexanedicarboxylate (DPCP).

Specifically, in step (1), DMCD (a compound represented by Chemical Formula 2, wherein R is a methyl group) or CHDA (a compound represented by Chemical Formula 2, wherein R is a hydrogen atom) is converted into an intermediate reactant having a functional group that can be easily separated. This intermediate reactant then undergoes a nucleophilic reaction with phenol to produce DPCD. DPCD then undergoes an ester exchange reaction with a diol in the subsequent step (2), producing phenol as a by-product.

The intermediate reactant having a functional group that can be easily separated in step (1) can be a compound represented by the following chemical formula 2a:

【Chemical Formula 2a】

Wherein, R ₃ is F, Cl or Br.

In an embodiment of the present invention, the compound represented by Chemical Formula 2a may be 1,4-cyclohexanedicarbonyl chloride (hereinafter referred to as CHDC).

That is, in step (1) above, DMCD (wherein R is a methyl group) or CHDA (wherein R is a hydrogen group) as shown in Chemical Formula 2 can be converted into the intermediate compound CHDC. CHDC can undergo a nucleophilic reaction with phenol to form DPCD (see Reaction Scheme 1 below).

[Reaction Flowchart 1]

Depending on the desired properties and the compound represented by Chemical Formula 2, primary, secondary, or tertiary dicarboxylic acid esters or dicarboxylic acids can be used. The compound represented by Chemical Formula 2 is the starting material for forming the ester bonds in the polycarbonate polymer chain of the present invention. These compounds can undergo a nucleophilic reaction with phenol to form diphenyl esters other than the compound represented by Chemical Formula 3. These diphenyl esters undergo a polycarbonate melt polycondensation reaction with the compound represented by Chemical Formula 3.

The other diphenyl esters except the compound represented by Chemical Formula 3 may be one kind or a mixture of two or more kinds.

In order to make the bio-based polycarbonate of the present invention have high heat resistance, high transparency, high weather resistance and UV stability, the dicarboxylic acid ester or dicarboxylic acid other than the compound represented by Chemical Formula 2 may have a single or fused saturated homocyclic or heterocyclic ring at the center of its molecule. For example, at least one dicarboxylic acid ester or dicarboxylic acid compound selected from the group consisting of dimethyl tetrahydro-2,5-furandicarboxylate, dimethyl 1,2-cyclohexanedicarboxylate, dimethyl 1,3-cyclohexanedicarboxylate, dimethyl decahydro-2,4-naphthalene dicarboxylate, dimethyl decahydro-2,5-naphthalene dicarboxylate, dimethyl decahydro-2,6-naphthalene dicarboxylate, dimethyl decahydro-2,7-naphthalene dicarboxylate, tetrahydro-2,5-furandicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, decahydro-2,4-naphthalene dicarboxylic acid, decahydro-2,5-naphthalene dicarboxylic acid, decahydro-2,6-naphthalene dicarboxylic acid and decahydro-2,7-naphthalene dicarboxylic acid. Preferred are: dimethyl decahydro-2,6-naphthalenedicarboxylate or decahydro-2,6-naphthalenedicarboxylic acid, and compounds derived from bio-based materials, such as dimethyl tetrahydro-2,5-furandicarboxylate or tetrahydro-2,5-furandicarboxylic acid.

The intermediate reactant in step (1) can be obtained by reacting the compound represented by Chemical Formula 2 with a chlorinating agent. The chlorinating agent may include a compound selected from the group consisting of phosgene, triphosgene, thionyl chloride, oxalyl chloride, phosphorus trichloride, phosphorus pentachloride, phosphorus pentabromide and cyanuric fluoride. Preferably, in order to facilitate the removal of by-products generated by the reaction, the chlorinating agent may include a compound selected from phosgene, thionyl chloride and oxalyl chloride. More preferably, from a commercial perspective, the chlorinating agent may be phosgene.

The dosage of the chlorinating agent can be 1-4 times the total molar number of the compound represented by Chemical Formula 2, preferably 1.02-3 times, more preferably 1.05-2.5 times.

In addition, the reaction temperature may vary depending on the compound represented by Chemical Formula 2 and the chlorinating agent. Generally, the reaction temperature may be between -30 and 150° C., preferably 15-100° C., and more preferably 20-80° C. The reaction time may be between 5 minutes and 48 hours, preferably 10 minutes to 24 hours.

In the reaction between the compound represented by Chemical Formula 2 and the chlorinating agent, an organic solvent may be used to dissolve or disperse the compound represented by Chemical Formula 2. Such organic solvents may include, for example, benzene, toluene, xylene, mesitylene, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, monochlorobenzene, o-dichlorobenzene, tetrahydrofuran, dioxane, and acetonitrile. If the compound represented by Chemical Formula 2 melts within the above temperature range, the addition of an organic solvent is not required for the reaction.

At the same time, if the intermediate reactant is liquid at room temperature, the intermediate reactant can be used as a solvent to save the cost of the solvent, which is advantageous from a commercial perspective.

To increase the conversion rate of the intermediate reactants and the reaction yield, a catalyst may be added to the reaction. The catalyst is not particularly limited and may be an organic or inorganic catalyst. Organic catalysts may include, for example, dimethylformamide, dimethylacetamide, methylpyrrolidone, dimethylimidazolidinone, tetramethylurea, tetraethylurea, and tetrabutylurea. Inorganic catalysts may include, for example, aluminum chloride (AlCl ₃ ), ferric chloride (FeCl ₃ ), bismuth chloride (BiCl ₃ ), gallium chloride (GaCl ₃ ), antimony pentachloride (SbCl ₅ ), boron trifluoride (BF ₃ ), bismuth trifluoromethanesulfonate (Bi(OTf) ₃ ), titanium tetrachloride (TiCl ₄ ), zirconium tetrachloride (ZrCl ₄ ), titanium tetrabromide (TiBr ₄ ), and zirconium tetrabromide (ZrBr ₄ ). Specifically, the organic catalyst may be selected from dimethylformamide, tetramethylurea, and dimethylimidazolidinone; the inorganic catalyst may be selected from aluminum chloride and titanium tetrachloride. More preferably, from a commercial perspective, the organic catalyst may be dimethylformamide, and the inorganic catalyst may be aluminum chloride.

The dosage of the catalyst is not particularly limited and can be adjusted according to the type of the compound shown in Chemical Formula 2 and the chlorinating agent. The dosage of the catalyst can be 0.1-10 mol%, preferably 0.5-5 mol%, and more preferably 1-3 mol% of the total moles of the compound shown in Chemical Formula 2. When the dosage of the catalyst is less than the above range, the reaction rate will slow down. On the other hand, when the dosage of the catalyst exceeds the above range, not only will the reaction rate not be accelerated, but it is likely to cause a runaway reaction or an exothermic reaction.

Meanwhile, the dosage of phenol used to convert the intermediate reactant into the compound represented by Chemical Formula 3 can be 1-3 times, preferably 1.5-2.5 times, the total molar number of the compound represented by Chemical Formula 2. When the dosage of phenol exceeds the above range, the final yield of the compound represented by Chemical Formula 3 may be reduced.

In step (2), the compound represented by Chemical Formula 3, the compound represented by Chemical Formula 4, and 1,4:3,6-dianhydrohexitol obtained in step 1) undergo a polycarbonate melt polycondensation reaction to generate a compound containing a repeating unit represented by Chemical Formula 1.

In step 2), 1,4:3,6-dianhydrohexitol reacts with the compound represented by Chemical Formula 4 to form a carbonate bond (repeating unit 1), and 1,4:3,6-dianhydrohexitol reacts with the compound represented by Chemical Formula 3 to form an ester bond (repeating unit 2). The repeating units containing these bonds are represented by Chemical Formula 1.

If the dosage of 1,4:3,6-dianhydrohexitol is 1 mole and the dosage of the compound represented by Chemical Formula 3 is x moles, the dosage of the compound represented by Chemical Formula 4 is (1-x) moles, as shown in Reaction Scheme 2.

[Reaction Flowchart 2]

For example, in the absence of the compound represented by Chemical Formula 3, 1,4:3,6-dianhydrohexitol and the compound represented by Chemical Formula 4 undergo a melt polycondensation reaction to produce a 1,4:3,6-dianhydrohexitol homopolycarbonate (Tg of 160°C). As the dosage of the compound represented by Chemical Formula 3 increases, the amount of ester bonds in the polymer chain also increases. If the dosage of the compound represented by Chemical Formula 3 is 1, only 1,4:3,6-dianhydrohexitol and the compound represented by Chemical Formula 3 undergo a melt polycondensation reaction, thereby producing a homopolyester (Tg of 130°C; see Macromolecules, 2013, 46, 2930). Figure 2 shows the change in Tg of the polymer as the proportion of the compound represented by Chemical Formula 4 changes.

In summary, the ratio of carbonate bonds to ester bonds in the polymer chain varies depending on the dosage of the compound shown in Chemical Formula 3 added. When carbonate bonds and ester bonds coexist in the polymer chain, the polycarbonate of the present invention has higher heat resistance than the 1,4:3,6-dianhydrohexitol polycarbonate disclosed in U.S. Patent Application Publication No. 2011/0003101 and U.S. Patent No. 8,399,598. Generally, polycarbonates exhibit high heat resistance and good mechanical properties compared to polyesters, but their chemical resistance, residual stress and molding cycle are poor. However, a polycarbonate that simultaneously contains carbonate bonds and ester bonds in a single chain not only overcomes the shortcomings of polymers with a single carbonate bond or ester bond, but also has other advantages.

The 1,4:3,6-dianhydrohexitol may be selected from the group consisting of isomannide, isosorbide and isoidide, preferably isosorbide.

In addition, in order to ensure the high degree of polymerization of the obtained bio-based polycarbonate, so that it has high heat resistance, high transparency and excellent mechanical properties, it is particularly important to maintain the high purity of 1,4:3,6-dianhydrohexitol in the melt polycondensation reaction.

1,4:3,6-dianhydrohexitol can be in the form of powder, flakes, or an aqueous solution. However, prolonged exposure to air can rapidly lead to oxidation and discoloration of the final polymer, resulting in substandard color and molecular weight. Therefore, exposure of 1,4:3,6-dianhydrohexitol to air should be minimized. Once exposed to air, it is best stored with a deoxidizer, such as an oxygen absorber. Furthermore, if 1,4:3,6-dianhydrohexitol is produced through a multi-step process, removing impurities is crucial. Specifically, when purifying 1,4:3,6-dianhydrohexitol by distillation, it is crucial to remove trace amounts of acidic liquid components and alkali metal components. The acidic liquid component can be removed through preliminary separation, and the alkali metal component can be removed through residue separation. The concentrations of each acidic liquid component and alkali metal component should be maintained at or below 10 ppm, preferably at or below 5 ppm, and more preferably at or below 3 ppm.

The compound represented by Chemical Formula 4 may be at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, di-tert-butyl carbonate, diphenyl carbonate, ditolyl carbonate, and substituted carbonates. Since the polycarbonate melt polycondensation reaction is carried out under reduced pressure, the compound represented by Chemical Formula 4 may specifically be dimethyl carbonate, diethyl carbonate, di-tert-butyl carbonate, diphenyl carbonate, or ditolyl carbonate. More specifically, the compound represented by Chemical Formula 4 is diphenyl carbonate.

In step (2), other diol compounds other than 1,4:3,6-dianhydrohexitol may be further used, and such diol compounds are not particularly limited. Various compounds including primary, secondary, and tertiary diol compounds may be used together with 1,4:3,6-dianhydrohexitol. In this case, if the dosage of the other diol compound other than 1,4:3,6-dianhydrohexitol is y moles, the dosage of 1,4:3,6-dianhydrohexitol is (1-y) moles.

In particular, when these diol compounds are petrochemical-derived diol compounds, they can be used to achieve a biobased content (ASTM-D6866) of at least 1 mol% derived from 1,4:3,6-dianhydrohexitol in the final polymer. In this case, y satisfies 0≤y<0.99, meaning that the amount of these diol compounds used can be less than 99 mol% based on 100 mol% of 1,4:3,6-dianhydrohexitol.

Preferably, these diol compounds have a single or fused saturated homocyclic or heterocyclic ring at the center of their molecules, resulting in polycarbonates with high heat resistance, high transparency, and improved weather resistance and UV stability. Furthermore, the larger the ring size of the diol with hydroxyl groups, which is generally symmetrical, the higher the heat resistance of the polycarbonate. However, its optical properties do not depend on the size of the ring chain or the position of the hydroxyl groups in the diol, but rather vary with the characteristics of the raw materials. The larger the ring chain size, the more difficult it is to achieve industrial production and application of the compound.

These diol compounds can be selected from 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, 2,2-bis(4-hydroxycyclohexyl)propane, and tetrahydro-2,5-furan dimethanol, which can be derived from bio-based materials. Preferably, 1,4-cyclohexanedimethanol, 2,2-bis(4-hydroxycyclohexyl)propane, and tetrahydro-2,5-furan dimethanol are selected.

The mass ratio of the cis/trans isomers of the compound represented by Chemical Formula 3 may be 1/99 to 99/1, preferably 10/90 to 90/10, and more preferably 20/80 to 80/20. Furthermore, the mass ratio of the cis/trans isomers of the cyclohexanedicarboxylate in the repeating unit of Chemical Formula 1 may be 1/99 to 99/1, preferably 20/80 to 80/20, and more preferably 30/70 to 70/30.

As the content of cis-cyclohexanedicarboxylate units in the repeating units of Chemical Formula 1 increases, the Tg of the polycarbonate increases, thereby increasing its heat resistance while relatively decreasing its transmittance. Conversely, as the content of trans-cyclohexanedicarboxylate units decreases, the Tg of the polycarbonate decreases, its heat resistance decreases, and its transmittance increases. Therefore, the mass ratio of the cis/trans isomers of the cyclohexanedicarboxylate units in the repeating units of Chemical Formula 1 is preferably 20/80 to 80/20, and more preferably 30/70 to 70/30, to adjust the heat resistance and transmittance of the polycarbonate.

In the melt polycondensation reaction in step (2), based on 1 mol of 1,4:3,6-dianhydrohexitol, the total amount of the compound represented by Chemical Formula 3 and the compound represented by Chemical Formula 4 is 0.7-1.3 mol, preferably 0.9-1.1 mol, and more preferably 0.95-1.05 mol.

The temperature of the melt polycondensation reaction can be increased at a rate of 0.1-10°C/min, preferably 0.2-5°C/min, more preferably 0.2-2°C/min. The reaction temperature is 120-320°C, preferably 150-290°C, more preferably 180-270°C. The reaction time is 1-10 hours, preferably 1.5-8 hours.

Furthermore, the phenol byproduct generated during the melt polycondensation reaction should be distilled out of the reaction system to shift the reaction equilibrium toward the production of polycarbonate. In particular, if the heating rate exceeds the above range, phenol may evaporate or sublime along with the raw materials. This bio-based polycarbonate can be produced in either a batch or continuous process.

In the method for preparing bio-based polycarbonate according to the present invention, a polycondensation catalyst may be further used to enhance the reactivity of the melt polycondensation reaction. Any conventional alkali metal and/or alkaline earth metal commonly used in polycarbonate melt polycondensation reactions can be used as the polycondensation catalyst. The catalyst can be used in combination with a basic ammonia or amine, a basic phosphorus, or a basic boron compound, but is preferably used alone. Exemplary alkali metal catalysts include LiOH, NaOH, KOH _{, CsOH} , _Li₂CO₃ , _Na₂CO₃ , _K₂CO₃ , _Cs₂CO₃ , LiOAc, NaOAc, KOAc, CsOAc _, and _the like. For example, the alkaline earth metal may be Ca(OH) ₂ , Ba(OH) ₂ , Mg(OH) ₂ , Sr(OH) ₂ , _CaCO3 , _BaCO3 , _MgCO3 , _SrCO3 , Ca(OAc) ₂ , Ba(OAc) ₂ , Mg(OAc) ₂ , Sr(OAc) ₂ , and the like. Furthermore, these alkali metals and/or alkaline earth metals may be used alone or in combination of two or more.

The dosage of the polycondensation catalyst used for each 1 mole of diols (i.e., 1,4:3,6-dianhydrohexitol and other diol compounds) used in the melt polycondensation reaction can be 0.1-30 micromoles, preferably 0.5-25 micromoles, and more preferably 0.5-20 micromoles. The polycondensation catalyst can be used at any time during the melt polycondensation reaction, but it is best to add it before the melt polycondensation reaction begins. If the dosage of the polycondensation catalyst is less than 0.1 micromoles per mole of diol substance, it is difficult to achieve the target degree of polymerization. If the amount of the catalyst used exceeds 30 micromoles, side reactions will occur, which will have a direct adverse effect on the target properties of the product, such as reducing transparency.

Furthermore, the method for preparing bio-based polycarbonate according to the present invention can adopt a gradual heating and decompression method to quickly remove by-products and promote the polymerization reaction. Specifically, the melt polycondensation reaction in step (2) includes a first reaction zone and a second reaction zone.

More specifically, after the feedstock is added, the first reaction zone is operated at a temperature of 130-250°C, preferably 140-240°C, more preferably 150-230°C, for 0.1-10 hours, preferably 0.5-3 hours. When the pressure is reduced within the above temperature range, the reduced pressure is 5-700 Torr, preferably 10-600 Torr.

The second reaction zone is conducted at a temperature of 210-290°C, preferably 220-280°C, and more preferably 230-270°C, for a reaction time of 0.1-10 hours, preferably 0.5-3 hours. When the pressure is reduced within the above temperature range, the reduced pressure is less than or equal to 20 Torr, preferably less than or equal to 10 Torr.

Furthermore, various additives may be used, if necessary, in the method for preparing bio-based polycarbonate of the present invention. For example, these additives may include antioxidants or heat stabilizers, such as hindered phenols, hydroquinones, phosphites, and substituted compounds thereof; UV absorbers, such as resorcinol and salicylic acid; colorants, such as phosphites and hydrogen phosphites; and lubricants, such as montanic acid and stearyl alcohol. Furthermore, dyes and pigments may be used as colorants; carbon black may be used as a conductive agent, colorant, or nucleating agent; and flame retardants, plasticizers, antistatic agents, and other additives may also be used. The amounts of these additives should be adjusted so as not to affect the properties of the final polymer, particularly its transparency.

The bio-based polycarbonate comprising the repeating unit of Chemical Formula 1 prepared by the polycarbonate preparation method according to the present invention has an intrinsic viscosity (hereinafter referred to as IV value) of 0.3-2.0 dL/g.

Modes for Carrying Out the Invention

The method of the present invention will be described in more detail below through the accompanying examples. However, these examples are merely for the purpose of explaining the present invention and are not intended to limit the present invention.

Preparation Example 1: Preparation of DPCD from CHDA

100 g (0.58 mol) of CHDA (SK Chemical) with a cis/trans isomer mass ratio of 88/12 and 200 g of dichloromethane were added to a 1 L four-necked round-bottom flask equipped with a four-blade stirrer, inlets for phosgene and nitrogen, an outlet for exhaust gas, and a thermometer. The mixture was stirred at room temperature. At atmospheric pressure, 1.28 mol of phosgene was introduced into the flask over 10 hours, followed by nitrogen over 2 hours to distill off the dissolved phosgene and hydrochloric acid gases, resulting in a transparent, homogeneous reaction solution. Gas chromatography (GC) analysis of the reaction solution revealed a CHDA mass ratio of 49% and a reaction yield of 86%.

121 g (1.28 mol) of phenol was dissolved in 121 g of dichloromethane to prepare a phenol solution. When the dichloromethane distilled from the reaction solution reached 50% by mass of its original supply, the phenol solution was added dropwise to the reaction solution via a dropping funnel over 2 hours, and the mixture was then stirred for 1 hour. At the end of the reaction, dichloromethane had distilled from the reaction solution, and the resulting crude DPCD was purified by recrystallization from ethanol. The recrystallized DPCD was dried at 90°C in a vacuum for 24 hours to obtain 154 g of DPCD. The ^1H NMR spectrum of the obtained DPCD is shown in Figure 1. The reaction yield was 82%, and gas chromatography analysis showed that the purity of the DPCD was 99.92%. Under the above reaction conditions, the mass ratio of cis/trans isomers was 82/18.

Preparation Example 2: Preparation of DPCD from CHDA

DPCD was prepared by repeating the procedure of Preparation Example 1, except that 1.27 g (0.017 mol) of dimethylformamide was added as an organic catalyst in addition to CHDA and dichloromethane. The reaction yield was 82%, and gas chromatography analysis of DPCD revealed a purity of 99.9%. Under these reaction conditions, the mass ratio of cis/trans isomers was 82/18.

Preparation Example 3: Preparation of DPCD from CHDA

30 g (0.17 mol) of CHDA (SK Chemical) with a cis/trans isomer mass ratio of 88/12 and 300 g of CHDC were added to a 1 L four-necked round-bottom flask equipped with a four-blade stirrer, inlets for phosgene and nitrogen, an outlet for exhaust gas, and a thermometer. The mixture was stirred at room temperature. At atmospheric pressure, 0.37 mol of phosgene was introduced into the flask over 5 hours, followed by nitrogen over 2 hours to distill off dissolved phosgene and hydrochloric acid gas, resulting in a transparent, homogeneous reaction solution. Gas chromatography (GC) analysis of the reaction solution revealed a CHDC mass ratio of 99%, and a reaction yield of 94%.

32 g (0.34 mol) of phenol was dissolved in 32 g of dichloromethane to prepare a phenol solution. The phenol solution was added dropwise to the reaction solution via a dropping funnel over 2 hours, and the mixture was then stirred for 1 hour. At the end of the reaction, CHDC and dichloromethane had been distilled from the reaction solution, and the resulting crude DPCD was purified by recrystallization from ethanol. The recrystallized DPCD was dried at 90°C in a vacuum for 24 hours to obtain 50 g of DPCD. The reaction yield of DPCD was 88%, and gas chromatography analysis showed that the purity of DPCD was 99.96%. Under the above reaction conditions, the mass ratio of cis/trans isomers was 82/18.

Preparation Example 4: Preparation of DPCD from DMCD

100 g (0.50 mol) of DMCD (SK Chemical) with a cis/trans isomer mass ratio of 77/23 and 2.0 g (0.015 mol) of aluminum chloride were added to a 1 L four-necked round-bottom flask equipped with a four-blade stirrer, inlets for phosgene and nitrogen, an outlet for exhaust gas, and a thermometer. The mixture was stirred at room temperature. At atmospheric pressure, 1.10 mol of phosgene was introduced into the flask over 10 hours, followed by nitrogen over 2 hours to distill off the dissolved phosgene and methyl chloride, resulting in a transparent, homogeneous reaction solution. Gas chromatography (GC) analysis of the reaction solution revealed a CHDC mass ratio of 98% and a reaction yield of 92%.

100 g (1.06 mol) of phenol was dissolved in 100 g of dichloromethane to prepare a phenol solution. The phenol solution was added dropwise to the reaction solution via a dropping funnel over 2 hours, and the mixture was then stirred for 1 hour. At the end of the reaction, dichloromethane had been distilled from the reaction solution, and the resulting crude DPCD was purified by recrystallization from ethanol. The recrystallized DPCD was dried at 90°C in a vacuum for 24 hours to obtain 150 g of DPCD. The reaction yield of DPCD was 92%, and gas chromatography analysis showed that the purity of DPCD was 99.94%. Under the above reaction conditions, the mass ratio of cis/trans isomers was 79/21.

Example 1: Preparation of bio-based polycarbonate

A 5 L benchtop reactor was charged with 1,995 g (13.7 mol) of isosorbide ("ISB"; Roquette Freres), 443 g (1.37 mol) of DPCD obtained in Preparation Example 1, 2,632 g (12.3 mol) of DPC (Changfeng), and 6.1 × ^10-4 g (1.9 × ^10-3 _mmol ) of cesium carbonate ( _Cs2CO3 ) as a catalyst for a polycondensation reaction. The mixture was heated to 150°C. Once the temperature reached 150°C, the pressure was reduced to 400 Torr, and then the temperature was increased to 190°C over 1 hour. During the temperature increase, phenol was produced as a by-product of the polycondensation reaction. When the temperature reached 190°C, the pressure was reduced to 100 Torr and maintained for 20 minutes, and then the temperature was increased to 230°C over 20 minutes. Once the temperature reached 230°C, the pressure was reduced to 10 Torr, and the temperature was raised to 250°C over 10 minutes. The pressure was then reduced to 1 Torr or less at 250°C, and the reaction continued until the target stirring torque was reached. The reaction was terminated when the target stirring torque was reached. The polymer product was pressurized and discharged in the form of strands. The strands were rapidly cooled in a water bath and cut into sheets. The mass ratio of the cis/trans isomers of the cyclohexanedicarboxylate units in the resulting polymer chain was 70/30. Compared to the starting material DPCD, the cis isomer content was reduced, while the trans isomer content was increased. The resulting bio-based polycarbonate had a Tg of 162°C and an IV of 0.62 dL/g. The ^1H NMR spectrum and IR spectrum of the final product are shown in Figures 3 and 4.

Example 2-6: Preparation of bio-based polycarbonate

The steps in Example 1 were repeated, except that the polymer was prepared using the raw materials listed in Table 1.

Example 7: Preparation of bio-based polycarbonate from CHDM

The procedure of Example 1 was repeated to prepare a bio-based polycarbonate, except that, in addition to DPCD and DPC, 10.1 g (0.07 mol) of CHDM (SK Chemicals) and 92.1 g (0.63 mol) of isosorbide (Roquette Freres) were also added. The resulting polymer chain had a cis/trans isomer ratio of 38/62 for the cyclohexanedicarboxylate units. The resulting bio-based polycarbonate had a Tg of 129°C and an IV of 0.51 dL/g.

Comparative Example 2: Preparation of Isosorbide Homopolycarbonate

The procedure of Example 1 was repeated to prepare isosorbide homopolycarbonate, except that 150.0 g (0.7 mol) of DPC (Aldrich) was added instead of DPCD. The prepared isosorbide homopolycarbonate had a Tg of 160° C. and an IV of 0.49 dL/g.

Comparative Example 3: Preparation of Isosorbide/DPCD Homopolyester

The procedure of Example 1 was repeated to prepare an isosorbide/DPCD homopolyester, except that 227.1 mmol (0.7 mol) of DPCD was added instead of DPC. The mass ratio of the cis/trans isomers of the cyclohexanedicarboxylate units in the resulting polymer chain was 36/64. The resulting bio-based polycarbonate had a Tg of 130°C and an IV of 0.46 dL/g.

Comparative Example 4: Preparation of DDDA Copolymerized Isosorbide Polycarbonate

The procedure of Example 1 was repeated to prepare dodecanedioic acid (DDDA, Aldrich)-co-isosorbide polycarbonate, except that 32.2 g (0.14 mol) of DDDA was used instead of DPCD, and 120.0 g (0.56 mol) of DPC (Aldrich) was added. The resulting DDDA-co-isosorbide polycarbonate had a Tg of 121°C and an IV of 0.34 dL/g.

Comparative Example 5: Preparation of bio-based polycarbonate with high cis-isomer content

The procedure of Example 1 was repeated to prepare a bio-based polycarbonate, except that 97.3 g (0.3 mol) of DPCD (having a cis/trans isomer ratio of 90/10) was added. The resulting polymer chain had a cis/trans isomer ratio of 85/15 for the cyclohexanedicarboxylate units. The resulting bio-based polycarbonate had a Tg of 113°C and an IV of 0.37 dL/g.

<Measurement of Light Transmittance>

The light transmittance of an extruded sheet having a thickness of 4 mm was measured according to ASTM D1003.

<Determination of tensile strength>

The tensile strength was measured according to ASTM D638.

<Measurement of flexural strength>

The flexural strength was measured according to ASTM D790.

<Determination of Impact Strength>

Impact strength was measured on notched specimens at room temperature according to ASTM D256.

<Determination of Heat Deformation Temperature>

The heat distortion temperature was measured under a load of 1.80 MPa according to ASTM D648.

<Determination of pencil hardness>

The pencil hardness was measured by a pencil hardness tester according to ASTM D3502.

The components and properties of the polymer samples obtained in Examples 1-6 and Comparative Examples 1-5 are shown in Table 1.

Table 1

As shown in Table 1, the bio-based polycarbonate prepared from 1,4-diphenyl-cyclohexanedicarboxylate (DPCD) shown in Chemical Formula 3 according to the method of the present invention has better heat resistance, surface hardness and impact strength than traditional diol-modified isosorbide polycarbonate.

In Comparative Example 4, the presence of a long-chain aliphatic dicarboxylic acid resulted in an increase in the photoelastic coefficient, reducing the light transmittance from the level of highly transparent poly(methyl methacrylate) (PMMA) to the level of commercial BPA-based polycarbonate. Furthermore, the glass transition temperature was found to be relatively low.

In particular, in Comparative Example 5, due to the high content of the cis isomer of the cyclohexanedicarboxylate unit in the polymer chain, the glass transition temperature is significantly lower than that of Comparative Example 1. It is also noted that the light transmittance is relatively low.

Accordingly, the method for preparing bio-based polycarbonate of the present invention can control the properties of the bio-based polycarbonate by adjusting the ratio of carbonate bonds to ester bonds, depending on the desired properties. Furthermore, the bio-based polycarbonate prepared by the method of the present invention exhibits high heat resistance and transparency, and therefore can be used in a variety of applications, such as automotive glass replacements, optical lenses or films, baby bottles, and food containers.

Claims (10)

1. A method for preparing bio-based polycarbonate, comprising the following steps: (1) Converting the compound represented by Formula 2 into an intermediate reactant represented by Formula 2a, optionally subjecting the intermediate reactant to a nucleophilic reaction with phenol in the presence of at least one dicarboxylic acid ester or dicarboxylic acid having a single or fused saturated allotropic ring or heterocyclic ring at the molecular center, different from the compound of Formula 2, to generate a reaction product comprising the compound represented by Formula 3; and (2) The compound represented by chemical formula 3, the compound represented by chemical formula 4 and 1,4:3,6-bis-dehydrohexitol prepared in step (1) undergo a polycarbonate melt polycondensation reaction to generate a bio-based polycarbonate comprising repeating units represented by chemical formula 1. 【Chemical Formula 1】 【Chemical Formula 2】 【Chemical Formula 2a】 【Chemical Formula 3】 [Chemical Formula 4] Its features are: R is either methyl or hydrogen; _R1 and _R2 are either substituted or unsubstituted _C1 - _C18 aliphatic groups or substituted or unsubstituted _C1 - _C18 aromatic groups, respectively. _R3 is F, Cl, or Br. x is a real number that satisfies 0 < x < 1, and The mass ratio of the cis/trans isomers of the repeating unit in Formula 1 is from 20/80 to 80/20. 2. The method as described in claim 1, wherein _R3 is Cl. 3. The method according to claim 1, wherein the intermediate reactant in step (1) is obtained by reacting a compound represented by chemical formula 2 with a compound selected from the group consisting of phosgene, triphosgene, thionyl chloride, oxalyl chloride, phosphorus trichloride, phosphorus pentachloride, phosphorus pentabromide and cyanuric trifluoroethylene. 4. The method according to claim 1, characterized in that: the conversion of the intermediate reactant in step (1) is carried out at atmospheric pressure and a reaction temperature of -30 to 150°C for a reaction time of 5 minutes to 48 hours. 5. The method according to claim 1, wherein the dosage of phenol used in step (1) is 1-3 times the total molar amount of the compound represented by chemical formula (2). 6. The method according to claim 1, characterized in that: the nucleophilic reaction with phenol in step (1) is carried out with the addition of at least one selected from the group consisting of tetrahydro-2,5-furandicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, decahydro-2,4-naphthalenedicarboxylic acid, decahydro-2,5-naphthalenedicarboxylic acid, decahydro-2,6-naphthalenedicarboxylic acid, decahydro-2,7-naphthalenedicarboxylic acid, tetrahydro-2,5-furandicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, decahydro-2,4-naphthalenedicarboxylic acid, decahydro-2,5-naphthalenedicarboxylic acid, decahydro-2,6-naphthalenedicarboxylic acid, and decahydro-2,7-naphthalenedicarboxylic acid. 7. The method according to claim 1, wherein the compound represented by chemical formula 4 is dimethyl carbonate, diethyl carbonate, di-tert-butyl carbonate, diphenyl carbonate, or dimethyl carbonate. 8. The method according to claim 1, characterized in that: the melt polycondensation reaction in step (2) is carried out in the presence of at least one diol compound; said diol compound is selected from: 1,2-cyclohexanediethanol, 1,3-cyclohexanediethanol, 1,4-cyclohexanediethanol, tricyclodecanediethanol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxospiro[5.5]undecane, 2,2-bis(4-hydroxycyclohexyl)propane and tetrahydro-2,5-furandiethanol. 9. The method of claim 8, wherein the dosage of the diol compound used is less than 99 mol% based on 100 mol% of 1,4:3,6-bis(dehydrohexitol). 10. The method according to claim 1, wherein the melt polycondensation reaction in step (2) includes a first reaction zone and a second reaction zone, wherein the first reaction zone is carried out at a temperature of 130-250°C and a reduced pressure of 5-700 Torr for 0.1-10 hours, and the second reaction zone is carried out at a temperature of 210-290°C and a reduced pressure of 20 Torr for 0.1-10 hours.