Aromatic petroleum resin with reduced proportion of low molecular weight oligomers and process for its preparation

Abstract

The method for producing an aromatic petroleum resin according to the present application includes a step of thermally polymerizing monomers including an aromatic vinyl-based monomer in the absence of a catalyst, wherein the thermal polymerization is performed in one step only in a single reactor, and the single reactor is a continuous stirred tank reactor (CSTR).

Description

Technical Field

[0001] This invention relates to a pure monomer resin and its preparation method. More particularly, this invention relates to a pure monomer resin with a significantly reduced proportion of low molecular weight oligomers and its preparation method. Background Technology

[0002] Pure monomer resin (PMR) has lower volatility (VOC), a lighter color (water white), and better thermal stability than other aromatic resins. PMR is used in applications including electric vehicle tire additives and adhesives, and is considered a high-value-added product.

[0003] Currently, commercially available PMR is typically produced through polymerization using catalysts such as Friedel-Crafts catalysts and Lewis acid catalysts. However, this process has several drawbacks, including resin decomposition due to the use of catalysts and contamination from residual halides. Furthermore, it also presents disadvantages such as wastewater generation due to the unavoidable need for a neutralization process.

[0004] Although the inventors of this invention have developed a method for polymerizing pure monomer resins under catalyst-free conditions, this method suffers from the problem of generating a large amount of low molecular weight oligomers as byproducts. These low molecular weight oligomers broaden the molecular weight distribution, leading to deviations in product performance and lowering the softening point. Therefore, although low molecular weight oligomers must be removed to adjust the softening point, their low thermal polymerization reactivity makes it difficult to reintroduce them as raw materials, thus hindering the production of petroleum resin products. Therefore, even when producing pure monomer resins under catalyst-free conditions, it is necessary to minimize the generation of low molecular weight oligomers as byproducts.

[0005] The background technology of this invention is disclosed in US Patent No. 3932332. Summary of the Invention

[0006] [Technical Issues] One object of the present invention is to provide a pure monomer resin and a method for preparing the same, wherein the pure monomer resin can minimize the generation of low molecular weight oligomers as byproducts.

[0007] Another object of the present invention is to provide a pure monomer resin and a method for preparing the same, wherein the pure monomer resin has an elevated softening point and a narrow molecular weight distribution.

[0008] Another object of the present invention is to provide a pure monomer resin and a method for preparing the same, wherein the pure monomer resin does not cause resin decomposition due to the use of a catalyst or pollution caused by residual halides, and has excellent physical properties.

[0009] Another object of the present invention is to provide a pure monomer resin and a method for preparing the same, wherein the pure monomer resin does not require a separation process to remove the catalyst, and therefore no wastewater is generated during the neutralization process of the polymer resin.

[0010] Another object of the present invention is to provide a pure monomer resin and a method for preparing the same, which can reduce catalyst costs and process costs incurred by using catalysts, and can reduce the number of process control points.

[0011] Another object of the present invention is to provide a pure monomer resin and a method for preparing the same, which allows for easy recovery, separation and reuse of the solvent and unreacted monomers.

[0012] Another object of the present invention is to provide a pure monomer resin that allows for easy control of its properties and a method for preparing the same.

[0013] Another object of the present invention is to provide a pure monomer resin and a method for preparing the same, which ensures environmental friendliness by reducing the generation of VOCs and wastewater.

[0014] The above and other objectives of the present invention can be achieved by the embodiments of the present invention described below.

[0015] [Technical Solution] 1. One aspect of the present invention relates to a method for producing a pure monomer resin with a reduced proportion of low molecular weight oligomers. The method comprises thermal polymerization of monomers including aromatic vinyl monomers under catalyst-free conditions, wherein the thermal polymerization is carried out by single-stage polymerization in a single reactor, which is a continuous stirred tank reactor (CSTR).

[0016] 2. In embodiment 1, the monomer may include about 60 wt% to about 100 wt% of aromatic vinyl monomers and about 0 to about 40 wt% of comonomers, wherein the comonomers include hydrogenated aromatic vinyl monomers, C4 to C4... 10 Olefin monomers, or combinations thereof.

[0017] 3. In embodiments 1 and 2, the aromatic vinyl monomer may be selected from styrene, alkylstyrene, divinylbenzene, indene, alkylindene, vinyltoluene, mixed C9 oils, and their derivatives.

[0018] 4. In embodiments 1 to 3, the monomer and solvent can be continuously fed into the reactor, wherein the monomer is present in an amount of about 20 wt% to about 100 wt%, and the solvent is present in an amount of about 0 to about 80 wt%.

[0019] 5. In embodiments 1 to 4, thermal polymerization can be carried out at a temperature of about 150°C to about 300°C and at a pressure of about 5 bar to about 30 bar.

[0020] 6. In embodiments 1 to 5, thermal polymerization can be completed solely through single-stage polymerization in a continuous stirred tank reactor (CSTR), and the polymer obtained by thermal polymerization can be obtained without undergoing secondary thermal polymerization in a plug flow reactor (PFR).

[0021] 7. In Examples 1 to 5, the method can satisfy the following Equation 1: [Equation 1] 100×[(A1-A2) / A1]≥10, In Equation 1 above, A2 represents the ratio (%) of the area of ​​low molecular weight oligomers (residence time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers obtained by single-stage thermal polymerization in CSTR, and A1 represents the ratio (%) of the area of ​​low molecular weight oligomers (residence time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers obtained by two-stage thermal polymerization.

[0022] 8. Another aspect of the present invention relates to a pure monomer resin. The pure monomer resin can be prepared by the method described above and can have a weight-average molecular weight (Mw) of about 300 g / mol to about 10,000 g / mol, a z-average molecular weight (Mz) of about 1,000 g / mol to about 20,000 g / mol, a molecular weight distribution (polydispersity index, PDI) of about 1 to about 3, and a softening point of about 0°C to about 150°C.

[0023] 9. In embodiment 8, the pure monomer resin may contain less than about 100 ppm of residual halides.

[0024] 10. In embodiments 8 and 9, the pure monomer resin can satisfy the following equation 2: [Equation 2] I O = O A ×A2<35, In Equation 2 above, I O Indicates the low molecular weight oligomer index, O A A1 represents the ratio (%) of the olefin region (4.0 ppm to 6.5 ppm region) to the total peak area calculated by integration on the graph obtained by 1H-NMR analysis. A2 represents the ratio (%) of the area of ​​low molecular weight oligomers (retention time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers.

[0025] 11. In embodiments 8 to 10, the pure polymer resin may have a ratio (Mz / Mw) of less than about 2.5 (z-average molecular weight, specific gravity-average molecular weight).

[0026] 12. In embodiments 8 to 11, the pure polymer resin may have an aromatic fraction of about 40% to about 62.5%, an aliphatic fraction of about 35% to about 60%, and an olefin fraction of about 5% or less.

[0027] 13. Another aspect of the invention relates to an adhesive. The adhesive may include a pure monomeric resin according to embodiments 8 to 12.

[0028] 14. Another aspect of the invention relates to a method for reducing the proportion of low molecular weight oligomers in a pure monomer resin. This method is carried out by using a single reactor in the polymerization of aromatic vinyl monomers, wherein the single reactor is a continuous stirred tank reactor (CSTR).

[0029] 15. In embodiment 14, the method can satisfy the following equation 1: [Equation 1] 100×[(A1-A2) / A1]≥10, In Equation 1 above, A2 represents the ratio (%) of the area of ​​low molecular weight oligomers (residence time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers obtained by single-stage thermal polymerization in CSTR, and A1 represents the ratio (%) of the area of ​​low molecular weight oligomers (residence time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers obtained by two-stage thermal polymerization.

[0030] [Beneficial Effects] The embodiments of the present invention provide a pure monomer resin and a method for preparing the same. This pure monomer resin can minimize the generation of low molecular weight oligomers as byproducts, has an elevated softening point and a narrow molecular weight distribution, does not cause resin decomposition due to the use of catalysts or pollution caused by residual halides, has good physical properties, does not require a separation process to remove the catalyst to prevent wastewater generation during the neutralization of polymer resins, can reduce catalyst costs and process costs due to the use of catalysts, can reduce process control points, allows easy recovery, separation and reuse of solvents and unreacted monomers, allows easy control of physical properties, and is environmentally friendly by reducing VOC and wastewater generation. Attached Figure Description

[0031] Figure 1 This is a diagram illustrating the reaction process according to an embodiment of the present invention.

[0032] Figure 2 This is a graph depicting the gel permeation chromatography (GPC) of Example 1 and Comparative Example 1.

[0033] Figure 3 This is a graph depicting the gel permeation chromatography (GPC) of Example 2 and Comparative Example 2. Detailed Implementation

[0034] As used herein, the terms “comprises,” “comprising,” “includes,” and “have” are inclusive and thus specify the presence of the stated feature, integer, step, operation, element, and / or component, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Furthermore, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” may also be intended to include the plural forms.

[0035] In this document, unless otherwise explicitly stated, components should be interpreted as including a balance of 5% or less.

[0036] In this article, "low molecular weight oligomers" refers to aromatic vinyl oligomers with a weight average molecular weight of less than 700 g / mol.

[0037] Pure monomer resin (PMR) Pure monomeric resins include aromatic vinyl polymers. In one embodiment, the pure monomeric resin is prepared by thermal polymerization under catalyst-free conditions.

[0038] Figure 1 This is a diagram of the reaction process according to an embodiment of the present invention.

[0039] Reference Figure 1 Pure monomer resins can be prepared by a method that includes a step of thermal polymerization of the monomer solution in a single reactor. Here, thermal polymerization is carried out by single-stage polymerization under catalyst-free conditions in a continuous stirred tank reactor (CSTR) 1.

[0040] In this invention, single-stage polymerization in a single reactor means that polymerization is completed in a single reactor without any secondary polymerization in subsequent reactors.

[0041] The continuous stirred tank reactor 1 can be selected from any typical reactor in the art without limitation, and the polymerization reaction can be carried out by continuous feeding and mixing of monomers. By carrying out thermal polymerization in the continuous stirred tank reactor as described above, the temperature can be maintained uniformly during the reaction to provide a low probability of the occurrence of local hot spots, thereby providing a narrow molecular weight distribution.

[0042] In one embodiment, the monomer is mixed with a solvent and fed into a reactor, wherein the monomer may be present in an amount of about 20 wt% to about 100 wt%, and the solvent may optionally be present in an amount of about 80 wt% or less.

[0043] The monomer may include about 60 wt% to about 100 wt% of aromatic vinyl monomers and optionally about 40 wt% or less of comonomers.

[0044] The aromatic vinyl monomers may be selected from styrene, alkylstyrene, divinylbenzene, indene, alkylindene, vinyltoluene, mixed C9 oils, and their derivatives. For example, the aromatic vinyl monomers may include about 30 wt% to 100 wt% of styrene monomers and optionally about 70 wt% or less of alkylstyrene monomers.

[0045] In one embodiment, the comonomer may be added together with the aromatic vinyl monomer. The comonomer may include a hydrogenated aromatic vinyl monomer in which hydrogen is added to an aromatic group, C4 to C54 monomers, etc. 10 Olefin monomers, or combinations thereof. In one embodiment, the comonomer may include vinylcyclohexane, vinylcyclohexene, isoprene, isoprene, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, or combinations thereof. The comonomer is used to improve the compatibility of polymers and additives in adhesive / binder compositions by modifying the resin structure.

[0046] The solvent may include at least one selected from benzene, toluene, xylene, and mixtures thereof.

[0047] In one embodiment, a free radical initiator may be further added to modulate the reactivity. The initiator may include cumene hydroperoxide, tert-butyl hydroperoxide, tert-butylperoxybenzoate, tert-butyl-4,4-di(tert-butylperoxy)valerate, etc.

[0048] Thermal polymerization can be carried out at temperatures from about 150°C to about 300°C, for example, from about 200°C to about 295°C, specifically from about 250°C to 290°C. Within this range, thermal polymerization can be carried out with good monomer conversion or polymerization rate while suppressing side reactions, and can achieve uniform properties with a narrow molecular weight distribution.

[0049] Thermal polymerization can be carried out at reaction pressures of about 5 bar to about 30 bar, for example, about 10 bar to about 25 bar. Within this range, thermal polymerization can be carried out with good reaction stability while increasing monomer reactivity.

[0050] Thermal polymerization can be carried out from about 5 minutes to about 180 minutes, for example from about 20 minutes to about 120 minutes, specifically from about 30 minutes to about 60 minutes. Within this range, thermal polymerization can be carried out while suppressing side reactions and can ensure a narrow molecular weight distribution.

[0051] Since thermal polymerization is accomplished solely through a single-stage polymerization in a continuous stirred tank reactor (CSTR), a significant reduction in the proportion of low molecular weight oligomers can be achieved. In one embodiment, the proportion of low molecular weight oligomers can be reduced by about 10% or more, preferably about 20% or more, compared to pure monomer resins prepared by a single thermal polymerization in a continuous stirred tank reactor (CSTR) followed by a secondary thermal polymerization in a plug flow reactor (PFR).

[0052] In one embodiment, the method according to the present invention can satisfy the following equation 1: [Equation 1] 100×[(A1-A2) / A1]≥10, Where A2 represents the ratio (%) of the area of ​​low molecular weight oligomers (residence time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers obtained by single-stage thermal polymerization in CSTR, and A1 represents the ratio (%) of the area of ​​low molecular weight oligomers (residence time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers obtained by two-stage thermal polymerization.

[0053] According to the present invention, the proportion of low molecular weight oligomers, weight-average molecular weight, molecular weight distribution (PDI), or softening point of the pure monomer resin can be adjusted by controlling the reaction temperature, monomer concentration, or reaction time.

[0054] In one embodiment, the outlet of the continuous stirred tank reactor (CSTR) may be provided with a filter (not shown). The filter may be formed of one or more materials selected from metals, polymers, ceramics, etc., and may have a pore size of about 100 nm to about 10 μm, preferably about 100 nm to about 1 μm, and is not particularly limited, as long as it can filter out foreign matter.

[0055] The polymerization products can undergo a solvent separation process to recover pure monomer resin. During solvent separation, the solvent and a portion of low molecular weight oligomers can be separated from the product. The solvent separation process can be carried out using a thin-film evaporator.

[0056] In one embodiment, a hydrogenation reaction can be further carried out. For example, the hydrogenation reaction can be carried out by feeding the obtained pure monomer resin into a continuous hydrogenation reactor filled with a hydrogenation catalyst. The hydrogenation reaction can be carried out at a pressure of about 50 bar to about 150 bar and a temperature of about 150°C to about 300°C, but is not limited thereto. When the hydrogenation reaction is carried out under these conditions, the destruction of the molecular structure can be prevented. The hydrogenation catalyst can be selected from any hydrogenation catalyst known to those skilled in the art, without limitation. Specifically, the hydrogenation catalyst may include at least one selected from Ni, Fe, Cu, Co, Mo, Pd, Rh, Pt, Nb, Au, Ru, Raney Ni, and mixtures thereof. To improve reactivity, the hydrogenation catalyst may be present in a molar ratio of about 0.001 to about 0.5, preferably about 0.05 to about 0.2, relative to 1 mole of the monomer of the petroleum resin, but is not limited thereto.

[0057] Since the pure monomer resin according to the invention is prepared under catalyst-free conditions, the pure monomer resin contains less than about 100 ppm of residual halides and includes about 40% to about 62.5% aromatic fraction, about 35% to about 60% aliphatic fraction and about 5% or less, preferably about 2% or less, more preferably about 1.7% or less olefin fraction in the total polymer.

[0058] In one embodiment, when polymerized only with aromatic vinyl monomers, the pure monomer resin can have a low molecular weight oligomer index (I) of less than about 35. O As shown in Equation 2 below: [Equation 2] I O = O A ×A2<35, Among them I O Indicates the low molecular weight oligomer index, O A A1 represents the ratio (%) of the olefin region (4.0 ppm to 6.5 ppm region) to the total peak area calculated by integration on the graph obtained by 1H-NMR analysis. A2 represents the ratio of the area of ​​low molecular weight oligomers (retention time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers.

[0059] In one embodiment, the pure monomer resin may have a low molecular weight oligomer index (I) of less than about 35, for example from about 1 to about 24.5, more specifically from about 10 to about 20. O Within this range, pure monomeric resins can ensure uniform properties, suppress VOC generation, and exhibit good adhesion when produced as adhesives.

[0060] Pure monomer resins can have a softening point of about 0°C to 150°C, for example, about 70°C to about 130°C.

[0061] The pure monomer resin can have a weight-average molecular weight (Mw) of about 300 g / mol to about 10,000 g / mol, specifically about 1,000 g / mol to about 7,000 g / mol, preferably about 1,350 g / mol to about 7,000 g / mol, and a z-average molecular weight of about 1,000 g / mol to about 20,000 g / mol, specifically about 1,500 g / mol to about 15,000 g / mol, preferably about 2,000 g / mol to about 15,000 g / mol, and a molecular weight distribution (PDI) of about 1 to about 3, for example about 1 to about 2.7, specifically about 1.1 to about 2.65.

[0062] Furthermore, pure monomeric resins can have a ratio (Mz / Mw) of less than about 2.5, specifically 2.0 or less, for example about 1.84 or less, more specifically about 1.6 to about 1.835 (z-average molecular weight to specific gravity-average molecular weight). Within this range, pure monomeric resins can have uniform properties.

[0063] In one embodiment, the pure monomer resin has low VOC, low yellowness index and good thermal stability.

[0064] Since the pure monomer resin according to the present invention does not have the problem of resin decomposition or pollution, and has good physical properties, the pure monomer resin can be used in adhesives, electric vehicle tire additives, etc.

[0065] Another aspect of the invention relates to a method for controlling the properties of a pure monomer resin. The method includes controlling the reaction temperature, monomer concentration, and reaction time in a single-stage thermal polymerization of a monomer solution in a continuous stirred tank reactor (CSTR) under catalyst-free conditions. In one embodiment, the molecular weight distribution (PDI) of the pure monomer resin can be narrowed by reducing the concentration of aromatic vinyl monomers fed into the CSTR. In another embodiment, the reaction temperature in the continuous stirred tank reactor can be reduced to decrease the amount of low molecular weight oligomers produced.

[0066] In one implementation, the method can satisfy the following equation 1: [Equation 1] 100×[(A1-A2) / A1]≥10, Where A2 represents the ratio (%) of the area of ​​low molecular weight oligomers (residence time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers obtained by single-stage thermal polymerization in CSTR, and A1 represents the ratio (%) of the area of ​​low molecular weight oligomers (residence time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers obtained by two-stage thermal polymerization.

[0067] The invention will now be described in more detail with reference to some embodiments. It should be understood that these embodiments are provided for illustrative purposes only and should not be construed as limiting the invention in any way.

[0068] [Invention Method] Example Example 1 A monomer solution was prepared by mixing 1350 g of styrene and 150 g of α-methylstyrene in 1500 g of solvent (xylene). Polymerization was carried out at 270 °C and 25 bar (reaction time: 80 min) while the monomer solution was continuously fed into a CSTR (internal volume: 400 ml). Pure monomer resin was recovered by separating the solvent and a portion of low molecular weight oligomers from the polymerization product in a thin-film evaporator (TFE) at 230 °C and 2 mbar.

[0069] Comparative Example 1 A monomer solution was prepared by mixing 1350 g of styrene and 150 g of α-methylstyrene in 1500 g of solvent (xylene). A primary polymerization (reaction time: 40 min) was carried out at 280 °C and 25 bar while the monomer solution was continuously fed into a CSTR (internal volume: 400 ml). A secondary polymerization (reaction time: 60 min) was then carried out at 280 °C and 25 bar while the product of the primary polymerization was continuously fed into a PFR (internal volume: 600 ml) connected to the CSTR. The pure monomer resin was recovered by separating the solvent and a portion of low molecular weight oligomers from the polymerization product in a thin-film evaporator (TFE) at 230 °C and 2 mbar.

[0070] GPC analysis results of the pure monomer resins prepared in Example 1 and Comparative Example 1 before they were fed into the thin-film evaporator are as follows: Figure 2 As shown in the image.

[0071] The reaction conditions are shown in Table 1, and the property evaluation results are shown in Table 2.

[0072] Table 1

[0073] Table 2

[0074] As can be seen from Example 1 and Comparative Example 1, the proportion of low molecular weight oligomers in the pure monomer resin prepared by the method according to the present invention is reduced by 19.23%, as calculated according to Equation 1, and the softening point is increased. Furthermore, it can be seen that the pure monomer resin according to the present invention exhibits a narrow molecular weight distribution and a significant reduction in olefin content.

[0075] Example 2 Except for polymerization at 260°C, pure monomer resin was prepared in the same manner as in Example 1.

[0076] Comparative Example 2 Pure monomer resins were prepared in the same manner as in Example 2, except that polymerization was carried out under the conditions listed in Table 3.

[0077] GPC analysis results of the pure monomer resins prepared in Example 2 and Comparative Example 2 before they were fed into the thin-film evaporator are as follows: Figure 3 As shown in the image.

[0078] The reaction conditions are shown in Table 3, and the property evaluation results are shown in Table 4.

[0079] Table 3

[0080] Table 4

[0081] As can be seen from Example 2 and Comparative Example 2, the proportion of low molecular weight oligomers in the pure monomer resin prepared by the method according to the present invention is reduced by 11.1%, as calculated according to Equation 1, and the softening point is increased. Furthermore, it can be seen that the pure monomer resin according to the present invention exhibits a narrow molecular weight distribution and a significant reduction in olefin content.

[0082] Example 3 Pure monomer resins were prepared in the same manner as in Example 1, except that only styrene was used as the monomer and polymerization was carried out under the conditions listed in Table 5.

[0083] Comparative Example 3 Pure monomer resins were prepared in the same manner as in Example 3, except that polymerization was carried out under the conditions listed in Table 5.

[0084] The reaction conditions are shown in Table 5, and the property evaluation results are shown in Table 6.

[0085] Table 5

[0086] Table 6

[0087] As can be seen from Example 3 and Comparative Example 3, the proportion of low molecular weight oligomers in the pure monomer resin prepared by the method according to the present invention is reduced by 25%, as calculated according to Equation 1, and the softening point is increased. Furthermore, it can be seen that the pure monomer resin according to the present invention exhibits a narrow molecular weight distribution and a significant reduction in olefin content.

[0088] Example 4 A monomer solution was prepared by mixing 2430 g of styrene and 270 g of isoprene in 300 g of solvent (xylene). Polymerization was carried out at 270 °C and 25 bar (reaction time: 80 min) while the monomer solution was continuously fed into a CSTR (internal volume: 400 ml). Pure monomer resin was recovered by separating the solvent and a portion of low molecular weight oligomers from the polymerization product in a thin-film evaporator (TFE) at 230 °C and 2 mbar.

[0089] Example 5 A monomer solution was prepared by mixing 2160 g of styrene and 540 g of isoprene in 300 g of solvent (xylene). Polymerization was carried out at 270 °C and 25 bar (reaction time: 80 min) while the monomer solution was continuously fed into a CSTR (internal volume: 400 ml). Pure monomer resin was recovered by separating the solvent and a portion of low molecular weight oligomers from the polymerization product in a thin-film evaporator (TFE) at 230 °C and 2 mbar.

[0090] Table 7

[0091] Table 8

[0092] As can be seen from the above embodiments, the pure monomer resin prepared by the method according to the present invention has a low molecular weight oligomer ratio of 12.5% ​​or less and a softening point of 90°C or higher, and exhibits a narrow molecular weight distribution.

[0093] Property Evaluation (1) Molecular weight The weight-average molecular weight (Mw), number-average molecular weight (Mn), and z-average molecular weight (Mz) were measured using polystyrene standard samples by gel permeation chromatography (GPC) (Viscotek TDA302 and Agilent 1200 series (Pump)).

[0094] The resin to be measured was dissolved in tetrahydrofuran to a concentration of 4000 ppm to prepare a resin solution, and 100 μl of the resin solution was injected into a GPC column. Tetrahydrofuran was injected as the mobile phase of the GPC column at a flow rate of 1.0 mL / min, and analysis was performed at 35 °C. The column was a PL-mixed C2-cell + PL 50 Å (Agilent) column. An RI detector (Viscotek RI) was used, and measurements were performed at 35 °C. Mw, Mn, and Mz values ​​were obtained from calibration curves derived after measurements of polystyrene standards. Twelve polystyrene standards with molecular weights of 104 / 118 / 236 / 580 / 1480 / 2340 / 2970 / 5030 / 8450 / 10850 / 20650 / 24600 were used.

[0095] PDI (polydispersity index) is calculated by dividing the measured weight-average molecular weight by the number-average molecular weight.

[0096] (2) Low molecular weight oligomers % GPC analysis was performed before the polymer solution was fed into the thin-film evaporator to obtain the ratio of the area of ​​low molecular weight oligomers (retention times of 21.6 min to 24.1 min) to the total polymer area.

[0097] (3) Softening point For each resin, the softening point of Anton Paar RKA5 was averaged based on two measurements according to ASTM E 28.

[0098] (4) NMR analysis Nuclear magnetic resonance (1H-NMR) analysis was performed on the pure monomer resins prepared in the examples and comparative examples.

[0099] Specifically, samples were prepared by dissolving each pure monomer resin prepared in the examples and comparative examples in a solvent (CDCl3) to a concentration of 2.5 wt%, and then analyzed using a nuclear magnetic resonance spectrometer (600 NMR, 14.1 Tesla, Bruker) under the following conditions: 600 MHz, acquisition time: 2.75 s, delay time: 1 s, number of scans: 128, pulse: 30°, and solvent: CDCl3.

[0100] Based on the results of 1H-NMR analysis, the aromatic fraction (aromaticity, %) of each pure monomer resin was obtained according to Equation 1: [Equation 1]

[0101] In Equation 1, Ar AThis represents the ratio of the area of ​​the hydrogen peaks bound to aromatic hydrocarbons to the total peak area in the aromatic region, specifically the region from 6.5 ppm to 8.5 ppm, obtained by 1H-NMR analysis. A This represents the ratio of the area of ​​the hydrogen peak bound to aromatic hydrocarbons in the olefin region, specifically in the region from 4.0 ppm to 6.5 ppm, to the total peak area in the figure, and Al A This represents the ratio of the peak area of ​​hydrogen atoms bound to aliphatic hydrocarbons in the aliphatic region, specifically within the range of 0.1 ppm to 4.0 ppm, to the total peak area. The peak area is calculated by integration.

[0102] It should be understood that various modifications, alterations, changes, and equivalent implementations can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a pure monomer resin with a reduced proportion of low molecular weight oligomers, comprising: Thermal polymerization of monomers, including aromatic vinyl monomers, is carried out under catalyst-free conditions. The thermal polymerization is carried out through single-stage polymerization in a single reactor. The single reactor is a continuous stirred tank reactor (CSTR).

2. The method for preparing pure monomer resin according to claim 1, wherein, The monomer may include 60 wt% to 100 wt% of aromatic vinyl monomers and 0 to 40 wt% of comonomers, wherein the comonomers include hydrogenated aromatic vinyl monomers, C4 to C64 ... 10 Olefin monomers, or combinations thereof.

3. The method for preparing pure monomer resin according to claim 1, wherein, The aromatic vinyl monomers are selected from styrene, alkylstyrene, divinylbenzene, indene, alkylindene, vinyltoluene, mixed C9 oils, and their derivatives.

4. The method for preparing pure monomer resin according to claim 1, wherein, The monomer and solvent are continuously fed into the reactor, wherein the monomer is present in an amount of 20 wt% to 100 wt% and the solvent is present in an amount of 0 to 80 wt%.

5. The method for preparing pure monomer resin according to claim 1, wherein, The thermal polymerization is carried out at a temperature of 150°C to 300°C and a pressure of 5 bar to 30 bar.

6. The method for preparing pure monomer resin according to claim 1, wherein, The thermal polymerization is completed solely through single-stage polymerization in the continuous stirred tank reactor (CSTR), and the polymer obtained by the thermal polymerization does not undergo secondary thermal polymerization in a plug flow reactor (PFR).

7. The method for preparing pure monomer resin according to claim 1, wherein, The method satisfies the following equation 1: [Equation 1] 100×[(A1-A2) / A1]≥10, In Equation 1 above, A2 represents the ratio (%) of the area of ​​the low molecular weight oligomer (residence time: 21.6 min to 24.1 min) to the total polymer area in the GPC analysis of the polymer obtained by single-stage thermal polymerization in the CSTR, and A1 represents the ratio (%) of the area of ​​the low molecular weight oligomer (residence time: 21.6 min to 24.1 min) to the total polymer area in the GPC analysis of the polymer obtained by two-stage thermal polymerization.

8. A pure monomer resin prepared by the method of any one of claims 1 to 7, wherein the pure monomer resin has: Weight-average molecular weight (Mw) from 300 g / mol to 10000 g / mol; z-average molecular weight (Mz) from 1000 g / mol to 20000 g / mol; Molecular weight distribution from 1 to 3 (polydispersity index, PDI); and Softening point from 0℃ to 150℃.

9. The pure monomer resin according to claim 8, wherein, The pure monomer resin contains less than 100 ppm of residual halides.

10. The pure monomer resin according to claim 8, wherein, The pure monomer resin satisfies the following equation 2: [Equation 2] I O = O A ×A2<35, In Equation 2 above, I O Indicates the low molecular weight oligomer index, O A A1 represents the ratio (%) of the olefin region (4.0 ppm to 6.5 ppm region) to the total peak area calculated by integration on the graph obtained by 1H-NMR analysis. A2 represents the ratio (%) of the area of ​​low molecular weight oligomers (retention time: 21.6 min to 24.1 min) to the total polymer area in GPC analysis of polymers.

11. The pure monomer resin according to claim 8, wherein, The pure monomer resin has a ratio (Mz / Mw) of less than 2.5 (z-average molecular weight, specific gravity-average molecular weight).

12. The pure monomer resin according to claim 8, wherein, The pure polymer resin has an aromatic fraction of 40% to 62.5%, an aliphatic fraction of 35% to 60%, and an olefin fraction of 5% or less.

13. An adhesive comprising the pure monomeric resin according to claim 9.

14. A method for reducing the proportion of low molecular weight oligomers in a pure monomer resin, said method being carried out using a single reactor in the polymerization of aromatic vinyl monomers, wherein, The single reactor is a continuous stirred tank reactor (CSTR).

15. The method according to claim 14, wherein, The method satisfies the following equation 1: [Equation 1] 100×[(A1-A2) / A1]≥10, In Equation 1 above, A2 represents the ratio (%) of the area of ​​the low molecular weight oligomer (residence time: 21.6 min to 24.1 min) to the total polymer area in the GPC analysis of the polymer obtained by single-stage thermal polymerization in the CSTR, and A1 represents the ratio (%) of the area of ​​the low molecular weight oligomer (residence time: 21.6 min to 24.1 min) to the total polymer area in the GPC analysis of the polymer obtained by two-stage thermal polymerization.

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