Citrate-based plasticizer composition and resin composition comprising same

Abstract

This invention relates to a plasticizer composition comprising both low-carbon alkyl-based citrate esters and high-carbon alkyl-based citrate esters as citrate esters, wherein the ratio of mixed to unmixed types and the ratio of low-carbon alkyl to high-carbon alkyl types are controlled to achieve the desired effect. When this plasticizer composition is applied to a resin, it enables the stress resistance and mechanical properties to be maintained at an equal or higher level, balances migration and volatilization loss properties and plasticizing efficiency, and significantly improves lightfastness and heat resistance.

Description

Technical Field

[0001] This invention relates to a citrate-based plasticizer composition comprising a mixture of low-carbon and high-carbon alkyl citrates and a resin composition containing them. Cross-referencing of related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0005439, filed on January 15, 2020, the entire contents of which are incorporated herein by reference. Prior Technology

[0003] Typically, plasticizers are formed by the reaction between alcohols and polycarboxylic acids (such as phthalic acid or adipic acid) to form esters corresponding to the plasticizer. Considering domestic and international regulations concerning phthalate-based plasticizers that are harmful to human health, ongoing research is being conducted on compositions of plasticizers that can replace phthalate-based plasticizers (e.g., terephthalate-based, adipate-based, and other polymer-based plasticizers).

[0004] At the same time, there is an increasing demand for environmentally friendly products related to flooring materials, wallpaper, soft and hard sheets, etc., obtained from the plastisol industry, calendering industry, extrusion / injection mixing industry, etc. In order to enhance the quality characteristics, processability and production capacity of various end products used in such environmentally friendly products, appropriate plasticizers must be used depending on fading, migration, mechanical properties, etc.

[0005] Depending on the properties required in various industrial applications, such as tensile strength, elongation, lightfastness, migration properties, gelling properties, and absorption rate, PVC resin is mixed with supplementary materials (such as plasticizers, fillers, stabilizers, viscosity reducers, dispersants, antifoaming agents, foaming agents, etc.).

[0006] For example, among plasticizer compositions applicable to PVC, the relatively inexpensive and most commonly used di(2-ethylhexyl) terephthalate (DEHTP) has high hardness or sol viscosity, a relatively slow absorption rate, and poor migration and stress migration properties.

[0007] To improve these properties, the transesterification product with butanol was considered as a plasticizer composition containing DEHTP. However, while using this product improved plasticizing efficiency, it resulted in poor volatility loss or thermal stability, and slightly deteriorated mechanical properties, thus necessitating improvements to physical properties. Currently, there is generally no solution; the only approach is to compensate for this drawback by combining it with other minor plasticizers.

[0008] However, the use of minor plasticizers has the following disadvantages: changes in physical properties are difficult to predict; the unit price of the product will increase; the improvement in physical properties is not significant unless under certain circumstances; and unexpected problems may occur, such as compatibility issues with the resin.

[0009] Similarly, to improve the poor migration and volatilization loss properties of DEHTP products, materials based on trimellitate esters, such as tri(2-ethylhexyl) trimellitate or triisononyl trimellitate, are used to improve migration or volatilization loss properties. However, this also results in poor plasticizing efficiency, thus requiring large amounts to be added to provide the resin with adequate plasticizing effect. In addition, the unit price of this material is relatively high, making commercialization impossible.

[0010] Therefore, it is necessary to develop products that address the environmental problems of phthalate-based products as existing products, or environmentally friendly products with improved physical properties, in order to improve the environmental problems of phthalate-based products. Summary of the Invention

[0011] The technical problem to be solved

[0012] The present invention provides a plasticizer composition containing citrate ester, wherein low-carbon and high-carbon alkyl groups are appropriately controlled and combined, and thus, compared with conventional plasticizers, it can improve mechanical properties and stress resistance, while simultaneously improving migration resistance and volatility loss properties and plasticizing efficiency in a balanced manner, and improving heat resistance (maintenance). Technical means to solve the problem

[0013] To address the aforementioned problems, according to an embodiment of the present invention, a plasticizer composition is provided, comprising a citrate-based composition containing three or more citrates represented by Formula 1 below, wherein the alkyl groups of the citrates are derived from C5 and C8 alcohols, the C5 alcohols including one or more selected from the group consisting of n-pentanol, 2-methylbutanol, and 3-methylbutanol, and the C8 alcohols including 2-ethylhexanol.

[0014] [Formula 1]

[0015] In Formula 1, R1 to R3 are each independently an alkyl group having 5 or 8 carbon atoms, while R4 is hydrogen or acetyl.

[0016] To address the aforementioned problems, according to other aspects of the present invention, a resin composition is provided, comprising: 100 parts by weight of a resin; and 5 to 150 parts by weight of the aforementioned plasticizer composition.

[0017] The resin may be selected from one or more of the following groups: linear vinyl chloride polymers, paste-like vinyl chloride polymers, ethylene vinyl acetate copolymers, ethylene polymers, propylene polymers, polyketides, polystyrene, polyurethane, natural rubber, and synthetic rubber. Advantages of the invention

[0018] According to embodiments of the present invention, when used in resin compositions, the plasticizer composition can improve mechanical properties and stress resistance compared to conventional plasticizers, while simultaneously achieving a balanced improvement in volatility loss properties and plasticizing efficiency, as well as improving migration resistance and retention. Implementation

[0019] In the following description of the invention and the scope of the patent application, the interpretation of terms or vocabulary shall not be limited to their general or dictionary meanings, and the terms or vocabulary shall be based on the meaning and conceptual interpretation of the terms that the inventor may appropriately define in order to best interpret the invention in accordance with the technical concept of the invention.

[0020] [Definition of Terminology]

[0021] The term “composition” as used in this description includes materials corresponding to the composition and mixtures of reaction products and decomposition products derived from materials corresponding to the composition.

[0022] The term "linear vinyl chloride polymer" as used in this description refers to a vinyl chloride polymer that is polymerized via suspension polymerization or bulk polymerization. This polymer has a porous particle shape with many pores, and the particle size ranges from tens to hundreds of micrometers. It is non-adhesive and has excellent flowability.

[0023] The term "paste-like vinyl chloride polymer" as used in this description refers to a vinyl chloride polymer polymerized via microsuspension polymerization, microcrystal seed polymerization, or emulsion polymerization. This polymer has a non-porous, tiny, and dense particle shape, with sizes ranging from tens to thousands of nanometers, exhibiting adhesiveness and poor flowability.

[0024] Unless otherwise specifically disclosed, the terms “comprising,” “having,” and their derivatives are not intended to exclude the presence of any additional components, steps, or procedures. Unless otherwise stated to the contrary, to avoid any uncertainty, all components claimed by the use of the term “comprising” may include any additional additives, auxiliaries, or compounds, including polymers or any other materials. Conversely, the term “substantially composed of” excludes any components, steps, or procedures that are not essential for operability and excludes them from the scope of any continuous description. The term “composed of” excludes any components, steps, or procedures that are not specifically stated or listed.

[0025] [Determination Method]

[0026] In this specification, the content analysis of the component in the composition was performed by gas chromatography using an Agilent Co. gas chromatography instrument (product name: Agilent 7890 GC, column: HP-5, carrier gas: helium (flow rate 2.4 mL / min), detector: FID, injection volume: 1 μL, initial value: 70℃ / 4.2 min, final value: 280℃ / 7.8 min, program rate: 15℃ / min).

[0027] In this specification, "hardness" refers to the Shore hardness (Shore "A" and / or Shore "D") at 25°C, measured using ASTM D2240 at 3T 10s, and can be used as an indicator to evaluate plasticizing efficiency. The lower the hardness, the better the plasticizing efficiency.

[0028] In this specification, “tensile strength” is determined according to ASTM D638. Using a UTM testing instrument (manufacturer: Instron, model: 4466), the specimen was stretched at a crosshead rate of 200 mm / min (1 T), the point at which the specimen was cut was determined, and the tensile strength was calculated using the following Equation 1.

[0029] [Equation 1] Tensile strength (kgf / cm²) = Load value (kgf) / Thickness (cm) × Width (cm)

[0030] In this specification, “elongation” is measured according to ASTM D638. Using a UTM, the specimen is stretched at a crosshead rate of 200 mm / min (1 T), the point at which the specimen is cut is determined, and the elongation is calculated using the following Equation 2.

[0031] [Equation 2] Elongation (%) = Length after stretching / Initial length × 100

[0032] In this specification, "migration loss" is measured according to KSM-3156. A specimen with a thickness of 2 mm or greater was obtained, and glass plates were bonded to both sides of the specimen and a load of 1 kgf / cm² was applied. The specimen was placed in a hot air convection oven (80°C) for 72 hours, then removed and cooled to room temperature for 4 hours. The glass plates bonded to both sides of the specimen were then removed, and the weights of the glass plates and the specimen plate before and after standing in the oven were measured. Migration loss was calculated using Equation 3 below.

[0033] [Equation 3] Migration loss (%) = {[(initial weight of sample at room temperature) – (weight of sample after standing in oven)] / (initial weight of sample at room temperature)} × 100

[0034] In this description, "volatile loss" is obtained by treating the sample at 80°C for 72 hours and measuring the weight of the sample.

[0035] [Equation 4] Volatilization loss (wt%) = {[(initial weight of sample) – (weight of sample after treatment)] / (initial weight of sample)} × 100

[0036] The details of the conditions (such as temperature, rotation rate, and time) in a variety of measurement conditions vary more or less depending on the circumstances, and the measurement methods and conditions will be specified in different cases.

[0037] The invention will now be described in more detail to aid in understanding it.

[0038] According to an embodiment of the present invention, the plasticizer composition includes a citrate-based composition containing three or more citrates represented by Formula 1, wherein the alkyl group of the citrate is derived from C5 alcohols and C8 alcohols, the C5 alcohols including one or more selected from the group consisting of n-pentanol, 2-methylbutanol and 3-methylbutanol, and the C8 alcohols including 2-ethylhexanol.

[0039] [Formula 1]

[0040] In Formula 1, R1 to R3 are each independently an alkyl group having 5 or 8 carbon atoms, while R4 is hydrogen or acetyl.

[0041] The plasticizer composition according to an embodiment of the present invention is characterized in that the citrate is a mixture of the C5 alcohol and the C8 alcohol. Compared to unmixed citrates, it exhibits an excellent balance of physical properties. Using a lower alcohol with fewer carbon atoms than the C5 alcohol or a higher alcohol with fewer carbon atoms than the C8 alcohol results in significant deterioration of mechanical properties and poor retention. Similarly, using a lower alcohol or a higher alcohol with more carbon atoms than the defined carbon number results in significant deterioration of stress resistance and migration resistance. Accordingly, it is desirable to use the C5 alcohol and the C8 alcohol as the alcohol.

[0042] Specifically, the citrate-based composition may include: citrates based on low-carbon alkyl groups, including low-carbon unmixed citrates having C5 alcohol-derived alkyl groups, and low-carbon mixed citrates having C5 alcohol-derived alkyl groups and C8 alcohol-derived alkyl groups, wherein the C5 alcohol-derived alkyl groups are more numerous than the C8 alcohol-derived alkyl groups; and citrates based on high-carbon alkyl groups, including high-carbon mixed citrates having C5 alcohol-derived alkyl groups and C8 alcohol-derived alkyl groups, wherein the C8 alcohol-derived alkyl groups are more numerous than the C5 alcohol-derived alkyl groups, and high-carbon unmixed citrates having C8 alcohol-derived alkyl groups.

[0043] More specifically, according to embodiments of the present invention, the citrate-based composition contained in the plasticizer composition contains four types of citrates, which can be broadly classified as citrates based on high-carbon alkyl groups having two or more C8 alkyl groups (Formulas 1-4 to 1-6), and citrates based on low-carbon alkyl groups having two or more C5 alkyl groups (Formulas 1-1 to 1-3). Similarly, the low-carbon alkyl-based citrates can be further subdivided into low-carbon unmixed citrates (Formula 1-1), wherein the C5 alkyl group is bonded to all three ester groups, and low-carbon mixed citrates (Formulas 1-2 and 1-3), wherein the C5 alkyl group is bonded to two ester groups. Similarly, the high-carbon alkyl-based citrates can be divided into high-carbon unmixed citrates (Formulas 1-6) and high-carbon mixed citrates (Formulas 1-4 and 1-5). In detail, with regard to the citrate esters shown in Formulas 1-3 and 1-5, there are optical isomers due to the presence of the palmitated carbon, but in this specification, these optical isomers are not treated as different compounds and are not treated separately.

[0044] In this text, the term "having...alkyl binding" means "having an...alkyl group bound to the three ester groups of the citrate ester".

[0045] Similarly, the terms "unmixed" or "mixed" are distinguished based on the alkyl groups bonded to the three esters, whether they are bonded to only alkyl groups with the same number of carbon atoms or to alkyl groups with different numbers of carbon atoms. When alkyl groups with the same number of carbon atoms are bonded to all three ester groups, it is considered "unmixed." When alkyl groups with different numbers of carbon atoms are bonded to the three ester groups, it is considered "mixed." More specifically, the distinction between mixed and unmixed is based on the number of carbon atoms. For example, when only pentyl groups with the same number of carbon atoms are bonded, even if n-pentyl and branched pentyl groups are mixed, their carbon number is the same, and therefore it is considered "unmixed" in this specification.

[0046] Formulas 1-1 to 1-6, representing the citrate ester-based and the citrate ester-based components respectively, are shown below:

[0047] [Equation 1-1]

[0048] [Equation 1-2]

[0049] [Equation 1-3]

[0050] [Equations 1-4]

[0051] [Equations 1-5]

[0052] [Equations 1-6]

[0053] In formulas 1-1 to 1-6, RL ​​is n-pentyl or branched pentyl, RH is 2-ethylhexyl, and Ra is hydrogen or acetyl.

[0054] The plasticizer composition may be a product obtained by direct transesterification of citric acid or a mixture of citric acid derivatives with an alkyl alcohol having 5 or 8 carbon atoms, or a product obtained by transesterification of an alkyl citrate with 5 (or 8) carbon atoms with an alcohol having 8 (or 5) carbon atoms. Here, the applied alcohol may be a structural isomer or a mixture of any single substance. For example, the 5-carbon alcohol may be purified n-pentanol, or branched pentanol (which, in a product obtained solely from pentanol, is purified to have any isomer composition), or a mixture thereof. For example, the 8-carbon alcohol may be 2-ethylhexanol alone. The alcohol having five carbon atoms may be a mixture of unpurified isomers of pentanol or a mixture of two or more selected from the group consisting of: 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 2-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, and 2,2-dimethylpropyl, collectively referred to as branched pentanol. Preferably, the isoamyl alcohol may be selected from the group consisting of 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, and 2,2-dimethylpropyl.

[0055] The plasticizers according to embodiments of the present invention comprise the four types of citrate esters mentioned above, and can achieve excellent effects by appropriately combining them with various types of alkyl groups.

[0056] Specifically, due to the balance of alkyl groups between the high-carbon immiscible citrate and the low-carbon immiscible citrate, and the coexistence of mixed types in the composition, as well as certain properties (e.g., the controlled ratio of the low-carbon to the high-carbon alkyl groups among all alkyl groups, and, when any alkyl group is derived from a mixed alcohol, the ratio of certain branched alkyl groups among the branched alkyl groups), plasticizing efficiency and physical properties (e.g., migration / volatility loss) are balanced. The interaction of the four types of citrate contained in the composition significantly improves mechanical properties, stress resistance, and maintains these properties.

[0057] Therefore, it is possible to achieve products that do not have the environmental problems of existing phthalate-based products and have improved volatility loss, and to significantly improve the migration and volatility loss of conventional terephthalate-based products, and to achieve products with significantly improved mechanical properties and stress resistance compared to existing commercially available products.

[0058] To achieve the above effects more appropriately and better, it is important to meet the conditions for RL and RH as defined in Equations 1 to 6.

[0059] As defined above, RL and RH can be n-pentyl or branched pentyl, and 2-ethylhexyl, respectively. These alkyl groups determine the interactions between the various types of citrates contained in the citrate-based plasticizer composition and the weight of the overall composition, and play an important role in achieving the desired effect.

[0060] Preferably, RL is an alkyl group having 5 carbon atoms, and may be n-pentyl or branched pentyl. Specifically, the branched pentyl group may be selected from one of the following groups: 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 2-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, and 2,2-dimethylpropyl. More preferably, RL may be n-pentyl, 2-methylbutyl, or 3-methylbutyl.

[0061] According to an embodiment of the invention, the C5 alcohol substantially comprises n-pentanol. C5 alcohols have a wide variety of isomers. Among these isomers, n-pentanol is preferably included as a C5 alcohol. n-Pentanol is a straight-chain alcohol, and the intermolecular interactions and steric hindrance can be appropriately controlled, thus improving the performance of the plasticizer. This may be due to a synergistic effect related to the fact that 2-ethylhexanol (a higher alcohol) is a branched-chain alcohol.

[0062] Similarly, the C5 alcohol includes n-pentanol, but may include at least one branched alcohol selected from 2-methylbutanol and 3-methylbutanol, wherein the content of n-pentanol is 50% by weight or higher based on the total weight of the C5 alcohol. The C5 alcohol may be used in the form of isomer mixtures, wherein the plasticizer performance is further improved when the content of n-pentanol in the mixture is 50% by weight or higher.

[0063] In the plasticizer composition according to embodiments of the present invention, the ratio of each alkyl group can be adjusted to further optimize the realization of the effects according to the present invention. Firstly, the weight ratio of the citrate ester based on a low-carbon alkyl group to the citrate ester based on a high-carbon alkyl group can be controlled to be 95:5 to 10:90, preferably 90:10 to 10:90, or 90:10 or 15:85, more preferably 90:10 to 20:80, and even more preferably 90:10 to 30:70. By using the citrate ester based on a low-carbon alkyl group, represented by formulas 1-1 to 1-3, which is higher than the citrate ester based on a high-carbon alkyl group (formulas 1-4 to 1-6), the weight of the entire plasticizer composition can be controlled, and thereby, it is expected that the performance of the plasticizer composition can be significantly improved.

[0064] More specifically, the factor controlling the structural properties of the plasticizer composition according to embodiments of the present invention is controlling the weight ratio of the unmixed citrate esters represented by formulas 1-1 and 1-6 to the mixed citrate esters represented by formulas 1-2 to 1-5. The weight ratio of the unmixed citrate esters to the mixed citrate esters can be from 80:20 to 5:95, preferably from 70:30 to 10:90, and more preferably from 60:40 to 20:80. In the esterification method used to prepare this composition, the amount of the product containing the mixed alkyl groups can be controlled by controlling the reaction, and therefore plays an important role in achieving the desired effect.

[0065] Similarly, controlling the weight ratio of the high-carbon unmixed citrate esters represented by Formulas 1-6 to the high-carbon mixed citrate esters represented by Formulas 1-4 and 1-5 in the high-carbon alkyl-based citrate ester also plays a similar role. This weight ratio can be from 5:95 to 80:20, more preferably, from 10:90 to 60:40, and even more preferably, from 20:80 to 50:50. That is, it should be noted that the effect of the resulting plasticizer composition can be improved by controlling the weight ratio between the citrate esters included in the high-carbon alkyl-based citrate ester through appropriate control during the reaction.

[0066] When the components of the plasticizer composition according to the present invention are composed within the above range, considering the equivalence ratio of the reactants, the actual yield of the reaction, the conversion rate, etc., the production capacity in the process can be improved, the above mechanical properties (e.g., tensile strength and elongation) can be prevented from deteriorating, and the lightfastness can be significantly improved.

[0067] Meanwhile, the substituent defined as Ra in the citrate ester can be hydrogen or acetyl. For the improvement and optimization of the physical properties of the plasticizer, especially processability, melting properties, and mechanical properties (e.g., elongation), hydrogen is preferred due to the reduction in plasticizing efficiency. Similarly, when the substituent is acetyl, problems that are difficult to eliminate, such as reduced economic efficiency due to production issues (e.g., increased costs due to additional processes and treatment equipment resulting from the generation of acetic acid waste), must be taken into consideration.

[0068] The method for manufacturing plasticizer composition according to an embodiment of the present invention is a method known in the art, and any method can be applied without specific limitations, as long as the above-mentioned plasticizer composition can be obtained.

[0069] For example, this composition can be prepared by direct esterification of a citrate ester or its anhydride with two or more alcohols. It can also be prepared by transesterification of a citrate ester and an alcohol.

[0070] The plasticizer composition according to an embodiment of the present invention is a material obtained by appropriately carrying out the esterification reaction. Therefore, as long as the above conditions are met, in particular, as long as the ratio of branched alcohols in the alcohol mixture of the isomers is controlled, there are no particular limitations on the preparation method.

[0071] For example, the steps of carrying out this direct esterification reaction include introducing citrate and two or more alcohols, adding a catalyst and reacting under a nitrogen atmosphere; removing unreacted alcohols and neutralizing unreacted acids; and distilling under reduced pressure to remove water and filtering.

[0072] The alcohol can be a monohydric alcohol having alkyl groups corresponding to RH and RL in formulas 1-1 to 1-6. The weight ratio of the monohydric alcohol having the RL alkyl group to the monohydric alcohol having the RH alkyl group can be an important factor in determining the proportion of components in the resulting composition. For example, the weight ratio of C5 alcohol to C8 alcohol can be 90:10 to 10:90, more preferably, 90:10 to 20:80, more preferably, 90:10 to 25:75, and even more preferably, 90:10 to 30:70.

[0073] Based on 100 mol% of the acid, the alcohol can be used in the range of 150 to 500 mol%, 200 to 400 mol%, 200 to 350 mol%, 250 to 400 mol%, or 270 to 330 mol%. By controlling the content of this alcohol, the proportion of components in the final composition can be controlled.

[0074] The catalyst can be, for example, an acid catalyst (e.g., sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, p-toluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, and alkyl sulfates), a metal salt (e.g., aluminum lactate, lithium fluoride, potassium chloride, cesium chloride, calcium chloride, ferric chloride, and aluminum phosphate), a metal oxide (e.g., heteropolyacids, natural / synthetic zeolites, cation and anion exchange resins), and an organometallic compounds (e.g., tetraalkyl titanates and their polymers). A specific example of such a catalyst is a tetraalkyl titanate. Preferably, as an acid catalyst with a low activation temperature, suitable candidates include p-toluenesulfonic acid and methanesulfonic acid.

[0075] The amount of catalyst used can vary depending on the type. For example, based on 100% by weight of the reactants, the amount of homogeneous catalyst can be 0.01 to 5% by weight, 0.01 to 3.0% by weight, 1.0 to 5.0% by weight, or 2.0 to 4.0% by weight, while based on the total amount of the reactants, the amount of heterogeneous catalyst can be 5 to 200% by weight, 5 to 100% by weight, 20 to 200% by weight, or 20 to 150% by weight.

[0076] The reaction temperature range can be 180 to 280°C, 200 to 250°C, or 210 to 230°C.

[0077] As another example, the transesterification reaction can be a reaction between a citrate ester and an alcohol whose alkyl group has a different number of carbon atoms than the alkyl group of the citrate ester (for citrate esters with higher carbon alkyl groups, lower carbon alkanols; for citrate esters with lower carbon alkyl groups, higher carbon alkanols). The alkyl groups of the citrate ester and the alcohol can be interleaved.

[0078] The "transesterification reaction" used in this invention refers to the reaction of an alcohol and an ester to exchange the alkyl group of the ester with the alkyl group of the alcohol.

[0079] In the case of citrate esters included in the plasticizer composition according to the present invention, three types can be formed when two ester groups are exchanged and when one ester group is exchanged, depending on the ester group bonding position. Accordingly, a mixture of up to eight compounds (including structural isomers and optical isomers) can be present in the final composition.

[0080] Furthermore, compared to the esterification reaction between acids and alcohols, the advantage of this transesterification reaction is that it does not generate wastewater.

[0081] The composition ratio of the mixture obtained via the transesterification reaction can be controlled according to the amount of alcohol added. Based on 100 parts by weight of the citrate compound, the amount of alcohol added can be 10 to 200 parts by weight, specifically 20 to 150 parts by weight, and more particularly, 30 to 120 parts by weight. For reference, the proportion of components in the final composition can be determined by the amount of alcohol added in the direct esterification reaction.

[0082] That is, in the citrate-based composition, since the molar fraction of the citrate participating in the transesterification reaction can be increased by increasing the amount of alcohol added, the content of citrate (which is the product) in the mixture can be increased, and thereby the content of unreacted citrate tends to decrease.

[0083] According to an embodiment of the present invention, the molar ratio of the reactants (citric acid ester and alcohol) can be, for example, 1:0.005 to 1:10, 1:0.05 to 1:8, or 1:0.1 to 1:6, and within this range, the processing efficiency and economic convenience are excellent, and a plasticizer composition that can achieve the above-mentioned effects can be obtained.

[0084] According to an embodiment of the present invention, the transesterification reaction can be carried out at a temperature of 120 to 190°C, preferably 135 to 180°C, more preferably 141 to 179°C, for 10 minutes to 10 hours, more preferably 30 minutes to 8 hours, and more preferably 1 to 6 hours. Within this temperature and time range, the component ratios in the final plasticizer composition can be effectively controlled. The reaction time can be calculated from the time it takes for the reactant temperature to rise and reach the reaction temperature.

[0085] This transesterification reaction can be carried out under acid catalysts or metal catalysts. This can shorten the reaction time.

[0086] The acid catalyst can be, for example, sulfuric acid, methanesulfonic acid, or p-toluenesulfonic acid, and the metal catalyst can be, for example, an organometallic catalyst, a metal oxide catalyst, a metal salt catalyst, or the metal itself.

[0087] The metallic component may be, for example, any one of the group consisting of tin, titanium and zirconium, or a mixture of two or more of them.

[0088] Furthermore, following the transesterification reaction, a step of removing unreacted alcohols and reaction byproducts by distillation can be added. This distillation can be, for example, a two-step distillation that uses boiling point differences to separate the alcohols and byproducts individually. As another example, the distillation can be a mixture distillation. In this case, it can be reliably ensured that the ester-based plasticizer composition achieves the desired composition ratio. This mixture distillation refers to the simultaneous distillation of unreacted alcohols and byproducts.

[0089] According to another embodiment of the present invention, a resin composition comprising the above-described plasticizer composition and a resin is provided.

[0090] The resin may be those known in this art. For example, mixtures selected from one or more of the following groups may be used, but are not limited to: linear vinyl chloride polymers, paste-like vinyl chloride polymers, ethylene vinyl acetate copolymers, ethylene polymers, propylene polymers, polyketones, polystyrene, polyurethanes, natural rubber, and synthetic rubber.

[0091] Based on 100 parts by weight of the resin, the content of the plasticizer composition may be 5 to 150 parts by weight, preferably 5 to 130 parts by weight, or 10 to 120 parts by weight.

[0092] Typically, resins using this plasticizer composition can be processed into resin products via melt processing or plastisol processing, and resins obtained by melt processing and resins obtained by plastisol processing can be manufactured in different ways depending on their respective polymerization methods.

[0093] For example, in the case of vinyl chloride polymers being used in melt processing, solid resin particles with a large average particle size are obtained by suspension polymerization or the like and used, and this vinyl chloride polymer is a linear vinyl chloride polymer. In the case of vinyl chloride polymers being used in plastisol processing, a sol-state resin in which tiny resin particles are distributed is obtained by emulsification polymerization or the like and used, and this vinyl chloride polymer is a paste-like vinyl chloride resin.

[0094] In the case of linear vinyl chloride polymers, the plasticizer content can range from 5 to 150 parts by weight, preferably 5 to 80 parts by weight, based on 100 parts by weight of the polymer. In the case of paste-like vinyl chloride polymers, the plasticizer content can range from 5 to 150 parts by weight, preferably 40 to 120 parts by weight, based on 100 parts by weight of the polymer.

[0095] The resin composition may additionally include fillers. Based on 100 parts by weight of the resin, the amount of filler may be 0 to 300 parts by weight, preferably 50 to 200 parts by weight, and more preferably 100 to 200 parts by weight.

[0096] The packing material can be any packing material known in this art and is not particularly limited. For example, the packing material can be a mixture of one or more of silicon oxide, magnesium carbonate, calcium carbonate, hard coal, talc, magnesium hydroxide, titanium dioxide, magnesium oxide, calcium hydroxide, aluminum hydroxide, aluminum silicate, magnesium silicate, and barium sulfate.

[0097] In addition, the resin composition may include other additives, such as stabilizers, as needed. The content of the other additives (e.g., stabilizers) relative to 100 parts by weight of resin may be, for example, 0 to 20 parts by weight, preferably 1 to 15 parts by weight.

[0098] The stabilizer may be, for example, but not particularly limited to, a calcium-zinc based (Ca-Zn based) stabilizer (e.g., a calcium-zinc complex stearate) or a barium-zinc based (Ba-Zn based) stabilizer.

[0099] This resin composition can be applied to both melt processing and plastisol processing as described above. For example, melt processing can be applied to calendering, extrusion, or injection processing, while plastisol processing can be applied to coating processes.

[0100] [Example]

[0101] The invention will be described in more detail below with reference to examples. Examples of the invention can be modified into various other types, and the scope of the invention should not be limited to the examples described below. Examples of the invention are provided to fully explain the invention to those skilled in the art.

[0102] [Example] [1] [to] [5]

[0103] In a reactor equipped with a stirrer, condenser, and decanter, 500 g of citric anhydride, 642 g of n-pentanol, 406 g of 2-ethylhexanol, and 2 g of tetrabutyl titanate (TnBT) were introduced, and an esterification reaction was carried out under a nitrogen atmosphere. The reaction was completed, and unreacted alcohols were removed. The catalyst and the composition were then neutralized and washed with an alkaline solution. A purification procedure to remove unreacted alcohols and water was performed to obtain the composition of Example 1, which contains tri(n-pentyl) citrate, di(n-pentyl)(2-ethylhexyl) citrate, di(2-ethylhexyl)(n-pentyl) citrate, and tri(2-ethylhexyl) citrate in amounts of 26.5 wt%, 45.1 wt%, 24.2 wt%, and 4.2 wt%, respectively.

[0104] In the above reactions, the types and amounts of reactants were adjusted to obtain compositions having the compositions shown in Table 1 below, as in Examples 2 to 5.

[0105] [Example] [6] [to] [8]

[0106] In a reactor equipped with a stirrer, a condenser and a decanter, 500 g of citric anhydride, 1,320 g of 2-ethylhexanol and 2 g of tetrabutyl titanate (TnBT) were introduced and esterified under a nitrogen atmosphere to obtain tris(2-ethylhexyl) citrate.

[0107] In a reactor equipped with a stirrer, a condenser, and a decanter, 1,000 g of the prepared tri(2-ethylhexyl) citrate and 200 g of n-pentanol (20 parts by weight, based on 100 parts by weight of TEHC) were introduced, and a transesterification reaction was carried out at 160 °C for 2 hours under a nitrogen atmosphere to obtain the composition of Example 6, which contains tri(n-pentyl) citrate, di(n-pentyl)(2-ethylhexyl) citrate, di(2-ethylhexyl)(n-pentyl) citrate, and tri(2-ethylhexyl) citrate in amounts of 2.1 wt%, 16.9 wt%, 44.0 wt%, and 37.0 wt%, respectively.

[0108] In the above reactions, the types and amounts of reactants were adjusted to obtain compositions having the compositions shown in Table 1 below, as in Examples 7 and 8.

[0109] [Comparative Example] [1]

[0110] Dioctyl phthalate (DOP, LG Chemical, LTD.) was used as a plasticizer.

[0111] [Comparative Example] [2]

[0112] Diisononyl phthalate (DINP, LG Chemical, LTD.) was used as a plasticizer.

[0113] [Comparative Example] [3]

[0114] Di(2-ethylhexyl) terephthalate (GL300, LG Chemical, LTD.) was used as a plasticizer.

[0115] [Comparative Example] [4] [to] [6]

[0116] The same reaction as in Example 1 was carried out, but only 2-ethylhexanol was used instead of 2-ethylhexanol and n-pentanol as the alcohols in Example 1 to obtain tris(2-ethylhexyl) citrate of Comparative Example 4.

[0117] In Comparative Examples 5 and 6, the alcohol in Comparative Example 4 was replaced with the alcohols shown in Table 1 below.

[0118] [Comparative Example] [7] [to]

[14]

[0119] Perform the same reaction as in Example 6, but change the alcohol used in the direct esterification reaction and the higher and lower alcohols used in the transesterification reaction to those shown in Table 1 below, to obtain the citrate composition.

[0120] - nP: n-Pentanol - 3-MB:3-Methylbutanol - 2-EH:2-Ethylhexanol - n-Hp: n-Heptanetanol - nB: n-Butanol - n-Hx: n-Hexanol - IN: Isononyl alcohol - In Table 1 above, "C5 20% TEHC" refers to 20 parts by weight of C5 alcohol based on 100 parts by weight of TEHC, and similar statements can be interpreted in the same manner.

[0121] [Experimental Example] [1] [Evaluation of chip performance]

[0122] Using plasticizers from examples and comparative examples, samples were prepared according to the following formulations and manufacturing conditions and ASTM D638.

[0123] [(1)] [Compound:] 100 parts by weight of linear vinyl chloride polymer (LS100S), 30 parts by weight of plasticizer, and 3 parts by weight of stabilizer (BZ-153T).

[0124] [(2)] [Mix]: Mix at 98°C and 700 rpm.

[0125] [(3)] [Sample manufacturing:] 1T, 2T and 3T sheets were obtained by treating the sample with a tumbling mill at 160°C for 4 minutes, and with a press at 180°C for 2.5 minutes (low pressure) and 2 minutes (high pressure).

[0126] [(4)] [Evaluation Items]

[0127] 1) Hardness: Using ASTM D2240, a 3T specimen was tested at 25°C for 10 seconds to obtain the Shore hardness (Shore "A" and "D"). It is assessed that the smaller the value, the better the plasticizing efficiency.

[0128] 2) Tensile Strength: Using the ASTM D638 method and a UTM testing apparatus (manufacturer: Instron, model: 4466), the specimen was stretched at a crosshead rate of 200 mm / min, and the point at which a 1T specimen was cut was measured. The tensile strength was calculated as follows:

[0129] Tensile strength (kgf / cm²) = Load value (kgf) / Thickness (cm) × Width (cm)

[0130] 3) Elongation determination: "Elongation" is determined according to ASTM D638. After elongation using a UTM at a crosshead rate of 200 mm / min, the point at which a 1T specimen is cut is measured, and the elongation is calculated as follows:

[0131] Elongation (%) = Length after elongation / Initial length × 100.

[0132] 4) Determination of migration loss: According to KSM-3156, a specimen with a thickness of 2 mm or greater was obtained, and glass plates were bonded to both sides of the 1T specimen, with a load of 1 kgf / cm² applied. The specimen was placed in a hot air convection oven (80°C) for 72 hours, then removed and cooled to room temperature for 4 hours. The glass plates bonded to both sides of the specimen were then removed, and the weights of the glass plates and the specimen were measured before and after the oven drying period. Migration loss was calculated using the following formula.

[0133] Migration loss (%) = {[(Initial weight of sample at room temperature) - (Weight of sample after standing in oven)] / (Initial weight of sample at room temperature)} × 100

[0134] 5) Determination of volatilization loss: The prepared sample was treated at 80°C for 72 hours and the weight of the sample was determined.

[0135] The calculation of evaporation loss is as follows: Volatilization loss (wt%) = {[(initial weight of sample) - (weight of sample after treatment)] / (initial weight of sample)} × 100

[0136] 6) Stress test (stress resistance): A 2 mm thick specimen was held in a bent state at 23°C for 168 hours, and the degree of migration (exudation) was then observed. The results are presented numerically. Values ​​closer to 0 represent excellent properties.

[0137] 7) Determination of tensile retention (%): The tensile retention is determined by heating the specimen at 100°C for 168 hours and measuring the remaining elongation. The method for determination is the same as that for elongation.

[0138] (5) Evaluation Results

[0139] The evaluation results of the test projects are shown in Tables 2 and 3 below.

[0140]

[0141]

[0142] Referring to Tables 2 and 3 above, Examples 1 to 8, which apply the plasticizer composition according to embodiments of the present invention, exhibit significantly improved plasticizing efficiency and migration loss compared to Comparative Examples 1 to 3 using conventional products. Examples 1 to 8 also demonstrate excellent tensile retention and stress resistance.

[0143] Similarly, Comparative Examples 4 to 6 were obtained by applying citrate esters made from one type of alcohol, wherein the alkyl group of the citrate ester was not mixed with two or more alcohols. It was found that all the physical properties of Comparative Examples 4 to 6 were inferior to those of Examples 1 to 8, and it can be seen that the variation in physical properties is highly dependent on the number of carbon atoms.

[0144] Meanwhile, Comparative Examples 7 to 14 were obtained by mixing the alkyl groups of two types of alcohols, similar to the examples according to the present invention, but the carbon number of the lower alcohol was not adjusted to C5 and the carbon number of the higher alcohol was not adjusted to C8.

[0145] Observing these results, in Comparative Examples 7 to 9 and 13 and 14, the lower alcohols with fewer than C5 carbon atoms or the higher alcohols with fewer than C8 carbon atoms exhibited significantly poor tensile strength and elongation, and extremely poor tensile retention. Therefore, this confirms a substantial loss of flexibility in high-temperature environments and also demonstrates deterioration in volatility.

[0146] Similarly, although Comparative Example 10 (in which the lower alcohol has fewer than C5 carbon atoms and the higher alcohol has more than C8 carbon atoms) has a similar average weight to the examples of the present invention, it exhibits lower elongation than the other comparative examples. It can be seen that the loss in physical properties (e.g., migration loss and volatility loss) is greater. This confirms that its stress resistance is not as good as that of the examples of the present invention.

[0147] Furthermore, it can be seen that Comparative Examples 11 and 12 (where the number of carbon atoms in the higher alcohol is greater than C8 or the number of carbon atoms in the lower alcohol is greater than C5) exhibit poor elongation, migration loss, and stress resistance, with trends similar to Comparative Example 10.

[0148] Therefore, when citrate esters are used as plasticizers in examples of the present invention, it can be found that: two or more alcohols must be used, but C5 and C8 alcohols can be used together, thereby mixing the alkyl groups of the citrate ester; and in this case, a plasticizer with excellent performance can be achieved.

Claims

1. Use of a plasticizer composition for improving the mechanical properties of linear vinyl chloride polymers, wherein the plasticizer composition comprises a citrate-based composition containing three or more citrate esters represented by Formula 1 below, wherein the alkyl group of the citrate esters is derived from C5 and C8 alcohols, wherein the C5 alcohol includes n-pentanol and at least one branched alcohol selected from 2-methylbutanol and 3-methylbutanol, and wherein the content of n-pentanol is 50% by weight or higher based on the total weight of the C5 alcohols, wherein the C8 alcohol includes 2-ethylhexanol: [Formula 1] wherein R1 to R3 are each independently an alkyl group having 5 or 8 carbon atoms, and R4 is hydrogen or acetyl, wherein the molar ratio of the C5 alcohol to the C8 alcohol is 90:10 to 30:

70. The citrate-based composition comprises: a citrate based on low-carbon alkyl groups, including a low-carbon unmixed citrate having C5 alcohol-derived alkyl groups and a low-carbon mixed citrate having C5 alcohol-derived alkyl groups and C8 alcohol-derived alkyl groups, wherein the C5 alcohol-derived alkyl groups are more numerous than the C8 alcohol-derived alkyl groups; and a citrate based on high-carbon alkyl groups, including a high-carbon mixed citrate having C5 alcohol-derived alkyl groups and C8 alcohol-derived alkyl groups, wherein the C8 alcohol-derived alkyl groups are more numerous than the C5 alcohol-derived alkyl groups, and a high-carbon unmixed citrate having C8 alcohol-derived alkyl groups, wherein the weight ratio of the citrate based on low-carbon alkyl groups to the citrate based on high-carbon alkyl groups is 95:5 to 10:

90.

2. As claimed in claim 1, wherein the weight ratio of the total of the non-mixed citrate esters to the total of the mixed citrate esters is 80:20 to 5:

95.

3. As in the purpose of request item 1, wherein, The plasticizer composition is present in a concentration of 5 to 150 parts by weight, based on 100 parts by weight of a linear vinyl chloride polymer.

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