Plasticizer blend of 2-ethylhexyl methyl terephthalate and bis(2-ethylhexyl) terephthalate

Abstract

This invention provides a plasticizer for plastic materials such as polyvinyl chloride (PVC). The plasticizer is a blend of di-(2-ethylhexyl) terephthalate (DOTP) and methyl 2-ethylhexyl terephthalate (MOTP). The blend of DOTP and MOTP provides a non-phthalate alternative to plasticizers such as diisononyl phthalate and also produces favorable melt temperature, gel point, plastisol viscosity, efficiency, plasticizer compatibility, and drying time properties.

Description

Technical Field

[0001] This invention relates to plasticizers, and more particularly to mixtures of di-(2-ethylhexyl) terephthalate (DOTP) and 2-ethylhexylmethyl terephthalate (MOTP) and their use as plasticizers. Background Technology

[0002] Phthalate esters (1,2-phthalates) have historically been used as additives in plastics to make them softer and more flexible. Some phthalates have been linked to health problems, depending on their specific chemical structure. Diisononyl phthalate (DINP) is a commonly used plasticizer; however, due to human health concerns, plastic manufacturers have been searching for non-phthalate alternatives to DINP. Di-(2-ethylhexyl) terephthalate, also known as dioctyl terephthalate or DOTP, is used as a plasticizer in a variety of polymer materials. Terephthalates are 1,4-phthalates and are toxicologically less harmful than phthalates. DOTP is considered an alternative plasticizer to diisononyl phthalate (DINP). DOTP is available from Eastman Chemical Company under EASTMAN 168. TM Commercial purchase. EASTMAN 168 TM It contains more than 97 wt% DOTP and less than 3 wt% 2-ethylhexyl methyl terephthalate (MOTP) as trace components generated during the manufacturing process.

[0003] DOTP's performance is not always sufficient to replace DINP in many flexible polymers such as polyvinyl chloride (PVC). A unique non-phthalate plasticizer is needed that can be used in materials such as PVC to replace DINP.

[0004] The inventors have discovered a new alternative to DINP: a blend of di-(2-ethylhexyl) terephthalate (DOTP) and greater than 3 wt% of methyl 2-ethylhexyl terephthalate (MOTP). The MOTP and DOTP plasticizer blend exhibits better performance than commercially available DOTP and is a viable alternative to DINP. Summary of the Invention

[0005] In one embodiment, the present invention is a plasticizer comprising less than 97 wt% of di-(2-ethylhexyl) terephthalate and more than about 3 wt% of 2-ethylhexyl methyl terephthalate, wherein the total weight percentage of di-(2-ethylhexyl) terephthalate and 2-ethylhexyl methyl terephthalate is equal to 100 wt%.

[0006] In another embodiment, the present invention is a plasticizer comprising about 4 wt% to 60 wt% of 2-ethylhexyl methyl terephthalate and about 96 wt% to 40 wt% of di-(2-ethylhexyl) terephthalate, wherein the total weight percentage of di-(2-ethylhexyl) terephthalate and 2-ethylhexyl methyl terephthalate is equal to 100 wt%.

[0007] In another embodiment, the present invention is a plasticizer comprising about 20 wt% to 25 wt% of 2-ethylhexyl methyl terephthalate and about 80 wt% to 75 wt% of di-(2-ethylhexyl) terephthalate, wherein the total weight percentage of di-(2-ethylhexyl) terephthalate and 2-ethylhexyl methyl terephthalate is equal to 100 wt%.

[0008] In another embodiment, the present invention is a composition comprising one or more liquid plasticizers in combination with PVC resin and other standard formulation additives, wherein the plasticizer composition is:

[0009] a) A plasticizer comprising 20 wt%-25 wt% of 2-ethylhexyl methyl terephthalate and 80 wt%-75 wt% of di-(2-ethylhexyl) terephthalate, wherein the total weight percentage of di-(2-ethylhexyl) terephthalate and 2-ethylhexyl methyl terephthalate is equal to 100 wt%; and

[0010] b) Optionally, one or more compounds selected from the group consisting of: dioctyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, dibutyl terephthalate, diisobutyl terephthalate, dioctyl terephthalate, diisodecyl phthalate, diundecyl phthalate, trioctyl trimellitate, diisononyl cyclohexanediol, epoxidized soybean / tall oil, epoxidized linseed oil, pentaerythritol tetravalerate, dioctyl adipate, polymers formed by polymerization of a diol with one or more of adipic acid, phthalic acid and sebacic acid, triethyl citrate, triethyl acetylic acid, tributyl citrate, tributyl acetylic acid, and compounds formed by polymerization of benzoic acid and C7-C 12 Benzoate esters obtained by reacting linear / branched alkyl residues within the range, C2-C8 linear / branched diols / diols. Detailed Implementation

[0011] definition

[0012] Throughout this specification and the following claims, reference will be made to a number of terms which will be defined to have the following meanings.

[0013] A value can be expressed as “about” or “approximately” to a given number. Similarly, a range can be expressed herein as “about” to a particular value and / or to “about” or another particular value. When such a range is expressed, the other side includes from one particular value and / or to another particular value. Likewise, when a value is expressed as an approximation using the antecedent “about”, it should be understood that a particular value forms the other side.

[0014] As used herein, the terms “a / an” and “the / described” mean one or more species.

[0015] As used herein, the term “and / or” when used in a series of two or more items means that any one of the listed items may be used alone, or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B and / or C, the composition may contain A alone; B alone; C alone; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B and C.

[0016] As used herein, the term “comprising”, “comprises”, or “comprise” is an open-ended transitional term used to transition from a subject described before the term to one or more elements described after the term, wherein the one or more elements listed after the transitional term are not necessarily the only elements constituting the subject.

[0017] As used in this article, the term “having” (“having”, “has”, “have”) has the same open-ended meaning as “containing” provided above.

[0018] As used in this article, the term “including”, “includes”, “include” has the same open-ended meaning as “comprising”, “comprises”, “comprise” provided above.

[0019] As used in this article, “selected from” can be used with “or” or “and”. For example, “Y selected from A, B and C” means that Y can be A, B or C alone. Or, “Y selected from A, B or C” means that Y can be: A, B or C alone; or a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B and C.

[0020] As used herein, the term "fast-melting plasticizer" is defined as follows. For most applications, the plasticizer reference standard is di-2-ethylhexyl phthalate (DEHP), as it has been the most widely used plasticizer since its commercialization in the late 1930s. A plasticizer that melts at a lower temperature than the temperature required for DEHP at the same concentration in a given polymer system is considered a "fast-melting plasticizer." Similarly, a plasticizer that melts at a higher temperature than the temperature required for DEHP at the same concentration in a given polymer system is considered a "slow-melting" plasticizer.

[0021] invention

[0022] Existing non-phthalate plasticizer options (DOTP, DINCH) provide adequate, but not particularly outstanding, plasticizer properties in blends with PVC. Some processes using phthalate plasticizers, required to switch to non-phthalate plasticizers for regulatory reasons, often necessitate modifications to their manufacturing processes to accommodate the reduced performance of non-phthalate plasticizers. In such processes, fast-melting plasticizers are frequently added to formulations to achieve desired properties, leading to increased formulation costs. Measurable properties in typical PVC processes include melt temperature, gel point, plastisol viscosity, efficiency, plasticizer compatibility, and drying time. Compared to existing non-phthalate plasticizers, this invention delivers the desired lower melt temperature and gel point, lower plastisol viscosity, higher efficiency, better plasticizer compatibility, and shorter drying time.

[0023] The plasticizer invention disclosed herein is a reaction product of dimethyl phthalate (DMT) and 2-ethylhexanol, as shown in the following reaction.

[0024]

[0025] The reaction is not allowed to proceed to completion. Instead, the reaction is stopped when the final product contains approximately 20% monoester. In MOTP-rich blends, monoesters, 2-ethylhexyl terephthalate (MOTP), and DOTP are better plasticizers than diesters and DOTP when used alone or in plasticizer blends containing only small amounts (i.e., <3 wt%) of MOTP.

[0026] The properties of plasticizers are directly related to the level of MOTP in the product. Therefore, the useful range of MOTP in MOTP / DOTP plasticizer blends is expected to be approximately 3 wt%–60 wt% MOTP and approximately 97 wt%–40 wt% DOTP. The optimal range of MOTP in MOTP / DOTP plasticizer blends is approximately 20 wt%–25 wt% MOTP and approximately 80 wt%–75 wt% DOTP.

[0027] This plasticizer blend is expected to be used in a wide range of PVC dispersions, suspensions, and blended resins, such as resins having molecular weights defined by a K-value range, including K = approximately 60 to 84, and resin particle sizes ranging from about 0.5 micrometers to 5 micrometers. The plasticizer blend is also expected to be used in PVC resins in which up to 10% of the vinyl chloride content is replaced by vinyl acetate or C1-C3 acrylates.

[0028] Hydrogenation of terephthalates induces chirality in the resulting cyclohexanedicarboxylate product. If the alkyl chain of the terephthalate is longer than two carbons, the cis / trans ratio obtained in the cyclohexanedicarboxylate product is approximately 45:55. It is known in the art that, from a plasticizer perspective, the cis isomers of cyclohexanedicarboxylate perform slightly better than the trans esters. It is also known in the art that 1,4-disubstituted cyclohexanedicarboxylates have better UV stability than their 1,4-disubstituted terephthalate analogs. Regarding the UV degradation performance of the hydrogenated version of the invention, while its performance is indeed superior to that of the general plasticizer DOTP and the present invention, the improved performance is insufficient to warrant further investigation. It should be noted that the hydrogenated version of the invention does not provide significant performance improvements in terms of gel point or melting temperature. It is also important to point out that hydrogenated analogs of MOTP have considerable volatility, which may not be a desirable property in PVC plasticizers. Therefore, blending the hydrogenated material with other plasticizers and other standard PVC formulation components would be a reasonable approach to obtain the desired performance.

[0029] Example

[0030] The invention can be further illustrated by the following examples, but it should be understood that, unless otherwise expressly stated, these examples are included for illustrative purposes only and are not intended to limit the scope of the invention.

[0031] abbreviation

[0032] mL is milliliters; wt% is weight percentage; eq is equivalent; hrs or h is hours; mm is millimeters; m is meters; GC is gas chromatography; ℃ is degrees Celsius; ℉ is degrees Fahrenheit; rt is room temperature; min is minutes; tR is retention time; g is grams; mmol is millimoles; mol is moles; kg is kilograms; L is liters; w / v is weight / volume; μL is microliters; Tg is glass transition temperature; MW is molecular weight; phr is parts per hundred parts of resin.

[0033] General synthesis procedure

[0034] In a round-bottom flask equipped with a Dean-Stark apparatus, 2-ethylhexyl-1-ol (820.5 g, 6.3 mol), dimethyl terephthalate (582.6 g, 3 mol), and tetraisopropyl titanate (0.27, 200 ppm) were combined. The reaction mixture was heated to 170 °C to remove methanol. After recovering an appropriate amount of methanol, the %MOTP of the reactants was sampled (20.22%). The reaction was maintained for 30 min, and the %MOTP was sampled again (21.14%). The resulting crude product was treated with a 2.5% NaOH aqueous solution, and the mixture was heated at 90 °C for 30 min. The aqueous layer was separated, and the organic layer was treated with water (300 g), and the mixture was heated at 90 °C for 30 min. The crude organic layer still contained excess residual DMT (>1.0%). A second alkaline wash was performed, reducing the residual DMT to 0.04%. The organic layer was separated, and the organic matter was filtered through diatomaceous earth. The organic layer was then concentrated under vacuum (~3 mmHg) for 20 minutes. The material was then treated with activated carbon (0.5 g) and stirred at 90 °C for 30 min. The mixture was then filtered through diatomaceous earth to obtain a product containing 24.55 wt% MOTP and 75.45 wt% DOTP.

[0035] Plasticized sols were prepared by combining the components of the formulation shown in Table 1 into a suitable Flack Tek mixing container. A Flack Tek DAC 600.2VAC Speed ​​Mixer was used. TM Stir each sample at 1600 rpm for 40-second intervals. Monitor the temperature between mixing intervals to ensure it does not rise above 95℉. Once the samples are thoroughly mixed to a uniform consistency, degas them under vacuum (~75 Torr) at 1000 rpm for 5 minutes. Once prepared, the plastisol is evaluated multiple times to assess viscosity, gel point, and melt temperature. The plastisol can then be melted at different temperatures to produce PVC films and components for subsequent testing.

[0036] Table 1: Standard plastisol formulations used in the study.

[0037] Components Phr plasticizer 60 Geon 121A (PVC homopolymer dispersion resin) 100 Drapex 6.8 (Epoxidized Soybean Oil) 3 Akcrostab LT-4798 (stabilizer) 3

[0038] The viscosity of the plastisol was measured using a parallel plate rheometer. At 25°C, the viscosity ranged from 0.1 to 100 seconds. -1 Shear scans were performed between samples. The sample gap was set to 500 micrometers. The viscosity of the plastisol was measured at two different time intervals: 24 hours and 168 hours. (The measurement was taken in 10 seconds.) -1 The observed viscosity was closely correlated with the viscosity obtained at 10 RPM using a Brookfield viscometer. The results are shown in Table 2 below. This invention demonstrates a significant reduction in viscosity compared to DINP, and also exhibits better viscosity than Eastman 168. TM Lower viscosity.

[0039] Table 2: Viscosity of Plasticized Sol

[0040]

[0041] gel point

[0042] Melting results were determined using a parallel plate rheometer according to ASTM D2538. Samples were analyzed on a TA Instruments DHR-1 parallel plate rheometer equipped with an environmental testing chamber, a 25 mm parallel plate geometry, and a 1000 μm gap. Temperature scans from 40 to 150 °C were performed in oscillating mode at a heating rate of 5 °C / min. The temperature at the intersection of the G' / G” curves was used as an indication of the “gelation” point. The temperature at which the complex viscosity was maximized was taken as the melting temperature. See Table 3 for comparison with DINP and Eastman 168. TM In comparison, the present invention has a significantly lower gel point and melting temperature.

[0043] Table 3: Melting Characteristics

[0044] plasticizer gelation point (°C) Melting temperature (°C) DINP 74 131 <![CDATA[Eastman 168 TM ]]> 73 132 20% MOTP 67 120

[0045] efficiency

[0046] Efficiency is the degree to which the plasticizer softens molten PVC parts, defined by a hardness value. Shore A hardness was determined according to ASTM D2240. Molten parts were prepared using 25g of plasticizer sol in a circular button mold. The parts were melted at 375℉ for 30 minutes, removed from the mold, and allowed to equilibrate at room temperature for 24 hours. Hardness was measured on a Rex hardness tester. The instrument was calibrated for the expected hardness range using appropriate calibration standards. Table 4 below shows the efficiency results. This invention has a lower Shore A hardness value, indicating compliance with DINP and Eastman 168. TM It has higher efficiency compared to other methods.

[0047] Table 4: Shore A Hardness

[0048] plasticizer Xiao's A DINP 72.5 <![CDATA[Eastman 168 TM ]]> 72.8 20% MOTP 70.8

[0049] The drying time of dry blend formulations is an indicator of the compatibility of the plasticizer with the PVC resin. Drying time is evaluated using ASTM D2396. At a given temperature, the dry components are mixed in a torque rheometer drum for a specified time period. The plasticizer is then dispersed into the dry components, and changes in torque are monitored to determine the drying time. Table 5 below shows the drying time results. This invention has advantages over DINP and Eastman 168. TM Both have significantly shorter drying times.

[0050] Table 5: Drying Time

[0051] plasticizer Drying time (mins) DOTP 3.57 DINP 3.27 20% MOTP 2.83

[0052] Optimal concentration

[0053] The performance of this invention is directly related to the amount of MOTP present. (Commercial Eastman 168) TM The product contains less than about 3 wt% MOTP. Increasing the amount of MOTP in this invention has several positive aspects: lowering the gel point and melt temperature of a given formulation, reducing the viscosity of the plasticized sol, shortening drying time, and improving efficiency. However, increasing the level of MOTP can also negatively impact the volatility of the product. Depending on the manufacturing process, volatility may be undesirable behavior in plasticizers. Therefore, the optimal amount of MOTP will be a balance between positive performance properties and volatility. The ultimate goal of this performance is to meet / exceed the performance of the currently popular phthalate plasticizer DINP. Therefore, the desired MOTP weight percentage will be the proportion that provides performance equal to or exceeding that of DINP. Table 6 below shows the effect of increasing the MOTP level on volatility, determined by EPA Method 24. EPA Method 24 is a gravimetric analysis in which the sample is held at 110°C for one hour.

[0054] Table 6: Volatility of Method 24

[0055] VOC (wt%) EPA 24 DINP 0.18 168 0.35 10% MOTP 0.69 20% MOTP 0.91 40% MOTP 1.52 60% MOTP 2.11

[0056] A series of samples were prepared with increased amounts of MOTP. The melt characteristics of the plastisol were tested to determine the effect of MOTP concentration on gel point and melt temperature. When plotted, the data showed a linear correlation between gel point, melt temperature, and MOTP concentration. Since the goal is to produce a product that just exceeds DINP performance, an MOTP loading of approximately 20% appears to be a good target, providing enhanced plasticizer properties without a significant increase in volatility. Table 7 below shows the effect of MOTP concentration on melt characteristics.

[0057] Table 7: Effect of MOTP on melting properties

[0058]

[0059]

[0060] For plastisol viscosity, increasing the level of MOTP will decrease viscosity, but based on melt results, levels above 20% offer little value. Similarly, the optimal balance between melt performance, viscosity reduction, and volatility appears to lie within the 20% MOTP range. Table 8 shows the effect of MOTP concentration on viscosity.

[0061] Table 8: Viscosity vs. % MOTP

[0062]

[0063] Exudation tests were conducted according to ASTM D3291. The plasticized sol film was melt-melted at 375℉ for 15 minutes using a Mathis furnace. The film was allowed to equilibrate under ambient conditions for 24 hours before being cut into 1” x 1.5” strips. Twelve strips were cut for each formulation, with four strips used at each time interval. Exudation levels were semi-quantitatively assessed on a scale of 1–3, with 3 being the worst. The average results are shown in Tables 9 / 10 / 11. The 20% MOTP product showed the best compatibility within the wt%.

[0064] Table 9: 4-hour circumferential precipitation

[0065] CTRL 10% MOTP 20% MOTP 40% MOTP 60% MOTP 2 2 1 1 2 2 2 1 1 2 2 2 1 1 2 3 2 1 1 2 2.25 2 1 1 2

[0066] Table 10: 24-hour circumferential precipitation

[0067] CTRL 10% MOTP 20% MOTP 40% MOTP 60% MOTP 3 3 2 2 3 3 3 2 2 3 3 3 2 3 3 3 3 2 3 3 3 3 2 2.5 3

[0068] Table 11: 7-day circumferential precipitation

[0069] CTRL 10% MOTP 20% MOTP 40% MOTP 60% MOTP 3 3 1 1 3 3 3 1 1 3 3 3 0 1 3 3 3 0 1 3 3 3 0.5 1 3

[0070] As mentioned above, MOTP and DOTP plasticizer blends have better performance than commercially available DOTP and are a viable alternative to DINP.

[0071] Certain embodiments of the invention have been disclosed in the specification, and although specific terminology has been used, it is used in a general and descriptive sense only and not for limiting purposes. The scope of the invention is set forth in the appended claims.

Claims

1. A plasticizer comprising 20 wt%-25 wt% of 2-ethylhexyl methyl terephthalate and 80 wt%-75 wt% of di-(2-ethylhexyl) terephthalate, wherein the total weight percentage of di-(2-ethylhexyl) terephthalate and 2-ethylhexyl methyl terephthalate is equal to 100 wt%.

2. A composition comprising: A. PVC resin; and B. Plasticizer blends, comprising: a) 20wt%-25wt% of 2-ethylhexyl methyl terephthalate and 80wt%-75wt% of di-(2-ethylhexyl) terephthalate, wherein the total weight percentage of di-(2-ethylhexyl) terephthalate and 2-ethylhexyl methyl terephthalate is equal to 100wt%; and b) Optionally, one or more compounds selected from the group consisting of: dioctyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, dibutyl terephthalate, diisobutyl terephthalate, dioctyl terephthalate. Diisodecyl phthalate, Diundecyl phthalate, Trioctyl trimellitate Diisononyl cyclohexanedicarboxylate, epoxidized soybean / tal oil, epoxidized linseed oil Pentaerythritol tetravalerate, dioctyl adipate, polymers formed by the polymerization of diols with one or more of adipic acid, phthalic acid, and sebacic acid, triethyl citrate, triethyl acetyl citrate, tributyl citrate, tributyl acetyl citrate, polymers formed by the polymerization of benzoic acid and C7-C 12 Benzoate esters obtained by reacting linear / branched alkyl residues within the range, C2-C8 linear / branched diols / diols.

3. The composition according to claim 2, wherein the plasticizer is present in an amount of 5-500 parts per 100 parts (Phr) of resin.

4. The composition of claim 2, wherein the PVC resin has a molecular weight defined by a K value range, the K value range including K = 60 to 84, and b) the resin particle size is in the range of 0.5 micrometers to 5 micrometers.

5. The composition according to claim 2, wherein the PVC resin has up to 10% vinyl chloride content replaced by vinyl acetate or C1-C3 acrylate.

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