Improved tin stabilizers for post-halogenated polymers

Abstract

The present invention relates to stabilized chlorinated polyvinyl chloride (CPVC) polymer formulations and the stabilizers used therein. The stabilization is achieved by using sulfide-containing organotin species in conjunction with co-stabilizers and organic extenders that provide increased thermal stability compared to conventional organotin stabilizers.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 482,144, filed January 30, 2023. Priority to U.S. Provisional Patent Application No. 63 / 482,144, filed January 30, 2023, is hereby claimed.

[0002] 1. Field of the Invention The present invention relates to a stabilizer composition for subsequently halogenated halogen-containing polymers. More particularly, the present invention relates to a heat stabilizer for subsequently halogenated halogen-containing polymers, such as chlorinated polyvinyl chloride (CPVC). [Background technology]

[0003] 2. General Background of the Invention Polyvinyl chloride (PVC) is a thermally unstable polymer at conventional processing temperatures, and many stabilizer systems are available to address its inherent thermal instability. One way to ameliorate the inherent instability of PVC is to subject the polymer to a post-halogenation treatment, thereby producing chlorinated PVC, or CPVC. The resulting polymer has advantages over PVC that are well known to those skilled in the art; see, for example, U.S. Pat. Nos. 4,006,126; 4,039,732; and 4,350,798.

[0004] CPVC can be processed in the same ways as PVC, and stabilization techniques originally developed primarily for PVC have been successfully employed to improve the stability of CPVC. Stabilizer systems based on dibutyltin bis(ethylhexyl mercaptoacetate), also known as dibutyltin bis(EHMA), have dominated CPVC for many years, although other tin-based systems, such as those based on the dimethyl and di-octyl analogs of the dibutyl species, have also found use.

[0005] Heat stabilizers for PVC have been the subject of extensive research for over 70 years, with various ligands, alkyl groups, and extenders / co-stabilizers developed and optimized for specific applications. The use of sulfides as ligands in PVC heat stabilizers (known as "sulfiding") has primarily been applied in pipe and substrate applications as co-ligands with reverse esters. While sulfiding allows manufacturers to obtain lower-cost PVC stabilization systems, performance compared to traditional ligands such as EHMA typically suffers in terms of improved long-term stability. CPVC typically presents even greater challenges than PVC for successful processing, and much effort has been expended to efficiently process CPVC. Therefore, improvements in the long-term stability of known CPVC-based formulations are welcomed by processors.

[0006] In the field of PVC stabilization, there are several techniques to enhance one or more aspects of stabilization performance, including, but not limited to, the use of co-stabilizers, the use of excess free ligand (U.S. Pat. No. 6,919,392 B1), changing the ratio of mono-alkyl to di-alkyl components (mono / di ratio), and increasing the tin content by "sulfurization" (PVC Handbook, Wilkes, 2005). More specifically, so-called "sulfurization" refers to the process by which a certain amount of ligand in a given stabilizer is converted to tin, formally S 2- This technique involves synthetically replacing the sulfur compounds by the addition of a sulfide source, represented as Bu2Sn(EHMA)2. This addition can be accomplished by several methods known to those skilled in the art, and the resulting new stabilizers have higher sulfur and tin contents than the non-sulfurized reference stabilizers. In the systems under study, the reference compounds are Bu2Sn(EHMA)2 and Bu2Sn(EHMA) 2-2x (S) x (where x is typically in the range of 0.1 to 0.45).

[0007] The use of sulfide-based stabilizers in PVC typically improves early- and mid-life color compared to their non-sulfide counterparts, but not long-term stability. Sulfiding primarily finds application in reverse ester stabilizers for pipe applications, where sulfurized stabilizers can offer economic advantages over their non-sulfide counterparts. Because PVC and CPVC typically react similarly for stabilization, sulfide-based stabilizers are expected to provide similar results in CPVC stabilization. However, contrary to this expectation, the stabilizers of the present invention surprisingly improve long-term stability in CPVC formulations alone and can further enhance performance when used in combination with a range of extenders.

[0008] The following PCT applications are incorporated herein by reference: WO 2001 / 66638 "HALOGEN CONTAINING POLYMER COMPOUNDS CONTAINING MODIFIED ZEOLITE STABILIZERS". [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 4,006,126 [Patent Document 2] U.S. Patent No. 4,039,732 [Patent Document 3] U.S. Patent No. 4,350,798 [Patent Document 4] U.S. Patent No. 6,919,392 [Patent Document 5] International Publication No. 2001 / 66638 [Non-patent literature]

[0010] [Non-Patent Document 1] PVC Handbook, Wilkes, 2005 Summary of the Invention [Means for solving the problem]

[0011] The present invention includes compositions containing known post-halogenated halogen-containing polymer stabilizers that have been improved by sulfiding and weight-extension to enhance performance without increasing the tin content of the stabilizer. Known stabilizers include high dibutyltin bis(EHMA) and dimethyl and di-octyl analogs of these stabilizers. Thermolite® 31, an example of a commercially available high dibutyltin bis(EHMA) stabilizer, was used in Test 1, detailed below. However, one skilled in the art will understand that other equivalent stabilizers can be used with the same or similar results.

[0012] The present invention also includes methods of using the novel stabilizers to improve the long-term stability of subsequently halogenated halogen-containing polymers. The tests described below were conducted using representative CPVC formulations detailed in Table 3. Continued testing with other commercially available CPVC compounds is expected, and identical or similar results are anticipated. Additionally, other subsequently halogenated halogen-containing polymers are expected to produce identical or similar results. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention comprises novel stabilizers for use in the preparation of post-halogenated halogen-containing polymers. Although the examples and tests were performed with CPVC, it is expected that other post-halogenated polymers will exhibit the same or similar behavior.

[0014] The novel stabilizers of this invention are made by sulfurizing a conventional high-di-EHMA stabilizer and extending it with a conventional organic extender. The resulting stabilizers have demonstrated improved long-term stability of subsequently halogenated, halogen-containing polymers, in some cases by more than 50%.

[0015] The present invention also includes methods for improving the long-term stability of CPVC using the novel stabilizers described herein.

[0016] The present invention also includes the resulting CPVC compounds containing the novel stabilizers described herein. [Example]

[0017] Example 1: A common stabilizer used in PVC is Thermolite® 31, available from PMC Organometallix, Inc. A sulfurized version of this stabilizer, Stabilizer B (BuSnS x (EHMA) 2-2x A series of stabilizers (defined as Stabilizer B) were prepared and their usefulness investigated in PVC formulations (Table 1). Their performance was compared to Thermolite® 31 and extensions (i.e., a combination of Stabilizer B and an organic liquid to reduce the tin content to that of the original stabilizer, Thermolite® 31). A common method for assessing the thermal stability of PVC involves processing the compound in Brabender®, extracting samples at predetermined times, and obtaining color readings in a predetermined color space. For the samples tested here, the CIE color space was used, with particular focus on the b-scale. See Table 2.

[0018] In a representative PVC formulation shown in Table 1, Stabilizer B provided poorer color control and shorter long-term stability compared to the non-sulfurized control, Stabilizer A. Attempts to improve the performance of Stabilizer B with organic extenders, Extender 1 epoxidized soybean oil (ESBO) and Extender 2 dodecyl mercaptan (DDM), were unsuccessful. Similar results were expected in CPVC.

[0019] In contrast to the findings in PVC, Stabilizer B, alone or in combination with extenders, was determined to provide surprisingly improved thermal stability performance in CPVC systems. Tables 4 and 5 summarize the formulations tested, and Tables 6 and 7 summarize the results of the Brabender tests for long-term stability.

[0020] A. High dibutyltin EHMA / sulfide synthesis, stabilizer B 151.8 grams (1 equivalent), 120.5 grams (0.59 equivalents) of dibutyltin dichloride, and 50 grams of water were added to a reactor and stirred. 104 grams (0.523 equivalents) of 20% aqueous sodium hydroxide was added to this mixture over approximately 10 minutes. A mixture of 37.1 grams (0.45 equivalents) of 35% aqueous sodium hydrogen sulfide and 45.0 grams (0.225 equivalents) of 20% aqueous sodium hydroxide was prepared and added to the reactor over approximately 10 minutes with continued stirring. The pH was adjusted to 4.5-5.5 with additional 20% aqueous sodium hydroxide. Stirring was continued and the pH was maintained for 30 minutes. The reaction mixture was transferred to a separatory flask and allowed to settle for 60 minutes. The lower organic (product) phase was transferred to the reactor. The material was stirred and heated to 100°C while vacuum was applied. The mixture was cooled to room temperature and filtered through a filter aid, yielding a clear product.

[0021] This method of sulfurizing high di(EHMA) stabilizers is provided as an exemplary method, and it will be understood by those skilled in the art that other known sulfurization methods can be used to obtain equivalent sulfide stabilizers.

[0022] In this test, the sulfurized high dibutyltin bis(EHMA) stabilizer, "Stabilizer B," contained 24.5% tin and 13.7% mercaptosulfur. It is expected that other resulting compositions will produce the same or similar results.

[0023] B. PVC Compound Formulation: PVC resin SE-950 available from Shintech Corp., Thermolite® 31 available from PMC Organometallix, Inc., lubricant package Advalube® 3315 available from PMC Biogenix, Inc., impact modifier Durastrength® 535 available from Arkema Inc., calcium carbonate Omyacarb® FT available from Omya Corp., titanium dioxide R101 available from Dupont de Nemours, and commercially available dodecyl mercaptan (DDM) and epoxidized soybean oil (ESBO) were used in the PVC formulation of Example 1. Later equivalent or alternative brands of these components may also be used.

[0024] Test conditions: The PVC compounds were blended at standard temperatures known to those skilled in the art according to a standard additive addition sequence. The PVC compounds were evaluated in a standard window profile formulation (see Table 1) compared to Thermolite® 31, a non-sulfided counterpart for PVC applications. The color stability of each compound was evaluated using a Brabender® operating at 190 degrees Celsius / 60 rpm with samples taken at 1-minute intervals. The color of each chip was measured in the CIE lab color space relative to a reference white tile, and the "b value" is reported in Table 2. All compounds were compared on an equal tin basis.

[0025] Stabilizer B did not provide improved color, as indicated by a higher b-value, compared to its non-sulfurized counterpart. Additionally, Stabilizer B did not provide improved long-term stability compared to Thermolite® 31. Attempts were then made to improve the performance of Stabilizer B using conventional organic extenders, in this case ESBO and DDM. These extenders again did not provide improved performance compared to Thermolite® 31 based on the b-values ​​and long-term stability in Table 2. Other conventional organic extenders known to those skilled in the art are expected to provide similar results. Thus, on an equal tin basis, neat or extended Stabilizer B did not provide any long-term stability improvement in PVC stability compared to Thermolite® 31.

[0026] C. CPVC Compound Compound CPVC, like its precursor PVC, is inherently unstable and requires the use of additives to enable its processing and the achievement of desired end-use physical properties. Representative CPVC formulations, outlined in Table 3, were used in the evaluation. It is expected that other CPVC formulations will yield similar results.

[0027] CPVC resin RB1167S, available from Lubrizol Corporation; processing aids Plasistrength® 551 and Plasistrength® 770 and impact modifier Clearstrength® 859, available from Arkema, Inc.; wax lubricants AC-617, AC-629, and AC-316, available from Honeywell International, Inc.; TiO2 from DuPont de Nemours, Inc.; and Irganox® 1010, available from BASF, were used in the CPVC compound formulations. It is expected that later equivalent or substitute brands will provide the same or similar results.

[0028] The CPVC compounds were blended according to standard additive addition order and temperature. The thermal stability of each CPVC compound was evaluated using a Brabender operating at 190°C / 50 rpm. Stabilizer performance was judged by the long-term stability achieved under these conditions.

[0029] Test conditions: In representative CPVC-based formulations shown in Table 3, Stabilizer B was evaluated against Thermolite® 31 (non-sulfided) at equal tin content. As detailed in Table 6, Stabilizer B provided only a slight improvement in long-term stability, within the experimental error of the test equipment. Subsequently, similar to the previous PVC work, Stabilizer B was evaluated using 20% ​​organic extender and mixtures of organic extenders in the stabilizer package; a summary of these stabilizer systems (all at equal tin) is shown in Table 4. These systems provided a meaningful increase in long-term stability compared to Thermolite® 31.

[0030] This series of tests continued with higher levels of organic filler (30% vs. 20%). Table 5 provides an overview of the stabilized systems, and Table 7 summarizes the long-term stability results for these systems using the Brabender® test. Thermolite® 31 and compounds 12 to 22 were run again with the same tin content (0.46% tin in the total formulation). Improved long-term stability was observed, with increases of up to 58%.

[0031] When sulfurized tin stabilizers are used in combination with extenders, improvements in long-term stability of greater than 50% have been achieved. This dramatic improvement allows converters to use higher temperatures and / or higher shear to increase productivity in CPVC processing. In addition, reprocessing CPVC with higher inherent stability allows converters a wider range of processing conditions. Alternatively, converters can choose to add lower levels of stabilizers and co-stabilizers to produce compounds at lower compounding costs without compromising product quality or extrusion speed.

[0032] [Table 1]

[0033] [Table 2]

[0034] [Table 3]

[0035] [Table 4]

[0036] [Table 5]

[0037] [Table 6]

[0038] [Table 7]

[0039] Further testing is expected to yield similar results.

[0040] Proposed Test 2 A. An elevated dimethyltin bis(EHMA) stabilizer, such as a sulfurized version of TM181FS commercially available from PMC Organometallix, Inc., is prepared and extended with a conventional organic extender as described in the previous examples to form "Stabilizer C."

[0041] B. Compare the performance of TM181FS or equivalent in PVC stabilization to Stabilizer C using the Brabender® and color scale as described in the previous examples.

[0042] C. Compare the performance of TM181FS or equivalent in CPVC stabilization to Stabilizer C using Brabender® and color scale as described in the previous examples. Additional testing may be performed on other commercial CPVC compositions not listed above.

[0043] As explained in the previous examples, Stabilizer C is expected to perform better than its non-sulfurized high dimethyltin bis(EHMA) counterpart in CPVC stabilization.

[0044] Proposed Experiment 3 A. An enhanced di-octyltin bis(EHMA) stabilizer, such as a sulfurized version of T890F commercially available from PMC Organometallix, Inc., is prepared and extended with a conventional organic extender as described in the previous examples to form "Stabilizer D."

[0045] B. Compare the performance of T890F or equivalent in PVC stabilization to Stabilizer D using Brabender® and color scale as described in the previous examples.

[0046] C. Compare the performance of T890F or equivalent in CPVC stabilization to Stabilizer D using Brabender® and color scale as described in the previous examples. Additional testing may be performed on other commercial CPVC compositions not listed above.

[0047] As illustrated in the previous examples, Stabilizer D is expected to be superior to its non-sulfurized high di-octyltin bis(EHMA) counterpart in CPVC stability.

[0048] The present invention includes a stabilizer for a post-halogenated halogen-containing polymer. In a preferred embodiment, the stabilizer comprises at least (a) dibutyltin bis(ethylhexyl mercaptoacetate) (dibutyltin bis(EHMA)), where the dibutyltin bis(EHMA) has a ligand, (b) where a portion of the ligand in the dibutyltin bis(EHMA) is synthetically substituted with sulfide, and (c) an organic stabilizer extender.

[0049] In some embodiments, the stabilizer comprises at least (a) dimethyltin bis(ethylhexyl mercaptoacetate) (dimethyltin bis(EHMA)), where the dimethyltin bis(EHMA) has a ligand, (b) where some of the ligands in the dimethyltin bis(EHMA) are synthetically substituted with sulfides, and (c) an organic stabilizer extender.

[0050] In some embodiments, the stabilizer comprises at least (a) dioctyltin bis(ethylhexylmercaptoacetate) (dioctyltin bis(EHMA)), where the dioctyltin bis(EHMA) has a ligand, (b) where some of the ligands in the dioctyltin bis(EHMA) are synthetically substituted with sulfide, and (c) an organic stabilizer extender.

[0051] In a preferred embodiment, the organic stabilizer extender in the stabilizer described above is (i) epoxidized soybean oil (ESBO) or (ii) dodecyl mercaptan (DDM).

[0052] The present invention also includes the use of the stabilizers of the present invention in the preparation of subsequently halogenated halogen-containing polymers. In a preferred embodiment, the method is used to stabilize subsequently halogenated halogen-containing polymers, more preferably the polymer is chlorinated polyvinyl chloride (CPVC).

[0053] The present invention also includes articles comprising post-halogenated halogen-containing polymers prepared using the stabilizers of the present invention. In a preferred embodiment, the article comprises CPVC as the post-halogenated halogen-containing polymer.

[0054] The present invention also provides compounds of formula R 4-2x-y Sn(S) x L y The sulfurized stabilizer composition includes a sulfurized stabilizer composition for stabilizing subsequently halogenated polymers, wherein the alkyl group and L are ligands. In a preferred embodiment, x in the formula is most preferably 0.05 to 0.75, and y is most preferably 1.5 to 2.8. However, broader ranges of x and y are also suitable, e.g., x is 0.01 to 1.5, and y is 0.5 to 4.0. In a preferred embodiment of the sulfurized stabilizer composition, R can be a linear or branched alkyl, and more preferably, the linear or branched alkyl is C1 to C10. In a preferred embodiment of the sulfurized stabilizer composition, L can be derived from conventional ligands used in tin-based heat stabilizers for subsequently halogenated polymers, preferably including, but not limited to, mercaptoesters, mercaptides, thioalcohols, and carboxylates.

[0055] The stabilizers of the present invention are preferably used as stabilizer systems to provide thermal protection to subsequently halogenated polymers, and may be used alone or in combination with other conventional heat stabilizers. In some embodiments, the stabilization system is used in combination with conventional organic or inorganic co-stabilizers, including but not limited to mercaptans, fatty acid esters, epoxidized fatty acids, and hydrocarbon oils and waxes. Preferably, these stabilization systems have a ratio of sulfurized tin-based component to organic extender of 1:1 to 5:1.

[0056] The tests and examples proposed above are based on conventional CPVC stabilizers. Further testing is expected to show that the same vulcanization and weighting process described will improve the performance of other PVC or halogen-containing polymer stabilizers for use with CPVC or other subsequently halogenated halogen-containing polymers. For example, crosslinked stabilizers may be vulcanized and, in some cases, weighted to enhance CPVC stability. Other stabilizers may be vulcanized and, in some cases, weighted to enhance CPVC stability.

[0057] The foregoing formulations are provided by way of example only and are not intended to limit the scope of the present invention. Those skilled in the art will appreciate that equivalents of the brands used in the foregoing tests and examples may be used to achieve the same or similar results. Additionally, continued testing as described herein may yield many more alternatives to these examples than are known to those skilled in the art.

Claims

1. 1. A stabilizer for a subsequently halogenated halogen-containing polymer, comprising: a. dibutyltin bis(ethylhexyl mercaptoacetate) (dibutyltin bis(EHMA)), wherein the dibutyltin bis(EHMA) has a ligand; b. wherein a portion of the ligand in the dibutyltin bis(EHMA) is synthetically substituted with sulfide; and c. Organic stabilizer extender A stabilizer, including

2. 1. A stabilizer for a subsequently halogenated halogen-containing polymer, comprising: a. dimethyltin bis(ethylhexyl mercaptoacetate) (dimethyltin bis(EHMA)), where the dimethyltin bis(EHMA) has a ligand; b. wherein a portion of the ligands in the dimethyltin bis(EHMA) are synthetically substituted with sulfide, and c. Organic stabilizer extender A stabilizer, including

3. 1. A stabilizer for a subsequently halogenated halogen-containing polymer, comprising: a. dioctyltin bis(ethylhexylmercaptoacetate) (dioctyltin bis(EHMA)), wherein the dioctyltin bis(EHMA) bears a ligand; b. wherein an amount of the ligands in the dioctyltin bis(EHMA) is synthetically substituted with sulfide, and c. Organic stabilizer extender A stabilizer, including

4. The stabilizer of any one of claims 1 to 3, wherein the extender is selected from the group consisting of epoxidized soybean oil (ESBO) or dodecyl mercaptan (DDM).

5. 4. Use of a stabilizer according to any one of claims 1 to 3 in the preparation of subsequently halogenated halogen-containing polymers.

6. 6. The method of claim 5, wherein the post-halogenated halogen-containing polymer is chlorinated polyvinyl chloride (CPVC).

7. An article comprising a subsequently halogenated halogen-containing polymer prepared using the stabilizer of any one of claims 1 to 3.

8. 8. The article of claim 7, wherein the post-halogenated halogen-containing polymer is CPVC.

9. Formula R ４－２ｘ－ｙ Sn(S) ｘ L ｙ 1. A sulfurized stabilizer composition for the stabilization of subsequently halogenated polymers of the formula: wherein R is alkyl and L is a ligand, x is 0.05 to 0.75, and y is 1.5 to 2.

8.

10. 10. The composition of claim 9, wherein R is a C1 to C10 linear or branched alkyl.

11. 10. The composition of claim 9, wherein L is from conventional ligands used in tin-based heat stabilizers for subsequently halogenated polymers, including, but not limited to, mercaptoesters, mercaptides, thioalcohols, and carboxylates.

12. 10. The stabilizer composition of claim 9 used as a stabilizer system to provide thermal protection to a subsequently halogenated polymer, used alone or in combination with other conventional heat stabilizers.

13. 13. The stabilization system defined in claim 12 used in combination with conventional organic or inorganic co-stabilizers, including but not limited to mercaptans, fatty acid esters, epoxidized fatty acids, and hydrocarbon oils and waxes.

14. 14. The stabilization system defined in claim 13, wherein the ratio of sulfurized tin-based component to organic extender is from 1:1 to 5:1.

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