WO2011046736A2

WO2011046736A2 - Use of epoxidized alkyl soyates to plasticize cellulose alkanoates

Info

Publication number: WO2011046736A2
Application number: PCT/US2010/050430
Authority: WO
Inventors: Shixiong Zhu; Roger W. Avakian
Original assignee: Polyone Corporation
Priority date: 2009-10-13
Filing date: 2010-09-27
Publication date: 2011-04-21
Also published as: WO2011046736A3

Abstract

Cellulose alkanoate resins are plasticized with epoxidized alkyl soyates. The soyate-plasticized cellulosics are more compatible than citrate-plasticized cellulosics and are totally bio-derived.

Description

USE OF EPOXIDIZED ALKYL SOYATES TO PLASTICIZE CELLULOSE ALKANOATES

CLAIM OF PRIORITY

[0001] This application claims priority from U.S. Provisional Patent

Application Serial Number 61/251,005 bearing Attorney Docket Number 1200912 and filed on October 13, 2009, which is incorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates to the use of soyates as plasticizers for cellulosic polymers.

BACKGROUND OF THE INVENTION

[0003] Plasticizers from petroleum feedstocks and other synthetic sources have been dominant in industry since the mid-Twentieth Century following the polymerization of vinyl chloride and a need to make that polyvinyl chloride flexible. Phthalate plasticizers have been most prevalent.

[0004] Other polymers which have benefited from plasticizers are cellulose alkanoates, such as cellulose triacetate, to render films of such polymers more flexible. For cellulosic polymer, citrates from synthetic sources have been most prevalent as plasticizers because of favorable performance and more recently, because of its renewable status and reduced biochemical effects.

[0005] Plasticizers from biological, renewable sources have been explored in recent years because of concerns about availability of petroleum feedstocks, cost, and asserted health concerns.

[0006] U.S. Pat. No. 6,797,753 (Benecke et al.) teaches the manufacture of a number of epoxidized esters from fatty acids, including epoxidized propylene glycol disoyate and epoxidized methyl soyate. SUMMARY OF THE INVENTION

[0007] What the art needs is a bio-derived plasticizer for use with cellulose alkanoates which out-performs even the currently used citrate plasticizers.

[0008] The present invention solves the problem in the art by using an epoxidized alkyl soyate, such as epoxidized methyl soyate, to plasticize cellulose alkanoate polymer resins at ambient temperature or at elevated temperature, depending on the particular soyate and the particular alkanoate.

[0009] Because the goal of any plasticizer is to associate with the polymer resin(s) and reduce flexural modulus, one would have thought that citrates would be fully vetted as suitable plasticizers for cellulose alkanoates. But as the Comparative Examples show below, citrates can be too aggressive and actually solvate the cellulose alkanoate polymer resin.

[00010] The theory most prevalent concerning plasticizers is that the continuum of concentric circles around a nominal polymer resin from a highly solvating plasticizer in the closest ring to a mere external lubricant at the outermost ring needs to be understood for each polymer resin, because the value of the plasticizer to associate with a polymer resin particle and render it less stiff exists between those extreme rings. The highly solvating plasticizer will dissolve the polymer resin. The external lubricant will not penetrate the particle of polymer resin. Neither is satisfactory for a plasticized polymer resin.

[00011] Moreover, whether a plasticizer is to be used alone or in combination with other plasticizers is quite dependent on whether the candidate plasticizer is to be the primary plasticizer or a secondary plasticizer.

[00012] There are several different interpretations about what constitutes a primary plasticizer. For purposes of this invention, a "primary" plasticizer will denote both the plasticizer with the largest mass component in the plasticized polymer composite and also the plasticizer with the most significant plasticizing effect on the polymer resin(s). [00013] Within the concentric circles of plasticization, for any given polymer or polymer family, only the brute force of experimentation will yield the data necessary to understand which plasticizers will work with which polymer resins. Often, the actual plasticization results are unpredictable and surprising because establishment of a solubility parameter scale, such as the Hillebrand Solubility Parameter, is an exercise in hindsight reconstruction of what actually exists, by application of a theory.

[00014] The technology is further complicated by different performances at different temperatures. Certainly, ambient temperature performance is vital for use, but also elevated temperature for plasticization is also vital for efficient manufacturing.

[00015] Unexpectedly, it has been found that epoxidized alkyl monosoyates are more effective as plasticizers than citrates, even though citrates have three ester moieties per molecule and monosoyates only one.

[00016] Even more unexpectedly, it has been found that a soyate, with a fatty acid carbon chain of about 16 to about 22 carbon atoms is a suitable plasticizer for a cellulose alkanoate, at all.

[00017] Therefore, one aspect of the present invention is a plasticized composite of bio-derived materials, comprising (a) a cellulose alkanoate resin and (b) an epoxidized methyl soyate plasticizer mixed sufficiently in the resin to reduce flexural modulus of the resin.

[00018] Another aspect of the present invention is a method of using an epoxidized alkyl soyate as a plasticizer for a cellulose alkanoate comprising the step of mixing the soyate with the alkanoate at a temperature sufficient to form a plasticized composite described above.

[00019] Another aspect of the present invention is an article of the plasticized composite described above.

[00020] Other features and advantages of the invention will be explained below, partially in relation to the drawings. BRIEF DESCRIPTION OF THE DRAWING

[00021] Fig. 1 is a graph of the results in Table 3 of plasticizer uptake at room temperature for Examples 1-3 and Comparative Examples A-C.

[00022] Fig. 2 is a graph of the results in Table 3 of plasticizer uptake at room temperature for Examples 4-6 and Comparative Examples D-F.

EMBODIMENTS OF THE INVENTION

[00023] Epoxidized Soyates

[00024] Any bio-derived epoxidized alkyl soyate is a suitable candidate for use in the present invention. It is understood that "soyate" is a carboxylate moiety which refers to any naturally occurring or subsequently refined mixture of fatty acids and their esters, where the fatty acids include stearic acid, oleic acid, linoleic acid, linolenic acid, and the like. Epoxidation of such fatty acid esters, such as methyl soyate, typically generates an epoxy group, also called a glycidyl group or oxirane ring, replacing a double bond in the fatty acid backbone.

[00025] The epoxidized alkyl soyate can be commercially purchased.

Non-limiting examples of epoxidized alkyl soyates include epoxidized methyl soyate, epoxidized ethyl soyate, epoxidized butyl soyate, epoxidized octyl soyate, and combinations thereof. Of these epoxidized methyl soyate (CAS No. 68082-35-9) is preferred.

[00026] A commercial source of epoxidized soyates is the Vikoflex^®

7010 brand epoxidized methyl soyate from Arkema of Philadelphia, PA and the reflex™ 100 brand epoxidized methyl soyate from PolyOne Corporation of Avon Lake, OH.

[00027] Epoxidized alkyl soyate, to be useful in the present invention, should have from about 0.5 to about 12, and preferably from about 5 to about 10 percentage epoxy groups in the molecule.

[00028] Production of Epoxidized Alkyl Soyates [00029] If the epoxidized alkyl soyate is to be made rather than purchased, then the epoxidized alkyl soyate can be a reaction product of epoxidized soybean oil with an alcohol such as methanol or other alkyl alcohol in the presence of a metallic hydroxide as a catalyst at a temperature of between 23°C - 45°C and a 1 atmosphere (ambient) pressure and 50% relative humidity for approximately 36 hours using a round bottom flask reaction vessel.

Epoxidized soybean oil (ESO), a known commercial commodity from biological origin. Another description of the synthesis of epoxidized methyl soyate can be found in Miyagowa et al., "Thermo-Physical and Impact

Properties of Epoxy Containing Epoxidized Linseed Oil, 1 Anhydride-Cured Epoxy" Macromol. Mater. Eng. 2004, 289, 629-635. Other teachings of possible reactions to form epoxidized alkyl soyates are found in U.S. Pat. No. 6,797,753 identified above.

[00030] Cellulose Alkanoate

[00031] Any cellulose alkanoate is a candidate for plasticization by epoxidized alkyl soyates. Among the better known cellulose alkanoates are cellulose acetate (CA), cellulose diacetate, cellulose triacetate, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB).

[00032] The cellulose alkanoates can have a number average molecular weight ranging from about 6,000 to about 150,000 and preferably from about 12,000 to about 75,000.

[00033] For CA, the weight percentage of acetyl groups can range from about 20 to about 50 and preferably from about 32 to about 43 weight percent. For CAP, the weight percentage of acetyl groups can range from about 0.5 to 5 about and preferably from about 2 to about 4 weight percent, and the weight percentage of propionyl groups from about 20 to about 50 and preferably from about 40 to about 50 weight percent. For CAB, the weight percentage of acetyl groups can range from about 2 to about 30, and the weight percentage of butyryl groups from about 15 to about 50. [00034] Each of CA, CAP, and CAB is available in powder form from

Aldrich Chemical. Another commercial source of CAP is Eastman Chemical of Kingsport, TN, but it has been noted that the commercial pelletized form includes a minor amount of plasticizer believed to be triethylene glycol bis(2- ethylhexanoate). Any commercially available source of cellulose alkanoate should take into consideration the possibility of a plasticizer therein.

[00035] Optional Ingredients

[00036] Additives to improve processing or performance of the concentrate of the cellulose alkanoate can be added according to preferences of those skilled in the art. For example, functional additives for cellulosics can include anti- oxidants, anti-stats, scavengers, blowing agents, biocides, exfoliated nanoclays, thickeners, colorants, and the like, and combinations thereof. Generally, minor amounts of such additives provide improvement of performance to the cellulosic resin during processing with the other ingredients or in performance of the cellulosic article after manufacturing. One skilled in the art without undue experimentation can determine the appropriate concentration.

[00037] Table 1 shows acceptable, desirable, and preferred ranges of the resin, plasticizer, and other ingredients.

[00038] Processing [00039] Mixing in a batch process typically occurs in a Banbury-type internal mixer operating at a temperature high enough to fuse, or flux, the combination of resin and plasticizer. The temperature can range from about 120°C to about 320°C and preferably from about 160°C to about 250°C. The mixing speeds are typically above 1000 rpm in order to mechanically heat the mixture above the fusion, or flux, point. The output from the mixer is a solid compound in chips or pellets for later extrusion into final profiled articles, molding into final shape articles, or calendering into a single layer have a thickness useful for sheets, tapes, and other thin final-shape articles.

[00040] Alternatively, a suitable solvent can be used in conjunction with the epoxidized alkyl soyate to dissolve the cellulose alkanoate, followed by casting of the liquid mixture onto a surface, and then removal of the volatile solvent to yield a plasticized film.

[00041] Moving from batch processing to continuous processing involves the use of an extruder or other continuous mixing equipment according to techniques known to those skilled in the art.

USEFULNESS OF THE INVENTION

[00042] Any product currently made from a citrate-plasticized cellulose alkanoate can now be made fully bio-derived with improved plasticization performance using an epoxidized alkyl soyate-plasticized cellulose alkanoate of the present invention.

[00043] Non-limited examples of uses of the epoxidized alkyl soyate- plasticized cellulose alkanoate include appliances, such as refrigerators, freezers, washers, dryers, toasters, blenders, vacuum cleaners, coffee makers, and mixers; building and construction, such as fences, decks and rails, floors, floor covering, pipes and fittings, siding, trim, windows, doors, molding, and wall covering; consumer products, such as hand tools, power hand tools, rakes, shovels, lawn mowers, shoes, boots, golf clubs, fishing poles, watercraft, and nail polish; electrical/electronic, such as printers, printing inks, computers, optical films, business equipment, LCD projectors, mobile phones, connectors, chip trays, circuit breakers, and plugs; pharmaceuticals; industrial, such as containers, bottles, drums, material handling, gears, bearings, gaskets and seals, valves, wind turbines, and safety equipment; packaging, such as food and beverage, cosmetic, detergents and cleaners, personal care, pharmaceutical and wellness; transportation, such as automotive aftermarket parts, bumpers, window seals, instrument panels, consoles, under hood electrical, and engine covers; and wire and cable insulating or jacketing for cars and trucks, airplanes, aerospace, construction, military, telecommunication, utility power, alternative energy, and electronics.

[00044] An especially desirable use is films, tapes, and sheets, particularly those with pressure-sensitive adhesive on one surface. Currently, many commercially available adhesive tapes made of cellulosic resins rely upon citrate plasticizers.

[00045] One reason for such usefulness versatility is that the plasticizer is fully bio-derived and the resin is also fully bio-derived. In the current marketplace, fully bio-derived polymer compounds are highly desired if their processing, performance, and cost are within currently acceptable ranges.

[00046] Subsequent extrusion or molding techniques are well known to those skilled in the art of thermoplastics polymer engineering. Without undue experimentation but with such references as "Extrusion, The Definitive Processing Guide and Handbook"; "Handbook of Molded Part Shrinkage and Warpage"; "Specialized Molding Techniques"; "Rotational Molding

Technology"; and "Handbook of Mold, Tool and Die Repair Welding", all published by Plastics Design Library (www.williamandrew.com), one can make articles of any conceivable shape and appearance using composites of the present invention.

[00047] Epoxidized alkyl soyate-plasticized cellulose alkanoate can be considered as a plastisol when flowable and the correct powder form of the cellulose alkanoate is used. An alkanoate plastisol can be formed into desired shapes using a variety of coating techniques, as known to those persons having ordinary skill in the art.

[00048] Dip Coating: When the plastisol coating becomes a functional part of the mold itself, the process is called dip coating. The metal insert may or may not have a requirement for an adhesive primer. Common uses include tool handles and grips; textiles; wire grates and baskets; plating racks; conveyor hooks; and the like. Dip coating can be either hot dipping or cold dipping.

[00049] Hot Dipping: By far the most common dip-coating processing technique, hot dipping requires an item to be heated first before immersion into the plastisol. The heat causes the plastisol coating to gel on the hot form.

[00050] Cold Dipping: Preheating the metal part is not required; the amount of pickup obtained depends largely on the viscosity and thixotropic ration of the plastisol.

[00051] Molding: Several types of molding are common to plastisol applications. Slush Molding is used to produce hollow, flexible items by filling a mold with plastisol, heating sufficiently to gel a layer next to the inner mold surface, and then draining the excess plastisol. The gelled layer is then completely fused and stripped from the mold. Rotational Molding involves hollow flexible or rigid forms with complex shapes. The process is done using a two-part mold filled with a predetermined weight of plastisol, inserted into a heated oven and rotated on two planes simultaneously. Dip Molding refers to the process of dipping a solid mold; gelling, fusing and stripping the hollow part. Open Molding is a process of molding directly in, or into, a finished article such as automotive air filters.

[00052] Other Coating and Casting: Several types of coating employ movement of the plastisol relative to the item or the item relative to the plastisol. Several types of casting employ flow of plastisol on to a stationary substrate. One skilled in the art readily can employ knife coating, roll coating, reverse roll coating, spin coating, solvent casting, etc. according to techniques taught in encyclopedias, other technical literature, or the patent literature, without undue experimentation.

EXAMPLES

[00053] Comparative Examples A-F and Examples 1-6

[00054] Table 2 shows the ingredients and their sources.

¹ average Mn -50,000 by GPC, 39.7 wt. % acetyl

² average Mn -75,000 by GPC, -2.5 wt. % Acetyl, -1.8 wt. % Hydroxyl, -46 wt. % Propionyl

³ average Mn -65,000 by GPC, 28.0-31.0 wt. % Acetyl, 16.5-19.0 wt. % Butyryl, 0.9-1.3 wt. % Hydroxyl

[00055] Table 3 shows the combinations of plasticizer and resin and the resulting compatibility properties. Each of the Examples and Comparative Examples underwent the following test for compatibility: the CAP and CAB resins were hot pressed at 200 °C, and CA resin was hot pressed at 250 °C into thin sheets of 0.5 mm thickness and then cut into approximately 5mm x 5mm squares and then saturated in 1 mL of plasticizer. Any weight gain was measured over the course of specific hours of saturation at both room

temperature and at a constant 50°C.

[00056] Fig. 1 shows the performance of Examples 1-3 and Comparative

Examples A-C at room temperature, approximately 17°C. Fig. 2 shows the performance of Examples 4-6 and Comparative Examples at 50°C.

[00057] Comparative Example G and Examples 7-9

[00058] Table 4 shows a test of the use of acetone as a solvent to help incorporate EMS in CA. CA was first dissolved in acetone at room temperature, and then EMS was added to the CAJ Acetone solution. The solution was then cast onto an aluminum pan to form a film. The majority of the acetone was then removed via evaporation at room temperature. To ensure all volatiles were evaporated, the subsequent film was then placed in vacuum oven for 48 hours at 23°C. Various properties were then measured.

[00059] All of the Examples 2, 3, 5, and 6 resulted in a cellulose alkanoate resin which had its flexural modulus reduced. The ambient temperature Examples 2-3 had at least 383 hours of plasticization and reduced flexural modulus. The 50°C temperature Examples 5-6 had at least 144 hours of plasticization. Examples 7-9 show that plasticization and reduced flexural modulus is possible via use of solvent to assist incorporation of the EMS into cellulose acetate, after it was learned that Examples 1 and 4 did not plasticize without solvent assistance.

[00060] Fig. 1 shows that, at room temperature, EMS in CA (Example 1) does not plasticize. Nonetheless, EMS can be incorporated by use of a solvent, as seen in Examples 7-9. EMS in CAP (Example 2) slowly plasticizes until after 216 hours when the weight gain increases to 50% and plateaus.

Nonetheless, EMS can be incorporated into CAP at higher temperatures because of higher solvation power at those higher temperatures, as seen in Fig. 2. EMS in CAB (Example 3) rapidly plasticizes until it triples in weight and plateaus. At room temperature, EMS has good compatibility with CAB

[00061] By comparison, citrate in CA does not plasticize at room temperature (Comparative Example A) without use of a solvent. Citrate in CAP (Comparative Example B) dissolves the CAP after 144 hours and before 216 hours. Likewise, citrate in CAB does the same thing (Comparative Example C).

[00062] Fig. 2 offers the same comparison as in Fig. 1, except at 50°C.

EMS in CA (Example 4) still does not plasticize, even at 50°C. As stated previously, EMS can be incorporated into CA by used of a solvent. The experiment was repeated for EMS in CA at 100°C and 125°C. No plasticization occurred, indicating that heat alone would not be enough to EMS to plasticizer CA.

[00063] EMS in CAP (Example 5) rapidly plasticizes until after 300 hours when the weight gain increases to 400% and plateaus. This is also OK because in comparison to the room temperature performance, EMS in CAP has a significantly increased solvation power at 50°C. It is quite common that platicizers are incorporated into resin at elevated temperatures.

[00064] EMS in CAB (Example 6) again rapidly plasticizes until it quadrupled in weight and then dissolved. Of the three alkanoates, CAB can be employed with EMS as the plasticizer at room temperature rather than elevated temperatures, making it a candidate for use as a plastisol for the coating techniques described above, such as slush molding and dip coating.

[00065] By comparison, citrate in CA does not plasticize at 50°C and actually loses weight (Comparative Example D) because CA was slowly dissolved in citrate. Citrate in CAP (Comparative Example E) dissolves the CAP after 45 hours and before 144 hours. More abruptly, citrate in CAB dissolves the CAB before 45 hours have elapsed (Comparative Example C).

[00066] From a comparison of Examples 4-6 to Comparative Examples

D-F, it can be stated that EMS can be readily incorporated into cellulose alkanoates; depending on the application and specific types of cellulosics. A solvent may also used to facilitate the incorporation of the soyate plasticizer into the alkanoate.

[00067] Table 4 shows the comparative solvent casting results. The hard, clear CA film served as the control. With the presence of EMS at 20%, 33%, and 50% (Examples 7-9, respectively), the use of acetone as a solvent to assist the plasticization of CA with EMS was successful. All three Examples had no weight loss, were soft, and did not exude any EMS.

[00068] With a variety of cellulose alkanoates tested with EMS, a person having ordinary skill in the art, without undue experimentation, can tailor the plasticization regime for those cellulose alkanoates in order to prepare a superior performing, fully bio-derived plasticized cellulosic article, whether molded, extruded, solvent casted, coated, dipped, or calendered.

[00069] As with any transformational technology, existing manufacturing equipment must be taken into consideration if the new technology is to be accepted in the marketplace. Because of the range of plasticizing effects for the epoxidized alkyl soyates with the cellulose alkanoates, it is possible for a person having ordinary skill in the art to "drop in" a replacement bio-derived plasticized cellulosic material for a synthetically-derived plasticized resin, without major equipment alteration or replacement. Therefore, the plasticized composites of the invention are versatile and sustainable solutions.

[00070] The invention is not limited to the above embodiments. The claims follow.

Claims

What is claimed is:

1. A plasticized composite of bio-derived materials, comprising:

(a) a cellulose alkanoate resin and

(b) an epoxidized methyl soyate plasticizer mixed sufficiently in the resin to reduce flexural modulus of the resin.

2. The composite of Claim 1, wherein the cellulose alkanoate is selected from the group consisting of cellulose acetate (CA), cellulose diacetate, cellulose triacetate, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB), and combinations thereof.

3. The composite of Claim 1 or Claim 2, wherein the epoxidized alkyl soyate is selected from the group consisting of epoxidized methyl soyate, epoxidized ethyl soyate, epoxidized butyl soyate, epoxidized octyl soyate, and combinations thereof.

4. The composite of Claim 3, wherein the epoxidized alkyl soyate has from about 0.5 to about 12 epoxy groups per molecule.

5. The composite of Claim 4, wherein the epoxidized alkyl soyate is the reaction product of epoxidized soybean oil with an alcohol.

6. The composite of any of Claims 3-5, wherein acetyl groups on cellulose acetate can range from about 20 to about 50 weight percent, wherein propionyl groups on cellulose acetate propionate can range from about 20 to about 50 weight percent, and wherein butyryl groups on cellulose acetate butyrate can range from about 15 to about 50 weight percent.

7. The composite of any of the above Claims, further comprising a functional additives selected from the group consisting of anti-oxidants, anti- stats, scavengers, blowing agents, biocides, exfoliated nanoclays, thickeners, colorants, and the like, and combinations thereof.

The composite of Claim 7, wherein the composite has the following gredients in the following approximate ranges:

9. The composite of any of the above Claims wherein the composite has a shape of a sheet, a tape, a molded article, a coated article, a dipped article, an extruded article, a solvent cast article, or a calendered article.

10. A method of using an epoxidized alkyl soyate as a plasticizer for a cellulose alkanoate to make a composite of any of Claims 1-9, comprising the step of mixing the soyate with the alkanoate at a temperature sufficient to form a plasticized composite.

11. The method of Claim 10, wherein the temperature is at ambient.

12. The method of Claim 10, wherein the temperature is above ambient.

13. The method of Claim 10, wherein, before the mixing step occurs, the cellulose alkanoate is dissolved in a solvent and wherein, after the mixing step occurs, the solvent is evaporated.

14. The method of Claim 13, wherein the solvent comprises acetone.

15. The method of Claim 12, wherein the temperature ranges from about 120°C to about 320°C.

16. The method of any of Claims 10-15, wherein after the mixing step, the method comprises shaping the composite into a final article by molding, extruding, dipping, coating, calendering, or solvent casting.

17. The method of any of Claim 16, wherein the shaping step uses substantially the same equipment as used for a citrate-plasticized cellulose alkanoate composite.

18. An article made of a composite of any of Claims 1-9.

19. An article made using the method of any of Claims 10-17.

20. The article of Claim 18 or Claim 19, wherein the article is selected from the group consisting of appliances; building and construction products;

consumer products; electrical/electronic products; packaging; industrial products; transportation products; and wire and cable insulating or jacketing; films; tapes; sheets; and combinations thereof.