BIODEGRADABLE VCI PACKAGING COMPOSITIONS

Abstract

A breathable biodegradable volatile corrosion inhibitor polyester composition comprises one or more biodegradable homopolymer polyesters and/or one or more biodegradable random copolymer polyesters, one or more volatile corrosion inhibitors (VCI), and one or more fillers wherein said composition has a higher water-vapor transmission rate than polyethylene.

Claims

1-20. (canceled)

21. A biodegradable volatile corrosion inhibitor polyester composition, comprising: polyester comprising one or more biodegradable random copolymer polyesters and/or one or more biodegradable homopolymer polyesters; volatile corrosion inhibitors comprising: (i) one or more salts of carboxylic acid, (ii) one or more ammonium salts, and (iii) one or more of benzoic acid, sorbic acid, and a benzoic acid derivative; and at least one filler.

22. The composition of claim 21, comprising one or more copolymer polyesters having the formula: ##STR00003## wherein R.sup.1, is ##STR00004## x is an integer in the range of 2 to 10, y is an integer in the range of 2 to 8; and m and n are selected such that the weight average molecular weight of the copolymer polyester is about 80,000 to about 175,000.

23. The composition of claim 21, comprising one or more copolymer polyesters selected from polybutylene sebacate-co-terephthalate (PBST) and polybutylene adipate-co-terephthalate (PBAT).

24. The composition of claim 21, comprising one or more copolymer polyesters that does not contain any repeat units derived from succinic acid.

25. The composition of claim 21, comprising one or more homopolymer polyesters selected from polylactides, polycaprolactones, polyglycolides, polyhydroxyalkanoates, and combinations thereof.

26. The composition of claim 25, wherein the homopolymer polyester comprises a polylactide and the filler comprises talc.

27. The composition of claim 21, comprising a blend of one or more copolymer polyesters and one or more biodegradable homopolymer polyesters, wherein the total weight of copolymer polyesters is about 50 wt % to about 95 wt % based on the total weight of the blend, and the total amount of homopolymer polyesters is about 5 wt % to about 50 wt % based on the total weight of the blend.

28. The composition of claim 21, wherein the weight average molecular weight of the one or more copolymer polyesters is about 90,000 to about 150,000, and the weight average molecular weight of the one or more homopolymer polyesters is about 125,000 to about 140,000.

29. The composition of claim 21, wherein the volatile corrosion inhibitors are present in a total amount of about 0.1 wt % to about 10 wt % based on the total weight of the polyester.

30. The composition of claim 21, wherein the volatile corrosion inhibitors comprise one or more of sodium octanoate, ammonium benzoate, and sorbic acid.

31. The composition of claim 21, wherein the one or more salts of carboxylic acid comprise one or more alkali metal salts of aliphatic carboxylic acids having 5 to 18 carbon atoms.

32. The composition of claim 21, wherein the volatile corrosion inhibitors consist of: (i) one or more salts of carboxylic acid, (ii) one or more ammonium salts, and (iii) one or more of benzoic acid, sorbic acid, and a benzoic acid derivative.

33. The composition of claim 21, wherein the at least one filler comprises talc, calcium carbonate, a silicate, sodium carbonate, clay, barite, or a combination thereof.

34. The composition of claim 21, comprising about 3 to about 53 parts by weight of filler based on 100 total parts by weight of the polyester.

35. The composition of claim 21, wherein the composition exhibits a corrosion-protective effect of Grade 3 or higher according to NACE Standard TM0208.

36. A film comprising the composition of claim 21, wherein the film has a thickness of about 0.5 mils to about 8 mils.

37. A volatile corrosion inhibitor-containing concentrate, comprising: volatile corrosion inhibitors comprising: (i) one or more salts of carboxylic acid, (ii) one or more ammonium salts, and (iii) one or more of benzoic acid, sorbic acid, and a benzoic acid derivative; and polyester comprising one or more biodegradable random copolymer polyesters and/or one or more biodegradable homopolymer polyesters; wherein a ratio of volatile corrosion inhibitors to polyester in the concentrate is in the range of about 1:20 to about 10:20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention relates to biodegradable VCI compositions that are desirable for many uses including packaging of various items, apparatus, machines, parts, and the like. Such items are contained within, encased, wrapped, or otherwise exist within the biodegradable VCI packaging compositions of the present invention. The packaging material preferably is in the form of a sheet or film that can be used to form a container, enclosure, or box for the above-noted items to be protected against corrosion.

[0014] An essential component of the biodegradable VCI composition is one or more biodegradable homopolymer polyesters or one or more random copolymer polyesters, or both. Polymers that can be used as one or more homopolymer polyesters such as a polylactide, polycaprolactone, a blend of PLA and polycaprolactone, a polyglycolide, or polyhydroxyalkanoates (PHA), or any combination thereof, that desirably is relatively pure, that is contains no contaminates or polymers therein. That is, it generally contains less than about 3 or about 1 wt. % of any contaminate, desirably less than about 0.5 wt. %, and preferably less than about 0.1 wt. % or nil, has no contaminates whatsoever that exist.

[0015] Typical molecular weights of commercial polylactide homopolymers or other homopolymer polyesters can be utilized wherein the weight average molecular weight thereof is from about 100,000 to about 175,000, desirably from about 110,000 to about 150,000, and preferably from about 125,000 to about 140,000 g/mol. One or more polylactides can be utilized that differ in molecular weight, and/or are obtained from a different manufacturer. As by way of example only, a suitable polylactide that can be used in the present invention is PLA 3052D, made by Natureworks.

[0016] In addition to the one or more biodegradable homopolymer polyesters, or in lieu thereof, one or more random copolymer polyesters such as an aliphatic-aromatic random copolyester or a random aliphatic copolyester can be utilized. The number and type of random copolyesters are large and generally have the formula:

##STR00001##

where R.sup.1, independently comprises=

##STR00002##

[0017] wherein, x, independently, is an integer from about 2 to about 10, or about 34 (dimer fatty acid), wherein, y, independently, is an integer of from 2 to about 8.

[0018] Desirably, —(CH.sub.2).sub.x—can be derived from an adipic acid, sebacic acid, or azelaic acid, and —(CH.sub.2).sub.y—can be derived from 1,4-butanediol or ethylene glycol.

[0019] The number of “m” and “n” repeat units is such that the total weight average molecular weight of the random copolymer is as set forth below.

[0020] Examples of suitable compostable random copolymer polyesters include polybutylene sebacate-co-terephthalate (PBST), with polybutylene adipate-co-terephthalate (PBAT) being preferred. The weight average molecular weight of the one or more random copolymer polyesters, independently, can range from about 80,000 to about 175, 000 with a desirable weight average molecular weight being from about 90,000 to about 150,000, and preferably from about 100,000 to about 130,000.

[0021] The weight average molecular weight of the above-noted polylactide homopolymer polyesters as well as the random copolymer polyesters was determined by gel permeation chromatography (GPC) wherein the polymer was dissolved in chloroform, the solvent for GPC was tetrahydrofuran and the temperature was 23° C.

[0022] It is an important aspect of the present invention that random copolyesters, not contain any repeat units derived from succinic acid. Such compositions have generally been found to have poor physical properties such as low tear resistance as well as low transparency, both of which are important properties for corrosion inhibiting compositions. Also, generally aliphatic-copolyesters such as PBS (poly)(butylene succinate) have poor mechanical properties and are/or also expensive. Hence, if utilized, the amount of any repeat units derived from succinic acid is very small such as less than about 10%, and desirably less than 2% based upon the total number of repeat groups in the copolymer. Preferably nil, that is no copolyesters derived from a succinic acid are utilized whatsoever based upon the total weight of the one or more biodegradable polyesters of the present invention.

[0023] When a mixture of the one or more random copolymer polyesters is utilized with one or more of the homopolymer polyesters, the amount thereof (i.e. copolymer(s)) is from about 50 wt. % to about 95 wt. %, desirably from about 60 wt. % to about 90 wt. %, and preferably from about 70 wt. % to about 85 wt. % based upon 100 total parts by weight of all of the biodegradable polyesters. The amount of one or more homopolymer-polyester is from about 5 wt. % to about 50 wt. %; desirably from about 10 wt. % to about 40 wt. %, and preferably from about 15 wt. % to about 30 wt. % based on 100 total parts by weight of all of the biodegradable polyesters. If the polyester inhibitor composition is not a blend, the amount of the homopolymer or the random copolymer is of course, 100 wt. %.

[0024] As an example, it has been found that high ratios of the one or more random copolyesters to the amount of the one or more homopolyesters such as PLA is important with regard to increasing the mechanical performance of the product and shelf life.

[0025] According to the present invention, biodegradable VCI packaging compositions can be made from one or more homopolymers as noted above, or from one or more copolymers as noted above, or from a blend containing one or more homopolymers with one or more copolymers. Moreover, one or more fillers are generally always utilized with any of the three above-noted blends since they unexpectedly have been found to improve properties thereof as set forth hereinbelow.

[0026] One or more volatile corrosion inhibitors of the present invention that can be utilized comprise of various triazoles and derivatives thereof such as benzotriazole and tolytriazole; various benzoates such as ammonium benzoate; various ammonium salts; various carbamates; various phosphates; and various alkali acid salts such as set forth in U.S. Pat. Nos. 4,973,448; 5,139,700; 5,715,945; 6,028,160; 6,156,929; 6,617,415; and 6,787,065, hereby fully incorporated by reference. Useful VCI's of the present invention preferably include various inorganic nitrites or alkali metal nitrites with potassium nitrite and sodium nitrite being preferred, as well as various sodium salts such as sodium octanoate, sodium benzoate, various benzoate acid derivatives such as 2 or 3 or 4-hydroxy-benzoic acid, ammonium benzoate and various alkali metal salts (e.g. sodium or potassium) of aliphatic carboxylic acids such as sorbic acid or a dicarboxylic acid. Such acids have from about 5 to about 18 carbon atoms.

[0027] Fillers are an important aspect of the present invention to provide ease of processing, e.g. extruding the resin and anti-blocking effect for the bags made with such material, cost reduction, retention of tensile strength, reduced density of the end product, and higher stiffness. It has also been found that various one or more fillers such as talc, calcium carbonate, sodium carbonate, silicates, clay, and barites, or any combination thereof, help adjust the WVTR rates. That is, mixing the same into the overall biodegradable VCI packaging compositions improved the porosity and thus promote a desired access of more water molecules to various one or more VCI compounds. It has also been found that the higher water vapor transmission rate (WVTR) of biodegradable polyester films than that of polyethylene (PE) based films allows for lower loadings of VCI compounds for short-term applications of the biodegradable VCI packaging compositions of the present invention. Talc is a preferred filler. The total amount of the one or more fillers is generally from about 3 to about 53 parts by weight, desirably from about 5 to about 33 parts by weight, and preferably from about 5 to about 18 parts by weight based upon 100 total parts by weight of the one or more homopolymer polyesters and/or one or more random copolymer polyesters. Depending on the aspect ratio of the fillers added, they can reduce or increase the breathability than hence help with tailoring desired shelf life and usage life for different applications based on the type of filler used. The present invention is free of starch as a filler, that is, it has no starch.

[0028] A unique advantage of the present invention due to the various factors that contribute to a high WVTR of the present invention is that only low amounts of such VCI compounds need be utilized. That is, the various one or more VCI's compounds range from about 0.1 wt. % to about 10 wt. %, desirably from about 0.3 wt. % to about 5 wt. %, and preferably from about 0.5 wt. % to about 2 or about 0.9 wt. % based on the total weight, e.g. 100 total parts by weight, of the one or more homopolymer polyesters and/or the one or more random copolymer polyesters. In other words, the total amount of one or more VCI's utilized in the present invention can vary widely.

[0029] The preparation of the various different formulations of the biodegradable VCI packaging composition of the present invention can generally be carried out in any manner known to the art and to the literature. With respect to the present invention, various pre-masterbatches are initially prepared and then subsequently all are mixed together at a temperature above the melting point biodegradable compounds such as the various types of polyesters disclosed herein above. For example, from about 1 to about 10 parts by weight of one or more VCI's are added to about 20 parts by weight of one or more random polyesters and/or one or more of the homopolymer polyester polymers of the present invention to form a VCI masterbatch. Since the final total amount of VCI in the final composition is less than 10 wt. %, based upon the total weight of the one or more homopolymer polyesters and/or the one or more copolymer polyesters, the amount of VCI masterbatch is subsequently added to an existing fair amount of biodegradable polyesters to yield a biodegradable polyester composition having, as noted above, that is from about 0.1 wt. % to about 10 wt. %, desirably from about 0.3 wt. % to about 5 wt. %, and preferably from about 0.5 wt. % to about 2 wt. % of a VCI therein based on the total weight of only said polyesters. The preparation of the VCI masterbatch can generally be carried out in any heating and mixing device, such as an extruder, an internal mixer, or preferably a twin-screw extruder, wherein the mixing temperatures are above the melting point of the random copolyesters.

[0030] A filler masterbatch is generally made in the same manner wherein small amounts by weight of the filler are added to a large amount of the one or more random copolyesters, and/or one or more homopolymer polyester polymers. Subsequently, a small amount of the filler masterbatch is added to a larger amount of the biodegradable polyesters to form an end composition having the desired amount of filler therein. Of course, the blending temperature of the one or more fillers to form the filler masterbatch is a temperature above the melting point of the one or more random copolyesters.

[0031] In other words, to prepare the formulations of the present invention, a composition is made containing 100 parts by weight of the one or more homopolymer polyesters and/or one or more random copolymer polyesters. To this is added an appropriate amount of the VCI so that based upon a final total amount of 100 parts by weight of the desired biodegradable polyesters, the amount of VCI is, as noted above, from about 0.1 wt. % to about 10 wt. % thereof. Then the filler masterbatch added in appropriate amounts so that the total final amount of the one or more biodegradable polyesters is 100 parts by weight and the amount of the one or more fillers is within the above-noted weight ranges. That is, once the various desired masterbatches have been made with respect to the one or more VCI compounds, the one or more filler compounds, all of the necessary masterbatches are mixed together with additional amounts of biodegradable random copolyesters and/or a desired amount of a one or more biodegradable homopolyesters to form the final biodegradable VCI packaging composition. The mixing can be carried out in any desired mixing device such as calender, an extruder, and so forth and shaped either into pellets, granulars, and the like, or directly formed into the end product such as a sheet, bag or wrapper having a desired thickness. With regard to the present invention, sheets having a thickness of from about 0.5 to about 8 mils, and desirably from about 0.8 to about 5.0 mils, and preferably about 1.5 to about 2.5 mil thickness that subsequently can be utilized to form a container, an enclosure, or the like to protect generally a metal article or item from corrosion. Moreover, the packaging composition of the present invention can be one or more laminates having one or more sheets therein. For example, a first sheet can comprise the one or more homopolymer polyester polymers and the above noted one or more random copolymer polyesters that contain a VCI therein and one of the above noted fillers therein. A second sheet of the laminate can comprise only said one or more biodegradable random copolymer polyesters optionally comprising a filler and optionally comprising a VCI. It should be obvious that many other different types of laminates can be made from the biodegradable volatile corrosion inhibitor polyester compositions of the present invention.

[0032] According to the present invention, breathable biodegradable volatile corrosion inhibitor packaging compositions can be prepared having a broad range of WVTR such as from about 100 to about 2000, desirably from about 300 to about 1000, and preferably from about 400 to about 600[g/(m2 d)] at 38° C./90% RH, normalized to 1 mil according to ASTM F1249.

[0033] The present invention will be better understood by reference to the following examples which serve to illustrate the present invention, but not to limit the same. The following standard tests realized for determining properties of the prior art as well as the present invention.

[0034] EXAMPLE 1: PBAT pellets were dried at 50° C., for minimum of 2 hours and mixed with grinded sodium nitrite powder (VCI#1) at 70 to 30 ratio. The mixture was then fed to the feed port of a twin-screw counter-rotating LabTech® extruder having L/D of 44 and screw diameter of 26 mm, in which most of the zones were controlled at temperatures in the range from about 270° F. to 290° F. The die temperature was maintained at 300° F. The motor speed was about 150 rpm and generates a “strand” which was cooled in a water bath, pelletized into pellets about 3.18 mm (0.125 in) and dried.

[0035] The VCI MB was then mixed with similarly dried PBAT and PBAT/filler pellets and/or PLA at stated in Table 1 and extruded into a film via blown film line, run at 5 ft/min at 60 micron thickness.

[0036] A control sample was made with a blend of LDPE and LLDPE with comparable level of VCI in it for comparison.

[0037] In Contact corrosion testing the panel inside the PE based resin, which have lower WVTR showed several corrosion areas along the edges and more than three spots on the panels' body when tested according to IEC 68-2-30 Cyclic Chamber Testing. The panels in PE bags which would be the control received grade 3, while the panels in this example with biodegradable resins, PBAT/filler, and PBAT/PLA/filler blend, showed no corrosion and were graded at 5, after 7 cycles.

[0038] The WVTR of the LDPE/LLDPE (Control) sample was below 11 [g/(m2.Math.d)] versus above 300 [g/(m2.Math.d)] at 38° C./90% RH for said above Example 1.

[0039] The VCI testing according to NACE Standard TM0208, showed grade 3 for the biodegradable sample for the present invention and grade 2 for the PE based control sample with comparable VCI content.

TABLE-US-00001 Example PBAT PLA Filler VCI 1 1 100 0 8.18777 0.98253 1 100 5.77367 8.18777 0.98253

[0040] The same drying procedure and compounding equipment and procedure was used for all examples included here.

Example 2

[0041] Another samples was made in a similar process of making a MB first and then blending that with the film resins in which a different powder mixture chemistry was used and the effectiveness of the chemistry was evaluated. The power mixture was composed of, 68% sodium octanoate, 7% 4-Hydroxy Benzoate, 3% Benzotriazole, and 22% Ammonium benzoate. This mix is going to be called VC1#2 going forward. The mixture was then mixed with PBAT pellets at 70 to 30% ratio to make a master-batch.

[0042] This was compared to, 87% sodium octanoate, 9% 4-Hydroxy Benzoate, 4% Benzotriazole, called VCI#3. Each powder mixture was then mixed with PBAT pellets at 70 part to 30 part ratio to make the master-batch. After that, the film was made by mixing the above MB at the loadings below with PLA, PBAT and filler through MB and the rest of comprised as PBAT.

[0043] The contact testing in cyclic atmospheric chamber running according to (IEC 68-2-30) for both examples showed the first mixture VCI#2 to get a grade 4-5 protection compared to the VCI#3 which got grade 2 rating.

[0044] The NACE Standard TM0208 test showed grade 3 for the first formulation and grade 1 for the second set.

TABLE-US-00002 Example PBAT PLA Filler VCI 2 VCI 3 2 83.89 16.11 6.44468 1.15237 0 2 83.89 16.11 6.44468 0 1.15237

Example 3

[0045] Similar to Example 1 and just with a different VCI chemistry, the VCI#2 was added at similar loading PBAT/filler in one case, and to LDPE/LLDPE blend in another case as the control. The PBAT/VCI film showed no corrosion (grade 5) while quite a few spot (grade 3) was observed in control, LDPE/LLDPE film with comparable VCI concentration after 1 week of testing, 7 cycles of (IEC 68-2-30).

TABLE-US-00003 Example PBAT PLA Filler VCI 2 3 100 0 8.188 0.98253

Example 4

[0046] VCI#2, was added to PBAT/filler mix at the same loading, with the difference between the two set being the filler level, one at lower filler and one at higher filler level.

[0047] The set with higher filler level showed better protection in the cyclic chamber test running according to (IEC 68-2-30) after two weeks (14 cycles). The rating for the higher filler was 4-5 while it was 3-4 for lower filler samples. The water vapor transmission rate of the higher filler film was 412 [g/(m2 d)] versus the WVTR of the lower loading being 323 [g/(m2 d)] (normalized) tested at 38° C./90% RH.

TABLE-US-00004 Example PBAT PLA Filler VCI 2 4 100 0 17.417 1.06635 4 100 0 8.18777 0.98253

Example 5

[0048] VCI#3 that showed weaker result in example #2, however, when used with higher filler level, showed improved result. While lower filler containing sample showed grade 2 after 14 cycles of (IEC 68-2-30) test, higher filler sample showed grade 3.

TABLE-US-00005 Example PBAT PLA Filler VCI 3 5 100 0 17.417 1.06635 5 100 0 8.18777 0.98253

[0049] While in accordance with the patent statutes, the best mode and preferred embodiment have been set forth, the scope of the invention is not limited thereto, but rather by the scope of the attached claims.