WO1995014740A1

WO1995014740A1 - Apertured structures of biodegradable copolyesters

Info

Publication number: WO1995014740A1
Application number: PCT/US1994/012937
Authority: WO
Inventors: Francis Glenn Gallagher; Dean Scott Gray; Cathy Jane Hamilton; Raymond Frank Tietz; Frederick Theodore Wallenberger
Original assignee: E.I. Du Pont De Nemours And Company
Priority date: 1993-11-24
Filing date: 1994-11-15
Publication date: 1995-06-01
Also published as: AU8133694A

Abstract

Apertured structures such as netting and trash bags are made from compostable ethylene terephthalate-type copolyesters having small amounts of comonomers containing sulfo groups and other comonomers, such as aliphatic diacids, mixed with particulates, and optionally plasticizers, and having sufficient amorphous content sufficiently distributed throughout the article, are capable of disintegrating rapidly under typical waste composting conditions.

Description

TITLE

Apertured Structures of Biodegradable Copolyesters This invention concerns improvements in and relating to structures of biodegradable copolyesters that are compostable and products therefrom, more particularly copolyesters of the types disclosed in aforesaid U. S. Patents Nos. 5_.053,482_. 5,097,004, 5,097,005, 5,171,308, 5,171,309, and 5,219,646 and in U. S. Applications Nos., 07/834,795, 07,834,796, 07/834,793, 07/973,240, and 07/977,650 and in corresponding PCT applications publication Nos WO 91/18036, WO 92/13020, and WO 92/13019, and PCT/ US92/ 08170, PCT/US92/08171, PCT/ US92/ 08172 and PCT/US92/08173, the disclosures of all of which are hereby incorporated herein by reference, and more specifically to improvements in and relating to enhancing the ability of such structures to disintegrate under composting conditions, and products therefrom, including coatings, adhesives, and shaped articles such as apertured structures of films, fibers, foams, coated papers, molded objects, nonwovens, and especially extruded nets, and disposable products, such as trash bags, therefrom.

We have disclosed in the above U. S. Patents and in copending Applications and published foreign equivalents various copolyesters that are compostable, i.e., degradable under conditions typically existing in waste-composting processes, have low ingredient costs and yet provide adequate strength and toughness properties, and blends of such copolyesters with starch, such as are fiber and film forming, and advantageous incorporation of other materials such as fillers, plasticizers, for example. The bulk of the monomers resulting from the degradation of such copolyesters are readily digested by organisms in compost (using this term generally, to include waste, more generally) to create carbon dioxide and water. This ability to degrade is highly desirable, but may not be sufficient, in practice, by itself, since in practice, generally, many composting operations are likely to be operated for a limited period, such as a few weeks, at which time operations are likely to sieve out sizeable pieces of structures that have not physically disintegrated. Sizeable pieces of structures that are screened out in this way are likely to be considered non-degradable materials, and so are likely to be incinerated or sent to a landfill. We consider it desirable that structures of compostable polymers physically disintegrate at least to such extent that pieces that are sizable enough to be discernible will not be screened out with non-degradable materials, such as polyethylene and polypropylene, for example, so they will not be considered to be similarly resistant to biodegradarion. Thus, we draw a distinction between physical disintegration (that avoids sizeable pieces remaining visible recognizable and intact after a limited period of composting) and biodegradation (which is a biochemical process on a molecular scale). Both processes may be in progress at the same time. 5 A problem solved by the present invention is to obtain (physical) disintegration of articles, i.e., of structures, in addition to biodegradation on a molecular scale, which latter has been achieved and disclosed in our patents and applications mentioned hereinbefore- Composting of yard waste such as grass clippings, tree and shrub o branches and twigs is a growing method of reducing solid waste volume for municipal landfills or more desirably making a useful product to improve the fertility of fields and gardens. A practical limitation of this procedure has been that much of the yard waste has been collected from homes using bags which have been emptied by labor intensive means. Though so-called 5 degradable bags have sometimes been used, the disintegration of such bags has been so slow that large amounts of discernable fragments of the bags have remained in the product after a time sufficient to form mature compost suitable for application to landscapes and gardens, and this has reduced the attraction and commercial value of the product 0 Thus, problems solved by this invention include :

1) - provision of low cost, rapidly disintegrating, apertured structures, such as trash bags, which have an ability to continue to degrade in soil (as long as water is present) to low molecular weight fragments which can be ultimately biodegraded by microorganisms into biogas and biomass as are natural 5 materials like wood.

2) - provision of netting which has adequate strength and toughness to collect yard waste under ambient conditions but which has the ability to disintegrate during a normal yard waste composting cycle into fragments which are small enough to be indistinguishable to most people in the compost 0 We have found, according to the present invention, that certain of the copolyester compositions disclosed in the previous applications (especially TJ. S. Patent No. 5,219,646) are susceptible to rapid environmental stress cracking (ESC) under composting conditions when blended with particulate, and optionally a plasticizer, if processed in such a way as to leave an adequate 5 amount of the article in an amorphous state. We have found that the rate of stress cracking is generally reduced when molecular orientation of the copolyester is increased, for example by drawing, but that netting that has been extruded from such as ESC-susceptible composition, then drawn, and optionally steam heat set, yields a strong, yet rapidly disintegrating, article whose fragments can quickly (within 2-3 weeks) become indistinguishable from yard waste compost because such article has sufficient amorphous portions sufficiently distributed throughout the article. It should be recognized that this increase in disintegration rate under composting conditions could be extremely important to the practical utility of these products as disposable products. Some composting operations may operate with relatively short times (1-2 weeks) at the high temperatures and high humidity which are optimal for rapid disintegration via hydrolysis. We have noted rapid disappearance of traces of disposables via physical processes such as ESC followed by the slower processes of hydrolysis and biodegradation of the fragments that provides an economically attractive as well as an aesthetically and environmentally acceptable result

Accordingly, one embodiment of the invention is an apertured structure comprising, by weight, 40 to 98% of a fiber and film forming copolyester consisting essentially of recurring structural units of the formulae:-

-[-C(0)-R-C(0)-OGO-]_a-[-C(0)-Q-0-]_b- wherein up to about 40 mole % of R is selected from the group consisting of a chemical bond and one or more divalent, non-aromatic, i~G[o hydrocarbylene radicals, and the remainder of R is at least about 85 mole % p-phenylene radical, wherein G is up to about 30 mole % of a polyethylene ether radical selected from the group consisting of

-(CH₂)2-0-(CH2)2- and -(CH₂)2-0-(CH₂)2-0-(CH2)2- and the remainder of G is selected from the group consisting of polyalkylene ether radicals of molecular weight at least about 250, and -(CH₂)2-/ -( H2)3-, and -(CH₂)4- radicals, wherein Q is derived from an hydroxy acid of formula

HO[-C(0)-Q-0-]_xH, where Q is selected from the group consisting of a chemical bond and hydrocarbylene radicals -(Cr_2)_n-, where n is an integer from 1 to 5, -C(R')H-, and -C(R')HCH2-, wherein R' is selected from the group of - CH3 and -CH2CH3, and wherein x and Q are such that the hydroxy acid has a melting point at least 5 C below its decomposition temperature, and wherein "a" and "b" are mole fractions of the polymer, and the mole fraction "a" may be 0.6 to 1 and, correspondingly, mole fraction "b" may be 0 to 0.4, and wherein about 0.1 to about 15 mole % of the polymer contains alkali metal or alkaline earth metal sulfo groups, said copolyester being in an amorphous state as defined herein, and correspondingly 2 to 60% of a particulate.

The particulate may be inorganic or biodegradable organic solid particles of particle size from 0.1 to 50 microns. Especially suitable inorganic particulates are CaCOβ, iron oxide (Fe₂θ3and Fe3U4), and Ti0₂. Suitable biodegradable organic particulates are starch (including corn, and rice starch), zein, wood pulp and other degradable materials such as are mentioned in Coughlin et al in U.S Pat No. 4,480,061.

Optionally, such apertured structures (including articles) may include up to 10% by weight of a plasticizer, especially such as disclosed in copending Patent Application No. 08/ (QP-5010), filed simultaneously herewith, the disclosure of which is hereby incorporated herein by reference.

An especially preferred embodiment of this invention is extruded, drawn netting of the above composition containing amorphous intersections which is optionally steam-heat set

Another embodiment is an apertured film of the above composition which may optionally be laminated or adhered to a degradable substrate.

Other embodiments include bags of any of the above, such as trash bags for collecting waste materials for composting.

It is a finding of this invention that extruded and melt-quenched articles, such as monofils, films, coatings or nets of the above composition which have a substantial amorphous content and distribution, and which contain sufficient amount and distribution of particulate, disintegrate in a shorter period of time in composting than unmodified polymer compositions.

This rapid disintegration is believed to be due to enhancement of the tendency for these products to undergo physical processes such as environmental stress cracking (ESC) and ageing. It has been found that drawing, which decreases the crystallizable amorphous content, increases the strength , toughness and resistance to embrittlement at low temperatures,but it also tends to increase the time the products take to disintegrate by physical processes such as ESC. Drawing an extuded melt quenched net of the composition described, however yields a product having a surprising combination of properties , i.e., fast disintegration in the compost simulation test as well as good toughness and resistance to cold embrittlement. This type of net has a structure in which the stronger thinner drawn connecting strands are connected by larger relatively undrawn, amorphous crossover nodes. There are several processes by which such nets can be prepared. A general process and suitable equipment as used in Example 1 are described in U.S. Pat. No. 2,919,467 to F.B. Mercer, U.S. Pat No. 3,554,853 to F.B. Mercer, U.S. PatNo. 3,270,370 to F.B. Mercer, U.S. Pat No. 3,384,530 to F.B. Mercer, U.S. PatNo. 3,551,543 to F.B. Mercer, U.S. Pat No. 3,444,588 to K.F. Martin and F.B. Mercer, as well as Can. Pat No. 643,076, 652,196 and 721,655 to F.B. Mercer. A similar net structure should be prepared when the strands extruded from a center rotating die and a concentric static die are joined beyond the die face (the so- called Polynet process) then quenched and drawn. The so-called Conwed process which extrudes net via reciprocating dies and provides a highly unoriented cross member should also yield a suitable net (see U.S. PatNo.,4,190,692 to R.L. Larsen). Drawing of apertured film (see G.B.

1,544,608 to Hercules Inc.) should also yield an article of the invention. Such prior processes should be modified, as needed, for making apertured structures according to the present invention. For instance, the nature of the compostable copolyesters should be taken into consideration, as described in the aforesaid patents and applications. Also, it should be noted in Example 1 herein that the extruded netting was quenched in a water bath at room temperature (25°C), which is important to avoid cold embrittlement. Thus temperatures below 15°C should generally be avoided.

Such a drawn net product when used to make bags for collection of yard waste was found to have a tendency to relax back to the as-extruded net dimensions at elevated ambient temperatures, which might be experienced in outdoor exposure in warm climates. This drastically reduces the bag's capacity and utility. It has been found that a post draw steam heat treatment of the net while it is under restraint will eliminate this drawback without substantially decreasing the disintegratability of the net

Evaluations of copolyester/particulate/plasticizer compositions and shaped articles have shown that it is not sufficient (for obtaining rapid disintegratability) merely to specify percentage contents of these materials. It is necessary that an adequate amount of the copolyester be present in and distributed throughout the articles in an amorphous state.

We have shown the existence of such an amorphous state in the crossover nodes of a melt extruded/ quenched/ drawn net made with 2G-T/5/5SI (73/25/2) by separately analyzing the dissected crossovers and connecting strands by Differential Scanning Calorimetry (DSC). We have found that the crossover nodes have shown an exothermic crystallization peak at about 118 C with the evolution of about 9 J/g, whereas the drawn interconnecting strands have shown no Crystallization peak. In the precusor melt extruded/quenched undrawn net, both crossover nodes and connecting strands showed a Crystallization peak at about 119 C and the evolution of about 16 J/g. We have shown the existence of this differential in amorphous character of crossover nodes vs. connecting strands in a melt extruded, quenched, drawn net made according to this invention by evaluating such a net made with 2G-T/5/5SI (81/17/2) and 5% CaC0₃ particulate. Also by dyeing samples of the net with an aqueous solution of a basic dye (Sevron Blue ER 200%) at 60 C for 2.5-10 minutes we have shown that the crossover nodes dye a deeper blue color than the connecting strands. This apparent difference in dye rate is consistent with the nodes being more amorphous (less oriented and crystalline) than the connecting strands. The Compost Simulation (CS) test is relied on and used herein to determine whether an adequate amount and distribution of the desired amorphous state is present in articles of this invention. This test can in practice, show if enough of the article is in the desired amorphous state so that physical changes in the article leading to disintegration can take place rapidly enough to be commercially useful .

The test, is described in more detail hereinafter, but essentially consists of storing a sample of the article in a pH 7 buffer solution at 60 C and testing the integrity of the sample by flexing it each day until fracture is noted. A pH 7 buffer was chosen because such conditions are known to prevent autocatalysis of hydrolysis .which would result in molecular weight reduction and strength loss. The test in other aspects simulates the high (normally 100% R.H.) humidity and temperature present in the early stages of a compost process. The intent is to ensure that in the test physical processes like ESC and ageing are the predominant embrittlement mechanism. It is believed that embrittlement and significant loss of physical properties of the compositions described under composting conditions are the result of changes that are essentially physical in nature, and that are brought about by the high humidity and temperature experienced, especially in the early stages of composting, without necessarily directly involving biodegradation processes, such as enzyme-catalyzed hydrolysis . Large reductions in molecular weight of the polyester component due to hydrolysis are not necessary in these early composting stages.

Stress cracking can occur in many polymeric materials. ESC was originally identified in polyethylene, brittle failure having been observed at very low stresses in the presence of mobile polar liquids (J.R. Martin,

J.F. Johnson, and A.R. Cooper , J. Macromol. Sci-Revs. Macromol. Chem. C8 , ppl37-155 (1972); C.J. Singleton, E. Roche, P.H.Geil, J. Appl. Poly. Sci., Vol 21 (1977), pp 2319-2340.) Theories about the physical mechanisms by which ESC takes place have included plasticization of amorphous regions and reduction of surface energy by ESC agents. Inhomogeneities (including particulates) in polymers have been postulated to lead to stress concentrations and increased mobility of polymer chains in their vicinity, and can lead to craze initiation especially at the polymer surface (J. Breen and D. J. Van Dijk, J. Mat Sci. Vol 26 (1991), pp 5212-5220).

Ageing is a process which may be related to ESC. It occurs in amorphous polymers which are in the glassy state, i.e., below the glass transition temperature (Tg). It results in a loss of strength and toughness, L.C.E. Struck, "Physical Ageing in Amorphous Polymers and Other Materials", (1978), Elsevier. Many of the copolyesters used in this invention have Tg's around room temperature or somewhat above. This means that under composting conditions (60 C, 100% R.H.) they would be above the glass transition and so ageing and embrittlement by this mechanism would not be expected. We believe, however, that in the compositions of the invention ageing can occur under these conditions. Without limiting the invention to any theory, we speculate that there may be an ordering effect at the surface between polymer and particulate which may reduce the mobility of the polymer chain segments and preserve them in the glassy state at higher temperatures than would be expected in the absence of particulate. We believe that under moist, warm composting conditions this disturbed amorphous polymer may equilibrate to a state in which the polymer segments have a lower free volume (crystallization may actually take place), and this may result in embrittlement .

A. Ramirez, J.A.Manson, R.W. Hertzberg , Poly. Eng. Sci. Vol. 22, pp 975-981 (1982) have reported that amorphous polyethylene terephthalate (2-GT) exhibits unusually high resistance to crack propagation. One might not have expected, therefore, amorphous and low crystallinity copolymers of 2GT to be good candidates for fast disintegration via this mechanism.

From our experiments on the polymers and articles of this invention, we have concluded that ESC does occur with our articles and that the presence of water is critical to the embrittlement mechanism. Thus a 10 mil thick film prepared by hot pressing a blend of 25% starch and 75% 2G/DEG (90/10)-T/5/5SI (78/20/2) (Polymer A of Example 2 of U. S. Patent No. 5,219,646) placed at room temperature in a sealed polyethylene bag with 25 ml of 5% octanoic acid in water and stored for 40 hrs broke into small fragments on mild shaking, whereas a similar film without starch particulate, treated similarly, remained intact. (Further experiments with a 0.5 mil thick extruded film containing no particulate, showed that aqueous propionic, hexanoic, heptanoic, and octanoic acids gave rapid embrittlement at room temperature while acetic, nonanoic, decanoic and undecylenic acids gave no embrittlement Dibutyl tartarate and methyl isobutyl ketone/ water mixtures also resulted in disintegration.) A film extruded from a mixture of 31% 2G/DEG (92/8)-T/5/5SI (73/25/2), 60 wt% (43 vol %) CaC03 and 9 wt% poly(ethylene adipate) (Rucoflex S101-55) disintegrated in the CS test after only 4 days exposure and was found to have undergone substantially no reduction in molecular weight, indicating that the mechanism is mainly a physical one and not due to a reduction in molecular weight due to hydrolysis (see item 4 in Table 3, herein). The importance of water was shown by immersing samples of 0.5 mil thick film of composition 2G/DEG (90/10)-T/5/5SI (73/25/2) in (1) pure water, (2) aqueous mixtures of hexanoic acid, and of heptanoic acid, and (3) pure hexanoic and heptanoic acids. The only samples which disintegrated after 16 to 27 hr exposure at room temperature were those exposed to the aqueous acid mixtures, i.e., (2).

Tests Compost Simulation Test - A sample of the article should be placed in a capped glass vial with sufficient pH 7 aqueous buffer solution (Baker's Analyzed 0.046-0.050 M phosphate, 0.023-0.025 M potassium, 0.050-0.054 M sodium) to completely immerse the sample and the vial and its contents should be shaken in a 60 C hot air thermostat The vial should be opened and the sample tested once a day by flexing it 4 times. The Tables herein record the number of days unitl the sample breaks. The test is passed for the purposes of this invention if the article breaks within 18 days. Cold Embrittlement Test - Films or monofils are immersed in an ice/ water bath and flexed over about a 1 cm span for a maximum of 3 minutes. The sample fails by breaking or passes by not breaking.

The invention is further illustrated in the following Examples, in which all parts and percentages are by weight, unless otherwise indicated as, for instance the copolyester compositions.

Example 1 This Example demonstrates a rapidly compost-disintegratable net which is prepared by direct extrusion drawing and steam heat setting. The composition used was made by combining 4 parts of melt-extruded pellets of a polymer having the composition

2G-T/5/5SI (80/18/2) and 1 part of melt-extruded pellets from a mixture of 15 parts CaQ_>3 particulate, 25 parts polyethylene adipate) (Rucoflex S101-35), 10 parts iron oxide pigment (Bayferrox Brown 686, and 50 parts of polymer with the composition 2G-T/5/5SI (81/17/2) to give a final composition of 90 parts copolyester, 3 parts CaCθ3, ⁵ parts poly(ethylene) adipate, and 2 parts iron oxide.

The above mixture of pellets was melt-extruded from a rotating circular die over a sizing mandrel following the teachings of Can. 643076, 652196 and 721655. The die had 57 slots (0.085" x 0.032") in the edges of a 4" diameter circular die. The extruded net passed down over a cylindrical former 120 mm in diameter and about 200 mm long, positioned about 3 cm below the die, into a water bath quench. The netting was advanced by a set of rolls into an orienter where two sets of rolls running at different speeds drew the net through a water bath. Table 1 gives the conditions under which the net was made:

Table 1 Die Temp. (C) 216

Quench Temp. (C) 25 Die Speed (rpm) 400

OrienterBath Temp. (C) 60

Slow Draw Roll (m/min) 5.2

Fast Draw Roll (m/min) 20

Draw Ratio 3.9 Net Linear Density (g/m) 34

The extruded, drawn (E/D) net was dimensionally unstable at ambient summer temperature, i.e. it shrank to less than 1/2 its original size in the machine direction and to less than 1/3 in the cross direction at temperatures above 90 F. Steam heat setting in a stretched configuration not only improved dimensional stability but also improved the net strength by reforming the configuration of the crossovers (whereas dry heat setting on the other hand resulted in embrittlement and strength loss).

The E/D netting was presoaked at room temperature in water containing 20g/l of a non-ionic surfactant (Merpol LFH). This made the net pliable and reduced the friction between the net and the driven

Opener/Stretcher Insert of a Tube-Tex machine (Duplex Model M5-130 made by Tubular Textile Machinery Corporation). The net was stretched to 20" width and fed through the 14" long steam zone at about 7 yards/min. This dimensionally stabilized the netting in up to 120 F dry heat and reformed the crossovers so that the mesh was 4-sided (vs. a weaker 6-sided configuration in the E/D net). Such stabilized net is referred to as extruded/ drawn/heat set (E/D/HS). Samples of both the E/D and E/D/HS nets were evaluated by the SC test. Both samples embrittled at the intersections of the crossovers and strands after 13 days. The nets were found to be similarly weak and disintegratable on being inspected after 2 weeks exposure in actual composting using a 1/1 mixture of municipal/ solid waste and sewage sludge. Similar results were obtained with 3/1/2 and 4.8/1.6/3.2 ratios of CaCθ3/poly(ethylene adipate)/iron oxide, made by combining 1 part of concentrate pellets having a ratio CaCθ3/poly(ethylene adipate)/iron oxide of (24/8/16) with, respectively, 7 and 4 parts of copolyester pellets.

Similar results were obtained using a polymer having the composition 2G-T/5/5SI (78/20/2) in the same range of compositions. For comparison, E/D and E/D/HS nets were made using the above two polymers without any particulate and plasticizer additions and subjected to the CS test The 2G-T/5/5SI (80/18/2) polymer E/D net disintegrated after21 days in the CS test, whereas the E/D/HS net disintegrated in 20 days. The 2G-T/5/5SI (78/20/2)polymer net in both the E/D and E/D/HS state disintegrated in 20 days in the CS test None of the nets described in this Example embrittled in the CE test.

Example 2 This Example demonstrates how the compost simulation (CS) test has been used to identify which articles are according to this invention. The components indicated in Table 2 were mixed in an extruder, and the collected extrudate was either directly pelletized or ground. 10-25 g samples were melted and extruded using a press spinner through a 50 mesh screen pack and a 0.025 inch diameter L/D=3 spinneret at a delivery rate of 1.6 cc/min into an 18 inch long room temperature water bath located about 2 inches below the spinneret, and the strands were collected at a windup speed of 8.5 m/min. The resulting melt-extruded/ quenched monofils were used for the CS test in this Example to simulate typical crossover intersections in extruded/ quenched nets. Comparison monofils (and compositions) which are not of this invention are listed as "Comp" whereas monofils according to the present invention are numbered in Table 2.

Table 2

POLYMER Particulates (%) Plasticizer (%) DA

Comp A None None 34 Comp A Fe₃0₄(2) None 24

Comp A Fe₃0₄(2) PEA3500(5) 24

1 A Fe₃θ4(2)CaC0₃(3) None 8

2 A Fe₃θ4(2)CaC0₃(5) PEA3500(2.5) 8

3 A Fe₃0₄(2)CaC03(3) PEA3500(2.5) 11 4 A Fe₃θ4(2)CaC0₃(3) PEA3500(5) 11

5 A Fe₃0₄(2)CaC0₃(3) PEA3500(10) 10

6 A Fe₃0₄(2)CaCθ3(3) PEA3500(10) 13

Comp B None None 25

7 B Fe₃0₄(2) PEA3500(10) 12 8 B Fe₃0₄(2)CaC0₃(2) PEA3500(10) 11

9 B Fe₃0₄(2)CaC0₃(5) PEA3500(10) 11

10 B Fe₃0₄(2)CaC0₃(5) PEA3500(7.5) 11

11 B Fe₃0₄(2)CaC03(5) PEA3500(2.5) 7

12 B CaC0₃(5) PEA3500(5) 9 13 B CaC0₃(5) PEA3500(2.5) 11

14 B CaC0₃(5) PEA3500(1) 10

15 B Fe₃O (2)CaCθ3(10) PEA3500(10) 5

16 B Fe3θ (2)CaCO₃(10) PEA3500(7.5) 9

17 B Fe₃O4(2)CaCO₃(10) PEA3500(2.5) 9 18 B CaCO₃(10) PEA3500(5) 9

19 B CaCO₃(10) PEA3500(2.5) 7

20 B CaCO₃(10) PEA3500(1) 7

21 C Fe₃θ4(2)CaC0₃(3) PEG2000(5) 4

22 C Fe₃0₄(2)CaCθ3(3) PEG2000(2.5) 6 23 C Fe₃0₄(2)CaC03(5) PEG3400(5) 6

24 D CaC0₃(5) PEA2000(5) 6

25 D Clay A(5) PEA2000(5) 3

26 D Clay A(17) PEA2000(5) 2

27 D Clay C(5) PEA2000(5) 4 28 D Clay C(17) PEA2000(5) 3

29 D Clay S(5) PEA2000(5) 3

30 D Clay S(17) PEA2000(5) 2

Polymer A = 2G-T/5/5SI (80/18/2) Polymer B = 2G-T/5/5SI (81/17/2) Polymer C = 2G-T/5/5SI (78/20/2) Polymer D = 2G-T/5/5SI (73/25/2) Fe3θ4 = Bayferrox Brown 686 from Miles Inc. CaCθ3 = 1 micron average particle size, 99% < 8 micron

Clay A = ASP NC from Englelhard Industries, Menlo Park, NJ. Clay C = Catalpo from Engelhard Industries, Menlo Park, NJ. Clay S = Satintone from Engelhard Industries, Menlo Park, N J. PEA2000 = poly(ethylene adipate) Rucoflex S101-55 PEA3500 = poly(ethylene adipate) Rucoflex SI 01-35

PEG2000 = poly(ethylene ether) glycol Molecular weight 2000 PEG3400 = poly(ethylene ether) glycol Molecular weight 3400

Samples of these undrawn monofils were drawn over a 60 C heated pin about 3-4X to simulate typical connecting strands in drawn nets. All the drawn monofils took a longer time to disintegrate when exposed to the aqueous pH 7 buffer at 60 C than the undrawn monofils.

Only the undrawn monofils from compositions 1 and 11 - 20 embrittled when flexed after exposure to ice/ water at 0 C in the Cold Embrittlement Test, whereas the other undrawn monofils from the compositions in Table 2 and all the drawn monofils did not so embrittle.

Example 3 This Example shows the preparation of films that may be formed into apertured structures. The films were made by mixing the ingredients indicated and feeding them to a twin screw extruder attached to a 10 inch (25 cm) wide film die with about a 0.01 inch (0.025 cm) gap. The extruded film was electrostatically pinned on an 8 inch (20 cm) diameter smooth quench drum cooled to about 26 C (about room temperature). The quench drum was adjusted to a speed between 5 to 15 ft/min (1.5 to 4.5 m/min) to yield a film with a thickness of 1 to 4 mils (25 to 100 microns). Strips of the as extruded films about 0.5 inch (1.3 cm) wide and 3 to 4 inches (7.5 to 10 cm) long were evaluated by the CS test in a 25 cc sealed glass vial with 20 cc of the pH 7 buffer solution placed in a thermostated hot air shaker at 60 C, being flexed with a spatula everyday until fracture was observed. Table 3 records the number of days within which fracture was observed, it being understood that this testing was stopped on the 28th day if no fracture had occurred by then. Table 3

Polymer Particulate (%) Plasticizer (%) Days

Comp E None None >28

Comp E None PEA2000 >28 Comp E CaCO₃(40) None 21

1 E CaCO₃(40) PEA2000(5) 17

2 F CaCO₃(40) PEA2000(5) 17

3 G Com Starch (46.7) PEA2000(3.6) 3

4 D CaCO₃(60) PEA2000(9) 4

Polymer E = 2G/DEG (90/10)-T/5/5SI (73/25/2)

Polymer F = 2G/DEG/PEG(600) (85/8/7)-T/5/5SI (86.2/12/1.8)

Polymer G =2G/DEG (90/10)-T/5/5SI (78/20/2)

Polymer D = 2G-T/5/5SI (73/25/2) Corn Starch = Cream brand Pure Corn Starch Dial Corporation Phoenix Az

PEA2000 = Rucoflex S101-55

Film 3 above corresponds to what was referred to in Example 8,

Polymer 8A, of U. S. Patent No. 5,219,646.

The above films 1 to 4 may be formed into apertured structures such as trash bags that have a capability of disintegrating rapidly (within 18 days) according to the present invention.

As indicated earlier a netting structure is generally preferred according to the present invention. Apertured trash bags of such netting have been found especially useful in contrast to closed trash bags, when used for collecting compostable materials. Compost enclosed in trash bags of solid (non-reticulate) film will likely begin to degrade anaerobically. This is an odorous process (producing methane, for example, which has an unpleasant smell and is toxic) which is a disadvantage in comparison with aerobic degradation (producing mainly carbon dioxide) such as is significantly less odorous and healthier. Use of netting, or apertured film, is preferred for these reasons, also.

Claims

WHAT IS CLAIMED IS:

1. An apertured structure comprising, by weight, 40 to 98% of a fiber and film forming copolyester consisting essentially of recurring structural units of the formulae:-

~[-C(0)-R-C(0)-OGO-]_a-[-C(0)-Q-0-]_b- wherein up to about 40 mole % of R is selected from the group consisting of a chemical bond and one or more divalent, non-aromatic, C -CIQ hydrocarbylene radicals, and the remainder of R is at least about 85 mole % p-phenylene radical, wherein G is up to about 30 mole % of a polyethylene ether radical selected from the group consisting of

-(CH2)2-0-(CH2)2- and -(CH^-O-tCH^-O- CH^- and the remainder of G is selected from the group consisting of polyalkylene ether radicals of molecular weight at least about 250, and

-(CH2)₂-, -(CH^-, and -(CH₂)4- radicals, wherein Q is derived from an hydroxy acid of formula

HO[-C(0)-Q-0-]_xH, where Q is selected from the group consisting of a chemical bond and hydrocarbylene radicals -(CH_))_n-, where n is an integer from 1 to 5,

-C(R')H-, and -C(R')HCH2-, wherein R' is selected from the group of - CH3 and -CH₂CH3, and wherein x and Q are such that the hydroxy acid has a melting point at least 5 C below its decomposition temperature, and wherein "a" and "b" are mole fractions of the polymer, and the mole fraction "a" may be 0.6 to 1 and, correspondingly, mole fraction "b" may be 0 to 0.4, and wherein about 0.1 to about 15 mole % of the polymer contains alkali metal or alkaline earth metal sulfo groups, said copolyester being in an amorphous state as defined herein, and correspondingly 2 to 60% of a particulate,

2. An apertured structure according to Claim 1, comprising up to 10% by weight of a plasticizer.

3. An apertured structure according to Claim 1 or 2 that is in the form of netting.

4. An apertured structure according to Claim 1 or 2 that is in the form of an apertured film.

5. An apertured structure according to any of Claims 1 to 4 that is in the form of a bag.