CA2178319A1 - Thermoplastic photodegradable and biodegradable polymer blend - Google Patents

Abstract

A photodegradable and fully biodegradable plastic material, which can be molded using conventional molding techniques and which has good physical and mechanical properties includes a blend of polyisoprene and polycaprolactone resins. The material biodegrades in soil and sea water environments. All blend ingredients are completely decomposed by microorganisms. Polyisoprene is a natural polymer present in a large variety of plant species or is man made.
Polycaprolactone is a synthetic polymer resin known to be decomposed by microorganisms. The plastic material has thermoplastic properties which permits processing of the material using conventional plastic-working techniques. The presence of C16-C18 saturated fatty acids and organic peroxide compatibilizers improve the properties of the blend, especially when large quantities of polyisoprenes are used which allows the production of high quality blown films.

Description

WO95/1S999 2 ~ 7 8 3 1 9 gCTlCAg3~00530 THERMOPLASTIC ~o~nE~ nART ~ AND
sI~-lDF~--~Ar)A~TT~ POLYMER BLEND
This invention relates to fully biodegradable and photodegradable polymer blends and to methods of making the same .
~ ore specifically, the present invention relates to blends of polyisoprene and polycaprolactone which have thermoplastic properties, and which are biodegradable in soil and sea water environments, and photodegradable.
As a result of concerns about the environment and ~li cposal of waste materials, a great deal of effort has been directed towards the development of biodegradable plastic materials. The main emphasis of such e~fort has been placed on the ---h~n; pmq of photodegradation and biodegradation.
Photodegradation is the ~P ~ ~ _ sition of photosensitive materials initiated by the ultraviolet component of natural light, and biodegradation results from the action of microorganisms such as bacteria, fungi or algae.
Photodegradablity is an inherent ~JLO~L Ly of some polymers and in certain cases it can be Pnh_n~-e-l by the use of photosensitizing additives. Photodegradable plastics have found use in applications such as agricultural mulch film, trash bags, and retail shopping bags.
Several different types of plastics have been produced which are fully or partially biodegradable. Some effort haD been made to modify non-biodegradable polymers with starch in concentratLons of 2-1596. However some ~ UllLLUV~:~Dy remains as to whether such materials are completely biodegradable. Some newer materials which use starch as part of the polymer matrix at levels of 60-100~ ~re reported to be completely biodegradable. Certain polyester polymers have been shown to be biodegradable. These include aliphatic esters such as polyl-ydLu~yb~ltyrate-valerate (PHBV) and polycaprolactone .
Polycaprolactone blends are known which contain a variety of thermoplastic resins including polyethylene, polystyrene and nylon and are degr~dable in soil or sea water.

Wo 95/15999 2 1 7 8 3 1 9 PCTrCA93/00530 E~owever, because of the presence of non-biodegradable resin components, such blends are not completely biodegradable. In addition, the blends do not possess accelerated photo-degradation abilities as measured against the properties of widely used commercial plastics.
The polyisoprene-polycaprolactone blend disclosed by rAnAAiAn Patent No. 1,111,179 which issued to Eric G. Kent on October 20, 1981 is described as having thermoplastic propertieS. The patented invention is used for molding components of orthopedic devices specifically because of the mechanical and thermal properties of the material. CAnA~ n Patent No. 1,080,875, which issued to Eric G. Kent on July 1, 1980 also describes a blend containing polyisoprene and polycaprolactone. secause of its mechanical properties, the blend is used in the manufacture of sporting goods, specifically golf ball covers. Japanese Patent No. JP
89293048 describes a multi-component biodegradable coating consisting of polycaprolactone, olefinic polymers, wax, petroleum resin and fats and their derivatives including metal salts. The possibility of introducing a natural resin (polyisoprene) into such a coating is mentioned. Moreover, one of the resins mentioned is natural rubber. Fertilizer grains are coated by such a coating, which is degraded by microorganisms in the soil.
None of the above mentioned patents suggests using a composition for manufacturing a product using known plastic working methods such as injection molding, extrusion, blow molding or similar techniques which have signi~;~Ant importance in applications for biodegradable and photodegradable pl~stics. Iqoreover, none o~ the patents suggests a composition which is photodegradable or biodegradable in sea water. Only the Japanese patent mentions a composition with the ability to biodegrade in soil.
Known biodegr~dable polymers have suffered slow acceptance due to limitations in processing and high costs relative to conventional, non-degr2dable polymers.
An object of the pre8ent invention is to provide a ~ wo gs/lsgg9 2 1 7 8 3 1 ~ PCTICA93100530 plastic material which can be made economically is completely biodegradable and photodegradable, and which has thermoplastic properties comprising a blend of polyisoprene and polycaprolactone .
Another object of the invention is to provide a biodegradable and photodegradable plastic material comprising a blend of polyisoprene and polycaprolactone which can be used to manufacture articles using conventional plastic processing techniques. More specifically, the invention is intended to provide a plastic composition comprising a blend of polyisoprene, polycaprolactone and compatibilizers which can be used to produce good quality blown films.
Another object of the invention is to provide a biodegradable and photodegradable article formed from a blend of polyisoprene and polycaprolactone which has improved mechanical properties and perf ormance at high temperatures because of a post-forming radiation treatment.
Yet another object of the invention is to provide a method of making a fully biodegradable and photodegradable plastic article by mixing polyisoprene and polycaprolactone to form a blend, and processing the thus produced blend using conventional plastic working techniques to form the article.
The invention provides a polyisoprene/polycapro-lactone polymer blend having thermoplastic properties which is fully biodegradable in soil and sea water and is photo-degradable .
The polyisoprene/polycaprolactone blend of the invention includes lO to 500 parts by weight (pbw) of polycaprolactone per lO0 pbw polyisoprene resin, preferably 25 to 200 pbw of polycaprolactone per lO0 pbw polyisoprene. Some additives such as, inter alia, casein, Antin~ Rnts, dyes, fillers, vulcanized vegetable oils, fatty acids, peroxides, coupling agents, fragrances, blowing agents, antistatic agents, fire retardants and pigments commonly used i~ the plastic and rubber industry may be inc~L~ol~Led into the blends in small amounts.
Polyisoprene can be obtained form natural rubber, or ~ 2 1 7 8 3 1 9 CT/CAg3/00530 WO 95115999 - ~ ~ = P
can be produced as a 6ynthetic polymer. Natural rubber contains polyisoprene and is produced by many different plant species. In its natural state, the rubber is biodegradable;
however, the use of stabilization techniques results in reduced biodegradability. Natural rubber, in its pure form, is not acceptable without vulcanization for producing useful products using conventional techniques such as iniection and blow molding, and extrusion which are used for thermoplastic polymeric materials. The main reasons for this are the poor flow characteristics of natural rubber (unless suitably prepared), unsuitable mechanical properties, and tackiness prior to vulcanization.
Polycaprolactone is a synthetic polymer resin known to be ~ier ~sed by microorganisms. However the applications ~or polycaprol2ctone in commercial manufacturing are limited because o i~s relatively high price.
The properties of the polyisoprene/polycaprolactone blends of this invention are very different from the properties described above for the individual polymers. The blends have thermoplastic properties which allow processing using conventional plastic working techniques such as in~ection molding, blow molding ~nd extrusion. The blend h~s no tackiness and does not stick to cold metal elements of the equipment. The flow properties above the softening point of the blend permit processing using known plastic working techniques. A blend in accordance with the invention containing even low levels of polycaprolactone (209~1) i5 capable of being permanently oriented when force is applied, and will significantly increase the tensile modulus and reduce or eliminate the elastic pLOy~ L l y characteristic of some grades of polyisoprene to levels typical of some commonly used plastics .
The polyisoprene/polycaprolactone blends can be produced using techniques known to be suitable for blending rubber or plastic such as extrusion, two roll milling and Banbury milling. The blending temperature should be above 60~C and preferably in the range 65-170C. In some cases, when the blend contains larger amounts of polyisoprene ( e6pecially synthetic polyisoprene ), the addition of coupling agents is rec de~.
It was found that saturated fatty acids in combination with peroxides create good coupling systems for polyisoprenel/polycaprolactone blends. Noreover, both polymers should be completely blended and dispersed before peroxides are added. The thermoplastic resin obtained from the mixing of the two polymers should be ground or pelletized for future use if the resin is intended for injection molding, blow molding or extrusion manufacturing processes. When compression or transfer molding processes are to be used for manufacturing goods, the resin can be stored in the form of sheets .
Such polyisoprene/polycaprolactone blends have a relatively stable chemical structure when exposed to heat during processing. They can be processed with standard eguipment used for injection molding, blow molding, thermoforming, extrusion, compression or transfer molding to manufacture bottles, containers, films, etc.
The mechanical properties of manufactured goods produced using the polyisoprene/polycaprolactone blend can be i ~ ov~d by expo8ing them to electron beam or gamma radiation.
Under irradiation, the polyisoprene present in the blend becomes cross-linked, and -^~^h~ni~^^l properties such as tensile strength, elongation at break and impact strength are signific2ntly improved, especially for blends with larger amounts of polyisoprene.
Articles made from polyisoprene/polycaprolactone blends which are placed in soil or sea water will biodegrade at variable rates. The biodegradation rate depends on conditions such as moisture level (soil), air (oxygen) concentration, temperature, presence of microorganisms, etc.
It is expected that there should be no products of degradation other than carbon dioxide and water. An article made from the blends will degrade guickly when exposed to sunlight. The presence of ultraviolet radiation in the sunlight, light wo 95/15999 ` 2 1 7 8 3 1 9 PCTICAg3/00530 intensity and temperature will individually influence the degradation rate.
The following examples describe prefcrred ts of the invention.
EXI~MPLE 1 13.6 kg of polyisoprene in the form of natur21 rubber grade SMR-L was premasticated using a two roll mill at a t~ ~_LaLure of 50-75C. After fifteen minutes of masticatiOn, when the temperature rose to 75C, 6 . 8 kg of polycaprolactone, in the form of Tone* P-787 Polymer (Union Carbide) was added slowly over an 8 minute period. The blend was mixed at 75C for the next 5 minute~, as per standard milling pL~,ceduLe, and was then cooled and ground to achieve a particle size of 6-30 mesh blend. The resulting blend is described in the following examples as Blend A.
~MPLE 2 13 . 6 kg of polyisoprene in the form of natural rubber grade SrlR-L was mixed with 13 . 6 kg of polycaprolactone in the form of Tone P787 (Union Carbide). ~ixing and grinding were done as described in Example 1 with ~he exception that the time for addition of the polycaprolactone to the polyisoprene was extended to 12 minutes. The resulting blend is described in the following examples as Blend B.

9.1 kg of polyisoprene in the form of natural rubber grade SMR-L was mixe~ with 18 . 2 kg of polycaprolactone in the form of Tone P-787 Polymer and 283 g of Orange* PV-RL 01 ( Hoechst ) . ~ixing and grinding were done according to the method of Example 1 with the exception that the time f or addition of the polycaprolactone to the polyisoprene was extended to 18 minutes. The blend is described in the following ex~mples as blend C.
EXA~PLE 4 13 . 6 of polyisoprene in the form of natural rubber grade SMR-L was premasticated using a two roll mill at a temperature of 50-95C for 15 minutes. After mastication, when the t _-~tule had rl8en to 95C, 2.3 kg of edible

2 1 7 8 3 1 9 /n 530 Wo 9S/IS999 PCT/CA93 o technical grade casein ~90 Mesh~ was added and mixed for another 15 minutes 95C. At this time, the temperature of the blend was reduced to 75C and 6.8 kg of polycaprolactone in the form of Tone P-787 Polymer wa3 added Glowly over an 3 minute period. The blend was mixed at 75C for the next 5 minutes, as per standard milling procedure, and was then cooled and ground to achieve a particle size of 6-30 mesh blend. The re6ulting blend is described in the following examples as Blend D.

An injection molding machine, with a reciprocating screw, was fed with polyi60prene/polycaprolactone Blend A.
The temperature of the heating zones were as follows: Zone 1 - 180C, Zone Z - 190C, Zone 3 - 200C. The nozzle heater was at 70% capacity. A mold designed to produce test specimens with variable thicknesses, including tensile bars according to ASTM D-638M, was used. The mold was cooled with tap water at 15C. Total shot size was 23.5 g. The machine was operated using standard procedures for molding plastics.
The moldings obtained showed adequate replication of cavities and good surface finish.

A Reotex E~EB-l extruder, with a 50 mm extruding screw, was used for molding 100 ml bottles using polyisoprene/
polycaprolactone ~31end C. The temperature of the heating zones were as follows: Zone 1 - 150C, Zone 2 - 170C, Zone 3 -170C. The extrusion head t~ _LLure was 190C. The 100 ml bottle mold was cooled with tap water at 15C. T~e bottles thus obtained had adequate finish and surface quality.
~MPI.E 7 A hot press with cooling system was equipped with a mold heated to 120C. 6.5 g of polyisoprene/polycaprolactone 31end B or D was placed in the mold cavity measuring 0 . 3 mm x 140 mm x 140 mm. The mold was closed under 300 psi pressure, heat was shut down and the cooling system was actuated. A
- molding was obtained in the sheet form with no defects and a good surface finish.

Wo 95/15999 2 1 7 8 3 1 9 PcTlcAg3mos3o ~
EXAMPT ~ 8 Injection molded specimens in the form of tensile bars (produced according to ASTM D-638M) were obtained using polyisoprene~polycaprolactone Blend A. Specimens were exposed to electron beam (EB) radiation with 120 KGray. Specimen6 were later tested according to ASTM D-638M for tensile strength and elongation at break at a r ~ ure of 23~2C, together with control specimens not exposed to radiation. The ~esults o~ testing, which indicate i~ uv~ 1 in the mechanical propertieg of polyisoprene/polycaprOlactOne Blend A
~fter exposure to EB radiAtion, are shown in Table 1.

TENSILE PRO~rh~lrS OF SPECIMENS
Specimen Dûge Tempereture Tensile Strength ~lon~tion No. (kGy) (~C) (MPa) At 3reak (%) 120 23 12.2 135S.O
2 0 23 3.2 232.9 Blow molded bottles made from polyisoprene/poly-c~prolactone Blend C, produced as described in Ex2mple 6, and bottles produced from high density polyethylene (HDPE) were pl~lced in exterior conditiong in garden soil, approximately 5 cm deep, from late March to late May in Vancouver, B.C. The bottlcs were inspected at the end of the experiment and tested for weight 1088, ag well as for surface damage visible with the naked eye and under a microscope. The results listed in Table 2 indicate biodegradation of bottles made from polyisoprene/polycaprolactone Blend C. The bottles made from polyethylene were ~lnr~hpn~ed.

W0 95/lS999 2 ~ 7 8 3 1 9 rCrlCA93/00530 D~r-~An~ION IN GARDEN SOIL OF BOTTLES
MADE FROM BLEND C IN COMPARISON WI~H
POLYETHYLENE BOTTLES
Bottle Exposure Weight Weight Weight Appearance Materials Period Initial After Loss (days) ~g) Exposure (g) (g) Blend C 70 13.661 12.787 0.874 Extensive sur~ace deterioration and coloniza-tion Polyethylene 70 13 . 312 13 . 294 0 . 018 No change E~AMPLE 1 0 Plastic sheets compre3sion molded from polyisoprene/
polycaprolactone Blend B or D in a similar manner to that described in Example 7, and id~nt;c~1 sheets made fro~ HDPE were immersed in sea water for a period of 30 or 90 days (at water temperature of lOt2C) from the be~;nn;n~ of February to the end of ~ay. The specimen s~yOouLs area was screened from direct sunlight. The sheets were inspected at the end of the period and tested for weight 1088, ch~nge in dimensions, surface damage, and growth o~ microorganisms visible with the naked eye 2nd under a microscope. The results li3ted in Table 3 indicate biodegradation of the sheets made from the polyisoprene/
polycaprolactone blends.

WO95115999 - ~ ~ 2 1 ~ 8 3 1 9 PC~ICA93100530 DEGRADATION IN SEA WATER OF SHEETS
MADE FROM BLEND B AND D IN COMPARISON
WITH HDPE SHEETS
Sheet Exposure Weight Los6 Appearance Materials Perlod per l00 cm2 ( days ) Sample ( g ) *
Blend B 30 0 . 07 Deposit o~ micro-organisms beginning l00 0.26 surface deterioration Blend D 30 0 . 08 Deposit of micro-org~nisms begLnning l00 0 . 38 surface deterioration HDPE 30 0 No visible change * Based on one sLde of specimen.
~MPLE 1 1 Hot-pressed film spe~ approximately 0.25 mm (l0 mil) made from polyisoprene/polycaprolactone Ble~d C were placed in a QW accelerated weathering machine along with linear low density polyethylene ~LLDPE - Dupont Sclair 2114) ~ilm specimens prepared in similar manner and were exposed according to ASTM D4329. WB-313 lamps were employed to irradiate the specimens with ultraviolet rays. The test condition consisted of alternating cycles of 8 hours of W
light followed by 4 hours of condensation. The temperature for the light cycle was 40C and 50C for the condensation cycle. Sample specimens were tested ~or tensile strength (TS) and elongation at break (EB) according to ASTM D882 after 200 hours and 400 hours accelerated aging. The results are shown in Table 4 and Table 5. The polyisoprene/polycapro-lactone Blend C showed greater 1088 o~ tensile strength and elongation at break in comparison with polyethylene.

'~ ~ 7 (17 1 t~ PCTICA93100530 W095115999 - ~ I I O J I

TENSILE ~lr~;NLlr~ (TS) OF BLEND C IN
COMPARISON WITH LLDPE AFTER
EXPOSURE TO Arr~r.~RA~ n WF~All~MT;~RTNG
Polymer Exposure 200 Hours Exposure 400 Hours TS TS Changes TS TS Changes Initial Final ( ~ ) IQitial Final MPa 2Pa MPa Mpa Blend C 19.2 13.4 -30 19.2 7.8 -59 Polyethylene 12.5 14.9 +19 12.5 9.9 -21 ELONGATION AT BREAg ( EB ) OF BLEND C
IN COMPARISON WITH POLYETHYLENNE AFTER.
~;~S~O~iUK~; TO Prr~T.~RATFn W~A~M~RTNG
Polymer Exposure 200 Hours Exposure 400 Hours EBEB Changes EB EB Changes Initial Final ( % ) Initial Final ( % ) (~) (4) (%) (~) Blend C 1120 666 -41 1120 18 -98 Polyethylene 36 17 -53 36 7 -81 It has also been found that the mixing of fatty acid and organic peroxide compatibllizers with polyisoprene/
polycaprolactone blends i ~ uv(,8 the production of high quality blown f ilms . This aspect of the invention will be described with reference to the following examples and the accompanying drawings, wherein:
Figure 1 is a graph of elongation at break versus stearic/palmitic acid content o~ blown polyisoprene/
polycaprolactone films;
Figure 2 is a graph of tensile strength versus stearic/palmitic acid content of polyisoprene/polycaprolactone f ilms;
- Figure 3 is a graph of elongatlon at break versus organic peroxide content of polyisoprene/polycaprolactone films;
Figure 4 i8 a graph of tensile strength versus organic 2t783~9 PCTICA93100~3Q

peroxide content of polyisoprene/polycaprolactone films containing stearic/palmitic Qcid; and Figures 5 and 6 are graphs of tensile strength and elongation at break for a variety of mixtures of polyisoprene (PI), polycaprolactone (PCL) and stearic/palmitic acid6.

5 kg of synthetic polyisoprene (Natsyn 2210* -Goodyear) was blended with 5 kg of polycaprolactone ~Tone 787* -Union Carbide) using a Brabender extruder with a 3/4 screw (L:D
= 25). Blending was carried out at 150C and the screw speed was established at 28 rpm. The blend was extruded through a 1/8" diameter die, cooled in a water bath and pelletized using a 2 " }~illion pelletizer . The preblended pellets were then mixed with various amount of additive, namely C16 - C18 saturated fatty acids (Emersol 132* - Henkel) and an organic peroxide (Trigonox 29/40* - Akzo), and blended again in the extruder at 140C with a 3crew speed established at 15 rpm. Emersol 132 is a mixture of palmitic and stearic acids. The active ingredient in Trigonox 29/40 is 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane. The blend was then extruded again through the 1/8" diameter die, cooled in water clnd pelletized. As set out in Table 6, a total of nine blends or specimens containing v~lriable quantities of additives were made as well as one control with no additives.
* - trndemark Wo 95/1s999 2 1 7 8 3 1 q PCT/CA93/oos3n Peroxide stearic/
(Trigonox 29/40 ) Palmitic Acid Specimen No. phr* phr*

3 0.00 0.00

4 0.00 2.00 0.03 2.00 6 0.06 2.00 7 0.12 2.00 8 0.20 2.00 9 0.06 0.00 lO 0.06 3.00 11 0.06 4.00 12 0 . 06 6 . 00 * Parts o~ additive per hundred parts of resin.
A Brabender extruder with a 3/4" screw (~:D = 25) and ancillary equipment (die, air cooling ring, compressed air supply and take off ) for making blown films was charged with granulated polyisoprene/polycaprolactone specimens 3 through 12 of Table 6.
The temperature of the heating zones were as follows:
zone 1 - 95C, Zone 2 - 100C, Zone 3 - 100C, Zone 4 - 95C and Die - 103C. Screw speed was established at 16 rpm and the take off equipment speed indicator was at 16. The film blowing pressure was .75 - 10 kPa, and the air pressure supplied to the cooling ring was 35 - 200 kPa.
The blown film sleeve made under the above described conditions was approximately 0.17 mm thick and 100 mm wide. The mechanical properties of elongation at break and tensile strcngth of the f ilm were tested f or the machine direction according to ASTM D-882. The results obtained from testing are set out in Table 7.

PCTICA93/nO530 _ Tensile Strength (MD) Elongation at Break Specimen No. MPa 36 . 44 440 413 . 1 890 514 . 4 860 614 . 4 830 713.5 740 815 . 3 700 911 . 2 550 1014 . 8 875 1115.5 880 1214 . 7 865 The results of the tests are set out in graph form in Figs. 1 to 4. The addition of small quantities of fatty acid increases the elong~tion at break. Small quantities of both additives increase the tensile strength of the f ilm.
The following Example 13 describes the preparation of polyisoprene~polycaprolactone blown films containing relative high proportions o~ polyisoprene.

5 kg of synthetic polyisoprene (Natsyn-22lo -Goodyear) was blended with 5 kg of poiycaprolactone (Tone 787 -Union Carbide) and 400 g stearic/palmitic acid (Emersol 132 -Henkel) using a Brabender extruder with 3/4" screw (L:D=25).
The blending was cerried out at 155C and the screw speed was est;-hl i ~hed at 28 rpm. The blend was extruded through a 1/8 "
diameter die, cooled in a water bath and pelletized using a 2"
Killion pelletizer. The pellets were then mixed with 8 g* of organic peroxide ~Trigonox 29/40-Akzo), and blended again in the extruder at 140C with screw speed established at 15 rpm, followed by extrusion through a 1/8" die and pelletization.
The pellets were again mixed with synthetic polyisoprene (Natsyn 2210) in ~uantities:
Blend 13 - 3122 g pellets and 1500 g synthetic polyisoprene, and *Based on total peroxide content of Trigonox 29/40 2 ~ 7 8 3 1 ~ CT/CA93100~30 Wo 9511Sg99 P
40 g ste2ric/palmitic acid.
Blend 14 - 3122 g pellets and 3000 g synthetic polyisoprene, and 240 g stearic/palmitic acid.
Blend 15 - 3122 pellets, 4500 g synthetic polyi30prene, and 330 g stearic/palmitic acid.
The materials were extruded again at 155C with the screw speed at 28 rpm and then pelletized. Finally, the thus obtained pellets of Blends 13, 14 and 15 were mixed with additional amounts of organic peroxide ~Trigonox 29/40 Akzo) in the quantities:
Blend 13 - 4000 g pellets and 1.05 g~ organic peroxide (Trigonox 29/40 ) .
Blend 14 - 5000 g pellets and l . 96 g* organic peroxide ~Trigonox 29 /40 ) .
Blend 15 - 6000 g pellets and 2.84 g* organic peroxide (Trigonox 29~40 ) .
Polyisoprene/polycaprolactone blends with peroxide were blended and extruded at 140C and at a screw speed 15 rpm, cooled in a water bath elnd pelletized again for further processing into blown ~ilms.
The equipment and procedure to make a blown film using the various blends is described in Example 12. The tensile strength and elongation at break test results for films made from blends 13 to 15 are set out in Table 8 and illustrated graphically in ~ig. 5.
TAi3~E 8 Specimens PI/PC~ Tensile Strength ~D Elongation at or Break M
slend No. D~Pa 9~
13 2/1 7.53 620 14 3/1 4 . 95 530 15 4/1 3 . 12 500 *Based on total peroxide content of Trigonox 29/40 WO gSI15999 Example 14 describes the mechanical properties of blown films produced from polyisoprene/polyc2prolactone mixtures using multiple stages of blending.

In a first stage (Stage 1) of blend preparation, A1 kg (see Table 9 for specific data) of synthetic polyisoprene (Natsyn 2210 - Goodyear) was blended with ~ kg of polycaprolactone (B~=Tone 787 and B2=Tone 767E - Union Carbide) and C~ kg of stearlc/palmitic acids (Emersol 132 - E~enkel) using a Brabender extruder with 3/4" screw (~:D=25). The blending was done at a temperature T1 and the screw speed was est~blished at 28 rpm. The blend was extruded through a 1/8" diameter die, cooled in a water bath, and pelletized using a 2 " Killion pelletizer .
In a second stage ~ St~ge 2 ), the pellets were miYed with D1 kg* of organic peroxide (Trigonox 29/40 - Akzo) and again blended in the extruder at T2=140C with the screw 6peed established at 15 rpm, followed by extrusion through a 1/8~ die, cooling and pelletizing.
In a third stage ( Stage 3 ), pellets were again mixed with synthetic polyisoprene (Natsyn 2210) in quantities of A2 and stearic/palmitic acids (Emersol 132 - E}enkel) in quantities C2. The mixture was again extruded at Ts=150C, cooled and pelletized .
Finally, in a fourth stage ( Stage 4 ), the pellets obtained were mixed with an additional amount D2 kg* of organic peroxide (Trigonox 29/4-Akzo), extruded at a tL.~ errlLuL~:
T4=140C with a screw speed at 15 rpm, cooled and pelletized.
~ ive di~erent blends 16 to 20 of polyisoprene/polycaprolactone were obtained. Conditions of blend preparation are listed in Table 9. The blends were processed into blown films.
*B2sed on total peroxide content of Trigonox 29/40 2 1 7 8 3 1 ~ Ag3/00s3n C) Q, ~ ~ ~ U O o o o o c) c) - ~u ~ ~, n n 'n CQ ~
r O N O
" ~ O O O
a ~N QN
C) ~ O O O
~ r c) c~ c~
Ct~ C4 ~ N N N
-- O C' O ~D O ~r Ll E N U O O O O O
o ~r ~ ~ r~ u~
~,~ C~ E rn ~ m r i c~ ; ~
o o o o c~
a- ~ a ~- a _I
F Et-- OU rn ',n ~ 'n c~ c~ E
~ ~ N N N N N
-r O ~O o O O _I O O _~ rn o o o r.~ In o _I O N ~ O N ~1 O O _I O _I o O O
N
¢ m u .~ u ~: m u ~ ~ U ~: m m U
o m _I ~ ~ ~ N

2 1 7 8 3 1 9 PcT/CA93lons3o Wo 95/15999 The equipment and procedure to make blown film using the blends is described in Example 12. The tensile strength and elongation at break test results ~or films m~de rom blend 16 ~nd 20 are listed in Table 10, and illustrated graphically in Fig. 6. In Fig. 6, bars P. represent tensile strength and barG s represent elongation at break.

Specimens Tensile Strength MD Elongation at Break or Blend No. MPa %
16 7 . 53 620 17 6 . 28 360 18 6 . 61 480 19 6.39 560

6 . 72 700 SU~ARY
The material described hereinbefore, namely the blend of polyisoprene and polycaprolactone resins, possesses a unique combination of the following properties:
~1~ thermoplastic properties that allow the material to be processed using conventional thermoplastic-working techniques; and ( 2 ) degradability properties that allow the material to completely degrade following the natural ---h~niRTrlC~ of biodegradation and photodegradation.
Blends of the material can be successfully processed using techniques such as injection molding, blow moldlng, thermoforming, extrusion, compression molding, and transer molding to produce articles commonly made with thermoplastic resins .
The addition of polycaprolactone to polyisoprene results in increased tensile modulus, and significantly reduced or eliminated elasticity in comparison to the original polyisoprene properties and imparts the ability for polymer orientation. Moreover, polycaprolactone alleviates the problem *Based on total peroxide content of Trigonox 29/40 W095/15999 ~ 2 1 7 8 3 1 9 PCTICA93/00530 of polyisoprene sticking to cold metal molds during thermoplastic processing.
Blends of the material will biodegrade in soil or sea water and will photodegrade upon exposure to aunlight, and are expected to generate only carbon dioxide and water as products of degradation.
The composition of the blends includes 10 to 500 parts by weight (pbw) of polycaprolactone per 100 pbw polyisoprene, with the preferred range being 25 to 200 pbw polycaprolactone to 100 pbw polyisoprene. Additives commonly used in the plastic and rubber industry may be added to the blends in small amounts in order to e~hance properties.
As demonstrated in Examples 13 and 14, in accordance with the present invention it has proven possible to make blown films with a polyisoprene/polycaprolactone ratio of 4:1 ~20%
polycaprolactone in total polymer content ) . The thorough mixing of the polyisoprene and the polycaprolactone be~ore the introduction of the peroxide appears to be important. In addition to Trigonox 29/40, after organic peroxides which may be added to the blend include inter alia Trigonox 21 (t-butylperoxy-2-ethylhexanoate), Trigonox 41C50 (t-butyl peroxyiso~u~yL~l~e) and Laurox* (dilauroyl peroxide).
The prior art describes polyisoprene/polycapro-l~ctone blends which possess thermoplastic properties ( see rAn;~liAn Patent5 Nog. 1,080,875 and 1,111,179) but, because of the use of _ n~nts such as sulphur vulcanized natural rubber or ionomer copolymer, the feature of degradability is not addressed. Manufacturing goods using conventional thermoplastic processes is not mentioned. In the one case where biodegradability is mentioned, (Japanese Patent 89293048), polyisoprene/polycaprolactone comprise a part of a formulation, for which thermoplastic properties, and photodegradable are not re~Iuired or f eatured . ~ence, the known prior art does not teach ~n~d rh~ rlAf~tiCitY and degradability propertie~ .
* trademark

Claims (24)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A biodegradable and photodegradable, thermoplastic polymer composition comprising a blend of 10 to 500 parts be weight polycaprolactone per100 parts by weight polyisoprene, and a small quantity of at least one saturatedhigher faffy acid and an organic peroxide.

2. A composition according to claim 1, including 25 to 200 parts by weight polycaprolactone per 100 parts be weight polyisoprene.

3. A composition according to claim 1 or 2, wherein the polyisoprene is in the form of natural rubber.

4. A composition according to claim 1, wherein the flow properties of the composition above the softening point permit processing of the composition using conventional thermoplastic working methods.

5. A composition according to claim 1 which can be permanently oriented by the application of force.

6. A composition according to claim 1, including polyisoprene and polycaprolactone in a weight ratio of up to 4:1, and a small quantity of saturated higher fatty acids.

7. A composition according to claim 1, including polyisoprene and polycaprolactone in a weight ratio of up to 4:1, and a small quantity of stearic/palmitic acids.

8. A composition according to claim 7, wherein said organic peroxide is 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane.

9. A method for making a biodegradable and photodegradable, thermoplastic polymer composition comprising the steps of:
(a) blending 10 to 500 parts by weight polycaprolactone with 100 parts weight polyisoprene at a temperature above 60°C and a small quantity of at least one saturated higher fatty acid and an organic peroxide; and (b) processing the resulting polymer blend into a form suitable for further thermoplastic working.

10. A method according to claim 9, wherein the polycaprolactone is first thoroughly blended with the polyisoprene, at least onesaturated fatty acid and the organic peroxide are added to the blend, and the blend is thoroughly mixed to produce the polymer blend for further working.

11. A method according to claim 10, wherein 50 to 200 parts by weight polycaprolactone is blended with 100 parts by weight polyisoprene.

12. A method according to claim 10, wherein blending is performed at a temperature of 65 to 75°C.

13. A method according to claim 10, including the step of: (c) adding to the composition a small quantity of an additive selected from the group consisting of casein, antioxidants, dyes, fillers, vulcanized vegetable oils, coupling agents, fragrances blowing agents, antistatic agents, fire retardants and pigments.

14. A method according to claim 10, including the step of molding the blend to form a biodegradable and photodegradable plastic article.

15. A method according to claim 14, wherein the blend is injection molded.

16. A method according to claim 14, wherein the blend is blow molded.

17. A method according to claim 14, wherein the blend is extruded.

18. A method according to claim 14, including the step of irradiating the article.

19. A method according to claim 14, wherein the blend contains polyisoprene and polycaprolactone in a weight ratio of up to 4:1, and the blend is used to produce a blown film.

20. A method according to claim 19, wherein the blend contains a small quantity of saturated higher fatty acids.

21. A method according to claim 19, wherein the blend contains a small quantity of stearic/palmitic acids.

22. A method according to claim 20, wherein the blend contains a small quantity of an organic peroxide.

23. A method according to claim 22, wherein the organic peroxide is 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane.

24. A method according to claim 23, including the step of irradiating the blown film.