CLEAR, AUTOCLAVABLE THERMOPLASTIC FORMULATION FOR MEDICAL LIQUID CONTAINERS

Abstract: A clear, flexible, thermoplastic material capable of being processed into hollow shapes by conventional thermoplastic processing methods and subsequently autoclaved, comprises three components; from about 40 to 70 % by weight of a polyolefin consisting essentially of polypropylene, admixed with from about 5 to 40 % by weight of a polymer selected from the group consisting of ethylene loweralkyl acrylate; and from about 5 to 40 % by weight of a thermoplastic elastomer composition selected from the group consisting of a block copolymer consisting essentially of ethylene butylene and having terminal polystyrene units, a block copolymer consisting essentially of butadiene styrene and having terminal polystyrene units, an olefin elastomer of the ethylene propylene type, and butyl rubber (polybutadiene isoprene). The above material is particularly desirable for manufacturing medical liquid containers such as autoclavable, flexible, collapsible, intravenous solution containers.

Description: -i- CLEAR, AUTOCLAVABLE THERMOPLASTIC FORMULATION FOR MEDICAL LIQUID CONTAI Background of Invention The present application relates generally to medical plastic formulations and particularly to medical liquid containers such as flexible, collapsible, intra- venous solution containers. The materials disclosed exhibit the particular advantages of being essentially transparent, soft and flexible, essentially free of extractables, and able to resist high temperatures present in autoclaving. Various materials have been utilized for intra¬ venous solution containers in the past. In particular, U.S. Patent No. 4,140,162 discloses a formulation for medical liquid containers containing both polypropylene and a block copolymer. A third ingredient disclosed comprises polyethylene or polyethylene vinyl acetate. The present invention is distinguished from the '162 patent by the use of ethylene methyl acrylate, which is lower in cost and provides more desirable physical properties such as improved thermal stability and a wider range of processing temperatures. Other formula¬ tions of block copoly ers which include polypropylene may be found in U.S. Patent No. 3,792,124. These formu¬ lations are not suitable for flexible medical liquid containers, however, in that they are ionic, which would alter the solutions contained therein. Summary of the Invention In accordance with this invention, a clear, flexible, thermoplastic material is provided, capable of being processed into hollow shapes by conventional plas- tic processing methods and subsequently autoclaved. The material comprises: (A) from about 40 to 70% by weight of a polyolefin, usually polypropylene aάir.ixed with (B) from about 5 to 40% by weight of an ethylene loweralkyl acrylate; and (C) from about 5 to 40% by weight of one of several block copolymers: ethylene butylene having terminal polystyrene units, butadiene styrene having terminal polystyrene units, an olefin elastomer of the " B URSA OMPI ethylene propylene type, or butyl rubber (polybutadiene isoprene) . Ingredient (A) as described above is a poly¬ olefin consisting essentially of polypropylene units. Many commercial varieties of polypropylene contain small amounts of ethylene units. This does not make a major impact on the properties of the propylene material. Ingredient (B) generally comprises ethylene methyl acrylate (EMA) and is commercially available from Gulf Oil Chemicals Co., Orange, Texas, under the numbers 2205 and 2255. EMA is a random copolymer consisting of a polyethylene backbone with methyl acrylate side branches. Gulf's present commercial product contains approximately 20% by weight of methyl acrylate. EMA's distinguishing properties include a low melt temperature and corresponding easy heat sealability, as well as good thermal stability in the range of 600 to 630° F., and "rubbery" mechanical properties, including low stiffness, high elongation, clarity and high impact strength. A comparison of ethylene methyl acrylate to ethylene vinyl acetate may be seen in the following Table I: Table I EMA EVA Processing Range, F 300-620 450 Max Thermal Stability Excellent Poor Corrosive Possibility No Yes Pellets Require Protection from Moisture During Storage NO No Moisture Barrier Fair Fair Adhesion to Substrates: Paper Excellent Excellent-Good OP? Excellent Poor Cellophane (PVDC-Coated) Excellent Poor Aluminum Foil (Unprirced) Poor Poor Price, /lb. 59-1/2 41-1/2-61-1/2 fd/cu. in. 2 1.4-2.0 OMPI The general mechanical properties of EMA may be found in Table II below. J Table II Property Comparison of EMA to LDPΞ EMA LDPE Melt Index 2.4 2 Density, gm/cc 0.942 0.917 Vicat Softening Point, F. 138 194 Tensile Str. psi 1620 1850 Elongation, % 720 650 Hardness, Shore D 35 46 Flex, stiffness, psi 4000 18,500 Stress Crack Resist. No 90% (Hostapal, 122 F) Failures Failures Dielectric Constant S 100 kHz 3.1 2.3 Dissipation Factor • 9 100 KhZ 0.015 0.0002 Low- Temp. Brittle- No 10% ness to -105F Failures Failures Price, ^/lb. 59-1/2 43-1/2 As shown in Table II, the most notable property changes brought about by the copolynerization of ethylene with methyl acrylate are: depression of melting point, signi¬ ficant reduction in flexural modulus, and improvement in stress crack resistance. A key attribute cf EMA resin, compared with other coρoly--ters of low density polyethyl¬ ene is EMA's great thersal stability. EMA can be pro¬ cessed at very high temperatures; up to 600 to 630°F. without polymer breakdown anc/or chain cission. Some of the other low density polyethylene copolymers, like EVA, when mixed with high * cerr.perature~resistant plastics such as polypropylene and high density polyethylene and heated in excess of 450°F. begin to break down and liberate acids that attack netal surfaces of extrusion equipment. O. PI Although EMA is the preferred embodiment of element B of the material, other loweralkyl ethylene acrylates may be utilized such as ethylene ethyl acry¬ late and ethylene butyl acrylate, with similar results. "Loweralkyl" is defined as an alkyl group having 1-5 carbon atoms, such as ethyl, methyl, butyl, etc. The third element (C) of this novel plastic material comprises from about 5 to 40% by weight of a thermoplastic composition; usually a block copolymer of ethylene butylene having terminal polystyrene units. Ethylene butylene block copolymers having terminal polystyrene units are commercially available under the trademark Kraton G® from the Shell Chemical Co. Other rubbery block copolymers such as butadiene styrene hav- ing terminal polystyrene units may also be utilized. For example, the impermeable polymeric compositions disclosed in U.S. Patent 3,686,364 assigned to Polymer Corporation Limited, hereby incorporated by reference, discloses a series of butadiene styrene block copolymers useful as the third element in the present application. Similarly, the block copolymers disclosed in U.S. Patent 3,865,776 assigned to Shell Oil Company, hereby inco po¬ rated by reference, may also be utilized. Similarly, U.S. Patent 3,970,719 assigned to Philips Petroleum Company discloses block copolymers wherein alpha olefins and/or mixtures of alpha olefins are manufactured. These are sold under the trademark Solprene 406, 411, 414 and 475 and may also be utilized. Ethylene propylene dienemonomer, available from Exxon as Vistalon #721, #404,.#457, #714, #707 or #719, or ethylene propylene dienemonomer elastomer, available from Heisler Corporatio under the number HC-5214, may also be used as the third ingredient of the material. Polyisobutylene elastomers sold by Exxon as LM Vistanex, Vistanex MML-80, 100 and 120 and isobutylene isoprene copolymers such as Exxon Butyl 077 and butyl rubber, from Polysar of Canada, may also be utilized as the third ingredient. The following Table III discloses a series of examples of the above listed material, showing in particu lar, the proportionate percentages, by weight, of element A, B and C. Table III Preferred Embodiments PP EMA EEA KRATON MATZ 10D 90% 10% (2205) 70% 30% MATZ 7D 80% 20% (2255) 70% 30% MZ03-3 70% 30% 70% 30% In a preferred embodiment, 10% ethylene methyl acrylate was mixed with 90% polypropylene. The resulting combi¬ nation was then mixed in a proportion of 70% EMA poly¬ propylene to 30% element C. The resulting material exhibited the following properties, as seen in Table IV. TϋREΛ OMPI • tabJo IV M/V17. ΪOΪ) Irradiated Irradiated Injection Molded and and ■ lOst nars Control Autoclaved Irradiated Autoclaved Irradiated Autoclaved 'tensi le (psi) 2006 2041 1947 1947 1935 1971 liltonηntion (% ) 490 233 707 273 473 177 100% Modulus (psi) 1909 2228 1053 2159 1948 2112 Yi eld (psi) 2066 2228 2041 2230 2065 2305 • lOti l.now. 9976 4973 1.4097 5702 9460 3784 (IJH? in/in ) MΛT7, 71) • tensile (psi ) 1042 .1812 18.18 1795 1947 1042 I Rloncjatlon (V. ) 520 440 587 367 600 303 CΛ I 00'ft MrxTiil uπ (pui ) πn 1883 1648 1017 1795 1842 Yiold (p?si ) 1653 1707 1653 1748 1724 1760 9087 7910 10107 6501 11013 6090 ( l-D-F in/in 3 ) M203-3 onπile (psi) 1994 1042 1030 1760 1771 1042 Klnnqnbion (* ) 607 360 663 5J3 540 520 100% Modulus (psi) 1560 1007 1490 1690 1467 1713 Yiαld (psi) 1525 1666 1525 1455 1400 1670 In addition, the resulting formulation was found to be highly suitable for sheet extrusion, injec¬ tion molding or blow molding into flexible, transparent, autoclavable intravenous solution containers. In par- ticular, the resulting container was found to be of sufficient strength to withstand heavy impact during shipment and use, while at the same time being suffi¬ ciently flexible to collapse easily during drainage of intravenous solution from the container. The following examples further illustrate specific embodiments of the invention. Exa ple 1 A block copolymer having thermoplastic rubber characteristics consisting essentially of a rubbery olefin polymer of generally equal proportions of ethylen and butylene units in terminal blocks of polystyrene was added to a rotational mixer in the amount of 40% by weight with 10% by weight of a blend of 90% polypropylen and 10% EMA. The block copolymer used was Kraton 2705 sold by the Shell Chemical Company. Mechanical proper- ties of Kraton 2705 are as follows: Hardness, shore A 52 Tensile properties, ASTM D-412 Tensile strength, psi 1650 Elongation at break 800 Modulus at 100% extension, psi 200 Set after break, % 55 Tear strength, pli (ASTM D-624) 130 Compression set at 70°C, % (ASTM D-395) 32 Yerzley resilience, % (ASTM D-945) 75 Specific gravity 0.90 The ingredients were pre ixed in the rotational mixer and then introduced into an extruder for extrusion into a rod. The rods were then chopped into smaller pellet sized pieces. The chopped pellets were utilized in the commercially available blow molding apparatus, specifically a continuous extrusion machine, with a secondary blow station manufactured by Ro ellog Fell- bach of Oeffingen. The material was found to be suc¬ cessfully fabricated into a transparent, flexible, col- lapsible intravenous solution container which was auto- clavable under a typical sterilizing cycle without an distortion. Exarvo -le 2 The above listed percentages were duplicated utilizing as element C of the composition, a different block copolymer, said block copolymer being either a linear or a branched block copolymer having at least two polymer blocks A and at least one polymer block B, each polymer block A being selected from the group consisting of monoalkenyl arine polymers and hydrogenated products thereof wherein no more than 25% of the arine double bonds had been reduced and polymer block B is a hydro¬ genated polymer block of a C4-5 conjugated diene polymer wherein at least about 30% of the aliphatic unsaturation has been reduced by hydrogenation. Specifically, each polystyrene block has an average molecular weight be- tween about 2,000 and 50,000 and the hydrogenated poly- butadiene block has an average molecular weight between about 20,000 and 300,000. Example 3 A block copolymer of general form polyalpha- methyl-styrene-polybutadine-polyethylmethl styrene (hereinafter referred to as alpha-beta-alpha block co¬ polymer) was prepared and blended with uncured butyl rubber. The alpha-beta-alpha block copolymer had an alpha methyl styrene content of approximately 35% weight and a molecular weight of about 60,000. Three separate blends were prepared using 30, 40 and 50 parts by weight of butyl rubber respectively with 100 parts by weight of alpha-beta-alpha block copolymer. The blending was carried out on a πiicromil, the mil rolls were at elevated temperatures in the range of about 130°C. to about 150°C. The resulting blends were then admixed with components A and B as previously described. Examp —le 4 In this Example, the same percentages of ele- ments A and B of the composition are disclosed in Example 2. Element C comprises 10% by weight of a thermoplastic composition comprising a block copolymer having at least two monoalkenyl arine polymer blocks and at least one substantially completely hydrogenated diene polymer block. For example, polymer block A is a block copolymer having the structure polystyrene-completely hydrogenated polybutadiene-polystyrene with block molecular weights of 25,000-100,000-25,000. An alternative formulation is a block copolymer of the same structure and block identi¬ ty but having block molecular weights of 10,000-50,000- 10,000. Example 5 A block copolymer of general form polyethyl- methyl styrene polybutadiene polyethyl methyl styrene was prepared with different quantities of uncured butyl rubber. The alpha-beta-alpha block copolymer had an alpha methyl styrene content of approximately 35 per¬ cent by weight and a molecular weight of about 60,000. The nonterminal elastomer block may be polybutadiene, or polybutadiene and butyl rubber. The resulting block copolymer was then admixed with components A and B. Examole 6 Other specific aliphatic olefins, aromatic olefins and/or mixtures thereof may be selected from the following list and utilized according to the teach- ings herein: TPR thermoplastic rubber 1600, ϋniroyal, Inc. Naugatuk, Connecticut; Combinations of isotatic polypropylene and ethylene propylene rubber; TPR thermoplastic rubber 1900, ϋniroyal. Inc., Naugatuk, Connecticut; As in an additional ingredient, from .25 to .5% of a nucleating agent such as sodium benzoate or illad 3900 polyolefin clarifies both manufactured by iniicen Corp., nay be added to the above listed formulations to improve clarity. The foregoing description and drawings merely explain and illlustrate the invention, and the invention is not so limited thereto, except insofar as the appended claims are limited to those skilled in the art who have the disclosure before them and are able to make modifica¬ tions and variations therein without departing from the scope of the invention.

Claims: HAT IS CLAIMED IS: 1. A clear, flexible thermoplastic material capable of being processed into hollow shapes by conven¬ tional plastic processing methods and subsequently auto¬ claved comprising: (a) from about 40 - 70% by weight of a poly¬ olefin consisting essentially of polypropylene, admixed with, (b) from about 5 - 40% by weight of ethylene loweralkyl acrylate polymers, and (c) from about 5 to 40% by weight of a thermo¬ plastic elastomer composition selected from the group consisting of: an ethylene butylene block copolymer having terminal polystyrene units, a butadiene styrene block copolymer having terminal polystyrene units, an olefin elastomer of the ethylene propylene type; and butyl rubber. 2. A clear, flexible thermoplastic material capable of being blow molded and autoclaved comprising: (a) from about 40 to 70% by weight of a poly¬ olefin consistng essentially of propylene admixed with, (b) from about 5 to 40% by weight of a poly¬ mer selected from the group consisting of ethylene lower¬ alkyl acrylates, and (c) from about 5 to 40% by weight of a ther¬ moplastic elastomer selected from the group consisting of polyolefin elastomers, polyester elastomers, block copolymers cf styrene and butadiene or isoprene or buta¬ diene isoprene, and block copolymers of styrene and ethylene or butylene or ethylene butylene. "BU E OMPI 3. The thermoplastic formulation as disclosed in Claim 1 wherein said ethylene butylene block copoly¬ mer has a central block comprising 50 to 85% by weight of the copolymer molecule of a rubbery olefin polymer of generally equal proportions of ethylene and butylene units; and terminal blocks of polystyrene. 4. The thermoplastic formulation as disclosed in Claim 1 wherein said thermoplastic composition com¬ prises: a block copolymer having at least two polymer blocks A and at least one polymer block B, each polymer block A being selected from the group consisting of monoalkenyl arene polymers and hydrogenated products thereof wherein no more than 25% of the arene double bonds have been reduced and polymer block B is a hydrogenated polymer block of a C 4-5 conjugated diene polymer wherein at least about 30% of the aliphatic un¬ saturation has been reduced by hydrogenation. 5. The thermoplastic formulation as disclosed in Claim 1 and wherein said block copolymer has thermo¬ plastic terminal blocks selected from polystyrene and polyalphamethyl styrene and the nonterminal elastomer block is a polymer of a conjugated diolefinic hydrocarbon and a polvmer comprising isobutylene and butyl rubber. 6. The thermoplastic formulation as disclosed in Claim 1 wherein said block copolymer has at least two monoalkenylarene polymer blocks and at least one sub¬ stantially completely hydrogenated diene polyaer block. 7. The thermoplastic formulation as disclosed in Claim 3 wherein said polyolefin (a) and said polymer (b) are mechanically combined in a mixture of approxi¬ mately 90% by weight polyolefin and 10% by weight poly- mer, said mixture then being mechanically combined with said thermoplastic composition in a ratio of approxi¬ mately 70% by weight polyolefin/pclymer mixture to ap¬ proximately 30% by weight thermoplastic composition. 8. The thermoplastic formulation as disclosed in Claim 1 wherein said ethylene loweralkyl acrylate is selected from the group consisting of ethylene methyl acrylate, and said polyolefin and said polvmer are mechanically combined in a mixture of approximately 90% by weight polyolefin and 10% by weight ethylene methyl acrylate, said mixture then being mechanically combined with ethylene propylene dienemonomer elastomer in a ratio of approximately 70% by weight polyolefin/ethylene methyl acrylate to approximately 30% ethylene propylene di onomer elastomer. 9. The thermoplastic formulation as disclosed in Claim 5 wherein said thermoplastic elastomer block copolymer is polyalphamethylstyrene-polydiolefin-poly- alphamethylstyrene block copolymer containing about 30- 35 percent by weight of alphamethylstyrene. 10. The thermoplastic formulation as disclosed in Claim 5 wherein said nonelastomeric block is polybuta¬ diene. 11. The composition of Claim 5 wherein said isobutylene polvmer is butyl rubber. 12. The thermoplastic composition as disclosed in Claim 6 wherein said block copolymer has the structure polystyrene hydrogenated polybutadiene polystyrene. 13. A clear, flexible, collapsible container capable of being blow molded and autoclaved, made from the thermoplastic material disclosed in Claim 1 or 2. 14. A clear, flexible, collapsible medical liquid container capable of being blow molded and auto¬ claved, made from the thermoplastic material disclosed in Claim 1 or 2. 15. The thermoplastic formulation as disclosed in Claim 1 or 2 wherein a nucleating agent selected from the group consisting of sodium benzoate is added in a concentration of .25 to .5% by weight thereby markedly improving the clarity of said thermoplastic formulation. 'BU OM

Inventors: TRIEBER ALAN JAY, ZOMORODI MOSTAFA, TRIEBER, ALAN, JAY, ZOMORODI, MOSTAFA
Applicants: ABBOTT LAB, ABBOTT LABORATORIES
Application year: 1982
Main classification: C08L23
IPC codes: A61J1, A61L2, C08L23, C08L53