EP0082154A1

EP0082154A1 - Clear, autoclavable thermoplastic formulation for medical liquid containers

Info

Publication number: EP0082154A1
Application number: EP82901673A
Authority: EP
Inventors: Mostafa Zomorodi; Alan Jay Trieber
Original assignee: Abbott Laboratories
Current assignee: Abbott Laboratories
Priority date: 1981-06-29
Filing date: 1982-04-15
Publication date: 1983-06-29
Also published as: PH18514A; WO1983000158A1; IT8222101A0; ES8403500A1; IT1153547B; BR8207774A; ES513453A0; CA1191985A; JPS58501035A; ZA823100B

Abstract

Matériau thermoplastique transparent flexible, pouvant être traité pour obtenir des formes creuses par des procédés de traitement thermoplastiques conventionnels, puis autoclavés, et comprenant trois composants: de 40 à 70 % environ en poids d'une polyoléfine consistant essentiellement en polypropylène, mélangée avec 5 à 40 % environ en poids d'un polymère sélectionné dans le groupe consistant en acrylate d'un alkyle inférieur éthylénique, et de 5 à 40 % environ en poids d'une composition élastomère thermoplastique sélectionnée parmi le groupe consistant en un copolymère en bloc, essentiellement du butylène d'éthylène et ayant des unités terminales de polystyrène, un copolymère en bloc consistant essentiellement en styrène de butadiène et ayant des unités terminales de polystirène, un élastomère d'oléfine du type éthylène propylène, et du caoutchouc butylique (polybutadiène isoprène). Le matériau décrit ci-dessus est particulièrement approprié à la fabrication de conteneurs de liquides médicaux tels que des conteneurs autoclavables flexibles pliants pour des solutions intraveineuses.Flexible transparent thermoplastic material, which can be treated to obtain hollow shapes by conventional thermoplastic treatment methods, then autoclaved, and comprising three components: from 40 to 70% by weight of a polyolefin consisting essentially of polypropylene, mixed with 5 to Approximately 40% by weight of a polymer selected from the group consisting of acrylate of a lower ethylenic alkyl, and from 5 to 40% approximately by weight of a thermoplastic elastomer composition selected from the group consisting of a block copolymer, essentially ethylene butylene and having polystyrene end units, a block copolymer consisting essentially of butadiene styrene and having polystirene end units, an olefin elastomer of the ethylene propylene type, and butyl rubber (polybutadiene isoprene). The material described above is particularly suitable for the manufacture of containers for medical liquids such as flexible collapsible autoclavable containers for intravenous solutions.

Description

CLEAR, AUTOCLAVABLE THERMOPLASTIC FORMULATION FOR MEDICAL LIQUID CONTAINERS

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 intravenous 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 formulations of block copolymers which include polypropylene may be found in U.S. Patent No. 3,792,124. These formulations 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 ethylene propylene type, or butyl rubber (polybutadiene isoprene).

Ingredient (A) as described above is a polyolefin 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:

The general mechanical properties of EMA may be found in Table II below.

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, significant reduction in flexural modulus, and improvement in stress crack resistance. A key attribute cf EMA resin, compared with other coρolymers of low density polyethylene is EMA's great thersal stability. EMA can be processed 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 temperature- 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. Although EMA is the preferred embodiment of element B of the material, other loweralkyl ethylene acrylates may be utilized such as ethylene ethyl acrylate 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 having 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 incorporated 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 Corporation 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.

In a preferred embodiment, 10% ethylene methyl acrylate was mixed with 90% polypropylene. The resulting combination was then mixed in a proportion of 70% EMA polypropylene to 30% element C. The resulting material exhibited the following properties, as seen in Table IV.

In addition, the resulting formulation was found to be highly suitable for sheet extrusion, injection molding or blow molding into flexible, transparent, autoclavable intravenous solution containers. In particular, the resulting container was found to be of sufficient strength to withstand heavy impact during shipment and use, while at the same time being sufficiently flexible to collapse easily during drainage of intravenous solution from the container. The following examples further illustrate specific embodiments of the invention.

Example 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 premixed 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 Romellog Fellbach of Oeffingen. The material was found to be successfully fabricated into a transparent, flexible, collapsible intravenous solution container which was autoclavable under a typical sterilizing cycle without an distortion.

Example 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 hydrogenated 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 between about 2,000 and 50,000 and the hydrogenated polybutadiene 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 copolymer) 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.

Example 4

In this Example, the same percentages of elements 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 identity 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 percent 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 millad 3900 polyolefin clarifies both manufactured by Miniiken 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 modifications and variations therein without departing from the scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A clear, flexible thermoplastic material capable of being processed into hollow shapes by conventional plastic processing methods and subsequently autoclaved comprising: (a) from about 40 - 70% by weight of a polyolefin 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 thermoplastic 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 polyolefin consistng essentially of propylene admixed with, (b) from about 5 to 40% by weight of a polymer selected from the group consisting of ethylene loweralkyl acrylates, and

(c) from about 5 to 40% by weight of a thermoplastic elastomer selected from the group consisting of polyolefin elastomers, polyester elastomers, block copolymers of styrene and butadiene or isoprene or butadiene isoprene, and block copolymers of styrene and ethylene or butylene or ethylene butylene.

3. The thermoplastic formulation as disclosed in Claim 1 wherein said ethylene butylene block copolymer 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 comprises: 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 unsaturation has been reduced by hydrogenation.

5. The thermoplastic formulation as disclosed in Claim 1 and wherein said block copolymer has thermoplastic 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 substantially 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 approximately 90% by weight polyolefin and 10% by weight polymer, said mixture then being mechanically combined with said thermoplastic composition in a ratio of approximately 70% by weight polyolefin/pclymer mixture to approximately 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 dimonomer 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 polybutadiene.

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 autoclaved, 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.