CA1114982A - Thermoplastic composition for the manufacture of medical apparatuses and instruments - Google Patents

Abstract

THERMOPLASTIC COMPOSITION FOR THE MANUFACTURE OF
MEDICAL APPARATUSES AND INSTRUMENTS
Abstract of the disclosure:
The invention relates to a thermoplastic composition for the manufacture of medical apparatuses and instruments, which come into contact with parenteral liquids. This composi-tion consists of from 50 to 99.5 parts by weight of a chlorinat-ed polyolefin having a chlorine content of from 15 to 45 % by weight and an average molecular weight of from 30,000 to 300,000 and of from 0.5 to 50 parts by weight of polymers of acrylic and/or methacrylic acid esters.
The receptacles prepared have a low permeability for gases and microorganisms. Their water vapor permeability is also low, but may be adjusted within definite limits.

Description

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The present invention relates to a thermoplastic compo-sition for the manufacture of medical apparatuses and instruments.
It is known to use receptacles made from pasticizer-containing polyvinyl chloride for collecting, treating andadministering parenteral liquids, for example blood, blood substitutes, infusion solutions and other physiological liquids. This application requires, on the one hand, a high strength of the receptacle and, on the other hand, good flexural properties, a sterilization resistance and a good weldability and furthermore a high transparency in order to enable an observation of a possible agglutination of the blood. These PVC mixtures have the disadvantage that the plasticizer contained therein may migrate or be extracted.
German Auslegeschrift 2,502,182 points to this fact. Plasti-cizer-containing poly~inyl chloride has the further disad-vantage that it has a relatively high water vapor permeabi-.~ lity, which after extended storage of aqueous liquids in receptacles made therefrom leads to evaporation losses.
Therefore, plastics containers must be enclosed additional-; ly in metal containers.
Polyvinyl chloride mixtures which contain so-called polymer plasticizers show a less pronounced migration and a lower extractibility of the plasticizers. However, a pH
shifting occurs in the course of the water vapor steriliza-tion in an autoclave at a temperature of 120C, due to a limited hydrolyzability of the polymer plasticizers and, as a consequence of the extraction of oxidizable substances, 29 an increase of the permanganate indices in the aqueous : .

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extract. For this reason, the aforesaid German Auslege-schrift 2,503,182 proposes the use of a definite polyure-thane Or high purity as plasticizer for PVC.
A very high purity, however, involves procedures which render the mixtures according to the aforesaid German Auslegeschrift expensive and on the other hand, the water vapor permeability of these mixtures, too, is above the desired value.
The present invention, consequently, was confronted with the problem of providing a thermoplastic composition for the manufacture of medical apparatuses and instruments, which should not have the aforesaid disadvantages, that is to say, which contains no extractible or hydrolyzable components while having a low water vapor permeability, a high transparency and strength and a good weldability.
This problem is solved by using for the manufacture of medical apparatuses and instruments coming into contact with parenteral liquids, for example blood, blood substitu-tes, infusion solutions and other physiological liquids a thermoplastic composition consisting of a definite mixture of a special chlorinated polyolefin and polymers of acrylic and/or methacrylic acid esters.
The present invention, consequently, relates to a ther-moplastic composition for the manufacture of medical appara-tuses and instruments which come into contact with paren-teral liquids, characterized by consisting of from 50 to 99.5, preferably of from 70 to 98, parts by weight of chlo-rinated polyolefin having a chlorine content of from 15 to 29 45, preferably of from 25 to 40 % by weight and an average C~

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molecular weight of from 30,000 to 300,000, preferably of from 40,000 to 100,000 (calculated from the chlorine content and from the molecular weight of the starting polyethylene, determined by gel chromatography; cf. WeRlau, Makromoleku-lare Chemie, 26, (1958), pages 96 - 101) and of from 0.5 to 50, preferably of from 2 to 30, parts by weight of polymers of acrylic and/or methacrylic acid esters.
The present invention moreover relates to a method of using this thermoplastic composition for the manufacture of corresponding medical apparatuses and to these medical apparatuses.
Suitable chlorinated polyolefins are chlorination pro-ducts of polyolefins especially polyethylene, polypropylene and copolymers of ethylene and propylene, especially low ~- 15 pressure polyethylene and copolymers of ethylene having low portions of, for example, from 1 to 5 mol % of propene, butene-1 or hexene-1.
The polyolefins used for the chlorination advantageous-ly have a reduced specific viscosity (RSV)-determined with a 0.1 ~ solution in decahydronaphthalene, at 135C, accord-ing to ISO/R 1191 - of from 1 to 10, preferably of from 1.2 to 5 dl/g. When using polyolefins of higher RSV value (higher molecular weight) for the chlorination, there are obtained thermoplastic compositions which are difficult to process, whereas polyolefins of lower RSV values yield compositions which have rather bad mechanical properties.
Since the water vapor permeability of the compositions is influenced by the crystallinity of the chlorinated 29 polyolefins, there are used preferably chlorinated polyole-,~ . .

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fins which have a residual crystal content of from 1 to 20, preferably o~ from 5 to 15, % determined by differential thermoanalysis.
The polyolefins are preferably chlorinated in aqueous suspension, for example according to the process of German Auslegeschrift 1,420,415.
The thermoplastic composition to be used according to the present invention may be prepared by mixing both poly-mers, preferably according to the melt mixing process.
The transparency of mixtures of this type may be improved by using a poiymer of acrylic and/or methacrylic acid ester, whose refractive index is substantially adapted to that of the chloroolefin, for example by using a copolymer of two adequate acrylates or methacrylates.
A better homogenization and, consequently, a better transparency is obtained when polymerizing the acrylic and/or methacrylic acid esters in the presence of the chlorinated polyolefin. For this reason, preference is given to the use of one of the thermoplastic compositions prepared according to the present invention.
The acrylic and/or methacrylic acid esters are poly-;; merized in the presence of the chlorinated polyolefins, preferably in aqueous suspension, for example, in the folowing manner: The chloroolefin is suspended in water in the presence of conventional suspension auxiliaries, forexample partially saponified polyvinyl acetate, alkyl celluloses, for example methyl cellulose, hydroxyalkyl celluloses, for example hydroxypropyl cellulose, alkoxyal-29 kyl-celluloses, for example methyl-oxyethyl cellulose, , ' . "', "~ ' '' ' . ' - ' ' " ' `~
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or gelatin, the monomer(s) is (are) added thereto and the batch is stirred at room temperature or at slightly elevated temperature in order to swell the chloroolefin in the monomer or monomer mixture. Thereafter the free radical-forming agent and optionally a molecular weight regulatorare added and the batch is heated to the polymerization temperature, which generally is in the range of from 30 to 120C, preferably of from 40 to 100C. Alternatively, the chloropolyolefin may first be swelled in the monomer or monomer mixture and/or be dissolved therein, the resulting dispersion or solution may be dispersed in water while adding the suspension agent while the rest of the procedure is as described above.
Suitable free radical-forming agents are conventional compounds for this purpose, for example peroxides such as benzoylperoxide, lauroylperoxide, peresters such as tertiary butylperoxybenzoate or tertiary butylperpivalate, percar-bonates, for example isopropylperoxydicarbonate, azo com-pounds, for example azobisisobutyronitrile and the like or corresponding mixtures. The quantity of the initiator is generally in the range of from about 0.1 to 3 weight - percent calculated on the monomers. It naturally depends on the efficiency of the initiator, on the polymerization temperature etc.
Suitable molecular weight regulators include, for example, long chain mercaptans, for example dodecylmercap-tan, dimerized C~methylstyrene, halogenated hydrocarbons, aldehydes, ketones etc.
29 On principle, the above polymerization, which results ~_. .
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to a certain extent in a grafting of the monomer(s) onto the chlorinated polyolefin so that the chloroolefin, the polymer of acrylic and/or methacrylic acid esters and graft polymers of these esters onto the chloropolyolefin can be found at the same time, may alternatively be performed in solution or as bulk polymerization, this procedure, however, generally being not really advantageous in the present case.
In dependence on the intended use, the properties of the thermoplastic composition according to the invention may be optimized by varying the content of polymeric acrylic and/or methacrylic acid esters within the claimed range.
An increase of the chloropolyolefin content results in a better elasticity, whereas the stiffness (hardness) and transparency are improved when the content of polyacrylic and/or methacrylic ac d esters is increased.
Suitable acrylic or methacrylic acid esters are espe-cially those in which the alcohol component has of from 1 to 6 carbon atoms, since the polymers of these compounds are compatible with the chloropolyolefins and do not lead to turbidity. The alcohol component may be substituted by hydroxyl groups or by the furan group. Individual esters may be polymerized as well as mictures of several esters.
Examples of esters capable of being polymerized individual-ly or in the presence of chloropolyolefins are: methylmeth-acrylate, hydroxyethylmethacrylate, hydroxypropylmethacry-late9 furfurylmethacrylate, ethylacrylate, isopropylacry-late and butylacrylate.
29 Optionally the acrylic and/or methacrylic acid esters :' ' .' :-- ' . ' , ' " ' ' :
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used accordinK to the present invention may contain small amounts of further monomers, provided that the properties of the plastic composition aimed at by the present inven-tion, especially the low water vapor permeability and the high transparency are not substantially impaired. Examples of these monomers are: acrylonitrile, methacrylonitrile, methacrylamide, vinyl esters, especially of saturated carboxylic acids having from 2 to 12 carbon atoms, for example vinyl acetate and vinyl propionate; furthermore N-vinyllactams such as N-vinylpyrrolidone; copolymerizable unsaturated hydrocarbons such as ethylene, propylene or styrene and the like. Small amounts are those in the range up to 10 weight percent, preferably up to 5 weight percent, although some monomers may contain greater amounts without being liable to a modification of their properties, which can be determined by simple tests.
The term "acrylic and/or methacrylic acid esters" may include in this context mixtures of the above esters with - monomers of the above kind.
The thermoplastic compositions prepared according to the present invention may be used for the production of a great variety of medical apparatuses and instruments and parts thereof, which come into direct or indirect contact with parenteral liquids, for example blood bags, fexible containers for infusion solutions, infusion tubes, suction tubes and catheters. By parenteral liquids there are to be understood blood as well as blood serum or any injec-table solution for medical purposes such as solutions of 29 blood substitutes etc.
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A prerequisite for a high stability to storage of medi-cal containers is that only a neglectible gas exchange between the closed container and the exterior such as an evaporation of the liquid present in the container or an oxygen absorption from the exterior or no exchange at all occurs. Furthermore, microorganisms which decompose the parenteral liquid should not penetrate into the container.
The thermoplastic composition according to the invention fulfills the above requirements and in addition thereto, the water vapor permeability is substantially lower than that of plasticizer-containing polyvinyl chloride. It is, however, sufficiently high to prevent a turbidity during the sterilization with water vapor, which would fade very slowly, partially only after several days. The water vapor permeability may be easily optimized by the selection of - the monomeric esters. It is increased when methylmethacry-late is partially replaced by hydroxypropylmethacrylate, for example.
The plastic- composition according to the present inven-tion may be molded in conventional processing machines suchas extruders or calenders to have the desired shape. In order to prevent a decomposition during processing, stabi-lizers must be added. For this purpose only physiological-; ly acceptable stabilizers, for example fatty acid salts of -~ 25 calcium, magnesium, aluminum and zinc, organic phosphites, aliphatic epoxides, polyhydric alcohols and phenolic anti-oxidants, should be used. A stabilizer combination consist-- ing of from 1 to 3 weight percent of calcium-aluminum steara- -.

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te, 0.5 to 1 weight percent Or a secondary or tertiary or-ganic phosphite, 1 to 3 weight percent of an aliphatic ep-oxide and 0.05 to 10 weight percent Or a phenolic antioxy-dant, calculated on the thermoplastic composition, has proved advantageous. Furthermore, conventional light stabilizers, lubricants, pigments and fillers, for example barium sulfate as contrast medium for radiographic purposed, may be used.
The additives may be added during the preparation of the thermoplastic composition or subsequently.
10In most cases, the mechanical strength of the shaped articles prepared from the compositions according to the present invention is sufficiently high for the intended use. In some cases, however, it may be advantageous to improve the mechanical strength by incorporating supporting tissus made from inorganic or organic material, such as ; glass fibers or plastics fibers, for example of polyester or polyamide. For this purpose sandwich sheets may be used alternatively, the inner sheet of which coming into contact with the parenteral liquids, consists of the molding compo-- 20 sitions according to the invention (and acts as a lining) and the outer sheet of which is composed of a material which should have a great mechanical strength and be also as transparent as possible. The water vapor permeability of the outer supporting sheet may be relatively high, since the inner sheet is little permeable.
The ~ollowing examples illustrate the invention:
E X A M P L E 1:
81 Parts by weight of a fine grained chlorinated - 29 polyethylene having a chlorine content of 40 weight percent ' .

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and a residual crystallinity of 4 percent (determined by differential thermoanalysis) which ha~ been obtained by chlorinating a low pressure polyethylene having a RSV value of 2.3 dltg (measured in a 0.1 % solution in decahydronaph-thalene at 135C) are suspended with 160 parts of waterand 0.2 part Or a partially saponified polyvinyl acetate (viscosity 2 cP in 2 ~ aqueous solution, acetyl content 42 %) in a stainless steel vessel having a content of 40 li-ters by means of an anchor agitator. 19 Parts by weight of methylmethacrylate are introduced under pressure with the exclusion of oxygen and while stirring at room tempera-ture the chlorinated polyethylene is swollen in the monomer.
Thereafter 0.06 part by weight of tertiary butylperpiva-late is added and polymerization is initiated by heating the contents of the vessel to 90C. After 2 hours the resulting mixture is allowed to cool and the fine grained product is withdrawn, washed and dried. The yield, calcu-lated on the feed monomer, is 99.9 %.
The product is stabilized with 1 weight percent of Ca/Al stearate, 0.5 weight percent of trisnonylphenylphos-phite, 3 weight percent of epoxidized soybean oil and 0.1 weight percent of tetrakis-/ methylene-3-(3',5'-di-tertiary butyl-4'-hydroxyphenyl) propionate 7 methane (IrganoxR .
1010).
The obtained polymer is rolled on mixing rolls at 175C
to form a rough sheet and the letter is squeezed into sheets of a thickness of 400 /um. The clearness of the sheet ob-tained (dispersion 21 percent) is substantially better than 29 that of a corresponding sheet prepared from the feed chlo-., .~., .,;, . . .

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ropolyethylene (dispersion 55 ~).
The sheets are sterilized in an autoclave at 120C
and the aqueous extract is examined according to DIN (German industrial standard) 58 361/4 (blood bag examination).
Table 1 shows the result obtained, compared with a sheet made from soft PVC of the state of the art (70 % of PVC and 30 % of dioctylphthalate).
It can be seen from the ta~le that the values obtain-ed in all of the examinati~ns are below the tolerable limits and that a part thereof is even better than that of soft PVC.

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The Examp1es 2 to 16 demonstrate further propertie~ of the thermoplastic compositions according to the present invention, which are of decisive importance for their use for medical apparatuses and instruments which come into contact with parenteral liquids.
E X A M P L E S 2 and 3: -Example 1 is repeated, except that a chlorinated poly-ethylene having a chlorine content of 34 weight % and a residual crystallinity of 10 % is used, which has been prepared by chlorinating a low pressure polyethylene having a RSV value of 1.5 dl/g, by employing varying quantities of methylmethacrylate (MMA). Calendered sheets of 400 /um thickness are prepared from the polymer obtained for exami- .
nating the tensile strength and the elongation at break and 15 molded plates for determining the ball indentation hardness. ~-It can be seen from table 2, that the hardness of the thermoplastic composition depends on the content of methyl-methacrylate.
Table 2 Example Ball indentation Elongation Tensile hardness at breakstrength N/mm2 % N/mm2 ;
2: 85 % CPE/15 % MMA 16 742 10.9 3: 80 % CPE/20 ~ MMA 32 534 12.7 .
E X A M P L E S 4 and 5:

29Examples 2 and 3 are repeated by using instead of me-.

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thylmethacrylate hydroxypropylmethacrylate (HPMA). Table 3 shows the water vapor permeability of sheets of 400 /um thickness prepared from various samples in comparison to that of a sheet made from soft PVC. The water vapor permeability is increased by incorporating hydroxy groups.
Consequently, it may be adjusted to the desired value.

Table 3 10 Example Water vapor permeability g/m2 . 24 h 2: 80 % CPE/20 % MMA 0.33 4: 85 ~ CPE/15 g HPMA 1.42 15 5: 80 ~ CPE/20 % HPMA 2.03 COmDariSOn: 70 % PVC/30 % DOP 2.52 . _ _ _ _ .
; E X A M P L E S 6 to 8:
According to Example 1, varying quantities of methyl-methacrylate (MMA) are polymerized in the presence of a chlorinated polyethylene (CPE) having a chlorine content of 38 weight %, which has been obtained by chlorinating a low pressure polyethylene having a RSV value of 1.5 dl/g.
Calendered sheets of 400 /um thickness are prepared from the resulting product and from the feed chloropolye-thylene and their transparency and dispersion are compared with that of a soft PVC sheet. The result can be seen in - table 4. The clearness of the sheet is improved, when the . ~ 29 proportion of methylmethacrylate is increased. It attains .. . .
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nearly the value of a soft PVC sheet in the case of a pro-portion of MMA of 15 %.
Table 4 5 Example Transparency Dispersion 6: Comparison: CPE 89 51 7: 90 % CPE/10 % MMA 90 23 8: 85 % CPE/15 % MMA 90 16 Comparison: 70 % PVC/30 % DOP 92 10 E X A M P L E 9:
Example 2 is repeated with the exception that after cooling of the aqueous liquor to 50 to 60C there are added as stabilizers 1 weight % of Ca/Al stearate, 0.5 weight % of distearyl-pentaerythritol-diphosphite, 0.25 weight % of tetrakis-/methylene-3-3',5'-di-tertiary butyl-4'-hydroxyphenyl) propionate/ methane and 3 weight % of a - solid epoxidized ~olefin having from 26 to 28 carbon atoms, while stirring for half an hour to one hour. The thermostability and the rheological properties determined - after the polymer has been treated in usual manner are the same as that determined upon subsequent stabilization of the powder.
E X A M P L E S 10 and 11-_ _ .
- Example 5 is repeated, except that instead of pure hy-droxypropylmethacrylate (HPMA) there is polymerized a mixture Or hydroxypropylmethacrylate and methylmethacrylate 29 (MMA) in the presence of the chlorinated polyethylene.

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Table 5 shows the water vapor permeability of the products prepared, in comparison with that of the products obtained in Examples 2 and 5. The water vapor permeability can be optimized according to the intended use by varying the monomer ratio.
Table 5 Example water vapor permeability of a sheet of 400 /um thickness g/m2 . 24 h 2: 80 % CPE/20 % MMA 0.33 10: 80 % CPE/18 % MMA/ 2 % HPMA 0.51 11: 80 % CPE/10 % MMA/10 % HPMA 1.14 5 _80 % CPE/20 ~ HPMA 2.03 _ _ ~ . .
`. E X A M P L E S 12 to 14:
_ _ _ _ _ . _ _ Example 5 is repeated except that there is polymeriz-ed a mixture of ethylacrylate (EA) and methylmethacrylate in the presence of the chlorinated polyethylene. The yield, calculated on the monomer mixture and the light - dispersion can be seen in table 6.
Table 6 `:
25 Example Yield Dispersion % %
12: 80 % CPE/18 % MMA/2 % EA 99 19 13: 80 % CPE/16 % MMA/4 ~ EA 97 21 29 14: 80 ~ CPE/14 % MMA/6 % EA 96 22 - ' . . .

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E X A M P L E S 15 and 16:
_ _ 80 Parts of a chlorinated polyethylene having a chlor-ne content of 34 % and a refractive index nD of 1.5222 which has been prepared by chlorinating a low pressure polyethylene having a RSV value of 1.5 dl/g are mixed on mixing rolls at 175C with 20 parts of polymethylmeth-acrylate (nD 1.492; average molecular weight 100,000) and squeezed into sheets of 400 /um thickness. A milky sheet is obtained whose mechanical and physiological properties correspond to those of the graft polymer of the same compo-sition. This mixture may be used when a good transparency is not required. When the polymethylmethacrylate is replac-ed by a copolymer whose refractive index is adpated to that of the chlorinated polyethylene, there are obtained transpa-rent sheets. To demonstrate this, a copolymer consistingof 70 weight ~ of methylmethacrylate and 30 weight % of furfurylmethacrylate (FMA) (nD of the homopolymer 1.5381) is mixqd on mixing rolls with the same chlorinated poly-ethylene. Table 7 shows the results obtained.
Table 7 Example Mixture Dispersion ~ 15: 80 % CPE/20 % PMMA 100 - 25 16: 80 % CPE/20 % copo of 70 % MMA and 30 ~ FMA 28 E X A M P L E 17:
97 Parts by weight of a fine grained chlorinated poly-29 ethylene having a chlorine content of 36 weight ~ and a ~ .

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residual crystallinity of 8 % (deterrnined by differential thermoanalysis), which has been obtained by chlorinating a low pressure polyethylene having a RSV value of 1.5 dl/g (determined in a 0.1 g solution in decahydronaphthalene at 135C), are suspended in 160 parts of water and 0.05 part of a partially saponified polyvinylacetate (viscosity 2 cP
in 2 % aqueous solution, acetyl content 42 %) in a stainless steel vessel having a content of 40 liters, by means of an anchor agitator. 3 Parts by weight of methylmethacrylate are introduced under pressure with the exclusion of oxygen and the chlorinated polyethylene is swollen in the monomer while stirring at room temperature. Thereafter 0.02 part by weight of tertiary butylperpivalate is added and poly-merization is initiated by heating the contents of the vessel to 90C. After 2 hours, the resulting mixture is allowed to cool and the fine grained product is withdrawn, washed and dried. The yield, calculated on the feed monomer, is 99.9 ~.
~! The product is stabilized with 1 weight % of Ca/Al stearate, 0.5 weight % of trisnonylphenyl phosphite, 3 weight % of epoxidized soybean oil and 0.1 weight % of tetrakis-/ methylene-3-(3'-5'-di-tertiary butyl-4'-hydroxy-phenyl)propionate 7 methane (Irgano ~ 1010).
The polymer obtained is rolled on mixing rolls at 175C
to form a rough sheet and the latter is squeezed into sheets of 400 /um thickness. The obtained sheet has the - following properties, which are important for its use according to the invention:
29 dispersion 25 %, transparency 89 %, MFI (150C/30 kp) 130 . - .

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(g/lO'), shore hardness (Shore A) 67, tencile strength 8.5 N/mm2 "lotched impact strength: 12 (Nmm/mm2), elongation at break: 490 %.

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Claims (9)

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

1. A thermoplastic composition, suitable for use in the manufacture of medical apparatus and instruments, which come into contact with parenteral liquids, comprising from 50 to 99.5 parts by weight of chlorinated polyolefin having a chlorine content of from 15 to 45% by weight and an average molecular weight of from 30,000 to 300,000 and from 0.5 to 50 parts by weight of a polymer of acrylic acid esters, methacrylic acid esters, or mixtures of said esters.

2. A thermoplastic composition as claimed in claim 1, in which the composition is obtained by polymerization of the acrylic acid esters, methacrylic acid esters or the mixtures thereof in the presence of the chlorinated polyolefin.

3. A thermoplastic composition as claimed in claim 1 in which the methacrylic acid ester is a methacrylic acid methyl ester or a methacrylic acid hydroxypropyl ester.

4. A thermoplastic composition as claimed in claim 1, claim 2 or claim 3 in which the chlorinated polyolefin is a chlorinated low pressure polyethylene having a reduced specific viscosity, determined in a 0.1% solution in decahydronaphthalene at 135°C, of from 1 to 10 dl/g.

5. A thermoplastic composition as claimed in claim 1 in which the composition is stabilized with 1 to 3 weight % of Ca/Al stearate, 0.5 to 1 weight % of a secondary or tertiary organic phosphite, 1 to 3 weight % of an aliphatic epoxide and 0.05 to 1.0 weight % of a phenolic antioxidant.

6. A thermoplastic composition as claimed in claim 1 in which the composition additionally contains at least one member of the group of pigments and fillers.

7. A thermoplastic composition as claimed in claim 5 or claim 6 in which the additives are added during the preparation of the thermoplastic composition.

8. Medical apparatus and instruments which come into contact with parenteral liquids characterized by the fact that they consist of the thermoplastic composition as claimed in claim 1.

9. A medical apparatus as claimed in claim 8 in the form of a bag.