EP0828791A1

EP0828791A1 - Flexible composition based on vinyl chloride polymer, use of said composition for manufacturing articles and articles made of said composition

Info

Publication number: EP0828791A1
Application number: EP96917412A
Authority: EP
Inventors: Dominique Grandjean; Zdenek Hruska; Danny Van Hoyweghen; Henri Wautier
Original assignee: Solvay SA
Current assignee: Solvay SA
Priority date: 1995-06-02
Filing date: 1996-05-22
Publication date: 1998-03-18
Also published as: WO1996038503A1; US6046274A; AU5999696A; BE1009403A3; ZA964266B; JPH11511184A

Abstract

A flexible composition contains a vinyl chloride polymer and a block copolymer. The block copolymer contains a polyethylene oxide block and a block made of a polymer that is different from but can be mixed with the vinyl chloride polymer. Also disclosed is a diblock polyethylene oxide and poly- epsilon -caprolactone copolymer usable in this composition, as well as the use of this composition for manufacturing various articles and an article made from this composition.

Description

Flexible composition based on vinyl chloride polymer. use of this composition for the manufacture of an article and article comprising this composition

The present invention relates to a flexible composition comprising a vinyl chloride polymer and a block copolymer, a use of this composition for the manufacture of an article, as well as an article comprising this composition. For a long time, flexible compositions based on vinyl chloride polymer have been used in a wide variety of industrial applications. Mention may be made of applications, for example, in the fields of building, the automobile, decoration and medical accessories.

In this latter field, it is particularly advantageous to have materials having good compatibility and perfect harmlessness with respect to biological tissues and the medicinal principles with which these materials can come into contact.

The excellent properties of flexible polyvinyl chloride, such as its high transparency, and the wide range of degree of flexibility available with this material make it a very widespread constituent in many medical applications.

In order to improve the biocompatibility of polymeric materials such as polyvinyl chloride, several methods have been developed.

Some of these processes use surface treatments, treatments of a physical or chemical nature. For example, the patent application

EP-A-0 093 094 describes a process according to which the surface of the polymer to be treated is made more hydrophilic after several cycles of bringing into contact with solutions followed by evaporation of the solvent. This type of process, with handling of solvents, is complicated and costly to implement industrially.

Other types of process call for the incorporation of modifying agents in the formulation of the composition. Thus, patent application JP-A-01 181 873 describes a mixture of flexible polyvinyl chloride and of a block copolymer obtained by reaction of a polycarboxylic polyester with a polysiloxane polyol or polysiloxane polyamine. Similarly, an article (TSAI et al., ASAIO JOURNAL (1994), vol. 40, n ° 3, pp. M619-M624) describes a block copolymer poly-ε-caprolactone / polydimethylsiloxane / poly-ε- caprolactone , incorporated into a flexible vinyl chloride polymer composition.

However, if the latter type of surface modification improves the compatibility of polyvinyl chloride with biological tissues and blood in particular, it does not guarantee perfect neutrality with regard to these. In particular, the adsorption of certain components such as proteins or blood cells remains too high. This causes a decrease in their actual concentration in the medium when the latter is brought into contact with the polymeric surface. However, in many applications, it is essential that the concentration of certain components, including in particular proteins, in solutions or in tissues, remain constant over time. It is also important that the additives used in these formulations exhibit minimal desorption when brought into contact with biological tissue.

The subject of the invention is therefore a flexible composition of vinyl chloride polymer which allows this composition to be brought into contact with media comprising organic macromolecules, more particularly proteins or peptides, without sensitive adsorption thereof to the surface of the composition, nor significant desorption of its constituents.

Therefore, the invention relates to a flexible composition comprising a vinyl chloride polymer and a block copolymer, which is characterized in that the block copolymer is chosen from copolymers comprising a block of polyethylene oxide and a block of a polymer miscible with the vinyl chloride polymer, different from the latter itself.

The term “vinyl chloride polymer” is intended to denote any homopolymer of vinyl chloride, any copolymer of vinyl chloride, as well as mixtures of these homo- and / or copolymers. Homopolymers have given very good results.

The composition is said to be flexible when it additionally comprises a substantial amount of plasticizer, in particular at least 20 parts of plasticizer per 100 parts of vinyl chloride polymer (by weight). Any type of plasticizer can be used, the amount present obviously being adapted accordingly. For example, phthalates, citrates, trimellitates and phosphates alkyl are widely used. The plasticizer used can also be polymeric, which has the advantage of reducing its exudation. The plasticizer can also be presented, for example, in the form of groups or side chains grafted onto the vinyl chloride polymer. By block copolymer is meant any polymer consisting of at least two distinct types of monomers and having at least one long block of at least one of the monomers. The block copolymers which can be used in the context of the invention can be of any type. Linear block copolymers are preferred, however. Biblock copolymers have provided excellent results. The use of mixtures of different block copolymers also falls within the scope of this invention.

The relative amount of block copolymer according to the invention in the composition is not limited. However, the Applicant has found that it is preferable to use a concentration of at least 0.5 parts per 100 parts by weight of plasticized polymer of vinyl chloride, at least 1 part more preferably, and at least 3 parts even more preferably. Advantageously, this concentration is at most 10 parts per 100 parts of plasticized vinyl chloride polymer, at most 8 parts more advantageously, and at most 6 parts more advantageously still. A block is said to be made of polyethylene oxide if it contains a long repeating unit sequence of formula (O-CH2-CH2) _n . The length of the block of polyethylene oxide may be any, but an average molecular mass at least equal to 500 g / mol and more particularly still to 3000 g / mol is preferred (all the molecular masses specified within the scope of this invention are averages in number).

The polymer miscible with the vinyl chloride polymer can be of any kind, with the exception of this polymer itself. It can be a homopolymer as well as a copolymer. This polymer is said to be miscible with the vinyl chloride polymer when, when mixed with the latter, the resulting mixture is monophasic, that is to say it only has one glass transition temperature, intermediate between the glass transition temperatures of the components of the mixture taken separately.

Among the polymers miscible with the vinyl chloride polymer, non-limiting mention may be made of certain polyesters, certain polyacrylates or polymethacrylates, certain copolymers of vinyl acetate or of acrylonitrile, etc. More particularly, aliphatic polyesters and polymethyl methacrylate can be used. Very good results have been obtained with poly-ε-caprolactone.

The average molecular mass of the block of polymer miscible with the vinyl chloride polymer can also be arbitrary. However, it has been observed that it is preferable to use a block copolymer such that the average molecular weight of said block is greater than or equal to the average molecular weight of the polyethylene oxide block.

It has been found particularly advantageous that the average molecular weight of the block of polymer miscible with the vinyl chloride polymer is at least equal to 4000 g / mol.

Although there is generally no upper limit on the average molecular weight of the polymer block miscible with the vinyl chloride polymer, it has been found that an average molecular weight less than or equal to 30,000 g / mol provides interesting results. An average molecular mass less than or equal to 20,000 g / mol has enabled particularly interesting results.

It should be noted that the block copolymer may comprise, in the same molecule, several blocks of polyethylene oxide and / or several blocks of polymer miscible with the vinyl chloride polymer, and / or one or more blocks of other types. Excellent results have been obtained with a two-block copolymer consisting of a block of polyethylene oxide and a block of a polymer miscible with the vinyl chloride polymer.

The average molecular weight of the block copolymer can be arbitrary. Advantageously, it is at least 4500 g / mol. Good results have been obtained with an average molecular weight of at least 8500 g / mol. Particularly interesting results have been obtained with an average molecular weight of at least 10,000 g mol.

It is obvious that in addition to the vinyl chloride polymer, the plasticizer and the block copolymer characteristic of the invention, the composition may also include other components, polymeric or not. Very good results have been obtained with a composition essentially consisting of a vinyl chloride polymer, a plasticizer and a block copolymer characteristic of the invention. In addition, the usual additives such as stabilizers, lubricants, dyes, - 5 -

pigments, anti-blocking agents, ... can be used.

The incorporation of the block copolymer can be carried out according to any process known to those skilled in the art. For example, the block copolymer can be hot mixed with the vinyl chloride polymer during the final processing, or during an intermediate compounding. Another solution may consist in introducing the block copolymer into the polymerization medium of vinyl chloride, during the synthesis of this polymer.

The invention also relates to a block copolymer which can be used in the composition described above and which is characterized in that the block copolymer is a block copolymer comprising a polyethylene oxide block of average molecular mass at least equal to 300 g / mol , preferably at least equal to 500 g / mol, and a block of poly-ε-caprolactone of average molecular mass at least equal to 500 g / mol.

The new biblock copolymer according to the invention corresponds to the general statistical formula

R- (O-CH2-CH2) nO- [C- (CH ₂ ) 5-O-] _m -H (I)

IIO in which R represents a monovalent hydrocarbon radical and n and m represent whole numbers such that the average molecular mass of the polyethylene oxide block is at least equal to 300 g / mol, preferably at least equal to 500 g / mol, and that of the poly-ε-caprolactone block is at least equal to 500 g / mol. Preferably, the average molecular weight of the polyethylene oxide block is at least equal to 3000 g / mol. Preferably, that of the poly-ε-caprolactone block is at least equal to 3000 g / mol and more particularly still to 4000 g / mol.

A biblock copolymer of this type which is particularly preferred is that in which the average molecular mass of the block of poly-ε-caprolactone is greater than or equal to that of the block of polyethylene oxide. Preferably, the molecular mass of the poly-ε-caprolactone block does not exceed 30,000 g / mol and more particularly 20,000 g / mol. Advantageously, the average molecular weight of the biblock copolymer is at least 4500 g / mol. Preferably, it is at least 8500 g / mol and more particularly still at least 10000 g / mol.

Advantageously, the hydrocarbon radical R being in position terminal of the polyethylene oxide block is an aliphatic radical (which can be linear, branched or cyclic) or an aromatic radical. Preferably, the radical R- represents an aliphatic radical containing not more than 20 carbon atoms. Excellent results have been obtained with a block copolymer in which the terminal radical R of the polyethylene oxide block represents a linear alkyl radical and in particular a methyl radical.

The new biblock copolymer according to the invention can be synthesized by any method known to a person skilled in the art and, in particular, by anionic polymerization of ε-caprolactone in the presence of monohydroxylated polyethylene oxide (R- (O-CH2-CH2) _n -OH) with the intervention of organometallic initiators, more particularly organoaluminic or organozincic.

Advantageously, the polymerization initiator is an organoaluminum or organozinc compound produced in situ by reaction between polyethylene oxide monohydroxylated and a precursor of the alkylaluminium or alkylzinc type in a weight ratio at least equimolecular, for example from 1 to 4, to produce aluminum or zinc alkoxides. When the monohydroxylated polyethylene oxide is reacted with an equimolar amount of alkyl aluminum or alkyl zinc precursor, an aluminum or zinc monoalkoxide of general formula is produced:

_{/ R} ', R-

R- (O-CH ₂ -CH ₂ ) _n -O-Al (II) or R- (O-CH2-CH ₂ ) _n -O-Zn (III)

\ R "\ R" in which R has the meaning given above and R 'and R "independently of one another represent a linear or branched alkyl radical. Advantageously, the hydrocarbon radicals R' and R" independently of one another represent a linear or branched alkyl radical containing from 1 to 16 carbon atoms. Preferably, these radicals are identical and represent a linear or branched alkyl radical containing from 2 to 6 carbon atoms.

One procedure giving excellent results consists in dissolving monohydroxylated polyethylene oxide (for example polyethylene oxide containing a methyl terminal radical) with stirring and under nitrogen in the appropriate quantity of ε-caprolactone, bringing the solution obtained to a temperature - erasing of the order of approximately 80 ° C until a homogeneous solution is obtained, cooling the solution to approximately 30-35 ° C and then introducing trialkylaluminium (for example triethylaluminium) or dialkylzinc (by example of diethylzinc) in an equimolar amount relative to the monohydroxylated polyethylene oxide. Under these conditions, an aluminum monoalkoxide (of general formula II) or a zinc monoalkoxide (of general formula III) is formed in situ which initiates the polymerization of ε-caprolactone. Conversion rates close to 100% are achieved in a few tens of minutes.

The composition according to the invention notably has the advantage of substantially preventing the adsorption of organic macromolecules, such as proteins or biological cells, on its surface. An additional advantage is the low desorption of its constituents. Another advantage of the composition according to the invention lies in the improvement in the sliding properties which it provides vis-à-vis the usual flexible compositions of vinyl chloride polymer. It therefore finds its preferred field of application for the production of articles used in the medical art.

Therefore, the invention also relates to a use of the composition as described above for the manufacture of an article.

Another object of the invention is still an article comprising at least one layer consisting essentially of a composition as described above. For example, the article may comprise at least one layer of any kind and a layer in contact with the biological medium, the latter essentially consisting of a composition according to the invention.

The article concerned by the present invention can be of any kind. It can be, for example, a hollow body, such as a container or a pipe, or a flat product. In the case of a flat product, the film or sheet is preferred. The field of use of the article according to the invention can be arbitrary, however it is in the field of accessories for medical use that it is preferred to use it. By medical use is meant all applications related to the art of preserving or restoring human or animal health. This includes surgery, pharmacy or dentistry. The nature of the accessories for medical use can also be arbitrary: flat product, container, sheath, hose, pocket, among others.

In the case of accessories for medical use, the article is preferably in the form of a pocket or a pipe. Said pocket and said pipe can contain or transport, for example, blood, plasma, various solutes and any biological fluid in general. In the case of a pipe, the sliding properties, particularly improved after sterilization with steam or after staying in a humid atmosphere, are in particular useful for producing catheters or similar accessories. Likewise, the weak adhesion of microbes, in particular bacteria, is advantageous in the case of catheters, in particular by reducing the risks of inflammation during prolonged use. Examples

Example 1, not in accordance with the invention, is given by way of comparison. Examples 2 and 3 illustrate the invention, without limitation. Example 1 (for reference) In an internal mixer of the PLASTOGRAPHE® BRABENDER® type,

65 g of a flexible composition of MEDIGRANUUL® vinyl chloride polymer, sold by DRAKA POLNA B.V, of the PSV 3250 type were kneaded for 12 minutes. The speed of rotation of the cams was 50 rpm and the set temperature for the kneader was 150 ° C. After mixing, the composition was introduced between the plates of a press

SCHWABEΝTHAΝ®, conditioned for 5 minutes at 170 ° C. Films of 300 μm thickness were obtained by pressing for 5 minutes under a pressure of 200 bars. Example 2 Example 1 is repeated, with the only difference that 2.6 g of block copolymer are added, in the mixer, to the flexible composition of vinyl chloride polymer (i.e. 4 parts of block copolymer per 100 parts of the latter). The block copolymer consists of a block of polyethylene oxide of average molecular mass equal to 750 g / mol and of a block of poly-ε-caprolactone of average molecular mass equal to 4100 g / mol. Example 3

Example 2 is reproduced, with the only difference that the block copolymer consists of a block of polyethylene oxide of average molecular weight equal to 5000 g / mol and of a block of poly-ε-caprolactone of average molecular weight equal to 5700 g / mol.

Several types of tests were carried out in order to evaluate the behavior of the films coming from the different examples, in particular during contact with media commonly used in medical applications. Exudation of the block copolymer The films were stored at ambient temperature and relative humidity, for 3 months Vi, between two sheets of white paper. The exudation was assessed by the possible appearance of translucent or opaque dots or veil on the surface of the films, which were completely transparent at the start. Desorption of the block copolymer in contact with water A film surface corresponding to 61 cm 3 was immersed in 25 ml of demineralized water for 24 hours, at room temperature and with constant stirring. The quantity of block copolymer having migrated into water was determined by thin layer chromatography, followed by detection by the Dragendorff reagent (formation of a colored complex with polyethylene oxide) and measurement of the optical density at 520 nm. The chromatography was carried out using silica type 5729 from the firm MERCK as stationary phase and mixtures of methylene chloride / acetone (85/15 by volume) and chloroform / methanol (75/25 by volume) as mobile phases. The results were expressed by weight of block copolymer having migrated into the aqueous phase. Protein adsorption

Solutions of bovine serum albumin (hereinafter referred to as BSA) labeled with europium were first prepared. The labeling with europium was carried out by mixing a BSA solution (5.5 μg / ml in a 50 mM bicarbonate buffer, pH = 8.53) with a labeling solution (Eu-DTTA-C6H4 -NCS, DELFIA® kit type 1244-302) and incubation for 24 hours at 4 ° C. The labeled product was dialyzed intensively with distilled water in order to remove all of the non-fixed europium on the BSA. The labeled BSA was diluted in a phosphate buffered saline solution.

12 mm diameter discs were cut from the films from the different examples. Each of these discs was placed in a cavity of a plate whose surfaces were previously blocked, with respect to the adsorption of proteins, by 24 hours contact at 4 ° C. with a 5% solution of skim milk in phosphate buffered saline. 2 ml of the labeled BSA solution, of given concentration, were added, and the whole incubated for 2 hours at 37 ° C. The discs were then washed at least five times with a 0.02% solution of non-ionic detergent Tween® 20 in phosphate buffer and five more times with distilled water. After transferring the discs into the cavities of a clean plate, 1 ml of accentuation solution (supplied with the kit, releases europium) was added to each cavity. The whole was incubated for 10 minutes at room temperature. 100 μl samples of the accent solution were analyzed using a DELFIA fluorimeter ("time-resolved fluorimetry"). The results were expressed by weight of BSA adsorbed by disc. Blood contact

4 ml of human blood and 0.4 ml of aqueous solution (0.129 molar) of sodium citrate, acting as an anticoagulant, were mixed in a closed glass tube. A piece of film (5 cm x 0.8 cm) from the different examples was introduced into each tube and, after reclosing, left in contact with the blood for 3 hours at room temperature and with slow stirring. The films were then rinsed twice with a 0.09% NaCl solution and the blood platelets fixed to the polymer by passage through a 3% solution of glutaraldehyde. After drying, the quantity of blood platelets adhering to the films was estimated by scanning electron microscopy (magnification 500X).

The results of the various evaluations are collated in Table 1

Table 1: Evaluation results

Claims

1 - Flexible composition comprising a vinyl chloride polymer and a block copolymer, characterized in that the block copolymer is chosen from copolymers comprising a polyethylene oxide block and a block of a polymer miscible with the chloride chloride polymer vinyl, different from the latter itself.

2 - Composition according to claim 1, wherein the concentration of the block copolymer is between 0.5 and 10.0 parts per 100 parts by weight of the plasticized vinyl chloride polymer.

3 - Composition according to any one of the preceding claims, in which the polymer block miscible with the vinyl chloride polymer consists of poly-ε-caprolactone.

4 - Composition according to any one of the preceding claims, in which the average molecular weight of the block of polymer miscible with the vinyl chloride polymer is greater than or equal to the average molecular weight of the block of polyethylene oxide.

5 - Composition according to any one of the preceding claims, in which the average molecular weight of the polyethylene oxide block is at least equal to 3000 g / mol.

6 - Composition according to any one of the preceding claims, in which the average molecular weight of the block of polymer miscible with the vinyl chloride polymer is less than or equal to 30,000 g / mol.

7 - Block copolymer usable in a composition according to any one of the preceding claims, characterized in that said copolymer is a biblock copolymer comprising a polyethylene oxide block of average molecular mass at least equal to 300 g / mol and a block of poly-ε-caprolac¬ tone of average molecular mass at least equal to 500 g / mol. 8 - Block copolymer according to claim 7, in which the polyethylene oxide block and the poly-ε-caprolactone block each have an average molecular weight at least equal to 3000 g / mol.

9. A block copolymer according to claim 8, in which the average molecular weight of the poly-ε-caprolactone block is greater than or equal to the average molecular weight of the polyethylene oxide block and does not exceed 30,000 g / mol.

10 - Use of a composition according to any one of claims 1 to 6 for the manufacture of an article.

11 - Article comprising at least one layer consisting essentially of a composition according to any one of claims 1 to 6.

12 - Article according to claim 11, in the form of film or sheet.

13 - Article according to claim 11, in the form of accessory for medical use.

14 - Article according to claim 13, in the form of a pocket for medical use.