CA2382954A1 - Radio-opaque molded plastic parts - Google Patents

Abstract

The invention relates to the use of derivatives of the iodobenzoic acid for producing radio-opaque molded parts and to plastic materials, molded plastic materials and molded plastic bodies that contain at least one ester of the iodobenzoic acid.

Description

-1_ X-ray-contrastable plastics mouldings The Application relates to the use of derivatives of iodobenzoic acid in the production of X-ray-contrastable moulded bodies of plastics, as well as to plastics, plastics moulding compositions and plastics moulded bodies containing at least one derivative of iodobenzoic acid.
For the medical field and for children's toys, transparent plastics moulded bodies are sought that have good mechanical properties and can be detected in the body in X-ray examinations. Such materials should also have adequate stability to light at least for use in the interior of buildings.
Commercially available moulded bodies based on polycarbonates are not suitable for that purpose because their contrast in X-ray images is too low. Attempts have therefore been made to replace polycarbonates with X-ray contrast media containing barium or bismuth. However, such contrast media are not sufficiently suitable for toxicological reasons and owing to their effects altering the mechanical and optical properties of commercially available polymers.
Nor does the use of iodine-containing compounds as described in US-3 469 704, DE-A-17 20 812, GB-A-11 63 816, US-3 382 207 and US-3 535 300 in moulding compositions or moulded bodies fulfil the desired profile of properties for medical applications and parts of toys. It has been found, for example, that such moulding compositions or mouldings turn a reddish colour under indoor lighting after only a few weeks and/or possess poor mechanical properties and/or possess inadequate heat stability and/or contain an amount of iodine that is too small to be detectable in an X-ray image.
The object of the invention is, therefore, to provide X-ray contrast media that do not adversely affect the material properties of plastics.

Surprisingly, it has been found that derivatives of iodobenzoic acids fulfil the desired profile of requirements. Moulded bodies that are detectable by means of X-rays can be produced using only small amounts of iodobenzoic acid derivatives.
Accordingly, the present Application relates to the use of iodobenzoic acid derivatives as X-ray contrast media, especially in plastics, especially for transparent plastics, as well as to plastics, plastics moulding compositions and plastics moulded bodies containing at least one ester of iodobenzoic acid.
Derivatives of iodobenzoic acid according to the invention are amides, alkylamides, dialkylamides and, especially, esters. Preference is given to esters and amides that are prepared from mono- or poly-hydric, aliphatic or aromatic alcohols or amines.
Aliphatic alcohols and amines are, for example and preferably, alcohols and amines having from 1 to 30 carbon atoms. The carbon chain can be linear or branched.
The carbon chain can contain one or more alcohol or amine functionalities, it being possible for the alcohol or amine functionality to be located at any desired positions in the carbon chain. The alcohol may optionally also be halogenated.
Preference is given to esters based on methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tent-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-butanol, 2-methyl-2-butanol, 3-methyl-1-butanol, 3-methyl-2-butanol, 2,2-dimethylpropanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, as well as, optionally, the structural isomers thereof, 1,2-ethylene glycol, trimethylolmethane, pentaerythritol, 1,2-propanediol and 1,3-propanediol.
In the case of polyhydric alcohols, mixed esters, for example partly with an iodobenzoic acid and partly with a different acid, or incompletely esterified compounds are also suitable according to the invention.
Aromatic alcohols are especially phenols and bisphenols.

WO 01/16225 PCTlEP00/07983 In addition to iodine, the iodobenzoic acid derivatives can additionally be halogenated by F, Cl or Br. Unhalogenated monoiodobenzoic acid derivatives are preferred, and the derivatives of 4-iodobenzoic acid are particularly preferred.
Mixtures of different iodine-containing benzoic acid derivatives are also suitable according to the invention.
The derivatives of iodobenzoic acid are known or are prepared according to known methods.
The derivatives of iodobenzoic acid are preferably added to the plastics in amounts of from 0.001 to 20 wt.%, preferably from 1 to 6 wt.%.
The term plastics is to be understood as meaning preferably thermoplastics, especially transparent thermoplastics, preferably the polymers of ethylenically unsaturated monomers and/or polycondensation products of bifunctional reactive compounds. Mixtures of several plastics are also possible within the scope of the invention.
Particularly suitable plastics are diphenol-based polycarbonates or copolycarbonates, polyacrylates or copolyacrylates and polymethacrylates or copolymethacrylates, such as, for example and preferably, polymethyl methacrylate, polymers or copolymers with styrene, such as, for example and preferably, transparent polystyrene or polystyrene acrylonitrile (SAID, transparent thermoplastic polyurethanes, as well as polyolefins, such as, for example and preferably, transparent polypropylene types or polyolefins based on cyclic olefins (e.g.
TOPAS~, Hoechst), polycondensation products or copolycondensation products of terephthalic acid, such as, for example and preferably, polyethylene or copolyethylene terephthalate (PET or CoPET) or glycol-modified PET (PETG).

WO 01!16225 PCT/EP00/07983 Special preference is given to polycarbonates or copolycarbonates, especially unhalogenated polycarbonates and/or copolycarbonates, having molecular weights M W from 600 to 100,000, preferably from 2,000 to 80,000, particularly preferably from 18,000 to 40,000.
Thermoplastic aromatic polycarbonates within the scope of the present invention are both homopolycarbonates and copolycarbonates; the polycarbonates can, in a known manner, be linear or branched.
The polycarbonates can also be wholly or partially brominated.
The preparation of such polycarbonates is carried out in a known manner from diphenols, carbonic acid derivatives, optionally chain terminators and optionally branching agents.
Details relating to the preparation of polycarbonates have been laid down in many patent specifications for about 40 years. Reference is made here, for example, only to Schnell, "Chemistry and Physics of Polycarbonates", Polymer Reviews, Volume 9, Interscience Publishers, New York, London, Sydney 1964, to D.
Freitag, U. Grigo, P.R. Miiller, H. Nouvertne', BAYER AG, "Polycarbonates" in Encyclopedia of Polymer Science and Engineering, Volume 11, Second Edition, 1988, pages 648-718, and finally to Dres. U. Grigo, K. Kirchner and P.R.
Miiller "Polycarbonate" in BeckerBraun, Kunststoff Handbuch, Volume 3/l, Polycarbonate, Polyacetale, Polyester, Celluloseester, Carl Hanser Verlag Munich, Vienna 1992, pages 117-299.
Diphenols in the polycarbonate preparation are preferred:
4,4'-dihydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl)-propane, 2,4-bis-(4-hydroxy phenyl)-2-methylbutane, 1,1-bis-(4-hydroxyphenyl)-p-diisopropylbenzene, 2,2-bis (3-methyl-4-hydroxyphenyl)-propane, 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane, bis-(3,5-dimethyl-4-hydroxyphenyl)-methane, 2,2-bis-(3,5-dimethyl-4-hydroxy-phenyl)-propane, bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfone, 2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1,1-bis-(3,5-dimethyl-4-hydroxy-phenyl)-p-diisopropylbenzene, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane and 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.
Particularly preferred diphenols are 2,2-bis-(4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane, 1,1-bis-(4-hydroxy-phenyl)-cyclohexane and 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.
Preferred branching agents are triphenols, trimesic acid (trichloride), cyanuric acid trichloride and 3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.
In order to achieve improved plastics compositions it is possible and expedient to additionally incorporate at least one further additive conventionally present in thermoplastic plastics, preferably polycarbonates and copolycarbonates, such as, for example, stabilisers (as described, for example, in EP 0 839 623 A1 or EP 0 A1), especially heat stabilisers, especially organic hindered phenols, hindered amines (HALS), phosphites or phosphines, for example and preferably triphenylphosphine, mould-release agents, for example and preferably fatty acid esters of glycerol or of tetramethanolmethane, it being possible for unsaturated fatty acids also to be wholly or partially epoxidised, especially glycerol monostearate or pentaerythritol tetrastearate (PETS), flameproofing agents, antistatics, LTV
absorbers, for example and preferably hydroxybenzotriazoles and hydroxytriazines, fillers, foaming agents, colourants, pigments, optical brightening agents, transesterification catalysts and nucleating agents or the like, preferably in amounts of in each case up to 5 wt.%, more preferably from 0.01 to 5 wt.%, based on the total mixture, particularly preferably from 0.01 to 1 wt.%, based on the amount of plastics.
The incorporation of the esters of iodobenzoic acid and, optionally, of the additives or mixtures of additives is effected in the generally conventional manner, for example, before or during the polymerisation or by subsequent mixing with the plastics, preferably by extrusion.
The plastics compositions so obtained are generally in the form of solutions, dispersions, emulsions, dusts, powders, granules, platelets or flakes (moulding compositions) and are used in the production of shaped articles (moulded bodies).
The production of the plastics moulded bodies takes place by conventional methods, such as, for example, hot pressing, spinning, extrusion or injection moulding.
The plastics compositions according to the invention generally contain from 0.01 to 10 wt.%, preferably from 1 to 3 wt.%, organically bonded iodine.
Shaped articles are preferably light-permeable articles, especially for medical applications, . such as, for example and preferably, probes or joint parts, or alternatively they are small objects used by children. However, it is also possible, of course, to produce conventional shaped articles, such as films, tapes, sheets, wall sheets, mufti wall sheets, containers, tubes and other profile sections, using the plastics compositions according to the invention. The plastics compositions can also be processed to cast films.
The use of the plastics composition according to the invention in the production of mufti-layer systems is also of interest. In that case, the plastics composition according to the invention is applied in a thin layer to a shaped article of a plastic that is not with an X-ray contrast medium. The application can take place simultaneously with or immediately after the shaping of the moulded body, for example by co-extrusion or mufti-component injection moulding. However, it is also possible to apply the composition to the finished shaped base body, for example by laminating with a film or by coating with a solution.

_ 'j Plastics compositions containing esters of iodobenzoic acid are used preferably in the production of small parts used by children, especially in the production of toys such as building bricks.
The Examples which follow serve to illustrate the invention. The invention is not limited to the Examples. Hereinbelow, percentages and parts mean percent by weight and parts by weight.

_g_ Example 1 29.3 parts of 4-iodobenzoyl chloride (Aldrich) are dissolved in 100 parts of pyridine.
3.1 parts of ethylene glycol (Aldrich) are then added dropwise, with stirring.
After 10 minutes, heating is carned out for one hour at 75°C. The product is then taken up in methylene chloride, washed with water, as well as acid and basic, and dried.
98.7 % of the theoretical yield of the diester are obtained. The melting point of the colourless compound was 146°C.
Ezample 2 95.5 parts of additive-free, unstabilised polycarbonate having a mean molecular weight of approximately 30,000 (MW according to GPC), solution viscosity:
r1=1.293 (Makrolon 2808~, Bayer AG) are compounded together with 0.3 part of PETS and 4 parts of 1,2-ethylene glycol bis-4-iodobenzoic acid ester (from Example 1) at 300°C using a twin-screw extruder and then injection moulded to form colour sample sheets (155 mm x 75 mm x 2 mm).
Example 3 The stability to light of the colour sample sheets from Example 2 is tested by means of irradiation with a UV lamp, a Xe-WOM lamp and daylight. The results are indicated in Table 1.
Table 1 Stability to light of samples of Example 2 having a thickness of 2 mm:
before weathering after weathering 8 h UV lamp 254 colourless no discernible change nm 200 h Xe-WOM colourless no discernible red colour 2 months indoor colourless no discernible change light w0 01/16225 PCT/EP00/07983 Example 4 4 parts of ethylene glycol bis-4-iodobenzoic acid ester (from Example 1 ) are dissolved with 96 parts of polymethyl methacrylate (Plexiglas~) in 150 parts of methylene chloride and processed to a film having a thickness of 180 p.rn and dried in vacuo. The film is then exposed to light for 8 hours under a LJV lamp at 254 nm.
No discolouration can be detected visually. Furthermore, the VIS spectra between 400 and 1,200 nm before and after the LTV irradiation are congruent within the framework of measuring accuracy.
Example 5 13.3 g of 4-iodobenzoyl chloride are dissolved in 30 ml of dichloroethane and 4 ml of pyridine. 6.5 g of dibutylamine are slowly added dropwise to the solution, and stirring is carried out for a further 30 minutes at room temperature. The reaction mixture is washed with water, 10 % sodium hydroxide solution, 10 %
hydrochloric acid and again with water, dried over sodium sulfate and finally concentrated.
Yield:
18 g of light-yellow crystals. The product can be melted at 320°C with polycarbonate without any discolouration occurring.
Example 6 A cast film of Makrolon 2808 with S % of the product of Example 5 is produced with the aid of methylene chloride. The film is transparent and colourless.
When the film is exposed to light for 14 hours using a LJV lamp at 254 nm, no discolouration can be observed visually.
Comparison Example 1 161.1 g (0.11 mol.) of oligo-[2,2-bis-(4-hydroxyphenyl)-propane carbonate]
chlorocarbonic acid ester (degree of polymerisation approximately 5) (prepared according to U. Grigo, K. Kirchner and P.R. Miiller "Polycarbonate" in BeckerBraun, Kunststoff Handbuch, Volume 3/1, Polycarbonate, Polyacetale, Polyester, Celluloseester, Carl Hanser Verlag Munich, Vienna 1992, pages 143 formula (3.9)) are dissolved in 1,000 g of dichloromethane. A clear solution consisting of 89.1 g (0.189 mol.) of 2,4,6-triiodophenol, 35.6 g (0.40 mol.) of 45 sodium hydroxide solution and 800 g of water is added at 20-25°C, with stirring.
After 5 minutes, 0.71 g of N-ethylpiperidine is added, and the mixture is stirred intensively for 30 minutes. The dichloromethane phase is separated from the aqueous phase and washed free of electrolyte. The solvent is evaporated off and the concentrated solution is dried at 120°C under a water jet vacuum.
Yield: 202 g of colourless solid Analyses: phenolic OH: 160 mg/kg, saponifiable Cl: < 0.2 mg/kg Iodine content: approximately 27 1 S When the sample is heated for S minutes at 300°C in a crucible together with polycarbonate, no discolouradon is observed.
Comparison Examine 2 94.7 parts of polycarbonate (Makrolon 2808~, Bayer AG) are compounded together with 5.9 wt.% of iodated oligocarbonates from Comparison Example 1 (triiodophenol end groups) and 0.5 wt.% of mould-release agent PETS
(pentaerythritol tetrastearate) at 280°C using a twin-screw extruder and then injection moulded to test rods of various thicknesses.
The transparency of the moulded bodies was in each case more than 85 %. The X-ray detectability was demonstrated on test samples having a thickness of from 1.2 to 3.2 mm using the parameters conventional in the medical field.

Table 2 Stability to light of samples of Comparison Example 2 having a thickness of 2 mm:
before weathering after weathering 8 h UV lamp 254 colourless markedly discernible nm red colour 200 h Xe-WOM colourless markedly discernible red colour 2 months indoor colourless markedly discernible light red colour Comparison Example 3 94.7 parts of Makrolon 2808~ are compounded together with 0.3 part of PETS and 5 parts of 4,4'-diiodobiphenyl (Aldrich) at 280°C using a twin-screw extruder and then injection moulded to test rods of various thicknesses.
The transparency of the moulded bodies was in each case more than 85 %.
Samples having a thickness of 2 mm are weathered for 1,000 hours under Xe-WOM
0.35 W/m2 without being watered. The previously colourless samples were subsequently an intense red colour. When such a sample is exposed to light for hours using a UV lamp at 254 nm, a markedly discernible red colour can also be produced.
Comparison Example 4 9.87 g (0.067 mol.) of oligo-[2,2-bis-(4-hydroxyphenyl)-propane carbonate]
chlorocarbonic acid ester (see Comparison Example 1) are dissolved in 56 g of dichloromethane. A clear solution consisting of 2.48 g (0.01 mol.) of 4-iodobenzoic acid, 1.33 g (0.015 mol.) of 45 % sodium hydroxide solution and 72 g of water is added at 20-25°C, with stirring. After 5 minutes, 0.084 g of N-ethylpiperidine is added, and the mixture is stirred intensively for 30 minutes. The dichloromethane phase is separated from the aqueous phase and washed free of electrolyte. The solvent is evaporated off and the concentrated solution is dried at 120°C under a water jet vacuum.
Yield: 9.7 g of colourless solid Analyses: phenolic OH: 0.09 %, saponifiable Cl: 3 ppm, iodine content:
approximately 4.6 When the sample is heated for S minutes at 300°C in a crucible together with polycarbonate, no discolouration is observed. The iodine content is too low to obtain, analogously to Comparison Example 2, mixtures with polycarbonate having an iodine content that is detectable by means of X-rays.
Comparison Ezample 5 A solution film consisting of 50 parts of Makrolon 3208, 50 parts of oligomer according to Comparison Example 4 and 0.5 part of Tinuvin 234 is produced. The film exhibits no discolouradon even after 6 hours' exposure to light under a UV lamp (254 nm).
Comparison Ezample 6 23 parts of BPA are reacted with 17 parts of phosgene and 21 parts of 2,3,5-iodobenzoyl chloride under phase boundary conditions (according to WO 9859005) to form an oligomer having 2,3,5-iodobenzoyl end groups. When the sample is heated for 5 minutes at 300°C in a crucible together with polycarbonate, a marked red colour is observed.
Comparison Example 7 6 parts of 4-iodobenzoic acid are heated for 5 minutes at 300°C in a crucible together with 94 parts of polycarbonate. Some 4-iodobenzoic acid is deposited on the edge of the crucible by sublimation.

Comparison Example 8 4 parts of 3,5-diiodosalicylic acid are heated for 5 minutes at 300°C
in a crucible with 96 parts of polycarbonate. The mixture turns markedly red in colour.
Comparison Example 9 4 parts of 2,3,5-triiodobenzoic acid are heated for 5 minutes at 300°C
in a crucible with 96 parts of polycarbonate. The mixture turns markedly red in colour.
Comparison Example 10 A film consisting of 96 parts of Makrolon 2808 and 4 parts of 1,4-diiodotetrafluoro-1 S benzene (Aldrich) is produced by solution casting. After drying, the colourless and transparent film is exposed to light for 6 hours using a UV lamp at 254 nm. A
marked red colour is then discernible.
Comparison Example 11 6 parts of Iohexol (Sigma) are heated for S minutes at 300°C in a crucible with 94 parts of polycarbonate. Pronounced discolouration occurs.

Claims (10)

claims

1. Use of iodobenzoic acid derivatives as X-ray contrast media.

2. Use of iodobenzoic acid derivatives for the X-ray-detectable treatment of plastics.

3. Plastics compositions containing at least one iodobenzoic acid derivative.

4. Process for the preparation of plastics compositions as defined in claim 3, characterised in that at least one iodobenzoic acid derivative is added before, during or after the polymerisation of the plastics.

5. Use of plastics compositions containing iodobenzoic acid derivative in the production of plastics moulded bodies.

6. Method of producing X-ray-opaque moulded bodies, characterised in that at least one plastics composition as defined in claim 3 is used as starting material.

7. Plastics moulded bodies containing at least one iodobenzoic acid derivative.

8. X-ray-detectable moulded bodies based on (co)polycarbonates, or blends thereof, containing iodobenzoic acid derivative in amounts of from 0.001 to 20 wt.%.

9. Moulded bodies produced from plastics compositions according to claim 3.

10. Moulded bodies according to any one of the preceding claims containing mould-release agents, heat stabilisers and/or UV absorbers, in each case in amounts of from 0.001 to 1 wt.%.