AU2014201305B2 - Sterilisation of polymerisable monomer - Google Patents

Abstract

Sterilisation of polymerisable monomer Abstract The invention relates, inter alia, to a method for sterilisation of a polymerisable monomer. Said method provides a mixture (1) that contains at least the polymerisable monomer, a compound (a) and a compound (b), whereby compound (a) is selected from compounds (al) represented through general formula (1), whereby R1, R2, R3, and R4, independently of each other, represent a substituted or non substituted alkyl residue, halogen residue, nitro residue or cyano residue, compounds (a2) that are selected from the group consisting of dimers of compounds (al), and compounds (a3) that are selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols.

Description

1 Sterilisation of Polymerisable Monomer [0001] The invention relates to a method for sterilisation of a polymerisable monomer, in particu lar of a monomer for radical polymerisation, mixtures containing a polymerisable monomer, in particular a monomer for radical polymerisation, a kit for producing bone cement containing a mixture of said type, and a bone cement paste containing a mixture of said type. [0002] Conventional poly(methylmethacrylate) bone cements (PMMA bone cements) have been known for decades and are based on the ground-breaking work of Sir Charnley (Charnley, J.: Anchorage of the femoral head prosthesis of the shaft of the femur. J. Bone Joint Surg. 42 (1960) 28-30). [0003] The basic structure of PMMA bone cements has remained the same ever since. PMMA bone cements consist of a liquid monomer component and a powder component. The mono mer component generally contains (i) the monomer, methylmethacrylate, and (ii) an activator (e.g. N,N-dimethyl-p-toluidine) dissolved therein. The powder component comprises (i) one or more polymers that are made by polymerisation, preferably suspension polymerisation, based on methylmethacrylate and co-monomers, such as styrene, methylacrylate or similar mono mers, (ii) a radio-opaquer, and (iii) an initiator, (e.g. dibenzoylperoxide). Mixing the powder component and the monomer component, the polymers of the powder component in the methylmethacrylate swell which generates a dough that can be shaped plastically. Simultane ously, the activator, N,N-dimethyl-p-toluidine, reacts with dibenzoylperoxide which disintegrates and forms radicals in the process. The radicals thus formed trigger the radical polymerisation of the methylmethacrylate. Upon advancing polymerisation of the methylmethacrylate, the viscosi ty of the cement dough increases until the cement dough solidifies and thus is cured. [0004] Patent DE 102007050762 B3 proposes a kit for producing bone cement comprising two pastes as an alternative to the conventional powder-liquid polymethylmethacrylate bone ce ments. Said pastes each contain a polymerisable monomer, such as, for example, a methacry late monomer for radical polymerisation, a polymer that is soluble in said methacrylate mono mer, and a particulate polymer that is insoluble in said methacrylate monomer. In addition, one of said pastes contains a radical polymerisation initiator, whereas the other paste comprises a polymerisation activator. As a result of the selected composition, the bone cement produced from said pastes possesses sufficiently high viscosity and cohesion in order to withstand the pressure from bleeding until it is fully cured. When the two pastes are mixed, the polymerisation 2 initiator reacts with the accelerator to form radicals that initiate the radical polymerisation of the methacrylate monomers. Owing to the advancing polymerisation, the paste is cured while the methacrylate monomers are consumed. The pastes contained in the kit for producing bone cement are non-aqueous systems. Accordingly, the pastes contain at most traces of water. [0005] PMMA bone cements are medical products of class llb, or medical products of class Ill if antibiotics are added. In order to ensure the safety of the patients, the PMMA bone cements may be marketed in sterile condition in a doubly-sterile package only. In conventional PMMA bone cements consisting of a liquid monomer component and a powder component, the powder component is sterilised by subjecting it to ethylene oxide. Sterilisation of the powder component by gamma irradiation is customary as well. [0006] Often used for producing the monomer component, the polymerisable monomer, methylmethacrylate, is biocidal for most vegetative microbial life forms due to its lipophilic and thus denaturing properties. Therefore, these micro-organisms cannot exist in anhydrous methylmethacrylate. However, aside from the vegetative forms, micro-organisms also have generative forms, such as endospores. These generative survival forms of micro-organisms are formed by gram-positive bacteria, in particular of the Bacillus and Clostridium genus, as a means of persisting during unfavourable living conditions. In their resting state, endospores have no active metabolism and possess a multi-layered spore capsule that largely protects the core of the spore from the action of chemicals and other environmental effects. This renders spores extremely resistant to the action of heat and chemicals (Borick, P. M.: Chemical steriliz ers. Adv. Apple. Microbiol. 10 (1968) 291-312; Gould, G. W.: Recent advances in the under standing of resistance and dormancy in bacterial spores. J. Apple. Bacteriol. 42 (1977) 297-309; Gould, G. W.: Mechanisms of resistance and dormancy. p. 173-209. In Hurst, A. and Gould, G. W. (ed.), The bacterial spore. vol. 2 Academic Press, Inc. New York, 1983). Due to their high resistance, endospores are used as bio-indicators for validation and control of the efficacy of sterilisation processes. This is based on the assumption that the inactivation of endospores is indicative of all vegetative microbial forms of life being killed. Endospores of gram-positive bac teria are classified in international resistance class Ill. Resistance classes I include non-spore forming bacteria and vegetative forms of spore-formeing bacteria and resistance class II in cludes spores that are killed within a few minutes in a flow of steam at 105 OC. In accordance with DAB 2008 (Deutsches Arzneimittelbuch), all micro-organisms of resistance classes I-Ill must be killed or inactivated irreversibly.

3 [0007] Accordingly, there is a fundamental need to have methods for efficient sterilisation of polymerisable monomers, in particular of monomers for radical polymerisation. [0008] Methods for sterilisation of polymerisable monomers are known in the field of medical products. [0009] It is common to use physical sterilisation methods for sterilisation of medical products. In particular gamma irradiation, electron bombardment, UV irradiation, heat sterilisation, and auto claving with pressurised steam need to be mentioned in this context. However, said sterilisation methods are inherently disadvantageous due to the extensive use of equipment and process resources required by them. Sterilisation of polymerisable monomers by means of said physical sterilisation methods is inapplicable for other reasons as well though: Subjecting the materials to heat, gamma irradiation or X-ray irradiation would initiate radical polymerisation of the polymerisable monomers which would result in inadvertent premature curing of the bone ce ment. Steam sterilisation, in contrast, would result in hydrolysis of the polymerisable monomers which would prevent polymerisation of the polymerisable monomers. [0010] Sterilisation of polymerisable monomers is often attained through sterile filtration and subsequent aseptic packing. However, the aseptic production of polymerisable monomers is very expensive. Another associated problem is that viruses cannot be removed through sterile filtration. Moreover, sterilisation of pastes for producing bone cement by means of sterile filtra tion is not feasible due to the high viscosity of the pastes and the radio-opaquers and filling agents contained in said pastes. [0011] Aside from said physical methods, it is customary to use chemical compounds for sterili sation of medical products. These include, for example, ethylene oxide, formaldehyde, glutardi aldehyde, o-phthaldialdehyde, hypochlorite, chlorine dioxide, peracetic acid, and hydrogen per oxide. However, the use of said compounds is associated with significant disadvantages. For example ethylene oxide is sporocidal only in the presence of moisture such that its use in the absence of water does not result in the desired sterilisation effect. Moreover, pastes for produc ing bone cement are usually available in closed diffusion-tight film pouches or closed plastic cartridges. Ethylene oxide is incapable of penetrating into said containers though such that the packaged pastes cannot be sterilised by this means. In contrast, aldehydes are usually applied as aqueous solutions or in the gaseous state in the case of formaldehyde due to their mecha nism of action. Peracetic acid and hydrogen peroxide are strongly oxidising agents which are 4 also used in the form of aqueous solutions. However, for this reason, said compounds are not suitable for sterilisation of mixtures that must contain no or only small amounts of water. Chlo rine-based compounds are usually very effective sterilisation agents. They are disadvanta geous though in that chlorine-containing secondary products remain in the medical product after sterilisation. [0012] It is known from pharmaceutical industry that aqueous protein solutions, such as, e.g., vaccines, are very sensitive to the effects of oxidising sterilisation agents and various physical sterilisation methods, for example sterilisation with gamma radiation. For this reason, said aqueous protein solutions often have small amounts of the acylating agent, B-propiolactone, added to them for the purpose of sterilisation. B-propiolactone can be used to attain both inacti vation of viruses and of spores, in particular of endospores. These effects are likely to occur due to acylation of the amino groups of DNA/RNA or proteins. The water that is present as sol vent is capable of slowly decomposing B-propiolactone such that no active B-propiolactone is present any longer in aqueous protein solutions after just a short period of time. The principle of sterilisation of aqueous protein solutions by means of acylating agents, such as B propiolactone, is based on the fact that spores can swell in small amounts of aqueous media. This swelling renders the double walls of spores permeable to said acylating agents such that said acylating agents can penetrate into the spores and be effective therein. [0013] However, swelling of the spores is not feasible in mixtures containing a polymerisable monomer and small, if any, quantities of water. Therefore, swelling cannot be used in prepara tion of the penetration of the acylating agent into spores. Accordingly, sterilisation of said mix tures by means of acylating agents, such as B-propiolactone, appears to be not feasible. [0014] The invention is therefore based on providing an effective method for sterilisation of a polymerisable monomer, in particular a monomer for radical polymerisation. Said method is to produce, in particular, mixtures that are free of endospores. Preferably, said method should be suitable for sterilisation of polymerisable monomers, in particular of monomers for radical polymerisation, in mixtures containing no or only small quantities of water, such as no more than 2.0 % by weight of water, more preferably no more than 1.0 % by weight of water, and even more preferred no more than 0.5 % by weight of water, relative to the total weight of the mixture. Moreover, it is preferable for the mixture to contain no toxic or harmful residues, such as, for example, chlorine-containing residues, after the sterilisation is completed. Moreover, it is preferable to also overcome other disadvantages known from the prior art.

5 [0015] Further objects underlying the invention include the provision of a mixture (I) that can be used for sterilisation according to the method according to the invention, of a mixture (II) that can be obtained while carrying out the method according to the invention, of a kit for producing bone cement that can be obtained after carrying out the 5 method according to the invention, and of a bone cement paste that can be obtained after carrying out the method according to the invention. [0016] Said objects are met by the subject matters of the independent claims. [0016a] According to a first aspect of the invention there is provided a method for sterilisation of a polymerisable monomer, in which a mixture (I) is produced that contains 10 at least the polymerisable monomer, a compound (a) and a compound (b), whereby compound (a) is selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols. [0016b] According to a second aspect of the invention there is provided a mixture (I) 15 containing at least one polymerisable monomer, a compound (a) and a compound (b), whereby compound (a) is selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols, whereby the fraction of compound (b) is no more than 2 % by weight, relative to 20 the total weight of mixture (I). [0016c] According to a third aspect of the invention there is provided a mixture (II) containing at least one polymerisable monomer and a compound (c), whereby compound (c) is selected from the group consisting of alcohols, carboxylic acids having at least three carbon atoms, and esters, and is available through 25 reacting a compound (a) and a compound (b), whereby compound (a) is selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols. [0016d] According to a third aspect of the invention there is provided a kit for producing 30 bone cement comprising at least a paste A and a paste B, wherein at least one of pastes A and B contains a mixture (II) according to the third aspect of the invention.

5a [0016d] According to a fourth aspect of the invention there is provided a bone cement paste containing a mixture (II) according to the third aspect of the invention. [0017] The invention also provides a method for sterilisation of a polymerisable monomer, in particular of a monomer for radical polymerisation, in which a mixture (I) is 5 produced that contains at least the polymerisable monomer, in particular the monomer for radical polymerisation, a compound (a) and a compound (b), whereby compound (a) is selected from compounds (al) represented through general formula (I) 0 0 R4 R1 R3 R2 whereby R1, R2, R3, and R4, independently of each other represent H, represent a 10 substituted or non-substituted alkyl residue, halogen residue, nitro residue or cyano residue, compounds (a2) that are selected from the group consisting of dimers of compounds (al), and compounds (a3) that are selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols. The fraction of compound (b) is preferably no more than 2 % by weight, is relative to the total weight of the mixture. [0018] The invention also provides a mixture (I) containing at least one polymerisable monomer, in particular a monomer for radical polymerisation, a compound (a) and a compound (b), whereby compound (a) is selected from compounds (al) represented through general formula (I), 6 0 0 R4 RI R3 R2 whereby R1, R2, R3, and R4, independently of each other represent H, represent a substituted or non-substituted alkyl residue, halogen residue, nitro residue or cyano residue, compounds (a2) that are selected from the group consisting of dimers of compounds (al), and compounds (a3) that are selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols, whereby the fraction of compound (b) is no more than 2 % by weight, relative to the total weight of mixture (1). [0019] The invention further provides a mixture (II) containing at least one polymerisable mon omer, in particular a monomer for radical polymerisation, and a compound (c), whereby com pound (c) is selected from the group consisting of alcohols, carboxylic acids having at least three carbon atoms, and esters, and can be obtained through reacting a compound (a) and a compound (b), whereby compound (a) is selected from compounds (al) represented through general formula (1) 0 0 R4 R1 R3 R2 whereby R1, R2, R3, and R4, independently of each other, represent H, a substituted or non substituted alkyl residue, halogen residue, nitro residue or cyano residue, compounds (a2) that are selected from the group consisting of dimers of compounds (al), and compounds (a3) that are selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols. [0020] Moreover, the invention provides a kit for producing bone cement comprising at least one paste A and one paste B, whereby at least one of paste A and paste B contains a mixture || according to the description provided herein.

7 [0021] Moreover, the invention provides a bone cement paste containing a mixture II according to the description provided herein. [0022] The invention is partly based on the surprising finding that sterilisation of a polymerisable monomer, in particular of a monomer for radical polymerisation, by means of an acylating agent according to compound (a) in mixtures is feasible even if the fraction of water in said mixtures is no more than 2 % by weight, more preferably no more than 1.0 % by weight, and even more preferably no more than 0.5 % by weight, relative to the total weight of the mixture. Although the spores contained in the mixture cannot swell at said low quantity of water, the polymerisable monomer in the mixture is sterilised effectively which was surprising. [0023] Moreover, another surprising finding is that neither compound (a) nor the products ob tained by reacting compound (a) and compound (b) inhibit the polymerisation of the polymerisa ble monomers. This is true also when further components are contained in the mixture that is being subjected to the method for sterilisation, such as, for example, components of a paste for producing bone cement. [0024] The invention relates to a method for sterilisation of a polymerisable monomer, in particu lar of a monomer for radical polymerisation. [0025] A polymerisable monomer that is characterised by sterility is obtained in the method ac cording to the invention. In the scope of the invention, sterility shall be understood to mean a state that is free of viable micro-organisms. In this context, please refer to the corresponding definition provided in EN 556-1:2001. [0026] At least one polymerisable monomer, in particular at least one monomer for radical polymerisation, is being subjected to the method for sterilisation. [0027] Polymerisable monomer shall be understood to preferably mean compounds that com prise at least one polymerisable olefinic bond. [0028] In a broader scope, the term, polymerisable monomer, shall also be understood to mean macromers having terminal methacrylate groups, acrylate groups, itaconate groups, maleinate groups or fumarate groups. Said macromers can be liquid or semi-liquid. Moreover, said mac romers can be linear or branched compounds.

8 [0029] The polymerisable monomer, in particular the monomer for radical polymerisation, used according to the invention preferably has a molar mass of less than 1,000 g/mol. This also comprises polymerisable monomers that are components of a mixture of monomers, whereby at least one of the polymerisable monomers of the mixture of monomers has a defined structure with a molar mass of less than 1,000 g/mol. [0030] According to a preferred embodiment, the polymerisable monomer is selected from the group consisting of methacrylic acid esters (preferably mono-functional and multi-functional methacrylic acid esters), acrylic acid esters (preferably mono-functional and multi-functional acrylic acid esters), methacrylamide, methacrylic acid, acrylic acid, itaconic acid esters, itaconic acid, maleic acid esters, maleic acid, fumaric acid esters, and fumaric acid. The methacrylic acid esters and acrylic acid esters preferably are alkyl esters of methacrylic acid and acrylic acid, respectively. In this context, the alkyl group of the alkyl esters preferably has a chain length of 1 - 10 carbon atoms, more preferably a chain length of 1 - 4 carbon atoms, even more preferably a chain length of 1 - 2 carbon atoms, and particularly preferably one carbon atom. [0031] According to a particularly preferred embodiment, the polymerisable monomer is select ed from the group consisting of methacrylic acid methylester, methacrylamide, and ethylene glycol dimethacrylate. [0032] A mixture (1) is produced for sterilisation of the polymerisable monomer. [0033] Mixture (1) preferably is self-sterilising. A mixture is preferably said to be self-sterilising if sterilisation does not necessitate the addition of any further components or the influence of ex ternal factors, such as irradiation. [0034] Mixture (1) contains at least one compound (a) aside from the polymerisable monomer. [0035] Preferably, compound (a) is an acylating agent. Preferably, said acylating agent is capable of acylating amino groups of DNA/RNA or proteins. [0036] Compound (a) is therefore capable of killing micro-organisms and to thus have a sterilising effect. [0037] Compound (a) is selected from the group consisting of compounds (al), (a2), and (a3) according to the description provided herein.

9 [0038] Compound (a) can be a compound (al) represented through general formula (1) 0 0 R4 R1 R3 R2 [0040] In said formula, R1, R2, R3, and R4, independently of each other, can represent H, a substituted or non-substituted alkyl residue, a halogen residue, a nitro residue or a cyano residue. [0041] There stereochemistry of compounds (al) is not limited in any way. Preferably, the scope of the invention includes as compound (1) all isomers represented through general formu la (1), regardless of their exact configuration. [0042] The alkyl residues can be substituted or non-substituted alkyl residues, independently of each other. The at least one substituent of a substituted alkyl residue is preferably selected from the group consisting of halogen residues, nitro residues, and cyano residues. [0043] The alkyl residues can be saturated or unsaturated alkyl residues, independently of each other. Preferably, an unsaturated alkyl residue comprises at least one carbon-carbon double bond. [0044] The alkyl residues can be branched or unbranched alkyl residues, independently of each other. It is preferable for alkyl residues R1, R2, R3, and R4 to be unbranched alkyl residues. [0045] Independently of each other, the alkyl residues have a main chain length in the range of 1 - 4 carbon atoms, more preferably a main chain length in the range of 1 - 2 carbon atoms, and even more preferably one carbon atom. [0046] Fluorine residues, chlorine residues, and bromine residues are preferred halogen resi dues in general formula (1). Said residues each can represent one or more of residues R1, R2, R3, and R4, independently of each other. [0046a] According to a preferred embodiment, residues R1, R2, R3, and R4 each represent H.

10 [0046b] According to another preferred embodiment, residue R1 represents a methyl residue and residues R2, R3, and R4 represent H. [0046c] According to another preferred embodiment, residues R1, R2, and R3 represent H and residue R4 represent H represents a methyl residue. [0046d According to yet another preferred embodiment, residues R1 and R3 represent H and residues R2 and R4 represent a methyl residue. [0046e] According to a particularly preferred embodiment, compound (al) is B-propiolactone (CAS number 57-57-8). [0047] Compound (a) can just as well be a compound (a2) being a dimer of any of compounds (al). Said dimer is preferably represented through general formula (II) R3 R3 0 0 0O- O R2 0 R1 R2 R1 O whereby residues R1, R2, and R3, independently of each other, can have the meaning defined above. [0048] The stereochemistry of compounds (a2) is not limited in any way. Preferably, the scope of the invention includes the use, as compound (a2), of all dimers of compound (al), in particu lar of all isomers represented through general formula (II), regardless of their exact configura tion. [0048a] According to a particularly preferred embodiment, residues R1, R2, and R3 each repre sent H. [0049] Compound (a) can just as well be a compound (a3) that is selected from the group con sisting of dialkyldicarbonates. [0050] Dialkyldicarbonates can be represented through following general formula (Ill): 11 R5-O-CO-O-CO-O-R6 [0051] Residues R5 and R6 can be different from each other or identical. Preferably, residues R5 and R6 are identical. [0052] Residues R5 and R6 can be saturated residues or unsaturated residues, independently of each other. In this context, unsaturated residues comprise at least one carbon-carbon dou ble bond. [0053] Residues R5 and R6 can be branched alkyl residues or unbranched alkyl residues, inde pendently of each other. Preferably, residues R5 and R6 are unbranched. [0054] Residues R5 and R6 can be substituted alkyl residues or non-substituted alkyl residues, independently of each other. Halogen substituents, for example, preferably chlorine substitu ents, are conceivable as substituents of residues R5 and R6. Preferably, residues R5 and R6 are non-substituted. [0055] According to a preferred embodiment, residues R5 and R6, independently of each other, have a main chain length in the range of 1 - 8 carbon atoms, more preferably a main chain length in the range of 1 - 4 carbon atoms, even more preferably 1 - 2 carbon atoms, and particu larly preferably one carbon atom. [0056] According to a particularly preferred embodiment, compound (a) is B-propiolactone (CAS number 57-57-8). [0057] Preferably, the fraction of compound (a) is at least 0.0001 % by weight, more preferably at least 0.001 % by weight, even more preferably at least 0.01 % by weight, and particularly preferably at least 0.1 % by weight, relative to the total weight of mixture (1). Preferably, the fraction of compound (a) is no more than 50 % by weight, more preferably no more than 5 % by weight, even more preferably no more than 2 % by weight, and particularly preferably no more than 0.4 % by weight, relative to the overall weight of mixture (1). The fraction of compound (a) preferably is in the range of 0.0001 - 50 % by weight, more preferably in the range of 0.001 - 5 % by weight, even more preferably in the range of 0.001 - 2 % by weight, and particularly pref erably in the range of 0.1 - 0.4 % by weight, relative to the total weight of mixture (1).

12 [0058] Mixture (1), which is being produced for sterilisation of the polymerisable monomer, also contains a compound (b). [0059] Compound (b) is preferably selected from the group consisting of water and alcohols. [0060] It is preferable for the water to be doubly distilled water. Preferably, the water is pyrogen-free. [0061] The structure of the alcohol is not limited in any way. [0062] Preferably, the alcohol has a main chain length of 1 - 20 carbon atoms, more preferably a main chain length of 1 - 10 carbon atoms, and even more preferably a main chain length of 1 4 carbon atoms. [0063] The alcohol can be a saturated or an unsaturated alcohol. If the alcohol is unsaturated, the alcohol preferably contains at least one carbon-carbon double bond. [0064] Moreover, the alcohol can be substituted or non-substituted. The at least one substituent of the substituted alcohol is preferably selected from the group consisting of halogen substitu ents, nitro substituents, and cyano substituents. [0065] The alcohol can be a monoalcohol or a polyalcohol. Preferably, the alcohol is a monoal cohol. [0066] The alcohol can be a branched or an unbranched alcohol. Preferably, the alcohol is an unbranched alcohol. [0067] The alcohol is preferably selected from the group consisting of primary and secondary alcohols. [0068] The alcohol shall preferably be represented in the following through general formula (IV) R7-OH. [0069] The residue is not subject to any limitation. Preferably, the residue R7 is an alkyl resi due. Preferably, said alkyl residue has a main chain length of 1 - 20 carbon atoms, more prefer- 13 ably a main chain length of 1 - 10 carbon atoms, even more preferably a main chain length of 1 - 5 carbon atoms, particularly preferably a main chain length of 1 - 2 carbon atoms, and more particularly preferably 1 carbon atom. The alkyl residue can be saturated or unsaturated. The residue R7 can be substituted or non-substituted. Conceivable substituents are, for example, hydroxyl groups, nitro groups, cyano groups, and halogens. The residue R7 can be branched or unbranched. [0069a] According to a preferred embodiment, the primary alcohol is selected from the group consisting of methanol, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, tetra ethylene glycol, and pentaerythritol. The term, primary alcohol, shall preferably include polymerisable monomers, in particular monomers for radical polymerisation, having alcoholic hydroxyl groups, such as, for example, methacrylic acid-2-hydroxyethylester. [0069b] According to another preferred embodiment, the secondary alcohol is selected from the group consisting of isopropanol and butan-2-ol. [0069c] According to a particularly preferred embodiment, the alcohol is selected from the group consisting of methanol, ethanol, diethylene glycol, triethylene glycol, and tetraethylene glycol. [0070] The scope of the invention also includes the polymerisable monomer and compound (b) being the same compound. For example methacrylic acid-2-hydroxyethylester can be both the sterilising polymerisable monomer and also compound (b). [0071] Preferably, the fraction of compound (b) is at least 0.0001 % by weight, more preferably at least 0.001 % by weight, even more preferably at least 0.01 % by weight, and particularly preferably at least 0.1 % by weight, relative to the total weight of mixture (1). Preferably, the fraction of compound (b) is no more than 2.0 % by weight, more preferably no more than 1.0 % by weight, even more preferably no more than 0.5 % by weight, and particularly preferably no more than 0.4 % by weight, relative to the overall weight of mixture (1). The fraction of com pound (b) preferably is in the range of 0.0001 - 2.0 % by weight, more preferably in the range of 0.001 - 1.0 % by weight, even more preferably in the range of 0.001 - 0.5 % by weight, and par ticularly preferably in the range of 0.1 - 0.4 % by weight, relative to the total weight of mixture (1). [0071 a] According to a preferred embodiment, the ratio of the quantity of compound (b), nb, that is contained in mixture (1) to the quantity of compound (a), na, that is contained in mixture (1) is 14 represented through the inequation nb/na> 0.5, more preferably inequation nb/na > 0.8, and even more preferably inequation nb/na > 1. [0072] In addition to the polymerisable monomer, compound (a) and compound (b), mixture (1) can contain at least one further component (d), if applicable. [0073] The scope of the invention includes, for example, that mixture (1) is a part of a medical product that contains compounds (a) and (b) in addition to the polymerisable monomer, in par ticular the monomer for radical polymerisation. The scope of the invention includes, in particu lar, carrying out the method for sterilisation of a polymerisable monomer on a mixture (1) that contains, aside from compounds (a) and (b), at least one, but preferably all, components that are contained in a kit for producing a bone cement, whereby the component can, for example, be a paste. Accordingly, mixture (1) can just as well be a mixture containing, aside from com pound (a) and compound (b), the components of a polymethylmethacrylate bone cements that is described in DE 102007052116, DE 102007050762 or DE 102010005956. Moreover, mix ture (1) can just as well be a mixture containing, aside from compounds (a) and (b), the compo nents of inorganic bone cements or of polymerisable dental materials. Mixture (1) can just as well be a mixture that contains, aside from compound (a) and compound (b), the components of a monomer liquid that is contained in a kit for producing bone cement (for example polymethyl methacrylate bone cement). [0074] Conceivable as further components (d) are preferably substances selected from the group consisting of polymers (dl) that are soluble in the polymerisable monomer, polymers (d2) hat are insoluble in the polymerisable monomer, radical polymerisation initiators (d3), polymeri sation activators (d4), filling agents (d5), colourants (d6), pharmaceutical agents (d7), and mix tures thereof. [0074a] According to a preferred embodiment, the further component (d) is a polymer (dl) that is soluble in the polymerisable monomer. The polymer (dl) that is soluble in the polymerisable monomer preferably is a polymer with a mean (by weight) molar mass of less than 500,000 g/mol and more preferably is a polymer with a mean (by weight) molar mass of less than 150,000 g/mol. The specification of the molar mass refers to the molar mass determined by viscosimetry. The soluble polymer (dl) can be either cross-linked or non-crosslinked, and pref erably is non-crosslinked. The soluble polymer (dl) can be a homopolymer or a copolymer. Preferably, the soluble polymer (dl) is a polymer of a methacrylic acid ester. According to a 15 particularly preferred embodiment, the soluble polymer (dl) is a copolymer of methacrylic acid methylester. [0074b] According to another particularly preferred embodiment, the soluble polymer (dl) is selected from the group consisting of poly(methacrylic acid methylester) (PMMA), poly(methacrylic acid ethylester) (PMAE), poly(methacrylic acid propylester) (PMAP), poly(methacrylic acid isopropylester), poly(methylmethacrylate-co-methylacrylate), and poly(styrene-co-methylmethacrylate). The polymer (dl) is soluble in the polymerisable mono mer. According to definition, the polymer is soluble in the polymerisable monomer, if the solubil ity of the polymer in the polymerisable monomer at a temperature of 250C is at least 25 g/l, more preferably at least 50 g/l, and particularly preferably at least 100 g/l. [0074c] According to another preferred embodiment, the further component (d) is a polymer (d2) that is insoluble in the polymerisable monomer. Preferably, the insoluble polymer (d2) is partic ulate. According to a particularly preferred embodiment, the insoluble polymer (d2) has an av erage particle size in the range of 100 nm - 500 pm. The average particle size shall be under stood herein to mean a size range that applies to at least 90 percent of the particles. The insol uble polymer (d2) preferably has a mean (by weight) molar mass of at least 150,000 g/mol and more preferably a mean (by weight) molar mass of at least 500,000 g/mol. The specification of the molar mass refers to the molar mass determined by viscosimetry. The insoluble polymer (d2) can be either crosslinked or non-crosslinked, and preferably is crosslinked. In this context, the cross-linking is effected through a difunctional compound. The difunctional compound can be selected, for example, from the group consisting of alkylene glycol dimethacrylates. An ex pedient cross-linker is, for example, ethylene glycol dimethacrylate. The insoluble polymer (d2) can be a homopolymer or a copolymer. Preferably, the insoluble polymer (d2) is a polymer of a methacrylic acid ester. According to a preferred embodiment, the insoluble polymer (d2) is a homopolymer or a copolymer of a methacrylic acid alkylester. According to a particularly pre ferred embodiment, the insoluble polymer (d2) is selected from the group consisting of cross linked poly(methylmethacrylate-co-methacrylate) and cross-linked poly(methylmethacrylate). The insoluble polymer (d2) is insoluble in the polymerisable monomer. According to definition, the polymer is insoluble in the polymerisable monomer, if the solubility of the polymer in the polymerisable monomer at a temperature of 250C is less than 50 g/l, preferably is less than 25 g/l, more preferably is less than 10 g/l, and even more preferably is less than 5 g/l.

16 [0074d] According to yet another preferred embodiment, the further component (d) is a radical polymerisation initiator (d3). [0074e] According to yet another preferred embodiment, the further component (d) is a polymer isation activator (d4). Said polymerisation activator can be present in addition or alternative to the radical polymerisation initiator (d3). [0074f] According to yet another preferred embodiment, the further component (d) is a filling agent (d5). Preferably, the filling agent (d5) is selected from the group consisting of inorganic filling agents, organic filling agents, glass, metals, and carbon. Preferably, inorganic filling agents are selected from the group consisting of calcium sulfates (such as calcium sulfate, cal cium sulfate dihydrate or calcium sulfate hemihydrate), calcium carbonate, calcium phosphates (such as a-tricalcium phosphate or p-tricalcium phosphate), hydroxylapatite, barium sulfate, and zirconium dioxide. Organic filling agents are preferably selected from the group consisting of non-crosslinked polymer particles, cross-linked polymer particles, and polymer fibres. The glass, as filling agent, can be present, for example, in the form of a glass powder or in the form of glass fibres. The metal can preferably be tantalum or zirconium. [0074g] According to yet another preferred embodiment, the further component (d) is a colour ant (d6). [0074h] According to yet another preferred embodiment, the further component (d) is a pharma ceutical agent (d7). Preferably, said pharmaceutical agent (d7) is selected from the group con sisting of antibiotics, antiinfective agents, antiseptic agents, antiphlogistic agents, and growth factors. [0075] The mixture (1) can be liquid or semi-liquid at room temperature and a pressure of 1.013 bar. [0076] According to a preferred embodiment, mixture (1) containing at least the polymerisable monomer, compound (a) and compound (b), is present in a packaging means. Preferably, said packaging means is closed. Preferably, said packaging means is diffusion-tight. The packag ing means can, for example, be a cartridge. It is also possible for the packaging means to be contained in a cartridge. The cartridge can be part of an application device for bone cement paste. Said application device can preferably contain a mixing device. Said mixing device can 17 be suitable for mixing individual components of a kit for producing bone cement to generate a bone cement paste. [0077] A time of action of compound (a) on the polymerisable monomer of at least 20 minutes, and more preferably of at least 30 minutes, has proven to be advantageous for the method ac cording to the invention for sterilisation of a polymerisable monomer. [0078] Moreover, it is preferable for the temperature for sterilisation of a polymerisable mono mer at which compound (a) acts on the polymerisable monomer in the method according to the invention to be higher than or equal to the melting temperature of the polymerisable monomer. [0079] It is a feature of compound (b) to be reactive with compound (a). Different products are obtained upon reacting compound (a) and compound (b) depending on the structures of com pounds (a) and (b). Surprisingly, the reaction of compound (a) and compound (b) proceeds at a comparatively slow reaction rate in mixtures containing a polymerisable monomer. Therefore, compound (a) firstly develops its sterilising effect in mixtures containing compounds (b) before reacting with compound (b). Moreover, the duration of the sterilising effect of compound (a) can be limited by reacting compound (a) and compound (b). [0080] An essential advantage of the method according to the invention for sterilisation of a polymerisable monomer is that the sterilising effect is provided after producing mixture (1) in the absence of further external factors. Moreover, it is feasible, for example, to fill mixture (1) in a suitable packaging means, which preferably is diffusion-tight. In this context, compound (a) also contacts the inside of the packaging means such that not only the polymerisable monomer and further components that may be contained in mixture (1), if applicable, are sterilised, but the in side of the packaging means is sterilised as well. [0081] A mixture (II) is being obtained in the method according to the invention for sterilisation of a polymerisable monomer. [0082] Said mixture (II) comprises at least one polymerisable monomer. Said polymerisable monomer preferably is a polymerisable monomer according to the preceding description in the context of mixture (1).

18 [0083] In addition, mixture (II) contains a compound (c). Compound (c) is obtained by reacting compounds (a) and (b) described above. [0084] Said reaction preferably proceeds at room temperature and without any need for further external measures in the process. [0085] Different products are obtained upon reacting compounds (a) and (b) depending on the structures of said compounds. [0086] If compound (b) in mixture (1) is water and compound (a) is a compound (al) represented through general formula (1), the method according to the invention results in the lactone ring being opened to form a carboxylic acid. Preferably, said carboxylic acid can be represented through general formula (V) HOOC-CR1 R2-CR3R4-OH, whereby residues R1, R2, R3 and R4, independently of each other, can have the meaning de fined above. [0087] If compound (b) in mixture (1) is an alcohol represented through general formula (IV) and compound (a) is a compound (al) represented through general formula (1), the method accord ing to the invention results in the lactone ring being opened to form an ester. Preferably, said ester can be represented through general formula (VI) R700C-CR1 R2-CR3R4-OH, whereby residues R1, R2, R3, R4 and R7, independently of each other, can have the meaning defined above. [0088] If compound (b) in mixture (1) is water and compound (a) is a compound (a2) represented through general formula (II), the method according to the invention results in the lactone ring being opened to form a carboxylic acid. Preferably, said carboxylic acid can be represented through general formula (VII) HOOC-CR1 R2-CR3(OH)-CH 2

-CR

3 (OH)-CR1 R2-COOH, 19 whereby residues R1, R2, and R3, independently of each other, can have the meaning defined above. [0089] If compound (b) in mixture (1) is an alcohol and compound (a) is a compound (a2) repre sented through general formula (II), the method according to the invention results in the lactone ring being opened to form an ester. Preferably, said ester can be represented through general formula (VIII): R700C-CR1 R2-CR3(OH)-CH 2

-CR

3 (OH)-CR1 R2-COOR7, whereby residues R1, R2, R3, and R7, independently of each other, can have the meaning de fined above. [0090] If compound (b) in mixture (1) is water and compound (a) is a compound (a3) represented through general formula (Ill), the method according to the invention results in the formation of carbon dioxide and at least one alcohol. Preferably, said at least one alcohol can be represent ed through general formula (IX) R5-OH or through general formula (X) R6-OH whereby residues R5 and R6, independently of each other, can have the meaning defined above. [0091] If compound (b) in mixture (1) is an alcohol represented through general formula (IV) and compound (a) is a compound (a3) represented through general formula (Ill), the method accord ing to the invention results in the formation of carbon dioxide, an alcohol, and an ester. Prefera bly, said alcohol can be represented through general formula (IX) R5-OH or general formula (X) 20 R6-OH whereby residues R5 and R6, independently of each other, can have the meaning defined above. Preferably, said ester can be represented through general formula (XI) R70-CO-OR7 whereby residue R7 can have the meaning defined above. [0092] Resulting from the reaction of compound (a) and compound (b), compound (c) is select ed from the group consisting of alcohols, carboxylic acids having at least three carbon atoms, and esters. [0093] According to a preferred embodiment, the alcohol is selected from the group consisting of compounds represented through general formula (V), compounds represented through gen eral formula (VI), compounds represented through general formula (VII), compounds represent ed through general formula (VIII), compounds represented through general formula (IX), and compounds represented through general formula (X), whereby residues R1, R2, R3, R4, R5, R6, and R7 contained therein, independently of each other, can have the meaning described above. [0093] The carboxylic acid is preferably selected from the group consisting of hydroxycarboxylic acids. Preferably, the hydroxycarboxylic acid is a B-hydroxycarboxylic acid. According to a pre ferred embodiment, the carboxylic acid is selected from the group consisting of compounds rep resented through general formula (V) and compounds represented through general formula (VII), whereby residues R1, R2, R3, and R4 contained therein, independently of each other, can have the meaning described above. [0095] The ester is preferably selected from the group consisting of hydroxyesters and diesters. Preferably, the hydroxyester is a B-hydroxyester. Preferably, the diester can be a carbonic acid diester. According to a preferred embodiment, the ester is selected from the group consisting of compounds represented through general formula (VI), compounds represented through general formula (VIII), and compounds represented through general formula (XI), whereby residues R1, 21 R2, R3, R4 and R7 contained therein, independently of each other, can have the meaning de scribed above. [0096] According to a preferred embodiment, compound (c) is selected from the group consist ing of compounds represented through general formula (V), compounds represented through general formula (VI), compounds represented through general formula (VII), compounds repre sented through general formula (VIII), compounds represented through general formula (IX), compounds represented through general formula (X), and compounds represented through general formula (XI), whereby residues R1, R2, R3, R4, R5, R6, and R7 contained therein, in dependently of each other, can have the meaning described above. [0097] According to a particularly preferred embodiment, compound (c) is selected from the group consisting of 3-hydroxypropionic acid and 3-hydroxypropionic acid esters. [0098] Preferably, the fraction of compound (c) is at least 0.0001 % by weight, more preferably at least 0.001 % by weight, even more preferably at least 0.01 % by weight, and particularly preferably at least 0.1 % by weight, relative to the total weight of mixture (II). Preferably, the fraction of compound (c) is no more than 5.0 % by weight, more preferably no more than 2.0 % by weight, even more preferably no more than 1.0 % by weight, and particularly preferably no more than 0.5 % by weight, relative to the overall weight of mixture (II). The fraction of com pound (c) preferably is in the range of 0.0001 - 5.0 % by weight, more preferably in the range of 0.001 - 2.0 % by weight, even more preferably in the range of 0.01 - 1.0 % by weight, and par ticularly preferably in the range of 0.1 - 0.5 % by weight, relative to the total weight of mixture (II). [0099] In addition to the polymerisable monomer and compound (c), mixture (II) can comprise further components (d), if applicable. Said further components (d) preferably are the further components (d) according to the prceding description in the context of mixture (1). [0101] According to a preferred embodiment, mixture (II) containing at least the polymerisable monomer and compound (c), is present in a packaging means. Preferably, said packaging means is closed. Preferably, said packaging means is diffusion-tight. The packaging means can, for example, be a cartridge. It is also possible for the packaging means to be contained in a cartridge. The cartridge can be part of an application device for bone cement paste. Said application device can preferably contain a mixing device. Said mixing device can be suitable 22 for mixing individual components of a kit for producing bone cement to generate a bone cement paste. [0102] The invention also provides a kit for producing bone cement. [0103] Said kit for producing bone cement comprises at least a paste A and a paste B. At least one of pastes A and B contains one of the mixtures (II) described above. Preferably, paste A and paste B each contain one of the mixtures (II) described above, whereby paste A differs from paste B in at least one of its components. [0104] Pastes A and B can contain at least one further component aside from the polymerisable monomer and compound (c). Said at least one further component can be selected from the group of further components (d) described above. [0105] According to a preferred embodiment, paste A comprises a polymerisable monomer, in particular a monomer for radical polymerisation, a compound (c), and a polymer (d1) that is sol uble in the polymerisable monomer, and paste B comprises at least one polymerisable mono mer, a compound (c), and a polymer (d1) that is soluble in the polymerisable monomer. Prefer ably, at least one of the pastes A and B also contains a polymer (d2) that is insoluble in the polymerisable monomer. A polymer (d2) that is insoluble in the polymerisable monomer can be contained in paste A and paste B just as well. Moreover, at least one of the pastes A and B contains at least one radical polymerisation initiator (d3). Preferably, said radical polymerisation initiator (d3) is contained in the same paste that contains the polymer (d2) that is insoluble in the polymerisable monomer. Furthermore, it is preferable that at least one of the pastes A and B comprises a polymerisation activator (d4). Moreover, it is preferred that at least one of the pastes A and B contains a pharmaceutical agent (d7). [0106] According to a particularly preferred embodiment, paste A and paste B are present in the kit for producing bone cement in a first packaging means and a second packaging means, re spectively. Preferably, said packaging means are spatially separated from each other. Said packaging are preferably closed. Moreover, said packaging means are preferably diffusion tight. The packaging means can, for example, be cartridges. It is also possible for the packag ing means to be contained in cartridges. The cartridges can be part of an application device for bone cement paste. Said application device can preferably contain a mixing device. Said mix- 23 ing device can be suitable for mixing individual components of a kit for producing bone cement to generate a bone cement paste. [0107] The invention also relates to a bone cement paste. [0108] In this context, bone cement shall be understood to mean a paste that can be applied to a patient and can self-harden. [0109] Said bone cement paste contains a mixture (II) according to the preceding definition. [0110] According to a preferred embodiment, the bone cement paste contains at least one fur ther component. Said at least one further component can be selected from the group of further components (d) described above. [0111] According to a particularly preferred embodiment, the bone cement paste comprises, according to the invention, aside from the polymerisable monomer and compound (c), at least one polymer (d1) that is soluble in the polymerisable monomer, one polymer (d2) that is insolu ble in the polymerisable monomer, a radical polymerisation initiator (d3) if applicable, a polymer isation activator (d4) if applicable, and a pharmaceutical agent (d7) if applicable. [0112] The invention is illustrated in more detail through the examples presented in the follow ing, though without limiting the scope of the invention.

24 EXAMPLES: EXAMPLE 1: [0113] A total of 20 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. After adding 14 pl distilled water, 10 pl of a 40 % ethanolic Bacillus subtilis ATCC9357 spore suspension were added to each of the plastic bottles. Then 17 pl (20 mg) B-propiolactone were added. The screw cap vessels were closed, shaken thoroughly for a short period of time, and stored for seven days at 23 OC. EXAMPLE 2: [0114] A total of 20 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. After adding 35 pl distilled water, 10 pl of a 40 % ethanolic Bacillus subtilis ATCC9357 spore suspension were added to each of the plastic bottles. Then 34 pl (40 mg) B-propiolactone were added. The screw cap vessels were closed, shaken thoroughly for a short period of time, and stored for seven days at 23 OC. EXAMPLE 3: [0115] A total of 20 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. After adding 20 pl methanol, 10 pl of a 40 % ethanolic Bacillus subtilis ATCC9357 spore suspension were added to each of the plastic bottles. Then 17 pl (20 mg) B-propiolactone were added. The screw cap vessels were closed, shaken thoroughly for a short period of time, and stored for seven days at 23 OC. EXAMPLE 4: [0116] A total of 20 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. After adding 34 pl distilled water, 10 pl of a 40 % ethanolic Bacillus subtilis ATCC9357 spore suspension were added to each of the plastic bottles. Then 34 pl (40 mg) dimethyldicarbonate were added. The screw cap vessels were closed, shaken thoroughly for a short period of time, and stored for seven days at 23 OC.

25 REFERENCE EXAMPLE 1: [0117] A total of 20 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. Then 10 pl of a 60 % ethanolic Bacillus subtilis ATCC9357 spore suspension were added to each of the plastic bottles. The screw cap vessels were closed, shaken thoroughly for a short period of time, and stored for seven days at 23 OC. EXAMPLE 5: [0118] A total of 8.0 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. After adding 14 pl distilled water, 10 pl of a 60 % ethanolic Bacillus subtilis ATCC9357 spore suspension, and 17 pl (20 mg) B propiolactone were added to each of the plastic bottles. The preparations were then shaken briefly for homogenisation. Then a mixture of 1.0 g zirconium dioxide, 5.5 g of a linear polymethylmethacrylate-co-methacrylate, and 5.5 g of a cross-linked polymethylmethacrylate was added to said preparation in each of the screw cap vessels. A paste was thus formed. The preparations were then shaken briefly. The preparations were then stored at 23 OC for seven days. EXAMPLE 6: [0119] A total of 8.0 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. After adding 35 pl distilled water, 10 pl of a 60 % ethanolic Bacillus subtilis ATCC9357 spore suspension, and 35 pl (40 mg) B propiolactone were added to each of the plastic bottles. The preparations were then shaken briefly for homogenisation. Then a mixture of 1.0 g zirconium dioxide, 5.5 g of a linear polymethylmethacrylate-co-methacrylate, and 5.5 g of a cross-linked polymethylmethacrylate was added to said preparation in each of the screw cap vessels. A paste was thus formed. The preparations were then shaken briefly. The preparations were then stored at 23 OC for seven days. EXAMPLE 7: 26 [0120] A total of 8.0 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. After adding 20 p1 methanol, 10 p1 of a 60 % ethanolic Bacillus subtilis ATCC9357 spore suspension, and 35 p1 (40 mg) B-propiolactone were added to each of the plastic bottles. The preparations were then shaken briefly for ho mogenisation. Then a mixture of 1.0 g zirconium dioxide, 5.5 g of a linear polymethylmethacry late-co-methacrylate, and 5.5 g of a cross-linked polymethylmethacrylate was added to said preparation in each of the screw cap vessels. A paste was thus formed. The preparations were then shaken briefly. The preparations were then stored at 23 OC for seven days. REFERENCE EXAMPLE 2: [0121] A total of 8.0 g methylmethacrylate (Sigma-Aldrich, stabilised with hydroquinone) each were weighed out into five 50 ml screw cap vessels. Then 10 p1 of a 60 % ethanolic Bacillus subtilis ATCC9357 spore suspension were added to each of the plastic bottles. The prepara tions were then shaken briefly for homogenisation. Then a mixture of 1.0 g zirconium dioxide, 5.5 g of a linear polymethylmethacrylate-co-methacrylate, and 5.5 g of a cross-linked polymethylmethacrylate was added to said preparation in each of the screw cap vessels. The preparations were then shaken briefly. A paste was thus formed. The preparations were then stored at 23 OC for seven days. ANALYSIS OF EXAMPLES 1 - 7 AND REFERENCE EXAMPLES 1 AND 2: [0122] For analysis, the mixtures obtained in the examples and reference examples were tested for sterility. [0123] For this purpose, two samples were taken from each screw cap vessel after seven days of incubation. The samples were then incubated for 14 days and then tested for sterility in ac cordance with IS011737 part 2. The results are shown in Table 1: Example Number of sterile samples Number of non-sterile sam ples 27 1 8 2 2 10 0 3 10 0 4 10 0 Reference example 1 2 8 5 10 0 6 10 0 7 10 0 Reference example 2 2 8 Table 1: Test for sterility of the mixtures of examples 1 - 7 and reference examples 1 and 2 in accordance with ISO 11737 part 2. EXAMPLE 8: [0124] In the following, a paste A and a paste B were prepared by mixing the educts in separate screw cap vessels. Paste A Educt Weight 1 -Cyclohexyl-5-ethyl-barbituric acid 2.0 g 28 Methacrylamide 0.4 g Methylmethacrylate 18.9 g Linear methylmethacrylate-soluble 6.2 g polymethylmethacrylate-co-methylacrylate (molar mass < 500,000 g/mol) Cross-linked polymethylmethacrylate (sieve 15.5 g fraction < 100 pm) 2,4-Di-t-butyl-4-methyl-phenol 20 mg B-Propiolactone 86 mg Water 86 mg Paste B Educt Weight Lithium chloride 40 mg 2,4-Di-t-butyl-4-methyl-phenol 35 mg Methylmethacrylate 18.9 g Linear methylmethacrylate-soluble 16.9 g polymethylmethacrylate-co-methylacrylate (molar mass < 500,000 g/mol) Green lacquer 50 mg 29 Copper(II) hydroxide 2 mg B-Propiolactone 86 mg Water 86 mg [0125] The two pastes were then stored at room temperature for seven days. Then 3.5 g of paste A and 3.5 g of paste B were taken and kneaded together thoroughly. A green, non-tacky cement dough was thus produced. The dough was kneaded further by hand. After approxi mately 2 minutes and 40 seconds, the initiation of polymerisation was notable by the release of heat. The end of processability was reached after 4 minutes and 40 seconds. The cement dough was fully cured after approximately 6 minutes. EXAMPLE 9: A paste A and a paste B were produced in the following. Paste A Educt Weight 1 -Cyclohexyl-5-ethyl-barbituric acid 2.0 g Methacrylamide 0.4 g Methylmethacrylate 18.9 g Linear methylmethacrylate-soluble 6.2 g polymethylmethacrylate-co-methylacrylate (molar mass < 500,000 g/mol) Cross-linked polymethylmethacrylate (sieve 15.5 g 30 fraction < 100 pm) 2,4-Di-t-butyl-4-methyl-phenol 20 mg B-Propiolactone 86 mg Water 86 mg Paste B Educt Weight Aliquat 336 60 mg (trioctylmethylammoniumchloride) 2,4-Di-t-butyl-4-methyl-phenol 35 mg Methylmethacrylate 18.9 g Linear methylmethacrylate-soluble 16.9 g polymethylmethacrylate-co-methylacrylate (molar mass < 500,000 g/mol) Green lacquer 50 mg Copper(II) hydroxide 2 mg B-Propiolactone 86 mg Water 86 mg 31 [0126] The two pastes were stored at room temperature for a period of seven days. Then 3.5 g of paste A and 3.5 g of paste B were taken and kneaded together thoroughly. A green, non tacky cement dough was thus produced. The dough was kneaded further by hand. A release of heat was noted after approximately 3 minutes. The end of processability was reached after 4 minutes 40 seconds. The cement dough was fully cured after approximately 6 minutes and 20 seconds. EXAMPLE 10: [0127] A paste A and a paste B were produced in the following. Paste A Educt Weight 1 -Cyclohexyl-5-ethyl-barbituric acid 2.0 g Methacrylamide 0.4 g Methylmethacrylate 18.9 g Linear methylmethacrylate-soluble 11.5 g polymethylmethacrylate-co-methylacrylate (molar mass < 500,000 g/mol) Cross-linked polymethylmethacrylate (sieve 7.7 g fraction < 100 pm) 2,4-Di-t-butyl-4-methyl-phenol 20 mg B-Propiolactone 86 mg Water 86 mg 32 Paste B Educt Weight Aliquat 336 60 mg (trioctylmethylammoniumchloride) 2,4-Di-t-butyl-4-methyl-phenol 35 mg Methylmethacrylate 18.9 g Linear methylmethacrylate-soluble 11.5 g polymethylmethacrylate-co-methylacrylate (molar mass < 500,000 g/mol) Cross-linked polymethylmethacrylate (sieve 7.7 g fraction < 100 pm) Green lacquer 50 mg Copper(II) hydroxide 2 mg B-Propiolactone 86 mg Water 86 mg [0128] The two pastes were then stored at room temperature for seven days. Then 3.5 g of paste A and 3.5 g of paste B were taken and kneaded together thoroughly. A green, non-tacky cement dough was thus produced. The dough was kneaded further by hand. The end of pro cessability was reached after 5 minutes. The cement dough was fully cured after approximately 6 minutes.

Claims (14)

1. A method for sterilisation of a polymerisable monomer, in which a mixture (I) is produced that contains at least the polymerisable monomer, a compound (a) and a compound (b), 5 whereby compound (a) is selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols.

2. The method according to claim 1, wherein the fraction of compound (b) is no more than 2 % by weight, relative to the total weight of mixture (I). 10

3. The method according to claim 1 or 2, wherein the polymerisable monomer is a monomer for radical polymerization.

4. The method according to any one of the preceding claims, wherein the polymerisable monomer and compound (b) are the same compound.

5. The method according to any one of the preceding claims, characterised in the 15 ratio of the quantity of compound (b), nb, that is contained in mixture (I) to the quantity of compound (a), na, that is contained in mixture (I) is represented through the inequation nb/na > 0.5.

6. A mixture (I) containing at least one polymerisable monomer, a compound (a) and a compound (b), 20 whereby compound (a) is selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols. whereby the fraction of compound (b) is no more than 2 % by weight, relative to the total weight of mixture (I). 25

7. A mixture (II) containing at least one polymerisable monomer and a compound (c), whereby compound (c) is selected from the group consisting of alcohols, carboxylic acids having at least three carbon atoms, and esters, and is available through reacting a compound (a) and a compound (b), 34 whereby compound (a) is selected from the group consisting of dialkyldicarbonates, and compound (b) is selected from the group consisting of water and alcohols.

8. The mixture according to claim 6 or 7, wherein the polymerisable monomer is a 5 monomer for radical polymerisation.

9. The mixture according to any one of claims 6 to 8, wherein compound (c) is selected from the group consisting of 3-hydroxypropionic acid and 3-hydroxypropionic acid esters.

10. The mixture according to any one of claims 6 to 9, wherein the mixture contains 10 a polymer that is soluble in the polymerisable monomer.

11. The mixture according to any one of claims 6 to 10, wherein the mixture contains a polymer that is insoluble in the polymerisable monomer.

12. A kit for producing bone cement comprising at least a paste A and a paste B, wherein at least one of pastes A and B contains a mixture (II) according to any one of 15 claims 7 to 10.

13. The kit according to claim 12, wherein paste A and paste B are present in a first packaging means and a second packaging means, respectively.

14. A bone cement paste containing a mixture (II) according to any one of claims 7 to 10. 20 Heraeus Medical GmbH Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON