PREPARING STERILE ARTICLES FROM POLYMERS CONTAINING A STABILISER BASED ON A POLY(OXYALKYLENE)

Abstract: A method of preparing a sterile article is disclosed. A polymer having a halogen-containing repeating unit is prepared that contains about 0.005 to about 65 phr of a stabiliser having the general formula TGOT', where each T is independently selected from R-, R-CO-, -P(R)2, -P(OR)2, Si(R)3, or -Si(OR)3, T' is T or A[GOT]n, each A is independently selected from LS-Sn(R)3-q(OLJ)q,(CH2)pS-Sn(R)3-q(S(CH2)p-J)q, LCO2Sn(R)3-q(OLCO-J)q, or LSn(Y)3-q(LJ)q when n is O, from CO, E, CO-E-CO, Si(R)2, Si(OR)2, (Si(R)2G)r, (CO-E-CO-G)r, (CO-G)r, or (E-G)r when n is 1, and from P, PO and trimellitate when n is 2, Y is -SLJ, -SLJ, -SLOR, -OLJ, -OLR, -S(CH2)p, each R is independently selected from R', aralkyl from C6 to C12, and aryl from C6 to C12, E is alkylene from C1 to C12, m is 1 to 20, n is 0 to 2, p is 0 to 10, q is 0 to 3 and r is 1 to 20. An article is made from the polymer and the article is sterilised with ionising radiation. Also disclosed are novel stabilisers for use in this method.

Description: PREPARING STERILE ARTICLES FROM POLYMERS CONTAINING A STABILISER BASED ON A POLY(OXYALKYLENE) THE PRESENT INVENTION relates to the preparation of a sterile article made from a polymer having a halogen-containing repeating unit, where the polymer contains a compound based on a poly(oxyalkylene) (POA). In particular, it relates reducing the yellowing of an article made from polyvinyl chloride (PNC) after exposure to gamma radiation by incorporating compounds based on poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) into the PVC. PNC is a versatile thermoplastic that is widely used for making medical articles and for food packaging due to its clarity, gloss, unique versatility, excellent functional performance, inertness to fluids and relatively low cost. Medical devices and food packaging are usually sterilised before they are used. While ethylene oxide sterilisation imposes little or no harmful effects on the physical properties of PVC, radiation sterilisation, such as with gamma rays, can adversely effect the polymer, such as yellowing it. PEG, PEG dibenzoate, and PPG dibenzoate have been used as PVC plasticisers. They are primarily used as alternatives for phthlate plasticisers, such as dioctyl phthalate (DOP). The use of these materials may also improve other properties of PVC. (J.H. Lee, K.O Kim, Y.M. Ju J. Biomed. Mater. Res (Appl. Biomater) 48, pages 328 to 334 (1999); W.D. Arendt, J. Lang J. Winvyl & Additive Technology, 4(3), pages 184 to 188 (1998); W.D. Arendt Plat. Eng 35(9), pages 46 to 49 (1979); W.D. Arendt Plast. Eng. 25, pages 410 to 412 (1979). The present invention seeks to provide a method of preparing a sterile article. The invention also seeks to provide a stabiliser for use when preparing a sterile article from a polymer. Additionally, the invention comprises the combination of a stabiliser and a polymer. According to a first aspect of this invention there is provided a method of preparing a sterile article comprising: (A) preparing a polymer having a halogen-containing repeating unit, where said polymer contains about 0.005 to about 65 phr (as defined herein) of a stabiliser having the general formula TGOT', where each T is independently selected from R-, R-CO-, -P(OR) 2 , -Si(OR) 3 , or -Si(OR) 3 , T' is T or A[GOT] n , each A is independently selected from LS-Sn(R) 3-q (SLJ) q , L-0-Sn(R) 3 -q (OLJ) q , (CH 2 ) p S-Sn(R) 3-q (S(CH 2 ) p -J) q , LC0 2 SN(R) 3-q (OLCO-J) q , or LSn(Y) 3-q (LJ) q when n is O, from CO, E, CO-E-CO, Si(R) 2 , Si(OR) 2 , (Si(R) 2 G) r , (CO-E-CO-G) r , or (E-G) r when n is 1, and from P, PO, and trimellitate when n is 2, Y is - SLJ, -SLOR, - OLJ, -OLR, -S(CH 2 ) P -J, -S(CH 2 ) P R, OLCO-J, or OLCOOR, G is (0-CH 2 -R'CH) m , J is 0-(CH 2 CR'HO)T, L is CO(CH 2 ) p , each R is independently selected from R\ aralkyl from C 6 to C 12 , and alkaryl from C 6 to Cι 2, each R' is independently selected from hydrogen, alkyl from to Cι 2 , and aiyl from C 6 to C 12 , E is alkylene from to Cι 2 , aralkylene from C 6 to C 12 , alkaiylene from C 6 to C 12 , arylene from C 6 to Cι 2 , m is 1 to 20, n is 0 to 2, p is 0 to 10, q is 0 to 3 and r is 1 to 20; (B) making said article from said polymer; and (C) sterilising said article with ionising radiation. It is to be appreciated that the method utilises a stabiliser. With regard to the stabiliser it is to be understood that the ethers (T = R. R' = R) are preferred and R is preferably alkyl from to C 8 as those stabilisers are more effective. R' is preferably methyl or phenyl because they increase the lipophilicity of the stabilisers, resulting in better miscibility with the polymers. The A group is preferably CO-E-CO or (CO-E-CO-G) r because the lipophilicity of the materials can be tailored and these materials are easily prepared. The Y group is preferably -SLJ, -SLOR, -S(CH 2 ) P -J, or -S(CH 2 ) P -J, or -S(CH 2 ) P R because they more effective. Of the tin based stabilisers, sulphur-containing tin stabilisers are preferred because they are better thermo stabilisers. Finally, m is preferably 2 to 5 as smaller values may be less effective and greater values may not be compatible with PVC, resulting in a hazy appearance, n is preferably 0 to 1 because these stabilisers can better inhibit the discoloration of the polymers, p is preferably 1 to 2 because these stabilisers are readily available, q is preferably 1 to 2 because those stabilisers are also better thermal stabilisers, and r is preferably 2 to 5 because they mix well with PVC. Preferably, all the T groups are identical as those stabilisers are easier to prepare. The preferred stabilisers include PEG and PPG ethers: R-G-OR, PEG and PPG esters: R-CO-G-OCO-R, tin compounds: (R) q Sn-(MR"-G-OT) 4-q , silicates: (R) 3 -Si-G-Si(R) 3> phosphites: P-(GOT) 3 , phosphates: and OP- (GOT) 3 , phthalates. In certain embodiments of the invention the stabiliser may have the general formula R-CO-[OCH 2 -R'CH] m -OR. In alternative embodiment of the invention the stabiliser has the general formula R-CO-[OCH 2 -R'CH] m OCO-R. In a further embodiment of the invention said stabiliser has the general formula ( R ) q Sn-(MR"-OCH 2 -R'CH] m -OT) 4-q, P-[OCH 2 - R'CH) m -OT] 3 , where each R' is independently selected from alkyl from to 2 and aiyl from C 6 to C 12 , each R is independently selected from R', aralkyl from C 6 to C 12 , and alkaryl from C 6 to C 12 , M is 0 or S, each T is independently selected from R- and R-CO-, -P(R) 2 , -P(OR) 2 , -Si(R) 3 , or -Si(OR) 3 , m is 1 to 20, and q is 0 to 3. In such an embodiment it is preferred that M is S and R" is (CH 2 ) P CO-. Examples of PEG, PPG and their ethers and esters include tri(propylene glycol), poly(propylene glycol), poly(propylene glycol)diglycidl ether, dibutoxpropoxpropyyl adipatge, poly(propylene glycol di(e-ethylhexanoate), poly(propylene glycol) dibenzoate, di(propylene glycol) dibenzoate, poly(ethylene glycol) dibenzoate, and di)ethylene glycol) dibenzoate. Examples of tine compounds include dibutyltin bis (diethylene glycol monomethyl ether thioglycolate), dibutyltin bis(triethylene glycol monomethyl ether thioglycolate), dibutyltin bis(diethylene glycol monoethyl ether thioglycolate), dibutyltin bis(hϊethylene glycol monoethyl ether thioglycolate), dibutyltin bis(dipropylene glycol monoethyl ether thioglycoate), dibutyltin bis(tripropylene glycol monoethyl ether thioglycolate), bis(β-carbomethoxyethoxyethoxy)tin bis(isooctylthioglycoate), bis(β carboethoxyethoxyethoxy)tin bis(isooctylthioglycoate) , and bis(β- carboethoxyethoxyethoxyethoxy)tin bis(isooctylthioglycoate). Examples of silicates include polypropylene glycol) bistrimethylsily ether, poly(propylene glycol) bistrimethoxysily ether, poly(ethylene glycol) bistrimethylsily ether, and poly(ethylene glycol) bistrimethoxysily ether. Examples of phosphites include tri(methoxyethoxyethyl) phosphite, tri(ethoxyethoxyethyl) phosphite, tri(methoxypropoxypropyl) phosphite, tri(ethoxypropoxypropyl) phosphite, tri(methoxyethoxyethoxyethyl) phosphite, tri(ethoxyethoxyethoxyethyl) phosphite, tri(methoxypropoxypropbxypropyl) phosphite, and tri(ethoxypropoxypropoxypropyl) phosphite. Examples of phosphates include tri(methoxypropoxypropyl) phosphate, tri(ethoxypropoxypropyl) phosphate, tri(methoxyethoxyethoxyethyl) phosphate, tri(ethoxyethoxyethoxyethyl) phosphate, tri(methoxypropoxypropoxypropyl) phosphate, and tri(ethoxypropoxypropoxypropyl) phosphate. Examples of phthalates include di(diethylene glycol monomethyl ether) phthalate, di(triethylene glycol monomethyl ether) phthalate, di(diethylene glycol monoethyl ether) phthalate, di(triethylene glycol monoethyl ether) phthalate, di(dipropylene glycol monoethyl ether) phthalate, and di( : tripropylene glycol monoethyl ether) phthalate. Examples of trimellitates include tri(diethylene glycol monomethyl - ether) trimellitate, di(triethylene glycol monomethyl ether) trimellitate, di(diethylene glycol monoethyl ether) trimellitate, di(triethylene glycol monoethyl ether) trimellitate, di(dipropylene glycol monoethyl ether) trimellitate, and di(tripropylene glycol monoethyl ether) trimellitate. The preferred stabilizers are ethers and esters of PEG and PPG because many are commercially available. Polyethylene glycol and polypropylene glycol ethers and esters that are not commercially available are easily made by, for example, condensing polyethylene glycol or polypropylene glycol with an alcohol (to make an ether) or with an acid chloride (to make an ester), as is well-known in the art. Of the above compounds, the PEG and PPG ethers, silyl ethers, and esters are well known. Phthalates such as dimethyl glycol phthalate, diethyl glycol phthalate, dibutyl glycol phthalate; di-2- (2-methoxyethoxy)ethyl phthalate; di-2-(2-ethoxyethoxy)ethyl phthalate; di-2-(2- butoxyethoxy)ethy) phthalate; di-2-(2-hexy!oxyethoxy)ethyi phthalate; bis[2-[2-(2- ethoxyethoxy)ethoxy]ethyl] phthalate are also known. The known trimellitates include tris(2-methoxyethy!)trimellitates, and tris[2-(2- methoxyethoxy)ethyl]trimellitates; the known phosphorous compounds include tris(2-methoxyethyl)phosphite, tris[2-(2-methoxyethoxy)ethyl]phosphite, tris(2- methoxyethy!)phosphate, tris[2-(2-methoxyethoxy)ethyl]phosphate, tris[2-[2-(2- methoxyethoxy)ethoxy]ethyl] phosphate. The tin compounds, some of the phosphites, phosphates, phthalates, and trimellitates are believed to be novel compounds, in particular, compounds having the general formula (R) Sn-(MR"- OCH 2 - R'CH -OT) 4 .. q| --P-[(OCH 2 - R'CH) m -OT] 3l 0 where each R' is independently selected from alkyl from C, to C 12 , and aryl from C 6 to C 12 , and R, M, T, m, and q are the same as hereinabove defined, are believed to be novel. They can be made by, for example, reacting PCI 3 with methyl monoethers of PEG or PPG. Stabilizers containing an (CO-E-CO-G) r , (CO-G) rι (E-G) r , or (Si(R) 2 G) r group are polymers made by reacting a difunctional acid, acid chloride, or anhydride, such as phosgene, adipic acid, malonic anhydride, or dichlorosilane with a PEG or a PPG. The stabilisers used in the methods of the invention are effective against the oxidation of haloginated polymers suchas PVC, poly(vinylidene chloride), chlorinated polyethylene and chlorinated polypropylene. The preferred polymer is PVC because PVC is more frequently used in medical applications where it is subjected to gamma radiation. The polymer can be stabilized by the addition of about 0.005 to about 65 phr (parts by weight per 100 part by weight of the polymer) of the stabilizer to the polymer. Less stabilizer is less effective and more stabilizer offers little additional benefit; the preferred amount of stabilizer is about 0.2 to about 20 phr. The stabilizer can be added to the polymer in a variety of ways, such as by mixing the reactants at the beginning or during polymerisation. The stabiliser is preferably added after at least 70 Wt% of the monomer has polymerised. The stabiliser can be added as a solid or with a solvent as a slurry or a solution. Common organic solvents can be used, such as N-methylpyrrolidone, diglyme, acetamide, acetone, methanol, ethanol, isopropanol, dimethylsulfoxide, or dimethylformamide; water can also be used. Water miscible solvents, such as acetone, tefrahydrofuran, and methanol, are preferred for PVC. If the stabiliser is a solid, it is preferable to add the stabiliser in a solvent as that achieves a more uniform distribution of the stabiliser in the polymer. The stabiliser can also be added along with shortstop, or during the diying or compounding of the polymer. Vaiious method can be used for compounding, including milling, diy mixing and extrusion. The stabilisers function as antioxidants to inhibit vaiious forms of oxidation. The invention also relates to a method of making a sterile article comprising: (A) preparing poly(vinyl chloride) that contains about 0.2 to about 20 phi- of a stabiliser having the general formula TGOT', where each T is independently selected from R- and R-CO-, -P(R) 2 , - P(OR) 2 , -Si(R) 3 , or Si(OR) 3 , T' is T, G is (0-CH 2 -R'CH) m J is 0- (CH 2 CR'HO), L is CO(CH 2 ) p , each R is independently selected from alkyl from C \ to C 8 , each R' is independently selected from methyl or phenyl, E is alkylene from to C 6 , m is 2 to 5, n is 0 or 1, p is 1 or 2, q is 1 or 2 and r is 2 to 5; (B) making said article from said poly(vinyl chloride); and (C) sterilising said article with gamma radiation. In the method of making a sterile article, the various preferred stabilisers as described above may be utilised. According to a further aspect of this invention there is provided a compound having the general formula (R) q Sn-(MR"-OCH 2 -[R'CH] m -OT) 4-q , P- [(OCH 2 - R'CH) m OT] 3 , where M is 0 or S and R" is (CH 2 ) p CO-, CO-(CH 3 ) p CO-,-(CH 2 ) p , or CO(CH 2 ) p -. The compound may be utilised as a stabiliser for a polymer having a halogen-containing repeating unit. Thus, additionally, the invention comprises a polymer having a halogen- containing repeating unit, where the polymer contains about 0.005 to about 65 phr (as herein defined) of the compound as described. Preferably the polymer is poly(vinyl chloride). The following examples further illustrate this invention: EXAMPLES 1 TO 59 To a mixture of 150. OOg PVC (sold by Occidental Chemical Corporation as "Oxy 240" or by Oxy Vinyls as "OV 30"), 0.30 g stearic acid (used as a lubricant), 0.23 g of a zinc and calcium mixed salts of mixed fatty acids (used as a heat stabiliser; sold by Witco as "Mark 152 S"), 97.50 g dioctyl phthalate (used as a plasticiser to increase flexibility), minus the amount of stabiliser used, 15.00 g epoxidised soy bean oil (used as an HC1 scavenger to reduce degradation; sold by Witco as "Drapex 6.8"), was added vaiious amounts of different stabilisers. The mixture was thoroughly blended and hot milled at 300°F (182°C) for 5 minutes. The resulting PVC sheet was cut and pressed into a 4"x3"x114" (10x8x0.6 cm) plaque at 330°F (182°C). The plaque was divided into two smaller pieces. One was saved for comparison and one was subjected to γ radiation at a dose of 50 kGy. The irradiated piece was again divided into two pieces and one of these pieces was oven aged at 50°C for 48 hours. All of the samples were measured for yellowness index with a Macbeth 2020 Plus Color Eye Spectrometer, as described by the Hunter equations (see "The Measurement of Appearance" by Richard S. Hunter, John Wiley & Sons, New York, 1975). The following table gives the stabilizers used and the results. Sold by C.P. Hall Company as "PlasthairDBPA" Sold by Unitex Chemical as "Uniplex 400" Sold by Velsicol as "Benzoflex 2088" Sold by Velsicol as "Benzoflex 2870" Sold by Velsicol as "Benzoflex 2888" Sold by Velsicol as "Benzoflex 2160" Sold by Velsicol as "Benzoflex 2860" As can be observed from the above table, after gamma radiation the polymers that contained a stabilizer had significantly less discoloration than the control samples. The table also shows that a mixture of PEG- and PPG-based materials was also effective for stabilizing the PVC color after radiation. This feature makes it possible to tailor a stabilizer for a specific application if certain physical properties of the PVC are desired.

Claims: CLAIMS: A method of preparing a sterile article comprising: (A) preparing a polymer having a halogen-containing repeating unit, where said polymer contains about 0.005 to about 65 phr (as defined herein) of a stabiliser having the general formula TGOT', where each T is independently selected from R-, R-CO-, -P(OR) 2 , -Si(OR) 3 , or -Si(OR) 3 , T' is T or A[GOT] n , each A is independently selected from LS-Sn(R) 3-q (SLJ) q , L-0-Sn(R) 3 -q (OLJ) q , (CH 2 ) p S-Sn(R) 3-q (S(CH 2 ) p -J) q , LC0 2 SN(R) 3-q (OLCO-J) q , or LSn(Y) 3-q (LJ) q when n is O, from CO, E, CO-E-CO, Si(R) 2 , Si(OR) 2 , (Si(R) 2 G) r , (CO-E-CO-G) r , or (E-G) r when n is 1, and from P, PO, and trimellitate when n is 2, Y is - SLJ, -SLOR, - OLJ, -OLR, -S(CH 2 ) p -J, -S(CH 2 ) P R, OLCO-J, or OLCOOR, G is (0-CH 2 -R'CH) m , J is 0-(CH 2 CR'HO)T, L is CO(CH 2 ) p , each R is independently selected from R', aralkyl from C 6 to C 12 , and alkaiyl from C 6 to C 1 ι each R' is independently selected from hydrogen, - alkyl from to C 12> and aryl from C 6 to C 12 , E is alkylene from to Cι 2 , aralkylene from C 6 to C 12 , alkarylene from C 6 to C 12 , arylene from C 6 to 2 , m is 1 to 20, n is 0 to 2, p is 0 to 10, q is 0 to 3 and r is 1 to 20; (B) making said article from said polymer; and (C) sterilising said article with ionising radiation. 2. A method according to Claim 1 wherein said polymer is poly(vinyl chloride). 3. A method according to Claim 1 or 2 wherein said stabiliser is an ether. 4. A method according to Claim 1, 2 or 3 wherein R is alkyl from Q to C 8 . 5. A method according to Claim 1, 2 or 3 wherein R' is methyl or phenyl. 6. A method according to any one of the preceding Claims wherein T' is T. 7. A method according to Claim 6 wherein al T's are identical. 8. A method according to any of the preceding Claims wherein m is 2 to 5, n is 0 or 1, p is 1 or 2, q is 1 or 2, or r is 2 to 5. 9. A method according to Claims 1 to 8 wherein said stabiliser has the general fromula R-[OCH 2 -R'CH] m -OR. 10. A method according to any one of Claims 1 to 8 wherein said stabiliser has the general formula R-CO-[OCH 2 -R'CH] m OCO-R. 11. A method according to any one of Claims 1 to 8 wherein said stabiliser has the general formula ( R ) q Sn-(MR"-OCH 2 -R'CH] m -OT) 4-q, P-[OCH 2 - R'CH) m -OT] 3 , formula (R) q Sn-(MR"-OCH 2 - R'CH] m -OT) , P-[(OCH 2 - R'CH) m -0T] 3 where each R' is independently selected from alkyl from to C 12 and aiyl from C 6 to Cj 2 , each R is independently selected from R', aralkyl from C 6 to C] 2 , and alkaiyl from C 6 to C [2 , M is 0 or S, each T is independently selected from R- and R-CO-, -P(R) 2 , -P(OR) 2 , -Si(R) 3 , or -Si(OR) 3 , m is 1 to 20, and q is 0 to 3. 12. A method according to Claim 11 wherein M is S and R" is (CH 2 ) P CO-. 13. A method of making a sterile article comprising: (A) preparing poly(vinyl chloride) that contains about 0.2 to about 20 phr of a stabiliser having the general formula TGOT', where each T is independently selected from R- and R-CO-, -P(R) 2 , - P(OR) 2 , -Si(R) 3 , or Si(OR) 3 , T' is T, G is (0-CH 2 -R'CH) m J is 0- (CΗ 2 CRΗO), L is CO(CH 2 ) p , each R is independently selected from alkyl from to C 8 , each R' is independently selected from methyl or phenyl, E is alkylene from to C 6 , m is 2 to 5, n is O or 1, p is 1 or 2, q is 1 or 2 and r is 2 to 5; (B) making said article from said poly(vinyl chloride); and (C) sterilising said article with gamma radiation. 14. A method according to Claim 13 wherein said stabiliser has the general formula R-[OCH 2 -R'CH] m -OR. 15. A method according to Claim 13 wherein said stabiliser has the general formula R-CO-[OCH 2 -R'CH] 2 -OCO-R. 16. A method according to Claim 13 wherein said stabiliser has the general formula (R) q Sn-(MR"-OCH 2 -[R'CH] m -OT) 4-q , P-[(OCH 2 - R'CH) m - OT] 3 , 0 where M is 0 or S and R" is (CH 2 ) p CO-, C0-(CH 3 ) p C0-, -(CH 2 ) p , or CO(CH 2 ) p -. 17. A method according to Claim 16 wherein M is S and R" is (CH 2 ) P CO- 18. A compound having the general formula (R) q Sn-(MR"-OCH 2 -[R'CH] r OT) 4-q, P-[(OCH 2 - R'CH) m OT] 3 , O where M is O or S and R" is (CH 2 ) p CO-, CO-(CH 3 ) p CO-,-(CH 2 ) p , or CO(CH 2 ) p -. 19. A polymer having a halogen-containing repeating unit, where said polymer contains about 0.005 to about 65 phr (as herein defined) of a compound according to Claim 18. 20. A polymer according to Claim 19 wherein said polymer is poly(vinyl chloride).

Inventors: NAGY SANDOR, WANG QI, NAGY, SANDOR, WANG, QI
Applicants: OCCIDENTAL CHEM CO, STEPHENS DINAH, OCCIDENTAL CHEMICAL CORPORATION, STEPHENS, DINAH
Application year: 2001
Main classification: A61L2
IPC codes: A61L2, C08F2, C08J7, C08K5, C08L27, C08L71