A fluoropolymer having a reduced amount of polar end groups. The fluoropolymer is produced by free radical polymerization of fluorinated monomers and the initiation of the polymerization is carried out in the presence of a chloride salt. Polar end groups include hydroxy groups and ionized or ionizable end groups. Examples of ionized or ionizable end groups include acid groups and salts thereof such as sulfonic acid and salts thereof, xe2x80x94CH2xe2x80x94OSO3H groups, sulfates and carbonyl containing end groups such as carboxylic and carboxylate groups. Due to the presence of chloride salt at the initiation of the free radical polymerization, CF2Cl end groups are formed instead of the polar end groups. As a result, a fluoropolymer is obtained that has improved processibility and heat resistance.

The present invention relates to a process for producing a fluoropolymer that has a reduced amount of polar end groups, in particular ionized or ionizable end groups such as sulfonic acid groups or carbonyl containing end groups such as carboxylic acid groups and carboxylate groups. In particular, the invention relates to the use of a chloride salt in the initiation of the free radical polymerization of fluorinated monomers to produce a fluoropolymer that has an improved processibility and/or heat resistance. The invention further relates to fluoropolymers that can be obtained with the process.
Fluoropolymers have, depending on the monomers used and the applied initiator systems during the radical polymerization, different polar end groups; for example polar end groups quite often present in fluoropolymers are: xe2x80x94CH2OH, xe2x80x94COOxe2x88x92, xe2x80x94CH2xe2x80x94Oxe2x80x94SO3xe2x88x92, xe2x80x94SO3xe2x88x92. These polar end groups are not desired, because they can undergo further reactions (e.g. decarboxylation) during processing or heat treatment and are a cause for processing difficulties and finally also for discolorations.
For example, U.S. Pat. No. 6,211,319 describes perfluoroelastomers that have carbonyl containing end groups. It is disclosed in this patent that the presence of these carbonyl containing end groups, while providing desirable cure properties, may present problems in the processing of these polymers. In particular, the presence of these groups may cause the polymer to become too viscous. Accordingly, U.S. Pat. No. 6,211,319 proposes to reduce the number of carbonyl containing end groups by a decarboxylation which involves a heat treatment. However, this process has the disadvantage that an additional process step is needed which additionally involves supplying energy. Accordingly, such a process increases the cost of manufacturing and causes inconveniences in the manufacturing.
Additionally, the presence of carboxylic or carboxylate containing end groups generally diminishes beneficial properties of the fluoropolymer including thermal properties such as heat resistance. Methods have therefore been developed in the prior art to reduce the amount of these groups. Such methods include for example post fluorination as well as the use of special initiators such as sulfinates as disclosed in U.S. Pat. No. 5,285,002. However, these methods have disadvantages such as increasing cost and reducing convenience of manufacturing.
It is therefore desired to find a further method of reducing the content of polar end groups and to produce fluoropolymers that have improved processibility and/or thermal properties including improved heat resistance. Preferably, the method of making these polymers allows for a cost effective and convenient manufacturing.
In accordance with the present invention, it was found that when the fluoropolymer is produced by free radical polymerization of fluorinated monomers and the initiation of the polymerization is carried out in the presence of a chloride salt, a fluoropolymer results that has a reduced amount of polar end groups. Polar end groups include hydroxy groups and ionized or ionizable end groups. Examples of ionized or ionizable end groups include acid groups and salts thereof such as sulfonic acid and salts thereof, xe2x80x94CH2xe2x80x94OSO3H groups, sulfates and carbonyl containing end groups such as carboxylic and carboxylate groups. Due to the presence of chloride salt at the initiation of the free radical polymerization, CF2Cl end groups are formed instead of the polar end groups. As a result, a fluoropolymer is obtained that has improved processibility and heat resistance. By the term xe2x80x9cfluoropolymerxe2x80x9d in connection with this invention is meant a polymer that has a fluorinated backbone, i.e. a partially or fully fluorinated backbone.
In accordance with one aspect of the present invention, the ratio of the amount of chloride salt to initiator is selected such that the amount of polar end groups in the resulting fluoropolymer is at least 10% less, preferably at least 15% less and most preferably at least 20% less compared to a similar fluoropolymer produced without the presence of a chloride salt. By the term xe2x80x9csimilar fluoropolymerxe2x80x9d in this connection is meant that the fluoropolymer has approximately, i.e. within experimental error, the same chemical constitution and about the same molecular weight. The amount of polar end groups and the reduction thereof can be measured with common analytical methods including for example fourier transform infrared spectroscopy, NMR and titration methods.
An additional advantageous property of the obtained fluoropolymer is that due to the presence of the CF2Cl end groups, the fluoropolymer has improved bonding properties to other substrates including elastomeric layers such as silicone rubbers when bonded to these substrates in the presence of an organic compound having one or more hydride functions MH wherein M is selected from the group consisting of Si, Ge, Sn and Pb. This compound can be present in the fluoropolymer composition or can be present in a layer of the substrate. Also, by including the organic compound in the fluoropolymer that can be obtained with the process of this invention, the fluoropolymer can be cured using a peroxide cure system.
The use of sodium chloride or ammonium chloride in the free radical polymerization is disclosed in EP 320 940. However, the latter publication does not appreciate that the amount of polar end groups can be reduced by initiating the polymerization in the presence of chloride salt, nor does the publication appreciate the improved processibility and/or heat resistance of the fluoropolymer that results. Rather, this EP patent application teaches the use of a certain amount of cations, which may derive from a chloride salt but which may also derive from another salt, to improve the emulsion copolymerization of certain liquid vinyl ether monomers.
According to a further aspect of the present invention, there is also provided a fluoropolymer comprising CF2Cl end groups and that is free of acid groups and salts thereof or that contains said acid groups and their salts in an amount of not more than 0.1 milli equivalents NaOH per gram of fluoropolymer, with the proviso that when said fluoropolymer is a terpolymer of tetrafluoroethylene, hexafluoropropylene and C3F7[(CF2)3O]2CFxe2x95x90CF2, the fluoropolymer is free of iodide containing end groups.
Still further, the present invention also provides a fluoropolymer composition for making a fluoroelastomer, comprising the above fluoropolymer and a cure composition.
The invention also provides the use of a chloride salt in the initiation of a free radical polymerization of one or more fluorinated monomers to improve the processibility and/or heat resistance of the fluoropolymer resulting from said free radical polymerization.
In accordance with the process of the invention, a chloride salt is used in the initiation of the free radical polymerization of fluorinated monomers to obtain a fluoropolymer with a reduced amount of polar end groups. Suitable chloride salts for use in the invention include those of the formula:
M Clnxe2x80x83xe2x80x83(I)
wherein M represents a mono- or multi-valent cation and n corresponds to the valence of the cation. Suitable cations M include organic and inorganic cations. Particularly useful cations are ammonium and metal cations including mono-valent cations such as sodium and potassium as well as divalent cations such as calcium and magnesium. Examples of ammonium chloride salts include tetraalkyl ammonium chlorides such as tetrabutyl ammonium chloride.
The amount of chloride salt is selected relative to the amount of the polymerization initiator so that the amount of polar end groups is reduced by at least 10%, preferably at least 15% and most preferably at least 20%. In a particular preferred embodiment of the invention, the total amount acid groups and their salts in the fluoropolymer is not more than 0.1, preferably not more than 0.09 milli equivalents NaOH per gram of fluoropolymer. Generally, the amount of polar end groups decreases with an increase in the ratio of the amount of chloride salt to the amount of polymerization initiator. Typically, the molar ratio of chloride ions to initiator is between 1:0.1 and 0.1:10, preferably between 1:0.5 and 0.1:5.
The free radical polymerization is generally initiated through the use of free radical generating initiators. As initiators, one can use any of the known initiators commonly employed in the polymerization of fluorinated olefins such as tetrafluoroethylene. For example peroxides can be used as free radical initiators. Specific examples of peroxide initiators include, hydrogen peroxide, sodium or barium peroxide, diacylperoxides such as diacetylperoxide, dipropionylperoxide, dibutyrylperoxide, dibenzoylperoxide, benzoylacetylperoxide, diglutaric acid peroxide and dilaurylperoxide, and further water soluble per-acids and water soluble salts thereof such as e.g. ammonium, sodium or potassium salts. Examples of per-acids include peracetic acid. Esters of the peracid can be used as well and examples thereof include tert.-butylperoxyacetate and tert.-butylperoxypivalate. A further class of initiators that can be used are water soluble azocompounds. Suitable redox systems for use as initiators include for example a combination of peroxodisulphate and hydrogen sulphite or disulphite, a combination of thiosulphate and peroxodisulphate, a combination of peroxodisulphate and hydrazine or azodicarboxamide (including salts thereof, preferably alkali or ammonium salts). Further initiators that can be used are ammonium-alkali- or earth alkali salts of permanganic or manganic acid or manganic acids. The amount of initiator employed is typically between 0.03 and 2% by weight, preferably between 0.05 and 1% by weight based on the total weight of the polymerization mixture. The full amount of initiator may be added at the start of the polymerization or the initiator can be added to the polymerization in a continuous way during the polymerization until a conversion of 70 to 80% is achieved. One can also add part of the initiator at the start and the remainder in one or separate additional portions during the polymerization. Preferred initiator systems include peroxodisulphate and permanganate.
The free radical polymerization may be carried out in an organic solvent, can be a aqueous suspension polymerization or an aqueous emulsion polymerization. An aqueous emulsion polymerization is preferred in the present invention.
In the aqueous emulsion polymerization, the fluorinated monomers and optionally further non-fluorinated monomers are polymerized in the aqueous phase generally in the presence of a free radical initiator and a fluorinated surfactant or emulsifier, preferably a non-telogenic emulsifier. The emulsifier will generally be used in amounts less than 1% by weight, for example from 0.1 to 1% by weight based on the weight of the aqueous phase. Examples of fluorinated emulsifiers include salts, in particular ammonium salts of linear or branched perfluoro alkyl containing carboxylic and sulphonic acids having 4 to 11 carbon atoms in the alkyl chain. Specific examples include perfluorooctanoic acid ammonium salt (APFO, described in U.S. Pat. No. 2,567,011) C8F17SO3Li which is commercially available from Bayer AG, C4F9SO3Li and C4F9SO3K (described in U.S. Pat. No. 2,732,398). A further example of a perfluoroalkyl containing carboxylic acid salt is C8F17SO2N(C2H5)CH2COOK (described in U.S. Pat. No. 2,809,990).
Still further emulsifiers that can be used include perfluoropolyethercarboxylate emulsifiers such as disclosed in EP 219065. However, APFO is the preferred emulsifier as it can be more readily removed from the polymerization product at the end of polymerization.
The aqueous emulsion polymerization may also be carried out without addition of a fluorinated emulsifier. Such a polymerization is for example described in WO 96/24622 and WO 97/17381.
The aqueous emulsion polymerization can be carried out continuously in which, for example, monomers, water, optionally further emulsifiers, buffers and catalysts are fed continuously to a stirred reactor under optimum pressure and temperature conditions while the resulting emulsion or suspension is removed continuously. An alternative technique is batch or semibatch (semi-continuous) polymerization by feeding the ingredients into a stirred reactor and allowing them to react at a set temperature for a specified length of time or by charging ingredients into the reactor and feeding the monomers into the reactor to maintain a constant pressure until a desired amount of polymer is formed. The polymerization can be carried out in a standard or conventional vessel used for emulsion polymerization of gaseous fluorinated monomers.
The polymerization systems may comprise auxiliaries, such as buffers and, if desired, complex-formers or chain-transfer agents including for example alkanes such ethane and n-pentane, dialkyl ethers such as dimethyl ether, methyl tertiary butyl ether and chlorine or bromine containing chain transfer agents. The polymerization temperature may be from 10 to 180xc2x0 C., typically 30xc2x0 C. to 100xc2x0 C. Polymerization pressures may be from 1 to 40 bar, typically 3 to 30 bar.
The fluoropolymer may have a partially or fully fluorinated backbone. Particularly preferred fluoropolymers are those that have a backbone that is at least 30% by weight fluorinated, preferably at least 50% by weight fluorinated, more preferably at least 65% by weight fluorinated. In a particular embodiment, the fluoropolymer will be free of iodide containing end groups.
Examples of fluoropolymers for use in this invention include polymers of one or more fluorinated monomers optionally in combination with one or more non-fluorinated monomers. Examples of fluorinated monomers include fluorinated C2-C8 olefins that may have hydrogen and/or chlorine atoms such as tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), 2-chloropentafluoropropene, dichlorodifluoroethylene, vinyl fluoride, vinylidene fluoride (VDF) and fluorinated alkyl vinyl monomers such as hexafluoropropylene (HFP); fluorinated vinyl ethers, including perfluorinated vinyl ethers (PVE) and fluorinated allyl ethers including perfluorinated allyl ethers. Suitable non-fluorinated comonomers include vinyl chloride, vinylidene chloride and C2-C8 olefins such as ethylene (E) and propylene (P).
Examples of perfluorovinyl ethers that can be used in the invention include those that correspond to the formula:
CF2xe2x95x90CFxe2x80x94Oxe2x80x94Rf
wherein Rf represents a perfluorinated aliphatic group that may contain one or more oxygen atoms.
Particularly preferred perfluorinated vinyl ethers correspond to the formula:
CF2xe2x95x90CFO(RafO)n(RbfO)mRcf
wherein Raf and Rbf are different linear or branched perfluoroalkylene groups of 1-6 carbon atoms, in particular 2 to 6 carbon atoms, m and n are independently 0-10 and Rcf is a perfluoroalkyl group of 1-6 carbon atoms. Specific examples of perfluorinated vinyl ethers include perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE), perfluoro (n-propyl vinyl) ether (PPVE-1), perfluoro-2-propoxypropylvinyl ether (PPVE-2), perfluoro-3-methoxy-n-propylvinyl ether, perfluoro-2-methoxy-ethylvinyl ether and CF3xe2x80x94(CF2)2xe2x80x94Oxe2x80x94CF(CF3)xe2x80x94CF2xe2x80x94Oxe2x80x94CF(CF3)xe2x80x94CF2xe2x80x94Oxe2x80x94CFxe2x95x90CF2.
Suitable perfluoroalkyl vinyl monomers correspond to the general formula:
CF2xe2x95x90CFxe2x80x94Rdf
or
CH2xe2x95x90CHxe2x80x94Rdf
wherein Rdf represents a perfluoroalkyl group of 1 to 10, preferably 1 to 5 carbon atoms. A typical example of a perfluoroalkyl vinyl monomer is hexafluoropropylene.
According to a particular embodiment, the fluoropolymer is a polymer suitable for making a fluoroelastomer. Generally suitable fluoropolymers, including partially as well as perfluorinated polymers, for making a fluoroelastomer are substantially amorphous polymers that show hardly any melting point if at all. Such fluoropolymers are particularly suitable for providing fluoroelastomers, which are typically obtained upon curing of an amorphous fluoropolymer. Amorphous fluoropolymers include for example copolymers of vinylidene fluoride and at least one terminally ethylenically-unsaturated fluoromonomer containing at least one fluorine atom substituent on each double-bonded carbon atom, each carbon atom of said fluoromonomer being substituted only with fluorine and optionally with chlorine, hydrogen, a lower fluoroalkyl radical, or a lower fluoroalkoxy radical. Specific examples of copolymers include for example copolymers having a combination of monomers as follows: VDF-HFP, TFE-P, VDF-TFE-HFP, VDF-TFE-PVE, TFE-PVE, E-TFE-PVE and any of the aforementioned copolymers further including units derived from a chlorine containing monomer such as CTFE. Still further examples of suitable amorphous copolymers include copolymers having a combination of monomers as in CTFE-P.
Preferred amorphous fluoropolymers generally comprise from 20 to 85%, preferably 50 to 80% by moles of repeating units derived from VDF, TFE and/or CTFE, copolymerized with one or more other fluorinated ethylenically unsaturated monomer and/or one or more non fluorinated C2-C8 olefins, such as ethylene and propylene. The units derived from the fluorinated ethylenically unsaturated comonomer when present is generally between 5 and 45 mole %, preferably between 10 and 35 mole %. The amount of non-fluorinated comonomer when present is generally between 0 and 50 mole %, preferably between 1 and 30 mole %.
In an embodiment where a fluoroelastomer is desired, the fluoropolymer will typically be cured. The fluoropolymer may be cured by any of the methods known to those skilled in the art and will typically include a cure composition such that the fluoropolymer composition can be cured to a fluoroelastomer. The cure composition typically includes one or more components that cause the fluoropolymer chains to link with each other thereby forming a three dimensional network. Such components may include catalysts, curing agents and/or coagents.
In one embodiment of curing the fluoropolymer a so called peroxide cure system may be used. In a typical peroxide cure system, the fluoropolymer is provided with one or more cure sites that comprise a halogen capable of participating in a peroxide cure reaction and the composition for providing the fluoropolymer contains an organic peroxide. The halogen capable of participating in a peroxide cure reaction is typically bromine or iodine and may be distributed along the polymer chain and/or may be contained in the end groups of the fluoropolymer. Typically, the amount of bromine or iodine contained in the fluoropolymer is between 0.001 and 5%, preferably between 0.01 and 2.5%, by weight with respect to the total weight of the fluoropolymer. It has further been found that also chlorine is capable of participating in a peroxide cure reaction of the fluoropolymer if an organic compound having MH functions as described above is present. Accordingly, also fluoropolymers that contain chlorine atoms and/or bromine or iodine can be used for curing in a peroxide cure reaction. The amount of chlorine in the fluoropolymer may vary from 0.001% by weight to 10% by weight but is typically between 0.01% by weight and 5% by weight based on the weight of fluoropolymer. A particularly suitable polymer for use with a peroxide cure system is a polymer that includes units that are derived from CTFE or another chlorine containing monomer. Specific examples include copolymers that have a combination of CTFE-VDF-TFE-HFP as monomers. Of course a chlorine containing fluoropolymer for use in a peroxide cure system may additionally be modified with bromine and/or iodine. The fluoropolymer for use in the peroxide cure reaction typically will have a molecular weight of 104 to 5xc3x97105 g/mol and the molecular weight distribution can be monomodal as well as bimodal or multimodal.
In order to introduce halogens, which are capable of participation in the peroxide cure reaction, along the chain, the copolymerization of the basic monomers of the fluoropolymer is carried out with a suitable fluorinated cure-site monomer (see for instance U.S. Pat. Nos. 4,745,165, 4,831,085, and 4,214,060). Such comonomer can be selected for instance from:
(a) bromo- or iodo- (per)fluoroalkyl-perfluorovinylethers having the formula:
Zxe2x80x94Rfxe2x80x94Oxe2x80x94CFxe2x95x90CF2
wherein Z is Br or I, Rf is a (per)fluoroalkylene C1-C12, optionally containing chlorine and/or ether oxygen atoms; for example: BrCF2xe2x80x94Oxe2x80x94CFxe2x95x90CF2, BrCF2CF2xe2x80x94Oxe2x80x94CFxe2x95x90CF2, BrCF2CF2CF2xe2x80x94Oxe2x80x94CFxe2x95x90CF2, CF3CFBrCF2xe2x80x94Oxe2x80x94CFxe2x95x90CF2, and the like;
(b) bromo- or iodo (per)fluoroolefins such as those having the formula:
Zxe2x80x2xe2x80x94Rxe2x80x2fxe2x80x94CFxe2x95x90CF2
wherein Zxe2x80x2is Br or I, Rxe2x80x2f is a (per)fluoroalkylene C1-C12, optionally containing chlorine atoms; for instance: bromotrifluoroethylene, 4-bromo-perfluorobutene-1, and the like; or bromofluoroolefins such as 1-bromo-2,2-difluoroethylene and 4-bromo-3,3,4,4-tetrafluorobutene-1;
(c) non-fluorinated bromo-olefins such as vinyl bromide and 4-bromo-1-butene;
(d) chlorine containing monomers including chlorine containing fluorinated monomers such as for example chlorine containing fluorinated C2-C8 olefins such as CTFE and non-fluorinated chlorine containing monomers such as chlorinated C2-C8 olefins such as vinyl chloride and vinylidene chloride.
In replacement of or in addition to the cure site comonomer, the fluoropolymer can contain a cure site component in terminal position, deriving from a suitable chain transfer agent introduced in the reaction medium during the polymer preparation, as described in U.S. Pat. No. 4,501,869 or derived from a suitable initiator. Examples of useful initiators include X(CF2)nSO2Na with n=1 to 10 (where X is Br or I) or an initiator composition comprising ammonium persulfate and potassium bromide. The chlorine of the CF2Cl end groups introduced with the presence of the chloride salt in the initiation of the free radical polymerization can also participate in a peroxide cure reaction.
Examples of chain transfer agents include those having the formula RfBrx, wherein Rf is a x-valent (per)fluoroalkyl radical C1-C12, optionally containing chlorine atoms, while x is 1 or 2. Examples include CF2Br2, Br(CF2)2Br, Br(CF2)4Br, CF2ClBr, CF3CFBrCF2Br and the like. Further examples of suitable chain transfer agents include CH2Br2 and those disclosed in U.S. Pat. No. 4,000,356.
Suitable organic peroxides are those which generate free radicals at curing temperatures. A dialkyl peroxide or a bis(dialkyl peroxide) which decomposes at a temperature above 50xc2x0 C. is especially preferred. In many cases it is preferred to use a di-tertiarybutyl peroxide having a tertiary carbon atom attached to peroxy oxygen. Among the most useful peroxides of this type are 2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexyne-3 and 2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexane. Other peroxides can be selected from such compounds as dicumyl peroxide, dibenzoyl peroxide, tertiarybutyl perbenzoate, xcex1,xcex1xe2x80x2-bis(t-butylperoxy-diisopropylbenzene), and di[1,3-dimethyl-3-(t-butylperoxy)-butyl]carbonate. Generally, about 1-3 parts of peroxide per 100 parts of fluoropolymer is used.
The cure site component may also comprise a nitrile group containing cure site monomer. Preferred useful nitrile group containing cure site monomers include nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers, such as depicted below:
CF2xe2x95x90CFxe2x80x94CF2xe2x80x94Oxe2x80x94Rfxe2x80x94CN
CF2xe2x95x90CFO(CF2)l,CN
CF2xe2x95x90CFO[CF2CF(CF3)O]g(CF2O)vCF(CF3)CN
CF2xe2x95x90CF[OCF2CF(CF3)]kO(CF2)uCN
where, in reference to the above formulas: 1=2-12; g=0-4; k=1-2; v=0-6; and u=1-4, Rf is a perfluoroalkylene or a bivalent perfluoroether group. Representative examples of such a monomer include perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene), CF2xe2x95x90CFO(CF2)5CN, and CF2xe2x95x90CFO(CF2)3OCF(CF3)CN.
When the fluoropolymer includes a nitrile containing cure site component, a catalyst comprising one or more ammonia-generating compounds may be used to cause curing. xe2x80x9cAmmonia-generating compoundsxe2x80x9d include compounds that are solid or liquid at ambient conditions but that generate ammonia under conditions of cure. Such compounds include, for example, hexamethylene tetramine (urotropin), dicyan diamid, and metal-containing compounds of the formula:
Aw+(NH3)vYwxe2x88x92
where Aw+ is a metal cation such as Cu2+, Co2+, Co3+, Cu+, and Ni2+; w is equal to the valance of the metal cation; Ywxe2x88x92 is a counterion, typically a halide, sulfate, nitrate, acetate or the like; and v is an integer from 1 to about 7.
Also useful as ammonia-generating compounds are substituted and unsubstituted triazine derivatives such as those of the formula:
wherein R is a hydrogen or a substituted or unsubstituted alkyl, aryl, or aralkyl group having from 1 to about 20 carbon atoms. Specific useful triazine derivatives include hexahydro-1,3,5-s-triazine and acetaldehyde ammonia trimer.
The fluoropolymers including a nitrile containing cure site component can also be cured using one or more peroxide curatives along with the ammonia generating catalysts. Suitable peroxide curatives for this purpose include those listed above. It will further be understood by one skilled in the art that the curable fluoroelastomer may include a mixture of cure site components, such as a mixture of nitrile containing cure sites and cure sites including a halogen capable of participating in a peroxide cure reaction. In the latter case, a mixture of ammonia generating compounds and peroxides will generally be employed.
To cure the nitrile containing fluoropolymers all other well-known compounds can be used, like amino phenols (U.S. Pat. No. 5,677,389), ammonia salts (U.S. Pat. No. 5,565,512), amidoxines (U.S. Pat. No. 5,668,221) and other ammonia generating comp (PCT 00/09603) or imidates.
Another component which is usually included in a cure composition based on an organic peroxide and/or nitrile containing cure site component, is a coagent composed of a polyunsaturated compound, which is capable of cooperating with the peroxide to provide a useful cure. These coagents can be added in an amount equal to 0.1 and 10 parts per hundred parts fluoropolymer, preferably between 2-5 parts per hundred parts fluoropolymer. Examples of useful coagents include triallyl cyanurate; triallyl isocyanurate; triallyl trimellitate; tri(methylallyl) isocyanurate; tris(diallylamine)-s-triazine; triallyl phosphite; N,N-diallyl acrylamide; hexaallyl phosphoramide; N,N,Nxe2x80x2,Nxe2x80x2-tetraalkyl tetraphthalamide; N,N,Nxe2x80x2,Nxe2x80x2-tetraallyl malonamide; trivinyl isocyanurate; 2,4,6-trivinyl methyltrisiloxane; N,Nxe2x80x2-m-phenylenebismaleimide; diallyl-phthalate and tri(5-norbornene-2-methylene)cyanurate. Particularly useful is triallyl isocyanurate. Other useful coagents include the bis-olefins disclosed in EPA 0 661 304 A1, EPA 0 784 064 A1 and EPA 0 769 521 A1.
According to a further embodiment, the curing of the fluoropolymer may be effected using a polyhydroxy compound and the cure composition will thus comprise a polyhydroxy compound. The advantage of using a polyhydroxy compound for curing the fluoropolymer is that it will not be necessary to include special cure site components in the fluoropolymer. In addition to the polyhydroxy compound, a polyhydroxy curing system generally also comprises one or more organo-onium accelerators in addition to the polyhydroxy compound. The organo-onium compounds useful in the present invention typically contain at least one heteroatom, i.e., a non-carbon atom such as N, P, S, O, bonded to organic or inorganic moieties and include for example ammonium salts, phosphonium salts and iminium salts. One class of quaternary organo-onium compounds useful in the present invention broadly comprises relatively positive and relatively negative ions wherein a phosphorus, arsenic, antimony or nitrogen generally comprises the central atom of the positive ion, and the negative ion may be an organic or inorganic anion (e.g., halide, sulfate, acetate, phosphate, phosphonate, hydroxide, alkoxide, phenoxide, bisphenoxide, etc.).
Many of the organo-onium compounds useful in this invention are described and known in the art. See, for example, U.S. Pat. No. 4,233,421 (Worm), U.S. Pat. No. 4,912,171 (Grootaert et al.), U.S. Pat. No. 5,086,123 (Guenthner et al.), and U.S. Pat. No. 5,262,490 (Kolb et al.), U.S. Pat. No. 5,929,169, all of whose descriptions are herein incorporated by reference. Representative examples include the following individually listed compounds and mixtures thereof:
triphenylbenzyl phosphonium chloride
tributylallyl phosphonium chloride
tributylbenzyl ammonium chloride
tetrabutyl ammonium bromide
triaryl sulfonium chloride
8-benzyl-1,8-diazabicyclo [5,4,0]-7-undecenium chloride
benzyl tris(dimethylamino) phosphonium chloride
benzyl(diethylamino)diphenylphosphonium chloride
Another class of useful organo-onium compounds include those having one or more pendent fluorinated alkyl groups. Generally, the most useful fluorinated onium compounds are disclosed by Coggio et al. in U.S. Pat. No. 5,591,804.
The polyhydroxy compound may be used in its free or non-salt form or as the anionic portion of a chosen organo-onium accelerator. The crosslinking agent may be any of those polyhydroxy compounds known in the art to function as a crosslinking agent or co-curative for fluoropolymers, such as those polyhydroxy compounds disclosed in U.S. Pat. No. 3,876,654 (Pattison), and U.S. Pat. No. 4,233,421 (Worm). One of the most useful and commonly employed aromatic polyphenols is 4,4xe2x80x2-hexafluoroisopropylidenyl bisphenol, known more commonly as bisphenol AF. The compounds 4,4xe2x80x2-dihydroxydiphenyl sulfone (also known as Bisphenol S) and 4,4xe2x80x2-isopropylidenyl bisphenol (also known as bisphenol A) are also widely used in practice.
The cure composition based on polyhydroxy compounds may further include an acid acceptor. Acid acceptors can be inorganic or blends of inorganic and organic. Examples of inorganic acceptors include magnesium oxide, lead oxide, calcium oxide, calcium hydroxide, dibasic lead phosphite, zinc oxide, barium carbonate, strontium hydroxide, calcium carbonate, etc. Organic acceptors include epoxies, sodium stearate, and magnesium oxalate. The preferred acid acceptors are magnesium oxide and calcium hydroxide. The acid acceptors can be used singly or in combination, and preferably are used in amounts ranging from about 2 to 25 parts per 100 parts by weight of the fluoropolymer.
In a further embodiment of the invention, the cure composition may comprise an organic peroxide and a polyhydroxy based cure system as described above. Such cure composition can be used with a fluoropolymer that has a halogen capable of participating in a peroxide cure reaction as well as with fluoropolymers that do not contain such halogens. If the fluoropolymer has halogens capable of participating in the peroxide cure reaction, a cure composition having a polyhydroxy compound and a peroxide can provide for a so called dual cure. The use of an organic peroxide in the cure composition is particularly beneficial if the fluoropolymer is to form a fluoroelastomer layer bonded to another elastomer that is also formed with the use of a peroxide cure system such as for example in case of a silicone based elastomer.
The fluoropolymer composition may contain further additives, such as carbon black, stabilizers, plasticizers, lubricants, fillers, and processing aids typically utilized in fluoropolymer compounding can be incorporated into the compositions of the present invention, provided they have adequate stability for the intended service conditions.
The fluoropolymer compositions may be prepared by mixing a fluoropolymer, a cure composition and the organic compound having hydride function(s) and other additives in conventional rubber processing equipment. Such equipment includes rubber mills, internal mixers, such as Banbury mixers, and mixing extruders.
In a further embodiment of the present invention, the fluoropolymer comprises a thermoplastic fluoropolymer, in particular a melt processible thermoplastic fluoropolymer. By the term xe2x80x9cthermoplastic fluoropolymerxe2x80x9d is meant a fluoropolymer that is at least partially crystalline such that a distinct melting point, typically 100xc2x0 C. or more, can be identified for example through a DSC scan of the polymer. By the term xe2x80x9cmelt processiblexe2x80x9d is meant that the fluoropolymer has a melt viscosity such that it can be processed from the melt through typical melt extrusion equipment that is available. Specific examples of thermoplastic fluoropolymers that may be used with this invention are copolymers having the following combination of monomers: CTFE-VDF; CTFE-TFE, CTFE-TFE-HFP, CTFE-TFE-HFP-VDF; CTFE-TFE-HFP-VDF-PPVE, CTFE-TFE-E; TFE-HFP; TFE-VDF-HFP, TFE-P; TFE-PVE; bromine or chlorine containing E-TFE copolymers and bromine or chlorine containing TFE-HFP-VDF copolymers.
As mentioned above, the fluoropolymer has improved bonding properties to other substrates, particularly in the presence of an organic compound having hydride functions MH. Additionally, by including this compound in the fluoropolymer composition, a peroxide curable fluoropolymer composition can be obtained. Examples of the organic compound include siloxanes or silazenes that comprise one or more MH functions. Typically, when the organic compound is a siloxane or a silazene, the MH functions will be xe2x80x94SiH functions. Preferably, the SiH function will be an xe2x80x94OSiH or a xe2x80x94NSiH whereby the hydrogen is attached to a silicon atom that is further bonded to an oxygen or nitrogen atom. The siloxane of silazene may be a simple low molecular weight organic compound or may be a polymeric compound including for example a polysiloxane which may be linear, branched or cyclic. Specific examples include HSi(OCH2CH3)3, (CH3)2(CH3CH2O)SiH, 1,1,3,3 tetraisopropyl disiloxane, diphenyl-1,1,3,3-tetrakis(dimethylsiloxy)disiloxane available from United Chem, silylhydride terminated poly(dimethylsiloxane), poly(methyl hydro siloxane) and copolymers of dimethylsiloxane and methylhydrosiloxane, 1,3,5-trimethyl cyclosiloxane and 1-phenyl-3,3,5,5-tetramethyl cyclosiloxane. Polysiloxanes and siloxanes having SiH groups are known in the art and can be produced according to well-known procedures such as disclosed in for example: Encyclopedia of Polymer Science and Engineering, Second Edition, V15, Silicones, pgs. 204-308, John Wiley and Sons, 1989. Siloxanes having SiH groups are also generally commercially available. Preferably, the siloxane or polysiloxane will have a molecular weight between 150 g/mol and 10000 g/mol.
The organic compound may also be a compound that corresponds to the formula:
wherein R represents a hydrocarbon group optionally comprising one or more substituents and wherein the R groups may be the same or different and whereby two R groups may be linked to each other so as to form a ring, M is selected from Si, Ge, Sn and Pb, q is a value of 1 to 3, x is a value of 1 to 3, y and z represent a value of 0 to 3 and the sum of y+z=4xe2x88x92x. Examples of substituents that may be present on the hydrocarbon group R include alkoxy, aryloxy, halogens such as chlorine and bromine, nitrile groups, hydroxy groups and amino groups. The backbone of the hydrocarbon group may further be interrupted by one or more heteroatoms such as for example oxygen and nitrogen atoms. Typical examples of hydrocarbon groups include saturated or unsaturated linear, branched or cyclic aliphatic groups and aromatic groups. Specific examples are C1-C5 alkyl groups, aryl groups having 6 to 12 carbon atoms, arylalkyl and alkylaryl groups having 7 to 14 carbon atoms. Compounds of formula (II) above are known and have been described in for example J. Am. Chem. Soc., 116 (1994), page 4521-4522. Examples include tri(n-butyl)tin hydride, tri(ethyl)silyl hydride, di(trimethylsilyl)silylmethyl hydride, tri(trimethylsilyl)silyl hydride, tri(phenyl)silyl hydride. Compounds of formula (II) have further been disclosed in EP 761 735.

Process for producing fluoropolymers having a reduced amount of polar end groups


A denture cleanser composition comprising polybutene, with a molecular weight of about 300 to about 3000, an effervescence generator and a bleaching agent. Optionally, denture cleanser compositions may further comprise tablet binders, organic peroxyacid bleach precursors, surfactants including a dimethicone copolyol, lipophilic compounds such as flavorants and coolants, chelating agents, and other therapeutic and cosmetic active agents.

The present invention relates to a cleanser composition that is especially useful for cleansing dentures and the like. In particular, the present invention relates to denture cleansing compositions having enhanced anti-plaque activity together with excellent denture cleansing performance, which may be used to deliver additional therapeutic and cosmetic benefits.
Effervescent tablets and powders for cleansing dentures are well known in the art. The aim of a denture cleanser product is to clean the denture as fully and as quickly as possible to remove the accumulation of plaque, mucilaginous and bacterial deposits which collect while the denture is being worn. To wear a denture, which has not been completely cleaned of plaque and bacterial deposits, is not only unhygienic but can also, within a short time, result in detrimental effects to the mucous membrane. Moreover, bacterial deposits can lead to so-called bacterial corrosion of the plastics material used to produce the denture with consequent color change and malodor formation. Conventional denture cleansers typically do not maintain actives in the oral cavity long enough to optimally enhance or prolong the therapeutic, prophylactic and/or cosmetic benefits provided by the actives. In order to provide a denture cleanser with sufficient substantivity to provide sustained release of a denture cleansing agent and optionally additional denture care actives, the use of polybutene in a denture cleanser composition is herein disclosed.
Polybutene is recognized as a component of denture adhesives and as a gum base. U.S. Pat. No. 5,880,172, issued Mar. 3, 1999, to Rajaiah, et al., discloses a self-supporting denture adhesive that is peelable for easy removal, which incorporates polybutene as an optional ingredient. U.S. Pat. No. 5,496,541, issued Mar. 5, 1996, to Cutler, relates to a dentifrice chewing gum and teaches the use of polybutene as an optional gum base. Such known applications often employ a higher molecular weight polybutene in order to achieve the desired results.
In the present invention lower molecular weight polybutene is incorporated in the denture cleanser composition to provide a protective coating on the artificial teeth. The lower molecular weight polybutene is a flowable liquid that achieves good coating of the denture and is extremely substantive. Sustained release of the denture cleansing active agent is achieved. Through sustained release of additional denture care actives optionally incorporated in the present invention the denture surface receives optimal therapeutic and cosmetic benefits.
The present invention provides a denture cleanser composition that effectively cleanses dentures, dental plates, and other hard surfaces temporarily fixed within the oral cavity and provides a coating to the same surfaces thereby preventing the buildup of plaque and other debris. The coating inhibits and prevents staining of the denture. This coating also provides a slick, smooth feel to the denture surface, which consumers view as an indicator of clean teeth. The coating may also provide sustained release of other denture care actives and ingredients.
The present invention relates to a denture cleanser composition comprising polybutene with a molecular weight of about 300 to about 3000; an inorganic persalt bleaching agent; and an effervescence generator. Additional components may be added to the present invention including, without limitation, an organic peroxyacid bleach precursor, lipophilic compounds, dental abrasives, binders, humectants, surfactants, chelating agents and other denture care actives.
The denture cleanser compositions of the invention comprise polybutene, an effervescence generator and an inorganic persalt bleaching agent. In one embodiment, these essential components are supplemented by additional components, which may include an organic peroxyacid bleach precursor, lipophilic compounds, dental abrasives, binders, humectants, surfactants, chelating agents, and other cosmetic and therapeutic denture care actives. Each of these will be discussed in turn.
Definitions
The terms xe2x80x9cartificial teethxe2x80x9d and xe2x80x9cdenturesxe2x80x9d, as used herein, are meant to include dentures, dental plates, bridges and other hard surfaces of dental appliances which are temporarily fixed within the oral cavity and which are typically removed from the oral cavity for cleaning.
By xe2x80x9csafe and effective amountxe2x80x9d, as used herein, is meant an amount of an agent (e.g., anti-calculus agent) high enough to significantly improve the condition to be treated, but low enough to avoid serious side effects (at a reasonable benefit/risk ratio), within the scope of sound medical/dental judgment. The safe and effective amount of an agent (e.g., anti-calculus agent) may vary with the particular condition being treated, the age and physical condition of the patient being treated, the severity of the condition, the duration of treatment, the nature of concurrent therapy, the specific form of the source employed, and the particular vehicle from which the agent is applied.
The term xe2x80x9cnon-self supportingxe2x80x9d is used to describe a composition that lacks integrity and strength. In the instant case, this means that the composition is unable to be detached as one solid piece from the teeth even after several hours of use in the mouth. The composition cannot be cut and formed into definite shapes, such as a sheet or cone, which maintain their initial dimensions.
The term xe2x80x9cmucoadhesivexe2x80x9d or xe2x80x9cbioadhesivexe2x80x9d as used herein refers to the phenomenon where a natural or synthetic substance applied to a wet mucosal epithelium adheres, usually creating a new interface, to the mucous layer. (CRC Critical Review in Ther Drug Carrier, Vol.5, Issue 1, p.21 (1988)). Generally, mucoadhesion can be achieved via physical or chemical processes, or both. This mechanism is described in Journal of Controlled Release, Vol.2, p257 (1982) and Journal of Controlled Release, Vol.18 (1992) p. 249. The above references are incorporated by reference herein in their entirety.
Herein, the terms xe2x80x9ctartarxe2x80x9d and xe2x80x9ccalculusxe2x80x9d are used interchangeably and refer to mineralized dental plaque biofilms.
The term xe2x80x9cunit dose formxe2x80x9d refers to physically discrete units suitable as unitary dosages for human subjects and other mammals, each containing a predetermined quantity of active material calculated to produce the desired therapeutic effect.
The term xe2x80x9cviscosityxe2x80x9d as used herein refers to kinematic viscosity, measured using the standard test method for Kinematic Viscosity of Transparent and Opaque Liquids (the Calculation of Dynamic Viscosity), ASTM D-445. As reported, viscosity is measured at 99xc2x0 C. (210xc2x0 F.) unless otherwise indicated. A sample is placed in a U-shaped xe2x80x9cCannon-Fenskexe2x80x9d type viscometer (for transparent liquids) tube and submerged into a constant temperature bath. Flow is timed between two marks on the tube and viscosity is determined by simple calculations dependent on time and a standard factor supplied by the tube manufacturer.
xe2x80x9cMolecular weightxe2x80x9d, as referred to herein, is reported as a number average, determined using gel permeation chromatography. The number average molecular weight, or arithmetic mean, is a function of the number of molecules in a given mass of polymer. It is represented by the formula:       M    n    =                    ∑                              N            i                                          M            i                                      ∑                  N          i                      =          ∑                        n          i                                  M          i
where Ni, represents the number of molecules present for a given molecular weight, Mi and ni=Ni/xcexa3Ni is the number fraction of molecular weight, Mi.
Percentages and ratios herein are by weight of total composition, unless otherwise indicated.
Polybutene
Polybutene is a viscous copolymer of isobutylene and butene monomers. xe2x80x9cPolybutenexe2x80x9d, as used herein, refers to both hydrogenated (CAS #68937-10-0) and unhydrogenated (CAS #9003-29-6) forms of the polymer. Polybutene is a viscous, colorless, non-drying, liquid polymer. Forms of polybutenes range from a flowable liquid to a near semi-solid state. Polybutenes are clear, odorless, chemically stable, resistant to oxidation by light and heat, non-toxic and non-hazardous.
The composition of the present invention comprises polybutene, generally of a lower molecular weight from about 300 to about 3000, in another embodiment from about 500 to about 2200, and in another embodiment from about 750 to about 1500. The viscosity of the polybutene disclosed herein, ranges from about 30 cSt (centi Stoke) measured at 38xc2x0 C. to about 4,500 cSt measured at 99xc2x0 C., in another embodiment from about 200 cSt measured at 38xc2x0 C. to about 3,500 cSt measured at 99xc2x0 C. and in another embodiment from about 75 cSt measured at 99xc2x0 C. to about 700 cSt measured at 99xc2x0 C. Polybutene comprises from about 0.01% to about 100%, in another embodiment from about 1% to about 100%, in yet another embodiment from about 50% to about 100% by weight of the composition.
The lower molecular weight polybutene of the present invention does not exhibit elastomeric properties. Elastomers are amorphous polymers that have the ability to stretch out and spring back to their original shapes. Such elastomeric polymers must have a modest amount of cross-linking to prevent the polymeric chains from slipping over one another, and the chains must have an irregular shape to prevent the formation of crystalline regions within the polymeric chains. Synthetic elastomers, are described in more detail in Kirk-Othmer, Encyclopedia of Chemical Technology, Fourth Edition, Volume 8, Wiley-Interscience Publishers (1996), pages 934-955, incorporated herein by reference in its entirety, including all references incorporated into Kirk-Othmer. The polybutene of the present invention is not cross-linked and does not exhibit rubbery or elastic behavior. When subjected to a stretching or bending force, the polybutene of the present invention does not return to its original shape upon the removal of the force.
Lower molecular weight polybutene (Molecular Weight=300-3000), which is a flowable liquid known for its adhesive properties, is actually non-mucoadhesive. That is, the polybutene, while displaying excellent adhesion properties on the hard surfaces of the oral cavity, will not significantly adhere to the mucosa or wet, soft tissue of the mouth. Therefore, polybutene is extremely substantive when applied to the denture, making it suitable for once daily application and treatment. High retention of the polybutene is achieved, even when thorough brushing has occurred. Thus, the polybutene, once applied to the denture surface, is long lasting, and rinse resistant, which allows for sustained release of certain optional denture care actives. Importantly, the compositions of the present invention are not self-supporting neither before, during, nor after application to the artificial teeth.
Once applied to the denture, the polybutene has a very smooth, slick texture, perceived by the consumer as a desirable, clean feeling. The polybutene acts as a lubricant and reduces the friction normally produced when the tongue slides over these surfaces.
Suitable polybutenes for use herein include, but are not limited to: Indopol L-14, Molecular Weight (xe2x80x9cMWxe2x80x9d)=370; Indopol L-50, MW=455; Indopol L-65, MW=435; Indopol L-100, MW=510, H-15, MW=600; H-25, MW=670; H-35, MW=725; H-40, MW=750; H-50, MW=815; H-100, MW=940; H-300, MW=1330; H-1500, MW=2145; H-1900, MW=2270; Panalane L-14E, MW=370; Panalane H-300E, MW=1330; all trade names of BP Amoco Chemicals (Chicago, Ill.). Other suitable grades of polybutene include Parapol 450, MW=420; Parapol 700, MW=700; Parapol 950, MW=950; Parapol 1300, MW=1300; and Parapol 2500, MW=2700; all trade names of ExxonMobil Corporation.
Inorganic Persalt Bleaching Agent
Another essential element of the composition of the present invention is a bleaching agent. Typically the bleaching agent takes the form of an inorganic persalt and can be selected from any of the well-known bleaching agents known for use in denture cleansers such as the alkali metal and ammonium persulfates, perborates, percarbonates and perphosphates and the alkali metal and alkaline earth metal peroxides. Examples of suitable bleaching agents include potassium, ammonium, sodium and lithium persulfates and perborate mono- and tetrahydrates, sodium pyrophosphate peroxyhydrate and magnesium, calcium, strontium and zinc peroxides. Of these, however, the alkali metal persulfates, perborates and mixtures thereof are preferred for use herein. In one embodiment the inorganic persalt bleaching agent is selected from the alkali metal perborates. Indeed, it is a feature of the invention that the tablet compositions herein will provide excellent antimicrobial activity even in the absence of alkali metal persulfates.
The amount of bleaching agent in the total composition is generally from about 5 to about 70% preferably from about 10% to about 50%. In compositions comprising a mixture of alkali metal persulfates and perborates, the overall persulfate:perborate ratio is suitably from about 5:1 to about 1:5, more especially from about 2:1 to about 1:2.
Effervesence Generator
The denture cleansing compositions also comprise an effervescence generator, i.e. a material that, in the presence of water, releases carbon dioxide or oxygen with effervescence. The effervescence generator can be selected from generators which are effective under acid, neutral or alkaline pH conditions, but preferably it consists of a combination of a generator which is effective or most effective under acid or neutral pH conditions and a generator which is effective or most effective under alkaline pH conditions. Effervescence generators which are effective under acid or neutral pH conditions include a combination of at least one alkali metal carbonate or bicarbonate, such as sodium bicarbonate, sodium carbonate, sodium sesquicarbonate, potassium carbonate, potassium bicarbonate, or mixtures thereof, in admixture with at least one non-toxic, physiologically-acceptable organic acid, such as tartaric, fumaric, citric, malic, maleic, gluconic, succinic, salicylic, adipic or sulphamic acid, sodium fumarate, sodium or potassium acid phosphates, betaine hydrochloride or mixtures thereof. Of these, malic acid is preferred. Effervescence generators which are effective under alkaline pH conditions include persalts such as alkali and alkaline earth metal peroxoborates as well as perborates, persulphates, percarbonates, perphosphates, and mixtures thereof as previously described. For example, a mixture of an alkali metal perborate (anhydrous, mono-, or tetrahydrate) with a monopersulphate such as CaroatĈ, marketed by E I du Point de Nemours Co., which is a 2:1:1 mixture of monopersulphate, potassium sulphate and potassium bisulphate and which has an active oxygen content of about 4.5%, is suitable for use herein.
In one embodiment denture cleansing compositions in tablet form, incorporate an effervescence generator that takes the form of a solid base material which in the presence of water releases carbon dioxide or oxygen with effervescence. Suitably, the solid base material incorporates a (bi)carbonate/acid effervescent couple optionally in combination with a perborate/persulphate oxygen effervescence generator. The combination of generators is valuable for achieving optimum dissolution characteristics and pH conditions for achieving optimum cleaning and antimicrobial activity. The (bi)carbonate components generally comprise from about 5% to about 65%, preferably from about 25% to 55% of the total composition. The acid components generally comprise from about 5% to about 50%, preferably from about 10% to about 30% of the total composition.
Optional Ingredients
The denture cleansing compositions of the present invention can be supplemented by other known components of such formulations. Denture cleansing compositions of the invention can be supplemented by other usual components of such formulations, especially organic peroxyacid bleach precursors; lipophilic compounds including flavorants, physiological cooling agents, and perfumes; surfactants; chelating agents; enzymes; dyestuffs; sweeteners; tablet binders and fillers; foam depressants such as dimethylpolysiloxanes; foam stabilizers such as the fatty acid sugar esters; preservatives; lubricants such as talc, magnesium stearate, finely divided amorphous pyrogenic silicas, etc.; and additional therapeutic and cosmetic active agents. The free moisture content of the final composition is desirably less than about 1% and especially less than about 0.5%.
Tablet Binders and Fillers
Tablet binders and fillers suitable for use herein include polyvinyl-pyrrolidone, poly (oxyethylene) of molecular weight 20,000 to 500,000, polyethyleneglycols of molecular weight of from about 1000 to about 50,000, Carbowax having a molecular weight of from 4000 to 20,000, nonionic surfactants, fatty acids, sodium carboxymethyl cellulose, gelatin, fatty alcohols, clays, polymeric polycarboxylates, sodium carbonate, calcium carbonate, calcium hydroxide, magnesium oxide, magnesium hydroxide carbonate, sodium sulfate, proteins, cellulose ethers, cellulose esters, polyvinyl alcohol, alginic acid esters, vegetable fatty materials of a pseudocolloidal character. Of the above, polyethyleneglycols are highly preferred, especially those having molecular weight of from about 1,000 to about 30,000, preferably from about 12,000 to about 30,000.
Organic Peroxyacid Bleach Precursors
In one embodiment the present invention further comprises an organic peroxyacid precursor, which in general terms can be defined as a compound having a titre of at least 1.5 ml of 0.1N sodium thiosulfate in the following peracid formation test.
A test solution is prepared by dissolving the following materials in 1000 mls distilled water:
To this solution at 60xc2x0 C. an amount of activator is added such that for each atom of available oxygen present one molecular equivalent of activator is introduced. The mixture obtained by addition of the activator is vigorously stirred and maintained at 60xc2x0 C. After 5 minutes from addition, a 100 ml portion of the solution is withdrawn and immediately pipetted onto a mixture of 250 g cracked ice and 15 ml glacial acetic acid. Potassium iodide (0.4 g) is then added and the liberated iodine is immediately titrated with 0.1 N sodium thiosulphate with starch as indicator until the first disappearance of the blue colour. The amount of sodium thiosulphate solution used in ml is the titre of the bleach activator.
The organic peracid precursors are typically compounds containing one or more acyl groups, which are susceptible to perhydrolysis. The preferred activators are those of the N-acyl or O-acyl compound type containing an acyl radical Rxe2x80x94CO wherein R is a hydrocarbon or substituted hydrocarbon group having preferably from about 1 to about 20 carbon atoms. Examples of suitable peracid precursors include:
1) Acyl organoamides of the formula RCONR1R2, where RCO is carboxylic acyl radical, R1 is an acyl radical and R2 is an organic radical, as disclosed in U.S. Pat. No. 3,117,148. Examples of compounds falling under this group include:
a) N,N-diacetylaniline and N-acetylphthalimide;
b) N-acylhydantoins, such as N,Nxe2x80x2-diacetyl-5,5-dimethylhydantoin;
c) Polyacylated alkylene diamines, such as N,N,Nxe2x80x2Nxe2x80x2-tetraacetylethylenediamine (TAED) and the corresponding hexamethylenediamine (TAHD) derivatives, as disclosed in GB-A-907,356, GB-A-907,357 and GB-A-907,358;
d) Acylated glycolurils, such as tetraacetylglycoluril, as disclosed in GB-A-1,246,338, GB-A-1,246,339 and GB-A-1,247,429.
2) Acylated sulphonamides, such as N-methyl-N-benzoyl-menthane sulphonamide and N-phenyl-N-acetyl menthane sulphonamide, as disclosed in GB-A-3,183,266.
3) Carboxylic esters as disclosed in GB-A-836,988, GB-A-963,135 and GB-A-1,147,871. Examples of compounds of this type include phenyl acetate, sodium acetoxy benzene sulphonate, trichloroethylacetate, sorbitol hexaacetate, fructose pentaacetate, p-nitrobenzaldehyde diacetate, isopropeneyl acetate, acetyl aceto hydroxamic acid, and acetyl salicylic acid. Other examples are esters of a phenol or substituted phenol with an alpha-chlorinated lower aliphatic carboxylic acid, such as chloroacetylphenol and chloroacetylsalicylic acid, as disclosed in U.S. Pat. No. 3,130,165.
4) Carboxylic esters having the general formula AcL wherein Ac is the acyl moiety of an organic carboxylic acid comprising an optionally substituted, linear or branched C6-C20 alkyl or alkenyl moiety or a C6-C20 alkyl-substituted aryl moiety and L is a leaving group, the conjugate acid of which has a pKa in the range from 4 to 13, for example oxybenzenesulfonate or oxybenzoate. Preferred compounds of this type are those wherein:
a) Ac is R3xe2x80x94CO and R3 is a linear or branched alkyl group containing from 6 to 20, in one embodiment 6 to 12, in another embodiment 7 to 9 carbon atoms and wherein the longest linear alkyl chain extending from and including the carbonyl carbon contains from 5 to 18, in one embodiment 5 to 10 carbon atoms, R3 optionally being substituted (preferably alpha to the carbonyl moiety) by Cl, Br, OCH3 or OC2H5. Examples of this class of material include sodium 3,5,5-trimethylhexanoyloxybenzene sulfonate, sodium 3,5,5-trimethylhexanoyloxybenzoate, sodium 2-ethylhexanoyl oxybenzenesulfonate, sodium nonanoyl oxybenzene sulfonate and sodium octanoyl oxybenezenesulfonate, the acyloxy group in each instance preferably being p-substituted;
b) Ac has the formula R3(AO)mXA wherein R3 is a linear or branched alkyl or alkylaryl group containing from 6 to 20, in one embodiment from 6 to 15 carbon atoms in the alkyl moiety, R5 being optionally substituted by Cl, Br, OCH3, or OC2H5, AO is oxyethylene or oxypropylene, m is from 0 to 100, X is O, NR4 or COxe2x80x94NR4, and A is CO, COxe2x80x94CO, R6xe2x80x94CO, COxe2x80x94R6xe2x80x94CO, or COxe2x80x94NR4xe2x80x94R6xe2x80x94CO wherein R4 is C1-C4 alkyl and R6 is alkylene, alkenylene, arylene or alkarylene containing from 1 to 8 carbon atoms in the alkylene or alkenylene moiety. Bleach activator compounds of this type include carbonic acid derivatives of the formula R3(AO)mOCOL, succinic acid derivatives of the formula R3OCO(CH2)2COL, glycollic acid derivatives of the formula R3OCH2COL, hydroxypropionic acid derivatives of the formula R3OCH2CH2COL, oxalic acid derivatives of the formula R3OCOCOL, maleic and fumaric acid derivatives of the formula R3OCOCHxe2x95x90CHCOL, acyl aminocaproic acid derivatives of the formula R3CONR1(CH2)6COL, acyl glycine derivatives of the formula R3CONR1CH2COL, and amino-6-oxocaproic acid derivatives of the formula R3N(R1)CO(CH2)4COL. In the above, m is in one embodiment from 0 to 10, and R3 is in one embodiment C6-C12, in another embodiment C6-C10 alkyl when m is zero and C9-C15 when m is non-zero. The leaving group L is as defined above.
5) Acyl-cyanurates, such as triacetyl- or tribenzoylcyanurates, as disclosed in U.S. Pat. No. 3,332,882.
6) Optionally substituted anhydrides of benzoic or phthalic acid, for example, benzoic anhydride, m-chlorobenzoic anhydride and phthalic anhydride.
In one embodiment, organic peracid precursors are of types 1(c) and 4(a).
Where present, the level of peroxyacid bleach precursor, by weight of the total composition, is from about 0.1% to about 10%, in one embodiment from about 0.5% to about 5% and is generally added in the form of a bleach precursor agglomerate.
The bleach precursor agglomerates preferred for use herein generally comprise a binder or agglomerating agent, selected from those tablet binders or fillers described above, in a level of from about 5% to about 40%, in one embodiment from about 10% to about 30% by weight thereof.
Preferred from the viewpoint of optimum dissolution and pH characteristics are bleach precursor agglomerates which comprise from about 10% to about 75%, in one embodiment from about 20% to about 60% by weight thereof of peroxyacid bleach precursor, from about 5% to about 60%, in one embodiment from about 5% to about 50%, in another embodiment from about 10% to about 40% of a (bi) carbonate/acid effervescent couple, from about 0% to about 20% of a peroxoboroate, and from about 5% to about 40%, in one embodiment from about 10% to about 30% of an agglomerating agent. The final bleach precursor granules desirably have an average particle size of from about 500 to about 1500, in one embodiment from about 500 to about 1,000 um, this being valuable from the viewpoint of optimum dissolution performance and aesthetics. The level of bleach precursor agglomerates, moreover, is from about 1% to about 20%, in one embodiment from about 5% to about 15% by weight of composition.
Surfactants
Another optional ingredient of the denture cleansing compositions of the invention is a surfactant. The surfactant can be selected from the many available that are compatible with the other ingredients of the denture cleanser, both in the dry state and in solution. Such materials are believed to improve the effectiveness of the other ingredients of the composition by aiding their penetration into the interdental surfaces. Also, these materials aid in the removal of food debris attached to the teeth. Between 0.1% and 5%, by weight of the dry composition of a dry powder or granular anionic surface active agent, such as sodium lauryl sulfate, sodium N-lauroylsarcosinate, sodium lauryl sulfoacetate or dioctyl sodium sulfosuccinate or ricinoleyl sodium sulfosuccinate, may, for example, be included in the composition and in one embodiment the surfactant comprises between 0.5% and 4% of the composition.
Suitable cationic, non-ionic and ampholytic surface active agents include, for example, quaternary ammonium compounds such as cetyltrimethyl-ammonium bromide, condensation products of alkylene oxides such as ethylene or propylene oxide with fatty alcohols, phenols, fatty amines or fatty acid alkanolamides, the fatty acid alkanolamides themselves, esters of long-chained (C8-C22) fatty acids with polyalcohols or sugars, for example glycerylmonostearate or saccharose monolaurate or sorbitolpolyoxyethylenemono- or di-stearate, betaines, sulphobetaines or long-chain alkylaminocarboxylic acids.
In one embodiment the surfactant is a silicone surfactant having the general formula (I):
wherein X is selected from hydrogen, alkyl, alkoxy and acyl groups having from about 1 to about 16 carbon atoms, Y is CH3, q is 0, n is from about 1 to about 100, m is from about 1 to about 40, the molecular weight of the residue (C2H4Oxe2x80x94)x(C3H6Oxe2x80x94)yX is from about 50 to about 2000, and x and y are such that the weight ratio of oxyethylene:oxypropylene is from about 100:0 to about 0:100.
The silicone surfactant, a dimethicone copolyol, assists in dispersing the polybutene in an aqueous media whilst still allowing the polybutene to deposit onto denture surfaces. In one embodiment, the silicone surfactant is selected from dimethicone copolyols having a HLB value of greater than 14 and mixtures thereof. Highly preferred are end-capped (X is alkyl, more particularly methyl) dimethicone copolyols, especially where the pendant side chain is all oxyethylene (y is 0), such as that marketed under the Trade Name Silwet L7600. The silicone surfactant is generally present in a level of from about 0.01% to about 25%, in one embodiment from about 0.3% to about 10%, in another embodiment from about 0.5% to about 5%, by weight. It will be appreciated that the precise amount will depend on the amount of the polybutene used.
Lipophilic Compounds
The denture cleanser compositions of the present invention may also include a lipophilic compound. In general terms, lipophilic compounds suitable for use herein are oil-like materials which are soluble or solubilisable in the polybutene, typically at a level of at least about 1%, in one embodiment at least about 5%, by weight at 25xc2x0 C. Preferred lipophilic compounds are selected from flavorants, physiological cooling agents, perfumes and antimicrobial compounds. The polybutene acts to enhance the substantivity of the lipophilic compound to teeth and/or dentures, thereby providing enhanced and/or sustained flavor impact and antimicrobial efficacy.
Lipophilic flavorants suitable for use herein comprise one or more flavor components selected from wintergreen oil, oregano oil, bay leaf oil, peppermint oil, spearmint oil, clove oil, sage oil, sassafras oil, lemon oil, orange oil, anise oil, benzaldehyde, bitter almond oil, camphor, cedar leaf oil, marjoram oil, citronella oil, lavendar oil, mustard oil, pine oil, pine needle oil, rosemary oil, thyme oil, cinnamon leaf oil, and mixtures thereof.
Lipophilic antimicrobial compounds suitable for use herein include thymol, menthol, triclosan, 4-hexylresorcinol, phenol, eucalyptol, benzoic acid, benzoyl peroxide, butyl paraben, methyl paraben, propyl paraben, salicylamides, and mixtures thereof.
The carboxamides found most useful are those described in U.S. Pat. No. 4,136,163, Jan. 23, 1979 to Wason et al., and U.S. Pat. No. 4,230, 688, Oct. 28, 1980 to Rawsell et al.
Physiological cooling agents suitable for use herein include carboxamides, menthane esters, menthane ethers, and mixtures thereof. Suitable menthane ethers for use herein are selected from those with the formula:
where R5 is an optionally hydroxy substituted aliphatic radical containing up to 25 carbon atoms, preferably up to 5 carbon atoms, and where X is hydrogen or hydroxy, such as those commercially available under the trade name Takasago, from Takasago International Corporation. A particularly preferred cooling agent for use in the compositions of the present invention is Takasago 10 [3-1-menthoxy propan-1,2-diol (MPD)]. MPD is a monoglycerin derivative of 1-menthol and has excellent cooling activity.
The level of lipophilic compound in the compositions of the invention is generally in the range from about 0.001% to about 10%, in one embodiment from about 0.05% to about 5%, in another embodiment from about 0.1% to about 3%, by weight.
Chelating Agents
Chelating agents beneficially aid cleaning and bleach stability by keeping metal ions, such as calcium, magnesium, and heavy metal cations in solution. Examples of suitable chelating agents include sodium tripolyphosphate, sodium acid pyrophosphate, tetrasodium pyrophosphate, aminopoly-carboxylates such as nitrilotriacetic acid and ethylenediamine tetracetic acid and salts thereof, and polyphosphonates and aminopolyphosphonates such as hydroxyethanediphosphonic acid, ethylenediamine tetramethylene-phosphonic acid, diethylenetriaminepentamethylenephosphonic acid and salts thereof. The chelating agent selected is not critical except that it must be compatible with the other ingredients of the denture cleanser when in the dry state and in aqueous solution. Advantageously, the chelating agent comprises between 0.01% and 60%, by weight of the composition, in one embodiment between 0.5% and 30%. Phosphonic acid chelating agents, however, comprise from about 0.001% to about 1%, in one embodiment from about 0.01% to about 0.5%, by weight of composition.
Enzymes
Enzymes suitable for use herein are exemplified by proteases, alkalases, amylases, lipases, dextranases, mutanases, glucanases etc.
Therapeutic and Cosmetic Agents
The denture cleanser compositions of the present invention may further comprise one or more therapeutic or cosmetic active agents selected from the group consisting of anti-calculus agents, fluoride ions sources, stannous ion sources, additional whitening agents, anti-microbial, anti-plaque agents, anti-inflammatory agents, nutrients, antioxidants, anti-viral agents, anti-fungal agents, analgesic and anesthetic agents, H-2 antagonists, components other than polybutene which impart a clean feel to the dentures, pigments, dyes, lakes and colorants, and mixtures thereof. In one embodiment the therapeutic and cosmetic active agents are selected from the group consisting of triclosan, baking soda, sodium fluoride, potassium nitrate, sodium nitrate, nystatin, grapefruit seed extract, stannous fluoride, tetra sodium pyrophosphate, mono fluoro phosphate, Opatint DandC Red 27, polyphosphates, such as sodium hexametaphosphate, and cetylpyridium chloride.
The denture cleansing compositions of the invention can be in paste, tablet, granular or powder form, although tablet-form compositions are highly preferred herein. Compositions in tablet form can be single or multiple layered tablets.

Polybutene containing denture cleanser compositions


A crayon protector comprises a covering which is substantially cylindrical in configuration. The covering is made of unbreakable, non-cuttable, yet flexible material, for instance molded plastic. The covering is configured with open ends and a longitudinal slit which prevents complete encircling of the crayon. The covering is inserted on a crayon and substantially surrounds and reinforces it from breakage at its break zone. The slit facilitates insertion and removal and allows flexible expansion of the covering for use with crayons of varying diameters. The protector can also be used to prevent breakage of other relatively easily breakable writing implements, like chalk, pastel and charcoal sticks.

Every parent, at one time or another, has purchased a box of crayons for his or her children. Indeed, most parents have had to incur the expense of buying multiple boxes of crayons, following the breakage of crayons which children refuse to use in a broken state. While any given crayon is not expensive, the continual need to buy additional crayons in place of ones that have broken can become expensive and bothersome. In addition, the user of crayons of unique colors may wish to ensure that such crayons are maintained as long as possible, without breaking. Towards this end, protective coverings for crayons have been suggested.
Prior protective coverings for crayons contemplate the use of permanent wrappings or sheathings which are configured to be manufactured and used with an individual crayon. As the crayon material is used, the wrapping or sheathing is routinely peeled or cut away to allow exposure to additional crayon material. Once the crayon is completely spent, so is the wrapping and sheathing and the crayon is discarded. Examples of such prior crayon protection elements are found in U.S. Pat. Nos. 3,249,092, 5,522,960, 5,957,604, and 6,063,222. Other crayon protectors, as is shown in U.S. Pat. No. 2,205,907, are also designed to be used with one individual crayon and, following the use with the crayon, disposed of.
It is thus the object of the present invention to overcome the limitations and disadvantages of prior crayon protectors.
It is an object of the present invention to provide a crayon protector which is cylindrical in configuration and constructed of unbreakable, non-cuttable, yet flexible material.
It is a further object of the present invention to provide a crayon protector which substantially surrounds and reinforces a crayon at its break zone.
It is another object of the present invention to provide a crayon protector which is configured to be inserted onto a crayon, removed from the crayon after use, and reused on a different crayon.
It is still another object of the present invention to provide a crayon protector which has a longitudinal slit which allows it to be slidably inserted onto and removed from the crayon and also allows flexible expansion for the insertion of crayons of varying diameters.
It is still another object of the present invention to provide a crayon protector which is economical and efficiently manufactured for ready sale.
It is a further object of the present invention to provide a writing implement protector which can not only be used for crayons, but also for chalk, pastel and charcoal sticks, and similar breakable writing implements.
The present invention consists of a crayon protector comprising a covering which is substantially cylindrical in configuration. The covering is made of unbreakable, non-cuttable, yet flexible material, for instance molded plastic. The covering is configured with open ends and a longitudinal slit which prevents complete encircling of the crayon. The covering is inserted on a crayon and substantially surrounds and reinforces it from breakage at its break zone. The slit facilitates insertion and removal and allows flexible expansion of the covering for use with crayons of varying diameters. The protector can also be used to prevent breakage of other relatively easily breakable writing implements, like chalk, pastel, and charcoal sticks.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The crayon protector itself, however, as to its design, construction, and use, together with additional features and advantages thereof, are best understood upon review of the following detailed description with reference to the accompanying drawings.