CN102382218A - Aqueous dispersion of low molecular weight polytetrafluoroethylene and its manufacturing method - Google Patents
Aqueous dispersion of low molecular weight polytetrafluoroethylene and its manufacturing method Download PDFInfo
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Abstract
To provide a method for manufacturing an aqueous dispersion of a low molecular weight polytetrafluoroethylene (PTFE) on a low cost without addition of a fluorine-containing surfactant. The manufacturing method of the aqueous dispersion of the low mol.wt. polytetrafluoroethylene (PTFE) comprises performing the emulsion polymerization of tetrafluoroethylene (TFE) or a monomer copolymerizable with TFE and TFE without addition of a fluorine-containing surfactant, in the presence of a chain transfer agent and in an aqueous medium in which a polymerization initiator is dispersed. The chain transfer agent is at least one compound selected from the group consisting of hydrogen, 1-3C hydrocarbons and 1-3C halogenated hydrocarbons. The polymerization initiator is a water-soluble peroxide.
Description
The application divides an application, and the China national application number of its original application is 200810131815.8, and the applying date is on 06 24th, 2008, and denomination of invention is " aqueous dispersion of low molecular weight polytetrafluorethyleand and a method of manufacture thereof ".
Technical field
The present invention relates to aqueous dispersion of low molecular weight polytetrafluorethyleand and method of manufacture thereof.
Background technology
Molecular weight is that the low molecular weight polytetrafluoroethylene (PTFE) (being also referred to as the PTFE micro mist) below 600,000 has excellent chemicalstability, extremely low surface energy; Be difficult to take place fibrillation in addition; Thereby it is used to as the additive that improves sliding and film coated surface texture in the manufacturing of plastics, printing ink, makeup, coating, railway grease etc. (for example, referring to patent documentation 1) at present.
Method of manufacture as lower molecular weight PTFE; Known have a following method: at high temperature make HMW PTFE and specific fluorochemical come in contact reaction and (for example carry out the pyrolysated method; Referring to patent documentation 2), to the method (for example, referring to patent documentation 3) of the powder of HMW PTFE or formed body irradiation ionizing radiation etc.
There is the problem that generates harmful side products such as hydrogen fluoride in HMW PTFE pyrolysated method, makes the high problem of cost because of needs carry out fine operation but also exist.Method for the irradiation radioactive rays also generates harmful side products such as hydrogen fluoride, even relevant cost and the convenience aspect of slave unit also may not be favourable.And then, in the method, need the irradiation of the high radioactive rays of dose rate, but therefore the PTFE of radioactive rays more than 75kGry or electron beam irradiation can not be used for the direct purposes (for example, referring to non-patent literature 1) that contacts with human body in the U.S. not by the FDA permission.
As the method for manufacture of lower molecular weight PTFE, in the presence of chain-transfer agent, will also be known as the method for monomeric TFE direct polymerization.For example, in patent documentation 4, having proposed to use carbonatoms is that 1～3 fluoro paraffinic hydrocarbons or chlorine fluoro paraffinic hydrocarbons carry out the polymeric method as chain-transfer agent (telogen).
As industrial polymerization method, in the method like patent documentation 4, which kind of method to carry out polymerization and indeterminate with, but roughly be divided into suspension polymerization and letex polymerization.Consider that from the aspect that easy, the stricturization of MWD, the free fluorine ionic concn of operation are low the lower molecular weight PTFE that is directly obtained by polymerization is preferred.
In suspension polymerization; Polymerization starter is dispersed in the aqueous medium; Make as monomeric TFE polymerization or make can with the monomer and the TFE polymerization of TFE copolymerization, thus with the particulate powder direct separation (for example, referring to patent documentation 5 and 6) of lower molecular weight PTFE.Under the situation of suspension polymerization, can directly obtain the powder of lower molecular weight PTFE, and need not to use emulsifying agent, still be difficult to adjust the apparent density and the particle diameter of said powder.
Relative therewith; In letex polymerization, in the presence of chain-transfer agent, make polymerization starter and be dispersed in the aqueous medium as the fluorochemical surfactant of emulsifying agent; Make as monomeric TFE polymerization or make can with the monomer and the TFE polymerization of TFE copolymerization, obtain lower molecular weight PTFE thus.In this case, different with suspension polymerization, owing to there is a fluorochemical surfactant, therefore the state with the aqueous liquid dispersion that comprises the emulsified particle (being also referred to as micella, primary particle) below the 1 μ m obtains polymkeric substance (for example, referring to patent documentation 7).Resulting aqueous liquid dispersion can be directly or through being used for purposes such as water-borne coatings after it is concentrated.
When using the lower molecular weight PTFE that obtains by letex polymerization with pulverulence, can be through powder particle (micro mist) be processed in above-mentioned aqueous liquid dispersion condensation.
As the characteristic of the lower molecular weight PTFE powder particle that is obtained by letex polymerization, its specific surface area is than the big 5m of specific surface area of the lower molecular weight PTFE powder particle that is obtained by suspension polymerization
2/ g～15m
2/ g, and soft granules, the surface modification effect that therefore for example improves film coated surface texture etc. is higher.In addition, can obtain more than the oil number and the stable dispersion-s of substrate material.And, can adjust the aspect of apparent density and particle diameter, the lower molecular weight PTFE powder particle that preferably obtains from utilizing above-mentioned condensation process conditions by letex polymerization.
But, in above-mentioned letex polymerization, owing to need to use expensive material such as fluorochemical surfactant as emulsifying agent, so cost is higher.And, in the PTFE particle during remaining tensio-active agent, cause painted etc. sometimes.Therefore, seek not add these fluorochemical surfactants and the method for manufacture of carrying out polymeric PTFE.
Do not carry out the polymeric method as not adding fluorochemical surfactant, the TFE suspension polymerization that in aqueous medium, uses TFE and water-soluble peroxide to react is known (for example, referring to non-patent literature 2).In patent documentation 8, also put down in writing following content: do not add tensio-active agent, and in aqueous medium, be that polymerization starter carries out the TFE polymerization, thereby obtain aqueous liquid dispersion with the peroxo-disuccinic acid.
But the polymer solids constituent concentration of the aqueous liquid dispersion of putting down in writing among the embodiment of patent documentation 8 is very thin, is merely 6.5 weight %, if consider productivity, then lacks very much practicality.And, in patent documentation 8, do not put down in writing the emulsification particle diameter of the interpolation of any hint chain-transfer agent, resulting polymkeric substance and the data of molecular weight.
In addition; Because nearest result of study etc.; People have become obviously to the worry of the Perfluorocaprylic Acid [PFOA] that is used for letex polymerization (it is representational fluorochemical surfactant) to the load of environment gradually; EPA on April 14,2003 (USEPA) indicate to strengthen chemistry investigation (for example, referring to non-patent literature 3) to PFOA.
Patent documentation 1: japanese kokai publication hei 10-147617 communique
Patent documentation 2: japanese kokai publication sho 61-162503 communique
Patent documentation 3: japanese kokai publication sho 48-78252 communique
Patent documentation 4: japanese kokai publication sho 51-41085 communique
Patent documentation 5: No. 2004/050727 pph of International Publication
Patent documentation 6: Japan special hope 2005-2322 communique
Patent documentation 7: japanese kokai publication hei 7-165828 communique
Patent documentation 8: USP the 2nd, 534, No. 058
Non-patent literature 1:FDA file Sec.177.1550
Non-patent literature 2: " fluororesin handbook (the plain resin Ha of ふ つ Application De Block Star Network) editor: river, lining filial piety minister, Nikkan Kogyo Shimbun's (nineteen ninety), 27 pages
Non-patent literature 3:EPA reports " PRELIMINARY RISK ASSESSMENT OF THE DEVELOPMENTAL TOXICITY ASSOCIATED WITH EXPOSURE TO PERFLUOROOCTANOIC ACID AND ITS SALT ", the Internet URL:http: //www.epa.gov/opptintr/pfoa/pfoara.pfd >
Summary of the invention
In view of above-mentioned present situation, the object of the present invention is to provide the method for not using fluorochemical surfactant and making low molecular weight polytetrafluoroethylene with low cost.
The present invention relates to the method for manufacture of a kind of low molecular weight polytetrafluoroethylene (PTFE) aqueous liquid dispersion; This method for need not add fluorochemical surfactant and in the presence of chain-transfer agent, be dispersed with the letex polymerization of carrying out tetrafluoroethylene (TFE) in the aqueous medium of polymerization starter or can with the method for emulsion polymerization of the monomer and the TFE of TFE copolymerization; Said method is characterised in that; Said chain-transfer agent is that to be selected from by hydrogen, carbonatoms be that 1～3 hydrocarbon and carbonatoms are at least a compound in the group formed of 1～3 halohydrocarbon, and said polymerization starter is a water-soluble peroxide.
The present invention relates to lower molecular weight PTFE, it is characterized in that, said lower molecular weight PTFE is that the method for manufacture by above-mentioned lower molecular weight PTFE aqueous liquid dispersion obtains.
The present invention relates to lower molecular weight PTFE aqueous liquid dispersion, it is characterized in that, said lower molecular weight PTFE aqueous liquid dispersion is that the method for manufacture by above-mentioned lower molecular weight PTFE aqueous liquid dispersion obtains.
The present invention relates to lower molecular weight PTFE aqueous liquid dispersion, it is characterized in that, said lower molecular weight PTFE aqueous liquid dispersion does not contain Perfluorocaprylic Acid (PFOA) and salt and perfluorinated sulfonic acid (PFOS) and salt thereof in fact.
The present invention relates to lower molecular weight PTFE powder, it is characterized in that, said lower molecular weight PTFE powder is through obtaining the condensation of above-mentioned lower molecular weight PTFE aqueous liquid dispersion.
The present invention relates to lower molecular weight PTFE powder, it is characterized in that, the specific surface area of said lower molecular weight PTFE powder is 7m
2/ g～15m
2/ g and do not contain Perfluorocaprylic Acid (PFOA) in fact and salt and perfluorinated sulfonic acid (PFOS) and salt thereof.
The present invention relates to coating, it is characterized in that, said coating contains above-mentioned lower molecular weight PTFE.
The present invention relates to engineering plastics, it is characterized in that, said engineering plastics contain above-mentioned lower molecular weight PTFE.
The present invention relates to the material of making up, it is characterized in that said cosmetic material contains above-mentioned lower molecular weight PTFE.
The present invention relates to railway grease, it is characterized in that, said railway grease contains above-mentioned lower molecular weight PTFE.
The present invention relates to toning agent, it is characterized in that, said toning agent contains above-mentioned lower molecular weight PTFE.
The present invention relates to coating, it is characterized in that, said coating contains above-mentioned lower molecular weight PTFE powder.
The present invention relates to engineering plastics, it is characterized in that, said engineering plastics contain above-mentioned lower molecular weight PTFE powder.
The present invention relates to the material of making up, it is characterized in that said cosmetic material contains above-mentioned lower molecular weight PTFE powder.
The present invention relates to railway grease, it is characterized in that, said railway grease contains above-mentioned lower molecular weight PTFE powder.
The present invention relates to toning agent, it is characterized in that, said toning agent contains above-mentioned lower molecular weight PTFE powder.
Specify the present invention below.
Method of manufacture of the present invention is characterised in that it carries out letex polymerization under the condition of not adding fluorochemical surfactant; This method can obtain lower molecular weight PTFE with the state of aqueous liquid dispersion; There is not the above-mentioned problem that is caused by fluorochemical surfactant of the prior art in its low cost of manufacture.
Only use in aqueous medium not adding fluorochemical surfactant in the TFE suspension polymerization that TFE and water-soluble peroxide react; The known nuclear (emulsified particle) that in the initial system of reaction, likewise produces when carrying out letex polymerization; But in the polymer chain growth, emulsified particle generation aggegation, this agglutinating particle moves on the liquid level; Be reflected in the gas phase and carry out (for example, referring to non-patent literature 2).
It is generally acknowledged; For this for the polymerization of the TFE that does not add fluorochemical surfactant in the system; The polymer chain that has from the hydrophilic end group of water-soluble peroxide generated at the polymerization initial stage, and it has emulsifying effect, therefore in aqueous medium, formed emulsified particle.But think that along with the increase of the increase of the polymerization degree and the polymer solids constituent concentration in the aqueous medium, the emulsifying effect of the polymer chain of possess hydrophilic property end group significantly reduces, therefore the emulsified particle generation aggegation of instabilityization.
Relative therewith; In method of manufacture of the present invention; Surprisingly; Even do not add fluorochemical surfactant, in reaction system, also can keep polyreaction with emulsified state, can be that the state of the stabilized aqueous dispersion liquid about 12 quality % obtains lower molecular weight PTFE finally with solid component concentration.
And then; Through with by the same postprocessing working procedures of the resulting aqueous liquid dispersion of general emulsion polymerization of using fluorochemical surfactant; Can access lower molecular weight PTFE powder, and can this lower molecular weight PTFE powder be used for multiple use as various additives.
The mechanism that method of manufacture of the present invention demonstrates such excellent effect it be unclear that, but can infer, in polymerization of the present invention, owing to following situation obtains the aqueous liquid dispersion of TFE polymkeric substance with emulsified particle form stable dispersion:
(1) reaction through chain-transfer agent, water-soluble peroxide and TFE; Has the growth of hydrophilic end group that comes from water-soluble peroxide and polymer chain with emulsifying effect; But in the process of growth of this polymer chain; Chain-transfer agent and the chain transfer of polymkeric substance interchain cause the terminal inactivation of the growth of this polymer chain, therefore generate the TFE polymkeric substance of short chain, and the reduction of emulsifying effect can not take place along with the increase of the polymerization degree;
(2) higher as the chain transfer ability of the above-claimed cpd of above-mentioned chain-transfer agent, therefore the polymerization degree of above-mentioned short chain TFE polymkeric substance is lower, demonstrates higher emulsifying effectiveness;
(3) water-soluble peroxide also continues to decompose after the polymerization initial stage, and therefore the short chain TFE polymkeric substance of above-mentioned possess hydrophilic property end group continues to generate.
Promptly; In the present invention; Owing to use the water-soluble peroxide that hydrophilic radical is provided to polymer ends as polymerization starter and use the higher compound of chain transfer ability to carry out polymerization as chain-transfer agent, therefore can be at the solid component concentration after obtaining dispersion stabilization height and polymerization under the situation of not adding fluorochemical surfactant the aqueous liquid dispersion of high lower molecular weight PTFE.
Above-mentioned " lower molecular weight PTFE " typically refers to number-average molecular weight is the TFE polymkeric substance below 600,000.Number-average molecular weight demonstrates the distinctive fibrillation characteristic of PTFE (referring to patent documentation 1) greater than 600,000 " HMW PTFE ".The melt viscosity of HMW PTFE is high, has non melt processable.For HMW PTFE, can show the fibrillation characteristic when it is used as additive, so be prone between the PTFE particle aggegation takes place, dispersed relatively poor in substrate material.
The melt viscosity that above-mentioned lower molecular weight PTFE is preferably at 380 ℃ is 1 * 10
2(Pas)～7 * 10
5(Pas) TFE polymkeric substance.General as long as the melt viscosity of above-mentioned lower molecular weight PTFE in this scope, its number-average molecular weight just in above-mentioned scope (referring to patent documentation 1) then.
In this manual, lower molecular weight PTFE is meant that the melt viscosity at 380 ℃ is in the TFE polymkeric substance in the above-mentioned scope.
That is, the present invention relates to obtain through letex polymerization the polymerization method of such lower molecular weight PTFE.
In this manual; Above-mentioned melt viscosity is the following value that obtains of measuring: according to ASTM D 1238; Use the mouth mould of flow tester (Shimadzu Seisakusho Ltd.'s manufacturing) and
; Get 2g in advance at the sample of 380 ℃ of heating after 5 minutes, under the load of 0.7MPa, said sample is remained on said temperature and measure.Above-mentioned molecular-weight average is the value that is calculated respectively by the melt viscosity that utilizes said determination method mensuration to obtain.
Above-mentioned lower molecular weight PTFE is preferably fusing point at 324 ℃～333 ℃ TFE polymkeric substance.
In this manual, above-mentioned lower molecular weight PTFE both can be proplast (a TFE homopolymer), also can be modified Teflon (modified ptfe).
Above-mentioned TFE homopolymer is for only carrying out the polymkeric substance that polymerization obtains with tetrafluoroethylene (TFE) as monomer.
Above-mentioned modified ptfe is meant by the polymkeric substance that can obtain with the copolymerization of the modified monomer of TFE copolymerization and TFE.
Do not limit for the modified monomer in the above-mentioned modified ptfe is special,, for example can enumerate R 1216 perfluoroolefines such as (HFP) so long as can get final product with the monomer of TFE copolymerization; Trifluorochloroethylene fluorine chloro-alkenes such as (CTFE); Trifluoro-ethylene, vinylidene fluoride hydrogeneous fluoroolefins such as (VDF); Perfluoroalkyl vinyl ether; Perfluorobutyl ethylene; Ethene etc.In addition, employed modified monomer both can be a kind of, also can be two or more.
Do not limit for above-mentioned perfluoroalkyl vinyl ether is special, for example can enumerate with the perfluor unsaturated compound of following general formula (I) expression etc.
CF
2＝CF-ORf (I)
(in the formula, Rf representes the perfluor organic group.)
In this manual, above-mentioned " perfluor organic group " is meant, all is substituted by the organic group that fluorine atom forms with carbon atom bonded Wasserstoffatoms.Above-mentioned perfluor organic group can also have ether property oxygen.
As above-mentioned perfluoroalkyl vinyl ether, for example can enumerate, in above-mentioned general formula (I), Rf represent carbonatoms be 1～10 perfluoroalkyl perfluor (alkyl vinyl ether) (PAVE).The carbonatoms of above-mentioned perfluoroalkyl is preferably 1～5.
As the perfluoroalkyl among the above-mentioned PAVE, can enumerate for example perfluoro-methyl, perfluor ethyl, perfluoro propyl, perfluoro butyl, perfluor amyl group, perfluoro hexyl etc., but preferred perfluoroalkyl is the perfluoro propyl vinyl ether (PPVE) of perfluoro propyl.
As above-mentioned perfluoroalkyl vinyl ether, the perfluoroalkyl vinyl ether, Rf that further can enumerate Rf in the above-mentioned general formula (I) and be carbonatoms and be 4～9 perfluor (alkoxyalkyl) group is the perfluoroalkyl vinyl ether of the group represented with following formula
(in the formula, m representes 0 or 1～4 integer.), Rf is the perfluoroalkyl vinyl ether of the group represented of following formula
(in the formula, n representes 1～4 integer.), or the like.
As the modified monomer in the above-mentioned modified ptfe, preferred HFP, CTFE, VDF, PPVE, ethene.
In above-mentioned modified ptfe, above-mentioned modified monomer unit is preferably below the 1 quality % of total monomer units, more preferably 0.001 quality %～1 quality %.In this manual, above-mentioned modified monomer unit is the part of the molecular structure of modified ptfe, and it is meant the part from modified monomer; So-called total monomer units be meant in the molecular structure of modified ptfe from all monomeric parts.
Method of manufacture of the present invention is the method that the letex polymerization of under the situation of not adding fluorochemical surfactant, carrying out TFE obtains the stabilized aqueous dispersion liquid.In this manual, above-mentioned " under the situation of not adding fluorochemical surfactant, carrying out polymerization " be meant, do not add employed fluorochemical surfactant in the existing TFE letex polymerizations such as emulsifying agent of fluorocarbon system when polymerization begins and in the polymerization.
As stated; Compare with the letex polymerization of existing TFE; From not mixing the angle of fluorochemical surfactant when polymerization begins and the polymerization, method of manufacture of the present invention not only cost is low, and there is not the problem that is caused by fluorochemical surfactant in resulting lower molecular weight PTFE yet.
In this manual, above-mentioned fluorochemical surfactant is meant, contains the surface-active compound that demonstrates in the fluorochemicals of at least 1 fluorine atom in the molecular structure.As said fluorochemical surfactant; Can enumerate aspect practical by at least 1 Wasserstoffatoms by fluorine atom substituted carbonatoms be the tensio-active agent that hydrophilic radicals such as 7～12 hydrocarbon and carboxylic acid, carboxylate salt, sulfonic acid, sulfonic group constitute, in industry, can enumerate ammonium perfluorocaprylate, Perfluorocaprylic Acid sulfonium salt etc.
The method of manufacture of lower molecular weight PTFE of the present invention is in the presence of chain-transfer agent, to be dispersed with in the aqueous medium of water-soluble peroxide to carry out the TFE method of emulsion polymerization.
Above-mentioned aqueous medium is preferably the high purity pure water behind the de-ionized.
In the present invention, above-mentioned chain-transfer agent is that to be selected from by hydrogen, carbonatoms be that 1～3 hydrocarbon and carbonatoms are at least a compound in the group formed of 1～3 halohydrocarbon.
As above-mentioned carbonatoms is 1～3 hydrocarbon, can enumerate for example methane, ethane, propane, is 1～3 halohydrocarbon as above-mentioned carbonatoms, can enumerate for example methyl chloride, monochloroethane etc.Above-mentioned chain-transfer agent is preferably ethane or propane.
In method of manufacture of the present invention, above-mentioned chain-transfer agent can disposable interpolation before adding polymerization starter, also can above at twice interpolation before adding polymerization starter and in polyreaction, can also be added continuously in the system.
The addition of chain-transfer agent has different OK ranges along with the difference of the polymerizing conditions such as addition of its chain transfer ability, temperature of reaction, polymerization pressure or polymerization starter; Can not generally stipulate; But the addition of this chain-transfer agent is preferably 02 mole of %～20 mole % with respect to the TFE that exists in the reaction system, more preferably 1.0 moles of %～10 mole %.If said addition less than 02 mole of %, then may can not get the stabilized aqueous dispersion liquid with respect to the TFE that exists in the reaction system, and then possibly can not get the emulsified particle of lower molecular weight PTFE, and generate HMW PTFE.If said addition is greater than 20 moles of %; Be below the 100Pas then at 380 ℃ melt viscosity; The vaporization at high temperature composition is more, is inappropriate for the temperature of for example carrying out in the dispersive operation to matrix greater than the purposes of 300 ℃ of that kind, and purposes also is restricted sometimes.
In method of manufacture of the present invention,, can enumerate for example persulphate, water-soluble organo-peroxide as above-mentioned water-soluble peroxide.
As above-mentioned persulphate, can enumerate for example ammonium persulphate (APS), Potassium Persulphate (KPS).Known when persulphate is used for the polymerization starter of TFE, be mainly carboxyl (for example, patent documentation 3) from the end group of initiator.
As above-mentioned water-soluble organo-peroxide, can enumerate for example peroxo-disuccinic acid (DSP), peroxo-two pentanedioic acids.Said water-soluble organo-peroxide is the organo-peroxide of possess hydrophilic property functional group (for example carboxyl, sulfonic acid or hydroxyl); When these organo-peroxides are used for polymerization starter, be said hydrophilic end group from the polymer end groups of initiator.In the situation of peroxo-disuccinic acid, end group is a carboxyl.
As polymerization starter, both can only use a kind of above-mentioned water-soluble peroxide, also can use two or more.Wherein, the preferred polymers end group is the water-soluble peroxide of carboxyl.If consider suitable decomposition temperature, the simplicity of processing, cost, the polymer ends structure of said water-soluble peroxide, more preferably APS, KPS and DSP of polymerization starter then.
In the present invention; As stated, when any one system in persulphate, the water-soluble organo-peroxide is used for polymerization starter, become hydrophilic radical from the end of initiator; Even therefore under the situation that does not have fluorochemical surfactant, the stability of emulsion is also good.
The addition of above-mentioned water-soluble peroxide depends on the kind of this water-soluble peroxide, kind and the addition or the polymerizing conditions such as polymerization temperature and polymerization pressure of the chain-transfer agent that share to a great extent.Therefore; Suitable addition is according to the difference of polymerization system and difference; Can not generally stipulate, but have the angle of polymer chain of the hydrophilic end group of the emulsifying effect of providing from generation, said water-soluble peroxide is 20ppm～3000ppm with respect to aqueous medium preferably.If above-mentioned addition less than 20ppm, then generates HMW PTFE with respect to aqueous medium sometimes, and can not get the emulsified particle of lower molecular weight PTFE, as stated, it is bad to be prone to dispersion in matrix, to occur.
Method of manufacture of the present invention is preferably carried out in the presence of stablizer.As stablizer, preferred paraffin (paraffin wax, carbonatoms are the hydrocarbon 16 or more), contain fluorocarbon oil, fluoride compound, silicone oil etc., wherein preferred paraffin.Melting point of paraffin wax is preferably 40 ℃～65 ℃ usually.Through in the aqueous medium that comprises such stablizer, carrying out letex polymerization, can hinder the aggegation between the emulsified particle that generates in the polymerization system, can obtain lower molecular weight PTFE with the form of more stable emulsified particle.
From more stably making lower molecular weight PTFE emulsive angle, preferred above-mentioned paraffin is 0.1 mass parts～12 mass parts with respect to 100 mass parts aqueous mediums.With respect to 100 mass parts aqueous mediums, be limited to 1 mass parts under above-mentioned content is preferred, be limited to 8 mass parts on preferred.
Method of manufacture of the present invention is to constitute through the letex polymerization of in the aqueous medium of the stablizer that contains above-mentioned chain-transfer agent and water-soluble peroxide and add in case of necessity, carrying out TFE.
In above-mentioned polymerization, polymerizing conditions such as polymerization temperature, polymerization pressure are not special to be limited, and can wait suitable the selection according to the kind of employed TFE amount, modified monomer and the amount or the productivity of modified monomer.
Above-mentioned polymerization temperature is preferably 5 ℃～100 ℃, more preferably 50 ℃～90 ℃.
Above-mentioned polymerization pressure is preferably 0.1MPa～3.0MPa.
The above-mentioned emulsion polymerization can begin as follows: in the pressure-resistant reaction vessel that is equipped with stirrer, drop into aqueous medium, chain-transfer agent, monomer and stablizer in case of necessity, behind the adjustment temperature and pressure, add polymerization starter, begin letex polymerization thus.Said letex polymerization can be supplied with under the monomeric condition in said aqueous medium on the limit and carry out.
In the above-mentioned polymerization,, except that TFE, can also add modified monomer as stated as above-mentioned monomer.
Preferred on one side above-mentioned aqueous medium the stirring carried out the above-mentioned emulsion polymerization on one side; If but stirred strong; Then mechanical shear stress causes the emulsified particle aggegation; Polyreaction is carried out at liquid-vapo(u)r interface, and result's generation sometimes can not get the emulsified particle that is formed by lower molecular weight PTFE by the polymerization that suspension polymerization causes.Therefore, in said letex polymerization, as reaction scale, polymerization temperature and the polymerization pressure of polymerizing condition when identical, compare, preferably reduce stirring velocity with the suspension polymerization of general fluoropolymer.
Above-mentioned emulsion polymeric stirring velocity can not generate the condensation particle through the observation liquid-vapo(u)r interface to suit to select according to polymerization scale and other polymerizing conditions, does not limit especially.
In method of manufacture of the present invention, can through carry out above-mentioned letex polymerization obtain lower molecular weight PTFE aqueous liquid dispersion (latex, latex).Said aqueous liquid dispersion generally is that the emulsified particle below the 1 μ m of lower molecular weight PTFE is dispersed in the aqueous medium and forms.
Consider that from the aspect of dispersion stabilization the average primary particle diameter of preferred above-mentioned emulsified particle is 100nm～300nm.Though do not add fluorochemical surfactant, it is 100nm～300nm that method of manufacture of the present invention can make average primary particle diameter.
In this manual, above-mentioned " average primary particle diameter " is meant the median size of the emulsified particle of the lower molecular weight PTFE in the aqueous liquid dispersion (aqueous liquid dispersion after the so-called polymerization) of processing such as after polymerization stops, concentrating, dilute, make with extra care.
Above-mentioned average primary particle diameter is following definite: lower molecular weight PTFE concentration is adjusted to 0.22 quality % obtain aqueous liquid dispersion; Measure the transmitance of 550nm projection light with respect to this aqueous liquid dispersion of unit length; And through average primary particle diameter is measured to confirm in the directed footpath in the transmission electron microscope photo; Make working curve by above-mentioned transmitance and average primary particle diameter; For aqueous liquid dispersion as determination object, measure above-mentioned transmitance, confirm its average primary particle diameter based on said working curve.
For through carrying out the resulting aqueous liquid dispersion of above-mentioned letex polymerization, the solid component concentration that generally can under the state after the polymerization, make lower molecular weight PTFE is 7 quality %～25 quality %.Consider productivity, above-mentioned content preferably is limited to 8 quality % down, is limited to 10 quality % under preferred.
In this manual, the solid component concentration of lower molecular weight PTFE is obtained as following ratio: determination object 150 ℃ of dryings 3 hours, is obtained the quality (Zg) that the adds thermal residue ratio with respect to the quality (Xg) of this determination object.
Lower molecular weight PTFE also is one of the present invention, it is characterized in that, said lower molecular weight PTFE is obtained by above-mentioned method of manufacture of the present invention.
Lower molecular weight PTFE of the present invention can be aqueous liquid dispersion, powder (micro mist) or random shape.
As stated, lower molecular weight PTFE of the present invention is generally 7 * 10 at 380 ℃ melt viscosity
5Below the Pas.
Above-mentioned melt viscosity is preferably 5 * 10
4Below the Pas.
Even lower molecular weight PTFE of the present invention is aqueous liquid dispersion, powder or random shape; Can under the situation of not adding existing fluorochemical surfactant, make, therefore lower molecular weight PTFE of the present invention does not contain Perfluorocaprylic Acid (PFOA) and salt and perfluorinated sulfonic acid (PFOS) and salt thereof in fact yet.If lower molecular weight PTFE of the present invention does not contain Perfluorocaprylic Acid (PFOA) and salt and perfluorinated sulfonic acid (PFOS) and salt thereof in fact, therefore painted in the time of then can suppressing moulding be favourable.
In this manual, " not containing in fact " is meant, do not use them as raw material, and its content is that polymer solids becomes below the 100ppb of component.
The aqueous liquid dispersion of above-mentioned lower molecular weight PTFE both can be the aqueous liquid dispersion that directly obtains through the above-mentioned emulsion polymerization, also can be to the aqueous liquid dispersion after the aftertreatments such as said aqueous liquid dispersion concentrates, dilutes, makes with extra care.Said aftertreatment can utilize existing known method to carry out, not special the qualification.As said spissated method, can enumerate for example cloud point method of enrichment (layer partition method).
Above-mentioned aqueous liquid dispersion preferably contains the lower molecular weight PTFE particle that average primary particle diameter is 100nm～300nm.
Consider that from aspects such as the property handled in the aqueous liquid dispersion of above-mentioned lower molecular weight PTFE, the solid component concentration of preferred lower molecular weight PTFE is 20 quality %～80 quality %.Aqueous liquid dispersion with the solid component concentration in the above-mentioned scope can obtain through after accomplishing the above-mentioned emulsion polymerization, concentrating.
The powder of above-mentioned lower molecular weight PTFE can be through obtaining above-mentioned aqueous liquid dispersion condensation.Therefore that is, above-mentioned powder is a raw material with the aqueous liquid dispersion that obtains through letex polymerization, aftertreatment such as can not pulverize and obtains said powder, and can control its apparent density and median size.
Consider that from the property handled aspect the median size of preferred above-mentioned lower molecular weight PTFE powder is 1 μ m～30 μ m, more preferably 2 μ m～20 μ m.Median size is prone to fly upward owing to apparent density is little less than the powder of 1 μ m, and the property handled is relatively poor.Median size is difficult to fine dispersion in substrate material greater than the powder of 30 μ m, in substrate material, is prone to the block of lower molecular weight PTFE.
For above-mentioned median size; Use laser diffraction formula particle size distribution device (Japanese laser society make); Do not use cascade, under pressure 0.1MPa, 3 seconds condition of minute, measure size-grade distribution, said median size equals 50% corresponding particle diameter with resulting size-grade distribution integration.
As stated, the lower molecular weight PTFE powder that utilizes letex polymerization to obtain is that the aggegation through emulsified particle forms, so its specific surface area is generally 7m
2/ g～15m
2/ g is greater than the lower molecular weight PTFE powder that utilizes suspension polymerization directly to obtain.If said specific surface area is big, soft granules then, the surface modification effect that for example improves film coated surface texture etc. is higher.And, can obtain more than the oil number and the stable dispersion-s of substrate material.Thereby the specific surface area of said lower molecular weight PTFE is preferably 9m
2/ g～15m
2/ g.If said specific surface area is less than 7m
2/ g, then the fine dispersion in substrate material is relatively poor.
In this manual, utilize surface analysis meter (trade(brand)name: MONOSORB, QUANTA CHLROME society makes), the mixed gas that uses 30% nitrogen, 70% helium adopts liquid nitrogen to cool off as carrier gas, utilizes BET method measurement the specific area.
As the method for the aqueous liquid dispersion of above-mentioned lower molecular weight PTFE being carried out condensation; The general using mechanical shear stress makes the emulsified particle aggegation; But from reducing the angle that remains in the polymkeric substance of aqueous phase after the condensation; Preferably add ionogen such as nitric acid, sulfuric acid, an ammonium nitrate in the aqueous liquid dispersion before condensation as the condensation agent; When in ionogen, using acid, after the preferred condensation with in the alkali such as sodium hydroxide or Pottasium Hydroxide with condensation after water and condensation particle, and preferably further again with pure water cleaning condensation particle.
The lower molecular weight PTFE aqueous liquid dispersion and the specific surface area that do not contain Perfluorocaprylic Acid (PFOA) and salt thereof and perfluorinated sulfonic acid (PFOS) and salt thereof in fact are 7m
2/ g～15m
2/ g and the lower molecular weight PTFE powder that does not contain PFOA, PFOS and their salt in fact also belong to category of the present invention.
Such lower molecular weight PTFE aqueous liquid dispersion and lower molecular weight PTFE powder can be through embodiment of the present invention lower molecular weight PTFE aqueous liquid dispersion method of manufacture and easily obtain.
In addition; From not containing the angle of nonionogenic tenside in fact; Lower molecular weight PTFE aqueous liquid dispersion of the present invention is different from existing aqueous liquid dispersion, and existing aqueous liquid dispersion is to utilize nonionogenic tenside to make to reduce after the aqueous liquid dispersion stabilization of existing PFOA of containing and PFOS again or remove PFOA and PFOS and the aqueous liquid dispersion that obtains.
As the method that reduces or remove the fluorochemical surfactant in the aqueous liquid dispersion; For example can enumerate; Carry out the method (the special 2002-532583 of showing of Japan communique) of ion exchange resin treatment, the spissated method (No. 2004/050719 communique of international publication) that repeats to utilize cloud point, the method (japanese kokai publication sho 55-120630 communique) of use ultrafiltrationmembrane process etc.; Even the present invention does not use these methods, do not contain PFOA and PFOS in fact yet.
As stated, lower molecular weight PTFE of the present invention obtains under the situation of not adding fluorochemical surfactant, does not therefore have painted grade by the problem due to this tensio-active agent.Thereby said lower molecular weight PTFE can be used as additive aptly.
Do not limit for the purposes of above-mentioned additive is special, it can be aptly with the additive of doing formed material, printing ink, cosmetic material, coating, railway grease, toning agent are carried out modification.
As above-mentioned formed material, can enumerate for example engineering plastics such as polyoxy benzoyl polyester, polyimide, polymeric amide, polyamidoimide, polyacetal, polycarbonate, polyphenylene sulfide.
The additive that lower molecular weight PTFE of the present invention can be used as formed material suitably is used for for example following purposes: be used to improve the not viscosity of photocopying roll and the purposes of sliding properties; The purposes of the texture of the engineering plastics moulding article such as cover of the sheet surface layer of raising furniture, the test board of automobile, tame electrical article; The sliding of the mechanical part of generation mechanical frictions such as the button of raising light load bearing, gear, cam, push-button telephone, projector, camera component, sliding material and the purposes of wear resistance; And as the processing aid of engineering plastics etc.
Lower molecular weight PTFE of the present invention can be used as the additive of coating to improve the sliding of varnish and coating.
Lower molecular weight PTFE of the present invention can be as the additive of the material of making up with the sliding that improves makeup such as foundation cream etc.
In addition, lower molecular weight PTFE of the present invention also be suitable for improving grease proofness or the water-repellancy of wax etc. purposes, improve the purposes of the sliding of railway grease and toning agent.
The formed materials such as engineering plastics, coating, cosmetic material, railway grease or the toning agent that contain such lower molecular weight PTFE also are one of the present invention.In addition, the formed materials such as engineering plastics, coating, cosmetic material, railway grease or the toning agent that contain above-mentioned lower molecular weight PTFE powder also are one of the present invention.
The method of manufacture of lower molecular weight PTFE aqueous liquid dispersion of the present invention is owing to have above-mentioned formation; Thereby can under the situation of not using fluorochemical surfactant, carry out letex polymerization, can produce aqueous liquid dispersion and the powder of lower molecular weight PTFE thus with low cost.Lower molecular weight PTFE of the present invention does not contain PFOA, PFOS and their salt in fact, and it can be aptly with the additive of doing formed material, printing ink, makeup, coating, railway grease, toning agent etc. are carried out modification.The specific surface area of the powder that is obtained by aqueous liquid dispersion is bigger, is 7m
2/ g～15m
2/ g, the fine good dispersibility in substrate material, surface modification effect is also high.
Embodiment
The present invention will be described in more detail to enumerate embodiment below, but the present invention is not limited in said embodiment.In addition, only otherwise special declaration, " part " in each embodiment and the comparative example and " % " are meant " mass parts " and " quality % " respectively.
Comparative example 1
Use the telescopic internal volume to drop into the 3.2L deionized water in as the stainless steel autoclave of 6L and 3.2g is the ammonium perfluorocaprylate (APFO) of emulsifying agent as fluorine, airtight autoclave to being equipped with stainless steel anchor type stirring rake and temperature regulation.Through repeating being pressed into, outgasing of nitrogen more than 2 times, remove the oxygen in the system, utilize ethane that tetrafluoroethylene (TFE) is pressed into 0.8g as chain-transfer agent then, the groove internal pressure is made as 0.10MPa.Under the stirring of 500rpm, with heating up in the groove, after temperature reaches 85 ℃ in the groove, be pressed into TFE once more, the groove internal pressure is adjusted to 0.80MPa.
To utilize TFE to be pressed in the groove as the aqueous solution (it dissolves 425mg ammonium persulphate (APS) and obtains in the 20ml deionized water) of polymerization starter.The decomposition of polymerization starter causes the groove internal pressure to reduce, and therefore supplies with TFE continuously, and the groove internal pressure is maintained 0.80 ± 0.05MPa.In the reaction always with temperature regulation in the groove at 85 ± 1 ℃, mixing speed is controlled to be 500rpm.At the consumption of TFE is moment of 800g to stop to stir, and the groove internal pressure is opened into normal pressure, next uses the nitrogen replacement gas phase, thereby obtains the aqueous liquid dispersion of lower molecular weight PTFE.
In the above-mentioned lower molecular weight PTFE aqueous liquid dispersion of 2000g, add 2g nitric acid; Make its condensation through giving violent mechanical shear stress; Next the powder of resulting moisture state is washed; Filter then, utilize 160 ℃ dry 18 hours of heated air circulation type drying machine, obtain the powder of lower molecular weight PTFE thus.
Comparative example 2
In system, do not add APFO and ethane; Interpolation 850mg ammonium persulphate (APS) is dissolved in the 20ml deionized water and the aqueous solution that obtains as polymerization starter; Stirring velocity in the reaction is controlled at 700rpm, in addition, likewise carries out polyreaction with comparative example 1.At the consumption of TFE is moment of 355g to stop to stir.Liquid-vapo(u)r interface in the reaction vessel after the polymerization particle diameter that swimming is the polymer beads more than the 1000 μ m, therefore said particle is reclaimed.
Powder to resulting moisture state is washed, and filters then, utilizes 160 ℃ dry 18 hours of heated air circulation type drying machine, obtains the powder of TFE polymkeric substance thus.The resulting powder output in dry back is 349g.
Comparative example 3
The addition of ethane is become 2g, the addition of APS is become 850mg, in addition, likewise obtain the aqueous liquid dispersion of PTFE with comparative example 1.
Above-mentioned aqueous liquid dispersion and comparative example 1 are likewise carried out condensation, cleaning, drying process, obtain the powder of lower molecular weight PTFE.
Embodiment 1
In system, do not add APFO, and to make polymerization starter and chain-transfer agent be the amount shown in the table 1, the stirring velocity in the reaction is controlled to be 700rpm, in addition, likewise obtain the aqueous liquid dispersion of lower molecular weight PTFE with comparative example 1.In resulting aqueous liquid dispersion, polymer beads does not almost appear on liquid-vapo(u)r interface.
Above-mentioned aqueous liquid dispersion and comparative example 1 are likewise carried out condensation, cleaning, drying process, obtain lower molecular weight PTFE powder as object.
The TDS-80C (the first industrial pharmacy) that in above-mentioned aqueous liquid dispersion, adds quality with respect to lower molecular weight PTFE and be 6.0 quality % is a tensio-active agent as nonionic; After utilizing ammoniacal liquor that pH is adjusted to 9.0 again; Leave standstill under 65 ℃ temperature in normal pressure; Make moisture evaporation thus and concentrate, so that the solids component of lower molecular weight PTFE reaches 60 quality %.The average primary particle diameter of the PTFE primary particle in the aqueous liquid dispersion after concentrating is identical with concentrated preceding aqueous liquid dispersion.
Embodiment 2
Stirring velocity in the reaction is controlled to be 600rpm, in addition, likewise obtains the aqueous liquid dispersion of lower molecular weight PTFE with embodiment 1.In resulting aqueous liquid dispersion, polymer beads does not almost appear on liquid-vapo(u)r interface.
Above-mentioned aqueous liquid dispersion and embodiment 1 are likewise carried out condensation, cleaning, drying process, obtain lower molecular weight PTFE powder as object.
Embodiment 3
Stirring velocity in the reaction is controlled to be 500rpm, in addition, likewise obtains the aqueous liquid dispersion of lower molecular weight PTFE with embodiment 1.In resulting aqueous liquid dispersion, polymer beads does not almost appear on liquid-vapo(u)r interface.Above-mentioned aqueous liquid dispersion and embodiment 1 are likewise carried out condensation, cleaning, drying process, obtain powder as the lower molecular weight PTFE of object.
The aqueous liquid dispersion of the lower molecular weight PTFE that in each embodiment and comparative example 1, obtains is carried out the physical property evaluation of following (1)～(2), the powder that in each embodiment and each comparative example, obtains is carried out the physical property evaluation of following (3)～(7).
(1) solid component concentration in the aqueous liquid dispersion (P%)
150 ℃ of heating 3 hours, utilize formula: P=Z/X * 100 (%) to confirm said solid component concentration (P%) aqueous liquid dispersion (Xg) based on the thermal residue (Zg) that adds after the heating.
(2) average primary particle diameter
Adjust to the aqueous liquid dispersion of 0.22 quality % for the concentration of polymkeric substance; Measure the transmitance of 550nm projection light with respect to this aqueous liquid dispersion of unit length; And confirm average primary particle diameter through the directed footpath of measuring in the transmission electron microscope photo, make working curve by above-mentioned transmitance and average primary particle diameter, for aqueous liquid dispersion as determination object; Measure above-mentioned transmitance, confirm its average primary particle diameter based on said working curve.
(3) apparent density
Measure according to JIS K 6891.
(4) median size
Use laser diffraction formula particle size distribution device (Japanese laser society make); Do not use cascade; Under pressure 0.1MPa, 3 seconds condition of minute, measure size-grade distribution, it is 50% o'clock pairing particle diameter that said median size equals resulting size-grade distribution integration.
(5) melt viscosity
According to ASTM D 1238; Use the mouth mould of flow tester (Shimadzu Seisakusho Ltd.'s manufacturing) and
; Get 2g and measuring the sample of temperature (340 ℃ or 380 ℃) heating after 5 minutes in advance, under the load of 0.7MPa, said sample is remained on said temperature and measure.
(6) fusing point
The differential scanning calorimetric determination device RDC220 (DSC) that uses SII NanoTechnology society to make; After using indium, lead to carry out temperature correction in advance as standard model; About 3mg lower molecular weight PTFE powder is put into aluminum ware (press seal container); Under 200ml/ minute airflow, heat up with 10 ℃/minute 250 ℃～380 ℃ temperature provinces, be fusing point with the melting caloric smallest point in the said zone.
(7) specific surface area
Utilize the BET method, use surface analysis meter (trade(brand)name: MONOSORB, QUANTA CHLROME society make), measurement the specific area.In addition, the mixed gas that uses 30% nitrogen, 70% helium uses liquid nitrogen to cool off as carrier gas.
Above result lists in table 1.
[table 1]
The melt viscosity of ※ 1 sample is very high, more than the mensuration upper limit for flow tester (Shimadzu Seisakusho Ltd.'s manufacturing).
Can know by above result; In each embodiment; The aqueous liquid dispersion that can likewise not contained the emulsified particle that lower molecular weight PTFE of APFO and perfluorinated sulfonic acid with the comparative example that has carried out letex polymerization 1, but in the comparative example that does not use ethane 2, can not get lower molecular weight PTFE; And can not get aqueous dispersion as resultant, can not utilize letex polymerization to react.
Industrial applicibility
The method of manufacture of lower molecular weight PTFE aqueous liquid dispersion of the present invention is owing to have above-mentioned formation, thereby can make lower molecular weight PTFE with low cost.Lower molecular weight PTFE of the present invention can be aptly with the additive of doing formed material, printing ink, makeup, coating, railway grease, toning agent etc. are carried out modification.By the fine good dispersibility of powder in substrate material that aqueous liquid dispersion obtains, the modified effect on surface is also high.
Claims (2)
1. a lower molecular weight PTFE aqueous liquid dispersion is characterized in that, said lower molecular weight PTFE aqueous liquid dispersion does not contain Perfluorocaprylic Acid (PFOA) and salt and perfluorinated sulfonic acid (PFOS) and salt thereof in fact.
2. a lower molecular weight PTFE powder is characterized in that, the specific surface area of said lower molecular weight PTFE powder is 7m
2/ g～15m
2/ g and do not contain Perfluorocaprylic Acid (PFOA) in fact and salt and perfluorinated sulfonic acid (PFOS) and salt thereof.
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| JP5287310B2 (en) * | 2009-02-06 | 2013-09-11 | ダイキン工業株式会社 | Low molecular weight polytetrafluoroethylene aqueous dispersion, low molecular weight polytetrafluoroethylene powder and method for producing low molecular weight polytetrafluoroethylene |
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| JP6958640B2 (en) * | 2018-02-07 | 2021-11-02 | ダイキン工業株式会社 | Method for Producing Composition Containing Low Molecular Weight Polytetrafluoroethylene |
| JP7078441B2 (en) * | 2018-04-05 | 2022-05-31 | 三菱鉛筆株式会社 | Polytetrafluoroethylene aqueous dispersion |
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