Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F291/00—Macromolecular compounds obtained by polymerising monomers on to macromolecular compounds according to more than one of the groups C08F251/00 - C08F289/00
  • C08F291/02—Macromolecular compounds obtained by polymerising monomers on to macromolecular compounds according to more than one of the groups C08F251/00 - C08F289/00 on to elastomers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F279/00—Macromolecular compounds obtained by polymerising monomers on to polymers of monomers having two or more carbon-to-carbon double bonds as defined in group C08F36/00
  • C08F279/02—Macromolecular compounds obtained by polymerising monomers on to polymers of monomers having two or more carbon-to-carbon double bonds as defined in group C08F36/00 on to polymers of conjugated dienes

Definitions

• the present invention relates to a process for the manufacture of graft copolymers by polymerization-grafting in emulsion-suspension. This process makes it possible to obtain a product which, while retaining good mechanical properties, in particular of impact and tensile strength, has excellent hot fluidity and a very good surface appearance, in particular excellent gloss.
• the process consists in carrying out a prepolymerization grafting in aqueous emulsion in the presence of an elastomer latex necessarily in one-dimensional form and then, in order to remedy the drawbacks of the other processes which do not make it possible to obtain good quality products, to add at the end of the emulsion, just before passing into suspension, a new fraction of one-dimensional latex.
• the method applies to the manufacture of graft copolymers usually obtained by graft polymerization of a mixture of monomers composed of at least one vinyl aromatic derivative and at least one acrylic or methacrylic derivative on an elastomeric substrate containing ethylenic bonds.
• the term “one-dimensional latex”, as opposed to polydispersed latex, means a latex consisting of spherical particles all having strictly the same diameter. In reality, such an ideal product does not exist.
• a latex is characterized by the particle size distribution curve expressed in weight, number and surface area as it is shown in "Emulsion Polymerization” 1955 - Intersclence Publishers, Inc., 'New York - pages 293-294 s 'acting as polydispersed latex.
• a latex is therefore said to be monodimensional when its particle size distribution curves in weight, number and surface are practically superimposable, as shown in "High Polymer Latices" - 1966, Vol. 1 Maclaren and Sons LTD - London, pages 10 and 12.
• a latex is said to be one-dimensional when the ratio of its mean diameter D'p expressed in weight to its mean diameter Dn expressed in number is less to 1.1 with:
• the first step called emulsion polymerization
• 60 to 95% and preferably 70 to 90% of the total amount of the one-dimensional latex used in the composition of the graft copolymer is used, the rest of the latex , called complementary one-dimensional latex, being added at the end of the emulsion before the step of suspending the reaction medium and after the desired ax / b ratio is reached.
• This complementary one-dimensional latex is not necessarily the same as that used at the start of emulsion polymerization, the important thing being that it is a one-dimensional latex of graftable elastomer.
• the latex used at the start of the emulsion generally has a gel content of 80 to 95% for a swelling index of approximately 8 to 18.
• the stabilization systems are those commonly used, these are for example fatty acid soaps, alkyl and alkyl aryl sulfonates, salts of resin acids, water-soluble polyoxyalkylenes.
• the stabilization systems it is preferred to use the potassium or sodium salts of lauric acid in an amount of 0.1 to 4 parts by weight relative to the dry counted latex.
• all the elastomers having a minimum unsaturation rate of 3% by weight and being in the form of one-dimensional latex are suitable for the process which is the subject of the invention.
• These elastomers are either homopolymers, such as for example polyisoprene, polychloroprene, polybutadiene, or copolymers which, by way of indication, may be copolymers based on ethylene, propylene, isobutylene, or also copolymers of styrene and butadiene, acrylonitrile and butadiene.
• Natural rubber is also suitable as an elastomer in the process which is the subject of the invention.
• the most commonly used elastomers in the manufacture of the copolymers according to the invention are polybutadienes and copolymers of styrene and butadiene.
• the styrene content is usually less than 20% by weight.
• the monomers according to the process of the invention can be introduced entirely during the emulsion polymerization step. They can also be introduced separately or as a mixture, continuously or discontinuously. Additional monomer can also be introduced at the end of emulsion polymerization when the desired ax / b ratio is reached.
• vinyl aromatic derivatives which can be used as monomers in the process
• examples that may be mentioned include styrene, a-methylstyrene and substituted styrenes such as o-methylstyrene, m-methylstyrene, p-methylstyrene, dimethylstyrenes , trimethylstyrene and halogenostyrenes such as 2,5-dichlorostyrene.
• acrylic or methacrylic derivatives which can be used as monomers in the process, mention may also be made, by way of examples, of acrylic and methacrylic acids, methyl acrylate, ethyl acrylate, butyl acrylate, methacrylate. methyl, ethyl methacrylate, butyl methacrylate, acrylonitrile, methacrylonitrile.
• a third monomer such as, for example, vinyl chloride, a vinyl ester such as acetate or propionate, a vinyl ether such as ethyl vinyl ether.
• the mixtures of styrene and acrylonitrile are particularly suitable for the application of the process which is the subject of the invention.
• the weight ratio styrene-acrionionria is between 60/40 and 80/20 and preferably close to 70/30 so that the resin formed has a composition close to the azeotropic composition.
• the styrene-methyl methacrylate mixture is also well suited.
• the implementation of the process according to the invention can be carried out in a reactor provided with thermal regulation and with a stirring system suitable for the conventional emulsion and suspension processes.
• the operation is carried out in a known manner.
• the quantity of latex necessary for the manufacture of the graft copolymer in the emulsion phase and the monomers are introduced into the reactor containing the quantity of water sufficient for the reaction.
• the monomers can be introduced regularly during the emulsion polymerization by means, for example, of a metering pump.
• the stirring being such that good homogenization of the reaction medium is ensured, the temperature is maintained between 20 and 100 ° C and preferably between 40 ° C and 80 ° C.
• the reaction is continued until the selected ax / b ratio is reached.
• the complementary monodimensional latex is added as well as any additional monomer, then the suspension polymerization of the second stage of the process is started by introducing into the reaction medium a solution of protective colloids.
• This suspension polymerization is also carried out under known conditions of stirring, of temperature and of reaction time.
• the reaction temperature is generally between 40 and 150 ° C and preferably between 60 ° C and 120 ° C for a time sufficient for the complete polymerization of the monomers.
• the reactor When the reaction is complete, the reactor is emptied, then after decantation, centrifugation and drying, the graft copolymer is recovered in the form of beads.
• the dry pearls In general, the dry pearls contain less than 0.1% of residual monomers.
• the method described can also be carried out in other known ways. It is possible, for example, to carry out the emulsion-suspension polymerization continuously in several reactors in cascade.
• the initiators are generally of two types: those water-soluble traditionally effective in the processes of emulsion polymerization and those liposoluble preferable in suspension.
• initiators of emulsion polymerization potassium persulfate, ammonium persutfate, sodium peroxide, hydrogen peroxide, azo compounds such as azo-bis-isobutyronitrite or 2,2-azo-bis (2,4-dimethylvaleronitrile), and as suspension polymerization initiator: peroxy dicarbonates such as bis (4t-butyl cyclohexyl) peroxy dicarbonate, dicyclohexyl peroxydicarbonate, bis (2-ethyl hexyl) peroxydicarbonate, di-n butyl peroxy dicarbonate, dlisopropyl peroxydicarbonate; alkyl peroxides such as lauroyl peroxide, decanoyl peroxide; aromatic peroxides such as benzoyl
• the catalysts used are preferably potassium persulfate in the emulsion polymerization step and t-butyl perpivalate, lauroyl peroxide, di-ti-butyl perbenzoate used alone or in combination in the polymerization step in suspension. These catalysts are not exclusive. It is obvious that all the catalysts known for these types of polymerization are suitable for the process of the invention.
• chain transfer agents during the emulsion polymerization step is recommended to improve the fluidity of the final graft copolymer.
• the best known are linear or branched mercaptans, thioethers, the dimer of ⁇ -methylstyrene, certain olefinic compounds.
• the protective colloids used in the suspension polymerization step are well known conventional products. These are, for example, hydroxyethyl cellulose, methyl cellulose, polyacrylic acid, polyacrylamide, carboxy methyl methyl cellulose, polyvinyl alcohol, polyglycols, gelatins, water-soluble alginates and their mixture, the preferred ones being hydroxyethyl cellulose and polyvinyl alcohol. It is also possible to use mineral agents such as tricalcium phosphate for example. They are generally used in aqueous solution in an amount of 0.1 to 3 parts by weight relative to the weight of copolymer to be manufactured.
• a lubricant is added to the reaction mixture before the suspension polymerization step.
• lubricants are conventional, it can be mixtures of paraffin wax and hydrocarbon oil, refined mineral oils, or esters such as butyl stearate and dioctyl phthalate. They are used in amounts which can vary from 1 to 4 parts by weight per 100 parts by weight of graft copolymer.
• the method according to the invention makes it possible to manufacture graft copolymers containing by weight from 10 to 70% and preferably from 40 to 60% of elastomer.
• Grafted copolymers containing 40 to 70% of elastomer generally have very high resilience, which makes it possible to market grafted copolymers of different qualities prepared by mixing, at variable rates, of grafted copolymer with other polymers or copolymers .
• these grafted copolymers can be mixed with grafted copolymers of polyvinyl chloride on various elastomers, with acrylonitrile-butadiene-styrene copolymers, with grafted acrylonitrile and styrene copolymers on low-unsaturation elastomers such as copolymers.
• EPDM ethylene-propylene-diene monomer
• butyl or acrylic rubbers and also with resins such as polyvinyl chloride, styrene-acrylonitrile resins and their derivatives.
• resins such as polyvinyl chloride, styrene-acrylonitrile resins and their derivatives.
• Such mixtures usually have an elastomer content by weight of between 5 and 60% and more generally between 10 and 40%.
• This manufacturing process according to the invention of grafted copolymers reduces the agglomeration of the grafted latex in emulsion at the time of suspension, which gives the gloss of the final product and makes it possible, thanks to the new introduction of latex at the end of emulsion, to '' ensure the magnification of a sufficient number of particles to ensure good mechanical properties of the final product, cohesion of the whole being ensured by the polymerization-grafting in suspension of the rest of the monomers.
• This process has the advantage of being made from one-dimensional latexes.
• one-dimensional latexes have not made it possible to carry out a grafting such that the final product has both good mechanical properties, good fluidity and a suitable surface appearance.
• This advantage is of great interest, being well known that fine one-dimensional latexes can be easily produced inexpensively.
• the graft copolymers of the examples are mixed with the copolymer in an internal mixer.
• the mass is taken up in an open mixer, then granulated.
• the granules are injected using a screw press.
• the injection conditions for each of the qualities are as follows:
• the operation is carried out in a single reactor of 161 equipped with a temperature regulation operating between 30 and 140 ° C. and provided with an agitator whose speed of rotation is variable between 60 and 500 rpm the reactor is designed to withstand internal pressures below 15 bar and is provided with several orifices allowing various additions. Several metering pumps and several airlocks designed to withstand high pressures can be fitted to this reactor.
• the quantities of products used are expressed in parts by weight reduced to 100 parts by weight of graft copolymer.
• Comparative examples 1, 2 and 3 do not form part of the field of the invention, they are given by way of comparison and intended to clarify the limits and to show its advantages.
• reaction medium is suspended without having carried out emulsion polymerization beforehand.
• the graft copolymer prepared contains 50% polybutadiene, 38% styrene and 12% acrylonitrile.
• the reactor is loaded with 50 parts of latex counted as dry extract. The dilution is adjusted so that the total water, including that of the latex, is 160 parts. A solution of 0.5 parts of potassium persulfate in 5 parts of water is introduced, then a mixture containing 38 parts of styrene, 12 parts of acrylonitrile, 0.4 parts of tertiododecyl mercaptan, 1.5 parts of trinonyl phenyl phosphite, 0.2 part of perp i valate of t-butyl. 1.5 parts of polyvinyl alcohol, then dissolved in 50 parts of water, are then added. The reactor is closed. The mixture is stirred at 250 rpm and heated at 60 ° C for 10 hours.
• Comparative example 2 ax / b less than 30
• the suspension of the reaction medium takes place at a time when the grafting by emulsion polymerization is still insufficient.
• a graft copolymer containing 50% of polybutadiene, 38% of styrene and 12% of acrylonitrile is prepared.
• the reactor is loaded with the 50 parts of polybutadiene counted as dry extract.
• the dilution is adjusted to 150 parts of water, including that of the latex.
• the mixture is stirred at 80 rpm and heated to 62 ° C.
• a solution of 0.5 part of potassium persulfate in 10 parts of water is introduced, then a continuous supply of a mixture of 12.7 parts of styrene and 4 parts of acrylonitrile is started.
• introduced into the reactor in one hour of reaction at 60 ° C. A sample taken at this time gives a dry extract of 27.9%.
• the mechanical properties measured on quality 1 are as follows:
• the dry extract of 27.9% measured at the end of the emulsion grafting corresponds to a conversion rate of the monomers present actually introduced into the emulsion of 80%.
• the emulsion grafting is insufficient and it is found that the product has a high resilience but a clearly insufficient gloss.
• the graft copolymer is prepared only by emulsion polymerization.
• the latex used is identical to that of Example 1 but not stabilized.
• the graft copolymer prepared contains 50% polybutadiene, 38% styrene, 12% acrylonitrile.
• the reactor is loaded with the 50 parts of polybutadiene counted as dry extract.
• the dilution is adjusted with 180 parts of water.
• the mixture is heated to 62 ° C. with stirring at 80 rpm.
• a solution of 0.5 parts of potassium persulfate in 10 parts of water is introduced and a continuous addition of the monomers and a continuous addition of 2.5 parts of rosin salt in 35 parts of water are started simultaneously. , while maintaining the temperature at 60 ° C. These two continuous power supplies last 4 hours.
• the monomer mixture added consists of 38 parts of styrene, 12 parts of acrylonitrile and 0.35 part of tertiododecyl mercaptan. The reaction is then allowed to proceed at 60 ° C for 6 hours.
• the grafted copolymer is then flocculated using a solution of magnesium sulphate then dried and mixed with resin to give quality 1.
• the product obtained has a clearly insufficient Izod shock.
• the residual styrene at the end of the reaction is 0.7% and the residual moisture before drying is 43%.
• the average humidity before drying is of the order of 22% and the residual monomers are less than 0.1 % .
• ABS acrylonitrile-butadiene-styrene
• the reactor is loaded with A parts of latex 1 expressed by weight of dry extract - the reference of the latex is given in brackets in Table I.
• the dilution is adjusted so that the total water including that provided by the latex represents B parts.
• the stirring is brought to the reactor at 80 rpm and the reaction medium is heated to 62 ° C. C parts of potassium persulfate dissolved in 10 parts of water are added. the regulation is adjusted to 60 ° C. and the continuous feeding of the following mixture is started: styrene D parts, acrylonitrile E parts, tertiododecyl mercaptan (TDM) F parts.
• TDM tertiododecyl mercaptan
• This continuous supply carried out using a metering pump is adjusted with a flow rate such that all of the mixture is introduced into the reaction medium in G hours.
• a dry extract is made on a sample of the grafted latex. This dry extract is used to calculate the ax / b ratio.
• H parts of latex 2 are then introduced via an airlock - the reference of the latex is given in brackets in table 1 - the dilution of which has been adjusted beforehand so that the total water represents I parts then also through an airlock, J parts of styrene, K parts of acrylonitrile, L parts of CT, M parts of antioxidant of the phosphite type, N parts of t-butyl perpivalate, P parts of lauroyl peroxide, Q parts of t-butyl perbenzoate.
• the stirring is brought to 300 rpm and introduced by another airlock R parts of polyvinyl alcohol (PVA) dissolved in S parts of water.
• PVA polyvinyl alcohol
• Table 1 The suspension cycle indicated in Table 1 is then always carried out with stirring.
• the reactor is cooled and emptied.
• the pearls are washed with water, centrifuged and then dried in an oven. the mechanical properties of the mixtures are given in table II.
• a graft copolymer of the methyl methacrylate-butadiene-styrene (MBS) type is prepared.
• the reactor is loaded with 40 parts of latex “p” from Example 4 expressed as dry extract.
• the mixture is stirred at 80 rpm and the dilution is adjusted so that the total water represents 120 parts. It is heated to 65 ° C.
• a solution of 0.4 part of potassium persulfate in 8 parts of water is introduced and a continuous feeding of total duration 3 hours is started with a mixture composed of 28 parts of methyl methacrylate, 12 parts of styrene. and 0.2 part of tertiododecyl mercaptan.
• the graft copolymer beads are washed with lukewarm water, centrifuged and then dried.
• This graft copolymer is mixed, so that the final mixture contains 20% of polybutadiene, with a methyl methacrylate-styrene copolymer containing by weight 70% of methyl methacrylate and 30% of styrene, and of intrinsic viscosity measured in the dimethylformamide 0.5 dl / g.
• This mixture injected at 175 ° C at 120 bars has the following mechanical properties:

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• 1977
  • 1977-07-12 FR FR7721435A patent/FR2397431A1/fr active Granted
• 1978
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