Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J151/00—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
  • C09J151/003—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
• • 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
  • C08F257/00—Macromolecular compounds obtained by polymerising monomers on to polymers of aromatic monomers as defined in group C08F12/00
  • C08F257/02—Macromolecular compounds obtained by polymerising monomers on to polymers of aromatic monomers as defined in group C08F12/00 on to polymers of styrene or alkyl-substituted styrenes

Definitions

• the present invention relates to a process for producing aqueous latexes essentially consisting of composite polymeric particles, which comprises:
• step (a) a first radicalic polymerization step in aqueous emulsion of monomers selected from vinylaromatics and mixtures of vinylaromatics/conjugated dienes, thus obtaining the first latex;
• step (b) a second radicalic polymerization step in aqueous emulsion which consists in polymerizing, on the latex obtained in step (a) , chloroprene or mixtures of chloroprene and monomers copolymerizable with chloroprene, the latter in a quantity not higher than 10% by weight with respect to the chloroprene, thus obtaining the latex object of the present invention.
• Polychloroprene is a special rubber mainly consisting of the homopolymer of chloroprene, its properties are: resistance to gasolines, ozone and aging; flexibility at low temperatures; good adhesion; tensile and elasticity properties after vulcanization; flame resistance and therefore with a wide range of applications both as a rubber and as latex.
• .it is used in the production of rubber articles, cables, glues and adhesives.
• CR has the tendency of crystallizing; this leads to an increase in the viscosity of the raw compounds and hardness of the vulcanized products.
• the crystallization rate can be attenuated by reducing the content of the 1,4-trans configuration. This can be obtained with a higher polymerization temperature (increasing however the 1,4-trans configuration and 1,2- and 3,4- structures) or by inserting a comonomer.
• Copolymers with methacrylic acid however are obtained using particular expedients, such as: polymerization at pH 2 ⁇ 4 polymerization technology in semi-continuous.
• the present invention relates to a process for producing aqueous latexes which comprises : a) a first radicalic polymerization step in aqueous emulsion of a polymerizable composition ( essentially consisting of vinylaromatic monomers or mixtures of vinylaromatics/conjugated dienes, preferably styrene or sty- rene/conjugated diene mixtures, even more preferably sty- rene or styrene/butadiene mixtures, thus obtaining a first la ex;
• a polymerizable composition essentially consisting of vinylaromatic monomers or mixtures of vinylaromatics/conjugated dienes, preferably styrene or sty- rene/conjugated diene mixtures, even more preferably sty- rene or styrene/butadiene mixtures, thus obtaining a first la ex;
• step (b) a second radicalic polymerization step in aqueous emulsion which consists in polymerizing, on the latex obtained in step (a) , chloroprene or mixtures of chloroprene and monomers copolymerizable with chloroprene, the latter in a quantity not higher than 10% by weight with respect to the chloroprene, thus obtaining the latex object of the present invention.
• step (a) the polymerization of a styrene-butadiene mixture is effected, in which the styrene varies from 100% by weight to 30% by weight .
• latexes are obtained with composite particles in which the chloroprene is bound, partly physically, partly chemically, to other monomers in polymeric form.
• the latex obtained at the end of step (a) consists of polymeric particles deriving from the homopolymerization of vinylaromatic compounds or the copolymerization of these with conjugated dienes.
• Typical examples of vinylarom tic compounds are styrene, ⁇ -methyl styrene, ⁇ -methyl styrene, 4-methylstyrene.
• Typical examples of conjugated dienes are 1,3-butadiene and isoprene.
• chloroprene can also be used as co- monomer, mixed with the above monomers in a ratio ranging from 0% to 15% by weight, preferably from 0% to 10% by weight, of the total of monomers used.
• the second step of the process of the present inven- tion consists in polymerizing, on the latex obtained in step (a) , chloroprene or mixtures of chloroprene and monomers copolymerizable with chloroprene, the latter in a quantity not higher than 10% by weight with respect to the chloroprene, thus obtaining the latex object of the present invention.
• the polymerization can be carried out in the presence of either ionic or non-ionic emulsifying agents, or a mixture of both, at temperatures ranging from 5°C to 120°C, preferably from 10°C to 90°C, in an acid, neutral or basic aqueous medium.
• the pH can be regulated with the addition of a mineral acid or non-polymerizable organic acids soluble in water such as acetic acid, the system can be buffered to prevent a shift in the pH during the reaction with sodium phosphate or carbonate.
• the polym- erization is started by radicals which can be generated either by the thermal decomposition of peroxides or diazo- compounds or by oxide-reduction reaction (redox pair) .
• the initiator system used for the polymerization comprises: salts soluble in water of peroxydisulf ric acid such as sodium, potassium and ammonium, organic peroxides such as diisopropyl benzene hydroperoxide, tertiary butyl hydroperoxide, pinane hydroperoxide and preferably redox systems.
• peroxydisulf ric acid such as sodium, potassium and ammonium
• organic peroxides such as diisopropyl benzene hydroperoxide, tertiary butyl hydroperoxide, pinane hydroperoxide and preferably redox systems.
• redox systems include the combination of sodium peroxydisulfate/sodium dithionite, diisopropyl benzene hydroperoxide/sulfoxylated sodium formaldehyde; other redox systems use bivalent iron as reducing agent combined with auxiliary reducing agents (sulfoxylated sodium formaldehyde) .
• Emulsifying agents which can be used are both anionic and non-ionic; the former can be alkyl aryl sulfonates containing up to 18 carbon atoms in the alkyl chain, alkyl sulfates and alkyl sulfonates, condensation products of formaldehyde with naphthalene sulfonic acid, sodium and potassium salts of resinic acids, oleic acid and fatty acids.
• the non-ionic emulsifying agents used are condensation products of ethylene and propylene oxide with alkyl phenols.
• the polymerization is carried out in the presence of molecular weight regulators to regulate both the gel and the molecular weight of the polymer itself without significantly altering the polymerization kinetics .
• the molecular weight regulators which can be used are: dialkyl xanthogen disulfides containing linear or branched alkyl chains such as methyl, ethyl, propyl, isopropyl, butyl, hexyl, heptyl, octyl; alkyl mercaptans containing from 4 to 20 carbon atoms in the alkyl chain, primary, secondary, tertiary and branched such as butyl, hexyl, octyl, dodecyl, tridecyl mercaptans and the relative mixtures.
• the conversions at the end of step (a) range from 60% up to 100% and, prefera- bly, from 70% to 99%, obtaining final solids ranging from 5% to 60% by weight, preferably from 30% to 50% by weight.
• the polymerization can be interrupted by the addition of a polymerization inhibitor such as phenothiazine, hydroxyla- ine sulfate, sodium tetrasulfide, sodium polysulfide mixed with mono-isopropyl hydroxyla ine .
• the residual monomers can be removed or left and used in the second polymerization step. The optional removal can be carried out with stripping in a stream of vapour in a column.
• the gel content of the polymer can range from 0% to 90% by weight and can be regulated using suitable quantities of chain trans- fer agents, polymerization temperatures, conversion and di- vinylbenzene as cross-linking agent.
• the gel content is the percentage of polymer insoluble in tetrahydrofuran at 25°C. This is determined by dissolving 1 g of polymer in 100 ml of tetrahydrofuran under stirring for 24 hours; the insoluble polymer is cascade filtered at 325 mesh (macrogel) and 0.2 microns (microgel) and dried at 70°C until a constant weight is reached.
• the polymerization can be carried out in continuous, batchwise or in semi-continuous; as far as the polymerization procedure is concerned, reference should be made to what is known in literature [High polymer Latexes, D.C. Blackley, vol.l, page 261 (1966); Encyclopedia of polymer Science and Technology] .
• the average particle dimensions of the polymer obtained in this first step can range from 1 nm to 1000 nm and, preferably from 5 nm to 500 nm, and are regulated by varying the polymerization temperature, the types and quantities of surface-active agents, the ratio of the latter with the monomeric mixture, the type and quantity of polymerization initiator.
• the measurement of the average particle dimensions is effected with Coulter N4 after suitable dilution of the sample.
• the polymeric emulsion obtained in this first polymerization step can be prepared in the same reactor used for the subsequent polymerization of the second step, or in different reactors.
• the present invention also comprises the possibility of using in the first step a preformed polymeric emulsion of the corresponding (co)polymers, provided they have the particle dimensions according to the present invention.
• Step (b) consists in polymerizing, on the latex obtained in step (a) , a monomeric mixture containing chloroprene as main monomer.
• pres- ent such as 1, 3-butadiene, styrene, acrylonitrile
• the comonomers are preferably selected from 1,3- butadiene, styrene, acrylonitrile, acrylic acid, methacrylic acid, butyl acrylate, methyl methacrylate, sulfur, 2, 3-dichloro-l, 3-butadiene.
• the polymerization can be carried out in the presence of or without emulsifying agents, either ionic or non-ionic, or a mixture of both, at temperatures ranging from 5°C to 100°C and preferably from 5°C to 60°C, in an acid, neutral or basic aqueous medium.
• the pH can be regulated with the addition of mineral acid or non-polymerizable organic acids soluble in water such as acetic acid.
• the polymerization is initiated by radicals which can be generated either by the ther- mal decomposition of peroxides and diazo-compounds or by oxide-reduction (redox pair) .
• the initiator system used for the polymerization comprises: salts soluble in water of peroxydisulfuric acid such as sodium, potassium and ammonium, organic peroxides such as diisopropyl benzene hydroperoxide, tertiary butyl hydroperoxide, pinane hydroperoxide and preferably redox systems .
• peroxydisulfuric acid such as sodium, potassium and ammonium
• organic peroxides such as diisopropyl benzene hydroperoxide, tertiary butyl hydroperoxide, pinane hydroperoxide and preferably redox systems .
• redox systems include the combination of sodium peroxydisulfate/sodium dithionite, diisopropyl benzene hydroperoxide/sulfoxylated sodium formaldehyde.
• Other redox systems use bivalent iron as reducing agent combined with auxiliary reducing agents (sulfoxylated sodium formaldehyde) .
• Emulsifying agents which can be used are both anionic and non-ionic; the former can be alkyl aryl sulfonates con- taining up to 18 carbon atoms in the alkyl chain, alkyl sulfates and alkyl sulfonates, condensation products of formaldehyde with naphthalene sulfonic acid, sodium and potassium salts of resinic acids, oleic acid and fatty acids.
• the non-ionic emulsifying agents used are condensation products of ethylene and propylene oxide with alkyl phe- nols.
• the polymerization is carried out in the presence of molecular weight regulators to regulate both the gel and the molecular weight of the polymer itself without signifi- cantly altering the polymerization kinetics.
• the molecular weight regulators which can be used, are: dialkyl xanthogen disulfides containing linear or branched alkyl chains such as methyl, ethyl, propyl, isopropyl, butyl, hexyl, heptyl, octyl; alkyl mercaptans containing from 4 to 20 carbon at- oms in the alkyl chain, primary, secondary, tertiary and branched such as butyl, hexyl, octyl, dodecyl, tridecyl mercaptans and the relative mixtures.
• the final conversions range from 60% up to 100% and, preferably, from 70% to 99%.
• the final content of solids ranges from 25% to 65% by weight, preferably from 45% to 60% by weight.
• the polymerization can be interrupted by the addition of a polymerization inhibitor such as phenothiazine, hydroxylamine sul- fate, sodium tetrasulfide, sodium polysulfide mixed with mono-isopropyl hydroxylamine.
• a polymerization inhibitor such as phenothiazine, hydroxylamine sul- fate, sodium tetrasulfide, sodium polysulfide mixed with mono-isopropyl hydroxylamine.
• the following products can be added to the final composite latex thus obtained: ionic and/or non-ionic surface-active agents, aqueous solutions of potassium, sodium or ammonium hydroxide in order to stabilize the aqueous dispersion towards coagula- tion.
• antioxidants can be added in a quantity of 0.1% to 5% by weight with respect to the weight of the polymer.
• the commonest antioxidants which can be used are of the phenol or amine type.
• the gel content of the composite polymer can range from 5% to 90% by weight and depends on the type of polymer obtained in step (a) .
• the above gel content can be further regulated using suitable quantities of chain transfer agents, polymerization temperatures and conversion.
• the average dimensions of the end polymeric particles can range from 50 nm to 1500 nm and are regulated by the particle dimensions obtained during step (a) and the polymerization technology used for this second step; the latter in fact can be carried out either batchwise or in a semi-continuous process.
• the ratio between the monomers polymerized in step (a) with respect to the monomers polym- erized in step (b) ranges from 5/95 to 50/50, preferably from 7/93 to 20/80.
• the emulsions thus obtained can be used as raw material in the adhesive and glue sector, in textile and cellulose impregnation, foams, dipping, bitumen and cement modi- fication and in coating in general or as rubber obtained from the latex in the tyre industry, air springs, plastic material modifiers and other rubber articles.
• polychloroprene latexes with a medium and high crystallization rate
• the starting rigidity of the formulate must be reacquired in relatively short times .
• N (BF/1000) *60*L 2 / (3.14*A*H)
• N rigidity index in N
• BF arithmetic average obtained from the values provided by the instrument expressed in mN
• L curvature length (25 mm)
• A curvature angle (10 degrees)
• H height of the test-sample (38.1 mm)
• S thickness of the test-sample in mm.
• the recovery trend of the rigidity index is obtained by graphically indicating the values in relation to the cooling time of the test-samples. The higher the recovery of the rigidity, the better the sample evaluated.
• the pres- ence of styrene in the composite particles increases the rigidity index with respect to the % polymer consisting of polychloroprene alone.
• the rigidity recovery trend is substantially analogous both for products prepared according to the present invention and for products of polychloroprene alone under the same polymerization conditions for the chloroprene monomer, demonstrating that there are no significant alterations in the characteristics of the polychloroprene (crystallinity and crystallization rate) .
• crystallization rate crystallization rate
• a high thermal holding tem- peratue is important.
• the use of a latex reinforced with Polystyrene or high-styrene SBR as described in the present invention is considerably improved with respect to a latex with polychloroprene alone or its possible mechanical mix- ture with an high-styrene SBR latex.
• the products prepared according to the present invention have, in fact, maintained good adhesive capacities, equal to those of polychloroprene latexes, providing however an excellent thermal holding temperature to the glued end-product.
• the evaluations were carried out in an oven at an increasing temperature by subjecting test-samples, glued with the latex to be tested, to stretching, until detachment. Preparation method of the test-samples: Cut strips of cotton having dimensions of 2 x 15 cm, and pass two layers of latex. After 10 minutes of drying, pass a third layer of latex and leave the strips to dry for 15 minutes.
• the adhesion strength was evaluated in peeling tests at room temperature, according to the regulation ISO 868, 1 hour, 48 hours and 7 days after the preparation of the test-samples.
• the thermal holding temperature was, on the other hand, measured by subjecting the test-samples to constant stretching under the following conditions:
• the following products were then fed to the reactor over a period of 6 hours: 1539 g of styrene; 219 g of butadiene; 0.38 g of t-dodecyl mercaptan; 374 g of potassium oleate (aqueous solution at 8.5%) ; 86 g of Daxad 16; 125 g of potassium persulfate (aqueous solution at 3%) .
• the latex remained at a constant temperature for 2 hours, and was subsequently cooled and filtered.
• the copolymer obtained has a styrene/butadiene composition of 82.5/17.5 (high-styrene SBR) 2 b) Polymerization of the second step
• the non-reacted monomer was removed by steam distillation at reduced pressure.
• the final particles have a content of high-styrene SBR prepared in Example 3 a) of 15% and a polychloroprene content of 85%.
• the final latex was formulated according to the quantities of Table 1. The evaluations of the rigidity index after 5 minutes and with time are indicated in Table 2 and in Graph 2. COMPARATIVE EXAMPLE 1
• the table indicates the rigidity indexes after 5 min- utes of cooling and the final rigidities of the pieces of felt treated with: the latexes prepared according to the present invention (Examples 1, 2 and 3) ; polychloroprene homopolymer latex (Comparative example l) ; latex of mechanical mixture of polychloroprene with polystyrene (Co - parative example 2) .
• the comparative examples have much lower final rigidities with respect to the examples of the invention.
• Example 1 The final rigidity tends to be higher for Example 1, where the polychloroprene is reinforced with 15% of polystyrene, whereas with the same composition as polymer a) , it tends to become higher, the higher the ratio between polymer a) /polymer b) .
• the behaviour of Comparative example 2 is extremely poor, in that it has an excessive rigidity after 5 minutes of cooling which remains almost unaltered until the end of the evaluation. Whereas Example 1 has a rigidity index after 5 minutes at the limit of processabil- ity, Examples 2 and 3 have a much higher index than Comparative Example 1, providing a good compromise between processability and final rigidity, above all excellent for Example 2 containing 15% of high-styrene SBR.
• the table indicates the evaluations of cotton/cotton and SBR/SBR adhesion in relation to the conversion for: the latexes prepared according to the present invention (Examples 4, 5 and 6) ; the latexes of polychloroprene alone (Comparative examples 4 and 5) ; the mechanical mixture of polychloroprene latex with high-styrene SBR latex (Comparative example 3) .
• the latter was the only one which did not provide an acceptable adhesion strength on the two supports, all the other latexes gave an almost equivalent adhesion strength regardless of the latex sample.
• the latexes prepared according to the present invention (Examples 4, 5 and 6) prepared both at a low and high polymeric conversion, provided a much higher thermal holding temperature with respect to the latexes of Comparative examples 4 and 5 of polychloroprene homopolymer.
• Graph 1 indicates the trend of the rigidity index in relation to the cooling time of the felt treated with: the latex prepared according to the present invention with 15% of polystyrene (Example 1) ; the latex of polychloroprene homopolymer (Comparative example 1) ; the mechanical mixture of polychloroprene latex 85% and polystyrene latex 15% (Comparative example 2) .
• the rigidity trend of the mechanical mixture (Comparative example 2) is extremely poor and totally different from the others, indicating that the sample is rigid right from the beginning and does not recover further rigidity during the cooling.
• the trends of the latex of Example 1 compared with Comparative example 1, on the other hand, are substantially identical, demonstrating that there is no alteration in the characteristics of polychloroprene .
• Graph 2 indicates the rigidity index trend in relation to the cooling time of the felt treated with: the latex prepared according to the present invention with 10% of high-styrene SBR (Example 2) ; the latex prepared according to the present invention with 15% of high-styrene SBR (Example 3) ; the latex of polychloroprene homopolymer (Comparative example 1) .
• the rigidity index trend during the cooling time is substantially analogous for all three latexes, demonstrating that the present invention does not alter the characteristics of polychloroprene.
• the latexes prepared according to the present invention however have a higher rigidity than the polychloroprene homopolymer.
• the rigidity of the felt treated also increases.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
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• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Polymerisation Methods In General (AREA)
• Graft Or Block Polymers (AREA)
• Adhesives Or Adhesive Processes (AREA)
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• 2001
  • 2001-08-02 IT IT2001MI001687A patent/ITMI20011687A1/it unknown
• 2002
  • 2002-07-26 EP EP02754955A patent/EP1417242A1/en not_active Withdrawn
  • 2002-07-26 US US10/484,801 patent/US20040242754A1/en not_active Abandoned
  • 2002-07-26 JP JP2003519123A patent/JP4271569B2/ja not_active Expired - Fee Related
  • 2002-07-26 WO PCT/EP2002/008455 patent/WO2003014176A1/en not_active Ceased

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