Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
  • C08G18/4263—Polycondensates having carboxylic or carbonic ester groups in the main chain containing carboxylic acid groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/0804—Manufacture of polymers containing ionic or ionogenic groups
  • C08G18/0819—Manufacture of polymers containing ionic or ionogenic groups containing anionic or anionogenic groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
  • C08G18/72—Polyisocyanates or polyisothiocyanates
  • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
  • C08G18/75—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic
  • C08G18/751—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing only one cycloaliphatic ring
  • C08G18/752—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing only one cycloaliphatic ring containing at least one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group
  • C08G18/753—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing only one cycloaliphatic ring containing at least one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group containing one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group having a primary carbon atom next to the isocyanate or isothiocyanate group
  • C08G18/755—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing only one cycloaliphatic ring containing at least one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group containing one isocyanate or isothiocyanate group linked to the cycloaliphatic ring by means of an aliphatic group having a primary carbon atom next to the isocyanate or isothiocyanate group and at least one isocyanate or isothiocyanate group linked to a secondary carbon atom of the cycloaliphatic ring, e.g. isophorone diisocyanate

Definitions

• Dispersions of crosslinked polymer microparticles in aqueous media processes for the preparation of these dispersions and coating compositions, these
• the invention relates to dispersions of crosslinked polymer microparticles in aqueous media.
• Basecoat-Clearcoat lacquers are produced by overpainting a clear lacquer after pre-painting a pigmented basecoat and a short flash-off time without a baking step (wet-on-wet method) and then
• Base coat and clear coat are baked together. There has been no lack of attempts to produce at least the base layers of these two-layer systems from aqueous coating compositions.
• the coating compositions for the production of these base layers must be processable according to the rational "wet-on-wet” process customary today, i.e. after a pre-drying time that is as short as possible, they must be able to be overpainted with a (transparent) top coat without a baking step, without showing any annoying signs of dissolving and "strike in” phenomena.
• metal effect depends crucially on the orientation of the metal pigment particles in the paint film.
• a metal effect basecoat which can be processed in the "wet-on-wet" process must accordingly provide paint films in which the metal pigments are in a favorable spatial orientation after application and in which this orientation is quickly fixed in such a way that it does not become apparent during the further painting process can be disturbed.
• the rheology viscosity curve during application, pseudoplasticity, thixotropy, flow and drainage properties
• rheology viscosity curve during application, pseudoplasticity, thixotropy, flow and drainage properties
• these possibilities can only be used to a very limited extent or not at all in aqueous systems.
• controlling the theological properties of the coating compositions used is extremely important, particularly in the production of high-quality multi-layer coatings, in particular metallic effect coatings.
• a rapid increase in viscosity after application very favorably affects the orientation and fixation of the metal pigment particles in metallic effect basecoats.
• aqueous coating compositions can be influenced by adding crosslinked polymer microparticles.
• EP 38 127 discloses a process for the production of multilayer coatings of the basecoat-clearcoat type, in which aqueous base coating compositions are used which contain stably dispersed, crosslinked polymer microparticles and have a pseudoplastic or thixotropic character. Incorporation of crosslinked polymer microparticles in coating compositions can lead to faults which are due to incompatibilities between the microparticles and other paint components, in particular between microparticles and the other binder components.
• aqueous coating compositions which contain polyurethanes and possibly also polyester as main binder constituents have very advantageous properties and are particularly suitable for use as base coating compositions in two-coat metal effect coatings of the basecoat clearcoat type (cf., for example, US Pat. No. 4,558,090 ).
• microparticles of crosslinked acrylic polymers which are highlighted as particularly suitable in EP 38127, are incorporated into such coating compositions, then disorders due to incompatibilities between the microparticles and the other binder components, in particular signs of turbidity, are observed in the coatings obtained.
• EP 38127 points out that the crosslinked polymer microparticles can also consist of crosslinked polycondensates, such as crosslinked polyester microgel particles. However, it is also noted that it can be difficult to produce truly cross-linked polycondensates, such as polyester. In GB 1403794 cited in EP 38127 a
• a process for the preparation of dispersions of polymer microparticles in organic solvents is described, which is intended to be applicable both to polymers which are obtained via polyaddition reactions and to polymers which are obtained via polycondensation reactions.
• the solid, sparingly soluble monomer is dispersed in the organic reaction medium, which contains a suitable stabilizing agent, using milling processes.
• the dispersion which may also contain other monomers, is then heated to the polymerization temperature.
• the polymerization must be carried out in the presence of a stabilizer which stabilizes the resulting polymer.
• aqueous dispersions of crosslinked polymer microgel particles with a diameter which is less than one micrometer cannot be produced.
• Aqueous dispersions which contain particles with a diameter of more than 1 ⁇ m show signs of sedimentation and are generally unusable as rheology aids and can lead to faults in the finished paint film.
• the object on which the present invention is based was accordingly to prepare dispersions of crosslinked polymer microparticles in aqueous media, with the aid of which the rheological properties of aqueous coating compositions can be influenced which, as constituents in base coating compositions of the basecoat clearcoat type, show the positive effects explained above and which can be optimally matched with as little effort as possible, in particular to aqueous coating compositions which contain polyurethanes and optionally also polyesters as main binder constituents.
• a mixture of components (A) and (B) has been dispersed in an aqueous medium, where - component (A) consists of one or more polyester polyols containing at least 2 hydroxyl groups and - Component (B) from one or more polyisocyanate compound (s)
• component (A) has a sufficient number of ionic groups, preferably carboxylate groups, to form a stable dispersion and at least some of component (A) and / or (B) has more than 2 hydroxyl or.
• ionic groups preferably carboxylate groups
• rheological properties of aqueous coating compositions can be influenced in a targeted manner with the aid of the dispersions according to the invention.
• the diameter of the crosslinked polymer microparticles contained in the dispersions according to the invention is less than one micrometer, preferably between 0.05 and 0.2 ⁇ m.
• a great advantage of the dispersions according to the invention can be seen in the fact that the particle size of the crosslinked polymer microparticles can be controlled by simple means (for example via the amount of the ionic groups contained in the starting component (A)) and that effortlessly crosslinked particles with a diameter of less than 1 ⁇ m, preferably 0.05 to 0.2 ⁇ m, can be obtained.
• the swelling behavior of the crosslinked particles can also be influenced in a simple manner within a large range.
• the network structure of the particles can be influenced in the microgel dispersions according to the invention by the targeted incorporation of certain chain segments.
• the chemical composition of the polymer microparticles contained in the dispersions according to the invention can be varied within a very large range in a simple manner, the dispersions according to the invention can be optimally adapted to the binder components otherwise contained in the coating compositions using simple means.
• the dispersions according to the invention can be processed into aqueous coating compositions from which, particularly in the cases in which polyurethanes and possibly also polyester are contained as main binder constituents, coatings can be produced which have excellent optical properties and no clouding whatsoever.
• coatings according to the invention are used in sasis coating compositions for the production of multi-layer coatings of the Sasecoat-Clearcoat type applied in the wet-on-wet process - in particular of metallic effect coatings - excellent multi-layer coatings are obtained which have no strike-in and, in the case of metallic coatings, no cloud formation phenomena and show an excellent metallic effect.
• coating compositions which contain polyurethanes and possibly also polyesters as main binder components.
• results can also be achieved with other binder systems which are often better than those which can be achieved with microparticles based on acrylic polymers as the only microparticle component.
• the present invention also relates to a process for the preparation of the dispersions discussed above, which is characterized in that the dispersions are prepared by (1) dispersing a mixture of components (A) and (B) in an aqueous medium, where
• Component (B) consists of one or more polyisocyanate compound (s) and component (A) has a sufficient number to form a stable dispersion ionic groups, preferably carboxylate groups, and at least part of component (A) and / or (B) contains more than 2 hydroxyl groups or isocyanate groups per molecule and
• No. 3,870,684 contains no indication that the dispersions disclosed therein can be used as auxiliaries in the sense discussed above in aqueous coating compositions.
• the process according to the invention gives stable aqueous dispersions which contain crosslinked polymer microparticles, the diameter of which is below 1 ⁇ m, preferably between 0.05 and 0.2 ⁇ m. It is of course also possible to use the method according to the invention to produce polymer microparticles whose diameter is above 1 ⁇ m.
• US Pat. No. 4,293,679 describes a process for the preparation of aqueous dispersions of crosslinked polymer microparticles containing urea groups, in which a prepolymer having hydrophilic, free isocyanate groups and which has been prepared from a polyol consisting of at least 40% by weight of ethylene oxide units and a polyisocyanate compound in one dissolved water-soluble organic solvent and then reacted with water in large excess with stirring.
• the size of the resulting particles depends very much on the viscosity of the prepolymer solution, the stirring speed and the addition of surface-active substances.
• relatively low-viscosity prepolymer solutions must be processed with high-performance high-speed stirrers and with the addition of surface-active substances.
• the dispersions according to the invention and the process for their preparation are to be explained in more detail below:
• the first step in the preparation of the dispersions according to the invention consists in providing a mixture of components (A) and (B), care being taken that component (A) prefers a sufficient number of ionic groups to form a stable dispersion Carboxylat phenomenon, and that at least part of component (A) and / or (B) contains more than 2 hydroxyl or isocyanate groups per molecule.
• stable dispersion means dispersions in which the dispersed particles coagulate only after application and release of the dispersing medium.
• stabilizing groups such as e.g. Polyooxyalkylene groups, to be incorporated into component (A).
• anionic stabilization preferably via carboxylate groups, being preferred.
• the average person skilled in the art can determine the optimum concentration of ionic groups in component (A) for the formation of a stable dispersion with the aid of simple routine examinations.
• concentration of ionic groups usually required to form a stable dispersion is between 0.01 and 2 milliequivalents per gram of component (A).
• the possibly necessary neutralization of groups capable of salt formation with the aid of bases or acids is preferably carried out shortly before the dispersion or during the dispersion of the mixture consisting of components (A) and (B) in the aqueous dispersion medium.
• Carboxyl and sulfonic acid groups are particularly suitable as groups capable of salt formation. These groups are preferably neutralized with a tertiary amine.
• Suitable tertiary amines for neutralizing the groups capable of forming anions are, for example, trimethylamine, triethylamine, dimethylaniline, diethylaniline, triphenylamine, N, N dimethylethanolamine, morpholine and the like.
• the content of ionic groups or the degree of neutralization of the groups suitable for salt formation is an important parameter by means of which the size of the crosslinked polymer microparticles formed can be controlled.
• Component (A) consists of one or more polyester polyols containing at least 2 hydroxyl groups.
• polyester polyols are in particular the reaction products of polyvalent polyols with polycarboxylic acids or polycarboxylic anhydrides which are known per se in polyurethane chemistry.
• Suitable polyols for the production of the polyester polyols are e.g. Ethylene glycol, propanediol 1,2 and 1,3, butanediol 1,3 and 1,4, the isomeric pentanediols, hexanediols or octanediols, e.g.
• the polycarboxylic acids suitable for the production of the polyester polyols consist primarily of low molecular weight polycarboxylic acids or their anhydrides with 2-18 carbon atoms in the molecule.
• Di- and tricarboxylic acids are preferably used.
• Suitable acids are, for example, oxalic acid, succinic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, adipic acid,fuginic acid, sebacic acid, maleic acid,
• Glutaric acid hexachlorheptanedicarboxylic acid, tetrachlorophthalic acid and trimellitic acid.
• their anhydrides if they exist, can also be used.
• Polyester polyols which have been prepared by polymerization of lactones can also be used as component (A). Particularly good results have been achieved with polyester polyols, the molecules of which each carry on average one carboxylate group and at least two, preferably more than two, hydroxyl groups.
• the (A) component is selected so that it can be stably dispersed on its own in the aqueous medium.
• the connections between the structure of polyester polyols (acid number, molecular weight %) and their dispersing behavior are well known to the average person skilled in the art and with the help of a few less preliminary tests he can select the optimal polyester polyol component to solve the respective problem.
• polyester polyols used as (A) components which contain groups reactive toward isocyanate groups. Care must be taken to ensure that the mixture formed from the components remains stably dispersible in the aqueous medium and that the crosslinked polymer microparticles formed from this dispersion have the desired size.
• component (A) examples include the polyether polyols known per se in polyurethane chemistry. In principle, all come as component (B)
• Organic compounds containing isocyanate groups in question include: trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, ethyl ethylene diisocyanate, 2,3-dimethylethylene diisocyanate, 1-methyltrimethylene diisocyanate, 1,3-cyclopentylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate , 4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-biphenylene diisocyanate, 1,5-waphthylene diisocyanate, 1,4-maphylene diisocyanate, 1-isocyanatomethyl-5-isocyanato 1,3,3- trimethylcyclohexane,
• prepolymers containing isocyanate groups as polyisocyanate components.
• Suitable prepolymers are reaction products made from polyisocyanates, polyether and / or polyester polyools and, if appropriate, conventional chain extenders.
• the polyisocyanate components whose isocyanate groups are bonded to (cyclo) aliphatic radicals are preferably used.
• polyisocyanate compounds containing isocyanate groups bonded to aromatic groups can only be used in exceptional cases (e.g. as part of component (B)).
• the crosslinking density of the resulting polymeric microparticles can be influenced by the molar ratio of components (A) and (B) and the number of groups or isocyanate groups contained in components (A) and (B), which are reactive towards isocyanate groups, and by the reaction conditions chosen for the preparation of the crosslinked polymer microparticles become.
• a decrease in the degree of crosslinking leads to greater swelling of the polymer microgel particles and, as a result, to an increase in the pseudoplastic flow behavior of the dispersions formed.
• the swelling behavior of the polymer microgel particles can also be controlled via the chemical nature of the components (A) or (B) (incorporation of more or less hydrophilic molecular segments; incorporation of more or less rigid molecular parts).
• Particularly preferred mixtures of components (A) and (B) consist of polyester polyols, the molecules of which each carry an average of one carboxyl group and at least three hydroxyl groups, and triisocyanate compounds, the isocyanate groups of which are bonded to (cyclo) aliphatic radicals.
• the mixture consisting of components (A) and (B) can be dispersed in bulk in the aqueous dispersing medium.
• Organic solvents with a boiling point below 100 ° C. are advantageously used. Particularly good ones
• Results can be obtained with acetone and methyl ethyl ketone.
• the aqueous dispersion medium in which the mixture of (A) and (B) is dispersed consists of water, which may also contain organic solvents.
• solvents that may be present in water are heterocyclic, aliphatic or aromatic hydrocarbons, mono- or polyhydric alcohols, ethers, esters and ketones such as e.g. N-methylpyrrolidone, toluene, xylene, butanol, ethyl and butyl glycol and their acetates, butyl diglycol, ethylene glycol dibutyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, acetone, isophorone or mixtures thereof.
• heterocyclic aliphatic or aromatic hydrocarbons
• mono- or polyhydric alcohols e.g. N-methylpyrrolidone, toluene, xylene, butanol, ethyl and butyl glycol and their acetates
• butyl diglycol ethylene glycol dibutyl ether, ethylene glyco
• dispersion which consists of particles, the size of which can be influenced by targeted variation of the parameters discussed above.
• the dispersion thus obtained is then heated to such an extent that the components
• Solvent can be used before the components
• Reaction temperature is, if appropriate, distilled off in vacuo; however, it is also possible to distill off the organic solvent in the course of the crosslinking reaction.
• - Component (A) made of polyester polyols, the molecules of which carry an average carboxylate group and at least two, preferably more than two, hydroxyl groups and
• component (B) from polyisocyanate compounds which preferably contain more than two isocyanate groups bonded to (cyclo) aliphatic radicals,
• Isocyanate group-inert organic solvents preferably acetone and / or methyl ethyl ketone, has been dissolved or dispersed, and (2) the dispersion thus obtained has subsequently been heated to such an extent that components (A) and (3) have been converted to crosslinked polymer microparticles, where the solvent used to dissolve or disperse the mixture consisting of components (A) and (B) either before the reaction of components (A) and (B) at a temperature which is below the reaction temperature required to form the crosslinked microparticles or at a temperature which is at least as high as the reaction temperature necessary to form the crosslinked particles has been distilled off.
• the present invention also relates to coating compositions which, in addition to the dispersions according to the invention, can also comprise further film-forming material, optionally pigments and other customary additives and which are preferably suitable for producing base layers of multilayer, protective and / or decorative coatings.
• compositions described above are preferably used in processes for the preparation of multilayer coatings on substrate surfaces, in which
• cover layer compositions which are not pigmented or only transparent pigmented are suitable as cover layer compositions.
• cover layer compositions can be conventional solvent-borne clearcoats, water-borne clearcoats or powder clearcoats.
• Pretreated metal substrates are particularly suitable as substrates, but non-pretreated metals and any other substrates such as e.g. Wood, plastics and the like are coated with a multilayer protective and / or decorative coating using the base coating compositions according to the invention.
• a hexane diol 1,6, isophthalic acid and trimellitic anhydride (3: 1: 1) is used to produce a polyester with an SZ of 43 and an OH equivalent weight of 433. This polyester is 80% dissolved in methyl ethyl ketone. Preparation of the isocyanate
• Example 2 In a cylindrical, double-walled glass reactor equipped with a stirrer, thermometer, reflux condenser and feed vessel, 866 parts of the polyester polyol solution prepared in Example 2 are weighed out and diluted with 100 parts of methyl ethyl ketone. Then 480 parts of the isocyanate prepared in Example 1 are added. The mixture is stirred and, after 20 minutes at room temperature, a mixture of 32 parts of methyl ether ethanol and 1162 parts of deionized water is added over the course of 30 minutes. A fine-particle dispersion is formed. The temperature is then slowly increased to 90 ° C. and the reflux condenser is replaced by a distillation bridge so that the methyl ethyl ketone can distill off.
• the reaction mixture is held at 90 ° C for 2 hours and then cooled to room temperature.
• the dispersion obtained has an average particle size of 113 nm, a solids content of 46% and a pH of 6.75.
• Particles are mixed with about 1 g of the dispersion with 40 ml of tetrahydrofuran and left to stand for 24 hours. The sample is then centrifuged at 21,000 rpm for 30 minutes. To determine the soluble fractions, the serum is dried at 130 ° C. for 2 hours and the residue that remains is weighed out. To determine the insoluble, i.e. cross-linked portion, the centrifugate is dried at 130 ° C for 2 hours and weighed.
• Example 2 In a cylindrical, double-walled glass reactor equipped with a stirrer, thermometer, reflux condenser and feed vessel, 866 parts of the polyester polyol solution prepared in Example 2 are weighed in and 600 parts of the polyisocyanate prepared in Example 1 are added. The mixture is stirred at room temperature for 20 minutes and then a mixture of 32 parts of dimethylethanolamine and 1260 parts of water is added over a period of 30 minutes. A fine-particle dispersion is formed. The reflux condenser is now replaced by a distillation bridge and the temperature is slowly raised to 90 ° C. After about 1 hour the methyl ethyl ketone has distilled off and the reaction mixture has a temperature of 90 ° C. The reaction temperature of 90 ° C is maintained for a further 3 h and finally it is cooled to room temperature.
• the dispersion obtained has a solids content of 47%, a pH of 6.75, a proportion of insoluble particles of 59.6% and an average particle size of 91 nm.
• the dispersion obtained has a solids content of 40%, a pH of 6.85 and an average particle size of 83 nm.
• the proportion of crosslinked particles is 27.6% by weight.
• Dispersion IV is prepared in the same way as dispersion III, except that instead of 222 parts of isophorone diisocyanate, 266 parts of isophorone diisocyanate are used.
• the dispersion thus obtained has a solids content of 42% by weight, a pH of 6.95 and an average particle size of 95 nm.
• the proportion of crosslinked particles is 29.7% by weight.
• the basecoats described above were used to produce two-layer metallic effect finishes using the customary wet-on-wet method.
• the paintwork showed an excellent metallic effect and a very good clear coat level.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Paints Or Removers (AREA)
• Polyurethanes Or Polyureas (AREA)

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• 1986
  • 1986-02-28 DE DE19863606512 patent/DE3606512A1/de not_active Withdrawn
• 1987
  • 1987-02-06 JP JP62501165A patent/JP2697737B2/ja not_active Expired - Lifetime
  • 1987-02-06 BR BR8707620A patent/BR8707620A/pt not_active IP Right Cessation
  • 1987-02-06 EP EP87101620A patent/EP0234361B2/de not_active Expired - Lifetime
  • 1987-02-06 ES ES87101620T patent/ES2014260T5/es not_active Expired - Lifetime
  • 1987-02-06 EP EP87901051A patent/EP0294376A1/de active Pending
  • 1987-02-06 WO PCT/EP1987/000056 patent/WO1987005305A1/de not_active Application Discontinuation
  • 1987-02-06 AT AT87101620T patent/ATE52265T1/de not_active IP Right Cessation
  • 1987-02-06 US US07/267,126 patent/US4945128A/en not_active Expired - Fee Related
  • 1987-02-06 DE DE8787101620T patent/DE3762419D1/de not_active Expired - Lifetime
  • 1987-02-27 CA CA000530756A patent/CA1299309C/en not_active Expired - Lifetime

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