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
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/4007—Curing agents not provided for by the groups C08G59/42 - C08G59/66
  • C08G59/4014—Nitrogen containing compounds
  • C08G59/4021—Ureas; Thioureas; Guanidines; Dicyandiamides

Definitions

• Epoxy resins show excellent adhesion and electrical insulation properties. They serve e.g. as a matrix for fiber composites, e.g. in the construction of wind turbines and aerospace as structural components. In electronics, they are used as electrical laminates in printed circuit boards. In addition, they are widely used as structural adhesives, as casting varnishes and as powder coating resins.
• the curing of epoxy resins proceeds according to various mechanisms.
• the curing with amines for the crosslinking of the epoxide groups is very often described.
• Another mechanism describes the reaction of an initiator or accelerator with epoxide groups, forming a highly reactive intermediate which can react with other epoxide groups without the need for further crosslinkers.
• the initiators can also lower the activation energy of the reaction of crosslinker or hardener molecules, so that the curing temperatures are significantly reduced.
• Compounds which have these properties are generally tertiary amines, imidazoles or substituted ureas, which can reduce, for example, the curing temperature of dicyandiamide.
• One-component mixtures contain, in addition to resin and other constituents (such as fillers, thixotropic agents, pigments, etc.) a latent curing at room temperature, have a significantly longer pot life and require for curing elevated temperatures, especially above 100 ° C and usually longer curing times.
• a typical example of a latent curing agent is dicyandiamide (compare EP 148 365 A1, US Pat. No. 2,637,715 B1).
• chemically latent accelerators are added to such one-component blends, while accepting shortening of storage stability and processing time to lower the curing temperature.
• latent accelerators are, for example, in particular urones, such as 3- (3,4-dichlorophenyl) -1, 1-dimethylurea (diuron) (compare GB 1,153,639 A1, GB 1,293,142 A1, US 3,386,956 B1, US 6,231,959 B1).
• These compounds are usually 1,1-dialkyl-3-aryl ureas, wherein the aromatic may be substituted or unsubstituted, or else hydrogenated. At elevated temperatures, these compounds release dimethylamine and the aryl isocyanate, which synergistically accelerate the curing reaction with dicyandiamide. This can be cured at much lower temperatures. The temperature at which this dissociation of the uron starts, thus initiating the crosslinking reaction, depends on the nature of the substituents. At the same time it is found that the lower the temperature at which the cure begins, the lower the stability of such a mixture at temperatures below the cure temperature.
• the present invention therefore an object of the invention to provide latent accelerators for epoxy resin systems, which do not have the disadvantages of the prior art.
• latent accelerators is meant additives to a resin-hardener mixture, which the pot life, i. the time in which the mixture is processable, preferably not lower and at the same time the reactivity, i. accelerate the crosslinking at elevated temperature.
• the accelerators for epoxy resin systems according to the invention should therefore have a high reactivity and very good storage stability at room temperature or at temperatures below the curing temperatures and, moreover, should be as halogen-free as possible or toxicologically harmless.
• R 1 and R 2 are each independently a linear or branched aliphatic hydrocarbon radical having 1 to 4 carbon atoms.
• R 1 and R 2 may be, for example, methyl, ethyl, propyl and butyl.
• urea derivatives are, for example, N, N-diethylurea, NN-dipropylurea, N, N-ethylmethylurea and N, N-dimethylurea.
• a preferred urea derivative is N, N-
• the accelerators proposed according to the invention not only have a very good reactivity and storage stability, but also exert no negative influence on the mechanical properties of the cured material.
• JP-OS 81-133856 in which the combination of N, N-dimethylurea with phenol novolaks as a curing agent for epoxy resin in the
• asymmetrically substituted urea derivatives of the general formula (I) are used as accelerators in combination with dicyandiamide as latent curing agent.
• R 1 and R 2 are each independently a linear or branched aliphatic hydrocarbon radical having 1 to 4 carbon atoms.
• R 1 and R 2 are each independently a linear or branched aliphatic hydrocarbon radical having 1 to 4 carbon atoms.
• methyl, ethyl, propyl and butyl radicals in question which may be linear or optionally also branched.
• urea derivatives according to the invention are N, N-dimethylurea, N, N-diethylurea, NN-dipropylurea and N, N-ethylmethylurea.
• the urea derivative N, N-dimethylurea is preferably used.
• Epoxy resins based on bisphenol A and F are mainly used in the field of fiber composites, adhesives and higher molecular weight as solid resins in powder coatings.
• the cured epoxy resin is expected to have a high flame resistance and high temperature resistance.
• halogenated systems of bisphenol A eg Tetrabromobisphenol A derivatives or trifluoromethyl substituted variants thereof.
• Particularly flame-resistant composites are produced, for example, with epoxy resins based on resorcinol and tetrakisphenylolethane.
• the proportions of dicyandiamide and urea derivative to the corresponding epoxy resin can be varied within wide limits. However, it has proved to be particularly advantageous that the dicyandiamide in an amount of about 1 to 15 wt .-%, preferably about 2 to 12 wt .-%, particularly preferably about 2 to 8 wt .-%, based on the epoxy resin, use.
• the urea derivative is used in an amount of about 0.5 to 15 wt .-%, preferably about 1 to 12 wt .-%, based on the epoxy resin.
• a particularly preferred amount is about 1 to 10% by weight, based on the epoxy resin.
• the urea derivative and the dicyandiamide are used in as finely divided a form as possible, wherein the components have a preferred average particle size of about 0.5 to 100 .mu.m, in particular about 10 to 50 .mu.m, preferably about 2 to 10 microns, respectively.
• the curing reaction of the inventively proposed accelerators and hardeners with the respective epoxy resins can be carried out by the usual methods, wherein the curing at temperatures between about 70 and 220 ° C, in particular between about 80 and 160 ° C is performed.
• urea derivative as accelerator and dicyandiamide as latent hardener is suitable for example.
• Coatings, electrical laminates and adhesives are Coatings, electrical laminates and adhesives.
• the advantages of the accelerator / hardener combination according to the invention are the excellent reactivity and very good storage stability. Surprisingly, the mechanical properties of the appropriately cured resins are also excellent and comparable to those of the already used blocked accelerators UR 200 (Diuron) and UR 300 (Fenuron).
• the inventively proposed hardener / accelerator systems are ideally suited for technical use.
• Epikote 828 (from Resolution): bisphenol A resin, EEW 185 DER 664 UE (Dow): solid resin, EEW 910 (resin)
• Dyhard UR 200 (Degussa): micronised diuron or 3- ((3,4-dichlorophenyl) -1, 1-dimethylurea, particle size 98% ⁇ 10 ⁇ m, 50% about 2.5 ⁇ m (UR 200)
• Dyhard UR 300 micronized fenuron or 3-phenyl-1, 1-dimethylurea, particle size 98% ⁇ 10 ⁇ m, 50% about 2.5 ⁇ m (UR 300)
• Dyhard UR 500 micronized TDI-uron or toluyl-bis-1,1-dimethylurea, particle size 98% ⁇ 10 ⁇ m, 50% about 2.5 ⁇ m (UR 500)
• Dyhard MIA 5 micronized adduct of methylimidazole with bisphenol A resin (Epikote 828), particle size 98% ⁇ 70 ⁇ m
• N, N-dimethylurea or 1,1-dimethylurea ground in the laboratory, particle size 98% ⁇ 10 ⁇ m, 50% about 2.5 ⁇ m (1,1-DMH)
• N, N-diethylurea or 1,1-diethylurea ground in the laboratory, particle size 98% ⁇ 10 ⁇ m, 50% about 2.5 ⁇ m (1,1-DEH)
• MDI-Uron, (1, 1'-methylenedi-p-phenylene) bis (3,3-dimethylurea) was prepared by known methods from MDI (1,1'-methylenedi-p-phenylene) diisocyanate and dimethylamine (eg EP 402 020 A1, CS 233 068 B1) and then ground in the laboratory, particle size 98% ⁇ 10 microns, 50% about 2.5 microns
• Example 1 (according to the invention):
• the temperature program for the determination of the peak temperature was heated from 30 to 350 ° C at a rate of 10 ° C / min.
• the onset of the reaction was determined from the same measurement by applying the tangent to the reaction peak.
• the material of the gel time determination at 120 ° C was used.
• the formulation was fully cured by heating to 200 ° C (temperature program: 30 to 200 ° C, heating rate 20 ° C / min) and holding this temperature for 30 minutes. After cooling to room temperature (RT), the sample was heated at a heating rate of 10 ° C / min from 30 to 200 ° C and determined from the Tg.
• the formulations according to the invention have significantly better properties with regard to latency: whereas in formulations with MDI uron at 40 ° C. a doubling of the viscosity already occurs after 15 days, this is only after the 1,1-dimethylurea about 40 days the case.
• the processability of the formulation is less than 25 days, while it is more than twice as high for formulations containing 1,1-dimethylurea (over 50 days).
• the processability of the 1,1-dimethylurea-containing formulations is also significantly higher at room temperature than in formulations with MDI-urone.
• the mechanical properties of the accelerators according to the invention in powder coating formulations are absolutely comparable to the methylimidazole adduct (Dyhard MIA 5) of the prior art with simultaneously lower yellowing tendency and better leveling properties.

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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)
• Epoxy Resins (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Paints Or Removers (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Reinforced Plastic Materials (AREA)

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• 2003
  • 2003-05-30 DE DE10324486A patent/DE10324486A1/de not_active Withdrawn
• 2004
  • 2004-05-28 CN CNB2004800151472A patent/CN100560633C/zh not_active Expired - Lifetime
  • 2004-05-28 WO PCT/EP2004/005787 patent/WO2004106402A2/de not_active Ceased
  • 2004-05-28 ES ES04735210.9T patent/ES2524323T3/es not_active Expired - Lifetime
  • 2004-05-28 CA CA2527099A patent/CA2527099C/en not_active Expired - Fee Related
  • 2004-05-28 EP EP04735210.9A patent/EP1629025B1/de not_active Expired - Lifetime
  • 2004-05-28 PL PL04735210T patent/PL1629025T3/pl unknown
  • 2004-05-28 JP JP2006529945A patent/JP4587323B2/ja not_active Expired - Lifetime
  • 2004-05-28 US US10/558,160 patent/US7750107B2/en not_active Expired - Lifetime

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