Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C279/00—Derivatives of guanidine, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups
  • C07C279/28—Derivatives of guanidine, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups having nitrogen atoms of guanidine groups bound to cyano groups, e.g. cyanoguanidines, dicyandiamides
• • 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

• the invention relates generally to the curing of epoxy resins and, more particularly, to improvement of the curing agents used with epoxy resins.
• Dicyandiamide also called cyanoguanidine
• cyanoguanidine is well- known as a curing agent for epoxy resins, but it is also known to have a serious deficiency. It is only soluble in solvents which are undesirable, either because they are not usable in most applications, such as water, or because the solvents are relatively expensive and environmentally undesirable, such as dimethylformamide and the like.
• a curing agent which combines a metal salt of an imidazole and another compound, which may be dicyandiamide. These curing agents are used in a one-part epoxy composition which is curable at elevated temperatures, but which can be stored at ambient temperature for long periods.
• reaction product of dicyandiamide with formaldehyde and an amine terminated polyether may be used to cure epoxy resins, as is shown in U.S. Pat. No. 4,581,422.
• X is sigma bond
• O, S, R' and R" are independently selected from -H, -CH 3 , -CH 2 CH 3 , -CH 2 CH 2 CH 3 , -CH 2 CH(CH 3 ) 2
• n is an integer from 2 to 12
• a is 0 or an integer from 1 to 5
• b is 0 or an integer from 1 to 5
• c is 0 or an integer from 1 to 5
• d is an integer from 1 to 4.
• R'" is -H, -CH 3 , -CH 2 CH 3 , -CH 2 CH 2 CH 3 ,
• Such bis-dicyandiamides are soluble in various solvents, preferably acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropanol, acetone/methanol, acetone/ethanol, acetone/isopropanol, methyl ethyl ketone/methanol, methyl ethyl ketone/ethano1, and methyl ethyl ketone/isopropanol.
• the substituted bis-dicyandiamides will be employed in amounts up to about 24 wt.% of the epoxy resin precursors, preferably 2 to 16 wt.%.
• the invention is a method for curing epoxy resins and the product of that method in which a reactive amount of a bis-dicyandiamides as defined above is added to an epoxy resin precursor in amounts up to about 24 wt.%, preferably 2 to 16 wt.%, and the curing carried out under curing conditions.
• dicyandiamide i.e. cyanoguanidine
• cyanoguanidine is an undesirable curing agent for epoxy resins, since it requires the use of objectionable solvents such as dimethylformamide and the like. If more soluble compounds could be found which provide equivalent or improved curing properties, then cyanoguanidine could be replaced and the undesirable solvents avoided. Reduced production costs from the use of less expensive solvents also could be the result of such a change in curing agents.
• the present inventors have found a group of bis-dicyandiamides which have significant advantages over the presently used compound.
• X is sigma bond, 0, S,
• R' and R" are independently selected from -H, -CH 3 , -CH 2 CH 3 , -CH 2 CH 2 CH 3 , -CH 2 CH(CH 3 ) 2
• n is an integer from 2 to 12
• a is 0 or an integer from 1 to 5
• b is 0 or an integer from 1 to 5
• c is 0 or an integer from 1 to 5
• d is an integer from 1 to 4.
• R'" is -H, -CH 3 , -CH 2 CH 3 , -CH 2 CH 2 CH 3 ,
• the bis-dicyandiamides of this invention and the di-substituted cyanoguanidines of EP 310,545 differ in the degree of reactive functionality.
• the amine radicals react with the epoxide radicals.
• the degree of reactive functionality of the cyanoguanidine will depend on the degree of functionalization for the cyanoguanidine, which is related to the number of exchangeable nitrogen hydrogens of the cyanoguanidine.
• dicyandiamide (cyanoguanidine) has a defined degree of functionality of four, that is, it is capable of addition to four epoxide radicals.
• the degree of functionality is three and it is capable of reacting with three epoxide radicals.
• the degree of functionality is two, and it is capable of reacting with two epoxide radicals.
• the bis-dicyandiamides of the present invention have a degree of functionality of four to six.
• the degree of reactive functionality for the curing agent will affect the type of polymer network formed in the cured polymer system and consequently will affect the performance properties in B-Stage or a prepreg, such as the viscosity as a function of cure, the solvent resistance for the polymer, the glass transition temperature (Tg) for the polymer, and the coefficient of thermal expansion ( ⁇ g ).
• the network will have a high degree of linear structures with only a minor degree of branching.
• the polymer network will have a high degree of branched or star-like structures and a minimum of linear type structures.
• the branched or star-like structures will affect the resin flow properties (resin flow viscosity) for the B- Staged resin during lamination. If the resin flow viscosity is low then the laminates or composites formed will experience a high degree of resin flow, generating laminates or composites with voids or resin-poor products.
• Linear structures in the cured polymer will yield poor solvent resistance due to the solvation of the polymer fragments or swelling of the polymer.
• Branched or star-like structures provide improved solvent resistance due to the formation of a more highly cross-linked network. Linear structures will yield a polymer of lower Tg and may yield higher coefficient of thermal expansion than a polymer with branched structures.
• the parent compound, dicyandiamide is soluble only in a small group of generally available solvents, including dimethyl formamide, dimethylsulfoxide, dimethylacetamide, N-methyl-2-pyrrolidinone and methanol.
• the bis-dicyandiamides of the invention are soluble in a number of more desirable solvents, including acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, and isopropanol or mixed solvents such as acetone/methanol, acetone/ethanol, acetone/isopropanol, methyl ethyl ketone/methanol, methyl ethyl ketone/ethanol, methyl ethyl ketone/isopopanol, methyl isobutyl ketone/methanol, methyl isobutyl ketone/ethanol, and methyl isobutyl ketone/isopropano
• acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetone/methanol, acetone/ethanol, acetone/isopropanol, methyl ethyl ketone/methanol, methyl ethyl ketone/ethanol, and methyl ethyl ketone/isopropanol are preferred solvents.
• the compounds of the invention are generally soluble in amounts up to about 20 wt.% in such solvents.
• the bis-dicyandiamides of the invention may be used with various epoxy resin precursors known in the art.
• these will include diglycidyl bisphenol-A(DGEBA), diglycidyl tetrabromobis-phenol-A, triglycidyl triphenol methane, triglycidyl triphenol ethane, tetraglycidyl tetraphenolethane, tetraglycidyl methylene dianiline and oligomers and mixtures thereof.
• DGEBA diglycidyl bisphenol-A
• DGEBA diglycidyl bisphenol-A
• the catalyst will include imidazole, 2-methylimidazole, 2-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-(2-cyanoethyl)-2-ethyl-4- methylimidazole, 4-phenylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4- m e t h o x y - N , N - d i m e t h y l b e n y l a m i n
• An advantage of the bis-dicyandiamides of the invention is their ability to replace the dicyandiamide commonly used to cross-link epoxy resins in the preparation of reinforced laminates for the electronics industry and without requiring the use of undesirable solvents.
• the methods used to prepare such laminates are well known to those skilled in the art and need not be discussed in detail here in connection with the present invention since the procedures are not revised significantly to accommodate the bis-dicyandiamides of the invention.
• the fabric which is to be used to reinforce the laminate typically made of glass fibers, is coated with epoxy resins combined with the crosslinking agents and a catalyst as desired.
• the coated fabric is then heated in order to drive off solvents and to cure (polymerize and crosslink) the epoxy resins and the crosslinking agents.
• Multiple layers of coated fabric are commonly combined to provide the laminates needed for electronic circuit boards.
• the resulting product is often referred to as a "prepreg” or "B-stage” material. Further curing is later carried out to complete the laminate.
• the curing agents of the invention may be prepared by various methods known to those skilled in the art. For example, the method of May (J. Org. Chem., 12, 437-442, 442-445 (1947)) and Curd (J. Chem. Soc, 1630-1636 (1948)) reaction of an aryl isothiocyanate with sodium cyanamide, followed by reaction with methyl iodide to generate a N-cyano-S-methyl-N'-arylisothiourea which upon reaction with ammonia yields a cyanoguanidine. The method of Curd (J. Chem. Soc, 729-737 (1946))) and Rose (Brit.
• Patent 577,843 employs the reaction of an aryl diazonium salt with dicyandiamide to yield a substituted aryl-azo-dicyandiamide or triazene which thermally decomposes to yield nitrogen and the corresponding substituted cyanoguanidine.
• a metal salt of dicyanamide preferably is used, such as sodium dicyanamide.
• a bis-dicyandiamide is made by dissolving a diamine in a suitable solvent, such as butanol, ethanol, propanol and water, or mixed with hydrochloric acid to form a slurry.
• Sodium dicyanamide is added in an approximately stoichiometric quantity.
• the reaction is carried out at temperatures between about 75o and 110oC and at pressures of atmospheric to 2068 kPa for a period of time necessary to complete the reaction.
• a temperature of about 100o to 110oC will be used with the reaction time being about 2 to 24 hours.
• the solvent is distilled off and the bis-dicyandiamine is recovered by crystallization and washing. If hydrochloric acid is used, the solids are filtered, washed, and then redissolved and crystallized from solution.
• the mixture was refluxed for 4 hours and then the water was distilled azeotropically. The mixture was allowed to cool and a white precipitate formed. The solvent was removed on a rotary evaporator and water was added to leach the salt from the product. A second liquid phase that was more dense than water formed and was separated and stripped on a rotary evaporator leaving 11 g (13% yield) of a white amorphous resin.
• Solubility testing for all bis-dicyandiamide derivatives and the unsubstituted parent compound (DICY) were conducted by using a weight ratio of dicyandiamide to solvent of 1:10. For example, to 0.1 grams of the substituted dicyandiamide was added 1.0 gram of solvent. The sample was agitated slightly and dissolution recorded at 25 oC; complete dissolution receives a rating of +, partial dissolution is +5, and no dissolution is rated as -. The sample was then heated to 50°C for 30 minutes and the solubility recorded using the same rating system. TABLE 1
• NMP N-Methyl-2-pyrrolidinone
• NMP N-Methyl-2-pyrrolidinone
• Part A 2.22 g of DYDICY was dissolved in 5.60 g of 1- methoxy-2-propanol and heated to 50oC for 30 minutes with stirring. 0.044 g of 2-Methyl-imidazole (2MI) and 6.92 g of methyl ethyl ketone (MEK) was added to the above solution with stirring.
• 2MI 2-Methyl-imidazole
• MEK methyl ethyl ketone
• Part B 50.0 g of Dow epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA).
• DGEBA diglycidyl Bisphenol-A
• DGEBA brominated DGEBA
• Part A and Part B were mixed together and allowed to age for 24 hours.
• the resin varnish was then B-Staged on a hot plate in thin casting pan.
• the B-Staged resin was ground into fine powder and then cured at 170oC in hydraulic press at 200 psi.
• the polymer yields the following properties as a function of cure.
• Tg (DSC) 136oC
• Tg (TMA) 120 ⁇ 7oC
• ⁇ g 50 ⁇ 12 ppm/oC
• ⁇ 180 103 ⁇ 3 ppm/oC.
• Part A 1.24 g of DYDICY was dissolved in 9.06 g of 1-methoxy-2-propanol and heated to 50oC for 30 minutes with stirring. 0.11 g of 2-Methyl-imidazole (2MI) and 11.15 g of methyl ethyl ketone (MEK) was added to the above solution with stirring.
• Part B 50.0 g of Dow epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA).
• Part A and Part B were mixed together and allowed to age for 24 hours.
• the resin varnish was then B-Staged on a hot plate in thin casting pan.
• the B-Staged resin was ground into fine powder and then cured at 170 oC in hydraulic press at 200 psi.
• the polymer yields the following properties as a function of cure.
• Tg (DSC) 127°C
• Tg (TMA) 113 ⁇ 3oC
• ⁇ g 44 ⁇ 2 ppm/°C
• ⁇ 180 96 ⁇ 2 ppm/oC.
• Part A 2.30 g of DIANEDICY was dissolved in a mixture of 7.50 g of 1-methoxy-2-propanol, 7.50 g of methyl ethyl ketone and 0.054 g of 2-MI with stirring.
• Part B 25.0 g of Dow Epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA).
• DGEBA diglycidyl Bisphenol-A
• DGEBA brominated DGEBA
• Part A and Part B were mixed together and allowed to age for 24 hours at room temperature.
• the resin varnish was then B-Staged on a hot plate in a thin casting pan.
• the B-Staged resin was ground into a fine powder and then cured at 170°C in a hydraulic press at 200 psi.
• the polymer yields the following properties as a function of cure.
• Tg (DSC) 106oC
• Tg (TMA) 101 ⁇ 2oC
• ⁇ g 40 ⁇ 2 ppm/oC
• ⁇ 180 129 ⁇ 5 ppm/oC.
• Part A 1.28 g of DIANEDICY was dissolved in a mixture of 7.50 g of 1-methoxy-2-propanol, 7.50 g of methyl ethyl ketone and 0.054 g of 2-MI with stirring.
• Part B 25.0 g of Dow Epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA).
• DGEBA diglycidyl Bisphenol-A
• DGEBA brominated DGEBA
• Part A and Part B were mixed together and allowed to age for 24 hours at room temperature.
• the resin varnish was then B-Staged on a hot plate in a thin casting pan.
• the B-Staged resin was ground into a fine powder and then cured at 170oC in a hydraulic press at 200 psi.
• the polymer yields the following properties as a function of cure.
• Tg (DSC) 116oC
• Tg (TMA) 109 ⁇ 2oC
• ⁇ g 31 ⁇ 2 ppm/oC
• ⁇ 180 107 ⁇ 5 ppm/°C.
• Example 13 Example 13:
• Part A 1.46 g of DIPPDICY was dissolved in a mixture of 7.50 g of 1-methoxy-2-propanol, 7.50 g of methyl ethyl ketone and 0.054 g of 2-MI with stirring.
• Part B 25.0 g of Dow Epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA).
• Part A and Part B were mixed together and allowed to age for 24 hours at room temperature.
• the resin varnish was then B-Staged on a hot plate in a thin casting pan.
• the B-Staged resin was ground into a fine powder and then cured at 170°C in a hydraulic press at 200 psi.
• the polymer yields the following properties as a function of cure. Time (min.) Tg ( oC)
• Tg (DSC) 117oC
• Tg (TMA) 79 ⁇ 3oC.
• Part A 2.62 g of DIPPDICY was dissolved in a mixture of 7.50 g of 1-methoxy-2-propanol, 7.50 g of methyl ethyl ketone and 0.054 g of 2-MI with stirring.
• Part B 25.0 g of Dow Epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA). Part A and Part B were mixed together and allowed to age for 24 hours at room temperature. The resin varnish was then B-Staged on a hot plate in a thin casting pan. The B-Staged resin was ground into a fine powder and then cured at 170oC in a hydraulic press at 200 psi.
• DGEBA diglycidyl Bisphenol-A
• brominated DGEBA brominated DGEBA
• the polymer yields the following properties as a function of cure.
• Tg (DSC) 86oC
• ⁇ g 50 ⁇ 4 ppm/oC
• ⁇ 180 194 ⁇ 8 ppm/oC.
• Part A 2.30 g of DIANEDICY was dissolved in a mixture of 7.50 g of 1-methoxy-2-propanol, 7.50 g of methyl ethyl ketone and 0.054 g of 2-MI with stirring.
• Part B 25.0 g of Dow Epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA).
• DGEBA diglycidyl Bisphenol-A
• DGEBA brominated DGEBA
• Part A and Part B were mixed together and allowed to age for 24 hours at room temperature.
• the resin varnish was then B-Staged on a hot plate in a thin casting pan.
• the B-Staged resin was ground into a fine powder and then cured at 170 °C in a hydraulic press at 200 psi.
• the polymer yields the following properties as a function of cure.
• Tg (DSC) 112 oC.
• Part A 1.46 g of DIPPDICY was dissolved in a mixture of 7.50 g of 1-methoxy-2-propanol, 7.50 g of methyl ethyl ketone and 0.054 g of 2-MI with stirring.
• Part B 25.0 g of Dow Epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA).
• DGEBA diglycidyl Bisphenol-A
• DGEBA brominated DGEBA
• Part A and Part B were mixed together and allowed to age for 24 hours at room temperature.
• the resin varnish was then B-Staged on a hot plate in a thin casting pan.
• the B-Staged resin was ground into a fine powder and then cured at 170oC in a hydraulic press at 200 psi.
• the polymer yields the following properties as a function of cure.
• Tg (DSC) 104oC.
• Part A 2.62 g of DIPPDICY was dissolved in a mixture of 7.50 g of 1-methoxy-2-propanol, 7.50 g of methyl ethyl ketone and 0.054 g of 2-MI with stirring.
• Part B 25.0 g of Dow Epoxy 71881 resin (diglycidyl Bisphenol-A (DGEBA) and brominated DGEBA).
• Part A and Part B were mixed together and allowed to age for 24 hours at room temperature.
• the resin varnish was then B-Staged on a hot plate in a thin casting pan.
• the B-Staged resin was ground into a fine powder and then cured at 170°C in a hydraulic press at 200 psi.
• the polymer yields the following properties as a function of cure.
• Tg (DSC) 101oC.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Epoxy Resins (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=25152246

Family Applications (1)

Country Status (3)

Families Citing this family (4)

Family Cites Families (3)

• 1992
  • 1992-10-28 EP EP92922950A patent/EP0612330A1/de not_active Ceased
  • 1992-10-28 JP JP5509266A patent/JPH0816148B2/ja not_active Expired - Lifetime
  • 1992-10-28 WO PCT/US1992/009172 patent/WO1993010168A1/en not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events