Phenolic resin composition for use in the polyurethane cold-box and/or no-bake process and corresponding two-component binder systems, uses, and processes

Abstract

Described is a phenolic resin composition for use in the polyurethane cold-box and/or no-bake process. The phenolic resin composition comprises an ortho-condensed phenolic resol having etherified and/or free methylol groups in a total amount of 40 to 60% by weight based on the total mass of the phenolic resin composition, free formaldehyde in an amount of less than 0.1% by weight based on the total weight of the phenolic resin composition, one or more reaction products of formaldehyde with one or more CH-acidic reactant compounds, other constituents in a total amount of at least 38% by weight, wherein the amount of water in the phenolic resin composition is not more than 1.0% by weight in each case based on the total mass of the phenolic resin composition. Also described is a two-component binder system for use in the polyurethane cold-box and/or no-bake process, a use of a CH-acidic compound as a formaldehyde scavenger for producing a phenolic resin composition for use in the polyurethane cold-box and/or no-bake process, a process for producing a phenolic resin composition, a process for producing a two-component binder system and a process for producing a feeder, a foundry mold or a foundry core from a molding material mixture and finally corresponding feeders, foundry molds and foundry cores.

Claims

1. A phenolic resin composition for use in the polyurethane cold-box and/or no-bake process, comprising an ortho-condensed phenolic resol having etherified and/or free methylol groups in a total amount of 40 to 60% by weight based on the total mass of the phenolic resin composition, free formaldehyde in an amount of less than 0.1% by weight based on the total weight of the phenolic resin composition, one or more reaction products of formaldehyde with one or more CH-acidic reactant compounds, other constituents in a total amount of at least 38% by weight, wherein the amount of water in the phenolic resin composition is not more than 1.0% by weight in each case based on the total mass of the phenolic resin composition.

2. The phenolic resin composition as claimed in claim 1, wherein the total amount of reaction products of formaldehyde with one or more CH-acidic reactant compounds is greater than 0.1% by weight.

3. The phenolic resin composition as claimed in claim 1, wherein the other constituents comprise one or more CH-acidic compounds, and/or a solvent selected from the group consisting of fatty acid alkyl esters, alkyl silicates, alkyl silicate oligomers and mixtures thereof.

4. The phenolic resin composition as claimed in claim 3, wherein at least one of the one or more CH-acidic compounds has the same structure as the CH-acidic reactant compound of the or of one of the reaction products.

5. The phenolic resin composition as claimed in claim 3, wherein the or at least one of the CH-acidic reactant compounds is a carbonyl compound capable of enolate formation.

6. The phenolic resin composition as claimed in claim 3, wherein the or at least one of the CH-acidic reactant compounds is selected from the group consisting of dialkyl malonate.

7. The phenolic resin composition as claimed in claim 3, comprising an ortho-condensed phenolic resol having etherified and/or free methylol groups in a total amount of from 40 to 60% by weight, free formaldehyde in an amount of less than 0.1% by weight based on the total mass of the phenolic resin composition, one or more reaction products of formaldehyde with one or more CH-acidic reactant compounds, other constituents in a total amount of at least 38% by weight, wherein the other constituents comprise a solvent selected from the group consisting of fatty acid alkyl esters, alkyl silicates, alkyl silicate oligomers and mixtures thereof.

8. The phenolic resin composition as claimed in claim 3 wherein the ortho-condensed phenolic resol has a ratio of the total amount of etherified and/or free methylol groups to aromatic rings in the range from 0.2:1 to 2:1.

9. A two-component binder system for use in the polyurethane cold-box and/or no-bake process, consisting of a phenolic resin composition according to claim 1 as a phenolic resin component, and a polyisocyanate component comprising a polyisocyanate having at least two isocyanate groups per molecule.

10. A process for producing the phenolic resin composition in claim 1 comprising the steps of: producing or providing a base mixture comprising an ortho-condensed phenolic resol having etherified and/or free methylol groups and free formaldehyde in an amount of more than 0.25% by weight, wherein the base mixture contains not more than 2% by weight of water, mixing the base mixture with one or more CH-acidic compounds to afford a reaction mixture and reacting the free formaldehyde with the one or more CH-acidic compounds to afford one or more reaction products, wherein the CH-acidic compounds are altogether present in a molar excess based on the total amount of free formaldehyde in the mixture, wherein the reaction mixture contains not more than 2% by weight of water, and subsequently adding other constituents so that the phenolic resin composition results.

11. The process as claimed in claim 10, wherein the production of the base mixture comprises the steps of: reacting one or more phenolic monomers with formaldehyde, wherein the molar ratio of the total amounts of formaldehyde to phenol monomers is in the range from 1.3:1 to 2:1.

12. The process as claimed in claim 10, wherein the reaction of the free formaldehyde with the one or more CH-acidic compounds to form one or more reaction products is effected at a temperature in the range from 80 to 126 C.

13. The process as claimed in claim 10, wherein the molar ratio of the total amount of CH-acidic compounds to the total amount of formaldehyde in the reaction mixture is greater than 2:1.

14. The process as claimed in claim 10, wherein the reaction of the free formaldehyde with the one or more CH-acidic compounds to form one or more reaction products is at least performed until 50 mol % of the free formaldehyde present in the base mixture have reacted, and/or in the reaction mixture the proportion of free formaldehyde is less than 0.2% by weight, based on the total mass of the reaction mixture.

15. A process for producing a two-component binder system, as claimed in claim 9, comprising the steps of: providing or producing a phenolic resin composition as claimed in claim 1 as a phenolic resin component and combining the provided or produced phenolic resin component with a polyisocyanate component comprising a polyisocyanate having at least two isocyanate groups per molecule, so that the two-component binder system results.

16. A process for producing a feeder, a foundry mold or a foundry core from a molding material mixture, wherein the molding material mixture is bound by means of a two-component binder system as claimed in claim 9.

17. A feeder, foundry mold or foundry core, producible by a process as claimed in claim 15.

18. The phenolic resin composition as claimed in claim 5, wherein the or at least one of the CH-acidic reactant compounds is a -dicarbonyl compound.

19. The phenolic resin composition as claimed in claim 3, wherein the or at least one of the CH-acidic reactant compounds is diethyl malonate or dimethyl malonate.

Description

COMPARATIVE EXAMPLE 1NONINVENTIVE: PRODUCTION OF A PHENOLIC RESIN COMPOSITION WITHOUT USE OF A CH-ACIDIC COMPOUND

(1) Step 1:

(2) A premix was produced by mixing 45.96 kg of phenol, 38.14 kg of an aqueous formaldehyde solution (50% by weight of formaldehyde based on the total mass of the aqueous formaldehyde solution) and 0.07 kg of zinc acetate dihydrate in a reaction vessel. The pH was 5, measured at 20 C.

(3) Step 2:

(4) The produced premix was heated to reflux temperature and held at reflux. Meanwhile, samples were taken continuously and the refractive indices of the respective sampled mixtures were determined at 20 C. until a refractive index of 1.490 was attained. The product was a premix having a refractive index of 1.490.

(5) This premix having a refractive index of 1.490 was distilled at atmospheric pressure until a temperature of 125 C. was attained (in the residue). The product was a premix distilled at atmospheric pressure.

(6) The distillation was then continued under vacuum. To this end the distillation conditions were chosen such that a vacuum in the reaction vessel of 60 mbar was attained. The vacuum distillation was performed at a temperature not exceeding 126 C. (measured in the residue) and not falling below 100 C. (measured in the residue).

(7) During the distillation under vacuum, samples were taken continuously and the refractive indices of the respective sampled mixtures were determined at 20 C. until a refractive index of 1.610 was attained.

(8) After attaining a refractive index of 1.610, the distillation was terminated; the product was a vacuum-treated premix having a refractive index of 1.610.

(9) Step 3:

(10) The vacuum-treated premix having a refractive index of 1.610 was cooled to at least 40 C. The resulting product is referred to as the base mixture and is intended for further processing.

(11) The pH (assessed according to method 1) of the base mixture and the free formaldehyde content (measured according to method 2) of the base mixture were determined at 20 C. The pH assessed according to method 1 was 5.0 and the free formaldehyde content measured according to method 2 was 0.35% by weight based on the total mass of the base mixture.

(12) The amount of resulting base mixture was 60.4% by weight based on the total mass of the premix produced in step 1.

(13) The base mixture had a water content of 0.4% by weight.

(14) Step 4:

(15) Solvents and additives were added to the base mixture according to the table Comparative example 1 and the product was thus finished. The result was a finished product having a composition according to the table Comparative example 1.

(16) TABLE-US-00001 TABLE Comparative example 1: Composition Comparative example 1: Mass [kg] Base mixture 50.85 DBE 18.10 Solvesso 19.10 RME 11.50 Silan 187 0.30 Hydrofluoric acid 40% 0.15

(17) The finished product had a content of free formaldehyde (measured according to method 2) of 0.18% by weight based on the total mass of the finished product.

EXAMPLE 1INVENTIVE: PRODUCTION OF A PHENOLIC RESIN COMPOSITION USING A CH-ACIDIC COMPOUND

(18) Steps 1 to 3: Producing a Base Mixture

(19) Step 1:

(20) A premix was produced by mixing 45.96 kg of phenol, 38.14 kg of an aqueous formaldehyde solution (50% by weight of formaldehyde based on the total mass of the aqueous formaldehyde solution) and 0.07 kg of zinc acetate dihydrate in a reaction vessel. The pH was 5, measured at 20 C.

(21) Step 2:

(22) The produced premix was heated to reflux temperature and held at reflux. Meanwhile, samples were taken continuously and the refractive indices of the respective sampled mixtures were determined at 20 C. until a refractive index of 1.490 was attained.

(23) After attaining a refractive index of 1.490 the premix was distilled at atmospheric pressure until a temperature of 125 C. was attained (in the residue). The product was a premix distilled at atmospheric pressure.

(24) The distillation was then continued under vacuum. To this end, the distillation conditions were chosen such that a vacuum in the reaction vessel of 60 mbar was attained. The vacuum distillation was performed at a temperature not exceeding 126 C. (in the residue) and not falling below 100 C.

(25) During the distillation under vacuum samples were taken continuously and the refractive indices of the respective sampled mixtures were determined at 20 C. until a refractive index of 1.610 was attained.

(26) After reaching the refractive index of 1.610, the vacuum distillation was terminated. The product was a vacuum-treated premix having a refractive index of 1.610.

(27) Step 3:

(28) The vacuum-treated premix having a refractive index of 1.610 was cooled to 100 C. at atmospheric pressure. The resulting product is referred to as the base mixture and is intended for further processing.

(29) The pH (assessed according to method 1) of the base mixture and the free formaldehyde content (measured according to method 2) of the base mixture were determined at 20 C. The pH assessed according to method 1 was 5.0 and the free formaldehyde content measured according to method 2 was 0.35% by weight based on the total mass of the base mixture.

(30) The base mixture had a water content of 0.4% by weight.

(31) Step 4Reacting Free Formaldehyde with a CH-Acidic Compound to Form Reaction Products:

(32) The base mixture was mixed with 3 kg of diethyl malonate (as an example of a CH-acidic compound) at 100 C. to afford a reaction mixture and the reaction mixture was held at 100 C. for 10 minutes so that a reaction between the free formaldehyde from the base mixture and the diethyl malonate took place. The reaction mixture was subsequently cooled initially to 80 C. over 30 minutes and then to at least 40 C. The product was a cooled reaction mixture.

(33) The content in the cooled reaction mixture of free formaldehyde (measured according to method 2) was determined at 20 C. The free formaldehyde content measured according to method 2 was 0.15% by weight based on the total mass of the cooled reaction mixture.

(34) The amount of cooled reaction mixture was 61.8% by weight, based on the total mass of the premix produced in step 1.

(35) Step 5Adding Other Constituents to Complete a Phenolic Resin Composition According to the Invention:

(36) Solvents and additives were correspondingly added to the cooled reaction mixture as per the table Example 1 and the product was thus finished. The result was a finished product having a composition according to the table Example 1.

(37) TABLE-US-00002 TABLE Example 1: Composition Example 1: Mass [kg] Reaction mixture 53.85 DBE 15.10 Solvesso 19.10 RME 11.50 Silan 187 0.30 Hydrofluoric acid 40% 0.15

(38) The finished product has a content of free formaldehyde (measured according to method 2) of 0.08% by weight based on the total mass of the finished product and is a phenolic resin composition according to the invention.

COMPARATIVE EXAMPLE 2NONINVENTIVE: PRODUCTION OF A PHENOLIC RESIN COMPOSITION WITHOUT USE OF A CH-ACIDIC COMPOUND

(39) Step 1:

(40) A premix was produced by mixing 46.7 kg of phenol, 21.4 kg of commercially available paraformaldehyde (91% by weight of formaldehyde based on the total mass of the commercially available paraformaldehyde), 0.06 kg of zinc acetate dihydrate and 1.4 kg of methanol in a reaction vessel. The pH (assessed according to method 1) was 5, measured at 20 C.

(41) Step 2:

(42) The produced premix was heated to 110 C. and held at 110 C. for 45 minutes.

(43) After the 45 minutes at 110 C. the heated premix was distilled at atmospheric pressure until a temperature of 125 C. was attained (in the residue). The product was a premix distilled at atmospheric pressure.

(44) The distillation was then continued under vacuum. To this end the distillation conditions were chosen such that a vacuum in the reaction vessel of 60 mbar was attained. The distillation was subsequently continued at a temperature not exceeding 126 C. (in the residue).

(45) During the distillation under vacuum samples were taken continuously and the refractive indices of the respective sampled mixtures were determined at 20 C. until a refractive index of 1.613 was attained.

(46) After attaining a refractive index of 1.613 the distillation was terminated; the product was a vacuum-treated premix having a refractive index of 1.613.

(47) Step 3:

(48) The vacuum-treated premix having a refractive index of 1.613 was cooled to at least 40 C. The resulting product is referred to as the base mixture and is intended for further processing.

(49) The pH (assessed according to method 1) of the base mixture and the free formaldehyde content (measured according to method 2) of the base mixture were determined at 20 C. The pH assessed according to method 1 was 5.1 and the free formaldehyde content measured according to method 2 was 0.4% by weight based on the total mass of the base mixture.

(50) The base mixture had a water content of 0.4% by weight.

(51) The amount of base mixture was 78.4% by weight, based on the total weight of the premix produced in step 1.

(52) Step 4:

(53) Solvents and additives were added to the base mixture according to the table Comparative example 2 and the product was thus finished. The result was a finished product having a composition according to the table Comparative example 2.

(54) TABLE-US-00003 TABLE Comparative example 2: Composition Comparative example 2: Mass [kg] Base mixture 54.50 DBE 20.00 RME 20.00 Solvesso 5.10 Silan 187 0.30 Hydrofluoric acid 40% 0.10

(55) The finished product had a content of free formaldehyde (measured according to method 2) of 0.22% by weight based on the total mass of the finished product.

EXAMPLE 2INVENTIVE: PRODUCTION OF A PHENOLIC RESIN COMPOSITION USING A CH-ACIDIC COMPOUND

(56) Steps 1 to 3: Producing a Base Mixture

(57) Step 1:

(58) A premix was produced by mixing 46.7 kg of phenol, 21.4 kg of commercially available paraformaldehyde (91% by weight of paraformaldehyde based on the total mass of the commercially available paraformaldehyde), 0.06 kg of zinc acetate dihydrate and 1.4 kg of methanol in a reaction vessel. The pH (assessed according to method 1) was 5, measured at 20 C.

(59) Step 2:

(60) The produced premix was heated to 110 C. and held at 110 C. for 45 minutes.

(61) After the 45 minutes at 110 C. the heated premix was distilled at atmospheric pressure until a temperature of 125 C. was attained (in the residue). The product was a premix distilled at atmospheric pressure.

(62) The distillation was then continued under vacuum. To this end the distillation conditions were chosen such that a vacuum in the reaction vessel of 60 mbar was attained. The distillation was subsequently continued at a temperature not exceeding 126 C. (measured in the residue).

(63) During the distillation under vacuum samples were taken continuously and the refractive indices of the respective sampled mixtures were determined at 20 C. until a refractive index of 1.613 was attained.

(64) After attaining a refractive index of 1.613 the distillation was terminated; the product was a vacuum-treated premix having a refractive index of 1.613.

(65) Step 3:

(66) The vacuum-treated premix having a refractive index of 1.613 was cooled to at least 100 C. The resulting product is referred to as the base mixture and is intended for further processing.

(67) The pH (assessed according to method 1) of the base mixture and the free formaldehyde content (measured according to method 2) of the base mixture were determined at 20 C. The pH assessed according to method 1 was 5.1 and the free formaldehyde content measured according to method 2 was 0.4% by weight based on the total mass of the base mixture.

(68) The base mixture had a water content of 0.4% by weight.

(69) Step 4Reacting Free Formaldehyde with a CH-Acidic Compound to Form Reaction Products:

(70) The base mixture was mixed with 3 kg of diethyl malonate (as an example of a CH-acidic compound) at 100 C. to afford a reaction mixture and the reaction mixture was held at 100 C. for 10 minutes so that a reaction between the free formaldehyde from the base mixture and the diethyl malonate took place. The reaction mixture was subsequently cooled initially to 80 C. over 30 minutes and then to 40 C. The product was a cooled reaction mixture.

(71) The content in the cooled reaction mixture of free formaldehyde (measured according to method 2) was determined at 20 C. The free formaldehyde content measured according to method 2 was 0.15% by weight based on the total mass of the cooled reaction mixture.

(72) The amount of cooled reaction mixture was 79.2% by weight, based on the total mass of the produced premix.

(73) Step 5Adding Other Constituents to Complete a Phenolic Resin Composition According to the Invention:

(74) Solvents and additives were added to the cooled reaction mixture as per the table Example 2 and the product was thus finished. The result was a finished product having a composition according to the table Example 2.

(75) TABLE-US-00004 TABLE Example 2: Composition Example 2 Mass [kg] Reaction mixture 57.50 DBE 17.00 RME 20.00 Solvesso 5.10 Silan 187 0.30 Hydrofluoric acid 40% 0.10

(76) The finished product had a content of free formaldehyde (measured according to method 2) of 0.07% by weight based on the total mass of the finished product and is a phenolic resin composition according to the invention.

EXAMPLE 3INVENTIVE: PRODUCTION OF A PHENOLIC RESIN COMPOSITION USING A CH-ACIDIC COMPOUND (VARIOUS OTHER CONSTITUENTS IN EXAMPLES 3A AND 3B)

(77) Steps 1 to 3: Producing a Base Mixture

(78) Step 1:

(79) A premix was produced by mixing 42.0 kg of phenol, 20.0 kg of commercially available paraformaldehyde (91% by weight of paraformaldehyde based on the total mass of the commercially available paraformaldehyde) and 0.1 kg of zinc acetate dihydrate in a reaction vessel. The pH (assessed according to method 1) was 5.0, measured at 20 C.

(80) Step 2:

(81) The produced premix was heated to 110 C. and held at 110 C. for 60 minutes and heated from 110 C. to 120 C. and held at 120 C. for 60 minutes. The product was a premix held at 120 C. for 60 minutes.

(82) The premix held at 120 C. for 60 minutes was heated further at atmospheric pressure and distilled until a temperature of 125 C. was attained (in the residue). The product was a premix distilled at atmospheric pressure.

(83) The distillation was then continued under vacuum. To this end the distillation conditions were chosen such that a vacuum in the reaction vessel of 60 mbar was attained. The distillation was subsequently continued at a temperature not exceeding 126 C. (measured in the residue).

(84) During the distillation under vacuum samples were taken continuously and the refractive indices of the respective sampled mixtures were determined at 20 C. until a refractive index of n.sub.D.sup.20=1.610 was attained.

(85) After attaining a refractive index of 1.610 the distillation was terminated; the product was a vacuum-treated premix having a refractive index of 1.610.

(86) Step 3:

(87) The vacuum-treated premix having a refractive index of 1.610 was cooled to 100 C. at atmospheric pressure. The resulting product is referred to as the base mixture and is intended for further processing.

(88) The pH (assessed according to method 1) of the base mixture and the free formaldehyde content (measured according to method 2) of the base mixture were determined at 20 C. The pH assessed according to method 1 was 5.1 and the free formaldehyde content measured according to method 2 was 0.45% by weight based on the total mass of the base mixture.

(89) The base mixture had a water content of 0.4% by weight.

(90) Step 4Reacting Free Formaldehyde with a CH-Acidic Compound to Form Reaction Products:

(91) The base mixture was mixed with 3 kg of dimethyl malonate (Example 3a)/3 kg of diethyl malonate (Example 3b) (each as an example of a CH-acidic compound) at 100 C. to afford a reaction mixture and the reaction mixture was held at 100 C. for 10 minutes so that a reaction between the free formaldehyde from the base mixture and the dimethyl malonate (Example 3a)/diethyl malonate (Example 3b) took place. The reaction mixture was subsequently cooled initially to 80 C. over 30 minutes and then to at least 40 C. The result was a cooled reaction mixture.

(92) The content in the cooled reaction mixture of free formaldehyde (measured according to method 2) was determined at 20 C. The free formaldehyde content measured according to method 2 was 0.07% by weight (Example 3a)/0.08% by weight (Example 3b) based on the total mass of the cooled reaction mixture.

(93) The amount of cooled reaction mixture was in each case 86% by weight based on the total mass of the premix produced in step 1.

(94) Step 5Adding Other Constituents to Complete a Phenolic Resin Composition According to the Invention (Example 3a/Example 3b):

(95) Solvents and additives were added to the cooled reaction mixture as per the tables Example 3a/Example 3b and the product was thus finished. The result was a finished product having a composition according to table Example 3a/Example 3b.

(96) TABLE-US-00005 TABLE Example 3a: Composition Example 3a Mass [kg] Reaction mixture 54.00 DBE 15.10 Solvesso 19.10 RME 11.50 Silan 187 0.30

(97) TABLE-US-00006 TABLE Example 3b: Composition Example 3b: Mass [kg] Reaction mixture 53.85 DBE 14.10 Tetraethyl orthosilicate (TEOS) 32.05

(98) The finished products according to Example 3a and Example 3b each had a content of free formaldehyde of less than 0.05% by weight determined according to method 2; a phenolic resin composition according to the invention is concerned in each case.

EXAMPLE 4: PRODUCING TWO-COMPONENT BINDER SYSTEMS ACCORDING TO THE INVENTION

(99) 4.1 Compositions Example 1, Example 2, Example 3a and Example 3b as described above were each combined with MDI mixtures 1 (Table 5), 2 (Table 6) and 3 (Table 7) to produce two-component binder systems according to the invention for use in the polyurethane cold-box process.

(100) A total of twelve two-component binder systems were obtained from the combinations of the compositions according to Example 1, Example 2, Example 3a and Example 3b with the MDI mixtures 1 (cf. table 5), 2 (cf. table 6) and 3 (cf. table 7) defined below.

(101) 4.2 Compositions Example 3a and Example 3b) as described above were each combined with MDI Mixtures 4 (table 8) and 5 (table 9) to prepare two-component binder systems according to the invention for use in the polyurethane no-bake process.

(102) A total of four two-component binder systems were obtained from the combinations of the compositions according to Example 3a and Example 3b with the MDI mixtures 4 (cf. table 8) and 5 (cf. table 9) defined below.

(103) TABLE-US-00007 TABLE 5 MDI Mixture 1: Mass [kg] MDI 75.00 Solvesso 24.70 POCl.sub.3 0.30

(104) TABLE-US-00008 TABLE 6 MDI Mixture 2: Mass [kg] MDI 75.00 POCl.sub.3 0.3 Tetraethyl orthosilicate (TEOS) 24.70

(105) TABLE-US-00009 TABLE 7 MDI Mixture 3: Mass [kg] MDI 75.00 POCl.sub.3 0.3 Solvesso 24.70

(106) TABLE-US-00010 TABLE 8 MDI Mixture 4: Mass [kg] MDI 75.00 Tetraethyl orthosilicate (TEOS) 25.00

(107) TABLE-US-00011 TABLE 9 MDI Mixture 5: Mass [kg] MDI 75.00 Solvesso 25.00

EXAMPLE 5: PRODUCTION OF FOUNDRY CORES BY THE POLYURETHANE COLD-BOX PROCESS

(108) Each of the altogether twelve two-component binder systems from Example 4.1 was employed in customary fashion for producing a foundry core by the polyurethane cold-box process.

(109) The foundry cores obtained fulfilled all physical requirements.

(110) The decomposition properties of the foundry cores were rated as particularly favorable.

EXAMPLE 6: PRODUCTION OF FOUNDRY CORES BY THE POLYURETHANE NO-BAKE PROCESS

(111) Each of the four two-component binder systems from Example 4.2 was employed in customary fashion for producing a foundry core by the polyurethane no-bake box process.

(112) The foundry cores obtained fulfilled all physical requirements.

(113) The decomposition properties of the foundry cores were rated as particularly favorable.

(114) Analytical Methods:

(115) Method 1: Testing to Assess the pH of a Sample Mixture (e.g. Base Mixture, Reaction Mixture or Phenolic Resin Composition)

(116) 20 g of a sample mixture are admixed with 160 g of a mixture of 20 g of water and 140 g of ethanol p.a. and homogenized by stirring. The thus obtained solution is temperature-con-trolled to 20 C. and the pH is determined by means of a pH meter, for example a Schott CG 842 pH meter.

(117) Method 2: Determination of the Free Formaldehyde Content in [%]

(118) Solutions Required:

(119) TABLE-US-00012 IPA/water: Mixture of iso-propanol (IPA) (purity: p.A.) and dist. water (iso-propanol:H.sub.2O mixing ratio = 3:1) KCN solution Aqueous KCN solution (KCN concentration: 0.1 mol/l) Phosphate Production: buffer Initially charge 348 g of K.sub.2HPO.sub.4 and 136 g of KH.sub.2PO.sub.4 solution: into a 1 L volumetric flask, make up to 1 L with deion- ized water and mix until a clear solution is formed. Borate Production: buffer Initially charge 76.4 g of K.sub.2B.sub.4O.sub.7 2H.sub.2O (purity: p.A.) solution: into a 1 L volumetric flask, make up to 1 L with deion- ized water and mix until a clear solution is formed. Hg(NO.sub.3).sub.2 Aqueous Hg(NO.sub.3).sub.2 solution (Hg(NO.sub.3).sub.2 concentration: solution: 0.05 mol/l) Indicator Solution of diphenylcarbazone in methanol (diphenyl- solution: carbazone concentration: 1% by weight)
Performance:

(120) When performing the method, care must be taken to ensure that the sample weight is chosen according to the expected formaldehyde content and preferably such that about 10-20 ml of Hg(NO.sub.3).sub.2 solution are needed for the titration. The following table gives guidelines for the sample weight to be chosen:

(121) TABLE-US-00013 Expected formaldehyde content [%] Sample weight [g] <0.05% >10 g 0.05-0.5% 10-3 g 0.5-1.0% 3-2 g
Measurement:
Determination of Blank Value:

(122) A blank value must be determined before each measurement. To this end, 100 ml of IPA/water are initially charged into a 400 ml beaker. This is mixed with a magnetic stirrer and first 40 ml of borate buffer solution and then 20 ml of KCN solution are added. After two minutes, 5 ml of phosphate buffer solution and 3-5 drops of indicator solution are added so that coloration of the solution is observed.

(123) Titration is performed with a 0.05 molar aqueous Hg(NO.sub.3).sub.2 solution. The end point of the titration is indicated by the color change from pink/orange to violet. The color should be stable for at least 10 seconds after reaching the end point.

(124) The consumption of 0.05 M Hg(NO.sub.3).sub.2 solution is recorded as the blank value.

(125) Determination of sample weight and consumption of titration solution:

(126) The sample is weighed using an analytical balance in a 400 ml beaker (=sample weight) and dissolved in 100 ml of IPA/water. This is mixed with a magnetic stirrer and first 40 ml of borate buffer solution and then 20 ml of KCN solution are added. The pH of the solution should be in the region of 9.3.

(127) The reaction time is measured from the moment of addition of the KCN solution and is 2 minutes.

(128) At the end of the two-minute reaction time, 5 ml of phosphate buffer solution and 3-5 drops of indicator solution are added so that coloration of the solution is observed.

(129) Titration is performed with a 0.05 molar aqueous Hg(NO.sub.3).sub.2 solution. The end point of the titration is indicated by the color change from pink/orange to violet. The color should be stable for at least 10 seconds after reaching the end point.

(130) The consumption of 0.05 M Hg(NO.sub.3).sub.2 solution is recorded as the consumption value.

(131) Calculation:

(132) The content of free formaldehyde in [% by weight] is calculated according to the following formula:

(133) $\mathrm{Free}\mathrm{formaldehyde}\left[\%\mathrm{by}\mathrm{weight}\right]=\frac{\begin{array}{c}\left(\mathrm{Blank}\mathrm{value}\left[\mathrm{ml}\right]-\mathrm{consumption}\mathrm{value}\left[\mathrm{ml}\right]\right)\\ 0.294\left[g\text{/}\mathrm{ml}\right]\end{array}}{\mathrm{Sample}\mathrm{weight}\left[g\right]}$