Phenol resin for use in the phenol resin component of a two-component binder system

Abstract

The present invention relates to a phenolic resin for use in the phenolic resin component of a two-component binder system for the polyurethane cold box process, to a two-component binder system for use in the polyurethane cold box process, to a molding material mixture for curing by contacting with a tertiary amine, to the use of a corresponding phenolic resin, of a corresponding phenol component, of a corresponding two-component binder system or of a corresponding molding material mixture. The present invention relates, moreover, to an article from the group consisting of feeders, foundry molds and foundry cores, producible from a corresponding molding material mixture, to a process for preparing a phenolic resin, and to a process for producing an article from the group consisting of feeders, foundry molds and foundry cores.

Claims

1. A phenolic resin for use in the phenolic resin component of a two-component binder system for the polyurethane cold box process, wherein the phenolic resin comprises: (a) a resole having the following structural units: ##STR00023## where at one, two or three of the positions 2, 4 and 6, instead of a bond to hydrogen, there is a bond to a further structural unit of the resole, (a2) one or more structural units of the formula (A2) ##STR00024## where the substituent R is an (a2-i) unsubstituted, (a2-ii) aliphatic, (a2-iii) branched or unbranched, (a2-iv) saturated or unsaturated radical having a total of 5 to 35 carbon atoms, and where at one, two or three of the positions 2, 4 and 6, instead of a bond to hydrogen, there is a bond to a further structural unit of the resole, (a3) one or more structural units of the formula (A3) ##STR00025## where the substituent R′ is substituted at position 2 or 4 and is an (a3 i) unsubstituted, (a3-ii) aliphatic, (a3-iii) branched or unbranched, (a3-iv) saturated or unsaturated radical having a total of 1 to 15 carbon atoms, and where at one, two or three of the remaining positions 2, 4 and 6, instead of a bond to hydrogen, there is a bond to a further structural unit of the resole, ##STR00026## as a link connecting two phenol rings, ##STR00027## as a link connecting two phenol rings.

2. The phenolic resin as claimed in claim 1, wherein the substituent R in the structural unit or at least in one of the structural units of the formula (A2) is an (a2-i) unsubstituted, (a2-ii) aliphatic, (a2-iii) unbranched radical having a total of 5 to 35 carbon atoms.

3. The phenolic resin as claimed in claim 1, wherein the substituent R in the structural unit or at least in one of the structural units of the formula (A2) is (a2-iv) mono- or polyunsaturated.

4. The phenolic resin as claimed in claim 1, wherein the substituent R in the structural unit or at least in one of the structural units of the formula (A2) is an (a2-i) unsubstituted, (a2-ii) aliphatic, (a2-iii) unbranched radical having a total of 15 carbon atoms which (a2-iv) is triunsaturated.

5. The phenolic resin as claimed in claim 1, wherein the structural units of the formula (A2) is one or more structural units of the formula (A2-A): ##STR00028## where one, two or all of the bonds shown with dashes represents a double bond, where at one, two or three of the positions 2, 4 and 6, instead of a bond to hydrogen, there is a bond to a further structural unit of the resole.

6. The phenolic resin as claimed in claim 1, wherein the substituent R′ in the structural unit or at least in one of the structural units of the formula (A3) is disposed in ortho-position to the phenolic OH.

7. The phenolic resin as claimed in claim 1, wherein the substituent R′ in the structural unit or at least in one of the structural units of the formula (A3) is an (a3-i) unsubstituted, (a3-iii) branched or unbranched, (a3-iv) saturated alkyl radical having 1 to 9 carbon atoms.

8. The phenolic resin as claimed in claim 1, wherein the molar ratio of the structural units a1 to a2 in the resole of the constituent (a) is in the range from 10:1 to 99:1.

9. The phenolic resin as claimed in claim 1, wherein the molar ratio of the structural units a1 to a3 in the resole of the constituent (a) is in the range from 1:1 to 10:1.

10. The phenolic resin as claimed in claim 1, wherein the molar ratio of the structural units a2 to a3 in the resole of the constituent (a) is in the range from 5:1 to 30:1.

11. The phenolic resin as claimed in claim 1, wherein the molar ratio of the structural units a4 to a5 in the resole of the constituent (a) is in the range from 90:10 to 10:90.

12. The phenolic resin as claimed in claim 1, wherein the structural units of the formula (A2) is one or more structural units of the formula (A2-A): ##STR00029## where one, two or all of the bonds shown with dashes represents a double bond and where the substituent R′ in the structural unit or at least in one of the structural units of the formula (A3) is disposed in ortho-position to the phenolic OH, and the substituent R′ represents a methyl group.

13. A phenolic resin component for use as a component of a two-component binder system for the polyurethane cold box process, comprising a phenolic resin as claimed in claim 1 and also a solvent for the phenolic resin.

14. A two-component binder system for use in the polyurethane cold box process, comprising a phenolic resin component and an isocyanate component separate from it, wherein the phenolic resin component comprises a phenolic resin as claimed in claim 1.

15. A mixture for curing by contacting with a tertiary amine or with a mixture of two or more tertiary amines, wherein the mixture is preparable by mixing components of the two-component binder system as claimed in claim 14.

16. The phenolic resin as claimed in claim 1 for binding a mold base material or a mixture of mold base materials in the polyurethane cold box process.

17. An article from the group consisting of feeders, foundry molds and foundry cores, producible from a mixture as claimed in claim 15.

18. A process for preparing a phenolic resin, comprising the following steps: (A) providing or preparing phenol, (B) providing or preparing one or more compound having the general formula (I) ##STR00030## where the substituent R is an (a2-i) unsubstituted, (a2-ii) aliphatic, (a2-iii) branched or unbranched, (a2-iv) saturated or unsaturated radical having a total of 5 to 35 carbon atoms, (C) providing or preparing one or more compound having the general formula (II) ##STR00031## where the substituent R′ is substituted at position 2 or 4 and is an (a3 i) unsubstituted, (a3-ii) aliphatic, (a3-iii) branched or unbranched, (a3-iv) saturated or unsaturated radical having a total of 1 to 12 carbon atoms, (D) providing or preparing formaldehyde (E) providing divalent metal ions as metal catalyst, and (F) incorporating by condensation the compounds provided or prepared in steps (A) to (D) using the metal ions provided in step (E) as metal catalyst, wherein the polycondensation takes place in a weakly acidic medium.

19. The phenolic resin as claimed in claim 9, wherein the molar ratio of the structural units a1 to a3 in the resole of the constituent (a) is in the range from 1.5:1 to 3.5:1.

20. The phenolic resin as claimed in claim 10, wherein the molar ratio of the structural units a2 to a3 in the resole of the constituent (a) is in the range from 10:1 to 20:1.

Description

(1) The invention is elucidated further below by means of examples.

EXAMPLE 1: PREPARATION OF AN INVENTIVE PHENOLIC RESIN

(2) A reaction vessel fitted with condenser, thermometer and stirrer was charged with the following: 20 parts by weight of phenol 15 parts by weight of ortho-cresol 0.025 part by weight of zinc acetate dihydrate 0.015 part by weight of zinc stearate.

(3) The condenser was set to reflux. The temperature was brought, rising continuously over the course of an hour, to 110° C. and was maintained at this temperature.

(4) Over a period of 90 minutes, 17 parts by weight of paraformaldehyde (91%) were added in 20 portions.

(5) The reaction mixture is subsequently stirred further and 3.0 parts by weight of cardanol are added. The reaction mixture is heated at 110° C. for a further 30 minutes.

(6) Subsequently the condenser was changed over to an atmospheric distillation and the temperature was raised over the course of an hour to 125-126° C., causing the distillative removal of the volatile constituents from the product solution.

(7) Thereafter there was a vacuum distillation, in which the remaining volatile constituents were removed.

(8) The phenolic resin of the invention is attained in a yield of around 80%.

EXAMPLE 2: PREPARATION OF A NONINVENTIVE PHENOLIC RESIN

(9) A reaction vessel fitted with condenser, thermometer and stirrer was charged with the following: 20 parts by weight of phenol 15 parts by weight of ortho-cresol 0.025 part by weight of zinc acetate dihydrate 0.015 part by weight of zinc stearate.

(10) The condenser was set to reflux. The temperature was brought, rising continuously over the course of an hour, to 110° C. and was maintained at this temperature.

(11) Over a period of 90 minutes, 17 parts by weight of paraformaldehyde (91%) were added in 20 portions.

(12) The reaction mixture is subsequently heated at 110° C. for a further 30 minutes.

(13) Subsequently the condenser was changed over to an atmospheric distillation and the temperature was raised over the course of an hour to 125-126° C., causing the distillative removal of the volatile constituents from the product solution.

(14) Thereafter there was a vacuum distillation, in which the remaining volatile constituents were removed.

(15) A phenol/o-cresol resin is attained in a yield of around 80%.

EXAMPLE 3: PREPARATION OF A NONINVENTIVE PHENOLIC RESIN

(16) A reaction vessel fitted with condenser, thermometer and stirrer was charged with the following: 33 parts by weight of phenol 0.025 part by weight of zinc acetate dihydrate 0.015 part by weight of zinc stearate.

(17) The condenser was set to reflux. The temperature was brought, rising continuously over the course of an hour, to 110° C. and was maintained at this temperature.

(18) Over a period of 90 minutes, 17 parts by weight of paraformaldehyde (91%) were added in 20 portions.

(19) The reaction mixture is subsequently heated at 110° C. for a further 30 minutes.

(20) Subsequently the condenser was changed over to an atmospheric distillation and the temperature was raised over the course of an hour to 125-126° C., causing the distillative removal of the volatile constituents from the product solution.

(21) Thereafter there was a vacuum distillation, in which the remaining volatile constituents were removed.

(22) A phenolic resin is attained in a yield of around 80%.

EXAMPLE 4: DETERMINATION OF THE MISCIBILITY OF THE RESINS PREPARED IN EXAMPLES 1 TO 3 WITH TETRAETHYL SILICATE

(23) 100 g of the resin for testing were charged to a glass beaker and tetraethyl silicate was added in portions until the resulting resin solution was found to be hazy at 25° C. Here it was ensured that after each addition of a portion of tetraethyl silicate, stirring took place for long enough to produce a homogeneous solution.

(24) After the addition of the first portions of tetraethyl silicate, the resulting mixture was heated to 60° C. and cooled back to 25° C. before the subsequent addition. The addition of portions of the tetraethyl silicate was repeated multiply until hazing of the resin was observed that could not be eliminated even by sufficiently long (>90 minutes) stirring of the solution at 25° C.

(25) The measurement was repeated three times and the average was formed.

(26) The results are reported in table 1 below:

(27) TABLE-US-00001 Maximum miscibility: 100 g phenolic resin with a maximum of x g tetraethyl Resin silicate (TEOS)* at 25° C. From example 1 150 g TEOS/100 g phenolic resin From example 2 100 g TEOS/100 g phenolic resin From example 3  66 g TEOS/100 g phenolic resin *The limit of miscibility is considered to be reached when the mixture turns hazy.

(28) From the results it is apparent that the inventive phenolic resin from example 1 exhibits a higher miscibility with tetraethyl silicate than the noninventive phenolic resins from examples 2 and 3.

EXAMPLE 5: DETERMINATION OF FRACTURE FORCE, FRACTURE DISPLACEMENT, AND INSTANTANEOUS STRENGTH

(29) The phenolic resins prepared in examples 1 and 2 were each mixed 1:1 with a mixture of 13 parts by weight of DBE and 37 parts by weight of tetraetyl silicate. The resulting phenolic resin component was used for producing test specimens.

(30) A molding material mixture was produced using the phenolic resin component prepared, mold base materials, and a polyisocyanate component. In the cold box process, test specimens in the form of flexural rods were produced as described below, and a determination was made of their initial flexural strengths.

(31) The isocyanate component is prepared by mixing 80 parts of diphenylmethane diisocyanate (for example, Lupranat M20S, BASF), 19 parts of tetraethyl silicate and 1 part of additive according to patent DE 102012201971.

(32) The production of a test specimens (+GF+ standard flexural strength test specimens) is carried out in line with the VDG datasheet P73. For this purpose, the mold base material is charged to a mixing vessel. The phenolic resin component and polyisocyanate component are then weighed into the mixing vessel in such a way that they do not mix directly with one another. Mold base material, the phenolic resin component prepared, and polyisocyanate component are mixed subsequently in a paddle mixer (Multiserw, model RN10/P) for 2 minutes at around 220 revolutions/minute to give a molding material mixture.

(33) The test specimens are produced using a universal core shooting machine LUT equipped with an LUT/G Gasomat, both from Multiserw. Directly after its production as described above, the completed molding material mixture is introduced into the shooting head of the core shooting machine.

(34) The parameters of the core shooting procedure are as follows: shooting time: 3 seconds, delay time after shooting: 5 seconds, shooting pressure: 4 bar (400 kPa). For curing, the test specimens are gassed for 10 seconds at a gassing pressure of 2 bar (200 kPa) with dimethylpropylamine (DMPA). They are subsequently purged with air for 9 seconds with a purging pressure of 4 bar (400 kPa) and determinations were then made of the fracture displacement, the fracture force, and the instantaneous strength of the test specimens produced.

(35) The instantaneous strength is measured using a Multiserw test instrument LRu-2e at defined times (15 seconds, 1 hour, 24 hours; see table 2) after the end of the purge.

(36) The fracture force and fracture displacement are measured using a Multiserw test instrument LRu-DMA at defined times (15 seconds, 1 hour, 24 hours; see table 2) after the end of the purge.

(37) The results of the measurements are reproduced in the table below, table 2.

(38) TABLE-US-00002 TABLE 2 15 s (instant) 1 h 24 h Fracture force [N] Phenolic resin from example 1 102 161 183 Phenolic resin from example 2 119 162 187 Fracture displacement [mm] Phenolic resin from example 1 0.87 0.48 0.55 Phenolic resin from example 2 0.62 0.46 0.53 Instantaneous strength [N/cm.sup.2] Phenolic resin from example 1 268 381 390 Phenolic resin from example 2 307 386 426