JPS6345895B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a binder for cold-curing foundry sand. The present invention is useful in the foundry industry for the production of cores and molds that are hardened in cooled tools used in the production of castings from iron, steel and non-ferrous metals. [Background of the Invention] Currently, cold-curing molding sand containing a phenol-formaldehyde synthetic resin or a furan synthetic resin as a binder is used for the production of molds and cores. Thus, for steel casting, resin sands are used that use phenol-formaldehyde resins and phenol-furan resins as binders. However, the caking properties of resins and their ability to cold cure deteriorate over time.
The shelf life of these resins does not exceed 3 to 6 months. In order to guarantee the required mechanical strength properties of the foundry sands to be produced, the consumption rate of the resin in these foundry sands is 2-3% by weight, which impairs occupational hygiene and health conditions. , and increase the manufacturing cost of foundry sand. To overcome these drawbacks, resin modifiers, namely silanes, are used, which make it possible to obtain the desired durability with small amounts of binder in the foundry sand. Recent conventional binders that are most similar to the binders of the present invention with respect to the results achieved are synthetic resins and general formula R'( _CH2 ) _o Si(OR) ₃ , where n is 1 to 3. , R′ is a reactive functional group bonded to the silicon atom, usually through an alkyl chain, e.g. a propylene group (CH ₂ ) ₃ , and R is a hydrocarbon group having 2 to 3 carbon atoms) (Tsukofsky S.S., Rias A.M., “Molds and cores from cold-cured sand,”
pp. 77-83, ``Macinostroenigie'' Publishers, 1978). The amount of silane introduced into the resin for modification purposes is 0.2-1.0% by weight of the resin
Configure. For binders based on phenol-furan resins, phenol-formaldehyde resins and urea-furan resins, amino functional groups (NH ₂ )
Use a silane with Binders modified with these silanes are
It has a limited shelf life due to hydrolysis of the silane within the resin. Due to hydrolysis, the modifying effect decreases over time and disappears completely. That is, the mechanical strength of the resin is reduced. For this reason, silane cannot be directly incorporated into plant-produced resins. Moreover, since the modifying effect is lost after 5-6 days, fresh lots of binder often have to be prepared, which leads to low labor productivity and additional power consumption; and increases the rate of silane consumption. It is believed that a shelf life for the modifying properties of the silane that will be consistent with the lifetime of the resin, which is in the range of 3 to 6 months, is optimal. SUMMARY OF THE INVENTION The present invention is concerned with modifying the resins incorporated into binders for cold-curing foundry sand so that the binders retain their caking properties over extended storage periods. This purpose was achieved by using the general formula R′(CH ₂ ) _o Si(CH ₃ ) _n (OR) _3-n (in the formula, n is an integer from 1 to 3, m is 0 or 1, _{and R} ' is _NH2 , _NH2CH2NH , _C6H5NH ,
_{C6H5O ,}

【formula】

[Formula], R is an aliphatic hydrocarbon group having a branched structure having 7 to 10 carbon atoms) is used, and the above components are contained in weight%.
This is achieved by a room-temperature curing binder for molding sand characterized in that the following amounts of polycondensation type synthetic resin 99.0 to 99.8 and 0.2 to 1.0 of the silane having the above structure are present. According to the present invention, the caking property can be reduced for 3 to 4 months.
Thus, it is now possible to prepare cold-curing foundry sand binders that retain for a period substantially equal to the shelf life of the resin used. This gives the possibility of intensive preparation of binders,
Reduce the consumption rate of binder and increase labor productivity, improve the quality of castings and increase their precision. According to the invention, it is desirable to use γ-aminopropyltri-(β-ethylhexyloxy)silane as the silane. It is preferred to use thermosetting products of the polycondensation of formaldehyde with phenol and/or furyl alcohol and/or carbamide as synthetic resins. Further objects and advantages of the invention will become apparent from the following detailed description of a binder for cold-curing foundry sand and examples illustrating its preparation and use. Thermosetting products of the polycondensation of formaldehyde with phenol and/or furyl alcohol and/or carbamide can be used as polycondensation synthetic resins. The modern concept of the mechanism of action of silanes as modifiers for synthetic resins is that they remain efficient until they are condensed into siloxanes. In resins containing water, hydrolysis of the silane occurs and the resulting silanols are then condensed. the result,
The shelf life of the modification properties of currently known silanes in resin compositions does not exceed 10-15 days. The inventors have taken into account that silane is easily hydrolyzed due to the high polarity of the bond ≡Si-O- _Cal . The hydrolytic stability of this bond can be increased by using an alkoxy group having 3 or more carbon atoms. The inventors have found that it is preferable to use alkoxy groups of isomeric structure that create additional steric effects that enhance the Si-O- _Cal bond. As a result, the inventors found that R′(CH ₂ ) _o Si(CH ₃ ) _n (OR) _3-n is the most effective to guarantee the stability of the modification effect during storage of silanized resins. (In the formula, n is an integer from 1 to 3, m is 0 or 1, and R' is NH ₂ , NH ₂ CH ₂ NH, C ₆ H ₅ NH,
_{C6H5O ,}

【formula】 〔Example〕

Example 1 Phenol-formaldehyde resin 99.6% by weight
γ-Aminopropyltri-(β-ethylhexyloxy)- in a container equipped with a mechanical stirrer.
Mix with 0.4% silane by weight for 35 minutes. 1.0 part by weight of the resulting modified resin is mixed for 1.0 minutes with 100 parts by weight of quartz sand in a container equipped with a mechanical stirrer, and then mixed with the curing catalyst, i.e. an aqueous solution of benzenesulfonic acid with a density of 1.25-1.30 g/ ^cm3. 1.0 part by weight is added and the mixture thus prepared is stirred for an additional minute. The compressive strength of the resulting room-temperature-cured molding sand is determined by
Measurements are taken 1 hour and 24 hours after mixture preparation on laboratory equipment available from Fisher Company. Crumble is measured according to standard methods. Storage period 0 days: Compressive strength (Kgf/cm ² ) After 1 hour 8 After 24 hours 34 Crumbling after 24 hours (%) 0.2 Storage period 7 days of modified binder: Compressive strength (Kgf/cm ² ) After 1 hour 8 After 24 hours 34 Crumbling after 24 hours (%) 0.2 Storage period of modified binder 3 months: Compressive strength (Kgf/cm ² ) After 1 hour 6 After 24 hours 30 After 24 hours Crumbling (%) 0.2 Storage period of modified binder 4 months: Compressive strength (Kgf/cm ² ) After 1 hour 6 After 24 hours 25 Crumbling after 24 hours (%) 0.4 Example 2 Phenol formaldehyde resin 99.8 weight%
is stirred with 0.2% by weight of γ-glycidoxypropyltri-(β-ethylhexyloxysilane) for 35 minutes in a vessel with a mechanical stirrer. 1 part by weight of the resulting modified resin is mixed with 100 parts by weight of quartz sand in a container equipped with a mechanical stirrer for 1.0 minutes;
Thereafter, a curing catalyst, ie 1.0 part by weight of an aqueous solution of benzenesulfonic acid having a density of 1.28-1.30 g/cm ³ is added and the mixture thus prepared is stirred for 1 minute. The compressive strength of the resulting room-temperature-cured molding sand is determined by
Measurements are taken 1 hour and 24 hours after preparation of the mixture on laboratory equipment available from Fisher Company. Crumble is measured according to standard methods. Storage period 0 days: Compressive strength (Kgf/cm ² ) After 1 hour 11 After 24 hours 32 Crumbling after 24 hours (%) 0.2 Storage period 7 days of modified binder: Compressive strength (Kgf/cm ² ) After 1 hour 11 After 24 hours 32 Crumble after 24 hours (%) 0.2 Storage period of modified binder 3 months: Compressive strength (Kgf/cm ² ) After 1 hour 9 After 24 hours 28 After 24 hours Crumbling (%) 0.2 Storage period of modified binder: 4 months: Compressive strength (Kgf/cm ² ) After 1 hour 7 After 24 hours 21 Crumbling after 24 hours (%) 0.4 Example 3 Phenol-furan resin 99.5 The weight percent is mixed with 0.5 weight percent β-(3,4-epoxycyclohexyl)-tri-(β-ethylhexyloxysilane) for 35 minutes in a container equipped with a mechanical stirrer.
2.0 parts by weight of the resulting modified resin are mixed for 1.0 minutes with 100 parts by weight of quartz sand in a container equipped with a mechanical stirrer, and then mixed with the curing catalyst, i.e. an aqueous solution of benzenesulfonic acid having a density of 1.28-1.30 g/ ^cm3. 0.4 part by weight is added and the resulting mixture is stirred for an additional minute. The compressive strength of the resulting room-temperature-cured molding sand is determined by
Measurements are taken 1 hour and 24 hours after preparation of the mixture on laboratory equipment available from Fisher Company. Crumble is measured according to standard methods. Storage period 0 days: Compressive strength (Kgf/cm ² ) After 1 hour 12 After 24 hours 45 Crumbling after 24 hours (%) 0.02 Storage period 7 days of modified binder: Compressive strength (Kgf/cm ² ) After 1 hour 12 After 24 hours 45 Crumbling after 24 hours (%) 0.02 Storage period of modified binder 3 months: Compressive strength (Kgf/cm ² ) After 1 hour 12 After 24 hours 31 After 24 hours Crumbling (%) 0.05 Storage period of modified binder: 4 months: Compressive strength (Kgf/cm ² ) After 1 hour 9 After 24 hours 31 Crumbling after 24 hours (%) 0.05 Example 4 Phenol formaldehyde resin 99.5 weight%
Phenoxypropyl tri-(β-ethylhexyloxy) in a container equipped with a mechanical stirrer.
Mix with 0.5% silane by weight for 35 minutes. 1.0 parts by weight of the resulting modified resin is mixed for 1 minute with 100 parts by weight of quartz sand in a container equipped with a mechanical stirrer, and then mixed with the curing catalyst, i.e. an aqueous solution of benzenesulfonic acid with a density of 1.28-1.30 g/cm ³ 1 part by weight is added and the resulting mixture is stirred for an additional minute. The compressive strength of the cold-cured foundry sand thus prepared is tested in laboratory equipment available from GE Fisher Company, 1 hour and 24 hours after preparation of the mixture. Crumble is measured according to standard methods. Storage period 0 days: Compressive strength (Kgf/cm ² ) After 1 hour 10 After 24 hours 24 Crumbling after 24 hours (%) 0.1 Storage period 7 days of modified binder: Compressive strength (Kgf/cm ² ) After 1 hour 10 After 24 hours 40 Crumble after 24 hours (%) 0.1 Storage period of modified binder 3 months: Compressive strength (Kgf/cm ² ) After 1 hour 8 After 24 hours 38 After 24 hours Crumbling (%) 0.1 Storage period of modified binder 4 months: Compressive strength (Kgf/cm ² ) After 1 hour 6 After 24 hours 31 Crumbling after 24 hours (%) 0.2 Example 5 Phenol formaldehyde resin 99.8 weight%
is mixed with 0.2% by weight of methyl(phenylaminomethyl)di-(β-ethylhexyloxysilane) for 35 minutes in a container with a mechanical stirrer.
1.0 parts by weight of the resulting modified resin was mixed with 100 parts by weight of quartz sand for 1 minute in a container equipped with a stirrer,
Thereafter, a curing catalyst, ie 1.0 part by weight of an aqueous solution of benzenesulfonic acid having a density of 1.28-1.30 g/cm ³ , is added and the resulting mixture is stirred for a further 1 minute. The compressive strength of the cold-cured foundry sand thus prepared is measured 1 hour and 24 hours after preparation of the mixture in laboratory equipment available from GE Fisher Company. Crumble is measured according to standard methods. Storage period 0 days: Compressive strength (Kgf/cm ² ) After 1 hour 8 After 24 hours 35 Crumbling after 24 hours (%) 0.1 Storage period 7 days of modified binder: Compressive strength (Kgf/cm ² ) After 1 hour 8 After 24 hours 35 Crumble after 24 hours (%) 0.1 Storage period of modified binder 3 months: Compressive strength (Kgf/cm ² ) After 1 hour 6 After 24 hours 32 After 24 hours Crumbling (%) 0.1 Storage period of modified binder 4 months: Compressive strength (Kgf/cm ² ) After 1 hour 5 After 24 hours 28 Crumbling after 24 hours (%) 0.2 Example 6 Phenol formaldehyde resin 99.8 weight%
N-β- in a container with a mechanical stirrer
(Aminoethyl-γ-aminopropyltri-β-
(ethylhexyloxysilane) 0.2% by weight and mix for 35 minutes. 1.0 parts by weight of the resulting modified resin is mixed for 1.0 minutes with 100 parts by weight of quartz sand in a container with a mechanical stirrer, and then mixed with the curing catalyst, i.e. 1.28 parts by weight.
1.0 part by weight of an aqueous solution of benzenesulfonic acid having a density of ~1.30 g/cm ³ is added and the mixture thus prepared is stirred for a further 1 minute. The compressive strength of the resulting room-temperature-cured molding sand is determined by
Measurements are taken 1 hour and 24 hours after preparation of the mixture on laboratory equipment available from Fisher Company. Crumble is measured according to standard methods. Storage period 0 days: Compressive strength (Kgf/cm ² ) After 1 hour 11 After 24 hours 39 Crumbling after 24 hours (%) 0.2 Storage period 7 days of modified binder: Compressive strength (Kgf/cm ² ) After 1 hour 11 After 24 hours 39 Crumbling after 24 hours (%) 0.2 Storage period of modified binder 3 months: Compressive strength (Kgf/cm ² ) After 1 hour 9 After 24 hours 37 After 24 hours Crumbling (%) 0.2 Storage period of modified binder: 4 months: Compressive strength (Kgf/cm ² ) After 1 hour 7 After 24 hours 35 Crumbling after 24 hours (%) 0.4

Claims (1)

[Claims] 1. In a room-temperature curing molding sand binder consisting of a polycondensation type synthetic resin and silane, the silane has the general formula R'(CH ₂ ) _o Si(CH ₃ ) _n (OR) _3-n ( In the formula, n is an integer from 1 to 3, m is 0 or 1, _and R' _{is NH2} , _NH2CH2NH , _C6H5NH ,
C ₆ H ₅ O, [Formula] [Formula], R is an aliphatic hydrocarbon group having 7 to 10 carbon atoms and having a branched structure); A binder for cold-curing foundry sand, characterized in that the components are present in the following amounts in weight percent: polycondensation type synthetic resin 99.0 to 99.8 and silane having the above structure 0.2 to 1.0. 2 γ-Aminopropyl tri-(β
-ethylhexyloxy)-silane,
A binder according to claim 1.