CA1217591A - Resin binders for foundry molding sands - Google Patents
Resin binders for foundry molding sandsInfo
- Publication number
- CA1217591A CA1217591A CA000447364A CA447364A CA1217591A CA 1217591 A CA1217591 A CA 1217591A CA 000447364 A CA000447364 A CA 000447364A CA 447364 A CA447364 A CA 447364A CA 1217591 A CA1217591 A CA 1217591A
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- Prior art keywords
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- copolymer
- aqueous dispersion
- weight
- dispersion
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
- B22C1/22—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins
- B22C1/2206—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins obtained by reactions only involving carbon-to-carbon unsaturated bonds
- B22C1/222—Polyacrylates
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B26/00—Compositions of mortars, concrete or artificial stone, containing only organic binders, e.g. polymer or resin concrete
- C04B26/02—Macromolecular compounds
- C04B26/04—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Ceramic Engineering (AREA)
- Mechanical Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An aqueous dispersion of a copolymer comprising:
(A) from 20 to 90 percent by weight of an unsaturated carboxylic acid of the formula
An aqueous dispersion of a copolymer comprising:
(A) from 20 to 90 percent by weight of an unsaturated carboxylic acid of the formula
Description
The present invention relates to aqueous dispersions of polymeric synthetic resins, particularly to such dispersions useful as binders for ready-to-use heat-curable foundry molding sands, and to such ready-to-use foundry molding sands and methods for making the same.
In industry, polymeric binders are used in the making of molds and mold cores from foundry molding sands for use in metal casting. As a rule, the molding sands are formulated with the binders, usually Furman resins or finlike resins, in such a way that the quartz sand grains, in an unit ally warm state, are coated with a thin film of binder. The sand formulations so prepared are then fully cured in an appropriate metal implement such as a core boy, at temperatures between 150 and 300C, within a short time which may range from 60 to 180 seconds, for example. After removal, the shaped parts, for example, mold core and shell, are hard, stable and ready for industrial use.
The polymeric binders are generally used in the form of solutions, less frequently as dispersions or emulsions.
Acrylic resins have also been proposed in the past as polymeric binders. From published Japanese patent application 76 93725 (Chum. Abstr. 85, 196291t) for example, it is known to process an emulsion polymer comprising 60 parts of methyl methacrylate, 38 parts of bottle acrylate, 2 parts of methacrylic acid, and 100 parts of water into a molding sand with 4 parts of water glass and 100 parts of sand. The nonvolatile component of the binder is said to represent from 0.1 to 5 weight percent, based on the sand.
According to published Japanese patent application 76 93722, 0.3 kg of an emulsion polymer made from 52 parts of styrenes 44 parts of bottle acrylate, 4 parts of of I
methacrylic acid, 100 parts of water, initiator, and emulsifier mixed with 10 kg of sand is said to make a good foundry molding sand.
Published Japanese patent application 73 15771 (Chum. Abstr. 80, 184725) discloses the addition of alkylpolyacrylate binders to sand and cement. The use of 100 g of a polymethacrylate emulsion per 1000 g of sand and 100 g of port land cement is given as an example.
The use of dissolved polymers is known from a number of patent publications. According to published Japanese patent application 76 93723 (Chum. Abstr. 86, 94030k), from 1 to 10 weight percent of a synthetic resin powder and from 0.5 to 30 weight percent of a solvent of low boiling point may be admixed with the sand.
USSR patent 406,616 (Chum. Abstr. 81, 53540) recommends the use of a 10-15~ aqueous solution of a methacrylic acid/dialkylmaleate copolymer as a binder.
From published German patent application DOS
1,032,896, it is known to use polyacrylic acid or copolymers with up to 50% of styrenes or of vinyl acetate in aqueous solution as a binder for foundry molding sands Nowadays there are serious objections of both an ecological and economic nature to the use of organic solvents as vehicles for polymeric binders for foundry sands.
The use of solutions of polymeric binders in water has been proposed as an alternative. The selection of monomers, by quality and quantity, is limited rather severely by the requirement of water volubility. Also, polymer solutions necessarily have a relatively high viscosity. In order that they may be satisfactorily worked Lo Lo into the sands, their viscosity must be reduced; in other words, they must be appropriately diluted.
While the use of emulsion polymers has also been proposed in the past, the polymer types considered for this use lack satisfactory binder properties.
The principal requirements which polymeric binders for heat curing foundry molding sands must meet today are:
(1) high dimensional accuracy of molds and cores;
In industry, polymeric binders are used in the making of molds and mold cores from foundry molding sands for use in metal casting. As a rule, the molding sands are formulated with the binders, usually Furman resins or finlike resins, in such a way that the quartz sand grains, in an unit ally warm state, are coated with a thin film of binder. The sand formulations so prepared are then fully cured in an appropriate metal implement such as a core boy, at temperatures between 150 and 300C, within a short time which may range from 60 to 180 seconds, for example. After removal, the shaped parts, for example, mold core and shell, are hard, stable and ready for industrial use.
The polymeric binders are generally used in the form of solutions, less frequently as dispersions or emulsions.
Acrylic resins have also been proposed in the past as polymeric binders. From published Japanese patent application 76 93725 (Chum. Abstr. 85, 196291t) for example, it is known to process an emulsion polymer comprising 60 parts of methyl methacrylate, 38 parts of bottle acrylate, 2 parts of methacrylic acid, and 100 parts of water into a molding sand with 4 parts of water glass and 100 parts of sand. The nonvolatile component of the binder is said to represent from 0.1 to 5 weight percent, based on the sand.
According to published Japanese patent application 76 93722, 0.3 kg of an emulsion polymer made from 52 parts of styrenes 44 parts of bottle acrylate, 4 parts of of I
methacrylic acid, 100 parts of water, initiator, and emulsifier mixed with 10 kg of sand is said to make a good foundry molding sand.
Published Japanese patent application 73 15771 (Chum. Abstr. 80, 184725) discloses the addition of alkylpolyacrylate binders to sand and cement. The use of 100 g of a polymethacrylate emulsion per 1000 g of sand and 100 g of port land cement is given as an example.
The use of dissolved polymers is known from a number of patent publications. According to published Japanese patent application 76 93723 (Chum. Abstr. 86, 94030k), from 1 to 10 weight percent of a synthetic resin powder and from 0.5 to 30 weight percent of a solvent of low boiling point may be admixed with the sand.
USSR patent 406,616 (Chum. Abstr. 81, 53540) recommends the use of a 10-15~ aqueous solution of a methacrylic acid/dialkylmaleate copolymer as a binder.
From published German patent application DOS
1,032,896, it is known to use polyacrylic acid or copolymers with up to 50% of styrenes or of vinyl acetate in aqueous solution as a binder for foundry molding sands Nowadays there are serious objections of both an ecological and economic nature to the use of organic solvents as vehicles for polymeric binders for foundry sands.
The use of solutions of polymeric binders in water has been proposed as an alternative. The selection of monomers, by quality and quantity, is limited rather severely by the requirement of water volubility. Also, polymer solutions necessarily have a relatively high viscosity. In order that they may be satisfactorily worked Lo Lo into the sands, their viscosity must be reduced; in other words, they must be appropriately diluted.
While the use of emulsion polymers has also been proposed in the past, the polymer types considered for this use lack satisfactory binder properties.
The principal requirements which polymeric binders for heat curing foundry molding sands must meet today are:
(1) high dimensional accuracy of molds and cores;
2) high resistance to erosion by molten metal;
(3) a mold and core surface that is as smooth and as pore-free as possible;
(4) hardness and handle ability after removal, for example while still warm;
(5) little need to clean the castings;
(6) ease of removability of the core sand after casting;
(7) reusability of the sand;
(8) high curing rates and complete cure;
(9) usability in automated production; and
(10) minimal evolution of noxious gases, which is of primary importance in this connection.
These requirements are met by a binder which is an aqueous dispersion of a copolymer comprising:
(A) from 20 to 90 percent, by weight of the copolymer, of at least one unsaturated carboxylic acid of the formula R2\ / COO
I = C
~2~5~
wherein M is a proton or an alkali metal or alkaline earth metal or an ammonium cation;
Al, R2, and R3 are, independent of each other, hydrogen, alkyd having l to 6 carbon atoms, or -(CH2)n-COOM, where n is O or ], but where no more than two -COO groups are present and where those groups -COO wherein M is an alkali metal or alkaline earth metal cation are no more than 20 percent by weight of all groups -COO in the polymer; and B) from lo to 80 percent of at least one further lo monomer, different from and copolymerizable with (A).
"Sand" within the meaning of the present invention means the usual refractory, granular base substance consisting of washed and classified quartz sand, and in some cases also of roommate, zirconium, or olivine sands. In addition, grog, magnesite, stillimanite, or corundum materials are used. (Grain diameters mostly in the range between 0.1 and 0.5 mm).
By definition, the copolymer of the invention is present in aqueous dispersion, that is to say, its composition is based in every case on its dispersibility in an aqueous phase. The copolymer preferably has a minimum film forming temperature (MET) in conformity with DIN 53787 of less than 100C. Moreover, it preferably has a glass transition temperature of Tea in conformity with DIN 53445/DIN 7724 greater than 150C.
Under certain conditions, the deflection temperature (heat distortion point) or the glass transition temperature of the copolymer can be influenced in a predictable manner by proper selection of the monomers and their proportions. [See Vieweg-Esser, Kunststoffhandbuch ("Plastics Handbook"), vol. IX, Polymethacrylates, pp. 333-340; Carl Hanson Verlag, 1975.]
I
A factor that is material to the invention is that the copolymer has a relatively high con-tent of carboxyl groups -COO
(M = H) or of carboxylate groups (M = alkali metal or ammonium cation or alkaline earth metal cation, in the latter case combined with an anion) such that the amount of the carboxylic acid monomers of the aforementioned formula which carry the -COO groups should not be less than 20 weight percent of all -the monomers of the copolymer and may amount to as much as 90 weight percent thereof.
The amount of carboxylate groups with alkali metal or alkaline earth metal cations should not be more than 20 percent of the -COO groups contained in the copolymer.
The R1, R2 and R3 groups in the aforementioned formula, if they do not represent or contain -COO groups, preferably are hydrogen or methyl.
Malefic acid, fumaric acid, and itaconic acid, and especially acrylic acid and methacrylic acid are particularly well suited for use as unsaturated carboxylic acid monomers. The copolymer may advantageously contain various different monomers of this type, designated as (A) monomers.
The components (B) of the copolymer are, by definition, monomers which are copolymerizable with (A), in other words, monomers susceptible of free radical polymerization. They may be represented by the formula R4 I
H2C = C - R5 for example, wherein R4 is hydrogen or methyl; R5 is -COORS or -CONR7R8, phenol or alkyl-substituted phenol, -(CH2)m-0-Rg, -CH=CH2, or an inert heterocyclic group; R6 is alkyd having from 1 to 18 carbon atoms; R7 and R8 are, independently of each other, hydrogen Z
or alkyd having from 1 to 18 carbon atoms; and Rug is alkyd having from 1 -to 6 carbon atoms or - - Rio wherein Rho is alkyd having from 1 to 5 carbon atoms.
The components (B) of the copolymer can optionally also comprise other monomers containing a functional group which is capable of non-radical cross linking by reacting with another functional group or by reacting with a multi functional non-radically cross linking agent (which itself is not susceptible of radical polymerization) at a temperature above 60 centigrade. Said monomers containing a junctional group capable of non-radical cross linking preferably are from 0.3 to 30 percent by weight more preferably from 0.5 to 20 percent by weight of said copolymer.
The components (B) of the copolymer thus fall into the groups (a) acrylic and methacrylic acid esters with C1 to C18 alcohols, and especially with C1 to C8 alcohols, and more particularly methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, bottle acrylate, bottle methacrylate, and ethylhexyl acrylate;
(b) acrylic and methacrylic acid asides, and asides which are Cluck alkyl-substituted on the nitrogen, and more particularly methacrylamide and especially acrylamide;
(c) monomers containing a functional group capable of non-radical cross linking and which are different from (a) and (b);
(d) styrenes and alkylated styrenes, for example alpha-methylstyrene, and styrenes which have been alkylated in the nucleus, for example, para-methylstyrene;
(e) vinyl ethers and vinyl esters, and particularly the methyl vinyl to hexylvinyl ethers, as well as vinyl acetate, vinyl propionate,and vinyl bitterroot;
(f) heterocyclic vinyl compounds such as vinylpyridine, vinylpyrrolidone, vinylimidazole, and vinyl carbazole, and particularly the N-vinyl compounds; and (g) butadiene.
It is apparent that the composition of component (B) is no-t particularly critical so long as it corresponds to the definitions and characteristics set forth.
Component (B) is advantageously composed of several monomers. Particularly preferred are the derivatives of acrylic and methacrylic acid, that is to say, their esters and asides, and especially methyl methacrylate and ethyl acrylate.
In a particularly preferred embodiment, the copolymer of the invention thus is formed of (A) acrylic acid and/or methacrylic acid in amounts from 20 to 90 weight percent, and (B) acrylic and/or methacrylic acid esters, or acrylamides and/or methacrylamides, or both, optionally together with heterocyclic vinyl compounds. The acrylate and/or methacrylate ester monomers preferably represent more than 70 weight percent of component (B). Particularly preferred is an embodiment in which the ratio between the components (A) and (B), as defined immediately above, is about 1:1.
Of particular interest is copolymerization of monomers of type (c).
Such monomers containing a functional group which is capable of non-radical cross linking by reacting with another functional group or by reacting with a multi functional non-radically cross linking agent at a temperature above 60 centigrade are known per so.
Functional groups which qualify are hydroxy-, epoxy-, ~Z~7~
N-methylolamide and ethers derived -thereof and so called "blocked"
isocyanate groups besides aside, car boxy and ester groups.
Crosslinkiny in this case will either occur through a condensation reaction (e.g. by elimination of water, alcohol, amine or formaldehyde) or through an addition reaction (e.g. by nucleophilic attack at an epoxide or a "blocked" isocyanate function).
Particularly preferred are derivatives of acrylic and methacrylic acid containing such functional groups.
They may be represented by the formula H2C = - Y
for example, wherein R4 is hydrogen or methyl, Y is a group -N-CH20H, N-CH20Rl1 or a group -Q-B-Z, Q is oxygen or -NR12.
B is an optionally branched hydrocarbon chain having from 1 to 8 carbon atoms, Z is a hydroxy group or a group - C Ho or a group -NHR13, Roll, R12 and R13 are alkyd having from 1 to 8 carbon atoms.
The monomers capable of non-radical cross linking preferably comprise from 0.3 to 30 percent by weigh-t of the copolymer.
A prerequisite for cross linking in the present case is evidently the presence of at least two partners within different chains of the copolymer, which will cross link by condensation or addition reaction in a temperature range beginning at 60C (and ranging up to 200C).
In addition to such partners cross linking may require the presence of a multi functional non-radically cross linking agent, which itself is not susceptible of radical polymerization, but will react with the partners mentioned above at 60C and above. Such cross linking agents are known per so.
~Z~75~
They must provide at least two functional groups, e.g. hydroxy, epoxy, (blocked) isocyananto, or amino groups fixed to a spacing unit, ordinarily a hydrocarbon chain. The hydrocarbon backbone may contain from 2 to 10 preferably 2 to 20 carbon atoms with a minimum of 2 functional groups and a maximum number of functional groups equal to the number of carbon atoms in the backbone of the molecule.
A certain proportion of -SHEA- units may be replaced by ether functions in the backbone of the agents, without impairing their function.
In general the partners engaged in cross linking i.e.
different monomers, or monomers and multi functional non-radically cross linking agents should be present in a molar ratio of from 20:1 to 1:1.
Multi functional non-radically cross linking agents with at least two isocyanate groups in the molecule preferably are utilized with isocyanate groups "masked" or "blocked". Such blocking entity comprises the addition products of diisocyanates with polyoles, in particular of 2,4- or 2,6- toluylen diisocyanate with a trio e.g.
with CH3CH2C(CH20H)3, which react with phenol to yield phenol urethanes.
Such "blocked isocyanates~ are commercially available, e.g.
under the registered trade name DESMODUR A (Bayer A). As polyepoxy compounds useful in cross linking the epoxy polymers formed in the reaction between bisphenol A and epichlorohydrin there shall be named e.g. the product EPIKOTE 1001~ (Shell Chemise, of Epikote Handbuch, MY = 900).
As mentioned above the condensation or addition reactions involved in non-radical cross linking preferably comprise reaction between the following functional groups:
~17~
at the monomer at -the multi functional non-radically cross linking agent i) - COO v) HESSIAN - -R = alkyd ii) - COO vi) HO - SHEA -iii) -SHEA H
O vii) HO - C -ivy ) - if - NHCH20H by viii) blocked isocyana-te Main modes of reaction will most likely comprise:
i) with iii), iv) v) vi) or vii) ii) with iii), iv) v) vi), voyeur viii) iv) with v), vi), vii) or viii) Also preferred is an embodiment in which the component (B) is formed in whole or in part of styrenes and/or its derivatives according to aforementioned group (d).
As a rule, the molecular weight of the copolymers to be used in accordance with the invention will range from 5 x 104 to 1 x 106, and more particularly from 2 x 105 to 5 x 105.
Aqueous dispersions of the copolymers may be prepared conventionally by emulsion polymerization. Either the emulsion-addition or the monomer-addition method may be employed, the initial charge consisting of a portion of the water and either the total amount or portions of the initiator and of the emulsifier.
In this process, the particle size can be controlled to advantage through the amount of emulsifier in the initial charge. Suitable Jo - 10 -,, .
I
emulsifiers are, in particular, anionic and non ionic surfactan-ts.
As a rule, the amount of emulsifier used should not exceed 3 weight percent, based on the polymer.
In addition to the compounds commonly used in emulsion polymerization, for example proxy compounds such as hydrogen peroxide or ammonium per sulfate, suitable initiators are redo systems such as bisulfite/ammonium persulfate/iron, as well as ago initiators. The amount of initiator will usually range from 0.005 -to 0.5 weight percent, based on the polymer.
To some extent, the polymerization temperature depends on the initiator. For example, when ammonium per sulfate is used, polymerization is advantageously carried out in the 60 to 90C
range. With redo systems, lower temperatures, for example, 30C, may be used.
In addition to the addition method, the batch method of polymerization may be employed. The initial charge then consists of the total amount or a portion of the monomers with all auxiliary substances, and polymerization is initiated by means of redo systems. The monomer/water ratio should then be based on the reaction heat being liberated. No difficulties will generally be encountered if a 50 percent emulsion is prepared by first emulsifying half of the monomers and of the auxiliary substances in the total amount of the water, then initiating polymerization at room temperature, cooling the batch after the reaction, and adding the other half of the monomers together with auxiliary substances.
The particle diameter of the emulsions used in accordance with the invention will usually range from 0.05 to 5 microns and preferably ranges from 0.1 to 1 micron.
The materials commonly used as molding sands may be conventionally mixed with an aqueous dispersion of a copolymer I
according to the invention, the amounts used being those required to obtain the desired polymer content. At this stage also the multi functional non-radically cross linking agents are admixed.
Suitable mixers are forced-motion mixers, for example. In this simple manner, sufficiently free flowing foundry molding sends are generally obtained.
The binders in accordance with the invention for heat curing foundry molding sands meet -the aforementioned practical requirements to a surprisingly high degree. From both an ecological and an economic point of view, they represent a particularly happy solution.
Among their advantageous properties are high dimensional accuracy of the molds and cores made with them; good erosion resistance; hardness and handle ability of the cores after removal, even while still warm; an unusually smooth and pore-free surface and correspondingly perfect castings; no need for cleaning the castings;
and reusability of the molding sands.
Particularly surprising is that there is very little evolution of noxious gases, or of gases generally, in the use of the molding sands.
A better understanding of the invention and of its many advantages will be had by referring to the following specific Examples, given by way of illustration.
Preparation of a copolymer dispersion In a lottery Wilt jar equipped with reflex condenser, stirrer, and feed vessel, 1.4 g of ammonium per sulfate and 0.35 g of sodium laurel sulfate were dissolved in 1440 g distilled water at 80C. A monomer/emulsifier mixture previously prepared from 180 g of ethyl acrylate, ]20 g of methyl methacrylate, 300 g of I
methacrylic acid, 1.2 g of 2-ethylhexyl thioglycolate, and 14 g of polyoxyethylene/sorbi-tan moonlit was added drops -to the resulting solution over a period of 4 hours at 80C with stirring, and the resulting mixture was maintained at 80C for 2 hours. After cooling to room temperature, it was filtered -through a close meshed stainless steel woven wire screen.
The low viscosity dispersion had a dry solids content of 30 percent. The copolymer contained 50 percent of methacrylic acid, 30 percent of ethyl acrylate, and 20 percent of methyl methacrylate by weight, had a molecular weight of about 200,000, a minimum film forming temperature (DIN 53787) of 56C, and a glass -transition temperature Max (DIN 53445/DIN 7724) of 157C.
The procedure of Example 1 is used, except that the monomer/emulsifier mixture previously prepared consists of 180 g of ethyl acrylate 102 g of methyl methacrylate 18 g of methacrylamide 300 g of methacrylic acid 1.2 g of 2-ethylhexyl thioglycolate and 14 g of polyoxyethylene/sorbitan moonlit The low viscosity dispersion had a dry solids content of 30 percent.
The copolymer had a molecular weight of about 200 000, a minimum film forming temperature (DIN 53 787) of 54C and a glass transition temperature Tax (DIN 53 445/DIN 7724) of 156C
The procedure of Example 1 is used, except that the monomer/emulsifier mixture previously prepared consists of 300 g of methacrylic acid 180 g of ethyl acrylate ~2~L7~
90 g of methyl methacrylate 30 g of Vinyl pyrrolidone 1.2 g of 2-ethylhexyl thioglycolate and 14 g of polyoxyethylene/sorbitan moonlit The low viscosity dispersion had a molecular weight of about 200 000 a dry solids content of 30.5 percent, a minimum film forming temperature (DIN 53 787) of 42C and a glass transition temperature.
Tax (DIN 53 445/DIN 7724) of 151C.
The procedure of Example 1 is used except that 2.8 g of ammonium per sulfate are employed instead of 1.4 g. Moreover -the monomer/emulsifier mixture previously prepared consists of 300 g of methacrylic acid 180 g of ethyl acrylate 120 g of styrenes 1.2 g of 2-ethylhexyl thioglycolate and 14 g of polyoxyethylene/sorbitan moonlit The low viscosity dispersion had a dry solids content of about 29.5 percent the copolymer had a molecular weight of about 150,000, a minimum film forming temperature (DIN 53 787) of 53C and a glass transition temperature Tax (DIN 53 445/DIN 7724) of 151C.
The procedure of Example 1 is used, except that the monomer/emulsifier mixture previously prepared consists of 300 g of methacrylic acid 120 g of methyl methacrylate 180 g of ethylacrylate 1.2 g of 2-ethylhexyl thioglycolate and 14 g of polyoxyethylene/sorbitan moonlit After the reaction was completed the reaction mixture is cooled to I 75~
room temperature. Thereafter 12. 3 g of an aqueous solution containing 25 percent of ammonia are added. Further work up as in Example 1. The copolymer had a minimum film forming temperature (DIN 53 787) of 52C and a glass transition temperature T Max (DIN 53 445/DIN 7724) of 154C.
In a 2-1 Wilt jar as used in Example 1. 1. 4 g of ammonium per sulfate and 0. 2 g of the sodium salt of a sevenfold methylated and sulfated triisobutyl phenol were dissolved in 580 g distilled water.
A monomer/emulsifier mixture previously prepared from 258 g of methacrylic acid, 42 g of itaconic acid, 180 g of ethylacrylate, 120 g of methyl methacrylate, 9 g of the emulsifier used before, 2.8 g of ammonium per sulfate and 860 g distilled water was added drops to the above solution over a period of 4 hours at 80C with stirring, and the resulting mixture was maintained at 80C for 2 hours. After cooling to room temperature, it was filtered through a close meshed stainless steel woven wire screen.
The low viscosity dispersion had a dry solids content of 29. 7 percent. The copolymer had a molecular weight of about 200,000, a minimum film forming temperature (DIN 53 787) of 58C and a glass transition temperature. Tea (DIN 53 445/DIN 7724) of 158C .
The procedure of Example 1 is used except that the monomer/emulsifier mixture previously prepared consists of ]20 g of methacrylic acid 120 g of acrylic acid 360 g of methyl methacrylate 1.2 g of 2-ethylhexyl thioglycolate 14 g of polyoxyethylene/sorbitan moonlit I
The low viscosity dispersion had a molecular weight of about 200,000 a dry solids content of` about 29.9 percent, a minimum film forming temperature (DIN 53 787) of 50C and a glass transition temperature Tax (DIN 53 445/DIN 7724) of 157C.
In place of ethyl acrylate in Examples 1-6 a vinyl ether or vinyl ester, e.g. vinylacetat or butadiene can be employed in such quantities as to ensure a To of >140C of the copolymer. Usually the quantities of such monomers will be below 30 percent by weight of the copolymer.
In a 2-liter Wilt jar as in Example 1 4.2 g of ammoniurn per sulfate and 1.05 g sodium laurel sulfate were dissolved in 4300 g distilled water at 80C. A monomer/emulsifier mixture previously prepared from 900 g of methacrylic acid, 360 g of ethyl acrylate, 360 g of methylmethacrylate, 180 g of hydroxyethyl acrylate, 42 g of polyoxyethylene/sorbitan moonlit and 3.6 g of 2-ethylhexyl thioglycolate was added drops to the resulting solution over a period of 4 hours at 80C with stirring and the resulting mixture was maintained at 80C for 2 hours. After cooling to room temperature, it was filtered through a close meshed stainless steel woven wire screen.
The low viscosity dispersion has a dry solids content of 30 percent. The copolymer has a molecular weight of about 250,000, a minimum film forming temperature (DIN 53 787) of 50C and a glass transition temperature Tea (DIN 53 445/DIN 7724) of 146C.
The procedure of Example 8 is used except that 4250 g of distilled water are used. Furthermore the monomer/emulsifier mixture, which was prepared previously, and is then added consists of ,, Jo Lo 900 g of methacrylic acid 504 g of ethyl acrylate 306 g of methyl methacryla-te g of N-methylol methacrylamide 3.6 g of 2-ethylhexyl -thioglykolate 42 g of polyoxyethylene/sorbitan-monooleate g of distilled water The low viscosity dispersion has a dry solids content of 30 percent.
The copolymer has a molecular weight of about 270,000, a lo minimum film forming temperature (DIN 53 787) of 57C and a glass transition temperature To (DIN 53 445/DIN 7725) of ICKY.
EXAMPLE lo The same procedure as in Example 9 was used except that 90 g of N-butoxymethyl methacrylamide were used in place of N-methylol methacrylamide.
The physical data of the copolymer are rather similar to -the ones of Example 9.
Other copolymers having a different monomeric composition may be prepared in the same manner.
EXAMPLE if Preparation of a molding sand mixture ready for use 97 kg of foundry molding quartz sand were mixed at room temperature in a forced-motion mixer with 3 parts by weigh-t of an aqueous acrylic resin dispersion containing 30 percent of the copolymer of Example l. In this way, a sufficiently free-flowing, ready-to-use foundry molding sand mixture was obtained.
EXAMPLE lo Preparation of a molding sand mixture with addition of a multi functional non-radically cross linking agent 3 kg of dry foundry molding quartz sand were thoroughly mixed at room temperature with 3 g Al percent by weight) of a so finely powdered (average particle size about 20 us) solid epoxy resin (= solid bisphenol A-epichlorohydrine epoxy resin with an epoxy equivalent of 450 - 500 g viscosity at 25C of 1.2 - 1.7 poise; deformation temperature 50 - 70C: commercial product (Epikote 1001~ from Shell Chemise) in a forced-motion mixer.
Then 90 g (3 percent by weight) of an aqueous dispersion of the copolymer of Example 1 or, alternatively Example 8 are admixed in homogeneous distribution.
Production of a foundry mold core from a sand mixture The molding sand mixture of Example 1 or Example 12 was blown by compressed air into an iron mold which had a temperature between 150 and 200C. The filled mold was held for about 0.5 to 3 minutes at that temperature. Then it was opened while hot and the foundry core was removed. It was perfectly stable, retained its shape, and withstood handling.
Production of a metal casting The mold core of Example 13 was introduced into and secured in a box mold for iron casting. Iron was then poured intake the mold.
On cooling, a casting with a hollow which had the dimensions of the core of Example 13 was obtained. The core had completely collapsed.
No gas evolution occurred on contact with the liquid iron. The casting was practically free of pores.
5 percent (based on the total dispersion) of a monomer/initiator mixture consisting of trimethylolpropane trimethacrylate and up to 20 percent, based on the trimethylolpropane trimethacrylate, of tert-butyl perbenzoate or, alternatively, of a commercially available peroxide-free initiator I I
("Akzo-Starter 407") was stirred into an acrylic resin dispersion as in Example 1. This mixture was processed further in -the same concentration as in Examples 1 to I
Here, too, hard and handle able shaped bodies were obtained which exhibited no tendency toward gas evolution.
These requirements are met by a binder which is an aqueous dispersion of a copolymer comprising:
(A) from 20 to 90 percent, by weight of the copolymer, of at least one unsaturated carboxylic acid of the formula R2\ / COO
I = C
~2~5~
wherein M is a proton or an alkali metal or alkaline earth metal or an ammonium cation;
Al, R2, and R3 are, independent of each other, hydrogen, alkyd having l to 6 carbon atoms, or -(CH2)n-COOM, where n is O or ], but where no more than two -COO groups are present and where those groups -COO wherein M is an alkali metal or alkaline earth metal cation are no more than 20 percent by weight of all groups -COO in the polymer; and B) from lo to 80 percent of at least one further lo monomer, different from and copolymerizable with (A).
"Sand" within the meaning of the present invention means the usual refractory, granular base substance consisting of washed and classified quartz sand, and in some cases also of roommate, zirconium, or olivine sands. In addition, grog, magnesite, stillimanite, or corundum materials are used. (Grain diameters mostly in the range between 0.1 and 0.5 mm).
By definition, the copolymer of the invention is present in aqueous dispersion, that is to say, its composition is based in every case on its dispersibility in an aqueous phase. The copolymer preferably has a minimum film forming temperature (MET) in conformity with DIN 53787 of less than 100C. Moreover, it preferably has a glass transition temperature of Tea in conformity with DIN 53445/DIN 7724 greater than 150C.
Under certain conditions, the deflection temperature (heat distortion point) or the glass transition temperature of the copolymer can be influenced in a predictable manner by proper selection of the monomers and their proportions. [See Vieweg-Esser, Kunststoffhandbuch ("Plastics Handbook"), vol. IX, Polymethacrylates, pp. 333-340; Carl Hanson Verlag, 1975.]
I
A factor that is material to the invention is that the copolymer has a relatively high con-tent of carboxyl groups -COO
(M = H) or of carboxylate groups (M = alkali metal or ammonium cation or alkaline earth metal cation, in the latter case combined with an anion) such that the amount of the carboxylic acid monomers of the aforementioned formula which carry the -COO groups should not be less than 20 weight percent of all -the monomers of the copolymer and may amount to as much as 90 weight percent thereof.
The amount of carboxylate groups with alkali metal or alkaline earth metal cations should not be more than 20 percent of the -COO groups contained in the copolymer.
The R1, R2 and R3 groups in the aforementioned formula, if they do not represent or contain -COO groups, preferably are hydrogen or methyl.
Malefic acid, fumaric acid, and itaconic acid, and especially acrylic acid and methacrylic acid are particularly well suited for use as unsaturated carboxylic acid monomers. The copolymer may advantageously contain various different monomers of this type, designated as (A) monomers.
The components (B) of the copolymer are, by definition, monomers which are copolymerizable with (A), in other words, monomers susceptible of free radical polymerization. They may be represented by the formula R4 I
H2C = C - R5 for example, wherein R4 is hydrogen or methyl; R5 is -COORS or -CONR7R8, phenol or alkyl-substituted phenol, -(CH2)m-0-Rg, -CH=CH2, or an inert heterocyclic group; R6 is alkyd having from 1 to 18 carbon atoms; R7 and R8 are, independently of each other, hydrogen Z
or alkyd having from 1 to 18 carbon atoms; and Rug is alkyd having from 1 -to 6 carbon atoms or - - Rio wherein Rho is alkyd having from 1 to 5 carbon atoms.
The components (B) of the copolymer can optionally also comprise other monomers containing a functional group which is capable of non-radical cross linking by reacting with another functional group or by reacting with a multi functional non-radically cross linking agent (which itself is not susceptible of radical polymerization) at a temperature above 60 centigrade. Said monomers containing a junctional group capable of non-radical cross linking preferably are from 0.3 to 30 percent by weight more preferably from 0.5 to 20 percent by weight of said copolymer.
The components (B) of the copolymer thus fall into the groups (a) acrylic and methacrylic acid esters with C1 to C18 alcohols, and especially with C1 to C8 alcohols, and more particularly methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, bottle acrylate, bottle methacrylate, and ethylhexyl acrylate;
(b) acrylic and methacrylic acid asides, and asides which are Cluck alkyl-substituted on the nitrogen, and more particularly methacrylamide and especially acrylamide;
(c) monomers containing a functional group capable of non-radical cross linking and which are different from (a) and (b);
(d) styrenes and alkylated styrenes, for example alpha-methylstyrene, and styrenes which have been alkylated in the nucleus, for example, para-methylstyrene;
(e) vinyl ethers and vinyl esters, and particularly the methyl vinyl to hexylvinyl ethers, as well as vinyl acetate, vinyl propionate,and vinyl bitterroot;
(f) heterocyclic vinyl compounds such as vinylpyridine, vinylpyrrolidone, vinylimidazole, and vinyl carbazole, and particularly the N-vinyl compounds; and (g) butadiene.
It is apparent that the composition of component (B) is no-t particularly critical so long as it corresponds to the definitions and characteristics set forth.
Component (B) is advantageously composed of several monomers. Particularly preferred are the derivatives of acrylic and methacrylic acid, that is to say, their esters and asides, and especially methyl methacrylate and ethyl acrylate.
In a particularly preferred embodiment, the copolymer of the invention thus is formed of (A) acrylic acid and/or methacrylic acid in amounts from 20 to 90 weight percent, and (B) acrylic and/or methacrylic acid esters, or acrylamides and/or methacrylamides, or both, optionally together with heterocyclic vinyl compounds. The acrylate and/or methacrylate ester monomers preferably represent more than 70 weight percent of component (B). Particularly preferred is an embodiment in which the ratio between the components (A) and (B), as defined immediately above, is about 1:1.
Of particular interest is copolymerization of monomers of type (c).
Such monomers containing a functional group which is capable of non-radical cross linking by reacting with another functional group or by reacting with a multi functional non-radically cross linking agent at a temperature above 60 centigrade are known per so.
Functional groups which qualify are hydroxy-, epoxy-, ~Z~7~
N-methylolamide and ethers derived -thereof and so called "blocked"
isocyanate groups besides aside, car boxy and ester groups.
Crosslinkiny in this case will either occur through a condensation reaction (e.g. by elimination of water, alcohol, amine or formaldehyde) or through an addition reaction (e.g. by nucleophilic attack at an epoxide or a "blocked" isocyanate function).
Particularly preferred are derivatives of acrylic and methacrylic acid containing such functional groups.
They may be represented by the formula H2C = - Y
for example, wherein R4 is hydrogen or methyl, Y is a group -N-CH20H, N-CH20Rl1 or a group -Q-B-Z, Q is oxygen or -NR12.
B is an optionally branched hydrocarbon chain having from 1 to 8 carbon atoms, Z is a hydroxy group or a group - C Ho or a group -NHR13, Roll, R12 and R13 are alkyd having from 1 to 8 carbon atoms.
The monomers capable of non-radical cross linking preferably comprise from 0.3 to 30 percent by weigh-t of the copolymer.
A prerequisite for cross linking in the present case is evidently the presence of at least two partners within different chains of the copolymer, which will cross link by condensation or addition reaction in a temperature range beginning at 60C (and ranging up to 200C).
In addition to such partners cross linking may require the presence of a multi functional non-radically cross linking agent, which itself is not susceptible of radical polymerization, but will react with the partners mentioned above at 60C and above. Such cross linking agents are known per so.
~Z~75~
They must provide at least two functional groups, e.g. hydroxy, epoxy, (blocked) isocyananto, or amino groups fixed to a spacing unit, ordinarily a hydrocarbon chain. The hydrocarbon backbone may contain from 2 to 10 preferably 2 to 20 carbon atoms with a minimum of 2 functional groups and a maximum number of functional groups equal to the number of carbon atoms in the backbone of the molecule.
A certain proportion of -SHEA- units may be replaced by ether functions in the backbone of the agents, without impairing their function.
In general the partners engaged in cross linking i.e.
different monomers, or monomers and multi functional non-radically cross linking agents should be present in a molar ratio of from 20:1 to 1:1.
Multi functional non-radically cross linking agents with at least two isocyanate groups in the molecule preferably are utilized with isocyanate groups "masked" or "blocked". Such blocking entity comprises the addition products of diisocyanates with polyoles, in particular of 2,4- or 2,6- toluylen diisocyanate with a trio e.g.
with CH3CH2C(CH20H)3, which react with phenol to yield phenol urethanes.
Such "blocked isocyanates~ are commercially available, e.g.
under the registered trade name DESMODUR A (Bayer A). As polyepoxy compounds useful in cross linking the epoxy polymers formed in the reaction between bisphenol A and epichlorohydrin there shall be named e.g. the product EPIKOTE 1001~ (Shell Chemise, of Epikote Handbuch, MY = 900).
As mentioned above the condensation or addition reactions involved in non-radical cross linking preferably comprise reaction between the following functional groups:
~17~
at the monomer at -the multi functional non-radically cross linking agent i) - COO v) HESSIAN - -R = alkyd ii) - COO vi) HO - SHEA -iii) -SHEA H
O vii) HO - C -ivy ) - if - NHCH20H by viii) blocked isocyana-te Main modes of reaction will most likely comprise:
i) with iii), iv) v) vi) or vii) ii) with iii), iv) v) vi), voyeur viii) iv) with v), vi), vii) or viii) Also preferred is an embodiment in which the component (B) is formed in whole or in part of styrenes and/or its derivatives according to aforementioned group (d).
As a rule, the molecular weight of the copolymers to be used in accordance with the invention will range from 5 x 104 to 1 x 106, and more particularly from 2 x 105 to 5 x 105.
Aqueous dispersions of the copolymers may be prepared conventionally by emulsion polymerization. Either the emulsion-addition or the monomer-addition method may be employed, the initial charge consisting of a portion of the water and either the total amount or portions of the initiator and of the emulsifier.
In this process, the particle size can be controlled to advantage through the amount of emulsifier in the initial charge. Suitable Jo - 10 -,, .
I
emulsifiers are, in particular, anionic and non ionic surfactan-ts.
As a rule, the amount of emulsifier used should not exceed 3 weight percent, based on the polymer.
In addition to the compounds commonly used in emulsion polymerization, for example proxy compounds such as hydrogen peroxide or ammonium per sulfate, suitable initiators are redo systems such as bisulfite/ammonium persulfate/iron, as well as ago initiators. The amount of initiator will usually range from 0.005 -to 0.5 weight percent, based on the polymer.
To some extent, the polymerization temperature depends on the initiator. For example, when ammonium per sulfate is used, polymerization is advantageously carried out in the 60 to 90C
range. With redo systems, lower temperatures, for example, 30C, may be used.
In addition to the addition method, the batch method of polymerization may be employed. The initial charge then consists of the total amount or a portion of the monomers with all auxiliary substances, and polymerization is initiated by means of redo systems. The monomer/water ratio should then be based on the reaction heat being liberated. No difficulties will generally be encountered if a 50 percent emulsion is prepared by first emulsifying half of the monomers and of the auxiliary substances in the total amount of the water, then initiating polymerization at room temperature, cooling the batch after the reaction, and adding the other half of the monomers together with auxiliary substances.
The particle diameter of the emulsions used in accordance with the invention will usually range from 0.05 to 5 microns and preferably ranges from 0.1 to 1 micron.
The materials commonly used as molding sands may be conventionally mixed with an aqueous dispersion of a copolymer I
according to the invention, the amounts used being those required to obtain the desired polymer content. At this stage also the multi functional non-radically cross linking agents are admixed.
Suitable mixers are forced-motion mixers, for example. In this simple manner, sufficiently free flowing foundry molding sends are generally obtained.
The binders in accordance with the invention for heat curing foundry molding sands meet -the aforementioned practical requirements to a surprisingly high degree. From both an ecological and an economic point of view, they represent a particularly happy solution.
Among their advantageous properties are high dimensional accuracy of the molds and cores made with them; good erosion resistance; hardness and handle ability of the cores after removal, even while still warm; an unusually smooth and pore-free surface and correspondingly perfect castings; no need for cleaning the castings;
and reusability of the molding sands.
Particularly surprising is that there is very little evolution of noxious gases, or of gases generally, in the use of the molding sands.
A better understanding of the invention and of its many advantages will be had by referring to the following specific Examples, given by way of illustration.
Preparation of a copolymer dispersion In a lottery Wilt jar equipped with reflex condenser, stirrer, and feed vessel, 1.4 g of ammonium per sulfate and 0.35 g of sodium laurel sulfate were dissolved in 1440 g distilled water at 80C. A monomer/emulsifier mixture previously prepared from 180 g of ethyl acrylate, ]20 g of methyl methacrylate, 300 g of I
methacrylic acid, 1.2 g of 2-ethylhexyl thioglycolate, and 14 g of polyoxyethylene/sorbi-tan moonlit was added drops -to the resulting solution over a period of 4 hours at 80C with stirring, and the resulting mixture was maintained at 80C for 2 hours. After cooling to room temperature, it was filtered -through a close meshed stainless steel woven wire screen.
The low viscosity dispersion had a dry solids content of 30 percent. The copolymer contained 50 percent of methacrylic acid, 30 percent of ethyl acrylate, and 20 percent of methyl methacrylate by weight, had a molecular weight of about 200,000, a minimum film forming temperature (DIN 53787) of 56C, and a glass -transition temperature Max (DIN 53445/DIN 7724) of 157C.
The procedure of Example 1 is used, except that the monomer/emulsifier mixture previously prepared consists of 180 g of ethyl acrylate 102 g of methyl methacrylate 18 g of methacrylamide 300 g of methacrylic acid 1.2 g of 2-ethylhexyl thioglycolate and 14 g of polyoxyethylene/sorbitan moonlit The low viscosity dispersion had a dry solids content of 30 percent.
The copolymer had a molecular weight of about 200 000, a minimum film forming temperature (DIN 53 787) of 54C and a glass transition temperature Tax (DIN 53 445/DIN 7724) of 156C
The procedure of Example 1 is used, except that the monomer/emulsifier mixture previously prepared consists of 300 g of methacrylic acid 180 g of ethyl acrylate ~2~L7~
90 g of methyl methacrylate 30 g of Vinyl pyrrolidone 1.2 g of 2-ethylhexyl thioglycolate and 14 g of polyoxyethylene/sorbitan moonlit The low viscosity dispersion had a molecular weight of about 200 000 a dry solids content of 30.5 percent, a minimum film forming temperature (DIN 53 787) of 42C and a glass transition temperature.
Tax (DIN 53 445/DIN 7724) of 151C.
The procedure of Example 1 is used except that 2.8 g of ammonium per sulfate are employed instead of 1.4 g. Moreover -the monomer/emulsifier mixture previously prepared consists of 300 g of methacrylic acid 180 g of ethyl acrylate 120 g of styrenes 1.2 g of 2-ethylhexyl thioglycolate and 14 g of polyoxyethylene/sorbitan moonlit The low viscosity dispersion had a dry solids content of about 29.5 percent the copolymer had a molecular weight of about 150,000, a minimum film forming temperature (DIN 53 787) of 53C and a glass transition temperature Tax (DIN 53 445/DIN 7724) of 151C.
The procedure of Example 1 is used, except that the monomer/emulsifier mixture previously prepared consists of 300 g of methacrylic acid 120 g of methyl methacrylate 180 g of ethylacrylate 1.2 g of 2-ethylhexyl thioglycolate and 14 g of polyoxyethylene/sorbitan moonlit After the reaction was completed the reaction mixture is cooled to I 75~
room temperature. Thereafter 12. 3 g of an aqueous solution containing 25 percent of ammonia are added. Further work up as in Example 1. The copolymer had a minimum film forming temperature (DIN 53 787) of 52C and a glass transition temperature T Max (DIN 53 445/DIN 7724) of 154C.
In a 2-1 Wilt jar as used in Example 1. 1. 4 g of ammonium per sulfate and 0. 2 g of the sodium salt of a sevenfold methylated and sulfated triisobutyl phenol were dissolved in 580 g distilled water.
A monomer/emulsifier mixture previously prepared from 258 g of methacrylic acid, 42 g of itaconic acid, 180 g of ethylacrylate, 120 g of methyl methacrylate, 9 g of the emulsifier used before, 2.8 g of ammonium per sulfate and 860 g distilled water was added drops to the above solution over a period of 4 hours at 80C with stirring, and the resulting mixture was maintained at 80C for 2 hours. After cooling to room temperature, it was filtered through a close meshed stainless steel woven wire screen.
The low viscosity dispersion had a dry solids content of 29. 7 percent. The copolymer had a molecular weight of about 200,000, a minimum film forming temperature (DIN 53 787) of 58C and a glass transition temperature. Tea (DIN 53 445/DIN 7724) of 158C .
The procedure of Example 1 is used except that the monomer/emulsifier mixture previously prepared consists of ]20 g of methacrylic acid 120 g of acrylic acid 360 g of methyl methacrylate 1.2 g of 2-ethylhexyl thioglycolate 14 g of polyoxyethylene/sorbitan moonlit I
The low viscosity dispersion had a molecular weight of about 200,000 a dry solids content of` about 29.9 percent, a minimum film forming temperature (DIN 53 787) of 50C and a glass transition temperature Tax (DIN 53 445/DIN 7724) of 157C.
In place of ethyl acrylate in Examples 1-6 a vinyl ether or vinyl ester, e.g. vinylacetat or butadiene can be employed in such quantities as to ensure a To of >140C of the copolymer. Usually the quantities of such monomers will be below 30 percent by weight of the copolymer.
In a 2-liter Wilt jar as in Example 1 4.2 g of ammoniurn per sulfate and 1.05 g sodium laurel sulfate were dissolved in 4300 g distilled water at 80C. A monomer/emulsifier mixture previously prepared from 900 g of methacrylic acid, 360 g of ethyl acrylate, 360 g of methylmethacrylate, 180 g of hydroxyethyl acrylate, 42 g of polyoxyethylene/sorbitan moonlit and 3.6 g of 2-ethylhexyl thioglycolate was added drops to the resulting solution over a period of 4 hours at 80C with stirring and the resulting mixture was maintained at 80C for 2 hours. After cooling to room temperature, it was filtered through a close meshed stainless steel woven wire screen.
The low viscosity dispersion has a dry solids content of 30 percent. The copolymer has a molecular weight of about 250,000, a minimum film forming temperature (DIN 53 787) of 50C and a glass transition temperature Tea (DIN 53 445/DIN 7724) of 146C.
The procedure of Example 8 is used except that 4250 g of distilled water are used. Furthermore the monomer/emulsifier mixture, which was prepared previously, and is then added consists of ,, Jo Lo 900 g of methacrylic acid 504 g of ethyl acrylate 306 g of methyl methacryla-te g of N-methylol methacrylamide 3.6 g of 2-ethylhexyl -thioglykolate 42 g of polyoxyethylene/sorbitan-monooleate g of distilled water The low viscosity dispersion has a dry solids content of 30 percent.
The copolymer has a molecular weight of about 270,000, a lo minimum film forming temperature (DIN 53 787) of 57C and a glass transition temperature To (DIN 53 445/DIN 7725) of ICKY.
EXAMPLE lo The same procedure as in Example 9 was used except that 90 g of N-butoxymethyl methacrylamide were used in place of N-methylol methacrylamide.
The physical data of the copolymer are rather similar to -the ones of Example 9.
Other copolymers having a different monomeric composition may be prepared in the same manner.
EXAMPLE if Preparation of a molding sand mixture ready for use 97 kg of foundry molding quartz sand were mixed at room temperature in a forced-motion mixer with 3 parts by weigh-t of an aqueous acrylic resin dispersion containing 30 percent of the copolymer of Example l. In this way, a sufficiently free-flowing, ready-to-use foundry molding sand mixture was obtained.
EXAMPLE lo Preparation of a molding sand mixture with addition of a multi functional non-radically cross linking agent 3 kg of dry foundry molding quartz sand were thoroughly mixed at room temperature with 3 g Al percent by weight) of a so finely powdered (average particle size about 20 us) solid epoxy resin (= solid bisphenol A-epichlorohydrine epoxy resin with an epoxy equivalent of 450 - 500 g viscosity at 25C of 1.2 - 1.7 poise; deformation temperature 50 - 70C: commercial product (Epikote 1001~ from Shell Chemise) in a forced-motion mixer.
Then 90 g (3 percent by weight) of an aqueous dispersion of the copolymer of Example 1 or, alternatively Example 8 are admixed in homogeneous distribution.
Production of a foundry mold core from a sand mixture The molding sand mixture of Example 1 or Example 12 was blown by compressed air into an iron mold which had a temperature between 150 and 200C. The filled mold was held for about 0.5 to 3 minutes at that temperature. Then it was opened while hot and the foundry core was removed. It was perfectly stable, retained its shape, and withstood handling.
Production of a metal casting The mold core of Example 13 was introduced into and secured in a box mold for iron casting. Iron was then poured intake the mold.
On cooling, a casting with a hollow which had the dimensions of the core of Example 13 was obtained. The core had completely collapsed.
No gas evolution occurred on contact with the liquid iron. The casting was practically free of pores.
5 percent (based on the total dispersion) of a monomer/initiator mixture consisting of trimethylolpropane trimethacrylate and up to 20 percent, based on the trimethylolpropane trimethacrylate, of tert-butyl perbenzoate or, alternatively, of a commercially available peroxide-free initiator I I
("Akzo-Starter 407") was stirred into an acrylic resin dispersion as in Example 1. This mixture was processed further in -the same concentration as in Examples 1 to I
Here, too, hard and handle able shaped bodies were obtained which exhibited no tendency toward gas evolution.
Claims (14)
1. An aqueous dispersion of a synthetic resin, adaptable to use as a binder for heat curable foundry molding sands, said resin being a copolymer comprising:
(A) from 20 to 90 percent by weight of an unsaturated carboxylic acid of the formula wherein R1, R2 and R3 are independently hydrogen, alkyl having from 1 to 6 carbon atoms, or -(CH2)n -COOM, where M is a proton or an alkali metal or alkaline earth metal or an ammonium cation, and n is 0 or 1, but where no more than two -COOM groups are present in the acid molecule and where those groups COOM wherein M is an alkali metal or alkaline earth metal cation are not more than 20 percent by weight of all -COOM groups present in said copolymer; and (B) from 10 to 80 percent by weight of at least one monomer different from and copolymerizable with (A).
(A) from 20 to 90 percent by weight of an unsaturated carboxylic acid of the formula wherein R1, R2 and R3 are independently hydrogen, alkyl having from 1 to 6 carbon atoms, or -(CH2)n -COOM, where M is a proton or an alkali metal or alkaline earth metal or an ammonium cation, and n is 0 or 1, but where no more than two -COOM groups are present in the acid molecule and where those groups COOM wherein M is an alkali metal or alkaline earth metal cation are not more than 20 percent by weight of all -COOM groups present in said copolymer; and (B) from 10 to 80 percent by weight of at least one monomer different from and copolymerizable with (A).
2. An aqueous dispersion as in Claim 1 wherein (B) comprises monomers, containing a functional group which is capable of non-radical crosslinking by reacting with another functional group or by reacting with a multifunctional non-radically crosslinking agent at a temperature above 60°C.
3. An aqueous dispersion as in Claim 2 wherein the monomers containing a functional group capable of non-radical crosslinking are from 0.3 to 30 percent by weight of said copolymer.
4. An aqueous dispersion as in Claim 2 wherein said functional groups are selected from the group consisting of amide, N-methylolamide, hydroxy, epoxy and blocked isocyanate functions.
5. An aqueous dispersion as in Claim 2 wherein said monomers containing a functional group capable of non-radical crosslinking are derivatives of acrylic or methacrylic acid.
6. An aqueous dispersion as in Claim 2, wherein said multifunctional non-radically crosslinking agents contain a hydrocarbon backbone having from 2 to 103 carbon atoms with a minimum of 2 functional groups and a maximum number of functional groups equal to the number of carbon atoms in the backbone.
7. An aqueous dispersion as in Claim 6, wherein said multifunctional non-radically crosslinking agents consist of a hydrocarbon backbone having from 2 to 20 carbon atoms with a minimum of 2 functional groups and a maximum number of functional groups equal to the number of carbon atoms in the backbone.
8. An aqueous dispersion as in Claim 1 which additionally comprises from 1 to 10 percent, by weight of said copolymer, of a crosslinking monomer having a boiling point of at least 150°C and from 0.1 to 5 percent, by weight of said crosslinking monomer, of a polymerization-initiator soluble in said crosslinking monomer.
9. An aqueous dispersion as in Claim 1 which comprises from 10 to 60 percent of said copolymer, by weight of said dispersion.
10. An aqueous dispersion as in Claim 1 wherein said copolymer has a minimum film forming temperature below 100°C and a glass transition temperature greater than 140°C.
11. An aqueous dispersion as in Claim 10 wherein said copolymer has a glass transition temperature greater than 150°C.
12. A method for making a ready-to-use foundry molding sand containing a binder, which method comprises mixing a dispersion as in Claim 1 with sand.
13. A ready-to-use foundry molding sand which is a mixture of sand and an amount of a dispersion as in Claim 1 such that said mixture contains from 0.1 to 10 percent, by weight of said mixture, of said copolymer.
14. A ready-to-use foundry molding sand as in Claim 13 containing 1 ? 0.5 percent by weight of said copolymer.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3305361.8 | 1983-02-17 | ||
| DE19833305361 DE3305361A1 (en) | 1983-02-17 | 1983-02-17 | BINDING AGENT FOR FOUNDRY SAND |
| DEP3402255 | 1984-01-24 | ||
| DE19843402255 DE3402255A1 (en) | 1984-01-24 | 1984-01-24 | Binder medium for foundry moulding sands |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1217591A true CA1217591A (en) | 1987-02-03 |
Family
ID=25808302
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000447364A Expired CA1217591A (en) | 1983-02-17 | 1984-02-14 | Resin binders for foundry molding sands |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0119468B1 (en) |
| CA (1) | CA1217591A (en) |
| DE (1) | DE3462311D1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102007012489A1 (en) * | 2007-03-15 | 2008-09-25 | AS Lüngen GmbH | Composition for the production of feeders |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1032896B (en) * | 1951-10-01 | 1958-06-26 | Goodrich Co B F | Binders for foundry molds and cores and processes for their manufacture |
| SU406616A1 (en) * | 1970-09-11 | 1973-11-21 | MIXTURE FOR CASTING STEM AND FORMS | |
| NL7414722A (en) * | 1973-11-19 | 1975-05-21 | Dow Chemical Co | PROCESS FOR THE PREPARATION OF AN WATERY DISPERSION OF AN INHAERENT WATER DISPERSIBLE INTERPOLYMER. |
| JPS5512839A (en) * | 1978-07-07 | 1980-01-29 | Otsuka Kagaku Yakuhin | Binder for fire retardant fiber and production of fire retardant material |
| DE3151372A1 (en) * | 1981-12-24 | 1983-07-07 | Henkel KGaA, 4000 Düsseldorf | "REMOVABLE PROTECTIVE COATS RESULTING FROM AQUEOUS EMULSIONS AND THEIR USE FOR THE TEMPORARY PROTECTION OF PAINTED AND METAL OBJECTS" |
-
1984
- 1984-02-14 CA CA000447364A patent/CA1217591A/en not_active Expired
- 1984-02-15 EP EP84101553A patent/EP0119468B1/en not_active Expired
- 1984-02-15 DE DE8484101553T patent/DE3462311D1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3462311D1 (en) | 1987-03-12 |
| EP0119468A1 (en) | 1984-09-26 |
| EP0119468B1 (en) | 1987-02-04 |
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