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
• • 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
  • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
  • C04B20/10—Coating or impregnating
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G8/00—Condensation polymers of aldehydes or ketones with phenols only
  • C08G8/28—Chemically modified polycondensates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/544—Silicon-containing compounds containing nitrogen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
  • C08L61/04—Condensation polymers of aldehydes or ketones with phenols only
  • C08L61/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
  • C08L61/14—Modified phenol-aldehyde condensates

Definitions

• the present invention relates to a resin composition for producing resin-coated sand for shell molds, and resin-coated sand obtained using the same.
• Resin coated sand is a material in which the surface of sand or ceramic aggregate is coated with a resin layer that serves as a binder.
• Phenol resin is generally used as the resin layer of resin coated sand.
• Patent Document 1 describes a lignin-modified novolac obtained by reacting acid-modified lignin, phenols, and aldehydes as the biomass-derived resin in a coated sand containing a biomass-derived resin and an aggregate. It is described that a type phenolic resin is used. Patent Document 1 discloses that a lignin-modified novolac-type phenolic resin obtained using lignin modified with carboxylic acid or lignin modified with acetic acid is carbon neutral and has excellent transverse rupture strength and bending properties. is listed.
• Patent Document 1 has room for improvement in terms of mechanical strength and expandability.
• the inventors of the present invention have developed the invention in view of the above problems, and by using a lignin-modified novolac type phenolic resin with a reduced content of free phenol, it has high mechanical strength and low expansion property.
• the present invention was completed based on the discovery that a resin composition that can be suitably used as a binder for coated sand can be obtained.
• a resin composition for resin coated sand includes a lignin-modified novolac type phenolic resin, The resin composition, wherein the content of free phenols in the lignin-modified novolac-type phenolic resin is 2% by mass or less.
• the lignin-modified novolac-type phenolic resin according to item [1] which is a novolac-type phenolic resin obtained by reacting lignin, phenols, and aldehydes in the presence of an acid catalyst. Resin composition.
• a resin-coated sand comprising aggregate, a lubricant, and the resin composition according to any one of items [1] to [10].
• a resin composition whose cured product has excellent mechanical strength and low expansion property, and can be suitably used as a binder for resin-coated sand, and resin-coated sand. .
• the resin composition of this embodiment is used as a binder for resin-coated sand, and contains a lignin-modified novolac type phenolic resin.
• the lignin-modified novolac type phenolic resin used in the resin composition of the present embodiment has a content of free phenols of 2% by mass or less.
• a cured product of a resin composition containing the same has excellent mechanical strength and low expansion.
• a resin composition containing such a lignin-modified novolac type phenolic resin has little or reduced generation of tar and soot. Therefore, a mold manufactured from resin-coated sand obtained by using such a resin composition as a binder has high mold strength and has reduced generation of tar or soot.
• the components used in the resin composition of this embodiment are described below.
• the lignin-modified novolac type phenolic resin used in the resin composition of this embodiment has a content of free phenols of 2% by mass or less.
• the free phenols contained in the lignin-modified novolak phenolic resin are the phenols used as raw material components for producing the lignin-modified novolak phenolic resin, and are the phenols that remain in an unreacted state. Refers to the type.
• the resulting resin composition has mechanical strength and expandability suitable for use as a binder for resin-coated sand.
• the lignin-modified novolak phenolic resin used in the resin composition of this embodiment is a novolak phenolic resin obtained by reacting lignin, phenols, and aldehydes in the presence of an acid catalyst.
• the lignin-modified novolac type phenolic resin used in the resin composition of the present embodiment has a number average molecular weight of, for example, 200 to 1,500, preferably 400 to 1,200, and more preferably 500 to 1,500. ⁇ 1,000.
• the resulting cured resin composition can have improved mechanical strength.
• the lignin modification rate of the lignin-modified novolak phenolic resin used in the resin composition of the present embodiment is preferably 10% or more and 50% or less, more preferably 14% or more and 50% or less.
• the lignin-modified novolak phenolic resin used in the resin composition of the present embodiment preferably has a softening point of 70°C or higher and 105°C or lower, more preferably 75°C or higher and 95°C or lower.
• the lignin-modified novolak phenolic resin containing a predetermined amount of free phenols used in the resin composition of the present embodiment preferably contains lignin, phenols, and aldehydes in the presence of an acid catalyst. Produced by reaction.
• the lignin-modified novolac type phenolic resin used in this embodiment has the above-mentioned desired physical properties by adjusting the manufacturing conditions.
• the materials and manufacturing conditions used for manufacturing the lignin-modified novolac type phenolic resin used in the resin composition of this embodiment will be described in detail.
• Phenols used in the production of the lignin-modified novolak phenolic resin used in this embodiment include phenol, phenol derivatives, and combinations thereof.
• phenol derivative phenol having an arbitrary substituent introduced into the benzene ring can be used.
• substituent include a hydroxy group; a lower alkyl group such as a methyl group and an ethyl group; a halogen atom such as fluorine, chlorine, bromine, and iodine; an amino group; a nitro group; and a carboxy group.
• phenols that can be used include phenol, catechol, resorcinol, hydroquinone, o-cresol, m-cresol, p-cresol, o-fluorophenol, m-fluorophenol, p-fluorophenol, and o-chloro.
• alkylphenols having 2 to 18 carbon atoms can also be used.
• the alkylphenols may have a branched alkyl chain or an unsaturated bond.
• the substitution position of the alkyl chain on the benzene ring may be any of ortho, meta, and para substitution.
• alkylphenols examples include ethylphenol, propylphenol, isopropylphenol, butylphenol, secondary butylphenol, tertiary butylphenol, amylphenol, tertiary aminophenol, hexylphenol, heptylphenol, octylphenol, tertiary octylphenol, nonylphenol, Tertiary nonylphenol, decylphenol, undecylphenol, dodecylphenol, tridecylphenol, tetradecylphenol, pentadecylphenol, cardanol, cardol, urushiol, hexadecylphenol, methyl cardol, heptadecylphenol, laccol, thiol, octadecyl Examples include phenol. Further, as the alkylphenols, vegetable oils such as cashew nut shell liquid (cashew oil) and sumac extract can be used.
• phenol cresol, xylenol, alkylphenol, and bisphenol
• phenol cresol, butylphenol, and bisphenol A are preferably used. is preferred.
• the lignins used in the production of the lignin-modified novolak phenolic resin used in this embodiment include at least one selected from lignin and lignin derivatives.
• Lignin along with cellulose and hemicellulose, is a major component forming the structure of plants, and is also one of the most abundant aromatic compounds in nature. Lignin is partially bonded and exists as lignocellulose in plants, so lignin often refers to substances obtained from plants through decomposition, etc. Examples include kraft lignin, lignin sulfonic acid, and soda.
• Examples include pulp lignin such as lignin and soda-anthraquinone lignin; organosol lignin; lignophenol in which phenol is added to high-temperature, high-pressure water-treated lignin or blasted lignin during extraction with concentrated sulfuric acid; and phenolized lignin.
• the origin of lignin is not particularly limited, and includes wood and herbs that contain lignin and form woody parts, such as coniferous trees such as cedar, pine, cypress, and spruce, beech, white birch, oak, zelkova, and eucalyptus.
• Examples include broad-leaved trees such as, grasses (herbs) such as rice, wheat, corn, and bamboo.
• the term "lignin derivative” refers to a compound having a unit structure constituting lignin or a structure similar to a unit structure constituting lignin.
• the lignin derivative has a phenol derivative as a unit structure. Since this unit structure has chemically and biologically stable carbon-carbon bonds and carbon-oxygen-carbon bonds, it is resistant to chemical deterioration and biological decomposition.
• lignin derivatives include guaiacylpropane (ferulic acid) represented by formula (A) of the following formula (1), syringylpropane (sinapinic acid) represented by the following formula (B), and syringylpropane (sinapinic acid) represented by the following formula (C).
• Examples include 4-hydroxyphenylpropane (coumaric acid).
• the composition of lignin derivatives varies depending on the biomass used as the raw material.
• Lignin derivatives containing a guaiacylpropane structure are mainly extracted from conifers.
• Lignin derivatives containing mainly guaiacylpropane and syringylpropane structures are extracted from broad-leaved trees.
• Lignin derivatives mainly containing a guaiacylpropane structure, a syringylpropane structure, and a 4-hydroxyphenylpropane structure are extracted from herbs.
• the lignin derivative is preferably one obtained by decomposing biomass. Since biomass captures and fixes atmospheric carbon dioxide during the process of photosynthesis, biomass contributes to suppressing the increase in atmospheric carbon dioxide, and industrial use of biomass can help reduce global warming. This can contribute to suppressing the Examples of biomass include lignocellulose biomass.
• lignocellulosic biomass include leaves, bark, branches, and wood of plants containing lignin, and processed products thereof.
• plants containing lignin include the above-mentioned broad-leaved trees, coniferous trees, and herbs.
• Biomass decomposition methods include chemical treatment, hydrolysis treatment, steam explosion method, supercritical water treatment method, subcritical water treatment method, mechanical treatment method, sulfuric acid cresol method, pulp manufacturing method, etc. Can be mentioned. From the viewpoint of environmental load, steam explosion method, subcritical water treatment method, and mechanical treatment method are preferred. From the viewpoint of cost, the pulp manufacturing method is preferred. Moreover, from the viewpoint of cost, it is preferable to use a by-product of biomass utilization.
• Lignin derivatives can be prepared, for example, by decomposing biomass at 150 to 400° C., 1 to 40 MPa, and for 8 hours or less in the presence of various cooking liquors or solvents. Further, the lignin derivative can be prepared by the method disclosed in JP-A No. 2009-084320, JP-A No. 2012-201828, and the like.
• lignin derivatives include those obtained by decomposing lignocellulose, which is a combination of lignin, cellulose, and hemicellulose.
• the lignin derivative may include a lignin decomposition product, a cellulose decomposition product, a hemicellulose decomposition product, etc. which are mainly composed of a compound having a lignin skeleton.
• the lignin derivative may also contain biomass-derived or process-derived inorganic substances, but when used in the application of this embodiment, the content of the inorganic substance should be 10% by mass or less based on the entire lignin derivative used. preferable.
• the lignin derivative has many reaction sites where the curing agent acts through an electrophilic substitution reaction on the aromatic ring, and since the less steric hindrance in the vicinity of the reaction site, the better the reactivity, the It is preferable that at least one of the ortho-position and para-position of the ring is unsubstituted, and lignin derived from coniferous trees or herbs, which contains a large amount of guaiacyl nucleus or 4-hydroxyphenyl nucleus structure as the aromatic unit of lignin, is preferable.
• the lignin derivative those disclosed in JP-A No. 2009-084320, JP-A No. 2012-201828, etc. can be used.
• the lignin derivative may also have a functional group (lignin secondary derivative).
• the functional groups possessed by the lignin secondary derivative are not particularly limited, but, for example, two or more of the same functional groups are preferably capable of reacting with each other or reacting with other functional groups.
• Specific examples include, in addition to epoxy groups and methylol groups, vinyl groups having carbon-carbon unsaturated bonds, ethynyl groups, maleimide groups, cyanate groups, and isocyanate groups.
• lignin derivatives into which a methylol group has been introduced (methylolated) are preferably used.
• Such lignin secondary derivatives undergo self-crosslinking due to a self-condensation reaction between methylol groups, and also crosslink to alkoxymethyl groups and hydroxyl groups in the crosslinking agent described below.
• a lignin-modified novolac type phenolic resin having a particularly homogeneous and rigid skeleton and excellent solvent resistance is obtained.
• the lignin derivative used in this embodiment may have a carboxyl group.
• Lignin obtained through pulp processing or high-temperature, high-pressure water treatment may have carboxyl groups.
• Lignin-modified novolac type phenolic resin obtained from a lignin derivative having a carboxyl group has many crosslinking points for the curing agent described below, so it is possible to improve the crosslinking density of the resulting crosslinked product, resulting in improved solvent resistance. A crosslinked product with excellent properties can be obtained.
• the carboxyl group can be confirmed by the presence or absence of absorption of a peak at 172 to 174 ppm when subjected to 13 C-NMR analysis attributed to the carboxyl group. can.
• the lignin used in the production of the lignin-modified novolac type phenolic resin used in this embodiment has a weight average molecular weight of, for example, 2,000 or more and 100,000 or less.
• the lower limit of the weight average molecular weight is preferably 2,500 or more, more preferably 3,000 or more, and even more preferably 4,000 or more.
• the upper limit of the weight average molecular weight is preferably 90,000 or less, more preferably 80,000 or less, and even more preferably 75,000 or less.
• a resin composition containing a lignin-modified novolak phenolic resin obtained using lignin having a weight average molecular weight in the above range has excellent curability, and the cured product has high mechanical strength and low expansion property. It is.
• the weight average molecular weight is a polystyrene-equivalent number average molecular weight measured by gel permeation chromatography, and can be determined by the method described in Examples.
• the lignin used in the production of the lignin-modified novolak phenolic resin used in this embodiment has a number average molecular weight of, for example, 200 or more and 5,000 or less.
• the lower limit of the number average molecular weight is preferably 300 or more, more preferably 350 or more, and even more preferably 400 or more.
• the upper limit of the number average molecular weight is preferably 4,000 or less, more preferably 3,000 or less, and even more preferably 2,000 or less. Lignins having a number average molecular weight within the above range are preferable because they have excellent reactivity and therefore excellent workability in the process of producing a lignin-modified novolak phenolic resin.
• the obtained lignin-modified novolac type phenolic resin has excellent curability and the cured product thereof has high mechanical strength.
• the number average molecular weight is a polystyrene equivalent number average molecular weight measured by gel permeation chromatography, and can be determined by the method described in Examples.
• a lignin derivative is dissolved in a solvent to prepare a measurement sample.
• the solvent used at this time is not particularly limited as long as it can dissolve the lignin derivative, but from the viewpoint of measurement accuracy of gel permeation chromatography, for example, tetrahydrofuran and N-methyl-2-pyrrolidone are preferable. .
• the lignin used in the production of the lignin-modified novolak phenolic resin used in this embodiment may contain insoluble matter due to biomass, process-derived inorganics, and plant-derived high molecular weight organic matter. In addition to selection, insoluble matter is determined by filtration. Further, in order to increase the lignin modification rate of the obtained lignin-modified novolac type phenolic resin, the insoluble content of the lignin used is preferably 30% by mass or less in an appropriate solvent. Furthermore, the molecular weight of the lignin-modified novolac type phenolic resin can be determined by similarly filtering out insoluble matter.
• the content of insoluble matter in the lignin-modified novolak phenol resin is preferably 15% by mass or less, more preferably 10% by mass or less.
• the lignin-modified novolak phenolic resin has good curability, and in particular can be uniformly cured.
• RI differential refractive index
• UV ultraviolet absorbance
• the number average molecular weight and weight average molecular weight of the target can be calculated from a calibration curve showing the relationship between retention time and molecular weight of standard polystyrene prepared separately. Refractive index is preferred as the detection mode.
• the GPC system "HLC-8320GPC (manufactured by Tosoh)" is connected in series with "TSKgelGMHXL (manufactured by Tosoh)” and "G2000HXL (manufactured by Tosoh),” which are organic general-purpose columns filled with styrene polymer filler. .
• 200 ⁇ L of the measurement sample described above was injected into this GPC system, developed at 40°C with tetrahydrofuran as an eluent at 1.0 mL/min, and held using differential refractive index (RI) and ultraviolet absorbance (UV). Measure time.
• the number average molecular weight and weight average molecular weight of the target can be calculated from a calibration curve showing the relationship between retention time and molecular weight of standard polystyrene prepared separately. Refractive index is preferred as the detection mode.
• the molecular weight of the standard polystyrene used to create the calibration curve is not particularly limited, but for example, the weight average molecular weight is 2,110,000, 1,090,000, 427,000, 190,000. , 37,900, 18,100, 5,970, 2,420 and 500 standard polystyrene (manufactured by Tosoh) can be used.
• the type and characteristics of the lignins used in the production of the lignin-modified novolak phenolic resin of the present embodiment are not particularly limited, but for example, lignins having a softening point of 80° C. or higher can be used. Such lignin is preferable because it has good workability and handleability.
• the softening point of lignins can be measured using a ring and ball softening point tester (for example, ASP-MG2 model manufactured by Meltech Co., Ltd.) according to JIS K2207.
• a ring and ball softening point tester for example, ASP-MG2 model manufactured by Meltech Co., Ltd.
• JIS K2207 JIS K2207.
• lignin contains a large amount of water, it is measured after being absolutely dried at 70° C. or lower.
• a good sample cannot be prepared due to the thermal meltability of lignin on a hot plate at 150 to 200° C., for example, it is determined that the softening point is too high to measure.
• the volatile content of lignins is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.
• the main volatile content is often water, and can be calculated by, for example, spreading 4 g in an aluminum cup and drying it at 80°C for 20 hours.
• lignins obtained by decomposing biomass When using lignins obtained by decomposing biomass, a large amount of low molecular weight components may be mixed in, which may cause volatile matter and odor during heating, and a decrease in the softening point. These components can be used as they are, or can be removed by heating, drying, etc. the lignin to adjust the softening point and odor.
• aldehydes used in the production of the lignin-modified novolak phenolic resin used in this embodiment include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n -Butyraldehyde, caproaldehyde, allylaldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde, paraxylene dimethyl ether and the like.
• Preferred examples include formaldehyde, paraformaldehyde, trioxane, polyoxymethylene, acetaldehyde, paraxylene dimethyl ether, and combinations thereof.
• One type of aldehyde may be used alone, or two or more types may be used in combination. Among these, it is preferable to use formaldehyde or acetaldehyde from the viewpoint of productivity and low cost.
• the acid catalyst used in the production of the lignin-modified novolak phenolic resin used in this embodiment may be any catalyst that can be used as a reaction catalyst, and organic acids, inorganic acids, and combinations thereof can be used.
• organic acids include acetic acid, formic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, benzoic acid, salicylic acid, sulfonic acid, phenolsulfonic acid, para-toluenesulfonic acid, and the like.
• the inorganic acid include hydrochloric acid, sulfuric acid, sulfuric acid ester, phosphoric acid, and phosphoric acid ester.
• the molar ratio (F/P) of aldehydes to phenols is, for example, 0.4 or more, preferably 0.45 or more. , more preferably 0.5 or more.
• the upper limit of the molar ratio (F/P) of aldehydes to phenols is, for example, 1.0 or less, preferably 0.9 or less, and more preferably 0.85 or less.
• the step of reacting lignin, phenols, and aldehydes in the presence of an acid catalyst includes reacting the lignins and phenols at a temperature of 70°C to 120°C.
• the following steps of mixing under heating to disperse lignins to obtain a mixture step 1), mixing an acid catalyst simultaneously with step 1 or after step 1 (step 2), and after step 2,
• the method may also include a step of mixing aldehydes.
• the step of reacting lignins, phenols, and aldehydes in the presence of an acid catalyst may be carried out at a temperature of, for example, 60°C to 120°C, preferably 80°C to 105°C, for example. , is preferably carried out with a reaction time of 10 minutes to 100 minutes. This allows the reaction to proceed efficiently and sufficiently.
• the starting materials are mixed uniformly, and the resulting lignin-modified novolak phenolic resin can be uniformly cured due to the entanglement and interaction between the molecules, resulting in excellent dimensional accuracy. Molding can be realized.
• the reaction time is not particularly limited and may be appropriately determined depending on the type of starting materials, molar ratio of the mixture, amount and type of catalyst used, and reaction conditions.
• the above steps 1, 2, and 3 are preferably carried out without a solvent, but an organic solvent or water may be used as the solvent. Instead of adding water, hydrated lignin may be used.
• the organic solvent include alcohols, ketones, esters, ethers, and hydrocarbons.
• alcohols include methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, octanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin, and the like.
• ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone.
• esters include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methoxybutyl acetate, amyl acetate, methyl lactate, ethyl lactate, butyl lactate, and the like.
• Ethers include propyl ether, dioxane, methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, methyl carbitol, ethyl carbitol.
• butyl carbitol methyl cellosolve acetate, ethyl cellosolve acetate, propyl cellosolve acetate, butyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate.
• hydrocarbons examples include toluene, xylene, pentane, hexane, cyclohexane, heptane, octane, decane, solvent naphtha, industrial gasoline, petroleum ether, petroleum benzine, ligroin, and the like. These may be used alone or in combination of two or more.
• the conventional method of increasing the molecular weight of lignin-modified novolak phenolic resin by adjusting the reaction ratio of phenols, lignins, and aldehydes increases the viscosity of the reactants and makes dehydration difficult. In some cases, the period was long. In addition, there were cases in which a large amount of unreacted phenols remained. In contrast, in this embodiment, the process time can be shortened and the resin yield can be increased compared to the conventional case of increasing the molecular weight by using the reaction ratio of phenols, lignins, and aldehydes. can.
• the properties of the resulting lignin-modified novolac type phenolic resin can be improved.
• the physical properties of the resin material can be adjusted within a desired range.
• the amount of unreacted free phenols contained in the obtained lignin-modified novolak-type phenolic resin can be reduced to 2% by mass or less based on the lignin-modified novolak-type phenolic resin.
• the lignin-modified novolac type phenolic resin obtained by the above method preferably has a number average molecular weight of 200 or more and 1,500 or less, more preferably 400 or more and 1,200 or less, and even more preferably 500 or more and 1,500 or less. It has a number average molecular weight of 000 or less.
• the lignin-modified novolac type phenolic resin having a number average molecular weight in the above range has excellent mechanical strength and low expansion, making it suitable for use as a binder for resin-coated sand.
• the lignin-modified novolac type phenolic resin obtained by the above method preferably has a softening point of 70°C or more and 105°C or less, more preferably 75°C or more and 95°C or less.
• the resin composition of this embodiment may also contain a lubricant.
• a lubricant By using a lubricant, it is possible to improve the strength and blocking resistance of a mold manufactured from resin-coated sand.
• a lubricant for example, amide compounds such as ethylene bisstearamide, ethylene bisoleic acid amide, methylene bisstearic acid amide, oxystearic acid amide, stearic acid amide, palmitic acid amide, oleic acid amide, methylolamide, etc. may be used. is preferred.
• Other usable lubricants include calcium stearate, polyethylene wax, paraffin wax, montan wax, carnauba wax, and the like. These may be used alone or in combination of two or more.
• the lubricant in an amount of 0.3 to 5 parts by mass based on 100 parts by mass of the lignin-modified novolak phenolic resin. If it is less than 0.3 parts by mass, the effect of improving strength and blocking resistance is small, and if it exceeds 5 parts by mass, the curing speed becomes slow and the adhesive force between aggregates (sand) is inhibited, which is not preferable.
• the method of blending the lubricant is not particularly limited, but it is desirable to add it in a molten state after the reaction, or to add it in a kneader at a temperature of 70° C. or higher. Further, the mixing time after addition is not particularly limited, but it is preferable to mix for 5 minutes or more.
• the lubricant can also be mixed with a solid resin.
• the lubricant can also be added after producing the resin composition, when kneading the resin composition (binder) and aggregate (sand) to produce resin-coated sand.
• the resin composition of this embodiment may also contain a silane coupling agent.
• a silane coupling agent By using a silane coupling agent, it is possible to improve the strength and blocking resistance of a mold manufactured from resin-coated sand.
• the silane coupling agent include N- ⁇ (aminoethyl)- ⁇ -aminopropyltrimethoxysilane, N- ⁇ (aminoethyl)- ⁇ -aminopropylmethyldimethoxysilane, and ⁇ -aminopropyltriethoxysilane.
• Aminosilane coupling agents can be used.
• the silane coupling agent is desirably used in an amount of 0.05 to 5 parts by mass per 100 parts by mass of the lignin-modified novolak phenolic resin. By using the amount in such a range, it is possible to obtain the effect of improving the strength of the mold and improving the blocking resistance.
• the method of blending the silane coupling agent is not particularly limited, but it is desirable to add it in a molten state after the reaction, or to add it in a kneader at a temperature of 70° C. or higher. Further, the mixing time after addition is not particularly limited, but it is preferable to mix for 5 minutes or more.
• the silane coupling agent can also be added when producing resin coated sand by kneading the resin composition (binder) and aggregate (sand) after producing the resin composition.
• the resin composition of this embodiment can be manufactured by kneading and stirring a predetermined amount of the above components by a known method.
• the resin-coated sand of this embodiment is composed of aggregate and a resin layer covering the aggregate, and the resin layer is formed from the resin composition of this embodiment described above.
• Method for producing resin-coated sand is not particularly limited, for example, first, a resin composition is produced by the method described above, and then the aggregate and the resin composition are heated and mixed.
• fire-resistant granular materials such as silica sand mainly composed of quartz, chromite sand, zircon sand, olivine sand, mullite sand, synthetic mullite sand, magnesia, alumina-based artificial sand, and Sun Pearl. Examples include sand, recovered sand, recycled sand, etc. Further, the particle size distribution and particle size of the refractory granular material can be selected without any particular restriction as long as it has a fire resistance that can withstand casting and is suitable for mold formation.
• the aggregate is heated.
• the heating temperature is appropriately set depending on the type of aggregate, and is, for example, 100°C or higher, preferably 110°C or higher, and, for example, 200°C or lower, preferably 170°C or lower.
• the heated aggregate and the lignin-modified novolak type phenolic resin are mixed and stirred at a predetermined ratio, and if necessary, a curing agent, a curing accelerator, a lubricant, and a silane coupling agent are added, While cooling, knead and stir until the lumpy aggregate is broken up into granules. Thereafter, a lubricant is added if necessary, and the mixture is further kneaded and stirred.
• the aggregate is coated with the lignin-modified novolac type phenolic resin, and resin-coated sand is obtained.
• the resin-coated sand produced by the above method includes a resin layer made of a resin composition containing a lignin-modified novolac-type phenolic resin.
• Such resin-coated sand has high mechanical strength and low expansion. Therefore, the resin coated sand of this embodiment is suitably used as a mold material.
• the resin-coated sand is filled into the mold by a known method such as a gravity drop method or a blowing method, and after the resin-coated sand is cured by heating, it is removed from the mold. Take it out.
• the heating conditions are, for example, 200°C or higher, preferably 250°C or higher, and, for example, 350°C or lower, preferably 300°C or lower.
• the heating time is, for example, 30 seconds or more, preferably 1 minute or more, and, for example, 5 minutes or less, preferably 3 minutes or less.
• resin-coated sand are not limited to those mentioned above, and can be used in various industrial fields.
• Lignin-modified novolac-type phenolic resin 1 was produced by the following method.
• a lignin derivative used in the synthesis of a lignin-modified novolac type phenolic resin was prepared by the following procedure. To 1500 parts by weight of cedar wood flour with a moisture content of 50%, 5000 parts by weight of pure water as a cooking liquid, 180 parts by weight of sodium hydroxide, 120 parts by weight of sodium carbonate, and 7.5 parts by weight of 9,10-anthraquinone as a cooking aid.
• the mixture was placed in a stainless steel autoclave with a capacity of 10 L, and a cooking reaction was carried out at 170° C. for 3 hours with stirring. After the reaction, the cooking liquor was cooled to room temperature, the pulp components were removed with a screen, and the black liquor containing lignin was separated. Dilute sulfuric acid was added to the separated black liquor to adjust the pH to 8, and the resulting precipitate was centrifuged. After washing twice with 500 parts by mass of water, the precipitate was suspended in 5 times the amount of water, and the pH was readjusted to 2 with dilute sulfuric acid.
• the precipitated lignin is centrifuged again, washed with water, filtered by suction, spread on a vat, air-dried, and dried in a vacuum oven at 70°C or lower to obtain a brown powdery alkali lignin 140 with a solid content of 70% or more.
• 150 parts by weight (in terms of solid content) were obtained from the parts by mass.
• the solid content percentage of lignin was calculated from the residual percentage after putting 4 g of sample into an aluminum cup and heating and drying it at 135° C. for 1 hour.
• the number average molecular weight (Mn) of the obtained lignin derivative was 2,000, and the weight average molecular weight (Mw) was 14,000.
• lignin-modified novolac type phenol resin 1 was synthesized by the following procedure. Add 100 parts by weight of phenol to a four-necked flask equipped with a stirrer, cooling tube, and thermometer, gradually add 15.8 parts by weight (solid content) of the above lignin derivative, and mix and disperse at 60°C or higher. Then, 1.3 parts by weight of oxalic acid was added, and 43.1 parts by weight of 37% formaldehyde aqueous solution was gradually added over 60 minutes to react at 100°C. Then, the mixture was heated to 150° C. or higher by dehydration under reduced pressure, and when the desired phenol concentration was reached, the mixture was taken out to obtain 94.5 parts by weight of lignin-modified novolac type phenol resin 1.
• Lignin-modified novolac type phenol resin 2 was produced by the following method.
• (Preparation of lignin derivative) 200 parts by weight of cedar wood flour with a moisture content of 50% and 567 parts by weight of pure water as a cooking liquid were charged into a stainless steel autoclave equipment with a capacity of 10 L, and the mixture was treated at 300° C. for 1 hour with stirring. The cooking liquor after the reaction was cooled to room temperature and filtered to obtain a solid content containing lignin. The obtained solid content was immersed in 250 parts of acetone for 12 hours. This was filtered, and acetone was distilled off from the filtrate at 70° C. or below and dried to obtain 15.2 parts by weight of a lignin derivative.
• the number average molecular weight (Mn) of the obtained lignin derivative was 580, and the weight average molecular weight (Mw) was 2,510.
• Lignin-modified novolac type phenol resin 3 was produced by the following method.
• (Preparation of lignin derivative) Using 5000 parts by weight of pure water, 150 parts by weight of sodium hydroxide, 80 parts by weight of sodium sulfide, 70 parts by weight of sodium carbonate as a cooking liquid and 7.5 parts by weight of 9,10-anthraquinone as a cooking aid, the mixture was heated at 170°C. A lignin derivative was obtained in the same manner as in Preparation Example 1, except that the cooking reaction was carried out for 2 hours and the mixture was dried at 100° C. or lower. The number average molecular weight (Mn) of the obtained lignin derivative was 1,920, and the weight average molecular weight (Mw) was 15,100.
• Lignin-modified novolak-type phenolic resin 7 was produced by the following method.
• Preparation of lignin derivative A lignin derivative was obtained in the same manner as in Preparation Example 1.
• Preparation of lignin-modified novolac type phenolic resin 125.2 parts by weight of lignin-modified novolak was prepared in the same manner as in Preparation Example 1, except that 40.5 parts by weight (solid content) of the above lignin derivative and 54.8 parts by weight of 37% formaldehyde aqueous solution were used.
• Type phenol resin 7 was obtained.
• the resin compositions obtained in each Example and Comparative Example were measured for the following physical properties.
• Amount of tar and soot generated 100 parts by weight of the phenolic resin composition obtained in each Example and Comparative Example and 15 parts by weight of hexamine were pulverized and mixed in a small pulverizer to obtain a thermosetting resin composition with a median diameter of about 30 ⁇ m. Further, it was cured at 150° C. for 30 minutes and crushed to obtain a cured product. Next, 1.5 g of the cured product was placed in a small crucible with a diameter of 25 mm and a height of 30 mm, and aluminum foil was placed on the crucible.
• the crucible small is placed in a crucible (large) having a diameter of 65 mm and a height of 55 mm, and the crucible is covered. This was heated at 430° C. for 30 minutes, and after being left to cool, the weights of the crucible (large), aluminum foil, and lid were measured, and the amount of tar and soot generated from the resin composition due to the heat treatment was calculated using the following formula.
• the coefficient of thermal expansion was measured in accordance with JACT test method SM-7. That is, using RCS, a test piece with a diameter x length of 30 ⁇ x 50 mm was prepared by firing at 250°C for 120 seconds, and the coefficient of thermal expansion was measured in an atmosphere of 1000°C. The smaller the value, the lower the coefficient of thermal expansion, which can be expected to reduce cracking during casting.
• the melting point was measured in accordance with JACT test method C-1 (melting point test method). That is, the RCS to be measured was quickly sprayed onto a metal rod with a temperature gradient, and after 60 seconds, a nozzle with a diameter of 1.0 mm moving along a guide rod was placed at a position 10 cm away from the metal rod. , the RCS on the metal bar is blown away by moving it back and forth once from the low temperature area to the high temperature area at an air pressure of 0.1 MPa. The melting point (°C) was determined by reading the temperature of the boundary line between the blown RCS and the unblown RCS up to 1°C.
• the cured products of the resin compositions of Examples had high mechanical strength and reduced amounts of tar and soot.

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