Method for manufacturing buck molded article

Abstract

Provided is a method for producing a bulk molded article having excellent fusion rate, surface properties, and smoke generation properties, the method comprising: a pre-foaming step in which foamable resin pellets are heated and foamed; a curing step for curing the foamed particles obtained in the pre-foaming step; and a molding step in which a mold is filled with the cured foamed particles containing a base resin and a foaming agent, and then steam is introduced into the mold multiple times from at least one surface of the mold to heat and weld the foamed particles, thereby obtaining a block-shaped molded article. The base resin contains 50 wt% or more of a (meth) acrylate unit as a constituent unit, and in the molding step, vacuum extraction is performed from at least one surface other than a steam introduction surface while at least one steam is introduced.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a block-shaped molded product, in particular to a method for manufacturing a block-shaped molded product for lost foam casting, and belongs to the field of molded product manufacturing, in particular to the field of lost foam casting. Background Art

[0002] When performing metal casting, the following lost foam casting is known: a mold made of a foamed molded body is buried in casting sand, molten metal is flowed into the foamed molded body to replace the foamed molded body with the metal, thereby casting a casting. The foamed molded body used for lost foam casting is usually a molded body obtained by cutting from a large block molded product. Such a block molded product has a problem of poor internal welding due to its large size.

[0003] As materials for forming block-shaped molded products, expandable polystyrene resin (EPS for short); expandable methyl methacrylate and styrene copolymer resin (STMMA for short); expandable polymethyl methacrylate resin (EPMMA for short) are generally used.

[0004] Among them, EPS has the advantages of low price and easy molding, and is widely used. Patent document 1 (CN101456234A) discloses a method for producing EPS block-shaped molded products, including the following steps: a. mold closing, mold locking, and feeding, b. vacuum filling and feeding, c. pre-vacuuming, d. multiple steam penetrations, with a total penetration time of 18 to 29 seconds, e. heating and pressure maintenance, f. decompression and cooling, g. mold unlocking, mold opening, demolding, ejection, and resetting. Among them, the density of the EPS block-shaped molded products produced by vacuum filling is good, and the pre-vacuuming before heating makes the block-shaped molded products mature evenly, and the surface and middle quality of the block-shaped products are consistent. On the other hand, EPS is not easy to thermally decompose, and it is easy to smoke when used for lost foam casting, resulting in residues on the casting.

[0005] In order to reduce the residue caused by EPS, Patent Document 2 (CN113680965A) discloses a method for preparing a lost mold molded product of a full mold casting of a mixture of STMMA beads and EPS beads, wherein the STMMA beads and EPS beads are pre-foamed at a weight ratio of 1:5-5:1, and then dried, matured, molded, and dried in sequence. Patent Document 3 (CN107552725A) discloses a method for preparing a lost mold mold of a large-size full mold casting block molded product of STMMA, wherein a larger-sized STMMA with a particle size between 0.7 mm and 0.90 mm is used as a pattern original bead. Summary of the invention

[0006] Problem that the invention aims to solve

[0007] However, the inventors have found that in the above-mentioned prior art, although the smoke and residue are reduced by reducing the amount of EPS or not using EPS, the STMMA block molded products or EPMMA block molded products manufactured according to the prior art methods have the problem of insufficient and uneven welding. In particular, this problem is more prominent when manufacturing large block molded products.

[0008] In view of the above circumstances, an object of the present invention is to provide a method for producing a block-shaped molded product having excellent welding rate, surface properties and smoke generation properties, in particular, a method for producing a block-shaped molded product for lost foam casting.

[0009] Solutions for solving problems

[0010] The inventors have conducted intensive studies to solve the above problems and have completed the present invention.

[0011] One embodiment of the present invention provides a method for manufacturing a block-shaped molded product, comprising:

[0012] A pre-foaming step, heating the foamable resin particles to make them foam;

[0013] A aging step, aging the foamed particles obtained in the pre-foaming step;

[0014] The molding step includes filling the mold with the matured foamed particles, and introducing steam into the mold from at least one side of the mold multiple times, so that the foamed particles are heated and fused to obtain a block-shaped molded product.

[0015] The expandable resin particles include a base resin and a foaming agent, wherein the base resin includes 50% by weight or more of a (meth)acrylate unit as a structural unit,

[0016] In the molding step, vacuum is drawn from at least one surface other than the steam introduction surface while steam is introduced at least once.

[0017] In a preferred embodiment of the present invention, in the above-mentioned manufacturing method, in the molding step, vacuuming is performed from at least one surface other than the steam introduction surface simultaneously with the first steam introduction.

[0018] In a preferred embodiment of the present invention, in the above-mentioned manufacturing method, in the molding step, vacuum is drawn from at least one pair of opposing surfaces of the mold.

[0019] In a preferred embodiment of the present invention, in the above manufacturing method, the vacuuming is performed simultaneously with a single steam introduction, or is continuously performed simultaneously with multiple consecutive steam introductions.

[0020] In a preferred embodiment of the present invention, in the above-mentioned production method, in the molding step, steam is introduced from at least one pair of opposing surfaces of the mold.

[0021] In a preferred embodiment of the present invention, in the above-mentioned manufacturing method, in the molding step, the last steam introduction is performed simultaneously from four or more surfaces of the mold.

[0022] In a preferred embodiment of the present invention, in the above-mentioned production method, in the molding step, the last steam introduction is performed simultaneously from all surfaces of the mold.

[0023] In a preferred embodiment of the present invention, in the above manufacturing method, in the molding step, the last steam introduction is not performed simultaneously with vacuuming.

[0024] In a preferred embodiment of the present invention, in the above production method, the base resin contains methyl methacrylate units and acrylate units in a total amount of 50% by weight or more.

[0025] In a preferred embodiment of the present invention, in the above production method, the acrylic acid ester unit is a butyl acrylate unit.

[0026] In a preferred embodiment of the present invention, in the above-mentioned manufacturing method, in the molding step, the vacuum degree in the mold is reduced to -0.03 MPa or less before the first steam introduction.

[0027] In a preferred embodiment of the present invention, in the above-mentioned manufacturing method, the density of the block-shaped molded product is 14 kg / m 3 Above and 30kg / m 3 the following.

[0028] In a preferred embodiment of the present invention, in the above-mentioned manufacturing method, the thinnest portion of the block-shaped molded product is 100 mm or more and 1200 mm or less.

[0029] In a preferred embodiment of the present invention, the above-mentioned manufacturing method further comprises:

[0030] The cooling step is to cool the block-shaped molded product obtained in the molding step.

[0031] In a preferred embodiment of the present invention, in the above-mentioned manufacturing method, the cooling step is a step of maintaining the vacuum for more than 400 seconds without applying water to the mold.

[0032] In a preferred embodiment of the present invention, in the above-mentioned manufacturing method, the block-shaped molded product is used for lost foam casting.

[0033] Effects of the Invention

[0034] According to the embodiment of the present invention, a block-shaped molded product for lost foam casting having excellent welding rate, surface properties and smoke generation can be obtained, and in particular, a large block-shaped molded product having high welding rate on both the surface and the center can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a perspective view showing a rectangular parallelepiped mold.

[0036] Description of Reference Numerals

[0037] 1Front

[0038] 2Right

[0039] 3 above

[0040] 4Thickness direction DETAILED DESCRIPTION

[0041] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0042] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0043] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0044] In this specification, the word "may" includes both performing a certain process and not performing a certain process.

[0045] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0046] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0047] In this specification, when "normal temperature" or "room temperature" is used, unless otherwise specified, the temperature may be 10-40°C.

[0048] The method for producing the block-shaped molded product of the present invention comprises:

[0049] A pre-foaming step, heating the foamable resin particles to make them foam;

[0050] A aging step, aging the foamed particles obtained in the pre-foaming step;

[0051] The molding step includes filling the mold with the matured foamed particles and introducing steam into the mold from at least one side of the mold multiple times, thereby heating and fusing the foamed particles to obtain a block-shaped molded product.

[0052] The expandable resin particles include a base resin and a foaming agent, wherein the base resin includes 50% by weight or more of a (meth)acrylate unit as a structural unit,

[0053] In the molding step, vacuum is drawn from at least one surface other than the steam introduction surface while steam is introduced at least once.

[0054] Foamable resin particles

[0055] First, the expandable resin particles used in the pre-foaming step in the method of the present invention are described. It should be noted that the "expandable resin particles" in the present invention refer to resin particles that have the ability to expand (i.e., expandability) and have not been expanded (or pre-foamed).

[0056] Base resin

[0057] The foamable resin particles used in the method of the present invention include a substrate resin and a foaming agent, wherein the substrate resin contains more than 50% by weight of (meth) acrylate units as structural units in terms of weight percentage relative to 100% by weight of the substrate resin. It should be noted that in this specification, "(meth) acrylate" refers to the general term for acrylates and methacrylates. If the content of (meth) acrylate units in 100% by weight of the substrate resin is less than 50% by weight, it is difficult to fully exert the effect of suppressing smoke. When there is a lot of smoke, defects occur on the surface of the casting due to the influence of carbon residues. From the viewpoint of further exerting the technical effect of the present invention, the content of (meth) acrylate units in 100% by weight of the substrate resin is preferably more than 60% by weight, more preferably more than 70% by weight, and more preferably more than 80% by weight. There is no particular limitation on the upper limit of this content, which can be 100% by weight, or for example 99% by weight, 98% by weight, or 95% by weight.

[0058] From the viewpoint of excellent foamability and moldability, it is preferred that the base resin contains methyl methacrylate units and acrylate units as structural units. It should be noted that in this specification, "methyl methacrylate units" refer to structural units derived from methyl methacrylate monomers, and "acrylate units" refer to structural units derived from acrylate monomers.

[0059] From the viewpoint of excellent foamability and moldability and surface properties, in the above-mentioned base resin, the ratio of the content of methyl methacrylate unit and acrylate unit relative to the total content of methyl methacrylate unit and acrylate unit (100 weight %) is preferably: (a) methyl methacrylate is 80 weight % or more and 99 weight % or less, and acrylate is 1 weight % or more and 20 weight % or less; (b) more preferably methyl methacrylate is 90 weight % or more and 98 weight % or less, and acrylate is 2 weight % or more and 10 weight % or less; (c) more preferably methyl methacrylate is 94 weight % or more and 98 weight % or less, and acrylate is 2 weight % or more and 6 weight % or less; (d) even more preferably methyl methacrylate is 94.5 weight % or more and 98.0 weight % or less, and acrylate is 2.0 weight % or more and 5.5 weight % or less.

[0060] Examples of the above-mentioned acrylic acid ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, etc., and butyl acrylate is particularly preferred because it has a large effect of lowering the glass transition temperature of the base resin. In other words, the acrylic acid ester unit is preferably a butyl acrylate unit derived from butyl acrylate. According to this configuration, foamable resin particles with better foamability and moldability can be obtained.

[0061] In addition, from the viewpoint of improving the foaming molding strength, the substrate resin can also contain the structural unit derived from the aromatic vinyl compound as a structural unit. As the aromatic vinyl compound, styrene, α-methylstyrene, p-methylstyrene, tert-butylstyrene and chlorostyrene etc. can be listed. From the viewpoint of suppressing the soot produced during casting, the amount of the aromatic vinyl compound is preferably as little as possible, preferably less than 50% by weight of the substrate resin, more preferably less than 20% by weight, and further preferably less than 5% by weight relative to 100% by weight of the substrate resin. From the viewpoint of obtaining excellent surface properties and suppressing soot at the same time, it is preferred that the substrate resin does not contain the structural unit derived from the aromatic vinyl compound.

[0062] In addition, the base resin may also contain a structural unit derived from a crosslinking agent. As a crosslinking agent, for example, a compound having two or more functional groups showing free radical reactivity can be cited. Among the compounds having two or more functional groups showing free radical reactivity, as a crosslinking agent, a difunctional monomer having two functional groups is preferably used. As a difunctional monomer, for example: (a) ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, etc., compounds formed by esterifying the two terminal hydroxyl groups of ethylene glycol or the oligomer of ethylene glycol with acrylic acid or methacrylic acid; (b) neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, butanediol di(meth)acrylate, etc., compounds formed by esterifying the hydroxyl groups of dihydric alcohols with acrylic acid or methacrylic acid; (c) aromatic compounds having two alkenyl groups such as divinylbenzene, etc. As the bifunctional monomer, hexanediol di(meth)acrylate such as 1,6-hexanediol diacrylate is preferred because the molecular weight of the base resin can be easily adjusted.

[0063] In the substrate resin, the content of the structural unit derived from the crosslinking agent can be less than 0.20% by weight of the substrate resin, preferably less than 0.15% by weight, and more preferably less than 0.10% by weight, based on 100% by weight of the substrate resin. In addition, the substrate resin may not contain structural units derived from the crosslinking agent. Through the above-mentioned constitution, there are the advantages of (a) excellent foamability of the foamable resin particles, (b) excellent surface quality of the foamed molded body formed by in-mold molding of the foamable particles, (c) excellent strength, and less residue during combustion.

[0064] Foaming agent

[0065] The foaming agent contained in the expandable resin particles used in the method of the present invention is not particularly limited. Examples of the foaming agent include (a) aliphatic hydrocarbons such as propane, isobutane, n-butane, isopentane, n-pentane, and neopentane, which are hydrocarbons having a carbon number of 3 or more and 5 or less, and (b) volatile foaming agents such as difluoroethane and tetrafluoroethane, which have an ozone depletion coefficient of 0, such as hydrofluorocarbons. These foaming agents may be used alone or in combination of two or more.

[0066] In the expandable resin particles used in the method of the present invention, the content of the blowing agent is preferably 5 to 12 parts by weight, more preferably 7 to 10 parts by weight, relative to 100 parts by weight of the base resin. This configuration has the advantage of providing expandable resin particles having sufficient expandability without requiring heavy polymerization equipment.

[0067] Foaming aid

[0068] The expandable resin particles used in the method of the present invention may also contain a foaming aid. The foaming aid is not particularly limited. As the foaming aid, a solvent having a boiling point of 200° C. or less at atmospheric pressure may be preferably used, such as aromatic hydrocarbons such as styrene, toluene, ethylbenzene or xylene; alicyclic hydrocarbons such as cyclohexane or methylcyclohexane; or acetates such as ethyl acetate or butyl acetate.

[0069] In the foamable resin particles used in the method of the present invention, the content of the foaming aid is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, relative to 100 parts by weight of the base resin. This configuration has the advantage of tending to obtain a foamed molded article with excellent appearance.

[0070] Other additives

[0071] The expandable resin particles used in the method of the present invention may optionally contain other additives in addition to the base resin and the foaming agent. Examples of the above-mentioned other additives include solvents, plasticizers, bubble regulators, flame retardants, flame retardant aids, thermal radiation inhibitors, pigments, dyes, and antistatic agents. There are no particular restrictions on the types and amounts of these additives, and they can be selected according to common sense within the scope of not damaging the technical effects of the present invention.

[0072] Weight average molecular weight

[0073] The molecular weight of the expandable resin particles used in the method of the present invention is not particularly limited, and can be selected according to common sense within the scope that does not impair the technical effect of the present invention. The weight average molecular weight measured by gel permeation chromatography (GPC) and converted to polystyrene can be, for example, 50,000 to 800,000, preferably 100,000 to 400,000, and more preferably 250,000 to 350,000. Through this structure, a foamed molded body with excellent surface quality and less residue during combustion can be obtained. It should be noted that when the weight average molecular weight is measured by gel permeation chromatography (GPC) for the expandable resin particles, the foaming agent contained in the expandable resin particles volatilizes in the GPC measurement, so what is actually measured is the weight average molecular weight of the base resin contained in the expandable resin particles. Therefore, the "molecular weight of the expandable resin particles" here can also be understood as the molecular weight of the base resin contained in the expandable resin particles, which is not affected by the foaming agent. It should be noted that the same is true when low molecular weight compounds other than the foaming agent are included. In other words, low molecular weight compounds other than the foaming agent do not affect the above-mentioned "molecular weight of the expandable resin particles" like the foaming agent.

[0074] Volume average particle size

[0075] The volume average particle size (hereinafter also referred to as the average particle size) of the foamable resin particles used in the method of the present invention is not particularly limited and can be selected according to common sense within the range that does not impair the technical effects of the present invention. For example, it can be 0.30 mm to 1.50 mm. When the volume average particle size of the foamable resin particles is less than 0.30 mm, there is a tendency that the foamable resin particles will lead to a decrease in foamability during foaming and / or an increase in the amount of adhesion during foaming. When the volume average particle size of the foamable resin particles is greater than 1.50 mm, for the foamable particles formed by foaming the foamable resin particles, when the foamable particles are filled into the molding machine, there is a tendency that the filling property into a narrow space becomes poor. It should be noted that the narrow space in the molding machine corresponds to a thinner portion in the obtained foamed molded body.

[0076] From the viewpoint of achieving both excellent welding rate and surface properties, the volume average particle size is preferably 0.40 mm to 1.20 mm, more preferably 0.50 mm to 1.10 mm, further preferably 0.60 mm to 1.00 mm, and particularly preferably 0.70 mm to 0.90 mm.

[0077] In this specification, the volume average particle size of the expandable resin particles refers to: the particle size of the expandable resin particles is measured on a volume basis using a particle size analyzer (such as an image processing type Millitrac JPA particle size analyzer), and the result is expressed as a cumulative distribution, and the volume accumulation becomes 50%.

[0078] Particle size range

[0079] The particle size range of the expandable resin particles used in the method of the present invention is not particularly limited, and can be selected according to common sense within the range that does not impair the technical effects of the present invention. In the manufacture of expandable resin particles, the particle size range is usually adjusted by sieving the expandable resin particles, and in this case, the retained particle size range (hereinafter also referred to as the retained range) is used as the particle size range of the expandable resin particles.

[0080] From the viewpoint of having both excellent welding rate and surface property, the particle size range of the foamable resin particles is preferably a range consisting of a lower limit selected from 0.10 mm, 0.20 mm, 0.30 mm, 0.40 mm and 0.50 mm and an upper limit selected from 2.00 mm, 1.80 mm, 1.70 mm, 1.60 mm, 1.50 mm and 1.40 mm. From the viewpoint of having both excellent welding rate and surface property, the difference between the upper limit and the lower limit is preferably 1.6 mm or less, more preferably 1.3 mm or less, and further preferably 1.0 mm or less.

[0081] As the expandable resin particles used in the method of the present invention, commercial products can be used, or they can be prepared for use. Commercial products of expandable resin particles include the KANEPEARL series manufactured by Kaneka Co., Ltd. and the STMMA manufactured by Zhejiang Keister New Materials Co., Ltd. The preparation method of the expandable resin particles is not particularly limited, and can be implemented according to common sense within the scope of not damaging the technical effects of the present invention.

[0082] Typically, the above-mentioned production method includes: a copolymerization step; a blowing agent impregnation step; a drying step; and a screening step. The operation and conditions of each step are not particularly limited and can be selected according to common sense within the range that does not impair the technical effects of the present invention.

[0083] As the copolymerization process, suspension polymerization in which polymerization is carried out in an aqueous suspension can be cited. The "aqueous suspension" in the present invention refers to a liquid in which resin particles and / or monomer droplets are dispersed in water or an aqueous solution by stirring or the like. A water-soluble surfactant and a monomer can be dissolved in the aqueous suspension. In addition, a water-insoluble dispersant, a polymerization initiator, a chain transfer agent, a cross-linking agent, a bubble regulator, a flame retardant, a solvent, a plasticizer, etc. can also be dispersed together with the monomer. As the dispersant, for example, poorly water-soluble inorganic salts such as tricalcium phosphate, magnesium pyrophosphate, calcium pyrophosphate, hydroxyapatite, kaolin, calcium carbonate, magnesium carbonate, and magnesium phosphate can be cited.

[0084] In the blowing agent impregnation step, the blowing agent is impregnated into the resin particles obtained in the copolymerization step to obtain expandable resin particles. In the blowing agent impregnation step, the treatment temperature (also referred to as the impregnation temperature) and the treatment time (also referred to as the impregnation time) when the blowing agent is impregnated into the copolymer are not particularly limited.

[0085] In the drying step, the expandable resin particles obtained in the above-mentioned blowing agent impregnation step are dried. The drying means is not particularly limited, and for example, a tank-type or cylindrical stirring dryer, a box-type or belt-type ventilation dryer, a fluidized bed dryer, etc. can be used. The drying step is preferably carried out at a temperature below the foaming temperature of the expandable resin particles, and is more preferably carried out at 30°C to 60°C from the viewpoint of productivity.

[0086] In the sieving step, the dried expandable resin particles are sieved to obtain expandable resin particles having a desired particle size range.

[0087] Method for producing block-shaped molded product

[0088] Pre-foaming process

[0089] In the pre-foaming step of the present invention, the expandable resin particles are heated to expand (i.e., pre-foamed). The apparatus, foaming conditions, and desired expansion ratio used in the foaming of the expandable resin particles are not particularly limited and can be appropriately set according to common sense within the scope of not impairing the technical effects of the present invention.

[0090] As a specific foaming method, there can be cited a method of sequentially performing the following (1) to (3): (1) adding foamable resin particles into a container equipped with a stirrer, (2) heating the foamable resin particles using a heat source such as steam, and then (3) foaming until a desired expansion ratio is reached to obtain foamed particles. When steam is used as a heat source, the pre-foaming temperature is typically 100° C. or higher, preferably 101° C. or higher, and the upper limit of the pre-foaming temperature depends on the physical limit of the steam temperature, and is typically 110° C. or lower.

[0091] From the viewpoint of saving raw materials and obtaining a block-shaped molded product with excellent strength and light weight, in the pre-foaming process, the expansion ratio of the foamable resin particles is preferably 20 times or more and less than 120 times in terms of volume ratio, more preferably 30 times to 100 times, further preferably 35 times to 80 times, and particularly preferably 40 times to 75 times. It should be noted that the expansion ratio of the foamable resin particles (hereinafter also referred to as the volume ratio) refers to: the multiple of the increase in the bulk volume of the foamable resin particles after foaming, that is, the ratio of the bulk volume of the foamable resin particles after foaming to the bulk volume before foaming.

[0092] From the viewpoint of achieving both excellent welding rate and surface properties, it is preferred to thoroughly foam the foamable resin particles in the pre-foaming process, that is, to foam the foamable resin particles to the maximum possible ratio, and no further foaming occurs in the subsequent processes. In this case, the foaming ratio of the foamable resin particles is the foaming ratio of the block-shaped molded product.

[0093] Aging process

[0094] In the aging process of the present invention, the foamed particles obtained in the aforementioned pre-foaming process are aged. The apparatus used, the aging conditions, etc. are not particularly limited and can be appropriately set according to common sense within the scope that does not impair the technical effects of the present invention. Typically, for example, the obtained foamed particles can be aged at room temperature for 8 hours to 200 hours. From the viewpoint of further achieving the effects of the present invention, the preferred aging time is 30 to 180 hours, and in particular, from the viewpoint of surface properties, the further preferred aging time is 40 to 160 hours, and particularly preferably 48 to 150 hours.

[0095] Molding process

[0096] In the molding process of the present invention, after the matured foamed beads are filled into the mold, steam is introduced into the mold from at least one side of the mold multiple times, so that the foamed beads are heated and fused to obtain a block-shaped molded product. In the present invention, in order to obtain a block-shaped molded product for lost foam casting with excellent fusion rate, surface properties and smoke generation, it is necessary to evacuate from at least one side other than the steam introduction side while introducing steam at least once.

[0097] In the molding process of the present invention, from the viewpoint of further achieving the effect of the present invention, it is preferred to preliminarily reduce the pressure in the mold before the first steam introduction, more preferably to set the vacuum degree in the mold to below -0.03 MPa, and even more preferably to set the vacuum degree in the mold to below -0.05 MPa.

[0098] It should be noted that in the present invention, the process of preliminarily reducing the pressure in the mold before steam introduction is different from vacuuming while steam introduction, and they cannot be replaced with each other. If the mold is only reduced in pressure in advance without vacuuming while steam introduction at least once, the foamed molded article having excellent welding rate, surface property and smoke generation property of the present invention cannot be obtained.

[0099] In the aforementioned "multiple steam introductions", there is no particular limitation on the steam blowing pressure used for each steam introduction, and normal conditions may be used, for example, 0.01 to 0.80 MPa, preferably 0.05 to 0.50 MPa. Here, "steam blowing pressure" refers to the pressure of the steam supplied to the mold. In the molding process of the present invention, the steam pressure in the mold can generally be in the range of 0.01 MPa to 0.1 MPa, preferably in the range of 0.02 MPa to 0.08 MPa. The steam pressure in the mold can generally be measured by a sensor provided in the mold. From the viewpoint of further improving the welding rate and surface properties of the molded body, it is preferred to set the maximum value that the steam pressure in the mold in the molding process can reach to less than 0.08 MPa.

[0100] The "multiple times" in the aforementioned "multiple steam introductions" means two or more times. From the viewpoint of effective and uniform heating to further achieve the effect of the present invention, "multiple times" is preferably three or more times. There is no particular upper limit to the number of times, but from the viewpoint of energy saving, it is preferably ten times or less, more preferably eight times or less, and even more preferably five times or less.

[0101] The following description will be made by taking the first steam introduction as an example. Unless otherwise specified, the conditions and preferred methods for the second and subsequent steam introductions may be the same as those for the first steam introduction.

[0102] In a preferred embodiment of the present invention, in the molding step, vacuum is drawn from at least one surface other than the steam introduction surface simultaneously with the first steam introduction.

[0103] The steam introduction surface for introducing steam and the surface other than the steam introduction surface for evacuation are not particularly limited as long as they are different surfaces. In the case where steam is not introduced to the surface opposite to the steam introduction surface, it is preferred to evacuate the surface opposite to the steam introduction surface from the viewpoint of effectively and uniformly heating and further achieving the effect of the present invention.

[0104] From the viewpoint of further achieving the effect of the present invention, when vacuuming is performed simultaneously with the first steam introduction, it is preferred that vacuuming is performed from at least one pair of opposing surfaces of the mold, and more preferably from two pairs of opposing surfaces of the mold. In addition, from the same viewpoint as above, steam is preferably introduced from at least one pair of opposing surfaces of the mold, and more preferably from two pairs of opposing surfaces of the mold, during the first steam introduction.

[0105] As a specific operation of vacuuming while introducing steam for the first time, steam can be introduced from any N faces of the mold (N is any integer less than 6), and vacuuming can be performed from at least any one of the remaining (6-N) faces. From the viewpoint of further achieving the effect of the present invention by effectively and uniformly heating, it is preferred that (1) steam is introduced from any pair of opposing faces of the mold, and vacuuming is performed from at least any one face other than the pair of opposing faces (preferably one or two pairs of opposing faces); (2) steam is introduced from any two pairs of opposing faces of the mold, and vacuuming is performed from at least any one face of the remaining two faces (preferably two faces).

[0106] In the following text, for the sake of convenience, Figure 1 , a three-dimensional view of a rectangular parallelepiped mold is shown in FIG. The pair of faces with the largest area of ​​the mold are defined as the front and back (located on the outside and inside of the drawing respectively), the two faces located on the upper and lower sides in the drawing are defined as the top and bottom of the mold respectively, and the remaining two faces are defined as the left and right faces (located on the left and right sides of the drawing respectively).

[0107] From the viewpoint of further realizing the effects of the present invention, it is more preferred that: (1) steam is introduced from the front and rear sides, and vacuum is simultaneously performed from the top, bottom, left and right sides, or the top and bottom sides, or the left and right sides; (2) steam is introduced from the top, bottom, left and right sides, or the top and bottom sides, or the left and right sides, and vacuum is simultaneously performed from the front and rear sides; (3) steam is introduced from the front, left or top, and vacuum is simultaneously performed from the back, right or bottom; (4) steam is introduced from the back, right or bottom, and vacuum is simultaneously performed from the front, left or top.

[0108] The second and subsequent steam introductions may be carried out under appropriate conditions selected from the conditions described above for the first steam introduction, without particular limitation.

[0109] In the molding process of the present invention, of course, vacuuming can also be performed at the same time as any one or more steam introductions other than the first steam introduction. In other words, in the molding process of the present invention, vacuuming can be performed only at the same time as the first steam introduction, or at the same time as the steam introduction other than the first steam introduction. Vacuuming can be performed continuously during multiple continuous steam introductions, or it can be performed multiple times during multiple intermittent steam introductions. It should be noted that when vacuuming is performed multiple times, each vacuuming can be performed from the same surface of the mold, or from different surfaces, without special restrictions.

[0110] Regarding the last steam introduction in the molding process of the present invention, from the viewpoint of further achieving the effect of the present invention, the last steam introduction is preferably carried out from four or more surfaces of the mold at the same time, and more preferably from all surfaces of the mold at the same time. The last steam introduction may or may not be carried out while vacuuming. From the viewpoint of further achieving the effect of the present invention, it is preferred that the last steam introduction is carried out from all surfaces of the mold at the same time without vacuuming.

[0111] In the molding step of the present invention, from the viewpoint of further achieving the effects of the present invention, it is preferred that steam is introduced at least once to each surface of the mold after all the multiple steam introductions have been performed.

[0112] Cooling process

[0113] The manufacturing method of the present invention may further include a cooling step, wherein the block-shaped molded product obtained in the aforementioned molding step is cooled. There are no particular restrictions on the cooling operation and conditions, and they can be appropriately set according to common sense within the scope of not damaging the technical effects of the present invention. From the viewpoint of further achieving the effects of the present invention, the vacuum can be maintained for a certain period of time without applying water to the mold, so that the block-shaped molded product is cooled.

[0114] The time for maintaining the vacuum in the cooling process is not particularly limited as long as it is long enough to cool the block-shaped molded product. From the viewpoint of further improving the surface property of the foamed molded product, the time for maintaining the vacuum is preferably more than 400 seconds, more preferably more than 450 seconds, and more preferably more than 500 seconds. From the viewpoint of economy, the time for maintaining the vacuum is preferably less than 3000 seconds, more preferably less than 1500 seconds, and more preferably less than 1000 seconds.

[0115] Block molding

[0116] By the method of the present invention, it is possible to prepare a foaming molding having excellent welding rate, surface property and fuming property. This foaming molding can typically be a block molding used to make a lost foam mold in lost foam casting. The lost foam casting is the following process: the block molding is cut as required to make a mold with a desired shape, and when metal casting is carried out, the mold made is buried in foundry sand, and molten metal is flowed therein to replace, thereby casting a casting. The surface quality of the lost foam obtained by the block molding prepared by the method of the present invention is excellent and the residue during combustion is few, so it can be suitably used in various metal castings.

[0117] When a large block-shaped molded product is prepared by the method of the present invention, the technical effect of the present invention is particularly prominent. Therefore, as the size of the block-shaped molded product, it is preferred that the thickness of the thinnest part of the block-shaped molded product is 100 to 1200 mm.

[0118] The block-shaped molded products of the present invention include molded products called plates or sheets, such as plates, sheets, slabs, plate-shaped molded products, plate-shaped molded products, sheet-shaped molded products, and sheet-shaped molded products are all included in the block-shaped molded products of the present invention. The shape of the block-shaped molded product is not particularly limited, and from the perspective of productivity, it is preferably a regular shape such as a rectangular parallelepiped. In the case where the block-shaped molded product is a rectangular parallelepiped, the minimum side length is the thickness of the aforementioned thinnest part, preferably 100 to 1200 mm. From the perspective of further obtaining a high welding rate, the thickness of the thinnest part is preferably 650 mm or less, and more preferably 600 mm or less. The side length other than the minimum side length of the rectangular parallelepiped is not particularly limited, and can be appropriately set according to the size of the mold to be manufactured, for example, it can be selected from 200 to 7000 mm.

[0119] The density of the block-shaped molded product is not particularly limited, but is preferably 14 to 30 kg / m 3 , more preferably 15 to 28 kg / m 3 .

[0120] In addition, it should be noted that in the manufacture of foamable resin particles, the composition of the substrate resin does not change. In addition, in the foamable particles manufactured using the foamable resin particles, the structure of the foamable resin particles changes, but the composition of the substrate resin contained in the foamable resin particles does not change. In addition, in the foamed molded body manufactured using the foamable resin particles manufactured using the foamable resin particles, the structure of the foamable particles changes, but the composition of the substrate resin contained in the foamable particles does not change. Therefore, the type of structural unit obtained by analyzing the foamable resin particles, the foamable particles, or the foamed molded body, the content of each structural unit, and the weight-average molecular weight can be respectively regarded as: the type of structural unit contained in the substrate resin as these raw materials, the content of each structural unit, and the weight-average molecular weight of the substrate resin.

[0121] Example

[0122] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0123] Each expandable resin particle used in Examples and Comparative Examples will be described.

[0124] Expandable resin particles A: Expandable MMA / BA polymer particles ("KANEPEARL AX-B" manufactured by Kaneka Co., Ltd., average particle size 0.8 mm, cutoff range 0.5 to 1.4 mm) were used as expandable resin particles in Examples 1-6, 11-16 and Comparative Example 1-2.

[0125] Expandable resin particles B: expandable MMA / BA polymer particles (produced in Production Example 1 described later, average particle size 0.8 mm, cutoff range 0.4-1.6 mm), which were used as expandable resin particles in Example 10.

[0126] Expandable resin particles C: expandable MMA / St polymer particles (produced in Production Example 2 described later, average particle size 0.8 mm, cutoff range 0.5 to 1.4 mm), which were used as expandable resin particles in Examples 7 and 8.

[0127] Expandable resin particles D: expandable MMA / MA polymer particles (produced in Production Example 3 described later, average particle size 0.6 mm, cutoff range 0.5 to 1.4 mm), which were used as expandable resin particles in Example 9.

[0128] Expandable resin particles E: Expandable polystyrene particles (produced in Production Example 4 described later, average particle size 0.8 mm, cutoff range 0.5 to 1.4 mm) used as expandable resin particles in Comparative Example 3.

[0129] Here, the above-mentioned MMA refers to methyl methacrylate, the above-mentioned BA refers to butyl acrylate, St refers to styrene, and MA refers to methyl acrylate.

[0130] [Manufacturing example]

[0131] Production Example 1 (Production of Expandable Resin Particles B)

[0132] 150 parts by weight of water, 0.15 parts by weight of tricalcium phosphate, 0.0075 parts by weight of sodium α-olefin sulfonate, 0.08 parts by weight of lauroyl peroxide, 0.1 parts by weight of 1,1-bis(tert-butylperoxy)cyclohexane, 0.1 parts by weight of 1,6-hexanediol diacrylate, and 0.265 parts by weight of n-dodecyl mercaptan were added to a 6L autoclave equipped with a stirrer. Then, 97.5 parts by weight of methyl methacrylate (MMA), 2.5 parts by weight of butyl acrylate (BA) (total monomer amount was 100 parts by weight), and 1 part by weight of toluene were added to the aqueous suspension in the autoclave, and the temperature of the aqueous suspension was raised to 80°C for polymerization. 0.12 parts by weight of tricalcium phosphate were added to the aqueous suspension by additional addition after 1 hour and 45 minutes from the time when the temperature of the aqueous suspension reached 80°C (polymerization initiation). The polymerization conversion rate at this time was 43%.

[0133] Then, 4 hours and 20 minutes after the initiation of polymerization, 1.5 parts by weight of cyclohexane and 9 parts by weight of butane rich in n-butane (n / iso=70 / 30) were added to the aqueous suspension, and then the temperature of the aqueous suspension was raised to 101° C. to perform polymerization and impregnation of the blowing agent for 10 hours. Then, the aqueous suspension was cooled, and the product obtained after cooling was washed, dehydrated and dried to obtain expandable resin particles.

[0134] The expandable resin particles obtained above are sieved to obtain expandable resin particles B.

[0135] Production Example 2 (Production of Expandable Resin Particles C)

[0136] Expandable resin particles C were obtained in the same manner as in Production Example 1 except that the monomer mixture used was changed to 70 parts by weight of methyl methacrylate and 30 parts by weight of styrene (St) and sieves of different mesh sizes were used.

[0137] Production Example 3 (Production of Expandable Resin Particles D)

[0138] The amount of tricalcium phosphate initially used was changed to 0.13 parts by weight, the amount of n-dodecyl mercaptan was changed to 0.24 parts by weight, the monomer mixture was changed to 94.5 parts by weight of methyl methacrylate and 5.5 parts by weight of methyl acrylate (MA), the amount of tricalcium phosphate added was changed to 0.12 parts by weight, the timing of its addition was changed to 30 minutes after the initiation of polymerization, and a sieve with a different mesh size was used. The same operation as in Preparation Example 1 was performed to obtain expandable resin particles D.

[0139] Production Example 4 (Production of Expandable Resin Particles E)

[0140] In a 6L autoclave equipped with a stirrer, 100 parts by weight of pure water, 0.15 parts by weight of tricalcium phosphate, 0.005 parts by weight of sodium dodecylbenzenesulfonate, 0.3 parts by weight of benzoyl peroxide as an initiator, 0.0815 parts by weight of 1,1-bis(tert-butylperoxy)cyclohexane, 0.3 parts by weight of palm oil as a plasticizer, and 0.06 parts by weight of polyethylene wax as a nucleating agent were added. Then, 100 parts by weight of styrene monomer and 0.8 parts by weight of toluene were added while stirring at 250 rpm, and then the temperature was raised to 98°C. Then, the temperature was maintained at 98°C for 4 hours to obtain polystyrene resin particles.

[0141] Next, 6.8 parts by weight of butane was injected into the autoclave, and the temperature was raised to 120° C. again. After being kept at 120° C. for 2 hours, the autoclave was cooled to room temperature and the polymerization slurry was taken out of the autoclave. The taken out polymerization slurry was washed and dehydrated to obtain expandable polystyrene resin particles.

[0142] The obtained expandable polystyrene resin particles were sieved to obtain expandable resin particles E.

[0143] [Example]

[0144] Example 1

[0145] The above-mentioned expandable resin particles A are used as expandable resin particles, and the following steps (1) to (11) are sequentially carried out to obtain a block-shaped molded product (ie, a foamed molded article).

[0146] (1) Expandable resin particles are placed in a pressure foaming machine (BHP manufactured by Daikai Industry Co., Ltd.).

[0147] (2) Steam was blown into the foaming machine at a steam blowing pressure of 0.10 to 0.16 MPa and a pressure in the foaming machine of 0.005 to 0.030 MPa to heat the foamable resin particles. The maximum temperature in the foaming machine was 105°C.

[0148] (3) The expandable resin particles are expanded to a volume ratio of 65 times by the above-mentioned (2).

[0149] (4) The obtained expanded beads were left to stand at room temperature (25° C.) for 72 hours to obtain expanded beads having a volume ratio of 65 times.

[0150] (5) Into a molding machine (PEONY-205DS manufactured by DAISEN) having a mold of 2000 mm in length, 1000 mm in width and 525 mm in thickness, expanded beads having a volume ratio of 65 times were filled.

[0151] (6) After filling, the mold was evacuated using a vacuum pump so that the vacuum degree in the mold before heating was -0.07 MPa.

[0152] (7) The heating inside the mold is carried out according to the steps shown in Table 1. In the heating step ①, if Figure 1 As shown, while steam heating is performed from the largest surface (front and back) of the rectangular parallelepiped, a vacuum pump is used to evacuate the other four surfaces (up, down, left and right) where steam is not introduced. The steam injection pressure at this time is set to 0.15-0.25 MPa.

[0153] (8) In the heating step ②, steam heating is performed on the four surfaces (upper, lower, left, and right) to which steam introduction is not performed in the heating step ①. At this time, the two surfaces (front and back) not subjected to steam heating are not evacuated.

[0154] (9) In the heating step ③, steam heating is applied to the entire surface of the mold. Heating is applied until the pressure in the final mold reaches 0.030 to 0.060 MPa, so that the foamed particles are fused to each other. At this time, the foaming pressure (maximum surface pressure) measured by the sensor arranged in contact with the surface of the molded body in the mold becomes 0.070 to 0.080 MPa. The maximum surface pressure refers to the foaming pressure at the surface of the molded body when the last heating of the mold is completed, which is recorded in Table 1.

[0155] (10) After the foaming pressure reaches 0.070 to 0.080 MPa, the mold is evacuated for 1000 seconds using a vacuum pump to cool the mold. Then, the foamed molded product is removed from the mold.

[0156] (11) The foamed molded body was placed at 60°C for 3 days to obtain a foamed molded body as a block molded product. The obtained block molded product was 2000 mm long, 1000 mm wide and 525 mm thick, and the molded body density was 18.5 kg / m 3 .

[0157] Examples 2 to 16, Comparative Examples 1 to 3

[0158] The same operation as in Example 1 was performed except that the foamable resin particles and various manufacturing conditions were changed as described in Table 1 to obtain a foamed molded body. It should be noted that in Examples 7 and 13, the volume ratio of the foamed particles obtained by pre-foaming was set to 50 times, and the density of the obtained molded body was 24 kg / m 3 In Example 14, the dimensions of the block-shaped molded product were 2000 mm in length, 1000 mm in width, and 500 mm in thickness. In Example 15, the dimensions of the block-shaped molded product were 4750 mm in length, 1860 mm in width, and 660 mm in thickness.

[0159] The block-shaped molded products obtained in the above-mentioned examples and comparative examples were subjected to the following performance evaluations, and the results are collectively shown in Table 1.

[0160] [evaluate]

[0161] <Evaluation of block-shaped products>

[0162] Method for measuring the welding rate (front, center, back)

[0163] Using the obtained foamed molded body, the following (1) to (3) are carried out in sequence to measure the ratio (D) of the fractured surfaces of the "front", "center" and "back" of the foamed molded body. (1) The foamed molded body is divided into five equal parts along the thickness direction (i.e., the direction of the smallest side length), and the foamed molded body is cut perpendicularly to the thickness direction of the foamed molded body using a hot wire slicer. (2) Among the five parts obtained by the five equal parts, the two parts originally located at the two ends of the foamed molded body are respectively recorded as "front" and "back", and the part originally located in the middle of the foamed molded body is recorded as "center". For each of the "front", "center" and "back" parts, the surface perpendicular to the thickness direction is bent in the width direction at the center of the length direction to break the part. (3) Visually observe the fractured surfaces of each obtained part, count all the particles constituting the fractured surface and the foamed particles broken outside the particle interface, and calculate the ratio (D) according to the following formula.

[0164] Ratio (D) (%) = (the number of particles fractured at locations other than the particle interface in the fracture surface / the number of particles constituting the fracture surface) × 100.

[0165] The numerical values ​​of the ratio (D) calculated for each of the "front", "center" and "rear" parts are shown as the fusion ratio in Table 1. The numerical values ​​of the fusion ratio described in Table 1 are rounded to the nearest unit.

[0166] Surface evaluation method (○, △, ×)

[0167] The surface state of the foam molded article was visually observed, and the surface properties of the foam molded article were evaluated based on the following criteria based on the observation results.

[0168] ◎ (Excellent): There are almost no gaps between particles on the surface, that is, the surface is very beautiful.

[0169] ○ (Good): There are few gaps between particles on the surface, that is, the surface is beautiful.

[0170] × (poor): There are many gaps between particles on the surface, that is, the surface appearance is poor.

[0171] Evaluation method of smoke generation

[0172] The obtained block-shaped body was dried, cut into 100×100×25 mm pieces, and ignited with an open flame in a ventilated room. The smoke during combustion was visually observed to confirm the generation of black smoke.

[0173] ○ (Excellent smoke resistance): Almost no black smoke.

[0174] △ (good smoke resistance): produces less black smoke than ×.

[0175] × (poor smoke resistance): A large amount of black smoke was generated.

[0176] Table 1

[0177]

[0178] As can be seen from the above examples, according to the manufacturing method of the present invention, a block-shaped molded product having excellent welding rate, surface properties and smoke generation properties can be obtained, which is suitable for lost foam casting.

[0179] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0180] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for producing a block-shaped molded product, characterized in that: include: A pre-foaming step, heating the foamable resin particles to make them foam; A aging step, aging the foamed particles obtained in the pre-foaming step; The molding step includes filling the mold with the matured foamed particles, and introducing steam into the mold from at least one side of the mold multiple times, so that the foamed particles are heated and fused to obtain a block-shaped molded product. The expandable resin particles include a base resin and a foaming agent, wherein the base resin includes 50% by weight or more of a (meth)acrylate unit as a structural unit, In the molding step, vacuum is drawn from at least one surface other than the steam introduction surface while steam is introduced at least once.

2. The manufacturing method according to claim 1, characterized in that: In the molding step, vacuum is drawn from at least one surface other than the steam introduction surface simultaneously with the first steam introduction.

3. The manufacturing method according to claim 1 or 2, characterized in that: In the molding step, vacuum is drawn from at least one pair of opposing surfaces of the mold.

4. The production method according to any one of claims 1 to 3, characterized in that The vacuuming is performed while introducing steam once, or is continuously performed while introducing steam multiple times in succession.

5. The manufacturing method according to any one of claims 1 to 4, characterized in that: In the molding step, steam is introduced from at least a pair of opposing surfaces of the mold.

6. The manufacturing method according to any one of claims 1 to 5, characterized in that: In the molding step, the last steam introduction is performed simultaneously from four or more surfaces of the mold.

7. The production method according to any one of claims 1 to 5, characterized in that In the molding step, the last steam introduction is performed simultaneously from all surfaces of the mold.

8. The manufacturing method according to claim 7, characterized in that: In the molding process, the last steam introduction is not performed simultaneously with vacuuming.

9. The production method according to any one of claims 1 to 8, characterized in that: The base resin contains methyl methacrylate units and acrylate units in a total amount of 50% by weight or more.

10. The manufacturing method according to claim 9, characterized in that: The acrylate unit is a butyl acrylate unit.

11. The production method according to any one of claims 1 to 10, characterized in that: In the molding process, before the first steam introduction, the vacuum degree in the mold is reduced to below -0.03 MPa.

12. The manufacturing method according to any one of claims 1 to 11, characterized in that: The density of the block-shaped product is 14 kg / m 3 Above and 30kg / m 3 the following.

13. The manufacturing method according to any one of claims 1 to 12, characterized in that: The thinnest part of the block-shaped molded product is greater than 100 mm and less than 1200 mm.

14. The production method according to any one of claims 1 to 13, characterized in that: Also includes: The cooling step is to cool the block-shaped molded product obtained in the molding step.

15. The manufacturing method according to claim 14, characterized in that: The cooling process is a process of maintaining vacuum for more than 400 seconds without applying water to the mold.

16. The manufacturing method according to any one of claims 1 to 15, characterized in that: The block-shaped product is used for lost foam casting.

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