JPH05269783A - Production of reaction injection molded product - Google Patents

Abstract

PURPOSE:To enhance the molding efficiency of a molded product having a hollow part by arranging a foamed object molded from a solvent-soluble or hot-melt polymer in a mold as a core and supplying a reactive liquid raw material into the mold to mold a reaction injection molded product and taking out the molded product from the mold before removing the core by solvent treatment or heat treatment. CONSTITUTION:A foam core 1 molded from a solvent-soluble or hot-melt polymer is arranged in a mold wherein an aluminum foil 5 is bonded to the inner surface of a wood mold formed from a wood retaining mold 3. A reactive solution 2 prepared by mixing a plurality of reactive raw materials is introduced into the mold and cured to obtain a molded product having a hollow part. The core of the molded product taken out of the mold is dissolved by a solvent or melted by a heating means 1 to be removed. Therefore, the molding efficiency of the molded product is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded product having an undercut shape and a hollow portion. More specifically, the core of the foam that is molded integrally with the resin (hereinafter referred to as the matrix) during molding is removed from the molded product by heating or a solvent after molding, so that a molded product with an undercut shape or hollow part can be efficiently manufactured. The present invention relates to a method for producing a molded product by reaction molding.

[0002]

2. Description of the Related Art A method of producing a molded article by supplying a reactive liquid raw material into a mold in which a core is arranged and polymerizing in the mold by reaction molding is a generally known method. For example, Japanese Patent Application Laid-Open No. 1-247123 discloses a method of producing a hollow product by placing a silicone rubber core in a mold, performing reaction injection molding (RIM), and then pulling out the core. ing.

According to such an invention, it becomes possible to integrally manufacture a molded product having a complicated hollow portion with high productivity. However, such a manufacturing method has a problem that it cannot be used for a product having a shape in which the core cannot be pulled out.

Further, in Japanese Patent Laid-Open No. 3-266743, after the meltable material is introduced into a mold in which a core made of a heat-meltable or water-soluble material is supported and molded, heat or water is added. A method is disclosed in which a resin bumper beam is molded by introducing the resin into a core, melting or melting the core, and allowing the core to flow out from the molded product.

According to such an invention, there is no restriction on the shape of the core, and it becomes possible to manufacture a molded product having a hollow portion having a complicated shape. Therefore, the undercut shape can be freely adopted, the manufacturing process is simplified, and the production efficiency is increased. However, since the low-melting-point metal core as shown in the examples of the publication is heavy, it is difficult to operate, and the low-melting-point metal is melted to produce a core,
When the core is stored until it is used for molding or is taken out from the molded product, there is a problem that the treatment of the metal after melting becomes difficult. Even if a plastic core becomes large, its own weight will be considerably heavy and it will be difficult to operate, and even a small core can be dissolved in water,
There is a problem that it takes a very long time when melted by heating.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reaction liquid injection molding product in which a reactive liquid raw material is fed into a mold in which a core is arranged and polymerized in the mold, and an undercut shape or An object of the present invention is to provide a method for efficiently molding a molded product having a hollow portion.

[0007]

The object of the present invention is to provide a reactive liquid raw material in a mold in which a core is arranged and polymerize in the mold, which is easily soluble in a solvent. Alternatively, it can be achieved by using a foam molded from a heat-meltable polymer as a core, removing the molded product from the mold, and removing the core by solvent treatment or heat treatment.

The present invention will be described in detail below. (Reaction molding) In reaction molding, a liquid raw material composed of a monomer, a catalyst system, a curing agent, etc., is used alone as a reaction stock solution in a stable form, and the flow of a plurality of reaction stock solutions is mixed using mixers or collisions. This is a method of forming a molded product by mixing and causing a chemical reaction.

In reaction molding such as reaction injection molding (RIM), RTM, and casting, a low-viscosity reaction stock solution is reacted in a mold to produce various plastic molded products.
Along with technological advances in this field, the range of applicable resins such as norbornene-based polymers, epoxy resins, polyurethane resins, nylon resins, unsaturated polyester resins, polyurea resins, and phenol resins has been expanding.

(Reaction molding raw material) The molding raw material according to the present invention may be any raw material used for reaction molding, and is not particularly limited.

Specifically, norbornene type, epoxy type, urethane type, nylon type, unsaturated polyester type,
Examples include urea-based and phenol-based monomers or prepolymers, which include catalysts, cocatalysts, curing agents,
In addition to the required amounts of reaction accelerators, vulcanizing agents, reaction modifiers, etc., depending on the purpose, fillers such as titanium oxide, calcium carbonate, aluminum hydroxide, talc, carbon black, and coloring agents such as various pigments and dyes. , An antioxidant, an ultraviolet absorber, an antifogging agent, an antistatic agent, a flame retardant, and a modifier such as an adhesion improver such as a dicyclopentadiene-based petroleum resin or a hydrogenated product thereof.

For example, when a reaction stock solution containing a norbornene-based monomer and a metathesis catalyst system is supplied into a mold and bulk ring-opening polymerization is performed, a norbornene-based polymer molded product is obtained. Further, a reaction product solution containing a polyol and an isocyanate is reacted in a mold to obtain a polyurethane resin molded product. Similarly, a nylon RIM containing a polyesteramide prepolymer and caprolactam as a reaction stock solution, an epoxy RIM containing an epoxy compound and a curing agent such as polyamine or polyamide as a reaction stock solution, an unsaturated polyester,
Examples thereof include polyester RIM using a vinyl monomer and a catalyst as a reaction stock solution.

Among them, the molding of the norbornene-based polymer by the RIM method has a remarkably low injection pressure as compared with the usual thermoplastic resin injection molding, so that an inexpensive and lightweight mold can be used, and in the mold. Since the raw material (1) has good fluidity, it is preferable for producing an insert molded product, a large-sized molded product, and a molded product having a complicated shape. Therefore, norbornene type R
The IM will be described in more detail.

Norbornene-based Monomer The norbornene-based monomer used in the present invention may be any one having a norbornene ring, but when a polycyclic norbornene-based monomer having a tricyclic or higher ring is used, a polymer having a high heat distortion temperature can be obtained. The heat resistance required of the obtained composite molded article can be satisfied. Further, in the present invention, the ring-opening polymer to be produced can be a thermosetting type,
For that purpose, at least 10% by weight, preferably 30% by weight or more, of the total monomers may be used.

Specific examples of the norbornene-based monomer include bicyclic compounds such as norbornene and norbornadiene, tricyclic compounds such as dicyclopentadiene and dihydrodicyclopentadiene, tetracyclic compounds such as tetracyclododecene, tricyclopentadiene and the like. Pentacycles, heptacycles such as tetracyclopentadiene, alkyl substitution products thereof (eg methyl, ethyl, propyl, butyl substitution products, etc.),
Alkenyl substitution products (eg vinyl substitution products), alkylidene substitution products (eg ethylidene substitution products), aryl substitution products (eg phenyl, tolyl, naphthyl substitution products), ester groups, ether groups, cyano groups, halogens Substitutes having polar groups such as atoms are exemplified. These monomers may be used alone or in combination. Among them, tricyclic or pentacyclic compounds are favored from the viewpoint of availability, reactivity, heat resistance and the like.

The crosslinkable monomer has two reactive double bonds.
It is a polycyclic norbornene-based monomer having at least one, and specific examples thereof include dicyclopentadiene, tricyclopentadiene, and tetracyclopentadiene.
Therefore, when the norbornene-based monomer and the crosslinkable monomer are the same, it is not necessary to use any other crosslinkable monomer.

It should be noted that monocyclic cycloolefins such as cyclobutene, cyclopentene, cyclopentadiene, cyclooctene, and cyclododecene, which are capable of ring-opening polymerization with one or more of the above norbornene-based monomers, are used together within the range not impairing the object of the present invention. be able to.

The catalyst used metathesis catalyst system may be any metathesis catalyst system comprising a known metathesis catalyst and activator as catalyst for ring opening polymerization of norbornene monomers, specific examples include tungsten, molybdenum, tantalum Metathesis catalysts such as halides, oxyhalides, oxides, organic ammonium salts, etc., and specific examples of activators (cocatalysts) include alkylaluminum halides, alkoxyalkylaluminum halides, aryloxyalkylaluminums. Examples thereof include halides and organic tin compounds.

The metathesis catalyst is usually about 0.01 to 50 mmol, based on 1 mol of the norbornene-based monomer.
It is preferably used in the range of 0.1 to 20 mmol.
The activator is preferably used in the range of 1 to 10 (molar ratio) with respect to the catalyst component. Both the metathesis catalyst and the activator are preferably used by dissolving them in the monomer, but they may be used by suspending or dissolving them in a small amount of solvent as long as the properties of the product are not substantially impaired.

In a preferred method for producing a norbornene-based polymer, generally, a norbornene-based monomer is divided into two liquids and placed in another container, and a metathesis catalyst is added to one of the two liquids and an activator is added to the other of the two liquids. Prepare the reaction solution. The two kinds of reaction liquids are mixed and then poured into a mold or a mold having a predetermined shape (both are collectively referred to as a mold), where ring-opening polymerization is performed in bulk.

(Core) The core is formed of a foam molded from a polymer that is easily soluble in a solvent or heat-meltable. The expansion ratio of the core is 1.1 to 100 times, preferably 1.2 to
60 times, and more preferably 1.5 to 30 times as much foam is used. If the expansion ratio is low, the dissolving operation with a solvent takes time, and a large amount of solvent is required. If the expansion ratio is high, the core may not be able to withstand the resin pressure at the time of molding and may be deformed or damaged, or may float when the reaction solution is injected.

As the material, a thermoplastic polymer is usually used, but a polymer having no polymerization inhibitory property at the time of polymerization of the matrix raw material does not cause stickiness in the molded product and has less unreacted monomer odor, which is more preferable. .. Also,
It is not preferable to use a readily-soluble foam as a core in the reaction solution. In order to prevent polymerization inhibition of the reaction solution and to prevent the core from dissolving in the reaction solution, if necessary, use a polymer or reaction solution that does not inhibit polymerization at the interface between the matrix raw material and the core. A polymer that is difficult to dissolve can be applied by spraying or brushing, or a film can be wrapped around a core to reduce the polymerization inhibition at the interface and be molded. As the surface treatment agent for such cores, vinyl acetate-based,
Examples thereof include rubber-based, hydrocarbon-based, urethane-based, epoxy-based, phenol-based adhesives, paints, coating agents, films and the like.

Further, even a polymer having a crosslinked structure can be used as a core as long as it can be rapidly decomposed by a solvent. Further, the core may be molded by adding a filler so as to be easily dissolved in the solvent. Fillers used include carbon black, calcium carbonate,
Examples thereof include powders of alumina, kaolin, etc., but are not limited thereto. If the core is thick and work is possible, the core may be removed using a knife or hand as much as possible before the solvent or heat treatment.

Cores that are dissolved and removed with a solvent Cores that are dissolved and removed with a solvent have a heat distortion temperature of usually 30 ° C. or higher, more preferably 50 ° C. or higher, even more preferably 80 ° C. or higher. When the heat deformation temperature is low, the core is deformed by the mold temperature or the reaction heat during molding, and a molded product having a desired shape cannot be obtained. The higher the heat distortion temperature, the better if it is easily dissolved in a solvent.

Specific examples of the raw material for forming the solvent-soluble core include polyethylene, polypropylene, polyvinyl acetate, ethylene-vinyl acetate copolymer, polystyrene, a copolymer of maleic anhydride and styrene, and ABS resin. , Polyvinyl chloride, polynorbornene-based resin, polyvinyl pyrrolidone, polyvinyl formal, polyvinyl butyral, polyvinyl ether, cellulose acetate,
Resins such as polyacrylic acid, polyacrylic acid ester, polyethylene terephthalate, polybutylene terephthalate, polymethacrylic acid, polymethacrylic acid ester, polyurethane, polybutadiene, polyisoprene, polychloroprene, styrene-butadiene diene copolymer, styrene-butadiene- Examples thereof include styrene copolymers, styrene-isoprene-styrene copolymers, polynorbornene elastomers, polyurethane elastomers, and the like. Specific examples for forming the water-soluble core include polyvinyl alcohol, polyvinylpyrrolidone, and gelatin. However, the present invention is not limited to these.

From the viewpoints of polymerization inhibitory property, appropriate heat resistance, easy solubility in a solvent, easy availability, etc., polyethylene, polypropylene, polyvinyl acetate, ethylene-vinyl acetate copolymer, polystyrene, ABS. Resins and polyvinyl chloride cores are preferable, and polyethylene, ethylene-vinyl acetate copolymer, polystyrene and ABS resin cores are more preferable. . From the viewpoint of safety, it is preferable to use a core of a material that is soluble in water because it is easy to process after the core is dissolved and there is little risk of flammability and toxicity.

Cores to be removed by heating The cores to be removed by heating usually have a heat deformation temperature of 30.
C. to 150.degree. C., more preferably 40.degree. C. to 130.degree. C., and further preferably 50.degree. C. to 110.degree. If the heat distortion temperature is too low, the core deforms due to the mold temperature or the reaction heat during molding, and if the heat distortion temperature is too high, the heating temperature must be raised to near the glass transition temperature of the matrix, and the shrinkage of the molded product itself or Deformation such as warpage occurs, and it takes time to remove the core by melting it.

Specific examples of the core to be taken out by heating are polyethylene, polypropylene, polyvinyl acetate, ethylene-vinyl acetate copolymer, polystyrene, a copolymer of maleic anhydride and styrene, ABS resin, polyvinyl chloride, poly Norbornene-based resin, polyvinylpyrrolidone,
Resins such as polyvinyl ether, cellulose acetate, polyacrylic acid ester, polymethacrylic acid ester, polyethylene terephthalate, polybutylene terephthalate, polyurethane, polybutadiene, polyisoprene, polychloroprene, styrene-butadiene copolymer, styrene-butadiene-styrene Examples thereof include, but are not limited to, copolymers, styrene-isoprene-styrene copolymers, polynorbornene-based elastomers, and polyurethane-based elastomers.

The method of removing the core, which can be removed by dissolving in a solvent or by heating, is appropriately determined depending on the equipment and the shape and size of the core. In general,
In the method using a solvent, the operation until the core is taken out is fast and it can be taken out cleanly, but the processing liquid after removal is required, whereas the method by heating takes time until the core is heated. However, it is necessary to remove the core while it is molten, but on the other hand, there is an advantage that the removed core can be disposed of as it is.

From the viewpoint of polymerization inhibitory property, appropriate heat resistance and easy availability, polyethylene, polypropylene, polystyrene,
ABS resin and polyvinyl chloride core are preferred.

In the case of removing the core which can be removed by dissolving with a solvent or by heating, the above-mentioned 2
It is also possible to use various methods in combination. As such an embodiment, for example, most of the core is melted by heating,
A method of washing out the residue with a solvent or a method of washing a heated core (in an unmelted state) with a solvent to shorten the treatment time can be considered.

(Manufacturing Method of Core) As the core, one molded separately by foam molding is used. A volatile liquid or a decomposable liquid is added to the raw material for the foaming means of the foam. A gas such as air or nitrogen is blown into the raw material. The raw material is foamed by spraying. The raw material is foamed using the reactive gas. After dissolving in a soluble substance, the soluble substance may be removed. Combining technologies such as injection molding and extrusion molding with these foaming means,
Mold the foam.

For example, a method of rapidly filling a smaller amount of resin than the capacity of the cavity to cause foaming, or injecting and filling a high-pressure resin and then retracting the movable mold to expand the capacity of the cavity for foaming. and so on. The foam molded by the latter method gives a foam having a so-called skin layer in which foaming is hardly seen on the surface.

When a foam having such a skin layer is used as a core, the matrix resin does not soak into the foam, and the interface with the matrix can be formed smoothly even when there is inhibition of matrix polymerization. There is an advantage that the residual monomer odor can be reduced and the foam inside the foam expands due to the reaction heat at the time of polymerization and sticks the matrix to the mold surface so that sink marks do not occur in the molded product.

Other than that, a method of foam-molding using polystyrene foam beads and a method of foam-molding with a vinyl chloride paste can be mentioned, but the method is not limited to these.

(Core Support) If necessary, the core may be provided with a support made of a solvent or a synthetic resin which is not melted or melted by heat treatment, metal, wood or the like at a desired position of the core, It is possible to prevent the core from floating in the mold by the reaction solution, and to form a gap between the core and the inner surface of the mold to form a uniform resin layer as the outer peripheral layer. The shape of the support can be various shapes such as a cylindrical shape, a flat plate shape, a conical shape, and a truncated cone shape. To provide the support, there is an appropriate method such as fixing the support by adhering it to the surface of the core, or winding the support in a rubber band.

(Mold) As the mold, those made of various materials such as various synthetic resins, aluminum, low melting point alloy, wood and iron can be used, and may be a simple mold.

(Molding conditions) In reaction molding, a plurality of reaction raw materials are separately transferred to a mixer, and the raw materials are mixed by a mixing device such as a power mixer or a static mixer or by collision mixing to prepare a reaction liquid. This is a molding method in which the reaction liquid is introduced into a mold and cured to obtain a molded product.

The general molding method varies depending on the molding method, but in casting, the mixing pressure is 1 to 5 Kg / cm ² , RT
The mixing pressures in M is 5 to 50 kg / cm ^2, injection pressure in reaction injection molding collide mixed with 50~150Kg / cm ^2.
Depending on the type of material and properties such as viscosity, an appropriate molding method,
Molding conditions are selected.

Regarding the activity of the reaction solution, the amount of the catalyst system and the curing agent is appropriately changed and used depending on the size of the molded product and the filling rate of the raw materials. The time for one cycle is often adjusted to 5 minutes or less, but it may exceed 1 hour and is not particularly limited.

In the present invention, a collision mixing device conventionally known as a RIM molding device can be used for mixing two kinds of reaction stock solutions. In this case, the containers containing the two types of reaction stock solutions serve as separate flow sources. The two streams are mixed instantaneously with the mixing head of a RIM machine and then poured into a mold where they are immediately bulk polymerized to give a molding.

In addition to the impingement mixer, a low pressure injector such as a dynamic mixer or static mixer can be used. When the pot life at room temperature is as long as 1 hour, it may be injected or injected into the preheated mold several times after the mixing of the two reaction solutions in the mixer is completed. , May be continuously injected. In the case of this method, the device can be downsized as compared with the impingement mixing device, and in addition to having the advantage that it can be operated at low pressure, when the filling amount of the filler such as glass fiber is large, By slowing down the speed, it becomes possible to uniformly impregnate the reaction solution into the system.

Further, the present invention is not limited to the method using two kinds of reaction stock solutions. As will be readily appreciated by those skilled in the art, various modifications are possible, such as, for example, putting the monomer and the desired additive in the third container and using it as the third stream.

The reaction solution is usually stored and operated in an atmosphere of an inert gas such as nitrogen gas, but the molding die does not necessarily need to be sealed with an inert gas. The mold temperature is often set between 30 ° C. (room temperature) and 200 ° C. The mold temperature is determined by the balance between the effect of promoting the polymerization reaction and the ability to absorb heat generated during curing.

The case of bulk ring-opening polymerization of the norbornene-based monomer will be described in detail below. Bulk ring-opening polymerization of norbornene-based monomer The mold temperature is usually room temperature or higher, preferably 40 to 200.
C., particularly preferably 50 to 130.degree. The components used in the polymerization reaction are preferably stored and manipulated under an atmosphere of an inert gas such as nitrogen gas. The pressure in the mold is about 0.1 to 10 kg / cm ² , and the polymerization time is usually shorter than 20 minutes, preferably within 5 minutes.

The norbornene-based polymer may be blended with additives such as an antioxidant, a filler, a reinforcing material, a foaming agent, a pigment, a coloring agent and an elastomer. These additives are usually dissolved or dispersed in the reaction solution and blended, but in some cases, they may be placed in a mold.

As the elastomer to be added to the reaction solution,
For example, natural rubber, polybutadiene, polyisoprene,
Styrene-butadiene copolymer (SBR), styrene-
Butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), ethylene-propylene-diene terpolymer (EPD)
M), ethylene-vinyl acetate copolymer (EVA), and hydrides thereof. When these elastomers are added to the reaction solution, not only impact resistance is given to the obtained polymer, but also the viscosity of the reaction solution can be adjusted.

(How to remove core) When the heat deformation temperature of the core is sufficiently higher than the reaction heat at the time of polymerization of the matrix, the molded product taken out from the mold is in the same shape as when the mold is set. Remains in. When the heat distortion temperature of the core is low, it is partially or wholly melted by the heat of reaction during the polymerization of the matrix. Even such a core is removed from the molded product by the solvent or heating.

When a solvent is used, the core is dissolved with a solvent that readily dissolves the core, depending on the core used. The use of solvents that attack the matrix is not preferred. Since the part of the core fixed to the mold is exposed to the outside, the solvent is injected from this part to dissolve the core. When the support is attached, the core is exposed to the outside when the support is peeled off. Therefore, a solvent is injected from this portion to dissolve the core. The liquid in which the polymer is dissolved can be taken out from the portion where the solvent is injected.

At the time of molding, a foam having heat resistance that does not melt under the reaction heat is used, and when the molded product is formed into a shape in which the core is convex from the surface of the molded product, Even if they are stacked, a gap is created between the molded products, the molded products do not contact each other and rub against each other, and they are stacked or molded in a concave shape so that they can be transported or stored without scratching the surface. It can be stacked by stacking it on the part that has been marked. In this case, the work of removing the core may be performed on site immediately before use. This method is a very efficient method that saves the labor of packaging during transportation and prevents the generation of defective products.

The fact that the solvent core is easily soluble in the solvent means that the core is dissolved in the solvent in a short time at room temperature. The more easily soluble the core is, the easier it is to remove the core by dissolving it in the solvent.

Specific examples of the solvent include water, formic acid, acetic acid,
Acetic anhydride, alkali, pentane, hexane, heptane,
Hydrocarbon solvents such as isoheptane, isooctane, industrial gasoline, petroleum ether, petroleum benzine, cyclohexane, methylcyclohexane, benzene, xylene, solvent naphtha, decalin, creosote oil, turpentine oil, methylene chloride, chloroform, carbon tetrachloride, dichlorofluoro. Methane, ethyl chloride, 1,2-dichloroethane, 1,2-dibromoethane, tetrachloroethane,
Halogenated hydrocarbons such as dichloroethylene, trichloroethylene, perchloroethylene, dichloropropane, amyl chloride and monochlorobenzene, methanol, ethanol, isopropyl alcohol, n-butyl alcohol, t-butyl alcohol, fusel oil, benzyl alcohol, ethylene glycol, Alcohol solvents such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether, ether solvents such as ethyl ether, isopropyl ether, n-butyl ether, anisole, dioxane and tetrahydrofuran, methyl formate, ethyl formate, butyl formate, methyl acetate, ethyl acetate, Ester solvents such as isopropyl acetate, amyl acetate, ethyl propionate, methylal, acetal, acetone, methyl ethyl ketone Emissions, methyl isobutyl ketone,
Aldehyde and ketone solvents such as acetylacetone and cyclohexanone, nitromethane, nitroethane,
Nitrogen-containing compounds such as 1-nitropropane, 2-nitropropane, nitrobenzene, acetonitrile, diethylamine, triethylamine, ethylenediamine, pyridine, monoethanolamine and dimethylformamide, sulfur-containing compounds such as carbon disulfide, thiophene and dimethylsulfoxide, and the like. In addition to various organic solvents such as a mixture thereof, an inorganic acid such as hydrochloric acid and sulfuric acid, an alkali such as sodium hydroxide and potassium hydroxide, and a mixture thereof.

Although any of these solvents can be appropriately selected and used according to the material of the core to be used, workability and working environment, it is not preferable to use a solvent that easily dissolves the matrix resin. If the matrix resin is a crosslinkable polymer, there is no need to consider this point unless it swells significantly, but if the matrix resin is a thermoplastic polymer, it is necessary to pay attention to this point when selecting the solvent. is there.

When an organic solvent is used, the polymer dissolved in the solvent may be removed by a precipitating agent or a flocculating agent, and then the solvent may be recovered by distillation and reused.

Specifically, polymers such as polyvinyl alcohol, polyvinylpyrrolidone and gelatin are water and warm water; polyethylene, polypropylene, polystyrene, copolymers of maleic anhydride and styrene, ABS resins and the like are toluene and xylene. Hydrocarbon solvents such as decalin; methanol and acetone for polyvinyl ether; cyclohexanone, nitrobenzene, tetrahydrofuran, pyridine, butyl acetate for polyvinyl chloride,
Dichloroethane, methyl isobutyl ketone, etc .; acetone for cellulose acetate; acetone, ethyl acetate, dichloroethane, benzene for polyacrylic acid ester and polymethacrylic acid ester; sulfuric acid, formic acid, etc. for polyurethane; polybutadiene, polyisoprene, polychloroprene In the case of an elastomer such as a styrene-butadiene copolymer, a styrene-butadiene-styrene copolymer, a styrene-isoprene-styrene copolymer, or a polyurethane, toluene can be used.

These solvents may be appropriately selected depending on the type of core and matrix resin used. Further, the working time can be shortened by heating the solvent during use.

[0057] Method As a method of removing by melting the core by a heating means heating is allowed to stand in an oven or a thermostatic chamber at each molded article specified temperature, after which the core is entirely melted, remove the tang component There is a method of directly pressing the core with a metal rod or the like heated above the heat resistant temperature of the resin of the core to melt the core, or a method of melting only the resin of the core with high frequency or electromagnetic waves. It is not limited to this. When the heat deformation temperature of the core is sufficiently lower than the heat of polymerization reaction of the matrix, the core is melted at the time of demolding the molded product, so that the melted core can be removed as it is.

[0058]

[Effects] According to the present invention, in a method for producing a reaction injection molded product in which a reactive liquid raw material is supplied into a mold in which a core is arranged and polymerized in the mold, a molded product having an undercut shape or a hollow portion is formed. There is provided a method for efficiently molding.

[0059]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The parts in the examples are based on weight unless otherwise specified.

Example 1 A plate of polystyrene foam having a thickness of 2 cm and an expansion ratio of 2 was cut into 10 cm squares with a knife, and 2 cm was cut off from the two opposite corners to obtain a shape as shown in FIG. I made a core. The core was set in the center of the mold and a metal plate weight was placed on the top to prevent the core from floating. Formwork is inside size, width 2
It was made by sticking aluminum foil on the inner surface with a wooden mold of 0 cm, height 14 cm, and depth 6 cm.

The mold 3 having the core set therein was heated to 60 ° C. in an oven.

On the other hand, 100 parts of a mixed monomer prepared by mixing dicyclopentadiene (DCP) and methyltetracyclododecene (MTD) in a weight ratio of 9: 1 was added to a styrene-isoprene-styrene block copolymer (SIS) (quine). 6.5 parts of Tuck 3421, trade name of Zeon Corporation) were added and mixed. This solution was placed in two containers, one containing diethyl aluminum chloride (DE
AC) was added at a concentration of 41 mmol, n-propyl alcohol was added at a concentration of 41 mmol, and silicon tetrachloride was added at a concentration of 21 mmol (solution A).

On the other hand, tri (tridecyl) ammonium molybdate was added to the mixed monomer so as to have a concentration of 10 mmol, and a phenolic antioxidant (Etanox 702, manufactured by Ethyl Corporation) was added per 100 parts of the mixed monomer. ) 4 parts were added (solution B).

Both reaction liquids (mixing ratio of liquid A / liquid B 1/1)
Was rapidly injected into the above-mentioned mold using a gear pump and a power mixer at almost normal pressure to the lower surface of the weight. After the injection, a polymerization reaction was performed for about 3 minutes to obtain a molded product.
The core was melted by the heat of polymerization, and only a part of the foam remained. When toluene was poured into the polystyrene of the core, the polystyrene immediately dissolved and could be immediately poured from the molded product.
A hollow integrally molded product was obtained.

Comparative Example 1 A molded article was molded in the same manner as in Example 1 except that a polystyrene non-foamed sheet was used as the core. The non-foamed sheet was prepared by laminating two sheets having a thickness of 1 mm with a commercially available adhesive for plastics.

The core was partially melted at the interface with the matrix due to the heat of polymerization, but remained in its original shape. Toluene was poured into the core part to dissolve the core part. The core was dissolved in toluene, but it took 30 minutes or more to dissolve all the cores.

[Example 2] An experiment was conducted in the same manner as in Example 1 except that a polystyrene foam having a foaming ratio of 2 times was used and polyvinyl chloride having a foaming ratio of 1.5 was used. The core was not melted by the heat of reaction.

A metal rod heated to 120 ° C. was pressed against the core to melt and remove the core. About 5 to remove the core
It took a minute.

[Brief description of drawings]

FIG. 1 is a perspective view showing a partially broken surface when a core is set and a reaction solution is injected.

FIG. 2 is a cross-sectional view (cross section taken along the line aa ′ in FIG. 1) when a core is set and a reaction solution is injected.

FIG. 3 is a cross-sectional view (bb 'cross section in FIG. 1) when a core is set and a reaction solution is injected.

[Explanation of symbols]

 1 Foam core 2 Reaction liquid 3 Wooden form 4 Metal plate fun 5 Aluminum foil

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29C 45/44 7179-4F // B29K 105: 04 B29L 22:00 4F

Claims (3)

[Claims] 1. A method for producing a reaction injection-molded article in which a reactive liquid raw material is supplied into a mold in which a core is arranged to polymerize in the mold, and foamed by a polymer which is easily soluble in a solvent or a heat-meltable polymer. A method for producing a reaction injection-molded product, which comprises removing a molded product from a mold after using the body as a core and removing the core by solvent treatment or heat treatment. 2. The method according to claim 1, wherein the core is a foam having a skin layer. 3. The production method according to claim 1, wherein the solvent treatment or the heat treatment is carried out after the molded article is stored or transported.