JPH078928B2 - Foaming resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a foaming resin composition used in a full molding method or the like.

(Prior Art) The use of a synthetic resin foam in a casting model is known in the full molding process. Regarding the use of the synthetic resinous material for casting, examples are found in the lost wax method in the old days and the full mold method in the new ones.

The lost wax method is a method in which a prototype is made of wax, the surface is covered with a refractory, and then the wax is eluted and removed to form a mold. It is unsuitable as a method, and its application is limited to relatively small castings.

On the other hand, the full mold method is to make a model from a plastic foam made of polystyrene, polyacrylic acid, polymethacrylic acid, polyacrylamide, etc., bury it in sand, inject the molten metal as it is, and melt it. This is a method in which the model of the plastic foam is burned and disappears by the heat of 1, and the molten metal enters the cavity to obtain a casting.
Therefore, the full mold method is a casting method in which the steps from model production to mold work are remarkably simplified.

In the full-mold method, the conventional plastic foam model has a large amount of soot (carbon-like substance) when it burns.
In addition, it is pointed out that gas is generated, the casting surface is polluted, and pinholes are formed inside the casting.

As a vanishing model with these defects improved, Japanese Examined Patent Publication No. 40-
It has been proposed that Ammonium perhydrochloride described in JP-B No. 24164 be contained in a model for vanishing, and that one containing a catalyst for depolymerization described in JP-B-41-16925.

However, when these methods are examined in detail, there is a drawback that the work of making a model is surprisingly difficult and the effect is relatively small.

For this reason, various proposals have been made for plastic foams, particularly in terms of polymers.

In particular, the following foams containing methacrylic acid ester as a main component have been proposed.

JP-B-49-23458 describes a foam containing isobutyl methacrylate, which has good thermal decomposability, as a main component, and methyl methacrylate as a copolymerization component.

Furthermore, foams containing methyl methacrylate as a main component have also been proposed. However, when the polymer of methyl methacrylate was used, the foaming agent could not be sufficiently impregnated, and the expandable particles obtained had a low expansion ratio.

Therefore, for the purpose of improving the foaming characteristics, Japanese Patent Publication No.
Japanese Patent Laid-Open Publication No. 7-74 proposes a method of copolymerizing methyl methacrylate and styrene. In addition, Japanese Patent Publication No. 40-40160 describes a method of adding α-methylstyrene during the polymerization of methyl methacrylate and copolymerizing it for the purpose of improving foaming characteristics. Further, JP-A-60-184447 describes the use of a foam of a copolymer of methyl methacrylate and α-methylstyrene as a fugitive prototype.

(Problems to be solved by the invention) However, the glass transition temperature of the foam containing isobutyl methacrylate as a main component and methyl methacrylate as a copolymerization component is extremely lower than that of polystyrene foam,
The use of primary foaming and molding equipment for polystyrene foam has the drawback of increasing the degree of shrinkage of the primary foamed particles and the molded product.

In addition, a foam containing methyl methacrylate as a main component and styrene or α-methylstyrene as a copolymerization component uses aromatic hydrocarbons, so that soot is also generated and the casting surface is contaminated. I got it.

The present invention solves these problems, and provides a resin composition for foaming, which does not impair foamability and moldability, has little black smoke and soot during combustion, and can be easily polymerized. To do.

(Means for Solving Problems) The present invention provides a compound represented by the general formula (I). (However, R ₁ is hydrogen or a methyl group, R ₂ is a divalent organic group, R ₃ is an alicyclic hydrocarbon group having 6 to 20 carbon atoms, and n is 0 or 1.) The present invention relates to a foaming resin composition containing a polymerizable monomer represented by and a copolymer containing methyl methacrylate as an essential component.

First, the polymerizable monomer represented by formula (I) will be described.

R ₁ in the general formula (I) is hydrogen or methyl, but a methyl group is preferable because it shows good foaming characteristics.

R ₂ in the general formula (I) is a divalent organic group, but an alkylene group having 1 to 12 carbon atoms, an oxaalkylene group having 1 to 12 carbon atoms and the like are preferable. Here, the oxaalkylene group, a divalent organic group having an oxygen atom attached thereto during each of two or more alkylene _{groups, -R 4 -O-R 5 -} , - R 6 -O-
_{R 7 -O-R 8 -,} - R 9 -O-R 10 -O-R 11 -O-R 12 -
(However, R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ and R ₁₂ are alkylene groups) and the like. The R _{2, specifically, -CH 2 -, - C 2} H 4 -, - C 3 H 6 -, - C
_{4 H 8 -, - C 5} H 10 -, - C 2 H 4 -O-C 2 H 4 -, - C 3 H 6 -O-
_{C 3 H 6 -, - C} 2 H 4 -O-C 2 H 4 -, - C 3 H 6 -O-C 3 H 6 -, -
Such _{C 2 H 4 -O-C 2} H 4 -O-C 2 H 4 and the like.

Although n in the general formula (I) is 0 or 1, it is preferable that n is 0 in view of better foaming characteristics, ease of production of the monomer represented by the general formula (I), and economical efficiency. .

R ₃ in the general formula (I) is an alicyclic hydrocarbon group having 6 to 20 carbon atoms. If the carbon number is less than 6, the foamability will be reduced.
If the carbon number exceeds 20, the mechanical strength of the polymer will decrease.

The monomer represented by the general formula (I) is produced by a known method. For example, when n is 0 in the general formula (I), the structural formula is represented by R ₃ OH (where R ₃ is the same as R ₃ in the general formula (I)). Obtained by condensation reaction of all with acrylic acid, methacrylic acid, acrylic acid chloride, methacrylic acid chloride, etc. in the presence of acid or alkali catalyst, and transesterification reaction with methyl acrylate, methyl methacrylate, etc. You can Further, compounds wherein n is 1 in the general formula (I), the above alicyclic hydrocarbon monools and HO-R ₂ -OH
(Wherein, R ₂ is Formula (same as is as R ₂ in I)) a diol component represented by, for example, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, p-toluenesulfonic acid, such as silicotungstic acid condensed in the presence of an acid catalyst, HO-R ₂ -O
-R ₃ (provided that, R ₂ and R ₃ is R ₂ and R ₃ in the general formula (I)
The same) and the same condensation reaction or transesterification reaction as described above.

Examples of the alicyclic hydrocarbon monool represented by the structural formula R ₃ OH include cyclohexanol, 2,2,5-trimethylcyclohexanol, cycloheptanol, cyclooctanol, cyclodecanol, cyclododecanol, isoborneol and borneol. , Π-borneol, ω-borneol, 1-adamantanol, 2-adamantanol, 3
-Methyl-1-adamantanol, 3,5-dimethyl-1-
Adamantanol, 3-ethyladamantanol, 3-methyl-5-ethyl-1-adamantanol, 3,5,8-triethyl-1-adamantanol, 3,5-dimethyl-8-ethyl-1-adamantanol, Fuente alcohol, 2-
Methylcamphanol, l-menthol, 8-hydroxy-
Tricyclo [5.2.1.0 ^2,6 ] decane, 9-hydroxy-tricyclo [5.2.1.0 ^2,6 ] decane, 3,7,7-trimethyl-4-
Examples thereof include hydroxy-bicyclo [4.1.0] heptane and 3-hydroxy-2,6,6-trimethyl-bicyclo [3.1.1] heptane. Therefore, examples of the monomer represented by the general formula [I] include those having structures corresponding to these.

Among the monomers represented by the general formula (I), cyclohexyl methacrylate, cyclododecyl methacrylate, tricyclo acrylate [5.
2.1.0 ^2,6 ] deca-8yl, tricyclo acrylate [5.2.
1.0 ^2,6 ] deca-9yl, tricyclomethacrylate [5.2.
1.0 ^2,6 ] deca-8yl, tricyclomethacrylate [5.2.
10 _2,6 ] Deca-9yl, bornyl methacrylate, isobornyl methacrylate, norbornyl methacrylate, norbornane methyl methacrylate, l-menthyl methacrylate, adamantyl methacrylate, dimethyladamantyl methacrylate and the like are preferably used.

It is preferable that the monomer represented by the general formula (I) contains one kind or two or more kinds as a component in the copolymer in an amount of 3 to 90% by weight. If the amount of the monomer represented by the general formula (I) is too small, the expansion ratio tends to decrease, and if it is too large, the bending strength of the foamed molded product tends to decrease.

The copolymer also contains methyl methacrylate as an essential component. Methyl methacrylate is preferably contained in the copolymer in an amount of 10 to 97% by weight. If the amount of methyl methacrylate is too small, the foamability tends to be poor, and if it is too large, the mechanical strength of the copolymer tends to decrease.

The copolymer may contain a monomer represented by the general formula (I) and a polymerizable monomer other than methyl methacrylate as a component. Other polymerizable monomers are styrene,
Styrene-based monomers such as vinyltoluene, isopropylstyrene, α-methylstyrene, nucleus-substituted methylstyrene, chlorostyrene, and tert-butylstyrene, butyl acrylate, ethyl acrylate, acrylic acid esters such as methyl acrylate, and methacrylic acid. Methacrylic acid esters such as butyl, ethyl methacrylate, 2-ethylhexyl methacrylate, acrylonitrile, methacrylonitrile, vinyl acetate, α-methylethylene, monofunctional polymerizable monomers such as diethylmalate, divinylbenzene, ethylene glycol Examples thereof include polyfunctional monomers such as dimethacrylate and trimethylolpropane trimethacrylate. When another polymerizable monomer is used, the monofunctional polymerizable monomer is preferably contained in the copolymer in an amount of 10% by weight or less as a component, and the polyfunctional polymerizable monomer is used as a copolymer. It is preferable that the polymer is contained in an amount of 5% by weight or less as a component. When the amount of other polymerizable monomer is large, the foaming property is likely to be deteriorated.

The copolymer can be obtained by any method such as solution polymerization, emulsion polymerization and suspension polymerization.

Examples of the polymerization initiator used in the polymerization of the copolymer include monofunctional organic peroxides such as benzoyl peroxide, lauroyl peroxide, tert-butyl benzoate, and tert-butyl perpivalate, 1,1 -Di-t-butylperoxy 3,3,5-trimethylcyclohexane, di-t-butylperoxyhexahydroterephthalate, di-t-butylperoxy-trimethyladipate, di-t-butylperoxyisophthalate, etc. Organic peroxides such as bifunctional organic peroxides,
Azo compounds such as azobisisobutyronitrile and azobisdimethylpareronitrile are used.

The polymerization initiator may be added before the monomer is added to the polymerization vessel, after the monomer is added, or together with the monomer. The polymerization initiator is preferably used in an amount of 0.01 to 10% by weight based on the total amount of monomers.

In addition, n-dodecyl mercaptan, n-octyl mercaptan, n-butyl mercaptan, tert-butyl mercaptan and the like can be used to control the molecular weight of the copolymer. These are preferably used in an amount of 1 mol% or less based on the monomers.

The polymerization temperature is appropriately selected between 0 and 200 ° C.

As the suspending agent used when the polymerization is carried out by suspension polymerization, one widely used as a suspending agent can be used, and a water-soluble agent such as polyvinyl alcohol, methyl cellulose or polyacrylamide can be used. Polymers and poorly soluble inorganic substances such as calcium phosphate and magnesium pyrophosphate. The water-soluble polymer is preferably added in an amount of 0.03 to 1% by weight, and the sparingly soluble inorganic substance is preferably added in an amount of 0.05 to 0.5% by weight. Further, an anionic surfactant such as sodium dodecylbenzene sulfonate can be added as a suspending agent, which is preferably used together when a sparingly soluble inorganic substance is used as a suspending agent. The amount used is preferably 0.001 to 0.02% by weight based on the total amount of the monomers. Also, in suspension polymerization, in order to adjust the particle size of the obtained polymer, sodium sulfate,
An electrolyte such as sodium chloride or sodium acid sulfite can be added to the aqueous medium. The amount of the electrolyte used is preferably 0.0005 to 3% by weight based on the total amount of the monomers.

When the polymerization is carried out by solution polymerization, benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, dichloroethylene or the like can be used as the solvent.

In the present invention, a polymer other than the above copolymer is
It can also be used together with the above copolymer. Examples of the polymer other than the above copolymer include one or more polymers of the above other polymerizable monomers. When these other polymers are used in combination, it is preferably used in an amount of 10% by weight or less based on the copolymer.

As the foaming agent used in the present invention, a readily volatile organic compound which is a liquid or a gas under normal temperature and normal pressure and which does not dissolve the above-mentioned polymer can be used. As such,
Examples thereof include aliphatic hydrocarbons such as propane, butane, pentane, hexane and petroleum ether, cyclic hydrocarbons such as cyclohexane, and halogenated aliphatic hydrocarbons such as methylene chloride, trichlorotrifluoroethane and dichlorodifluoroethane. The amount of these foaming agents used is
It is preferably used in the range of 1 to 2 parts by weight with respect to 100 parts by weight.

In order to impregnate a polymer with a volatile organic compound, when suspension polymerization is adopted as a method for producing the polymer, the volatile organic compound is added to the polymerization system in the latter half of the polymerization,
It can be preferably carried out by press fitting. Here, the latter half of the polymerization means a point of time when the polymerization conversion rate is 50% by weight or more, preferably 70% by weight or more. Alternatively,
There is a method in which spherical or pellet-shaped particles of the polymer in the present invention are suspended in an aqueous medium and a volatile organic compound is added thereto. Impregnation in suspension is preferably carried out at 20 to 130 ° C. As another method, the polymer of the present invention and the easily volatile organic compound may be melt mixed.
In this case, an extruder is mainly used.

Further, as the foaming agent, a pyrolytic chemical foaming agent which generates gas such as N ₂ gas or CO ₂ gas by thermal decomposition may be used. Examples of such compounds include azodicarbonamide,
Azobisisobutyronitrile, diazoaminobenzene,
Examples include N, N'-dinitrolipentamethylenetetramine, benzenesulfonyl hydrazide, and trihydroradinotriazine. Such a blowing agent is 0.5 to 10 with respect to the polymer.
It is preferably contained by weight.

When the pyrolytic foaming agent is used, the polymer of the present invention and the foaming agent are melt-mixed at a temperature not higher than the decomposition temperature of the foaming agent. Also at this time, the extruder is mainly used.

A plasticizer may be present during impregnation of the polymer with the blowing agent. As the plasticizer, an organic solvent capable of dissolving or swelling the polymer can be used, and its boiling point is
Those having a temperature of about 10 ° C lower than the softening point of the polymer and 150 ° C or lower are preferable. Examples of the plasticizer include aromatic hydrocarbons such as ethylbenzene, toluene, styrene, benzene and xylene, and halogenated hydrocarbons such as 1,2-dichloropropane, trichloroethylene and perchloroethylene. The plasticizer is preferably used in an amount of 0 to 5% by weight based on the polymer.

Further, the foaming resin composition according to the present invention may contain known additives such as pigments, flame retardants, antioxidants, antistatic agents and the like.

The foaming of the resin composition for foaming according to the present invention is performed by a method such as heating or depressurizing. As the method, the method of foaming and molding a styrene resin, which is widely used industrially, can be applied as it is. For example, when the resin is particles, after pre-expanding with steam, steam can be further expanded in a molding machine to obtain a molded product. It is also possible to obtain a foam using an extrusion foaming machine.

The foaming ratio of the resin composition for foaming according to the present invention can be arbitrarily selected from a low ratio to a high ratio.

In addition to the full-molding method, the foam obtained from the foaming resin composition according to the present invention can be used in addition to the full-molding method, solar-related heat insulating materials, hot water tank heat insulating materials, metal tile underlayment materials, heat insulating materials for food containers, vehicles. Heat insulating material for ships, heat insulation material for hot water pipes,
Examples include air conditioner wind tunnels, sizing boards, structural materials for automobiles, and metal co-molded panels.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples. In the following, "part" and "%" are based on weight.

Examples 1 to 11 and Comparative Examples 1 to 3 In a mixed solution of monomers in the amounts shown in Table 1, lauroyl peroxide as a polymerization initiator 5 g and 1,1-di-t-butylperoxy 3,3, 5-trimethylcyclohexane 0.5 g
In addition, the amount of n-octyl mercaptan shown in Table 1 was dissolved as a molecular weight modifier. This solution was added to 1500 g of water in a 3 l autoclave with stirring at 270 rpm to an aqueous solution in which 2 g of tricalcium phosphate, 6 g of 0.5% sodium dodecylbenzenesulfonate solution and 0.75 g of sodium sulfate were dispersed or dissolved. Then, the atmosphere in the autoclave was replaced with N ₂ . Then, the temperature was raised to 70 ° C., and when the temperature was stirred for 5 hours at that temperature, the amounts of pentane and toluene shown in Table 1 were added. Then, the temperature was raised to 100 ° C., and the mixture was stirred at the same temperature for 4 hours. Then, it was cooled, the polymer particles for foaming were taken out, washed with hydrochloric acid, washed with water, dehydrated and dried.

The average particle size and the total amount of volatile components of the obtained polymer particles for foaming were measured and shown in Table 1. In the present invention, the average particle size is obtained by sieving particles obtained by polymerization into each particle size, and sieving each particle sequentially from particles having a small particle size to prepare a curve plotting the cumulative weight against the particle size. , Shows the particle size with a cumulative weight of 50%. The total volatile content was 2 g of the sample in an aluminum dish.
Measure the weight by heating at 00 ℃ for 10 minutes, [(weight of sample before heating)-(weight of sample after heating)] / (height of sample)
It was expressed as × 100.

The expandable polymer particles were immersed in boiling water at 100 ° C. for the heating time shown in Table 1 to produce pre-expanded particles. The specific volume of the pre-expanded particles was measured and is shown in Table 1. The specific volume was determined by packing the pre-expanded particles in a graduated cylinder having a volume of 1000 ml, measuring the weight, and calculating the volume / weight.

Further, the pre-expanded particles were aged in the air at 25 ° C for 24 hours, put in a molding die, and 1.
A foamed molded product was obtained by heating with steam of 0 kg / cm ² · G (120 ° C.) for the time shown in Table 1. The specific volume of this foamed molded product was measured and is shown in Table 1.

With respect to the obtained foamed molded product, the presence or absence of shrinkage and the surface smoothness were visually evaluated, and then ignition was performed to evaluate the generation of black smoke and soot. The evaluation results are shown in Table 1.

(Effect of the Invention) The foaming resin composition according to the present invention has no shrinkage of the foam obtained thereby, and has good surface smoothness,
Moreover, black smoke and soot are not generated during combustion.

Claims (1)

[Claims] 1. A general formula (I) (However, R ₁ is hydrogen or a methyl group, R ₂ is a divalent organic group, R ₃ is an alicyclic hydrocarbon group having 6 to 20 carbon atoms, and n is 0 or 1.) A foaming resin composition comprising a polymerizable monomer represented by and a copolymer having methyl methacrylate as an essential component.