JP4424637B2 - Expandable resin particles and foamed molded products - Google Patents

Description

【００３９】
【発明の効果】
本発明により、耐スチレン性に優れ、かつ金型成型を行うのに充分な発泡性及び成形性を有する成形品が得られる発泡性樹脂粒子及びこれを用いた発泡成形品が提供される。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an expandable resin particle and an expanded molded article. More specifically, expandable resin particles that have excellent resistance to styrene monomer (hereinafter referred to as styrene resistance) and have sufficient foamability and moldability to perform mold molding, and foam molding obtained by using the same. Related to goods.
[0002]
[Prior art]
Conventionally, as the foamable resin having excellent styrene resistance, polyvinyl chloride, polyurethane, cross-linked acrylic resin, and the like are known, and used in fields requiring high styrene resistance such as FRP core materials. Yes. However, polyvinyl chloride and polyurethane have environmental problems such as generation of hazardous substances such as chlorofluorocarbon and recyclability, and acrylic resin is a board-like material obtained by extrusion foaming, and therefore has the disadvantage of poor workability. is there.
[0003]
[Problems to be solved by the invention]
The present invention has been made to remedy such drawbacks, and has an expandable resin particle having excellent styrene resistance and sufficient foamability and moldability to perform mold molding, and foaming using the same. A molded article is provided.
[0004]
[Means for Solving the Problems]
The present invention relates to a foamable resin copolymerized by suspension polymerization in a proportion of 40 to 96% by weight of methacrylic acid ester, 3 to 20% by weight of methacrylic acid and 1 to 40% by weight of unsaturated nitrile, and containing a readily volatile foaming agent. Expandable resin particles having a dispersity (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) determined from a molecular weight in terms of polystyrene, which is 3.0 or more and 10.0 or less, using the particles The present invention relates to a foamed article to be obtained.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In general, suspension polymerization is carried out by dispersing a vinyl monomer in which an organic peroxide is dissolved as a polymerization initiator in an aqueous dispersion medium containing a dispersing agent. Suspension polymerization is carried out by mixing ~ 96 wt%, methacrylic acid 3-20 wt%, and unsaturated nitrile 1-40 wt%.
[0006]
Examples of the methacrylic acid ester in the present invention include methacrylic acid esters such as methyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, and 2-ethylhexyl methacrylate.
In the present invention, if the amount of methacrylic acid is less than 3% by weight, the effect of improving styrene resistance is low, and if it exceeds 20% by weight, dispersion during suspension polymerization tends to become unstable and the polymerization tends to be impossible. .
[0007]
The unsaturated nitrile in the present invention is a vinyl cyanide compound such as acrylonitrile or methacrylonitrile. In the present invention, the unsaturated nitrile is 1% by weight or more and 40% by weight or less, more preferably 3% by weight or more and 35% by weight or less. If the blending amount is less than 1% by weight, the foamability is not sufficient, and if it exceeds 40% by weight, the moldability tends to decrease. The amount of methacrylic acid ester used is in the range of 40 to 96% by weight because the amount of methacrylic acid and unsaturated nitrile used is within the above range for the above reasons.
[0008]
In the present invention, the degree of dispersion of the obtained copolymer is 3.0 or more and 10.0 or less, more preferably 3.0 or more and 8.0 or less. The degree of dispersion of 0.0 or less can be obtained by selecting the polymerization temperature, the kind and amount of the polymerization initiator, the composition of the monomer, the addition timing and the amount of use of the chain transfer agent. If the degree of dispersion is less than 3.0, the foamability is not sufficient, and if it is greater than 10.0, the strength of the molded product is lowered.
[0009]
As the polymerization initiator used in the present invention, a conventionally known organic peroxide having a decomposition temperature (10 hour half-life temperature) of 110 ° C. or less can be applied.
Such organic peroxides include octanoyl peroxide (62 ° C), lauroyl peroxide (62 ° C), stearoyl peroxide (62 ° C), benzoyl peroxide (74 ° C), t-butylperoxy-2ethylhexa Noate (72 ° C), bis (t-butylperoxy) trimethylcyclohexane (90 ° C), bis (t-butylperoxy) cyclohexane (91 ° C), t-butylperoxybenzoate (105 ° C), t-butyl Examples include peroxyisopropyl carbonate (97 ° C.).
[0010]
The amount of these organic peroxides used is arbitrarily determined depending on the targeted molecular weight, and is preferably used in the range of 0.3 to 2.0% by weight based on the total amount of monomers.
These organic peroxides may be used in combination of two or more in order to obtain copolymer particles having a higher polymerization rate.
[0011]
The polymerization temperature in the present invention is preferably from 50 to 110 ° C., more preferably from 60 to 95 ° C., from the polymerization rate.
The polymerization time is determined by the type and amount of the polymerization initiator, the composition of the monomer, the polymerization temperature, the timing of addition of the chain transfer agent, the amount used, and the like, and is usually 3 to 7 hours.
As the dispersant used in the suspension polymerization, those conventionally used widely in suspension polymerization of polystyrene can be applied.
[0012]
This includes water-soluble cellulose derivatives such as polyvinyl alcohol, alkyl cellulose, hydroxyalkyl cellulose, carboxyalkyl cellulose, water-soluble polymers such as sodium polyacrylate and polyvinyl pyrrolidone, and difficulties such as tricalcium phosphate and magnesium phosphate. There are soluble inorganic substances. The amount of these dispersants to be used is arbitrarily determined depending on the target particle size, but usually the water-soluble polymer is added in an amount of 0.02 to 1% by weight based on the total amount of monomers. Preferably, the hardly soluble inorganic substance is added in an amount of 0.05 to 1.0% by weight.
[0013]
Further, an anionic surfactant such as sodium dodecylbenzenesulfonate can be added as a dispersion aid. This is preferably used in combination when a hardly soluble inorganic substance is used as a dispersant. The amount used is preferably 0.001 to 0.02% by weight based on the total amount of monomers.
In addition, an electrolyte such as sodium chloride, sodium sulfate, sodium hydrogen sulfite, sodium carbonate, sodium hydroxide, sodium hydrogen carbonate or the like may be added to the aqueous medium in order to adjust the particle size of the polymer obtained in suspension polymerization. it can. The amount of electrolyte used is preferably 0.001 to 1% by weight based on the total amount of monomers.
[0014]
The weight average molecular weight in terms of polystyrene of the resin particles in the present invention is preferably in the range of 150,000 to 600,000, more preferably in the range of 200,000 to 500,000. If the weight average molecular weight is less than 150,000, the strength of the foamed molded product tends to be low, and if it exceeds 600,000, the foamability tends to be low and it is difficult to obtain a low-density product.
The polymerization rate in the present invention is generally determined by the selection of the polymerization temperature and the type of organic peroxide, but is preferably 95% or more.
[0015]
In the present invention, the chain transfer agent is preferably added at least twice in the suspension polymerization step, and the polymerization rate is at least once in the polymerization step when the polymerization rate is 0% or more and less than 25%. More preferably, the chain transfer agent is added at least once at a time of 25% to 65%.
In the present invention, the total amount of chain transfer agent to be added when the polymerization rate is 25% or more and 65% or less in the polymerization step is the amount of chain transfer agent added when the polymerization rate is 0% or more and less than 25%. It is preferable to increase the weight ratio by 5 times or more.
[0016]
As the chain transfer agent used in the present invention, sulfur compounds such as t-dodecyl mercaptan and n-octyl mercaptan, α-methylstyrene dimer and the like can be applied. The amount of chain transfer agent added at the initial stage of polymerization is preferably 0.01 to 0.1% by weight, more preferably 0.015 to 0.05% by weight, based on the total amount of monomers. . The amount of the chain transfer agent added when the polymerization rate is 25% or more and 65% or less is preferably 0.05 to 0.7% by weight, more preferably 0.00%, based on the total amount of monomers. 15 to 0.5% by weight.
[0017]
For the impregnation of the foaming agent into the resin particles of the present invention, the formulation generally used for expandable styrene resin particles can be applied as it is. As the foaming agent that can be used, a readily volatile organic compound that is liquid or gas at normal temperature and normal pressure and does not dissolve the resin composition can be used. Such as aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, and normal pentane, cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane, methyl chloride, ethyl chloride, trichlorotrifluoroethane, dichloromethane. And halogenated aliphatic hydrocarbons such as difluoroethane.
[0018]
The amount of these volatile foaming agents used is preferably 3 to 15% by weight, more preferably 3 to 10% by weight, based on the polymer. When the amount of the foaming agent is less than 3% by weight, it is difficult to impart foamability, and when it exceeds 15% by weight, the effect as a foaming agent is not improved.
The impregnation of the readily volatile foaming agent into the resin particles can be performed during the polymerization or after the completion of the polymerization. In the middle of the polymerization, the polymerization rate is 50% or more, preferably 70% or more. The impregnation under suspension polymerization is preferably performed at 90 to 130 ° C.
[0019]
A plasticizer can be present during the impregnation of the readily volatile blowing agent into the polymer. As the plasticizer, an organic solvent capable of dissolving or swelling the polymer can be used, and the boiling point thereof is preferably a temperature not lower than about 10 ° C. and not higher than 150 ° C. below the softening point of the polymer. Examples of plasticizers include aromatic hydrocarbons such as ethylbenzene, toluene, styrene, benzene and xylene, halogenated hydrocarbons such as 1,2-dichloropropane and trichloroethylene, dioctyl adipate, dioctyl phthalate, dibutyl sebate, butyl stearate, Examples include epoxidized soybean oil and vegetable oil. The plasticizer is preferably used in an amount of 0.5 to 6% by weight based on the polymer.
[0020]
The resin particles of the present invention are impregnated with a foaming agent, dehydrated and dried, and then coated with various additives conventionally used for expandable polystyrene resin particles.
In the foaming step, an agglomeration inhibitor can be used to prevent agglomeration in the primary foaming. Examples of the agglomeration inhibitor include silicones, metal soaps such as zinc stearate and calcium stearate, and higher fatty acid amides such as ethylene bisamide and stearic acid amide. The agglomeration inhibitor is preferably used in an amount of 0.05 to 0.5% by weight based on the expandable resin particles.
[0021]
In the molding process, a fusion accelerator can be used to improve the fusion of the resin particle body. Examples of the fusion promoter include triesters, diesters, monoesters, sucrose esters, castor hardened oil of higher fatty acids such as stearic acid triglyceride and oleic acid glyceride. The fusion accelerator is preferably used in the range of 0.005 to 0.2% by weight with respect to the expandable resin particles.
[0022]
Coating of these additives on the resin particles is not particularly limited and can be performed by a conventionally known means. For example, it can be performed by a riboblender, a V-type blender, a Henschel mixer, a Redige mixer, or the like.
Foaming of the expandable resin particles of the present invention is performed with water vapor, hot air, hot water or the like. As the method, a foaming method of styrene resin widely used in industry can be applied.
The foamable resin particles of the present invention can be molded by a conventional method of molding a styrenic resin, in which the pre-foamed particles are sent into a closed mold and heated or decompressed. The foam molded product obtained by using the expandable resin particles according to the present invention is excellent in styrene resistance and excellent in foamability and moldability.
[0023]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited to these.
[Example 1]
<Polymerization reaction>
A 16-liter autoclave attached with a stirrer was charged with 8000 g of pure water, 16.0 g of tricalcium phosphate, 0.40 g of sodium dodecylbenzenesulfonate, and 0.40 g of sodium hydrogen sulfite while stirring at 200 rpm. Subsequently, 3400 g of methyl methacrylate, 400 g of methacrylic acid, 200 g of acrylonitrile, 26.7 g of benzoyl peroxide (manufactured by NOF Corporation: Niper B), 2.0 g of t-butyl peroxyisopropyl carbonate (manufactured by NOF Corporation: perbutyl I) Then, 1.6 g of n-octyl mercaptan (manufactured by Kao Corporation: Thiocalcol 08) was mixed, dissolved uniformly, charged into an autoclave, the inside of the system was replaced with nitrogen gas, and the temperature was raised to 60 ° C.
[0024]
After 1.5 hours of completion of the temperature increase, 4.0 g of tricalcium phosphate was added. After 1.6 hours, when the polymerization rate reached about 50%, 1-6.0 g of n-octyl mercaptan was added, and after 2 hours, 4.0 g of tricalcium phosphate and 0.20 g of sodium dodecylbenzenesulfonate were added. Added. Subsequently, the temperature was kept at 90 ° C. for 5 hours to complete the polymerization reaction.
[0025]
<Impregnation of foaming agent>
After completion of the polymerization, 6.0 g of tricalcium phosphate was added, and the temperature was raised to 110 ° C. In a state where the temperature was kept at 110 ° C., 280 g of butane as a blowing agent was press-fitted and further kept for 8 hours, and then cooled to room temperature and taken out from the autoclave.
<Post-processing>
The slurry taken out was washed, dehydrated and dried, and then particles having a particle size between 16 mesh and 30 mesh were collected to obtain 3540 g of resin particles. To the obtained resin particles, 0.71 g of dimethyl silicone, 5.31 g of zinc stearate, and 2.30 g of castor hydrogenated oil were sequentially added and mixed to obtain expandable resin particles.
[0026]
<Foam molding>
The obtained expandable resin particles were pre-foamed with a small pre-foaming machine using steam as a heat medium so that the bulk density was 0.03 g / ml, and aged for 24 hours, and then a polystyrene molding machine (Daisen CVS). -300), a box-shaped product was obtained at a steam pressure of 0.09 MPa.
[0027]
<Evaluation>
Table 1 shows the molecular weight (polystyrene equivalent weight average molecular weight, dispersity), foaming degree, appearance of molded product, styrene resistance and recyclability of the obtained expandable resin particles.
The physical properties were measured according to the following methods.
Molecular weight: Measured by gel permeation chromatography (GPC).
(Eluent: tetrahydrofuran, detector: RI detector)
-Foaming degree: Expressed by the expansion ratio (ml / g) when held in boiling water for 3 minutes when the amount of volatile components of the foamable resin particles was 8.0% by weight.
-Molded article appearance: Judged by visual inspection.
○: Good △: Surface smoothness is slightly inferior ×: Surface smoothness is very poor ・ Styrene resistance: The obtained molded product was immersed in styrene monomer at room temperature for 24 hours, and the change in state was judged visually. .
○: No dissolution / shrinkage ×: Completely dissolved ・ Recyclability: Molded product is heated and reduced with a volume reduction machine (product name: Styrofoam Post SPBH-20, Suruga Seiki Co., Ltd.) used for recycling polystyrene molded products In an ingot, the ingot was further pulverized, and it was confirmed whether it could be injection molded into a raw material.
○: Possible to injection molding (recyclable)
×: Cannot be ingot (cannot be recycled)
[0028]
[Example 2]
As shown in Table 1, suspension polymerization and impregnation with a blowing agent were carried out in the same manner as in Example 1 except that the composition of the monomer was changed. The test results are shown in Table 1.
[Comparative Example 1]
<Polymerization reaction>
In a 16 liter autoclave attached to a stirrer, 8000 g of pure water, 16.0 g of tricalcium phosphate, 0.40 g of sodium dodecylbenzenesulfonate, and 0.40 g of sodium hydrogen sulfite were placed with stirring at 200 rpm. Subsequently, 3400 g of methyl methacrylate, 400 g of methacrylic acid, 200 g of acrylonitrile, 26.7 g of benzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd .: Nyper B) and t-butylperoxyisopropyl carbonate (manufactured by Nippon Oil & Fats Co., Ltd .: Perbutyl I) (2.0 g) and n-octyl mercaptan (Kao Co., Ltd .: Thiocalcol 08) (4.0 g) were mixed and dissolved, purged with nitrogen gas, and heated to 60 ° C.
[0029]
After 1.5 hours of completion of the temperature increase, 4.0 g of tricalcium phosphate was added. After further incubation for 3.5 hours, 4.0 g of tricalcium phosphate and 0.20 g of sodium dodecylbenzenesulfonate were added. Subsequently, the temperature was kept at 90 ° C. for 5 hours to complete the polymerization reaction. After impregnation with the foaming agent, the same procedure as in Example 1 was performed. The test results are shown in Table 1.
[0030]
[Comparative Example 2]
<Polymerization reaction>
In a 16 liter autoclave attached to a stirrer, 8000 g of pure water, 16.0 g of tricalcium phosphate, 0.40 g of sodium dodecylbenzenesulfonate, and 0.40 g of sodium hydrogen sulfite were placed with stirring at 200 rpm. Subsequently, 3600 g of methyl methacrylate, 400 g of methacrylic acid, 26.7 g of benzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd .: Nyper B), t-butyl peroxyisopropyl carbonate (manufactured by Nippon Oil & Fats Co., Ltd .: perbutyl I) while stirring similarly. After 2.0 g and 1.6 g of n-octyl mercaptan (manufactured by Kao Corporation: Thiocalcol 08) were mixed and dissolved, the mixture was purged with nitrogen gas and heated to 60 ° C.
[0031]
After 1.5 hours of completion of the temperature increase, 4.0 g of tricalcium phosphate was added. After 1.6 hours, when the polymerization rate reached about 50%, 16.0 g of n-octyl mercaptan was added, and after 1.2 hours, 4.0 g of tricalcium phosphate and sodium dodecylbenzenesulfonate were added. 20 g was added. Subsequently, the temperature was kept at 90 ° C. for 3 hours to complete the polymerization reaction. After impregnation with the foaming agent, the same procedure as in Example 1 was performed. The test results are shown in Table 1.
[0032]
[Comparative Example 3]
<Polymerization reaction>
In a 16 liter autoclave attached to a stirrer, 8000 g of pure water, 8.0 g of tricalcium phosphate, 0.12 g of sodium dodecylbenzenesulfonate, and 0.40 g of sodium hydrogen sulfite were placed while stirring at 200 rpm. Subsequently, while stirring in the same manner, 4000 g of methyl methacrylate, 26.7 g of benzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd .: Niper B), 2.0 g of t-butyl peroxyisopropyl carbonate (manufactured by Nippon Oil & Fats Co., Ltd .: perbutyl I), 1.6 g of n-octyl mercaptan (manufactured by Kao Corporation: Thiocalcol 08) was mixed and dissolved, purged with nitrogen gas, and heated to 60 ° C.
[0033]
After 1.5 hours of completion of the temperature increase, 4.0 g of tricalcium phosphate was added. After an additional 1.9 hours, 16.0 g of n-octyl mercaptan was added when the polymerization rate reached about 50%. After another hour, 4.0 g of tricalcium phosphate and 0.20 g of sodium dodecylbenzenesulfonate were added. Subsequently, the temperature was kept at 90 ° C. for 3 hours to complete the polymerization reaction. After impregnation with the foaming agent, the same procedure as in Example 1 was performed. The test results are shown in Table 1.
[0034]
[Comparative Example 4]
<Polymerization reaction>
In a 16 liter autoclave attached to a stirrer, 8000 g of pure water, 8.0 g of tricalcium phosphate, 0.12 g of sodium dodecylbenzenesulfonate, and 0.40 g of sodium hydrogen sulfite were placed while stirring at 200 rpm. Subsequently, 3600 g of methyl methacrylate, 400 g of acrylonitrile, 26.7 g of benzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd .: Nyper B), t-butyl peroxyisopropyl carbonate (manufactured by Nippon Oil & Fats Co., Ltd .: perbutyl I) 2 while stirring similarly. 0.0 g, 1.6 g of n-octyl mercaptan (manufactured by Kao Corporation: thiocalcol 08) were mixed and dissolved, purged with nitrogen gas, and heated to 60 ° C.
[0035]
4.3 hours after completion of the temperature increase, 16.0 g of n-octyl mercaptan was added when the polymerization rate reached about 50%. After incubating for another 3 hours, 4.0 g of tricalcium phosphate and 0.20 g of sodium dodecylbenzenesulfonate were added. Subsequently, the temperature was kept at 90 ° C. for 5 hours to complete the polymerization reaction. After impregnation with the foaming agent, the same procedure as in Example 1 was performed. The test results are shown in Table 1.
[0036]
[Comparative Example 5]
<Polymerization reaction>
In a 16 liter autoclave attached to a stirrer, 8000 g of pure water, 16.0 g of tricalcium phosphate, and 0.40 g of sodium dodecylbenzenesulfonate were placed with stirring at 200 rpm. Subsequently, 3600 g of styrene, 400 g of methacrylic acid, 13.3 g of benzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd .: Nyper B), t-butyl peroxyisopropyl carbonate (manufactured by Nippon Oil & Fats Co., Ltd .: perbutyl I) with stirring in the same manner. After mixing and dissolving 0 g, the mixture was purged with nitrogen gas.
[0037]
After completion of the preparation, the temperature was raised to 90 ° C. After 1.5 hours of completion of the temperature increase, 4.0 g of tricalcium phosphate was added. After 2.5 hours, 4.0 g of tricalcium phosphate and 0.20 g of sodium dodecylbenzenesulfonate were added. Subsequently, the temperature was kept at 120 ° C. for 3 hours to complete the polymerization reaction. After impregnation with the foaming agent, the same procedure as in Example 1 was performed. The test results are shown in Table 1.
[0038]
[Table 1]

[0039]
【The invention's effect】
INDUSTRIAL APPLICABILITY According to the present invention, there are provided expandable resin particles that are excellent in styrene resistance and capable of obtaining a molded product having foamability and moldability sufficient to perform mold molding, and a foam molded product using the same.

Claims (3)

Expandable resin particles copolymerized by suspension polymerization at a ratio of 40 to 96% by weight of methacrylic acid ester, 3 to 20% by weight of methacrylic acid and 1 to 40% by weight of unsaturated nitrile, and containing a readily volatile foaming agent. Expandable resin particles having a dispersity (Mw / Mn, Mw: weight average molecular weight, Mn: number average molecular weight) determined from a molecular weight in terms of polystyrene of 3.0 or more and 10.0 or less. The expandable resin particles according to claim 1, wherein the readily volatile foaming agent is an aliphatic hydrocarbon and the content thereof is 3 wt% or more and less than 15 wt%. A foam molded product obtained by using the expandable resin particles according to claim 1.