JPH1160786A - Production of foamable styrenic resin granule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject granules with a small amount of residual styrene, high polymerization rate, smelling less of decomposition products of a peroxide and useful for food vessels and the like by using a specific polymerization initiator. SOLUTION: This method for producing foamable styrenic resin granules comprises polymerizing a styrenic monomer in a suspended state and adding a foaming agent. Therein, a peroxide of the formula (R<1> is a 8-18C alkyl; R<2> is a 1-8C alkyl), such at t-hexylperoxy-2-ethylhexylcarbonate, is used together with benzoyl peroxide as the polymerization initiator. The polymerization initiator is preferably used in an amount of e.g. about 0.01-2 wt.% based on the amount of the monomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a food container, a fish box,
The present invention relates to a method for producing expandable styrene resin particles used for packaging materials and the like. More specifically, the present invention relates to a method for producing expandable styrene resin particles having a high polymerization rate, a small amount of residual styrene, and a small odor due to peroxide decomposition products.

[0002]

2. Description of the Related Art It is known to use various polymerization initiators in producing expandable styrene resin particles. For example, a method using a combination of benzoyl peroxide and t-butylperoxybenzoate is known (Japanese Patent Application Laid-Open No.
19125 and 60-47037).

[0003]

Various compounds are effective as polymerization initiators for producing expandable styrene resin particles. However, any of the above-mentioned methods has a problem that the amount of residual styrene is large. Was. An object of the present invention is to provide a method for producing expandable styrene resin particles having a small amount of residual styrene, a high polymerization rate, and a low odor due to peroxide decomposition products.

[0004]

Means for Solving the Problems The present inventors have conducted research over a long period of time, and as a result, have confirmed that the production of expandable styrene resin particles using a specific polymerization initiator achieves the above object. It was completed. That is, the first invention is a method for producing foamable styrene resin particles by suspension polymerizing a styrene monomer and adding a foaming agent,
General formula (1) as a polymerization initiator

[0005]

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(Wherein R ¹ represents a branched or straight-chain alkyl group having 8 to 18 carbon atoms, and R ² represents a branched or straight-chain alkyl group having 1 to 8 carbon atoms). A method for producing expandable styrene resin particles. A second invention is a method for producing expandable styrene resin particles, wherein the peroxide used in the first invention and benzoyl peroxide are used in combination.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, specific examples of the peroxide represented by the general formula (1) include t-butyl peroxy-2-ethylhexyl carbonate, t-amyl peroxy-2-ethylhexyl carbonate, t-butyl peroxy-2-ethylhexyl carbonate and t-butyl peroxy-2-ethylhexyl carbonate.
-Hexyl peroxy-2-ethylhexyl carbonate, t-octyl peroxy-2-ethylhexyl carbonate, t-butyl peroxydecyl carbonate,
t-hexyl peroxydecyl carbonate, t-butyl peroxide decyl carbonate, t-hexyl peroxide decyl carbonate, t-butyl peroxyhexadecyl carbonate, t-hexyl peroxyhexadecyl carbonate, t-butyl peroxyoctadecyl carbonate, t-hexyl peroxyoctadecyl carbonate And the like. Of these, t-hexyl peroxy-2-ethylhexyl carbonate and t-butyl peroxide decyl carbonate are particularly preferred because they can reduce the amount of residual styrene. The above peroxides are usually prepared by adding t-alkyl hydroperoxide and alkyl chloroformate in the presence of
It is obtained by reacting at a temperature of 30 ° C.

In the present invention, the amount of the polymerization initiator used varies depending on the polymerization temperature and other conditions, but is usually 0.01 to 2% by weight, more preferably 0.1 to 2% by weight, based on the whole monomers.
0.5 to 1% by weight. If it is less than 0.01% by weight, there is no effect of addition, and if it exceeds 2% by weight, it becomes difficult to control the polymerization rate.

In the present invention, the polymerization time can be further shortened by using the peroxide represented by the general formula (1) and benzoyl peroxide together, and the use of the peroxide represented by the general formula (1) is also possible. The amount can be reduced. The amount of benzoyl peroxide used is 0.001 to 2% by weight, preferably 0.1 to 2% by weight, based on the whole monomer, separately from the compound of the general formula (1).
01 to 1% by weight is used. If it is less than 0.001% by weight, the effect of the combined use is small, and if it exceeds 2% by weight, it becomes difficult to control the polymerization rate.

The styrene monomer used in the present invention includes styrene and substituted styrene such as α-methylstyrene, chlorostyrene, t-butylstyrene and the like. A mixture of a styrene monomer and another vinyl monomer copolymerizable therewith may be used. Examples of such another vinyl monomer include acrylic acid such as acrylonitrile, methyl methacrylate, and ethyl acrylate or methacrylic acid. And dimethyl maleate, dimethyl fumarate, divinyl benzene and the like. And, it is preferable that styrene is contained in 50% by weight or more of all the monomers.

In the present invention, the polymerization method is suspension polymerization. The polymerization temperature is selected depending on the molecular weight of the polymer to be produced and various physical properties and is not limited, but is usually from 60 to 150 ° C, preferably from 65 to 130 ° C. At that time, constant temperature or programmed temperature polymerization is used. If the temperature is lower than 60 ° C., the polymerization rate decreases,
C. or higher makes it difficult to control the polymerization rate, and both are not preferred.

In the production method of the present invention, a protective colloid of a water-soluble polymer and a poorly soluble inorganic substance can be added to the polymerization system as a dispersant. Examples of the water-soluble polymer protective colloid agent include polyvinyl alcohol, methyl cellulose, and the like, and among these, polyvinyl alcohol is preferable. Examples of the hardly soluble inorganic substance include calcium phosphate, magnesium pyrophosphate, bentonite and the like. The amount of the dispersant added is usually 0.01 to 2% by weight, preferably 0.1 to 1% by weight, based on water. If the amount is less than 0.01% by weight, coarse particles are contained. If the amount exceeds 2% by weight, the viscosity of the suspension polymerization system tends to be high, and stirring tends to be difficult. When a hardly soluble inorganic substance is used as a dispersant, it is preferable to use a small amount of a surfactant such as sodium dodecylbenzenesulfonate. These are used in an amount of 0.1 to 2% by weight of a poorly soluble inorganic substance in water to be used, and 1% by weight of a surfactant.
Preferably, it is in the range of ~ 500 ppm.

The foaming agent used in the present invention preferably has a boiling point lower than the softening point of the resin to be produced and has the property of not dissolving or slightly swelling the styrene resin. is there. Examples of these blowing agents include aliphatic hydrocarbons such as propane, butane and pentane, cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane, and halogenated hydrocarbons such as methyl chloride. Can be. Of these, butane and pentane are industrially preferred. The amount of foaming agent used is
Usually, the proportion is 3 to 12% by weight, preferably 4 to 8% by weight, based on the monomers used. The blowing agent is injected during or after the polymerization. If the amount is less than 3% by weight, the foaming is not sufficient, and if the amount exceeds 12% by weight, a large amount of the foaming agent remains in the molded product after molding, and the strength of the molded product is lowered, which is not preferable. Injection temperature is 90
~ 115 ° C, preferably 100 ~ 130 ° C after press-fitting
It is preferable to sufficiently perform impregnation of the foaming agent by heating the mixture.

[0014]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In each of the examples, parts and% indicate parts by weight and% by weight, respectively, unless otherwise specified. Abbreviations in the examples indicate the following compounds. BuE: t-butylperoxy-2-ethylhexyl carbonate AmE: t-amylperoxy-2-ethylhexyl carbonate HxE: t-hexylperoxy-2-ethylhexyl carbonate OcE: t-octylperoxy-2-ethylhexyl carbonate BuD: t-butylperoxy Dodecyl carbonate BPO: benzoyl peroxide BuZ: t-butylperoxybenzoate

Example 1 In a 5000 ml autoclave equipped with a stirrer, 2,000 ml of ion-exchanged water, 5 g of tribasic calcium phosphate, 0.1 g of sodium dodecylbenzenesulfonate (product name: Newrex R, manufactured by NOF Corporation), sodium sulfate 1
g and stirred at a rotation speed of 250 revolutions / minute. Ethylene bisstearic acid amide as cell size regulator 2
g, BuE 5 g as a polymerization initiator, and styrene 20
After adding 00 g and replacing the space with nitrogen, polymerization was performed while heating at 90 ° C. for 4 hours and 90 to 120 ° C. for 4 hours.
Further, polymerization was carried out at 120 ° C. for 2 hours. Then, the temperature is set to 9
After cooling to 0 ° C., 120 g of n-pentane was injected, and the temperature was raised to 115 ° C. in 1 hour and maintained at 115 ° C. for 3 hours.
Thereafter, the mixture was cooled to 30 ° C. in 2 hours to obtain expandable polystyrene particles. The amount of residual styrene in the particles measured by gas chromatography was 0.22%. 5 g of the obtained particles were placed in a glass bottle having a capacity of 20 ml.
After being left for 1 hour in a constant temperature layer at ℃, the odor in the container was examined. As a result, almost no off-flavor was recognized. Table 1 shows the results.
It was shown to.

[0016]

[Table 1]

Examples 2 to 6 The procedure of Example 1 was repeated, except that the type and amount of the polymerization initiator were changed as shown in Table 1. The results are as shown in Table 1.

Comparative Examples 1 and 2 As shown in Table 1, B was used instead of BuE as a polymerization initiator.
Except using uZ, it carried out according to Example 1 or Example 2. The results were as shown in Table 1. Example 1
6 and Comparative Examples 1 and 2, it was found that the production method of the present invention had a high polymerization rate, so that the amount of residual styrene was small and the odor of the polymer was small.

[0019]

According to the production method of the present invention, a specific polymerization initiator is used to produce foamable styrene resin particles having a high polymerization rate, a small amount of residual styrene, and a small odor due to peroxide decomposition products. The industrial use value is extremely high because it is possible.

Claims (2)

[Claims] 1. A method for producing expandable styrene resin particles by suspension polymerizing a styrene monomer and adding a foaming agent, wherein the polymerization initiator is represented by the general formula (1): (Wherein, R ¹ represents a branched or straight-chain alkyl group having 8 to 18 carbon atoms, and R ² represents a branched or straight-chain alkyl group having 1 to 8 carbon atoms). For producing expandable styrene resin particles. 2. The method for producing expandable styrene resin particles according to claim 1, wherein benzoyl peroxide is used in combination as a polymerization initiator.