CN101910267B - Flame-retardant expandable styrene resin particle, and method for production thereof - Google Patents

Abstract

Disclosed is a method for producing a flame-retardant expandable styrene resin particle by the suspension polymerization of a styrene monomer. The method is characterized by involving the steps of: adding 0.45 to 2.0 parts by weight of tetrabromocyclooctane to 100 parts by weight of the styrene monomer, thereby producing a styrene resin particle; and impregnating the styrene resin particle with a physical foaming agent during or after the suspension polymerization of the styrene monomer while adjusting the temperature of the impregnation to a temperature falling within the range from 80 to 110 DEG C, thereby producing the frame-retardant expandable styrene resin particle.

Description

Flame-retardant expandable styrene-based resin particles and preparation method thereof

technical field

The present invention relates to a flame-retardant expandable styrene-based resin particle and a preparation method thereof. More particularly, the present invention relates to a flame-retardant expandable styrene-based resin particle using tetrabromocyclooctane as a flame retardant and a preparation method thereof.

Background technique

Styrene-based resin foam moldings have been largely used as construction materials because they have excellent strength and heat insulation. The preparation method of such a styrene-based resin foamed molded article includes: making a styrene-based monomer suspension polymerized to obtain styrene-based resin particles; impregnating the obtained styrene-based resin particles with a physical blowing agent to obtain Expandable styrene-based resin particles; pre-expanding the obtained expandable styrene-based resin particles to obtain styrene-based resin pre-expanded particles; packing the obtained pre-expanded particles into a mold for foaming with a desired shape; and under the action of its foaming pressure, the pre-expanded particles are thermally melted and integrated.

On the other hand, the above-mentioned styrene-based resin foam moldings have a problem of being flammable. Especially when used as building materials, they may contribute to the spread of flames in the event of a fire. Therefore, attempts have been made to solve this problem by adding flame retardants to styrene-based resin foam moldings.

Examples of known methods of adding a flame retardant include a method of dissolving a flame retardant in a styrene-based monomer, and a method of impregnating a styrene-based resin particle with a physical blowing agent and simultaneously impregnating it with a flame retardant. method. Examples of the former method include the methods disclosed in Japanese Patent Laid-Open No. 2003-335891 (Patent Document 1) and Japanese Patent Laid-Open No. 2002-194130 (Patent Document 2), and examples of the latter method include Japanese Patent Publication No. 6 (1994)-18918 A (Patent Document 3) and Japanese Patent Laid-Open No. 2007-246606 (Patent Document 4).

Patent Document 1: Japanese Patent Laid-Open No. 2003-335891

Patent Document 2: Japanese Patent Laid-Open No. 2002-194130

Patent Document 3: Japanese Patent Publication No. 6(1994)-18918

Patent Document 4: Japanese Patent Laid-Open No. 2007-246606

Contents of the invention

The problem to be solved by the invention

In the former method, hexabromocyclododecane (HBCD) is mainly used as a flame retardant. HBCD is a substance that is feared to be accumulated in a living body, and therefore it is desired to reduce its use. In the latter method, since the impregnation of the flame retardant is performed on the styrene-based resin particles, the amount of impregnation is limited, and thus it is desired to increase the impregnation amount of the flame retardant to improve flame retardancy.

In addition, there is another problem that when the impregnation amount of the flame retardant is too large for the styrene-based resin particles, the flame retardant acts as a nucleating agent so that the size of the air bubbles is different from that of the resulting styrene-based resin particles. Bubbles are too small. This problem is especially detrimental to the latter approach. That is, in the latter method, a large amount of flame retardant exists near the surface of the styrene-based resin particles, resulting in the formation of bubbles in the pre-expanded particles that are small in the surface region. As a result, the bubbles may not be able to withstand the heat during production of the foamed molded body by the molding method to cause melting, adversely affecting the appearance of the foamed molded body. In addition, there are many flame retardants near the surface of the styrene-based resin particles, which tends to cause so-called occlusion, that is, fusion and connection between pre-expanded particles after pre-expanding. Also, in some cases, the flame retardant undergoes secondary agglomeration in the impregnated solution with the blowing agent, so that the flame retardant is not uniformly dispersed. As a result, the absorption of the flame retardant by the styrene-based resin particles may be uneven. The uneven absorption will result in the presence of particles partially absorbed with more flame retardant, and such particles have poor heat resistance. Therefore, the particles may not be able to withstand the heat during the production of the expanded molded body by the molding method, shrinking into hardened particles. The foamed molded body is usually formed into a predetermined shape by cutting a heated nickel-chromium alloy (Nichorme) wire, and in this case, the nickel-chrome alloy wire bounces on the hardened particles, causing unevenness on the cut surface. Uneven shape of the wire, thereby significantly reducing the value of the resulting shaped body. In addition, threads having uneven shapes may not be able to develop sufficient adhesive strength when the foamed molded product is bonded to a panel and used.

Furthermore, there is a problem that thermal fusion between pre-expanded particles of styrene-based resin may be poor.

means of solving problems

The inventors of the present invention have found that by using a specific amount of a specific flame retardant and setting the temperature of impregnation with a physical blowing agent to a specific temperature to complete the present invention, a foamable styrene-based resin can be provided Particles, the expandable styrene-based resin particles have excellent thermal fusion properties between particles when expanded and allow production of expanded molded articles with excellent flame retardancy.

The present invention therefore provides a method for preparing flame-retardant expandable styrene-based resin particles, the method comprising: adding styrene-based monomers relative to 100 parts by weight of 0.45 parts by weight to 2.0 parts by weight of tetrabromocyclooctane to obtain styrene-based resin particles; then, impregnating the styrene-based resin particles with a physical blowing agent during or after the suspension polymerization of styrene-based monomers, while The impregnation temperature was adjusted to 80 to 110° C. to obtain flame-retardant expandable styrene-based resin particles.

The present invention also provides a flame-retardant expandable styrene-based resin particle, which comprises styrene-based resin particles and is contained in the styrene-based resin particle. Physical blowing agents and tetrabromocyclooctane in resin particles;

When the content rate of tetrabromocyclooctane contained in the surface region of the styrene-based resin particle is "a" (% by weight), the content of tetrabromocyclooctane contained in the entirety of the styrene-based resin particle is When the rate is b (weight %), the tetrabromocyclooctane contained in the styrene-based resin particles satisfies the relational formula "a"≤1.1×"b";

The amount of tetrabromocyclooctane contained in the whole of the styrene-based resin particles is 0.45 parts by weight to 2.0 parts by weight relative to 100 parts by weight of the styrene-based resin particles; and

When the flame-retardant expandable styrene-based resin particles are expanded at an expansion ratio of 50 times, a foam having an average cell size of 50 μm to 350 μm is provided.

The effect of the invention

The preparation method of the present invention can provide a flame-retardant expandable styrene-based resin particle capable of controlling cell size, having no variation in cell thickness during foaming and having satisfactory heat fusion property during molding.

In addition, the use of a surfactant during suspension polymerization can improve the dispersion stability of the monomer mixture droplets in the suspension polymerization system.

The monomer mixture contains a flame retardant additive, which can improve the flame retardancy of the expandable styrene-based resin particles.

The impregnation temperature is adjusted so that the foamed molded article obtained by expanding the above-mentioned flame-retardant expandable styrene-based resin particles 50 times has an average cell size of 50 μm to 350 μm to provide more satisfactory thermal fusion properties expandable styrene-based resin particles.

Brief description of the drawings

FIG. 1 is an electron micrograph of a cross section of pre-expanded particles of Example 1. FIG.

FIG. 2 is an electron micrograph of a cross section of pre-expanded particles of Example 3. FIG.

3 is an electron micrograph of a section of pre-expanded particles of Comparative Example 4. FIG.

4 is an electron micrograph of a section of pre-expanded particles of Comparative Example 5. FIG.

5 is an electron micrograph of a cross section of pre-expanded particles of Comparative Example 6. FIG.

Implementation

In the present invention, suspension polymerization of a styrene monomer is first performed to obtain styrene-based resin particles, and in this case, tetrabromocyclooctane (TBCO) and a polymerization initiator are added to the styrene monomer .

Examples of styrenic monomers include styrene, α-methylstyrene, p-methylstyrene, tert-butylstyrene, chlorinated styrene, and the like. These monomers may be used alone or in combination of two or more thereof. Among these monomers, styrene is particularly preferred. In addition, esters of acrylic or methacrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and cetyl methacrylate; or esters of acrylic acid or methacrylic acid such as acrylonitrile, fumaric acid Monomers such as dimethyl ester and ethyl fumarate can be copolymerized with styrenic monomers. In addition, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate can also be copolymerized with styrenic monomers.

The amount of TBCO used is 0.45 to 2.00 parts by weight based on 100 parts by weight of the styrene monomer. This range ensures flame retardancy and thermal fusion properties at the time of molding, and suppresses changes in cell thickness.

The polymerization initiator is not particularly limited, and a suitable polymerization initiator can be appropriately selected according to the polymerization temperature. Examples include organic peroxides such as benzoyl peroxide, lauroyl peroxide, tert-butyl perbenzoate, tert-butyl peroxypivalate, tert-butylperoxyisopropyl carbonate, peracetic acid tert-butyl ester, 2,2-bis(tert-butyl peroxy)butane, tert-butyl peroxy-3,3,5-trimethylcyclohexanoate, di-tert-butyl peroxide hexahydroterephthalene Formate esters and 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane; and azo compounds such as azobisisobutyronitrile and azobis(dimethylvaleronitrile ). These polymerization initiators can be used individually or in combination of 2 or more types. The polymerization initiator may be used in an amount of 0.05 to 3.0 parts by weight based on 100 parts by weight of the styrene monomer.

A monomer mixture is obtained by dissolving TBCO in a styrenic monomer. The monomer mixture may contain flame retardant aids. Examples of flame retardant aids include cumene hydroperoxide, dicumyl peroxide, tert-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and the like. The amount of the flame retardant additive can be 0.1 to 0.5 parts by weight based on 100 parts by weight of the styrene monomer.

The monomer mixture is dispersed in an aqueous medium and subjected to suspension polymerization.

Examples of aqueous media include water and mixtures of water and water-soluble organic media such as methanol and ethanol. The aqueous medium may contain additives such as surfactants and dispersants.

Examples of surfactants include anionic surfactants, cationic surfactants, zwitterionic surfactants and nonionic surfactants.

Examples of anionic surfactants include fatty acid oils such as sodium oleate and potassium castor oil; alkyl sulfate ester salts such as sodium lauryl sulfate and ammonium lauryl sulfate; alkylbenzenesulfonates such as dodecylbenzene Sodium sulfonate; Alkyl naphthalene sulfonate; Alkane sulfonate; Dialkyl sulfosuccinate; Ether sulfate, polyoxyethylene alkyl sulfate, etc.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester , polyoxyethylene alkylamine, glycerin fatty acid ester, oxyethylene-oxypropylene block polymer, etc.

Examples of cationic surfactants include alkylamine salts such as dodecylamine acetate and stearylamine acetate; quaternary ammonium salts such as dodecyltrimethylammonium chloride; and the like.

Examples of zwitterionic surfactants include lauryl dimethyl amine oxide and phosphate or phosphite surfactants.

The above surfactants may be used alone or in combination of two or more. The amount of the surfactant may be 0.002 to 1.0 parts by weight based on 100 parts by weight of the aqueous medium.

Examples of dispersants include water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyvinylpyrrolidone, and polyacrylamide; and poorly soluble inorganic salts such as magnesium pyrophosphate, tricalcium phosphate, and hydroxyapatite. These dispersants may be used alone or in combination of two or more. The amount of the dispersant may be 0.2 to 10 parts by weight relative to 100 parts by weight of the styrene-based monomer.

Suspension polymerization of styrenic monomers. Suspension polymerization is generally carried out at 50°C to 120°C for 1 hour to 20 hours. As a result of the suspension polymerization, styrene-based resin particles are obtained.

In addition, during or after the suspension polymerization, the styrene-based resin particles are impregnated with a physical foaming agent, thereby obtaining flame-retardant expandable styrene-based resin particles. Here, the impregnation temperature for impregnation is adjusted to 80°C to 110°C. Such adjustment allows providing a flame-retardant expandable styrene-based resin particle capable of controlling the size of the cells and having no change in the thickness of the cells upon expansion. and satisfactory thermal fusion properties when molded.

During the suspension polymerization, the styrene-based resin particles are impregnated with the physical blowing agent, which can be performed by pressing the physical blowing agent into the aqueous medium. On the other hand, when the impregnation of the styrene-based resin particles with a physical foaming agent is performed after suspension polymerization, the styrene-based resin particles may be taken out from the aqueous medium for impregnation, or the styrene-based resin particles may be Leave in aqueous medium for maceration.

A physical blowing agent refers to a blowing agent that has a foaming function without decomposition, that is, the so-called volatile blowing agent. Examples of physical blowing agents include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane and hexane. These physical blowing agents may be used alone or in combination of two or more.

The average particle diameter of the obtained flame-retardant expandable styrene-based resin particles may be, for example, 0.3 mm to 2.0 mm.

Flame-retardant expandable styrene-based resin particles undergo a well-known pre-expansion process and expansion-molding process to become an expanded molded body. In particular, when the particles are expanded 50 times, the average diameter of the cells constituting the expanded molded body is 50 μm to 350 μm. This range allows the expanded particles constituting the expanded molded body to have satisfactory thermal fusion property.

The present invention also provides a flame-retardant expandable styrene-based resin particle obtained by the above method. When the content rate of tetrabromocyclooctane contained in the surface layer region of the resin particle based on styrene is a (weight %), and the content rate of tetrabromocyclooctane contained in the whole of the resin particle based on styrene is When b (% by weight), tetrabromocyclooctane contained in the styrene-based resin particles satisfies the relational expression a≦1.1×b. By satisfying this relationship, it is possible to provide flame-retardant expandable styrene-based resin particles satisfying both flame retardancy and heat-fusibility requirements. This relationship is more preferably represented by the formula a≦1.05×b.

Here, since it is difficult to directly measure the content "a" of tetrabromocyclooctane in the particle surface region, it is a value measured according to the following method. That is, a test piece having a thickness of 0.2 mm was cut out from the surface of the foamed molded body obtained by expanding the flame-retardant expandable styrene-based resin particles 50 times. Since the surface of the foamed molded body is formed by the surface of the flame-retardant expandable styrene-based resin particles, the test piece exhibits the state of the surface region of the flame-retardant expandable styrene-based resin particles . The amount of tetrabromocyclooctane in the test piece was measured, and its ratio to the total weight of the test piece was calculated to obtain the content a (% by weight) of tetrabromocyclooctane contained in the surface region of each particle. Details of the measurement method are described in Examples.

On the other hand, the content "b" of tetrabromocyclooctane contained in the entirety of each particle refers to tetrabromocyclooctane used as a raw material for producing flame-retardant expandable styrene-based resin particles. The ratio of the amount to the amount of styrenic monomer.

Example

Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. The measurement methods of the molecular weight, volume expansion ratio, expansion ratio, flame retardancy, average cell size, and thermal fusion property of the styrene-based resin particles are as follows.

(Molecular weight of styrene-based resin particles)

Weight average molecular weight (Mw) was measured using gel permeation chromatography (GPC). Its measurement method is as follows. Here, the weight average molecular weight (Mw) means the weight average molecular weight shown as the molecular weight of polystyrene (PS).

Measurements were performed using chromatography after dissolving 50 mg of the sample in 10 ml of tetrahydrofuran (THF) and filtering it with a non-aqueous 0.45 μm chromatography disc. The conditions of the chromatograph are as follows.

Liquid chromatograph: trade name "Gel Permeation Chromatography HLC-8020", manufactured by Tosoh

Column: trade name "TSKgel GMH-XL-L", Φ7.8mm×30cm×2, produced by Tosoh Company

Column temperature: 40°C

Carrier gas: Tetrahydrofuran (THF)

Carrier gas flow: 1ml/min

Injection pump temperature: 35°C

Detection: RI

Injection volume: 100 microliters

Standard polystyrene for the calibration curve: Showa Denko’s product name is “shodex”, weight-average molecular weight: 1,030,000; 870

(volume foam ratio)

After allowing the pre-expanded particles as a sample to fall freely into the graduated cylinder, tap the bottom of the graduated cylinder to make the sample volume constant, measure the volume and mass of the sample, and calculate the volume expansion ratio according to the following formula. In the case of a styrene-based resin, the specific gravity of the resin is 1.0.

Volume foaming ratio (multiple) = sample volume in graduated cylinder (ml) / sample mass (g) × numerical specific gravity

(foaming ratio)

Measure the size and mass of the test piece (for example, 50×50×25 mm) of the foamed molded product in a manner expressed with 3 or more significant figures, and calculate the foaming ratio according to the following formula. In the case of a styrene-based resin, the specific gravity of the resin is 1.0.

Foaming ratio (multiple) = test piece volume (cm ³ )/test piece mass (g) × resin specific gravity

(flame retardant)

Cut out 5 pieces of test pieces each with a thickness of 10 mm, a length of 200 mm and a width of 25 mm from the foamed molded body, and give the prescribed ignition limit indicator line and combustion limit indicator line. By burning each test piece up to the ignition limit indicator line using a candle as an ignition source, and then leaving the flame, the time (seconds) from that point to when the flame was extinguished was measured. When the average time until the flame is extinguished in 5 tests does not exceed 3 seconds and no test piece burns beyond the combustion boundary indicator line, the molded article is evaluated as a pass. A candle used as a source of ignition is such that when the length of the wick is about 10 mm, it gives a flame in static combustion having a length of 50 mm or more and a width of about 7 mm or more.

(mean bubble size)

The molded foam was cut, and an image was taken with a scanning electron microscope (S-3000N manufactured by Hitachi, Ltd.) magnified 100 times from the inside of 1/10 to 9/10 or more of the cut surface from the outside of the cut surface. The captured images were printed on A4 paper with 4 images per sheet, and the average chord length (t) of the bubbles was calculated from the number of bubbles on any straight line (length 60mm) according to the following formula. Arbitrary straight lines try to avoid bubbles touching the drawn straight line at the contact point (when they touch at a certain point, the bubble is counted). Measured at 6.

Average chord length t=60/(number of bubbles×photo magnification)

Then, the bubble size D is calculated according to the following formula.

D=t/0.616

(heat fusion)

After molding, the foamed molded body was dried at 70° C. for 48 hours, and then a piece with a thickness of 50 mm was cut out near the center in the thickness direction using a nichrome wire. The cut plate-shaped molded body of 350 mm×450 mm×50 mm was cut in half at the center in the longitudinal direction. Among all the particles present in the cross-section, the percentage (%) of the particles whose expanded particles themselves were broken out of the total particles was calculated. When the fusion ratio is 80% or more, it is evaluated as "excellent ◎", when it is 60% or more but less than 80%, it is "good ○", when it is 40% or more but less than 60%, it is "acceptable △", and when it is less than 40% When it is "difference ×".

Example 1

In a 100-liter autoclave, 60 g of tricalcium phosphate (TCP-10 produced by Ohira Chemical Co., Ltd.) as a dispersant and 0.8 g of sodium dodecylbenzenesulfonate as a suspension stabilization aid (surfactant) 40kg of ion-exchanged water, mixed with dissolved 200g tetrabromocyclooctane (Pyrogard FR-200 produced by Daiichi Kogyo Pharmaceutical Co., Ltd.), 120g dicumyl peroxide, 140g benzoyl peroxide (purity 75%) and 30g 40 kg of styrene monomer in t-butyl peroxybenzoate was then dissolved and dispersed under stirring to form a suspension.

Then, the polymerization reaction of the styrene monomer was performed at 90° C. for 6 hours and further at 110° C. for 4 hours under stirring at 70 rpm. During the reaction at 90° C., that is, 2 hours and 3 hours after the start of the reaction, 6 g of tricalcium phosphate (TCP-10 manufactured by Ohira Chemical Co., Ltd.) was added to the suspension. After the reaction was finished, the temperature was lowered to room temperature (25° C.), and the contents were taken out from the autoclave to be subjected to a centrifugation process and dried, thereby obtaining styrene resin particles.

The obtained styrene resin particles were classified into particles of 0.6 mm to 0.7 mm.

2000 g of water, 9 g of magnesium pyrophosphate, and 0.3 g of sodium dodecylbenzenesulfonate were added to a 5-liter autoclave to prepare an aqueous medium, and 2000 g of the above-mentioned particles were added and stirred at 300 rpm.

Then, the temperature was raised to 95° C., and while maintaining this temperature, 180 g of butane was pressed in. The particles were immersed in butane for 3 hours, and then cooled to obtain expandable styrene resin particles. The obtained expandable styrene resin particles were left to stand at 15° C. for 4 days for aging, and then subjected to a pre-expanding step. The pre-expanding step is performed under the condition that the expandable styrene-based resin particles are charged into a pre-expanding machine and pre-expanded with steam. As a result of pre-expansion, pre-expanded particles having a volume expansion ratio of 50 times were obtained. Fig. 1 shows a cross-sectional SEM (scanning electron microscope) photograph of the obtained pre-expanded particles. Fig. 1 shows that in Example 1, pre-expanded particles in which the change in cell thickness was suppressed were obtained.

In addition, the pre-expanded particles were allowed to stand at room temperature for 24 hours for aging, and they were loaded into the cavity of a known steam molding machine for expanded polystyrene, and heated with 0.6 kg/cm ² G steam for 30 seconds, and water-cooled for 20 seconds to obtain a 300mm×450mm×100mm block-shaped foam molding that was foamed at a foaming ratio of 50 times.

Table 1 shows the flame retardancy, average cell size, and thermal fusion properties of the obtained block-shaped foam moldings.

Example 2

Except having changed the quantity of tetrabromocyclooctane into 400g, it carried out similarly to Example 1, and obtained the expanded molding.

Example 3

Except having changed the quantity of tetrabromocyclooctane into 600 g, it carried out similarly to Example 1, and obtained the expanded molding. Fig. 2 shows a cross-sectional SEM photograph of the obtained pre-expanded particles. Fig. 2 shows that in Example 3, pre-expanded particles in which changes in cell thickness were suppressed were obtained.

Example 4

Except having changed the quantity of tetrabromocyclooctane into 800 g, it carried out similarly to Example 1, and obtained the expanded molding.

Example 5

Except having changed the immersion temperature into 80 degreeC, it carried out similarly to Example 2, and obtained the foaming molding.

Example 6

Except having changed the immersion temperature into 100 degreeC, it carried out similarly to Example 2, and obtained the foaming molding.

Example 7

Except having changed the immersion temperature into 110 degreeC, it carried out similarly to Example 2, and obtained the foaming molding.

Example 8

Except not adding dicumyl peroxide, the same procedure as in Example 3 was carried out to obtain a foamed molded body.

Example 9

Except having used 2.2 g of α-olefin sulfonate instead of sodium dodecylbenzenesulfonate, it carried out similarly to Example 5, and obtained the expanded molded body.

Example 10

Except having changed the immersion temperature into 110 degreeC, it carried out similarly to Example 9, and obtained the foaming molding.

Example 11

Except that the tricalcium phosphate was changed from TCP-10 produced by Ohira Chemical Co., Ltd. to C13-09 produced by Budenheim Co., the same procedure as in Example 2 was carried out to obtain a foamed molded body.

Example 12

A foamed molded body was obtained in the same manner as in Example 2 except that 85 g of magnesium pyrophosphate was used instead of tricalcium phosphate.

Example 13

A foam molding was obtained in the same manner as in Example 3 except that 85 g of magnesium pyrophosphate was used instead of tricalcium phosphate.

Comparative example 1

Except having changed the quantity of tetrabromocyclooctane into 80 g, it carried out similarly to Example 1, and obtained the expanded molding.

Comparative example 2

Except having changed the quantity of tetrabromocyclooctane into 160g, it carried out similarly to Example 1, and obtained the expanded molding.

Comparative example 3

Except having changed the immersion temperature into 115 degreeC, it carried out similarly to Example 2, and obtained the foaming molding.

Comparative example 4

Except having changed the quantity of tetrabromocyclooctane into 1200g, it carried out similarly to Example 1, and obtained the expanded molding. Fig. 3 shows a cross-sectional SEM photograph of the obtained pre-expanded particles. Figure 3 shows that because the amount of flame retardant used in Comparative Example 4 is larger, the bubbles are smaller.

Comparative example 5

Styrene resin particles were obtained in the same manner as in Example 1 except that tetrabromocyclooctane was not added. The obtained styrene resin particles were classified into particles of 0.6 mm to 0.7 mm.

Except that 10 g of tetrabromocyclooctane was added to the aqueous medium under stirring at 300 rpm, the foamed molding was obtained in the same manner as in Example 1. Fig. 4 shows a cross-sectional SEM photograph of the obtained pre-expanded particles. Figure 4 shows that because more flame retardant exists in the surface region in Comparative Example 5, the size of the bubbles in the surface layer is smaller, while the size of the bubbles in the central region is larger, resulting in a change in the thickness of the bubbles.

Comparative example 6

Styrene resin particles were obtained in the same manner as in Example 1 except that tetrabromocyclooctane was not added. The obtained styrene resin particles were classified into particles of 0.6 to 0.7 mm.

Except that 30 g of tetrabromocyclooctane was added to the aqueous medium under stirring at 300 rpm, a foamed molded article was obtained in the same manner as in Example 1. Fig. 5 shows a cross-sectional SEM photograph of the obtained pre-expanded particles. Figure 5 shows that because more flame retardant exists in the surface region in Comparative Example 6, the size of the bubbles in the surface layer is smaller, while the size of the bubbles in the central region is larger, resulting in a change in the thickness of the bubbles.

Table 1 shows the flame retardancy, average cell size, and thermal fusion properties of the block-shaped foamed molded articles obtained in Examples 2 to 13 and Comparative Examples 1 to 6.

Table 1 shows that by using a specific amount of a specific flame retardant and setting the temperature of impregnation with a physical blowing agent to a specific temperature, it is possible to provide an expandable styrene-based resin particle, which when expanded It has excellent thermal fusion properties and allows the production of foam moldings with excellent flame retardancy.

The content of tetrabromocyclooctane in the surface layer part and the whole of the expandable styrene-based resin particles obtained in Examples 1 to 13 and Comparative Examples 1-6 were measured as follows, and the results are shown in Table 1. middle.

(Measuring method of content rate of tetrabromocyclooctane)

Cut the surface of the foamed 50-fold molded body into sheets with a thickness of 0.2 mm, a length of 20 cm, and a width of 20 cm with a slicer (FK-4N produced by Fujishima Koki Co., Ltd.), and then process it as a flame-retardant foamable The surface part of the styrene resin particle. The tetrabromocyclooctane content of the cut surface was measured. The measurement of the content rate of tetrabromocyclooctane was carried out by the series analysis method (thin film method) using a fluorescent X-ray analyzer (RIX-2100 manufactured by Rigaku Corporation). Specifically, 2 to 3 g of the cut surfaces were hot-pressed at 200 to 230° C. to prepare a film with a thickness of 0.1 mm to 1 mm, a length of 5 cm, and a width of 5 cm. The weight of the film was measured to calculate the basis weight, and the amount of Br was calculated from the X-ray intensity by series analysis using C ₈ H ₈ as the balance component. Since the percentage of Br contained in tetrabromocyclooctane is 75%, the amount of tetrabromocyclooctane in the film can be calculated from the obtained amount of Br. The calculation result was made into the tetrabromocyclooctane content rate contained in the surface layer part of the flame-retardant expandable styrene resin particle.

The content rate of tetrabromocyclooctane contained in the flame-retardant expandable styrene resin particle in the whole is the same as the addition amount at the time of immersion of tetrabromocyclooctane.

Figure 2 shows the content of tetrabromocyclooctane contained in the surface layer and the whole of the flame-retardant expandable styrene resin particles, and the content of tetrabromocyclooctane contained in the surface layer and the content of the whole. The ratio of tetrabromocyclooctane content.

Table 2

Overall TBCO content "b" (wt%) TBCO content in the surface layer "a" (wt%) Surface area/whole ratio of TBCO content b×1.1 Example 1 0.50 0.49 0.98 0.55 Example 2 1.00 1.01 1.01 1.1 Example 3 1.50 1.52 1.01 1.65 Example 4 2.00 2.01 1.01 2.2 Example 5 1.00 0.99 0.99 1.1 Example 6 1.00 1.03 1.03 1.1 Example 7 1.00 1.01 1.01 1.1 Example 8 1.50 1.50 1.00 1.65 Example 9 1.00 1.01 1.01 1.1 Example 10 1.00 1.00 1.00 1.1 Example 11 1.00 1.00 1.00 1.1 Example 12 1.00 0.99 0.99 1.1 Example 13 1.50 1.55 1.03 1.65 Comparative example 1 0.20 0.20 1.00 0.22 Comparative example 2 0.40 0.41 1.01 0.44 Comparative example 3 1.00 1.01 1.01 1.1 Comparative example 4 3.00 2.95 0.98 3.3 Comparative example 5 0.50 0.56 1.12 0.55 Comparative example 6 1.50 1.71 1.14 1.65

Table 2 shows that an expandable styrene-based resin particle satisfying the formula "a"≦1.1×"b", which has excellent thermal fusion between particles when expanded and Allows the production of foam moldings with excellent flame retardancy. Table 2 also shows that, on the other hand, the foam moldings in Comparative Examples 5 and 6 that do not satisfy this formula are poor in thermal fusion and/or flame retardancy.

Claims (7)

1. method for preparing the resin particle of the foamable styrene-based of flame retardant resistance, described method comprises: the described styrene monomer that adds with respect to 100 weight parts in the suspension polymerization of styrene monomer is the tetrabromo cyclooctane of 0.45 weight part to 2.0 weight part, to obtain the resin particle of styrene-based; And then, during the suspension polymerization of described styrene monomer or flood afterwards the resin particle of described styrene-based with pneumatogen, simultaneously dipping temperature is adjusted to 80 to 110 ℃, to obtain the resin particle of the foamable styrene-based of described flame retardant resistance

Wherein said suspension polymerization is carried out in the presence of tensio-active agent.

2. the method for the resin particle of the foamable styrene-based of preparation flame retardant resistance according to claim 1, wherein said styrene monomer also contains flame retardant.

3. the method for the resin particle of the foamable styrene-based of preparation flame retardant resistance according to claim 2, wherein said flame retardant is selected from cumene hydroperoxide, dicumyl peroxide, tertbutyl peroxide and 2,3-dimethyl-2,3-diphenyl butane.

4. according to claim 2 or the method for the resin particle of the foamable styrene-based of 3 described preparation flame retardant resistances, the consumption of wherein said flame retardant is 0.1 weight part to 0.5 weight part with respect to the described styrene monomer of 100 weight parts.

5. the method for the resin particle of the foamable styrene-based of each described preparation flame retardant resistance according to claim 1～3, wherein regulate described dipping temperature, so that the resin particle by making the foamable styrene-based of described flame retardant resistance can have the average bubble size of 50 μ m to 350 μ m with 50 times the blowing ratio expanded moldings that obtains that foams.

6. the method for the resin particle of the foamable styrene-based of each described preparation flame retardant resistance according to claim 1～3, wherein said styrene monomer is selected from vinylbenzene, alpha-methyl styrene, p-methylstyrene, t-butyl styrene and Benzene Chloride ethene.

7. the resin particle of the foamable styrene-based of flame retardant resistance, it comprises: the resin particle of styrene-based, and be contained in pneumatogen and tetrabromo cyclooctane in the resin particle of described styrene-based;

When the weight percent containing ratio of the contained tetrabromo cyclooctane in the rim surface zona of the resin particle of described styrene-based is " a ", when the weight percent containing ratio of contained tetrabromo cyclooctane was " b " in the integral body of the resin particle of described styrene-based, contained tetrabromo cyclooctane satisfied relational expression " a "≤1.1 * " b " in the resin particle of described styrene-based;

The amount of contained tetrabromo cyclooctane is 0.45 weight part to 2.00 weight part with respect to the resin particle of the described styrene-based of 100 weight parts in the integral body of the resin particle of described styrene-based; And

When the resin particle of the foamable styrene-based of described flame retardant resistance foamed with 50 times blowing ratio, it was the foam of 50 μ m to 350 μ m that average bubble size is provided.

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