JP2009203417A - Modified polystyrene-based resin pre-expanded particles, and acoustic modified polystyrene-based resin expansion-molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide modified polystyrene-based resin pre-expanded particles that can exhibit the excellent weldability and can give the expansion-molded item which is excellent in chemical resistance and bending strength and which has voided parts. <P>SOLUTION: The modified polystyrene-based resin for producing its pre-expanded particles is obtained by impregnating polyolefin-based resin particles with styrene-based monomers followed by polymerizing, and contains a polystyrene-based resin of 100-500 pts.wt. based on 100 pts.wt. of the polyolefin-based resin. The modified polystyrene-based resin has a ratio of the absorbance D<SB>698</SB>at 698 cm<SP>-1</SP>to the absorbance D<SB>2850</SB>at 2,850 cm<SP>-1</SP>of 0.1-2.5 and a gel fraction of 15-50 wt.%. The pre-expanded particles of the modified polystyrene-based resin are formed by impregnating the particle of the above resin with a hydrocarbon-based foaming agent and then pre-expanding them. The pre-expanded particle contains a residual foaming agent of 0.3-2.5 wt.% and has a bulk density of 0.012-0.20 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to modified polystyrene resin pre-expanded particles and a modified polystyrene resin expanded foam obtained using the same.

  Conventionally, a foam has been used as a sound absorbing material by forming a void in the foam. As a styrene-modified polyolefin resin foam molded article having such voids, Patent Document 1 discloses that styrene-modified polyolefin resin foam pieces are heat-foamed and thermally fused together, and 10 to 10 between the pieces. A styrene-modified polyolefin resin foam molding having 40% voids is disclosed.

  However, in order to form a porosity of 10 to 40% in the foamed molded product, it is necessary to suppress secondary foaming during molding. As a result, the foaming pressure of the foam small pieces is reduced, and the heat between the foam small pieces is reduced. There was a problem that the fusing property was lowered and the mechanical strength of the obtained foamed molded article was low.

Patent Document 2 discloses that the bulk density is 0.012 to 0.20 g / cm ³ and 698 cm ⁻¹ and 2850 cm ⁻ obtained from the infrared absorption spectrum of the particle surface measured by ATR infrared spectroscopy. Styrene modification in which the absorbance ratio at ¹ (D ₆₉₈ / D ₂₈₅₀ ) is in the range of 0.1 to 2.5 and contains 100 to 1000 parts by weight of styrene resin component with respect to 100 parts by weight of polyolefin resin component A foam-molded article obtained by foam-molding polyolefin resin pre-expanded particles and having a porosity of 5 to 50% has been proposed.

  However, as with the foamed molded product of Patent Document 1, this foamed molded product also has a problem that the heat-fusibility between the pre-expanded particles is low, and the resulting foamed molded product has low mechanical strength.

  Furthermore, Patent Document 3 describes that the gel fraction is contained in the base resin in an amount of 2 to 40% by weight (page 11, line 11), but Patent Document 3 has no voids. Only the foam is described, and a foam having voids cannot be obtained only by adjusting the gel fraction.

Japanese Patent Laid-Open No. 7-80873 WO 2004/085528 JP 2006-88456 A

  The present invention is a modified polystyrene resin pre-expanded particle (hereinafter referred to as “modified polystyrene-based resin pre-expanded particle”) that exhibits excellent heat-fusibility in in-mold foam molding, and is capable of obtaining a foam molded article having excellent chemical resistance and bending strength and having voids. (Sometimes abbreviated as “pre-expanded particles”) and a sound-absorbing modified polystyrene-based resin foam molded article (hereinafter referred to as “foam molded article”) obtained by using this modified polystyrene resin pre-expanded particle. Provide).

The modified polystyrene resin pre-expanded particles of the present invention are obtained by impregnating and polymerizing a polyolefin resin particle with a styrene monomer, and 100 to 500 parts by weight of a polystyrene resin per 100 parts by weight of the polyolefin resin. Ratio of absorbance D _{698 at 698} cm ⁻¹ and absorbance D _{2850 at 2850} cm ⁻¹ obtained from the infrared absorption spectrum of the particle surface containing the modified polystyrene resin contained and measured by ATR infrared spectroscopy (D ₆₉₈ / D ₂₈₅₀ ) is 0.1 to 2.5, and a modified polystyrene resin particle having a gel fraction of 15 to 50% by weight is impregnated with a hydrocarbon foaming agent and then pre-foamed. The residual foaming agent is contained in an amount of 0.3 to 2.5% by weight, and the bulk density is 0.012 to 0.20 g / cm ³ .

  The modified polystyrene resin constituting the modified polystyrene resin pre-expanded particles is obtained by impregnating and polymerizing polyolefin resin particles with a styrene monomer. The polyolefin resin constituting the polyolefin resin particles is not particularly limited. For example, branched low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, Polyethylene resins such as ethylene-methyl methacrylate copolymer, polypropylene resins such as propylene homopolymer, ethylene-propylene random copolymer, propylene-1-butene copolymer, ethylene-propylene-butene random copolymer Polyethylene-based resin is preferable, and high-density polyethylene is more preferable.

  The polyolefin-based resin particles are produced in a known manner. For example, the polyolefin-based resin is supplied to an extruder, melt-kneaded, extruded into a strand, and the strand is cut at predetermined intervals to obtain polyolefin-based resin particles. Obtainable. The strand may be cut immediately after being extruded from the extruder or after a predetermined time has elapsed, or after the strand is cooled with water or the like. The polyolefin resin particles may contain additives such as a colorant, a flame retardant, an antioxidant, and an ultraviolet absorber as necessary.

  The styrene monomer impregnated in the polyolefin resin particles is not particularly limited. For example, styrene, α-methyl styrene, vinyl toluene, chlorostyrene, ethyl styrene, isopropyl styrene, t-butyl styrene, dimethyl styrene. Etc.

  Next, a procedure for producing modified polystyrene resin particles by impregnating and polymerizing polyolefin resin particles with a styrene monomer will be described. First, polyolefin resin particles are dispersed in an aqueous medium containing a dispersant, and then a styrene monomer and a polymerization initiator are added to prepare a dispersion. As will be described later, the styrenic monomer is added to the aqueous medium in two portions, and if necessary, the styrenic monomer to be added first and the first styrenic monomer, The styrene monomer added at the second time is referred to as a second styrene monomer for distinction.

  The first styrene monomer and the polymerization initiator may be mixed in advance. Examples of the aqueous medium include lower alcohols such as methyl alcohol and ethyl alcohol, water, and the like, and water is preferable.

  The dispersant is not particularly limited, and examples thereof include poorly water-soluble inorganic substances such as calcium phosphate, magnesium pyrophosphate, sodium pyrophosphate, and magnesium oxide, and surfactants such as sodium dodecylbenzenesulfonate.

  If the amount of the first styrene monomer added to the aqueous medium is small, the amount of the second styrene monomer will increase, and a large amount of polystyrene resin will be distributed on the surface layer of the resin particles. While mechanical strength and chemical resistance such as impact strength and bending strength of the body may be reduced, if it is large, it may not be absorbed by the polyolefin resin particles, and a large amount of polymer powder of polystyrene resin may be generated. Therefore, 10-80 weight part is preferable with respect to 100 weight part of polyolefin resin particles.

  The polymerization initiator is not particularly limited as long as it is conventionally used in seed polymerization, and examples thereof include benzoyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, and dicumyl peroxide. 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butylperoxy-3,5,5-trimethylhexanoate, t-butyl-peroxy-2-ethylhexyl carbonate, etc. Or two or more of them may be used in combination.

  When the amount of the polymerization initiator added to the aqueous medium is too small, it takes too much time to polymerize the styrene monomer. On the other hand, when the amount is large, the molecular weight of the resulting polystyrene resin is lowered. 0.1-1.5 weight part is preferable with respect to 100 weight part of a system monomer, and 0.3-0.6 weight part is more preferable.

  Next, after heating the obtained dispersion to a temperature at which the first styrene monomer does not substantially polymerize and impregnating the polyolefin resin particles with the first styrene monomer, polymerization of the dispersion is started. The first styrene monomer is polymerized in the polyolefin resin particles by heating above the decomposition temperature of the agent.

  Subsequently, the second styrene monomer is added to the dispersion and polymerized while impregnating the polyolefin resin particles with the second styrene monomer to obtain modified polystyrene resin particles. it can.

  If the amount of the second styrene monomer added to the dispersion is small, the amount of the first styrene monomer will increase and will not be absorbed by the polyolefin resin particles, and there will be a large amount of polymerized powder of polystyrene resin. On the other hand, if the amount is large, a large amount of polystyrene-based resin is distributed on the surface layer of the resin particles, and mechanical strength and chemical resistance such as impact strength and bending strength of the obtained foamed molded product may be lowered. Therefore, 50-200 weight part is preferable with respect to 100 weight part of polyolefin resin particles.

  The total amount of the styrene monomer added to the dispersion is 100 to 500 parts by weight of the polystyrene resin component with respect to 100 parts by weight of the polyolefin resin component in the resulting modified polystyrene resin. Specifically, 150 to 250 parts by weight is preferable with respect to 100 parts by weight of the polyolefin resin particles.

  As described above, the weight ratio of the polystyrene resin component to the polyolefin resin component in the modified polystyrene resin is limited to the above ratio, and the content of the polystyrene resin component in the modified polystyrene resin is small. And when the amount of polyolefin resin component increases, the heat resistance increases too much, and when the modified polystyrene resin particles are pre-foamed, they cannot be foamed to the desired bulk density, and the resulting molded foam is lightweight. On the other hand, if the amount is too large, the mechanical strength and chemical resistance of the obtained foamed molded product are impaired.

Then, the ratio between the absorbance D ₂₈₅₀ in the absorbance D ₆₉₈ and 2850 cm ^-1 in the 698cm ^-1 obtained from an infrared absorption spectrum of the surface of the obtained modified polystyrene-based resin (D ₆₉₈ / D ₂₈₅₀₎ (hereinafter "absorbance ratio" Is limited to 0.1 to 2.5, preferably 1.5 to 2.4.

  This is because when the absorbance ratio is low, the ratio of the polyolefin resin on the surface of the modified polystyrene resin particles becomes high, the heat resistance is excessively increased, and when the modified polystyrene resin particles are pre-foamed, the desired volume is increased. This is because the foam cannot be expanded to the density, and the lightweight property of the obtained foamed molded article is impaired.

  On the other hand, when the absorbance ratio is high, the ratio of the polystyrene resin on the surface of the modified polystyrene resin particles is high, and the chemical resistance and impact resistance of the obtained foamed molded product are lowered.

Here, the ratio (D ₆₉₈ / D ₂₈₅₀ ) of the absorbance D _{698 at 698} cm ^{−1 and} the absorbance D _{2850 at 2850} cm ⁻¹ obtained from the infrared absorption spectrum of the surface of the modified polystyrene resin particles is measured as follows. The

The surface of the modified polystyrene resin particles is subjected to particle surface analysis by ATR infrared spectroscopy to obtain an infrared absorption spectrum. The absorbance ratio (D ₆₉₈ / D ₂₈₅₀ ) is calculated from the infrared absorption spectrum. This procedure was performed on 10 of the modified polystyrene resin particles, and the absorbance D ₆₉₈ at 698cm ^-1, in each of the absorbances D ₂₈₅₀ at 2850 cm ^-1, 8 pieces of absorbance additive excluding the minimum and maximum values calculates an average value, and the absorbance D ₆₉₈ at 698cm ^-1, and the absorbance D ₂₈₅₀ at 2850 cm ^-1, can be calculated from these absorbance D _698, D ₂₈₅₀ absorbance ratio (D ₆₉₈ / D _2850). In addition, the particle | grain surface analysis by ATR method infrared spectroscopy can use the measuring apparatus marketed with the brand name "Fourier transform infrared spectrophotometer MAGMA560" from Nicolet, for example.

  In addition, if the gel fraction of the modified polystyrene resin particles is low, even if in-mold foam molding is performed using the modified polystyrene resin pre-foamed particles, a foam molded article having voids cannot be obtained. If it is high, the modified polystyrene resin pre-expanded particles become hard and the softening point of the modified polystyrene resin constituting the modified polystyrene resin pre-expanded particles becomes high, and the modified polystyrene resin particles are pre-expanded. When making it, it cannot be foamed to a desired bulk density, and the lightweight property of the resulting foamed molded article is impaired, so it is limited to 15 to 50% by weight, and preferably 20 to 40% by weight.

Here, the gel fraction of the modified polystyrene resin particles is measured as follows. The weight W ₁ of the modified polystyrene resin particles is measured. Next, the modified polystyrene resin particles are immersed in 100 ml of toluene at 130 ° C. for 24 hours.

Next, the residue in toluene is filtered using an 80-mesh wire mesh, the residue remaining on the wire mesh is dried at 130 ° C. for 1 hour, and the weight W _{2 of} the residue remaining on the wire mesh is measured. The gel fraction of the modified polystyrene resin particles can be calculated based on the following formula.
Gel fraction (% by weight) = 100 × W ₂ / W ₁

  The modified polystyrene resin particles are impregnated with a hydrocarbon foaming agent. In addition, as a procedure for impregnating the modified polystyrene resin particles with the hydrocarbon-based foaming agent, a known procedure is used. Specifically, the modified polystyrene resin particles, the dispersant and water are supplied into the autoclave. Then, the modified polystyrene resin particles are dispersed in water to produce a dispersion, and a hydrocarbon-based foaming agent is injected into the dispersion, and the hydrocarbon-based foam is added to the modified polystyrene resin particles. The method of impregnating a foaming agent is mentioned. The dispersant is not particularly limited, and examples thereof include poorly water-soluble inorganic substances such as calcium phosphate, magnesium pyrophosphate, sodium pyrophosphate, and magnesium oxide, and surfactants such as sodium dodecylbenzenesulfonate. The hydrocarbon-based blowing agent is not particularly limited, and examples thereof include propane, normal butane, isobutane, pentane, isopentane, cyclopentane, and hexane.

  If the amount of the hydrocarbon foaming agent impregnated into the modified polystyrene resin particles is small, the modified polystyrene resin particles may not be pre-foamed. On the other hand, if the amount is large, plasticization by the hydrocarbon foaming agent may be performed. Depending on the effect, the modified polystyrene resin particles may break when foamed, so that the foaming agent is impregnated at a ratio of 15 parts by weight or more with respect to 100 parts by weight of the modified polystyrene resin particles. It is preferably impregnated at a ratio of ˜30 parts by weight, and more preferably impregnated at a ratio of 10 to 20 parts by weight.

  The modified polystyrene resin pre-expanded particles of the present invention are obtained by pre-expanding modified polystyrene resin particles impregnated with a hydrocarbon-based blowing agent. The pre-foaming of the modified polystyrene resin particles may be performed using a general-purpose pre-foaming apparatus.

In addition, if the bulk density of the modified polystyrene resin pre-expanded particles is low, the closed cell ratio of the modified polystyrene resin pre-expanded particles decreases, and the pre-expanded particles shrink during in-mold foam molding, resulting in good foaming. On the other hand, if the molded body cannot be obtained, if it is high, the lightweight property of the obtained foamed molded body is lowered, so that it is limited to 0.012 to 0.20 g / cm ³ , and 0.017 to 0.05 g / cm ^3. preferable.

In addition, the bulk density of the modified polystyrene resin pre-expanded particles refers to that measured in the following manner. First, it filled to the graduation of 500 cm ³ of modified polystyrene-based resin pre-expanded particles in a graduated cylinder of 500 cm ^3. If the graduated cylinder is visually observed from the horizontal direction and any modified polystyrene resin pre-expanded particles have reached the scale of 500 cm ³ , the modified polystyrene resin pre-expanded graduated cylinder at that point End filling in.

Next, the weight of the modified polystyrene resin pre-expanded particles filled in the graduated cylinder is weighed with two significant figures after the decimal point, and the weight is defined as W ₃ (g). Then, the bulk density of the modified polystyrene resin pre-expanded particles is calculated by the following formula.
The bulk density of the modified polystyrene resin pre-expanded particles ^{(g / cm 3) = W} 3/500

  In addition, if the amount of the remaining foaming agent in the modified polystyrene resin pre-expanded particles is small, the heat-fusible property of the resulting foamed molded article is lowered, whereas if it is large, the plasticization of the modified polystyrene resin pre-expanded particles is performed. Since the secondary foaming of the modified polystyrene resin pre-foamed particles becomes too large at the time of in-mold foam molding, a foam molded product having voids cannot be obtained. , 0.3 to 2.5% by weight, preferably 0.5 to 1.5% by weight.

  Here, the content of the remaining foaming agent in the modified polystyrene resin pre-expanded particles can be measured by the following method. The modified polystyrene resin pre-expanded particles are precisely weighed using a measuring basket having a rectangular parallelepiped storage portion of 5 mm in length × 5 mm in width × 35 mm in depth, and these modified polystyrene resin pre-expanded particles are manufactured by Shimadzu Corporation. It is set at the cracking furnace inlet of the pyrolysis furnace PYR-1A, purged with helium for about 15 seconds, and the mixed gas at the time of sample setting is discharged. After sealing, the sample is inserted into a 150 ° C. core and heated for 60 seconds to release gas, and this released gas is quantified using a gas chromatograph GC-14B (detector: TCD) manufactured by Shimadzu Corporation. The measurement conditions were as follows: Polapack Q (80/100) 3 mmφ × 1.5 m manufactured by GL Sciences, Inc., column temperature (100 ° C.), carrier gas (helium), carrier gas flow rate (1 ml / min), The inlet temperature (120 ° C) and the detector temperature (120 ° C) are used.

  Further, when the L / D of the modified polystyrene resin pre-expanded particles is small, the porosity of the obtained foamed molded product may be lowered, and the sound absorption of the foamed molded product may be lowered. Since the filling property may be lowered when the pre-expanded particles are filled in the mold during foam molding, 2 to 4 is preferable.

In addition, L / D of a modified polystyrene resin pre-expanded particle is measured in the following manner. First, the maximum length L ₁ of the pre-expanded particles is measured. Then, assuming a straight line connecting two points on the surface of the pre-expanded particle specified in measuring the maximum length L ₁ , the maximum length L ₂ of the pre-expanded particle is measured in a direction orthogonal to the straight line. To do. L / D of the pre-expanded particles can be calculated based on the following formula.
The pre-expanded particles _{L / D = L 1 / L} 2

  A sound-absorbing modified polystyrene resin foam molded article can be obtained by in-mold foam molding using the modified polystyrene resin pre-expanded particles.

  Specifically, the modified polystyrene resin pre-foamed particles are filled in a mold and a heating medium such as water vapor is supplied into the mold to heat and expand the modified polystyrene resin pre-foamed particles. The foamed particles are thermally fused and integrated with each other by the foaming pressure of the foamed particles to obtain a sound-absorbing modified polystyrene-based resin foam-molded article having voids.

  The modified polystyrene resin pre-expanded particles have an absorbance ratio limited to 0.1 to 2.5, and the content ratio of the polyolefin resin and the polystyrene resin in the surface portion of the pre-expanded particles is optimized, At the time of in-mold foam molding, the pre-foamed particles are thermally fused and integrated with a sufficient foaming pressure without shrinking.

  Moreover, the modified polystyrene resin pre-expanded particles have a gel fraction of 15 to 50% by weight and a residual foaming agent of 0.3 to 2.5% by weight based on the total amount of the pre-expanded particles. It is possible to obtain a sound-absorbing modified polystyrene resin foamed molded article in which foamed particles are firmly heat-sealed and integrated while forming appropriate voids between the foamed particles. Therefore, the obtained foamed molded article is excellent in excellent sound absorption and mechanical strength such as bending strength.

  Furthermore, since the foamed particles constituting the foamed molded product obtained by in-mold foam molding contain a moderate amount of polyolefin resin on the surface, the resulting foamed molded product has chemical resistance and impact resistance. Also excellent in properties.

If the density of the obtained foamed molded product is low, the mechanical strength of the foamed molded product may be reduced. On the other hand, if the density is high, the lightweight property of the foamed molded product may be reduced. preferably ^{0.20g / cm 3, 0.017~0.05g / cm} 3 is more preferable.

The density of the foamed molded product was measured by the method described in JIS K6767: 1999 “Foamed Plastics and Rubber—Measurement of Apparent Density”. That is, a test piece of 50 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) is cut so as not to change the original cell structure of the foamed molded product, and its weight (g) and volume (cm ³ ) are cut. Measure and calculate by the following formula. The test piece was cut out from a foamed molded article that had passed 72 hours or more after molding, and the temperature (23 ° C. ± 2 ° C.) × relative humidity (50% ± 5%) or temperature (27 ° C. ± 2 ° C.) × relative humidity (65%). (± 5%) at room temperature for 16 hours or more.
Density (g / cm ³ ) = Test specimen weight (g) / Test specimen volume (cm ³ )

  Further, when the porosity of the obtained foamed molded product is small, the sound absorbing property of the foamed molded product may be lowered. On the other hand, when the porosity is large, mechanical strength such as bending strength of the foamed molded product may be lowered. Therefore, 5 to 50% is preferable, and 10 to 20% is more preferable.

In addition, the porosity of the foamed molded product was measured according to the measuring method described in ASTM D2856-87. Specifically, five test pieces (cubes each having a side of 25 mm) composed of cut surfaces having no skin such as molding surfaces on all six surfaces were cut out from the foamed molded product, and the apparent volume W _{4 of the} test pieces was measured using calipers. Measure. Next, the volume W ₅ of the test piece is measured by the 1-1 / 2-1 atmospheric pressure method using an air comparison type hydrometer, and the porosity of the foamed molded product can be calculated based on the following formula. In addition, the air comparison type hydrometer can use what is marketed by Tokyo Science company by the brand name "1000 type | mold".
Porosity (%) of foam molded article = 100 × (W ₄ −W ₅ ) / W ₄

  And when the bending bending amount of the obtained foaming molding is small, the compressive strength of the foaming molding may be lowered, whereas when it is large, the bending strength may be lowered, so 10 to 30 mm is preferable.

  In addition, the bending deflection amount of the foamed molded product is measured in accordance with the method described in JIS K9511: 1999 “Foamed plastic heat insulating material”. That is, a rectangular parallelepiped test piece having a length of 75 mm, a width of 300 mm, and a height of 15 mm was cut out from the foamed molded product, and the bending deflection amount of the test piece was measured at a compression speed of 10 mm / min using a Tensilon universal testing machine, Measurement is performed under the conditions of a wedge 10R, a support 10R, and a distance between supporting points of 200 mm. As a Tensilon universal testing machine, what is marketed under the brand name "UCT-10T" from Orientec can be used.

  The foamed molded article obtained as described above can be used for various applications, and in particular, has an air gap and is excellent in sound absorption, as well as heat insulation, light weight and mechanical strength. It can be suitably used for industrial members such as interior materials and building materials.

  Since the modified polystyrene resin pre-expanded particles of the present invention have the above-described configuration, they are strongly heat-fused with an appropriate foaming force while forming an appropriate gap during in-mold foam molding. The foamed molded product thus obtained has excellent sound absorption, mechanical strength such as bending strength and impact resistance, and chemical resistance.

  When the L / D is 2 to 4 in the modified polystyrene resin pre-expanded particles, the foamed molded product obtained using the modified polystyrene resin pre-expanded particles has an appropriate porosity. However, the foamed particles are strongly heat-bonded and integrated with each other, and have excellent sound absorption and mechanical strength.

Example 1
100 parts by weight of high-density polyethylene (manufactured by Tosoh Corporation, manufacturing method described below) is supplied to an extruder, melt-kneaded, extruded into a 0.6 mm diameter strand, and this strand is cut every 2.3 mm. As a result, cylindrical high-density polyethylene particles were obtained.

  The average weight of the high density polyethylene particles was 0.6 mg. Note that the average weight of the high-density polyethylene particles is an arithmetic average value of the weights of 100 high-density polyethylene particles arbitrarily extracted.

  Next, 120 g of magnesium pyrophosphate, 3.0 g of sodium dodecylbenzenesulfonate, and 2.3 kg of pure water were supplied to a 5 liter autoclave equipped with a stirrer and stirred to obtain a dispersion.

  The dispersion was heated to 30 ° C., 500 g of high-density polyethylene particles were dispersed in the dispersion and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.

  Next, after raising the temperature of the suspension to 110 ° C., 1.20 kg of styrene monomer in which 5.6 g of t-butylperoxyisopropyl monocarbonate was dissolved in the suspension was dropped over 6 hours. did. After dropping, the high-density polyethylene particles were impregnated with styrene monomer by holding at 110 ° C. for 1 hour and 30 minutes. After impregnation, the suspension was heated to 140 ° C. and held at this temperature for 2 hours and 30 minutes for polymerization to obtain modified polystyrene resin particles. The high density polyethylene particles were impregnated with the entire amount of styrene monomer.

  Subsequently, the suspension was cooled to room temperature (about 23 ° C.), and the modified polystyrene resin particles were taken out from the autoclave. 1.7 kg of modified polystyrene resin particles and 2.3 liters of water are placed in another 5 liter autoclave with a stirrer, and further 90 g of magnesium pyrophosphate, 1 g of sodium dodecylbenzenesulfonate, and 15 g of dicumyl peroxide as a cross-linking agent. (3.0 parts by weight with respect to 100 parts by weight of the high-density polyethylene particles) was fed into the autoclave.

  Thereafter, the inside of the autoclave was heated to 143 ° C., and stirring was continued for 2 hours and 30 minutes to adjust the gel fraction of the modified polystyrene resin particles.

  Subsequently, the suspension was cooled to room temperature (about 23 ° C.), and the modified polystyrene resin particles were taken out from the autoclave. 1.7 kg of modified polystyrene resin particles and 2.3 liters of water are placed in another 5 liter autoclave with a stirrer, and further 2 g of sodium dodecylbenzenesulfonate as a dispersant, 26 g of cyclohexane as a plasticizer, and as a foaming agent 255 g of butane [normal butane / isobutane (weight ratio) = 70/30] (15 parts by weight with respect to 100 parts by weight of the modified polystyrene resin particles) was supplied into the autoclave.

  Thereafter, the temperature inside the autoclave was raised to 70 ° C. and stirring was continued for 4 hours, whereby the modified polystyrene resin particles were impregnated with butane to obtain expandable resin particles. Next, the inside of the autoclave was cooled to room temperature, the expandable resin particles were taken out from the autoclave, and the expandable resin particles were dehydrated and dried.

Next, the obtained expandable resin particles were supplied to a prefoaming device and prefoamed to obtain modified polystyrene resin prefoamed particles having a bulk density of 0.033 g / cm ³ . The obtained pre-expanded particles were left at 60 ° C. for 6 days. The amount of residual butane in the modified polystyrene resin pre-expanded particles was 1.2% by weight.

Then, the modified polystyrene resin pre-expanded particles were filled in a rectangular parallelepiped molding die having a length of 400 mm, a width of 300 mm, and a height of 30 mm. Next, after introducing 0.12 MPa of water vapor into the molding die for 50 seconds and heating to pre-expand the secondary foamed particles, the maximum surface pressure of the foamed molded product is reduced to 0.01 MPa. To obtain a foamed molded product having a density of 0.033 g / cm ³ . Both the appearance of the obtained foamed molded product and the thermal fusion between the foamed particles were good.

  The manufacturing method of the high density polyethylene used above is demonstrated below. In addition, the following manufacture was performed in inert gas atmosphere, and the used raw material and solvent used what was refine | purified previously, dried, and deoxygenated by the well-known method. As component a and component c, those synthesized by a known method were used. As the hexane solution (0.714M) of triisobutylaluminum, one commercially available from Tosoh Finechem Co., Ltd. was used.

[Preparation of clay mineral (component b) treated with organic compound]
To 3 liters of water, 3 liters of ethanol and 250 liters of 37 wt% concentrated hydrochloric acid were added. After adding 330 g (1.1 mol) of N, N-dimethyl-octadecylamine to the resulting solution, the solution was heated to 60 ° C. By this heating, the amine was converted into hydrochloric acid. 1 kg of hectorite was added to the resulting solution to obtain a suspension. The suspension was stirred at 60 ° C. for 3 hours, and the supernatant was removed. The denatured hectorite was washed with 5 liters of water at 60 ° C. Further, the modified hectorite (component) having an average particle size of 4.5 μm was obtained by drying the modified hectorite at 60 ° C. and 10 ⁻³ torr (about 0.13 Pa) for 24 hours and then pulverizing with a jet mill. b) was obtained.

[Adjustment of macromonomer production catalyst]
6.97 g (20 mmol) of dimethylsilanediylbis (cyclopentadienyl) zirconium dichloride (component a) was suspended in 2.07 liters of hexane. A contact product of component a and triisobutylaluminum was obtained by adding 2.93 liters of a hexane solution (0.714M) of triisobutylaluminum to the obtained suspension. 500 g of the modified hectorite (component b) was added to the solution containing the contact product. The resulting solution was stirred at 60 ° C. for 3 hours, allowed to stand, the supernatant was removed, and the residue was washed with a triisobutylaluminum heptane solution (0.03M). Further, a hexane solution (0.15 M) of triethylaluminum was added to the washed product to obtain a catalyst slurry (100 g / liter).

[Manufacture of macromonomer]
After supplying 30 liters of hexane, 290 g of butene-1 and 25 milliliters of a hexane solution of triisobutylaluminum (0.714 mol / liter) to a 50 liter autoclave, the temperature inside the autoclave was raised to 75 ° C. 125 ml of the catalyst slurry was added to the autoclave, and a hydrogen / ethylene mixed gas (0.65 mmol / 1 mol) was supplied until the ethylene partial pressure reached 1.2 MPa, followed by heating to 90 ° C. to initiate polymerization. did. During the polymerization, a hydrogen / ethylene mixed gas was continuously introduced so that the partial pressure of ethylene was maintained at 1.2 MPa.

  After 90 minutes from the start of the polymerization, the temperature inside the autoclave was lowered to 50 ° C., the pressure inside the autoclave was reduced to 0.1 MPa, and then nitrogen was injected until the internal pressure of the autoclave reached 0.6 MPa. This operation was repeated 5 times to obtain a macromonomer. The number average molecular weight Mn of the macromonomer was 8000, and the weight average molecular weight Mw / number average molecular weight Mn was 2.1. When the terminal structure of the macromonomer was analyzed by NMR, Z was 0.70.

[Manufacture of polyolefin resin]
Further, 25 ml of a hexane solution (0.714 mmol / liter) of triisobutylaluminum was supplied to a 50 liter autoclave containing the macromonomer, and then the inside of the autoclave was raised to 85 ° C. After stirring for 30 minutes while maintaining this temperature, diphenylmethylene (1-cyclopentadienyl) (2,7-di-tert-butyl-9-fluorenyl) zirconium dichloride (component c) 0. 0.5 liter of 25 mmol toluene solution was added. After the addition, the mixture was stirred for 1 hour while maintaining the temperature at 85 ° C.

  Next, 25 g of butene-1 was added into the autoclave, and a hydrogen / ethylene mixed gas (0.65 mmol / 1 mol) was introduced until the ethylene partial pressure reached 0.1 MPa to initiate polymerization. During the polymerization, a hydrogen / ethylene mixed gas was continuously introduced so that the partial pressure of ethylene was maintained at 0.1 MPa. The polymerization temperature was maintained at 85 ° C. 180 minutes after the start of the polymerization, the inside of the autoclave was decompressed, and the contents were suction filtered and dried to obtain 4.2 kg of high density polyethylene.

The obtained high-density polyethylene has a weight average molecular weight Mw of 88000, a weight average molecular weight Mw / number average molecular weight Mn of 5.0, and the ratio of the newly generated resin amount to the total resin amount is 23% by weight. there were. The obtained high-density polyethylene has a melt flow rate (MFR) of 8.0 g / 10 min, a density of 0.944 g / cm ³ , a crystallinity of 62%, a melt tension of 33 mN, and 110-100 ×. The log MFR was 20 mN, and the contraction factor was 0.90 g ′.

(Examples 2 to 5)
Except that the gel fraction of the modified polystyrene resin pre-expanded particles and the amount of residual butane gas are the values shown in Table 1, in-mold foam molding was performed in the same manner as in Example 1 to obtain a foam molded article. .

  The gel fraction is adjusted by the addition amount of dicumyl peroxide as a crosslinking agent (addition amount with respect to 100 parts by weight of the high-density polyethylene particles), and the residual butane gas amount is adjusted by adding butane [normal butane / isobutane ( Weight ratio) = 70/30] (addition amount with respect to 100 parts by weight of the modified polystyrene resin particles). The amount of each added is shown in Table 1 in parts by weight.

(Example 6)
The strand was cut every 1.2 mm to produce cylindrical high-density polyethylene particles, and the same procedure as in Example 1 was performed except that the L / D of the modified polystyrene resin pre-foamed particles was adjusted to 1. In-mold foam molding was performed to obtain a foam molded article.

(Example 7)
In-mold foaming in the same manner as in Example 1 except that the amount of polystyrene in the modified polystyrene resin constituting the modified polystyrene resin particles is 150 parts by weight with respect to 100 parts by weight of high-density polyethylene. Molding was performed to obtain a foamed molded body.

(Example 8)
Example except that ethylene-vinyl acetate copolymer was supplied instead of supplying high-density polyethylene to the extruder, and 0.08 MPa water vapor was introduced into the molding die for 50 seconds to perform in-mold foam molding. In-mold foam molding was performed in the same manner as 1 to obtain a foam molded body. In Table 1, the amount of “ethylene-vinyl acetate copolymer” in the modified polystyrene resin is shown in the column of “High density polyethylene” for convenience.

Example 9
The strand was cut every 2.8 mm to produce cylindrical high-density polyethylene particles, and the L / D of the modified polystyrene resin pre-expanded particles was adjusted to 4 in the same manner as in Example 1. In-mold foam molding was performed to obtain a foam molded article.

(Comparative Example 1)
In-mold foam molding was performed in the same manner as in Example 1 except that the gel fraction of the modified polystyrene resin pre-expanded particles was 3.8% by weight to obtain a foam molded article. The foamed molded article was inferior in sound absorption due to its low porosity.

(Comparative Example 2)
In-mold foam molding was performed in the same manner as in Example 1 except that the gel fraction of the modified polystyrene resin pre-expanded particles was 55.0% by weight to obtain a foam molded article. Since the degree of cross-linking of the surface of the pre-foamed particles is high, the heat-fusability between the foam particles obtained by foaming the pre-foamed particles is lowered, and only a foam-molded product having an inferior bending deflection can be obtained.

(Comparative Example 3)
In-mold foam molding was performed in the same manner as in Example 1 except that the amount of residual butane in the modified polystyrene resin pre-expanded particles was 0.2% by weight to obtain a foam molded article. Since the amount of residual butane in the pre-foamed particles is low, secondary foaming of the pre-foamed particles hardly occurs in the in-mold foam molding, and the heat-fusibility between the foamed particles obtained by foaming the pre-foamed particles is poor, Only foam-molded products with inferior bending deflection were obtained.

(Comparative Example 4)
In-mold foam molding was performed in the same manner as in Example 1 except that the amount of residual butane in the modified polystyrene resin pre-expanded particles was 3.0% by weight to obtain a foam molded article. Since the amount of residual butane in the pre-foamed particles is high, foaming of the pre-foamed particles occurs more than necessary, and only a foam molded product with a low porosity can be obtained, and the obtained foam molded product has poor sound absorption Met.

(Comparative Example 5)
In-mold foaming in the same manner as in Example 1 except that the amount of polystyrene in the modified polystyrene resin constituting the modified polystyrene resin particles is 50 parts by weight with respect to 100 parts by weight of high-density polyethylene. An attempt was made to obtain a foam molded article by molding, but the pre-foamed particles did not foam, and a foam molded article could not be obtained.

(Comparative Example 6)
In-mold foaming in the same manner as in Example 1, except that the amount of polystyrene in the modified polystyrene resin constituting the modified polystyrene resin particles is 650 parts by weight with respect to 100 parts by weight of high-density polyethylene. Molding was performed to obtain a foamed molded body. Since the amount of polystyrene in the modified polystyrene resin constituting the pre-expanded particles is high, the expansion of the pre-expanded particles occurs more than necessary, and only a foamed molded article having a low porosity can be obtained. The foamed molded product was inferior in sound absorption.

The absorbance ratio (D ₆₉₈ / D ₂₈₅₀ ) and gel fraction of the resulting modified polystyrene resin particles and the residual butane amount and bulk density of the modified polystyrene resin pre-expanded particles were measured, and the results are shown in Table 1. It was shown to. Furthermore, the density, bending deflection amount, porosity and sound absorption coefficient of the obtained foamed molded article were measured, and the results are shown in Table 1.

(Sound absorption rate)
The sound absorption coefficient of the foamed molded article was measured in accordance with the method described in JIS A1405: 1998 “Acoustics—Measurement of sound absorption coefficient and impedance by impedance tube—standing wave ratio method”. Specifically, the sound absorption coefficient of 0 to 6 kHz was measured using a vertical incident sound absorption coefficient measuring device TYPE10041 (Frobe Probe Microphone) manufactured by Electronic Instruments. Table 1 shows the value of the sound absorption coefficient at 1 kHz. The sample was 30 mm thick, and was measured by being in close contact with the back plate of the sample holder.

Claims (3)

A modified polystyrene resin obtained by impregnating and polymerizing polyolefin resin particles with a styrene monomer and containing 100 to 500 parts by weight of a polystyrene resin with respect to 100 parts by weight of the polyolefin resin. The ratio (D ₆₉₈ / D ₂₈₅₀ ) of absorbance D _{698 at 698} cm ⁻¹ and absorbance D _{2850 at 2850} cm ⁻¹ obtained from the infrared absorption spectrum of the particle surface measured by infrared spectroscopy is 0.1 to 2.5. In addition, the modified polystyrene resin particles having a gel fraction of 15 to 50% by weight are impregnated with a hydrocarbon foaming agent and pre-foamed, and the remaining foaming agent is 0.3 to 2.5. Modified polystyrene-based resin pre-expanded particles having a weight percentage and a bulk density of 0.012 to 0.20 g / cm ³ . Modified polystyrene resin pre-expanded particles, wherein L / D is 2-4. The modified polystyrene resin pre-expanded particles according to claim 1 or 2 are filled in a mold and subjected to foam molding, and the density is 0.012 to 0.20 g / cm ³ and the porosity is 5 to 5. A sound-absorbing modified polystyrene-based resin foam-molded article having 50% and a bending deflection of 10 to 30 mm.