JP5154194B2 - Polypropylene resin foam particles - Google Patents

Description

  The present invention relates to expanded polypropylene resin particles. Specifically, the present invention relates to expanded polypropylene resin particles that can be used favorably as a raw material for an in-mold expanded molded article.

  In-mold foam moldings obtained by filling polypropylene resin foam particles in molds and heat-molding with water vapor are the advantages of in-mold foam moldings, such as shape flexibility, lightness, and heat insulation. have. In addition, compared with in-mold foam molded products using similar synthetic resin foam particles, for example, compared to in-mold foam molded products obtained using polystyrene resin foam particles, chemical resistance, heat resistance, post-compression strain The recovery rate is excellent, and the dimensional accuracy, heat resistance, and compressive strength are excellent as compared with the in-mold foam-molded article using the polyethylene resin expanded particles. Due to these characteristics, in-mold foam molded articles obtained using polypropylene resin foam particles are used in various applications such as heat insulating materials, shock-absorbing packaging materials, automobile interior members, and automobile bumper core materials.

  In the case of a relatively high-magnification foamed molded product with a foaming ratio of 20 to 50 times when filled in a mold that can close the polypropylene-based resin expanded particles but cannot be sealed, and heat-molded with steam, Since the strength of the foamed molded product is weakened, there is a problem that, after molding, when the inside of the molded product cell is depressurized, it is pressed by the atmospheric pressure to cause contraction and deformation. In particular, when used for a buffer packaging material, the magnification is often 30 to 50 times. Therefore, after molding, a so-called curing process is required in which the molded body is placed in a drying chamber at 60 to 80 ° C. to recover shrinkage and deformation. Conventionally, this curing requires 20 to 24 hours, requires a large curing space and energy costs, and is a serious problem in terms of productivity.

Patent Document 1 discloses polypropylene-based resin expanded particles using a propylene-based random copolymer or random block copolymer as a base resin, and a melt flow index required from the expanded particles is 0.5 to 6 g / 10. DSC curve obtained by differential scanning calorimetry, wherein Z average molecular weight (polystyrene conversion) is 1.2 × 10 ⁶ or more, melting point is 130 ° C. or more, provided that 1 to 3 mg of foamed particles is 10 ° C. / Two or more endothermic peaks appear in the DSC curve obtained when the temperature is raised from room temperature to 200 ° C. at a temperature rising rate of minutes, and the endothermic energy of the endothermic peak appearing on the higher temperature side than the intrinsic peak among these endothermic peaks. 1 to 20 J / g of polypropylene-based resin foamed particles have good shrinkage recovery characteristics even without applying internal pressure, and molded Cycle, moldings curing recovery time is short, it is disclosed that good production efficiency. In the method described in Patent Document 1, the obtained foamed particles are formed into a plate-shaped molded body, and the shrinkage ratio of the plate-shaped molded body with respect to the mold dimensions (the mold dimensional shrinkage ratio) is evaluated. However, even if the shrinkage ratio with respect to the mold size in the case of a plate-shaped molded body is good, the molded body has an opening as in the case of a box-shaped molded body and is more easily deformed than the plate-shaped bottom surface. In some cases, it is not sufficient to reduce the deformation rate of the molded body only by improving the mold shrinkage ratio of the plate-shaped molded body.

On the other hand, in Patent Document 2, for the purpose of obtaining expanded particles with high expansion ratio and small expansion ratio variation, polypropylene resin expanded particles include ethylene and / or butene as comonomer components in the resin. -1 is 3 to 10% by weight, the ratio Mz / Mw of the Z-average molecular weight Mz to the weight-average molecular weight Mw of the resin is in the range of 1.5 to 2.5, and the resin foam particles have melting energy. Polypropylene-based resin expanded particles having a secondary crystal of 11 to 30 J / g are disclosed.
JP 2000-198872 A JP-A-8-259724

  An object of the present invention is to provide an in-mold foam molded article obtained by filling polypropylene resin expanded particles in a mold and heat-molding with water vapor. It is to obtain an excellent molded article.

As a result of intensive studies to solve the above problems, the inventors of the present application have determined that the polypropylene resin has a Mz / Mw within a specific range, a Z average molecular weight within a specific range, and a melt flow rate within a specific range. In the presence of a foaming agent in a pressure-resistant container, polypropylene resin particles having a base resin as a base resin are dispersed in water together with a dispersant, etc., heated to a predetermined foaming temperature under pressure, and then dispersed in the pressure-resistant container. By forming a polypropylene resin foamed particle having two melting peaks in the DSC curve obtained by releasing the product into a low pressure region, the mold shrinkage ratio of the molded product is sufficiently small in a relatively short curing time. Furthermore, it has been found that even a molded body having a shape such as a box shape that is easily deformed can be obtained with a molded body having a small molded body deformation rate and excellent surface properties with less wrinkles. This has led to the completion of the present invention.

That is, the first present invention,
As a comonomer component, ethylene and / or butene-1 is contained in an amount of 1 to 10% by weight, the Z average molecular weight (Mz) is 7.2 × 10 ⁵ or more and less than 1.2 × 10 ⁶ , and the Z average molecular weight (Mz ) and Ri ratio (Mz / Mw) is der 3.0 or less than 2.5 of the weight average molecular weight (Mw), the substrate to melt flow rate polypropylene resin is 3~7.5g / 10 min Polypropylene resin particles used as resin
Polypropylene resin obtained by dispersing in water together with a dispersant in the presence of a foaming agent in a pressure vessel, heating to a predetermined foaming temperature under pressure, and then releasing the dispersion in the pressure vessel to a low pressure region Expanded particles,
In a DSC curve obtained when 3-6 mg of expanded particles are heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./min with a differential scanning calorimeter (DSC), two melting peaks are shown on the low temperature side and the high temperature side. characterized in that it has, to a polypropylene resin foamed beads.

  A second aspect of the present invention relates to an in-mold foam molded product having an expansion ratio of 20 to 50 times, which is formed by molding the above-described polypropylene resin foamed particles in a mold.

  According to the present invention, it is possible to obtain a molded article having a small mold shrinkage ratio, and a molded article having a shape that is easily deformed, such as a box shape. .

The polypropylene resin used as the base resin of the present invention contains 1 to 10% by weight of ethylene and / or butene-1 as a comonomer component, and has a Z average molecular weight (hereinafter sometimes referred to as Mz). 7.2 × 10 ⁵ or more and less than 1.2 × 10 ⁶ and the ratio of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) (hereinafter sometimes referred to as Mz / Mw) exceeds 2.5. 3.0 or less.

  The propylene-based resin used in the present invention contains propylene as a main component as a monomer and contains 1 to 10% by weight of ethylene and / or butene-1 as a comonomer component, preferably 2 to 5% by weight. It becomes. Specific examples of the polypropylene resin include ethylene-propylene random copolymer, butene-1-propylene random copolymer, ethylene-butene-1-propylene random copolymer, ethylene-propylene block copolymer, ethylene- Examples include butene-1-propylene block copolymers, and ethylene-propylene random copolymers, butene-propylene random copolymers, and ethylene-butene-1-propylene random copolymers are preferable.

The polypropylene resin used in the present invention has a Z average molecular weight of 7.2 × 10 ⁵ or more and less than 1.2 × 10 ⁶ , preferably 80 × 10 ⁵ or more and 110 × 10 ⁵ or less. When the Z average molecular weight Mz is less than 7.2 × 10 ⁵ , the deformation ratio of the molded body increases, and when it is 1.2 × 10 ⁶ or more, the shrinkage ratio against the mold increases.

  The polypropylene resin used in the present invention has a ratio (Mz / Mw) of Z average molecular weight (Mz) to weight average molecular weight (Mw) of more than 2.5 and not more than 3.0, preferably 2.6. It is above 2.9. When Mz / Mw is 2.5 or less, the mold shrinkage ratio of the molded body is good, but after molding, the inside of the molded body cell is depressurized, and is compressed and deformed by being pressed to atmospheric pressure. When the strength of the resin (cell membrane strength) is weak and deformation increases, even if the deformation of the molded body recovers after curing, wrinkles remain on the surface of the molded body, and only a molded body with poor appearance can be obtained. When / Mw is larger than 3.0, the mold shrinkage ratio increases.

  The weight average molecular weight (Mw) and the Z average molecular weight (Mz) are obtained by gel permeation chromatography (GPC) using Mw and Mz obtained under the following measurement conditions. The ratio (Mz / Mw) between the average molecular weight and the weight average molecular weight was calculated.

<Measurement conditions>
Measuring apparatus: Gel permeation chromatograph Alliance GPC 2000 type (manufactured by Waters)
Column: 2 TSKgel GMH _6- HT, 2 TSKgel GMH _6- HTL (inner diameter 7.5 mm × length 300 mm, manufactured by Tosoh Corporation)
Mobile phase: O-dichlorobenzene (containing 0.025% BHT)
Column temperature: 140 ° C
Flow rate: 1.0 mL / min
Sample concentration: 0.15% (W / V) -O-dichlorobenzene Injection amount: 500 μL
Molecular weight calibration: Polystyrene conversion (calibration with standard polystyrene)

  Polypropylene resin having a Z average molecular weight (Mz) and a ratio of the Z average molecular weight to the weight average molecular weight (Mz / Mw) specified in the present invention is adjusted using polymerization catalysts such as metallocene catalyst and post metallocene catalyst. The polymerized polypropylene resin can also be obtained by performing a decomposition treatment with an organic peroxide or the like. Such a polypropylene resin can also be selected from commercially available polypropylene resins. In addition, a commercially available polypropylene resin may be decomposed with an organic peroxide. It is preferable to use a method in which a commercially available polypropylene resin is decomposed with an organic peroxide because a polypropylene resin having a desired ratio of Z average molecular weight to weight average molecular weight can be easily obtained.

  In order to decompose a commercially available polypropylene resin with an organic peroxide, generally, the organic peroxide can be added to a polypropylene resin heated and melted in an extruder. The amount of the organic peroxide used is preferably 0.001 to 0.1 parts by weight with respect to 100 parts by weight of the polypropylene resin, although it depends on the ratio between the target Z average molecular weight and the weight average molecular weight. .

  The polypropylene resin having the desired Mz and Mz / Mw is preferably obtained by adjusting the melt flow rate (MFR) and the amount of organic peroxide of the original polypropylene resin.

  Examples of organic peroxides that can be used include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butylperoxylaurate, 2,5-dimethyl2,5di (benzoyl) Peroxy) hexane, t-butylperoxybenzoate, dicumyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, t-butylperoxyisopropyl monocarbonate and the like.

  The melt flow rate of the polypropylene resin of the present invention (hereinafter sometimes referred to as MFR) is preferably 3 to 12 g / 10 min. If the MFR is less than 3 g / 10 min, the flowability of the resin tends to be insufficient and the foamability tends to deteriorate. If the MFR exceeds 12 g / 10 min, the resin fluidity becomes too high and the cell membrane of the expanded particles is broken. There is a possibility that the closed cell ratio is lowered and the moldability in the mold is deteriorated.

  The melt flow rate is measured by the method of JIS K 7210. The test temperature is 230 ° C. and the load is 2.16 kg.

  The polypropylene resin is usually melted in advance using an extruder, kneader, Banbury mixer, roll, etc., so that it is easy to produce foamed particles, and resin particles in a cylindrical shape, an elliptical shape, a spherical shape, a cubic shape, a rectangular parallelepiped shape, etc. It is preferable to process into a shape. The size of the resin particles is preferably processed so that the weight of one particle is 0.1 mg to 30 mg, more preferably 0.3 mg to 10 mg. The weight of one resin particle is an average resin particle weight obtained by taking 100 resin particles at random, measuring the weight, and averaging per one particle, and is expressed in mg / grain.

  As an additive to the polypropylene resin, when a hydrocarbon foaming agent such as propane, butane, pentane, hexane or the like is used, an inorganic nucleating agent such as talc, silica, calcium carbonate is added in an amount of 0.005 to 0.005. It is preferable to add 5 parts by weight. Moreover, when using inorganic foaming agents, such as air, nitrogen, a carbon dioxide gas, and water, it is preferable to use the said inorganic nucleating agent and / or a water absorbing substance.

  In the present invention, the water-absorbing substance means a substance that can contain water in the resin particles when the substance is added to the resin particles and the resin particles are brought into contact with water or impregnated with a foaming agent in a water dispersion system. Specifically, water-soluble inorganic substances such as sodium chloride, calcium chloride, magnesium chloride, borax, zinc borate, water-absorbing organic substances such as melamine, isocyanuric acid, melamine / isocyanuric acid condensate, polyethylene glycol, polyethylene oxide, etc. Polyethers, alloys of polyethers and PP, alkali metal salts of ethylene (meth) acrylic acid copolymers, alkali metal salts of butadiene (meth) acrylic acid copolymers, alkali metal salts of carboxylated nitrile rubber, isobutylene- Alkali metal salt of maleic anhydride copolymer and alkali metal salt of poly (meth) acrylic acid They include hydrophilic polymers.

  The amount of water-absorbing substance added varies depending on the target foaming ratio, the foaming agent used, and the type of water-absorbing substance used, and cannot be described in general, but when using a water-soluble inorganic substance, the amount is 100 parts by weight of polypropylene resin. On the other hand, it is preferable that it is 0.01-1 weight part, and when using a hydrophilic polymer, it is preferable that it is 0.1-5 weight part with respect to 100 weight part of polypropylene resins. Moreover, you may use together these 2 or more types of these water-soluble inorganic substances and hydrophilic polymers.

  The method for producing the polypropylene resin expanded particles of the present invention is not particularly limited, but the polypropylene resin particles are dispersed in water together with a dispersant in the presence of a foaming agent in a pressure resistant container, and predetermined foaming is performed under pressure. A method of discharging the dispersion in the pressure vessel to the low pressure region after heating to a temperature is preferable.

  As the blowing agent used in the present invention, hydrocarbon blowing agents such as aliphatic hydrocarbons such as propane, butane, pentane and hexane, cycloaliphatic hydrocarbons such as cyclopentane and cyclobutane, air, nitrogen, Examples thereof include inorganic foaming agents such as carbon dioxide and water.

  When polypropylene resin particles are dispersed in water in a pressure-resistant container and heated to impregnate the foaming agent, it is preferable to use a dispersant and a dispersion aid in order to prevent fusion of the resin particles.

  Examples of the dispersant include tertiary calcium phosphate, basic magnesium carbonate, calcium carbonate, magnesium phosphate, aluminum oxide, barium sulfate, titanium oxide, and kaolin. The amount of the dispersant used may be 0.1 to 5 parts by weight with respect to 100 parts by weight of the polypropylene resin particles when the charging ratio of the polypropylene resin particles and water is in the range of 1/3 to 1/1. It is preferable because the dispersion stability is ensured, and the dispersant does not easily adhere to the surface of the obtained foamed particles, and there is a tendency not to inhibit the fusion of the foamed particles during molding.

  Examples of the dispersion aid include surfactants such as sodium dodecylbenzene sulfonate and sodium alkyl sulfonate. The amount of the dispersion aid used is 0.001 to 0.1 parts by weight with respect to 100 parts by weight of the polypropylene resin particles when the charging ratio of the polypropylene resin particles and water is in the range of 1/3 to 1/1. It is preferable that the dispersion stability is ensured and the dispersant does not easily adhere to the surface of the obtained foamed particles, and there is a tendency not to inhibit the fusion of the foamed particles during molding.

  The temperature in the pressure vessel when the dispersion is discharged from the pressure vessel into the low pressure region (hereinafter sometimes referred to as the foaming temperature) is a temperature near the melting point of the polypropylene resin particles, and the type of resin and the foaming agent Although it varies depending on the type, it is generally preferable that the melting point is between −15 ° C. and melting point + 15 ° C.

  In the present invention, the melting point of the polypropylene resin particles is 10 to 10 ° C. up to 40 ° C. after the sample 3 to 6 mg is heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./min with a differential scanning calorimeter (DSC). It means the melting peak temperature of the DSC curve obtained when the temperature is lowered at a rate of ° C./min and again raised to 220 ° C. at a rate of 10 ° C./min.

  As described above, the expanded polypropylene resin particles of the present invention are obtained. When obtaining expanded foam particles having a high expansion ratio, after obtaining the expanded polypropylene resin particles by the above-described method, air is then passed through the expanded particles. A so-called two-stage foaming method may be employed in which after impregnation with an inert gas or the like to impart foaming force, heating is performed to further foam.

  In the DSC curve obtained when the polypropylene resin foamed particles of the present invention were heated at a rate of 10 ° C./min from 3 ° C. to 220 ° C. with a differential scanning calorimeter (DSC), the low temperature side It is preferable to have two melting peaks on the high temperature side. By having two melting peaks, the range of the molding conditions such as the heating temperature range when the expanded polypropylene resin particles are subjected to in-mold foam molding is widened.

In the present invention, at the two melting peaks of the DSC curve, the ratio of the melting peak heat quantity on the high temperature side (Q _H / (Q _H + Q _{L) that} can be calculated from the low temperature side melting peak heat quantity Q _L and the high temperature side melting peak heat quantity Q _H. ) × 100) (hereinafter sometimes referred to as DSC ratio) is preferably in the range of 10 to 40%. Here, the melting peak calorie Q _L on the low temperature side is the amount of heat surrounded by the tangent to the melting start baseline from the maximum point between the low temperature side melting peak, the low temperature side peak, and the high temperature side peak, and the high temperature side melting peak heat Q _H refers to the amount of heat which is surrounded by tangents to the melting completion baseline from the maximum point between the fusion peak on the high temperature side of the DSC curve and the low temperature side peak and the high temperature side peak.

  When the DSC ratio is less than 10%, the closed cell ratio of the polypropylene resin expanded particles is low, and the deformation rate of the molded product tends to increase. When the DSC ratio exceeds 40%, there may be a case where the secondary foaming force in the in-mold foam molding of the polypropylene resin foamed particles may not be sufficiently obtained, and the foamed molded product having a frustrating shape and inferior fusion between the particles. May be obtained.

  The polypropylene-based resin expanded particles of the present invention obtained as described above are, for example, previously pressurized with air in a pressure-resistant container and imparted with a foaming ability by pressurizing air into the polypropylene-based resin particles, and then closed. Filled in a mold that can be sealed but cannot be sealed, and molded with a water vapor pressure of about 0.2 to 0.4 MPa (gauge pressure) as a heating medium and molded in a heating time of about 3 to 30 seconds. By fusing the foamed particles together, and then cooling the mold to a level that can suppress deformation of the in-mold foam molded article after taking out the in-mold foam molded article by water cooling, an in-mold foam molded article can be obtained. I can do it.

The foaming ratio of the obtained in-mold foam molded product is preferably 20 to 50 times, and if it is within the range, generally, the molded product is deformed by the reduced pressure in the cell after molding, and the molded product is deformed. Since the rate tends to increase, the expanded polypropylene resin particles of the present invention can be suitably used. The foaming ratio of the in-mold foamed molded product is calculated by (foaming ratio of the molded product) = 1 / (W / V) × 0.0 from the dry weight (W: g) of the foam and the submerged volume (V: cm ³ ). 9 (resin density of polypropylene resin).

The present invention will be described with reference to examples and comparative examples, but the present invention is not limited thereto.
In this example, the evaluation was performed as follows.

<Bulk density of polypropylene resin expanded particles>
The polypropylene resin expanded particles are put into a 10 L container, and the weight (g) of the expanded particles in the container is measured. The obtained weight was divided by the container capacity (L) to obtain the bulk density (g / L).

<Mold shrinkage ratio>
The mold shrinkage ratio was determined by taking a 400 × 300 × 60 mm thick plate-like in-mold foam molded product from the mold after molding and cooling, immediately curing at 75 ° C. for 12 hours, and allowing to stand at room temperature for 24 hours. Was measured to determine the shrinkage ratio relative to the mold dimensions. When the shrinkage rate is 3.0% or more, the dimensional accuracy of the in-mold foam molded article is deteriorated, and it is considered that there is a problem in practical use.

<Deformation rate of molded body>
After forming the foamed particles in a mold with a box-shaped box having an outer dimension of 350 mm long × 350 mm wide × 180 mm high and 18 mm thick, after standing at room temperature for 1 hour and curing at 75 ° C. for 8 hours, It was allowed to stand at room temperature for 24 hours, and the difference between the center dimension of the opening and the side dimension / side dimension × 100 (%) of the box-shaped molded body was calculated and used as the molded body deformation rate.
When the deformation ratio of the molded product is 4.0% or more, the shape deformation is too large, and problems in practice are likely to occur.

<Surface property>
Visually observe the surface state of the molded body measured for mold shrinkage, ○ if there is almost no “wrinkles” on the surface, △ if there is a slight “wrinkle” on the surface but the entire surface is flat, surface In the case where there were many “wrinkles” and the entire surface was wavy, it was marked with “x”.

(Production Example 1)
An ethylene-propylene random copolymer having an ethylene amount of 4.0% by weight and an MFR of 2.0 g / 10 min was decomposed while adjusting the amount of organic peroxide in the extruder, and the base materials 1 to 5 and 8 to 11 in Table 1 A resin was obtained.

(Production Example 2)
An ethylene-propylene random copolymer having an ethylene amount of 3.4% by weight and an MFR of 4.0 g / 10 min was decomposed while adjusting the amount of organic peroxide in the extruder to obtain base resins 6 and 7 in Table 1. .
Table 1 shows MFR, Mz, MZ / Mw and the like of the obtained base resin.

(Examples 1 and 2)
Base resin No. 1. After dry blending 0.01 parts by weight of talc (Talcan Powder PKS, Hayashi Kasei Co., Ltd.) as a cell nucleating agent, in a 50 mm single screw extruder (20VSE-50-28 type, manufactured by Osaka Seiki Co., Ltd.) Melt kneaded. The obtained melt-kneaded resin was extruded into a strand form from a circular die, cooled with water, and cut with a pelletizer to obtain polypropylene resin particles having a weight of 1.8 mg / grain.

  Capacity: 100 parts by weight of polypropylene resin particles (670 g), 300 parts by weight of water, 2.0 parts by weight of calcium triphosphate (manufactured by Taihei Chemical Industrial Co., Ltd.) as a dispersing agent, and 0.04 parts by weight of sodium alkyl sulfonate as a dispersing aid Into a 4.5 L pressure-resistant autoclave, 10 parts by weight of isobutane was added as a blowing agent under stirring. The autoclave contents were heated to a foaming temperature of 134 ° C. Thereafter, after holding for 30 minutes, the valve at the bottom of the autoclave is opened, and the contents of the autoclave are discharged to atmospheric pressure through an opening orifice having a diameter of 4.0 mm. The bulk density is 38 g / L (Example 1), and the bulk density is 26. Expanded particles of 0.5 g / L (Example 2) were obtained. The temperature and the amount of isobutane were adjusted so that the DSC ratio was 25 ± 1%.

  Molding conditions of the foamed particles are as follows: the foamed particles are placed in a pressure-resistant container and pressurized with air to give the internal pressure of the particles, in-mold foam molding is performed with a vapor pressure of 0.30 MPa (gauge pressure), and the mold after cooling After being cured at a predetermined temperature and time, it was taken out to room temperature. The results are shown in Table 2.

(Example 3)
A molded body in the same manner as in Example 1 except that the weight of one polypropylene resin particle was 1.3 mg / grain and the bulk density of the obtained foamed particles was adjusted to 17.0 g / L in Example 1. Evaluation was performed. The results are shown in Table 2.

(Examples 4 and 5)
Base resin No. 1, 0.1 parts by weight of zinc borate as a cell nucleating agent was dry blended, and then melt-kneaded in a 50 mm single screw extruder (20VSE-50-28 type, manufactured by Osaka Seiki Co., Ltd.). The obtained melt-kneaded resin was extruded into a strand shape from a circular die, cooled with water, and cut with a pelletizer to obtain polypropylene resin particles (mini-pellets) having a weight of 1.8 mg / particle.

  100 parts by weight of polypropylene resin particles (2400 g), 200 parts by weight of water, 0.75 parts by weight of kaolin (ASP-170 manufactured by Engelhard) as a dispersant, 0.018 parts by weight of sodium dodecylbenzenesulfonate as a dispersion aid Into a pressure-resistant autoclave having a capacity of 10 L, 9 parts by weight of carbon dioxide gas was added as a foaming agent under stirring. The temperature of the autoclave was raised and heated to a foaming temperature of 144 ° C., and then carbon dioxide was added to adjust the internal pressure of the autoclave to 3.0 MPa (gauge pressure). Then, after holding for 30 minutes, the valve | bulb of the autoclave lower part was opened, the autoclave content was discharge | released under atmospheric pressure through the opening orifice of diameter 4.0mm, and the expanded particle was obtained. The expansion ratio of the obtained expanded particles was a bulk density of 38 g / L. The temperature and the amount of carbon dioxide gas were adjusted so that the DSC ratio was 25 ± 1%.

  Molding conditions of the foamed particles are as follows: the foamed particles are placed in a pressure-resistant container and pressurized with air to give the internal pressure of the particles, in-mold foam molding is performed with a vapor pressure of 0.30 MPa (gauge pressure), and the mold after cooling And then cured at a predetermined temperature and time, and then taken out to room temperature. The results of the molded body evaluation are shown in Table 2.

(Example 5)
The foamed particles having a bulk density of 38 g / L obtained in Example 4 were put in a pressure vessel and pressurized with air to give an internal pressure of 0.4 MPa (absolute pressure), and water vapor of 0.1 MPa (gauge pressure) was used. Heating was performed to obtain 30 times (bulk density 17 g / L) expanded particles, and the expanded particles were evaluated.
Molding conditions for the foamed particles are as follows: The foamed particles are placed in a pressure-resistant container and pressurized with air to give the internal pressure of the particles, and in-mold foam molding is performed with a vapor pressure of 0.3 MPa (gauge pressure). And then cured at a predetermined temperature and time, and then taken out to room temperature. The results of the molded body evaluation are shown in Table 2.

(Example 6)
The base resin used is No. 1 in Table 1. Except for setting to 2, foamed particles were obtained in the same manner as in Example 1, and molding evaluation was performed. The results are shown in Table 2.

(Example 7)
The base resin used is No. 1 in Table 1. Except for setting to 2, foamed particles were obtained in the same manner as in Example 2, and molding evaluation was performed. The results are shown in Table 2.

(Example 8)
The base resin used is No. 1 in Table 1. Except for setting to 2, foamed particles were obtained in the same manner as in Example 3, and molding evaluation was performed. The results are shown in Table 2.

Example 9
The base resin used is No. 1 in Table 1. Except for setting to 3, foamed particles were obtained and evaluated for molding in the same manner as in Example 1. The results are shown in Table 2.

(Example 10)
The base resin used is No. 1 in Table 1. Except for setting to 3, in the same manner as in Example 2, foamed particles were obtained and evaluated for molding. The results are shown in Table 2.

(Example 11)
The base resin used is No. 1 in Table 1. Except for setting to 3, in the same manner as in Example 3, foamed particles were obtained and evaluated for molding. The results are shown in Table 2.

(Example 12)
The base resin used is No. 1 in Table 1. Except for setting to 4, foamed particles were obtained and evaluated for molding in the same manner as in Example 1. The results are shown in Table 2.

(Example 13)
The base resin used is No. 1 in Table 1. Except for setting to 4, in the same manner as in Example 2, foamed particles were obtained and evaluated for molding. The results are shown in Table 2.

(Example 14)
The base resin used is No. 1 in Table 1. Except for setting to 4, foamed particles were obtained and evaluated for molding in the same manner as in Example 3. The results are shown in Table 2.

(Example 15)
The base resin used is No. 1 in Table 1. Except for setting to 5, foamed particles were obtained and evaluated for molding in the same manner as in Example 1. The results are shown in Table 2.

(Example 16)
The base resin used is No. 1 in Table 1. Except for setting to 5, in the same manner as in Example 2, foamed particles were obtained and evaluated for molding. The results are shown in Table 2.

(Example 17)
The base resin used is No. 1 in Table 1. Except for setting to 5, foamed particles were obtained and evaluated for molding in the same manner as in Example 3. The results are shown in Table 2.

(Comparative Example 1)
The base resin used is No. 1 in Table 1. Except for setting to 6, foamed particles were obtained in the same manner as in Example 1, and molding evaluation was performed. The results are shown in Table 3.

(Comparative Example 2)
The base resin used is No. 1 in Table 1. Except for setting to 6, foamed particles were obtained and evaluated for molding in the same manner as in Example 2. The results are shown in Table 3.

(Comparative Example 3)
The base resin used is No. 1 in Table 1. Except for setting to 6, foamed particles were obtained in the same manner as in Example 3, and molding evaluation was performed. The results are shown in Table 3.

(Comparative Example 4)
The base resin used is No. 1 in Table 1. Except for setting to 7, foamed particles were obtained and evaluated for molding in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 5)
The base resin used is No. 1 in Table 1. Except for setting to 7, foamed particles were obtained and evaluated for molding in the same manner as in Example 2. The results are shown in Table 3.

(Comparative Example 6)
The base resin used is No. 1 in Table 1. Except for setting to 7, foamed particles were obtained and evaluated for molding in the same manner as in Example 3. The results are shown in Table 3.

(Comparative Example 7)
The base resin used is No. 1 in Table 1. Except for setting to 8, foamed particles were obtained and evaluated for molding in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 8)
The base resin used is No. 1 in Table 1. Except for setting to 8, foamed particles were obtained and evaluated for molding in the same manner as in Example 2. The results are shown in Table 3.

(Comparative Example 9)
The base resin used is No. 1 in Table 1. Except for setting to 8, foamed particles were obtained and evaluated for molding in the same manner as in Example 3. The results are shown in Table 3.

(Comparative Example 10)
The base resin used is No. 1 in Table 1. Except that it was set to 9, in the same manner as in Example 1, foamed particles were obtained and evaluated for molding. The results are shown in Table 3.

(Comparative Example 11)
The base resin used is No. 1 in Table 1. Except that it was set to 9, in the same manner as in Example 2, foamed particles were obtained and evaluated for molding. The results are shown in Table 3.

(Comparative Example 12)
The base resin used is No. 1 in Table 1. Except for setting to 9, in the same manner as in Example 3, foamed particles were obtained and evaluated for molding. The results are shown in Table 3.

(Comparative Example 13)
The base resin used is No. 1 in Table 1. Except for using 10, foamed particles were obtained and evaluated for molding in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 14)
The base resin used is No. 1 in Table 1. Except for using 10, foamed particles were obtained and evaluated for molding in the same manner as in Example 2. The results are shown in Table 3.

(Comparative Example 15)
The base resin used is No. 1 in Table 1. Except for using 10, foamed particles were obtained and evaluated for molding in the same manner as in Example 3. The results are shown in Table 3.

(Comparative Example 16)
The base resin used is No. 1 in Table 1. Except that it was set to 11, foamed particles were obtained in the same manner as in Example 1, and molding evaluation was performed. The results are shown in Table 3.

(Comparative Example 17)
The base resin used is No. 1 in Table 1. Except that, the foamed particles were obtained and evaluated for molding in the same manner as in Example 2. The results are shown in Table 3.

(Comparative Example 18)
The base resin used is No. 1 in Table 1. Except that it was set to 11, foamed particles were obtained and evaluated for molding in the same manner as in Example 3. The results are shown in Table 3.

  As for the surface properties of the in-mold foamed molded product, when Mz is 700,000 or less and Mz / Mw is 2.5 or less, it looks bad and is not practical.

  In Examples, a molded article having a good molded article deformation rate and mold shrinkage ratio was obtained. In the comparative examples, the deformation ratio of the molded product was 4% or more, the mold shrinkage ratio was 3% or more, and wrinkles were generated on the surface, resulting in poor surface properties.

  The molded body in which the polypropylene copolymer resin foamed particles of the present invention are molded in a mold has a relatively high magnification and is less likely to be deformed with a short curing time even in a shape that is easily deformed, such as for buffer packaging materials. It has excellent stability and can be produced economically industrially.

It is an example of the DSC curve of the polypropylene resin expanded particle of this invention. The amount of heat enclosed by the tangent to the melting start baseline from the maximum point between the low-temperature side melting peak and the low-temperature side peak and the high-temperature side peak is the low-temperature side melting peak calorie Q _L , and the high-temperature side melting peak of the DSC curve a heat surrounded by tangents to the melting completion baseline from the maximum point between the low-temperature side peak and the high temperature side peak is high-side melting peak heat quantity Q _H.

Claims (2)

As a comonomer component, ethylene and / or butene-1 is contained in an amount of 1 to 10% by weight, the Z average molecular weight (Mz) is 7.2 × 10 ⁵ or more and less than 1.2 × 10 ⁶ , and the Z average molecular weight (Mz ) and Ri ratio (Mz / Mw) is der 3.0 or less than 2.5 of the weight average molecular weight (Mw), the substrate to melt flow rate polypropylene resin is 3~7.5g / 10 min Polypropylene resin particles used as resin
Polypropylene resin obtained by dispersing in water together with a dispersant in the presence of a foaming agent in a pressure vessel, heating to a predetermined foaming temperature under pressure, and then releasing the dispersion in the pressure vessel to a low pressure region Expanded particles,
In a DSC curve obtained when 3-6 mg of expanded particles are heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./min with a differential scanning calorimeter (DSC), two melting peaks are shown on the low temperature side and the high temperature side. characterized in that it comprises a polypropylene resin foamed beads. An in-mold foam-molded article having an expansion ratio of 20 to 50, which is formed by molding the polypropylene-based resin expanded particles according to claim 1 in a mold.