JP4965163B2 - Polypropylene resin pre-expanded particles and in-mold expanded molded body - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a polypropylene resin pre-expanded particle, and more specifically, a polypropylene resin pre-expanded particle that enables good surface properties and dimensional stability in an in-mold expanded molded article having a thin shape, and the pre-expanded particle It relates to an in-mold foam molded product obtained from the above.

  Polypropylene resin in-mold foam molded products have superior chemical resistance, heat resistance, buffer performance, and compression strain recovery performance compared to polystyrene resin in-mold foam molded products. Compared to polyethylene resin in-mold foam molded products. Even so, since it is excellent in heat resistance and compressive strength, it is widely used as a buffer packaging material, a returnable box, and an automobile member.

  In particular, as buffer packaging materials of various shapes, they can be molded flexibly and without cutting work in accordance with the shape of products and members to be included, so that they are widely used from electronic machines to industrial materials.

  However, although it can be molded into various shapes, the molding temperature range for obtaining good products is narrower than that of polystyrene, etc., so adjustment of heating steam pressure, adjustment of heating time, and adjustment of cooling time during molding The user needs skill in molding technology. In addition, when trying to obtain a molded body having a complicated shape, it is satisfactory if there is a so-called “thin” shape that is thin and narrow so that only a few pre-expanded particles enter the thickness direction. It may be difficult to obtain shape and surface properties. For this reason, the buffering performance and strength are not sufficiently obtained at such locations, and problems such as poor fusion between the pre-expanded particles are likely to occur, which is a great restriction on the shape design. In-mold foam molding using pre-expanded polypropylene resin particles generally uses a raw material with a low resin melting point temperature, which tends to increase the secondary foamability (secondary foaming ratio) when steam heated. Therefore, when a thin-walled shape is formed, using a resin having a low melting point temperature can be a means for solving the above-mentioned problem. In some cases, a so-called “inside-down” phenomenon is likely to occur in the molding aimed at a box-shaped molded body. Inward tilting means that there is a difference between the end dimensions and the central dimension in a box-shaped molded product. The absolute value varies depending on the size of each designed product. It becomes a defective product that cannot be used.

  In view of the above problems, for example, in a dispersion medium in which an organic peroxide is present in order to obtain pre-foamed particles having good secondary foamability and fusibility with polypropylene-based prefoamed particles for in-mold foam molding Shows a method of modifying a resin surface by dispersing a polypropylene-based resin (Patent Document 1). However, this method requires equipment that takes into account metal erosion due to organic peroxides, tends to cause non-uniform effects in the dispersion medium, and tends to cause quality variations.

  A technique using a terpene resin or a polypropylene resin containing a petroleum resin as a base material for pre-expanded particles in order to obtain an in-mold molded article having an excellent surface appearance is disclosed (Patent Document 2). From the viewpoint of economy, it is not preferable to use a new polypropylene resin.

In Patent Document 3, it is found that polypropylene resin pre-expanded particles made of a resin having a specific melt index obtained by mixing a resin having a specific melt index are excellent in surface properties and fusion. However, there is no specific description as to whether or not it can be applied to a molded body having a thin wall shape that requires higher secondary foamability and fusing property.
JP 2002-167460 A JP 2005-29773 A JP 2000-327825 A

  An object of the present invention is to provide a polypropylene resin pre-expanded particle that has a good secondary foaming property and is capable of obtaining a foamed molded article having excellent surface properties and dimensionality when performing in-mold foam molding. There is to do.

  As a result of intensive research in view of the above circumstances, the inventors of the present invention contain at least one of a petroleum resin and a terpene resin, a hydrophilic polymer, and a compound having a triazine skeleton in a polypropylene resin. The present inventors have found that polypropylene-based pre-expanded particles based on a polypropylene-based resin composition can be a foam-molded article having a beautiful surface property and good dimensionality, and have completed the present invention.

That is, the first aspect of the present invention is a polypropylene resin pre-expanded particle obtained by using water as a foaming agent, and is made of an ethylene-propylene-butene random copolymer or an ethylene-propylene random copolymer. A polypropylene resin composition comprising one or more of a resin based on (a) a petroleum resin and a terpene resin, and (b) one or more of a hydrophilic polymer and a compound having a triazine skeleton as a base resin The present invention relates to a polypropylene resin pre-foamed particle.

  According to a second aspect of the present invention, the polypropylene resin pre-expanded particles described above are obtained by filling a mold for in-mold foam molding and heating and molding with water vapor. It relates to a molded body.

A third aspect of the present invention is a polypropylene resin made of an ethylene-propylene-butene random copolymer or an ethylene-propylene random copolymer , (a) one or more of a petroleum resin and a terpene resin, and (b) hydrophilic. Resin particles comprising a polypropylene resin composition comprising at least one of a functional polymer and a compound having a triazine skeleton are dispersed in an aqueous dispersion medium in a sealed container, and the particles are heated to form water as a dispersion medium. after impregnated into the particles as foaming agent, and characterized in that pre-expanded by releasing the low pressure and in 80 ° C. or more atmosphere than the internal pressure in the closed container, the production of pre-expanded polypropylene resin particles Regarding the method.

  According to the present invention, in the polypropylene-based pre-expanded particles obtained using water as a foaming agent, as a base resin, one or more of petroleum resin and terpene resin, a hydrophilic polymer, and a compound having a triazine skeleton are used. By providing a polypropylene resin pre-foamed particle using a polypropylene resin composition containing at least one of them, a foam molded article having good secondary foamability and excellent surface properties and dimensional properties is provided. I can do it.

  For this reason, by using the polypropylene resin pre-expanded particles of the present invention, various shapes including complicated shapes can be obtained without impairing the heat resistance, solvent resistance, heat insulation and buffering properties inherent to the polypropylene resin. The molded product can be easily obtained.

  As the polypropylene resin constituting the polypropylene resin pre-expanded particles of the present invention, as long as it contains propylene as a monomer in an amount of 80% by weight or more, more preferably 85% by weight or more, and further preferably 90% by weight or more. The composition and the synthesis method are not particularly limited, for example, propylene homopolymer, ethylene-propylene random copolymer, propylene-butene random copolymer, ethylene-propylene block copolymer, ethylene-propylene-butene ternary. A copolymer etc. are mentioned.

  The polypropylene resin in the present invention is not particularly limited as the resin melting point, preferably 130 ° C. or higher and lower than 170 ° C., more preferably 135 ° C. or higher and lower than 165 ° C., further preferably 140 ° C. or higher and lower than 160 ° C.

  The melt index of the polypropylene resin in the present invention is not particularly limited as long as the pre-expanded particles can be produced, and is preferably 0.2 g / 10 min or more and 50 g / 10 min or less, and preferably 1 g / 10 min or more and 30 g / min. More preferably, it is 10 min or less. When the melt index is within this range, it is easy to achieve both high secondary foamability and good dimensionality. When the melt index is less than 0.2 g / 10 min, the melt viscosity is too high and it is difficult to obtain highly foamed pre-expanded particles, and when it is greater than 50 g / 10 min, the melt viscosity with respect to the elongation of the resin during foaming is too low. , Easy to break. The melt index may be adjusted, for example, by using an organic peroxide.

  A synthetic resin other than the polypropylene resin may be added to the polypropylene resin as long as the effects of the present invention are not impaired, so that the base resin may be used. Synthetic resins other than polypropylene resins include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, linear ultra low density polyethylene, ethylene-vinyl acetate copolymer ethylene-acrylic acid. Examples thereof include ethylene resins such as copolymers and ethylene-methacrylic acid copolymers, and styrene resins such as polystyrene and styrene-maleic anhydride copolymers.

  In the polypropylene resin composition of the present invention, at least one of petroleum resin and terpene resin is used as the polypropylene resin.

  In the present invention, the petroleum resin refers to a thermoplastic resin obtained by cationically polymerizing a cracked oil fraction produced by so-called pyrolysis of petroleum, and also includes these hydrogenated products. Specifically, it is a resin mainly composed of petroleum unsaturated hydrocarbons such as cyclopentadiene, higher olefinic hydrocarbons, or aromatic hydrocarbons (50% by weight or more). Among these petroleum resins, it is preferable to use a hydrogenated petroleum resin that is a hydrogenated product and has high compatibility with a polypropylene resin.

The terpene resin is a hydrocarbon compound represented by a composition of (C ₅ H ₈ ) _n , that is, a terpene homopolymer, or a copolymer of a monomer and a terpene copolymerizable with a terpene, and hydrogenation thereof. Thing etc. are mentioned. Usually, the n is an integer of 2 to 30, but is preferably an integer of 8 to 20. Examples of the terpene represented by the composition formula (C ₅ H ₈ ) _n include, for example, pinene, dipentene, carene, myrcene, osymene, limonene, terpinolene, terpinene, sabinene, tricyclene, bisabolen, gingiberene, santalen, camphorene, mylene, Examples include totarene.

  Of these, homopolymers or copolymers comprising pinene, dipentene, etc., and hydrogenated products thereof are particularly preferred, and hydrogenated products are preferred because of their high compatibility with polypropylene resins. Among the hydrogenated products, those having a hydrogenation rate of 80% or more, particularly 90% or more are preferable.

  Among these petroleum resins and terpene resins, the softening point measured by the ring and ball method is preferably 80 ° C to 150 ° C. The addition amount is preferably 1 part by weight or more and 40 parts by weight or less, and more preferably 3 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the polypropylene resin. If it is less than 1 part by weight, it will be difficult to obtain a beautiful surface property at the time of thermoforming the pre-expanded particles, and if it exceeds 40 parts by weight, the heat resistance inherent in the polypropylene resin may be impaired. is there.

  The polypropylene resin composition used as the base resin for the polypropylene resin pre-expanded particles of the present invention comprises at least one of a compound having a hydrophilic polymer and a triazine skeleton in the polypropylene resin.

  In the present invention, the hydrophilic polymer refers to an ethylene-acrylic acid-maleic anhydride terpolymer, an ethylene- (meth) acrylic acid copolymer, and an ethylene- (meth) acrylic acid copolymer crosslinked with a metal ion. Examples thereof include carboxyl group-containing polymers such as ionomer resins. These may be used alone or in combination of two or more. In particular, an ethylene ionomer resin obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with an alkali metal ion such as sodium ion or potassium ion is preferable because it provides a good water content and good foamability. Further, an ethylene ionomer resin obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with potassium ions is more preferable because it gives a larger average cell diameter.

  The amount of the hydrophilic polymer used is not particularly limited depending on the kind of the hydrophilic polymer, but is usually 0.01 parts by weight or more and 20 parts by weight or less, preferably 0.5 parts by weight with respect to 100 parts by weight of the polypropylene resin. More preferred is 5 parts by weight or more. If it is less than 0.01 part by weight, it is difficult to obtain pre-expanded particles having a high expansion ratio, and if it exceeds 20 parts by weight, the heat resistance and the mechanical strength may be greatly reduced.

  In the present invention, the compound having a triazine skeleton preferably has a molecular weight per unit triazine skeleton of 300 or less. Here, the molecular weight per triazine skeleton is a value obtained by dividing the molecular weight by the number of triazine skeletons contained in one molecule. When the molecular weight per unit triazine skeleton exceeds 300, variation in foaming ratio and variation in cell diameter may be noticeable. Examples of the compound having a molecular weight per unit triazine skeleton of 300 or less include melamine (chemical name 1,3,5-triazine-2,4,6-triamine), ammelin (1,3,5-triazine-2- Hydroxy-4,6-diamine), ammelide (1,3,5-triazine-2,4-hydroxy-6-amine), cyanuric acid (1,3,5-triazine-2,4,6-triol) ), Tris (methyl) cyanurate, tris (ethyl) cyanurate, tris (butyl) cyanurate, tris (2-hydroxyethyl) cyanurate, melamine isocyanuric acid condensate and the like. These may be used alone or in combination of two or more. Among these, it is preferable to use melamine, isocyanuric acid, and melamine / isocyanuric acid condensate in order to obtain pre-expanded particles having a high expansion ratio with small variations in expansion ratio and cell diameter.

Furthermore, if necessary, for example, cell nucleating agents such as talc, antioxidants, metal deactivators, phosphorus processing stabilizers, UV absorbers, UV stabilizers, fluorescent brighteners, metal soaps, etc. Stabilizers or crosslinkers, chain transfer agents, lubricants, plasticizers, fillers, reinforcing agents, pigments, dyes, flame retardants, antistatic agents, etc. are added to the base resin to the extent that the effects of the present invention are not impaired. It is good also as a system resin mixture.
In the present invention, for example, after melt-kneading a polypropylene resin composition in an extruder, the melt-kneaded product is extruded into a string shape from a die having a small hole, and then cut with a cutting machine equipped with a take-up machine. System resin particles can be obtained. The particle weight of the obtained polypropylene resin particles is preferably 0.5 to 5.0 mg / particle.

  In the present invention, the polypropylene-based resin particles are expanded to form pre-expanded particles. As the expansion method of the pre-expanded particles, water is used as a foaming agent, which is an inexpensive and easy-to-install facility. Is used.

  That is, resin particles composed of a polypropylene resin composition containing one or more of a petroleum resin or a terpene resin, a hydrophilic polymer, or a compound having a triazine skeleton are dispersed in water in a sealed container. The particles are dispersed in a medium, the particles are heated, and water, which is a dispersion medium, is impregnated into the particles as a foaming agent. Preferably, the polypropylene resin composition particles are dispersed in an aqueous dispersion medium in a pressure vessel and heated to a temperature higher than the softening temperature of the polypropylene resin composition to obtain water-containing resin particles having a water content of 0.1 to 10%. After that, by pressurizing with nitrogen or air and releasing it in an atmosphere of atmospheric pressure of 80 ° C. or higher, the water in the water-containing resin is instantaneously evaporated, so that a polypropylene resin preliminary having a desired expansion ratio and physical properties is obtained. Obtain expanded particles.

  In an atmosphere of atmospheric pressure of 80 ° C. or higher, the temperature is maintained at 80 ° C. or higher and 100 ° C. or lower, preferably 90 ° C. or higher and 100 ° C. or lower, with high-temperature air, water vapor, or the like. When the temperature is less than 80 ° C., it is difficult to obtain pre-expanded particles having a high expansion ratio, and the pre-expanded particles tend to shrink due to the effect of cooling the pre-expanded particles immediately after expansion.

  There are no particular limitations on the sealed container at the time of producing the pre-foamed particles, and any container that can withstand the pressure and temperature in the container at the time of producing the pre-foamed particles may be used. For example, an autoclave type pressure-resistant container may be mentioned.

  In the preparation of the dispersion, as the dispersant, for example, inorganic dispersants such as tribasic calcium phosphate, basic magnesium carbonate, calcium carbonate, and so on, for example, sodium dodecylbenzenesulfonate, sodium n-paraffinsulfonate, α-olefinsulfone. It is preferable to use a dispersion aid such as acid soda. Among these, the combined use of tricalcium phosphate and sodium dodecylbenzenesulfonate is more preferable. The amount of dispersant and dispersion aid used varies depending on the type and the type and amount of polypropylene resin used, but usually 0.2 to 3 parts by weight of the dispersant is added to 100 parts by weight of water. It is preferable to add 0.001 to 0.1 parts by weight of a dispersion aid. Moreover, in order to make a polypropylene resin particle favorable in the dispersibility in water, it is preferable to use normally 20-100 weight part with respect to 100 weight part of water.

  The expansion ratio of the polypropylene resin pre-expanded particles obtained by the above production method is preferably 5 to 50 times, more preferably 7 to 45 times.

  Moreover, once the pre-expanded particles of 5 times to 35 times are manufactured, the pressure in the pre-expanded particles is made higher than the normal pressure by pressurizing the pre-expanded particles in a sealed container and impregnating with nitrogen, air, etc. After that, the foamed particles may be expanded 50 times or more by a method such as a two-stage foaming method in which the foamed particles are heated and further foamed with steam or the like.

  Here, the pre-expanded particles thus obtained or the expanded particles preferably have two melting point peaks in the DSC curve obtained by differential scanning calorimetry, and the high-temperature melting crystal content ratio is preferably 10% or more, More preferably, it is 13% or more. When the high-temperature melting crystal content ratio is less than 10%, it is difficult to form a molded article having a beautiful appearance when the pre-expanded particles are molded in a mold having a thin portion in the mold or are molded with a small amount of steam. The high temperature melting crystal ratio of 50% is the lower limit that can practically maintain the stable production of pre-expanded particles and sufficient moldability during in-mold molding using the pre-expanded particles.

  Here, the high-temperature melting crystal amount ratio in the present invention means that when a sample of 4 to 10 mg is heated from 40 ° C. to 200 ° C. at a rate of 10 ° C./min in differential scanning calorimetry (DSC), a polypropylene resin reserve The melting peak calorie α (J / g) of the melting peak (hereinafter referred to as the low temperature peak) based on the crystalline state originally possessed by the base resin of the expanded particles and the melting peak (hereinafter referred to as the high temperature side) from the peak. When the melting peak calorific value β (J / g) of “high temperature peak.” Is the ratio (β / (α + β)) (%) of the high temperature peak calorie to the total melting peak.

  To make the polypropylene resin pre-expanded particles of the present invention into an in-mold foam molded article, the polypropylene resin pre-expanded particles or the expanded particles are filled in a mold for in-mold foam molding and heated with water vapor to be molded. . Specifically, a) a method in which foamed particles are pressurized with an inorganic gas, impregnated with inorganic gas in the particles to give a predetermined internal pressure, filled into a mold, and heated and fused with steam or the like ( Japanese Patent Publication No. 51-22951), b) A method in which foamed particles are compressed by gas pressure, filled in a mold, and heated and fused with steam or the like using the recovery force of the particles (Japanese Patent Publication No. 53-33996), etc. Can be used.

  EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited only to these Examples.

<Measurement of foaming ratio>
The pre-foamed particle density was calculated from the weight of the pre-foamed particles used as a sample and the volume obtained by immersing the sample in ethanol in a volumetric flask, and the base resin density was divided to obtain the expansion ratio.

<Secondary foaming ratio measurement>
The secondary expansion ratio in the present invention is a physical property value obtained by the following measuring method.
(1) Measure the pre-foamed particle bulk density ρ1 in vacuum.
(2) The inorganic foaming agent is sufficiently applied to the surface of the pre-expanded particles, and the pre-expanded particles are treated so as not to be fused by steam heating.
(3) The pre-expanded particles treated in (2) are put into a container having a structure in which heating of the pre-expanded particles by water vapor such as a wire net works sufficiently, and the container is placed in a molding machine (for example, P150 (manufactured by Toyo Metal Co., Ltd.)). After installing and heating at a steam pressure of 3.0 kgf / cm ² -G for 5 seconds, it is cooled with water for 50 seconds.
(4) The inorganic dispersant adhering to the surface of the taken pre-expanded particles is washed away and dried in a thermostatic chamber at 75 ° C. for 12 hours.
(5) The vacuum pre-expanded particle bulk density ρ2 after drying is measured, and the secondary expansion ratio X2 = ρ1 / ρ2 (times) is calculated from ρ1 and ρ2.
The above operation was performed twice for each specimen, and the average value was defined as the secondary foaming ratio.

<Molding evaluation>
In the molding evaluation, pre-expanded particles having an internal pressure of 2.0 atm with air are used, and a mold having a shape shown in FIG. 1 (molded body design outer dimensions: 327 mm × 353 mm × 256 mm, thin portion dimensions: 103 mm × 153 mm × 5 mm) is used. Using this, molding was performed at a heating steam pressure of 2.0 and 3.0 kgf / cm2-G, and the thin-walled portion surface a and dimension c (longitudinal direction central portion) were evaluated.

(1) Surface property An internal pressure of 0.1 kg / cm ² -G or more is applied to the pre-expanded particles, the mold can be closed but cannot be sealed, and molded by steam heating at 3.0 kgf / cm ² -G. About the surface of the molded body
When the outline of the expanded particle appearing on the surface of the molded body a is fused with the adjacent particles, and a molded body free from wrinkles on the surface of the expanded particle exposed on the surface of the molded body is obtained.・ ・ ・ ○
When a molded body is obtained in which gaps are observed between the expanded particles or wrinkles are observed on the surface of the expanded particles exposed on the surface of the molded body. ... ×

(2) Dimensionality After being molded by steam heating at 3.0 kgf / cm ² -G, it was allowed to stand at 25 ° C. for 2 hours, then left in a temperature-controlled room at 65 ° C. for 5 hours, then taken out, 25 The dimension (b) of the molded body 3 test body that was allowed to cool at 0 ° C. was measured and averaged, and the difference from the required product quality of 345 mm was obtained. Passed.
Polypropylene resin a ethylene-propylene-butene random copolymer Melting point 147.6 ° C. Melt flow rate 9.3 g / 10 min
Polypropylene resin b ethylene-propylene-butene random copolymer Melting point 145.6 ° C. Melt flow rate 7.0 g / 10 min
Polypropylene resin c ethylene-propylene random copolymer Melting point 142.0 ° C. Melt flow rate 7.0 g / 10 min
Petroleum resin A Arakawa Chemical Industries, Ltd. Product name Alcon P140 (softening point 140 ° C)
Petroleum resin B Arakawa Scientific Co., Ltd. product name Alcon P115 (softening point 115 ° C)
Terpene resin A Product name Clearon M-105 (softening point 105 ° C) manufactured by Yasuhara Chemical Co., Ltd.

Example 1
Dry blend of 100 parts by weight of polypropylene resin a with 0.3 parts by weight of powdered talc, 3 parts by weight of petroleum resin A, and 0.5 parts by weight of melamine made by BASF as a compound having a triazine skeleton. Extruded with a single screw extruder to obtain polypropylene resin particles. 100 parts by weight (2.4 kg) of the obtained resin particles are put into a 10 L capacity pressure vessel having a stirrer, and 2.0 parts by weight of tribasic calcium phosphate (manufactured by Ohira Chemical Industry Co., Ltd.) and sodium normal paraffin sulfonate 0 Dispersed in 200 parts by weight of water in the presence of 0.03 parts by weight. While stirring the dispersion, the dispersion was heated to 153.0 ° C., and then the internal pressure of the pressure vessel was adjusted by pressurization with compressed air so as to be 2.98 MPa. Next, the discharge valve with an inner diameter of 25 mm installed at the lower part of the pressure vessel is released, and the pellet and water dispersion are brought to an atmospheric temperature of 100 ° C. with water vapor through a circular orifice with a diameter of 4 mm attached to the rear end of the discharge valve. Release into the adjusted atmosphere to obtain pre-expanded particles having an expansion ratio of 17.0 times and a high-temperature melting crystal ratio of 17%.

  The obtained pre-expanded particles were impregnated with an internal pressure of 3.0 MPa by air impregnation and heated with 60 kPa steam to obtain expanded particles with an expansion ratio of 30.0 times. The secondary expansion ratio of the foamed particles was 3.1 times, and the moldability evaluation results were good for both surface properties and dimensional properties.

（実施例２）
実施例１で用いたポリプロピレン系樹脂ａを用いる代わりに、ポリプロピレン系樹脂ｂを用い、石油樹脂Ｂを５重量部、トリアジン骨格を有する化合物としてイソシアヌル酸０．８重量部を押し出し、分散液を１５０．５℃に加熱し、該耐圧容器の内圧１．９９ＭＰａになるように調整する方法により、発泡倍率１４．５倍、高温融解結晶比率３０％の予備発泡粒子を得た。

(Example 2)
Instead of using the polypropylene resin a used in Example 1, the polypropylene resin b was used, 5 parts by weight of petroleum resin B and 0.8 part by weight of isocyanuric acid were extruded as a compound having a triazine skeleton, and the dispersion liquid was 150 parts. Pre-expanded particles having an expansion ratio of 14.5 times and a high-temperature melting crystal ratio of 30% were obtained by heating to 0.5 ° C. and adjusting the pressure vessel so that the internal pressure was 1.99 MPa.

  The obtained pre-expanded particles were given an internal pressure of 4.0 MPa by air impregnation, and heated with 40 kPa steam to obtain expanded particles having an expansion ratio of 29.8 times. The secondary expansion ratio of the expanded particles was 2.8 times, and the results of evaluation of moldability were good in both surface properties and dimensional properties.

(Example 3)
Instead of using the polypropylene resin used in Example 1, polypropylene resin c was used, 10 parts by weight of terpene resin A was used instead of petroleum resin A, and ethylene- (meth) acrylic was used instead of the compound having a triazine skeleton. Example 1 except that 3 parts by weight of an ethylene ionomer resin obtained by crosslinking an acid copolymer with sodium ions was added, the dispersion was heated to 148.5 ° C., and the internal pressure of the pressure vessel was adjusted to 3.00 MPa. By the same method, pre-expanded particles having an expansion ratio of 14.2 times and a high-temperature melting crystal ratio of 23% were obtained.

  The obtained pre-expanded particles were given an internal pressure of 4.0 MPa by air impregnation, and heated with 40 kPa steam to obtain expanded particles having an expansion ratio of 30.1 times. The secondary foaming ratio of the foamed particles was 3.0 times, and the moldability evaluation results were good in both surface properties and dimensional properties.

(Comparative Example 1)
In the same manner as in Example 1 except that the petroleum resin used in Example 1 was not added and the dispersion was heated to 153.5 ° C. and adjusted to an internal pressure of 2.98 MPa in the pressure vessel, the expansion ratio was 16.2. Thus, pre-expanded particles having a high-temperature melting crystal ratio of 19% were obtained.

  An internal pressure of 3.2 MPa was applied to the obtained pre-expanded particles by air impregnation, and heated with 60 kPa of steam to obtain expanded particles having an expansion ratio of 30.4 times. The secondary expansion ratio of the foamed particles was 2.6 times, and the moldability evaluation result was an unsatisfactory surface property.

(Comparative Example 2)
Except that the petroleum resin B used in Example 2 was not added and the dispersion was heated to 151.2 ° C., the same procedure as in Example 2 was carried out with a foaming ratio of 14.0 times and a high temperature melting crystal ratio of 28% Expanded particles were obtained.

  The obtained pre-expanded particles were impregnated with an internal pressure of 4.2 MPa by air impregnation, and heated with 45 kPa steam to obtain expanded particles having an expansion ratio of 29.6 times and a high temperature melting crystal ratio of 28%. The secondary expansion ratio of the expanded particles was 2.4 times, and the results of evaluation of moldability were unsatisfactory levels for both surface properties and dimensional properties.

  As shown in Examples 1 to 3 and Comparative Examples 1 and 2, it is found that pre-expanded particles made of polypropylene resin containing petroleum resin and terpene resin can obtain good surface properties as a result of molding.

It is a perspective appearance figure of a fabrication object for evaluating dimensionality.

Claims (3)

A polypropylene resin pre-expanded particle obtained using water as a foaming agent,
A polypropylene resin comprising an ethylene-propylene-butene random copolymer or an ethylene-propylene random copolymer ,
(A) one or more of petroleum resin and terpene resin,
(B) one or more of a hydrophilic polymer and a compound having a triazine skeleton,
Characterized in that the base resin of the comprising at polypropylene resin composition, pre-expanded polypropylene resin particles. The pre-expanded polypropylene resin particles according to claim 1, packed into mold foam molding mold, characterized in that it is obtained by molding by heating with steam, a polypropylene resin mold foamed articles. Polypropylene resin comprising ethylene-propylene-butene random copolymer or ethylene-propylene random copolymer , (a) one or more of petroleum resin, terpene resin, (b) hydrophilic polymer, compound having triazine skeleton Resin particles comprising a polypropylene resin composition comprising one or more of these are dispersed in an aqueous dispersion medium in a closed container, the particles are heated, and water as the dispersion medium is used as a blowing agent in the particles. after impregnating, and characterized in that pre-expanded by releasing the low pressure and in an atmosphere of more than 80 ° C. than the internal pressure in the closed container, a manufacturing method of polypropylene resin pre-expanded particles.

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