JP4940688B2 - Method for producing polypropylene resin pre-expanded particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polypropylene-based resin pre-expanded particle that does not cause a rasping frictional noise (squeaky sound) at a high frequency when a friction develops between pre-expanded particles, expanded moldings, or an expanded molding and another plastic product, metal products, etc., and a polypropylene-based resin expanded molding. <P>SOLUTION: The method for producing a polypropylene-based pre-expanded particle comprises feeding a resin particle consisting essentially of a polypropylene-based resin to a pressure-resistant vessel, heating the resin particle to a fixed temperature and releasing the resin particle to an atmosphere under pressure lower than that of the pressure-resistant vessel. The polypropylene-based resin has the flexural rigidity measured based on JIS K7106 of &ge;900MPa and &le;1,700MPa. The resin particle comprises &ge;0.1 pts.wt. and &le;2.5 pts.wt. of ethylene-bis-stearic acid amide based on 100 pts.wt. of the polypropylene-based resin. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a method for producing polypropylene-based pre-expanded particles that can be suitably used for producing an in-mold foam-molded product of a polypropylene-based resin used for buffer packaging materials, boxing, heat insulating materials, automobile bumper core materials, and the like.

  As a use of polypropylene resin foam moldings, it is widely used for cushioning packaging materials, bumper core materials, automobile members and the like. However, these polypropylene-based resin foam molded products and polypropylene resin pre-expanded particles have a high frequency of annoying frictional sound (curk sound) when friction occurs between the foam molded products or between other plastic products and metal products. ) May occur.

  Conventionally, as a method for preventing these friction sounds, Patent Document 1 attaches a higher fatty acid amide or the like to the surface of a polypropylene resin foam, and Patent Document 2 attaches a higher fatty acid amide or the like to the surface of a granular polyolefin foam. A method is disclosed. However, these require a step of applying a higher fatty acid amide or the like on the surface of the foam, which is disadvantageous in terms of productivity and production cost. In addition, the higher fatty acid amide adhered during in-mold molding is peeled off, causing a problem of contaminating the molding die.

  Patent Document 3 discloses a method in which a fatty acid amide is kneaded into a polypropylene resin. The technique disclosed here is a production method in which a foaming agent is contained in polypropylene resin particles and then heated and foamed with steam, and the purpose is to make the cell structure of the pre-foamed particles fine and uniform by adding a fatty acid amide. It is a thing.

  Patent Document 4 discloses a method of adding a mixture containing either a polyhydric alcohol fatty acid ester or a fatty acid amide to a polyolefin-based resin. The technique disclosed here is a manufacturing method in which a polyolefin resin particle contains a foaming agent and is heated and foamed with steam, as in Patent Document 3, and the cell structure of the polyolefin resin pre-foamed particle is uniformly coarsened. It is intended.

In Patent Document 5, for the purpose of improving the secondary workability of a polypropylene resin foamed molded article, a fatty acid metal salt 0.05 to 3.0 wt% on a polypropylene resin having a flexural rigidity of 4000 to 8000 kg / cm ² (392 to 785 MPa). % And fatty acid amide 0.05 to 2.0% by weight is disclosed. However, a polypropylene resin having a flexural rigidity of 8000 kg / cm ² or less has a low compressive strength, which causes a problem that the weight of the molded article cannot be reduced.

Further, in Patent Document 6, 2.5 to 15 parts by weight of a fatty acid amide compound is added to a polypropylene resin without damaging the polypropylene resin foamed molded article due to vibration caused by vibration and suppressing the generation of powder that peels off due to friction. A method of inclusion is disclosed. However, as the content of the fatty acid amide compound is increased, the dispersion of the resin particles in the pressure vessel tends to become unstable when the polypropylene resin pre-expanded particles are produced. In addition, since the dispersant tends to remain on the surface of the pre-expanded particles obtained by this method, poor fusion tends to occur during in-mold molding.
JP 59-2010954 A JP-A 61-23632 JP 58-1229028 A JP-A-11-209503 JP-A-8-59876 JP 2003-49019 A

  The problem of the present invention is that when the friction occurs between the pre-foamed particles, the foam-molded bodies, or between the foam-molded body and other plastic products, metal products, etc. An object of the present invention is to provide a polypropylene resin foamed pre-foamed particle and a polypropylene resin foamed molded article in which no occurrence occurs.

  As a result of intensive studies to solve the above problems, the present inventors have made 0.1 parts by weight or more and 2.5 parts by weight of ethylenebisstearic acid amide with respect to 100 parts by weight of a polypropylene resin having a predetermined bending rigidity. The polypropylene resin particles contained in a part or less are charged into a pressure vessel together with water, a dispersant, a foaming agent, etc., and after heating the contents, the contents are released into an atmosphere at a lower pressure than in the pressure vessel. It was found that by using polypropylene resin pre-expanded particles, polypropylene pre-expanded particles that do not generate annoying frictional noise with high frequency can be obtained, and the present invention has been completed.

That is, the first of the present invention is a polypropylene resin foam molded article having a porosity of 10% or more and 50% or less, obtained by filling the polypropylene resin foam preliminary particles in a mold and heating. Polypropylene resin foamed preliminary particles are prepared by charging a resin container mainly composed of polypropylene resin and water dispersion composed of water, a dispersing agent and a foaming agent into a pressure vessel, heating to a predetermined temperature, and then under pressure. When a mixture of the resin particles and water than said pressure vessel obtained by releasing the low pressure atmosphere, bending stiffness was measured in accordance with JIS K7106 of the polypropylene-based resin is below 1700MPa or more 900MPa There, and the resin particles, for the 100 parts by weight of polypropylene resin ethylenebis stearic acid amide 0.1 parts by weight or more, 2 Characterized in that .5 is obtained containing less parts by weight, about polypropylene resins onset foam moldings.

  In the production method of the present invention, the dispersibility of the resin particles is good, and the polypropylene resin pre-expanded particles obtained and the polypropylene resin foam-molded product obtained from the pre-expanded particles are pre-foamed particles, When friction occurs between the bodies or between the foamed molded body and other plastic products, metal products, etc., an unpleasant frictional sound (kicking sound) with a high frequency does not occur. Since ethylene bis-stearic acid amide is contained in the resin particles, it does not peel off during in-mold foam molding.

  The polypropylene-based foam molded article of the present invention has the same density and higher strength when compared with a normal foam-molded article. Therefore, applications requiring strength and light weight, such as buffer packaging materials, bumper core materials, automobiles, etc. It can be suitably used for a member.

  The polypropylene resin used in the present invention is a polymer comprising propylene monomer units of 50% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and is polymerized with a Ziegler type titanium chloride catalyst or a metallocene catalyst. Those having high stereoregularity are preferred. Specific examples include, for example, propylene homopolymer, ethylene-propylene random copolymer, propylene-butene random copolymer, ethylene-propylene-butene random copolymer, ethylene-propylene block copolymer, maleic anhydride -Propylene random copolymer, maleic anhydride-propylene block copolymer, propylene-g-maleic anhydride graft copolymer, etc. are mentioned, and each is used alone or in combination. In particular, an ethylene-propylene random copolymer, a propylene-butene random copolymer, and an ethylene-propylene-butene random copolymer can be suitably used. Further, these polypropylene resins are preferably non-crosslinked, but crosslinked resins can also be used.

  The polypropylene resin used in the present invention has a flexural rigidity measured in accordance with JIS K7106 of 900 MPa to 1700 MPa, preferably 950 MPa to 1600 MPa. If the bending rigidity is lower than 900 MPa, the molded product has a low compressive strength, and thus the foamed molded product cannot be reduced in weight.

  The polypropylene resin used in the present invention has a melt index (hereinafter referred to as MI) measured at a temperature of 230 ° C. and a load of 2.16 kg in accordance with JIS K7210, and is 0.1 g / 10 min or more and 15 g / 10 min or less. Is more preferably 2 g / 10 min or more and 12 g / 10 min or less.

  The melting point of the polypropylene resin is preferably 130 ° C. or higher and 168 ° C. or lower, more preferably 135 ° C. or higher and 160 ° C. or lower, and particularly preferably 140 ° C. or higher and 155 ° C. or lower. If the melting point is within this range, a foamed molded article having excellent moldability, mechanical strength, and heat resistance tends to be obtained. Here, the melting point refers to a peak temperature of an endothermic peak measured by a differential scanning calorimeter. Specifically, 1 to 10 mg of polypropylene resin is heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./min. Then, it is cooled at a rate of 10 ° C./min to 40 ° C., and is the peak temperature of the endothermic peak in the DSC curve obtained when the temperature is raised again to 220 ° C. at a rate of 10 ° C./min.

  The amount of ethylene bis stearamide used in the present invention is 0.1 to 2.5 parts by weight, preferably 1.5 to 2.5 parts by weight, based on 100 parts by weight of the polypropylene resin. Part or less, more preferably 1.5 parts by weight or more and 2.0 parts by weight or less. If the added amount of ethylene bis-stearic acid amide is less than 0.1 parts by weight, the effect of suppressing the generation of frictional noise is not exhibited. If the amount of the amide compound added exceeds 2.5 parts by weight, the dispersion of the resin particles in the pressure vessel tends to become unstable when the polypropylene resin pre-expanded particles are produced. Since a large amount of the dispersant tends to remain on the surface of the expanded particles, poor fusion tends to occur during in-mold molding. In addition, the use of a predetermined amount of ethylene bis-stearic acid amide is effective in suppressing the generation of frictional noise, and when producing pre-expanded polypropylene resin particles, the resin particles are dispersed in the pressure vessel. The dispersion stability of the resin particles is improved. For example, even when 1.5 parts by weight of erucic acid amide exemplified in JP-A-8-59876 as a fatty acid amide is used with respect to 100 parts by weight of a polypropylene resin, dispersion of resin particles in a pressure vessel is unstable. Thus, it becomes difficult to produce polypropylene resin pre-expanded particles.

  A known method can be used as a method for adding ethylene bis stearic acid amide to the polypropylene resin, but among them, a method of dry blending the polypropylene resin and ethylene bis stearic acid amide is preferable in terms of ease of production.

  Next, the manufacturing method of the polypropylene resin pre-expanded particles of the present invention will be described. The polypropylene resin to which ethylene bis-stearic acid amide has been added is melted using a known method, for example, using an extruder, a kneader, a Banbury mixer (trademark), a roll, or the like, and the weight of one grain is 0.00. It is processed into 2 to 10 mg, preferably 0.5 to 6 mg polypropylene resin particles. Generally, it is preferable to melt by using an extruder and to manufacture by a strand cut method. For example, a polypropylene resin extruded in a strand form from a circular die is cooled and solidified with water, air, or the like to cut polypropylene resin particles having a desired shape.

  Moreover, the cell diameter of a polypropylene resin pre-expanded particle can be adjusted to a desired value by adding a cell nucleating agent during the production of the resin particles. As the cell nucleating agent, inorganic nucleating agents such as talc, calcium carbonate, silica, kaolin, titanium oxide, bentonite and barium sulfate are generally used. The amount of cell nucleating agent added varies depending on the type of polypropylene resin used and the type of cell nucleating agent, and cannot be specified unconditionally, but is generally 0.001 part by weight or more with respect to 100 parts by weight of polypropylene resin particles. The amount is preferably 2 parts by weight or less.

  Furthermore, when manufacturing the polypropylene resin particles, various additives can be added as necessary within the range not impairing the properties of the polypropylene resin. Examples of additives include: colorants such as carbon black and organic pigments; antistatic agents comprising nonionic surfactants such as alkyldiethanolamides, alkyldiethanolamines, hydroxyalkylethanolamines, fatty acid monoglycerides, and fatty acid diglycerides; IRGANOX 1010 ( Hindered phenolic antioxidants such as IRGAFOS168 (TM), IRGAFOS P-EPQ (TM), IRGANOX1076 (TM), IRGANOX1330 (TM), IRGANOX1425WL (TM), IRGANOX3114 (TM), ULTRANOX626 (TM); Phosphorus processing stabilizers such as IRGAFOS 126 (trademark) and WESTON 619 (trademark); Lactic processing stabilizers such as HP-136 (trademark) Hydroxylamine processing stabilizers such as FS042 ™, metal deactivators such as IRGANOX MD1024 ™; benzotriazole UV absorbers such as TINUVIN326 ™ and TINUVIN327 ™; TINUVIN120 ™ Benzoate light stabilizers; hindered amine light stabilizers such as CHIMASSORB119 (trademark), CHIMASSORB944 (trademark), TINUVIN622 (trademark), TINUVIN770 (trademark); flame retardant aids such as halogenated flame retardants and antimony trioxide; FLAMESTAB NOR116 (Trademark), non-halogen flame retardants such as MELAPUR MC25 (trademark); acid neutralizers such as hydrotalcite and calcium stearate; IRGASTAB NA11 (trademark), etc. Such crystal nucleating agent are exemplified.

  The pre-expanded polypropylene resin particles in the present invention are prepared by charging a resin particle mainly composed of a polypropylene resin and an aqueous dispersion composed of water, a dispersant and a foaming agent into a pressure-resistant container, heating to a predetermined temperature, It is obtained by releasing the mixture of the resin particles and water under a reduced pressure in an atmosphere at a lower pressure than in the pressure vessel. Specifically, an aqueous dispersion medium containing the resin particles, a foaming agent, a dispersant and a dispersion aid is charged into a sealed container, and the temperature is increased while stirring (hereinafter sometimes referred to as a foaming temperature). After impregnating the resin particles with a foaming agent and adding additional foaming agent as necessary, the inside of the sealed container is held at a constant pressure (hereinafter sometimes referred to as foaming pressure), and then the contents are removed from the bottom of the sealed container. An example is a method of discharging in an atmosphere lower than the internal pressure of the sealed container. The sealed container to be used is not particularly limited as long as it can withstand the pressure in the container and the temperature in the container at the time of producing the pre-foamed particles, and examples thereof include an autoclave type pressure resistant container.

  Examples of the blowing agent include aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, and normal pentane, and mixtures thereof; inorganic gases such as air, nitrogen, and carbon dioxide; and water.

  The amount of foaming agent used varies depending on the type of polypropylene resin used, the type of foaming agent, the target foaming ratio, etc., and cannot be specified unconditionally, but is generally about 2 weights per 100 parts by weight of polypropylene resin particles. It is preferable that it is 60 parts by weight or more.

  As the dispersant, for example, a poorly water-soluble inorganic compound such as basic tricalcium phosphate, basic magnesium carbonate, calcium carbonate, aluminum oxide, and kaolin is preferably used. As the dispersion aid, for example, an anionic surfactant such as sodium dodecylbenzene sulfonate or sodium linear alkyl fin sulfonate is preferably used. Among these, the use of basic tricalcium phosphate and linear alkyl fin sulfonic acid soda is preferable because good dispersibility can be obtained. The amount of the dispersant and the dispersion aid used varies depending on the type, the type and amount of the polypropylene resin used, the type of foaming agent, etc., but usually 0.1 part by weight of the dispersant with respect to 100 parts by weight of water. The amount is preferably 3 parts by weight or less and 0.001 part by weight or more and 0.1 parts by weight or less for the dispersion aid.

  In order to improve the dispersibility of the polypropylene resin particles in water, it is usually preferable to use 20 to 100 parts by weight of the resin particles with respect to 100 parts by weight of water.

  The aqueous dispersion of polypropylene resin particles thus adjusted in a closed container is heated to a predetermined foaming temperature with stirring, and is maintained for a certain time, usually 5 to 180 minutes, preferably 10 to 60 minutes. At the same time, the pressure in the sealed container rises, and the foaming agent is impregnated with the resin particles. Thereafter, the foaming agent is additionally supplied until a predetermined foaming pressure is reached, and is maintained for a certain time, usually 5 to 180 minutes, preferably 10 to 60 minutes. Thus, an aqueous dispersion of polypropylene resin particles held at the foaming temperature and foaming pressure is released into a low-pressure atmosphere (usually atmospheric pressure) by opening a valve provided at the bottom of the sealed container. Resin pre-expanded particles can be produced.

  When the aqueous dispersion of resin particles is discharged into a low-pressure atmosphere, it can also be discharged through an opening orifice of 2 to 10 mmφ for the purpose of adjusting the flow rate and reducing the magnification variation. In some cases, the low-pressure atmosphere is filled with saturated steam for the purpose of increasing the expansion ratio.

  The foaming temperature varies depending on the melting point [Tm (° C.)] of the polypropylene resin used, the type of foaming agent, etc., and cannot be specified unconditionally, but is generally determined from the range of Tm−30 (° C.) to Tm + 10 (° C.). . The foaming pressure varies depending on the type of polypropylene resin to be used, the type of foaming agent, and the foaming ratio of the desired pre-foamed particles, and cannot be defined unconditionally, but is generally determined from the range of 1 to 8 MPa (gauge pressure). .

  The polypropylene resin pre-expanded particles obtained as described above can be made into a polypropylene resin expanded foam by a conventionally known molding method. For example, a) a method in which pre-expanded particles are pressurized with an inorganic gas, impregnated with the inorganic gas in the pre-expanded particles to give a predetermined internal pressure of the pre-expanded particles, filled in a mold, and heated and fused with water vapor. B) A method in which the pre-expanded particles are compressed by gas pressure and filled in a mold, and the recovery power of the pre-expanded particles is used for heat fusion with water vapor. A method such as a method of filling a mold and heat-sealing with water vapor can be used.

  As the inorganic gas, air, nitrogen, oxygen, helium, neon, argon, carbon dioxide, or the like can be used. These may be used alone or in combination of two or more. Among these, highly versatile air and nitrogen are preferable.

As described above, the polypropylene resin foam molded article of the present invention can be obtained. In the present invention, in the polypropylene based in-mold foam molded article, particularly in the foam molded article having a porosity of 10% to 50%. Demonstrate the effect of suppressing the generation of friction noise. Here, the porosity of the polypropylene resin foam molded product according to the present invention is obtained by determining the apparent volume V (cm ³ ) from the outer dimensions of the composite foam molded product, and further inserting a certain amount of ethanol into the polypropylene resin foam molded product. It was obtained by the following formula by dipping in a measuring cylinder and measuring the increased volume V ₁ (cm ³ ) at that time.
Porosity (%) = (V−V ₁ ) / V × 100

  For example, U.S. Pat. No. 6,060,529 discloses a foamed molded article in which pre-expanded particles are incompletely fused. However, in such a molded article in which pre-foamed particles are incompletely fused, frictional noise is generated. Since it tends to occur, the effects of the present invention are particularly achieved.

  In order to produce a molded body having a porosity of 10% to 50%, for example, when the melting point of the polypropylene resin used as the base resin is Tm (° C.), the temperature is preferably Tm-25 (° C. ) To Tm (° C) water vapor, and further, the temperature is Tm-20 (° C) to Tm-5 (° C). You can get a body.

  Next, the manufacturing method of the polypropylene resin pre-expanded particles and the polypropylene resin foam molded article of the present invention will be described in detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples. Evaluation of the pre-expanded particles and the foamed molded product was performed by the method described below.

<Anti-friction effect of pre-expanded particles>
200 cm ³ of pre-foamed particles were wrapped in 30 × 30 cm gauze and the mouth was tied, and compressed at a speed of 500 mm / min, and the sound generation at that time was heard by the side. Evaluation criteria are as follows.
A: No friction noise is generated. O: Friction noise is hardly generated, but slightly generated when compressed several times.
X: A large friction noise is generated.

<Dispersion stability in autoclave>
As an index for evaluating dispersibility, when polypropylene resin particles dispersed in an aqueous dispersion medium in an autoclave are heated to a temperature higher than the softening temperature of the polypropylene resin particles, the inside of the autoclave cannot be stirred and pre-foamed. X, the state of polypropylene resin particles remaining in the autoclave after prefoaming was observed, and if two or more resin particles were adhered, dispersibility ○, If all the resin particles are not adhered to each other, the dispersibility is good and ◎.

<Friction noise prevention effect in foamed molding>
The polypropylene resin foamed molded article was moved on a horizontal acrylic resin plate at a load of 0.05 MPa at a rate of 5 cm / sec to observe the presence or absence of frictional noise. Evaluation criteria are as follows.
A: Friction noise is not generated at all. B: Friction noise is hardly generated, but it is slightly generated when moved several times.
X: A large frictional noise is generated when moved.
XX: A large friction sound is generated only by compressing with a load of 0.05 MPa.

<Fusion rate of foam molding>
About 5 mm of notch was put into the polypropylene resin foam molded body with a cutter knife, and it was bent and broken along the notch. The ratio at which the expanded particles were broken on the fracture surface was determined by visual observation.

Example 1
The base resin is MI = 7/10 min, melting point is 146 ° C., 100 parts by weight of random polypropylene with a flexural rigidity of 1000 MPa, 1.0 part by weight of ethylenebisstearic acid amide, and 0.3 parts by weight of talc as a cell nucleating agent The random polypropylene, ethylenebisstearic acid amide and talc were dry blended. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand shape from a circular die, cooled with water, and cut with a cutter to obtain resin particles having a weight of 1.8 mg / grain.

100 parts by weight (50 kg) of the obtained resin particles, 300 parts by weight of water, 1.6 parts by weight of basic tricalcium phosphate and 0.03 parts by weight of sodium alkyl sulfonate are charged into a pressure-resistant autoclave having a capacity of 0.35 m ³ , Under stirring, 20 parts of isobutane was added as a foaming agent, and then the contents of the autoclave were heated to a foaming temperature of 140 ° C. Thereafter, isobutane was additionally injected and the pressure was increased to a foaming pressure of 2.2 MPa. After maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave was opened, and the autoclave contents were passed through a 4.4 mmφ orifice. Release under atmospheric pressure to obtain pre-expanded particles.

  The pre-expanded particles obtained were impregnated with air by air pressure treatment to give an internal pressure of 0.08 to 0.12 MPaG, and then filled into a 320 × 320 × 60 mm mold, and a molding temperature of 0.30 MPaG It was heated and fused with the above steam to obtain a foamed molded product. The evaluation results are shown in Table 1.

(Example 2)
Pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1 except that 2.0 parts by weight of ethylenebisstearic acid amide was added. The evaluation results are shown in Table 1.

(Example 3)
Pre-expanded particles and a foamed molded product were obtained in the same manner as in Example 1 except that 2.4 parts by weight of ethylenebisstearic acid amide was added. The evaluation results are shown in Table 1.

  As a result of Examples 1 to 3, it was possible to obtain polypropylene resin expanded particles and a polypropylene resin expanded molded article in which no frictional noise was generated.

Example 4
Pre-expanded particles and a foamed molded product were obtained in the same manner as in Example 1 except that 0.3 parts by weight of ethylenebisstearic acid amide was added. The evaluation results are shown in Table 1.

  Polypropylene resin foam particles and polypropylene resin foam moldings that hardly generate frictional noise could be obtained.

(Example 5)
Pre-expanded particles were obtained in the same manner as in Example 1 except that 2.0 parts by weight of ethylenebisstearic acid amide was added. After applying an internal pressure of 0.04 MPa to the resulting pre-expanded particles, foaming was performed in the same manner as in Example 1 except that the foamed molded body was heated and fused with steam at a molding temperature of 0.2 MPaG. A molded body was obtained. The evaluation results are shown in Table 1.

  The resulting foamed molded article had a porosity of 35%, but no friction noise was generated.

(Comparative Example 1)
Pre-expanded particles and a molded foam were obtained in the same manner as in Example 1 except that ethylene bis-stearic acid amide was not added. Table 1 shows the results of evaluation performed in the same manner as in Example 1. Polypropylene resin foam particles and a polypropylene resin foam molded article that generate a large frictional sound were obtained.

(Comparative Example 2)
Except for adding 3.0 parts by weight of ethylenebisstearic acid amide, it was attempted to obtain pre-expanded particles in the same manner as in Example 1. However, pre-expanded particles could be obtained due to dispersibility deterioration in the autoclave. There wasn't.

(Comparative Example 3)
Pre-expanded particles were obtained in the same manner as in Example 1 except that ethylene bis stearamide was not added. After applying an internal pressure of 0.04 MPa to the resulting pre-expanded particles, foaming was performed in the same manner as in Example 1 except that the foamed molded body was heated and fused with steam at a molding temperature of 0.2 MPaG. A molded body was obtained. The evaluation results are shown in Table 1.

  The porosity of the obtained foamed molded product was 35% as in Example 5, but a large frictional sound was generated only by compression with a load of 0.15 MPa.

  From the results of Example 5 and Comparative Example 3, by adding ethylenebisstearic acid amide, it is possible to exert an effect of suppressing frictional noise particularly for a foamed molded article having a porosity of 10% to 50%. I understand.

Claims (1)

A polypropylene resin foam molded article having a porosity of 10% or more and 50% or less, obtained by filling and heating polypropylene resin foam preliminary particles in a mold,
The polypropylene resin foamed preliminary particles are charged with resin particles mainly composed of polypropylene resin and water, a water dispersion composed of a dispersant and a foaming agent in a pressure vessel, heated to a predetermined temperature, and then subjected to pressure. Originally, it is obtained by discharging a mixture of the resin particles and water into an atmosphere at a lower pressure than in the pressure vessel ,
Wherein the polypropylene-based bending stiffness was measured in accordance with JIS K7106 of the resin is less 1700MPa or more 900 MPa, and the resin particles, for the 100 parts by weight of polypropylene resin ethylenebis stearic acid amide 0.1 parts by weight or more , characterized in that it is obtained by containing more than 2.5 parts by weight, polypropylene resins onset foam moldings.