JP4837356B2 - Thermoplastic resin in-mold foam molding and production method - Google Patents

Description

The present invention relates to a method for producing an in- mold foam molded body of a thermoplastic resin, which is formed by molding thermoplastic resin pre-foamed particles and has a high porosity that can be used mainly as a sound absorbing material and a water-permeable material.

  As a method for producing a foamed molded article having thermoplastic resin pre-expanded particles typified by polypropylene or the like and having continuous voids, a columnar polyolefin resin foamed particle having an L / D of 2 to 10 is used in a mold. (Patent Document 1) discloses a method of heating with steam after filling the particles so that the filling rate is 40 to 55% and particles are oriented in an irregular direction.

  In addition, there is disclosed a method of heat-molding polypropylene resin foamed particles having irregularities such as hollow cylinders or hollow irregular shapes or cross-shaped cross sections (Patent Documents 2 and 3). Furthermore, there is also a foamed molded article having a porosity of 10 to 60% using drum-shaped pre-foamed particles (Patent Document 4).

  In any case, in order to obtain water permeability, air permeability, and sound absorption, a pre-expanded particle having an irregular shape or a pre-expanded particle having an enlarged L / D is used to provide a void in the foam molded body. However, since the foamed molded article having such a structure contains a large number of voids, the compression property is reduced or the fusion strength between the pre-expanded particles is reduced as compared with a molded article without voids. There was a problem that the pre-expanded particles were easily peeled off at the end face portion, that is, the shape retention was poor. That is, there is a molded product or a manufacturing method that reinforces a part where the end face is easily peeled while maintaining air permeability, water permeability, and sound absorption performance, or is provided with water permeability, air permeability, and sound absorption only at a desired location. It was desired.

On the other hand, for example, as in Patent Document 5, there is a technique for integrally molding different pre-expanded particles into a substantially divided shape, but as description of different pre-expanded particles, including the expansion ratio, bead bulk density, cell diameter, Although different bead diameters and materials are disclosed, this document is a disclosure of pre-expanded particles that are close to general spheres, and L / D that requires specific molding conditions. There is no specific description of using different pre-expanded particles.
JP-A-3-224727 JP 7-138399 A JP 7-138400 A JP 2000-302909 A JP 2001-96559 A

  Accordingly, an object of the present invention is to provide a thermoplastic resin in-mold foam-molded article having a high porosity and shape retention using thermoplastic resin pre-foamed particles that can be easily and economically produced. There is to do.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that the thermoplastic resin in-mold foamed molded article is formed from thermoplastic resin pre-expanded particles having an L / D of 2 or more and 10 or less, By making the part formed from the thermoplastic resin pre-expanded particles having an L / D of 0.8 or more and 1.2 or less substantially in a partition shape, the part constituted by the L / D of 2 or more and 10 or less is sound absorbing or water permeable. Contributing to the performance, the part composed of L / D of 0.8 or more and 1.2 or less contributes to strength maintenance or anti-peeling function, so that sound absorption, water permeability and mechanical strength, or shape stability As a result, the present inventors have found that the compatibility of the properties can be achieved.

好ましい実施態様としては、前記熱可塑性型内発泡成形体外周部がＬ／Ｄが０．８以上１．２以下の熱可塑性樹脂予備発泡粒子から形成されそれ以外の部位がＬ／Ｄが２以上１０以下の熱可塑性樹脂予備発泡粒子から形成されたことを特徴とする、前記記載の熱可塑性樹脂型内発泡成形体の製造方法に関する。
That is, the first of the present invention is a portion formed from thermoplastic resin pre-foamed particles having an L / D of 2 or more and 10 or less, and a thermoplastic resin pre-treatment having an L / D of 0.8 or more and 1.2 or less. The present invention relates to a method for producing an in- mold foam molded article of a thermoplastic resin , characterized in that portions formed from expanded particles are present in a substantially partitioned shape.
Here, L is the length of the longest part of the expanded particles, D is an average value of the maximum diameter Dmax and the minimum diameter Dmin in a cross section perpendicular to the L direction, and L / D is a value calculated by the following equation. .

As a preferred embodiment, the outer peripheral part of the thermoplastic molded foam-molded body is formed from pre-expanded thermoplastic resin particles having an L / D of 0.8 or more and 1.2 or less, and other parts have an L / D of 2 or more. The present invention relates to a method for producing an in- mold foam molded article of a thermoplastic resin , characterized in that it is formed from 10 or less thermoplastic resin pre-expanded particles.

As a more preferred embodiment, the pre-foamed thermoplastic resin particles are pressurized with an inorganic gas, impregnated with the inorganic gas in the foamed particles to give a predetermined foamed particle internal pressure, filled into a mold, and then steamed. When heat-sealing , the L / D of the thermoplastic resin pre-expanded particles having an internal pressure of 2 to 10 is lower than the internal pressure of the thermoplastic resin pre-expanded particles of L / D of 0.8 to 1.2. The thermoplastic resin pre-expanded particles are simultaneously integrally molded in a mold, and the method for producing a thermoplastic resin in-mold foam molded article as described above,
In another preferred embodiment, the thermoplastic resin pre-expanded particles are pressurized with an inorganic gas, impregnated with the inorganic gas in the expanded particles to give a predetermined internal pressure of the expanded particles, filled into a mold, and then steamed. upon thereby heat sealing, L / D is 0.12MPa or more thermoplastic resin pre-expanded particles pressure of 2 to 10 at an absolute pressure 0.17MPa or less, thermoplastic L / D is 0.8 to 1.2 The above-mentioned thermoplastic resin in-mold foam molding, wherein the internal pressure of the resin pre-foamed particles is 0.18 MPa to 0.25 MPa in absolute pressure, and these thermoplastic resin pre-foamed particles are simultaneously integrally molded in the mold. The present invention relates to a method for manufacturing a body.

  In the present invention, a portion formed from thermoplastic resin pre-expanded particles having L / D of 2 or more and 10 or less, and a portion formed from thermoplastic resin pre-expanded particles having L / D of 0.8 or more and 1.2 or less. By adopting a configuration in which the portions are present in a substantially partitioned shape, it is possible to achieve both a predetermined porosity and compression characteristics or shape retention, and it is possible to make a desired portion have a high porosity. According to the production method of the present invention, a portion to which a sound absorbing function or a water permeation function is to be provided is formed with pre-expanded particles having an L / D of 2 or more and 10 or less, so that the porosity of the portion after molding is 25% or more. 50% or less, and the part requiring prevention of exfoliation of the pre-expanded particles or mechanical strength is formed by forming the pre-expanded particles having L / D of 0.8 or more and 1.2 or less. It becomes possible to set it as the structure which increased the intensity | strength of the porosity of the said site | part after 5% or less.

  This foamed molded article can be suitably used as a sound-absorbing material, a water-permeable material, etc. in automobile members, civil engineering / building materials, industrial materials and the like. In particular, it can be suitably used when sound absorbing performance is imparted to automobile members such as a raising material, a tibia pad, a luggage box, and a side projection material.

  The present invention will be described in detail below.

  The thermoplastic resin used in the present invention can be used as long as it is a thermoplastic resin used for in-mold foam molding, and examples thereof include polystyrene resins, polyolefin resins, and polymethyl methacrylate resins.

  Examples of polystyrene resins that can be used in the present invention include not only general foamable polystyrene resins, but also, for example, polystyrene resins containing 50% or more of styrene or methylstyrene, high impact polystyrene resins, styrene, Examples thereof include copolymer resins such as butadiene, styrene-ethylene copolymer, methyl methacrylate, and maleic anhydride, and these are used alone or in combination of two or more.

  Examples of polyolefin resins that can be used in the present invention include low / medium / high density polyethylene, linear low / ultra low density polyethylene, polyethylene resins typified by ethylene-vinyl acetate copolymer, polypropylene, and ethylene-propylene. Examples thereof include a polypropylene resin represented by a random copolymer and an ethylene-propylene block copolymer.

  Among these, polyolefin resin is preferably used, and polypropylene resin is more preferably used.

  The polypropylene resin in the present invention is a polymer having a propylene monomer unit of 50% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and is particularly 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-maleic anhydride graft copolymer, etc. are mentioned, and these are 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 that can be used in the present invention has a melt index (hereinafter referred to as MI) of 0.1 g / 10 min or more and 7 g / 10 min or less measured at a temperature of 230 ° C. and a load of 2.16 kg in accordance with JIS K7210. It is preferable that it is 2g / 10min or more and 6g / 10min or less. When MI is less than 0.1 g / 10 min, the foaming force when producing pre-expanded particles is low, and it tends to be difficult to obtain pre-expanded particles with a high expansion ratio. Moreover, it tends to be difficult to ensure the fusion strength between the pre-expanded particles when a foamed molded body is obtained. When MI exceeds 7 g / 10 minutes, it tends to be difficult to control the porosity of the foamed molded product with a stable value.

  The polypropylene resin preferably has a melting point of 130 ° C. or higher and 168 ° C. or lower, more preferably 135 ° C. or higher and 160 ° C. or lower, particularly preferably, in order to obtain a foamed molded article having excellent mechanical strength and heat resistance. 140 ° C. or higher and 155 ° C. or lower. When the melting point is within this range, there is a strong tendency to easily balance moldability, mechanical strength, and heat resistance. Here, the melting point means that 1 to 10 mg of resin is heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./min by a differential scanning calorimeter, then cooled to 40 ° C. at a rate of 10 ° C./min, and again The peak temperature of the endothermic peak in the DSC curve obtained when the temperature is increased to 220 ° C. at a rate of 10 ° C./min.

  The pre-expanded particles used in the present invention are those using the thermoplastic resin as a base resin, and L / D is 2 to 10 thermoplastic resin pre-expanded particles (hereinafter sometimes referred to as rod-shaped pre-expanded particles). ) And L / D of 0.8 to 1.2 thermoplastic resin pre-expanded particles (hereinafter sometimes referred to as spherical pre-expanded particles).

  Here, L / D referred to in the present invention is, as shown in FIG. 1, L is the length of the longest part of the expanded particles, D is an average value of the maximum diameter Dmax and the minimum diameter Dmin in a cross section perpendicular to the L direction. And is calculated by the following formula.

熱可塑性予備発泡粒子のＬ方向に垂直な断面形状は、円、楕円等の凹部のない閉じた曲線であり、ＤｍａｘおよびＤｍｉｎはＬ方向に沿って略一定の値をとる。予備発泡粒子の具体例としては、円柱形状、楕円柱形状が挙げられる。

The cross-sectional shape perpendicular to the L direction of the thermoplastic pre-expanded particles is a closed curve without a concave portion such as a circle or an ellipse, and Dmax and Dmin take substantially constant values along the L direction. Specific examples of the pre-expanded particles include a cylindrical shape and an elliptical column shape.

  First, the rod-shaped pre-expanded particles will be described in detail.

  By adopting rod-shaped pre-expanded particles having an L / D of 2 or more and 10 or less, it is possible to form a high void while maintaining an appropriate contact area between the expanded particles. When L / D exceeds 10, clogging at the filling port is likely to occur when filling the mold, causing not only filling failure but also variation in the void ratio between the parts of the foamed molded product. It becomes easy.

  The rod-shaped pre-expanded particles preferably have a cell diameter of 30 μm to 150 μm, and more preferably 50 μm to 100 μm. When the cell diameter is within this range, it is easy to firmly fuse the foamed particles while maintaining the voids generated when filling the mold. When the cell diameter is less than 30 μm, sinking and shrinkage are likely to occur when the foamed molded article is formed, and the shape retainability may deteriorate. When the cell diameter exceeds 150 μm, the porosity of the foamed molded product tends to be low. In particular, the porosity tends to decrease in the surface layer in contact with the mold surface.

  Further, the rod-shaped pre-expanded particles have two melting peaks in the DSC curve obtained by differential scanning calorimetry, the heat of fusion α (J / g) of the low temperature side peak, and the heat of fusion β (J of the high temperature side peak) Β / (α + β) is preferably 0.35 or more and 0.75 or less, more preferably 0.40 or more and 0.70 or less. When β / (α + β) is less than 0.35, it may be difficult to increase the porosity of the foamed molded product. This is presumably because the secondary foaming power of the foamed particles is increased and the porosity is reduced during molding. If β / (α + β) exceeds 0.75, fusion between the expanded particles may be difficult. When the temperature of the steam used for molding is increased in order to promote fusion, the porosity of the foamed molded product is lowered, and there is a risk that it is difficult to ensure both porosity and fusion.

  Here, the DSC curve obtained by differential scanning calorimetry of the expanded particles is obtained when 1 to 10 mg of expanded particles are heated from 40 ° C. to 220 ° C. at a temperature increase rate of 10 ° C./min by a differential scanning calorimeter. It is a DSC curve. As shown in FIG. 2, the contact on the low temperature side between the straight line passing through the maximum point A of the obtained DSC curve and the DSC curve is B, and the contact on the high temperature side is C. From the area surrounded by the line segment AB and the DSC curve, the heat of fusion α (J / g) of the low temperature side peak, and from the area surrounded by the line segment AC and the DSC curve, the heat of fusion β (J / g) of the high temperature side peak. Calculated.

  By using rod-shaped pre-expanded particles that satisfy the above requirements, it is possible to easily obtain a thermoplastic resin foam-molded part having a porosity of preferably 25% or more and 50% or less. The porosity of the foamed molded product is strongly related to the sound absorption characteristics, and the porosity is more preferably 30% or more and 45% or less. When the porosity is less than 25%, the sound absorption rate at the peak frequency is lowered, and sufficient sound absorption characteristics may not be obtained. When the porosity exceeds 50%, the contact area between the foamed particles is reduced, and the foamed molded product is liable to be cracked, which may reduce the mechanical strength.

  Here, the porosity means that a rectangular solid sample having a predetermined size (for example, 20 × 20 × 40 mm) is cut out from the foam so as not to include the surface skin layer, the apparent volume is obtained from the outer dimensions, and further the rectangular parallelepiped sample. Is immersed in a graduated cylinder containing a certain amount of ethanol, the increased volume (true volume) at that time is measured, and the difference between the apparent volume and the true volume is divided by the apparent volume.

  Next, spherical pre-expanded particles will be described.

  A substantially spherical pre-expanded particle having an L / D of 0.8 or more and 1.2 or less has a cell diameter of 200 μm or more and 400 μm or less, and has two melting peaks in a DSC curve obtained by differential scanning calorimetry. It is preferable that β / (α + β) is 0.15 or more and 0.35 or less when the heat of fusion α (J / g) of the side peak and the heat of fusion β (J / g) of the high temperature side peak are used. By satisfying these requirements, there is a tendency that a thermoplastic resin foam-molded portion having a small magnification variation, high strength, and low porosity can be stably produced. Here, the particles L / D are as spherical as possible from the viewpoints of filling of the present particles into the mold, fusion property after molding, and maintaining mechanical strength, preferably L / D is 0.9 or more and 1 .1 or less, that is, L / D is preferably close to 1.

  In the present invention, the rod-shaped pre-expanded particles and the spherical pre-expanded particles described above are used in combination and exist in a substantially partitioned shape, so that the water permeability, air permeability or sound absorption depends on the porosity and the shape of the molded body. Maintenance or mechanical strength maintenance can be made possible. Since the sound absorption rate does not greatly depend on the expansion ratio of the rod-shaped pre-expanded particles, any expansion ratio can be selected. Moreover, although it changes with the applications to be applied, the expansion ratio of the pre-expanded particles is preferably 5 to 60 times. In particular, a bulking material for automobile use, a luggage box, a tibia pad, and the like are more preferably 15 times or more and 45 times or less.

  Next, the molding apparatus used in the present invention will be described.

  As shown in FIG. 3, the mold apparatus according to the present invention is placed on a flow of air in a molding space 3 formed by a cavity mold 1 and a core mold 2 as a pair of molds arranged to face each other. And a filling device 6 for filling the raw material beads. The cavity mold 1 and the core mold 2 are respectively attached to housings having frame-shaped frames 11 and 12 and back plates 13 and 14, and a pair of cavity molds are provided on the back side of the cavity mold 1 and the core mold 2. A steam chamber 7 and a core-type steam chamber 8 are formed, respectively, and the cavity mold 1 and the core mold 2 are formed with a large number of vent holes communicating the both steam chambers and the molding space 5. Incidentally, the vent hole is actually a core vent made of a cylindrical body having a lid having an outer diameter of 7 to 12 mm, in which a plurality of round holes of about 0.5 mmφ and slits of about 0.5 mm width are provided. It is formed by fitting into a core vent mounting hole arranged in a perforated manner, or a core vent hole of about 0.5 mmφ formed directly on a mold.

  A supply pipe for supplying a working fluid such as steam or compressed air is connected to the cavity type steam chamber 7 and the core type steam chamber 8, respectively, and a discharge pipe connected to a decompression means or a drain pipe is connected to the cavity type steam chamber 7 and the core type steam chamber 8. A control valve (not shown) is provided in the middle of the supply pipe and the discharge pipe so that the supply and discharge of the working fluid to and from the molding space 15 can be controlled by operating the control valve.

  In the molding space 3, pre-expanded particles having different L / D are partitioned through partition members 4, and pre-foamed particle fillers 6 are connected to the respective partition molding spaces, and adjacent partition moldings are performed. It is comprised so that the pre-expanded particle | grains from which L / D differs can be filled in space.

  As a method of filling pre-expanded particles having different L / D using the partition member 4, one of the molds is provided with a movable partition member in the molding space via an air cylinder or the like, and this partition member Thus, there is a mold apparatus that partitions the molding space into a plurality of partition molding spaces. However, in this mold apparatus, an insertion hole is formed in the mold, and the partition member is removably attached to the insertion hole, so that the pre-expanded particles are inserted between the insertion hole and the inner wall surface of the insertion hole and the partition member. And protruding burrs tend to be easily formed on the surface of the molded body.

  As another method, a plurality of comb teeth extending in a cantilevered manner in the mold opening / closing direction are fixed to at least one mold at an interval at which at least one of the pre-foamed particles filling the adjacent partition molding space cannot pass through. The partition space is partitioned into a plurality of partition molding spaces, and a filler for supplying raw material beads is individually connected to each partition molding space, and the partition space is partitioned by the partition member. In this state, for example, after filling raw material beads with different expansion ratios in adjacent partition molding spaces, steam is supplied into the molding space to heat and fuse the adjacent raw material beads through comb teeth. A mold apparatus configured to obtain a body (FIG. 3). In the molded body formed by this mold apparatus, a groove is formed at a position corresponding to the fixed base of the partition member, and a through hole or a bottomed hole is formed at a position corresponding to the fixed comb tooth. Since a drive system for driving the members is not required, the molding apparatus can be remarkably simplified, and the manufacturing cost of the molding apparatus can be reduced. Further, since the partition area of the molding space can be easily changed by changing the mounting position of the partition member, it is possible to cope with a design change of the molded body. Further, since the pre-expanded particles having different L / D filled in the adjacent partition molding spaces are sufficiently fused through the gaps between the comb teeth, the L / D of the molded products is different. The effect that it is possible to sufficiently secure the bonding strength of the molding part molded with the pre-expanded particles is obtained.

  In consideration of the above points, it is preferable to use the latter mold apparatus in the present invention. Therefore, here, a mold apparatus using comb teeth as a partition member suitable for the present invention will be described in more detail.

  In the molding space, the part constituted by spherical pre-expanded particles is partitioned into parts constituted by rod-shaped pre-expanded particles via comb teeth, and each compartment molding space is filled with pre-expanded particles as raw materials. 6 are connected to each other so that pre-expanded particles having different L / Ds can be filled. The section shape, the number of sections, and the section position of the molding space can be arbitrarily set according to the performance and shape of the molded body to be manufactured. For example, heat of L / D being 2 or more and 10 or less is provided only in a portion where pre-expanded particles of L / D that are different between the outer peripheral portion and the inside of the molded body are required, or where sound absorption and air permeability are required. It is conceivable to arrange a site composed of pre-expanded particles of plastic resin. Among them, by forming the outer peripheral portion of the thermoplastic molded foam-molded body with spherical pre-foamed particles and forming the other portions with rod-shaped pre-foamed particles, the pre-foamed particles are easily peeled off at the end surface portion of the foam-molded product. The problem can be solved.

  As shown in FIGS. 4 to 6, as the partitioning means, even if the comb teeth arranged in parallel in the mold opening / closing direction are arranged in a mold-like manner on one mold (FIG. 4), both molds (FIG. 5), and further, a partition plate and a plurality of comb teeth arranged in parallel along the mold opening / closing direction and a support member for supporting the comb teeth in a cantilever manner (FIG. 6). )

  For example, in the case of the present invention, as shown in FIGS. 4 to 6, the rod-shaped pre-expanded particle portion and the spherical pre-expanded particle portion are partitioned at the position of the substantially “mouth” -shaped boundary surface when viewed from the front, A plurality of bottomed holes are formed at regular intervals (FIG. 7). The bottomed hole may be configured to be continuous or discontinuous, but may be configured to penetrate the molded body. Note that the boundary surface does not necessarily have to be formed in a “mouth” shape when viewed from the front, and the molded body can be partitioned along a boundary having an L shape, a straight shape, or a curved shape when viewed from the front (FIG. 8). ). Further, comb teeth may be arranged so that the boundary surface has a triangular wave shape, a rectangular wave shape, a sawtooth wave shape, or a sine wave shape (FIG. 9).

  The intervals between the comb teeth 18 are set to intervals at which the pre-expanded particles filled in at least one of the partition molding spaces cannot pass through, and are generally set at intervals at which the spherical pre-expanded particles cannot pass through. If the interval between the comb teeth is too narrow, sufficient adhesion between the raw material beads filled in the adjacent partition molding space cannot be ensured, and the strength of the molded body is reduced. It is preferable to set 30 to 90% of the diameter, more preferably 50 to 80%.

  Comb teeth are composed of elongated rod-like or pipe-like members, and their cross-sectional shapes are circular, oval, elliptical, polygonal shapes such as quadrilateral and hexagonal shapes, star shapes, L shapes, H shapes, etc. Can be used. Further, when this partitioning means is used, since the bottomed hole and the through hole are respectively formed at positions corresponding to the comb teeth of the molded body, the equivalent diameter of the comb teeth can be set as small as possible. For example, it is set to 1 to 10 mm, preferably 1.5 to 5 mm. The equivalent diameter here is a numerical value obtained by converting the cross-sectional area of each shape of the comb teeth into a diameter of a circle corresponding to the area.

  That is, in this molding apparatus, since the through hole or the bottomed hole is formed by the comb teeth in the molded body as described above, if the equivalent diameter of the comb teeth is set to be larger than 10 mm, the large through hole or the bottomed hole is formed. As a result, the strength between the different types of pre-expanded particles of the molded product is reduced, and the appearance of the molded product may be deteriorated. If the equivalent diameter of the comb teeth is set smaller than 1 mm, the strength of the comb teeth cannot be ensured sufficiently, and there is a risk that the comb teeth may be damaged or deformed.

  The comb teeth are preferably made of a metal material such as aluminum, iron, brass, or stainless steel, ceramic, or a heat-resistant synthetic resin material. In particular, it is preferable to use stainless spring steel that is elastically deformable and excellent in heat resistance and corrosion resistance. With this configuration, even if the comb teeth are slightly deformed due to filling pressure or foaming pressure, they can be restored to their original shape as long as they are within the elastic limit range. Therefore, molding such as poor filling or mold release due to plastic deformation of the comb teeth is possible. While preventing defects, the cross-sectional area of the comb teeth can be set as small as possible to suppress deterioration in the appearance and strength of the core material. In addition, from the viewpoint of mold release stability and durability of the comb member, the surface of the comb teeth is treated with Teflon (registered trademark) or anodized to reduce the frictional resistance between the comb teeth and the molded body. It is preferable to perform surface treatment such as treatment.

  Further, the length of the comb teeth is preferably set to 100 mm or less, more preferably 50 mm or less, depending on the thickness of the molded body. Even if the comb teeth are made of an elastically deformable material, the bending moment acting on the comb teeth due to the filling pressure and the foaming pressure varies depending on the length of the comb teeth. Therefore, by adjusting the length within the elastic deformation range, it is possible to prevent problems such as breakage of the comb teeth or plastic deformation.

  A method for producing the thermoplastic resin in-mold foam molded article of the present invention will be described.

In the present invention, by a conventionally known method for imparting foaming force, a part composed of thermoplastic resin pre-foamed particles having L / D of 2 or more and 10 or less, and heat having L / D of 0.8 or more and 1.2 or less. It is possible to mold a thermoplastic resin in-mold foam molded article in which both of the parts made of the plastic resin pre-foamed particles are present. Among the thermoplastic resin pre-expanded particles, when a polyolefin resin such as polypropylene resin is adopted, it is desirable to adopt the following pre-molding treatment or filling method because the pre-expanded particles made of the resin have a small foaming force. .
A) A method in which foamed particles are pressurized with an inorganic gas to impregnate the foamed particles with an inorganic gas to give a predetermined internal pressure of the foamed particles, and then filled into a mold and heated and fused with water vapor (impregnation method before molding) ),
B) A method in which foamed particles are compressed by gas pressure and filled into a mold, and the recovery force of the foamed particles is used to heat-fuse with water vapor (compression filling method),
C) A method in which foamed particles are filled in a state where the mold is opened about 10 to 50% without any pretreatment, and after the mold is completely closed, heat fusion with water vapor (cracking compression),
Such a method can be used.

  In the molding methods B) and C), there are almost no gaps between the pre-expanded particles after filling the mold, and they are closed. Therefore, it tends to be difficult to produce a molded body having sufficient voids. Therefore, among the above molding methods, in particular, the foamed particles of A) are pressurized with an inorganic gas to impregnate the foamed particles with the inorganic gas, and after applying a predetermined foamed particle internal pressure, the mold is filled. A method of heat-sealing with water vapor is preferable.

  Specifically, regarding the pressure treatment of the inorganic gas, the rod-shaped pre-expanded particles preferably have an internal pressure of the expanded particles of 0.12 MPa or more and 0.17 MPa or less in absolute pressure. It becomes easier to control the porosity, and a foam-molded part having a porosity of 25% to 50% can be more stably produced. The spherical pre-expanded particles preferably have an internal pressure of 0.18 MPa or more and 0.25 MPa or less in terms of absolute pressure. By setting such an internal pressure, it is possible to stably produce a foam molded portion having a porosity of 5% or less, a high fusion rate, and a high mechanical strength. There is no limitation in particular as said inorganic gas, For example, air, nitrogen, oxygen, helium, neon, argon, a carbon dioxide gas etc. can be used. These may be used alone or in combination of two or more. Among these, highly versatile air and nitrogen are preferable. The molding step includes a filling step for filling the molding space with pre-expanded particles, a heating step for heating and foam-fusing the pre-foamed particles filled in the molding space, and a cooling step for cooling the molded foam molded body, The process is roughly divided into four processes, ie, a mold release process for releasing the foamed molded product from the mold.

  Next, the heating process will be described. By supplying steam to the steam chambers 7 and 8 from the steam supply means 9 and 10 with the drain lines 16 and 17 of the cavity mold 1 and the core mold 2 opened, the air in the two steam chambers is removed from the system. To discharge. Next, steam is supplied to one steam chamber and discharged from the other steam chamber, whereby the air in the molding space is discharged and the pre-expanded particles and the mold are preheated. Next, in a state where both drain lines 16 and 17 are closed, steam is supplied to both the steam chambers 7 and 8 to heat and foam the pre-expanded particles. In the present invention, it is preferable to use steam having a gauge pressure of 0.18 to 0.25 MPa, although the fusion temperature of the pre-expanded particles varies depending on the crystallinity of the raw material. When the steam pressure is less than 0.18 MPa, there is a tendency that sufficient fusion strength cannot be obtained, and when the steam pressure exceeds 0.25 MPa, voids in the molded body are reduced, so that air permeability, water permeability or sound absorption is reduced. There is a tendency to cause a significant decrease in performance.

  In the next cooling step, cooling water is sprayed from a nozzle unit (not shown) toward the cavity mold 1 and the core mold 2, and the foam molded body in the molding space 3 is released through the cavity mold 1 and the core mold 2. It is a process of cooling and solidifying to a possible hardness of the molded body. The molded body of the present invention has a structure in which rod-shaped pre-expanded particles and spherical pre-expanded particles are present in a substantially partitioned shape. Since the part of the rod-shaped pre-expanded particles has a structure in which the pre-expanded particles are point-fused and have a large number of voids, the foaming pressure of the pre-expanded particles or the molded product decreases rapidly after heating, and a water cooling time of about 30 seconds is sufficient. It is. On the other hand, since the site | part which consists of spherical pre-expanded particles has a big foaming pressure after a heating equivalent to a normal thermoplastic resin foam, it is necessary to perform water cooling until a foaming pressure fully falls. Therefore, the water cooling time requires the same time as a foam using normal spherical pre-expanded particles. The water cooling time varies depending on the expansion ratio of the pre-expanded particles, but is generally in the range of 60 seconds to 200 seconds.

  In the mold release process, the cavity mold 1 and the core mold 2 are opened. In general, a partition member 4 is formed in the cavity mold 1 having the eject pin 5, and the separation mold resistance thereof is the core mold 2. Therefore, the foamed molded product remains on the cavity mold 1 side. However, when the molded body is attached to the movable mold, it is necessary to devise such as arranging a taper pin at the spherical pre-expanded particle portion having high mechanical strength. Thus, in a state where the foam molded body remains in the cavity mold 1, the foam molded body is protruded by the eject pin 5 and released from the mold.

  Since the foamed molded article immediately after release contains a lot of moisture, it is preferable to perform room temperature drying or high temperature drying. In particular, since the molded product of the present invention may have a moisture content of 200 to 300% immediately after molding, for example, the molded product of the present invention is allowed to stand for 1 to 2 hours at atmospheric pressure and room temperature to reduce the moisture content to 50% or less. Thereafter, curing is performed in a drying chamber at 65 to 75 ° C. for 5 to 24 hours, and finally, room temperature curing is performed for 5 to 24 hours to obtain a final molded body.

  The foamed molded article obtained as described above has excellent sound absorption effect or water permeability effect, and has mechanical strength or shape stability, so it can be used for various applications such as sound absorption material and drain material. Is possible. For example, floor spacers, tibia pads, shock absorbers inside pillars, shock absorbers inside door trims, and other interior materials for vehicles such as flooring materials for buildings such as concert halls and ordinary houses. It can be suitably used for a wall material including a core material constituting the wall material.

  As a specific example of application, when the sound absorption performance is mainly required and it is desired to prevent the peeling of the raw material in the assembly line with the floor spacer, the spherical pre-foamed particles are used for the outer periphery, and the other parts are rod-shaped pre-foams having sound absorption performance. What is necessary is just to comprise with particle | grains. In addition, toolboxes that require sound absorption performance and bending rigidity are composed of rod-shaped pre-expanded particles that have sound absorption performance in parts that do not require bending rigidity, and spherical pre-expanded parts that require bending rigidity. It is possible to cope with the structure by using particles, or by mixing rod-shaped pre-expanded particles and spherical pre-expanded particles in a sea-island shape. Further, the present invention is also applied to the case where the fusion-bonding strength is necessary locally in the assembly of the molded body mainly used for sound absorption or water permeation with the support portion or other parts. As described above, it is possible to achieve both sound absorption, water permeability, air permeability and strength at the site where fusion strength is required in the product, and it can be applied to a wide range of applications.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example.

Example 1
In order to produce the rod-shaped pre-expanded particles made of polypropylene, MI: 4.5 g / 10 min, melting point: 144 ° C., ethylene content: 2.8%, butene content: 1.3%, After adding 300 ppm of talc as a cell nucleating agent and melt-kneading in an extruder, it is extruded in a strand form from a circular die, cooled with water, cut with a cutter, and the weight of one grain is 1.8 mg / grain. Resin particles having L / D of 6.3 were obtained.

100 parts by weight (65 kg) of the obtained resin particles, 200 parts by weight of water, 0.5 parts by weight of basic tricalcium phosphate and 0.01 parts by weight of sodium alkyl sulfonate are charged into a pressure-resistant autoclave having a capacity of 0.35 m ³ . Under stirring, 16 parts of isobutane was added as a blowing agent, and then the autoclave contents were heated to a foaming temperature of 135 ° 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 expanded particles. The obtained expanded particles had L / D: 2.2, cell diameter: 103 μm, β / (α + β): 0.60, and bulk density: 0.019 g / cm ³ .

  For the spherical pre-expanded particles made of polypropylene, L / D: 1.05 was used, which is DBS45 (45 times product) manufactured by Kaneka Corporation.

  The foamed particles thus obtained were impregnated with air by air pressure treatment, and an internal pressure of 0.14 MPa in absolute pressure was applied to the rod-shaped pre-expanded particles and 0.20 MPa was applied to the spherical pre-expanded particles.

  The mold has a block shape of 300 x 400 x 50 mm, and the inner periphery is divided into 50 mm and the inside by a comb member. The comb part is made of stainless spring steel, the comb length is 49 mm, the comb diameter is φ2.5 mm, the comb spacing A 2.5 mm one was used.

  In the filling step, the spherical pre-expanded particles and rod-shaped pre-expanded particles are filled in this order with the mold opened 2 mm, and then the mold is completely closed, and the pre-expanded particles are heat-sealed with steam at a gauge pressure of 0.22 MPa. Went. Thereafter, water cooling was performed for 60 seconds to release the foam. The foamed molding obtained here had many voids and contained a large amount of water content by steam / cooling water, so it was left at room temperature for 1 hour, then dried at 75 ° C. for 24 hours, and then at room temperature for 24 hours. By performing the curing, a foamed molded article having both ensuring of porosity and shape retention was obtained.

(Comparative Example 1)
The rod-shaped pre-expanded particles used in Example 1 were impregnated with air by an air pressurization treatment to obtain pre-expanded particles having an absolute pressure of 0.14 MPa. This was filled in a 300 × 400 × 50 mm block mold, heated at a gauge pressure of 0.22 MPa, and water-cooled for 60 seconds to obtain a foam formed only of rod-shaped pre-expanded particles. This was left to stand at room temperature for 1 hour, and then subjected to drying at 75 ° C. for 24 hours and curing at room temperature for 24 hours.

  Table 1 shows the results of evaluation of the obtained molded body.

空隙率は前記したように、発泡体から２０×２０×４０ｍｍの直方体試料を、表面スキン層を含まないように切り出し、外形寸法より見掛け体積を求めた。更に、直方体試料を一定量のエタノールを入れたメスシリンダー中に浸漬し、その時の増加容積（真の体積）を測定し、見掛け体積と真の体積の差を、見掛け体積で除算した値を空隙率と定義した。

As described above, a 20 × 20 × 40 mm rectangular parallelepiped sample was cut out from the foam so as not to include the surface skin layer, and the apparent volume was determined from the external dimensions. Furthermore, a rectangular parallelepiped sample is immersed in a graduated cylinder containing a certain amount of ethanol, the volume increased (true volume) at that time is measured, and the value obtained by dividing the difference between the apparent volume and the true volume by the apparent volume is a gap. Defined as rate.

The sound absorption coefficient was measured by two methods, ie, a normal incidence measurement and a measurement method using a reverberation chamber. The numbers in the table represent the highest values. The normal incidence type measurement was based on JIS A1405, and the normal incident sound absorption coefficient was measured at 500 to 6400 Hz with a sample thickness of 40 mm. The sample was cut out from the obtained foamed molded article with a thickness of 40 mm so that the surface having the surface skin layer became the sound wave incident surface. The measurement was performed in a state where the sample was in close contact with the rigid wall that reflects sound waves, that is, in the absence of air behind. For the measurement, a normal incidence sound absorption measuring device SR-4100 manufactured by Ono Sokki Co., Ltd. was used. The reverberation chamber was measured according to JIS A1409 using a 9 m ³ reverberation chamber (manufactured by Nittobo Acoustic Engineering) and a sample size of 700 × 700 mm at 500 to 5000 Hz. Here, the sample used for the reverberation chamber measurement was a laminate of molded bodies molded with the molds shown in the examples or comparative examples.

  Peeling evaluation was performed by dropping the molded body 10 times from a position having a height of 1 m so that the corners hit the floor surface, and evaluating whether or not the pre-expanded particles were peeled from the molded body. Evaluation criteria were as follows: No peeling: ○, 2 times or less peeling: Δ, 3 times or more peeling: x.

It is the figure shown about L / D of the thermoplastic resin pre-expanded particle used for this invention. It is an example of the DSC curve obtained when measuring the thermoplastic resin pre-expanded particle of this invention using a differential scanning calorimeter. The horizontal axis is the temperature, and the vertical axis is the endothermic amount. The low temperature side is α and the high temperature side is β. It is the figure which showed the outline of the metal mold | die used by this invention. It is the figure which showed the division means of the metal mold | die used by this invention. It is the figure which showed another division means of the metal mold | die used by this invention. It is the figure which showed another division means of the metal mold | die used by this invention. It is the figure which showed that the rod-shaped pre-expanded particle and the spherical pre-expanded particle exist in the shape of a substantially partition through the frontal surface substantially "mouth" -shaped boundary surface. It is the figure which showed the other shape in which the rod-shaped pre-expanded particle and spherical pre-expanded particle exist in the substantially partition shape. It is the figure which showed the arrangement | sequence of the comb tooth of the partition member installed in the metal mold | die used in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cavity type 2 Core type 3 Molding space 4 Partition member 5 Eject pin 6 Filler 7 Cavity type vapor chamber 8 Core type vapor chamber 9 Cavity type vapor supply port 10 Core type vapor supply port 11 Cavity type frame 12 Core Mold frame 13 Cavity mold back plate 14 Core mold back plate 15 Core vent 16 Cavity mold drain port 17 Core mold drain port 18 Comb teeth 19 Partition plate

Claims (4)

Sites formed from thermoplastic resin pre-expanded particles having an L / D of 2 or more and 10 or less, and sites formed from thermoplastic resin pre-expanded particles having an L / D of 0.8 or more and 1.2 or less, characterized by the presence in the substantially compartment shape, method for producing a thermoplastic resin mold foamed articles.
Here, L is the length of the longest part of the expanded particles, D is an average value of the maximum diameter Dmax and the minimum diameter Dmin in a cross section perpendicular to the L direction, and L / D is a value calculated by the following equation. .

The outer peripheral part of the thermoplastic mold-molded molded body is formed from thermoplastic resin pre-expanded particles having an L / D of 0.8 or more and 1.2 or less,
The other portion is, L / D is equal to or formed from 2 to 10 of the thermoplastic resin pre-expanded particles, method for producing a thermoplastic resin mold foamed articles according to claim 1. When the thermoplastic resin pre-expanded particles are pressurized with an inorganic gas, the expanded particles are impregnated with the inorganic gas, and after applying a predetermined internal pressure of the expanded particles, the mold is filled and heated and fused with water vapor .
The thermoplastic resin pre-expanded particle internal pressure having an L / D of 2 to 10 is lower than the internal pressure of the thermoplastic resin pre-expanded particle having an L / D of 0.8 to 1.2, and these thermoplastic resin pre-expanded particles The method for producing a thermoplastic resin in-mold foam-molded article according to claim 1 or 2 , wherein the molding is simultaneously integrally molded in a mold. When the thermoplastic resin pre-expanded particles are pressurized with an inorganic gas, the expanded particles are impregnated with the inorganic gas, and after applying a predetermined internal pressure of the expanded particles, the mold is filled and heated and fused with water vapor .
L / D is an internal pressure of the thermoplastic resin pre-expanded particles of 2 or more and 10 or less, 0.12 MPa or more and 0.17 MPa or less in absolute pressure,
The internal pressure of the thermoplastic resin pre-expanded particles having an L / D of 0.8 or more and 1.2 or less is set to 0.18 MPa or more and 0.25 MPa or less in absolute pressure, and these thermoplastic resin pre-expanded particles are simultaneously integrally molded in the mold. The method for producing a foamed molded article in a thermoplastic resin mold according to claim 1 or 2 , characterized in that:

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