JP4160659B2 - Manufacturing method and manufacturing apparatus for foam molded article - Google Patents

Description

【００３６】
実施例２
発泡粒子の内圧を２．５ａｔｍとし、ラインスピードを１．５ｍ／分とした以外は実施例１と同様な条件で発泡成形体を製造した。得られた成形体の密度を表１に示す。
【００３７】
実施例３
無架橋直鎖状低密度ポリエチレン（α−オレフィン成分は４−メチルペンテン、密度０．９２５ｇ／ｃｍ³ 、メルトフローインデックス１．３ｇ／１０分）を基材樹脂とした発泡粒子（Ｍｐ１２４℃）を用い、嵩密度低下領域Ｄは設けたが、スチーム供給部１７ａからのスチームを供給しなかったこと以外は実施例１と同様な条件で発泡成形体を製造した。得られた成形体の密度を表１に示す。なお、実施例３においては、嵩密度の低下は下流の発泡粒子間融着領域Ｅから逆流して洩れてくるスチームで加熱することにより行った。
【００３８】
発泡粒子の嵩密度の測定は、上部に開口部を有する容積１０００ｃｍ³ の容器に、常温常圧下にて発泡粒子を充填し、次に、容器の開口部から溢れている発泡粒子を取り除いて、発泡粒子の嵩高さを容器の開口部と略一致させた場合の容器内の発泡粒子の重量を図り、該重量を容器の容積１０００ｃｍ³ で割ることにより求めた。
【００３９】
発泡成形体の密度の測定は、長さ５０ｃｍに切断した成形体について養生室（常圧、実施例１と２は６０℃、実施例３は８０℃）での２４時間放置、常温・常圧での２４時間放置を順次行った後、重量と体積を測定し、重量を体積で割ることにより求めた。尚、長尺の成形体の切断、養生室での放置は、製造後直ちに行った。
【００４０】
実施例１〜３で得られた発泡成形体は、発泡粒子間に空隙が認められないまでに良く埋まっており、成形体表面に粒子間凹みがほとんど認められず、粒子間融着性も良好であった。
【００４１】
【発明の効果】
以上説明したように本発明方法によれば、従来のポリオレフィン系樹脂発泡粒子を連続的に成型して発泡成形体を製造する方法と異なり、元の発泡粒子の嵩密度より密度が小さく、且つ外観の優れた発泡成形体を得ることができる。又、本発明方法によれば、同じ密度の発泡成形体を製造するのに、従来より高密度（低発泡倍率）の発泡粒子で足りるため、発泡粒子保管のスペースを節約できる。更に、本発明において発泡粒子に内圧を付与するには、発泡粒子を加圧無機ガス（通常は空気又は窒素）下に保持することにより行うが、かかる内圧の付与に際し、高密度（低発泡倍率）の発泡粒子の方が低密度（高発泡倍率）に比べ一般的に短時間で足りる。従って、本発明を使用すると製造時間の短縮化にも寄与することになる。
【００４２】
【図面の簡単な説明】
【図１】本発明方法に使用する成形装置の一実施態様を示す略図である。
【符号の説明】
３、５ ベルト
１１ ポリオレフィン系樹脂発泡粒子
１２ 成形体
１３ 突起
１７ａ 嵩密度低下領域のスチーム供給部
１７ｂ 発泡粒子間融着領域Ｅのスチーム供給部
Ａ 発泡粒子供給領域
Ｂ 冷却領域
Ｃ 通路
Ｄ 嵩密度低下領域
Ｅ 融着領域
Ｆ 供給開始部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for producing a foamed molded product.
[0002]
[Prior art]
Conventionally, as a method for molding polyolefin resin expanded particles, a method in which the expanded particles are filled in a mold and heated with steam to secondarily expand the expanded particles and fuse the particles together (hereinafter referred to as such molding). The method is called a batch molding method.) Only. On the other hand, in the case of polystyrene resin expanded particles, a method in which the expanded particles are continuously passed through a heating region while being conveyed between upper and lower belts (hereinafter referred to as a continuous forming method). The method of Japanese Patent Publication No. 52-2424 adopting the method of heating with steam, the method of Japanese Examined Patent Publication No. 41-1632 employing the method of heating at high frequency, and the method of heating with hot air are adopted. The method disclosed in Japanese Patent Publication No. 47-42621 is known. The continuous molding method has an advantage that a foamed particle molded body can be continuously produced and a long molded body can be obtained as compared with a batch type molding method.
[0003]
[Problems to be solved by the invention]
However, the method using high-frequency heating as described in Japanese Patent Publication No. 41-1632 has a problem that the apparatus is large and expensive, and there is a risk of generating sparks during high-frequency irradiation, and the heating temperature range is narrow. It is not suitable as a heating means for polyolefin resin foamed particles that must be heated inside. In addition, the hot air heating method described in Japanese Patent Publication No. 47-42621 is also difficult to control the heating temperature and is difficult to uniformly heat because the heat capacity is smaller than steam. It was unsuitable as a heating means for continuously forming particles.
[0004]
On the other hand, the method by steam heating is also an effective method for polyolefin resin expanded particles, but the polyolefin resin expanded particles can be obtained by a continuous molding method by steam heating as described in, for example, Japanese Patent Publication No. 52-2424. When trying to mold, steam for heating the foamed particles leaks to the foamed particle supply side, resulting in poor fusion of the particles due to insufficient heating, poor secondary foaming, etc., or when this steam leakage becomes severe, the particles flow back to the supply side. There was a problem such as. The reason for this is considered to be due to the difference in secondary foaming performance between the polystyrene-based resin expanded particles and the polyolefin-based resin expanded particles. That is, the polystyrene resin is amorphous, the retention of the foaming agent used in the production of the foamed particles is good, and the foamed particles contain a few percent of the foaming agent. Secondary foaming of the foamed particles occurs at a relatively low temperature (usually 100 ° C. or less). For this reason, when the polystyrene resin expanded particles are continuously formed, before the expanded particles reach the heating region, a moderate secondary expansion occurs to close the gap between the particles, and the polystyrene resin expanded particles are 1.0 kg. Combined with the ability to mold with steam at a relatively low pressure of around / cm ² G, it is possible to easily prevent the steam from leaking to the particle supply side. It is done.
[0005]
In contrast, polyolefin resin is crystalline, and the foaming agent used in the production of foamed particles escapes from the particles in a relatively short time. In order to achieve this, the temperature needs to be higher than in the case of expanded polystyrene-based resin particles. For this reason, it is not easy to secondarily foam the polyolefin resin foamed particles before the heating region to such an extent that the leakage of steam can be prevented, and high pressure steam is used to secondarily foam the polyolefin resin foamed particles. Since it is necessary to supply the polyolefin resin expanded particles to some extent before the heating region, it is difficult to prevent high-pressure steam from leaking only with the secondary expansion force of the expanded particles. It is thought. In order to obtain a good molded product by secondarily foaming the foamed particles and fusing the particles together, the polyolefin resin foam particles that require higher pressure steam than the polystyrene resin foam particles are required. In this case, the steam for heating is likely to leak, and as a result, the pressure of the steam for heating is lowered and the foamed particles cannot be sufficiently heated to obtain a good molded product. However, when the temperature becomes intense, the foamed particles flow backward to the supply side, making it impossible to mold.
[0006]
In view of the above problems, as a method for continuously molding the polyolefin resin expanded particles, the present applicant: (1) In the expanded particle supply region, expand the expanded particles to 40 to 70% of the original bulk volume. A method of heating with steam after compression (Japanese Patent Laid-Open No. 9-104026), and a method of heating with steam after gradually compressing foamed particles with increased internal pressure in the foamed particle supply region (Japanese Patent Laid-Open No. 9-104026). -104027). However, these methods still have the following problems.
[0007]
That is, in the method (1), since the expanded particles are heated in a compressed state of 40 to 70% of the original bulk volume, the resulting molded product is greatly reduced in relation to the bulk density of the original expanded particles. There is a problem that the density increases, that is, a problem that the expansion ratio is significantly reduced with respect to the apparent expansion ratio of the original expanded particles.
[0008]
On the other hand, in the method (2), since foamed particles having an increased internal pressure are used, a molded body having a higher expansion ratio than that of the molded body obtained by the method (1) can be obtained. The density could not be made smaller than the bulk density of the original expanded particles. In the method (1), the expanded particles are gradually compressed in the expanded particle supply region, and the particles are fused by steam heating in the compressed state.
[0009]
As described above, any of the conventional methods for continuously forming polyolefin resin expanded particles is a method in which the density of the molded product cannot be made smaller than the bulk density of the original expanded particles. Therefore, in the conventional method, since it is necessary to prepare foamed particles having a bulk density smaller than the density of the target molded body in advance, there is a problem that a space for storing the foamed particles must be widened. It was.
[0010]
The present invention has been made in view of the above points, and in continuous molding using polyolefin resin expanded particles (hereinafter referred to as expanded particles), a molded product having a density smaller than the bulk density of the expanded particles can be obtained. It aims at providing the manufacturing method and manufacturing apparatus of a foaming molding. If the present invention is used, it is possible to obtain a molded article having a high expansion ratio (molded article having a low density without reducing the density) without previously expanding the foamed particles more than necessary. Storage space can be saved.
[0011]
[Means for Solving the Problems]
That is, the method for producing a foamed molded article of the present invention is a polyolefin resin foaming between belts that move continuously along the upper and lower surfaces in a passage formed in a substantially rectangular cross section surrounded by a structural material. In the method of supplying particles and then successively passing through the heating region and the cooling region in the passage to continuously produce a foamed molded article, a step of reducing the bulk density of the foamed particles, and fusing the foamed particles together Providing a process and reducing the bulk density of the polyolefin-based resin foamed particles by making the maximum cross-sectional area in the passage of the process of reducing the bulk density of the foamed particles larger than the cross-sectional area of the supply start portion of the foamed particle supply region However, it is sufficient for the foamed polyolefin resin particles to be fused to each other by supplying steam at a temperature insufficient to fuse the foamed polyolefin resin particles into the passage. Characterized in that to obtain a body.
[0012]
Moreover, in this invention, it is preferable that the internal pressure of the polyolefin-type resin foam particle to supply is 2.0 atm or more.
[0014]
In addition, the foam molded body manufacturing apparatus of the present invention is a polyolefin resin foam between belts that move continuously along the upper and lower surfaces in a passage having a substantially rectangular cross section surrounded by a structural material. particles supplied and then a manufacturing apparatus for manufacturing a heating area and density than the bulk density of the cooling region are sequentially passed through a continuously original foamed particles are smaller foamed molded in the passage, foamed Means for lowering the bulk density of the particles and means for fusing the foamed particles are sequentially provided, and means for reducing the bulk density of the foamed particles is the maximum in the passage in the region where the bulk density of the foamed particles is reduced. The steam supply section for supplying steam in the passage with a temperature insufficient to fuse the polyolefin resin foam particles to each other, and the cross-sectional area of the foamed particle supply area is larger than the cross-sectional area of the supply start section of the foam particle supply area Characterized in that the formed.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the base resin for the expanded particles used in the present invention include high-density polyethylene, medium-density polyethylene, branched low-density polyethylene, polypropylene, polybutylene and other olefin homopolymers, linear low-density polyethylene, linear ultra-high density polyethylene, and the like. Olefin copolymers such as low density polyethylene, ethylene-propylene block copolymer, ethylene-propylene random copolymer, ethylene-propylene-butene random copolymer, or the above-mentioned polyolefin homopolymers and polyolefin copolymers And polyolefin resins such as a graft polymer of a styrene resin and / or an acrylic resin, and these may be used by appropriately mixing them. These resins are used uncrosslinked or in a crosslinked state.
[0017]
The expanded particles used in the present invention preferably have a bulk density of 0.009 to 0.4 g / cm ^{3, and} a non-crosslinked polypropylene resin or a non-crosslinked polyethylene resin is used as a base resin, and the difference between the expanded particles A DSC curve obtained by scanning calorimetry preferably has two endothermic peaks (see Japanese Patent Publication No. 63-44779 and Japanese Patent Publication No. 7-39501). The DSC curve refers to a DSC curve obtained when 0.5 to 4 mg of expanded particles are measured with a differential scanning calorimeter by raising the temperature from room temperature to 210 ° C. at a rate of temperature increase of 10 ° C./min. The base resin is a non-crosslinked polypropylene resin or a non-crosslinked polyethylene resin, and the expanded particles having two endothermic peaks in the DSC curve have surface smoothness and dimensional stability compared to those having no two endothermic peaks. And there exists an effect from which the molded object excellent in mechanical strength is obtained.
[0018]
The foamed particles in the present invention are prepared by, for example, dispersing a polyolefin-based resin and a foaming agent in water in a sealed container, heating the resin particles to a temperature equal to or higher than the softening point of the resin particles, and impregnating the resin particles with the foaming agent. The resin particles and water are released under a lower pressure atmosphere to foam the resin particles.
[0019]
The foamed particles used in the method of the present invention need to be given an internal pressure of atmospheric pressure or higher by applying a pressure treatment with air or the like, and preferably have an internal pressure of 2.0 atm (absolute pressure) or higher. Those having an internal pressure of 5 to 7.0 atm (absolute pressure) are particularly preferable. When the internal pressure is less than atmospheric pressure, it is difficult to make the density of the obtained molded product equal to or less than the bulk density of the expanded particles. If the internal pressure is not less than 2.0 atm even if the internal pressure is higher than atmospheric pressure, the density of the resulting molded product can be reduced below the bulk density of the expanded particles, but the foaming power is reduced, so the appearance of the molded product is slightly inferior. It will be a thing. Although there is no restriction | limiting in particular in the particle weight etc. of the foaming particle to be used, Usually, a thing with an average particle weight of about 0.5-5 mg is used.
[0020]
FIG. 1 shows an example of a molding apparatus for carrying out the continuous molding method for foamed particles according to the present invention. In the figure, A is a foamed particle supply area (hereinafter referred to as supply area A), and B is a cooling area of a molded body. (Hereinafter referred to as a cooling region B), C is a passage (hereinafter referred to as passage C) through which foamed particles and a molded body are transferred, and D is an expansion of the passage C and the bulk density of the foamed particles by steam heating. An area to be reduced (hereinafter referred to as a bulk density reduction area D), E is an area in which the foam particles are fused by steam heating (hereinafter referred to as a fusion area E), and F is a supply in the foam particle supply area. It is a start part (hereinafter referred to as supply start part F). This forming apparatus has a hopper 1 that stores foam particles, a belt 3 that travels endlessly between upper rolls 2a and 2b, and a belt 5 that travels endlessly between lower rolls 4a and 4b. The foamed particles 11 supplied to A are sandwiched between the upper and lower belts 3 and 5 that run endlessly and steam heated while passing through the passage C to reduce the bulk density of the foamed particles. The particles are fused to obtain a molded body. In the figure, reference numeral 18 denotes a support.
[0021]
In the molding apparatus of the present invention, the upper roll 2a and the lower roll 4a are driven to rotate, the upper roll 2b and the lower roll 4b are not rotated, and the upper belt 3 and the lower belt 5 are respectively rolled into the roll 2b. 4b is configured to slide on the peripheral surface 4b. A surface made of polytetrafluoroethylene (Teflon) or the like is provided on the surface of the rolls 2b and 4b in contact with the belt, so that the slipperiness on the surface is improved. The upper roll 2b is configured such that its position can be moved up and down by a driving means (not shown), and the inclination angle of the upper belt 3 in the supply region A can be varied by changing the position of the upper roll 2b. . 6 is an auxiliary plate, and the auxiliary plate 6 can change the height of the supply start portion F (the cross-sectional area of the supply start portion F) by adjusting the inclination angle of the upper belt 3 by moving the upper roll 2b up and down. It is configured as follows. Therefore, for example, by reducing the position of the upper roll 2b, the maximum cross-sectional area in the passage C of the bulk density reduction region D can be made larger than the cross-sectional area of the supply start part F. In addition, the supply start part F hits directly under the center 20 of the upper side roll 2b.
[0022]
The expanded particles supplied in the supply region A are next to upper and lower thickness regulating plates 7 and 8 and width regulating plates (not particularly shown) provided on both sides of the thickness regulating plates 7 and 8. ), And the lower portion 3a of the upper belt 3 and the upper portion 5a of the lower belt 5 in the passage C. In addition, it is configured to travel between the thickness regulating plates 7 and 8. The thickness regulating plates 7 and 8, the width regulating plate and the auxiliary plate 6 are made of a metal plate such as an aluminum plate, and the slippage of the belts 3 and 5 is improved on the surface in contact with the belts 3 and 5. Further, a sliding material made of Teflon or the like is fixed. The endless running belt is not limited to being provided only on the top and bottom, but can be provided on both side surfaces. If belts that run endlessly are also provided on both side surfaces, there is no risk of the molded body rubbing against the surface of the width regulating plate or the like, so the shape and appearance of the side surface of the molded body obtained can be improved. it can.
[0023]
In the present invention, it is sufficient to reduce the bulk density of the polyolefin-based resin foam particles in the bulk density lowering region D provided before the inter-foamed particle fusion region E. It is desirable that steam having a temperature insufficient for fusing is ejected from the steam supply unit 17a into the passage. If the temperature of the steam does not reach a temperature sufficient to reduce the bulk density of the foamed particles, the bulk density of the foamed particles cannot be reduced. The object of the present invention to increase the magnification cannot be achieved. On the other hand, when the temperature of the steam reaches a temperature sufficient to fuse the foamed particles to each other, density density is formed in the obtained molded body, or the surface state of the molded body is deteriorated.
[0024]
Although it is sufficient to reduce the bulk density of the polyolefin resin expanded particles, the steam temperature insufficient to fuse the polyolefin resin expanded particles to each other is slightly different depending on the magnitude of the internal pressure applied to the expanded particles. However, on the basis of the melting point (hereinafter referred to as Mp) indicated by the resin composition constituting the expanded particles, for example, when the expanded particles are composed of a non-crosslinked polypropylene resin, Mp-35 ° C to Mp- When the expanded particles are made of an uncrosslinked polyethylene resin at 15 ° C, the temperature is Mp-20 ° C to Mp-10 ° C. In addition, the above Mp raises the foamed particles 0.5 to 4 mg by a differential scanning calorimeter from room temperature to 210 ° C. at a rate of 10 ° C./min, then to 40 ° C. at a rate of 10 ° C./min, The temperature at the top of the main melting peak in the second DSC curve obtained when the temperature is raised again to 210 ° C. at a rate of 10 ° C./min.
[0025]
In order to inject steam into the passage from the steam supply unit 17a, the belts 3 and 5 need to have steam permeability. Usually, a stainless steel belt having a thickness of about 0.2 to 1.0 mm is used. A material having a large number of through holes having a diameter of 0.5 to 3.0 mm and a pitch of about 3 to 50 mm is used.
[0026]
The steam for heating for reducing the bulk density of the expanded particles supplied from the steam supply unit 17a passes from the through holes in the thickness regulating plates 7 and 8 to the passage C through the through holes provided in the belts 3 and 5. It comes to be supplied.
[0027]
In the present invention, in order to reliably compress the foamed particles on the upstream side of the bulk density reduction region D, for example, protrusions 13 can be provided above and below the passage C as shown in FIG. The expanded particles are affected by the heating steam supplied from the steam supply unit 17a and / or the steam supply unit 17b, and thermal expansion starts on the protrusion 13 or a point slightly upstream thereof. The thermal expansion acts so as to fill the gap between the expanded particles between the protrusions 13 and the protrusions 13, and as a result, the backflow of the expanded particles due to a large amount of heating steam leaking to the expanded particle supply side is prevented. Can do. The degree of compression can be adjusted by changing the protrusion height of the protrusion 13 or by changing the inclination angle of the upper belt 3 in the supply region A.
[0028]
The protrusions 13 may be provided on either the upper or lower side, may be provided on both the upper and lower sides, or may be provided on only one of the upper part or the lower part, or may be arranged with the positions of the upper and lower parts shifted. Further, the shape of the protrusion 13 is not limited to the trapezoidal shape as illustrated, and may be an arbitrary shape.
In order to improve the slipperiness between the protrusion 13 and the belts 3 and 5, a sliding material made of Teflon or the like is provided on the surface of the protrusion 13 in contact with the belts 3 and 5, or the entire protrusion 13 is formed of Teflon or the like. It is preferable.
[0029]
The expanded particles having a reduced bulk density are then sent to the fused region E between the expanded particles while being sandwiched between the belts 3 and 5. In this region, the expanded particles are heated by the steam ejected from the steam supply unit 17b into the passage C, and if there are voids between the expanded particles, the expanded particles expand to fill the voids and are fused to each other. . The region E where the foam particles are fused is provided with a steam supply portion 17b for forming the foam particles 11 by steam heating, and the heating steam or steam drain is provided upstream of the foam particle fusion region E. Has a suction part 9 for vacuum suction. By providing the suction portion 9 and performing suction, it is possible to prevent the drain (condensed water) from collecting in the passage and inhibiting the supply of the foamed particles. The suction part can also be provided on the downstream side of the fusion region E between the expanded particles. By providing the suction portion on the downstream side and sucking the drain, it is possible to prevent the occurrence of problems such as warping of the molded body due to a decrease in the cooling effect of the molded body caused by the drain.
[0030]
Heating steam for fusing the foam particles supplied from the steam supply unit 17b is supplied from the through holes in the thickness regulating plates 7 and 8 to the passage C through the through holes provided in the belts 3 and 5. It has come to be. The temperature of the steam for heating supplied from the steam supply unit 17b is based on the above Mp. Usually, when the foamed particles are made of a non-crosslinked polypropylene resin, the foamed particles are not cross-linked. When it consists of a polyethylene-type resin, it is Mp-10 degreeC-Mp + 10 degreeC.
[0031]
The foamed particles heated by the steam expand so as to completely fill the space between the particles in the passage C, and are fused with each other to form a molded product (at this point, it cannot be said to be a complete molded product) However, since fusion between the expanded particles is generated, it is called a molded body for convenience.) Then, it is transferred to the cooling region B provided with the cooling means 10 and cooled. As the cooling means 10, for example, a cooling plate in which a cooling water circulation pipe is inserted is used. The above process is repeated continuously, and the long molded object 12 is obtained. Although not particularly illustrated, the suction unit 9, the steam supply units 17a and 17b, and the cooling means 10 are not only provided on the thickness regulating plates 7 and 8, but also on the width regulating plate side. good.
[0032]
In the present invention, it is preferable that the cross-sectional area in the passage is substantially constant from the end point of the fusion region E between the expanded particles until the molded body is sufficiently cooled. When the molded body is compressed on the downstream side from the end point of the inter-foamed particle fusion region E until the molded body is sufficiently cooled (when the cross-sectional area of the space in the passage after the inter-foamed particle fusion region E is narrowed), A trace such as a resin flow pattern remains on the surface of the obtained molded body 12, and the surface state of the molded body 12 is lowered. Conversely, if the cross-sectional area of the space in the passage after the region E in which the expanded particles are fused is increased, there is a possibility that cooling cannot be performed sufficiently.
[0033]
【Example】
Example 1
The apparatus provided with the bulk density reduction area | region D shown in FIG. 1, the fusion | melting area | region E between foaming particles, and the trapezoid protrusion 13 was used. The width from the passage C after passing the upper roll 2b to the molded body outlet in the cooling region B was constant at 300 mm. Accordingly, the ratio of the height in the passage of the inter-foamed particle fusion region E to the height of the supply start portion F in the supply region A is the maximum cross-sectional area in the passage in the bulk density reduction region D and the supply start portion in the supply region A. The ratio of the cross-sectional area of F. The height of the passage C from the end of the protrusion 13 to the outlet of the cooling region B is constant at 52 mm, and the height of the passage C narrowed by the protrusion 13 is 20 mm. The length from the supply start portion F to the start end of the protrusion 13 is 1.3 m, the entire length of the protrusion 13 is 0.2 m, the length from the end of the protrusion 13 to the inlet of the cooling region B is 0.8 m, and the cooling region The length of B was 6 m.
[0034]
Expanded particles (internal pressure of 4.0 atm, bulk density of 0.05 g / w) using uncrosslinked ethylene-propylene random copolymer (ethylene component 4.1%, melt flow index 8 g / 10 min) as a base resin in the above apparatus. cm ³ , Mp138 ° C.) from the hopper 1 and sandwiched between the belts 3 and 5, the supply area A, the bulk density reduction area D, the fusion area E, and the cooling area B are sequentially transferred to produce a foam molded article. . Table 1 shows the height of the fusion zone E in the passage, the height of the supply start portion F, the steam pressure for heating introduced into the passage C from the steam supply portions 17a and 17b, the line speed, and the density of the obtained molded body. Show. In this embodiment, vacuum suction was performed in the suction section 9 as shown in FIG.
[0035]
[Table 1]

[0036]
Example 2
A foamed molded article was produced under the same conditions as in Example 1 except that the internal pressure of the foamed particles was 2.5 atm and the line speed was 1.5 m / min. Table 1 shows the density of the obtained molded body.
[0037]
Example 3
Expanded particles (Mp124 ° C.) using uncrosslinked linear low-density polyethylene (α-olefin component is 4-methylpentene, density 0.925 g / cm ³ , melt flow index 1.3 g / 10 min) as a base resin. Used, a bulk density reduction region D was provided, but a foamed molded article was produced under the same conditions as in Example 1 except that steam from the steam supply unit 17a was not supplied. Table 1 shows the density of the obtained molded body. In Example 3, the bulk density was lowered by heating with steam leaking backward from the fusion region E between the expanded foam particles downstream.
[0038]
For the measurement of the bulk density of the expanded particles, a container having a volume of 1000 cm ³ having an opening at the top is filled with the expanded particles under normal temperature and normal pressure, and then the expanded particles overflowing from the opening of the container are removed. The weight of the foamed particles in the container when the bulkiness of the foamed particles was made to substantially coincide with the opening of the container was determined by dividing the weight by the volume of the container of 1000 cm ³ .
[0039]
The measurement of the density of the foamed molded product was carried out for 24 hours in a curing room (normal pressure, 60 ° C. in Examples 1 and 2 and 80 ° C. in Example 3) for a molded product cut to a length of 50 cm. After standing for 24 hours, the weight and volume were measured, and the weight was divided by the volume. The long shaped body was cut and left in the curing room immediately after production.
[0040]
The foamed moldings obtained in Examples 1 to 3 were well embedded until no voids were observed between the foamed particles, almost no interparticle dents were observed on the surface of the molded body, and the interparticle fusion properties were also good. Met.
[0041]
【The invention's effect】
As described above, according to the method of the present invention, the density is smaller than the bulk density of the original foamed particles and the appearance is different from the conventional method of producing a foamed molded product by continuously molding the foamed polyolefin resin particles. Can be obtained. Further, according to the method of the present invention, foamed particles having a higher density (low expansion ratio) than before can be used to produce a foamed molded product having the same density, so that the space for storing the foamed particles can be saved. Furthermore, in the present invention, the internal pressure is applied to the expanded particles by holding the expanded particles under a pressurized inorganic gas (usually air or nitrogen). When applying the internal pressure, a high density (low expansion ratio) is applied. ) Foamed particles generally require less time than low density (high expansion ratio). Therefore, if this invention is used, it will also contribute to shortening of manufacturing time.
[0042]
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of a molding apparatus used in the method of the present invention.
[Explanation of symbols]
3, 5 Belt 11 Polyolefin resin foamed particles 12 Molded body 13 Protrusion 17a Steam supply portion 17b in the bulk density lowering region Steam supply portion A in the interfoaming region fusion region A Foamed particle supply region B Cooling region C Passage D Bulk density lowering Area E Fusion area F Supply start section

Claims (3)

A polyolefin-based resin foamed particle is supplied between belts that move continuously along the upper and lower surfaces in a passage having a substantially rectangular cross section surrounded by a structural material, and then a heating region in the passage In the method of continuously producing a foamed molded article by sequentially passing through the cooling region, a step of reducing the bulk density of the foamed particles and a step of fusing the foamed particles are provided to reduce the bulk density of the foamed particles. It is sufficient to make the maximum cross-sectional area in the passage of the process larger than the cross-sectional area of the supply start part of the foam particle supply region and to reduce the bulk density of the polyolefin resin foam particles. foamed molded body characterized by obtaining a molded foam product even density lower than the bulk density of the original expanded particles by a temperature steam insufficient to fusing the particles together is supplied into the passage Manufacturing method.   The method for producing a foamed molded article according to claim 1, wherein the polyolefin resin foam particles to be supplied have an internal pressure of 2.0 atm or more. A polyolefin-based resin foamed particle is supplied between belts that move continuously along the upper and lower surfaces in a passage having a substantially rectangular cross section surrounded by a structural material, and then a heating region in the passage And a manufacturing apparatus for successively producing a foamed molded article having a density lower than the bulk density of the original foamed particles by sequentially passing through the cooling region, between the foamed particles and the means for reducing the bulk density of the foamed particles and it is sequentially provided means for fusing the, means for reducing the bulk density of the expanded beads is the maximum of the cross-sectional area of the passage area to reduce the bulk density of the expanded beads, starting the supply of the foam particle supply region to be greater than the cross-sectional area of the parts, and foamed molded body characterized by forming the steam supply unit for supplying steam insufficient temperature in the passage to be mutually fused polyolefin resin expanded particles Manufacturing equipment.

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