A method for producing particle foam compressed objects with a shell.
Patent Information
- Authority / Receiving Office
- TH · TH
- Patent Type
- Patents
- Current Assignee / Owner
- JSP CORP
- Filing Date
- 2017-12-21
- Publication Date
- 2026-06-30
Abstract
Description
Manufacturing method for molded foam particles with a surface coating.
[0001] The present invention relates to a method for manufacturing a foam particle molded body with a surface, comprising blow molding a softened parison formed by extruding a polypropylene resin to form a hollow molded body, filling the hollow portion of the hollow molded body with polypropylene resin foam particles, supplying a heating medium from a pin inserted into the hollow molded body to heat-fuse the polypropylene resin foam particles to each other, and also heat-fuse the polypropylene resin foam particles to the hollow molded body.
[0002] A surfaced foam particle molded body is known, which has a structure in which a hollow molded body is used as a surface material and a molded body of thermoplastic resin foam particles is placed in the hollow part of the hollow molded body. Among such surfaced foam particle molded bodies, those having a structure in which a molded body of polypropylene resin foam particles is placed in the hollow part of a hollow molded body formed from a polypropylene resin composition are lightweight and have excellent strength. For this reason, surfaced foam particle molded bodies using polypropylene resin are used in various industrial fields, including car interior materials.
[0003] Patent Document 1 proposes the following method for manufacturing a foamed particle molded body with a surface using a polypropylene resin. First, a parison made of a polypropylene resin composition is suspended between a set of blow-molding dividers and sandwiched between the molds to form a hollow molded body. The hollow part of this hollow molded body is filled with polypropylene resin foamed particles, and then a heating medium such as steam is blown into the hollow molded body. As a result, the polypropylene resin foamed particles are heated and fused together to form a foamed particle molded body, and the surface of the foamed particle molded body is fused to the inner surface of the hollow molded body. After that, the mold is cooled and the molded product is removed from inside the mold to obtain a foamed particle molded body with a surface.
[0004] Furthermore, for a surfaced foam particle molded body, excellent adhesion between the inner surface of the hollow molded body formed from a polypropylene resin composition and the surface of the foam particle molded body is required. In this regard, Patent Document 1 proposes that a metallocene-based polypropylene resin having specific thermal properties be used as a resin for forming a hollow molded body. According to the invention disclosed in Patent Document 1, a surfaced foam particle molded body that is lightweight and has excellent adhesion between the inner surface of the hollow molded body and the surface of the foam particle molded body can be obtained. Here, metallocene-based polypropylene resin refers to a polypropylene resin polymerized with a metallocene-based polymerization catalyst.
[0005] Japanese Patent Publication No. 2008-273117
[0006] When a metallocene-based polypropylene resin with specific thermal properties is used as the resin for forming a hollow molded body, as in the invention disclosed in Patent Document 1, the foamed particle molded body with a surface layer exhibits excellent adhesion between the inner surface of the hollow molded body and the surface of the foamed particle molded body, as described above. However, in the invention disclosed in Patent Document 1, the resin tends to melt from the inner surface of the hollow molded body when heated with a heating medium. Therefore, when attempting to obtain a hollow molded body with a thin thickness, the uneven shape caused by the foamed particles filling the hollow portion tends to appear on the outer surface of the hollow molded body. For this reason, the invention disclosed in Patent Document 1 leaves room for further investigation regarding the surface properties of the foamed particle molded body with a surface layer when the surface layer is thinned.
[0007] The present invention aims to provide a method for manufacturing a foam particle molded body with a surface layer that exhibits excellent surface properties and excellent adhesion between the surface layer and the foam particle molded body, even when the thickness of the surface layer is thin.
[0008] The present invention provides a method for producing a foam particle molded body with a surface, comprising: (1) blow molding a softened parison formed by extruding a polypropylene resin to form a hollow molded body; filling the hollow portion of the hollow molded body with polypropylene resin foam particles; supplying a heating medium into the hollow molded body to heat-fuse the polypropylene resin foam particles to each other, and also heat-fusing the polypropylene resin foam particles to the hollow molded body; A method for producing a foamed particle molded body with a surface, characterized in that the polypropylene resin forming the hollow molded body has a melt elongation of 100 m / min or more at 190°C, a semi-crystallization time of the polypropylene resin at 100°C of 25 seconds or more and 80 seconds or less, a melt peak temperature of the polypropylene resin in differential scanning calorimetry of 130°C or more and 155°C or less, a partial melting heat of the polypropylene resin at 140°C or more of 20 J / g or more and 50 J / g or less, and a ratio of the partial melting heat of the polypropylene resin to the total melting heat of the polypropylene resin (partial melting heat / total melting heat) of 0.2 or more and 0.8 or less. (2) A method for producing a foamed particle molded body with a surface according to (1) above, characterized in that the polypropylene resin forming the hollow molded body has a melt tension of 3 cN or more at 190°C. The gist of this invention is: (3) A method for manufacturing a surface-covered foam particle molded body according to (1) or (2) above, characterized in that the average thickness of the hollow molded body is 0.3 mm or more and 1.5 mm or less; (4) A method for manufacturing a surface-covered foam particle molded body according to any one of (1) to (3) above, characterized in that the peel strength between the hollow molded body and the foam particle molded body is 0.4 MPa or more; and (5) A method for manufacturing a surface-covered foam particle molded body according to any one of (1) to (4) above, characterized in that the length of the surface-covered foam particle molded body in the extrusion direction is 500 mm or more.
[0009] According to the present invention, by forming a surface material using a polypropylene resin having specific physical properties, it is possible to provide a method for manufacturing a foam particle molded body with a surface material that has excellent surface properties and excellent adhesion between the surface material and the foam particle molded body, even when the thickness of the surface material is thin.
[0010] Figure 1 shows an example of an endothermic curve graph obtained by a differential scanning calorimeter (DSC) to explain the heat of fusion (ΔT) and total heat of fusion (ΔH) of a polypropylene resin composition used in the manufacturing method of the present invention. Figure 2 is a schematic cross-sectional view illustrating an example of the hollow molded body formation process in the blow molding process. Figure 3 is a schematic cross-sectional view schematically showing an example of a manufacturing apparatus for a foamed molded body with a skin. Figure 4 is a partially cut perspective view schematically showing an example of a foamed molded body with a skin.
[0011] The present invention relates to a method for manufacturing a molded article of foamed particles with a surface. The molded article of foamed particles with a surface has a structure in which a hollow molded body is used as a surface material and a molded article of polypropylene resin foamed particles (hereinafter also simply referred to as foamed particles) is placed in the hollow part thereof. The method for manufacturing this molded article of foamed particles with a surface comprises a step of forming the hollow molded body by blow molding (blow molding step), a step of filling the hollow part of the hollow molded body with foamed particles (foamed particle filling step), and a step of fusing the foamed particles inside the hollow molded body with each other and fusing the foamed particles with the hollow molded body (fusion step).
[0012] [Blow Molding Process] In the blow molding process, a hollow molded body is formed by blow molding a softened parison, which is formed by extruding a polypropylene resin.
[0013] Blow molding will be explained in more detail with reference to Figures 2 and 3. As shown in Figure 2, which illustrates an example of parison manufacturing, polypropylene resin is extruded from die 3 via an accumulator attached to the extruder, and a polypropylene resin parison 1 is suspended between a pair of left and right blow molding molds 2, 2, which can be opened and closed. Then, the molds are moved in the direction of the arrow toward the center in Figure 2 and clamped, air is introduced into the parison from the air introduction pipe 4 (blow pin), and air is sucked in from the suction pipes 5, 5 in the direction of the arrow toward the bottom in Figure 2 as needed to perform blow molding. This forms a hollow molded body that reflects the shape of the mold.
[0014] (Molten Polypropylene Resin Compound) A molten polypropylene resin compound is obtained by melting and kneading polypropylene resin in an extruder. Various additives may be added to the polypropylene resin or the molten polypropylene resin compound as needed.
[0015] (Additives) Examples of additives include conductivity imparters, antioxidants, heat stabilizers, weathering agents, UV inhibitors, flame retardants, inorganic fillers, antibacterial agents, electromagnetic shielding agents, gas barrier agents, and antistatic agents. These additives can be used insofar as they do not hinder the intended purpose of the present invention, but the amount added is generally 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 3 parts by weight or less, per 100 parts by weight of polypropylene resin. In this specification, K parts by weight corresponds to K parts by mass, and K by weight % corresponds to K by mass % (K is a real number).
[0016] (Hollow Molded Body) A hollow molded body formed in the blow molding process is a molded body made by forming a polypropylene resin into a predetermined shape, and is a molded body having a hollow portion.
[0017] (Polypropylene Resins) Examples of polypropylene resins used to form hollow molded articles include propylene homopolymers, copolymers of propylene and at least one comonomer selected from the comonomer group consisting of ethylene and / or α-olefins having 4 to 8 carbon atoms, or mixtures of two or more of these. Examples of copolymers of propylene and at least one comonomer selected from the comonomer group consisting of ethylene and / or α-olefins having 4 to 8 carbon atoms include propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-butene random copolymer, propylene-butene block copolymer, propylene-ethylene-butene random copolymer, and propylene-ethylene-butene block copolymer. Among these, it is preferable to use propylene-ethylene random copolymer as the polypropylene resin.
[0018] When a copolymer of propylene and at least one comonomer selected from the comonomer group consisting of ethylene and / or α-olefins having 4 to 8 carbon atoms is used as the polypropylene resin for forming the hollow molded article, the comonomer content in the polypropylene resin is preferably 0.5% by weight or more and 5.0% by weight or less, more preferably 1.0% by weight or more and 4.0% by weight or less, and even more preferably 2.0% by weight or more and 3.5% by weight or less.
[0019] The comonomer content in polypropylene resins can be determined by infrared absorption spectroscopy, using a calibration curve of a standard sample to calculate the relationship between the absorbance ratio of absorption peaks derived from the comonomer component and the weight ratio of the comonomer component, or by NMR spectroscopy.
[0020] Furthermore, the polypropylene resin used to form the hollow molded article preferably contains 50% by weight or more of a polypropylene resin having a melting peak temperature of 130°C or higher and 155°C or lower, more preferably more than 70% by weight, even more preferably more than 80% by weight, and particularly preferably more than 90% by weight.
[0021] (Melting Peak Temperature) The polypropylene resin used to form the hollow molded body has a melting peak temperature of 130°C to 155°C in differential scanning calorimetry. If the melting peak temperature of the polypropylene resin is too low or too high, it may become impossible to determine the partial melting heat of 140°C or higher, or the ratio of the partial melting heat to the total melting heat, in the differential scanning calorimetry of the polypropylene resin described later, within a specific range. From this viewpoint, it is preferable that the melting peak temperature is 135°C to 155°C.
[0022] (Identification of Melting Peak Temperature) The melting peak temperature can be measured using a differential scanning calorimeter (DSC) in accordance with JIS K7121 (1987). Examples of DSC differential scanning calorimeters (Q1000, manufactured by T.A. Instruments Japan Co., Ltd.) can be used. Using such equipment, the melting peak temperature can be specifically identified as follows.
[0023] Weigh out 3 mg to 5 mg of the sample resin whose melting peak temperature you want to determine. Heat the sample resin from room temperature to 200°C at a rate of 10°C / min, then immediately cool it to 30°C at a rate of 10°C / min. Next, heat the sample resin again to 200°C at a rate of 10°C / min. At this time, an endothermic curve will be obtained. At the peak of the obtained endothermic curve, the temperature corresponding to the peak portion (apex temperature) is identified as the melting point temperature. Since the endothermic curve originates from the heat of fusion of the resin, the melting point temperature, which is the temperature at the peak portion, corresponds to the melting peak temperature.
[0024] (Partial heat of fusion, ratio of partial heat of fusion to total heat of fusion) For polypropylene resins, the partial heat of fusion (ΔT) at 140°C or higher in differential scanning heat flux measurement is 20 J / g or more and 50 J / g or less, and the ratio of the partial heat of fusion at 140°C or higher to the total heat of fusion (ΔH) in differential scanning heat flux measurement (partial heat of fusion / total heat of fusion (ΔT / ΔH)) is 0.2 or more and 0.8 or less. If the above partial heat of fusion and the ratio of partial heat of fusion to total heat of fusion are too small, melting of the inner surface of the hollow molded body will proceed more easily during the fusion process. Although the adhesion between the foamed particles and the hollow molded body will be good, there is a risk that the uneven shape caused by the foamed particles will easily appear on the outer surface of the hollow molded body (risk of poor appearance). On the other hand, if the partial heat of fusion or the ratio of the partial heat of fusion to the total heat of fusion is too large, the melting of the hollow molded body will not proceed easily during the fusion process, which may reduce the adhesion between the foam particles and the hollow molded body. From the viewpoint of suppressing these appearance defects and reduced adhesion, the partial heat of fusion is more preferably 22 J / g or more and 45 J / g or less, and even more preferably 25 J / g or more and 40 J / g or less. Similarly, from the same viewpoint, the ratio of the partial heat of fusion to the total heat of fusion is more preferably 0.3 or more and 0.7 or less, and even more preferably 0.3 or more and 0.6 or less. Note that in differential scanning thermal flux calorimetry, the ratio of the partial heat of fusion at 140°C or higher to the total heat of fusion (ΔH) is sometimes simply called the heat of fusion ratio.
[0025] (Determination of the ratio of partial heat of fusion to total heat of fusion) In the present invention, the partial heat of fusion (ΔT) of polypropylene resin at 140°C or higher and the total heat of fusion (ΔH) of polypropylene resin in differential scanning calorimetry are determined as follows using a DSC curve obtained based on JIS K7122 (1987).
[0026] In differential scanning calorimetry (DSC), a sample resin of 3 mg to 5 mg is heated from room temperature to 200°C, and then immediately cooled to 30°C at a cooling rate of 10°C / min. Next, it is heated again to 200°C at a heating rate of 10°C / min. At this time, a DSC endothermic curve is obtained by plotting heat quantity (heat flow) on the vertical axis and temperature on the horizontal axis. The DSC endothermic curve is obtained as a curve exemplified in Figure 1, for example. Based on such a DSC endothermic curve, the partial heat of fusion (ΔT) and total heat of fusion (ΔH) above 140°C can be determined by performing the following steps 1, 2, and 3 in that order.
[0027] In step 1, a straight line (α-β) is drawn connecting point α at 80°C on the DSC endothermic curve and point β corresponding to the melting termination temperature (Te).
[0028] In step 2, draw a straight line parallel to the vertical axis of the graph from point σ at 140°C on the DSC endothermic curve, and let γ be the point where it intersects with the line (α-β).
[0029] In step 3, the amount of heat (Q1) corresponding to the area enclosed by the DSC curve and the line segments from point σ to point γ (σ-γ) and from point β to point γ (β-γ) (the region indicated by the symbol Z in Figure 1) is identified. Also, the amount of heat (Q2) corresponding to the area enclosed by the DSC curve and the line segment (α-β) is determined. Here, the partial heat of fusion (ΔT) above 140°C is defined as heat Q1. The total heat of fusion (ΔH) is defined as heat Q2. Therefore, by determining heat Q1 and Q2, the partial heat of fusion (ΔT) and the total heat of fusion (ΔH) above 140°C are determined.
[0030] In differential scanning thermal flux calorimetry, the starting point of the baseline (point α) is set to 80°C in this invention because the heat of fusion of polypropylene resin can be determined with high reproducibility. The 140°C used when determining the partial heat of fusion (ΔT) is a temperature that takes into account the actual steam temperature during the fusion process. Furthermore, the partial heat of fusion in the portion of the temperature range above 140°C, and the ratio of this partial heat of fusion to the total heat of fusion, are indicators selected based on the fact that showing specific values leads to significant results in achieving the intended objectives of this invention.
[0031] (Semi-crystallization time) The polypropylene resin forming the hollow molded body has a semi-crystallization time of 25 seconds to 80 seconds at 100°C. If the above semi-crystallization time is too short, even if the polypropylene resin satisfies the ratio of the partial heat of fusion to the total heat of fusion as described above, crystallization tends to proceed rapidly, which may prevent sufficient adhesion between the hollow molded body and the foamed particles. In addition, during blow molding, crystallization of the hollow molded body on the mold side tends to proceed rapidly, which may reduce the transferability of the mold shape. On the other hand, if the above semi-crystallization time is too long, although the adhesion between the foamed particles and the hollow molded body is good, the uneven shape caused by the foamed particles may easily appear on the outer surface of the hollow molded body. From the above viewpoint, the semi-crystallization time is preferably 25 seconds to 70 seconds, more preferably 25 seconds to 60 seconds, and even more preferably 25 seconds to 50 seconds. The 100°C used in measuring the semi-crystallization time is a temperature that takes into account the temperature of the steam supplied to the hollow part of the hollow molded body and the temperature of the mold used to cool the hollow molded body.
[0032] (Determination of Semi-Crystallization Time) In the present invention, the semi-crystallization time can be determined as follows. A polypropylene resin is prepared as a sample for measurement in the form of a film with a thickness of 0.2 mm (however, an error in thickness of 0.02 mm above or below 0.2 mm is permitted (0.18 mm or more and 0.22 mm or less)). This film sample is held on a support, and the support is placed in an air bath to melt the sample. Then, the sample, while still in a molten state, is immersed together with the support in an oil bath maintained at 100°C. The polarization of the sample, which changes as crystallization progresses in the oil bath, is measured. The change in polarization can be measured by measuring the transmitted light passing through the sample. The semi-crystallization time can then be calculated from this measured transmitted light data and the Aburami formula. As a device for measuring the semi-crystallization time, for example, a crystallization rate analyzer (MK-801) manufactured by Kotaki Seisakusho can be used.
[0033] In the present invention, even when the thickness of the hollow molded body is thin, the following reasons can be considered for achieving both the surface properties of the surface-covered foam particle molded body and the adhesion between the surface material and the foam particle molded body.
[0034] In the fusion process, the temperature of the steam supplied to the hollow portion of the hollow molded body is approximately 125°C or higher and 165°C or lower. On the other hand, the temperature of the mold on the outer surface side of the hollow molded body is approximately 40°C or higher and 90°C or lower. Therefore, the foamed particles filled in the hollow portion of the hollow molded body not only cause secondary foaming while the steam is being supplied, but also after the supply of the steam. After the supply of the steam ends, the hollow molded body is rapidly cooled by the mold. At this time, the ratio of the partial melting heat amount of the polypropylene-based resin forming the hollow molded body to the total melting heat amount of the polypropylene-based resin is within the above range (0.2 or more and 0.8 or less), and the semi-crystallization time is 25 seconds or more, the lower limit value. During the supply of the steam, the melting of the polypropylene-based resin proceeds appropriately, and even after the supply of the steam ends, the polypropylene-based resin does not rapidly crystallize, and that state is maintained for a certain period of time. For this reason, even after the supply of the steam ends, secondary foaming of the foamed particles occurs in a state where the hollow molded body is moderately softened. And it is considered that the adhesiveness between the foamed particles and the hollow molded body can be made stronger by the secondary foaming of the foamed particles after the supply of the steam ends. Also, at this time, since the semi-crystallization time is 80 seconds or less, the upper limit value, the crystallization of the hollow molded body can proceed appropriately, so it is considered that the surface shape of the foamed particles can be suppressed from appearing on the outer surface side of the hollow molded body.
[0035] (Melt elongation) The polypropylene-based resin forming the hollow molded body has a melt elongation at 190°C of 100 m / min or more. If the melt elongation is too small, it may be difficult to reduce the thickness of the hollow molded body, or it may be impossible to obtain a hollow molded body with a uniform wall thickness even if the thickness is small. From the above viewpoints, the melt elongation of the polypropylene-based resin at 190°C is preferably 110 m / min or more, and more preferably 120 m / min or more.
[0036] Note that 190°C in the measurement of melt elongation and melt tension described later is a temperature close to the temperature condition during parison formation, and is a measurement temperature at which the difference in the melt physical properties of the polypropylene-based resin clearly appears.
[0037] (Identification of Melt Elongation) Melt elongation can be measured as follows using a measuring device such as the Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. First, an orifice with a nozzle diameter of 2.095 mm and a length of 8.0 mm is set in a cylinder with a cylinder diameter of 9.55 mm and a length of 350 mm. The cylinder temperature is set to 190°C, and approximately 15 g of a polypropylene resin sample is placed inside the cylinder and left for 4 minutes. Then, the piston descent speed is set to 10 mm / min, and the molten polypropylene resin is extruded from the orifice in a string-like form to obtain a string-like material. At this time, this string-like material is placed on a pulley with a diameter of 45 mm, and the string-like material is taken up by a take-up roller while increasing the take-up speed at a constant rate so that the take-up speed reaches 200 m / min from 0 m / min in 4 minutes. This operation causes the string-like material to break, and the take-up speed just before the string-like material breaks is identified. This method of measuring the take-up rate is performed on 10 randomly sampled samples, and the arithmetic mean of these take-up rates can be used as the melt elongation. If the string-like material does not break, the maximum take-up rate (200 m / min) shall be used as the measured value.
[0038] (Melting Tension) The melting tension (MT) of the polypropylene resin forming the hollow molded body at 190°C is preferably 3 cN or more. By setting the melting tension (MT) of the polypropylene resin within the above range, drawdown in the blow molding process can be suppressed, and even with long, large-volume foamed particle molded bodies with a surface, the thickness of the hollow molded body can be stably reduced and its thickness made uniform. Furthermore, even with a complex mold shape, it becomes easier to form a hollow molded body that follows that complex shape, resulting in excellent mold shape reproducibility and further expanding the freedom of product shape design. In addition, the upper limit of the melting tension of the polypropylene resin forming the hollow molded body at 190°C is preferably about 30 cN or less, and more preferably 20 cN or less. By setting the upper limit of the melt tension within the above range, the propylene resin can stretch appropriately during the blow molding process, and control of parison widening by blow air, etc., becomes easier. As a result, hollow molded products with thin and uniform wall thickness can be stably obtained.
[0039] (Specification of melt tension) The melt tension can be measured using a measuring device such as the Capillograph 1D manufactured by Toyo Seiki Seisakusho, Ltd. First, an orifice with a nozzle diameter of 2.095 mm and a length of 8.0 mm is set in a cylinder with a cylinder diameter of 9.55 mm and a length of 350 mm. The set temperature of the cylinder and the orifice is 190°C. A required amount of a polypropylene-based resin sample is placed in the cylinder and left for 4 minutes to form a molten resin of the resin sample. Next, the molten resin is extruded from the orifice in a string shape at a piston speed of 10 mm / min. This string is hung on a pulley for tension detection with a diameter of 45 mm, and the string is pulled by a take-up roller while increasing the take-up speed at a constant acceleration so that the take-up speed reaches from 0 m / min to 200 m / min in 4 minutes. By this operation, the string is broken, and the maximum value of the tension immediately before the string breaks is obtained. Here, the reason why the time until the take-up speed reaches from 0 m / min to 200 m / min is set to 4 minutes is to suppress the thermal deterioration of the resin and enhance the reproducibility of the obtained value. The above operation is performed 10 times in total using different samples. Excluding three values in order from the largest value of the maximum values obtained in 10 times and three values in order from the smallest value of the maximum values, the value obtained by calculating the arithmetic mean of the remaining four intermediate maximum values is defined as the melt tension (cN) in the method of the present invention.
[0040] However, if the molten tension is measured using the method described above and the string-like material does not break even when the draw speed reaches 200 m / min, the value of the molten tension (cN) obtained by maintaining a constant draw speed of 200 m / min is adopted. Specifically, in the same manner as the measurement described above, molten resin is extruded from the orifice in the form of a string, and this string-like material is placed on a tension detection pulley. The draw speed is increased at a constant rate so that it reaches 200 m / min from 0 m / min in 4 minutes. After the rotation speed reaches 200 m / min, data acquisition of the molten tension is started and stopped after 30 seconds. The average value (Tave) of the maximum tension (Tmax) and minimum tension (Tmin) obtained from the tension load curve obtained during these 30 seconds is taken as the molten tension in the method of the present invention. Here, Tmax is the value obtained by dividing the total number of peaks (peaks) detected in the tension load curve by the number of detected peaks, and Tmin is the value obtained by dividing the total number of dips (troughs) detected in the tension load curve by the number of detected dips. When extruding the molten resin from the orifice in the above measurement, the measurement should be carried out in a manner that minimizes the inclusion of air bubbles in the string-like material.
[0041] When manufacturing molded articles with a surface layer of foamed particles, the thinner the surface layer of the molded article, the more likely it is that the uniformity of the surface layer thickness will decrease. Low uniformity of the surface layer thickness makes it difficult to form holes suitable for filling foamed particles in the hollow molded article during the foamed particle filling process, which may lead to filling defects. Furthermore, when filling foamed particles into the hollow molded article, pressure loss may occur due to rupture in thin parts of the hollow molded article, which may prevent the foamed particles from being filled at the set compression filling pressure. As a result, it may not be possible to obtain a good molded article with a surface layer of foamed particles. Moreover, the thinner the hollow molded article, the more difficult it becomes to achieve both good surface properties and good adhesion between the surface layer and the molded article. These tendencies become more pronounced as the molded article with a surface layer of foamed particles becomes longer and larger. Specifically, "long" refers to a molded article with a surface layer of foamed particles with an extrusion length of 500 mm or more. Furthermore, the length of the foamed particle molded body with a surface in the extrusion direction shall be the length of the longest part in the foamed particle molded body with a surface in the extrusion direction.
[0042] In this invention, by setting the melt elongation, partial melting heat, ratio of partial melting heat to total melting heat, and semi-crystallization time of the polypropylene resin forming the hollow molded body to a specific range, as well as the melt tension to a specific range, it is possible to stably obtain a foamed particle molded body with a thin and long surface layer, in which the thickness of the surface layer is uniform, the adhesion between the surface layer and the foamed particle molded body is excellent, and the occurrence of unintended shapes on the surface layer is suppressed, resulting in a foamed particle molded body with a good surface finish.
[0043] (Melt Flow Rate) The melt flow rate of the polypropylene resin is preferably 0.1 g / 10 min to 5 g / 10 min. The melt flow rate is the value measured in accordance with JIS K7210 (1999) under measurement conditions of 230°C and 21.18 N. A melt flow rate of 0.1 g / 10 min to 5 g / 10 min improves blow moldability, such as making it easier to control the thickness of the hollow molded article. From the above viewpoint, the melt flow rate is preferably 0.1 g / 10 min to 3 g / 10 min, more preferably 0.5 g / 10 min to 2 g / 10 min, and even more preferably 0.6 g / 10 min to 1.5 g / 10 min.
[0044] [Foam Particle Filling Process] After the blow molding process, a foam particle filling process is performed. In this process, foam particles are filled into the hollow part of the hollow molded body, for example, as shown in the example in Figure 3. In the example in Figure 3, two pins 7 and 8 (steam pins) are inserted into the hollow molded body 10, which will be the outer material of the foam molded body with a surface, to adjust the pressure in the hollow part of the hollow molded body. Foam particles are compressed and filled into the hollow part of the hollow molded body from a feeder (foam particle filling feeder) 9 for filling the foam particles while adjusting the pressure in the hollow part of the hollow molded body. The pins 7 and 8 and the foam particle filling feeder 9 are operated by cylinders 6 and 6.
[0045] The compression filling pressure used when filling the hollow molded body with foamed particles from a filling feeder is 0.02 MPa(G) or more and 0.4 MPa(G) or less, more preferably 0.05 MPa(G) or more and 0.25 MPa(G) or less. (G) represents gauge pressure.
[0046] (Polypropylene Resin Foamed Particles) Examples of base resins for the foamed particles used in the present invention include polypropylene resins such as conventionally used propylene homopolymers and copolymers of propylene and comonomers selected from the comonomer group consisting of ethylene and / or α-olefins having 4 to 8 carbon atoms. Among these, propylene homopolymers, propylene-ethylene random copolymers, propylene-butene random copolymers, and propylene-ethylene-butene random copolymers are preferred.
[0047] From the viewpoint of moldability of the foamed particles, fusion properties between the foamed particles and the hollow molded body, and mechanical strength of the resulting surface-covered foamed particle molded body, the melting peak temperature of these polypropylene resin foamed particles is preferably 130°C to 155°C, and more preferably 135°C to 150°C. Also, from the same viewpoint as for defining the preferred range of the melting peak temperature, the ratio of the melting peak temperature of the polypropylene resin forming the hollow molded body to the melting peak temperature of the polypropylene resin foamed particles is preferably 0.85 to 1.15, more preferably 0.90 to 1.10, and even more preferably 1.00 to 1.10.
[0048] The melting peak temperature of the foamed particles can be measured using differential scanning calorimetry (DSC) based on JIS K7121 (1987). Specifically, when 3 mg to 5 mg of foamed particles are heated from room temperature to 200°C at a heating rate of 10°C / min, the temperature corresponding to the endothermic curve peak (intrinsic peak) specific to polypropylene resin in the first DSC curve obtained is defined as the melting peak temperature of the foamed particles. If there are two or more endothermic curve peaks, the melting peak temperature is defined as the apex temperature of the endothermic curve peak with the greatest peak intensity.
[0049] Furthermore, similarly to the above, from the viewpoint of moldability of the foamed particles, fusion properties between the foamed particles and the hollow molded body, and mechanical strength of the resulting foamed particle molded body with a surface, the foamed particles used in the present invention are preferably those which, when heated from room temperature to 200°C at a heating rate of 10°C / min using differential scanning calorimetry of the foamed particles, show an endothermic curve peak (intrinsic peak) intrinsic to polypropylene resin in the first DSC curve obtained, and an endothermic curve peak (hereinafter also referred to as "high temperature peak") appears at a higher temperature than the intrinsic peak, and the heat amount of the high temperature peak is 10 J / g or more and 25 J / g or less.
[0050] Furthermore, in the present invention, it is possible to use foamed particles with a multilayer structure, so-called sheath / core structure, in which a foamed core layer made of a polypropylene resin and the surface of the foamed core layer are coated with a resin having a melting point or softening point lower than the melting point of the resin forming the core layer, or foamed particles made of a polypropylene resin polymerized with a metallocene polymerization catalyst. By using these foamed particles, the foamed particles can be fused together with steam supplied at a relatively low steam heating pressure.
[0051] In this invention, the foamed particles filled in the hollow molded body have an apparent density of approximately 0.018 g / cm³, from the viewpoint of easily controlling the secondary foaming properties of the foamed particles with a heating medium such as steam. ３ 0.3g / cm or more ３ Preferably, it is less than or equal to 0.022 g / cm³. ３ 0.15g / cm or more ３ The following applies:
[0052] Furthermore, the method for producing the foamed particles to be filled into the hollow molded body can appropriately employ known methods for producing foamed particles. For example, foamed particles can be obtained by dispersing resin particles in a pressurized container such as an autoclave containing a dispersion medium such as water and a surfactant added as needed, injecting a foaming agent under predetermined pressure and heating to impregnate the resin particles with the foaming agent, and after a predetermined time has elapsed, releasing the resin particles together with the dispersion medium from the container under high temperature and high pressure conditions into a low-pressure area to foam the resin particles.
[0053] [Fusion Process] After the foam particle filling process, a fusion process is carried out, in which the foam particles fuse together and the foam particles fuse together with the hollow molded body. In the fusion process, a pin for supplying a heating medium (sometimes called a steam pin) is inserted into the hollow molded body, and a heating medium such as steam is supplied to the hollow part of the hollow molded body from the inserted steam pin. As a result, the hollow part of the hollow molded body is heated, and the foam particles and the hollow molded body are heated, causing the foam particles to fuse together and the foam particles to fuse together with the hollow molded body. In this way, a foam particle molded body with a surface is formed.
[0054] The heating pressure of the steam supplied to heat and fuse the foam particles to form a foam particle molded body and to fuse the hollow molded body with the foam particles is preferably 0.15 MPa(G) or more and 0.60 MPa(G) or less, and more preferably 0.18 MPa(G) or more and 0.50 MPa(G) or less, depending on the type of foam particles. If the heating pressure of the steam supplied to the hollow part of the hollow molded body is too low, the fusion properties between the foam particles and between the hollow molded body and the foam particles will be low, and heating for a long time will be required to improve these fusion properties, which may lengthen the molding cycle. On the other hand, if the steam heating pressure is too high, it is economically disadvantageous, and if the steam heating pressure is too high, phenomena such as shrinkage of the foam particle molded body may occur after molding, which may prevent the acquisition of a foam molded body with a good surface and dimensional accuracy.
[0055] Furthermore, the mold temperature in the fusion process is preferably between 40°C and 90°C, and more preferably between 50°C and 80°C. If the mold temperature is too low, the adhesion between the hollow molded body and the foam particles may decrease. If the mold temperature is too high, the surface quality of the foam particle molded body with a surface may decrease, and the cooling time of the foam particle molded body with a surface may increase, potentially reducing productivity.
[0056] The fusion process will be further explained using the example in Figure 3. The hollow portion of the hollow molded body is heated by exhausting air from one of the pins 7 and 8 while supplying pressurized steam as a heating medium from the other pin. By performing this operation alternately for the required time, the foam particles and the hollow molded body are fused together, and the foam particles themselves are fused together to form a foam particle molded body 20. After that, the mold is cooled, the cylinders 6 and 6 are operated to remove the pins and feeder 9 from the molded body, the mold is opened, and the foam molded body with a surface 22 is removed. Figure 4 shows a partially cut perspective view of the foam molded body with a surface 22.
[0057] Furthermore, when the manufacturing method of the present invention is carried out, the foamed particles become an integral molded body, forming a foamed molded body among the foamed particle molded bodies with a surface. In addition, the hollow molded body covers the surface of the foamed molded body, and the inner surface of the hollow molded body is fused to the outer surface of the foamed molded body, so that the hollow molded body forms the surface material portion of the foamed particle molded body with a surface.
[0058] (Surface-covered foam particle molded body) By the manufacturing method of the present invention, a surface-covered foam particle molded body 22 is obtained in which a foam particle molded body 20 is placed in the hollow portion of a surface material formed from a hollow molded body 10 as shown in Figure 4.
[0059] The surfaced foam particle molded article obtained by the manufacturing method of the present invention preferably has a thickness (length of the surfaced foam particle molded article in a direction parallel to the direction of movement of the mold) of 10 mm or more and 35 mm or less. When the thickness of the surfaced foam particle molded article produced by the manufacturing method of the present invention is 10 mm or more and 35 mm or less, when steam is blown into the hollow part of the hollow molded article via a steam pin during the fusion process, it becomes easy to spread the steam throughout the space forming the hollow part, and it becomes easy to achieve excellent adhesion between the surface material and the foam inside (adhesion between the hollow molded article and the foam particles) at any part of the surfaced foam particle molded article.
[0060] (Average thickness of hollow molded body) The average thickness of the hollow molded body forming the surface material is preferably 0.3 mm or more and 1.5 mm or less. If the average thickness of the surface material is 0.3 mm or more and 1.5 mm or less, a foamed particle molded body with a surface that has an excellent balance between lightness and mechanical strength can be obtained. From the viewpoint of lightness, the average thickness of the hollow molded body is preferably 1.2 mm or less, and more preferably 1.0 mm or less.
[0061] (Determination of Average Thickness) The average thickness of the hollow molded body forming the surface material of the surface-covered foam particle molded body is determined by measuring the average thickness of the surface material. The average thickness of the surface material is measured at three perpendicular cross-sections to the longitudinal direction of the surface-covered foam particle molded body, located near the longitudinal center and both longitudinal ends (however, special shaped parts of the surface-covered foam molded body are avoided). The length of the surface material in the thickness direction (direction perpendicular to the bonding surface between the foam particle molded body and the surface material) of the surface material at six perpendicular cross-sections, spaced equally along the circumferential direction of the surface material, is measured, and the arithmetic mean of the obtained lengths at 18 locations can be taken as the average thickness of the surface material.
[0062] (Peel Strength) The foamed particle molded body with a surface obtained by the manufacturing method of the present invention preferably has a peel strength of 0.4 MPa or more between the hollow molded body forming the surface material and the foamed particle molded body formed from the foamed particles. If the peel strength is within the above range, the foamed particle molded body with a surface has excellent adhesion between the surface material and the foamed particle molded body.
[0063] (Determination of Peel Strength) Peel strength can be determined, for example, as follows: First, test pieces of a predetermined size, including the skin material on both sides, are cut from a total of five locations: the center and the four corners (excluding the rounded corners) of the foam particle molded body with a skin. Next, the upper and lower surfaces (skin surfaces) of the test pieces are fixed to a jig for measuring peel strength with adhesive. Then, a tensile test is performed by applying a tensile load to the jig using a tensile testing machine at a tensile speed of 2 mm / min, and the arithmetic mean of the maximum point stress of each test piece determined by this tensile test can be taken as the peel strength (MPa). A Tensilon universal testing machine (manufactured by Orientec Co., Ltd.) can be used as the tensile testing machine.
[0064] (Apparent density of foamed particle molded articles with surface) The foamed particle molded articles with surface obtained by the manufacturing method of the present invention have an apparent density of 0.015 g / cm³. ３ 0.15g / cm or more ３ Preferably, the following conditions are met: The apparent density of the foamed particle molded body is 0.015 g / cm³. ３ 0.15g / cm or more ３The following characteristics result in a lightweight molded product of foamed particles with a surface coating.
[0065] The present invention will be described in more detail below using examples.
[0066] Example 1. A propylene-ethylene random copolymer (r-PP) (manufactured by Nippon Polypropylene Co., Ltd., trade name: Novatec®, grade name: EG8B) was prepared as a propylene-based resin for forming a hollow molded body. The melt flow rate of this propylene-ethylene random copolymer was 0.8 g / 10 min [230°C, 21.18 N], the melt tension was 4.8 cN, the peak melting temperature was 145°C, and the ethylene component content was 3.0% by weight.
[0067] [Blow molding process] The prepared propylene-ethylene random copolymer was supplied to an extruder with an inner diameter of 65 mm. The propylene-ethylene random copolymer was heated and melted in the extruder at 210°C to form a molten resin mixture.
[0068] The molten resin mixture was filled into an accumulator adjusted to 210°C. The molten resin mixture was then extruded from a die connected to the downstream side of the accumulator to form a cylindrical parison. The conditions for the die lip clearance (die lip clearance) and die temperature are shown in Table 2.
[0069] The extruded, softened parison was placed between two open flat molds located directly below the die (dimensions of the molded space inside the mold: 730 mm long x 300 mm wide x 25 mm thick). The temperature of these flat molds was adjusted as shown in Table 2, and after clamping the parison between the molds, blow molding pins were driven into the parison. Air pressurized to 0.50 MPa(G) (where (G) indicates gauge pressure) was blown into the parison through the blow pins, and at the same time, the pressure between the outer surface of the parison and the inner surface of the mold was reduced, thereby forming a hollow molded body.
[0070] [Foam Particle Filling Process] After mold clamping, a steam pin (8 mm diameter) with a slit-shaped steam supply port on its side was driven into the hollow molded body from one side of the mold, towards the thickness direction of the foam particle molded body with a surface (protruding 20 mm from the mold surface), and a foam particle filling feeder (18 mm diameter) was driven into the hollow molded body. After the driving was completed, the internal pressure of the hollow molded body was adjusted to the compression filling pressure shown in Table 2 while exhausting steam from the steam pin, and foam particles were filled into the hollow part of the hollow molded body from the foam particle filling feeder. The filled foam particles had the apparent density, foaming ratio, and melting point shown in the foam particle column of Table 2, and were foam particles with a high-temperature peak heat value of 14 J / g, consisting of a propylene-ethylene random copolymer (ethylene content 2.5 wt%). A total of 11 steam pins were placed in the mold. The positions of the 11 locations were selected as follows. Eight locations (2 rows x 4 locations) were selected so that four locations on the circumferential surface of the mold were arranged in a single row at 200 mm intervals along the longitudinal direction of the mold, and these rows were spaced apart in the direction along the short direction of the mold, forming two rows near both ends of the mold. Furthermore, three locations were selected between the two rows near the center of the mold, arranged in a single row at 200 mm intervals along the longitudinal direction of the mold.
[0071] [Fusion Process] After the foam particle filling process, steam at 0.32 MPa(G) was supplied for 6 seconds from the other steam pin while exhausting from one steam pin inserted between the filled foam particles. Then, exhaust was released from the steam pin that had been supplying the steam, and steam at 0.32 MPa(G) was supplied for 6 seconds from the other steam pin that had been exhausting, performing alternating heating. After that, steam at 0.32 MPa(G) was supplied from all steam pins for 4 seconds to heat the foam particles. As a result, the foam particles fused together with each other within the hollow molded body. As a result, a foam particle molded body was formed within the hollow molded body, and the foam particle molded body and the hollow molded body fused together on the outer surface of the foam particle molded body and the inner surface of the hollow molded body.
[0072] The foam particle molded body was cooled by exhausting steam through a steam pin inserted inside. The mold was then opened to obtain a foam particle molded body with a surface layer. Burrs on the foam particle molded body with the surface layer were removed as appropriate. The physical properties of the hollow molded body forming the surface layer are shown in Table 1. The various physical properties of the obtained foam particle molded body with the surface layer are shown in Table 4.
[0073] Furthermore, in the manufacturing of the surfaced foam particle molded articles, evaluations were conducted regarding the drawdown resistance and parison widening performance during the blow molding process. The results of these evaluations are shown in Table 3.
[0074] Example 2. A foamed particle molded body with a surface was obtained in the same manner as in Example 1, except that the average thickness of the surface material was set to the average thickness shown in Table 4. The various physical properties of the obtained foamed particle molded body with a surface were determined in the same manner as in Example 1. The results are shown in Table 4. Furthermore, the drawdown resistance and parison widening resistance were evaluated in the same manner as in Example 1. The results are shown in Table 3.
[0075] Example 3. A foamed particle molded body with a surface was obtained in the same manner as in Example 1, except that a propylene-ethylene random copolymer (r-PP) (manufactured by Prime Polymer Co., Ltd., grade name: E222, melt flow rate 1.4 g / 10 min [230°C, 21.18 N], melt tension 6.0 cN, melting point 142°C, ethylene content 2.7 wt%) was used as the propylene-based resin for forming the hollow molded body, and this was supplied to an extruder with an inner diameter of 65 mm and heated and melted at 200°C to obtain a resin melted kneaded product. The physical properties of the hollow molded body forming the surface material are shown in Table 1. Furthermore, the various physical properties of the obtained foamed particle molded body with a surface were determined in the same manner as in Example 1. The results are shown in Table 4. Furthermore, evaluations of drawdown resistance and parison widening resistance were performed in the same manner as in Example 1. The results are shown in Table 3.
[0076] Comparative Example 1. A foamed particle molded body with a surface was obtained in the same manner as in Example 1, except that a propylene-ethylene random copolymer (r-PP) (manufactured by Sun Allomer Co., Ltd., grade name: PB222A, melt flow rate 0.75 g / 10 min [230°C, 21.18 N], melt tension 3.9 cN, melting point 146°C, ethylene content 1.5 wt%) was used as the propylene-based resin for forming the hollow molded body, and this was supplied to an extruder with an inner diameter of 65 mm, heated and melted at 210°C to obtain a resin melted and kneaded product. The physical properties of the hollow molded body forming the surface material are shown in Table 1. Furthermore, the various physical properties of the obtained foamed particle molded body with a surface were determined in the same manner as in Example 1. The results are shown in Table 4. Furthermore, evaluations of drawdown resistance and parison widening performance were performed in the same manner as in Example 1. The results are shown in Table 3.
[0077] Comparative Example 2. A foamed particle molded body with a surface was obtained in the same manner as in Example 1, except that a propylene-ethylene random copolymer (r-PP) (manufactured by Nippon Polypropylene Co., Ltd., trade name: Novatec, grade name: EG7F, melt flow rate 1.3 g / 10 min [230°C, 21.18 N], melt tension 2.9 cN, melting point 142°C, ethylene content 3.9 wt%) was used as the propylene-based resin for forming the hollow molded body, and this was supplied to an extruder with an inner diameter of 65 mm, the die lip clearance was set to 1.9 mm as shown in Table 2, and it was heated and melted at 210°C to obtain a resin melted kneaded product. The physical properties of the hollow molded body forming the surface material are shown in Table 1. Furthermore, the various physical properties of the obtained foamed particle molded body with a surface were determined in the same manner as in Example 1. The results are shown in Table 4. Furthermore, evaluations of drawdown resistance and parison widening performance were performed in the same manner as in Example 1. The results are shown in Table 3.
[0078] Comparative Example 3. A foamed particle molded body with a surface was obtained in the same manner as in Example 1, except that a propylene-ethylene block copolymer (b-PP) (manufactured by Nippon Polypropylene Co., Ltd., trade name: Novatec, grade name: EC9, melt flow rate 0.5 g / 10 min [230°C, 21.18 N], melt tension 7.0 cN, melting point 160°C, ethylene content 3.9 wt%) was used as the propylene-based resin for forming the hollow molded body, and this was supplied to an extruder with an inner diameter of 65 mm, the die lip clearance was set to 1.4 mm as shown in Table 2, and it was heated and melted at 210°C (die temperature 215°C) to obtain a molten resin kneaded product. In Comparative Example 3, when attempting to form a hollow molded body with a thin thickness, cracks occurred in the parison when the mold was clamped, making it impossible to obtain a foamed particle molded body with a surface thickness thinner than 1.5 mm. The physical properties of the obtained foamed particle molded body with a skin were determined in the same manner as in Example 1. The results are shown in Table 4. Furthermore, the drawdown resistance and parison widening properties were evaluated in the same manner as in Example 1. The results are shown in Table 3. The physical properties of the hollow molded body forming the skin material are shown in Table 1.
[0079] Comparative Example 4. A propylene-ethylene random copolymer (m-PP) polymerized with a metallocene catalyst (manufactured by Nippon Polypropylene Co., Ltd., trade name: Wintec, grade name: WFX6, melt flow rate 2 g / 10 min [230°C, 21.18 N], melt tension 1.2 cN, melting point 124°C, ethylene content 2.7 wt%) was used as the propylene-based resin for forming the hollow molded body (HPP). This was supplied to an extruder with an inner diameter of 65 mm, the die lip clearance was set to 1.1 mm as shown in Table 2, and it was heated and melted at 180°C to obtain a resin melt-kneaded product. The process was the same as in Example 1 except that a foamed particle molded body with a skin was obtained. The physical properties of the hollow molded body forming the skin material are shown in Table 1. The physical properties of the obtained foamed particle molded body with a skin were determined in the same manner as in Example 1. The results are shown in Table 4. Drawdown resistance and parison widening resistance were also evaluated in the same manner as in Example 1. The results are shown in Table 3.
[0080] The physical properties of the polypropylene resin forming the hollow molded body that serves as the surface material, as shown in Table 1, and the various physical properties of the foamed particle molded body with a surface, as shown in Table 4, were determined as follows.
[0081] (Melting point of polypropylene resin) The melting point of polypropylene resin corresponds to the peak melting temperature and was determined based on the DSC curve obtained using the heat flux differential scanning calorimeter described above. The heat flux differential scanning calorimeter used was a heat flux differential scanning calorimeter DSC (Q1000, manufactured by T.A. Instruments Japan Co., Ltd.).
[0082] (Total heat of fusion, partial heat of fusion, and heat of fusion ratio of polypropylene resins) The total heat of fusion, partial heat of fusion, and heat of fusion ratio of polypropylene resins were measured using a differential scanning calorimeter as described above. The heat of fusion ratio represents the ratio of the partial heat of fusion to the total heat of fusion.
[0083] (Semi-crystallization time of polypropylene resin) The semi-crystallization time was measured by the method described above. Specifically, first, a polypropylene resin used to form a hollow molded body was heat-pressed (press temperature 220°C) to produce a film-like sample. The thickness of the sample was adjusted to 0.2 mm (however, a thickness error of 0.02 mm above and below was permitted), and the dimensions and shape of the sample were a rectangular shape of 15 mm vertically x 15 mm horizontally. The sample was then sandwiched between cover glass, and the cover glass containing the sample was held on a support. The support was placed in the air bath of a crystallization rate analyzer (Kotaki Corporation, MK-801) and the sample was completely melted. Next, the cover glass containing the sample was placed in an oil bath maintained at 100°C so that the molten sample was positioned between polarizing plates. As the temperature of the sample gradually decreased in the oil bath, the crystallization of the sample progressed. With this crystallization of the sample, the optically anisotropic crystalline component increased, and a change occurred in the light transmitted through the polarizing plates. The light transmitted through the polarizing plate was measured (depolarization method). Then, the semi-crystallization time of the polypropylene resin was calculated from the time at which the degree of crystallinity became half, using the Abramm formula shown in Equation 1 below.
[0084]
[0085] However, in the above formula (1), Xc represents the crystallinity, k represents the crystallization rate constant, n represents the Avrami constant, t represents the time (seconds), I0 represents the depolarized light transmission intensity [the value of the transmitted light at the time when the measurement was started with the sample in a molten state (starting point)], It represents the depolarized light transmission intensity [the value of the transmitted light t seconds after the start of the measurement], and Ig represents the depolarized light transmission intensity [the value of the transmitted light in the state where the sample is solidified (end point)].
[0086] (Melt tension (MT), melt elongation) The melt tension and melt elongation were measured by the method using the Capirograph 1D of Toyo Seiki Seisakusho Co., Ltd. described above.
[0087] (Average thickness of the skin material) The measurement of the average thickness of the skin material in the foamed particle molded body with skin was performed on the longitudinal vertical cross-sections at three locations in the longitudinal center and near both longitudinal ends of the foamed particle molded body with skin. The thickness of the skin material in the thickness direction of the vertical cross-section was measured at six equally spaced locations along the circumferential direction of the skin in each vertical cross-section, and the arithmetic mean value of the obtained 18 thicknesses (average thickness of the skin material) was taken as the average thickness of the skin material.
[0088] (Uniformity of the thickness of the skin material) The uniformity of the thickness of the skin material was evaluated as follows based on the values of the thickness of the skin material obtained by performing the measurement method of the thickness of the skin material shown above. The evaluation criteria are shown below.
[0089] ○ (Good): The coefficient of variation of the thickness of the skin material is less than 15%. × (Bad): The coefficient of variation of the thickness of the skin material is 15% or more.
[0090] The coefficient of variation was calculated based on the following formula (number formula 2).
[0091]
[0092] Also, the standard deviation of the thickness of the skin material was calculated based on the following formula (number formula 3).
[0093]
[0094] In the above formula (number formula 3), V represents the standard deviation of the thickness of the skin material, and T ｉThis shows the measured thickness of the individual surface material at each measurement point. As mentioned above, if the thickness of the surface material was measured at 18 locations in the surface-covered foam particle molded body, T １ , T ２ , T ３ ...T １８ These 18 types of measurements are identified. Also, T ａｖ represents the arithmetic mean of the thickness of the surface material, and n represents the number of measurements. Furthermore, Σ is calculated for each individual measurement (T ｉ -T ａｖ ) ２ This is a mathematical symbol that indicates adding all of them together.
[0095] (Apparent density of foamed particles) The apparent density (g / L) of foamed particles filled into the hollow part of a hollow molded body during the foamed particle filling process was determined by submerging a group of foamed particles weighing W1 (g) in a graduated cylinder filled with water using a wire mesh or the like, measuring the volume of the foamed particle group V1 (L) from the rise in water level, and then dividing the weight of the foamed particle group by the volume of the foamed particle group (W1 / V1).
[0096] (Apparent density of foamed particle molded body (foam density)) The density (g / L) of the foamed particle molded body was determined by cutting out the foamed particle molded body from five locations: the center and four corners (excluding the R portion) of the plate-like surface of the foamed particle molded body with a surface, removing the surface material, and dividing the weight (W2 (g)) of the foamed particle molded body by the volume (V2 (L)) of the foamed particle molded body, which was determined by the immersion method (W2 / V2).
[0097] (Apparent density (overall density) of the surfaced foam particle molded body) The apparent density (g / L) of the surfaced foam particle molded body was determined from the value (W3 / V3) obtained by dividing the weight of the surfaced foam (W3 (g)) by the volume of the surfaced foam particle molded body (V3 (L)) determined by the submersion method. When determining the volume of the surfaced foam particle molded body by the submersion method, the marks (holes) left by the steam pins were sealed by covering them with adhesive tape.
[0098] (Surface properties of the surface material) The surface properties of the surface material were evaluated by assessing the surface smoothness of the surface material of the foam particle molded body with a surface, and the evaluation of surface smoothness was performed based on the results of surface roughness measurement. For surface roughness measurement, first, the surface material was cut out from a total of five locations: the center and the four corners (excluding the R portion) of the plate-like surface of the foam particle molded body with a surface, and the surface roughness of these test pieces was measured. As the measuring device for measuring the surface roughness of the surface material, the SE1700α surfcorder manufactured by Kosaka Laboratory Co., Ltd. was used. The test piece was placed on a horizontal table in the measuring device, the tip of a stylus with a tip radius of curvature of 2 μm was brought into contact with the surface of the test piece, and the test piece was moved in the extrusion direction at 0.5 mm / s, and the maximum height roughness Rz (μm) of the roughness curve element was measured by sequentially measuring the vertical displacement of the stylus, and this was taken as the surface roughness value. A predetermined length of three times or more the cutoff value was selected as the measurement length, which is defined as the distance the test piece is moved. The cutoff value was set to 8 mm, and the other parameters were determined according to the definition in JIS B0601 (2001) to obtain the maximum height roughness Rz (μm) of the roughness curve element. Based on the arithmetic mean of the maximum height roughness Rz of each test specimen, the surface smoothness was evaluated as follows.
[0099] ○ (Good): Rz is 20 μm or less. × (Poor): Rz is greater than 20 μm.
[0100] (Appearance) The surface condition of the obtained foamed particle molded body with a surface layer was visually inspected and its appearance was evaluated as follows.
[0101] ○ (Good): The shape of the mold is transferred to the surface. △ (Fairly Good): Die lines and other patterns are visible on some parts, such as the sides of the foam particle molded body with a surface layer. × (Poor): The mold shape is not transferred sufficiently, and die lines and other patterns are visible on the surface of the foam particle molded body with a surface layer.
[0102] (Peel Strength) From a total of five locations, including the center and four corners (excluding the rounded corners) of the obtained foam particle molded body with a skin, the upper and lower surfaces (skin surfaces) of a rectangular foam particle molded body test specimen (50 mm long, 50 mm wide, 25 mm thick) containing the skin material on both sides, measuring 50 mm long and 50 mm wide, were fixed to a jig for measuring peel strength using adhesive. A tensile load was applied to the foam particle molded body test specimen at a tensile speed of 2 mm / min using a Tensilon universal testing machine to perform a tensile test. The maximum point stress obtained from the tensile test was defined as the peel strength (MPa). The arithmetic mean values of the peel strengths of each test specimen obtained from the tensile test are shown in Table 4. In cases where the adhesion between the skin material and the foam particle molded body was very good, material fracture occurred between the foam particles.
[0103] (Flexural Modulus) The flexural modulus of the surface-covered foam particle molded body was measured as follows. In accordance with JIS K7171-1994, the obtained surface-covered foam particle molded body was used as a test sample, and a three-point bending test was performed under the conditions of indenter radius R1 = 25 mm, support base radius R2 = 3 mm, test speed 20 mm / min, and span 300 mm, and the flexural modulus (MPa) was measured.
[0104] (Specific Modulus) The specific modulus (MPa / g) was calculated as (flexural modulus) / (weight of the foamed particle molded body with surface) by dividing the flexural modulus by the weight of the foamed particle molded body with surface.
[0105] (Fussing rate of foamed particle molded articles) The fusion rate (%) of foamed particle molded articles is a value that indicates the degree of fusion between foamed particles in a foamed particle molded article with a surface, and was determined as follows.
[0106] From the center and four corners (excluding the rounded edges) of the plate-shaped surface of the foamed particle molded body with a surface layer, rectangular parallelepipeds measuring 100 mm in length, 100 mm in width, and 15 mm in thickness were cut out, excluding the surface material, and these were used as test specimens for measuring the bonding rate. For each of the five obtained test specimens, the top and bottom surfaces of the specimen were fixed to a jig for measuring peel strength with adhesive, and the specimen was fractured by performing a tensile test at a tensile speed of 2 mm / min using a Tensilon universal testing machine. The fracture surface formed by the fracture of the test specimen was visually observed, and the number of destroyed foamed particles and the number of foamed particles that peeled off at the interface were measured from the foamed particles observed on the fracture surface. The bonding rate (%) is a value obtained by the formula ((number of destroyed foamed particles) / (number of destroyed foamed particles + number of foamed particles peeled off at the interface)) × 100, and the bonding rate (%) for each test specimen was calculated based on this formula. The arithmetic mean of the fusion rates of each test specimen was defined as the fusion rate (%) of the foamed particle molded body.
[0107] Furthermore, the evaluations regarding drawdown resistance and parison widening, as shown in Table 3, were conducted as follows.
[0108] (Parison Expandability) By blowing pressurized air into a parison formed by extruding polypropylene resin from an extruder, the extent to which the parison could be expanded without bursting relative to the die diameter was visually confirmed. Specifically, the parison was extruded under the same conditions as in each example and comparative example, except that the clearance of the die lip was set to 2 mm. After extrusion was complete, the bottom of the parison was pinched, and heated air at 0.2 MPa(G) was blown into the parison to expand it, and this process was recorded on video. Based on the video footage, the diameter at which the parison expanded to its maximum extent (maximum expanded diameter) was measured, and the expansion ratio was calculated by dividing this value by the diameter of the die lip (die lip clearance) as (maximum expanded diameter of parison) / (diameter of die lip). Based on the expansion ratio, the following evaluations were specifically performed.
[0109] ○ (Good): The widening ratio is 1.3 or greater. △ (Fairly good): The widening ratio is 1.2 or greater but less than 1.3. × (Poor): The widening ratio is less than 1.2.
[0110] (Drawdown Resistance) The drawdown resistance of each example and comparative example was evaluated as follows. Except for setting the clearance of the die lip portion to 1 mm, polypropylene resin was extruded from the die to form parisons using the same conditions and methods as when manufacturing the surfaced foam particle molded articles of each example and comparative example. The time from when the length of the parison formed based on the conditions and methods of each example and comparative example reached 90 cm to when it reached 150 cm (parison elongation time) was measured for each example and comparative example. Based on this parison elongation time, the drawdown resistance of each example and comparative example was evaluated according to the following criteria. Note that the longer this time, the easier it is to control the wall thickness of the parison.
[0111] ◎ (Excellent): Parison extension time is 8 seconds or longer. ○ (Good): Parison extension time is 6 seconds or longer but less than 8 seconds. △ (Fairly Good): Parison extension time is 3 seconds or longer but less than 6 seconds. × (Poor): Parison extension time is less than 3 seconds.
[0112]
[0113]
[0114]
[0115]
[0116] 1. Parison 2. Mold 3. Die 4. Gas inlet tube 5. Suction tube 10. Hollow molded body (skin) 20. Foamed particle molded body 22. Foamed particle molded body with skin 6. Cylinder 7, 8. Pin 9. Filling feeder
Claims
DEPCT631. Method for the production of particle foam-based hollow objects with a shell consisting of: formation of the hollow object by blow molding in a softened state, formed by extrusion of polypropylene-based resin; filling of the hollow part of the hollow object with polypropylene-based resin foam particles; and delivery of a heating medium to the hollow object to heat and fuse the polypropylene-based resin foam particles with each other, and also to heat and fuse the polypropylene-based resin foam particles and the hollow object, at which the molten stretch at 190 °C of the polypropylene-based resin forming the hollow object is 100 m.The half-crystallization time at 100°C for polypropylene-based resins is 25 seconds or more and 80 seconds or less. In heat flux differential scanning calorimetry, the melt peak temperature of polypropylene-based resins is 130°C or more and 155°C or less. The partial heat of fusion at 140°C or more for polypropylene-based resins is 20 J / g or more and 50 J / g or less. The ratio of partial heat of fusion of polypropylene-based resins to total heat of fusion (partial heat of fusion / total heat of fusion) is 0.2 or more and 0.8 or less. Method for the production of particle foam compressed objects with a shell provided under claim 1, where the melt tension at 190 °C of the polypropylene-based resin forming the hollow compressed object is 3 centinewtons or greater.
4. A method for producing particle foam compacts with a shell provided under any of the claims 1 or 2 where the average thickness of the hollow compact is 0.3 mm or greater and 1.5 mm or less.
5. A method for producing particle foam compacts with a shell provided under any of the claims 1 to 3 where the peel resistance between the hollow compact and the particle foam compact is 0.4 megapascals or greater.
6. A method for producing particle foam compacts with a shell provided under any of the claims 1 to 4 where the distance in the extrusion direction of the shelled particle foam compact is 500 mm or greater.