JP7440743B2 - foam molded body - Google Patents

Description

The present invention relates to a foam molded article.

Ducts are installed on the dashboard and ceiling of automobiles to circulate air from air conditioners. For such ducts, foamed molded bodies are sometimes used in consideration of heat insulation and quietness (Patent Document 1).

Japanese Patent Application Publication No. 2015-124380

By the way, flame retardance is sometimes required for foamed molded products, and in order to improve the flame retardance, a flame retardant may be blended into the resin composition constituting the foamed molded product. However, depending on the amount of flame retardant added, flame retardancy may not be fully exhibited.

The present invention has been made in view of these circumstances, and provides a foamed molded article with excellent flame retardancy.

According to the present invention, there is provided a foam molded article formed by foam molding a resin composition containing a base resin and a flame retardant, and the foam molded article has an expansion ratio of 1.1 to 9.0 times. , the base resin contains a polyolefin, and the amount of the flame retardant in the resin composition is 0.1 to 10% by mass.

The present inventor has found that in a foam molded product having a specific expansion ratio and a specific base resin, a foam molded product with excellent flame retardancy can be obtained by controlling the content of the flame retardant within a specific range. The present invention has been completed.

Various embodiments of the present invention will be illustrated below. The embodiments shown below can be combined with each other.
Preferably, the foam molded article described above is a foam molded article in which the expansion ratio is 3.0 to 6.0 times.
Preferably, in the foam molded article described above, the foam molded article is a hollow or sheet-shaped foam molded article.
Preferably, the foam molded product described above is a foam molded product having an average cell diameter in the thickness direction of 100 to 1000 μm.
Preferably, the foamed molded article described above is a foamed molded article in which the foaming agent contains carbon dioxide gas.

An example of a cross-sectional photograph of the foam molded article 1 is shown. The configuration of a molding machine 10 that can be used to manufacture a foam blow molded article is shown. 3 is an enlarged view of the vicinity of the head 18 and molds 21 and 22 in FIG. 2. FIG. 4 is a view corresponding to FIG. 3, showing a head 18 and molds 21, 22 that can be used for manufacturing a foam sheet molded product. FIG. The molds 21 and 22 of FIG. 4 are shown in a closed state.

Embodiments of the present invention will be described below. Various features shown in the embodiments described below can be combined with each other. Further, the invention is established independently for each characteristic matter.

1. Foam molded body 1
As shown in FIG. 1, a foam molded article 1 according to an embodiment of the present invention is formed by foam-molding a resin composition containing a base resin and a flame retardant.

<Base resin>
The base resin includes polyolefin. Examples of the polyolefin include polyester, polypropylene, ethylene-propylene copolymer, and mixtures thereof. The base resin may be composed only of polyolefin or may contain other thermoplastic resins. Examples of other thermoplastic resins include polyamide resins and polyester resins. The content of polyolefin in the base resin is, for example, 50 to 100% by mass, specifically, for example, 50, 60, 70, 80, 90, 99, 100% by mass, and the numerical values exemplified here are It may be within the range between any two.

<Flame retardant>
The flame retardant is comprised of any compound that enhances the flame retardancy of the base resin. Examples of the flame retardant include phosphorus-based flame retardants, halogen-based flame retardants, and hindered amine-based flame retardants. Hindered amine flame retardants are particularly preferred from the viewpoint of improving the flame retardance of polyolefins.

The blending amount of the flame retardant in the resin composition is 0.1 to 10% by mass. This is because if the amount is too small, the effect of improving flame retardancy may be insufficient, and if the amount is too large, the moldability may be reduced. Specifically, this blending amount is, for example, 0.1, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10% by mass, and is exemplified here. It may be within the range between any two of the above values.

<Foam molded product 1>
Examples of the foam molded body 1 include a foam blow molded body formed by foam blow molding and a foam sheet molded body formed by foam sheet molding. Examples of foam blow-molded articles include foam ducts used in automobiles and the like. Examples of foamed sheet molded articles include automobile interior parts (eg, door trims).

The foaming ratio of the foam molded article 1 is 1.1 to 9.0 times, preferably 3.0 to 6.0 times. If the expansion ratio is too small, the insulation and lightness may become insufficient, and if the expansion ratio is too large, the rigidity may become insufficient. Specifically, the foaming ratio is, for example, 1.1, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 7.0, 8.0, and 9.0 times, and may be within a range between any two of the numerical values exemplified here. The foaming ratio is a value obtained by [density of the resin composition before foaming/density of the resin composition after foaming (bulk density)].

It is preferable that the foamed molded article 1 is hollow or sheet-shaped. In this case, since the foamed molded article 1 is easily combustible, the technical significance of imparting flame retardance is particularly great.

The wall thickness of the foam molded body 1 is, for example, 1.0 to 6.0 mm. If the wall thickness is too thin, the rigidity of the foam molded product 1 may become insufficient, and if the wall thickness is too large, the weight of the foam molded product 1 may become excessive. This wall thickness is preferably 2.0 mm or more, more preferably 3.0 mm or more. This is because the larger the wall thickness, the better the flame retardancy of the foamed molded product 1 is. Specifically, this wall thickness is, for example, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5. , 6.0 mm, and may be within a range between any two of the numerical values exemplified here.

The foam molded article 1 preferably has an average cell diameter of 100 to 1000 μm in the thickness direction. If the average cell diameter is too small, the heat insulation properties and lightness may become insufficient, and if the average cell diameter is too large, the rigidity may become insufficient. The average cell diameter is preferably 200 μm or more, more preferably 400 μm or more. This is because the larger the average cell diameter, the more pronounced the effect of improving flame retardancy by adding a flame retardant. Specifically, this average bubble diameter is, for example, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 μm, and is within the range between any two of the numerical values exemplified here. It's okay.

The average bubble diameter is measured by the following method.
- First, a cross-sectional photograph is taken at a magnification of 50 times as shown in Figure 1.
- Next, draw five reference lines R1 to R5 extending in the thickness direction in the cross-sectional photograph. The interval between the reference lines is 500 μm.
- For each reference line, count the number of bubbles that the reference line passes through.
・Measure the maximum length of each bubble in the thickness direction (the length at the part where the length in the thickness direction is the longest).
- Calculate the provisional average bubble diameter for each reference line according to Equation 1. Furthermore, the average bubble diameter is calculated by arithmetic averaging the provisional average bubble diameters calculated for each reference line.
(Formula 1) Tentative average bubble diameter = Total maximum length of all counted bubbles/Number of counted bubbles

Examples of the foaming agent used to foam the resin composition constituting the foamed molded product 1 include physical foaming agents, chemical foaming agents, and mixtures thereof, with physical foaming agents being preferred. As physical blowing agents, inorganic physical blowing agents such as air, carbon dioxide gas, nitrogen gas, water, etc., organic physical blowing agents such as butane, pentane, hexane, dichloromethane, dichloroethane, and supercritical fluids thereof are used. be able to. Examples of chemical blowing agents include those that generate carbon dioxide gas through a chemical reaction between an acid (eg, citric acid or a salt thereof) and a base (eg, baking soda). As the blowing agent, one containing carbon dioxide gas is preferred. This is because in this case, the average cell diameter becomes large, and the effect of improving flame retardancy by the flame retardant tends to become high.

2. Method for manufacturing foam molded product 1 Here, the method for manufacturing foam molded product 1 will be explained using a foam blow molded product and a foam sheet molded product as examples.

2-1. Foam blow molded article 2-1-1. Configuration of Molding Machine 10 A molding machine 10 that can be used to manufacture a foam blow-molded article will be described with reference to FIGS. 2 and 3. The molding machine 10 includes a resin supply device 20, a head 18, and first and second molds 21 and 22. The resin supply device 20 includes a hopper 12, an extruder 13, an injector 16, and an accumulator 17. The extruder 13 and the accumulator 17 are connected via a connecting pipe 25. The accumulator 17 and the head 18 are connected via a connecting pipe 27.
Each configuration will be explained in detail below.

<Hopper 12, extruder 13>
The hopper 12 is used to charge the raw resin 11 into the cylinder 13a of the extruder 13. Although the form of the raw resin 11 is not particularly limited, it is usually in the form of pellets. The raw resin 11 is composed of the resin composition described above. In one example, the raw resin 11 includes pellets of a base resin and pellets of a masterbatch containing a flame retardant in the base resin. By changing the blending ratio of base resin pellets and masterbatch pellets, the blending amount of flame retardant can be adjusted. The raw material resin 11 is charged into the cylinder 13a from the hopper 12, and then heated and melted into a molten resin in the cylinder 13a. Further, the material is conveyed toward the tip of the cylinder 13a by rotation of a screw disposed within the cylinder 13a.

<Injector 16>
The cylinder 13a is provided with an injector 16 for injecting a foaming agent into the cylinder 13a. As the foaming agent, those mentioned above can be used. The physical foaming agent is normally injected from the injector 16. The chemical blowing agent is normally introduced from the hopper 12.

<Accumulator 17, head 18>
A molten resin 11a obtained by melting and kneading raw resin and a foaming agent is extruded from the resin extrusion port of the cylinder 13a and injected into the accumulator 17 through the connecting pipe 25. The accumulator 17 includes a cylinder 17a and a piston 17b that is slidable inside the cylinder 17a, and the molten resin 11a can be stored in the cylinder 17a. Then, by moving the piston 17b after a predetermined amount of the molten resin 11a is stored in the cylinder 17a, the molten resin 11a is pushed out through the connecting pipe 27 through a die slit provided in the head 18, and is made to hang down into a cylindrical shape. A foam parison 23 is formed.

<First and second molds 21, 22>
The foamed parison 23 is guided between the molds 21 and 22. As shown in FIG. 3, the molds 21 and 22 have cavities 21a and 22a, and pinch-off parts 21b and 22b are provided to surround the cavities 21a and 22a. The cavities 21a and 22a are configured to assume the shape of the foam molded product 1 when the molds 21 and 22 are closed.

2-1-2. Method for producing a foam blow-molded article The method for producing a foam blow-molded article includes a molding step.

The molding process includes, for example, an extrusion process, a mold closing process, and a blowing process.

In the extrusion process, a foamed parison 23 is extruded between molds 21 and 22. In the mold closing process, by closing the molds 21 and 22 after the extrusion process, a part of the foamed parison 23 is confined within the cavities 21a and 22a between the molds 21 and 22. The portions of the foamed parison 23 that are confined within the cavities 21a and 22a become bag-shaped. In the blowing process, air is blown into the bag-shaped foamed parison 23. At this time, the foamed parison 23 is shaped along the surface shape of the cavities 21a and 22a, and a foamed blow-molded article is formed. Thereafter, the molds 21 and 22 are opened, the foam blow-molded article is taken out, and a desired molded article is obtained by performing post-processing such as removing burrs.

2-2. Foamed sheet molded article 2-2-1. Configuration of Molding Machine 10 The molding machine 10 that can be used to manufacture a foam sheet molded product will be described using FIG. 4. The configuration of the molding machine 10 is the same as described in "2-1-1. Configuration of the molding machine 10" except that the configurations of the head 18 and the molds 21 and 22 are different, so the description will not be repeated.

In foam sheet molding, as shown in FIG. 4, a sheet-shaped foam parison 23 (hereinafter referred to as "foam resin sheet 23a") is extruded from the head 18. For this reason, a T-die is usually used as the head 18.

The mold 21 has a convex portion 21c, and the mold 22 has a concave portion 22c. As shown in FIG. 5, when the molds 21 and 22 are closed, the convex portion 21c is housed in the concave portion 22c, and a cavity C is provided between the convex portion 21c and the concave portion 22c.

2-2-2. Method for manufacturing a foamed sheet molded article A method for manufacturing a foamed sheet molded article includes a molding step.

The molding process includes, for example, an extrusion process, a mold closing process, and a blowing process.

In the extrusion process, the foamed resin sheet 23a is extruded between the molds 21 and 22. In the mold closing process, by closing the molds 21 and 22 after the extrusion process, a part of the foamed resin sheet 23a is confined within the cavity C between the convex part 21c and the concave part 22c.

Preferably, the thickness of the foamed resin sheet 23a is smaller than the thickness of the cavity C. In this case, even when the foamed resin sheet 23a is confined within the cavity C, a gap exists within the cavity C. In this state, vacuum suction is performed using the molds 21 and 22. As a result, the foamed resin sheet 23a expands within the cavity C, and a foamed sheet molded article having the shape of the cavity C is obtained. According to such a method, the cells in the foamed resin sheet 23a are expanded by vacuum suction after the molds 21 and 22 are closed, so that a foamed molded product with a large expansion ratio and a large cell diameter can be obtained. Thereafter, the molds 21 and 22 are opened, the foamed sheet molded product is taken out, and post-processing such as burr removal is performed to obtain a desired molded product.

Note that the foamed sheet molded body may be manufactured by molding the foamed resin sheet 23a using another method. For example, it may be manufactured by molding (eg, vacuum molding) using one mold. Alternatively, a hollow foamed molded body may be formed by vacuum forming two foamed resin sheets 23a using separate molds and welding their peripheral edges to each other.

1. Preparation of Samples Samples of a foamed blow molded article, a foamed sheet molded article, and a non-foamed blow molded article were prepared according to the method shown below and the conditions shown in Tables 1 and 2.

The formulation values in Table 1 are mass ratios, and details of the various components in Table 1 are as follows.
WB140: Metallocene-based high melt tension polypropylene, manufactured by Borealis AG, product name "Daploy WB140"
BC4BSW: Polypropylene, manufactured by Nippon Polypro Co., Ltd., product name "Novatec PP BC4BSW"
AH561: Polypropylene, manufactured by Sumitomo Chemical Co., Ltd., product name "Sumitomo Noblen AH561"
NF325N: Gas-phase metallocene polyethylene, manufactured by Japan Polyethylene Co., Ltd., product name "Harmolex NF325N"
PEX999017: Carbon black masterbatch, manufactured by Tokyo Ink Co., Ltd. CF40EJ: Chemical foaming agent, manufactured by Tokyo Ink Co., Ltd.

1-1. Foam blow molded products (No. 1 to 8)
Using the molding machine 10 shown in FIGS. 2 and 3, a foam blow-molded article was produced in the following manner.

The raw material resin was one with the raw material formulations shown in Tables 1 and 2, and a flame retardant (manufactured by Tokyo Ink Co., Ltd., hindered amine flame retardant, PEX-FRJ-91) in the amount shown in Table 2. Using.

The temperature of each part was controlled so that the temperature of the foamed parison 23 was 190 to 200°C. The physical foaming agent was injected via an injector 16. The injection amount of the foaming agent and the gap between the die slits of the head 18 were set so that the foaming ratio and wall thickness of the molded product after cooling would be the values shown in Table 2.

A foamed parison 23 is formed by extruding the molten resin 11a obtained under the above conditions at a speed corresponding to the basis weight shown in Table 2, and the foamed parison 23 is blow-molded using the molds 21 and 22. Foam blow-molded products Nos. 1 to 8 were obtained.

1-2. Foamed sheet molded product (No. 9 to 12)
Using a molding machine 10 having the same configuration as in FIG. 2 except for having a head (T-die) 18 and molds 21 and 22 having the shape shown in FIG. By extruding the melted raw resin from the head 18 to produce a foamed resin sheet and molding this foamed resin sheet, No. 9 to 12 foamed sheet molded bodies were obtained.

1-3. Non-foamed blow molded products (No. 13-14)
No. 1 was prepared under the same conditions as in "1-1. Foamed blow-molded product" except that no foaming agent was used. No. 13 to 14 non-foamed blow molded articles were obtained.

2. Measurement of average bubble diameter in the thickness direction For each sample, the average bubble diameter in the thickness direction was measured. The results are shown in Table 2.

As shown in Table 2, the sample containing 0% flame retardant and the sample containing 1% flame retardant had similar average cell diameters in the thickness direction.

3. Burning rate evaluation No. For samples 1 to 14, FMVSS No. Burning rates were measured according to the 302 Flammability Test. The results are shown in Table 2.

Table 2 also shows the delay effect calculated based on the following equation.
Retardation effect (%) = 100 x {1 - (burning rate with 1% flame retardant) / (burning rate with 0% flame retardant)}

The following can be seen from Table 2.
No. No. 13 to 14 non-foamed blow-molded products. The foam blow molded products or foam sheet molded products No. 1 to 12 had a greater retardation effect. This result shows that the effect of improving flame retardancy by adding a flame retardant is greater in the foamed molded product than in the non-foamed molded product.

No. 1 to 4 and No. Comparing Nos. 5 to 8, when the physical blowing agent was carbon dioxide gas, the average cell diameter in the thickness direction was larger and the retardation effect was greater than when the physical blowing agent was nitrogen gas. This result shows that the effect of the flame retardant can be significantly exhibited by using carbon dioxide gas as a physical foaming agent or by increasing the average cell diameter in the thickness direction.

No. Looking at Nos. 9 to 12, it can be seen that in the foamed sheet molded article, the combustion rate is low before the addition of the flame retardant, and the flame retardance is significantly improved by the addition of the flame retardant.

1: Foamed molded product 10: Molding machine 11: Raw resin 11a: Molten resin 12: Hopper 13: Extruder 13a: Cylinder 16: Injector 17: Accumulator 17a: Cylinder 17b: Piston 18: Head 20: Resin supply device 21: No. 1 mold 21a: cavity 21b: pinch-off part 21c: convex part 22: second mold 22a: cavity 22b: pinch-off part 22c: recess 23: foam parison 23a: foam resin sheet 25: connecting pipe 27: connecting pipe C: cavity

Claims (4)

A foam molded article formed by foam molding a resin composition containing a base resin and a flame retardant with a physical foaming agent,
The foam molded product is a foam blow molded product or a foam sheet molded product formed by vacuum suction of a foam resin sheet with a mold,
The foaming ratio of the foamed molded product is 3.0 to 6.0 times,
The base resin includes a polyolefin,
The blending amount of the flame retardant in the resin composition is 0.1 to 10% by mass,
The foamed molded article wherein the flame retardant is a phosphorus-based flame retardant, a halogen-based flame retardant, or a hindered amine-based flame retardant . The foam molded article according to claim 1 ,
The foam molded product is a foam blow molded product. The foam molded article according to claim 1 or 2 ,
The foamed molded product has an average cell diameter in the thickness direction of 100 to 1000 μm. The foam molded article according to any one of claims 1 to 3 ,
A foamed molded article, wherein the physical foaming agent contains carbon dioxide gas.