JP6773967B2 - Manufacturing method of foam molded product - Google Patents

Description

The present invention relates to a method for producing a foam molded product.

For example, in an air conditioner such as an automobile, a tubular air conditioner duct for ventilating air is used.

As an air-conditioning duct, a foam molded product using a foamed resin obtained by foaming a thermoplastic resin with a foaming agent is known. Demand for foam molded products is increasing because they can achieve high heat insulation and weight reduction at the same time.

As a method for producing such a foamed molded product, a blow molding method in which a molten foam resin is molded with a split mold and air is blown into the inside to expand the foamed resin is widely known (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-034998

By the way, in applications such as air-conditioning ducts, it is desirable to increase the foaming ratio of the foamed molded product from the viewpoint of heat insulation and weight reduction, but increasing the foaming ratio lowers the dimensional accuracy and separates the foamed molded product. It becomes difficult to fit in.

The present invention has been made in view of such circumstances, and provides a method for producing a foamed molded product capable of improving the dimensional accuracy of a desired portion while maintaining a high foaming ratio.

According to the present invention, a step of forming a foamed parison using a melt-kneaded resin melt-kneaded by an extruder and molding the foamed parison to obtain a foamed molded product is provided, and the foamed parison is a first parison site. The second parison site is provided in contact with the first parison site, the first parison site is foamed, and the second parison site is foamed at a lower foaming ratio than the first parison site. A method for producing a foamed molded article, which is either or not foamed, is provided.

In the present invention, the foamed parison is provided with a first parison portion having a relatively high foaming ratio and a second parison portion having a foaming ratio smaller than that of the first parison portion or not being foamed. Among the foam molded products, the first molded product portion formed by molding the first parison portion has a relatively high foaming ratio, and the second molded body portion formed by molding the second parison portion has a relatively high foaming ratio. The foaming ratio becomes relatively low or unfoamed. For this reason, a portion of the foam molded product that requires higher dimensional accuracy is formed at the second parison portion, and a portion that does not require high dimensional accuracy is formed at the first parison portion, thereby maintaining a high foaming ratio. A foam molded product having improved dimensional accuracy of a desired portion can be obtained.

Hereinafter, various embodiments of the present invention will be illustrated. The embodiments shown below can be combined with each other.
Preferably, the value of (foaming ratio of the first parison site)-(foaming ratio of the second parison site) is 0.5 or more.
Preferably, the foamed parison is tubular.
Preferably, the melt-kneaded resin contains the first and second melt-kneaded resins, and the first and second melt-kneaded resins are melt-kneaded by separate extruders and supplied to the head, and the first melt-kneaded resin is supplied. The first parison moiety is formed by, the second parison moiety is formed by the second melt-kneaded resin, the first melt-kneaded resin contains a foaming agent, and the second melt-kneaded resin is less than the first melt-kneaded resin. An amount of foaming agent has been added or no foaming agent has been added.
Preferably, the foam molded body comprises a connecting portion for attaching the foam molded body to another member or fitting another member to the foam molded body, and the connecting portion is formed by a second parison portion. To.
Preferably, the second parison moiety has a portion that is compressed by the mold when molding the foamed parison.

According to another aspect of the present invention, the foam molded body includes a first molded body portion and a second molded body portion provided in contact with the first molded body portion, and the first molded body portion is. A foamed molded product is provided which is foamed and the second molded part is foamed or unfoamed at a lower foaming ratio than the first molded part.
Preferably, in the vicinity of the boundary between the first and second molded body portions, the wall thickness of the second molded body portion with respect to the wall thickness of the first molded body portion is 0.8 to 1.2.
Preferably, the value of (foaming ratio of the first molded body portion)-(foaming ratio of the second molded body portion) is 0.5 or more.
Preferably, the second molded body portion is a connecting portion for attaching the foamed molded body to another member or fitting another member to the foamed molded body.
Preferably, the connecting portion is a fitting portion for fitting another member to the foamed molded product.

An example of a foam blow molding machine 1 that can be used in the manufacturing method of the first embodiment of the present invention is shown. A cross-sectional view of the foamed parison 23 according to the first embodiment of the present invention is shown. An air-conditioning foam duct which is an example of the foam molded product 31 of the first embodiment of the present invention is shown, (a) is a front view, (b) is a left side view, and (c) is a right side view. The cross-sectional view of the foamed parison 23 formed by the 2nd Embodiment of this invention is shown. An air-conditioning foam duct which is an example of the foam molded product 31 of the second embodiment of the present invention is shown, (a) is a front view, (b) is a left side view, and (c) is a right side view.

Hereinafter, embodiments of the present invention will be described. The various features shown in the embodiments shown below can be combined with each other. In addition, the invention is independently established for each feature.

1. 1. First Embodiment In the method for producing a foamed molded product according to the first embodiment of the present invention, a foamed parison is formed using a melt-kneaded resin melt-kneaded by an extruder, and the foamed parison is molded to form a foamed molded product. The foamed parison site comprises a first parison site and a second parison site provided in contact with the first parison site, the first parison site is foamed, and the second parison site is provided. , Foamed or unfoamed at a lower foaming ratio than the first parison site.

The method of this embodiment can be carried out using the foam blow molding machine 1 illustrated in FIG. The foam blow molding machine 1 includes first and second resin supply devices 2a and 2b, a head 18, and a split mold 19. Each of the resin supply devices 2a and 2b 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.
Hereinafter, each configuration will be described in detail.

<Hopper 12, extruder 13>
The hopper 12 is used to put the raw material resin 11 into the cylinder 13a of the extruder 13. The form of the raw material resin 11 is not particularly limited, but is usually in the form of pellets. The raw material resin is, for example, a thermoplastic resin such as polyolefin, and examples of the polyolefin include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer and a mixture thereof. The raw material resin 11 is charged into the cylinder 13a from the hopper 12 and then melted by being heated in the cylinder 13a to become a molten resin. Further, it is conveyed toward the tip of the cylinder 13a by the rotation of the screw arranged in the cylinder 13a. The screw is arranged in the cylinder 13a, and the molten resin is kneaded and conveyed by its rotation. A gear device is provided at the base end of the screw, and the screw is rotationally driven by the gear device. The number of screws arranged in the cylinder 13a may be one or two or more.

<Injector 16>
The cylinder 13a is provided with an injector 16 for injecting a foaming agent into the cylinder 13a. Examples of the foaming agent injected from the injector 16 include a physical foaming agent, a chemical foaming agent, and a mixture thereof, and a physical foaming agent is preferable. As the physical foaming agent, inorganic physical foaming agents such as air, carbon dioxide, nitrogen gas, and water, organic physical foaming agents such as butane, pentane, hexane, dichloromethane, and dichloroethane, and their supercritical fluids are used. be able to. As the supercritical fluid, it is preferable to use carbon dioxide, nitrogen, etc., for nitrogen, the critical temperature is -149.1 ° C, the critical pressure is 3.4 MPa or more, and for carbon dioxide, the critical temperature is 31 ° C, the critical pressure. It is obtained by setting the pressure to 7.4 MPa or more. Examples of the chemical foaming agent include those that generate carbon dioxide gas by a chemical reaction between an acid (eg, citric acid or a salt thereof) and a base (eg, baking soda). The chemical foaming agent may be injected from the hopper 12 instead of being injected from the injector 16.

<Accumulator 17, head 18>
The melt-kneaded resin obtained by melt-kneading the raw material resin and the 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 slidable inside the cylinder 17a, so that the melt-kneaded resin can be stored in the cylinder 17a. Then, by moving the piston 17b after a predetermined amount of the melt-kneaded resin is stored in the cylinder 17a, the melt-kneaded resin is extruded from the die slit provided in the head 18 through the connecting pipe 27 to form the foamed parison 23. .. The shape of the foamed parison 23 is not particularly limited, and may be cylindrical or sheet-shaped.

By the way, a foaming agent is added to the melt-kneaded resin 11a of the resin supply device 2a, and is the amount of the additive added to the melt-kneaded resin 11b of the resin supply device 2b smaller than that of the melt-kneaded resin 11a? Alternatively, no foaming agent is added to the melt-kneaded resin 11b. The melt-kneaded resin is supplied to the head 18 from each of the resin supply devices 2a and 2b. As shown in FIG. 2, the melt-kneaded resins 11a and 11b are extruded from the die slit after merging in the head 18, so that the foamed parison 23 having the first and second parison portions 23a and 23b is formed. The parison portions 23a and 23b are formed so as to divide the foamed parison 23 in the circumferential direction. The parison sites 23a and 23b are formed so as to be in contact with each other adjacent to each other. The parison portion 23b has a strip shape extending in the vertical direction, and the parison portion 23a has a shape obtained by removing the parison portion 23b from the foamed parison 23. The ratio of the parison portions 23a and 23b can be changed by changing the ratio of the melt-kneaded resin 11a and 11b supplied to the head 18. The area ratio of the parison portion 23b to the parison portion 23a (area ratio of the outer surface) is, for example, 1 to 99%, preferably 1 to 50%, and more preferably 1 to 20%.

The parison site 23a is foamed, and the parison site 23b has a smaller expansion ratio than the parison site 23a or is unfoamed (solid). When no additive is added to the melt-kneaded resin 11b, the parison portion 23b becomes unfoamed. The foaming ratio of the parison portion 23a is not particularly limited, but is, for example, 1.5 to 6 times. The foaming ratio of the parison site 23b is not particularly limited, but is, for example, 1.0 to 5.5 times. A foaming ratio of 1.0 times means that the foam is not foamed. The value of (foaming ratio of parison portion 23a)-(foaming ratio of parison portion 23b) is preferably 0.5 or more, preferably 1.0 or more, and even more preferably 1.5 or more. The larger this value is, the higher the dimensional accuracy of the desired portion can be improved while maintaining a high foaming ratio. The upper limit of this value is not particularly specified, but is, for example, 4.0. In the calculation of this value, when the parison portion 23b is not foamed, the foaming ratio is 1.0. The composition of the raw material resin for forming the parison portions 23a and 23b may be the same or different. The foaming ratio of the parison parts 23a and 23b is such that the foamed parison 23 is cured as it is to form a foamed molded product, and a sample is cut out from the parts corresponding to the parison parts 23a and 23b in the foamed molded product, and the specific gravity of this sample Can be measured and calculated based on the following mathematical formula (1).
Foaming ratio = (specific gravity of unexpanded raw material resin 11) / (specific gravity of sample) ... (1)

<Split mold 19>
The foamed parison 23 is guided between a pair of split molds 19. By molding the foamed parison 23 using the split mold 19, the foamed molded product 31 as shown in FIG. 3 can be obtained. The molding method using the split mold 19 is not particularly limited, and may be blow molding in which air is blown into the cavity of the split mold 19 to perform molding, from the inner surface of the cavity of the split mold 19 to the inside of the cavity. The foamed parison 23 may be formed by vacuum forming with reduced pressure, or a combination thereof.

The foam molded body 31 includes a first molded body portion 32a formed by molding the parison portion 23a and a second molded body portion 32b formed by molding the parison portion 23b. The molded body parts 32a and 32b are integrally molded. The molded body portion 32b is indicated by a pattern composed of horizontal dotted lines in FIG. The molded body portion 32a is foamed, and the molded body portion 32b is foamed or unfoamed at a lower foaming ratio than the molded body portion 32a. The foaming ratio of the molded body portion 32a is not particularly limited, but is, for example, 1.5 to 6 times. The foaming ratio of the molded product portion 32b is not particularly limited, but is, for example, 1.0 to 5.5 times. A foaming ratio of 1 times means that the foam is not foamed. The value of (foaming ratio of the molded body portion 32a)-(foaming ratio of the molded body portion 32b) is preferably 0.5 or more, preferably 1.0 or more, and further preferably 1.5 or more. The larger this value is, the higher the dimensional accuracy of the desired portion can be improved while maintaining a high foaming ratio. The upper limit of this value is not particularly specified, but is, for example, 4.0. In the calculation of this value, when the molded body portion 32b is not foamed, the foaming ratio is 1.0. The composition of the raw material resin for forming the molded body portions 32a and 32b may be the same or different. The expansion ratio of the molded product portions 32a and 32b can be calculated based on the above formula (1) by cutting out a sample from the molded product portions 32a and 32b, measuring the specific gravity of the sample, and calculating the foaming ratio.

The wall thickness of the molded body parts 32a and 32b is not particularly limited, but in the vicinity of the boundary between the molded body parts 32a and 32b, the wall thickness of the molded body part 32b is 0.8 to 1.2 with respect to the wall thickness of the molded body part 32a. It is preferably 0.9 to 1.1, and more preferably 0.9 to 1.1. In the present embodiment, it is not essential to compress the foamed parison 23 at the time of molding, and the molded body portions 32a and 32b may or may not be compressed at the time of molding. Further, when the foamed parison 23 is compressed by the mold 19 at the time of molding, there may be a problem that the resin and air bubbles expelled from the compressed portion cause molding defects. According to the present embodiment, is the foaming ratio low? Alternatively, the occurrence of such a problem can be suppressed by allowing the unfoamed parison portion 23b to have a portion compressed by the mold 19 when molding the foamed parison 23.

In the present embodiment, the foam molded body 31 is a foam duct for air conditioning, and includes a hollow main body portion 31a, a mounting portion 31b, a fitting portion 31c, a suction port 31d, and a discharge port 31e. The gas sucked through the suction port 31d passes through the main body 31a and then is discharged from the discharge port 31e. The attachment portion 31b is used to attach the foam molded body 31 to another member (for example, an automobile body). Another member (for example, an air conditioning register) is inserted into the discharge port 31e and fitted into the fitting portion 31c.

If the dimensional accuracy of the fitting portion 31c (particularly the dimensional accuracy of the inner surface shape) is poor, the workability when fitting another member to the fitting portion 31c deteriorates, so that the dimensional accuracy of the fitting portion 31c should be improved. is important. Therefore, in the present embodiment, as shown in FIG. 3, the fitting portion 31c is formed by the molded body portion 32b. Generally, in foam molding, the dimensional accuracy tends to deteriorate as the foaming ratio increases. However, since the molded body portion 32b is foamed or unfoamed at a low foaming ratio, the fitting portion 31c is formed by the molded body portion 32b. By doing so, it becomes possible to improve the dimensional accuracy of the fitting portion 31c.

2. Second Embodiment The second embodiment of the present invention will be described with reference to FIGS. 4 to 5. This embodiment is similar to the first embodiment, and the main difference is that the mounting portion 31b is formed by the molded body portion 32b. Hereinafter, the differences will be mainly described.

In the present embodiment, as shown in FIG. 4, the parison portions 23a and 23b are horizontally inverted from the first embodiment to form the foamed parison 23. Then, using such a foamed parison 23, the foamed molded product 31 shown in FIG. 5 is formed.

The foam molded body 31 of the present embodiment is an air conditioning foam duct having the same configuration as that of the first embodiment. In the present embodiment, the mounting portion 31b and its vicinity are formed by the molded body portion 32b. Generally, in foam molding, the strength tends to decrease as the foaming ratio increases. However, since the molded body portion 32b is foamed or unfoamed at a low foaming ratio, the mounting portion 31b is formed by the molded body portion 32b. This makes it possible to increase the strength of the mounting portion 31b.

1: Foam blow molding machine 2a: First resin supply device 2b: Second resin supply device 11: Raw material resin 11a: Melt kneading resin 11b: Melt kneading resin 12: Hopper 13: Extruder 13a: Cylinder 16: Injector 17: Accumulator 17a: Cylinder 17b: Piston 18: Head 19: Split mold 23: Foamed parison 23a: First parison part 23b: Second parison part 25: Connecting pipe 27: Connecting pipe 31: Foam molded body 31a: Main body 31b: Mounting Part 31c: Fitting part 31d: Suction port 31e: Discharge port 32a: First molded body part 32b: Second molded body part

Claims (11)

A step of forming a foamed parison using a melt-kneaded resin melt-kneaded by an extruder and molding the foamed parison using a split die to obtain a foamed molded product is provided.
The foamed parison comprises a first parison site and a second parison site.
The first and second parison sites are provided in contact with each other in the cross section so as not to overlap in the cross section of the foamed parison.
The first parison part is foamed
A method for producing a foamed molded article, wherein the second parison site is foamed or unfoamed at a lower foaming ratio than the first parison site. The method according to claim 1, wherein the value of (foaming ratio of the first parison site)-(foaming ratio of the second parison site) is 0.5 or more. The method according to claim 1 or 2, wherein the foamed parison is tubular. The melt-kneaded resin contains the first and second melt-kneaded resins.
The first and second melt-kneaded resins are melt-kneaded by separate extruders and supplied to the head.
The first melt-kneaded resin forms the first parison portion, and the second melt-kneaded resin forms the second parison portion.
The first melt-kneaded resin contains a foaming agent and contains
The method according to any one of claims 1 to 3, wherein the second melt-kneaded resin contains a smaller amount of a foaming agent than the first melt-kneaded resin or no foaming agent is added. The foamed molded product includes a connecting portion for attaching the foamed molded product to another member or fitting another member to the foamed molded product.
The method according to any one of claims 1 to 4, wherein the connecting portion is formed by a second parison site. The method according to any one of claims 1 to 5, wherein the second parison portion has a portion that is compressed by a mold when molding the foamed parison. A foam molded product obtained by molding a foam parison.
The foam molded body includes a first molded body portion and a second molded body portion provided in contact with the first molded body portion so as not to overlap with each other.
The first molded part is foamed and
The second molded part is foamed or unfoamed at a lower foaming ratio than the first molded part.
A foam molded product in which the first and second molded product portions are in contact with each other on a surface perpendicular to the longitudinal direction of the foam molded product and passing through the second molded product portion . The foamed molded product according to claim 7, wherein the value of (foaming ratio of the first molded product portion)-(foaming ratio of the second molded product portion) is 0.5 or more. The foamed molded product according to claim 7 or 8, wherein the second molded body portion is a connection portion for attaching the foamed molded product to another member or fitting another member to the foamed molded product. The foamed molded product according to claim 9, wherein the connecting portion is a fitting portion for fitting another member to the foamed molded product. The foamed molded product according to any one of claims 7 to 10, wherein the foamed molded product is an air-conditioning foam duct.