JP2002210773A - Method for manufacturing partially foamed resin molded article by laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel foam molding method capable of partially foaming only a necessary region. SOLUTION: A molding process for molding a non-foamed molded object 6 having a predetermined shape comprising a foamable resin raw material not foamed at the time of molding but foamed by the irradiation with laser beam and a foaming process for partially foaming only the region irradiated with laser beam by irradiating only a part 6a becoming a foamed part of the non-foamed molded object 6 are successively performed. The foamable resin raw material contains a laser beam absorbable resin capable of being melted by the absorption of laser beam and a foaming agent capable of generating gas when the laser beam absorbable resin is heated and melted by the absorption of laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser for producing a partially foamed resin molded article in which a foamed portion and an unfoamed portion are integrally formed by partially foaming only a necessary portion by irradiating a laser beam. The present invention relates to a method for producing a partially foamed resin molded product by the method described above. Partially foamed resin molded products according to the present invention, for example,
It can be used for members that partially require soundproofing, heat insulation and heat retention.

[0002]

2. Description of the Related Art As one method of molding a foamed resin molded product, a foaming solution is injected between a skin material and a base material while a preformed skin material and a base material are set inside a mold. A known integral foam molding method is known.

[0003] Specifically, a skin material made of vinyl chloride resin (PVC) or the like is formed into a predetermined shape in advance by slush molding, vacuum molding, or the like, and is arranged along the female cavity surface of the foam molding die. . On the other hand, a base material made of polypropylene (PP) or the like is previously molded into a predetermined shape by injection molding or the like, and this is arranged along the male core surface of the foam molding die. Then, a foaming stock solution such as polyurethane is injected into the female mold cavity, and after closing the mold, the foaming stock solution is foamed and solidified between the skin material and the base material, thereby forming a foam having a predetermined shape and forming the foamed body. Weld the body, skin material and substrate. The molded product thus obtained is opened and removed from the mold, and after removing burrs and unnecessary skin material, the molded product is completed as a foamed resin molded product.

However, in such an integral foam molding method, a fluid having a low fluidity cannot be used as a material of the foam because the fluidity of the foaming liquid in the mold is required. There is a problem that the degree of freedom is low.

Japanese Patent Application Laid-Open No. 2000-229328 discloses that a foaming material obtained by mixing a foaming agent and a microwave absorbing material together with a preformed skin material and a base material is set in a molding die. A method of irradiating a foam with microwaves is disclosed.

More specifically, a skin material made of an olefin-based thermoplastic resin such as polypropylene is formed into a predetermined shape in advance by slash molding, and this is arranged along the surface of the female mold cavity of the foaming mold. Further, on the skin material set in the molding die, a foaming raw material comprising a mixture of a powdery or granular body of an olefin-based thermoplastic resin, a foaming agent, and a microwave absorbing material is arranged. On the other hand, a substrate made of an olefin-based thermoplastic resin such as polypropylene is formed into a predetermined shape in advance by injection molding or the like, and is arranged along the male core surface of the foaming mold. The foam mold is made of a non-metallic material that transmits microwaves, for example, a super-heat-resistant super engineering plastic such as polyimide. Then, after closing the mold, the mold is put into a microwave irradiation device, and the entire mold is irradiated with microwaves while being pressed in the mold clamping direction. The microwave transmitted through the mold is absorbed by the microwave absorbing material in the foaming material, and as a result, the microwave absorbing material generates heat. The heat melts the thermoplastic resin in the foaming raw material, decomposes the foaming agent to generate gas, and the gas causes the molten thermoplastic resin to foam. In addition, the surface of the skin material and the base material in contact with the molten thermoplastic resin are melted,
When the thermoplastic resin in the foaming raw material is cooled and solidified to form a foam, the foam, the skin material, and the base material are integrally welded.

[0007]

In recent years, from the viewpoints of weight reduction and cost reduction, parts of various fields such as automobile parts are frequently resinified into resin molded articles. Among such resin molded products, vibration and sound insulation and heat insulation and heat retention are not the whole of the resin molded product,
May be partially required. In such a case, a technique for partially foaming only a necessary portion of the resin molded product is required.

However, in the above-mentioned conventional method of foaming by irradiation with microwaves, since the molding die is placed inside a microwave irradiation apparatus and the entire foaming material including a foaming agent is irradiated with microwaves, it is necessary to use microwaves. It is impossible to partially foam only an important part.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a novel foam molding method capable of partially foaming only necessary portions. .

[0010]

That is, the present invention has been made to solve a new technical problem of partially foaming only a necessary portion, and a laser according to the present invention for solving such a problem. The method for producing a partially foamed resin molded article according to the above is a method for producing a partially foamed resin molded article in which a foamed portion and an unfoamed portion are integrally formed, and at least the foamed portion does not foam during molding. And, a molding step of molding an unfoamed molded article of a predetermined shape made of a foamed resin material that can be foamed by irradiation with laser light, and irradiating laser light only to a portion of the unfoamed molded article to be the foamed portion. And a foaming step of partially foaming only the portion irradiated with the laser beam.

In a preferred embodiment, the foamed resin raw material comprises a laser light absorbing resin which can be melted by absorbing the laser light, and a gas when the laser light absorbing resin is heated and melted by absorbing the laser light. And a foaming agent which can be generated.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a partially foamed resin molded article by a laser according to the present invention comprises sequentially performing a molding step and a foaming step, and partially foaming only a necessary portion. And a partially foamed resin molded product in which a non-foamed portion is integrally formed.

In the above-mentioned molding step, an unfoamed molded article of a predetermined shape made of a foamed resin raw material which is not foamed at least at the portion to be foamed at the time of molding and which can be foamed by irradiation with a laser beam.

The method for molding the unfoamed molded article is not particularly limited, and injection molding, extrusion molding, hollow molding (such as blow molding) and the like can be used. This unfoamed molded article may be formed by molding at least a portion to be a foamed portion from the foamed resin raw material. The entire unfoamed molded body may be molded from the foamed resin material, or only the foamed portion may be foamed. It is possible to form the unfoamed portion from the resin raw material while molding from a resin raw material not containing a foaming agent described later. In consideration of ease of molding, it is preferable to mold the entire unfoamed molded body from the foamed resin raw material.

The foamed resin raw material is not particularly limited as long as it does not foam at the time of molding and can be foamed by irradiation with a laser beam. And a foaming agent capable of generating a gas when the laser light absorbing resin is heated and melted by absorbing the laser light.

As the laser light absorbing resin, a thermoplastic resin that melts at a molding temperature, is heated and melted by absorbing laser light, and does not decompose when irradiated with laser light can be used. That is, the absorptivity of the laser light in the laser light absorbing resin can be set in a range where the resin can be heated and melted by the absorption of the laser light. The absorbency of the laser light can be appropriately adjusted by adding a colorant such as carbon black. In addition, if the foaming agent described below absorbs the laser beam and generates heat and generates gas, and the heat can melt the thermoplastic resin, it is not necessary to add a coloring agent.

Specific examples of the thermoplastic resin include polyethylene (PE), polypropylene (PP), polystyrene (PS) and acrylonitrile-butadiene-styrene polymer (ABS). In addition, what added reinforcing fiber, such as glass fiber and carbon fiber, may be used as needed.

On the other hand, the foaming agent is not particularly limited as long as it does not generate a gas at the time of molding and can generate a gas at the time of laser beam irradiation. A pyrolytic foaming agent that decomposes and generates gas when the laser light absorbing resin is heated and melted by absorbing laser light (higher than the molding temperature, and of the thermoplastic resin contained in the foamed resin material). Having a decomposition temperature lower than the decomposition temperature). It should be noted that if there is a foaming agent that does not generate gas at the time of molding and reacts directly with laser light to generate gas, such a foaming agent can be employed. It is of course possible to add an appropriate foaming aid.

Examples of the foaming agent include p-toluenesulfonyl semicarbazide (TSC, decomposition temperature: 235 ° C.),
Trihydrazinotriazine (decomposition temperature: 235 ° C.) and barium azodicarboxylate (decomposition temperature: 240 to 2
50 ° C.).

In the foaming step, a laser beam is applied only to a portion to be the foamed portion of the unfoamed molded body, and only a portion irradiated with the laser beam is partially foamed.
For example, when the unfoamed resin material contains the laser light-absorbing resin and the thermal decomposition type foaming agent, the thermoplastic resin contained in the laser light-absorbing resin is applied to the portion irradiated with the laser light. While being heated and melted by the absorption of laser light, the heat decomposes the foaming agent to generate gas, and the molten thermoplastic resin foams and expands with the gas. As a result, a partially foamed resin molded article in which a foamed portion formed at a portion irradiated with laser light and an unfoamed portion having the original shape remaining at a portion not irradiated with laser light are integrally formed. Can be manufactured.

Thus, according to the method of the present invention for producing a partially foamed resin molded article by using a laser, only a necessary portion can be partially foamed.
A resin molded product partially having a foamed portion having functions such as heat retention and weight reduction, that is, a resin molded product in which the foamed portion and an unfoamed portion having functions such as strength and airtightness are integrally formed. Can be provided.

Here, when it is desired to ensure airtightness, strength, and the like also in the foamed portion, it is preferable to form a non-foamed portion integrally on the surface of the foamed portion to form a multilayer structure.

The material and characteristics of the non-foamed portion can be variously selected and set according to the required function. Resins of the same type or different from the resin constituting the foamed portion, and in some cases, such as metal or glass It is also possible to employ different materials. However, except when bonding to the foamed part using an adhesive,
The non-foamed portion must be made of a resin which is compatible with the foamed portion and can be welded to each other. In the case where a non-foamed portion is previously formed on the surface irradiated with the laser beam in the foaming step, or when the non-foamed portion and the foamed portion are integrally joined by laser welding as described later, It is necessary to form a non-foamed portion with a resin that transmits laser light.

The method of forming the non-foamed portion is not particularly limited. For example, in the molding step, the non-foamed molded article may be integrally molded when molded, or may be formed separately after molding the unfoamed molded article or after forming the foamed portion by laser light irradiation. The foamed portion can be bonded with an adhesive or the like. When a molding die is used as described later, by performing the foaming step in a state where a non-foamed portion separately formed is arranged on the mold surface of the molding die, the foamed portion and the non-foamed It is also possible to join the parts integrally by laser welding.

More specifically, if it is desired to ensure airtightness in the foamed portion, a non-foamed portion made of an airtight film or the like can be formed on the surface of the foamed portion where airtightness is desired. Although the material of the airtight film is not particularly limited, polyethylene terephthalate (PET), P
E, PP, PS, etc. can be adopted. When it is desired to secure the strength of the foamed portion, a non-foamed portion including a high-strength portion having higher strength than the foamed portion can be formed on the surface of the foamed portion where the strength is desired to be secured. As such a high-strength portion, for example, the same material as the material constituting the foamed portion except that the foaming agent is not included,
Alternatively, a reinforcing material can be added as needed.

In addition, when expansion (expansion in an unconstrained state) due to foaming in the foamed portion becomes a problem from a design or functional point of view, the surface where swelling is to be suppressed is restricted by a mold. It is preferable to perform the foaming step while controlling expansion accompanying foaming. In addition, by performing the foaming step in a state where the mold is previously in contact with only the surface of the foamed portion where swelling is desired to be suppressed, the mold is expanded only on the other side where the mold is not in contact, or swelling is suppressed. Before irradiating the laser beam, a predetermined gap is provided between the molding die and the unfoamed molded body, and expansion after foaming is allowed while restricting the subsequent expansion while allowing the expansion by the gap. Can be.

When the molding die is disposed on the surface to be irradiated with the laser beam, the molding die is made of a material that is transparent to the laser beam (for example, glass or the laser beam). (A permeable resin material that is permeable to light). The material of the mold must basically be such that it does not weld to the thermoplastic resin constituting the foamed portion. However, when the surface on which the non-foamed portion is formed and the surface on which expansion due to foaming is desired match, the non-foamed portion can also be used as a molding die. The foamed portion can be made of a material that can be welded.

The type of the laser beam used in the foaming step is determined by the relationship between the absorption spectrum of the laser beam absorbing resin that absorbs the laser beam, the plate thickness, and the like. Those having a wavelength that can be heated and melted by absorption are appropriately selected. For example, YAG: Nd ³⁺
A laser (wavelength of laser light: 1060 nm) or a semiconductor laser (wavelength of laser light: 500 to 1000 nm) can be used. Irradiation conditions such as laser output, irradiation density, and processing speed (moving speed) can be appropriately set according to the type of resin and the like.

[0029]

The present invention will be described below in detail with reference to examples.

(Embodiment 1) In this embodiment shown in FIGS. 1 and 2, a partially foamed resin molded product according to the present invention is applied to a pipe-shaped synthetic resin product.

As shown in FIG. 2, the synthetic resin product 1 has a bulging portion 2, a pipe portion 3, and a connecting portion 4 integrally formed. An airtight seal 5 is welded to the outer peripheral surface of the bulging portion 2. In addition, this synthetic resin product 1
Is a hollow body that is divided into upper and lower parts, and is formed by integrally joining an upper divided body and a lower divided body that are separately formed.

The resin forming the bulging portion 2, the pipe portion 3 and the connecting portion 4 is added with a predetermined amount of carbon black as a coloring agent, and has a laser beam absorbing to a laser beam used as a heating source. It is polyethylene (PE) used as an absorbent resin.

The hermetic seal 5 is made of a PE film made of a transmissive resin having transparency to a laser beam as a heating source, and forms a non-foamed portion.

Only the swelling portion 2 of the synthetic resin product 1 is composed of a partially foamed foaming portion, and the pipe portions 3 and the connecting portions 4 provided on both sides of the swelling portion 2 remain unfoamed. Consisting of an unfoamed part. That is, the synthetic resin product 1 is a partially foamed resin molded product in which the bulging portion 2 as a foaming portion, and the pipe portion 3 and the connecting portion 4 as non-foaming portions are integrally formed.

Hereinafter, a method for producing the synthetic resin product 1 will be described.

(Molding Step) First, PE (melting point: 130 ° C., molding temperature: 200 ° C.) as a laser light absorbing resin to which an appropriate amount of carbon black as a coloring agent is added, and barium azodicarboxy as a foaming agent A foamed resin raw material having a rate (decomposition temperature: 240 to 250 ° C.) was prepared. Then, after forming an upper divided body and a lower divided body having a predetermined shape by injection molding, the two were integrally joined by vibration welding to form an unfoamed molded body 6 shown in FIG.

When the upper divided body and the lower divided body are injection-molded, a portion 6a of the unfoamed molded body 6 to be a foamed portion is formed.
An airtight seal 5 as a non-foamed portion was formed by two-color molding on the outer surface of and was welded.

(Foaming Step) Then, as shown in FIG. 1, a laser beam was applied to only the portion 6a of the unfoamed molded body 6 to be a foamed portion using a laser torch 7. The laser beam used for the irradiation was a YAG: Nd ³⁺ laser (wavelength: 106
0 nm). As shown by the arrow in FIG. 1, the laser irradiation is performed by reciprocating the laser torch 7 in the axial direction within the range of the foamed portion 6a while rotating the unfoamed molded body 6 around the axis. Performed by repeating.

As a result, the laser beam transmitted through the hermetic seal 5 made of a transparent resin is absorbed by the laser beam absorbing resin in the portion 6a to be a foamed portion, and the thermoplastic resin contained in the laser beam absorbing resin becomes As the PE was heated and melted, the heat decomposed the foaming agent to generate gas, and the molten thermoplastic resin was foamed and expanded by the gas.

In this way, by partially foaming only the portion irradiated with the laser beam, the bulging portion 2 as a foaming portion, and the pipe portion 3 and the connecting portion 4 remaining as an unfoamed portion are integrally formed. Thus, the synthetic resin product 1 of the present example was completed.

In the above foaming step, the hermetic seal 5 formed on the outer surface of the portion 6a to be the foamed portion is
The portion 6a is expanded by elastic deformation with expansion due to foaming.

As described above, according to the present embodiment, only the necessary portions can be partially foamed, so that the swelling portion 2 as a foaming portion having functions such as vibration proof and sound proofing properties, Pipe 3 as a non-foamed part with functions such as airtightness and airtightness
In addition, it is possible to provide a resin molded product in which the connection part 4 and the connection part 4 are integrally formed.

In this embodiment, since the airtight seal 5 as a non-foamed portion is integrally formed on the outer surface of the swelled portion 2 as a foamed portion, the swelled portion 2 is formed as a foamed portion. While exhibiting functions, airtightness can be ensured.

[0044]

As described above in detail, according to the method for manufacturing a partially foamed resin molded article by laser of the present invention, only a necessary portion can be partially foamed, so that vibration and sound insulation and heat insulation can be achieved. -It is possible to provide a resin molded product in which a foamed portion having functions such as heat retention and weight reduction and an unfoamed portion having functions such as strength and airtightness are integrally formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a state where a laser beam is applied to only a necessary portion of an unfoamed molded body according to an embodiment of the present invention.

FIG. 2 is a sectional view of a partially foamed resin molded product according to an example of the present invention.

[Explanation of symbols]

 2 ... bulging part (foaming part) 3 ... pipe part (non-foaming part) 4 ... connection part (non-foaming part) 5 ... airtight seal (non-foaming part)

Claims (2)

[Claims] 1. A method for producing a partially foamed resin molded article in which a foamed portion and an unfoamed portion are integrally formed, wherein at least a portion to be a foamed portion does not foam at the time of molding,
And, a molding step of molding an unfoamed molded article of a predetermined shape made of a foamed resin raw material that can be foamed by irradiation with laser light, And a foaming step of partially foaming only a portion irradiated with the laser beam, in order. 2. The foamed resin raw material may generate a gas when the laser light absorbing resin melts by absorbing the laser light and the laser light absorbing resin is heated and melted by absorbing the laser light. The method for producing a partially foamed resin molded product by a laser according to claim 1, further comprising a foaming agent.