KR20040078503A - Resin for steering wheel of automobile and preparation method of steering wheel for automobile using the same - Google Patents

Abstract

PURPOSE: A resin for a car steering wheel and a manufacturing method of a car steering wheel using the same are provided to improve environmental-friendliness, mechanical properties such as rigidity and tactility quality, and make its weight lighter compared to the conventional steering wheel, by using thermoplastic elastomer(TPE) and a MuCell process. CONSTITUTION: The resin for a car steering wheel is at least one TPE selected from styrene-butadiene-styrene block copolymer(SBS), styrene-ethylene-butylene-styrene(SEBS) and a mixture of a polypropylene resin and synthetic rubber (ethylene-propylene-diene-monomer(EPDM)). The manufacturing method of a car steering wheel using the resin comprises mixing TPE with CO2 gas that is a physical foaming agent and molding the mixture through a MuCell process.

Description

RESIN FOR STEERING WHEEL OF AUTOMOBILE AND MANUFACTURING METHOD OF CAR STEERING WHEEL USING THE SAME {RESIN FOR STEERING WHEEL OF AUTOMOBILE AND PREPARATION METHOD OF STEERING WHEEL FOR AUTOMOBILE USING THE SAME}

The present invention relates to a resin for a steering wheel of a vehicle and a method for manufacturing a vehicle steering wheel using the same, and more particularly, by forming a uniform and fine foam structure by the ultra-fine foam molding method using a thermoplastic elastomer resin material, the conventional thick Reduction of weight compared to the product and at the same time can improve the environmental problems caused by the use of polyurethane material, environmentally friendly resin for steering wheel of the car that can improve the mechanical properties while maintaining the quality of the conventional sensitivity and this The present invention relates to a method for manufacturing a used car steering wheel.

Injection molding is a technique that melts plastic in a cylinder, injects it into a mold through a nozzle, and then cools it to form a product having a desired shape, which is the most commonly used method in the plastics industry. Foam injection molding is a technique of forming a bubble structure inside the plastic by mixing the plastic and the physical or chemical blowing agent can obtain the weight saving effect of the product by the foaming.

Reaction Injection Molding (hereinafter referred to as RIM Molding) refers to the injection molding of two or more low-viscosity raw materials reacting with each other into a mold using a high-pressure mixer (Mixing Head). It is a process of manufacturing. That is, reaction injection molding refers to a plastic processing method in which molding is performed simultaneously with polymerization of monomers to polymers in a mold. As the most common example, a method of preparing polyurethane foam from monomers such as polyol and isocyanate is used to quantitatively measure the raw materials of the monomer reaction liquid in a quantitative manner, and then strongly mix them to inject into the mold, polymerize and cure. After the process, the product is demolded.

FIG. 1 is a schematic view of a steering wheel to which a general RIM molding method is applied, and shows a burr 70 occurring outside the skin layer and an artificially generated overflow 60 to suppress bubble generation.

2 shows a flowchart of a general RIM molding process. First, a mold is sprayed on the surface of the cavity 30 in a state in which the mold 10 is opened for the first time, and a coating agent to which a molded product is painted is applied (Barrier Coat application). Subsequently, the insert part, which is a steel part of the steering wheel, is fixed to the core side to insert the hub core 20, and the mold is closed (molding). Then, the polyol and the isocyanate raw material are injected through the nozzle, and the polyurethane is formed by the heat of reaction by the polymerization reaction of the raw material in the mixing head through the metering pump, and is injected through the resin inlet 80. At this time, the resin is injected only about 30% of the total molded article. The injected resin starts foaming during the depressurization and curing process through the chemical blowing agent (H ₂ O) and forms the entire molded article. During the decompression and curing process, bubbles are blown out to the surface of the product due to the internal high temperature and foaming pressure. Thereafter, after a sufficient curing process, the mold is opened and the finished molded product is taken (demolding).

However, the polyurethane material used to manufacture the steering wheel using the conventional Reaction Injection Molding (RIM) molding method cannot be regenerated and excessively consumes raw materials due to burrs generated outside the forming layer. The PVC steering wheel manufactured by the general injection molding process is foamed using chemical foaming agent (determining the foaming agent according to the physical properties of the resin) and the foam structure is not uniform, resulting in mechanical properties (tensile strength, surface quality, etc.). It is not satisfied, and the addition of a crosslinking agent for imparting flexibility and elasticity generates harmful gases, causing environmental problems, and thus is manufactured from the same solid molded products as general plastic products.

The present invention is to solve the problems of the prior art as described above, by replacing the raw material with a renewable thermoplastic elastomer (TPE) resin instead of polyurethane and PVC resin due to environmental problems, environmentally friendly, lightweight and emotional quality of the product An object of the present invention is to provide a resin for a steering wheel of a vehicle excellent in (touch feeling when held by hand).

Another object of the present invention is to provide a method for manufacturing a vehicle steering wheel by the ultra-fine foam molding method using the resin.

Another object of the present invention is to provide a steering wheel for a vehicle manufactured by the above method.

1 is a plan view showing a steering wheel manufactured using a conventional reaction injection molding (RIM) method,

2 is a flowchart showing a reaction injection molding process of a conventional steering wheel;

Figure 3 is a plan view showing a method for manufacturing a car steering wheel by the ultra-fine foam molding method using a resin according to the present invention,

Figure 4 is a flow chart showing the ultra-fine foam molding process of the steering wheel according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: mold 20: hub core 30: cavity

40: nozzle 50: cylinder 60: overflow

70: burr 80: resin inlet 90: hopper

In order to achieve the above object, the present invention is a resin for a vehicle steering wheel,

The resin is styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and polypropylene resin and synthetic rubber (ethylene-propylene-diene-monomer (EPDM)) A resin for automobile steering wheels, which is a thermoplastic elastomer resin selected from the group consisting of a mixture of

In addition, the present invention

a) styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and polypropylene resin and synthetic rubber (ethylene-propylene-diene-monomer (EPDM)) A thermoplastic elastomer resin selected from the group consisting of mixtures, and

b) CO ₂ gas, a physical blowing agent

It provides a method for manufacturing a steering wheel for a vehicle comprising the step of molding by mixing with an ultra-fine foam molding method.

In addition, the present invention provides a steering wheel for a vehicle manufactured by the method described above.

Hereinafter, the present invention will be described in detail.

The present invention is environmentally friendly by replacing with a renewable resin instead of the conventional polyurethane and PVC raw materials that cause environmental problems, resin for a car steering wheel that can achieve a lighter weight of the product by using an ultra-fine foam molding method and car steering using the same It relates to a manufacturing method of a wheel.

The thermoplastic elastomer resin (Thermoplastic Elastomer, hereinafter referred to as "TPE") used as a raw material in the present invention is recyclable and has excellent mechanical properties.

The thermoplastic elastomer resin (TPE) is styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and polypropylene resin and synthetic rubber (ethylene-propylene-diene- It is preferred that at least one selected from the group consisting of a mixture of monomers (EPDM)).

The content of the thermoplastic elastomer resin is preferably added to 60 to 90% by weight based on the weight of the non-foamed solid molded article. If the content of the thermoplastic elastomer resin is less than 60% by weight, there is a problem of unmolding that is not completely formed. If the content of the thermoplastic elastomer resin is greater than 90% by weight, the foam structure is not uniform due to excessive filling, and waste of raw materials and sensibility quality are deteriorated. there is a problem.

In addition, in the present invention, in order to manufacture a vehicle steering wheel using the TPE, it is preferable that the molding method uses an ultra-fine foam molding method having a uniform bubble structure throughout the product.

In other words, the general chemical foaming method is a method of making a molten resin through the hopper in the pre-mixed state of the plastic raw material and the chemical blowing agent, through the rotation of the screw.

On the other hand, in the ultra-fine foam molding of the present invention, when the raw material supplied through the hopper makes the molten resin through the rotation of the screw, the melted resin in the supercritical fluid state is mixed with the gas injected from the gas supply device attached to the screw. How to make. In other words, the ultra-fine foam molding of the present invention is a device that can inject gas to the screw device for making molten resin in the general injection molding apparatus is attached to form a supercritical fluid mixed with resin and gas and injected into the mold through the nozzle Says, how to mold. By using such an ultra-foaming molding method, it is possible to obtain an excellent effect of the weight reduction of the product and the emotional quality (touch feeling when held by hand).

Hereinafter, with reference to the accompanying drawings will be described in detail for the process of manufacturing a car steering wheel by the ultra-fine foam molding method of the present invention.

Figure 3 is a plan view showing a manufacturing method of a steering wheel using the ultra-expanded foam molding method according to the present invention and a thermoplastic elastomer resin (TPE) as a raw material.

Figure 4 is a flow chart showing the ultra-fine foam molding process of the steering wheel according to the present invention.

In the present invention, a recyclable TPE resin is mixed with a physical blowing agent (CO ₂ ) to form a polymer / gas solvent in a molten state, and the hub core is inserted into a mold and then molded in the same manner as general injection.

More specifically, the forming process of the steering wheel will be described step by step.

First, the first step is a raw material injection step to supply the thermoplastic elastomer resin raw material to the cylinder 50, which is a screw-mounted injection machine through the hopper 90.

After that, the molten resin is manufactured while the screw of the injection molding machine rotates while the mold 10 is opened.

Next, at the same time as the rotation of the screw, a gas, which is a physical blowing agent (CO ₂ ), is injected from the gas injection device.

Then, the molten resin in the supercritical state is formed by the rotation of the screw to melt and measure the resin.

In the next process, the insert part, which is a steel part of the steering wheel, is fixed to the core side to insert the hub core 20, and the mold 10 is closed for mold clamping.

After the above process, the molten resin of the supercritical state is injected into the mold 10 through the forward movement of the screw and the nozzle 40 and the resin inlet 80.

Next, the foaming process, the moment the resin is injected into the mold, the foam in the injected resin grows to form a relatively uniform bubble structure while completing the molding.

After the molding is completed, the molded product is cooled by circulation of cooling water through a cooling channel installed in the mold.

Lastly, take-out process is performed by opening the mold after sufficient cooling time and taking the finished molded product.

Such a manufacturing method of the present invention is characterized in that the cycle time is greatly reduced as a whole because the holding time is hardly needed due to the bubble growth therein.

Referring to the ultra-foam foaming method of the present invention in detail, first, a TPE resin and a gas are injected into a cylinder to form a polymer / gas solvent. In this case, a rapid pressure drop is required to form a uniform bubble hole, and the solubility of the resin varies according to the type of gas. In the present invention, CO ₂ is used. Bubbles are formed when bubbles are formed and then passed through the nozzle, injected into the mold through the resin inlet, and cooled to form a molded article. The process after being injected into the mold is the same as in general injection molding. However, in the ultra-foaming molding, precise control is necessary because the quality of the exterior part of the molded article is largely dependent on the molding process conditions such as gas mixing amount, temperature and pressure. In particular, since the polymer / gas solvent is injected into the mold under atmospheric pressure, foaming occurs at the same time as the injection. As a result, since gas and resin are present in two phases, the flow of gas on the surface may be increased to increase the amount of gas mixture. have. Therefore, the injection amount of CO ₂ gas is preferably injected at 1 to 3.5% by weight relative to the thermoplastic elastomer resin.

Ultra-foam foam molding of the present invention does not require a separate mold modification can be applied to the general injection wheel mold for injection molding as it is.

As described above, the ultra-foam foaming molding method used in the present invention has a short injection time due to the decrease in viscosity of the mixed melt, unlike the general injection molding, and has no holding time due to the growth of internal bubbles, and the material to be cooled by weight reduction. As the time decreases, the cooling time is also shortened.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, an Example is for illustrating this invention and is not limited only to these.

Example 1

A steering wheel was manufactured by the ultrafine foam molding method of FIG. 4 using the expanded thermoplastic elastomer resin (TPE) as a raw material as shown in Table 1 below. At this time, the conditions of the ultra-fine foam molding method are shown in Table 2 below.

[Comparative Examples 1 and 2]

As shown in Table 1, a steering wheel was manufactured by a conventional reaction injection method using a resin composition using polyurethane and PVC as raw materials.

Comparative Example 1 Comparative Example 2 Example 1 Raw materials Polyurethane PVC Foam TPE Weight (g) 850-900 1050-1100 800-850 Mold temperature (℃) 50 ± 5 Up and down 50 10-50 Molding temperature (℃) Polyols (23), Isocyanates (30) 210 to 230 210 to 230 Injection speed (mm / s) 150 50 to 60 100-200 Hold time (sec) - 15 1 to 3 Injection time (sec) 3 4 2-3 Cooling time (sec) 150 80 50 Ton 5 to 10 600 300

Example 1 Screw size (mm)-injection machine 60 SCF (% by weight) 1 to 3.5 Pump pressure (psi) 7000 Discharge pressure (psi) 2500 Flow rate (kg / hr) 1.35

week)

SCF: Injection amount of CO ₂ gas in the screw

Pump pressure: pressure of pump to inject gas

Delivery Pressure: Gas pressure injected into the screw through the nozzle

Experimental Example 1

In order to compare the physical properties of Example 1 and Comparative Examples 1 and 2, the hardness (Hardness), which is a measure of mechanical properties and emotional quality, was measured.

Table 3 compares the hardness (Hardness), which is a measure of the mechanical properties and emotional quality of the foamed TPE of the present invention compared to the conventional polyurethane and PVC.

Comparative Example 1 Comparative Example 2 Example 1 Test Methods Longitude (Type A) 62 to 65 70-75 62 to 65 ASTM D2240 Specific Gravity 0.97 1.20 0.970 ASTM D792 Tensile Strength (MPa) 4.8 11.7 6.9 ASTM D412 Elongation (%) 120 330 400 ASTM D412

As shown in Table 3, in the case of the present invention it can be seen that the mechanical properties are improved while maintaining the existing emotional quality.

Table 4 shows a comparison of the superiority of the product developed in the present invention compared to the conventional molding method.

division Comparative Example 1 Comparative Example 2 Example 1 Raw materials Polyurethane PVC Foamed TPE Raw Material Consumption (g / EA) 850-900 1050-1100 800-850 Cycle time (sec) 250 to 300 150 to 180 150 to 180

As can be seen in Table 4, the cycle time can be greatly reduced due to the ultra-fine foam molding, and the productivity can be improved, and the renewable resin can be used to cope with environmental regulations. Material cost can be reduced.

As described above, according to the present invention, as the raw material is changed to a TPE material instead of a polyurethane or PVC material when manufacturing a steering wheel of a vehicle, the present invention can be recycled and effectively cope with environmental regulations. By manufacturing a car steering wheel by the construction method, there are advantages of lightening the product, improving mechanical properties, and reducing material costs according to the foaming ratio.

Claims (5)

In resin for automobile steering wheel, The resin is styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and polypropylene resin and synthetic rubber (ethylene-propylene-diene-monomer (EPDM)) A resin for automobile steering wheels which is a thermoplastic elastomer resin selected from the group consisting of a mixture of a) styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and polypropylene resin and synthetic rubber (ethylene-propylene-diene-monomer (EPDM)) A thermoplastic elastomer resin selected from the group consisting of mixtures, and b) CO ₂ gas, a physical blowing agent Step of forming by mixing the ultra-fine foam molding method Method of manufacturing a steering wheel for a vehicle comprising a. The method of claim 2, The thermoplastic elastomer resin of a) is a method of manufacturing a steering wheel for an automobile is added at 60 to 90% by weight based on the weight of the non-foamed solid molded article. The method of claim 2, The CO ₂ gas of b) is a manufacturing method of the steering wheel for automobiles are introduced in 1 to 3.5% by weight relative to the thermoplastic resin. A steering wheel for automobiles manufactured by the method described in claim 2.