JPS6048309A - Manufacture of crush pad - Google Patents

Abstract

PURPOSE:To save energy required for manufacture of a crush pad as well as obtain the thick crush pad product having uniform thickness by a method in which a surface skin obtained from blow molding of soft PVC resin composition is incorporated with aggregate and integrated by injection and expansion of an expandible urethane resin. CONSTITUTION:A soft PVC resin composition based on a vinyl chloride resin having an average polymerization degree of 1,400 or more or the average polymerization degree of 400 or more of meltable portion containing 5% or more unmelted portion after dipped in tetrahydrofuran of 120 deg.C for one hour is molded into the surface skin of a crush pad by a blow molding method. The surface skin is incorporated with a rigid aggregate, and an expandible urethane resin is injected between the surface skin and the agregate and expanded to integrate them. An aimed product is thus obtained. EFFECT:The surface of the molding can be embossed by blow molding, the molding can be freely designed, and the loss of the material can be lessened.

Description

Detailed Description of the Invention The present invention involves molding a vinyl chloride resin composition into a desired external shape by blow molding, placing rigid aggregate inside the skin material, and injecting foamable urethane resin. The present invention relates to a method of manufacturing a crash pad for a vehicle that is integrated with foamed pads.

Conventionally, Claracy pads (also called instrumental panels and dash boards) for vehicles have been made of a skin made of a soft vinyl chloride resin composition, a rigid bone layer, and a soft vinyl chloride resin foam or foamed urethane as an intermediate layer between them. It has a three-layer structure with resin injected and foamed.

Generally, the skin material is a calender sheet made of a vinyl chloride resin composition with a desired grain pattern and good weather resistance and heat resistance.

In addition, the aggregate must have appropriate rigidity in order to support the weight of the various meters and to be attached to the vehicle body, and polypropylene, nylon, ABS, etc. are generally used in practical use. On the other hand, a sheet of foamable urethane or soft foamed vinyl chloride resin is used between the skin and the aggregate to provide a cushioning effect in the event of a collision. In addition to the above-mentioned 3# resin, various manufacturing methods have been put into practical use for molded crash pads. In the sludge mold method, a sol of vinyl chloride resin is poured into a mold and heated to gel it to form a skin, but the production speed is slow, and
The disadvantage is that the basis weight of the epidermis is heavy. Press vacuum method (P&V method), crush pad method (C&P method)
method), there are problems such as uneven grain and uneven thickness of the epidermis.
Formulated compositions are also expensive. Furthermore, the press vacuum method has the disadvantage that the epidermal layer is hard.

In addition, by direct injection molding of thermoplastic resin such as ABS,
Molded products have also been made, but they have the drawbacks of being hard and lacking in luxury appearance. Another method is to mold the skin material by injection molding, but the wall thickness of the molded product cannot be made thinner.
The disadvantages include that the thickness ratio of the molded product is large, it does not flow with a single-point gate, welds are noticeable with a multi-point gate, and distortions remain in the gate area and cause deformation.

As mentioned above, each of the above-mentioned methods has various drawbacks, and in addition, the press-vacuum method and the crush pad method require heat processing and reheating, which is disadvantageous in terms of energy saving.

The present invention does not have the drawbacks of the above-mentioned methods, and also has low energy loss in the molded product manufacturing process, which is a rational manufacturing method.

The gist of the present invention is that the average degree of polymerization is 1400 or more or 12
A soft vinyl chloride resin composition mainly composed of a vinyl chloride resin, which has an unmelted content of 5% or more after being immersed in tetrahydrofuran (THF) at 0°C for 1 hour and has an average degree of polymerization of the soluble content of 400 or more. A method for manufacturing a crash pad for a vehicle, in which a crash pad is molded into a desired crash pad external shape using a blow molding method, this is used as a skin material to incorporate a rigid bone structure, and is integrated by injecting and foaming a foamable urethane resin. be. In addition, the vinyl chloride resin composition is JISK 6
Hardness of 95 using JIS A type hardness needle specified in 301
Below, those of 45 or more are preferred. Furthermore, the crash pad molded article has a layer between the skin material layer and the injected foamable urethane resin layer to provide an adhesive effect and prevent polyurethane contact contamination. Here, Table 1 shows the advantages and disadvantages of each and price comparison.

The vinyl chloride resin that is the main component of the vinyl chloride resin composition used in the present invention has a degree of polymerization of 1,400 or more or 1,400 or more to prevent drawdown during blow molding.
It is necessary that the insoluble matter after immersion in tetrahydrofuran (THF) at 20° C. for 1 hour is 5 or more and the average degree of polymerization is 400 or more. With 120'CTHF for 1 hour, it is impossible to mold a skin material with a uniform thickness of a molded product with a parison of 500 mm during blow molding using a normal vinyl chloride resin without any insoluble matter. In particular, for vinyl chloride resins that do not contain insoluble matter, an average degree of polymerization of 2,500 or more is desirable, but when the molded article weighting is 100'Or or more, the phenomenon of drawdown becomes noticeable. When the basis weight of the parison reaches 3000f, it is not enough to improve the average degree of polymerization, so THF
A vinyl chloride resin is required that has an insoluble content (referred to as a gel fraction). Specifically, THF at 120℃
Polyvinyl chloride resin with an unmelted content of 5% or more after immersion for 1 hour and an average degree of polymerization of the soluble catalyst of 400 or more, preferably an unmelted content of 10% or more and an average degree of polymerization of the soluble catalyst. is 1
ooo or more is required.

These resin compositions meet the JIS standards specified in Month 5K6301.
A hardness of 95 or lower and 45 or higher on a Type A hardness scale is desirable, and a crash pad with a hardness of 80 or lower and 60 or higher is particularly good for its flexibility, feel and texture. Furthermore, an intermediate layer may be provided between the skin made of these resin compositions and the injected urethane resin, which serves both to provide adhesiveness and to prevent urethane contact contamination. The unmelted content of vinyl chloride resin is useful for preventing drawdown due to its viscoelastic effect when melted, and for providing a matte effect as a surface material for molded products. This results in shape retention effects such as prevention of scratches.

The soft vinyl chloride resin composition that is the main subject of the present invention is mixed with a binder, a stabilizer, a pigment, a filler, etc. according to the necessary hardness, stamping weight loss, aging resistance, etc.
Those listed in the Vinyl Chloride Material Handbook "Kogyo Kenkyukai Publishing" are typically mixed, and do not contradict the gist of the present invention. Also, EVA, ABS, NBR
, MBS 5C1-PE, etc., do not limit the scope of the invention. Furthermore, if there is insufficient adhesion between the skin material and the urethane resin, or if the urethane is insufficient in preventing contact staining, an intermediate layer is provided for the purpose of improving these.

The blow molding method, which is the gist of the present invention, has its own advantages.

First, the thickness of the molded product can be made thin and uniform. Furthermore, it is possible to simultaneously apply texture to the surface of the molded product.

The second point is that the freedom of design of molded products is greatly expanded. In particular, it is possible to create a clear grain pattern in the undercut portion and any other portion.

The third point is that there is no material loss.

In other words, in blow molding, the material is melted by an extruder and molded using a parison, so unlike injection molding, it is not subjected to high shear and high temperature thermal history, so unnecessary parts of the material are crushed and extruded. It can be supplied to the machine and is less likely to cause quality defects. Furthermore, since the design allows for the skin material for the glove box lid to be molded at the same time on unnecessary parts such as the meter part and the glove box part, there is an advantage that a molded product with a matching color can be obtained.

The fourth point is that thermal energy can be saved compared to the other manufacturing methods mentioned above.

From these advantages, it is clear that the blow molding manufacturing method according to the present invention is superior.

As mentioned above, crash pads are made by integrating the skin material and aggregate by injecting foamed urethane, but what is desirable is that the skin and urethane foam are bonded together, and it may be possible to use urethane foam. It is necessary that there is no contamination by contact with other people. If the adhesive is not integrated, there is a possibility that the skin material may peel off from the edges of the molded product, and staining may cause discoloration of the skin material, significantly reducing the commercial value. The urethane resin used for injection foams with the gas generated during the polymerization and curing reaction of polyol and incyanate, but the substances necessary for this reaction may migrate to the skin material and cause discoloration. It is said. Of course, countermeasures to this problem include improving the ductility and making good use of oxidation ring reactions, which create an intermediate layer between the skin layer and the urethane resin under high-temperature, long-term heat aging conditions. You can get better results.

Polymers such as thermoplastic polyurethane, vinyl acetate, and epoxy are suitable for the intermediate layer, but basically any polymer can be used as long as it improves adhesiveness. The intermediate layer has a thickness of 10 microns or more, preferably 5
If it is 0 micron or more, it becomes possible to improve the contamination property.

Next, examples of the present invention will be specifically described.

Tables 2 and 3 are evaluations of the drawdown properties of each blending composition.

Table 2 × Bad △ Poor ○ Good ◎ Excellent The above formulations were mixed in a super mixer, and kneaded and granulated in a 50-barrel extruder. The parison was removed using an extruder of 75 mm and a blow molding machine equipped with a 2-ton accumulator with a parison diameter of 200 mm and a parison wall thickness of 2 tubes for evaluation.

Table 3: ΔPoor ○Good ◎Table 4 shows the evaluation of the adhesion between the skin material and the urethane foam by blow molding and the urethane staining property.

Although it is not specified in the examples, sufficient consideration has been given to the formulation of urethane staining and adhesive properties in the composition constituting the skin material. It is clear that the presence of an intermediate layer between the resin and the urethane resin gives better results.

Table 4: Vinyl chloride resin composition PVC (15% gel fraction, average degree of polymerization 1400) 1 g
□ Heavy-duty DOP 90 Epoxidized soybean oil (Evosizer manufactured by Dainippon Ink)
3w-io.

Calcium stearate 1 Zinc stearate! Adhesive Thermoplastic polyurethane (Dainippon Ink's Pandex) is used by diluting it with an organic solvent.

Claims (3)

[Claims] (1) Soft material mainly made of vinyl chloride resin with an average degree of polymerization of 1400 or more, or an unmelted portion after 1 hour immersion in tetrahydrofuran at 120°C of 5% or more, and an average degree of polymerization of the soluble portion of 400 or more. A vehicle in which a vinyl chloride resin composition is molded into the desired crash pad external shape using a blow molding method, a rigid aggregate is incorporated as a skin layer, and a foamable urethane resin is injected and foamed to form an integrated vehicle. A method of manufacturing crash pads for cars. (2) The method for manufacturing a crash pad according to claim 1, wherein the soft vinyl chloride resin composition has a JIS A type hardness of 95 or less and 45 or more as defined in JIS K6301. (3) A method for manufacturing a crash pad according to claim 1, wherein a layer is provided between the skin material made of a soft vinyl chloride resin composition and a foamable urethane resin to provide an adhesive effect and prevent urethane staining and discoloration. .