JPS59232829A - Molding process of polyvinyl chloride formed product - Google Patents

Abstract

PURPOSE:To obtain a foamed molded product with excellent appearance having a nonfoamed skin film layer with a embossed pattern and a foamed body molded inside by putting and heating premolded foamed body in a mold in which the skin film lager made of nonfoaming thermoplastic resin film is moded on the embossed pattern surface of the mold cavity. CONSTITUTION:Vinyl chloride resin composition containing foaming agent is molded into a molded foamed body by injection molding. Said foamed body is put into a mold wherein; The inner surface of the cavity of said mold has the same shap as that of the obtained foamed body and on said inner surface, an embosse pattern is formed, and then the film which is made of nonfoaming plastic resin with thickness equal to or less than 2mm. and becomes the skin film layer of a final molded product, is formed on the inside surface of the mold. The skin film layer on the inner surface of the cavity is made integral by fuse-bonding with said foamed material by directly or indirectly heating. When the surface temperature of said foam is kept at 100 deg.C or more and at 400 deg.C or less, a good result is obtained, and especially, the temperature 100-400 deg.C makes a good result, especially, 140-220 deg.C is the most suitable range.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized in that the interior of the final molded product is foamed and the surface is non-foamed. This invention relates to a method for molding a polyvinyl chloride foam molded product having a good appearance.

Foamed thermoplastics, such as polyvinyl chloride, have thermal insulation, cushioning, soundproofing, vibration-proofing,
It is widely used in a variety of applications due to its light weight and low cost.

Molding methods for these foamed proboscises include extrusion molding, injection molding, cast molding, and blow molding.

Further, foaming methods include impregnating a resin with a volatile liquid, mixing a gas into a bath-melted resin or emulsion, and kneading a chemical blowing agent.

The present inventor has conducted intensive studies to obtain a foamed molded product using polyvinyl chloride with a good appearance with a non-foamed surface and a clear grain pattern, and as a result, the present invention was developed. .

The present invention involves forming a polyvinyl chloride resin composition containing a chemical foaming agent into a foamed molded product by injection molding, and then molding the molded product into a foamed molded product, which has a cavity of the same shape, and forms a textured pattern on the inner surface of this cavity, thereby forming a core cavity. A coating layer of a non-foamed thermoplastic resin having a size of 2 or less is formed on the inner surface of the cavity, which will become the surface layer of the final molded product. This is a molding method in which the foam is integrated by reheating and melting to produce a final foam molded product with a good appearance, which has a non-foamed skin layer with a textured surface, and a foamed interior. A common method for efficiently mass-producing foamed products of arbitrary shapes is to cut a vinyl chloride resin composition containing a chemical blowing agent by injection molding, but this method has a major drawback.

That is, foam molded products produced by injection molding have a pattern called sharkskin on the surface of the molded product, making it impossible to obtain a smooth surface. The skin layer on the surface of the molded product also tingles noticeably, and damaged foam cells remain on the surface, making it impossible to create a clear grain pattern.

Various methods have been attempted to overcome these drawbacks, one of which is a two-color injection molding technique called sandwich inch molding. This is a technology that uses a molding machine with two injection cylinders to obtain a molded product made of resin with a non-foamed surface layer and a foamed inner layer.

However, this method requires a special molded wall and two foamed and non-foamed walls.
The need for seed resin increases costs, and the use of non-foamed resin for the surface layer poses a national problem in producing molded products with low specific gravity.

It is also conceivable to paint the surface of the foam, but this has the drawbacks of not being able to create a textured pattern and of being expensive.

In the present invention, the blowing agent contained in the vinyl chloride resin composition includes azo, hydrazo, and nitroso organic compounds, and any blowing agent used in general thermoplastic resins may be used.

Further, the plasticizer is not limited in any way as long as it is used for vinyl chloride resin.

Fillers such as calcium carbonate, acrylic polymers that improve the retention of foam cells, olicomer, I-F materials for layer colors, ultraviolet absorbers, antioxidants, polyurethane,
The addition of KVA-based, olefin-based polymer modifiers, etc. is not limited.

Also, PVC-based IBVA graft, ethyleneco sword? There is no particular limitation on the resin as long as it is a resin such as limer or acetic acid picopolymer.

There is no problem in separating hollow bodies such as glass, glass phenol, and carbon ÷j.

On the other hand, if the skin layer of the final photoelectric molded product according to the present invention is a non-emissive thermoplastic resin, it is a thermoplastic resin that can be hot-melted with the vinyl chloride resin of the inner layer foam. The present invention f: is not limited in any way.

Furthermore, the form of the thermoplastic resin may be, for example, a soft vinyl chloride resin powder, sol, or sheet, or may be a polyurethane paint, which does not interfere with the present invention in any way.

Among these, there are disadvantages such as sol-like products tend to have uneven thickness, sheet-like products tend to have cracks at the mold alignment 1nj, and paints have the disadvantages that it is difficult to obtain thick products, but these also have some drawbacks. This does not interfere with the present invention.

The first step of the present invention is the step of molding a vinyl chloride resin composition containing a foaming agent into a foam molded article by injection molding.

In this step, the quality of the molded product is determined, so it is necessary to carefully examine the application force of the blowing agent, the molding conditions, the dart shape of the mold during molding, etc.

In the second step of the present invention, the foamed molded product obtained in the first step is provided with a cavity (4) having the same shape as that of the foam molded product, and a desired grain pattern (5) on the inner surface of the cavity. Departure? In this process, the foam is placed in a mold having a skin layer made of a thermoplastic resin that can be heat-sealed to the package, and the foam and the thermoplastic resin that will become the skin are directly or indirectly heat-sealed to integrate the foam.

Through this process, the skin layer of the molded product and the foam are fused together, making it a non-foaming material. It is possible to obtain a foam molded product with a pattern and a good appearance.

As an example, Figure 1 is a cross-sectional view of a handle with an iron core (1).
After forming the inner foam layer (2), the non-foamed skin layer (3) is formed.
), and Figure 2 shows a steel mold (6) with a steel mold (6).
? (5) and a cavity (4) provided with cooling holes (7).

To fuse and integrate the foam obtained in the first step with the skin layer, there are two methods: electrically heating the mold, heating in a heat-resistant oven, heating with steam, heating with a heating medium, There is an indirect heating method using frequency induction, and a direct heating method using high frequency induction heating. Table 1 shows the features of the winter method.

In other words, the indirect method heats the mold and seals it by heat conduction. The thermoplastic resin that has been applied to the surface of the surface in advance and the foamed molded product are heated with a heating wire.

In addition, the direct method involves placing the skin and foam inside the bottle in a mold with a low dielectric constant, such as Teflon, and fusing and integrating them by external heating using microwaves. This results in a foamed molded product with good quality.

These methods should be selected in consideration of equipment costs, molding cycles, and the cutting environment.The purpose of the present invention is to increase the surface temperature of the foam obtained in the first step to 100'C.
'The prerequisite for obtaining good results is to maintain the temperature below 400°C and integrate it with the resin of the skin layer.

In particular, it has been experimentally confirmed that the optimum temperature range is 140° C. or higher and 220° C. or lower. Below 140°C, the surface is insufficiently glued, and above 200°C, gloss becomes noticeable, and vinyl chloride resin is easily thermally decomposed, making time control extremely difficult.

Next, the present invention will be explained according to examples.

Polyvinyl chloride 100 heavy-duty part (Sumitomo Chemical 6-sSX-115-cho=1100) D OP
6
0 Calcium carbonate 10 parts by weight (Shiraishi Kogyo ■, Hakuenka ccu) Epoxidized dog bean oil 3 (Dainippon Ink Co., Ltd.) Hidec W-100) Calcium stearate l Zinc stearate
1 Foaming agent (ADCA) 2 (
Hydration chemical composition (tea vinylol AC'll'l) is used in a φ extruder to produce pellets with a diameter of 3 am.

An automobile steering wheel with an iron core was molded using an injection molding machine. The resulting foam had a specific gravity of 0.6 and a resin grain (
The damage was 280 mm, but phenomena such as shark skin were observed on the surface.

Molded articles were obtained from this foamed article using each heating method.

Example (1) Using a B450 ironworker, apply polyurethane paint to the wrinkled surface, insert the foam described in OIJ, and heat press for 21 hours.
The bottle was kept at a temperature of 0° C. for 5 minutes, and then the entire bottle was cooled with water for 10 minutes and the molded product was taken out.

The resulting molded product has a non-foamed layer of approximately ω microns and has a specific gravity of 0.
．． It is a good foam molded product with grains on the surface.

Example (2) A 100μ film made of a soft vinyl chloride resin containing 50 parts by weight of a phthalate ester plasticizer was placed on the embossed surface of the cavity using a Teflon mold, and the foam was placed therein,
Microwaves of 46 MHz were applied from the outside of the mold for 90 seconds, then the mold was cooled with water for 2 minutes, and the molded product was taken out.

The obtained molded product had a specific gravity of about 0.6, and had a non-foamed surface and a patterned surface with a good appearance.

As described above, the present invention is an excellent molding method for producing molded products with good appearance regardless of the appearance after injection molding.

Table-1 Features of each molding method

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a /% bundle which is one of the embodiments of the present invention. Figure 2 is a cross section of a mold with iron grains inside the cavity.

Claims (3)

[Claims] (1) After molding a vinyl chloride resin composition containing a foaming agent into a foam by an injection molding method, the molded product is molded into a foam having a cavity of the same shape, a pattern is provided on the inner surface of the cavity, and a pattern is formed on the surface of the cavity. By forming a skin layer of two or less non-foamed thermoplastic resin coatings and placing it in a mold and directly or indirectly heating the molded product,
A method for molding a polyvinyl chloride foam consisting of a non-foamed, apple-shaped skin layer and a foam inner layer, which is patented by bath-fusion integration. (2) A patent characterized in that the indirect heating method is a method using electric heat, a heat-resistant open air tank, steam, a heating medium, high-frequency induction heating, etc., and the surface of the molded product is heated to 100 to 400°C. A molding method according to claim 1. (3) Directly heating the surface of a molded product in a mold made of a material with a dielectric constant of 4 or less to 100 to 400°C using subfrequency dielectric heating. Claim 1 J1
How to form a sword.