JPS61138646A - Method for manufacturing rigid polyvinyl chloride foam molded products - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is used in the field of plastic manufacturing.

(Prior art) Conventionally, as a method for obtaining a hard polyvinyl chloride foam having an open cell structure, (I) a method of extracting an appropriate amount of plasticizer from a soft PvC foam containing a plasticizer using a solvent was proposed in Japanese Patent Publication No. 30-1989. 1092
In the publication.

(n) PVC paste resin, mixed plasticizer,
In addition to stabilizers and surfactants, trimethylol propane trimethacrylate (TMPT) is used as a reactive plasticizer.
The first step is to make a polyvinyl chloride lastisol using a polyvinyl chloride, and the plastisol absorbs an inert gas under pressure.The second step is to discharge the gas-absorbed plastisol from a nozzle and foam and gel it by high-frequency heating. A method consisting of steps is disclosed in Japanese Patent Publication No. 55-18735.

However, in the method (1) above, as the volume of the foam increases, the extraction rate of the plasticizer differs between the surface and inside of the foam, and the hardness of the resulting product is non-uniform.
In particular, there was a problem in that the surface hardness was low.

In addition, with method (n) above, a rigid PVC foam can be obtained for thin objects such as sheets, but for molded products, '(1) Due to the high frequency irradiation, the mold must be formed using a method other than the mold. It is impossible to make.

(ii) Since it is heated all at once to a temperature at which gelation and curing proceed simultaneously, a single polymerization reaction (exothermic reaction) rapidly proceeds, making the bubbles unstable and causing foam collapse. Therefore, the appearance of the product is impaired. In addition, even if pores form on the surface that contacts the mold, they will melt immediately, resulting in the formation of a skin layer with almost no pores on the surface of the product, making it unsuitable for products that require absorbency, such as printing materials. there were.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and is made of a hard polyvinyl chloride foam having uniform hardness, no bubble collapse, and an absorbent skin with micropores opened on the surface. The object of the present invention is to provide a product and a method for manufacturing the same, which can also use molds other than metal.

(Structure of the invention) The means of the present invention are as follows.

(1) It has an absorbent epidermis with micropores opened on the surface,
A rigid polyvinyl chloride foam molded product characterized by having an open cell structure inside which communicates with the absorbent skin.

(2) A plastisol composite obtained by mechanically foaming a polyvinyl chloride plastisol prepared by blending a polyvinyl chloride paste resin, a mixed plasticizer including a thermosetting plasticizer, a vinyl stabilizer, a bubble stabilizer, and a hardening agent. A rigid polyvinyl chloride foam molded product, characterized in that the plasticstisol foam is injected into a mold, the plasticstisol foam is gelled at 70 to 100°C, and the gelled product is subsequently cured at 160 to 200°C. manufacturing method.

The polyvinyl chloride (hereinafter abbreviated as PvC) base resin used in the present invention may be a homopolymer or a copolymer with vinyl acetate or the like.

The following conditions are required for the thermosetting plasticizer in the mixed plasticizer.

(a) It should not have very strong dissolving power for PVC at room temperature.

In other words, it must not give an unstable sol state.

(b) Although it does not polymerize at room temperature, it quickly crosslinks (polymerizes) at a high temperature of 150°C or higher using only heat or with the help of a curing agent.

It should not cause hardening during gelling carried out at 70 to 100°C and should provide sufficient hardness during subsequent curing of the gelled product at 160 to 200°C.

(c) Low volatilization loss.

The foamed PvC plastisol is poured into a mold and then sealed.
Required because it is heated in an oven or furnace.

DAP (diallyl phthalate) is unsuitable because it is highly volatile and causes foam collapse.

(d) It should have good compatibility with both PVC and the plasticizer used in combination before and after curing.

DAP prepolymers are unsuitable because they have poor solubility in other plasticizers and therefore increase the viscosity of the PVC plastisol and prevent foaming.

Considering the conditions (a) to (d) above, the thermosetting plasticizer is preferably an acrylic ester polymer having a high boiling point and having several active double bonds in the molecule. For example, trimethylol propane trimethacrylate, which has three active double bonds in the molecule, (T
MPT) is extremely suitable for the present invention because it creates many crosslinking points and increases the hardness of the foam.

Here, it is important to note that acrylic esters do not have a very strong dissolving power for PVC at room temperature, and that it is difficult to mechanically foam PvC plastisol unless a plasticizer that has a strong dissolving power for PVC is used. Considering that, when using acrylic ester plasticizers, the percentage of sentencing should be less than 50% of the total plasticizers.

As the vinyl stabilizer, a Ca/Zn liquid stabilizer or the like is suitable.

Suitable foam stabilizers include surfactants such as mixtures of alkali metal soaps and amine soaps, and silicone oils.

Peroxide suitable as a curing agent (polymerization catalyst) has a half-life of 1 minute (the time it takes for the peroxide to decompose and its active oxygen amount to reduce to 1/2). A material having an aromatic temperature of 150 to 180°C, such as tert-butyl peroxybenzoate, is preferable because a stable cell structure can be obtained.

Butyl peroxide (BPO)', lauryl peroxide (LPO), etc. are activated at relatively low temperatures and are suitable for early curing, but polymerization begins before the plastisol foam gels, resulting in only a brittle foam. It is inappropriate for invention.

Foaming of PvC plastisol is carried out mechanically by mixing and dispersing gas such as air with a continuous foaming machine such as an Oaks mixer or a Hobart mixer.

The effect of the present invention is that after the plastisol foam is injected into a mold, etc., it is first heated gently to a temperature of 70 to 100°C, so that the air bubbles in the plastisol foam grow and the mutual interaction formed inside the foam increases. The communicating bubbles (open cells) and the micropores formed on the surface in contact with the mold are gelled as they are without collapsing or melting.

Subsequently, the bubbles and pores are stabilized when heating to 160 to 200° C. to polymerize the thermosetting plasticizer and harden the gelled product.

The hard PvC foam molded product obtained in this way has an absorbent skin with micropores open on the surface, and the inside has an open cell structure that communicates with the absorbent skin, so it has excellent absorption properties. It exhibits good properties, has a good appearance, and has uniform hardness throughout the product.

(Example) Table 1 shows three types of PvC plastisol (a).

The compositions of (b) and (c) are shown.

Table 1 Unit: Part by weight x 1 Manufactured by Kanebuchi Chemical Industry Co., Ltd. Mix and stir the above ingredients to create PvC plastisol,
When air and other gases are mixed and dispersed in this using a continuous foaming machine, plastisol (a) is created.

In (b), it was possible to foam at a foaming ratio of 1.5 to 4 times depending on the amount of gas mixed.

On the other hand, plastisol (c) has an increased amount of acrylic ester plasticizer than plastisols (a) and (b), and the plasticizer accounts for 50% or more of the total plasticizer. It was not possible to foam the foam due to the decrease in the temperature.

The foamed PvC plastisol (a) was injected into a mold and heated in an oven under the following three different conditions. The surface hardness, foam condition and product appearance of the resulting PvC foam molded product were evaluated It is shown in Table 2. The hardness measurement method is based on the standard 5 RISOIOI of the Japan Rubber Association.

Table 2 As shown, the hard PvC foam molded product according to the present invention has a sufficiently high surface hardness, no bubble collapse, and a good appearance.

On the other hand, when gelling and curing are performed simultaneously by heating all at once as in Comparative Examples 1 and 2, or even when curing is performed after gelling, if the gelling temperature is high, the bubbles become unstable. The molded articles produced are not desirable.

Next, as various examples of rigid PvC foam molded products according to the present invention, PvC plastisols having the composition (a) above with varying expansion ratios (and thus foam densities) will be described. For those manufactured by heating under the same conditions, the water absorption rate was determined according to JIS K-676.
7. The results obtained by water absorption test method B are shown in Table 3.

Table 3 From this, it can be seen that the hard '1 PVc foam molded product according to the present invention has extremely excellent water absorption and water retention properties among plastic molded products.

The experimental results are all about water absorption, but since rigid PvC foam has acid and base resistance, the rigid PvC foam molded product according to the present invention is resistant to acidic and basic solutions. Needless to say, it is also excellent in absorbency.

Finally, the surface and cross section of Example 1 of the hard PvC foam molded product according to the present invention were photographed using a scanning electron microscope at a magnification of 50 times, and the results are shown in FIGS. 1 and 2.

From this, the rigid PvC foam molded product according to the present invention is
Although a layer with a thickness of 5 to 10 μm is formed on the surface that was in contact with the mold, with fewer bubbles than on the inside, some of the bubbles that remained unmelted opened on the surface and formed a layer with a diameter of 5 to 10 μm. It can be seen that it has micropores of 40μ, that is, it has an absorbent epidermis on its surface.

Furthermore, it can be seen that the inside of the rigid PvC foam molded product according to the present invention has a good open cell structure that communicates with the absorbent epidermis without any slippage. In FIG. 2, the black parts visible inside the bubbles are communication paths between adjacent bubbles.

Such an absorbent skin and internal open cell structure provide excellent water absorption, and the internal cells can store a large amount of water, resulting in excellent water retention. It is also clear that the air permeability is good.

Open-cell foam that does not collapse provides elasticity.

Increase mechanical strength.

Incidentally, in the molded product shown in the photograph, the number of micropores opening on the surface is 50 to 70 per 1.2 cm. The cell diameter of the internal open cell structure is 25 to 130μ, with an average of 100μ.

Note that the pore diameter and foam density of the rigid PvC foam molded product according to the present invention depend on the types of PVC paste resin, plasticizer, and bubble stabilizer, or how these are mixed;
It changes depending on the amount of air etc. mixed in, and is not limited to the range of numerical values listed in Table 3.

Further, the heating time in the method for manufacturing a rigid PvC foam molded product of the present invention can be selected depending on the size of the mold, the shape of the mold, and the type and amount of the plasticizer and bubble stabilizer. It is not limited to the time at which each example of a product was manufactured.

In addition, in the method for manufacturing a rigid PVC foam molded product of the present invention, the heating means does not need to rely on high frequency heating, so the mold into which the plastisol foam is injected is the rigid PVC foam molded product.
The present invention is not limited to the mold used to obtain each example of the C-form molded product.

(Effects of the Invention) As described above, in the hard PvC foam molded product according to the present invention, the open cells formed inside and the micropores formed on the surface gel without collapsing or melting. The product is then cured and has an absorbent skin with micropores open on the surface, and the interior has an open cell structure that communicates with the absorbent skin, so (i) the product has a good appearance; Uniform overall hardness (*U) High mechanical strength and excellent impact resistance (+v) Excellent absorption of water, acidic solutions and basic solutions (v) Excellent water retention capacity (Vl) It has the effect of being excellent in breathability.

Therefore, the rigid PVC foam molded product according to the present invention is suitable for, for example, filters, cushioning materials, packaging backings, heat insulating materials, sandwich core materials which are a type of building material, printing materials, printing materials, and containers for growing plants.

In addition to the above-mentioned excellent advantages, the method for manufacturing a rigid PvC foam molded product of the present invention has the advantage that molds other than metal can be used since any heating means can be used. has.

[Brief explanation of drawings]

Fig. 1 is an electron micrograph (50x) showing the surface of an example of the hard polyvinyl chloride foam molded product according to the present invention, and Fig. 2 is an electron micrograph (50x) showing a cross section on the same side.
It is. Preface to the drawings (No changes in '8) Figure 1 Figure 2 Procedures Amendment Book Showa ≦ θ 2nd, 27th

Claims (2)

[Claims] (1) It has an absorbent epidermis with micropores opened on the surface,
A rigid polyvinyl chloride foam molded product, characterized in that the interior has an open cell structure communicating with the absorbent skin. (2) A plastisol foam product obtained by mechanically foaming a polyvinyl chloride plastisol prepared by blending a polyvinyl chloride paste resin, a mixed plasticizer including a thermosetting plasticizer, a vinyl stabilizer, a bubble stabilizer, and a hardening agent. A method for producing a rigid polyvinyl chloride foam molded article, which comprises pouring into a mold, gelling the plastisol foam at 70 to 100°C, and curing the gelled product at 160 to 200°C.