JPH037739A - Regeneration of waste material of polyurethane resin - Google Patents

Abstract

PURPOSE:To produce a regenerated polyurethane having excellent physical properties such as high modulus of elasticity and high tensile strength by using a waste liquor of diol-containing polyol as a raw material of binder and molding under a constant condition. CONSTITUTION:Ground material of polyurethane resin waste material is mixed with a blend of diol and isocyanate or a prepolymer prepared from the diol and isocyanate as a binder and molded by heating under pressure at 130-160 deg.C under 160-300kg/cm<2>. The prepolymer is produced from the diol and the isocyanate in order to leave 5-15% unreacted -NCO group and the heating and pressurizing molding is carried out by using the prepolymer under a relatively high-pressure, high-temperature condition. The waste material is ground to preferably 10mu-5mm particle diameters.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for recycling polyurethane resin waste material in which a diol-containing polyol waste liquid can be used as a binder raw material.

<Conventional technology> Previously, unlike other thermoplastic resins, it was considered difficult to reuse and mold polyurethane resin waste into molded products, and most of it was buried or incinerated. . Recently, however, there has been a call for the reuse of this type of resin waste due to demands for resource conservation, cost reduction, and pollution prevention, and methods for this purpose have also been proposed. Proposals regarding methods for recycling polyurethane resin waste materials are given in, for example, JP-A-56-46726 and JP-A-56-46726.
7-23636, 57-45026, Special Publication No. 63-1
No. 2766, No. 63-35404, etc., in order to improve the surface condition, physical properties, productivity, etc. of recycled products, the particle size distribution of the main raw material (pulverized waste material), binder,
The mixing ratio, molding conditions, etc. have been devised, but the conventional general method for recycling polyurethane resin waste is to crush the polyurethane resin waste and add and mix the urethane binder prepared from triol polyol and polyisocyanate. Yes, temperature 50~150℃, press pressure lO~1
It was to be molded under heat and pressure at about 50 kg/cm2.

<Problems to be Solved by the Invention> The conventional regeneration method described above has a problem in that the polyol waste liquid cannot be used. The reason for this is that diol is mixed in the waste liquid. To explain in more detail, conventionally used triol-based polyols form a network structure of urethane bonds to connect the waste chips together three-dimensionally, whereas diols only have linear bonds; Therefore, if diol-containing polyol waste liquid is used, only recycled molded products that cannot be molded or are brittle can be obtained.

Another problem is that polyurethane resin waste is a thermosetting resin, so the scope of use of the waste is limited.
Although it has been recycled as a substitute for plastic parts, especially rubber, it has had the problem of inferior physical properties.

The present invention was made to solve each of the above problems,
The first problem to be solved is to make it possible to use diols, especially diol-based polyol waste liquid, instead of triol-based polyols, and the second problem is to improve the physical properties of recycled products obtained from the above waste materials. It is to let Therefore, it is an object of the present invention to provide a method for recycling polyurethane resin waste that can solve the above problems by finding a useful binder prepared from diols and optimal molding conditions for using it.

<Means for Solving the Problems> The method for recycling polyurethane resin waste of the present invention that can achieve the above object includes adding and mixing a diol and an isocyanate, or a prepolymer prepared from them as a binder, to a pulverized product of polyurethane resin waste. Moreover, the pressure is 16
0-300 kg/cm2. It is characterized by heating and press molding at a temperature of 130 to 160°C.

That is, in the present invention, a prepolymer to serve as a binder is produced from diol and isocyanate so that 5 to 15% of unreacted -NGO groups remain, and using this, the pulverized material of the waste material is processed under relatively lower conditions than normal conditions. It is characterized by heat-pressing molding under high-pressure and high-temperature conditions.

A preferred embodiment of the method of the invention can be shown in the flowchart of FIG. 1, and will be explained in more detail with reference to this figure.

First, the main raw material, polyurethane resin waste, is produced from defective bumpers, sheets, and liners generated from each molding factory.
Gates, Paris debris, etc.

In the pulverizing step, it is preferable to pulverize the waste material to a particle size of 10μ to 5 mm. The finer the grinding, the better the surface of the recycled product obtained, but if the particle size is less than 10μ, the grinding cost increases and is not economical, and it is necessary to increase the amount of binder added. On the other hand, if the particle size is 5 mm or more, the surface condition of the recycled product will be poor.

In the binder preparation step, the isocyanate and diol are mixed to create a prepolymer with preferably 5-15% free -NGO groups. This value depends on the pot life (pot life) of the binder and the reaction conditions, but if it is within the above range, the regeneration method of the present invention can be carried out satisfactorily. The content of free -NGO groups can be adjusted by adjusting the blending ratio of isocyanate and diol. Further, if necessary, a solvent such as methylene chloride or a plasticizer such as DOP is added to adjust the viscosity.

Note that the diol and isocyanate used here may be either fresh liquid or waste liquid. However, if possible, the compatibility is best when the binder raw material is the same as the waste material, and not only new products but also waste liquid polyols and isocyanates can be fully used. is advantageous.

The binder prepared as described above may be added to the pulverized waste material as a one-liquid type or as a two-liquid type.

If the amount of binder added to the pulverized material is increased, the physical properties may be improved, but the reaction time will be longer, reducing the merits of using waste materials in terms of cost and working conditions.

Furthermore, if the amount added is too small, the physical properties will deteriorate and the product will not be viable. Therefore, the amount of binder added to the pulverized material is preferably 5 to 20 wt%.

After the process of weighing the waste material mixed with the binder, the process moves to the molding process, and the molding conditions here are a press pressure of 160 to 300 kg/kg, depending on the specific binder mentioned above.
cm”, press temperature 130-160℃, press time 60
~270 seconds is the most economical condition, and physical properties (elasticity, elongation)
An excellent molded product can be obtained.

The products obtained in this way are trunk mats, mudguards, steps, etc. When bonded with a binder made from the same raw material as the waste material, the adhesive strength is 20 to 40% compared to a general urethane binder.
0% physical properties improve.

<Function> According to the recycling method of the present invention, diol can be used as a binder and a recycled product with high elasticity can be manufactured. This is thought to be due to the following effects.

Unreacted urethane bonds exist in the polyurethane resin waste. When the waste material is crushed, a large number of urethane hands can be exposed to the surface of the crushed material as shown in FIG.

When molded under the above conditions in the present invention, the bonding urethane hands that did not react in the conventional method are activated, and they bond to each other with diol HO-R-OH sandwiched between them, as shown in FIG. The addition of diol makes the bond more elastic, making the recycled product more similar to rubber.

<Example> Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A conductance mill used to make recycled rubber,
Pulverize urethane bumper waste material into a pulverized product with a particle size of 7000μ or less. At that time, 50% of the particles are distributed in the particle size range of 420 to 800μ so that the particle size distribution is continuous.
Grind it so that it becomes .

To this pulverized waste material, a binder prepared by collecting the calibration waste liquid generated in the bumper manufacturing process is added in an amount corresponding to 14% by weight. The binder is a one-part type and is a prepolymer made from waste polyol and isocyanate to have 10% free -NGO groups. The properties and compositions of the polyol waste liquid and isocyanate waste liquid are shown in the following table.

The above crushed waste material and urethane bumper are mixed in a mixer equipped with a rubber pack at the bottom for uniform solid-liquid mixing.
Mix for a minute. The resulting mixture was pasted under the following conditions: 200 kg/cm2 Press temperature: 1
A recycled product (flat test piece) was produced by heat-pressing molding at 45° C. for a press time of 180 seconds.

Example 2 Instead of using diol-based polyol waste liquid, a new diol (diol different from the diol used in the production of waste polyurethane resin: rEX-20oJ manufactured by Asahi Glass)
A recycled product was produced in the same manner as in Example 1 except that the following was used.

Comparative Example 1 New diol instead of new one! - The same recycled product was produced in the same manner as in Example 2, except that Riolu was used. The new polyol has an 08 value of 56% and a molecular weight of 3,000.

Comparative Example 2 An attempt was made to produce the same recycled product in the same manner as in Example 1, except that the hot-press molding conditions were as follows: Press pressure: 40 kg/cm 2 Press temperature: 120° C. Press time: 180 seconds. However, the crushed waste material did not adhere and solidify with the binder, and the molding ended in failure.

Comparative Test The tensile strength and elongation at 70°C were determined for the recycled products obtained by Example 1, Example 2, Comparative Example 1, and the conventional method (molding under normal pressing conditions using a binder prepared from new triol). Examined.

The results are shown in FIGS. 2 and 3, respectively.

From these figures, it is clear that using a binder prepared from diol (Example 1 and Example 2) improves the elasticity and strength of the recycled product, rather than using a conventional general binder (Comparative Example 1 and conventional method). It can be seen that using a binder made from the same raw material as the waste material (Example 1) can improve the physical properties rather than using a binder made from a raw material different from the waste material (Example 2).

Examination Test Example It was confirmed from Comparative Example 2 that a recycled product cannot be produced when molded under general press conditions even if a binder prepared from diol is used. It was investigated whether the temperature was appropriate as follows.

1) Press pressure Recycled products were molded at various press pressures, and the relationship between the tensile strength of the resulting molded products and the press pressure was investigated. The molding was carried out under other conditions: press temperature: 1 degree Celsius: 145° C., press time: 180 seconds, binder addition amount: 10%.

The results are shown in Figure 4. From the figure, the press pressure is 160 k.
It can be seen that good molding is possible if the pressure is higher than 160 g/cm.
0 kg/cm".

ii) Pressing temperature Recycled products were molded at various pressing temperatures, and the relationship between the tensile strength of the resulting molded products and the pressing temperature was investigated. The other conditions for molding here were: press pressure: 200 kg/cm
2. Pressing time was kept constant at 180 seconds and binder addition amount at 10%.

The results are shown in Figure 5. It can be seen from the figure that good molding is possible if the pressing temperature is 130° C. or higher. However, when the temperature exceeds 160°C, the urethane begins to burn, the surface of the product deteriorates, and the quality deteriorates. Therefore, it can be said that a suitable pressing temperature range is 130 to 160°C.

<Effects of the Invention> 2 The method for recycling polyurethane resin waste material of the present invention brings about the following effects.

First, diol-based polyol waste liquid, which could not be used in the past, can be used to recycle polyurethane resin waste materials, eliminating the cost of waste liquid disposal and reducing waste material recycling costs by not using new polyol liquid. I can figure it out.

Furthermore, since recycled products with high elasticity and high tensile strength can be obtained, substitutes for most rubber products can be made, and the range of reuse of polyurethane resin waste can be expanded.

Furthermore, all raw materials except the mold release agent required during molding can be sourced from the same polyurethane product molding factory, which is extremely advantageous in terms of resource conservation and pollution prevention measures. Since it can be bonded with a binder, the physical properties of recycled products can be improved.

[Brief explanation of drawings]

Figure 1 is a flowchart showing one aspect of the method for recycling polyurethane resin waste materials of the present invention, and Figure 2 is a comparison of tensile strength test results of recycled products manufactured by each example, comparative example, and conventional method. Figure 3 is a graph similarly related to the elongation test results, Figure 4 is a graph showing the relationship between the tensile strength of molded recycled products and molding press pressure when using a binder prepared from diol, and Figure 5. The figure is a graph showing the relationship between tensile strength and molding press temperature, and FIGS. 6 and 7 are diagrams schematically showing the state of the pulverized waste material before and after molding, respectively.

Claims (1)

[Claims] Diol and isocyanate, or prepolymers prepared from them, are added and mixed as a binder to the pulverized material of polyurethane resin waste, and then the mixture is heated at a pressure of 160 to 300 k.
A method for recycling polyurethane resin waste material, characterized by carrying out heating and pressure molding at a temperature of 130 to 160°C.