JPS5813162B2 - Shoe sole molding method that reuses waste material from polyurethane cast soles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION As is well known, cast polyurethane soles utilize the high reactivity of incyanate groups to complete the reaction in several tens of seconds to form a molded product, resulting in a relatively high defect rate. Because it contains a bridging structure, it is difficult to recycle compared to other thermoplastic resins, so all such urethane bottom scraps have been disposed of until now.

However, recently, with the increase in the production of shoes, the production of urethane soles has also increased, and measures to dispose of the resulting scrap have become an even more pressing issue due to the tightening of environmental regulations.

Taking the above-mentioned current situation into consideration, the inventor of the present application has investigated the reuse of urethane resin and PVC, which exhibits good compatibility, as a blend bottom.

(1) The cast polyurethanes shown in Table 1 were used as PVC bottom materials and polyurethane scraps in the experiments.

When recycling polyurethane, it is thought that the mixing ratio of isocyanate side and polyale side, which is the reaction condition during casting, that is, the NCO/OH ratio, and the difference in the type of polyurethane itself will affect the quality of dispersion into PVC. Therefore, we will first focus on polyester, which is the mainstream of urethane soles, and introduce different NCO/O
The H ratio and resin were selected and used as experimental materials.

(2) Since the cast polyurethane bottom is a foam, PVC
When blending, it is necessary to perform pre-treatment to improve homogeneous mixing with PVC by pulverizing or cutting into appropriate sizes, and the pulverizing was carried out by freeze-pulverizing, using a cutter or scissors.

(3) The PVC compound for shoe soles was mixed according to the four methods described in the claims.

In addition, the test piece for physical property details is press-molded to 0.04~
Table 2 shows the processing or molding conditions for producing a 3 mm thick sheet and using it as a measurement sample.

(4) As a basic performance evaluation as a bottom material, an abrasion test, tensile strength, tear strength, elongation, and hardness were measured.

The devices used were a taper set abrasion tester, a Schopper type tensile tester, and a Durometer A, respectively.

Cast urethane molding machines have molds with 20, 18, and 12 sides, and this number is an indicator of the length of one cycle from injecting the raw material into the mold to completing the reaction and taking out the product. This is the result.

In other words, the manufacturer of urethane bottom material must select a polyurethane resin that completes the reaction in one cycle (based on the model made by Desmas in West Germany), depending on the model used, and the hardness of the bottom material must be adjusted by the mold. A desired value can be obtained by changing the amount of injection and the equivalence ratio of OH/NCO.

Scrap generated from these various conditions is PVC.
The question is whether or not a blend with good physical properties can be obtained by uniformly mixing the materials.

Therefore, we investigated the effects of the above-mentioned differences on blend properties.

First, Figure 1 shows how polyurethane A is applied to the bottom PV in various proportions.
This figure shows the physical properties of the blend added to Compound C.

As a general trend, the best physical properties are obtained when scrap is added at around 10%, and a blend bottom with interesting properties can be expected within approximately 20% or over 60% as a practical addition range considering wear characteristics. .

In addition, when the amount of urethane added is 100%, that is, when using urethane alone, a thermoplastic rubber is obtained that exhibits extremely excellent abrasion resistance and physical properties that are comparable to those of ordinary vulcanized rubber. In addition to this, other uses that take advantage of its properties are expected.

Next, as shown in Figure 1, in the case of PVCrich, 1
Interesting characteristics were shown at around 0%, but we investigated whether different types of urethane resins would show similar trends in the PVC rich region.

When evaluating the performance of ordinary shoe sole materials, wear characteristics are usually cited as an important test item.

This is expressed as a wear loss per 1000 cycles, in mg.

Figure 3 shows whether there is a large difference in blend physical properties depending on the scrap used, from the viewpoint of wear characteristics.

As is clear from the figure, there is a slight difference in the additive limit that maintains good wear properties, and when the addition amount exceeds 10 phr, the same tendency is shown, and the physical properties deteriorate.This tendency also applies to tensile and tear properties. It was similar.

Figure 4 shows the homogeneous mixability of PVC and urethane, that is, how the difference in the mixing ratio of OH/NCO, which is thought to have a large effect on the blend properties, affects the blend properties from the wear characteristics. It is.

Compared to the urethane resin blending ratio of 100/107, the hard blend shows a significant decrease when 5 phr or more is added.

This is thought to be due to the increased crosslinking density and higher melting temperature, which resulted in poor compatibility.

Therefore, from the standpoint of recycling, it is considered desirable to avoid hard compounding as much as possible, including in the selection of resins.

That is, even when a hard compound is required, it is desirable to select and compound a resin that does not have a crosslinking density or melting temperature higher than necessary.

Note that the scrap is a foam, and the PVC is dispersed more quickly once it passes through the rolls.

Therefore, a heating type eder blend feeder is suitable as a mixer, and scrap cast under the optimum conditions for polyurethane resin shows excellent compatibility with PVC, and in particular, the best physical properties are obtained after about 5 to 10 hours. show.

Further, when the amount added is 60 Nc% or more, it gradually becomes rubber-like, but with an amount added of 60 Nc%, a practical bottom material was obtained by injection molding in preliminary experiments.

Note that Table 1 shows the polyurethane resin and vinyl chloride resin used as experimental samples, and Table 2 shows the processing and molding conditions.

[Brief explanation of the drawing]

The figures show examples of the present invention. Figure 1 shows the physical properties of a blend made by adding various proportions of polyurethane scrap to soft PVC for shoe soles, and Figure 2 shows the properties of a blend made by adding polyurethane scrap in various proportions to soft PVC for shoe soles. FIG. 3 is a diagram showing the influence of various blends on the wear characteristics, and FIG. 3 is a diagram showing the influence of the added amount of polyurethane scrap having different OH/NCO reaction ratios on the wear characteristics.

Claims (1)

[Claims] 1 Scraps of cast-molded shoe soles made of polyurethane are heated to about 140°C to 165°C and roll-kneaded for about 2 minutes to obtain a crepe-like sheet. 6～
Shredded into 7 mm square pellets, mixed with a compound such as vinyl chloride or ethylene-vinyl acetate copolymer, and mixed with a roll for about 5 minutes while heating to about 165 ° C. A method for forming a shoe sole by reusing waste materials from cast shoe soles made of polyurethane, which comprises forming a sheet and then press-molding the blended sheet while heating it to about 165°C. 2 Sliprap of scrap material from polyurethane cast shoe soles is heated to approximately 140°C to 165°C and kneaded with a roll for approximately 3 minutes, and then a compound such as vinyl chloride or ethylene-vinyl acetate copolymer is mixed in to form a slurry of approximately 165°C. These blend sheets were formed by roll mixing for about 5 minutes while heating to
A shoe sole molding method that reuses waste material from polyurethane cast soles, which is characterized by press molding while heating to 5°C. 3 Scraps of cast-molded polyurethane shoe soles are kneaded in a panbury, then mixed with a compound such as vinyl chloride or ethylene-vinyl acetate copolymer, heated to approximately 165°C, and mixed with a roll. After that, press it while heating it to 165℃, or press it with a head of 180℃, a nozzle of 180℃, and a cylinder of 160℃.
A shoe sole molding method that reuses waste materials from polyurethane cast soles, which is characterized by injection molding at a temperature of 1,000 kg/cm2 at an injection pressure of 1,000 kg/cm2. 4. Grinding scraps of waste material from polyurethane cast shoe soles by means such as cryo-pulverization, dry-blending this with a compound such as vinyl chloride or ethylene-vinyl acetate copolymer, and then subjecting it to injection molding. A shoe sole molding method that reuses waste material from polyurethane cast soles.