WO2021134906A1 - Environment-friendly thermoplastic elastomer foaming and setting process - Google Patents

Abstract

Disclosed is an environment-friendly thermoplastic elastomer foaming and setting process, comprising the following steps: (1) enabling a thermoplastic elastomer material to contact at least one inert gas in a reaction kettle having the pressure higher than atmospheric pressure so that the gas is driven to enter the material, the pressure maintaining temperature of the reaction kettle is 5-40℃ lower than the melting temperature of the material; (2) maintaining the temperature and then decreasing the pressure so that the thermoplastic elastomer material is formed into a primary foaming material, and then taking the primary foaming material out from the reaction kettle; and (3) transferring the primary foaming material into a mold of a setting machine, heating for secondary foaming and performing mold setting to obtain a finished product. Compared with the prior art, in the present invention, because the thermoplastic elastomer material is not subjected to a crosslinking operation, the finished product molded thereby can be conveniently recycled; in addition, because foaming and setting are implemented in one step in the mold of the setting machine, the problem that the material shrinks due to setting is solved.

Description

Foaming and shaping process of environmentally friendly thermoplastic elastomer Technical field

The invention relates to the field of supercritical foaming technology, in particular to a foaming and shaping technology for environmentally friendly thermoplastic elastomers.

Background technique

At present, in the field of shoe materials, a variety of shock-absorbing materials have obtained more and more opportunities to appear. The two most popular materials are TPU or PEBAX materials. In order to achieve better foaming effects, Previously, materials generally needed to be cross-linked. The cross-linking method was generally achieved by adding a cross-linking agent, or by irradiation cross-linking, but the disadvantages brought about by this were also obvious. That is, the cross-linked material will not be recycled, that is, the product obtained is less environmentally friendly and does not meet the current general direction of sustainable development in China.

The conventional ETPU shock-absorbing midsole is formed by using supercritical foaming to fully foam the TPU material to obtain a foamed molded body. Since this foamed molded body still belongs to the category of semi-finished products, it has the same shock absorption as the finished product. The midsole also needs to undergo a setting process by a setting machine. During the molding and heating setting process of the setting machine, the TPU or PEBAX material that has not undergone cross-linking operation will produce greater shrinkage when encountering high temperatures, which seriously affects the entire product. quality.

As a result, cross-linking will cause the disadvantage of not being able to be recycled, and non-cross-linking will affect the quality of the product. Based on the above contradiction, the applicant conducted in-depth research on this, and this case occurred.

Summary of the invention

The main purpose of the present invention is to provide an environmentally-friendly thermoplastic elastomer foaming and shaping process to solve the contradiction between environmental protection and product quality in the prior art.

In order to achieve the above objective, the solution of the present invention is:

An environmentally-friendly thermoplastic elastomer foaming and shaping process, which includes the following steps:

① Use thermoplastic elastomer materials to contact at least one inert gas in a reactor at a pressure higher than atmospheric pressure to drive the gas into the material; the pressure holding temperature of the reactor is lower than the melting temperature of the material 5 -40°C;

② Maintain the above temperature, and then reduce the pressure, the thermoplastic elastomer material forms a primary foaming material, and then take the primary foaming material out of the reactor;

③Transfer the primary foaming material to the mold of the setting machine, and obtain the finished product after heating the second foaming and the mold setting.

Further, in step ②, it also includes the step of taking out the primary foaming material and transferring it to a cold storage below 0°C for storage; step ③ is taking out the primary foaming material from the cold storage for heating.

Further, in step ①, before adding the thermoplastic elastomer material to the reactor, it further includes a step of processing the sole mold through a mold.

Further, in the secondary foaming step of step ③, the heating temperature is higher than the melting temperature of the material by 10-40 degrees Celsius, and the secondary foaming time is 5-60 minutes.

Further, the at least one inert gas in step ① is a supercritical fluid, which is nitrogen, carbon dioxide, or a mixed gas of the two, with a holding pressure of 10-70 MPa, and a holding time of 0.5-24 hours.

Further, the pressure reduction in step ② is achieved by exhausting, and the exhausting speed is 5s-600s.

Further, the thermoplastic elastomer material is one of TPE, TPU, TPEE or PEBAX or a mixture of two or more materials.

After adopting the above structure, the present invention relates to a foaming and shaping process of environmentally friendly thermoplastic elastomer. Compared with the prior art, the present invention has at least the following beneficial effects:

1. The present invention keeps the reactor at a stable temperature (always kept at a temperature of 5-40°C lower than the melting temperature of the material), so that the entire foaming process consumes very little energy and does not need to be compared with existing ones. The same technique is used to raise and lower the temperature of the reactor, which not only reduces energy consumption and costs, but also improves production efficiency.

2. The present invention performs one-time foaming in step ②, which is actually one-time partial foaming, and its volume expansion rate is generally not more than 30%. In the process of reducing the pressure of the entire reactor, the inert gas located inside the thermoplastic elastomer material Part of the material will rush out to the outside of the material, which will cause the material to expand. However, because the current temperature of the material is below the softening point, most of the gas remains inside the material (the remaining gas will be in the secondary foaming process Let the material expand and play a role), such a reactor of the same volume will be able to place more materials, thereby improving the utilization efficiency of the entire reactor, thereby reducing the cost of a single material in the entire production process.

3. The present invention realizes the reuse of the traditional shoe material production equipment-the shaping machine, thereby greatly reducing the production cost of the enterprise, and improving the market competitiveness of the enterprise. The use of the shaping machine only needs to use the current shoe material. The finished shoe can be obtained by conventional adjustment of the mold; the present invention innovatively proposes to perform secondary foaming in the cavity of the mold of the traditional setting machine, which is mainly to directly use the heat transfer oil in the traditional setting machine to heat the mold. Realization; Then when the foaming to the end process, the mold is directly used to complete the foaming and the finalization at the same time, which not only saves the direct cost of the equipment required for foaming, but also reduces the foaming product to the finalization process. This kind of labor cost is also due to the simultaneous completion of foaming and shaping, avoiding the performance problem of reheating the fully foamed material, which will cause the material to shrink, which serves multiple purposes.

Fourth, the present invention can further save the primary foaming material in a cold storage below 0°C in step ②, so that the efficiency between the primary foaming material and the secondary foaming setting in the setting machine can be inefficient. The problem of synchronization has been fully resolved, thereby further improving the efficiency and competitiveness of the entire process in actual production.

5. Since the present invention does not perform cross-linking operations on thermoplastic elastomer materials, the molded products are very convenient for recycling. At the same time, because it forms the foaming and shaping process in the mold of the shaping machine at one time, it does not need The foamed product is heated and shaped again, so that it also solves the shrinkage problem caused by non-crosslinking.

Detailed ways

In order to further explain the technical solution of the present invention, the present invention will be described in detail below through specific embodiments.

The present invention relates to a foaming and shaping process for environmentally friendly thermoplastic elastomers, which includes the following steps:

① Use thermoplastic elastomer materials to contact at least one inert gas in a reactor at a pressure higher than atmospheric pressure to drive the gas into the material; the pressure holding temperature of the reactor is lower than the melting temperature of the material 5 -40°C (preferably 5-10°C);

Preferably, the thermoplastic elastomer material is one of TPE, TPU, TPEE or PEBAX or a mixture of two or more materials.

Preferably, the at least one inert gas in step ① is a supercritical fluid, which is nitrogen, carbon dioxide or a mixed gas of the two, and its holding pressure is 10-70 MPa (preferably 50-70 MPa), The holding time is 0.5-24 hours.

Preferably, in step ①, before adding the thermoplastic elastomer material to the reactor, it further includes a step of processing the sole mold through a mold; the mold formed in this way can be molded in the mold of the setting machine at one time to obtain a finished product The shock-absorbing midsole.

② Maintain the above temperature, and then reduce the pressure. The thermoplastic elastomer material forms a primary foamed material, and then the primary foamed material is taken out of the reactor; specifically, the pressure is reduced in step ② by means of exhaust The exhaust speed is 5s-600s, and the pressure is released to 0 MPa at a time within this period of time. The faster the speed, the finer the cells obtained, the slower the speed, the larger the cells obtained, and the production can be based on Actually need to adjust the exhaust speed.

③ Transfer the primary foaming material to the mold of the setting machine, and obtain the finished product after heating the second foaming and the mold setting. Specifically, in the secondary foaming step of step ③, the heating temperature is higher than the melting temperature of the material by 10-40 degrees Celsius, and the secondary foaming time is 5-60 minutes.

Furthermore, in step ②, it also includes the step of taking out the primary foaming material and transferring it to a cold storage below 0°C for storage; step ③ is taking out the primary foaming material from the cold storage for heating. In this way, the problem of non-synchronization of efficiency between the material after the primary foaming and the secondary foaming and setting in the setting machine can be fully solved, thereby further improving the efficiency and competitiveness of the entire process in actual production.

In this way, the present invention relates to a foaming and shaping process for environmentally friendly thermoplastic elastomers. Compared with the prior art, the present invention has at least the following beneficial effects:

1. The present invention keeps the reactor at a stable temperature (always kept at a temperature of 5-40°C lower than the melting temperature of the material), so that the entire foaming process consumes very little energy and does not need to be compared with existing ones. The same technique is used to raise and lower the temperature of the reactor, which not only reduces energy consumption and costs, but also improves production efficiency.

2. The present invention performs one-time foaming in step ②, which is actually one-time partial foaming, and its volume expansion rate is generally not more than 30%. In the process of reducing the pressure of the entire reactor, the inert gas located inside the thermoplastic elastomer material Part of the material will rush out to the outside of the material, which will cause the material to expand. However, because the current temperature of the material is below the softening point, most of the gas remains inside the material (the remaining gas will be in the secondary foaming process Let the material expand and play a role), such a reactor of the same volume will be able to place more materials, thereby improving the utilization efficiency of the entire reactor, thereby reducing the cost of a single material in the entire production process.

3. The present invention realizes the reuse of the traditional shoe material production equipment-the shaping machine, thereby greatly reducing the production cost of the enterprise, and improving the market competitiveness of the enterprise. The use of the shaping machine only needs to use the current shoe material. The finished shoe can be obtained by conventional adjustment of the mold; the present invention innovatively proposes to perform secondary foaming in the cavity of the mold of the traditional setting machine, which is mainly to directly use the heat transfer oil in the traditional setting machine to heat the mold. Realization; Then when the foaming to the end process, the mold is directly used to complete the foaming and the finalization at the same time, which not only saves the direct cost of the equipment required for foaming, but also reduces the foaming product to the finalization process. This kind of labor cost is also due to the simultaneous completion of foaming and shaping, avoiding the performance problem of reheating the fully foamed material, which will cause the material to shrink, which serves multiple purposes.

Fourth, the present invention does not perform cross-linking operations on thermoplastic elastomer materials, so the molded products are very convenient to recycle. At the same time, because it forms the foaming and shaping process in the mold of the shaping machine at one time, it does not need The foamed product is heated and shaped again, so that it also solves the shrinkage problem caused by non-crosslinking.

The foregoing embodiments do not limit the product form and style of the present invention, and any appropriate changes or modifications made by those of ordinary skill in the art should be regarded as not departing from the patent scope of the present invention.

Claims (7)

1. A foaming and shaping process for environmentally friendly thermoplastic elastomers, characterized in that it comprises the following steps:

① Use thermoplastic elastomer materials to contact at least one inert gas in a reactor at a pressure higher than atmospheric pressure to drive the gas into the material; the pressure holding temperature of the reactor is lower than the melting temperature of the material 5 -40°C;

② Maintain the above temperature, and then reduce the pressure, the thermoplastic elastomer material forms a primary foaming material, and then take the primary foaming material out of the reactor;

③Transfer the primary foaming material to the mold of the setting machine, and obtain the finished product after heating the second foaming and the mold setting.

2. An environmentally friendly thermoplastic elastomer foaming and shaping process according to claim 1, characterized in that, in step ②, it also includes taking out the primary foaming material and transferring it to a cold storage below 0°C for storage. Step; Step ③ is to take out the primary foaming material from the cold storage for heating.

3. An environmentally-friendly thermoplastic elastomer foaming and shaping process according to claim 1, characterized in that, in step ①, before adding the thermoplastic elastomer material to the reactor, it further comprises processing the sole through a mold. The steps of the prototype.

4. An environmentally friendly thermoplastic elastomer foaming and shaping process according to claim 1, characterized in that, in the secondary foaming step of step ③, the heating temperature is higher than the melting temperature of the material by 10-40 In degrees Celsius, the time for secondary foaming is 5-60 minutes.

5. An environmentally friendly thermoplastic elastomer foaming and shaping process according to claim 1, wherein at least one inert gas in step ① is a supercritical fluid, which is nitrogen, carbon dioxide, or a mixture of the two For gas, its holding pressure is 10-70 MPa, and the holding time is 0.5-24 hours.

6. An environmentally-friendly thermoplastic elastomer foaming and shaping process according to claim 1, wherein the pressure reduction in step ② is achieved by exhausting, and the exhausting speed is 5s-600s.

7. An environmentally-friendly thermoplastic elastomer foaming and shaping process according to claim 1, wherein the thermoplastic elastomer material is one or two or more of TPE, TPU, TPEE or PEBAX mixture.