阅读说明：本技术 一种eva中底鞋材注塑件氮气超临界发泡工艺 (Nitrogen supercritical foaming process for EVA insole shoe material injection molding ) 是由 杜荣欣 许忠新 于 2021-07-28 设计创作，主要内容包括：本发明提供了一种EVA中底鞋材注塑件氮气超临界发泡工艺,包括如下步骤：注塑件制备,将EVA与OBCs按预设比例称重混合,加热至熔融状态使之混合均匀,通过注塑工艺制备EVA注塑件；釜内浸润,将所述注塑件置于高压釜内并密封,往高压釜内通入超临界流体加压至所述EVA注塑件饱和状态,卸压得溶胀EVA注塑件；以及釜外发泡,将所述溶胀EVA注塑件从高压釜内取出,置于130-160℃的热风烘箱中15-20分钟取出得发泡后的EVA注塑件。发泡技术简单,发泡过程中不需要借助置物架,发泡过程中加热方式采用热风式烘箱方式,EVA溶胀体受热均匀,发泡完全。(The invention provides a nitrogen supercritical foaming process for an EVA insole shoe material injection molding, which comprises the following steps: preparing an injection molding piece, namely weighing and mixing EVA and OBCs according to a preset proportion, heating to a molten state to uniformly mix the EVA and the OBCs, and preparing the EVA injection molding piece through an injection molding process; soaking in a kettle, placing the injection molding piece in a high-pressure kettle, sealing, introducing supercritical fluid into the high-pressure kettle, pressurizing to a saturated state of the EVA injection molding piece, and releasing pressure to obtain a swelling EVA injection molding piece; and foaming outside the autoclave, taking the swollen EVA injection molding out of the autoclave, placing the swollen EVA injection molding in a hot air oven at the temperature of 130-160 ℃ for 15-20 minutes, and taking out the swollen EVA injection molding to obtain the foamed EVA injection molding. The foaming technology is simple, a storage rack is not needed in the foaming process, a hot air type oven mode is adopted in the heating mode in the foaming process, the EVA swelling body is heated uniformly, and foaming is complete.)

1. The nitrogen supercritical foaming process for the EVA insole shoe material injection molding is characterized by comprising the following steps of:

preparing an injection molding piece, namely weighing and mixing EVA and OBCs according to a preset proportion, heating to a molten state to uniformly mix the EVA and the OBCs, and preparing the EVA injection molding piece through an injection molding process;

soaking in a kettle, placing the EVA injection molding piece in a high-pressure kettle, sealing, introducing supercritical fluid into the high-pressure kettle, pressurizing to a saturated state of the EVA injection molding piece, and releasing pressure to obtain a swelling EVA injection molding piece;

foaming outside the autoclave, taking the swollen EVA injection molding out of the autoclave, placing the swollen EVA injection molding in a hot air oven at the temperature of 130-160 ℃ for 15-20 minutes, and taking out the swollen EVA injection molding to obtain the foamed EVA injection molding.

2. The nitrogen supercritical foaming process for the EVA insole shoe material injection molding according to claim 1, characterized in that: the preset ratio of EVA to OBCs is 1: 1-10: 1.

3. The nitrogen supercritical foaming process for the EVA insole shoe material injection molding according to claim 2, characterized in that: and the step of infiltrating in the kettle comprises the steps of placing the EVA injection molding piece in the high-pressure kettle and sealing, introducing supercritical N2 into the high-pressure kettle and boosting the pressure to 20-25MPa, raising the temperature of the high-pressure kettle to 95-110 ℃, maintaining the pressure for 2-5h at constant temperature, and adjusting the rate of emptying N2 according to the product requirement to obtain the swelling EVA injection molding piece.

4. The nitrogen supercritical foaming process for the EVA insole shoe material injection molding according to claim 3, characterized in that: the constant temperature equipment is hot air type drying oven mode equipment.

5. The nitrogen supercritical foaming process for the EVA insole shoe material injection molding according to claim 4, characterized in that: the pressure bearing of the high-pressure kettle is more than 35 MPa.

Technical Field

The invention relates to the technical field of polymer preparation, in particular to a nitrogen supercritical foaming process for an EVA insole shoe material injection molding.

Background

EVA (ethylene-vinyl acetate copolymer) has the advantages of good buffering, shock resistance, heat insulation, moisture resistance, chemical corrosion resistance, no toxicity, no water absorption and the like. Is widely applied to the fields of foaming shoe materials, functional greenhouse films, packaging films, hot melt adhesives, electric wires and cables, toys and the like.

The invention patent of publication No. CN107501703A specifically discloses a method for manufacturing environment-friendly EVA (ethylene-vinyl acetate) foamed beads and a shoe insole, which comprises the steps of preparing high-elastic foamed beads by using EVA particles, or blend particles of EVA and OBCs, or blend particles of EVA and SEBS, or blend particles of EVA, OBCs and SEBS as raw materials and adopting an irradiation crosslinking technology and an intermittent supercritical nitrogen foaming technology, and then carrying out steam hot-press molding to obtain the foamed insole.

Above-mentioned patent adopts irradiation cross-linking technique and intermittent type formula supercritical nitrogen gas foaming technique preparation EVA expanded material, and preparation technology is complicated, adopts oven/drying tunnel foaming EVA material to put and need with the help of dedicated supporter, simultaneously because the EVA material is different from the heating pipe position, leads to being heated unevenly to foaming scheduling problem appears unevenly.

Disclosure of Invention

In order to solve the problems, the invention provides a nitrogen supercritical foaming process for an EVA insole shoe material injection molding, the foaming technology is simple, a storage rack is not needed in the foaming process, the heating mode in the foaming process adopts a hot air type oven mode, and an EVA swelling body is uniformly heated and completely foamed.

In order to achieve the above purpose, the invention adopts a technical scheme that: a nitrogen supercritical foaming process for an EVA insole shoe material injection molding comprises the following steps: preparing an injection molding piece, namely weighing and mixing EVA and OBCs according to a preset proportion, heating to a molten state to uniformly mix the EVA and the OBCs, and preparing the EVA injection molding piece through an injection molding process; soaking in a kettle, placing the injection molding piece in a high-pressure kettle, sealing, introducing supercritical fluid into the high-pressure kettle, pressurizing to a saturated state of the EVA injection molding piece, and releasing pressure to obtain a swelling EVA injection molding piece; and foaming outside the autoclave, taking the swollen EVA injection molding out of the autoclave, placing the swollen EVA injection molding in a hot air oven at the temperature of 130-160 ℃ for 15-20 minutes, and taking out the swollen EVA injection molding to obtain the foamed EVA injection molding.

Further: the preset ratio of EVA to OBCs is 1: 1-10: 1.

Further: and the step of infiltrating in the kettle comprises the steps of placing the EVA injection molding piece in the high-pressure kettle and sealing, introducing supercritical N2 into the high-pressure kettle and boosting the pressure to 20-25MPa, raising the temperature of the high-pressure kettle to 95-110 ℃, maintaining the pressure for 2-5h at constant temperature, and adjusting the rate of emptying N2 according to the product requirement to obtain the swelling EVA injection molding piece.

Further: the constant temperature equipment is hot air type drying oven mode equipment.

Further: the pressure bearing of the high-pressure kettle is more than 35 MPa.

Compared with the prior art, the technical scheme of the invention has the following advantages:

(1) according to the nitrogen supercritical foaming process for the EVA insole shoe material injection molding, disclosed by the invention, a process of foaming in a kettle soaking constant-temperature device is adopted, the foaming process is simple, the constant-temperature device is a hot air oven type device, the EVA injection molding can be uniformly heated in the foaming process, and the EVA injection molding with complete and smooth foaming and higher closed porosity can be obtained after foaming.

(2) According to the nitrogen supercritical foaming process for the EVA insole shoe material injection molding, an EVA foaming system with OBCs is not added, the foam holes are large, the foam hole density is small, the shape is irregular, and the distribution is not uniform. Because OBCs and EVA compatibility are good, and the mobility is stronger in the OBCs heating process, helps forming stable cell structure, therefore the in-process addition OBCs of EVA injection molding at the preparation, along with OBCs's increase, cell density increase, the cell diameter diminishes and the aperture is more even, the density of EVA injection molding diminishes, hardness and tear strength reduce to some extent, and elongation at break and resilience have obvious improvement.

(3) According to the nitrogen supercritical foaming process for the EVA insole shoe material injection molding, the supercritical fluid is adopted for in-kettle infiltration and out-kettle foaming, compared with the in-kettle foaming process, the size of the high-pressure kettle does not determine the production quantity, the same quantity of EVA injection molding is produced, the size of the high-pressure kettle cavity of the out-kettle foaming process can be reduced to 1/10-1/5 of the high-pressure kettle cavity of the in-kettle foaming equipment, the EVA injection molding with the same quantity as that of the in-kettle foaming process in the prior art can be produced by using a smaller high-pressure kettle, and the equipment maintenance and manufacturing cost is higher when the size of the high-pressure kettle is larger, so that the equipment cost is greatly reduced by the method.

Drawings

The invention is further illustrated with reference to the following figures and examples.

FIG. 1 is a flow chart of a nitrogen supercritical foaming process for an EVA insole shoe material injection molding in an embodiment of the invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention. On the contrary, the embodiments of the invention include all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", and the like, indicate orientations and positional relationships based on the orientations and positional relationships shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be considered as limiting the present invention.

Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, e.g., as being fixed or detachable or integrally connected; can be mechanically or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and alternate implementations are included within the scope of the preferred embodiment of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention.

In the embodiment, a nitrogen supercritical foaming process for an EVA insole shoe material injection molding is provided. As shown in figure 1, the nitrogen supercritical foaming process for the EVA insole shoe material injection molding comprises the following steps: s10, preparing an EVA injection molding, namely weighing and mixing EVA and OBCs according to a preset proportion, heating to a molten state to uniformly mix the EVA and the OBCs, and preparing the EVA injection molding through an injection molding process; s20, infiltrating in the kettle, placing the injection molding piece in a high-pressure kettle, sealing, introducing supercritical fluid into the high-pressure kettle, pressurizing to a saturated state of the EVA injection molding piece, and releasing pressure to obtain a swelling EVA injection molding piece; and S30, foaming outside the autoclave, taking the swollen EVA injection molding out of the autoclave, placing the swollen EVA injection molding in a constant-temperature hot air oven device at the temperature of 95-110 ℃ for 15-20 minutes, and taking out the swollen EVA injection molding to obtain the foamed EVA injection molding.

S10 injection molding, EVA (polyethylene-vinyl acetate) is a thermoplastic plastic and elastomer. EVA crosslinked foam is a foam having excellent physical properties, and has advantages such as low density and capability of absorbing load, and has excellent elasticity, flexibility, stress crack resistance, and good plasticity and processability, compared with other elastomers, and thus is widely used. However, the EVA foaming material has the defects of insufficient wear resistance, low-temperature hardening and the like, thereby limiting the application of the EVA foaming material in the industry. The OBCs (olefin block copolymer) is composed of octene and polyolefin resin, and has excellent toughness, good processability, excellent aging resistance and the like. The OBCs have elasticity, resilience, toughness and weather resistance as the traditional rubber, have excellent compatibility as other plastic raw materials, can be directly used for blending and processing molding of other elastomers, and have performance better than POE (polyolefin elastomer), so that the problems of high EVA hardness and low elasticity of a base material can be solved.

The proportion of EVA and OBCs can be adjusted according to performance requirements, wherein the proportion of EVA and OBCs can be any one proportion of 1: 1-10: 1, and the proportion is 8: 2,7: the ratio of 3 has the best effect. Weighing and mixing EVA and OBCs according to a preset proportion, heating to a molten state to uniformly mix the EVA and the OBCs, and preparing the EVA injection molding piece through an injection molding process.

And S20, infiltrating in a kettle, wherein the step of infiltrating in the kettle is to place the EVA injection molding piece in the autoclave, seal the autoclave, and introduce supercritical N2 into the autoclave to increase the pressure to any pressure value of 20-25MPa, preferably 20MPa, 23MPa and 25 MPa. The autoclave is warmed to any temperature value of 95-110 ℃, preferably 95 ℃, 100 ℃, 105 ℃. Maintaining the pressure at constant temperature for 2-4h, preferably 2h, 2.5h, 3h, 3.5h, and 4 h. And quickly emptying the N2 to obtain the swelling EVA injection molding when the EVA injection molding is in a supercritical N2 saturated state.

And S30, foaming outside the kettle, taking the swollen EVA insole shoe material injection molding out of the autoclave, placing the swollen EVA insole shoe material injection molding in a constant temperature device at 95-110 ℃ for 15-30min, and taking out to obtain the foamed EVA injection molding. The constant temperature equipment is one of hot air oven constant temperature equipment. The foaming temperature is any one of 130 ℃ and 160 ℃, preferably 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃ and 160 ℃. The foaming time is 10-20min, preferably 10min, 12min, 14min, 16min, 18min, and 20 min.

Example 1

S10 injection molding preparation, EVA and OBCs are processed according to the proportion of 70: 30, heating to a molten state to uniformly mix, and preparing an EVA insole shoe material injection molding piece by an injection molding process; s20, infiltrating in a kettle, placing the injection molding piece in a high-pressure kettle, sealing, introducing supercritical N2 into the high-pressure kettle, boosting the pressure to 23MPa, heating the high-pressure kettle to 95 ℃, keeping the temperature and the pressure for 2.5 hours until the EVA injection molding piece is in a supercritical N2 saturated state, and quickly exhausting clear gas to obtain a swelling EVA injection molding piece; and S30, foaming outside the kettle, taking the swollen EVA insole shoe material injection molding out of the autoclave, placing the swollen EVA insole shoe material injection molding in constant temperature equipment at 140 ℃ for 15min, and taking out to obtain the foamed EVA injection molding. The performance indexes of the EVA injection molded part prepared by the method are shown in the following table 1, namely the performance indexes of the EVA injection molded part after foaming in the example 1.

TABLE 1 Performance index of EVA injection molded part after foaming in example 1

Test items	Data results
		Density of	0.14g/cm³
Hardness of	45C
		Tensile strength	20Kg/cm²
Elongation percentage	270%
		Tear strength	14.5Kg/cm²
Peeling off	2.75Kg/cm²
		Compressing y	58%
Shrinkage of	0.13%
		Aging test	4G
Yellowing resistance test	4G
		Rebound Strength	59%

Example 2

S10 injection molding preparation, EVA and OBCs are mixed according to the ratio of 60: 40, heating to a molten state to uniformly mix, and preparing an EVA insole shoe material injection molding piece by an injection molding process; soaking in an S20 kettle, placing the injection molding piece in a high-pressure kettle, sealing, introducing supercritical N2 into the high-pressure kettle, boosting the pressure to 20MPa, heating the high-pressure kettle to 100 ℃, keeping the temperature and the pressure for 2 hours until the EVA injection molding piece is in a supercritical N2 saturated state, and quickly exhausting gas to obtain a swelling EVA injection molding piece; and S30, foaming outside the kettle, taking the swollen EVA injection molding out of the high-pressure kettle, placing in a constant temperature device at 135 ℃ for 13min, and taking out to obtain the foamed EVA injection molding. The performance indexes of the EVA insole shoe material injection molding prepared by the method are as follows, and the performance indexes of the EVA injection molding after foaming in example 2 in the table 2 are shown in the specification.

TABLE 2 Performance index of EVA injection molded part after foaming in example 2

Test items	Data results
		Density of	0.12g/cm³
Hardness of	48C
		Tensile strength	22.5Kg/cm²
Elongation percentage	260%
		Tear strength	15.2Kg/cm²
Peeling off	2.85Kg/cm²
		Compressing y	55%
Shrinkage of	0.12%
		Aging test	4G
Yellowing resistance test	4G
		Rebound Strength	56%

Example 3

S10 preparing an injection molding, namely weighing and mixing EVA and OBCs according to the proportion of 50:50, heating to a molten state to uniformly mix the EVA and the OBCs, and preparing the EVA insole shoe material injection molding through an injection molding process; soaking in an S20 kettle, placing the injection molding piece in a high-pressure kettle, sealing, introducing supercritical N2 into the high-pressure kettle, boosting the pressure to 20MPa, raising the temperature of the high-pressure kettle to 105 ℃, keeping the temperature and the pressure for 2 hours, quickly discharging clean gas until the inside of the EVA injection molding piece is in a supercritical N2 saturated state, and obtaining a swelling EVA injection molding piece; and S30, foaming outside the autoclave, taking the swollen EVA injection molding out of the autoclave, placing the swollen EVA injection molding in a constant temperature device at 150 ℃ for 12min, and taking out the swollen EVA injection molding to obtain the foamed EVA injection molding. The performance indexes of the EVA injection molded part prepared by the method are shown in the following table 3, the performance indexes of the EVA injection molded part after foaming in the example 3.

TABLE 3 Performance index of EVA injection molded part after foaming in example 3

Test items	Data results
		Density of	0.135g/cm³
Hardness of	51C
		Tensile strength	23.2Kg/cm²
Elongation percentage	245%
		Tear strength	15.8Kg/cm²
Peeling off	2.9Kg/cm²
		Compressing y	54%
Shrinkage of	0.125%
		Aging test	4G
Yellowing resistance test	4G
		Rebound Strength	55%

Example 4

S10 preparing an EVA injection molding, namely weighing and mixing EVA and OBCs according to the ratio of 80:20, heating to a molten state to uniformly mix the EVA and the OBCs, and preparing the EVA injection molding through an injection molding process; s20, infiltrating in a kettle, placing the injection molding piece in a high-pressure kettle, sealing, introducing supercritical N2 into the high-pressure kettle, boosting the pressure to 19MPa, raising the temperature of the high-pressure kettle to 85 ℃, keeping the temperature and the pressure for 2.5 hours, and quickly exhausting gas until the inside of the EVA insole shoe material injection molding piece is in a supercritical N2 saturated state to obtain a swelling EVA injection molding piece; and S30, foaming outside the kettle, taking the swollen EVA injection molding out of the high-pressure kettle, placing the swollen EVA injection molding in constant temperature equipment at 140 ℃ for 10min, and taking out to obtain the foamed EVA insole shoe material. The performance indexes of the EVA injection molded part prepared by the method are shown in the following table 4.

TABLE 4 Performance index of EVA injection molded part after foaming in example 4

Test items	Data results
		Density of	0.146g/cm³
Hardness of	42C
		Tensile strength	18.5Kg/cm²
Elongation percentage	275%
		Tear strength	14Kg/cm²
Peeling off	2.65Kg/cm²
		Compressing y	56%
Shrinkage of	0.14%
		Aging test	4G
Yellowing resistance test	4G
		Rebound Strength	59%

Example 5

S10 preparing an EVA injection molding, namely weighing and mixing EVA and OBCs according to a ratio of 85:15, heating to a molten state to uniformly mix the EVA and the OBCs, and preparing the EVA injection molding through an injection molding process; s20, infiltrating in a kettle, placing the injection molding piece in a high-pressure kettle, sealing, introducing supercritical N2 into the high-pressure kettle, boosting the pressure to 20MPa, heating the high-pressure kettle to 90 ℃, keeping the temperature and the pressure for 2 hours, and quickly exhausting gas until the inside of the EVA insole shoe material injection molding piece is in a supercritical N2 saturated state to obtain a swelling EVA injection molding piece; and S30, foaming outside the kettle, taking the swollen EVA injection molding out of the high-pressure kettle, placing the swollen EVA injection molding in constant temperature equipment at 135 ℃ for 10min, and taking out to obtain the foamed EVA insole shoe material. The performance indexes of the EVA insole shoe material injection molding prepared by the method are as follows, and the performance indexes of the EVA injection molding after foaming in example 5 in the table 5 are shown in the specification.

TABLE 5 Performance index of EVA injection molded part after foaming in example 5

Test items	Data results
		Density of	0.15g/cm³
Hardness of	37C
		Tensile strength	17.8Kg/cm²
Elongation percentage	275%
		Tear strength	13.6Kg/cm²
Peeling off	2.6Kg/cm²
		Compressing y	57%
Shrinkage of	0.143%
		Aging test	4G
Yellowing resistance test	4G
		Rebound Strength	61%

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, a schematic representation of the term does not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.