A method for producing a uniform closed cell foamed wire

Abstract

The present application relates to a kind of preparation methods of uniform closed-cell foamed wire, belong to supercritical foaming technical field.The foamed wire prepared by the present application is uniform in thickness, straight, small in density.It significantly changes the characteristics of traditional foamed wire, such as uneven thickness, not straight, large density.Firstly, the present application uses autoclave impregnation to impregnate nitrogen in the wire and form a dense bubble nucleus structure in the wire.After heating through a polytetrafluoroethylene tube, the wire forms the same shape as the inner diameter of the tube.Due to the "limiting foaming" effect, the wire is uniform in thickness.After being pulled and wound by a constant tension machine, the wire is straight.Due to the use of high-pressure nitrogen impregnation and subsequent temperature rising foaming method, the foamed wire with a density as low as 0.1 g / cm3 can be produced.The wire with uniform thickness, straightness and low density is equivalent to a standard part during processing, and can be woven into the required product using textile machines.The low density gives the material good cushioning and thermal insulation performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of preparation method of uniform closed-cell foamed wire, belong to supercritical foaming technical field. BACKGROUND

[0002] At present, foamed wire is mainly by supercritical gas carbon dioxide or nitrogen into reactor, immerse into polymer wire, after heating, pressure relief obtains foamed wire, or supercritical gas is added to double screw and melt polymer is mixed uniformly, after single screw cooling, extrusion foaming obtains foamed wire.

[0003] The above two kinds of foaming can obtain foamed wire, but all have respective defects:

[0004] 1, foamed wire in kettle foaming, due to uneven heating, often uneven, bending is serious.

[0005] 2, foamed wire in extrusion foaming, due to the low melt strength, it is difficult to make the density of less than 0.15g / cm 3 .

[0006] 3, foamed wire due to uneven or density is too large, it is difficult to realize the application in textile, and it is also difficult to make protective equipment or clothes with good protection effect.

[0007] In view of the above defects, the present design person actively researches and innovates, in order to create a kind of preparation method of uniform closed-cell foamed wire, so that it has more industrial use value. SUMMARY

[0008] To solve the above technical problems, the purpose of the present application is to provide a kind of preparation method of uniform closed-cell foamed wire.

[0009] The preparation method of the uniform closed-cell foamed wire of the present application, the specific preparation steps are:

[0010] (1) first extruding unfoamed wire base material with extruder, and winding with constant tension winding machine to obtain unfoamed wire;

[0011] (2) impregnating unfoamed wire in autoclave, and pressure relief to obtain preformed wire containing gas and volume increasing by 5%;

[0012] (3) the preformed wire is inserted into polytetrafluoroethylene tube with an inner diameter of 1-9 mm, heating pipe sleeve is added around the polytetrafluoroethylene tube, the heating temperature is within the melting point of wire base material ± 20 ℃, and the foamed wire is wound with constant tension winding machine, to obtain uniform foamed wire.

[0013] Further, the wire base material in step (1) comprises one of TPU, TPEE, TPA, PP, PE, PS thermoplastic material or an alloy thereof.

[0014] Further, the hardness of the wire base material in step (1) is 45-95A.

[0015] Further, the unfoamed wire obtained by winding with the constant tension winder in step (1) has a thickness of 0.5-5mm.

[0016] Further, the impregnation pressure of impregnation in step (2) is 10-60MPa, the impregnation temperature is 100-250℃, and the impregnation time is 0.5-10h.

[0017] Further, the impregnation gas of impregnation in step (2) is carbon dioxide or nitrogen or a mixture of the two.

[0018] Further, the inner diameter of the polytetrafluoroethylene tube in step (3) is one of circular, square, polygon.

[0019] Further, the length of the polytetrafluoroethylene tube in step (3) is 600mm, and the heating tube sleeve is divided into 6 segments, each with a length of 100mm, to achieve segmented temperature control.

[0020] Further, the heating temperature of the heating tube sleeve in step (3) is 0-250℃.

[0021] Further, the heating temperature of the heating tube sleeve in step (3) is 100-200℃.

[0022] By the above scheme, the present application has at least the following advantages:

[0023] The foamed wire prepared by the present application is uniform in thickness, straight and low in density. It significantly changes the characteristics of traditional foamed wire, which is uneven in thickness, not straight and high in density. The present application first uses autoclave impregnation to impregnate nitrogen in the wire and form a dense bubble structure in the wire. Since the gas impregnation content is proportional to the pressure, the gas content is high after high-pressure impregnation, and accordingly, the density after foaming can be very small. After heating by the polytetrafluoroethylene tube, the wire forms the same shape as the inner diameter of the tube. Due to the "limiting foaming" effect, the wire is uniform in thickness. After being pulled and wound by the constant tension machine, the wire is straight. By using high-pressure nitrogen impregnation and then foaming by heating, a foamed wire with a density as low as 0.1g / cm 3 can be prepared.

[0024] The wire uniform in thickness, straight and low in density is equivalent to a standard part during processing, and can be woven into the required product by a textile machine. The low density gives the material good cushioning and heat insulation performance.

[0025] The above description is only a summary of the technical solutions of the present application. In order to make the technical means of the present application clearer and to enable the present application to be implemented according to the content of the description, the preferred embodiments of the present application are described in detail as follows. DETAILED DESCRIPTION

[0026] The specific embodiments of the present application are described in further detail below in combination with examples. The following examples are used to illustrate the present application but are not used to limit the scope of the present application.

[0027] (1) The unfoamed wire base material is extruded by an extruder, and a constant tension winder is used to wind the unfoamed wire to obtain an unfoamed wire with a diameter of 0.5-5 mm;

[0028] The wire base material includes but is not limited to TPU, TPEE, TPA, PP, PE, and PS thermoplastic materials.

[0029] The hardness of the wire base material is 45-95A.

[0030] (2) The unfoamed wire is impregnated in an autoclave, the impregnation pressure is 10-60 MPa, the impregnation temperature is 100-250°C, the impregnation time is 0.5-10 h, and the wire containing gas and having a volume increase of 5% is obtained by pressure relief.

[0031] The impregnation gas is carbon dioxide or nitrogen or a mixture of the two.

[0032] (3) The wire is inserted into a polytetrafluoroethylene tube with an inner diameter of 1-9 mm, a heating tube sleeve is added around the polytetrafluoroethylene tube for heating, the heating temperature is within ±20°C of the melting point of the wire base material. The foamed wire is wound by a constant tension winder to obtain a foamed wire with uniform thickness.

[0033] Example 1

[0034] The thermoplastic polyurethane beads with a hardness of 90A are extruded by an extruder, and a constant tension winder is used to wind the wire to obtain a wire with a diameter of 2.8 mm.

[0035] The wire is placed in an autoclave, the temperature is 152°C, the pressure is 55 MPa, and the gas type is nitrogen. Impregnate for 4 hours, and release the pressure to obtain a wire containing gas.

[0036] The wire is inserted into a polytetrafluoroethylene tube with an inner diameter of 5 mm, the heating temperature is 160°C, and a constant tension winder is used to wind the wire to obtain a foamed wire with a diameter of 5 mm and a density of 0.14 g / cm 3 .

[0037] Example 2

[0038] Thermoplastic polyurethane beads with hardness of 95A were extruded by an extruder and wound by a constant tension winder to obtain a wire having a diameter of 1.8 mm.

[0039] The wire was put in an autoclave at a temperature of 160°C, a pressure of 55 MPa and nitrogen gas. The wire containing gas was obtained by immersing for 4 hours and releasing the pressure.

[0040] The wire was put into a polytetrafluoroethylene tube having an inner diameter of 5 mm, heated at a temperature of 172°C and wound by a constant tension winder to obtain a foamed wire having a thickness of 5 mm and a density of 0.08 g / cm 3 .

[0041] Example 3

[0042] Thermoplastic nylon beads with hardness of 45A were extruded by an extruder and wound by a constant tension winder to obtain a wire having a diameter of 2.4 mm.

[0043] The wire was put in an autoclave at a temperature of 142°C, a pressure of 55 MPa and nitrogen gas. The wire containing gas was obtained by immersing for 4 hours and releasing the pressure.

[0044] The wire was put into a polytetrafluoroethylene tube having an inner diameter of 6 mm, heated at a temperature of 151°C and wound by a constant tension winder to obtain a foamed wire having a thickness of 6 mm and a density of 0.10 g / cm 3 .

[0045] Comparative Example

[0046] Comparative Example 1

[0047] Thermoplastic nylon beads with hardness of 45A were extruded by an extruder and wound by a constant tension winder to obtain a wire having a diameter of 2.4 mm.

[0048] The wire was put in an autoclave at a temperature of 142°C, a pressure of 55 MPa and nitrogen gas. The wire containing gas was obtained by immersing for 4 hours and releasing the pressure.

[0049] The wire containing gas was put into an autoclave and filled with nitrogen gas at 7 MPa. The foamed wire was obtained by heating for 10 minutes at a temperature of 151°C and releasing the pressure. Since the foamed wire was not uniformly heated in the autoclave, the thickness of the foamed wire was not uniform and the diameter fluctuated between 3 and 6 mm. The density of the final wire was 0.12 g / cm 3 .

[0050] Comparative Example 2

[0051] The thermoplastic nylon beads with hardness of 45A are foamed by an extrusion foaming machine, the temperature of the extruder is 145℃, and then the foamed product is wound by a constant tension machine to obtain a wire with a diameter of 6mm and a density of 0.22g / cm 3 .

[0052] Comparing the performance of the examples 1-3 and the control examples 1 and 2, it can be seen that the closed-cell foamed wires prepared in the examples 1-3 are all uniform in diameter, and the density of the product is as low as 0.1g / cm 3 , and the product quality is excellent, while the closed-cell foamed wires prepared in the control examples 1 and 2 are prepared by the conventional foaming process in the art, and since the high-pressure nitrogen impregnation and then the temperature foaming are not adopted, and the limiting foaming process is not adopted, the final product is not uniform in diameter, and the density is too large, thus it can be confirmed that the present application firstly adopts the autoclave impregnation to impregnate the nitrogen in the wire, and forms a dense bubble structure in the wire, and after heating by the polytetrafluoroethylene tube, the shape same as the inner diameter of the tube is formed, and due to the effect of the "limiting foaming", the wire uniform in diameter is formed, and after being pulled and wound by the constant tension machine, the straight wire is formed. Since the high-pressure nitrogen impregnation and then the temperature foaming are adopted, the foamed wire with a density as low as 0.1g / cm 3 can be prepared.

[0053] The above only describes the preferred embodiments of the present application, and is not used to limit the present application, and it should be noted that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present application.

Claims

1. A method for preparing a uniform closed-cell foamed filament, characterized in that... The specific preparation steps are as follows: (1) First, extrude the unfoamed wire base material using an extruder, and then wind it up using a constant tension winding machine to obtain the unfoamed wire; the hardness of the wire base material is 45 to 95A; the thickness of the unfoamed wire obtained by winding is 0.5 to 5mm. (2) Impregnate the unfoamed wire in a high-pressure autoclave, and depressurize to obtain a pre-made wire containing gas and with a volume increase of about 5%; the impregnation pressure is 10-60 MPa, the impregnation temperature is 100-250℃, and the impregnation time is 0.5-10 h; the impregnation gas is carbon dioxide or nitrogen or a mixture of the two. (3) Insert the pre-made wire into a polytetrafluoroethylene tube with an inner diameter of 1 to 9 mm, and add a heating sleeve around the polytetrafluoroethylene tube for heating. The heating temperature is within ±20℃ of the melting point of the wire base material. Use a constant tension winding machine to wind the foamed wire to obtain a foamed wire of uniform thickness. The polytetrafluoroethylene tube is 600 mm long. The heating sleeve is divided into 6 sections, each 100 mm long, to achieve segmented temperature control. The heating temperature of the heating sleeve is 100 to 200℃.

2. The method for preparing a uniform closed-cell foamed filament according to claim 1, characterized in that: The wire base material mentioned in step (1) includes one of the thermoplastic materials such as TPU, TPEE, TPA, PP, PE, and PS or an alloy thereof.

3. The method for preparing a uniform closed-cell foamed filament according to claim 1, characterized in that: In step (3), the inner diameter of the polytetrafluoroethylene tube is either circular or polygonal.