Heat-shrinkable non-woven fabric and preparation method thereof

Abstract

The invention discloses a heat-shrinkable non-woven fabric and a preparation method thereof. The heat-shrinkable non-woven fabric is obtained by melt-blowing a thermoplastic polyurethane elastomer of which the crystallization temperature does not exceed 40 DEG C into a fabric and then cooling the fabric at 0-15 DEG C. The TPU is rapidly cooled and shaped by cooling equipment such as a cold channel after being drafted by hot air. And when the formed TPU screen cloth is subjected to heat treatment again, the TPU molecular chain segment which is rapidly cooled and shaped before begins to move, and the TPU screen cloth shrinks.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a heat-shrinkable non-woven fabric and a preparation method thereof. Background Art

[0002] Heat shrink film is a common product in the market, widely used in the sales and transportation of various products, primarily serving to stabilize, cover, and protect them. Current heat shrink film products are typically made of materials such as PVC, PE, and PET. Their high shrinkage temperatures make them unsuitable for temperature-sensitive materials, such as those in the clothing, medical, and electronics industries. Furthermore, these films are generally non-breathable, inflexible, and stiff.

[0003] Non-woven fabrics have pores that ensure a certain degree of breathability and are softer, making them more suitable for applications that require breathability and flexibility, such as medical bandages.

[0004] The patent specification with publication number CN115387023A discloses a method for preparing a thermoplastic polyurethane elastomer / polylactic acid (TPU / PLA) melt-blown composite non-woven fabric, comprising the following steps: 80-90 parts by weight of polylactic acid, 10-20 parts by weight of polyurethane elastomer, 5-10 parts by weight of compatibilizer, 0.1-0.5 parts by weight of antioxidant, 0.5-1 parts by weight of stabilizer, and 1-3 parts by weight of plasticizer are mixed uniformly, transferred into a twin-screw extruder, melted, drawn and solidified into shape, pelletized, and dried to obtain TPU / PLA plastic pellets; the obtained TPU / PLA plastic pellets are sliced, transferred into a twin-screw extruder for heating, melting, and homogenization, and the TPU / PLA melt is drawn by a high-speed hot air flow to form extremely fine fibers that condense onto a roller, and form a non-woven fabric through self-bonding to obtain a TPU / PLA melt-blown composite non-woven fabric.

[0005] Patent specification CN116770510A discloses a reaction-based method for preparing high-strength TPU meltblown nonwoven fabrics and the resulting products. The method involves extruding the isocyanate, polyol, chain extender, and optionally added catalyst required for TPU synthesis through a twin-screw extrusion reaction to produce a TPU melt with a molecular weight of less than 100,000 g / mol. This melt is then directly pumped into a meltblown die by a melt metering pump. The meltblown die is stretched by hot air to form a fiber web and then matured to produce a high-strength TPU meltblown nonwoven fabric with a molecular weight of over 130,000 g / mol. The twin-screw extrusion reaction temperature is 150-220°C; the meltblown die temperature is 210-270°C; the hot air temperature is 210-270°C with a pressure of 0.1-0.5 MPa; and the maturation temperature is 35-45°C. This patented technology addresses the conflict between TPU processability and TPU meltblown fiber strength. This one-step production eliminates the TPU pelletizing and pellet drying processes, simplifying the production process and reducing costs.

[0006] The non-woven fabrics with the above-listed patented technologies do not involve performance indicators related to heat shrinkage. Summary of the Invention

[0007] In view of the above technical problems and the shortcomings in the art, the present invention provides a heat-shrinkable non-woven fabric and a preparation method thereof.

[0008] The specific technical solutions are as follows:

[0009] In a first aspect, the present invention provides a heat-shrinkable nonwoven fabric, which is obtained by melt-blowing a thermoplastic polyurethane elastomer with a crystallization temperature (Tc) not exceeding 40°C into a cloth and then cooling it to 0-15°C (e.g., 8°C).

[0010] In the present invention, the crystallization temperature of the thermoplastic polyurethane elastomer can be obtained by differential scanning calorimetry (DSC) testing. An exemplary typical procedure is set up as follows: the thermoplastic polyurethane elastomer is first heated from -10°C to 250°C at a heating rate of 20K / min, then cooled from 250°C to -80°C at a cooling rate of 10K / min, then maintained at -80°C for 2 minutes, and finally heated from -80°C to 250°C at a heating rate of 20K / min to complete the test.

[0011] The heat-shrinkable nonwoven fabric of the first aspect can be heat-shrunk at a temperature of 40-80° C. (eg, 50° C., etc.) In some preferred embodiments, the heat-shrinkable nonwoven fabric of the first aspect has a heat shrinkage rate greater than 55% at 50° C.

[0012] In some embodiments, in the heat-shrinkable non-woven fabric of the first aspect, the crystallization temperature of the thermoplastic polyurethane elastomer may be 5 to 40° C., for example, 9° C., 10° C., 14° C., 17° C., etc.

[0013] In some preferred examples, the heat-shrinkable non-woven fabric described in the first aspect, as one of the raw materials for forming the thermoplastic polyurethane elastomer, the isocyanate includes at least one of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and dicyclohexylmethane diisocyanate (HMDI), and further preferably includes HDI, so that the obtained non-woven fabric has better heat shrinkage performance.

[0014] In some preferred examples, in the heat-shrinkable non-woven fabric of the first aspect, the chain extender as one of the raw materials for forming the thermoplastic polyurethane elastomer includes at least one of 1,4-butanediol (BDO) and 1,6-hexanediol (HDO).

[0015] In some preferred embodiments, in the heat-shrinkable nonwoven fabric described in the first aspect, the polyol used as one of the raw materials for forming the thermoplastic polyurethane elastomer is a polyester polyol. Furthermore, the raw materials for the polyester polyol may include a dibasic acid and a diol. In some preferred embodiments, the dibasic acid includes at least one of adipic acid and succinic acid. In some preferred embodiments, the diol includes at least one of BDO and HDO. For example, the polyester polyol preferably includes at least one of polybutylene adipate and polyhexylene adipate.

[0016] In some preferred examples, the polyol as one of the raw materials for forming the thermoplastic polyurethane elastomer includes poly(hexamethylene adipate), which can make the resulting non-woven fabric have better heat shrinkage properties.

[0017] In some preferred examples, in the heat-shrinkable non-woven fabric of the first aspect, the number average molecular weight of the polyol is 2500-4500 g / mol, for example, 3000 g / mol, 4000 g / mol, etc.

[0018] In some preferred examples, in the heat-shrinkable non-woven fabric described in the first aspect, the hard segment content in the thermoplastic polyurethane elastomer is 10%-25%, such as 13%, 16%, etc.

[0019] In some embodiments, the raw material composition of the thermoplastic polyurethane elastomer includes isocyanate, chain extender, and polyol. The hard segment content can be calculated according to the following formula: hard segment content = (mass of isocyanate + mass of chain extender) / (mass of isocyanate + mass of chain extender + mass of polyol).

[0020] In a second aspect, the present invention provides a method for preparing the heat-shrinkable non-woven fabric according to the first aspect, using a meltblowing process, the preparation method specifically comprising:

[0021] The thermoplastic polyurethane elastomer is added to a screw extruder, and the thermoplastic polyurethane elastomer is extruded to a melt-blowing die through a screw while being heated and melted, and then sprayed onto a receiving curtain under the action of hot air drawing, and then the receiving curtain is cooled in a cavity at 0-15°C (for example, 8°C, etc.) to obtain the heat-shrinkable non-woven fabric.

[0022] In some preferred examples, in the method for preparing the heat-shrinkable non-woven fabric described in the second aspect, the screw extrusion temperature is 200-260°C, such as 220°C, 230°C, etc.

[0023] In some preferred examples, in the method for preparing the heat-shrinkable non-woven fabric described in the second aspect, the temperature of the meltblowing die head is 200-250°C, for example, 230°C, 240°C, etc.

[0024] In some preferred examples, in the method for preparing the heat-shrinkable non-woven fabric described in the second aspect, the hot air temperature is 200-250°C, such as 230°C, 250°C, etc., and the wind pressure is 0.1-0.5MPa, such as 0.3MPa, etc.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] After being stretched with hot air, the TPU of the present invention is rapidly cooled and shaped by cooling equipment such as a cold channel. When the formed TPU mesh is subjected to heat treatment again, the TPU molecular segments that were previously rapidly cooled and shaped begin to move, causing the TPU mesh to shrink. The TPU design of the preferred formula of the present invention adopts a low hard segment and a high polyol molecular weight design. The TPU is mainly partially crystallized from the soft segment polyol, and has a low crystallization temperature, high crystallinity, and high crystallization enthalpy. After being heat treated again at a lower temperature, the molecular segments can begin to move and re-enter the crystal lattice, relying on the high crystallinity to achieve a relatively large shrinkage. The preferred TPU formula of the present invention can achieve low-temperature heat shrinkage and a large shrinkage rate. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0028] In the following examples, the operating methods without specifying specific conditions are generally carried out under conventional conditions or conditions recommended by the manufacturer.

[0029] In the following examples:

[0030] The heat shrinkage ratio is calculated as follows: heat shrinkage ratio = (non-woven fabric length before shrinkage - non-woven fabric length after shrinkage) / non-woven fabric length before shrinkage × 100%.

[0031] The crystallization temperature of the thermoplastic polyurethane elastomer was obtained by DSC testing. The program settings were as follows: the thermoplastic polyurethane elastomer was first heated from -10°C to 250°C at a heating rate of 20 K / min, then cooled from 250°C to -80°C at a cooling rate of 10 K / min, and then maintained at -80°C for 2 minutes. Finally, the temperature was increased from -80°C to 250°C at a heating rate of 20 K / min to complete the test.

[0032] The hard segment content is calculated according to the following formula: hard segment content = (mass of isocyanate + mass of chain extender) / (mass of isocyanate + mass of chain extender + mass of polyol).

[0033] Example 1:

[0034] Thermoplastic polyurethane elastomer is added to a screw extruder, heated and melted, and extruded through the screw to a meltblown die. The fabric is then stretched by hot air and then cooled by cold air in a cooling channel to produce a heat-shrinkable nonwoven fabric. During the production process, the following conditions were met: the screw extrusion temperature was 220°C; the meltblown die temperature was 230°C; the hot air temperature was 230°C; the air pressure was 0.3 MPa; and the cold air temperature was 8°C.

[0035] The thermoplastic polyurethane elastomer used in this example has a crystallization temperature of 9° C. and a hard segment content of 13%. The raw material composition includes a polyol, an isocyanate, and a chain extender. The polyol is polybutylene adipate, and the number average molecular weight of the polyol is 3000 g / mol. The isocyanate is MDI, and the chain extender is BDO.

[0036] The heat shrinkage rate of the heat-shrinkable non-woven fabric prepared in this embodiment at 50° C. is 56%.

[0037] Example 2:

[0038] Thermoplastic polyurethane elastomer is added to a screw extruder, heated and melted, and extruded through the screw to a meltblown die. The fabric is then stretched by hot air and then cooled by cold air in a cooling channel to produce a heat-shrinkable nonwoven fabric. During the production process, the following conditions were met: the screw extrusion temperature was 220°C; the meltblown die temperature was 230°C; the hot air temperature was 230°C; the air pressure was 0.3 MPa; and the cold air temperature was 8°C.

[0039] The thermoplastic polyurethane elastomer used in this example has a crystallization temperature of 14° C. and a hard segment content of 13%. The raw material composition includes a polyol, an isocyanate, and a chain extender. The polyol is polybutylene adipate, and the number average molecular weight of the polyol is 3000 g / mol. The isocyanate is HDI, and the chain extender is BDO.

[0040] The heat shrinkage rate of the heat-shrinkable non-woven fabric prepared in this embodiment at 50° C. is 67%.

[0041] Example 3:

[0042] Thermoplastic polyurethane elastomer (TPE) was added to a screw extruder, heated and melted, and extruded through a meltblown die. The fabric was then stretched by hot air and cooled by cold air in a cooling channel. During the production process, the following conditions were met: screw extrusion temperature of 220°C; meltblown die temperature of 230°C; hot air temperature of 230°C; air pressure of 0.3 MPa; and cold air temperature of 20°C. The resulting fabric was sticky and could not be formed and wound.

[0043] The thermoplastic polyurethane elastomer used in this example has a crystallization temperature of 9° C. and a hard segment content of 13%. The raw material composition includes a polyol, an isocyanate, and a chain extender. The polyol is polybutylene adipate, and the number average molecular weight of the polyol is 3000 g / mol. The isocyanate is MDI, and the chain extender is BDO.

[0044] Example 4:

[0045] Thermoplastic polyurethane elastomer is added to a screw extruder, heated and melted, and extruded through the screw to a meltblown die. The fabric is then stretched by hot air and then cooled by cold air in a cooling channel to produce a heat-shrinkable nonwoven fabric. During the production process, the following conditions were met: the screw extrusion temperature was 220°C; the meltblown die temperature was 230°C; the hot air temperature was 230°C; the air pressure was 0.3 MPa; and the cold air temperature was 8°C.

[0046] The thermoplastic polyurethane elastomer used in this embodiment has a crystallization temperature of 17°C and a hard segment content of 16%. The raw material composition includes polyol, isocyanate and chain extender, wherein the polyol is polyhexanediol adipate, the number average molecular weight of the polyol is 3000 g / mol, the isocyanate is MDI, and the chain extender is HDO.

[0047] The heat shrinkage rate of the heat-shrinkable non-woven fabric prepared in this embodiment at 50° C. is 79%.

[0048] Example 5:

[0049] Thermoplastic polyurethane elastomer is added to a screw extruder, heated and melted, and extruded through the screw to a meltblown die. The fabric is then stretched by hot air and then cooled by cold air in a cooling channel to produce a heat-shrinkable nonwoven fabric. During the production process, the following conditions were met: the screw extrusion temperature was 220°C; the meltblown die temperature was 230°C; the hot air temperature was 230°C; the air pressure was 0.3 MPa; and the cold air temperature was 8°C.

[0050] The thermoplastic polyurethane elastomer used in this embodiment has a crystallization temperature of 10°C and a hard segment content of 13%. The raw material composition includes a polyol, an isocyanate, and a chain extender, wherein the polyol is polybutylene adipate, the number average molecular weight of the polyol is 4000 g / mol, the isocyanate is MDI, and the chain extender is HDO.

[0051] The heat shrinkage rate of the heat-shrinkable non-woven fabric prepared in this embodiment at 50° C. is 61%.

[0052] Example 6:

[0053] Thermoplastic polyurethane elastomer is added to a screw extruder, heated and melted, and extruded through a screw into a meltblown die. The fabric is then stretched by hot air and cooled by cold air in a cooling channel to produce a heat-shrinkable nonwoven fabric. During the production process, the following conditions were met: the screw extrusion temperature was 230°C; the meltblown die temperature was 240°C; the hot air temperature was 250°C; the air pressure was 0.3 MPa; and the cold air temperature was 8°C.

[0054] The thermoplastic polyurethane elastomer used in this example has a crystallization temperature of 65° C. and a hard segment content of 35%. The raw material composition includes a polyol, an isocyanate, and a chain extender. The polyol is polybutylene adipate, and the number average molecular weight of the polyol is 2000 g / mol. The isocyanate is MDI, and the chain extender is BDO.

[0055] The heat shrinkable nonwoven fabric prepared in this embodiment has a heat shrinkage rate of 0 at 50°C.

[0056] The parameter conditions of each embodiment and the test results of the thermal shrinkage performance of the obtained nonwoven fabric are summarized in Table 1.

[0057] Table 1

[0058]

[0059] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A heat shrinkable nonwoven fabric, characterized in that: The heat-shrinkable non-woven fabric is obtained by melt-blowing a thermoplastic polyurethane elastomer with a crystallization temperature not exceeding 40° C. into a fabric and then cooling the fabric at 0-15° C.

2. The heat-shrinkable nonwoven fabric according to claim 1, characterized in that: The heat-shrinkable nonwoven fabric can be heat-shrinked at a temperature of 40-80°C.

3. The heat-shrinkable nonwoven fabric according to claim 1, wherein: The isocyanate as one of the raw materials for forming the thermoplastic polyurethane elastomer includes at least one of MDI, TDI, HDI, and HMDI.

4. The heat-shrinkable nonwoven fabric according to claim 1, wherein The chain extender, which is one of the raw materials for forming the thermoplastic polyurethane elastomer, includes at least one of BDO and HDO.

5. The heat-shrinkable nonwoven fabric according to claim 1, wherein: The polyol that is one of the raw materials for forming the thermoplastic polyurethane elastomer is a polyester polyol.

6. The heat-shrinkable nonwoven fabric according to claim 5, characterized in that: The raw materials of the polyester polyol include dibasic acid and diol, the dibasic acid includes at least one of adipic acid and succinic acid, and the diol includes at least one of BDO and HDO.

7. The heat-shrinkable nonwoven fabric according to claim 1 or 5, characterized in that: The number average molecular weight of the polyol is 2500-4500 g / mol.

8. The heat-shrinkable nonwoven fabric according to claim 1, wherein The hard segment content in the thermoplastic polyurethane elastomer is 10%-25%.

9. The method for preparing a heat-shrinkable nonwoven fabric according to any one of claims 1 to 8, characterized in that: The melt-blown process is adopted, and the preparation method specifically includes: The thermoplastic polyurethane elastomer is added to a screw extruder, and the thermoplastic polyurethane elastomer is extruded to a melt-blowing die through a screw while being heated and melted, and then sprayed onto a receiving curtain under the action of hot air drawing, and then the receiving curtain is cooled in a cavity at 0-15°C to obtain the heat-shrinkable non-woven fabric.

10. The method for preparing a heat-shrinkable nonwoven fabric according to claim 9, wherein: The screw extrusion temperature is 200-260℃; The temperature of the meltblowing die head is 200-250℃; The temperature of the hot air is 200-250°C and the air pressure is 0.1-0.5MPa.

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