HIGH-STRENGTH, HIGH-MODULUS AND HIGH-MELTING POINT PVA FIBER AND METHOD FOR MANUFACTURING SAME

Abstract

 A high-strength, high-modulus and high-melting point PVA fiber is a PVA fiber, manufactured by using a boron-containing gel-wet spinning method, having the strength greater than or equal to 13.5 CN/dtex, the modulus greater than or equal to 320 CN/dtex, the initial melting point greater than or equal to 108°C, the total stretching multiple up to 13.0∼14.5 times . The product has excellent performance and wide application range and is appropriate for the field of high-end industries. Also disclosed is a method for manufacturing the fiber.

Description

FIELD OF THE INVENTION

[0001] The invention relates to a synthetic fiber and a method for preparing the same, and in particular, to polyvinyl alcohol (PVA) fiber and a method for preparing the same, and more particularly, to a high-strength, high-modulus and high-melting point PVA fiber and a method for manufacturing the same.

BACKGROUND OF THE INVENTION

[0002] The use of PVA fiber is closely related to the performance, such as the strength, the modulus and the melting point. The fibers that the strength is 3~5CN/dtex, the modulus is 60~80CN/dtex, and the initial melting point is 85∼90 °C are mainly used for civil use; The fibers that the strength is 10∼11CN/dtex, the modulus is 220∼ 250CN/dtex, and the initial melting point is 100 °C are mainly used for the strengthening of the general cement products. The higher performance PVA fibers are not only used for reinforcing the cement products, but also used for reinforcing the high-performance concrete, the highway asphalt, the plastic, and the rubber.

[0003] The methods for manufacturing the PVA fiber include the conventional wet method, the dry wet method, the gel method, the boron-containing wet method etc. For the fiber obtained by the conventional wet method and the dry wet method, the Quality index is low, the strength is 3∼5CN/dtex, the modulus is 60~80CN/dtex, and the initial melting point is 85∼90 °C. As the initial melting point is low, the fiber must be treated with the condensed formaldehyde to meet the application requirements. The fiber is mainly used as the civil raw materials for replacing the cotton. With the development of petrochemical industry, the synthetic fibers such as terylene developed rapidly in the 1980s, but due to the inherent flaws of the PVA fibers, such as poor dyeability, low elasticity, poor dimensional stability, and poor maintenance, the PVA fiber automatically exits the field of garment. However, since the PVA fiber has excellent resistances to acid, alkali, light, weather and corrosion, it can be adapted to more extensive industry area as long as there is a big breakthrough in the strength and modulus of the fiber.

[0004] PVA as a polymer material itself is a flexible chain polymer of linear macromolecules, has the planar zigzag type structure. The theoretical strength and theoretical modulus are 210 CN/dtex and 1900 CN/dtex respectively. As long as the spinning method is suitable to overcome the excessive entanglement phenomenon caused by the hydrogen bonding interactions between macromolecules in the early stage of fiber formation, the high magnification stretching can be made, thereby obtaining a higher strength and modulus fibers. The gel method or the boron-containing wet method can be used to improve the PVA macromolecular entanglement phenomenon in the early stage of fiber formation. However, there are difficulties such as solvent recovery in the gel method, so there is no large industrial equipment at present. In the existing boron-containing wet process, the PVA Resin with the average polymerization degree equal to 1700 is used as raw materials, a certain amount of boron additives are added when preparing the spinning solution, the total stretching multiple reaches 10.0∼11.0 times, the fiber strength reaches about 11 CN/dtex, the modulus reaches 230∼280 CN/dtex, and the initial melting point is 85∼90 °C by the post-processing of fiber, but the product is also difficult to meet the requirements of the special fields.

SUMMARY OF THE INVENTION

[0005] The invention is directed to provide a high-strength, high-modulus and high-melting point PVA fiber to overcome the defects of the conventional art and satisfy the need in the application fields. The technical problems to be resolved are how to improve boron-containing wet spinning manufacturing method, so as to further improve the molecular structure of the proto-fibers, and avoid the PVA macromolecules entanglement in the early stage of fiber formation to improve the PVA fibers quality.

[0006] A high-strength, high-modulus and high-melting point PVA fiber called in the invention refers to the fiber that the strength being greater than or equal to 13.5 CN/dtex, the modulus being greater than or equal to 320 CN/dtex, the initial melting point being greater than or equal to 108 °C.

[0007] A method for manufacturing the high-strength, high-modulus and high-melting point PVA fiber is a boron-containing gel-wet spinning method. The method includes spinning solution (or spinning dope) preparation, filtration, defoaming, spinning and post-processing. The differences between said method and the existing boron-containing wet spinning method lie in the spinning solution and the spinning coagulating bath. The spinning solution preparation is/includes selecting PVA resins with an average polymerization degree of 1700∼ 2000, and adding the PVA resins, boric acid and copper sulfate as the additive to the water of 90∼100 °C to prepare the spinning solution, which contains 15 ∼ 17 wt% PVA (mass percent ratio, the same thereinafter), 1.2∼1.6 wt% boric acid (H₃BO₃), 0.05∼0.1 wt% copper sulfate (CuSO₄). The spinning solution is spurted by spinneret to form proto-fibers, which enters the spinning coagulating bath (the first bath). The spinning coagulating bath includes or consists of sodium hydroxide (NaOH) of 15∼50g/L, sodium sulfate (Na₂SO₄) of 300∼390g/L, and H₃BO₃ of 5~15g/L. The processing after the first bath in the present invention is the same as the post-processing in the boron-containing wet processing.

[0008] The method of the present invention selects the PVA with the polymerization degree greater than or equal to 1700 as the raw materials, adjusts the content of H₃BO₃ to 1.2∼1.6 wt% when preparing the spinning solution, adds CuSO₄ of 0.05~0.1 wt% at the same time to increase the kinematic viscosity of the spinning solution from 4~5 Pa · s to 6∼8 Pa·s. At the moment that the proto-fibers are spurted from the spinneret, the proto-fibers react immediately with the specific coagulating bath to generate the gel, that is to say, the coagulating bath strengthens the gel effect of the proto-fibers, and weakens the coagulating function of the proto-fibers at the same time, significantly reducing the PVA macromolecules entanglement in the early stage of fiber formation and greatly increasing the probability of the coupling. The total stretching multiple increases from the existing 10.0 ∼ 11.0 times to 13.0 ∼ 14.5 times by the fiber post-processing.

[0009] The boron-containing gel-wet spinning manufacturing method realizes the purpose of improving the PVA fiber quality by improving the molecular structure of the proto-fibers, and avoiding the PVA macromolecules entanglement in the early stage of fiber formation.

[0010] Compared with the existing boron-containing wet spinning method, the beneficial effects of the present invention lie in that:

1. The invention makes the single boron-containing wet spinning method of the PVA fiber manufacturing method extend to the boron-containing gel-wet spinning method, thereby effectively improving the total stretching multiple of the proto-fibers, so the strength, modulus and melting point of the prepared PVA fibers are significantly better than the PVA fibers quality obtained by the boron-containing wet spinning method.

2. The high-strength and high-modulus PVA fiber produced by the invention method has the strength greater than or equal to 13.5 CN/dtex, the modulus greater than or equal to 320 CN/dtex, the initial melting point greater than or equal to 108 °C.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 is the process flow chart of the PVA fiber manufacture method in the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] The non-limiting embodiments are described below in conjunction with the accompanying drawing.

[0013] The process flow chart includes spinning solution preparation, filtration, defoaming, spinning and post-processing.

[0014] The spinning solution preparation includes or consists of feeding, washing and dissolving as seen in the accompanying drawing.

[0015] The post-processing includes neutralization, wet drafting, washing, drying, preheating, high multiple extension, cooling, cutting off, packing, etc. as seen in the accompanying drawing.

[0016] The parameters set for each step respectively are that:

PVA as raw material: the degree of polymerization is 1700∼2000, the content of residual acetate is 0.2∼0.5%, the content of sodium acetate after washing with water is 0.2∼0.5%;

Additives preparation: the content of H₃BO₃ is 1.2∼1.6 wt%, the content of CuSO₄ is 0.05~0.1 wt%;

Dissolving: the dissolving temperature is 95 ∼ 100 °C, the dissolving time is 90 ∼ 120 minutes, the concentration of stock solution is 15∼17 wt%, the kinematic viscosity is 6∼8 Pa·s;

Defoaming: the defoaming temperature is 98∼100 °C, the defoaming time is 4∼6 hours;

Spinning: in the spinning coagulating bath, the content of NaOH is 15∼50 g/L, the content of Na₂SO₄ is 300∼390 g/L, and the content of H₃BO₃ is 5∼15 g/L; the negative stretch ratio is -15∼-40% in the bath, the spinning air bath stretching multiple is 2∼3 times;

Neutralization, wet drafting: the neutralization bath and wet drafting coagulating bath each includes or consists of 300∼390 g/L Na₂SO₄ and 5∼50 g/L H₂SO₄; the wet heat stretching multiple is 2.0∼ 2.8 times; and the wet heat stretching temperature is 80∼95 °C;

Washing: the soft water temperature is 30∼45 °C;

Preheating, extension: the preheating temperature is 210∼235 °C, the extension dry stretching multiple is 2.0∼4.0 times, the extension temperature is 210∼235 °C;

Cooling: the tow temperature after roller cooling is 25∼45 °C.

Embodiment 1:

[0017] 

PVA as raw material: the degree of polymerization is 1720, the content of residual acetate is 0.21%, and the content of sodium acetate after washing with water is 0.23%;

Additives preparation: the content of H₃BO₃ is 1.35 %; the content of CuSO₄ is 0.05 %;

Dissolving: the dissolving temperature is 97 °C, the dissolving time is 110 minutes, the concentration of stock solution is 16.8 wt%;

Defoaming: the defoaming temperature is 98 °C, the defoaming time is 4 hours;

Spinning: in the spinning coagulating bath, the content of NaOH is 18 g/L, the content of Na₂SO₄ is 310 g/L, the content of H₃BO₃ is 5.5 g/L, the negative stretching ratio is -20.8 % in the bath, the spinning air bath stretching multiple is 2.08 times;

Neutralization, wet drafting: in the neutralization bath and wet drafting coagulating bath, the content of Na₂SO₄ is 310 g/L, the content of H₂SO₄ is 12 g/L, the wet heat stretching multiple is 2.3 times, the wet heat stretching temperature is 85 °C;

Preheating, extension: the preheating temperature is 225 °C, the extension dry stretching multiple is 2.93 times, the extension oven temperature is 212 °C;

[0018] The main technical quality indexes of PVA fiber in the embodiment 1 are as follows:

index name	Unit	index value
Rupture strength	CN/dtex	13.74
Modulus	CN/dtex	330.88
Initial melting temperature	°C	109.65
fineness/size	dtex	1.94
Elongation	%	6.7

Embodiment 2:

[0019] 

PVA as raw material: the degree of polymerization of 1820, the content of residual acetate is 0.35%, the content of sodium acetate after washing with water is 0.2%;

Additives preparation: H₃BO₃ of 1.52 wt%, CuSO₄ of 0.05 wt%;

Dissolving: the dissolving temperature is 98 °C, the dissolving time is 120 minutes, the concentration of stock solution is 16.0 wt%;

Defoaming: the defoaming temperature is 98 °C; the defoaming time is 4.5 hours;

Spinning: in the spinning coagulating bath, the content of NaOH is 35 g/L, the content of Na₂SO₄ is 330 g/L, the content of H₃BO₃ is 6.5g/L, the negative stretch ratio is -30.8% in the bath, , the spinning air bath stretching multiple is 2.08 times;

Neutralization, wet drafting: in the neutralization bath and wet drafting coagulating bath, the content of Na₂SO₄ is 330 g/L, the content of H₂SO₄ is 40 g/L, the wet heat stretching multiple is 2.0 times, the wet heat stretching temperature is 88 °C;

Preheating, extension: the preheating temperature is 225 °C, the extension dry stretching is 3.44 times, and the extension oven temperature is 228 °C;

[0020] The main technical quality indicators of PVA fiber in the embodiment 2 are as follows:

The indicator name	Unit	index value
Rupture strength	CN/dtex	13.85
Modulus	CN/dtex	340.02
Initial melting temperature	°C	110.52
fineness/size	dtex	2.12
Elongation	%	5.88

Embodiment 3:

[0021] 

PVA as raw material: the degree of polymerization is 1950, the content of residual acetate is 0.28%, and the content of sodium acetate after washing with water is 0.40%;

Additives preparation: the content of H₃BO₃ is 1.25 wt%, the content of CuSO₄ is 0.08 wt%;

Dissolving: the dissolving temperature is 99 °C, the dissolving time is 120 minutes, the concentration of stock solution is 15.8 wt%;

Defoaming: the defoaming temperature is 99 °C; the defoaming time is 5 hours;

Spinning: in the spinning coagulating bath, the content of NaOH is 45 g/L, the content of Na₂SO₄ is 330 g/L, and the content of H₃BO₃ is 6 g/L; the negative stretch ratio is -29.9% in the bath; the spinning air bath stretching multiple is 2.06 times;

Neutralization, wet drafting: in the neutralization bath and wet drafting coagulating bath, the content of Na₂SO₄ is 340 g/L, the content of H₂SO₄ is 50 g/L, the wet heat stretching multiple is 2.5 times, the wet heat stretching temperature is 92 °C;

Preheating, extension: the preheating temperature is 230 °C, the extension dry stretching multiple is 2.8 times, the extension oven temperature is 220°C;

[0022] The main technical quality indicators of PVA fiber in the embodiment 3 are as follows:

The indicator name	Unit	index value
Rupture strength	CN/dtex	14.01
Modulus	CN/dtex	348.33
Initial melting temperature	°C	111.23
fineness/size	dtex	2.01
Elongation	%	6.08

Claims

1. A high-strength, high-modulus and high-melting point PVA fiber, characterized in that, the strength of the PVA fiber being greater than or equal to 13.5 CN/dtex, the modulus being greater than or equal to 320 CN/dtex, the initial melting point being greater than or equal to 108 °C.

2. A method of manufacturing the high-strength, high-modulus and high-melting point PVA fiber of claim 1 includes spinning solution preparation, filtration, defoaming, spinning and post-processing steps, characterized in that, the spinning solution preparation includes selecting PVA resins with an average polymerization degree of 1700∼2000, and adding the PVA resins together with boric acid and copper sulfate as the additives to the water of 90∼100 °C to prepare the spinning solution which includes 15∼17 wt% PVA, 1.2∼1.6 wt% boric acid, and 0.05∼0.1 wt% copper sulfate; and spinning coagulating bath includes 15∼50 g/L sodium hydroxide (NaOH), 300∼390 g/L sodium sulfate, and 5∼15 g/L boric acid.

Drawing