JPS6352130B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a monofilament using a melt-spinning and drawing method of thermoplastic resin. More specifically, the present invention relates to a method for producing high-strength, high-knot, high-strength filaments by melt extrusion and drawing through a specific oval nozzle. Conventionally, monofilaments obtained by melt-spinning and drawing thermoplastic resins have nozzles with a perfect circular cross-section, or long axis/short axis = 1.8~
4.0 and an area of 3.14 mm ² or more is specially arranged (Japanese Patent Publication No. 51-32724) to extrude the raw yarn, which is usually passed through a cooling water tank or, if necessary, solidified using a treatment bath. This was then stretched at a low magnification of 3 to 10 times at the optimum temperature depending on the resin used to obtain a product with a linear strength of 2 g/d to 7 g/d, but in order to make it even stronger, , 11-20
It is necessary to stretch at a high magnification of 2 times, and in this case, although the linear strength increases, there is a drawback that the knot strength decreases significantly with the magnification. In addition, in order to perform high-magnification drawing, the fineness of the undrawn yarn increases.
During the cooling process, vacuum bubbles were generated due to misalignment in the heat shrinkage inside the filament, and these bubbles caused a problem in which stretching breaks occurred frequently. The present inventors have arrived at the present invention as a result of intensive studies aimed at solving these problems of decrease in knot strength and stretching breakage, and providing a method for producing a monofilament with a well-balanced combination of high strength and high knot strength. . That is, the thermoplastic resin is expressed by the following formula for the cross-sectional area ^S of the flow path, the maximum moment of inertia I, the major axis a, and ^{the minor} axis b. This is a method for producing a monofilament characterized by melt extrusion through an elliptical nozzle having a cross section satisfying a/b≦1.6 and stretching the extrudate. However, the maximum moment of inertia of area I=max(Ix,
Iy) In other words, it refers to the larger moment of inertia with respect to the main axis x-axis or y-axis passing through the center of gravity of the figure. The cross-sectional shape of the nozzle applied in the present invention is within the scope of the claims (cross-sectional area S is 0.503 mm ² to 3.14 mm ² , maximum moment of inertia I is 0.09 S ² mm ⁴ to 0.30 S ² mm ⁴ , long axis a Although there is no particular restriction as long as the ratio a/b of 1.2 to 1.6) is satisfied, an elliptical shape is preferable. This is because the more complicated the cross-sectional shape of the nozzle, the more difficult and expensive it becomes to process the nozzle. Nozzle L/De [L: Land length (mm) De:

[Formula]] is suitably 10 to 15, and there is no particular restriction on the shape of the land, but
Straight is preferable from the viewpoint of processing accuracy and cost. In the nozzle hole arrangement, it is preferable that the axis of whichever has the smaller second moment of area with respect to the main axis x-axis passing through the center of gravity of the cross-sectional figure or the y-axis is along the nozzle hole circumference. This is because if the arrangement is reversed, the effect of eliminating the deviation of heat shrinkage during the cooling process of the undrawn yarn will be reduced. in this case,
If the cross-sectional area S is less than 0.503 mm ² , it will be more difficult to process the nozzle compared to a perfect circle, melt fractures will easily occur during spinning, and high-magnification stretching will not be possible.
Moreover, when the cross-sectional area S exceeds 3.14 mm ² , the spinning pressure is low, resulting in large discharge unevenness and easy breakage directly under the nozzle, resulting in poor yield. For this reason, the cross-sectional area S is
0.503mm ² ≦S≦3.14mm ² Must be satisfied.
At the same time, the maximum moment of inertia I is 0.09S ² mm ⁴
If it is less than (usually I = S ₂ /4π = 0.0796S ² mm ⁴ in a perfect circle), vacuum bubbles will occur in the undrawn yarn, making it impossible to draw at a high draw ratio, and even if it is possible to draw at a high draw ratio, the drawing will break. The yield is poor due to frequent occurrence and the nodule strength is low. Maximum cross section 2
If the moment of order I exceeds 0.30S ² mm ⁴ , these problems will be solved, but the monofilament will have a thin portion, which will easily tear during stretching and will be difficult to process into ropes, etc., which is not suitable. Therefore, the maximum moment of inertia I is 0.09S ²
It is necessary to satisfy mm ⁴ ≦I≦0.30S ² mm ⁴ . When S and I satisfy the above conditions, and as long as the ratio of major axis a/minor axis b is an ellipse of 1.2 to 1.6, the linear strength is high, and the nodule strength shows a fairly high value and is well-balanced. A monofilament is obtained. In addition, the draft ratio f [f = V ₁ /V ₀ , V ₀ is the extrusion linear velocity (m/min) at the nozzle exit, and V ₁ is the withdrawal linear velocity (m/min) should be 1.00≦f≦3.50. Yes (usually 0.5 to 1.5 for a perfect circle); if it is less than 1.0, the strength will not increase due to insufficient molecular orientation, and if it exceeds 3.5, problems such as nozzle breakage and whitening of the product will easily occur during molding. , the draft ratio f is also 1.00≦
It is preferable to satisfy f≦3.50. The resin extruded from the above-mentioned nozzle is usually passed through a cooling water tank or solidified using a treatment bath if necessary to create a raw thread, which is then stretched at a high magnification at an optimal temperature depending on the resin used. . The high-magnification stretching may be carried out in one stage by a wet method, or may be carried out using a heated roll method, a hot plate method, or a heated air bath method, or may be performed in multiple stages using a combination of any of these methods. Although the draw ratio has the most significant effect on the linear strength of the finished fibrous material, the method of the present invention allows for high draw ratios, resulting in high strength filaments. In addition, the knot strength is 30 to 50% higher when compared at the same stretching ratio, and the elongation is also high. The thermoplastic resin to which the present invention is applied is not particularly limited as long as it can be melt-spun, such as nylon, polyester, polyethylene, polypropylene, etc., but in particular high-density polyethylene, with a melt index of 0.1 g/ 10min～2.0g/
10 min, the density is ^preferably 0.950 to 0.960 g/cm. Such resin may be a copolymer with different monomers, and may also contain antioxidants, lubricants, ultraviolet absorbers, quenching agents, stabilizers, colorants, blowing agents, flame retardants, etc., as necessary. May contain. According to the present invention, it is possible not only to greatly improve the strength of conventional thermoplastic resin monofilament, but also to achieve stable production without yarn breakage (hereinafter referred to as "drawability", expressed as the number of yarn breakages per hour). ) becomes possible. In addition, the rope fishing nets that will be processed in the future are expected to be lightweight and resource-saving, and have many uses. For example, if you want to collect seafloor minerals such as manganese by attaching a mining basket to a rope, you would need a rope with a strength of 100 tons.
If the conventional monofilament of about 7 g/d is used, the rope will be about 15 cm in diameter, which is unrealistically thick. However, if the strength of the monofilament according to the present invention is 12 g/d (implemented) (See Examples 1 and 2), the diameter of the above rope is approximately 1/3
5cm, making it a practical rope. The present invention will be explained in more detail below by giving Examples and Comparative Examples. Examples 1-2, Comparative Examples 1-6 Melt index 0.45g/10min, density 0.955
A monofilament was produced by melt-extruding high-density polyethylene of g/cm ³ under the conditions shown in Table 1, cooling with water, and stretching in multiple stages. The results obtained are shown in Table 1. Note that the following conditions are common to each Example and each Comparative Example. Extruder: 40m/mφ, L/D=24 Screw: Compression ratio 3.2 Breaker plate: 2.0φ×86H Screen pack: 80, 100, 120, 150, 100 mesh, total 5 sheets Number of nozzle holes: 40 extruder temperature (℃); C ₁ 160, C ₂ 250, C ₃ 290,
D ₁ 290, D ₂ 290 Air gap; 5cm Cooling water tank temperature; 17℃ Stretching temperature; 1st stage 100℃, wet 2nd stage 115℃, heating roll 3rd 115℃, heating roll 4th 120℃, heating roll Monofilament physical property measurement method; JIS L
According to 1070, 1073. However, chuck distance: 30cm Tensile strength: 30cm/min Room temperature: 20℃ Humidity: 60%

【table】

[Table] By using the production method of the present invention, stretchability is improved and yarn breakage is almost completely eliminated. Regarding strength, in Comparative Examples 1 to 4, the maximum moment of inertia of area does not satisfy this condition, and in Comparative Example 1, the linear strength is low, probably because the draft f is low and the stretching ratio is not increased. low. In Comparative Example 2, the draft f
However, the stretching ratio does not increase and the linear strength is still low. In Comparative Example 3, the maximum second moment of area I
does not satisfy this condition, it is possible to stretch at a high magnification and the linear strength increases, but the stretchability is very poor. In Comparative Example 4, the maximum moment of inertia I of area still does not satisfy this condition, and the stretchability is poor. Comparative Example 5 has an oval shape even though S, I, and a/b are satisfied, and Comparative Example 6 has a dumbbell shape even though S and I are satisfied, and a/b is not satisfied. Perhaps because all of these conditions are not met, a monofilament with high strength and high knot strength cannot be obtained. Only in Examples 1 and 2 can stable production of high strength, high knot strength monofilaments be achieved.

Claims (1)

[Claims] 1. The thermoplastic resin has a flow path cross-sectional area S, a maximum cross-section 2
From an elliptical nozzle with a cross section that satisfies the following formula for the second moment and the ratio of major axis a and minor axis b: 0.503mm ² ≦S≦3.14mm ² 0.09≦I/S ² ≦0.30, 1.2≦a/b≦1.6 A method for producing a monofilament, comprising melt extrusion and stretching the extrudate. However, the maximum moment of inertia of area I=max(Ix,
Iy) That is, the moment of inertia of area with respect to the main axes x-axis and y-axis passing through the center of gravity of the figure, whichever is greater.