JPH02289162A - Production of nonwoven fabric of melt blow - Google Patents

Abstract

PURPOSE:To stably obtain the title high-quality nonwoven fabric by setting slit widths, set packs and jetting pressure of hot gas laid at left and right sides of die nose unsymmetrically with respect to left and right of the die nose and pulling and thinning a molten polymer. CONSTITUTION:In spinning a molten polymer by using a spinning die 1 equipped with a die nose 4 having an orifice 9 to deliver a molten polymer and symmetric slits 10a and 10b at left and right of the die nose, first, slit widths L1 and L2, set packs H1 and H2 and/or jetting pressure P1 and P2 of hot gas jetted from the slits formed at the left and right of the die nose are set unsymmetrically with respect to the left and right of the die nose, the molten polymer is pulled and thinned and further melt blown fibers are collected in a state of nonwoven fabric to give the aimed high-quality and elegant nonwoven fabric while preventing occurrence of polymer balls.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing non-woven fabrics using a melt-blowing method. The present invention relates to a method for producing a melt-blown fibrous non-woven fabric that is effective in producing a melt-blown non-woven fabric made of ultra-fine fibers.

[Prior art] In recent years, battery separators, filter materials, medical masks,
The industrial manufacturing method of nonwoven fabrics by the melt blowing method, which has been used in many application fields such as wipers, mainly involves blowing molten thermoplastic resin through a number of orifice holes arranged in a row at the tip of a die. High-temperature heated air is injected onto the discharged resin while the resin is being discharged from the die, and the ultra-fine melt-blown fibers, which have been made fine by the traction force of the jet flow, are placed in the form of a non-woven fabric on a net conveyor installed below the die. It is a supplementary collection.

By the way, in such a manufacturing method, polymer beads are often generated at the confluence where the molten resin and heated air collide, and it has been found that this is one of the causes of quality deterioration such as uneven area weight and decreased strength of the nonwoven fabric. ing.

In order to obtain such a high-quality nonwoven fabric that does not generate polymer beads, it is effective to make the gas flow injected from the die onto the net conveyor over the entire width of the obtained nonwoven fabric into a state with as little turbulence as possible. be.

Conventional techniques of the melt blow spinning method that take these points into consideration include, for example, Japanese Patent Application Laid-Open No. 48-48921;
The invention described in US Pat. No. 3,970,417 and the like is known.

However, in the invention described in the former patent publication, the spinning die has a basic configuration including a die nose having a large number of orifices, a lip plate for forming slits that are flow paths for heating gas, etc. However, as a means to prevent the above-mentioned polymer balls from occurring, the die should be made as precisely as possible, that is, the diameter of the orifice, the pitch, etc. should be finished as precisely as possible, and the slit from which hot gas can be ejected should be made as precisely as possible. The problem with this method is that it is necessary to take into account thermal strain as much as possible in order to make the gap as uniform as possible in the width direction of the die, and that extremely advanced processing technology is required.

On the other hand, the invention described in the latter US patent specification, as shown in FIGS. Heating can be achieved by adjusting the valves installed in each slit channel, or by adjusting the left and right slit intervals to equal intervals using push-pull bolts, as shown in Figure 5 of the same specification. The amount of gas injected and the slit gap are made as uniform as possible in the width direction of the die.

[Problems to be Solved by the Invention] However, in the prior art as described above, when trying to uniformly adjust the amount of heated gas injected from the left and right slits, the slit gap, etc. on the left and right sides, the heated air supply means and This is completely impractical as it requires very high precision machining and expensive manufacturing costs for the die, etc. Also, adjusting the slit gap using push-pull bolts requires adjusting a large number of bolts in the width direction of the die. However, in order to obtain a precise slit gap with high precision, many years of experience, skill, intuition, labor, etc. are required from each operator.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to manufacture the above-mentioned high-precision die, and also to produce a die without necessarily relying on the experience or intuition of an expert. In both cases, it is an object of the present invention to provide a method for producing a melt-blown nonwoven fabric that is significantly effective in preventing the formation of polymer balls and producing a nonwoven fabric of good quality and quality.

[Means for Solving the Problems] The method for producing a melt-blown nonwoven fabric of the present invention that achieves the above-mentioned object includes a die nose having an orifice for discharging molten polymer and a pair of slits for injecting heated gas. Using spinning dies formed on the left and right sides of the die nose, the molten polymer is discharged from the orifice while injecting heated gas from the pair of slits, and the molten polymer is drawn and thinned to be spun as melt-blown fibers. The slit width (L1, L2) formed on the left and right sides of the die nose, the setback (H1, H2), and the injection pressure (P
1. A melt-blown nonwoven fabric characterized in that at least one of P2) is set asymmetrically on the left and right sides of the die nose to perform traction thinning of the molten polymer, and further collect the melt-blown fibers in the form of a nonwoven fabric. This is a manufacturing method.

In addition, as another method for producing a melt-blown nonwoven fabric of the present invention, a die nose having an orifice for discharging a molten polymer and a pair of slits for injecting heated gas are formed on the left and right sides of the die nose. Using a die, the molten polymer is discharged from the orifice while injecting heated gas from the pair of slits, and when the molten polymer is drawn and thinned to be spun as melt-blown fibers, This is a method for manufacturing a melt-blown non-woven fabric, characterized in that the amount of heated gas injected is different between the left and right slits to perform traction thinning, and further the melt-blown fibers are collected in the form of a non-woven fabric.

[Function] Hereinafter, the method for producing a melt-blown nonwoven fabric of the present invention will be described in more detail based on the drawings and the like.

In the present invention, a spinning die typically includes a die nose in which a large number of orifices are formed in rows in the longitudinal direction of the die, and lip plates provided through slits on the left and right sides of the die nose. As for the tip of this spinning die, in addition to the lip plate system, the air jetting part has an upper knife (inner blade) and a lower knife (
Other types of spinning dies, such as a so-called air knife type spinning die surrounded by an outer blade (outer blade), may also be used.

The manufacturing method of the melt-blown nonwoven fabric of the present invention is based on the slit width (L1, L2) formed on the left and right sides of the die nose, which will be described later.
, setback (H+, H2), and injection pressure of heated gas ejected from the slit (P, P2),
The molten polymer is pulled and thinned with at least one set asymmetrically on the left and right sides of the die nose, and the melt blown fibers are collected in the form of a nonwoven fabric,
Alternatively, the amount of heated gas injected from slits formed on the left and right sides of the die nose is varied between the left and right slits to perform traction thinning, and the melt-blown fibers are further collected in the form of a nonwoven fabric.

FIG. 1 is a schematic cross-sectional view showing an example of the structure of a lip plate type spinning die that can be used to carry out the above-described method for producing a melt-blown nonwoven fabric of the present invention, and FIG. FIG. 2 is a schematic cross-sectional view of a main part (discharge block part) showing an example of the structure of an air knife type spinning die that can be used to carry out the method for producing a melt-blown nonwoven fabric of the present invention.

In FIG. 1, a spinning die 1 is composed of a spin block 2, which is a distribution section for molten polymer, and a discharge block 3.The discharge block 3 further includes a die nose 4, and a pair of die noses 4 on the left and right sides of the die nose 4. It is composed of a lip plate 5 and a lip fixing block 6, each of which is fixed with a bolt (not shown). The lip plate 5 can be slid forward and backward with respect to the die nose 4 by means of push-pull bolts 7 screwed into the lip fixing block 6. Further, 8 is a filter. Dynose 4 is
The cross section is an isosceles triangle, and a large number of orifices 9, which are discharge holes for molten polymer, are provided in a row in the longitudinal direction (vertical direction in the figure) at the tip. Reference numerals 10a and 10b near the tip of the die nose are slits serving as flow paths for heated gas, and a pair of lip plates 5 are opposed to each other at distances of slit widths L1 and L2 from both walls of the die nose, respectively. The molten polymer discharged from the plurality of orifices 9 collides with the heated gas injected from both the left and right slits 10a110b near the tip of the die nose 4, and then is injected together with the heated gas onto the net conveyor and captured in the form of a nonwoven fabric. It is collected to form a melt-blown nonwoven fabric.

Such a spinning die 1 includes a connecting pipe 15 kept warm by a heater.
On the left and right sides of the die 1, there is a heated air supply system 13 consisting of a hot air generator (not shown), a supply pipe 11, and a valve 12 for supplying heated gas to the die. .14 are connected to each other.

FIG. 2 shows a schematic structure of the discharge block section in an air knife type spinning die.The discharge block 3 has an upper knife (inner blade) 15 and a lower knife (outer blade).
16 and slits 10a, 10, which are flow paths for heating gas.
b is formed, 18 is an outer blade fixing block, and the lower knife (outer blade) 16 is a push-pull bolt 17.
It can slide forward and backward with respect to the die nose 4.

The cross-sectional shape near the discharge part of the die nose is generally approximately an inverted triangular shape as shown in Figures 1 and 2, but it is not necessarily limited to the same shape. However, the specific shape of the inverted triangle may also be an isosceles triangle, an equilateral triangle, or a scalene triangle. Further, the heated gas supplied to the spinning die refers to a gas such as air or steam heated by any heating means such as an electric heater or a steam heater, and usually heated air is used.

The slits formed on the left and right sides of the die nose are the heated gas flow path formed by both walls of the die nose and the lip plate wall in the lip plate type shown in FIG. 1, or the slits formed on the left and right sides of the die nose are In the air knife system outlined in Figures 1 and 2, the slit width, L2, refers to the heated gas flow path formed by the inner and outer blades. This refers to the distance in the cross-sectional direction of each slit. The slit width can be adjusted by adjusting means such as a push-pull bolt screwed into the vicinity of the discharge port of the lip plate, a hydraulic or pneumatic actuator, or a heated expansion bolt.

Furthermore, as shown in Figures 1 and 2, setbacks H1 and H2 refer to the protruding distance of the die nose from the lower surface of the left and right lip plates to the tip of the soybean in the case of the lip plate type, as shown in Figures 1 and 2. For the air knife type, this refers to the protruding distance of the die nose from the outer blade edge to the tip of the die nose, and the adjustment of setbacks H□ and H2 is as follows:
For example, this can be done by inserting a spacer between the spin block and the lip fixing block or the outer cutter fixing block. By adjusting the setback in this manner, the setback can be adjusted asymmetrically on the left and right sides, and the traction energy of the injected gas can be set asymmetrically.

In addition, the injection pressure of the heated gas refers to the pressure of the heated gas in the air reservoir chamber located upstream of the slit. In other words, in the lip plate method, the air reservoir chamber ( 19) in Figure 1, or in the case of the air knife method, refers to the pressure of the heated gas in the air reservoir chamber (19 in Figure 2) formed by the die nose, outer cutter, inner cutter, and outer cutter fixing block. For example, the pressure adjustment method is as follows:
This can be done by any arbitrary means, such as adjusting the valves interposed in the heating gas supply pipes communicating with the left and right slits, or controlling the rotational speed of the heating gas supply blower.

According to the various findings of the present inventors, when producing a melt-blown nonwoven fabric according to the method of the present invention, the preferable specific condition range for each asymmetric state for these values is, for example, the slit widths L1 and L2 are Depending on the tip angle of the slit, the narrower slit width is L.
1, it is preferable to adjust the ratio between L2 and Ll (L2/Ll) to be within the range of 1.1 to 2°0 in order to suppress polymer balls, and in this case, the slit The specific values for the widths L1 and N2 are -0.6 to 1, 4 mm s0, and 66 for boat fishing, respectively.
It is preferably within the range of 1° to 6 mm.

Also, for example, although the setbacks H1 and N2 also depend on the tip angle of the die nose, if the shorter setback is set to N3, the ratio of N2 and H□ (N2 /H1) is 1.1 to 1. It is preferable to adjust it so that it becomes .5.

In this case, the specific values of setbacks H1 and N2 are 0°6 to 1.8 mm and 0.7 to 2.5 mm, respectively.
It is preferable to set it within the range of . However, even within this range, if the setbacks H1, Hx are set to large values, the optimal spinning conditions may change due to the influence of the ambient temperature, so it is more preferable to set the setbacks H1, N
Both are in the range of 0.6 to 1.7 mm, and N2 /H1
It is preferable to adjust the ratio to 1.1 to 1.5.

For example, the injection pressure of the heated gas is the ratio of P2 and Pl (P
2/Pt) is preferably adjusted to fall within the range of 1.2 to 4.0. Injection pressure P1 in this case
, P2 are respectively 0.1 to 3. O
kg/CIIG, 0.12~6゜Q kg/ad G
It is preferable to set it within the range of .

In addition, in the present invention, the above-mentioned three types of values are not particularly different between the left and right sides (in addition, the amount of heated gas injected from the slits formed on the left and right sides of the die nose is different between the left and right slits). A method configured to perform traction thinning may also be adopted.

Here, the injection amount of heating gas refers to the injection amount of heating gas injected from the slit, and the injection amount can be adjusted by adjusting the valves installed in the heating gas supply pipe. Adjustment is performed when the ratio of N2 and N□ (N2 /Nl) is 1.2 or more, where the smaller of the two is set as N1,
It is preferable to adjust it to within a range of 20 or less. In other words, if it is less than 1.2, there will be little effect, although it depends on the assembly accuracy of the die, and if it is controlled to be more than 20,
The N2 side, where the gas ratio is high, becomes dominant, and the action of the accompanying air is also added, and the discharged polymer near the slit on the N□ side, where the gas ratio is low, tends to cause contamination, which is undesirable. From this point of view, particularly preferably 1
, 3 or more and 10 or less. The injection amount of the heating gas used may be changed or set as appropriate depending on factors such as the ejection amount, the width of the spinning die, and other specifications of the nonwoven fabric.

In the present invention, among the slit widths L1 and N2, the setbacks H1 and N2, the injection pressures P1 and P2 of the heated gas injected from the slits, and the injection amounts of the heated gases injected from the left and right slits, respectively, It is sufficient to perform traction thinning with at least one requirement set asymmetrically on the left and right sides of the dyno finish, and among these,
It is also possible to obtain an even better effect by performing spinning by combining two or more requirements to be set asymmetrically on the left and right sides. Here, the combination of these may be appropriately selected or combined in consideration of the fineness, basis weight, air permeability of the nonwoven fabric, surface quality of the nonwoven fabric, etc. of the melt blown fibers constituting the nonwoven fabric to be spun. For example, if you want to obtain a nonwoven fabric made of ultra-fine fibers, you can obtain a favorable result in terms of surface quality by combining the jetting pressure and the slit width, and if you want to increase air permeability, you can combine the jetting pressure and the slit width.
By appropriately combining the setback conditions for spinning, a more remarkable effect of suppressing the generation of polymer balls can be obtained.

In this way, the slit width, setback,
The reason that the generation of polymer balls can be suppressed by setting the injection pressure of the heated gas asymmetrically is that, for example, unlike the conventional spinning method, the heated air injected from the left and right slits is equalized on the left and right sides of the die nose. This is thought to be because when the molten polymer is spun out from the orifice in this state, vibrations occur in the molten polymer sprayed at the confluence section, and this vibration promotes the growth of polymer beads, which are then sprayed directly onto the screen.

On the other hand, if at least one of the slit width, setback, heated gas, injection pressure, and injection amount is set asymmetrically on the left and right sides of the die nose as in the present invention, the injection will be made from either one of the slits. The gas flow injected from the other slit becomes the main jet, and the gas flow injected from the other slit becomes a sub-jet subordinate to the main jet.The main jet is the basic, but the polymer discharged from the many orifices becomes the main jet along with the sub-jet. Since it is injected following the jet flow, the above-mentioned vibrations do not occur. In this case, the question is which of the two slits will the gas flow injected from form the main jet? In the case of the slit width, the gas flow that is set larger will form the main jet, In the case of setback, the gas flow is set to a smaller value, in the case of injection pressure, the gas flow is set to a higher injection pressure, and in the case of injection quantity, the gas flow is determined to be more injected. Forms the main jet.

In addition, in the present invention, if the injection pressure, injection amount, slit width, etc. of the heating gas are set asymmetrically, if the gas temperature supplied from the gas heating device is the same, a temperature difference may occur between the left and right sides due to heat radiation. It is desirable to have separate gas heating devices for the left and right sides.

In this way, the present invention intentionally sets the gas flows that are injected and collided from the left and right sides of the die nose to be asymmetrical, thereby forming a main jet and a sub-jet in the gas flow. , the main jet is centered and stabilized, and as a result, the generation of polymer beads at the merging portion is suppressed.

Furthermore, even if the assembly accuracy is somewhat poor or there are small scratches on the die nose, the generation of polymer balls can be suppressed.

[Examples and Comparative Examples] Hereinafter, the method for producing a melt-blown nonwoven fabric of the present invention will be specifically described based on Examples.

Examples 1 to 2, Comparative Examples 1 to 3 Using the spinning die 1 having the structure shown schematically in FIG. The slit width L2 is
The surface state of the nonwoven fabric was sequentially changed by adjusting the die bolt 7, and the surface state of the obtained nonwoven fabric was measured using a microscope with a magnification of 20 times to examine the occurrence of polymer beads.

The spinning conditions are that the tip angle θ is 30° and the tip has a diameter of 0.
The die nose 4 has a large number of 38 orifices 9 arranged in a row at a pitch of 1.1 ms, and the gas injection angle α is 40°.
Polypropylene resin was heated at 300°C to a die incorporating a lip plate with a slit width of 0.8 mai.
This is melted and discharged from the orifice 9 at a discharge rate of 0°25 g/min, while the left and right slits 10a, 10b
air heated to the same temperature at a pressure of 0.35 kg/
300m below lip plate 5 while injecting with ciG
A nonwoven fabric was produced by spraying the mixture onto a net conveyor placed at a distance of m.

This result is shown in Table 1, and as shown in Table 1, the right slit width L2 was widened by 0.1 to 0.2 mm to make it asymmetrical compared to the left slit width. Examples 1-2
It can be seen that fewer polymer balls were generated in Comparative Examples 1 to 3, which had the same slit width.

Examples 3 to 4, Comparative Examples 4 to 6 Next, the discharge block described in Examples 1 to 2 was replaced with an air knife type spinning die having the structure shown in FIG.
The left and right setbacks H1 and H2 were changed by adjusting the push/pull bolts 17, and the occurrence of polymer beads was investigated using the same measuring method as in Examples 1 and 2 above.

The spinning conditions were the same as those in Examples 1 and 2 above, except that the die format was changed and the slit widths L1 and L2 were set to the same 0.8 mm on both the left and right sides.

The results are shown in Table 2. As shown in the table, the right setback H2 is set to 0 for the left setback H1.
．． Examples 3 and 4 made asymmetric by lengthening by 15 to 0.3 mm
It can be seen that the occurrence of polymer balls was improved in Comparative Examples 4 to 6 with the same setback.

Examples 5-6, Comparative Example 7 Next, in the spinning apparatus used in Examples 1-2, the setbacks H1 and H2 were set to 1.5 mm on both the left and right sides, and the slit width L
1.L2 was also Q and 8rnm on both the left and right sides, and other spinning conditions and measurement conditions were the same as in Examples 1 and 2 above.
Pressure P of heated air supplied to slits 10a, 10b
Table 3 shows the results obtained by making i and P2 asymmetric by adjusting the left and right valves 12 and investigating the occurrence of polymer beads.

From this table, compared to the case of Comparative Example 7 in which the left and right supply pressures P and P2 were equal, 0.10 to 0.30 kg, respectively.
It can be seen that Examples 5 and 6 in which /a+fG was set lower produced fewer polymer beads.

Examples 7 to 10, Comparative Example 8 In the spinning apparatus shown in Examples 1 to 2 described above, the average value of one second back was 1.4 mm, and the difference R between the maximum value and the minimum value was R=0. 9mm.

The other one is 1.3 mm, R = 0.7 mm, and the average value of the slit width is 0.7 mm for one, t'R = 0.4 mm.

A spinning die was assembled with the other end being 0.7 mm and R=0.5 mm.

This equipment melt blow spins hot melt polymer.
At this time, when heated air of 5Nm37 minutes is injected equally from both slits (ratio 1: comparative example 8), N
When , is 3.5Nm' 7 minutes and N2 is 6.5Nm3/min (ratio 1.86: Example 7), Nl is 2.5N
m3/min, N2 is 7°5Nm'/min (ratio 3
: Example 8), Nt was 1. ONm3/min, N2 9. O
When Nm3/min (ratio 9: Example 9), when Nl was 0°5Nm3/min and N2 was 9.5Nm3/min (ratio 19: Example 10), the spinning results were as follows. As described in Table 4.

The results shown in Table 4 show that by setting an appropriate injection gas ratio as in Examples 7 to 10, a nonwoven fabric sheet with fewer polymer beads can be obtained.

Table 1 Table 4 [Effects of the Invention] As explained above, the present invention improves the processing precision of the spinning die to make the slit width equal on the left and right sides of the die nose, and to make the injection pressure equal on both slits. Unlike the conventional spinning method, the slit width (11, L2) formed on the left and right sides of the die nose, and the setback (H11H)
2) The spinning method uses traction thinning with at least one of the heating gas injection pressure (P1, P2) and injection amount set asymmetrically on the left and right sides of the die nose, so that the heating gas is injected from both slits. One jet stream of the heated gas forms the main jet flow, and the jet flow injected from the other slit forms the sub jet flow, which prevents vibrations and effectively suppresses the formation of polymer balls at the convergence part. be able to.

Therefore, according to the present invention, a high-quality nonwoven fabric is manufactured using a specially processed die with high precision, a highly skilled worker, and a highly skilled worker.
This allows for stable production without requiring any experience.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the structure of a lip plate type spinning die that can be used to carry out the method for producing a melt-blown nonwoven fabric of the present invention, and FIG. 1 is a schematic cross-sectional view of a main part (discharge block part) showing an example of the structure of an air knife type spinning die that can be used to carry out the method for producing a melt-blown nonwoven fabric of the invention. 1: Spinning die 3: Discharge block 4: Die nose 5: Lip plate 9 Niorifice 10a, 10b Nislit 19: Air reservoir chamber L1, L2 Nislit width H1, H2: Setback P□, P2: Injection pressure Patent application Daito Shi Co., Ltd. company

Claims (4)

[Claims] (1) Using a spinning die that has a die nose with an orifice for discharging molten polymer and a pair of slits for injecting heated gas on the left and right sides of the die nose, the heated gas is ejected from the pair of slits. The slit width (L) formed on the left and right sides of the die nose is
_1, L_2), setback (H_1, H_2), and injection pressure of the heated gas ejected from the slit (
A melt-blown nonwoven fabric characterized in that at least one of P_1 and P_2) is set asymmetrically on the left and right sides of the die nose to perform traction thinning of the molten polymer, and further collect the melt-blown fibers in the form of a nonwoven fabric. manufacturing method. (2) Using a spinning die having an orifice for discharging molten polymer and a pair of slits for injecting heated gas formed on the left and right sides of the die nose, the heated gas is ejected from the pair of slits. When discharging the molten polymer from the orifice while injecting the molten polymer to thin the molten polymer and spinning it as melt-blown fibers, the amount of heated gas injected from the slits formed on the left and right sides of the die nose is adjusted to the right and left sides. 1. A method for producing a melt-blown non-woven fabric, characterized in that the slits are differentiated to perform traction thinning, and the melt-blown fibers are further collected in the form of a non-woven fabric. (3) A patent characterized in that the amount of heated gas injected from the slits formed on the left and right sides of the die nose is made to differ between the left and right slits within a range of 1.2 to 20 in terms of injection amount ratio. A method for producing a melt-blown nonwoven fabric according to claim (2). (4) Claims characterized in that the shape of the die nose is approximately an inverted triangular cross section in the vicinity of the discharge part, and has a large number of orifices at the tip thereof for discharging the molten polymer. The method for producing a melt-blown nonwoven fabric according to item (1), item 2, or item (3).