JPS6051567B2 - Manufacturing method of foamed spread yarn - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a foamed spread yarn that prevents the accumulation of slag deposits near the molten resin outlet of a die without impairing the quality of the foamed spread yarn.

The manufacturing process for foamed spread fibers involves selecting a polyolefin resin such as polyethylene or polypropylene as the main raw material, and then using a blowing agent, such as sodium bicarbonate, that generates gases such as nitrogen gas or carbon dioxide at the molding temperature of the raw material polymer. A draft ratio of preferably 20 to 250 is obtained by melting and extruding this mixture through a die slit with a gap of about 0.1 to 2 TnIfL, and then applying a draft while cooling.
By applying a draft, a web-like molded product split into fine meshes is obtained.

As the die, either an annular die or a T die can be used, and the configuration of an apparatus using an annular die is shown in FIG.

That is, 1 is an annular die connected to an extruder (not shown), 2 is a band heater attached to the side and lower part of this annular die 1, and the temperature control detection end 3 allows
Controls the temperature of the entire die.

Reference numeral 4 denotes an air cooling ring of a parallel flow cooling type provided near the outer periphery of the annular die 1 on the exit side.

The bubbles 5 melted and extruded from the slit outlet 1a of the annular die 1 are drafted during the cooling process and formed into a foamed spread yarn, and then taken off by a take-up roll 6.

By the way, in the conventional method for manufacturing expanded expanded yarn described above, in order to produce expanded expanded yarn with a very fine mesh and regular splits, the bubbles 5 extruded from the annular die 1 are heated by an air cooling ring J4. There was a need for effective cooling.

However, even if foaming and opening is performed under these conditions, a good degree of opening can only be obtained within 1 to 2 hours after the start of molding, and after this time, what is commonly known as eye stain in this field. Slag-like deposits called slag-like deposits begin to accumulate near the die slit exit 1a, and quickly grow into lumps, making the opening degree uneven, causing breakage of the opening yarn, or causing large Problems such as lumps adhering to the spread yarn occur, and the die has to be cleaned every 2 to 3 hours.
Therefore, the main object of the present invention is to prevent the occurrence of this eye stain in the production of foamed spread yarn.

According to the observation results, there is a contrary relationship between the occurrence of eye stains, the cooling effect of bubbles, and the degree of fiber opening, and the higher the cooling effect of bubbles, the better the degree of fiber opening (fineness).
On the other hand, if the cooling effect is lowered, grain stains are less likely to occur, but the degree of opening becomes coarser.

As a result of analysis, it was found that the components of eye resin are mostly resin itself, and in some cases, it is thought that trace amounts of foaming agent components may remain.

Although the cause of eye discharge is not clear, it is assumed to be mechanistically as follows. For example, taking an annular die as an example, when molten resin flows through the annular slit, it is thought that a phenomenon occurs in which low-molecular-weight molecules float to the surface of the flow (POlymer Letters, Vol.
7, pp. 267-272, 1969). The flow velocity distribution of the molten resin becomes a parabolic distribution that is maximum at the center of the slit and becomes smaller as it approaches the inner wall of the slit.

Therefore, it is thought that the above-mentioned low molecules form a thin layer on the surface of the flow, move toward the slit exit, are exposed from the exit end, and are cooled to become semi-molten or solid eye resin. It will be done. The inventors focused on the die temperature near the exit of the molten resin as a measure to prevent the occurrence of this eye resin, and if they maintained it in a temperature range sufficient to melt the low molecular weight material of the eye resin, they could achieve the desired result. It was found that the purpose of this study was achieved to some extent.

In terms of equipment, it is necessary to provide a heating element that is controlled separately from the die body near the die slit outlet, as will be described later.

It is necessary to heat the die selectively in this way, and if the entire die is kept at a high temperature, the generation of eye stain can be prevented, but the molten resin will also deteriorate, resulting in a decrease in the quality of the product.

On the other hand, if a heating element is placed near the exit of the die slit, the low molecular weight substances that tend to accumulate near the exit of the molten resin will be melted by the heat and removed while remaining attached to the product, thereby preventing the formation of eye stains. In addition, since the molten resin does not deteriorate and the amount of low molecular weight substances that adhere to the product is extremely small, the quality of the product is hardly affected.

However, the inventors' research encountered a difficult problem here.

If the die is kept at a high temperature, the degree of opening becomes coarse, which significantly reduces the quality of the product.

Therefore, by increasing the air volume of the air cooling ring to increase the cooling effect of the parallel flow type, we were able to improve the degree of fiber opening to a certain extent, but on the other hand, the large air volume caused the bubbles to sway. It was found that the moldability became unstable. As a result of further intensive research, we found that no solution could be found using the parallel flow cooling method; however, it was found that if cooling air was blown directly toward the molten resin outlet, even if the above-mentioned heating element was used in combination, We were able to discover the unexpected fact that the degree of opening does not become coarse.

That is, this invention is a method of melt-extruding a mixture consisting of a polyolefin resin, a blowing agent, etc. through a die slit, cooling it and drafting it to form a foamed spread yarn. In order to prevent the occurrence of eye stain near the die slit outlet, a heating element is attached to the die part near the molten resin outlet to heat this part, and cooling air is blown toward the molten resin outlet. It is characterized by attaching.

The present invention will be described in detail below with reference to FIG.

1 is an annular die, and 1a is a slit exit of the annular die 1, from which a predetermined foamable polymer raw material is melted and extruded into a cylindrical shape, foamed and opened by a draft, and taken off by a take-off roll (not shown).

4 is a heating element such as a band heater attached to the main body of the annular die 1, and 3 is a temperature control detection end of the main body.

In this invention, also near the molten resin outlet 1a of the annular die 1,
Heating element 2 such as a band heater whose temperature is controlled separately from the above
Install a.

The mounting position may be on the top surface of the die outside the molten resin outlet 1a as shown in A, or on the die top surface outside the molten resin outlet 1a as shown in FIG.
It may be mounted on the upper surface of the die on both the inner and outer sides of a, or on the side surface of the die near the molten resin outlet 1a as shown in c, or even, although not shown, the mounting position of c may be combined with a or the opening. Of course, in order to accurately control the temperature using these heating elements 2a, it is necessary to attach the temperature control detection end 3a to the die portion close to the heating element 2a.

On the other hand, an air cooling ring 4a is disposed near the annular die 1 so as to preferably surround the outer peripheral surface of the outlet of the bubble 5,
The direction in which the cooling air is blown must be directed to the vicinity of the molten resin outlet 1a of the die, which is different from the conventional parallel flow cooling method.

Foaming and fiber opening is carried out with the above equipment configuration, and at that time, the temperature of the cooling flat air is 0 to 50°C, and the blowing speed is 3 to 20 TrL.
, /Sec.

This is because if the cooling air is below 0°C, grit is likely to accumulate at the die slit outlet 1a, and if it exceeds 50'C, the degree of opening of the molded product becomes rough, and the blowing speed is 207T.
When exceeding L,/Sec, the running of bubble 5 becomes unstable and 3rrL. This is because when it is less than /Sec, the degree of opening of the molded product becomes coarse. Further, the temperature of the die 1 is normally maintained in the range of 220 to 250°C when the raw material polymer is polypropylene with an MFI of 17, for example. In the conventional foaming and fiber opening process, the heating element is installed at a location quite far away from the molten resin outlet, so if cooling air is to be blown towards the molten resin outlet, the cooling effect must be taken into account. For example, in the case of polypropylene with M■:17, the occurrence of eye stain cannot be prevented unless the temperature of the die is raised to around 300°C. However, on the other hand, the high temperature causes the problem of deterioration of the molten resin.

In this invention, the temperature near the exit of the molten resin is adjusted to a range that does not substantially cause deterioration of the resin and a range that melts low molecular weight substances, so it is possible to prevent eye stains without deteriorating the resin. .

In this way, the method of this invention eliminates eye stain by arranging the heating zone of the die and achieves fine opening with cooling air, making it a great contribution to the field of manufacturing expanded expanded yarn. It is something that does.

EXAMPLE Using the apparatus shown in FIG. 2A, a foamed spread yarn was formed under the following conditions.

Polypropylene (Showa Yuka Co., Ltd. Showa Aroma MA)
6lO, MFIl7. O) 9 parts by weight, 1 part by weight of saponified ethylene vinyl acetate copolymer, 0.35 parts by weight of azodicarbonamide (foaming agent), and 0.05 parts by weight of calcium stearate (foaming aid). , 0.1 part by weight of propylene glycol (dispersant) were added and mixed in a blender, and the mixture was heated using a 4-φ extruder (temperature condition C1=1600CNC2=
Melt extrusion using CNC 3 = 2100C) and a 200mm diameter annular die (temperature 220°C), draft ratio 50, take-off speed 25TrL. I picked it up in 1 minute.

The temperature of die 1 is 220°C at temperature control detection end 3a.
At the same time, the damper opening is 20m! The air velocity is 1 from the air cooling ring 4a to the die slit outlet 1a.
0771. /Secl air with a temperature of 20°C was blown.

The obtained foamed spread yarn had a very fine mesh and was regularly split, and there was almost no occurrence of welts even after 4 hours of operation.

In addition, in the apparatus shown in Fig. 2A, when the heating element 2a was omitted, it was possible to prevent the occurrence of marks only after the die temperature D1 was raised to 280°C, but the deterioration of the resin itself This was unavoidable, and in this respect the quality of the foamed spread yarn was lowered.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the conventional manufacturing process of expanded expanded yarn, and Fig. 2 A, 0, and C show the configuration of equipment near the annular die, which are employed in different embodiments of the present invention. be. 1...Annular die, 1a...Die slit outlet or molten resin outlet, 2, 2a...Heating element, 3, 3a...Temperature control detection end ,
4, 4a... Air cooling ring, 5... Bubble, 6...
...Takeover roll.

Claims (1)

[Claims] 1. In a manufacturing method in which a mixture of polyolefin resin and a foaming agent is melt-extruded through a die slit and then drafted during the cooling and drawing process to produce a foamed spread yarn, a heating element is attached to the die near the molten resin outlet. 1. A method for producing a foamed spread yarn, which comprises heating the part by heating the part, and spraying cooling gas toward the vicinity of the molten resin outlet.