JPS6241311A - Improved polypropylene monofilament and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled monofilament having low shrinkage and high abrasion resistance, by kneading a PP resin having specific melt index and isotactic pentad fraction under melting, extruding and slowly cooling the molten resin, drawing the spun monofilament and heat-treating the drawn filament at a temperature above the melting point. CONSTITUTION:A polypropylene resin having a melt flow rate of 1.0-1.5g/10min and containing a boiling n-heptane insoluble part having an isotactic pentad fraction of >=0.950 is kneaded and extruded under melting and cooled slowly in a hot-water bath of 30-80 deg.C to obtain a monofilament. The monofilament is drawn and then heat-treated in an atmosphere heated at a temperature above the melting point of the polypropylene resin used as a raw material to obtain the objective monofilament having a linear strength of >=4.5g/d, a shrinkage of <=1.5% at 100 deg.C and improved abrasion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polypropylene monofilament (hereinafter referred to as PP monofilament) with improved shrinkage properties and abrasion resistance, and a method for producing the same. More specifically, we use a specific polypropylene resin that has low shrinkage when heated and prevents the generation of fuzz and powder during the manufacturing process of PP monofilament, secondary processing processes such as twisting, warping, knitting and weaving, and The present invention relates to a PP monofilament having practical strength and a method for producing the same.

Conventionally, PP monofilament has been mainly used as rope for boat fishing, due to its excellent strength, flexibility, and chemical resistance.
In addition to being widely used as agricultural binding cord, it has also recently been widely used for insect-proof nets, rice and wheat bags, and civil engineering sheets.

However, although the linear strength of PP monofilament is improved by drawing, it also shrinks more when heated.
It has the disadvantage that the surface tends to become fluffy and powdery.

If the shrinkability of PP monofilament is large, when fabricating fabric using iPP monofilament, shrinkage may occur during the weaving process, resulting in problems such as not being able to obtain the desired woven fabric, or making the woven product easily deformed when heated. Therefore, a PP monofilament with as little shrinkage as possible is required. For example, monofilaments for insect repellent nets are required to have a shrinkage rate as low as 1.5 or less when heated at 100°C.

In addition, since the molecular orientation of PP monofilaments that have molecular orientation due to stretching is easily destroyed by friction, monofilaments may be During the secondary processing steps such as twisting, warping, knitting and weaving to make products, the surface of the monofilament becomes fluffy, and powdery substances generated due to wear of the monofilament accumulate over time, causing problems in the manufacturing process and secondary processing. The resulting monofilament or 2
This causes various problems such as a decrease in the strength of the next processed product. In order to improve these drawbacks, in order to improve the fluidity and spinnability of the molten resin during extrusion, the extrusion temperature may be increased, the spinning speed may be slowed, or the draw ratio may be kept low during drawing. Although attempts have been made to suppress molecular orientation, this has resulted in disadvantages such as decreased productivity and workability and insufficient strength of the obtained monofilament. Particularly for PP monofilament textile products, the fuzzing and adhesion of powder on the product surface due to abrasion impairs the appearance and lowers the product value, so an immediate solution is required. As a method for improving this problem, a method can be considered in which the surface layer of the PP monofilament is coated with a hardened film having good abrasion resistance, but this method has the disadvantage that the manufacturing process becomes complicated and the manufacturing cost becomes extremely high.

The inventors have already developed a melt flow rate of 0.3 to 15.
By performing the stretching operation and/or heat treatment under specific conditions in the stretching process of a monofilament-like spun product obtained by melt extrusion using a conventional polypropylene resin having a weight of 0.0 g/l, linear strength of 4. We have proposed a method for producing PP monofilament that has a practical strength of 5.9/d or higher and improved abrasion resistance (patent application filed in 1973).
No. 9-279877). This manufacturing method is aimed at improving the so-called abrasion resistance of the obtained PP monofilament by preventing the generation of surface fuzz and powdery substances.
The shrinkage rate when heated to 00℃ is about 3 to 5 inches, and is 1.5-
It is difficult to achieve shrinkage rates below.

The present inventors continued to conduct intensive research to solve the above-mentioned problems regarding PP monofilaments. the result,
By using a specific polypropylene resin and performing the cooling operation in the extrusion process, the stretching operation and/or the heat treatment operation in the drawing process in monofilament production under specific conditions, the shrinkage rate of the resulting monofilament can be surprisingly significantly increased. It has been discovered that a monofilament can be obtained in which the surface fuzziness is reduced and the generation of fluff and powdery substances on the surface is prevented, and based on this knowledge, the present invention has been completed.

As is clear from the above description, one of the objects of the present invention is to provide a PP monofilament having practical strength with improved shrinkage and abrasion resistance using a specific polypropylene resin; is to provide a manufacturing method thereof.

The present invention has the following configuration.

(1) Melt flow rate is 1.5-15 g/l
0 minutes, boiling on-polypropylene resin having an isotactic pentad fraction of 0.950 or more in the heptane-insoluble part, having a linear strength of 4°5 N/d or more, and 100
A polypropylene monofilament with a shrinkage rate of 1.5 inches or less when heated at °C and improved abrasion resistance.

(2) Melt flow rate is 1.0 to 15 F/1
A monofilament obtained by melt-kneading and extrusion using a polypropylene resin with an isotactic pentad fraction of the n-heptane insoluble portion of 0.950 or more, followed by slow cooling in a hot water cooling tank at 30 to 80°C. having a linear strength of 4.5 F/d or more, characterized in that the monofilament-like spun product is stretched and subsequently heat-treated at an ambient temperature higher than the melting point of the raw material polypropylene resin of the monofilament-like spun product;
A method for producing polypropylene monofilament having a shrinkage rate of 1.5 inches or less when heated at 100°C and improved abrasion resistance.

The PP monofilament referred to in the present invention is not only a normal single monofilament in which each monofilament has an independent shape, but also a so-called flat string-like shape in which two or more single monofilaments are arranged in parallel and connected. It also includes a monofilament having a continuous thread structure, and the cross-sectional shape of the single monofilament may be any of a perfect circle, an ellipse, and an oval.

The polypropylene resin used in the present invention has a melt 70 rate a of 1.0 to 15 g/10 minutes and an isotactic pentad fraction of 0.950 or more in the insoluble portion of boiling n-hebutane, which is disclosed in, for example, JP-A-58-104907. Obtained by the method described in the publication.

That is, solid product (1) obtained by reacting an organoaluminum compound or a reaction product of an organoaluminium compound and an electron donor with titanium tetrachloride is further reacted with an electron donor and an electron acceptor. The solid product (II) is combined with an organoaluminium compound and an aromatic carboxylic acid ester (In), and the molar ratio m/■ of the aromatic carboxylic acid ester and the solid product (I[) is 0.
It can be obtained by polymerizing propylene in the presence of a catalyst having a molecular weight of 2 to 10.0, but is not limited to this method.

Still, here is the isotactic pentad fraction, Macromolecules, by A-Zambe et al.
) 6.

925 (1973), that is, the isotactic fraction in pentad units in a polypropylene molecular chain measured using +3 cm NMR. Therefore, the isotactic pentad fraction is the fraction of one propylene monomer unit in which five consecutive propylene units are isotactic bonded. The peak attribution method in the above-mentioned NMR measurement is described in Macromolecules 8, 687.
(1975). In addition, in the measurement by NMR in the examples described later, 2 of Fourier transform NMR is used.
70M)-12! Using the device, 27,000 times (]j
The signal detection limit was improved to 0.001 in terms of isotactic pentad fraction by Jg measurement.

The boiling n-heptane-insoluble portion of polypropylene used in the present invention refers to completely dissolving 5 g of polypropylene in 500 m of boiling xylene, then pouring the xylene solution into 51 methanol and collecting and drying the precipitated material. After that, the dry polypropylene is extracted with boiling n-heptane for 6 hours using a Soxhlet extractor.

The above-mentioned specific polypropylene resin used in the present invention has a much higher degree of crystallinity than conventional polypropylene resins. For example, this is a DSC (differential scanning calorimeter)
indicated by the measurement of

Furthermore, the crystallization rate from the molten state is faster than conventional polypropylene resins, and the growth rate of spherulites and the number of spherulite nuclei generated are also higher. As mentioned above, the above-mentioned specific polypropylene resin used in the present invention has a higher degree of crystallinity and a significantly faster crystallization rate than conventional polypropylene resins. This is thought to have contributed to the improvement.

Furthermore, the melt flow rate of the above-mentioned specific polypropylene resin used in the present invention (temperature 230°C, load 2.16
MF is the discharge amount of molten resin for 10 minutes in kg.
It's called R. ) is 1.0 to 151)/10 minutes. Midfielder
If R is less than 1.0 g/10 minutes, it will be difficult to maintain the shrinkage rate at 1.5 inches or less when heated at 100°C, and the fluidity of the molten resin will deteriorate when the resin is melted. This is undesirable because extrusion fluctuations occur during melt-kneading extrusion, the surface roughness of the obtained monofilament-shaped spun product before stretching becomes severe, and it becomes difficult to obtain stable monofilaments.

Moreover, if the MFR exceeds 15.9/10 minutes, the strength of the obtained monofilament will decrease, and a linear strength of 4.5 g/d or more will not be obtained, which is not preferable. If the linear strength of the obtained monofilament is not 4.5#/d or more,
Problems arise in that the monofilaments break during secondary processing steps such as twisting, warping, knitting and weaving, and the textile product becomes easily torn during practical use.

However, the specific polypropylene resin used in the present invention has n-
The isotactic pentad fraction of the heptane insoluble part is 0
．． It needs to be 950 or more. If the isotactic pentad fraction is less than 0.950, the effect of improving the shrinkage of the obtained PP monofilament will be insufficient, which is not preferable.

The specific polypropylene resin used in the present invention may contain a heat stabilizer, an antioxidant, an ultraviolet absorber, an anti-blocking agent, a coloring agent, and other additives as necessary. It was also found that the effect of improving heat shrinkage was further improved by adding a nucleating agent.

Next, the manufacturing method of the present invention will be explained.

The melt extrusion equipment used for producing the PP monofilament of the present invention may be any known and publicly available equipment, and the cooling equipment for the monofilament-like spun product after melt extrusion is 30 to 80°C.
Any publicly known device can be used as long as it is equipped with a hot water cooling tank. Further, as the drawing device, general devices normally used for producing PP monofilament, such as a hot water bath, a heated air bath, and a pressurized steam bath, can be used. Furthermore, it is essential that the heat treatment equipment be capable of heating to a temperature higher than the melting point of the raw material polypropylene resin.

Next, the manufacturing method of the present invention has an MFR of 1.0 to 151)
/10 minutes, using a polypropylene resin whose isotactic pentad fraction (Po) of the insoluble portion of boiling n-heptane is 0.950 or more, at a melt-kneading temperature of 200 to 300°C, preferably 230 to 280°C. After melt-mixing extrusion, the monofilament-like spun product obtained by slow cooling in a hot water cooling tank at 30 to 80°C is continuously stretched using the above-mentioned drawing device, and the raw material polypropylene of the monofilament-like spun product is obtained. Ambient temperature above the melting point of the resin, e.g. 165-20
The heat treatment is performed at a temperature of 0°C. Cooling of the monofilament-like spun product after melt-kneading and extrusion is from 30 to 80°C.
It is necessary to cool slowly at a temperature of ℃. Cooling temperature is 30
If it is less than 0.degree. C., the effect of promoting crystallization of the monofilament-like spun product will be small, and the shrinkage rate and abrasion resistance of the obtained PP monofilament will not be improved. In addition, if the cooling temperature exceeds 80°C, bumping phenomenon will occur at the water-contact part of the cooling tank of the monofilament-shaped spun product), and the surface of the monofilament-shaped spun product obtained will be rough, which will affect the stretchability in the subsequent process. This is undesirable because it has an adverse effect and reduces the linear strength and abrasion resistance of the resulting monofilament. Practically speaking, it is preferable to slowly cool the mixture at a temperature of 40 to 60°C.

The stretching method in the production method of the present invention may be a single-stage stretching method using a hot water bath, a heated air bath, or a pressurized steam bath, or a two-stage or multi-stage stretching method that combines these. In order to maintain a linear strength of 4.5.9/d or more, it is appropriate to stretch the film at a stretching ratio of 6 to 10 times, particularly preferably 6 to 8.5 times.

The heat treatment in the present invention must be carried out at an ambient temperature higher than the melting point of the raw material polypropylene resin used.

Here, the melting point of polypropylene resin refers to the endothermic peak temperature associated with melting of polypropylene resin crystals when a sample is heated at a rate of 10°C/min in a nitrogen atmosphere using a scanning differential calorimeter. say.

If the temperature of the heat treatment is lower than the melting point of the raw material polypropylene resin used, care must be taken because the effects of improving shrinkage and abrasion resistance that are the objectives of the present invention cannot be obtained. In addition, if the temperature of the heat treatment is too high, the molecular orientation of the monofilament will largely return and the linear strength will decrease significantly, which is undesirable.
The temperature is 5 to 200°C, preferably 165 to 190°C. Further, as a method of heat treatment, either a constant length method or a relaxation method may be used, but in order to fully exhibit the effects of the present invention, it is preferable to perform a relaxation heat treatment with a relaxation rate in the range of 3 to 10%. be.

However, the feeding speed of monofilament is usually 50 to 2, which is the general feeding speed when manufacturing PP monofilament.
It is desirable to manufacture at a feed rate in the range of 0.00 m/min.

The PP monofilament of the present invention uses a polypropylene resin that has a higher melting point, higher crystallinity, and significantly faster crystallization rate than ordinary polypropylene resins as a raw material polypropylene resin, and requires cooling after melt-kneading and extrusion for 30 to 80 minutes.
By slowly cooling at ℃ to form a monofilament-shaped spun product that is further crystallized, and by heat treatment at an ambient temperature higher than the melting point of the raw polypropylene resin in the heat treatment process, internal strain, that is, residual stress, is removed and crystallization is achieved. Because it is a monofilament whose width is greatly promoted, its shrinkability is greatly improved, and it can be used in monofilament manufacturing processes such as hook guides and traverse guides of winding machines that wind up monofilaments, or when the PP monofilament 2. Twisting, warping, knitting, weaving, etc. for commercialization using
In the next processing step, the surface of the PP monofilament does not become fluffed due to abrasion, the generation of powdery substances can be prevented, and it has a high linear strength of 4.5 g/d or more.

As a result, the PP monofilament according to the present invention can be suitably used for manufacturing ropes for ships and fishing, insect nets, sheets for civil engineering, and the like. Especially fineness 100-1
It can be suitably used in textile applications using PP monofilaments of 0.000 denier.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The evaluation method used in the Examples and Comparative Examples was as follows.

1) Melt flow rate Compliant with JIS K 7210.

2) Measurement of linear strength of monofilament JIS L 1
Compliant with 070.

3) Abrasion resistance test of monofilament When a monofilament test piece is pressed against a metal surface under a constant load and the test piece is moved back and forth, the degree of fuzz and powder generated on the surface of the test piece is determined according to the following criteria. It was evaluated by

○: No fluff or powder is generated after 4 reciprocating movements.
Furthermore, by repeating the number of reciprocations, powdery matter is generated, but no fuzz is generated, and when the powdery matter generated on the surface of the monofilament test piece is removed, the monofilament surface is close to its original state.

×: Fuzz and powdery substances are generated after 4 reciprocating movements, and as the number of reciprocating movements is increased, the generation of fibrous fuzz and powdery substances increases.

4) Measurement of shrinkage rate Using a PP monofilament with a length of 1 m as a test piece,
After leaving the test piece in a hot air heating constant temperature bath controlled at 100±1° C. for 15 minutes, it is taken out and the length of the test piece is measured and calculated according to the following formula.

S: Shrinkage rate 10 Length of test piece before heating, 1) Length of test piece after heating Example 1, Comparative Example 1 Tris (2,4-di-t-butylphenyl) phosphite as a thermal stabilizer 0.1% by weight, pentaerythritol-tetrakis (3-(3,5-di-t-phthyl-4
-Hydroxyphenyl)propionate 37770.0
3 wt.%, calcium stearate 0.1 wt.% MFR7.0#/10 minutes, melting point 162.2°C, boiling n-
Isotactic pentad fraction of heptane insoluble portion (P
o) is 0.961 using an extruder having a nozzle with a diameter of 1.2 fi (diameter of 40 m).
) was melt mixed and extruded at a melt mixing temperature of 220°C, and then cooled by passing through a cooling water bath at a temperature of 45°C to obtain an undrawn monofilament-like spun product.

Subsequently, the unstretched monofilament-like spun product was introduced into a hot water stretching tank at a temperature of 98°C and stretched at a stretching ratio of 6.5 times and a drawing speed of 100 m/min, and then introduced into a hot air tank at a temperature of 165°C for relaxation. Heat treatment was carried out at a rate of 7% (final take-up speed of 93 m/min) to obtain a monofilament with a fineness of 403 denier.

In addition, as Comparative Example 1, the heat stabilizer tris (2,4-di-
(t-butylphenyl)phosphite) 0.1% by weight, pentaerythritol-tetrakis[3-(3,5-di-t
-butyl-4-hydroxyphenyl)propionate 37770.03% by weight, calcium stearate 0.
MFR 6.8g/10min containing 1% by weight, melting point 161°C
Polypropylene resin pellets having P of 0.935 were melt-kneaded, extruded, cooled, stretched, and heat treated according to Example 1 to obtain a monofilament of 1 l-403 denier.

Using the monofilaments obtained in Examples and Comparative Examples, linear strength, shrinkage properties, and abrasion resistance were measured.

The results are shown in Table 1.

Examples 2 to 4, Comparative Examples 2 to 3 As Examples 2 to 4, undrawn monofilament-shaped spun products obtained according to Example 1 using the same polypropylene resin as used in Example 1 were carried out. After stretching according to Example 1, the temperature in the hot air tank was 165°C in Example 2, 175°C in Example 3, and 185°C in Example 4. All were heat-treated with a relaxation rate of 6 inches (final take-up speed 94 m/min), and the fineness was 405.
Each of the denier monofilaments was obtained.

In addition, as Comparative Examples 2 and 3, Comparative Example 1 was prepared by melting and cross-extruding the same polypropylene resin used in Example 1 in accordance with Example 1, cooling it by passing it through a cooling water tank at a temperature of 18°C, and leaving it untreated. A stretched monofilament-like spun product was obtained, and then the unstretched monofilament-like spun product was stretched according to Example 1, and then introduced into a hot air tank at a temperature of 165° C. with a relaxation rate of 6 cm (final take-up speed of 94 m). /min) to obtain a monofilament with a fineness of 405 denier. Comparative example 2
The same polypropylene resin as used in Example 1 was melt mixed and extruded in accordance with Example 1, and then cooled by passing it through a cooling water bath at a temperature of 45°C to obtain an unstretched monofilament-like spun product. After stretching the unstretched monofilament-like spun material in accordance with Example 1, it was introduced into a hot air tank at a temperature of 150°C and heat-treated at a relaxation rate of 5 cm (final take-up speed of 95 m/min) to obtain a monofilament with a fineness of 405 denier. I got it.

The linear strength, shrinkage rate, and abrasion resistance were measured using the monofilaments obtained on each experimental side and each comparative side.

The results are shown in Table 2.

Examples 5 to 7, Comparative Examples 4 to 6 As Examples 5 to 7, polypropylene resin similar to that used in Example 1 was melt-kneaded and extruded according to Example 1, cooled, and made into an unstretched monofilament. After obtaining the spun product, the unstretched monofilament-like spun product was subsequently introduced into a hot water stretching tank at a temperature of 98°C and stretched at a stretching ratio of 8.0 times and a stretching speed of 100 m/min, and subsequently heated with hot air. In Example 5, the hot air tank temperature was 165°C, in Example 6, the hot air tank temperature was 175°C, and in Example 7, the hot air tank temperature was 18°C.
At 5°C, the relaxation rate was 8.0% (final take-up speed 92 m).
/min) to obtain monofilaments each having a fineness of 405 denier.

In addition, as Comparative Examples 4 to 6, Comparative Example 4 used the same polypropylene resin as that used in Example 1, and Examples 5 to 7
The unstretched monofilament-like spun product was melt-kneaded and extruded in accordance with the above, and cooled to obtain an undrawn monofilament-like spun product, and the undrawn monofilament-like spun product was stretched in accordance with Examples 5 to 7, and subsequently placed in a hot air tank. The temperature of the hot air tank is 150℃, and the relaxation rate is 5cm (
Heat treatment was performed at a final take-up speed of 95 m/min), and fili
I got 405 denier monofilament.

As Comparative Examples 5 and 6, the same polypropylene resin as that used in Example 1 was melt-kneaded and extruded in accordance with Example 1, cooled to obtain an undrawn monofilament-like spun product, and then extruded at a temperature of 98°C. After being introduced into a hot water stretching tank and stretched at a stretching ratio of 5.0 times and a stretching speed of 100 m/min, the samples were subsequently introduced into a hot air tank, and Comparative Example 5 had a hot air tank temperature of 130°C, and Comparative Example 6 had a hot air tank temperature of 150°C. °C, with a relaxation rate of 3% (final take-up speed 97 m/min) and a fineness of 40.
Each of the 4 denier monofilaments was obtained.

Linear strength, shrinkage rate, and abrasion resistance were measured using the monofilaments obtained in the Examples and Comparisons.

　So/) GL beggar Z&I is shown here.

As is clear from Table 1, Table 2, the PP monofilament according to the present invention has a linear strength of 4.5 g/d or more, excellent abrasion resistance, and an extremely high shrinkage rate of 1.0%. It can be suitably used for products that are small and require a low shrinkage rate, such as insect nets. On the other hand, as shown in Comparative Example 1, the PP monofilament obtained by the production method of the present invention using ordinary polypropylene resin has excellent linear strength and abrasion resistance, but has a large shrinkage rate of 3.5%. It cannot be used for products that require low shrinkage.

As is clear from Examples 2 to 7 in Table 2, the unstretched monofilament-like spun product obtained by the production method of the present invention, that is, melt cross-extrusion, was slowly cooled in a hot water cooling tank at 45°C, and then stretched. The PP monofilament obtained by subsequent heat treatment at a temperature higher than the melting point of the raw material polypropylene resin has a linear strength of 4.5.9/d or higher and excellent abrasion resistance.
Moreover, it was found that the shrinkage rate was as small as 1.5% or less, and that it could be used satisfactorily for products requiring a low shrinkage rate.

On the other hand, when an unstretched monofilament-like spun product obtained by melt coextrusion was rapidly cooled in a cooling tank at a temperature of 18° C. and then stretched, the raw material polypropy was also inferior.

In addition, the PP monofilaments obtained in Comparative Examples 3 and 4, which were heat-treated at a temperature of 150°C below the melting point of the raw material polypropylene resin, had excellent linear strength but were inferior in shrinkage rate and abrasion resistance. . Furthermore, in order to improve the abrasion resistance, the PP monofilaments obtained in Comparative Examples 5 and 6, which were heat-treated at a temperature below the melting point of the raw material polypropylene resin with a slightly lower draw ratio and a heat treatment at a temperature below the melting point of the raw material polypropylene resin, had improved abrasion resistance but a straight line. The strength and shrinkage rate were poor.

As detailed above, the PP monofilament according to the present invention is required to have a linear strength of 4.51)/d or more, excellent abrasion resistance, and a shrinkage rate of 1.51% or less. It has been found that it can be suitably used in the product field.

that's all

Claims (2)

[Claims] (1) Melt flow rate is 1.0 to 15 g/10 minutes,
Made of a polypropylene resin with an isotactic pentad fraction of 0.950 or more in the boiling n-heptane insoluble portion, it has a linear strength of 4.5 g/d or more and has a shrinkage rate of 1.5% or less when heated at 100°C. Polypropylene monofilament with improved wear resistance. (2) Melt flow rate is 1.0 to 15 g/10 minutes,
Monofilament-like spinning obtained by melt-kneading and extruding a polypropylene resin with an isotactic pentad fraction of the boiling n-heptane insoluble portion of 0.950 or more, and then slowly cooling it in a hot water cooling tank at 30 to 80°C. A product having a linear strength of 4.5 g/d or more and 100°C, characterized by stretching the monofilament-like spun product and subsequently heat-treating it at an ambient temperature higher than the melting point of the raw material polypropylene resin of the monofilament-shaped spun product.
A method for producing polypropylene monofilament having a shrinkage rate of 1.5% or less upon heating and improved abrasion resistance.