JPS6127486B2 - - Google Patents

Description

[Detailed description of the invention]

Polyolefin fibers, represented by polypropylene fibers and polyethylene fibers, are used in many applications due to their characteristics such as lightness, strength, and ease of heat-sealing. On the contrary, one of these may become a drawback and hinder its use. For example, polyolefin fibers are used as raw materials for papermaking, and special papers or wet-laid nonwoven fabrics are obtained that take advantage of their thermoplasticity, flexibility, hydrophobicity, and electrical properties. However, polyolefin fibers have poor wettability and low specific gravity, so they are difficult to disperse in water and cause many troubles in the papermaking process. Furthermore, the product also has a waxy feel peculiar to polyolefins, and the gloss of the paper surface may flicker, detracting from its commercial value. In addition, polyolefin fibers are often used as fibers for fishing materials such as fishing ropes and fishing nets due to their strength and water resistance, but due to their low specific gravity, there is a demand for fibers that have the ability to settle in water. Furthermore, twisted yarns for ropes and nets made from polyolefin fibers have the disadvantage of having a slippery surface and being difficult to knot. In order to modify the physical properties of such polyolefin fibers and obtain fibers that are easier to use, various methods have been proposed for incorporating inorganic substances (for example, Japanese Patent Publication No. 47-29375, Japanese Patent Publication No. 51-37378, Japanese Patent Publication No. 54−
96119 etc.). However, in conventional methods, when high concentrations of inorganic substances are mixed to achieve the purpose, the spinnability deteriorates significantly and stable spinning is difficult, and voids occur inside the fibers during stretching, resulting in a decrease in specific gravity. It had the disadvantage that it could not be raised very much.
Furthermore, in order to obtain fibers with relatively high tenacity, the inorganic substance content must be at most 25% by weight.
The disadvantage is that the fineness is more than 10 denier, and high strength fibers with fineness less than this cannot be obtained. The object of the present invention is to improve these drawbacks and provide polyolefin fibers that can be applied to various uses. That is, the first invention of the present invention is a core-sheath type composite fiber in which both the inner layer and the outer layer are made of spinnable polyolefin resin, and the outer layer has a melt flow rate (or melt index) that is higher than that of the polyolefin resin in the inner layer. It is made of polyolefin resin with a melt flow rate (melt index) of 2 to 6 times, and the outer layer contains 10 to 60 inorganic powders with an average particle size (μ) of 1.5√ or less (D is the single fiber fineness of the heat-treated system).
% by weight, and the fiber cross-sectional area ratio of the outer layer is 20% of the total.
~65%, and A/√=4~12 {A is the fiber cross-sectional area ratio (%) of the outer layer, C is the inorganic substance content (weight %) in the outer layer}. Containing an inorganic substance, the undrawn yarn melt-spun into a mold was stretched 2.5 to 6 times at 60 to 135°C, and then subjected to relaxation heat treatment at 100 to 140°C with a shrinkage rate of 4 to 20%. It is a core-sheath type composite polyolefin fiber. The inner layer part and the outer layer part referred to in the first invention are:
In core-sheath type composite fibers, the part corresponding to the core is called the inner layer, and the part corresponding to the sheath is called the outer layer.
The polyolefin resin that forms these inner and outer layers is one or two of polypropylene, a copolymer of polypropylene and a small amount of ethylene or butene, a medium-low pressure and high pressure polyethylene, a copolymer of polyethylene and a small amount of other components, etc. The polyolefin resins forming the inner and outer layers, which are a mixture of more than one species, may be the same or different. The inorganic powders to be mixed in the outer layer include clay, silicates such as talcum wollastonite, carbonates such as calcium carbonate and magnesium carbonate, barite powder, sulfates such as gypsum, titanium white, alumina, zinc white, and copper oxide silica. It is important to select a substance that matches the physical properties required for the target fiber. For example, to promote the settling properties of polyolefin fiber, it is important to choose a substance with a high specific gravity. Of course it is advantageous. Depending on the application, colored fibers may be required, so in addition to the above substances, Canadian mica, vermiculite iron oxide, barium ferrite, diatomaceous earth, molybdenum disulfide, carbon black, etc. may be used. . The particle size of the inorganic substance powder has a great effect on spinning and drawing properties, so it is preferable that the particle size is as small as possible and has a narrow particle size distribution. However, various types of inorganic substance powders are manufactured for industrial use in a high range of average particle sizes. Therefore, it is easy to select an appropriate particle size. In the present invention, an inorganic powder having a particle size of 1.5√μ (D is the single fiber fineness of the heat treatment system) or less is used. This is because if the particle size is larger than 1.5√μ, the spinning draft will not increase, yarn breakage will occur, and it will be difficult to obtain fibers with a fineness (10D or less). Moreover, if the particle size becomes large, a large amount of inorganic substance powder falls off, making it impossible to obtain the originally intended fiber. The appropriate amount of inorganic substance powder to be added to the outer layer is 10 to 60% by weight. If it is less than 10% by weight, there will be little improvement in the specific gravity of the fibers, and the addition effect will be insufficient; if it is more than 60% by weight, the spinnability will decrease, making it impossible to obtain fibers with fineness. This is because spinning will eventually become impossible. As the amount of inorganic substance powder added increases, the melt viscosity of the polyolefin resin increases and its fluidity decreases, making it unable to withstand the draft tension during spinning and causing yarn breakage. One of the objects of the present invention is to obtain a fiber with a fineness through a stable spinning process by supporting the low spinnability of the outer layer while having an inner layer that can withstand high temperatures. However, when the amount of inorganic substances exceeds 60% by weight, it is no longer possible to maintain tension only in the inner layer, and when trying to obtain fibers with a fineness smaller than 10D, thread breakage occurs frequently. The ratio of the fiber cross-sectional area of the inner layer and the outer layer of the core-sheath type composite fiber of the present invention changes depending on the amount of the inorganic substance contained in the outer layer. This is because, as mentioned above, the inner layer compensates for the decrease in fluidity in the outer layer and prevents yarn breakage. When this is expressed as the fiber cross-sectional area ratio A (%) of the outer layer, 20A65 is appropriate. If A<20, the outer layer becomes too thin, causing surface peeling of the outer layer due to stretching, and the effect of modifying the polyolefin fiber by incorporating inorganic substance powder, which is the object of the present invention, becomes weaker. It is from. If A>65, the ratio of the inner layer that maintains spinnability and fiber strength becomes too small, resulting in poor spinnability and poor drawability even when the amount of inorganic powder is at least 10% by weight. Therefore, the fiber strength becomes low and fine fibers cannot be obtained. The present inventors have proposed the above-mentioned fiber cross-sectional area ratio A of the outer layer portion.
We investigated the interrelationship between C and the inorganic substance content C in the outer layer, and found that for the purpose of eliminating the luster of the fibers, A and √ should be within the range of values in which they are in a proportional relationship, and that value could be determined experimentally. If you ask, A/√=4~
We obtained the relational expression 12. If the fluctuation values of A and C are within this range, the desired gloss of the polyolefin fiber will be eliminated, the specific gravity will be increased, the knottability will be good, and spinning and drawing will be possible without any problems during the production of the fiber. necessary to do so. The relationship between A and C is shown in the graph of FIG. The range within the diagonal lines is the range that A and C can take. As described above, the core-sheath type polyolefin fiber according to the first aspect of the present invention has a waxy texture on the surface due to the inorganic powder contained in the outer layer, has a desirable appearance as a raw material for papermaking, and has a specific gravity. Due to its large size, it has good dispersibility in water,
Problems in the papermaking process were also resolved. Furthermore, a product that eliminates the drawbacks of conventional products can be obtained even when used for fishing ropes, fishing nets, and other marine materials. Next, according to the second aspect of the invention, a method for manufacturing the above-mentioned core-sheath type polyolefin fiber is disclosed. That is, the second aspect of the present invention is that when spinning a core-sheath polyolefin fiber, a spinnable polyolefin resin is used for the inner layer, and the melt flow rate (or melt index) of the outer layer is higher than that of the inner layer. Mixture of 10 to 65% by weight of inorganic substance powder that is 2 to 8 times the melt flow rate (or melt index) of the polyolefin resin and has an average particle size (μ) of 1.5√ or less (D is the single fiber fineness of the heat-treated yarn). The fiber cross-sectional area ratio of the outer layer is the same as that of the total fiber cross-sectional area.
20 to 65% and A/√=4 to 12 {A is the cross-sectional area ratio (%) of the outer layer, C is the inorganic substance content (weight %) in the outer layer}. A core-sheath containing an inorganic substance characterized by stretching an undrawn yarn melt-spun by 2.5 to 6 times at 60 to 135°C, and then subjecting it to relaxation heat treatment at 100 to 140°C with a shrinkage rate of 4 to 20%. This is a method for manufacturing type composite fiber. As mentioned above, the polyolefin resins used in the present invention have different melt flow rates for the outer layer and the inner layer. This is because since the inorganic powder is added to the outer layer, the fluidity is lower than that of the inner layer, resulting in poor spinning and drawing properties. The ratio of melt flow rate (or melt index) in the outer layer is 2 to 8 times that in the inner layer. If it is less than 2 times, sufficient spinnability and drawability cannot be obtained in the outer layer due to the amount of inorganic powder added, and if it is more than 8 times, the melt viscosity of the outer layer is too low, resulting in rain dripping and draft spots during spinning. This is because the resulting fibers also have low strength. Melt flow rate (MFR) is measured according to ASTM-D-1238 (L), and melt index (MI) is measured according to JIS-K-6760. When adding inorganic substance powder to such polyolefin resin, in order to improve dispersibility, the surface must be treated with fatty acids, fatty acid salts, wax, polymerizable monomers, etc., and then mixed using the master batch method or Henschel mixer. Bye. The spinning method is a conventional core-sheath type composite spinning method. 2
This is a method in which a pair of melt extruders is used, the outer layer and inner layer components are supplied through separate supply channels, and both components are combined in each of the spinning holes to form a composite fiber. The fiber cross-sectional area ratio A of the outer layer portion is calculated by observing the cross section of the single fiber with a microscope, measuring the single fiber outer diameter R and the inner layer outer diameter r, and using the following formula. A=R ² −r ² /R ² ×100 A can be freely changed by adjusting the rotation speed of the gear pump of each supply path. The spinning of the core-sheath type composite polyolefin fiber according to the present invention is also greatly influenced by the conditions of stretching and heat treatment after spinning. First, the stretching temperature is preferably 60 to 135°C. Below 60°C, the fluidity of the polyolefin resin is poor, making it difficult to improve the stretching ratio, and the voids generated inside the fibers are large and increase in number, which has an adverse effect on the specific gravity effect of the fibers. In addition, the outer layer may peel off or become discontinuous. On the other hand, if the temperature is too high,
This is because at temperatures above 135°C, partial melting occurs and stretching breaks occur. The stretching ratio is within the range of 2.5 to 6 times. In order to obtain fine fibers and high-strength fibers, it is necessary to use 2.5 times or more, but if it becomes 6 times or more, the outer layer will break or a discontinuous state will occur. Relaxation heat treatment is performed at a temperature of 100-140℃ and a shrinkage rate of 4-20%.
Do it with At temperatures above 100°C and above 4%, the voids within the fibers can be eliminated, but when the temperature rises above 140°C, single fibers adhere to each other and the dispersibility as a raw material for paper decreases. Furthermore, when the relaxation rate exceeds 20%, the fiber elongation increases and the stretching effect disappears. The fibers obtained by the present invention have a high specific gravity due to the inorganic powder contained in the outer layer, so they have good dispersibility in water and have high utility value as raw materials for paper, and can also be used as ropes for marine materials, fishing nets, etc. Even when used, it has good settling properties and knotting properties in water, improving the drawbacks of conventional polyolefin fibers. Furthermore, despite being endowed with such characteristics,
Due to the outer two-layer structure, there is almost no decrease in strength and fibers with a fine denier are produced, resulting in fibers with high utility value. The present invention will be explained below with reference to Examples. Example 1 MFR14.5 in the outer layer as polyolefin resin
crystalline polypropylene resin in the inner layer.
Using crystalline polypropylene resin with MFR 5.0 (MFR ratio 2.9), the average particle size is 0.8 as inorganic powder.
A core-sheath type composite polyolefin fiber of the present invention was manufactured using μ calcium carbonate powder. First, calcium carbonate was surface-treated in advance with 20% by weight of stearic acid using a mixer, mixed with crystalline polypropylene of MFR 14.5, and extruded at 250°C to create a masterbatch containing 40% by weight of inorganic powder. Next, using a two-pair extruder, 290% of the resin for the inner layer was added.
The resin was melted at 280°C, and as a resin for the outer layer, the above master bat and polypropylene with an MFR of 14.5 were mixed at a ratio of 1:1 to set C=20, melted at 280°C, and separately supplied to the spinning head. Two types of resin are composited into a core-sheath type using a concentric compound nozzle, spun at 80℃,
It was stretched at a magnification of 4.3 and heat treated at 130°C and a relaxation rate of 7%. Example 2 Using the same resin as in Example 1, a core-sheath composite fiber was spun, drawn at 110°C and a magnification of 4.3, and stretched at 130°C.
Heat treatment was performed at a relaxation rate of 7%. Example 3 The same resin as in Example 1 was used as the inner layer resin,
The masterbatch (C=
40) was used as it was to spin core-sheath composite fibers,
It was stretched at 80°C and a magnification of 4.3, and heat treated at 130°C and a relaxation rate of 7%. Example 4 Using the same resin as in Example 1, a core-sheath composite fiber was spun, drawn at 110°C and a magnification of 4.3, and stretched at 130°C.
Heat treatment was performed at a relaxation rate of 7%. Comparative Example 1 Only the outer layer resin of Example 1 was spun using a conventional nozzle. It was stretched at 110°C at a magnification of 3.5 and heat treated at 130°C at a relaxation rate of 5%. Comparative Example 2 Only the outer layer resin of Example 3 was spun. Spun with a regular nozzle and stretched at 110℃ and a magnification of 3.5.
Heat treatment was performed at 130°C and a relaxation rate of 5%. The spinning, drawing, fiber performance, etc. of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 1.

【table】

[Table] Example 5 As a polyolefin resin, in the outer layer part
Using a crystalline polypropylene resin with an MFR of 14.5 and a crystalline polypropylene resin with an MFR of 5.0 in the inner layer (MFR ratio 2.9), and using kaolin clay with an average particle size of 0.5μ as the inorganic material powder, the core of the present invention was A sheath-type composite polyolefin fiber was produced. First, 40% by weight of kaolin clay was mixed with the resin for the outer layer (C=40). Next, using the same extruder as in Example 1 and using the same method, the two resins were composited into a core-sheath type and spun.
It was stretched at 110°C and a magnification of 5.4, and heat treated at 130°C and a relaxation rate of 7%. Example 6 Using the same resin as in Example 5, a core-sheath type composite fiber was spun and stretched at 110°C and a magnification of 5.4.
Heat treatment was performed at a relaxation rate of 5%. Example 7 Using the same resin as in Example 5, a core-sheath type composite fiber was spun, drawn at 110°C and a magnification of 5.1, and stretched at 130°C.
Heat treatment was performed at a relaxation rate of 7%. Example 8 A core-sheath composite fiber was spun using the same resin as in Example 5, drawn at 110° C. at a magnification of 4.7, and heat-treated at 130° C. at a relaxation rate of 7%. Comparative example 3 MFR6.5 in the outer layer as polyolefin resin
crystalline polypropylene resin to crystalline
Using crystalline polypropylene resin with MFR 5.0 (MFR ratio 1.3), the same amount of inorganic powder as in Example 5 was mixed into the outer layer resin, and core-sheath type polyolefin fibers were produced in the same manner. did. After spinning, it was stretched at 110℃ and a magnification of 3.5, and then stretched at 130℃ and a relaxation rate of 6.
% heat treated. Comparative Example 4 Using the same resin as in Comparative Example 3, core-sheath type polyolefin fibers were spun by varying the amount of resin in the inner and outer layers, stretched at 110°C at a magnification of 3.5, and stretched at 130°C at a relaxation rate of 6%. Heat treated. The spinning and drawing conditions, fiber performance, etc. of Examples 5 to 8 and Comparative Examples 3 and 4 are shown in Table 2.

[Table] Example 9 As a polyolefin resin, the outer layer contains
Crystalline polyethylene resin with MI20.0 is used in the inner layer.
Using MI4.0 crystalline polyethylene resin (MI ratio
5.0), the core-sheath type composite polyolefin fiber of the present invention was produced using magnetite (triiron tetroxide) with an average particle size of 0.5μ as an inorganic substance. First, 40% by weight of magnetite was added to the resin for the outer layer.
Mixed. Next, using the same extruder as in Example 1 and the same method, the two resins were composite-spun into a core-sheath type.
It was stretched at a magnification of 3.6 and heat treated at 110°C and a relaxation rate of 6%. Example 10 Using the same resin as in Example 9, core-sheath composite fibers were spun by varying the ratio of resin amounts in the inner and outer layers.
It was stretched at 90°C and a magnification of 3.6, and heat treated at 100°C with a relaxation rate of 5%. Example 11 Using the same resin as in Example 9, core-sheath type composite fibers were spun by varying the ratio of resin amounts in the inner and outer layers.
It was stretched at 90°C and a magnification of 3.6, and heat treated at 110°C with a relaxation rate of 6%. Example 12 Using the same resin as in Example 9, core-sheath type composite fibers were spun with the ratio of resin amounts in the inner and outer layers changed as in Example 9 and Example 11, and stretched at 90°C and a magnification of 3.6. ,
Heat treatment was performed at 110°C and a relaxation rate of 6%. Comparative Example 5 As polyolefin resin, a crystalline polyethylene resin of MI6.0 was used for the outer layer, a crystalline polyethylene resin of MI4.0 was used for the inner layer, and 40 weight of the same magnetite as in Example 9 was used as the resin for the outer layer. % was mixed. Composite spinning of two types of resin into a core-sheath type, 90℃, magnification
3.2, and heat treated at 110°C with a relaxation rate of 6%. Comparative Example 6 Using the same resin as in Comparative Example 5, core-sheath type composite fibers were spun by changing the ratio of the amount of resin in the inner and outer layers,
It was stretched at 90°C and a magnification of 3.2, and heat treated at 110°C and a relaxation rate of 6%. The spinning and drawing conditions, fiber performance, etc. of Examples 9 to 12 and Comparative Examples 5 and 6 are shown in Table 3.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the fiber cross-sectional area ratio A of the outer layer portion and the inorganic substance content C of the outer layer portion of the composite fiber of the present invention. The diagonal lines indicate the possible ranges of A and C.

Claims (1)

[Claims] 1 A core-sheath type composite fiber consisting of a spinnable polyolefin resin in both the inner layer and the outer layer, and the melt flow rate (or melt index) of the outer layer is lower than the melt flow rate (melt index) of the polyolefin resin in the inner layer. Made of 2 to 6 times larger polyolefin resin, the outer layer has an average particle size (μ)
Contains 10 to 60% by weight of inorganic substance powder of 1.5√ or less (D is the single fiber fineness of the heat-treated yarn), the fiber cross-sectional area ratio of the outer layer is 20 to 65% of the total, and A/√
=4~12 {A is the fiber cross-sectional area ratio (%) of the outer layer, C
is an undrawn yarn melt-spun into a core-sheath type so as to satisfy the inorganic substance content (wt%) in the outer layer.
After stretching 2.5 to 6 times at 135℃, 100 to 140
A core-sheath type composite polyolefin fiber containing an inorganic substance, characterized by being subjected to relaxation heat treatment at a shrinkage rate of 4 to 20°C.