JPH06248506A - Polypropylene fiber and fiber-reinforced formed cement article - Google Patents

Abstract

PURPOSE:To obtain a cement-reinforcing fiber consisting of a polypropylene fiber having a breakage strength of >=6g/d, high crystallinity and excellent rigidity and easily dispersible in cement slurry. CONSTITUTION:The fiber for cement reinforcement is produced by adding fine powder of calcium carbonate having an average particle diameter of <1mum to a polypropylene having narrow molecular weight distribution width and high stereoregularity, melt-spinning the polymer and applying an alkali metal salt of a n-alkylphosphate to the obtained high-tenacity polypropylene fiber. The reinforced formed cement article contains 0.5-5wt.% of the fiber. A formed cement article having excellent bending strength and Charpy impact strength can be produced by this process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a higher strength than conventional ones, and even when dispersed in a cement slurry liquid, there is no floating phenomenon (floating seed phenomenon) of the fibers, and the fibers are uniformly dispersed. The present invention relates to a polypropylene fiber for cement reinforcement having a good sedimentation property, and a cement molded product reinforced with the fiber.

[0002]

2. Description of the Related Art It has been proposed to use various inorganic fibers and synthetic fibers as cement reinforcing fibers in place of asbestos. For example, JP-A-49-98424 and JP-A-49-98424
No. 104917, JP-A-49-104918, JP-A-61-86452, JP-A-62-171952 and the like use glass fiber, polyester fiber, vinylon fiber, polypropylene fiber, aromatic polyamide fiber, acrylic fiber. Is taught.

Cement moldings produced by a conventional method using these reinforcing fibers, for example, papermaking molding, extrusion molding, or cast molding, further improve the strength thereof, and the structure is further densified by a high-pressure pressing method. The method of curing under various conditions is generally used. This curing includes natural curing, steam curing, and autoclave curing, but natural curing requires long-term curing of 14 days or longer, and autoclave curing at a temperature of over 140 ° C is usually 12 to 1
It has the advantage of requiring 8 hours of curing.

When the cement matrix is cured under alkaline conditions at the above-mentioned high temperature, the polyester fiber, vinylon fiber, polyamide fiber, and acrylic fiber are subject to chemical changes such as decomposition and become dangerous and lose their function as reinforcing fibers. Will end up. Further, not only ordinary glass fibers but also alkali-resistant glass fibers, when subjected to the above-mentioned curing at high temperature, may be impaired for a month and the function as a reinforcing fiber may be lost or significantly reduced. The only ones that can withstand are polypropylene and poly-4-methylpentene, which are heat resistant alkaline.
Polyolefin fiber such as 1.

However, the conventional polypropylene fiber uses crystalline polypropylene having an HI of 96 to 97% by weight and an IPF of 93 to 94 mol%, usually 5 to 6 g.
The strength was / d. Further, there is also known a method in which polypropylene having a Q value as low as about 4 is used to improve drawability and dry drawing is performed at about 150 ° C., but this also has a maximum strength of about 7.5 g / d. However, because it is strongly inferior to other fibers, it was often used in a limited field as a ship doctor for strengthening cement products.

Regarding polypropylene fiber and its composite fiber using highly crystalline polypropylene, Japanese Patent Laid-Open No. 60-88
No. 59113, No. 62-41331, and Japanese Examined Patent Publication No. 3-20505, etc., but those examples only show the same breaking strength as conventional polypropylene. Conventionally, high crystallinity polypropylene has been mainly used in the field of injection molding, and only polymers having a wide Q value of 6 or more have been distributed in the market in order to suppress heat shrinkage. This resin had a large Q value and the stretch orientation was the same as that of conventional polypropylene.

[0007] Further, since the polyolefin fiber is inherently large in hydrophobicity and has a poor affinity with cement particles, the fiber surface was treated with a surfactant to make the fiber hydrophilic, but the wet papermaking method is used. When the fibers are added to the cement slurry liquid, the surfactant flows out and is removed from the fiber surface, so that it is difficult to uniformly disperse in the cement slurry liquid and the fibers are easily floated on the slurry surface.

Due to this non-uniform dispersion or floating phenomenon, the effective mixing amount of the fibers is reduced, and the predetermined reinforcing effect cannot be obtained, so that it becomes insoluble with calcium ions as described in JP-A-64-33036. When dialkyl phosphate salt is used as the fiber treatment agent and the fiber is added to the cement slurry liquid, the fiber treatment agent is quickly made difficult to dissolve on the fiber surface and fixed to the fiber surface, maintaining the hydrophilicity of the fiber and uniformly dispersing the fiber. There is an example of achieving prevention of the floating phenomenon.

[0009]

[Problems to be Solved by the Invention] Polypropylene fibers treated with an alkyl phosphate salt, when added to a cement slurry having a high concentration of calcium ions, have a poorly soluble alkyl phosphate calcium salt fixed on the fiber surface, Since the hydrophilicity of the fibers can be maintained, the fibers do not float up, but this method also failed if the calcium ion content was low.

That is, depending on the cement product manufacturing system, the reinforcing fiber may be dispersed in fresh water and then cement powder may be added to make a cement slurry. In such a case, since the calcium ion is small, the alkyl phosphite is used. The fibers treated with the fate salt have the surfactant removed and float up.

Further, polypropylene fibers produced by the conventional melt spinning method and treated with the above-mentioned alkyl phosphate salt have been widely used for reinforcing cement products because of their advantages of low specific gravity, excellent heat resistance and alkali resistance, and low cost. However, it was inferior in strength to other synthetic fibers. Since the strength of other synthetic fibers has been remarkably improved in recent years, relative strength decreases more and more, and in the field of cement-reinforcing short fibers that originally require strength, polypropylene fibers are also required to have higher strength.

In order to achieve the above-mentioned object, the present invention has a small Q value for high stretching and high strength, has a low crystalline component for improving orientation during stretching, and has extremely high stereoregularity. Using highly crystalline polypropylene, adding fine powder of calcium carbonate to this, melt spinning, and then drawing at a high temperature within a range where components do not fuse with each other, such as a dry drawing method, to increase the draw ratio, Obtain strong polypropylene fibers. Then, the surface is treated with the alkyl phosphate salt to obtain a cement reinforcing fiber. An object of the present invention is to obtain a fiber for cement reinforcement capable of significantly improving the strength, especially the Charpy impact force, of a fiber-reinforced cement molded body which is naturally cured or autoclaved by using this fiber.

Another object of the present invention is to obtain a cement-reinforcing fiber having good dispersibility even in water, which has a low calcium ion content, while improving the hydrophilicity and the sedimentation property in water while keeping the characteristics of the polyolefin fiber. There is.

[0014]

In order to achieve the object of the present invention, the present inventors have found that the conventional cement-reinforcing fiber simply uses a fiber having a high breaking strength to improve the strength of the cement molded product. From the idea of improving it, we took a step further and found that the strength of the cement molded body greatly contributed to the rigidity of the reinforcing fiber. For that purpose, the present invention has been accomplished by making the polypropylene fiber, which is a reinforcing fiber, a fiber having a higher crystallinity than the conventional fiber.

To achieve the above object, the polypropylene fiber of the present invention has a Q value (Q: weight average molecular weight / number average molecular weight ratio) of less than 5 and a boiling n-heptane insoluble content (HI: weight%) of 97 <. HI <100, isotactic pentad fraction (IPF: mol%) 94 <IPF <100, a highly crystalline polypropylene containing 4 to 20 g of calcium carbonate fine powder having an average diameter of less than 1 μm. 0.05 to 10% by weight of a normal alkyl phosphate alkali metal salt having 8 to 18 carbon atoms based on the weight of the fiber is attached to the polypropylene fiber having a breaking strength of the fiber of more than 6 g / denier. Is a polypropylene fiber for cement reinforcement.

[0016] In a further preferred aspect of the present invention, a core-sheath type polypropylene fiber having a polypropylene resin component as a sheath part and a fiber having the polypropylene resin component not containing calcium carbonate as a core part and having a breaking strength of 7 g / denier In addition, a normal alkyl phosphate alkali metal salt having 8 to 18 carbon atoms is contained in an amount of 0.05 to 1 with respect to the weight of the fiber.
It is a polypropylene fiber for cement reinforcement characterized in that 0% by weight is attached. By adopting such a core-sheath structure, the fiber strength is further improved and the object of the present invention can be achieved.

In the above construction, the polypropylene resin used in the present invention has a Q value of less than 5, preferably 4 or less, HI of 97% or more, preferably 98% or more, and IPF of 94.
% Or more, preferably 96% or more of highly crystalline polypropylene. The Q value of less than 5 is to improve the heat drawability. The HI of 97% or more and the IPF of 94% or more are obtained by selecting a polypropylene resin having a low crystal component and excellent stereoregularity to improve the crystal orientation by stretching and increase the fiber strength, thereby increasing the rigidity of the fiber. This is to improve the property.

The fine powder of calcium carbonate used in the present invention preferably has an average diameter of less than 1 μm, preferably less than 0.6 μm and does not contain particles of 2 μm or more. With such calcium carbonate, fibers having a denier of 1 to 20 can be stably spun.

The amount of calcium carbonate mixed in the fiber is 4
If it is less than 20% by weight, floating seeds are easily formed in the cement slurry even if the amount of the alkyl phosphate salt attached is increased, and if it exceeds 20% by weight, the stretchability of the fiber is deteriorated and desired strength cannot be obtained. It is preferably 10 to 20% by weight. Further, the calcium carbonate fine powder is preferably treated with a surfactant before being mixed in the polypropylene resin.

The alkyl phosphate salt has 8 carbon atoms.
A monoalkyl ester or dialkyl ester having a normal alkyl group of -18, which is a sodium salt or a potassium salt. Further, if the amount of the alkyl phosphate salt attached is less than 0.05% by weight, the dispersion of the fibers will be insufficient, and the amount may be 0.05% by weight or more.
Even if it exceeds the weight%, the effect is hardly improved.

The polypropylene fiber of the present invention contains 0.5 to 5 parts by weight of the dry cement matrix of the cement molded product.
It is preferable to add it in an amount of 0.5% by weight, and if it is less than 0.5% by weight, the fiber reinforcing effect cannot be obtained. Further, the cement molded product of the present invention is preferably autoclaved after being made from a cement slurry liquid.

Further, at least 10 of the above papermaking products
The strength of the molded product can be further improved by pressing at a pressure of 0 Kg / cm ² or more, preferably 200 Kg / cm ² , and this can be aged in water for less than 30 days or in an autoclave for 12 to 18 hours at about 170 ° C. Most preferably.

[0023]

According to the above-mentioned constitution of the present invention, there are few low crystalline components which hinder the crystal orientation due to stretching, and the boiling n
-Heptane insoluble matter is larger than conventional polypropylene,
It also has excellent stereoregularity because it assists the crystal orientation by stretching, that is, it has a larger isotactic pentad fraction than conventional polypropylene, and has a Q value significantly higher than that of conventional highly crystalline polypropylene to improve stretchability. Since it is made extremely low, the draw ratio is increased and a high strength polypropylene fiber for cement reinforcement can be obtained.

Thus, polypropylene, which is more highly oriented and crystallized than conventional polypropylene, is melt-spun at a relatively low temperature so as to avoid entanglement and cutting of molecules, and then at a high draw ratio at a high draw ratio. Polypropylene fiber having a breaking strength of more than 6 g / denier, which was not achieved by mass production of ordinary polypropylene with at least a single fiber, by stretching the fiber with a highly oriented crystallized fiber as compared with conventional polypropylene fiber. It is also possible to easily obtain a breaking strength of 9 g / denier or more by using the above preferred stretching conditions.

Further, when the fiber is placed in a moist state, ion exchange occurs between the calcium ion leached from calcium carbonate and the alkyl phosphate salt adhering to the fiber on the surface of the fiber, and the alkyl phosphate calcium salt adheres to the fiber surface, Is hydrophilized to an extent that it is well dispersed in water, and air bubbles and the like generated during stirring and mixing in water are less likely to adhere to the fiber, and the floating phenomenon of the fiber does not occur.

Further, under wet conditions, calcium ions are gradually leached from the surface of the fiber, and the surface of the fiber is covered with the mixture of the insoluble material of the fiber treating agent and the cement particles. Therefore, the affinity with the cement matrix is the same as that of the conventional polypropylene fiber. It is much more improved, and has the effect of reducing the loss of fibers from the breakable matrix of the cement molded body. Furthermore, since the strength of the fiber itself is also improved, the cement molded product using the fiber of the present invention for reinforcement has significantly improved both bending strength and impact strength as compared with conventional products.

[0027]

EXAMPLE The polypropylene used in the present invention has a melt flowability of the melt flow rate (M) for the sake of melt spinning.
FR: g / 10 minutes, measured according to JIS-K-7210,
Weighted 2169g, measurement temperature 230 ℃) 1 <MFR <1
00, more preferably 5 <MFR <30, most preferably 10 to 20, and the density is around 0.905 in the raw material pellet state, which is not different from ordinary polypropylene.

The melt-spinning temperature may be a temperature within a range that does not impair the stereoregularity, but it is preferably a relatively low temperature in order to reduce entanglement and rounding of molecules, for example, 260 to 280 ° C. for a single fiber. As for the stretching temperature, in order to improve the stretching property as much as possible, it is desirable to perform high stretching by a hot roll dry stretching method at 140 to 150 ° C.

Next, a measurement example of each factor defined in the present invention will be described. (1) The weight average molecular weight is M = [ΣNiMi ² ] / [ΣNiM by using, for example, a light scattering method, a viscosity method or an ultracentrifugation method.
i]. (2) The number average molecular weight is Mn = [ΣNiMi] / [ΣN] using, for example, a terminal group quantitative method, a freezing point depression method, and an osmotic pressure method.
i]. Generally, the weight average molecular weight / number average molecular weight is used as a measure of polydispersity, and the larger this value is 1 (monodisperse), the wider the molecular weight distribution curve is (broad). In addition, polymers with many branches also have high values. (3) The n-heptane-insoluble matter (HI) was obtained by completely dissolving 5 g of a polypropylene sample in 500 ml of boiling xylene, throwing them into 5 l of methanol, recovering and drying them, and then Soxhlet extraction with boiling n-heptane for 6 hours is referred to as the extraction residue. (4) Isotactic pentad fraction (IPF) is
Insoluble matter in n-heptane "Macromoleculars"
(Macromolecule, Vol. 6,925
(1973) and Vol. It was measured according to 8,687 (1975). (5) Melt flow rate (MFR) is 190 ° C
Nozzle passage amount (Unit: g / 10 minutes, JIS-K-72
According to 10, the load was measured at 2.169 kg).

Examples will be specifically described below. [Examples 1 to 8 and Comparative Examples 1 to 7] Polypropylene resin pellets shown in Table 1 and resin pellets obtained by kneading the resin with calcium carbonate fine powder pretreated with metal soap having an average particle size of 0.5 µm were used. And a core-sheath type composite fiber having an area ratio of the core component and the sheath component of 1: 1 in the fiber cross section in which the resin pellet containing calcium carbonate is the sheath component and the resin pellet not containing calcium carbonate is the core component, and calcium carbonate Each of the single fibers containing only the resin pellets containing was melt-spun. Each of these undrawn yarns is dry-drawn using a 150 ° C. hot roll in an atmosphere of 150 ° C., impregnated with various surfactant aqueous solutions of normal alkyl phosphate metal salts, left to stand overnight, and air-dried to 6 mm or 1 mm.
It was cut to 0 mm. At this time, the strength and elongation of the drawn yarn was measured using the air-dried fiber before cutting.

Then, in 7.2 liters of tap water, 680 g of ordinary Portland cement, 17 g of pulp and 1 mica powder from China
70 g, and 8.5 g of the short fibers of each of the above-mentioned Examples and Comparative Examples (however, Example 6 was 13 g, Comparative Example 3 was 2.
6 g, Comparative Example 5 is a conventional polypropylene fiber, Comparative Example 6
Is 43 g of asbestos instead of short fiber, Comparative Example 7 is 2
8.5 g of commercially available vinylon having a denier of 6 mm was added. ) Were sequentially added and mixed to prepare an 8 l cement slurry.

To this slurry liquid, 20 ml of 0.02% by weight of a flocculant (trade name: IKEFLOCK, manufactured by Ichikawa Kaori Co., Ltd.) was added, and the mixture was divided into 8 times in a mold container having a bottom area of 250 mm × 250 mm. This slurry liquid was poured and dehydrated through a 60-mesh wire net to produce paper, and these were sequentially stacked with the upper surface facing upward to obtain an 8-layer laminated product to obtain a flat semi-plastic molded product having a thickness of about 8 mm.

200 kg / cm ^{2 of} this semi-plastic molded product
After pressing for 1 minute under the pressure of, the compression molded product was allowed to stand at room temperature in a wet state for 28 days for natural curing, and the slurry state and the product during that period were evaluated. The results are shown in Table 1.

The test evaluation was carried out as follows. Floating fiber ratio (%): 10 for the prepared cement slurry
After allowing to stand for a minute, the floating fibers of the supernatant liquid are scooped up with a wire net and dried, and the fiber weight Ag is measured, and the floating fiber ratio (%) = 100 A / B is calculated from the fiber input amount Bg. Dispersion state: After putting the slurry in a mold container, the semi-plastic state molded product obtained by dehydration was observed for the surface irregularities and evaluated as follows. ⊚: A state with very few irregularities. ◯: A state where there are few irregularities. Δ: A state in which unevenness is slightly large. X: A state where there are many irregularities. Product appearance: Observe the front and back of the cement product after curing,
It evaluated as follows. ⊚: A state in which the fibers are hardly exposed on the product surface. ○: The state where the fibers are slightly exposed on the product surface. Δ: A state in which fibers are slightly exposed on the product surface. X: A state in which many fibers are exposed on the product surface. Eyebrow strength: Measured according to JIS-A-1408. Charpy impact strength: Measured according to JIS-B-7722.

[Examples 9 to 12 and Comparative Examples 8 to 11] Pressed products in the same manner as in Example 1 and 5 mm thick paper-made semi-plastic molded articles were autoclaved at 160 ° C for 18 hours. Was evaluated. The results are shown in Table 2.

[Examples 13 to 14, Comparative Examples 12 to 15]
Ordinary Portland cement (510 g), silica sand (340 g), asbestos (17 g), pulp (17 g) and the fibers of Example 1 and Comparative Examples 15 and 6 (8.5 g) were sequentially added to 7.2 liters of tap water to prepare an 8 liter cement slurry. After adding 20 ml of 0.02% by weight of a coagulant, the mixture was poured into a mold container 8 times and dehydrated through a 60 mesh wire net to obtain a flat semi-plastic molded product having a thickness of about 5 mm. It was The product was evaluated by subjecting this molded product to a natural curing method in which it is left in a wet state for 28 days and an autoclave curing treatment at 160 ° C. for 10 hours. The results are shown in Table 3.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

INDUSTRIAL APPLICABILITY The polypropylene fiber of the present invention is useful as a fiber for reinforcing cement because it has good hydrophobicity and has a small specific gravity and is well mixed with a cement slurry and is preferably dispersed. In the manufacturing process of cement products produced by the papermaking method, the floating phenomenon of fibers is not observed, the product has an excellent surface appearance, and the input fibers are uniformly dispersed, so that the reinforcing effect can be effectively achieved. Furthermore, since the fiber has a higher strength than the conventional polypropylene reinforcing fiber, it has excellent bending strength and impact strength.

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[Procedure amendment]

[Submission date] December 17, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction method] Change

[Correction content]

To achieve the above object, the polypropylene fiber of the present invention has a Q value (Q: weight average molecular weight / number average molecular weight ratio) of less than 5 and a boiling n-heptane insoluble content (HI: weight%) of 97 <. HI <100, isotactic pentad fraction (IPF: mol%) 94 <IPF <100, a highly crystalline polypropylene resin containing 3 to 20 g by weight of calcium carbonate fine powder having an average diameter of less than 1 μm. 0.05 to 10% by weight of a normal alkyl phosphate alkali metal salt having 8 to 18 carbon atoms based on the weight of the fiber is attached to the polypropylene fiber having a breaking strength of the fiber of more than 6 g / denier. Is a polypropylene fiber for cement reinforcement.

[Procedure 3]

[Document name to be amended] Statement

[Correction method] Change

[Correction content]

The amount of calcium carbonate mixed in the fiber is 3
If it is less than 20% by weight, floating seeds are easily formed in the cement slurry even if the amount of the alkyl phosphate salt attached is increased, and if it exceeds 20% by weight, the stretchability of the fiber is deteriorated and desired strength cannot be obtained. It is preferably 10 to 20% by weight. Further, the calcium carbonate fine powder is preferably treated with a surfactant before being mixed in the polypropylene resin.

[Procedure amendment]

[Submission date] March 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction method] Change

[Correction content]

In a further preferred aspect of the present invention, a core-sheath type polypropylene having a polypropylene resin component as a sheath portion and a fiber having the polypropylene resin component not containing calcium carbonate as a core portion and having a breaking strength of 7 g / denier or more is used. In the fiber, an alkali metal salt of normal alkyl phosphate having 8 to 18 carbon atoms is added in an amount of 0.05 with respect to the weight of the fiber.
It is a polypropylene fiber for cement reinforcement characterized by being adhered by 10 to 10% by weight. By adopting such a core-sheath structure, the fiber strength is further improved and the object of the present invention can be achieved. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 13, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Polypropylene fiber and fiber reinforced cement molding

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a higher strength than conventional ones, and even when dispersed in a cement slurry liquid, there is no floating phenomenon (floating seed phenomenon) of the fibers, and the fibers are uniformly dispersed. The present invention relates to a polypropylene fiber for cement reinforcement having a good sedimentation property, and a cement molded product reinforced with the fiber.

[0002]

2. Description of the Related Art It has been proposed to use various inorganic fibers and synthetic fibers as cement reinforcing fibers in place of asbestos. For example, JP-A-49-98424 and JP-A-49-98424
No. 104917, JP-A-49-104918, JP-A-61-86452, JP-A-62-171952 and the like use glass fiber, polyester fiber, vinylon fiber, polypropylene fiber, aromatic polyamide fiber, acrylic fiber. Is taught.

Cement moldings produced by a conventional method using these reinforcing fibers, for example, papermaking molding, extrusion molding, or cast molding, further improve the strength thereof, and the structure is further densified by a high-pressure pressing method. The method of curing under various conditions is generally used. This curing includes natural curing, steam curing, and autoclave curing, but natural curing requires long-term curing of 14 days or longer, and autoclave curing at a temperature of over 140 ° C is usually 12 to 1
It has the advantage of requiring 8 hours of curing.

When the cement matrix is cured under alkaline conditions at the above-mentioned high temperature, the polyester fiber, vinylon fiber, polyamide fiber, and acrylic fiber are subject to chemical changes such as decomposition and become dangerous and lose their function as reinforcing fibers. Will end up. Further, not only ordinary glass fibers but also alkali-resistant glass fibers, when subjected to the above-mentioned curing at high temperature, may be impaired for a month and the function as a reinforcing fiber may be lost or significantly reduced. The only ones that can withstand are polypropylene and poly-4-methylpentene, which are heat resistant alkaline.
Polyolefin fiber such as 1.

However, the conventional polypropylene fiber uses crystalline polypropylene having an HI of 96 to 97% by weight and an IPF of 93 to 94 mol%, usually 5 to 6 g.
The strength was / d. Further, there is also known a method in which polypropylene having a Q value as low as about 4 is used to improve drawability and dry drawing is performed at about 150 ° C., but this also has a maximum strength of about 7.5 g / d. However, because it is strongly inferior to other fibers, it was often used in a limited field as a ship doctor for strengthening cement products.

Regarding polypropylene fiber and its composite fiber using highly crystalline polypropylene, Japanese Patent Laid-Open No. 60-88
No. 59113, No. 62-41331, and Japanese Examined Patent Publication No. 3-20505, etc., but those examples only show the same breaking strength as conventional polypropylene. Conventionally, high crystallinity polypropylene has been mainly used in the field of injection molding, and only polymers having a wide Q value of 6 or more have been distributed in the market in order to suppress heat shrinkage. This resin had a large Q value and the stretch orientation was the same as that of conventional polypropylene.

[0007] Further, since the polyolefin fiber is inherently large in hydrophobicity and has a poor affinity with cement particles, the fiber surface was treated with a surfactant to make the fiber hydrophilic, but the wet papermaking method is used. When the fibers are added to the cement slurry liquid, the surfactant flows out and is removed from the fiber surface, so that it is difficult to uniformly disperse in the cement slurry liquid and the fibers are easily floated on the slurry surface.

Due to this non-uniform dispersion or floating phenomenon, the effective mixing amount of the fibers is reduced, and the predetermined reinforcing effect cannot be obtained, so that it becomes insoluble with calcium ions as described in JP-A-64-33036. When dialkyl phosphate salt is used as the fiber treatment agent and the fiber is added to the cement slurry liquid, the fiber treatment agent is quickly made difficult to dissolve on the fiber surface and fixed to the fiber surface, maintaining the hydrophilicity of the fiber and uniformly dispersing the fiber. There is an example of achieving prevention of the floating phenomenon.

[0009]

[Problems to be Solved by the Invention] Polypropylene fibers treated with an alkyl phosphate salt, when added to a cement slurry having a high concentration of calcium ions, have a poorly soluble alkyl phosphate calcium salt fixed on the fiber surface, Since the hydrophilicity of the fibers can be maintained, the fibers do not float up, but this method also failed if the calcium ion content was low.

That is, depending on the cement product manufacturing system, the reinforcing fiber may be dispersed in fresh water and then cement powder may be added to make a cement slurry. In such a case, since the calcium ion is small, the alkyl phosphite is used. The fibers treated with the fate salt have the surfactant removed and float up.

Further, polypropylene fibers produced by the conventional melt spinning method and treated with the above-mentioned alkyl phosphate salt have been widely used for reinforcing cement products because of their advantages of low specific gravity, excellent heat resistance and alkali resistance, and low cost. However, it was inferior in strength to other synthetic fibers. Since the strength of other synthetic fibers has been remarkably improved in recent years, relative strength decreases more and more, and in the field of cement-reinforcing short fibers that originally require strength, polypropylene fibers are also required to have higher strength.

In order to achieve the above-mentioned object, the present invention has a small Q value for high stretching and high strength, has a low crystalline component for improving orientation during stretching, and has extremely high stereoregularity. Using highly crystalline polypropylene, adding fine powder of calcium carbonate to this, melt spinning, and then drawing at a high temperature within a range where components do not fuse with each other, such as a dry drawing method, to increase the draw ratio, Obtain strong polypropylene fibers. Then, the surface is treated with the alkyl phosphate salt to obtain a cement reinforcing fiber. An object of the present invention is to obtain a fiber for cement reinforcement capable of significantly improving the strength, especially the Charpy impact force, of a fiber-reinforced cement molded body which is naturally cured or autoclaved by using this fiber.

Another object of the present invention is to obtain a cement-reinforcing fiber having good dispersibility even in water, which has a low calcium ion content, while improving the hydrophilicity and the sedimentation property in water while keeping the characteristics of the polyolefin fiber. There is.

[0014]

In order to achieve the object of the present invention, the inventors of the present invention should use a conventional cement reinforcing fiber having a high breaking strength as the fiber only. One step further from the idea of improving the strength, it was found that the strength of the cement molded body greatly contributed to the rigidity of the reinforcing fiber. for that purpose,
The present invention has been accomplished by making polypropylene fibers, which are reinforcing fibers, more highly crystalline than conventional fibers.

To achieve the above object, the polypropylene fiber of the present invention has a Q value (Q: weight average molecular weight / number average molecular weight ratio) of less than 5 and a boiling n-heptane insoluble content (HI: weight%) of 97 <. A resin containing 3 to 20 % by weight of calcium carbonate fine powder having an average diameter of less than 1 μm in a highly crystalline polypropylene having an HI <100 and an isotactic pentad fraction (IPF: mol%) of 94 <IPF <100. 0.05 to 10% by weight of a normal alkyl phosphate alkali metal salt having 8 to 18 carbon atoms based on the weight of the fiber is attached to the polypropylene fiber having a breaking strength of the fiber of more than 6 g / denier. Is a polypropylene fiber for cement reinforcement.

[0016] In a further preferred aspect of the present invention, a core-sheath type polypropylene fiber having a polypropylene resin component as a sheath part and a fiber having the polypropylene resin component not containing calcium carbonate as a core part and having a breaking strength of 7 g / denier In addition, a normal alkyl phosphate alkali metal salt having 8 to 18 carbon atoms is contained in an amount of 0.05 to 1 with respect to the weight of the fiber.
It is a polypropylene fiber for cement reinforcement characterized in that 0% by weight is attached. By adopting such a core-sheath structure, the fiber strength is further improved and the object of the present invention can be achieved.

In the above construction, the polypropylene resin used in the present invention has a Q value of less than 5, preferably 4 or less, HI of 97% or more, preferably 98% or more, and IPF of 94.
% Or more, preferably 96% or more of highly crystalline polypropylene. The Q value of less than 5 is to improve the heat drawability. The HI of 97% or more and the IPF of 94% or more are obtained by selecting a polypropylene resin having a low crystal component and excellent stereoregularity to improve the crystal orientation by stretching and increase the fiber strength, thereby increasing the rigidity of the fiber. This is to improve the property.

The fine powder of calcium carbonate used in the present invention preferably has an average diameter of less than 1 μm, preferably less than 0.6 μm and does not contain particles of 2 μm or more. With such calcium carbonate, fibers having a denier of 1 to 20 can be stably spun.

The amount of calcium carbonate mixed in the fiber is 3
If it is less than 20% by weight, floating seeds are easily formed in the cement slurry even if the amount of the alkyl phosphate salt attached is increased, and if it exceeds 20% by weight, the stretchability of the fiber is deteriorated and desired strength cannot be obtained. It is preferably 10 to 20% by weight. Further, the calcium carbonate fine powder is preferably treated with a surfactant before being mixed in the polypropylene resin.

The alkyl phosphate salt has 8 carbon atoms.
A monoalkyl ester or dialkyl ester having a normal alkyl group of -18, which is a sodium salt or a potassium salt. Further, if the amount of the alkyl phosphate salt attached is less than 0.05% by weight, the dispersion of the fibers will be insufficient, and the amount may be 0.05% by weight or more.
Even if it exceeds the weight%, the effect is hardly improved.

The polypropylene fiber of the present invention contains 0.5 to 5 parts by weight of the dry cement matrix of the cement molded product.
It is preferable to add it in an amount of 0.5% by weight, and if it is less than 0.5% by weight, the fiber reinforcing effect cannot be obtained. Further, the cement molded product of the present invention is preferably autoclaved after being made from a cement slurry liquid.

Further, at least 10 of the above papermaking products
The strength of the molded product can be further improved by pressing at a pressure of 0 Kg / cm ² or more, preferably 200 Kg / cm ² , and this can be aged in water for less than 30 days or in an autoclave for 12 to 18 hours at about 170 ° C. Most preferably.

[0023]

According to the above-mentioned constitution of the present invention, there are few low crystalline components which hinder the crystal orientation due to stretching, and the boiling n
-Heptane insoluble matter is larger than conventional polypropylene,
It also has excellent stereoregularity because it assists the crystal orientation by stretching, that is, it has a larger isotactic pentad fraction than conventional polypropylene, and has a Q value significantly higher than that of conventional highly crystalline polypropylene to improve stretchability. Since it is made extremely low, the draw ratio is increased and a high strength polypropylene fiber for cement reinforcement can be obtained.

Thus, polypropylene, which is more highly oriented and crystallized than conventional polypropylene, is melt-spun at a relatively low temperature so as to avoid entanglement and cutting of molecules, and then at a high draw ratio at a high draw ratio. Polypropylene fiber having a breaking strength of more than 6 g / denier, which was not achieved by mass production of ordinary polypropylene with at least a single fiber, by stretching the fiber with a highly oriented crystallized fiber as compared with conventional polypropylene fiber. It is also possible to easily obtain a breaking strength of 9 g / denier or more by using the above preferred stretching conditions.

Further, when the fiber is placed in a moist state, ion exchange occurs between the calcium ion leached from calcium carbonate and the alkyl phosphate salt adhering to the fiber on the surface of the fiber, and the alkyl phosphate calcium salt adheres to the fiber surface, Is hydrophilized to an extent that it is well dispersed in water, and air bubbles and the like generated during stirring and mixing in water are less likely to adhere to the fiber, and the floating phenomenon of the fiber does not occur.

Further, under wet conditions, calcium ions are gradually leached from the surface of the fiber, and the surface of the fiber is covered with the mixture of the insoluble material of the fiber treating agent and the cement particles. Therefore, the affinity with the cement matrix is the same as that of the conventional polypropylene fiber. It is much more improved, and has the effect of reducing the loss of fibers from the breakable matrix of the cement molded body. Furthermore, since the strength of the fiber itself is also improved, the cement molded product using the fiber of the present invention for reinforcement has significantly improved both bending strength and impact strength as compared with conventional products.

[0027]

EXAMPLE The polypropylene used in the present invention has a melt flowability of the melt flow rate (M) for the sake of melt spinning.
FR: g / 10 minutes, measured according to JIS-K-7210,
Weighted 2169g, measurement temperature 230 ℃) 1 <MFR <1
00, more preferably 5 <MFR <30, most preferably 10 to 20, and the density is around 0.905 in the raw material pellet state, which is not different from ordinary polypropylene.

The melt-spinning temperature may be a temperature within a range that does not impair the stereoregularity, but it is preferably a relatively low temperature in order to reduce entanglement and rounding of molecules, for example, 260 to 280 ° C. for a single fiber. As for the stretching temperature, in order to improve the stretching property as much as possible, it is desirable to perform high stretching by a hot roll dry stretching method at 140 to 150 ° C.

Next, a measurement example of each factor defined in the present invention will be described. (1) The weight average molecular weight is M = [ΣNiMi ² ] / [ΣNiM by using, for example, a light scattering method, a viscosity method or an ultracentrifugation method.
i]. (2) The number average molecular weight is Mn = [ΣNiMi] / [ΣN] using, for example, a terminal group quantitative method, a freezing point depression method, and an osmotic pressure method.
i]. Generally, the weight average molecular weight / number average molecular weight is used as a measure of polydispersity, and the larger this value is 1 (monodisperse), the wider the molecular weight distribution curve is (broad). In addition, polymers with many branches also have high values. (3) The n-heptane-insoluble matter (HI) was obtained by completely dissolving 5 g of a polypropylene sample in 500 ml of boiling xylene, throwing them into 5 l of methanol, recovering and drying them, and then Soxhlet extraction with boiling n-heptane for 6 hours is referred to as the extraction residue. (4) Isotactic pentad fraction (IPF) is
Insoluble matter in n-heptane "Macromoleculars"
(Macromolecule, Vol. 6,925
(1973) and Vol. It was measured according to 8,687 (1975). (5) Melt flow rate (MFR) is 230 ° C.
Nozzle passage amount (Unit: g / 10 minutes, JIS-K-72
According to 10, the load was measured at 2.169 kg).

Examples will be specifically described below. [Examples 1 to 8 and Comparative Examples 1 to 7] Polypropylene resin pellets shown in Table 1 and resin pellets obtained by kneading the resin with calcium carbonate fine powder pretreated with metal soap having an average particle size of 0.5 µm were used. And a core-sheath type composite fiber having an area ratio of the core component and the sheath component of 1: 1 in the fiber cross section in which the resin pellet containing calcium carbonate is the sheath component and the resin pellet not containing calcium carbonate is the core component, and calcium carbonate Each of the single fibers containing only the resin pellets containing was melt-spun. Each of these undrawn yarns is dry-drawn using a 150 ° C. hot roll in an atmosphere of 150 ° C., impregnated with various surfactant aqueous solutions of normal alkyl phosphate metal salts, left to stand overnight, and air-dried to 6 mm or 1 mm.
It was cut to 0 mm. At this time, the strength and elongation of the drawn yarn was measured using the air-dried fiber before cutting.

Then, in 7.2 liters of tap water, 680 g of ordinary Portland cement, 17 g of pulp and 1 mica powder from China
70 g, and 8.5 g of the short fibers of each of the above-mentioned Examples and Comparative Examples (however, Example 6 was 13 g, Comparative Example 3 was 2.
6 g, Comparative Example 5 is a conventional polypropylene fiber, Comparative Example 6
Is 43 g of asbestos instead of short fiber, Comparative Example 7 is 2
8.5 g of commercially available vinylon having a denier of 6 mm was added. ) Were sequentially added and mixed to prepare an 8 l cement slurry.

To this slurry liquid, 20 ml of 0.02% by weight of a flocculant (trade name: IKEFLOCK, manufactured by Ichikawa Kaori Co., Ltd.) was added, and the mixture was divided into 8 times in a mold container having a bottom area of 250 mm × 250 mm. This slurry liquid was poured and dehydrated through a 60-mesh wire net to produce paper, and these were sequentially stacked with the upper surface facing upward to obtain an 8-layer laminated product to obtain a flat semi-plastic molded product having a thickness of about 8 mm.

200 kg / cm ^{2 of} this semi-plastic molded product
After pressing for 1 minute under the pressure of, the compression molded product was allowed to stand at room temperature in a wet state for 28 days for natural curing, and the slurry state and the product during that period were evaluated. The results are shown in Table 1.

The test evaluation was carried out as follows. Floating fiber ratio (%): 10 for the prepared cement slurry
After allowing to stand for a minute, the floating fibers of the supernatant liquid are scooped up with a wire net and dried, and the fiber weight Ag is measured, and the floating fiber ratio (%) = 100 A / B is calculated from the fiber input amount Bg. Dispersion state: After putting the slurry in a mold container, the semi-plastic state molded product obtained by dehydration was observed for the surface irregularities and evaluated as follows. ⊚: A state with very few irregularities. ◯: A state where there are few irregularities. Δ: A state in which unevenness is slightly large. X: A state where there are many irregularities. Product appearance: Observe the front and back of the cement product after curing,
It evaluated as follows. ⊚: A state in which the fibers are hardly exposed on the product surface. ○: The state where the fibers are slightly exposed on the product surface. Δ: A state in which fibers are slightly exposed on the product surface. X: A state in which many fibers are exposed on the product surface. Eyebrow strength: Measured according to JIS-A-1408. Charpy impact strength: Measured according to JIS-B-7722.

[Examples 9 to 12 and Comparative Examples 8 to 11] Pressed products in the same manner as in Example 1 and 5 mm thick paper-made semi-plastic molded articles were autoclaved at 160 ° C for 18 hours. Was evaluated. The results are shown in Table 2.

[Examples 13 to 14, Comparative Examples 12 to 15]
Ordinary Portland cement (510 g), silica sand (340 g), asbestos (17 g), pulp (17 g) and the fibers of Example 1 and Comparative Examples 15 and 6 (8.5 g) were sequentially added to 7.2 liters of tap water to prepare an 8 liter cement slurry. After adding 20 ml of 0.02% by weight of a coagulant, the mixture was poured into a mold container 8 times and dehydrated through a 60 mesh wire net to obtain a flat semi-plastic molded product having a thickness of about 5 mm. It was The product was evaluated by subjecting this molded product to a natural curing method in which it is left in a wet state for 28 days and an autoclave curing treatment at 160 ° C. for 10 hours. The results are shown in Table 3.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

INDUSTRIAL APPLICABILITY The polypropylene fiber of the present invention is useful as a fiber for reinforcing cement because it has good hydrophobicity and has a small specific gravity and is well mixed with a cement slurry and is preferably dispersed. In the manufacturing process of cement products produced by the papermaking method, the floating phenomenon of fibers is not observed, the product has an excellent surface appearance, and the input fibers are uniformly dispersed, so that the reinforcing effect can be effectively achieved. Furthermore, since the fiber has a higher strength than the conventional polypropylene reinforcing fiber, it has excellent bending strength and impact strength. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 20, 1994

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

To achieve the above object, the polypropylene fiber of the present invention has a Q value (Q: weight average molecular weight / number average molecular weight ratio) of less than 5 and a boiling n-heptane insoluble content (HI: weight%) of 97 <. Resin containing 3 to 20% by weight of calcium carbonate fine powder having an average diameter of less than 1 μm in a highly crystalline polypropylene having an HI <100 and an isotactic pentad fraction (IPF: mol%) of 94 <IPF <100. 0.05 to 10% by weight of a normal alkyl phosphate alkali metal salt having 8 to 18 carbon atoms based on the weight of the fiber is attached to the polypropylene fiber having a breaking strength of the fiber of more than 6 g / denier. Is a polypropylene fiber for cement reinforcement.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

The amount of calcium carbonate mixed in the fiber is 3
%, Floating seeds are easily formed in the cent slurry even if the amount of the alkyl phosphate salt attached is increased, and if it exceeds 20% by weight, the stretchability of the fiber is lowered and desired strength cannot be easily obtained. It is preferably 10 to 20% by weight. Further, the calcium carbonate fine powder is preferably treated with a surfactant before being mixed in the polypropylene resin.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location D01F 8/06 7199-3B D06M 13/288 E04C 5/07 8504-2E

Claims (4)

[Claims] 1. A Q value (Q: weight average molecular weight / number average molecular weight ratio) of less than 5, a boiling n-heptane insoluble matter (HI: weight%) of 97 <HI <100, and an isotactic pentad fraction. (IPF: mol%) 94 <IPF <100 Highly crystalline polypropylene made of a resin containing 4 to 20 g by weight of calcium carbonate fine powder having an average diameter of less than 1 μm, and a fiber breaking strength of 6 g / denier A polypropylene fiber for cement reinforcement, characterized in that a polypropylene fiber having a strength of more than 10% of a normal alkyl phosphate alkali metal salt having 8 to 18 carbon atoms is attached to the fiber weight by 0.05 to 10% by weight. 2. A fiber having a polypropylene resin component according to claim 1 as a sheath and a core containing the polypropylene resin component according to claim 1, which does not contain calcium carbonate, has a breaking strength of 7.
g / denier core-sheath polypropylene fiber with 8 carbon atoms
Polypropylene fiber for cement reinforcement, characterized in that 0.05 to 10% by weight of normal alkyl phosphate alkali metal salt of about 18 is attached to the fiber weight. 3. A fiber-reinforced cement molded product, wherein the polypropylene fiber according to claim 1 is composed of a cement composition in which 0.5 to 5% by weight is added to a dry cement matrix. 4. A fiber-reinforced cement molded product, wherein the polypropylene fiber according to claim 2 comprises a cement composition in which 0.5 to 5% by weight is added to a dry cement matrix.